Thermal Interface Material Test Rig

Thermal interface materials are usually characterized using ASTM standard D 5470. The standard calls for thermal resistance measurements across materials of known thickness. By measuring materials of different thicknesses, a procedure is available for separating the fraction of the joint resistance associated with bulk properties and the fraction attributed to contact resistance. The standard assumes that materials do not change thickness during the test sequence, either due to mechanical loading or from thermal expansion.

Compliant thermal interface materials do not generally adhere to these constraints. To accurately measure the material thickness as it changes during testing a thermal interface test rig has been designed and manufactured in the MHTL. The system uses a Mitutoyo LSM 503H laser micrometer to measure in-situ thickness during the dynamic loading of the TIM. For most materials, submicron thickness measurements are possible.

One inch square samples can be tested over an operating range of 10 - 90 C mean interface temperature, 10 - 1000 psi interface pressure for heat fluxes up to 16 W/cm².

Thermal conductivities are then accurately determined based on the material thermal resistance and the actual thickness of the sample during the testing sequence.