Investigation of the thermal performance of micro-whisker structured silicon heatspreaders for power devices

Driving forces for developments in power electronics are the continuing miniaturization and enhancement of power densities. New packaging concepts are required allowing to dissipate loss power density levels of several hundred W/cm/sup 2/ at operation temperatures as low as possible. A promising attempt to decrease the thermal resistance to the ambient is the development of silicon substrates structured with microwhiskers perpendicular to its surface. An industrial application of this new heatspreader technology in power electronic modules makes necessary the specification of the substrate properties. In this work a new method for determination of thermal qualities based on laser heating of the heatspreader, surface temperature measurement by thermovision, and dynamic reverse modeling is described. For numerical determination of the thermal characteristics the measured data are evaluated with the help of a thermal model of the heatspreaders under various boundary conditions. The respective temperature distributions are calculated with a new simulation tool using an alternating direction implicit algorithm (ADI-method). Results obtained from heatspreaders with microwhisker treatment are compared with those from reference samples with a polished surface. Based on these results a view on future applications for power electronics assemblies are derived.