Interfacial reactions and mechanical properties of In–48Sn solder joint with electroplated Au/Ni ball grid array (BGA) substrate after multiple reflows

Abstract

The interfacial reactions and ball shear properties of an In–48wt%Sn solder joint with an electroplated Au/Ni ball grid array substrate were investigated with increasing numbers of reflows using scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectrometry, inductively coupled plasma-atomic emission spectroscopy, x-ray diffractometry, and bonding testing. After one reflow, two different intermetallic compound (IMC) layers, AuIn and AuIn2, were formed at the solder–substrate interface. The AuIn was completely transformed into the AuIn2 after three reflows. The AuIn2 IMC layer broke off, and a thin continuous Ni3(SnxIn1–x)4 IMC layer was formed between the molten solder and the exposed Ni substrate after four reflows. After 10 reflows, the AuIn2 IMC layer completely spalled off the substrate and the Ni3(SnxIn1–x)4 IMC layer was dissolved into the molten solder. These interfacial reactions greatly affected the shear properties of the solder joint.