Direct substrate cooling of power electronics

Liquid jet impingement can be used to efficiently generate high heat transfer coefficients for cooling. However, optimization of the jet impingement array is complicated as a large number of geometrical parameters, such as array size, jet spacing and jet diameter affect performance. In the studies described in this paper a custom designed half-bridge substrate tile, supporting two IGBT and two diode dies, is cooled using liquid jet impingement onto the underside of the active metal brazed (AMB) aluminium nitride substrate tile. In order to reduce redundancy in the cooling system, the impingement array is designed to directly target the hot spots on the underside of the tile. A number of jet impingement arrays are designed and compared in order to determine which impingement geometry provides the most effective cooling. The performance of each cooling array is presented as a function of temperature rise of the IGBT dies with fluid flow rate, pressure drop across the cooler and pumping power required. A 6 times 6 array of 0.5 mm diameter jets spaced at 2 mm is found to be the most efficient. At a pumping power requirement of 5 W the jet impingement cooler is able to maintain the IGBT dies at a temperature 22.38degC above the water temperature while dissipating 400 W of heat. Further experimental work is discussed.