Study of intermetallic growth on PWBs soldered with Sn/sub 3.0/Ag/sub 0.5/Cu

This paper describes the formation of intermetallic compounds at the interface and in the bulk of Sn3.0Ag0.5Cu reflow soldered on FR-4 PWBs. One plating system is organic solderability preservative (OSP) over bare copper and the other is immersion gold over electroless nickel (Au/Ni). The paper discusses the growth of these intermetallic phases after soldering, and after aging at 100 and 1000 hours at a homologous temperature of 0.85T/sub m/. In order to clarify the reliability of the bond between lead free solder (Sn3.0Ag0.5Cu) and copper pad, the mechanical properties such as shear strength, hardness, and elastic modulus of the intermetallics formed at the interface on printed wiring board was also investigated.