Interfacial reaction between PBGA solder ball and Au/Ni/Cu pad during laser reflow

Interfacial reaction between plastic ball grid array (PBGA) solder ball and Au/Ni/Cu pad during laser reflow soldering was studied. Results show that the morphology of intermetallic compounds at interface is strongly influenced by laser input energy. When laser input energy was small, a continuous AuSn₂ layer and needle-like AuSn₄ are found at the interface. With the increase of laser input energy, all the continuous AuSn₂ layer converts into needle-like AuSn₄, and some needle-like AuSn₄ phases break off at the interface and fall into the solder. With the increase of laser input further, all the AuSn₄ phases disappear at the interface, distributing evenly inside the solder as small particles.