Abstract
Effect of Cu core in BGA solder ball was investigated on the joint shear strength and the microstructural evolution after high temperature storage. When Sn-37Pb or Sn-36Pb-2Ag solder ball without Cu core was used, metastable (Au, Ni) Sn3 layer with high growth rate was formed on the bondline, which enhanced the formation of Pb layer in the solder. For Cu cored solder, equilibrium (Au, Cu, Ni) 6Sn5 reaction layer was formed and suppressed the Ni-Sn interaction. Because of the absence of Pb layer resulted from the slower growth rate of (Au, Cu, Ni) 6Sn5 reaction layer, Cu cored solder ball/pad joint was less degraded after high temperature storage.
