MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Effect of Au addition on Microstructural and Mechanical Properties of Sn-Cu Eutectic Solder
Seok-Hwan HuhKeun-Soo KimKatsuaki Suganuma
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2002 Volume 43 Issue 2 Pages 239-245

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Abstract

The effect of Au addition on the microstructural and the tensile properties of Sn–0.7 mass%Cu alloy was examined. Tensile strength and 0.2% proof stress remarkably increase up to 0.3 mass%Au primarily due to solid solution hardening. Beyond 0.3 mass%Au, due to precipitation of large intermetallic compounds, elongation decreases while tensile strength and 0.2% proof stress increase slightly. With Au addition to Sn–Cu binary alloy, the eutectic endothermic peak in DSC, i.e., the melting reaction at 227°C, becomes broader and shifts to the lower temperature range. With Au beyond 2 mass%, the broad peak becomes smaller splitting into two peaks and moving towards lower temperature while a new peak appears at about 212°C. These thermal reactions can be well explained by the formation of β-Sn, Cu6Sn5 and AuSn4 with Au more than 1 mass%. EPMA observation revealed that much amount of Au and Cu dissolve into Cu6Sn5 and AuSn4, respectively.

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© 2002 The Japan Institute of Metals and Materials
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