Dissolution and interfacial reaction between Cu and Sn-Ag-Cu solders

In electronic packaging, the dissolution of the Cu layer of the under-bump metallizations or surface finishes during reflow is one of the most important processing concerns. Therefore, the objective of this study is to investigate in depth the dissolution of Cu into SnAgCu solders with various Cu concentrations. The effect of solder volume on dissolution rate will also be studied. In this study, solder balls of different concentrations Sn3AgxCu (x=0/0.3/0.5/0.7wt.%) and different diameters, 500 or 760 mum, are employed to study the influence of Cu concentration as well as the solder volume. It is found that the Cu concentration and solder ball volume have very strong effect on the Cu consumption rate. The different initial Cu concentration in the SnAgCu ternary solder changed the dissolution driving force. The results of this study suggeste that a high Cu-content SnAgCu solder can be used to reduce the dissolution of Cu pad.