In-Situ, Precise and High-Speed Measurement for Novel TIM Characterization

Due to the thermal compliance necessary for high-performance thermal interface material (TIM), precise thermal measurements are becoming more and more important. The interface thermal resistance of high-performance chips may easily exceed 30% of the total thermal resistance between chip and ambient. According to the general definition of thermal resistance, two surface temperatures and strictly accurate heat flow must be measured at the same time. The ASTM-D5470 method is suitable to do this. Clarification of the role of contact thermal resistance requires characterization of effective thermal conductivity of the material. This requires knowing accurate dimensions of cross section area and thickness. To achieve this fine measurement, equipment has been developed that enables the measurement of the thermal resistance with high accuracy as well as the measurement of interface thickness with sub-micrometer resolution in a simultaneous series. The thickness is determined by the optical pin-gap sensing method. Complete data can be obtained for each second after the data logging has started. The instantaneous temperature responses of TIM and heat rods take less time than the whole piece of equipment does to reach 99% temperature equilibrium. According to the data, sufficient accuracy can be obtained at local thermal equilibrium in around ten minutes to analyze the TIM performance in this measurement setup. Local small thermal mass plays a significant role in the measurement. This measurement technique is also helpful for pressure sensitive and soft TIM with minimum compressive creep deformation.