Effects of la addition on microstructure and mechanical properties of SN-58BI solders joints with osp pads
Journal
Canadian Metallurgical Quarterly
Journal Volume
52
Journal Issue
3
Pages
285-294
Date Issued
2013
Author(s)
Abstract
Rapid whisker growth was significantly alleviated in a Sn–58Bi alloy doped with 0·5 wt-%La. Experimental results showed that many thin, plate form intermetallic phases appeared in the solder matrix. The absence of tin whiskers was correlated to the shape effect of RE containing intermetallic plates. After reflowing, Cu6Sn5 intermetallic compounds appeared at the solder/pad interfaces of Sn–58Bi and Sn–58Bi–0·5La packages with OSP pads, which grow linearly during the aging at 75 and 100°C for various times ranging from 100 to 1000 h. In addition, the interfacial intermetallics layers in Sn–58Bi–0·5La solder joints were also observed thinner than those in undoped Sn–58Bi joints. However, RE containing interfacial intermetallic compounds in Sn–58Bi–0·5La solder joints led to lower bonding strengths in both ball shear tests (0·4 mm s−1) and high speed ball shear tests (2000 mm s−1). All the reflowed and aged solder joints of both packages were ruptured through the solder balls indicating brittle characteristic.
Type
journal article