TWI697953B - Cleaning method - Google Patents

Abstract

A cleaning method includes providing a substrate on which an IC or some ICs are soldered; providing an atmospheric environment plasma generating apparatus; introducing a gas into the atmospheric environment plasma generating apparatus, and activating the gas to form a plasma by using the atmospheric environment plasma generating apparatus, wherein the atmospheric environment plasma generating apparatus sputters the plasma with a wind speed ranging from about 100 to about 300 m/s; and cleaning a surface of the substrate by using the sputtering plasma.

Description

Cleaning method

The embodiment of the present invention relates to a cleaning method, in particular, a method of using atmospheric plasma to clean pollutants on a circuit substrate on which an IC has been soldered.

Plasma is a form of matter mainly composed of charged ions and free electrons. In addition to solid, liquid and gaseous states, plasma is often regarded as the fourth state of matter. Utilizing the properties of plasma can trigger many special chemical and physical reactions, and has been widely used in various fields, such as dry etching in semiconductor manufacturing, cleaning of circuit boards, and changes in surface properties of materials.

In the traditional printed circuit board manufacturing process, a large number of wet etching processes are used to clean contaminants in the production process or on the workpiece. The wet etching process uses a lot of water and solvents, which is not only unfriendly to the environment, but also wastes water resources. Therefore, the dry etching process is becoming more widely used. In the traditional dry etching process, the organic pollutants are cleaned by oxygen or oxidizing gas, and the inorganic pollutants are special gases (such as SF ₆ , Cl ₂ or the like). However, special gases are expensive, have safety concerns, and are not friendly to the environment. Therefore, the development of a new cleaning method is an urgent problem to be solved.

One aspect of the present invention is a cleaning method that includes providing a circuit substrate with ICs soldered on; providing an atmospheric plasma generating device; introducing gas into the atmospheric plasma generating device, and using the atmospheric plasma generating device to activate the gas to form electricity And let the atmospheric plasma generator spray the plasma at a wind speed of about 100 to about 300 meters per second (m/s); and use the sprayed plasma to clean the surface of the circuit board on which the IC has been soldered.

According to some embodiments of the present invention, introducing the gas into the atmospheric plasma generating device includes providing about 20 to about 40 standard liters per minute (SLM) of the gas into the atmospheric plasma generating device.

According to some embodiments of the present invention, wherein using an atmospheric plasma generator to activate the gas to form a plasma includes forming a plasma having a plasma potential of about 60 to about 80 volts (V).

According to some embodiments of the present invention, the use of sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes contacting the plasma with the surface of the circuit substrate on which the IC has been soldered, and the atmospheric plasma generating device uses about 50 to about The scanning line speed of 200 millimeters per second (mm/s) scans and moves over the surface of the workpiece.

According to some embodiments of the present invention, using atmospheric plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using plasma to clean the surface of the circuit substrate on which the IC has been soldered about 10 to about 50 times.

According to some embodiments of the present invention, wherein using an atmospheric plasma generating device to activate the gas to form plasma includes providing about 500 to about 700 watts of radio frequency power to the atmospheric plasma generating device to activate the gas.

According to some embodiments of the present invention, wherein using an atmospheric plasma generator to activate the gas to form plasma includes providing about 500 to about 700 watts of multi-frequency power to the atmospheric plasma generator to activate the gas.

According to some embodiments of the present invention, in the step of using sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered, there is a first working distance between the atmospheric plasma generator and the circuit substrate on which the IC has been soldered, And the first working distance is about 5 to about 8 millimeters (mm).

According to some embodiments of the present invention, the gas is air, oxygen, nitrogen, carbon dioxide, argon, helium, or a combination thereof.

According to some embodiments of the present invention, using the sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the sprayed plasma to remove at least one organic pollutant on the surface.

According to some embodiments of the present invention, using the sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the sprayed plasma to remove at least one metal salt contaminant on the surface.

According to some embodiments of the present invention, the use of sprayed plasma to remove the metal salt pollutants on the surface includes using the sprayed plasma to oxidize the metal salt pollutants into metal oxides; and after the high-speed plasma gas flow impacts the surface The resulting lateral airflow removes metal oxides.

According to some embodiments of the present invention, using the sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the sprayed plasma to remove at least one inorganic contaminant on the surface.

10‧‧‧Gas

20‧‧‧Exhausted gas

100‧‧‧System

110‧‧‧Atmospheric Plasma Generator

120‧‧‧Atmospheric Plasma Generator Controller

130‧‧‧Working table

140‧‧‧Exhaust port

150‧‧‧Wire

160‧‧‧Inlet pipe

170‧‧‧Ground wire

180‧‧‧Plasma

190‧‧‧Side airflow

210‧‧‧PCB with IC soldered on

212‧‧‧surface

215A‧‧‧Inorganic pollutants

215B‧‧‧Etching contaminants

220‧‧‧Pollutant

220’‧‧‧ oxide

300‧‧‧area

H‧‧‧First working distance

The aspect of the disclosure will be better understood when reading the following detailed description in conjunction with the accompanying drawings. But it should be noted that in accordance with the standard practice of this industry, various features are not drawn to scale. In fact, the size of various features can be arbitrarily enlarged or reduced for clear discussion.

FIG. 1 is a schematic diagram of a system using a plasma cleaning method according to some embodiments of the present invention.

2A to 2C are partial enlarged schematic diagrams of the area 300 in FIG. 1 according to some embodiments of the present invention.

3A to 3C are partial enlarged schematic diagrams of the area 300 in FIG. 1 according to some embodiments of the present invention.

This disclosure will provide many different implementations or examples to implement different features of this disclosure. The composition and configuration of each specific embodiment will be described below to simplify the disclosure. These are examples only for demonstration and not intended to limit the disclosure. For example, a first element formed "above" or "above" a second element may include direct contact between the first element and the second element in the embodiment, and may also include more space between the first element and the second element. Other additional elements make the first element and the second element have no direct contact. In addition, in various examples of this disclosure, component symbols and/or letters will be used repeatedly. This repetition is for the purpose of simplification and clarity, and does not itself determine the relationship between the various embodiments and/or structural configurations. In addition, various features may be drawn at different scales for simplicity and clarity.

Furthermore, terms such as "below", "below", "lower", "above", "higher", and other similar relative spatial relationships can be used here to describe an element or The relationship between a feature and another element or feature. The terms of these relative spatial relations are intended to cover various directions in use or operation of the device in addition to the directions described in the diagrams. For example, if the device in the figure is turned over, elements that were originally described as "below" or "below" other elements or features become "above" the other elements or features. Therefore, the example term "below" can include both above and below directions. The above-mentioned device can be guided in other ways (rotated by 90 degrees or in other directions), and the spatial relationship at this time can also be interpreted in the above-mentioned way.

FIG. 1 is a schematic diagram of a cleaning system using an atmospheric plasma generator according to some embodiments. The system 100 includes an atmospheric plasma generating device 110, an atmospheric plasma generating device controller 120, a workbench 130, an exhaust port 140, an air inlet pipe 160, and a circuit board 210 on which an IC has been soldered.

According to some embodiments, the system 100 provides a cleaning method, including providing a circuit substrate 210 with an IC soldered on; providing an atmospheric plasma generating device 110; introducing gas 10 into the atmospheric plasma generating device 110, and using the atmospheric plasma to generate The device 110 activates the gas 10 to form a plasma 180, and the atmospheric plasma generating device 110 sprays the plasma 180 at a wind speed of about 100 to about 300 meters per second (m/s); and uses the sprayed plasma 180 to clean the The surface 212 of the circuit board 210 of the IC is soldered.

The gas 10 can be continuously provided by a gas supplier (not shown), and introduced into the atmospheric plasma generator 110 through the gas inlet pipe 160. In some embodiments, the step of introducing the gas 10 into the atmospheric plasma generator 110 includes providing about 20 to about 40 standard liters per minute (SLM) of the gas 10 into the atmospheric plasma generator 110. In addition, based on cost and safety considerations, this embodiment uses low-cost and environmentally friendly gases. Therefore, in some embodiments, the gas 10 may be air, oxygen, nitrogen, carbon dioxide, argon, helium, or a combination of the foregoing gases.

The atmospheric plasma generating device 110 can be electrically connected to the atmospheric plasma generating device controller 120 via a wire 150. The atmospheric plasma generator controller 120 can provide the power required by the atmospheric plasma generator 110 so that the atmospheric plasma generator 110 can activate the gas 10 to generate plasma 180. In another embodiment, the atmospheric plasma generator controller 120 may also include, but is not limited to, various external components, such as a computer, to control various process parameters in the system 100. The atmospheric plasma generator controller 120 may be a radio frequency power system or a multi-frequency power system. Therefore, in some embodiments, the step of using the atmospheric plasma generator 110 to activate the gas 10 to form the plasma 180 includes providing about 500 to about 700 watts of radio frequency power to the atmospheric plasma generator 110 to activate the gas 10. In some other embodiments, the step of using the atmospheric plasma generator 110 to activate the gas 10 to form the plasma 180 includes providing a multi-frequency power of about 500 to about 700 watts to the atmospheric plasma generator 110. Activated gas 10.

Any point in the plasma 180 has the same potential. In other words, the plasma 180 can be regarded as a plasma body having an equipotential (equilibrium potential), and the plasma potential (Vp) is the potential exhibited when the equipotential is measured relative to the ground (ground line 170). In some embodiments, using the atmospheric plasma generator 110 to activate the gas 10 to form a plasma 180 includes forming a plasma 180 having a plasma potential of about 60 to about 80 volts (V). If the plasma potential is lower than 60 volts, sufficient ion bombardment energy may not be provided to remove contaminants on the surface 212 of the circuit substrate 210 on which the IC has been soldered.

The atmospheric plasma generator 110 can be coupled to a flexible mechanism, so it can move linearly and clean different areas of the circuit substrate 210 on which the IC has been soldered below. In some embodiments, the step of using the sprayed plasma 180 to clean the surface 212 of the circuit substrate 210 on which the IC has been soldered includes contacting the plasma 180 with the surface 212 of the circuit substrate 210 on which the IC has been soldered. The pulp generating device 110 moves at a scanning line speed of about 50 to about 200 millimeters per second (mm/s). In one embodiment, the scanning line speed of the atmospheric plasma generator 110 is lower than 50 mm/sec, so that the circuit substrate 210 on which the IC has been soldered will accumulate too much heat, causing the circuit substrate to warp and deform or damage the components on the workpiece. In another embodiment, the scanning line speed of the atmospheric plasma generator 110 is higher than 200 mm/s, which will cause the residence time of the plasma 180 on the circuit substrate 210 with IC soldered to be too short , And there are situations where the cleaning is not thorough enough. In addition, there is a first working distance H between the atmospheric plasma generator 110 and the circuit board 210 on which the IC has been soldered. In some embodiments, the first working distance H between the atmospheric plasma generator 110 and the circuit substrate 210 on which the IC has been soldered is about 5 to about 8 millimeters (mm).

When there are organic pollutants on the surface 212 of the circuit substrate 210 on which the IC has been soldered, the plasma 180 can chemically react with the organic pollutants, causing the organic pollutants to react into a gaseous reaction product. The gaseous reaction product can then be discharged through the suction port 140. For example, in an embodiment, when the gas source of plasma 180 is oxygen, the chemical reaction formula of plasma 180 and organic pollutants is as follows: O ^* _(g) + C _x H _y(s) → xCO _{2 (g)} +1/2yH ₂ O _(g) . Therefore, in some embodiments, using the sprayed plasma 180 to clean the surface 212 of the circuit substrate 210 on which the IC has been soldered includes using the sprayed plasma 180 to remove at least one organic pollutant on the surface 212.

Next, please refer to FIGS. 2A to 2C, which are partial enlarged schematic diagrams of the area 300 in FIG. 1, according to some embodiments. In some embodiments, there are metal salt contaminants 220 on the surface 212 of the circuit substrate 210 on which the IC has been soldered. Therefore, the aforementioned step of using the sprayed plasma 180 to clean the surface 212 of the circuit substrate 210 on which the IC has been soldered may include The sprayed plasma 180 is used to remove at least one metal salt contaminant 220 on the surface 212.

In more detail, in Figure 2A, the plasma 180 sprays downward to contact the metal salt pollutants 220 and perform a chemical reaction, thereby oxidizing the metal salt pollutants 220 to metal oxides 220' in Figure 2B. . In addition, when the plasma 180 is sprayed downward, it will continue to impact the surface 212 of the circuit board 210 on which the IC has been soldered and generate a lateral airflow 190. Finally, in FIG. 2C, the metal oxide 220 ′ will be removed from the surface 212 of the circuit substrate 210 along with the lateral air flow 190. In some embodiments, the wind speed when the plasma 180 is sprayed is about 100 to about 300 meters per second. When the wind speed when the plasma 180 is ejected is lower than 100 m/s, the lateral airflow 190 generated by the plasma 180 impacting the surface 212 is not strong enough to remove the metal oxide 220' attached to the surface 212. When the wind speed when the plasma 180 is sprayed is higher than 300 m/s, the impact force of the plasma 180 on the circuit substrate 210 on which the IC has been soldered may be too strong to cause damage to the circuit substrate 210 on which the IC has been soldered.

The plasma 180 sprayed by the atmospheric plasma generator 110 can adjust the processing times of the same area of the circuit substrate 210 on which the IC has been soldered as required. If the cleaning frequency is less than 10 times, there may be residual or excessive contaminants on the surface 212 of the circuit substrate 210 on which the IC has been soldered. However, too many cleaning times (for example, more than 50 times) will increase the risk of damage to the surface 212 of the circuit substrate 210 on which the IC has been soldered. Therefore, in some embodiments, the step of using the plasma 180 to clean the surface 212 of the circuit substrate 210 on which the IC has been soldered includes using the plasma 180 to clean the surface 212 of the circuit substrate 210 on which the IC has been soldered for about 10 to about 50 times. . In some embodiments, after the step of contacting the plasma 180 to the surface 212 of the circuit substrate 210 on which the IC has been soldered, the residual acid ion concentration on the surface 212 is less than 4 milligrams per square inch (μg/in ² ). The conventional chemical reaction between plasma and metal salt pollutants produces solid metal oxides and volatile gas products. The gas product can be removed from the surface of the circuit substrate on which the IC has been soldered through the air extraction system, and the solid metal oxide will remain on the surface of the circuit substrate on which the IC has been soldered and cannot be removed by air extraction. However, according to some embodiments of the present disclosure, the lateral airflow generated after the high-speed plasma air flow impacts the surface of the circuit substrate on which the IC has been soldered can be used to remove the metal salt contamination attached to the surface of the circuit substrate on which the IC has been soldered Things.

Continuing to refer to FIGS. 3A to 3C, it is a partial enlarged schematic view of the area 300 in FIG. 1, according to some embodiments. In some embodiments, contaminants 220 are present on the surface 212 of the circuit substrate 210 on which ICs have been soldered. The contaminants 220 may include inorganic contaminants 215A and etchable contaminants 215B. The step of cleaning the surface 212 of the circuit substrate 210 on which the IC has been soldered by the slurry 180 may include using the sprayed plasma 180 to remove at least one inorganic contaminant 215A on the surface 212.

In more detail, in Figure 3A, the plasma 180 sprays downward to contact the pollutants 220, and the lateral airflow 190 generated when the plasma 180 impacts the surface 212 will also drive the plasma 180 to face the pollutants in the lateral direction. 220 Perform etching. As shown in FIG. 3B, the etchable pollutant 215B among the pollutants 220 is etched by the plasma 180 to be removed. After the etchable contaminant 215B is removed, the inorganic contaminant 215A loses its attachment points and is also removed. Continuing to refer to Fig. 3C, while the inorganic contaminant 215A has not yet been fixed on the surface 212 of the circuit substrate 210 on which the IC has been soldered, the lateral airflow 190 will take away the inorganic contaminant 215A from the circuit substrate 210 on which the IC has been soldered. The surface 212 is removed. Conventionally, inorganic contaminants cannot be removed from the surface of the circuit substrate on which the IC has been soldered by dry etching (for example, using plasma). However, through some embodiments of the present disclosure, when the plasma cleans the surface of the circuit substrate on which the IC has been soldered, it will first remove the etchable contaminants on the surface of the circuit substrate on which the IC has been soldered. While the etchable pollutants are removed, the inorganic pollutants are also taken away by the side airflow.

Finally, in order to verify that the cleaning method of this embodiment has an excellent ability to remove contaminants, the following tests were carried out.

Analysis of the residual acid radical ion before and after plasma treatment

The samples used for the test are commercially available circuit boards with integrated circuits (IC). The residual amount of acid radical ions on the circuit board before and after the plasma treatment using this embodiment is analyzed. As shown in Table 1 below, SPEC is an industry standard specification, which is the allowable standard residual amount on the circuit board. The difference between Examples 1 and 3 lies in the number of times of plasma cleaning. Specifically, the number of plasma cleaning in Example 1 is 0, that is, a sample that has not been plasma-treated. The number of plasma cleanings in Example 2 is 10 times. The number of plasma cleaning in Example 3 is 20 times.

Before plasma treatment, for example, a residual sulfate ions embodiment (SO ₄ ^2-) content 436.120636μg / in ^2, significantly exceeded the allowable value 4μg / in ² many. After 10 to clean the plasma treatment, a sulfate ion (SO ₄ ^2-) remaining in Example 2 content 4.926163μg / in ^2, it is still slightly larger than the standard, as defined 4μg / in ^2. And after the plasma treatment cleaning 20 times, Example 3 Embodiment residual sulfate ions (SO ₄ ^2-) content 1.18875μg / in ^2, much less than the standard, as defined 4μg / in ^2. Therefore, using the embodiment of the present invention to treat the surface of the circuit board with plasma can have an excellent cleaning effect.

The foregoing summarizes the features of several embodiments so that those familiar with the technology can better understand the aspect of the present disclosure. Those familiar with the technology should understand that this disclosure can be easily used as a basis for designing or modifying other manufacturing processes and structures for achieving the same purpose and/or achieving the same advantages of the embodiments introduced herein. Those familiar with the technology should also realize that the structure of such equivalents does not violate the spirit and scope of this disclosure, and various changes, substitutions and alterations can be made here without violating the spirit and scope of this disclosure. .

180‧‧‧Plasma

190‧‧‧Side airflow

210‧‧‧PCB with IC soldered on

212‧‧‧surface

220‧‧‧Pollutant

220’‧‧‧ oxide

300‧‧‧area

Claims (11)

A cleaning method includes: providing a circuit substrate with an IC soldered on; providing an atmospheric plasma generating device; introducing a gas into the atmospheric plasma generating device, and using the atmospheric plasma generating device to activate the gas to form electricity And let the atmospheric plasma generator spray the plasma at a wind speed of about 100 to about 300 meters per second (m/s); and use the sprayed plasma to clean one of the circuit substrates on which the IC has been soldered Surface; wherein, the plasma impacts the surface to generate a side airflow to clean the surface. The cleaning method described in claim 1, wherein introducing the gas into the atmospheric plasma generating device includes: providing about 20 to about 40 standard liters per minute (SLM) of the gas to the atmospheric plasma generating device in. The cleaning method according to the first item of the scope of patent application, wherein using the sprayed plasma to clean the surface of the circuit substrate on which IC has been soldered includes contacting the plasma with the surface of the circuit substrate on which IC has been soldered, And the atmospheric plasma generator moves at a scanning line speed of about 50 to about 200 millimeters per second (mm/s). Such as the cleaning method described in item 3 of the scope of patent application, Wherein using the plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the plasma to clean the surface of the circuit substrate on which the IC has been soldered about 10 to about 50 times. The cleaning method described in claim 1, wherein using the atmospheric plasma generator to activate the gas to form the plasma includes providing about 500 to about 700 watts of radio frequency power to the atmospheric plasma generator To activate the gas. The cleaning method according to claim 1, wherein using the atmospheric plasma generator to activate the gas to form the plasma includes providing about 500 to about 700 watts of multi-frequency power to the atmospheric plasma generation Device to activate the gas. The cleaning method as described in claim 1, wherein in the step of using the sprayed plasma to clean the surface of the circuit board on which the IC has been soldered, the atmospheric plasma generator and the IC have been soldered There is a first working distance between the circuit substrates, and the first working distance is about 5 to about 8 millimeters (mm). According to the cleaning method described in item 1 of the scope of patent application, the gas can be air, oxygen, nitrogen, carbon dioxide, argon, helium, or a combination of the above gases. The cleaning method according to claim 1, wherein using the sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the sprayed plasma to remove at least one organic pollutant on the surface. The cleaning method according to claim 1, wherein using the sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the sprayed plasma to remove at least one metal salt contamination on the surface Things. The cleaning method according to claim 1, wherein using the sprayed plasma to clean the surface of the circuit substrate on which the IC has been soldered includes using the sprayed plasma to remove at least one inorganic contaminant on the surface.

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