Evaluation of Absorbed Impact Energy of Sn-3.0Ag-0.5Cu (-xCo) Solder Joints with Co-P Plating a Using Ball Impact Test

Abstract

Sn-3.0mass%Ag-0.5mass%Cu (SAC) solder, which is widely used in Japan, has a relatively low impact reliability. This is because of the solder alloy hardness which induces a high stress concentration at the interface between the solder and the substrate. The impact reliability of the solder joint can be controlled by changing the composition of the under-bump metallurgy (UBM). This study aimed to determine the effect of electroless Co-P plating on the impact reliability of the solder joint using SAC, SAC-0.05Co and SAC-0.2Co solders. The intermetallic compound (IMC) layer formed at the interface between the three types of solder and the electroless Co-P plating was thinner than that of the SAC and electroless Ni-P plating. The hardness of the solders with electroless Co-P plating was lower than that with electroless Ni-P plating.The impact test results show that the solder joints with electroless Co-P plating are better at absorbing impact energy than SAC/Ni-P.