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

The driving forces of developments in power electronics are the continuing miniaturization and enhancement of power densities. New packaging concepts are required allowing the dissipation of a power loss density of up to seve ral hundred W/cm(2) at operation temperatures as low as possible. A promisi ng attempt to decrease the thermal resistance to the ambient is the develop ment of silicon substrates structured with microwhiskers perpendicular to i ts surface. An industrial application of this new heat spreader technology in power electronic modules makes necessary the specification of the substr ate properties. In this work, a new method for determination of thermal qua lities based on laser heating of the heat spreader, surface temperature mea surement by thermovision, and dynamic reverse modeling is described. For nu merical determination of the thermal characteristics, the measured data are evaluated with the help of a thermal model of the heat spreaders under var ious boundary conditions. The respective temperature distributions are calc ulated with a new simulation tool using an alternating-direction implicit a lgorithm (ADI-method). Results obtained from heat spreaders with microwhisk er treatment are compared with those from reference samples with a polished surface. Based on these results a view on future applications for power el ectronics assemblies are derived. (C) 2000 Elsevier Science Ltd. All rights reserved.