WO2020081273A1

WO2020081273A1 - Device for cleaning the waste gas of a furnace chamber of a reflow soldering furnace

Info

Publication number: WO2020081273A1
Application number: PCT/US2019/054974
Authority: WO
Inventors: Yuwei Wang; Peng Shu; Dong Zhang
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2018-10-17
Filing date: 2019-10-07
Publication date: 2020-04-23
Anticipated expiration: 2021-04-17
Also published as: TWI811455B; CN111054173A; TW202027845A

Abstract

The present invention discloses a waste-gas cleaning system for cleaning off contaminants in waste gas in a furnace chamber of a reflow soldering furnace, comprising: a primary cooling unit, a secondary cooling unit, and a filtering unit, ensuring that few contaminants in waste gas adhere to an inner wall of a cooling device; thus extending the maintenance cycle. The present application further provides a self-cleaning waste-gas cleaning system, comprising: a cooling unit, a filtering unit, a heating component, a first passage, and a second passage, allowing a gas to create a self-cleaning gas cycle in the cooling unit, the first passage, the filtering unit, and the second passage, so that the waste-gas cleaning system is maintained conveniently.

Description

DEVICE FOR CLEANING THE WASTE GAS OF A FURNACE CHAMBER OF A REFLOW

SOLDERING FURNACE

RELATED APPLICATIONS

[0001] This international application claims priority to Chinese Patent Application Serial No. 201811208963.5, filed October 17, 2018, entitled “AN EXHAUST GAS PURIFICATION SYSTEM.” The entirety of Chinese Patent Application Serial No. 201811208963.5 is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present application relates to a waste-gas cleaning system for a reflow soldering furnace, in particular to a waste-gas cleaning system for cleaning waste gas in a furnace chamber of a reflow soldering furnace.

BACKGROUND

[0003] In the manufacture of a printed circuit board, electronic components are installed on the circuit board generally by a process known as "reflow soldering". In a typical reflow soldering process, a soldering paste, for example, a tin paste, is deposited in a selected area on a circuit board, and the conducting wires of one or more electronic components are inserted into the deposited soldering paste. Then, the circuit board is passed through a reflow soldering furnace. In the reflow soldering furnace, the soldering paste is caused to reflow in a heating zone (that is, for being heated to fusion or a reflow temperature) and is then cooled in a cooling zone, thereby electrically and mechanically connecting the electronic components to the circuit board. The term "circuit board" used herein includes a basal plate element of an electronic component of any type, for example, a wafer basal plate. In a reflow soldering furnace, air or a basically inert gas, for example, nitrogen, is generally used as a working gas. For circuit boards having different process requirements, different working gases are used. The furnace chamber of a reflow soldering furnace is filled with a working gas, and soldering is performed in the working gas when a circuit board is conveyed into the furnace chamber by a conveying device.

[0004] In a reflow soldering furnace, a soldering paste comprises not only a solder but also a fluxing agent that promotes wetting of the solder and provides good solder joint seaming. Other additives including solvents and catalysts may also be included therein. After a soldering paste is deposited on a circuit board, the circuit board is conveyed by a conveyer to pass through a plurality of heating zones in the reflow soldering furnace. The heat in the heating zones melts the soldering paste, and volatile organic compounds (VOCs) mainly composed of the fluxing agent are evaporated into vapor, thus forming "contaminants". Accumulation of these contaminants in the reflow soldering furnace will cause certain problems. For example, when contaminants reach a cooling zone, they condense on the circuit board and contaminate the circuit board; consequently, subsequent cleaning steps have to be performed. Contaminants may also condense on the surface of a cooling device of a reflow soldering furnace, blocking its air vents. Moreover, condensates may also drip onto a subsequent circuit board; consequently, a component on the circuit board may be damaged, or the contaminated circuit has to be subsequently cleaned.

SUMMARY

[0005] It is necessary to remove waste gas containing contaminants in a furnace chamber of a reflow soldering furnace from the furnace chamber in order to keep a clean working atmosphere in the furnace chamber of the reflow soldering furnace; thus, contaminants are prevented from entering a cooling zone of the reflow soldering furnace and causing any of the above-mentioned problems in the reflow soldering furnace.

[0006] When a reflow soldering furnace uses a basically inert gas, for example, nitrogen, as a working gas, since a basically inert gas, for example, nitrogen, is expensive, it is generally hoped that waste gas released from the reflow soldering furnace is cleaned by a waste-gas cleaning system and then conveyed back to the reflow soldering furnace for reuse. When a reflow soldering furnace uses air as a working gas, waste gas released from the reflow soldering furnace, after being cleaned by a waste-gas cleaning system, may be directly released into the atmosphere or may be conveyed back to the reflow soldering furnace for reuse.

[0007] In one solution, waste gas is cooled in a cooling device to a temperature of about 80°C or lower, so that the contaminants in the waste gas are condensed from a gaseous form into a liquid or solid form, and then the contaminants in a liquid or solid form are removed. However, contaminants in a liquid or solid form that are formed by cooling are prone to adhere to an inner wall of the cooling device and are difficult to clean off; consequently, the maintenance cycle is short and maintenance costs are high; moreover, contaminants may also adhere to a heat exchange part, for example, a heat exchange plate or a heat exchange tube, of the cooling device, affecting the heat exchange efficiency.

[0008] In addition, for a waste-gas cleaning system according to the prior art, the connecting pipelines and various components of the waste-gas cleaning system need to be cleaned manually, which is very inconvenient.

[0009] After carrying out observations and research, the applicant has found that contaminants adhering to an inner wall of a cooling device and to a heat exchange part in a waste-gas cleaning system that are difficult to clean off are mainly a rosin in a solid form. The reason is that the rosin in a contaminant and other fluxing agents, when cooled from a high temperature to about 80°C, are directly condensed from a gaseous form into a solid form and adhere to an inner wall of the cooling device and to a heat exchange part; consequently, the maintenance cycle of the waste-gas cleaning system is short, and the heat exchange efficiency is affected.

[0010] In order to solve at least one of the above-mentioned problems, at least one objective of the present application is to provide a waste-gas cleaning system for cleaning the waste gas in a furnace chamber in a reflow soldering furnace, so that rosin is not prone to adhere to an inner wall of a cooling device; thus, the maintenance cycle is extended.

[0011] In order to achieve the above-mentioned objective, an aspect of the present application provides a waste-gas cleaning system for cleaning off contaminants contained in waste gas in a furnace chamber of a reflow soldering furnace, said system comprising: a primary cooling unit, said primary cooling unit being provided with a waste gas inlet and a gas outlet, said primary cooling unit being configured to cool, to a first temperature, the waste gas that has entered said primary cooling unit through said waste gas inlet, so that a part of the contaminants in the waste gas that has entered said primary cooling unit is cooled from a gaseous form into a liquid form and then discharged from said primary cooling unit, while a part of the remaining part of the contaminants in the waste gas that has entered said primary cooling unit remains in a gaseous form; a secondary cooling unit, said secondary cooling unit being provided with a gas inlet and a gas outlet, a gas inlet of said secondary cooling unit being in fluid communication with a gas outlet of said primary cooling unit, said secondary cooling unit being configured to cool, from said first temperature to a second temperature, the waste gas that has entered said secondary cooling unit through said primary cooling unit, so that a part of the contaminants in the waste gas that has entered said secondary cooling unit is cooled from a gaseous form into a liquid form and then discharged from said secondary cooling unit, while a part of the remaining part of the contaminants in the waste gas that has entered said secondary cooling unit remains in a gaseous form or pulverized form; and a filtering unit, said filtering unit being provided with a gas inlet and a clean gas outlet, a gas inlet of said filtering unit being in fluid communication with a gas outlet of said secondary cooling unit, said filtering unit being configured to filter the waste gas that entered said filtering unit and discharge at least one part of the filtered gas through a clean gas outlet of said filtering unit.

[0012] According to the above-described first aspect, said waste-gas cleaning system further comprises: a collecting unit, said primary cooling unit and said secondary cooling unit being provided with a waste liquid outlet, respectively, said collecting unit being controllably in fluid communication with the waste liquid outlets of said primary cooling unit and said secondary cooling unit, for collecting the discharged liquid waste gas.

[0013] According to the above-described first aspect, at said first temperature, waste gas is cooled from a gaseous form into liquid contaminants, including rosin organic substances; at said second temperature, contaminants in waste gas that are cooled from a gaseous form into a liquid form include other low-freezing acidic or ester or ether organic substances.

[0014] According to the above-described first aspect, said first temperature is in the range of 1 l0°C to l30°C; said second temperature is in the range of 60°C to 80°C.

[0015] According to the above-described first aspect, a waste gas inlet of said primary cooling unit is configured to be controllably in fluid communication with a furnace chamber of said reflow soldering furnace.

[0016] A second aspect of the present application provides a self-cleaning waste-gas cleaning system, comprising: a cooling unit, said cooling unit being provided with a self-cleaning gas inlet and a gas outlet; a filtering unit, said filtering unit being provided with a gas inlet and a self cleaning gas outlet; a heating component, said heating component being disposed in said filtering unit, for increasing a gas temperature in said filtering unit; a first passage, said first passage being connected to the gas outlet of said cooling unit and the gas inlet of said filtering unit, said first passage being configured to convey the gas in said cooling unit to said filtering unit; and a second passage, said second passage being connected to the self-cleaning gas outlet of said filtering unit and the self-cleaning gas inlet of said cooling unit, said second passage being configured to controllably convey the gas in said filtering unit to said cooling unit, wherein a self-cleaning gas cycle is created among said cooling unit, said first passage, said filtering unit, and said second passage.

[0017] According to the above-described second aspect, said waste-gas cleaning system further comprises: a fluidic power device, said fluidic power device being configured to cause a gas to be cycled in said filtering unit and said cooling unit through said first passage and said second passage.

[0018] According to the above-described second aspect, said cooling unit comprises a waste gas inlet, said waste gas inlet being configured to be controllably in communication with the furnace chamber of the reflow soldering furnace; said filtering unit comprises a clean gas outlet, said clean gas outlet being configured to controllably discharge the gas in said filtering unit.

[0019] According to the above-described second aspect, said waste-gas cleaning system further comprises: a collecting unit, said cooling unit and said filtering unit being provided with a waste liquid outlet, respectively, said collecting unit being controllably in fluid communication with the waste liquid outlets of said cooling unit and said filtering unit, for collecting the discharged liquid waste gas.

[0020] According to the above-described second aspect, said cooling unit is further provided with a gas replenishing hole, said gas replenishing hole being configured to be controllably in fluid communication with a protection gas, so that the protection gas enters said waste-gas cleaning system; said filtering unit is provided with an air vent, said air vent being configured to discharge the gas in said waste-gas cleaning system.

[0021] The concept, specific composition, and technical effects of the present application will be further described below with reference to the drawings, so that the objectives, characteristics, and effects of the present application can be sufficiently understood.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A is a simplified structural block diagram for a waste-gas cleaning system according to an embodiment of the present application;

[0023] Figure 1B is a block diagram for a flow path followed by a gas when the waste-gas cleaning system shown in Figure 1A is in a working state;

[0024] Figure 1C is a block diagram for a flow path followed by a gas when the waste-gas cleaning system shown in Figure 1A is in a maintenance state; [0025] Figure 2A is a three-dimensional structural diagram for a waste-gas cleaning device according to an embodiment of the present application;

[0026] Figure 2B is a front view of the waste-gas cleaning device shown in Figure 2A;

[0027] Figure 2C is a top view of the waste-gas cleaning device shown in Figure 2A;

[0028] Figure 3 is an exploded view of the waste-gas cleaning device shown in Figure 2A;

[0029] Figure 4 is a sectional view along the line A- A in Figure 2B;

[0030] Figure 5 is a sectional view along the line B-B in Figure 2C;

[0031] Figure 6 is a three-dimensional structural diagram for a cooling device in the waste-gas cleaning device shown in Figure 2A;

[0032] Figure 7A is a three-dimensional structural diagram for a waste-gas cleaning device according to another embodiment of the present application;

[0033] Figure 7B is a front view of the waste-gas cleaning device shown in Figure 7A;

[0034] Figure 7C is a top view of the waste-gas cleaning device shown in Figure 7A;

[0035] Figure 8 is an exploded view of the waste-gas cleaning device shown in Figure 7A;

[0036] Figure 9 is a sectional view along the line A- A in Figure 7B;

[0037] Figure 10A is a sectional view along the line B-B in Figure 7C;

[0038] Figure 10B is a sectional view along the line C-C in Figure 10A; and

[0039] Figure 11 is a three-dimensional structural diagram for a cooling device in the waste- gas cleaning device shown in Figure 7A.

DETAILED DESCRIPTION

[0040] Specific embodiments of the present application will be described below with reference to drawings that constitute part of the specification. It should be understood that although terms for indicating directions, such as "front", "rear", "upper", "lower", "left", "right", "inner", "outer", "top", and "bottom", are used herein to describe structural parts and components of each embodiment of the present application, use of these terms herein is only intended for convenience of explanation, and these terms are determined on the basis of the embodiment orientations shown in the drawings. Embodiments disclosed by the present application may be disposed in different directions, and so these terms indicating directions are only illustrative, instead of being construed as limiting. [0041] Those of ordinary skill in the art should know that waste gas or gas described in an embodiment refers to an element that is largely in gaseous form, and may also be composed of a part of a pulverized or granular ingredient.

[0042] Figure 1A shows a simplified structural block diagram for a waste-gas cleaning system according to an embodiment of the present application, for illustrating the connection relationships among the components of the waste-gas cleaning system 100. As shown in Figure 1A, the waste- gas cleaning system 100 is disposed outside a furnace chamber 118 of the reflow soldering furnace and is connected to the furnace chamber 118 of the reflow soldering furnace. When the reflow soldering furnace uses a basically inert gas, for example, nitrogen, as a working gas, the waste-gas cleaning system 100 receives waste gas released from the furnace chamber 118 of the reflow soldering furnace and conveys clean gas back to the furnace chamber 118. When the reflow soldering furnace uses air as a working gas, the waste-gas cleaning system 100 receives waste gas released from the furnace chamber 118 of the reflow soldering furnace, and conveys clean gas back to the furnace chamber 118, or, instead of conveying clean gas back to the furnace chamber 118, releases clean gas to the outside of the furnace chamber 118. As shown in Figure 1A, the waste-gas cleaning system 100 conveys clean gas back to the furnace chamber 118.

[0043] As shown in Figure 1A, the waste-gas cleaning system 100 comprises a primary cooling unit 110, a secondary cooling unit 120, and a filtering unit 130, which are connected in turn and connected to the furnace chamber 118 to clean waste gas released from the furnace chamber 118. The waste-gas cleaning system 100 may also convey clean gas back to the furnace chamber 118. In addition, the waste-gas cleaning system 100 may also self-clean the primary cooling unit 110, the secondary cooling unit 120, the filtering unit 130, and the connecting passages between them.

[0044] Specifically, the primary cooling unit 110 is provided with a waste gas inlet 111.1, a self-cleaning gas inlet 114, a gas outlet 111.2, and a first waste fluid outlet 141.1. The secondary cooling unit 120 is provided with a gas inlet 121.1, a gas outlet 121.2, and a waste fluid outlet 141.2. The filtering unit 130 is provided with a gas inlet 131.1, a self-cleaning gas outlet 134, a clean gas outlet 131.2, and a waste fluid outlet 141.3.

[0045] The waste gas inlet 111.1 of the primary cooling unit 110, by a valve component 117.1, is controllably in fluid communication with a high-temperature zone of the furnace chamber 118. The gas outlet 111.2 of the primary cooling unit 110, by a connecting passage 125.1, is in fluid communication with the gas inlet 121.1 of the secondary cooling unit 120. The gas outlet 121.2 of the secondary cooling unit 120, by a connecting passage 125.2, is in fluid communication with the gas inlet 131.1 of the filtering unit 130, and the clean gas outlet 131.2 of the filtering unit 130, by a valve component 117.2, is controllably in fluid communication with a low-temperature zone of the furnace chamber 118. Thus, waste gas released from the furnace chamber 118 is cleaned by passing through the primary cooling unit 110, the secondary cooling unit 120, and the filtering unit 130 in turn and is then conveyed back to the furnace chamber 118.

[0046] Further, the self-cleaning gas outlet 134 of the filtering unit 130, by a connecting passage 135, is connected to the gas inlet 114 of the primary cooling unit 110, and a passage opening/closing component 117.5 is disposed on the connecting passage 135 to controllably establish fluid communication between the self-cleaning gas outlet 134 of the filtering unit 130 and the gas inlet 114 of the primary cooling unit 110. Thus, gas released from the self-cleaning gas outlet 134 of the filtering unit 130 may enter the primary cooling unit 110, flow through the primary cooling unit 110 and the secondary cooling unit 120 in turn, and then return to the filtering unit 130, thereby creating a self-cleaning gas cycle in the waste-gas cleaning system 100.

[0047] According to an embodiment of the present application, on the primary cooling unit 110, instead of disposing the self-cleaning gas inlet 114 that is separate from the waste gas inlet 111.1, the same inlet may be used as a waste gas inlet and a self-cleaning gas inlet. Likewise, on the filtering unit 130, instead of disposing the self-cleaning gas outlet 134 that is separate from the clean gas outlet 131.2, the same outlet may also be used as the self-cleaning gas outlet 134 and the clean gas outlet 131.2.

[0048] The waste-gas cleaning system 100 further comprises a gas replenishing hole 112 disposed on the primary cooling unit 110, an air vent 132 disposed on the filtering unit 130, and a gas concentration measuring component for measuring a gas concentration in the filtering unit 130. As an example, the gas concentration measuring component is an oxygen concentration measuring component 155, which obtains a concentration of a working gas by measuring an oxygen concentration. The oxygen concentration measuring component 155 is disposed near the air vent 132. The gas replenishing hole 112 is controllably opened and closed by a valve component 117.3, and the air vent 132 is controllably opened and closed by a valve component 117.4. When the reflow soldering furnace uses a basically inert gas, for example, nitrogen, as a working gas, the working gas, namely, the basically inert gas, for example, nitrogen, may be replenished through the gas replenishing hole 112 to the waste-gas cleaning system 100, and the air vent 132 is configured to cooperate with the gas replenishing hole 112 when the gas replenishing hole 112 is working. By the disposition of the gas replenishing hole 112 and the air vent 132, the concentration of the working gas in the waste-gas cleaning system 100 may be adjusted to match the concentration of the working gas in the furnace chamber 118. The gas replenishing hole 112 may, by the valve component 117.3, be controllably in fluid communication with a working gas, namely, a basically inert gas, for example, nitrogen, and the air vent 132 is controllably in fluid communication with the atmosphere by the valve component 117.4.

[0049] A filtering component 136 is disposed in the filtering unit 130. The gas inlet 131.1 of the filtering unit 130 is disposed on an upstream side of the filtering component 136, and the self cleaning gas outlet 134 and the clean gas outlet 131.2 are disposed on a downstream side of the filtering component 136. Note that said "upstream" and "downstream" are relative to the flowing direction of a gas in the waste-gas cleaning system 100. The filtering component 136 may be a steel ball screen, a paper screen, etc.

[0050] A heating component 133 is further disposed in the filtering unit 130, and the heating component 133, located below the filtering component 136, is configured to heat the filtering component 136.

[0051] The waste-gas cleaning system 100 further comprises a fan 124 that is configured to drive a gas in the waste-gas cleaning system 100 to flow. In the embodiment shown in Figure 1A, the fan 124 is disposed in the filtering unit 130. Specifically, the fan 124 is disposed above the filtering component 136, the air inlet side of the fan 124 being in fluid communication with a cavity in the filtering unit 130, the air outlet side of the fan 124 being in fluid communication with the clean gas outlet 131.2, the self-cleaning gas outlet 134, and the air vent 132 of the filtering unit 130. In another embodiment, the fan 124 in the embodiment shown in Figure 1A may also be replaced by any other fluidic power device, for example, a blower or a pump, that is capable of driving a gas in the waste-gas cleaning system 100 to flow along an expected path.

[0052] The waste-gas cleaning system 100 further comprises a collecting unit 140, the waste fluid outlet 141.1 of the primary cooling unit 110, the waste fluid outlet 141.2 of the secondary cooling unit 120, and the waste fluid outlet 141.3 of the filtering unit 130 all being connected to the collecting unit 140, so that a fluid having passed through the primary cooling unit 110, the secondary cooling unit 120, and the filtering unit 130 may flow into the collecting unit 140. A valve component 117.6 is disposed at the inlet of the collecting unit 140. When the collecting unit 140 needs to be replaced or a fluid in the collecting unit 140 needs to be removed, the valve component 117.6 may be closed to disconnect the collecting unit 140 from the primary cooling unit 110, the secondary cooling unit 120, and the filtering unit 130.

[0053] The waste-gas cleaning system 100 further comprises thermodetectors 151 and 152 that are configured to measure a temperature in the primary cooling unit 110 and a temperature in the secondary cooling unit 120, respectively.

[0054] Note that, in the embodiment shown in Figure 1, the waste-gas cleaning system 100 comprises two levels of cooling units, the two levels of cooling units being in fluid communication by the connecting passage 125.1. In another embodiment, the waste-gas cleaning system may also comprise only the primary cooling unit 110 or the secondary cooling unit 120.

[0055] The waste-gas cleaning system 100 has a working state and a maintenance state. In a working state, the waste-gas cleaning system 100 cleans the gas released from the furnace chamber 118 of the reflow soldering furnace. In a maintenance state, the waste-gas cleaning system 100, instead of receiving any gas released from the furnace chamber 118 of the reflow soldering furnace, self-cleans the interior of the waste-gas cleaning system 100. By controlling the opening and closing of the valve components 117.1, 117.2, 117.3, 117.4, 117.5, and 117.6, the state of the waste-gas cleaning system 100 may be switched between a working state and a maintenance state. The flow paths of a gas in the two states of the waste-gas cleaning system 100 of the present application will be described below by taking, as an example, a reflow soldering furnace that uses a basically inert gas, for example, nitrogen, as a working gas.

[0056] Figure IB shows a flow path followed by a gas when the waste-gas cleaning system 100 shown in Figure 1A is in a working state. As shown in Figure IB, when the waste-gas cleaning system 100 is in a working state, the valve components 117.1, 117.2, and 117.6 are open, the valve components 117.3 and 117.4 are closed, and the passage opening/closing component 117.5 may be closed or at least partially opened. Waste gas (having a temperature of about 170°C) containing contaminants in the furnace chamber 118 of the reflow soldering furnace, after being released from a high-temperature zone of the furnace chamber 118, first passes through the primary cooling unit 110 and is cooled to a first temperature, for example, a temperature in the range of 110°C to 130°C. At this temperature, rosin and other organic substances in the waste gas contaminants in the primary cooling unit 110 are condensed from a gaseous form into a liquid form and may enter the collecting unit 140 through the waste fluid outlet 141.1 of the primary cooling unit 110, and the remaining waste gas is conveyed to the secondary cooling unit 120 and further cooled. Gas that has entered the secondary cooling unit 120 is cooled in the secondary cooling unit 120 to a second temperature, for example, a temperature in the range of 60°C to 80°C, so that other contaminant organic substances (for example, low-freezing acidic or ester or ether organic substances) are condensed from a gaseous form into a liquid form and enter the collecting unit 140 through the waste fluid outlet 141.2 of the secondary cooling unit 120, and the remaining waste gas is conveyed to the filtering unit 130 for filtration and cleaning. After waste gas entering the filtering unit 130 is filtered, granular and pulverized organic substances are moved from the waste gas, and thus clean gas is obtained. Finally, when the clean gas is conveyed back to a low-temperature zone of the furnace chamber 118 of the reflow soldering furnace, cleaning of the waste gas is completed.

[0057] When the waste-gas cleaning system 100 is in a working state, if the valve component 117.5 is closed, then clean gas filtered by the filtering unit 130 cannot be returned to the primary cooling unit 110 through the connecting passage 135. If the valve component 117.5 is open or partially open, then part of the clean gas filtered by the filtering unit 130 can return to the primary cooling unit 110 through the connecting passage 135; thus, the gas in the primary cooling unit 110 may be cooled by the clean gas having a lower temperature in the filtering unit 130, thereby saving the coolant used for heat exchange in the primary cooling unit 110.

[0058] Figure 1C shows a flow path followed by the gas when the waste-gas cleaning system 100 is in a maintenance state. As shown in Figure 1C, when the waste-gas cleaning system 100 is in a maintenance state, the valve components 117.1, 117.2, 117.3, and 117.4 are closed, and the valve component 117.6 and the valve component 117.5 are open. In this case, the heating component 133 in the filtering unit 130 heats the gas in the filtering unit 130, capable of increasing the temperature in the filtering unit 130, for example, to a temperature in the range of about l50°C to l70°C. At this temperature, a part of the solid contaminants that adhere to the filtering component 136 is converted into a liquid and another part is converted into a gas; the liquid can be discharged through the waste fluid outlet 141.3 of the filtering unit 130, while the gas, at a higher temperature, is conveyed back to the primary cooling unit 110 and the secondary cooling unit 120 through the connecting passage 135. The gas in the primary cooling unit 110 and the secondary cooling unit 110, by the above-mentioned waste-gas cleaning process, flows back to the filtering unit 130 through the connecting passages 125.1 and 125.2, so that the solid contaminant organic substances adhering to the components in the primary cooling unit 110 and the secondary cooling unit 120 and to inner walls of the connecting passage 125.1 and the cooling passage 125.2 are heated again into a liquid or a gas, and the liquid is discharged through the waste fluid outlet 141.1 of the primary cooling unit 110 and the waste fluid outlet 141.2 of the secondary cooling unit 120, while the gas is conveyed back to the filtering unit 130, completing a self-cleaning gas cycle.

[0059] In the self-cleaning gas cycle shown in Figure 1C, since the valve components 117.1 and 117.2 are closed, the self-cleaning gas cycle can be completed without affecting the working of the reflow soldering furnace. In other words, even if the reflow soldering furnace is working, the waste-gas cleaning system 100 can be in a maintenance state to self-clean its interior.

[0060] When the furnace chamber 118 of the reflow soldering furnace uses a basically inert gas, for example, nitrogen, as a working gas, a concentration of the working gas should be kept in a certain range in order to meet process requirements. Generally, a unit (for example, a unit for replenishing the working gas) for regulating a concentration of the working gas in the furnace chamber 118 is disposed in the reflow soldering furnace. When the waste-gas cleaning system 100 is in a working state, the gas in the furnace chamber 118 of the reflow soldering furnace is continuously cleaned by the waste-gas cleaning system 100 and is conveyed back to the furnace chamber 118 of the reflow soldering furnace. Therefore, the working gas in the waste-gas cleaning system 100 that is in a working state has a concentration close to a concentration unit of the working gas in the furnace chamber 118 of the reflow soldering furnace. However, when the waste- gas cleaning system 100 is disconnected from the furnace chamber 118 of the reflow soldering furnace and performs self-cleaning maintenance, the working gas in the waste-gas cleaning system 100 has a concentration generally lower than a concentration of the working gas in the furnace chamber 118. Therefore, according to the present application, after completion of the maintenance state of the waste-gas cleaning system 100 (including the maintenance process of the self-cleaning gas cycle or a maintenance process in any other cleaning mode), before the waste-gas cleaning system 100 is reconnected to the furnace chamber 118 of the reflow soldering furnace, a certain amount of working gas may be replenished to the waste-gas cleaning system 100, so that the working gas in the waste-gas cleaning system 100 reaches a concentration that is the same as or close to a concentration of the working gas in the reflow soldering furnace. For this purpose, the working gas is replenished through the gas replenishing hole 112 to the waste-gas cleaning system 100 and, at the same time, the gas in the waste-gas cleaning system 100 is discharged through the air vent 132, until it is determined, by the oxygen concentration measuring component 155, that the protection gas in the waste-gas cleaning system 100 has reached the concentration of the protection gas in the reflow soldering furnace.

[0061] When the waste-gas cleaning system 100 is used for a reflow soldering furnace that uses air as a working gas, gas cleaned by the waste-gas cleaning system 100 may be conveyed back to the furnace chamber 118 or, instead of being conveyed back to the furnace chamber 118, directly discharged into the atmosphere. If gas cleaned by the waste-gas cleaning system 100 is directly discharged into the atmosphere, then the clean gas outlet 131.2 of the filtering unit 130 shown in Figure 1B, by the valve component 117.2, is controllably in fluid communication with the atmosphere, instead of being connected to the furnace chamber 118.

[0062] According to the present application, known heat exchange devices of any type may be used as the primary cooling unit 110 and the secondary cooling unit 120 in the waste-gas cleaning system 100.

[0063] According to the present application, the primary cooling unit 110, the secondary cooling unit 120, and the filtering unit 130 of the waste-gas cleaning system 100 may be integrated, so that the whole waste-gas cleaning system 100 forms a box-type waste-gas cleaning device that can work with a reflow soldering furnace conveniently.

[0064] Two specific structural examples of the waste-gas cleaning device will be described below, in which Figures 2A to 6 show the specific structure of a waste-gas cleaning device 200 according to an embodiment of the present application, and Figures 7A to 11 show the specific structure of a waste-gas cleaning device 700 according to another embodiment of the present application.

[0065] Figures 2A to 2C are general structural diagrams for the waste-gas cleaning device 200, in which Figure 2A is a three-dimensional structural diagram for the waste-gas cleaning device 200, Figure 2B is a front view of Figure 2A, and Figure 2C is a top view of Figure 2A. As shown in Figures 2A to 2C, the waste-gas cleaning device 200 comprises a case 201; the case 201 is roughly in the shape of a box, in which a cavity is provided, comprising a top part 202, a bottom part 203, a left part 204, a right part 205, a front part 206, and a rear part 207. The top part 202, the bottom part 203, the left part 204, the right part 205, and the rear part 207 of the case 201 are connected, for example, by soldering to form a box cavity, and the front part 206 is detachably connected, by a clamp, etc., to the top part 202 and the bottom part 203 to seal the box cavity. Figure 2B shows the top part 202, the bottom part 203, the left part 204, the right part 205, and the front part 206, and Figure 2C shows the rear part 207.

[0066] As shown in Figures 2A to 2C, the waste-gas cleaning device 200 further comprises a waste gas inlet 211.1 and a clean gas outlet 231.2 that are disposed on the case 201. A connecting passage 251.1 is disposed on the waste gas inlet 211.1, and a valve component 217.1 is disposed on the connecting passage 251.1. The valve component 217.1 may be opened and closed. The waste gas inlet 211.1 is connected by the connecting passage 251.1 to a high-temperature zone (not shown) in the furnace chamber of the reflow soldering furnace. A connecting passage 251.2 is disposed on the clean gas outlet 231.2, and a valve component 217.2 is disposed on the connecting passage 251.2. The valve component 217.2 may be opened and closed. The clean gas outlet 231.2 is connected by the connecting passage 251.2 to a low-temperature zone (not shown) in the furnace chamber of the reflow soldering furnace. Waste gas discharged from the furnace chamber may enter the waste-gas cleaning device 200 through the waste gas inlet 211.1 , be cleaned as clean gas by the waste-gas cleaning device 200, and may then be conveyed through the clean gas outlet 231.2 to a low-temperature zone in the furnace chamber of the reflow soldering furnace.

[0067] As viewed from the front part of the waste-gas cleaning device 200 shown in Figure 2B, the waste gas inlet 211.1 is disposed at the back of the right part 205 of the case 201, and the clean gas outlet 231.2 is disposed on the left of the rear part 207 of the case 201, so that the flow direction of waste gas in the waste-gas cleaning device 200 is roughly from right to left.

[0068] The front part 201 of the case 206 comprises a first front plate 206.1 and a second front plate 206.2. The first front plate 206.1 is configured to seal a part of the cavity (see the filtering cavity 342 shown in Figure 3) in the case 201 in a front direction, and a second front plate 206.2 is configured to seal another part of the cavity (see the cooling cavity 341 shown in Figure 3) in the case 201 in a front direction. A plurality of openings 271 are disposed on the second front plate 206.2, so that a cooling device may be inserted into the cooling cavity 341 through the openings 271 on the second front plate 206.2 (this will be described in detail with reference to Figure 3).

[0069] The waste-gas cleaning device 200 further comprises a collecting device that is connected to the bottom part 203 of the case 201. In the example shown in the figure, the collecting device comprises two collecting flasks 240.1 and 240.2, which are respectively connected by a valve component 217.6 to the bottom part 203 of the case 201, so that contaminants condensed into a liquid may be controllably discharged into the collecting flasks 240.1 and 240.2. The bottom part 203 comprises a bottom plate that gradually tilts downward in a rear-to-front direction, the collecting flasks 240.1 and 240.2 being connected to the front side of the bottom plate (see Figure 4). The collecting flask 240.1 is configured to be in communication with the filtering cavity 342 (see Figure 3) in the case 201, and the collecting flask 240.2 is configured to be in communication with the cooling cavity 341 (see Figure 3) in the case 201. By the disposition of a tilted bottom plate, contaminants condensed into a liquid may flow into a collecting device more easily.

[0070] The waste-gas cleaning device 200 further comprises an air vent 232 and a gas replenishing hole 212 (see Figure 2C). As an example, the gas replenishing hole 212 is disposed near the waste gas inlet 211.1 on the top part 202 of the case 201. The air vent 232 is disposed on the connecting passage 251.1 at the clean gas outlet 231.2, and is located between the clean gas outlet 231.2 and the valve component 217.1. An oxygen concentration measuring device 455 (see Figure 4) is disposed at the bottom of the connecting passage 251.1 at the clean gas outlet 231.2; the oxygen concentration measuring device 455 is configured to measure an oxygen concentration of a gas released through the clean gas outlet 231.2. Thus, the flow direction of the protection gas replenished to the waste-gas cleaning device 200 is also roughly from right to left, so that the concentration of the working gas in the whole waste-gas cleaning device 200 is increased. A valve component is disposed on the air vent 232 and the gas replenishing hole 212, respectively; opening or closing of the air vent 232 and the gas replenishing hole 212 is controlled by valve components, for example, by solenoid valves. Those of ordinary skill in the art should understand that, in order to keep the gas pressure in the waste-gas cleaning device 200 within a specific range, the valve components disposed on the air vent 232 and the gas replenishing hole 212 should be opened at the same time or closed at the same time. Certainly, the air vent 232 and the gas replenishing hole 212 may also be disposed in other positions, as long as gas may be controllably input into the waste-gas cleaning device 200 through the gas replenishing hole 212 and may be controllably discharged from the waste-gas cleaning device 200 through the air vent 232. The waste-gas cleaning device 200 further comprises a fan 224. The driving component of the fan 224 is disposed on the left of the top part 202 of the case 201, and a vane wheel of the fan 224 is disposed in the filtering cavity 342 in the case 201 (see Figure 5). The vane wheel of the fan 224 is provided with an air inlet side and an air outlet side, wherein the air inlet side is in fluid communication with the filtering cavity 342 and the air outlet side is in fluid communication with the clean gas outlet 231.2. [0071] The waste-gas cleaning device 200 further comprises thermodetectors 213.1, 213.2, 213.3, 213.4, 213.5, and 213.6. The thermodetectors 213.1 and 213.2 are disposed at the waste gas inlet 211.1 and the clean gas outlet 231.2, respectively, and the thermodetectors 213.3, 213.4, and

213.5 are connected to the rear part 207 of the case 201 and extend into the cooling cavity 341 (see Figure 5) of the waste-gas cleaning device 200. The thermodetector 213.6 is connected to the left part 204 of the case 201 and extends into the filtering cavity 342 (see Figure 5) of the waste-gas cleaning device 200. As an example, the thermodetectors 213.1, 213.2, 213.3, 213.4, 213.5, and

213.6 are thermocouples. In another example, the waste-gas cleaning device 200 may also comprise only a part of the thermodetectors or be provided with another type of thermodetector.

[0072] The waste-gas cleaning device 200 further comprises a plurality of heating rods 222. The heating rods 222 are also connected to the left part 204 of the case 201 and extend into the filtering cavity 342 (see Figure 5) of the waste-gas cleaning device 200, for heating the filtering component 336 (see Figure 5) in the filtering cavity 342 in the self-cleaning process of the waste- gas cleaning device 200. In another example, the heating rods 222 may also be replaced by other heating devices. Certainly, the heating rods 222 may be omitted in a waste-gas cleaning device that does not need to perform self-cleaning.

[0073] Figure 3 is an exploded view of the waste-gas cleaning device 200, showing the internal structure and components of the waste-gas cleaning device 200. As shown in Figure 3, the case 201 internally comprises a separation plate 437 (for the specific structure of the separation plate 437, see Figure 4); the separation plate 437 separates the interior of the case 201 into the cooling cavity 341 and the filtering cavity 342, the cooling cavity 341 being located to the right of the filtering cavity 342. In addition, the separation plate 437 is provided with an upper opening 432 and a lower opening 431 (see Figure 4); the upper opening 432 and the lower opening 431 can be in communication with the cooling cavity 341 and the filtering cavity 342. The cooling cavity 341 is in communication with the waste gas inlet 211.1, and the filtering cavity 342 is in communication with the clean gas outlet 231.2. The cooling cavity 341 is provided with a cooling device that is configured to lower the temperature of the gas in the cooling cavity 341. The cooling device comprises a primary cooling device 310 and a secondary cooling device 320, the primary cooling device 310 being located to the right of the secondary cooling device 320. After entering the cooling cavity 341 through the waste gas inlet 211.1, the gas flows through the primary cooling device 310 and the secondary cooling device 320 in turn from right to left. The filtering cavity 342 is provided with a filtering component 336; the filtering component 336 is laterally installed in the filtering cavity 342, so that the gas, after entering the filtering cavity 342, flows through the filtering component 336 from bottom to top and flows out of the filtering cavity 342 through the clean gas outlet 231.2 above the filtering component 336.

[0074] The cooling cavity 341 is further provided with an enclosing plate 327; the enclosing plate 327 is disposed at the back in the top part of the cooling device; the enclosing plate 327 and the case 201 jointly form a part of a connecting passage flowed through by the self-cleaning gas, as will be described in detail below.

[0075] After being discharged from a high-temperature zone of the furnace chamber of the reflow soldering furnace, the waste gas enters the waste-gas cleaning device 200 through the waste gas inlet 211.1, wherein contaminants including rosin in the waste gas pass through the cooling cavity 341 and are condensed by the primary cooling device 310 and the secondary cooling device 320 from a gas into a liquid that then flows into the collecting flask 240.2; the remaining gas flows into the filtering cavity 342 through the opening 431 and is filtered by the filtering component 336 into clean gas in the filtering cavity 342; finally, the clean gas is conveyed through the clean gas outlet 231.2 to a low-temperature zone in the furnace chamber of the reflow soldering furnace.

[0076] Note that the cooling cavity 341 may also be disposed on the left of the filtering cavity 342; however, in this case, the waste gas inlet 211.1 needs to be located in the left part 204 of the case so that it remains in communication with the cooling cavity 341, and the clean gas outlet 231.2 needs to be located in the right part 205 of the case so that it remains in communication with the filtering cavity 342.

[0077] Still as shown in Figure 3, the primary cooling device 310 comprises a plurality of cooling plates 315, and the secondary cooling device 320 comprises a plurality of cooling plates 317. Each of the cooling plates 315, 317 may contain a coolant. The coolants in the cooling plates 315, 317 exchange heat with the waste gas by the peripheral side walls of the cooling plates 315, 317 to lower the temperature of the waste gas. The size of each opening among the plurality of openings 271 of the second front plate 206.2 of the case is configured to match the size of a corresponding cooling plate 315 or 317, so that each cooling plate 315 or 317, after being inserted into the corresponding opening 271, seals the corresponding opening 271. A coolant inlet 355 or 357 and a coolant outlet 365 or 367 are disposed on an end plate of each cooling plate 315 or 317 that is located outside the case 201; through the coolant inlet 355 or 357, a coolant may be added into the corresponding cooling plate 315 or 317; through the coolant outlet 365 or 367, the coolant in the corresponding cooling plate 315 or 317 may be discharged. The coolant inlet 355 or 357 and the coolant outlet 365 or 367 may be sealed.

[0078] In the embodiment shown in Figure 3, the coolant in the plurality of cooling plates 315 in the primary cooling device 310 is compressed gas, and the coolant in the plurality of cooling plates 317 in the secondary cooling device 320 is air. A muffler 208 (see Figure 2A) is disposed at the coolant outlet 365 of the plurality of cooling plates 315 in the primary cooling device 310 to reduce the noise generated when the compressed gas flows. At the coolant inlet 357 of the plurality of cooling plates 317 in the secondary cooling device 320, a screen is further disposed and is connected to a gas pipeline 318 and a drawing fan 319, so that air may be input at a certain speed through the coolant inlet 357 and output through the coolant outlet 367. Certainly, those of ordinary skill in the art may also select another type of coolant, for example, cooling water, based on the actual working environment.

[0079] Figure 4 is a sectional view along the line A- A in Figure 2B, showing the specific structure of the separation plate 437. As shown in Figure 4, the separation plate 437 in the case 201 is connected between the top part 202 and the bottom part 203 of the case 201, for separating the cooling cavity 341 from the filtering cavity 342. The separation plate 437 is provided with an upper opening 432 and a lower opening 431, the upper opening 432 being disposed in a position in the case higher than the filtering component 336 (not shown in Figure 4), the lower opening 431 being disposed in a position in the case lower than the filtering component 336 (not shown in Figure 4). The upper opening 432 is in fluid communication with an air outlet side 584 of a vane wheel 580 of the fan 224 (see Figure 5).

[0080] The enclosing plate 327 has an L-shaped cross section, comprising a horizontal plate 425 and a vertical plate 426 that are interconnected, wherein the horizontal plate 425 is butted against or roughly butted against the rear part 207 of the case 201, and the vertical plate 426 is butted against the top part 202 of the case 201, so that the enclosing plate 327 and the case 201 jointly form a connecting passage 635 (see Figure 6). The connecting passage 635 is aligned with and is in communication with the upper opening 432 of the separation plate 437, so that the gas in the filtering cavity 342 may enter the connecting passage 635 through the upper opening 432 of the separation plate 437. [0081] Thus, the gas in the cooling cavity 341 may flow into the filtering cavity 342 through the lower opening 431, flowing from bottom to top in the filtering cavity 342 to be filtered by the filtering component 336. In addition, a part of the filtered clean gas in the filtering cavity 342 may be conveyed to the reflow soldering furnace through the clean gas outlet 231.2, and the other part of the clean gas flows back to the cooling cavity 341 through the upper opening 432 and the connecting passage 635.

[0082] Figure 5 is a sectional view along the line B-B in Figure 2C, which shows the specific structures of the primary cooling device 310, the secondary cooling device 320, and the filtering component 336, and explains the flow path followed by the gas in the waste-gas cleaning process. As shown in Figure 5, the primary cooling device 310 comprises four cooling plates 315, and the secondary cooling device 320 comprises two cooling plates 317.

[0083] The four cooling plates 315 are arranged laterally (that is, arranged in a left-right direction) along the case 201. Each cooling plate 315 is provided with a cavity 546.1; the cavity 546.1 is in communication with the coolant inlet 355 and the coolant outlet 365 on the case 201, so that compressed gas, as a coolant, may flow into and out of the cavity 546.1 of the cooling plates 315. The two cooling plates 317 are also arranged laterally (that is, arranged in a left-right direction), each cooling plate 317 comprising a cavity 546.2, the cavity 546.2 being in communication with the coolant inlet 357 and the coolant outlet 367 on the case 201, so that air, as a coolant, may flow into and out of the cavity 546.2 of the cooling plates 317. Each of the cooling plates 315, 317 may be made of a heat-conducting material, for example, a metal, so that the gas surrounding the cooling plates 315, 317 may exchange heat with the coolant contained in the cooling plates 315, 317. By regulating the speed at which a coolant flows into or out of the cooling plates 315, 317, the gas in the primary cooling device 310 and the secondary cooling device 320 may be cooled to a temperature in a certain range.

[0084] Each of the cooling plates 315, 317 is vertically arranged (that is, arranged in a direction perpendicular to the top part 202 and the bottom part 203 of the case), and a vertical gas passage 548 is formed between two adjacent cooling plates. Each of the cooling plates 315, 317 is provided with a left side wall and a right side wall; when the waste gas in the cooling cavity 341 flows through the vertical gas passage 548, the waste gas exchanges heat with the coolant in the cavity 546.1 and the cavity 546.2 by the left and right side walls of the cooling plates 315, 317, so that the temperature of the waste gas is lowered. As the temperature of the waste gas is lowered, a part of the contaminants in the waste gas may be condensed into a liquid that flows downward to the bottom part 203 of the case along the left and right side walls of the cooling plates 315, 317. Note that the leftmost cooling plate, in addition to forming a vertical gas passage 548 with the adjacent cooling plate to its right, forms a vertical gas passage 548 with the separation plate 437 to its left. Likewise, the rightmost cooling plate, in addition to forming a vertical gas passage 548 with the adjacent cooling plate to its left, forms a vertical gas passage 548 with the right part 205 of the case.

[0085] In addition, each of the cooling plates 315, 317 further forms a bottom lateral gas passage 549.2 with the bottom part 203 of the case, or forms a top lateral gas passage 549.1 with the top part 202 of the case. Each top lateral gas passage 549.1 and bottom lateral gas passage 549.2 are in communication with at least one vertical gas passage 548 to form a gas passage 550 through which waste gas flows. As an example, the top lateral gas passage 549.1 and bottom lateral gas passage 549.2 are alternately disposed in the direction of the arrangement of the cooling plates 315, 317 to form a winding gas passage 550 shown in Figure 5. The waste gas inlet 211.1 is in communication with the rightmost vertical gas passage 548, and the lower opening 431 of the separation plate is in communication with the leftmost vertical gas passage 548, so that waste gas flows into the gas passage 550 through the rightmost vertical gas passage 548 and flows out of the gas passage 550 through the leftmost vertical gas passage 548. In another embodiment, the top lateral gas passage, the bottom lateral gas passage, and the vertical gas passage may also be arranged in another mode to form another air passage, as long as waste gas can flow in the gas passage and pass through each cooling plate.

[0086] Those of ordinary skill in the art should know that, in the present embodiment, in order to form the winding gas passage 550, each of the cooling plates 315, 317 forms only the bottom lateral gas passage 549.2 or the top lateral gas passage 549.1. When the bottom lateral gas passage 549.2 is formed between the cooling plates 315, 317 and the bottom part 203 of the case, the cooling plates 315, 317 need to be butted against the top part 202 of the case or the gap between them needs to be spanned in another manner, so that a fluid cannot pass between the cooling plates 315, 317 and the top part 202 of the case. Likewise, when the top lateral gas passage 549.2 is formed between the cooling plates and the top part 202 of the case, the cooling plates 315, 317 need to be butted against the bottom part 203 of the case or the gap between them needs to be spanned in another manner, so that a fluid cannot pass between the cooling plates 315, 317 and the bottom part 203 of the case.

[0087] In the embodiment shown in Figure 5, three cooling plates 315, 317 form the top lateral gas passage 549.1 with the top part 202 of the case. A group of sealing plates 554 connected to the bottom part 203 of the case is disposed respectively in the positions in which the three cooling plates 315, 317 are close to the bottom part 203 of the case. Each group of sealing plates 554 comprises two sealing plates 554, which are respectively butted against the left and right sides in the lower parts of the corresponding cooling plates 315, 317 to span the gap between the cooling plates 315, 317 and the bottom part 203 of the case, so that a fluid cannot flow between the cooling plates 315, 317 and the bottom part 203 of the case. By the disposition of the sealing plates 554, even if the bottom part 203 of the case is in a tilted shape as shown in Figure 4, a fluid is prevented from flowing between the cooling plates 315, 317 and the bottom part 203 of the case. Certainly, those of ordinary skill may also, without configuring any sealing plates 554, directly design a shape of a cooling plate so that the cooling plate matches the shape of the bottom part 203 of the case.

[0088] As shown in Figure 5, the thermodetector 213.3 is configured to detect a gas temperature at the gas inlet of the primary cooling device 310, the thermodetector 213.4 is configured to detect a gas temperature at the gas outlet of the primary cooling device 310, the thermodetector 213.5 is configured to detect a gas temperature at the gas outlet of the secondary cooling device 320, and the thermodetector 213.6 is configured to detect a gas temperature in a filtering device. These thermodetectors can detect, in real time, gas temperatures in the waste-gas cleaning device 200, and regulate the flow of a coolant based on detected temperatures. When a detected gas temperature is too high or the effect of regulating the coolant flow on gas temperature is not significant, the waste-gas cleaning device 200 may need to be self-cleaned.

[0089] The filtering component 336 is disposed in the middle of the filtering cavity 342, dividing the filtering cavity 342 into an upper sub-cavity and a lower sub-cavity, wherein the lower sub-cavity is in communication with the lower opening 431 of the separation plate, and the vane wheel 580 of the fan 224 is disposed in the upper sub-cavity, so that the air inlet side 582 of the vane wheel 580 of the fan 224 is in fluid communication with the upper sub-cavity. The air outlet side 580 of the vane wheel 584 of the fan 224 is in fluid communication with the clean gas outlet 231.2 and the upper opening 432 of the separation plate. When the vane wheel 580 rotates, the gas is caused to flow in the cooling cavity 341 and the filtering cavity 342 in a direction indicated by the arrows shown in Figure 5. As an example, the filtering component 336 is a steel ball screen, which, on the one hand, facilitates heat conduction and, on the other hand, can be cleaned for reuse, reducing costs.

[0090] Note that when the cooling cavity maintains a certain size, the lateral width of the cooling plate 315 of the primary cooling device 310, on the condition that a sufficient amount of coolant is contained, should be as small as possible, so that only a small amount of the rosin condensed into a liquid when waste gas flows through the primary cooling device 310 accumulates in the top part of the cooling plate 315. Therefore, the primary cooling device 310 comprises the cooling plates 315 that have a smaller lateral width but are present in a larger number, while the secondary cooling device 320 comprises the cooling plates 317 that have a larger lateral width but are present in a smaller number. In the embodiment shown in Figure 5, the lateral width of a cooling plate 315 of the primary cooling device 310 is one-third of the lateral width of a cooling plate 317 of the secondary cooling device 320. In another embodiment, another number of cooling plates 315, 317 may also be configured, and the lateral widths of the cooling plates 315 and 317 may also be in another proportion, as long as the coolant contained in the cooling plates 315, 317 suffices to cool waste gas to a required temperature.

[0091] Figure 6 is a three-dimensional structural diagram for a cooling device in the waste-gas cleaning device 200 shown in Figure 5, which shows the specific structures of and position relationships among the cooling plates, the separation plate 437, and the enclosing plate 327 to explain the flow path followed in the self-cleaning gas cycle. In order to show the internal structure of the cooling plates 315, 317, the end plates of the cooling plates 315, 317 (that is, the end plates provided with a coolant inlet and outlet as shown in Figure 3) are omitted in Figure 6. As shown in Figure 6, the separation plate 437, the cooling plate 544, and the cooling plate 543 in the waste- gas cleaning device 200 are vertically arranged roughly parallel to one another, and are spaced apart from one another to form the above-described gas passage 550.

[0092] The enclosing plate 327 is disposed at the back and above the cooling plate 544 and the cooling plate 543, and extends in a left-right direction. As an example of a disposition mode, a stepped support portion is disposed at the rear of the top of a part of cooling plates, for example, the part of the cooling plates that forms the bottom lateral gas passage 549.2 with the bottom part 203 of the case. The stepped support portion is configured to accommodate the L-shaped enclosing plate 327. This disposition mode allows the waste-gas cleaning device 200 to have a more compact structure. Those of ordinary skill in the art should know that, the enclosing plate 327 may not be L-shaped or a support portion may not be disposed on a cooling plate, as long as the cooling plates, the enclosing plate 327, and the case can be sealed as required to form the gas passage 550.

[0093] By the above-described disposition, the enclosing plate 327 can form the connecting passage 635 with the case 201, and a self-cleaning gas outlet 634 and a self-cleaning gas inlet 614 are provided at both ends of the connecting passage 635, wherein the self-cleaning gas outlet 634 is in communication with the upper opening 432 of the separation plate 437, and the self-cleaning gas inlet 614 is in fluid communication with the cooling cavity 341 at the primary cooling device 310. As an example, the self-cleaning gas inlet 614 is located near the waste gas inlet 211.1.

[0094] As an example, the upper opening 432 of the separation plate 437 has an adjustable size, so that the gas in the filtering cavity 342 can controllably flow into the connecting passage 635. In an embodiment of the present application, an adjustable baffle plate 638 is movably connected to the separation plate 437; the adjustable baffle plate 638 is movable forward and backward to cover the upper opening 432 or open the upper opening 432, or adjust the size of opening of the upper opening 432. The adjustable baffle plate 638 is provided with a guide groove 661 and the separation plate 437 is provided with a guide pin 662 inserted into the guide groove 661, so that the adjustable baffle plate 638 and the separation plate 437 are movably connected.

[0095] Thus, when the waste-gas cleaning device 200 is in a maintenance state, the gas in the filtering cavity 342 may flow into the connecting passage 635 through the upper opening 432 and flow to the primary cooling device 310 through the connecting passage 635.

[0096] Still as shown in Figure 6, the cavity 546.1 in the cooling plate 315 comprises a flow equalization plate 656.1; likewise, the cavity 546.2 in the cooling plate 317 comprises a flow equalization plate 656.2, a plurality of through holes being disposed in each flow equalization plate. As an example, a plurality of round holes 658.1 are evenly disposed in the flow equalization plate 656.1, and a plurality of strip holes 658.2 are disposed in the flow equalization plate 656.2. The flow equalization plates 656.1 and 656.2 are respectively disposed on the flow paths followed by the coolants in the cavities 546.1 and 546.2 so that the coolants may pass through the through holes and flow evenly and stably. For the cooling plates 317, air flows into the cavity 546.2 of the cooling plate through the coolant inlet 357, passes through the flow equalization plate 656.2 from bottom to top, then flows out through the coolant outlet 367, and exchanges heat with waste gas by the side walls of the cooling plates 317. For the cooling plates 315, compressed air flows into the cavity 546.1 of the cooling plate 315 through the coolant inlet 355, passes through the flow equalization plate 656.1 from bottom to top, then flows out through the coolant outlet 365, and exchanges heat with waste gas by the side walls of the cooling plates 315.

[0097] The process of cleaning waste gas in the waste-gas cleaning device 200 is roughly as follows: waste gas (having a temperature of about 170°C) containing contaminants, after being discharged from a high-temperature zone of the furnace chamber of the reflow soldering furnace, enters the gas passage 550 through the waste gas inlet 211.1. When the waste gas flows through the cooling plate 315 in the primary cooling device 310, the amounts of compressed gas flowing into and out of the cooling plate 315 are adjusted so that the waste gas is cooled to a temperature of about 110°C to 130°C (gas temperature at the outlet of the primary cooling device 310, detected by a thermodetector 213.4); at such a temperature, the organic substances including rosin and other fluxing agents in the waste gas are condensed from a gaseous form into a liquid form and may be discharged to the collecting flask 240.2. The remaining part of the waste gas flows through the cooling plate 317 in the secondary cooling device 320; the amounts of air flowing into and out of the cooling plate 317 are adjusted so that the remaining part of the waste gas is cooled to a temperature of about 60°C to 80°C (gas temperature at the outlet of the secondary cooling device 320, detected by a thermodetector 213.5); at such a temperature, other contaminant organic substances, for example, low-freezing acidic or ester or ether organic substances, in the waste gas are condensed from a gaseous form into a liquid form and may be discharged to the collecting flask 240.2. The remaining part of the waste gas flows into the filtering cavity 342 through the lower opening 431 of the separation plate 437, then flows through the filtering component 336 from bottom to top, and is filtered by the filtering component 336 to remove granular and pulverized organic substances from the waste gas, and clean gas is obtained. Finally, most of the clean gas is released through the clean gas outlet 231.2 to a low-temperature zone in the furnace chamber of the reflow soldering furnace, and the process of waste-gas cleaning is completed; a small part of the clean gas may, through the upper opening 432 and the connecting passage 635, flow back into the primary cooling device 310 and be mixed with waste gas to lower the temperature of the waste gas. By adjusting the size of opening of the lower opening 431, the amount of clean gas that flows back into the primary cooling device 310 through the upper opening 432 and the connecting passage 635 may be changed. Certainly, the lower opening 431 may also be completely closed to prevent clean gas from flowing back into the primary cooling device 310 through the upper opening 432 and the connecting passage 635.

[0098] The process of self-cleaning by the waste-gas cleaning device 200 is as follows: the waste gas inlet 211.1 and the clean gas outlet 231.2 are closed by the valve components 217.1 and 217.2; the gas in the filtering cavity 342 is heated by a heater 222 until the temperature in the filtering cavity 342 has risen to a range of about l50°C to l70°C (as detected by a thermodetector 213.6), so that a part of the solid contaminants on the filtering component 336 is converted into a liquid form and another part is converted into a gaseous form, wherein the contaminants in a liquid form flow to the bottom part 203 of the case. Under the action of the fan 224, high-temperature gaseous contaminants, from bottom to top, flow to the upper opening 432 of the separation plate, flow through the connecting passage 635, and then are conveyed back to the primary cooling device 310 and the secondary cooling device 320, heating again the contaminants adhering to an inner wall of the case, an outer wall of the cooling device, the enclosing plate 327, the filtering component 336, and the surfaces of other components in the waste-gas cleaning device 200 into a liquid, thereby cleaning the waste gas, wherein the liquid contaminants in the bottom part 203 of the case are collected by the collecting devices 240.1 and 240.2.

[0099] After completion of the self-cleaning process, a working gas, for example, nitrogen, is replenished to the waste-gas cleaning device 200 through the gas replenishing hole 212, and the gas in the waste-gas cleaning device 200 is released through the air vent 232. When a detected oxygen concentration in the waste-gas cleaning device 200 meets the requirement, communication is established between the waste-gas cleaning device 200 and the furnace chamber of the reflow soldering furnace.

[00100] Figures 7A to 11 show the structure of a waste-gas cleaning device 700 according to another embodiment of the present application, in which the waste-gas cleaning device 700 and the waste-gas cleaning device 200 differ mainly in that the specific structures of the cooling devices are different.

[00101] Figures 7A to 7C are general structural diagrams for the waste-gas cleaning device 700, in which Figure 7A is a three-dimensional structural diagram for the waste-gas cleaning device 700, Figure 7B is a front view of Figure 7A, and Figure 7C is a top view of Figure 7A. As shown in Figures 7A to 7C, the waste-gas cleaning device 700 comprises a case 701; the case 701 has a structure that is similar to the case 201 of the waste-gas cleaning device 200, comprising a top part 702, a bottom part 703, a left part 704, a right part 705, a front part 706, and a rear part 707, which will not be described again.

[00102] The clean gas outlet 731.2 of the waste-gas cleaning device 700 is disposed on the left of the rear part 707 of the case 701. Different from the waste gas inlet 211.1 of the waste-gas cleaning device 200, the waste gas inlet 711.1 of the waste-gas cleaning device 700 is disposed on the rear part 707 of the case 701, and the waste gas inlet 711.1 is disposed on the right of the rear part 707 of the case 701. Accordingly, the gas replenishing hole 712 is also disposed in the back of the top part 702 of the case 701 and near the waste gas inlet 711.1, while the positions of the air vent 732 and the oxygen concentration measuring device 955 (see Figure 9) remain unchanged.

[00103] The front part 706 of the case 701 comprises a first front plate 706.1 and a second front plate 706.2, wherein the second front plate 706.2 is also provided with a plurality of openings 771 for inserting a cooling device into the second cooling cavity 862. The waste-gas cleaning device

700 further comprises collecting flasks 740.1 and 740.2 that are connected to the bottom part 703 of the case and a fan 724 that is connected to the top part 702 of the case.

[00104] Figure 8 is an exploded view of the waste-gas cleaning device 700, which shows the cooling cavity 841 and the filtering cavity 842 in the waste-gas cleaning device 700 to explain the flow path followed by the gas in the waste-gas cleaning device 700. As shown in Figure 8, the case

701 internally comprises a separation plate 937 (the separation plate 937 has a structure that is the same as the separation plate 437; for details, see Figure 9); the separation plate 937 separates the interior of the case 701 into the cooling cavity 841 and the filtering cavity 842, and the cooling cavity 841 and the filtering cavity 842 are in communication with each other by the lower opening 931 (see Figure 9) of the separation plate 937. The cooling cavity 841 comprises a first cooling cavity 861 and the second cooling cavity 862; a primary cooling device 810 is disposed in the first cooling cavity 861; a secondary cooling device 820 is disposed in the second cooling cavity 862; after entering the cooling cavity 841 through the waste gas inlet 711.1, the gas flows through the primary cooling device 810 and the secondary cooling device 820 in turn from right to left. The filtering cavity 842 comprises a filtering component 836; after entering the filtering cavity 842, the gas flows through the filtering component 836 from bottom to top and may flow out of the filtering cavity 842 through the clean gas outlet 731.2. The secondary cooling device 820 has a structure that is the same as that of the secondary cooling device 320 in the waste-gas cleaning device 200, and so no similar descriptions will be provided again. An L-shaped enclosing plate 827 is disposed at the back of the upper part of the secondary cooling device 820; different from the enclosing plate 327 in the waste-gas cleaning device 200 shown in Figures 2A to 6, the enclosing plate 827 is disposed only at the secondary cooling device 820.

[00105] Still as shown in Figure 8, the primary cooling device 810 comprises cooling blades 863 and cooling tubes 865; each cooling tube 865 may contain a coolant, and a coolant in a cooling tube 865 exchanges heat with waste gas by a cooling blade 863. The secondary cooling device 820 comprises a plurality of cooling plates 817, the cooling plates 817 having sizes that match the openings 771 on the second front plate 706.2. It can be seen from the front part of the case that coolant inlets 855 and coolant outlets 815 are disposed on the primary cooling device 810, and coolant inlets 857 and coolant outlets 816 are disposed on the secondary cooling device 820. Note that two groups of coolant inlets 855 and coolant outlets 815 are not arranged side by side; one group of coolant inlets 855 and coolant outlets 815 are at a shorter distance from each other, while the other group of coolant inlets 855 and coolant outlets 815 are at a larger distance from each other (see Figure 7B). In the embodiment shown in Figure 8, the coolant in the cooling tubes 865 in the primary cooling device 810 is compressed gas, and the coolant in the plurality of cooling plates 817 in the secondary cooling device 820 is air. A muffler 708 is also disposed at each coolant outlet 815 of the primary cooling device 810.

[00106] Figure 9 is a sectional view along the line A- A in Figure 7B, showing the specific structure of the separation plate 937. The separation plate 937, structurally similar to the separation plate 437 in the waste-gas cleaning device 200 shown in Figures 2A to 6, is also provided with an upper opening 932 and a lower opening 931. In addition, the enclosing plate 827 comprises a horizontal plate 925 and a vertical plate 926, and they form a connecting passage 1135 with the case 701 (see Figure 11), wherein the upper opening 932 is also in fluid communication with an air outlet side 1084 of a vane wheel 1080 of the fan 724 (see Figure 10).

[00107] Figures 10A and 10B show the specific structures of the primary cooling device 810, the secondary cooling device 820, and the filtering component 836 to explain the flow path followed by the gas in the waste-gas cleaning process. Figure 10A is a sectional view along the line B-B in Figure 7C, and Figure 10B is a sectional view along the line C-C in Figure 10A; in addition, in order to show more clearly the specific structure of the primary cooling device 810, only the primary cooling device 810 is shown and other components are omitted in Figure 10B. [00108] As shown in Figures 10A and 10B, the primary cooling device 810 comprises four layers of cooling blades 863 and four layers of cooling tubes 865, the four layers of cooling tubes 865 containing coolants, wherein the cooling tubes 865 and the cooling blades 863 are interconnected to exchange heat with waste gas by the cooling blades 863, thereby lowering the temperature of the waste gas.

[00109] The four layers of cooling blades 863 are arranged longitudinally (that is, arranged in an up-down direction), each layer of cooling blades 863 being laterally arranged (that is, arranged in a left-right direction), there being a certain distance between two adjacent layers of cooling blades 863. A cooling tube 865 is provided with a cavity 1046.1. A cooling blade 863 is made of a heat-conducting material, for example, a metal, so that the waste gas in the first cooling cavity 861 may transfer heat by the cooling blade 863 to exchange heat with a coolant in the cavity 1046.1 of the cooling tube 865.

[00110] Each layer of cooling blades 863 is roughly U-shaped and is provided with a through groove 1064 and a side groove 1072 (reference may also be made to Figure 11), wherein the through groove 1064 is disposed in the bottom part 1066 of the cooling blade 863 and extends in a left-right direction. Waste gas passes through the through groove 1064 in the bottom part of the cooling blade 863, forming a longitudinal gas flow 1068 from top to bottom. Note that since the waste gas inlet 711.1 is disposed at the back of the case, waste gas, in addition to flowing from top to bottom, also flows from rear to front. The side groove 1072 is disposed on the two side walls 1067 of the cooling blade 863, and both ends of the through groove 1064 are in communication with a pair of side grooves 1072, respectively. The cooling tube 865 passes through a pair of side grooves 1072 to support the cooling blade 863, so that the cooling blade 863 is detachably connected to the cooling tube 865.

[00111] A plurality of through grooves 1064 are disposed on each layer of cooling blades 863, and the through grooves 1064 in at least a part of two adjacent layers of cooling blades 863 are alternately arranged, so that waste gas, instead of straightly passing through each layer of cooling blades 863 from top to bottom, passes through each layer of the cooling blades by following a winding path, thereby better exchanging heat with the cooling tubes 865 and the cooling blades 863. In the example shown in Figures 10A and 10B, the through grooves 1064 of a first layer and second layer of cooling blades 863 are alternately arranged, and the through grooves 1064 of a third layer and fourth layer of cooling blades 863 are alternately arranged. [00112] The cooling tubes 865 and side grooves 1072 are arranged in numbers that correspond to the plurality of through grooves 1064. In addition, each layer of cooling tubes 865 are in communication with the coolant inlet 855 and the coolant outlet 815 on the case 701 so that compressed gas, as a coolant, may flow into the cooling tubes 865 and then flow out of the cooling tubes 865. As an example, each layer of cooling tubes 865 converge through an input main pipe 1081 and/or an output main pipe 1085 (reference may also be made to Figure 11), and then connect the input main pipe 1081 and the output main pipe 1085 to the coolant inlet 855 and the coolant outlet 815 on the case 701. The input main pipe 1081 and the output main pipe 1085 are pipes that extend in a front-rear direction, with one end sealed and the other end connected to the coolant inlet 855 or the coolant outlet 815.

[00113] As an example, a first layer and a fourth layer of corresponding cooling tubes are connected to form U-shaped cooling tubes that open on the right, in which the openings of the first layer of the U-shaped cooling tubes are connected to the output main pipe 1085, and the openings of the fourth layer of the U-shaped cooling tubes are connected to the input main pipe 1081. Similarly, a second layer and a third layer of cooling tubes are connected to form U-shaped cooling tubes that open on the left, in which the openings of the second layer of the U-shaped cooling tubes are connected to the output main pipe 1085, and the openings of the third layer of the U-shaped cooling tubes are connected to the input main pipe 1081. Thus, only two groups of coolant inlets 855 and coolant outlets 815 need to be disposed on the case 701. In another embodiment, a separate input main pipe and output main pipe may also be disposed at either end of each layer of cooling tubes for connection to the case 701; in this case, four groups of coolant inlets and coolant outlets need to be disposed on the case.

[00114] In the example of the present application shown in the figures, the first layer and fourth layer of cooling tubes 865 include six cooling tubes, and the second layer and third layer include five cooling tubes.

[00115] Thus, by the cooling blades 863, the area of heat exchange between the cooling tubes 865 and the longitudinal gas flow 1068 may be expanded, so that the temperature of the longitudinal gas flow 1068 formed by the waste gas is lowered, and a part of the contaminants in the waste gas may be condensed into a liquid that flows through the through grooves 1064, from top to bottom, to the bottom part 703 of the case. [00116] The secondary cooling device 820 comprises two cooling plates 817, each cooling plate 817 having a structure the same as the cooling plate 317 shown in Figure 5 to form a vertical gas passage 1048. The cooling plate 817 is provided with a cavity 1046.2 for containing a coolant (for example, air), the cavity 1046.2 being in communication with an air inlet 716.1 and an air outlet

716.2 disposed on the case 701, so that air, as a coolant, may flow into and out of the cooling plate 817. A bottom lateral gas passage 1049.2 is formed between the cooling plate 817 on the right and the bottom part 703 of the case, and a top lateral gas passage 1049.1 is formed between the cooling plate 817 on the left and the top part 702 of the case. The top lateral gas passage 1049.1 and the bottom lateral gas passage 1049.2 are in fluid communication with the vertical gas passage 1048 to form a winding gas cooling passage 1050. In addition, the bottom lateral gas passage 1049.2 is in fluid communication with the primary cooling device 810, so that the longitudinal gas flow 1068 in the first cooling cavity 861, from top to bottom, flows through the primary cooling device 810 and then enters the gas cooling passage 1050.

[00117] As shown in Figure 10A, likewise, the filtering component 836 is disposed in the middle of the filtering cavity 842, dividing the filtering cavity 842 into an upper sub-cavity and a lower sub-cavity, wherein the lower sub-cavity is in communication with the lower opening 931 of the separation plate, and the upper sub-cavity is in communication with the clean gas outlet

731.2 and the upper opening 932 of the separation plate. The vane wheel 1080 of the fan 724 is disposed in the upper sub-cavity so that the air inlet side 1082 of the vane wheel 1080 of the fan 724 is in fluid communication with the upper sub-cavity. The air outlet side 1080 of the vane wheel 1084 of the fan 724 is in fluid communication with the clean gas outlet 731.2 and the upper opening 932 of the separation plate. When the vane wheel 1080 rotates, the gas is caused to flow in the cooling cavity 841 and the filtering cavity 842 in a direction indicated by the arrows shown in Figure 10A. As an example, the filtering component 836 is also a steel ball screen.

[00118] Note that the primary cooling device 810 in the present embodiment may also be any finned heat exchanger finished product known to those of ordinary skill in the art, so that costs are reduced.

[00119] Figure 11 is a three-dimensional structural diagram for a cooling device in the waste- gas cleaning device 700, showing the specific structures of and position relationships among the primary cooling device 810, the secondary cooling device 820, the separation plate 937, and the enclosing plate 827. Similar to the waste-gas cleaning device 200, a stepped card slot for accommodating the enclosing plate 827 is disposed at the back of the top part of the cooling plate 817 on the right of the secondary cooling device 820. The enclosing plate 827 may form a connecting passage 1135 with the case 701, the connecting passage 1135 being provided with a self-cleaning gas outlet 1134 and a self-cleaning gas inlet 1114, wherein the self-cleaning gas outlet 1134 is in communication with the upper opening 932 of the separation plate 937, and the self-cleaning gas inlet 1114 is in communication with the waste gas inlet 711.1. In the present embodiment, the position of the waste gas inlet 711.1 is close to the secondary cooling device 820, and the enclosing plate 827 only needs to be disposed at the back of the secondary cooling device 820 so that the self-cleaning gas inlet 1114 of the connecting passage 1135 is in communication with the waste gas inlet 711.1.

[00120] Likewise, an adjusting baffle plate 1138 is further connected to the separation plate 937 to adjust the size of opening of the upper opening 932. Such a disposition allows a part of the gas in the upper sub-cavity of the filtering cavity 342 to be released through the clean gas outlet 731.2 to the reflow soldering furnace and another part of the gas to flow, through the upper opening 932, into the connecting passage 1135 and flow to the vicinity of the waste gas inlet 711.1 through the connecting passage 1135.

[00121] The cavity 1046.2 in the cooling plate 817 comprises flow equalization plates 1156, a plurality of strip holes 1158 being disposed on each equalization plate.

[00122] The process of cleaning waste gas in the waste-gas cleaning device 700 is roughly as follows: waste gas (having a temperature of about 170°C) containing contaminants, after being discharged from a high-temperature zone of the furnace chamber of the reflow soldering furnace, enters the first cooling cavity 861 through the waste gas inlet 711.1. The waste gas first flows through the primary cooling device 810 from top to bottom and from rear to front; by adjusting the speeds of the compressed gas flowing into and out of the cooling tubes 865, the waste gas is cooled until the gas temperature at the outlet is in the range of about 110°C to 130°C. At such a temperature, organic substances, including rosin, in the waste gas are condensed from a gaseous form into a liquid form and flow, from top to bottom, through the through grooves 1064 to the bottom part 703 of the case. The remaining part of the waste gas flows, from right to left, through the cooling plate 817 in the secondary cooling device 820, and the speeds of air flowing into and out of the cooling plate 817 are adjusted so that the remaining part of the waste gas is cooled until the gas temperature at the outlet is in the range of about 60°C to 80°C; at such a temperature, other contaminant organic substances, for example, low-freezing acidic or ester or ether organic substances, in the waste gas are condensed from a gaseous form into a liquid form and flow to the bottom part 703 of the case along the side walls of the cooling plates 817. The remaining part of the waste gas flows into the filtering cavity 842 through the lower opening 931 of the separation plate 937, then flows through the filtering component 836 from bottom to top, and is filtered by the filtering component 836 to remove granular and pulverized organic substances from the waste gas, and clean gas is obtained. Finally, most of the clean gas is released through the clean gas outlet 731.2 to a low-temperature zone in the furnace chamber of the reflow soldering furnace, and the process of waste-gas cleaning is completed; a small part of the remaining clean gas may, through the upper opening 932 and the connecting passage 1135, flow back into the primary cooling device 810 and be mixed with waste gas to lower the temperature of the waste gas. By adjusting the size of opening of the lower opening 932, the amount of clean gas that flows back into the primary cooling device 810 through the upper opening 932 and the connecting passage 1135 may be changed. Certainly, the lower opening 932 may also be completely closed to prevent clean gas from flowing back into the primary cooling device 810 through the upper opening 932 and the connecting passage 1135. The liquid contaminants in the bottom part 703 of the case are collected by the collecting device 740.2.

[00123] The self-cleaning process of the waste-gas cleaning device 700 is similar to that of the waste-gas cleaning device 200, and so will not be described again.

[00124] In the two embodiments of the present application, the waste-gas cleaning device 200 and the waste-gas cleaning device 700 differ mainly in that their primary cooling devices are different. A cooling plate 315 in the primary cooling device 310 of the waste-gas cleaning device 200 has a smaller lateral area, which allows fewer contaminants to accumulate on the heat exchanging component (the cooling plate 315), thus providing a longer maintenance cycle. In contrast, the primary cooling device 810 of the waste-gas cleaning device 700 is a commercially available finished product, and thus costs are lowered.

[00125] While the present application has been described above with reference to the specific embodiments shown in the drawings, it should be understood that, without departing from the spirit, scope, or background taught by the present application, many variations may be made to a waste-gas cleaning system and waste-gas cleaning device of the present application. Those of ordinary skill in the art will also realize that the dispositions of the embodiments disclosed in the present application may be altered in different modes and that all such alterations fall into the spirit and scope of the present application and claims.

Claims

CLAIMS What is claimed is:

1. A waste-gas cleaning system, for cleaning off contaminants in the waste gas in a furnace chamber (118) in a reflow soldering furnace, characterized by comprising:

a primary cooling unit (110), said primary cooling unit (110) being provided with a waste gas inlet (111.1) and a gas outlet (111.2), said primary cooling unit (110) being configured to cool, to a first temperature, the waste gas that has entered said primary cooling unit (110) through said waste gas inlet (111.1), so that a part of the contaminants in the waste gas that has entered said primary cooling unit (110) is cooled from a gaseous form into a liquid form and then discharged from said primary cooling unit (110), while a part of the remaining part of the contaminants in the waste gas that has entered said primary cooling unit (110) remains in a gaseous form;

a secondary cooling unit (120), said second cooling unit (120) being provided with a gas inlet (121.1) and a gas outlet (121.2), a gas inlet (121.1) of said secondary cooling unit (120) being in fluid communication with a gas outlet (111.2) of said primary cooling unit (110), said secondary cooling unit (120) being configured to cool, from said first temperature to a second temperature, the waste gas that has entered said secondary cooling unit (120) through said primary cooling unit (110), so that a part of the contaminants in the waste gas that has entered said secondary cooling unit (120) is cooled from a gaseous form into a liquid form and then discharged from said secondary cooling unit (120), while a part of the remaining part of the contaminants in the waste gas that has entered said secondary cooling unit (120) remains in a gaseous form or pulverized form; and

a filtering unit (130), said filtering unit (130) being provided with a gas inlet (131.1) and a clean gas outlet (131.2), a gas inlet (131.1) of said filtering unit (130) being in fluid

communication with a gas outlet (121.2) of said secondary cooling unit (120), said filtering unit (130) being configured to filter the waste gas that has entered said filtering unit (130) and discharge at least one part of the filtered gas through a clean gas outlet (131.2) of said filtering unit (130).

2. The waste-gas cleaning system as claimed in claim 1, characterized by further comprising:

a collecting unit (140), said primary cooling unit (110) and said secondary cooling unit (120) being provided with a waste liquid outlet (141.1, 141.2), respectively, said collecting unit (140) being controllably in fluid communication with the waste liquid outlets (141.1, 141.2) of said primary cooling unit (110) and said secondary cooling unit (120), for collecting the discharged liquid waste gas.

3. The waste-gas cleaning system as claimed in claim 1, characterized in that

at said first temperature, waste gas is cooled from a gaseous form into liquid

contaminants, including rosin organic substances; and

at said second temperature, contaminants in waste gas that are cooled from a gaseous form into a liquid form include other low-freezing acidic or ester or ether organic substances.

4. The waste-gas cleaning system as claimed in claim 3, characterized in that

said first temperature is in the range of 1 l0°C to l30°C; and

said second temperature is in the range of 60°C to 80°C.

5. The waste-gas cleaning system as claimed in claim 1, characterized in that

a waste gas inlet (111.1) of said primary cooling unit (110) is configured to be controllably in fluid communication with the furnace chamber (118) of said reflow soldering furnace.

6. A self-cleaning waste-gas cleaning system, characterized by comprising:

a cooling unit (110, 120), said cooling unit (110, 120) being provided with a self-cleaning gas inlet (114) and a gas outlet (121.2);

a filtering unit (130), said filtering unit (130) being provided with a gas inlet (131.1) and a self-cleaning gas outlet (134);

a heating component (133), said heating component (133) being disposed in said filtering unit (130), for increasing a gas temperature in said filtering unit (130); a first passage (125.2), said first passage (125.2) being connected to the gas outlet (121.2) of said cooling unit (110, 120) and the gas inlet (131.1) of said filtering unit (130), said first passage (125.2) being configured to convey the gas in said cooling unit (110, 120) to said filtering unit (130); and

a second passage (135), said second passage (135) being connected to the self-cleaning gas outlet (134) of said filtering unit (130) and the self-cleaning gas inlet (114) of said cooling unit (110, 120), said second passage (135) being configured to controllably convey the gas in said filtering unit (130) to said cooling unit (110, 120),

wherein a self-cleaning gas cycle is created among said cooling unit (110, 120), said first passage (125.2), said filtering unit (130), and said second passage (135).

7. The waste-gas cleaning system as claimed in claim 6, characterized by further comprising:

a fluidic power device (124), said fluidic power device (124) being configured to cause a gas to be cycled in said filtering unit (130) and said cooling unit (110, 120) through said first passage (125.2) and said second passage (135).

8. The waste-gas cleaning system as claimed in claim 6, characterized in that

said cooling unit (110, 120) comprises a waste gas inlet (111.1), said waste gas inlet (111.1) being configured to be controllably in communication with the furnace chamber (118) of the reflow soldering furnace; and

said filtering unit (130) comprises a clean gas outlet (131.2), said clean gas outlet (131.2) being configured to controllably discharge the gas in said filtering unit (130).

9. The waste-gas cleaning system as claimed in claim 6, characterized by further comprising:

a collecting unit (140), said cooling unit (110, 120) and said filtering unit (130) being provided with a waste liquid outlet (141.1, 141.2, 141.3), respectively, said collecting unit (140) being controllably in fluid communication with the waste liquid outlets (141.1, 141.2) of said cooling unit (110) and said filtering unit (130), for collecting the discharged liquid waste gas.

10. The waste-gas cleaning system as claimed in claim 6, characterized in that said cooling unit (110, 120) is further provided with a gas replenishing hole (112), said gas replenishing hole (112) being configured to be controllably in fluid communication with a protection gas, so that the protection gas enters said waste-gas cleaning system (100); and said filtering unit (130) is provided with an air vent (132), said air vent (132) being configured to discharge the gas in said waste-gas cleaning system (100).