Development of a high-accuracy thermal interface material tester

An experimental apparatus has been designed and constructed to accurately measure the next generation of high-performance thermal interface materials with unprecedented precision and accuracy. The apparatus is based on a common implementation of ASTM D5470 using meter bars. However, the apparatus in the present study is unique in that it utilizes small thermistors to make precise thermal measurements (plusmn0.003 K). These measurements are used to calculate the thermal impedance at the interface of two conducting bodies while keeping input power at a minimum. Furthermore, a robust and conservative uncertainty analysis is employed to calculate how the measured uncertainties contribute to the calculated quantities of thermal impedance and effective thermal conductivity. Baseline tests are performed to demonstrate the sensitivity and uncertainty of the apparatus by measuring the contact resistance of the meter bars in contact with each other as a representative low-thermal- impedance case. A contact thermal impedance as low as 2.81E-5 m²ldrK/W was measured with a calculated absolute uncertainty of approximately 2%. The effective thermal conductivity of a gap pad was also measured to further validate the apparatus.