Novel Method for In Situ Thermal Property Evaluation of Thermal Interface Materials

In integrated circuit packages, the thermal interface material (TIM) performance can be impaired by various defects. Voiding is one of these phenomena occurring in polymeric and liquid metal/low melt alloy TIMs. The interface material used between the silicon die and the internal heat spreader (IHS), TIM1, is the primary focus of this technology. This method of non-destructive testing of the TIM uses a modulated computational load applied to different computational cores or other electronic elements and the resulting temperature-dependent response is used to identify any defects. This sensing method uses changes in the current consumption of the transistors that are temperature-dependent (e.g. due to the leakage current). The heat source (q) to a core can be varied periodically using software stressors. This periodic core usage over a fixed area (A) at a known frequency (f) generates a temperature response around the heat source that depends on the thermal diffusivity (α) of the subsequent layers (TIM, spreader, heat sink). This periodic response can be used to detect different voids that occur in TIM1 and allows a thermal measurement of TIM1, as well as detection of TIM failures (e.g. voids). We will present experimental and simulation results.