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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.42  No.5 (2001)  >  pp.739-744

MATERIALS TRANSACTIONS
<<Previous article Vol.42  No.5 (2001)   pp.739 - 744 Next article>>

Effect of Ag Addition on the Microstructural and Mechanical Properties of Sn-Cu Eutectic Solder

Seok-Hwan Huh1), Keun-Soo Kim1) and Katsuaki Suganuma1)
1) Institute of Scientific and Industrial Research, Osaka University

The effect of adding Ag up to 1 mass% on the microstructural and mechanical properties of Sn–Cu eutectic solder alloy was examined. Without Ag, primary β–Sn grains are surrounded by the eutectic network band of Cu6Sn5 needle precipitates/β–Sn. With increasing Ag content, the primary β–Sn grain size and the eutectic network size become finer. In the eutectic band fine Ag3Sn particles appear in addition to Cu6Sn5 precipitates. The DSC experiment revealed the presence of four endothermic reactions on heating for Sn–Cu–Ag alloys; the two peaks near 217°C correspond to the Sn–Cu–Ag ternary eutectic melting reaction and those at 223–225°C/224–226°C are for Sn–Cu binary melting. The 0.2% proof stress and tensile strength decrease with the addition of 0.1 mass%Ag and then gradually increase up to 1 mass%Ag. Even with 1% Ag, they are less than the values for a Sn–0.7Cu binary alloy. In contrast, elongation increases with increasing Ag content up to 1%. Thus, the addition of Ag to Sn–0.7Cu alloy can effectively improve its ductility. The strain rate dependence of 0.2% proof stress of Sn–0.7Cu–0.5Ag is similar to that of Sn–Ag eutectic alloy but is different from that of Sn–Cu eutectic alloy. A small amount of added Ag results in a change of the deformation mechanism of Sn–Cu alloy.


Keyword:
lead-free solder, tin-copper-silver alloy, mechanical properties, differential scanning calorimetry (DSC), strain rate

Received: November 30, 2000
Accepted: January 29, 2001 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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