WO2002011936A1

WO2002011936A1 - Solder plating system with plating carrier belt roller with locking sprocket pins

Info

Publication number: WO2002011936A1
Application number: PCT/US2001/023790
Authority: WO
Inventors: Wanus Prommate
Original assignee: Advance Micro Devices, Inc.
Priority date: 2000-08-08
Filing date: 2001-07-26
Publication date: 2002-02-14
Also published as: AU2001277219A1

Abstract

A solder plating system comprises a fabrication cell wherein a solder plating is applied to a device being processed. A carrier belt supports the device being processed and includes a plurality of alignment holes for being supported on a plurality of sprocketed carrier wheels. Each sprocketed carrier wheel includes a plurality of sprocket pins positioned in radials holes about the periphery of the carrier wheel for engaging the plurality of alignment holes in the carrier belt. Each sprocket pin includes a locking extension which secures the sprocket pin into the carrier wheel and prevents the sprocket pin from being dislodged from the radial hole.

Description

SOLDER PLATING SYSTEM WITH PLATING CARRIER BELT ROLLER WITH LOCKING SPROCKET PINS

Technical Field The present invention relates generally to a sprocket wheel for supporting a carrier belt, and more specifically to a sprocket wheel for supporting a carrier belt in a solder plating system.

Background of the Invention

The electronics industry has become increasingly dependent on integrated circuit components. At typical integrated circuit (IC) component includes a silicon wafer circuit positioned within a ceramic or plastic housing. The ceramic or plastic housing is typically mounted to a printed circuit board for interconnection with other components.

IC components include a housing that typically includes a plurality of pins embedded into the ceramic or plastic forming the base or sides of the housing. The pins would be positioned to align with holes or solder pads on a printed circuit board. The pins would then each be soldered using a tin/lead alloy solder to both secure the IC component to the printed circuit board and to electrically couple each pin with a trace on the printed circuit board. Pin and pad alignment patterns correspond to patterns such as PDIP, PLCC, TSOP, and SOIC for example.

To assure proper connection of each pin to the printed circuit board, the solder must bond with both the pin and board. Impurities that may collect, or oxidize, on the pins during the manufacturing and shipping process can make bonding difficult if solder is first applied at the board assembly facility. Therefore, it is common to apply solder to each pin during the fabrication of the IC component to assure proper bonding of such solder to the pin. To automate this process, a solder plating machine can be used.

Referring to Figure 1, solder plating machine 10 typically include a carrier belt 12 which sequentially move IC packages 13 (Figure 2) from a loading station 14, through a fabrication cell 16, and to an unloading station 18. To assure alignment within the tolerances required for the technology, the machine 10 typically includes a plurality of carrier rollers 20(a) - 20(e) for maintaining the precise position of the belt 12.

Referring to Figure 2, the belt 12 includes a plurality of sprocket holes 22(a) - 22(b) spaced for aligning with a plurality of sprocket pins 24(a) - 24(d) extending radially from the carrier roller 20. In known systems, each sprocket pin 24(a) - 24(d) is friction fit or adhesive secured within a radial hole in the perimeter of the carrier roller 20. A problem with such systems is the sprocket pins 24(a) - 24(d) can become bound (e.g. stuck) in the sprocket holes 22(a) - 22(b) with a force sufficient to break the friction fit or adhesive and, as such, pull the sprocket pins 24(a) - 24(d) out of the sprocket holes 22(a) - 22(d).

Accordingly, there is a strong need in the art for a solder plating system which permits for the precise alignment of IC components on a carrier belt, but does not suffer the disadvantages of the sprocket carrier wheel system discussed above.

Disclosure of the Invention

A first aspect of the present invention is to provide a solder plating system. The solder plating system comprises a fabrication cell wherein solder plating is applied to a device being processed. The system also comprises a carrier belt supporting the device being processed. To assure proper alignment, the carrier belt includes a plurality of alignment holes for engaging sprockets on a carrier wheel. The carrier wheel supporting the carrier belt includes a plurality of sprocket pins positioned in a plurality of radial holes about the periphery of the wheel for engaging the plurality of alignment holes in the carrier belt. Each sprocket pin includes a locking extension larger than a diameter of the radial hole to prevent the sprocket pin from being dislodged from the radial hole.

In a preferred embodiment, the carrier wheel includes a housing with a central hub and a peripheral ring. Each of the plurality of radial holes extends from an outer periphery of the peripheral ring to an imier periphery of the peripheral ring.

Each sprocket pin may include a blunted head extending beyond the outer periphery of the peripheral ring for engaging the plurality of alignment holes. Further, the locking extension may extend beyond the inner periphery of the peripheral ring such that the locking extension abuts the inner periphery of the peripheral ring.

The carrier wheel may further include a plug ring with an outer periphery smaller than the inner periphery of the peripheral ring such that the plug ring holds the locking extension abutted against the inner periphery of the peripheral ring. A backing plate may interconnect the central hub and the central hub and the peripheral ring, and the plug ring may be secured to the backing plate with screws. The central hub may includes an axial hole for mounting the carrier wheel on an axle.

In one embodiment, the locking extension on the sprocket pin may include a pin with a length larger than the diameter of the radial holes. In another embodiment, the locking extension may include a flange with a diameter larger than the diameter of the radial holes. An undercut may be positions at the base of the flange to assure proper seating against the inner periphery.

In either embodiment, the housing and each sprocket pin may be formed of an acid resistant material stainless steel and the plug ring may be formed of an acid resistant material such as a nylon polymer.

A second aspect of the present invention is to provide a method fabricating a carrier roller for a solder plating machine. The method comprises a) fabricating a carrier roller housing including an inner hub and a peripheral ring; b) forming a plurality of radial holes in the peripheral ring; c) fabricating a plurality of sprocket pins with a body diameter sized for positioning in the radial holes and a locking extension extending beyond the diameter of the radial holes; and d) positioning a sprocket pin in each of the radial holes such that the locking extension abuts an inner periphery of the peripheral ring.

The method may further include fabricating a blunt end on each sprocket pin on an end of the body opposite the locking extension. The step of positioning a sprocket pin in each of the radial holes may include assuring that the blunt end extends beyond an outer periphery of the peripheral ring.

Further yet, the method may include fabricating a plug ring and positioning the plug ring between the central hub and the peripheral ring to abut the locking extension of each sprocket pin against the inner periphery of the peripheral ring.

A third aspect of the present invention is to provide a carrier wheel for supporting a carrier belt in a solder plating system. The carrier wheel comprises a plurality of sprocket pins positioned in a plurality of radial holes about the periphery of the carrier wheel for engaging a plurality of alignment holes in the carrier belt. Each sprocket pin includes a locking extension larger than a diameter of the radial holes to prevent the sprocket pin from being dislodged from the radial hole.

The carrier wheel may further include a housing with a central hub and a peripheral ring. Each of the plurality of radial holes extends from an outer periphery of the peripheral ring to an inner periphery of the peripheral ring. Each of the sprocket pin includes a blunted head extending beyond the outer periphery of the peripheral ring for engaging the plurality of alignment holes and the locking extension extends beyond the inner periphery of the peripheral ring such that the locking extension abuts the inner periphery of the peripheral ring.

A plug ring with an outer periphery smaller than the inner periphery of the peripheral ring may be used such that the plug ring holds the locking extension abutted against the inner periphery of the peripheral ring. A backing plate may interconnect the central hub with the peripheral ring and the plug ring may be secured to the backing plate with screws. The central hub may include an axial hole for mounting the carrier wheel on an axle.

Brief Description of the Drawings

Figure 1 is a top view diagram of a conventional solder plating carrier system;

Figure 2 is a side view diagram of a conventional solder plating carrier belt engaged with a sprocketed carrier wheel;

Figure 3 is a top view diagram of a plating carrier system in accordance with one embodiment of this invention;

Figure 4 is a top view diagram of a sprocketed carrier wheel in accordance with one embodiment of this invention;

Figure 5a is a top view of a sprocket pin for a carrier wheel in accordance with one embodiment of this invention.

Figure 5b is a side view of a sprocket pin for a carrier wheel in accordance with one embodiment of this invention; and

Figure 6 is a side view of an alternative sprocket pin for a carrier wheel in accordance with one embodiment of this invention.

Description of the Preferred Embodiments

The present invention will now be described in detail with reference to the drawings. In the drawings, like reference numerals are used to refer to like elements throughout.

Referring to Figure 3, a solder plating system 40, as shown in relevant part, includes a carrier belt 42 for sequentially moving integrated circuit (IC) packages through a loading cell 44, a processing cell 46, and an unloading cell 48. The carrier belt 42 includes a plurality of sprocket holes 50, each for engaging a sprocket pin 52 protruding from an outer periphery 54 of a carrier wheel 56. The engagement of a sprocket pin 52 with a sprocket hole 50 assures that the carrier belt 42 remains precisely aligned as the belt moves through each of the loading cell 44, processing cell 46, and unloading cell 48. While only one carrier wheel 56 is shown, it will be appreciated that the system 40 may include many such wheels along the path of the carrier belt 42. The carrier wheel 56 includes an axial hole 58 such that an axle 62 can extend through the axial hole 58 and support the carrier wheel 56 in a support structure 60 while enabling the wheel to turn at a rotational speed coinciding with the speed of the carrier belt 42. A backing plate 64 is also secured to the support structure 60 and functions to assure that the carrier belt 42 maintains contact with the outer periphery 54 of the carrier wheel 56.

Turning to Figure 4, a more detailed diagram of the carrier wheel 56 is shown. The carrier wheel includes a housing 67 which includes central hub 68 and a peripheral ring 70. A plurality of radial holes 66 are positioned within the peripheral ring 70 extending from the outer periphery 54 to an inner periphery 72. Each radial hole 66 is circumferentially spaced from adjacent radial holes 66 by an equal angle. Therefore, a sprocket pin 52 in each radial hole 66 is positioned to engage equally sprocket holes 50 (Figure 3) in the carrier belt 42 (Figure 3). More specifically, the sprocket holes 50 are equally spaced at a distance which corresponds to the distance about the circumference of the carrier wheel 56 between adjacent sprocket pins 52.

Each radial hole 66 includes a diameter 74 which corresponds do the diameter 76 of a body 78 of the sprocket pin 52 such that the body 78 of the sprocket pin 52 may fit into the radial hole 66. A locking extension 80 which extends beyond the diameter 74 of the radial hole 66 and abuts against the inner periphery 72 of the peripheral ring 70. In the preferred embodiment, the sprocket pins 52 and the housing 67 are fabricated from a stainless steel alloy, however, other materials desirable for use in a solder plating system are included within the scope of this invention.

A plug ring 82 is positioned between the central hub 68 and the inner periphery 72 of the peripheral ring 70 and holds each sprocket pin 52 in an abutted positioned against the inner periphery 72 of the peripheral ring 70. In the preferred embodiment, the plug ring 82 is fabricated from a polymer such as nylon such that a secure press fit of the locking extension 80 can be obtained between the inner periphery 72 and the plug ring 82. A plurality of screws 84 hold the plug ring 83 to the housing 67. The central hub 68 includes an axial hole 58 for positioning an axle such that the carrier wheel 56 may be rotated thereabout.

Referring to Figures 5a and 5b, a first embodiment of the sprocket pin 52 is shown. The sprocket pin includes a body 78 with a diameter 76 for fitting within an radial hole 66 in the carrier wheel 56 (both of Figure 4). At a first end of the body 78, the locking extension 80 protrudes beyond the diameter 76. As shown specifically in Figure 5a, the locking extension 80 is a flange formed on the first end of the body 78. A second end of the body 78 which is opposite the first end, includes a blunted nose 86 which facilitates engagement between the sprocket pin 52 and the alignment hole 50 in the carrier belt 42 (both of Figure 3).

Referring to Figure 6, a second embodiment of the sprocket pin 52' is shown. Similar to the sprocket pin 52 of Figures 5a and 5b, the sprocket pin 52' includes a body 78' with a diameter 76' for fitting within a radial hole 66 in the carrier wheel 56 (both of Figure 4). At a first end of the body 78', the locking extension is formed as a flange 80' with a diameter larger than the diameter 76' of the body 78'. An undercut 92 is formed at the junction of the locking extension flange 80' and the body 78' to assure that a rounded corner between the flange 80' and the body 78' does not prevent proper protrusion of the sprocket pin 52' through the radial hole 66 in the carrier wheel 56. A second end of the body 78' includes a blunted nose 86'. The blunted nose 86' includes a shoulder 90' to ensure proper seating into the alignment hole 50 in the carrier belt 42 (Figure 3) and a spherically shaped side 88' to facilitate engagement into the alignment hole.

It should be appreciated that the foregoing systems and structures provide for operation of a solder plating system without disengagement of alignment pins from carrier wheels. Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications, and is limited only by the scope of the following claims.

Claims

CLAIMS What is claimed is:

1. A solder plating system comprising: a) a fabrication cell wherein a solder plating is applied to a device being processed; b) a carrier belt supporting the device being processed, the carrier belt including a plurality of alignment holes; c) a carrier wheel supporting the carrier belt and including a plurality of sprocket pins positioned in a plurality of radial holes about the periphery of the wheel for engaging the plurality of alignment holes, wherein each sprocket pin includes a locking extension larger than a diameter of the radial holes to prevent the sprocket pin from being dislodged from the radial hole.

2. The solder plating system of claim 1, wherein the carrier wheel includes a housing with a central hub and a peripheral ring, each of the plurality of radial holes extending from an outer periphery of the peripheral ring to an inner periphery of the peripheral ring.

3. The solder plating system of claim 2, wherein each sprocket pin includes a blunted head extending beyond the outer periphery of the peripheral ring for engaging the plurality of alignment holes and the locking extension extends beyond the inner periphery of the peripheral ring such that the locking extension abuts the inner periphery of the peripheral ring.

4. The solder plating system of claim 3, further including a plug ring with an outer periphery smaller than the inner periphery of the peripheral ring such that the plug ring holds the locking extension abutted against the inner periphery of the peripheral ring.

5. The solder plating system of claim 4, wherein the housing further includes a backing plate interconnecting the central hub and the peripheral ring, the plug ring being secured to the backing plate with screws.

6. The solder plating system of claim 5, wherein the central hub includes an axial hold for mounting the carrier wheel on an axle.

7. The solder plating system of claim 6, wherein the locking extension includes a pin with a length larger than the diameter of the radial holes.

8. The solder plating system of claim 7, wherein the housing and each sprocket pin is formed of an acid resistant material.

9. The solder plating system of claim 8, wherein the plug ring is formed of an acid resistant material.

10. The solder plating system of claim 9, wherein the acid resistant material is nylon.

11. The solder plating system of claim 6, wherein the locking extension includes a flange with a diameter larger than the diameter of the radial holes.

12. The solder plating system of claim 11, wherein each sprocket pin includes an undercut between a shaft of the sprocket pin and the flange.

13. The solder plating system of claim 12, wherein the housing and each sprocket pin is formed of an acid resistant material.

14. The solder plating system of claim 13, wherein the plug ring is formed of an acid resistant material.

15. The solder plating system of claim 14, wherein the acid resistant material is nylon.