Multi-purpose finish for printed wiring boards and method of manufacture of such boards

• US 20020015782A1
• Filed: 08/28/2001
• Published: 02/07/2002
• Est. Priority Date: 09/24/1999
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Brian T. Smith, Bruce F. Stacy, Chen Xu, Chonglun Fan, Joseph A. Abys
• Inventors: Smith, Brian T., Stacy, Bruce F., Abys, Joseph A., Fan, Chonglun, Xu, Chen
• Granted Patent: US 6,517,893 B2
• Time in Patent Office: Days
• US Class Current: 174/257
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/81444 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/85444 Gold (Au) as principal constituent
• CPC Class Codes: H01L 24/81 using a bump connector
• CPC Class Codes: H01L 24/85 using a wire connector wire bonding in general B23K20/004
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/207 Diameter ranges
• CPC Class Codes: H05K 2203/0571 Dual purpose resist, e.g. etch resist used as solder resist, solder resist used as plating resist
• CPC Class Codes: H05K 3/062 consisting of metals or alloys or metallic inorganic compounds H05K3/065 takes precedence
• CPC Class Codes: H05K 3/108 by semi-additive methods; masks therefor characterised by metallic etch mask H05K3/062; electroplating methods or apparatus H05K3/241
• CPC Class Codes: H05K 3/244 Finish plating of conductors, especially of copper conductors, e.g. for pads or lands selective plating methods H05K3/243; finish plating of conductors made by printing techniques H05K3/246; solder as finish H05K3/3457, e.g. by plating H05K3/3473
• CPC Class Codes: H05K 3/28 Applying non-metallic protective coatings H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673
• CPC Class Codes: H05K 3/384 by plating
• CPC Class Codes: Y10T 29/49144 by metal fusion
• CPC Class Codes: Y10T 29/49149 by metal fusion bonding
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 428/12528 Semiconductor component
• CPC Class Codes: Y10T 428/1275 Next to Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12875 Platinum group metal-base component
• CPC Class Codes: Y10T 428/12882 : Cu-base component alternative to Ag-, Au-, or Ni-base component
• CPC Class Codes: Y10T 428/1291 : Next to Co-, Cu-, or Ni-base component

Abstract

A printed wiring board (PWB) and a method of manufacturing the same. In one embodiment, the PWB includes: (1) a substrate having a conductive trace located thereon and (2) a multi-purpose finish including palladium alloy where palladium is alloyed with cobalt or a platinum group metal and is located on at least a portion of the conductive trace, which forms both a non-contact finish and a contact finish for the PWB.

Claims

1. A printed wiring board (PWB), comprising:

a substrate having a conductive trace thereon; and

a multi-purpose finish including palladium alloy, wherein palladium is alloyed with cobalt or a platinum group metal, said palladium alloy located on at least portions of said conductive trace, that forms both a non-contact finish and a contact finish for said PWB.

2. The PWB as recited in claim 1 wherein said palladium alloy is palladium-cobalt alloy and said palladium-cobalt alloy further includes nickel or iron.

3. The PWB as recited in claim 2 wherein said cobalt comprises about 1 wt. % or more of said palladium-cobalt alloy.

4. The PWB as recited in claim 1 wherein said palladium alloy is an etch resist layer.

5. The PWB as recited in claim 1 wherein said non-contact finish coats at least a portion of a non-contact area.

6. The PWB as recited in claim 1 wherein said contact finish coats at least a portion of a contact area.

7. The PWB as recited in claim 1 wherein said conductive trace is comprised of a metal selected from the group consisting of:

copper;

copper alloys;

aluminum;

aluminum alloys;

nickel;

nickel alloys;

silver;

gold; and

platinum.

8. The PWB as recited in claim 1 wherein palladium comprises a weight percent of said palladium alloy ranging from about 10 wt. % to about 95 wt. % and cobalt or a platinum group metal comprises a weight percent of said palladium alloy ranging from about 5 wt. % to about 90 wt. % of said palladium alloy.

9. The PWB as recited in claim 1 wherein palladium comprises a weight percent of said palladium alloy ranging from about 50 wt. % to about 95 wt. % and cobalt or a platinum group metal comprises a weight percent of said palladium alloy ranging from about 5 wt. % to about 50 wt. % of said palladium alloy.

10. The PWB as recited in claim 1 further comprising a material formed over said multi-purpose finish wherein said material is selected from the group consisting of:

palladium;

silver;

gold;

rhodium;

ruthenium;

platinum;

tin; and

organic solderability preservative (OSP).

11. The PWB as recited in claim 1 wherein an under-layer located under said palladium alloy comprises a material selected from the group consisting of:

nickel;

nickel alloys;

cobalt;

cobalt alloys;

iron; and

iron alloys.

12. The PWB as recited in claim 1 wherein said palladium alloy is located on all of said conductive traces.

13. The PWB as recited in claim 5 wherein said non-contact area is selected from the group consisting of:

a surface-mount pad,

a wire bond pad,

a solder pad, and

an interconnection.

14. The PWB as recited in claim 1 wherein said substrate is comprised of a material selected from the group consisting of:

epoxies;

polyimides;

fluorinated polymers;

ceramics;

polyesters;

phenolics; and

aramide paper.

16. The method as recited in claim 15 wherein said palladium alloy is palladium-cobalt alloy and said palladium-cobalt alloy further includes nickel or iron.

17. The method as recited in claim 16 wherein said cobalt comprises about 1 wt. % or more of said palladium-cobalt alloy.

18. The method as recited in claim 15 wherein said palladium alloy is an etch resist layer.

19. The method as recited in claim 15 wherein said non-contact finish coats at least a portion of a non-contact area.

20. The method as recited in claim 15 wherein said contact finish coats at least a portion of a contact area.

21. The method as recited in claim 15 wherein said forming comprises acid copper plating said conductive traces.

22. The method as recited in claim 15 wherein said depositing comprises plating said multi-purpose finish.

23. The method as recited in claim 19 further comprising surface mounting components to said non-contact area.

24. The method as recited in claim 19 further comprising wire bonding electrical components to said non-contact area.

25. The method as recited in claim 19 further comprising forming solder pads on said non-contact area.

26. The method as recited in claim 19 further comprising forming interconnections in said non-contact area.

27. The method as recited in claim 15 wherein said conductive traces are comprised of a metal selected from the group consisting of:

copper;

copper alloys;

aluminum;

aluminum alloys;

nickel;

nickel alloys;

silver;

gold; and

platinum.

28. The method as recited in claim 15 wherein palladium comprises a weight percent of said palladium alloy ranging from about 10 wt. % to about 95 wt. % and cobalt or a platinum group metal comprises a weight percent of said palladium alloy ranging from about 5 wt. % to about 90 wt. % of said palladium alloy.

29. The method as recited in claim 15 wherein palladium comprises a weight percent of said palladium alloy ranging from about 50 wt. % to about 95 wt. % and cobalt or a platinum group metal comprises a weight percent of said palladium alloy ranging from about 5 wt. % to about 50 wt. % of said palladium alloy.

30. The method as recited in claim 15 further comprising, forming a material over said multi-purpose finish, said material selected from the group consisting of:

palladium;

silver;

gold;

rhodium;

ruthenium;

platinum;

tin; and

organic solderability preservative (OSP).

31. The method as recited in claim 15 further including forming an under-layer on said conductive trace, selected from the group consisting of:

nickel;

nickel alloy;

cobalt;

cobalt alloy;

iron; and

iron alloy.

32. The method as recited in claim 19 wherein said non-contact area is selected from the group consisting of:

a surface-mount pad,

a wire bond pad,

a solder pad, and

an interconnection.

33. The method as recited in claim 15 wherein said substrate is comprised of material selected from the group consisting of:

epoxies;

polyimides;

fluorinated polymers;

ceramics;

polyesters;

phenolics; and

aramide paper.

15. A method of manufacturing a printed wiring board (PWB), comprising:

forming conductive traces on a substrate;

depositing a multi-purpose finish including palladium alloy, wherein palladium is alloyed with cobalt or a platinum group metal, on predetermined portions of said conductive traces; and

subjecting said PWB to an etching process, a portion of said multi-purpose finish remaining to form both a non-contact finish and a contact finish for said PWB.