Interaction kinetics between PBGA solder balls and Au/Ni/Cu metallisation during laser reflow bumping

In this paper, the interaction kinetics between eutectic PbSn solder and Au/Ni/Cu metallisation of plastic ball grid array packages during laser reflow bumping were investigated. The effects of processing variables, including laser reflow power and time, on the morphology of the intermetallic compounds formed at the solder/pad interface were studied by scanning electron microscopy and energy dispersive X-ray spectrometry. Furthermore, dissolution and diffusion of Au and Sn inside the solder bump within the duration of the laser heating was analysed by Auger electron spectroscopy (AES). The results reveal that the morphology of the intermetallic compounds was strongly influenced by the laser input energy. The AES results showed that Au atoms dissolved rapidly into the solder after the solder was melted.