Interface evaluation of a Bi–Zn eutectic solder alloy : effects of different substrate materials on thermal contact conductance.

Abstract

Industry is searching for ways of improving the process control required for the manufacture of electronic circuitry. In this respect, a numerical mathematical model for thermal contact conductance of solder/substrate couples is developed based on an inverse heat conduction problem. The intention of this research is combining the model results and wetting experiments in order to determine if there is a compromise between them in the matter of the Bi–Zn eutectic alloy. Substrate materials considered as priority for the electronics industry were tested. It was found that the heat transfer coefficients (h) and the contact angles (θ) might be related to each other. The Bi–Zn/copper, Bi–Zn/nickel, Bi–Zn/Invar and Bi–Zn/steel couples, in this order, generated θ varying from the smallest to the largest as well as h from the largest to the smallest. Microstructural coarsening effect has been realized with higher spacing between Zn fibers (λZn) referring to a condition of worse heat extraction imposed by an alloy/substrate couple during solidification.