Evaluation of Indium Thermal Interface Material (TIM) Cross-Sectioning Methods on Lidded High-Performance Microprocessors

Voids, cracks, and insufficient TIM volume hinder heat dissipation and jeopardize reliability of lidded high-performance microprocessors. Non-destructive tests can effectively inspect voiding condition in TIM, but destructive cross-section is imperative for indepth analysis. Soft Indium TIM is sandwiched between hard Silicon die and Copper lid. Artifacts are hence inevitably induced on the TIM during mechanical cross-sectioning. In this paper, three cross-sectioning techniques were evaluated for Indium TIM in lidded microprocessors - mechanical grinding with wax-coated Silicon Carbide papers, focused ion beam and ion milling. Thorough investigation on the pros and cons of each technique was conducted, to conclusively select the most appropriate weighted to requirements of turn-around time, area exposed and surface finish quality.