Mechanical Characterization of Metal Foams for Contact Resistance in Thermal Interface Applications

We present a study on the effective mechanical compliance of porous aluminum foams. We develop an experimental setup to characterize the elastic properties as well as evaluate surface deformation with respect to porosity as well as pore size in an effort to correlate the properties to contact resistance of the foams when used as thermal interface materials. There have been multiple studies in the past to evaluate the effective elastic modulus of porous structure as a function of porosity through experimentation, simulation as well as analytic models. This work also serves as a validation for analytic and experimental data published by various researchers in the past. This study is one aspect of a larger study to empirically correlate the area of contact to thermal contact resistance. We evaluate samples with three different porosity and three different PPI (pores per inch) specification. Additionally we analyze effect of presence of filler material in the voids — a phase change material. The filler is used as separate stand-alone TIM in the industry currently.