Reducing joint embrittlement in lead-free soldering processes

• US 8,191,757 B2
• Filed: 02/25/2008
• Issued: 06/05/2012
• Est. Priority Date: 08/24/2005
• Status: Expired due to Fees

• Current Assignee: Alpha Assembly Solutions Inc. (Element Solutions Inc)
• Original Assignee: Fry's Metals Incorporated (Element Solutions Inc)
• Inventors: Lewis, Brian G., Singh, Bawa, Laughlin, John, Pandher, Ranjit
• Primary Examiner(s): STONER, KILEY SHAWN
• Application Number:
  US12/036,604
• Publication Number:
  US 20080160310A1
• Time in Patent Office: 1,562 Days
• Field of Search: None
• US Class Current: 228/180.21
• CPC Class Codes: B23K 35/262 Sn as the principal constituent
• CPC Class Codes: H05K 1/09 Use of materials for the conductive, e.g. metallic pattern
• CPC Class Codes: H05K 2201/0355 Metal foils
• 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 3/3463 Solder compositions in relation to features of the printed circuit board or the mounting process
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

In the manufacture of products such as printed wiring boards or chip scale packaging and ball grid arrays, incorporating one or more elements selected from among Ni, Co, Cr, Mn, Zr, Fe and Si into a lead-free soldering process to reduce joint embrittlement. In varied embodiments this is accomplished by spraying onto a solder sphere or preform surface, by spraying onto a device substrate surface, or by incorporating into the device substrate alloy.

Claims

1. A method of forming a solder joint, comprising:

(a) providing a lead-free, tin-containing solder alloy;

(b) providing a printed wiring board substrate or a ball grid array substrate, said substrate being formed from a material comprising copper, and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof, and optionally also zinc;

(c) heating the solder alloy; and

(d) either before, during or after step (c) contacting the solder alloy with the substrate;

wherein said material of the substrate comprises 95 wt % or more Cu and at least one selected from among 0.04 to 5 wt % Zr, 0.04 to 5 wt % Fe, and 0.04 to 5 wt % Si; and

wherein the substrate is formed from one of the following alloy compositions (wt. %);

Cu-1Zr, Cu-2.35Fe-0.03P-0.12Zn, Cu-1.5Fe-0.18P-0.8Co-0.6Sn, Cu-0.6Fe-0.2P-0.05Mg, Cu-2.8Al-1.8Si-0.4Co, Cu-3.0Ni-0.65Si-0.15Mg, Cu-3.0Si-1.5Sn-0.1Cr.

4. The method of claim 1 wherein the lead-free, tin-containing solder is based on a Sn-Cu alloy including Ag.

5. The method of claim 1 wherein the lead-free, tin-containing solder is essentially free of Ni.

7. The method of claim 1 wherein the lead-free, tin-containing solder is essentially free of Ni, Co, Cr, Mn, Zr, Fe, and Si.

2. A method of forming a solder joint, comprising:

(a) providing a lead-free, tin-containing solder alloy , wherein the lead-free, tin-containing solder is essentially free of Ni, Co, Cr, Mn, Zr, Fe and Si;

(b) providing a printed wiring board substrate or a ball grid array substrate, said substrate being formed from a material comprising copper, and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof , and optionally also zinc;

(c) heating the solder alloy; and

(d) either before, during or after step (c) contacting the solder alloy with the substrate;

wherein the lead-free, tin-containing solder is based on a Sn-Cu alloy including Ag.

18. The method of claim 2 wherein the substrate comprises an electrodeposited foil or rolled foil bonded to a glass fiber epoxy laminate.

20. The method of claim 2 wherein the lead-free, Sn-containing solder is Sn-3.0Ag-0.5Cu (wt %).

3. A method of forming a solder joint, comprising:

(a) providing a lead-free, tin-containing solder alloy;

(b) providing a printed wiring board substrate or a ball grid array substrate, said substrate being formed from a material comprising copper, and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof, and optionally also zinc;

(c) heating the solder alloy; and

(d) either before, during or after step (c) contacting the solder alloy with the substrate;

wherein said material of the substrate comprises 95 wt % or more Cu and at least one selected from among 0.04 to 5 wt % Zr, 0.04 to 5 wt % Fe, and 0.04 to 5 wt % Si; and

wherein the lead-free, tin-containing solder is based on a Sn-Cu alloy including Ag.

6. The method of claim 3 wherein the lead-free, tin-containing solder is essentially free of Ni.

8. The method of claim 3 wherein the lead-free, tin-containing solder is essentially free of Ni, Co, Cr, Mn, Zr, Fe, and Si.

19. The method of claim 3 wherein the substrate comprises an electrodeposited foil or rolled foil bonded to a glass fiber epoxy laminate.

21. The method of claim 3 wherein the lead-free, Sn-containing solder is Sn-3.0Ag-0.5Cu (wt %).

9. A method of forming a solder joint, comprising:

(a) providing a lead-free, tin-containing solder alloy based on a Sn-Cu alloy including Ag;

(b) providing a printed wiring board substrate or a ball grid array substrate, said substrate being formed from a material comprising copper, and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof, and optionally also zinc;

(c) heating the solder alloy; and

(d) either before, during or after step (c) contacting the solder alloy with the substrate.

10. The method of claim 9 wherein in said material comprising copper and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof, each of said Ni, Co, Cr, Mn, Zr, Fe and Si has a concentration up to 3 wt %.

11. The method of claim 9 wherein the substrate comprises an electrodeposited foil or rolled foil bonded to a glass fiber epoxy laminate.

12. The method of claim 9 wherein said material comprising copper and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof comprises:

95 wt. % or more Cu

at least one of

from 0.04 to 5% Zr

from 0.04 to 5% Fe

from 0.04 to 5% Si

and optionally one or more of

0-0.5 wt. % P

0-0.5 wt. % Mg

0-0.5 wt. % Zn

0-2 wt % Co

0-3 wt % Sn

0-4 wt % Ni

0-0.5 wt % Cr

0-4 wt % Al

and any unavoidable impurities.

13. The method of claim 9 wherein said material comprising copper and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof comprises at least 95 wt % Cu and between about 0.5 and about 2 wt % Zr.

14. The method of claim 9 wherein said material comprising copper and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof comprises at least 95 wt % Cu and between about 0.3 and about 4 wt % Fe.

15. The method of claim 9 wherein said material comprising copper and one or more of Ni, Co, Cr, Mn, Zr, Fe and Si and/or alloys thereof comprises at least 95 wt % Cu and between about 0.3 and about 4 wt % Si.

16. the method of claim 11 wherein the lead-free, tin-containing solder is essentially free of Ni, Co, Cr, Mn, Zr, Fe, and Si.

17. The method of claim 9 wherein the lead-free, Sn-containing solder is Sn-3.0Ag-0.5Cu (wt %).