Nucleation and growth of intermetallic compounds on the prefabricated Cu6Sn5 layer

Abstract

In the 3D advanced packaging process, solder joints undergo multiple reflows and the intermetallic compounds will continue to grow on the Cu6Sn5 layer. However, the nucleation and growth mechanism of intermetallic compounds on the Cu6Sn5 layer is not clear. In this paper, the Cu6Sn5 layer was prefabricated on (001) Cu and the reaction between the prefabricated Cu6Sn5 layer and the Sn-based solder under the influence of solder composition was investigated. Results show that when the prefabricated Cu6Sn5 layer has a preferred orientation, the orientation can be retained after reflowing. When the orientation of the prefabricated Cu6Sn5 layer is randomly distributed, small Cu6Sn5 grains nucleate on the surface of the prefabricated Cu6Sn5 layer and grow along the <0001> crystal direction. Besides, the addition of Ag is beneficial to the heritability of orientation and inhibits the nucleation of small Cu6Sn5 grains on the surface of the prefabricated Cu6Sn5 layer.