Adam Gregory Pautsch

Integral micro-channel liquid cooling for power electronics

A novel integral micro-channel heat sink was developed, featuring an array of sub-millimeter channels fabricated directly in the back-metallization layer of the direct bond copper or active metal braze ceramic substrate, thus minimizing the material between the semiconductor junction and fluid and the overall junction-to-fluid thermal resistance. The ceramic substrate is bonded to a baseplate that includes a set of interleaved inlet and outlet manifolds for uniform fluid distribution across the actively cooled area of the heat sink. The interleaved manifolds greatly reduce the pressure drop and minimize temperature gradient across the heat sink surface. After performing detailed simulations and design optimization, a 200 A, 1200 V IGBT power module with the integral heat sink was fabricated and tested. The junction-to-fluid thermal resistivities for the IGBTs and diodes were 0.17°C⋆cm2/W and 0.14°C⋆cm2/W, respectively. The design is superior to all reported liquid cooled heat sinks with a comparable material system, including the micro-channel designs. It is also easily scaleable to larger heat sink surfaces without compromising the performance.

100 Amp, 1000 Volt Class 4H-Silicon Carbide MOSFET Modules

The development of large area, up to 70m/1kV (0.45cm x 0.45cm) 4H-SiC vertical DMOSFETs is presented. DC and switching characteristics of high-current, 100Amp All-SiC power switching modules are demonstrated using 0.45cm x 0.225cm DMOSFET die and commercial Schottky diodes. The switching performance from room temperature up to T=200°C of the All-SiC modules is presented, with as much as ten times lower losses than co-fabricated Si-based modules using commercial IGBTs.

Heat transfer in microchannels: substrate effects and cooling efficiency for rectangular and circular ducts

Recent advances in electronics lead to smaller sizes and higher heat generation rates. Heat removal at a very tight thermal envelope is only possible with liquid cooling technologies such as the microchannel heat sink cooling. While a large number of studies have focused on experimental analysis, there is a limited number of computational data to understand the interaction between flow, material properties and geometric variables. Therefore, a computational study is performed to examine the hydraulic and thermal characteristics of microchannel heat sinks operating in laminar flow regime. Square and circular cross-sectional shapes are studied where the hydraulic diameter varies from 60 to 240 microns for water as the working fluid. The relationships and strengths for both conductive and convective thermal resistances, wall heat transfer coefficient and the maximum source temperature are presented through Pareto charts. It is found that the convection thermal resistance values comparably higher than the conduction resistance values due to high conductivity of the heat sink materials. Copper and Aluminum heat sinks demonstrate comparable performance as convective thermal resistance dominates over conduction thermal resistance. Finally, it is shown that the wall heat transfer coefficient values are more dependent on the geometrical features than the flow rate values. However, the maximum source temperature values show dependency on the geometry and flow rates as well as the thermal conductivity of the substrate.