Thermal testing methods for evaluating thin thermally conductive materials

New applications for computers and other electronic equipment demand higher levels of power in electronic components. This coupled with a drive toward smaller packaging and portable devices leads to an increase in power density which requires increasingly sophisticated thermal management systems. For maximum heat removal, heat sinks and heat pipes require a thermal interface material to efficiently couple the heat source to the heat sink. Many applications for high performance thermal interface materials involve the use of thin (1 mm and under) sheets of material. In order to predict material performance and compare various interface options, it is useful to quantify directly the thermal resistance across the material including the interfacial resistance between the thermal transfer material and heat source or the heat sink. One accepted standard for measuring thermal conductivity and thermal impedance, ASTM D 5470, can provide the results for a sandwich of stacked layers of thin materials. This approach can lead to errors and significant over-estimation of performance if the interfacial resistance between layers and the effect of thickness are not properly taken into account. An alternative method is proposed for measuring the thermal impedance and apparent thermal conductivity using a single layer of thermally conductive material in the thickness range of about 0.10 to 1.0 mm.