Investigation on Thermal Contact Resistance Between Indium and Cap in Packaging

A method of predicting the thermal contact resistance (TCR) between indium and cap (copper) in semiconductor package by finite element simulation is presented in this paper. The effect of different interface pressures and surface roughness on the thermal contact resistance of the cap and indium interfaces contact was investigated. The deformation of the cap and indium under the interface pressure was analyzed by the finite element method. It was found that due to the low yield strength of indium, the small protrusions on the copper cap can be directly pressed into the indium, which increases the actual contact area and leads to the decrease in TCR. Moreover, larger surface roughness reduces the actual contact area and leads to the increase of TCR. Analysis shows that the reduction of TCR can be achieved by increasing the interfacial pressure or smoothing the contact surface.