Article comprising a Pb-free solder having improved mechanical p

Details Article comprising a Pb-free solder having improved mechanical p Article comprising a Pb-free solder having improved mechanical p

1995-07-17

1998-06-09

Ip, Sikyin

Alloys or metallic compositions

Tin base

420562, C22C 1300, C22C 1302

Patent

active

057628661

ABSTRACT:
A high-strength Pb-free solder alloy, based on the Sn--Ag--Zn system, is disclosed. The Pb-free solder alloy contains, in weight percent, 0.2-0.6% Zn, 1-6% Ag, one or both 0.2-0.6% In and 0.2-0.6% Bi, and the balance Sn. The addition of Zn significantly improves the mechanical strength and creep resistance of e.g., Sn--3.5% Ag eutectic solder while maintaining substantially the same level of ductility. The increase in strength is as much as 48% over that of the Sn--3.5% Ag alloy. This strengthening from the Zn additions is attributed to a uniform solidification structure and a substantial refinement of the precipitates in the alloy. Essentially all of the added Zn resides in the more corrosion-resistant, Ag-based, intermetallic precipitates, leaving the Sn-rich matrix primarily free of Zn in solid solution.

REFERENCES:
patent: 1437641 (1922-12-01), Ferriere et al.
patent: 4670217 (1987-06-01), Henson
patent: 4695428 (1987-09-01), Ballentine
Irving, B., "Host of New Lead-Free Solders Introduced," Welding Journal, vol. 71, No. 10, Oct. 1992, pp. 47-49.
McCormack, M. T. et al., "Progress in the Design of New Lead-Free Solder Alloys," JOM, vol. 45, No. 7, Jul. 1993, pp. 36-40.
W. B. Hampshire, "Solders" Electronic Materials Handbook, vol. 1, pp. 633-642, (1989).

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