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.
