Thermal and flow characteristics of device integrated metallic foam heat sinks with central impingement flow

Abstract

In this work, thermal and flow characteristics for the metallic foam heat sinks (FHSs) with the central impingement flow were studied with de-ionized water coolant. Such a flow configuration helps to reduce the pressure drop inherent for straight flow in porous foams. The reduction in the pressure drop is analyzed based on the one-dimensional porous medium model and verified with experimental measurement. The FHSs was fabricated and their thermal and flow characteristics were experimentally tested by integrating with a thermal test chip in BGA package format. The test chip has been built in with thermal diodes and resistors as heating source and junction temperature measurement. The foam materials were made of copper with the porosity ranging 60%-90% at the same pore density of 60 PPI (pores per inch), which were first brazed to the copper cavity and then assembled with a cover plate to form the flow channels. The cover plate was fabricated with an inlet slot at the center and two outlets at the two ends to provide a uniform impingement flow on the top of the foam. The idea is to split the fluid flow at the center of the heating component so that the pressure drop through the bulk foam material is reduced. As a result, the pressure drop is found to drop significantly without sacrificing the thermal performance for the present FHSs.