Effect of Solder Volume on Interfacial Reaction between Sn-3.0Ag-0.5Cu Solder Balls and the Substrates

Abstract

Nowadays, with the continuous miniaturization of electronic packages, the solder balls used to join chips and substrates are downsizing. While the decrease in solder size may have a detrimental effect on the reliability of solder joints. In this paper, Sn-3.0Ag-0.5Cu solder balls were reflow soldered on two kinds of pads (Cu and Ni-P) to give a comparative study of the volume effect. Cu/Sn-3.0Ag-0.5Cu and Ni-P/Sn-3.0Ag-0.5Cu joints displayed volume effect of different forms. In the reaction of Cu/Sn-3.0Ag-0.5Cu, scallop-type Cu6Sn5 grains formed at the interface. The grain size and thickness of Cu6Sn5 IMC together with the Cu consumption were influenced by solder volume. In the reaction of Ni-P/Sn-3.0Ag-0.5Cu, different type of interfacial IMCs formed for solder balls with different sizes. Changes of Cu content in solder balls play an important role in both kinds of reactions.