Manufacture of hourglass-shaped solder joint by induction heating reflow

Induction heating reflow method, which can achieve the solder bumping and interconnecting process in a simple way, was studied to control the height and shape of solder interconnects employed in electronic packaging application. A solder joint model was built to investigate the temperature distribution in the joint during the whole induction heating process by ANSYS software. Based on the simulation, the localized melting phenomenon is defined and identified by scanning electron microscope (SEM) observation. In this work, the barrel-shaped solder joints with high heights and the hourglass-shaped solder joints can be obtained which is useful to increase the solder joint lifetime. The mechanism of solder joint height and shape control, which can be explained by the local melt phenomenon, is discussed and demonstrated by the different morphologies of Ag₃Sn intermetallic compound (IMC). The findings of this paper will help to provide an understanding of the whole solder interconnecting process during induction heating reflow and the effects of electromagnetic field on solder interconnect shape controlling.