Quantification of thermal contact conductance in electronic packages

Numerically obtained values of typical electronic package interface pressures are presented. Combining these predicted pressures and the results of previous investigations, the individual thermal contact resistances and overall package resistance were determined for an 18-lead plastic dual-in-line package constructed from typical commercially available materials. The results indicate that the summation of the contact resistances may make up as much as 43% of the total package thermal resistance for the packages investigated. The results also indicate that models in which these contact resistances are neglected may predict mean chip temperatures significantly below those actually present. The results also indicate that materials with thermal expansion coefficients below that of silicon tend to result in higher interface pressures and, hence, higher contact conductance than expansion matched materials. However, if placed incorrectly, these higher pressures can have a detrimental effect on the overall reliability of semiconductor devices