| Abstract |
This paper describes an innovative method for the removal of heat from senliconductor power modules operating at ultra-sonic frequencies. In such applications switching losses are often so high that air cooling is inadequate, and liquid cooling must be used. Traditionally, this is achieved by bolting a standard module onto a liquid-cooled heat exchanger. While more effective than air cooling, a thermal barrier still exists between the module baseplate and separate heatsink, and this contributes significantly to the total junction -to-ambient thermal resistance.
To elinlinate this barrier, APT Europe has engineered an integral liquid cooled (ILC) power module package, where the module baseplate doubles as tl1e liquid cooled heat exchanger's upper lid. In this way, the cooling medimn is in direct contact with the module baseplate, and there is no interface. To illustrate the dramatic improvements in performance made possible by this approach, the thermal performance of air and liquid cooled power MOSFET switches, with the same silicon real-estate, is compared. Data is presented to illustrate the influence of flow rate on thermal resistance, and the impact of the choice of baseplate material on long term reliability is also analyzed. The design is such that, in the event of module failure, the heat exchanger portion can be reclaimed for further use. |
