WO2003067950A1

WO2003067950A1 - Elastic collet for pcb mounting jig and pcb jig assembly having the collet

Info

Publication number: WO2003067950A1
Application number: PCT/KR2003/000248
Authority: WO
Inventors: Sung-Hun Nam
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-02-06
Filing date: 2003-02-05
Publication date: 2003-08-14
Anticipated expiration: 2004-08-06
Also published as: KR100430879B1; AU2003207103A1; KR20030067068A

Abstract

The present invention relates to an elastic collet for PCB mounting jig and a PCB jig assembly having the collet, more particularly, to an elastic collet for PCB mounting jig and a PCB jig assembly having the collet, which prevents bending and the soldering defect of a printed circuit board (PCB) in the process of mounting and soldering chips and parts on PCB, thus simplifies the surface mount process. An printed circuit board (PCB) jig assembly having the collet in accordance with the present invention is characterized in comprising a plate-type jig having a plurality of through holes for mounting a PCB of a certain thickness on the top surface thereof and a plurality of elastic member being combined with the plurality of through holes respectively in order to fix the PCB mounted on the top surface of the jig detachably, wherein each of the elastic members is an elastic collet for the jig, having a hollow cylindrical shape having a inner diameter and a outer diameter, the outer diameter consisting of a large outer diameter portion and a small outer diameter portion to form a step on the outer surface of the elastic collet, and a plurality of through slots having a certain length, being formed on the circumference of the elastic collet, and stemming axially from a distal end of the large outer diameter portion, each of the through holes of the jig consists of a large inner diameter portion and a small inner diameter portion, wherein the outer diameter of the small outer diameter portion of the elastic collet is larger than the inner diameter of the small inner diameter portion of the through hole, and the outer diameter of the large outer diameter portion of the elastic collet is larger than the inner diameter of the large inner diameter portion of the through hole.

Description

ELASTIC COLLET FOR PCB MOUNTING JIG AND PCB JIG ASSEMBLY

HAVING THE COLLET

FIELD OF THE INVENTION

The present invention relates to an elastic collet for PCB mounting jig and a PCB jig assembly having the collet, more particularly, to an elastic collet for PCB mounting jig and a PCB jig assembly having the collet, which prevents bending and the soldering defect of a printed circuit board (PCB) in the process of mounting and soldering chips and parts on the PCB.

BACKGROUND OF THE INVENTION

Generally, a printed circuit board (PCB) is regarded as an electronic part having wirings and spaces needed for mounting electronic parts. Recently, multi- layered PCB has been extensively used.

Surface Mount Technology (SMT) refers to a technology of mounting and soldering electronic parts for surface mounting on a PCB. Especially, Reflow Soldering Machine, among equipments that is applied to the above-mentioned Surface Mount Technology, refers to an equipment which performs soldering electronic parts mounted on a PCB where cream-phased lead has been printed, by passing the PCB through a kiln whose temperature has been adjusted to predetermined soldering temperature. Since the size of the electronic parts is very small and the operating temperature is high, the above-mentioned Reflow Soldering Machine uses a jig assembly for fixing the PCB in the process of soldering in order to reduce defects and increase productivity.

The jig assembly for PCB is sometimes referred to as 'PCB bending jig', 'soldering jig', 'SMT reflow soldering jig' or 'PCB pallet'. In the present invention, we refer to it as 'PCB jig assembly'. Fig. 5 represents the status of conventional PCB jig assembly mounted with a PCB and Fig. 6 represents enlarged delineation of part C of Fig. 5, respectively.

In case of performing the soldering process on a PCB (20) using the conventional PCB jig assembly, the process comprises the steps of i ) applying cream solder on the PCB after mounting the PCB (20) on the PCB jig assembly, ii ) mounting the chips and parts with the high-speed chip mounter on the PCB (20), iii) passing it through the reflow soldering machine and iv) inspecting and testing of the chips.

In order to prevent soldering defects due to the vibration of the PCB and other disturbances during the above-mentioned processing, the conventional PCB jig assembly (40) comprises portions that the PCB is positioned, having a platform positioning lower than the remainder part of the conventional PCB jig assembly, and fixing pins (56) which are inserted into the pinhole formed on the PCB (20).

And the conventional PCB jig assembly (40) has a lever (55) which is movable along the declined guidance hole (51) formed on the side where the PCB (20) is positioned. So it is possible to fix the PCB (20) to the assembly by way of friction caused by the pushing force of the sliding lever after mounting the PCB (20) on the assembly and to detach it after performing the processes by sliding the lever. That is, the PCB jig assembly is furnished with the sliding-type clamp (50).

DISCLOSURE OF INVENTION

As already mentioned, however, since the PCB jig assembly using the conventional fixing pin and clamp has such a fixing mechanism as the PCB is fixed by the pushing force of the sliding lever, the lever may be loosen in the course of fransferring the PCB jig assembly, which induces the incorrect mounting of the parts, therefore the conventional PCB jig increases the defect rate of the product. Also, the conventional process using the conventional PCB jig assembly requires redundant working steps of contacting closely and releasing the PCB by sliding the lever in order to clamp and unclamp the PCB, resulting in complex processing and high cost. Also the conventional PCB jig assembly has the structure of pressing the side of the PCB, therefore the PCB is liable to bend. The bending of the PCB increases the defect rate of the product.

Further, since the clamping structure of the conventional PCB jig assembly furnished with the fixing pin and clamp lever is suitable to the rectangular shaped PCB, the redundant process is required to cut the unnecessary part of the PCB in case the PCB does not have the rectangular shape. The cutting process may have the PCB damaged and increase the nullified portion of the PCB, causing increase in the defect rate of the product and production cost.

Accordingly, it is a primary object of the present invention to provide an elastic collet for a PCB jig assembly, which is inserted into the pinhole formed on the PCB and fix the PCB with suitable grasping force, preventing drift of the PCB on the PCB jig assembly. The PCB can be detached from the elastic collet with suitable force.

It is an another object of the present invention to provide a PCB jig assembly having the collet, which can reduce the production cost caused by the redundant working steps of contacting closely and releasing the PCB by sliding the lever in order to clamp and unclamp the PCB, and by removing spare portions of the PCB in case the PCB does not have a rectangular shape.

The above object of the present invention can be accomplished by providing an elastic collet used for a printed circuit board (PCB) jig assembly in order to fix the printed circuit board (PCB) detachably on the jig assembly. The elastic collet of the present invention has a hollow cylindrical shape having a inner diameter and a outer diameter, outer surface of the cylinder consisting of a large outer diameter portion and a small outer diameter portion to form a step on the outer surface of the elastic collet, a plurality of through slots having a certain length, being formed on the circumference of the elastic collet, and stemming axially from a distal end of the large outer diameter portion.

Further, the elastic collet of the present invention is characterized in that each length of the through slots is longer than that of the large outer diameter portion. Also, the elastic collet of the present invention is characterized in that the distal ends of the large outer diameter portion and the small outer diameter portion are chamfered with a predetermined angle.

Also, the elastic collet of the present invention is characterized in that the elastic collet is plated with nickel, and that the thickness of the plating is in the range of 0.005 to 0.02 mm.

Another object of the invention can be accomplished by providing a printed circuit board (PCB) jig assembly comprising a plate-type jig having a plurality of through holes for mounting a PCB of a certain thickness on the top surface thereof and a plurality of elastic members being combined with the plurality of through holes respectively in order to fix the PCB mounted on the top surface of the jig detachably. Each of the elastic members is an elastic collet for the jig, having a hollow cylindrical shape having a inner diameter and a outer diameter, outer surface of the cylinder consisting of a large outer diameter portion and a small outer diameter portion to form a step on the outer surface of the elastic collet, a plurality of through slots having a certain length, being formed on the circumference of the elastic collet, and stemming axially from a distal end of the large outer diameter portion, and each of the through holes of the jig consists of a large inner diameter portion and a small inner diameter portion. Especially, the outer diameter of the small outer diameter portion of the elastic collet is larger than the diameter of the small inner diameter portion of the through hole, and the outer diameter of the large outer diameter portion of the elastic collet is larger than the diameter of the large inner diameter portion of the through hole.

Also, the PCB jig assembly of the present invention is characterized in that the length of the large outer diameter portion of the elastic collet is longer than the thickness of the PCB mounted on the jig.

Also, the PCB jig assembly of the present invention is characterized in that each length of the through slots is longer than that of the large outer diameter portion of the elastic collet. Also, the PCB jig assembly of the present invention is characterized in that both ends of the large outer diameter portion of the elastic collet are chamfered with a predetermined angle.

Also, the PCB jig assembly of the present invention is characterized in that the elastic collet is plated with nickel, and that the thickness of the plating is in the range of 0.005 to 0.02mm.

According to the present invention, since the SMT process using the PCB jig assembly having the collets of the present invention is performed in a state that the PCB mounted on the jig is not fixed by the conventional clamping mechanism pushing the PCB but fixed by grasping mechanism of the collet holding the PCB elastically, there is no bend and separation of the PCB during the SMT process.

According to the present invention, furthermore, since a PCB could be mounted and fixed on the jig assembly having the elastic collet regardless of the

PCB shape, it is possible to reduce production costs by preventing cut-off processing and the redundant PCB that are needed in case the PCB is not rectangular.

BRIEF DESCRIPTION OF DRAWINGS

The above mentioned and other advantages of the present invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken with the accompanying drawing, wherein:

Fig. 1 represents a PCB jig assembly mounted with a PCB according to the present invention, Fig. 2 is an exploded perspective view of a PCB jig assembly of the present invention,

Fig. 3 is a perspective view of an elastic collet of the present invention, Fig. 4 is a sectional view viewed form the A- A line of Fig. 1, Fig. 5 represents conventional PCB jig assembly mounted with a PCB, Fig. 6 represents an enlarged delineation of the clamp part C of Fig. 5. BEST MODE FOR CARRYING OUT THE INVENTION

Preferable example of the present invention is illustrated and described hereinafter with reference to the attached drawings.

Fig. 1 represents a PCB jig assembly mounted with a PCB according to the present invention, Fig. 2 is an exploded perspective view of a PCB jig assembly of the present invention, Fig. 3 is a perspective view of an elastic collet of the present invention, and Fig. 4 is a sectional view viewed form the A-A line of Fig. 1. An example of a PCB jig assembly (10) in accordance with the present invention, having a lower platform formed on the place a PCB (20) mounted and an elastic collet for fixing the PCB (20) not to move, is represented in Fig. 1.

As shown in Fig. 4, suitable numbers of pinholes (25) are formed on the PCB (20) according to the shape of the PCB (20), through holes (32) are positioned on the PCB jig (10) in accordance with pinholes (25) of the PCB (20), and elastic collets (30) are inserted and fitted by means of interference fit into the each through holes of the PCB jig (10), respectively.

The elastic collet (30) according to the present invention, as shown in Fig. 3, has the hollow cylindrical shape having a inner diameter and a outer diameter, outer surface of the cylinder consisting of a large outer diameter portion (30a) and a small outer diameter portion (30b) to form a step on the outer surface of the elastic collet, a plurality of through slots (30c) having a certain length, being formed on the circumference of the elastic collet, and stemming axially from a distal end of the large outer diameter portion. It is preferable that the through slots (30c) of the elastic collet are arranged symmetrically to the center with an equivalent interval and a certain width (W). Preferably, the length of each through slots (30c) is longer than that of the large outer diameter portion (30a) of the collet to give the sufficient elasticity in case the collet is inserted in the pinhole (25) of the PCB. Since both distal ends of the large and small outer diameter portions of the elastic collet are chamfered with a predetermined angle, the elastic collet can be easily inserted into the pinhole (25) of the PCB (20) and through hole of the PCB jig (10).

Since the outer diameter (D4) of the large outer diameter portion (30a) is designed to be slightly larger than the inner diameter of the pinhole (25) of the PCB, the elastic collet is frictionally fixed to the PCB in the way that the through slot shrinks elastically in the direction of the empty space (W) thereof when the large outer diameter portion (30 a) of the elastic collet is inserted into the pinhole (25) of the PCB (20). Further, since the outer diameter (D4) of the large outer diameter portion (30a) of the elastic collet is larger than the diameter (Dl) of the large inner diameter portion of the through hole (32) of the PCB jig (10), the large outer diameter portion of the elastic collet is put on the top surface of the PCB jig (10). From the above relationship, the skilled person in the art can calculate the suitable frictional force needed for holding the PCB during transfer, and also can determine the suitable size of the outer diameter (D4) of the large outer diameter portion (30a) and the width (W) of the through slot of the elastic collet and the diameter (D5) of the pinhole. It is preferable that the length of the large outer diameter portion (30a) is shorter by about 0.2 to 0.3mm than the thickness of the PCB, not to protrude over the top surface of the PCB (20) when the elastic collet is inserted into the pinhole (25) of the PCB (20). Generally, holding mechanism of a conventional collet is performed in the process of accommodating an object in the hollow portion of the collet and applying the pressure on the outer surface of the collet to shrink, which causes frictional force between the collet and the object accommodated. However, the elastic collet in accordance with the present invention is characterized in that holding mechanism is performed in the process of inserting the collet into a hole of an object to shrink, which gives rise to frictional force between the collet and the hole caused by the elasticity of the shrunk collet. Normally, the inner diameter of the hole is smaller than the outer diameter of the collet, and releasing of the object can be easily done by applying the force greater than the frictional force caused by the elastic force of the shrunk collet. Further, it is preferable that the elastic collet in accordance with the present invention is plated with nickel in order to give anti-wear and increase the elasticity. Preferably, the thickness of the Ni plating of the elastic collet is in the range of 0.005 to 0.02mm. The though hole (32) of PCB jig (10) fitting interferingly with the elastic collet (30) consists of the large inner diameter portion (32a) having the diameter of Dl and the small inner diameter portion having the diameter of D2 to form a step on the inner surface of the through hole (32). The small outer diameter portion of the elastic collet forms the interference fit with the small inner diameter portion of the through hole, since the outer diameters of the small outer diameter portion and the large outer diameter portion of the elastic collet are greater than the corresponding inner diameters of the through hole, respectively. The length (L) of the interference fit can be adjusted appropriately for the elastic collet not to escape when the PCB is mounted with the elastic collet (30). The length of the small outer diameter portion of the elastic collet should be shorter than the thickness of the PCB jig not to protrude below the PCB jig when being inserted.

It is obvious to the skilled person in the art that the position of the through hole be determined correspondingly to that of the pinhole determined according to the design pattern of the PCB. We would explain the operational mechanism of the present invention as below. If the PCB is mounted and pressed on the PCB jig assembly having the elastic collet (30) positioned correspondingly to the pinhole (25) formed according to the pattern of the PCB (20), the elastic collet is inserted into the pinhole (25) of the PCB (20) with elastic modification to hold the PCB. Without a modification or drift of the PCB, the PCB jig assembly in accordance with the present invention undergoes the conventional SMT processes, that is, applying the cream solder, high-speed chip mounting of chips and circuit elements such as tantal, and soldering through the Reflow Soldering Machine. The inspection and test on chips are followed. INDUSTRIAL APPLICABILITY

As above-mentioned, it is possible to simplify the SMT process and prevent drift and bending of PCB by removing unnecessary clamping and unclamping processes which are required in the conventional jig assembly, since the fixing of the PCB according to the present invention is done by the elastic collet which generates the elastic force when the large outer diameter portion of the elastic collet is inserted in the pinhole of the PCB.

Further, since it is possible to fix a PCB not having rectangular shape by using the PCB jig assembly in accordance with the present invention, the post- process of cutting after the mounting process is not required, and therefore, the defect generated in the time of cutting does not arise and the production cost is reduced.

It should be understood that the embodiments of the present invention described above and illustrated in the drawings is not construed as limiting the technical spirit of the present invention. The scope of the invention is defined only by the appended claims, and those skilled in the art can make various changes and modifications to the embodiments of the present invention within the scope of the invention. Thus, such changes and modifications fall within the scope of the invention as far as they are obvious to those skilled in the art.

Claims

WHAT IS CLAIMED IS:

1. An elastic collet used for a printed circuit board (PCB) jig assembly in order to fix the printed circuit board (PCB) detachably on the jig assembly, wherein the elastic collet has a hollow cylindrical shape having a inner diameter and a outer diameter, outer surface of the cylinder consisting of a large outer diameter portion and a small outer diameter portion to form a step on the outer surface of the elastic collet, and a plurality of through slots having a certain length, being formed on the circumference of the elastic collet, and stemming axially from a distal end of the large outer diameter portion.

2. The elastic collet as in claim 1, wherein each length of the through slots is longer than that of the large outer diameter portion.

3. The elastic collet as in claim 1, wherein the distal ends of the large outer diameter portion and the small outer diameter portion are chamfered with a predetermined angle.

4. The elastic collet as in any one of claim 1 to 3, wherein the elastic collet is plated with nickel.

5. The elastic collet as in claim 4, wherein the thickness of the plating is in the range of 0.005 to 0.02 mm.

6. A printed circuit board (PCB) jig assembly comprising a plate-type jig having a plurality of through holes for mounting a PCB of a certain thickness on the top surface thereof and a plurality of elastic member being combined with the plurality of through holes respectively in order to fix the PCB mounted on the top surface of the jig detachably, wherein each of the elastic members is an elastic collet for the jig, having a hollow cylindrical shape having a inner diameter and a outer diameter, outer surface of the cylinder consisting of a large outer diameter portion and a small outer diameter portion to form a step on the outer surface of the elastic collet, and a plurality of through slots having a certain length, being formed on the circumference of the elastic collet, and stemming axially from a distal end of the large outer diameter portion, each of the through holes of the jig consists of a large inner diameter portion and a small inner diameter portion, wherein the outer diameter of the small outer diameter portion of the elastic collet is larger than the inner diameter of the small inner diameter portion of the through hole, and the outer diameter of the large outer diameter portion of the elastic collet is larger than the inner diameter of the large inner diameter portion of the through hole.

7. The PCB jig assembly as in claim 6, wherein the length of the large outer diameter portion of the elastic collet is longer than the thickness of the PCB mounted on the jig.

8. The PCB jig assembly as in claim 6, wherein each length of the through slots is longer than that of the large outer diameter portion of the elastic collet.

9. The PCB jig assembly as in claim 6, wherein both ends of the large outer diameter portion of the elastic collet are chamfered with a predetermined angle.

10. The PCB jig assembly as in any one of claim 6 to 9, wherein the elastic collet is plated with nickel.

11. The PCB jig assembly as in claim 10, wherein the thickness of the plating is in the range of 0.005 to 0.02mm.