Effective Thermophysical Properties of Thermal Interface Materials: Part I — Definitions and Models

Abstract

The conductivity of thermal interface materials are typically determined using procedures detailed in ASTM D 5470. The disadvantages of using these existing procedures for compliant materials are discussed along with a proposed new procedure for determining thermal conductivity and Young’s modulus. The new procedure, denoted as the Bulk Resistance Method, is based on experimentally determined thermal resistance data and an analytical model for thermal resistance in joints incorporating thermal interface materials. Two versions of the model are presented, the Simple Bulk Resistance Model, based on the interface material thickness prior to loading and a more precise version denoted as the General Bulk Resistance Model, that includes additional parameters such as surface characteristics and thermophysical properties of the contacting solids. Both methods can be used to predict material in situ thickness as a function of load.