In high-power electronics modules, the heat generated by the power devices is transferred to the ambient environment by attaching a heat spreader to the semiconductor package. Once the heat spreader is selected, it has to be attached optimally tothe semiconductor package to ensure efficient thermal management through the thermal interface. In most power electronics modules, solder or thermally conductive epoxy is used to eliminate the air gaps from the module-heat spreader thermal interface byconforming to surface irregularities; however, these bonding agents introduce interfaces and/or interlayers of finite thickness. While strong interfaces are necessary to ensure mechanical integrity of the bonded components, they are responsible forlowering the electrical and thermal conductivities of the assemblage. Thermal resistance of the joint is directly proportional to the interface thickness and inversely proportional to the thermal conductivity of the interface material as well as to thearea of the heat transfer. Moreover, these layers are quite nonuniform and consist of voids, which introduces anomalous thermal spreading. In this paper, interfacial thermal resistance of a few common attachment materials (solder and thermally conductiveepoxy with conductivity as high as 60W/m-K) between the power module and the heat spreader are characterized. Processing parameters such as time, temperature, and pressure conditions of the solder reflow and epoxy curing are varied to fabricate testsamples for subsequent comparison of the resulting interfaces.
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