Method of soldering portions plated by electroless ni plating

• US 20090218387A1
• Filed: 06/10/2005
• Published: 09/03/2009
• Est. Priority Date: 06/10/2005
• Status: Active Grant

• Current Assignee: Senju Metal Industry Company Limited
• Original Assignee: Senju Metal Industry Company Limited
• Inventors: Okada, Hiroshi, Kurata, Ryoichi, Soma, Daisuke
• Granted Patent: US 8,887,980 B2
• Time in Patent Office: Days
• US Class Current: 228/256
• CPC Class Codes: B23K 35/262 Sn as the principal constituent
• CPC Class Codes: H05K 2201/10734 Ball grid array [BGA]; Bump grid array
• CPC Class Codes: H05K 2203/072 Electroless plating, e.g. finish plating or initial plating
• 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

Abstract

When electrodes of a BGA plated by electroless Ni plating are soldered with solder balls of a lead-free solder, peeling of soldered joints readily takes place under an external impact. When a BGA electrode plated by electroless Ni plating is soldered with a lead-free solder to which 0.03-0.1 mass percent of P is added, the growth of brittle SnNi intermetallic compounds formed on the portion being soldered and a P layer on the electroless Ni plating surface is suppressed, resulting in an increased bonding strength.

Claims

1-10. -10. (canceled)

11. A soldering method comprising soldering a portion plated by electroless Ni plating with a lead-free solder comprising Ag:

1.0-4.0 mass percent, Cu;

0.1-1.0 mass percent, P;

0.04-0.08 mass percent, and a remainder of Sn.

12. A soldering method as claimed in claim 11 wherein the solder has a liquidus temperature of at least 250°

C., and at 250°

C., the proportion of P compounds in solid phase is at most 0.2% and the remainder is in a molten state.

13. A soldering method as claimed in claim 11 wherein the solder contains at most 1 mass percent of Ni.

14. A soldering method as claimed in claim 11 wherein the solder contains 0.015-0.2 mass percent of Ni.

15. A soldering method as claimed in claim 11 wherein the solder contains at most 15 mass percent of In.

16. A soldering method as claimed in claim 11 wherein the solder contains 0.1-1.0 mass percent of In.

17. A soldering method as claimed in claim 11 wherein the lead-free solder contains 0.1-1.0 mass % of In and 0.015-0.2 mass percent of Ni.

18. A soldering method as claimed in claim 11 wherein the lead-free solder is in the form of a solder ball with a diameter of 0.04-1.0 mm.

19. A soldering method as claimed in claim 11 wherein when a solder bump is formed on an electrode of a BGA substrate having a diameter of 0.61 mm by soldering a solder ball of the lead-free solder with a diameter of 0.76 mm to the electrode which has been plated by electroless Ni plating with a thickness of 5 μ

m and the solder bump is subjected to a pull strength test, the bonding strength of a soldered joint formed between the solder bump and the electrode is such that fracture does not occur in an interface between the solder bump and the electrode.

20. A soldering method as claimed in claim 18 including heating the solder ball to form a solder bump which is soldered to the plated portion, the solder bump having a bonding strength of at least 40 N in a pull strength test.