Filler-depletion layer adjacent to interface impacts performance of thermal interface material

When installing thermal interface material (TIM) between heat source and sink to reduce contact thermal resistance, the interfacial thermal resistance (ITR) between the TIM and heat source/sink may become important, especially when the TIM thickness becomes smaller in the next-generation device integration. To this end, we have investigated ITR between TIM and aluminum surface by using the time-domain thermoreflectance method. The measurements reveal large ITR attributed to the depletion of filler particles in TIM adjacent to the aluminum surface. The thickness of the depletion layer is estimated to be about 100 nm. As a consequence, the fraction of ITR to the total contact thermal resistance becomes about 20% when the TIM thickness is about 50 μm (current thickness), and it exceeds 50% when the thickness is smaller than 10 μm (next-generation thickness).