PROJECTS  Design and Optimization of Water Cooled Heatsink

Water cooled heatsinks (cold plates) are often used for cooling of press-pack semiconductors. They allow considerably lower thermal resistances and reduced heatsink volume compared to air cooled heatsinks. In addition, this type of heatsink is more suitable for the high clamping force required in press-pack assemblies (high clamping pressure is crucial for good electrical and thermal contacts). Aluminum/copper or combinations of both are usually used.
In most cases, the heatsink is also used as the power terminal for the press-pack module. The electrical potential of the heatsink can therefore reach several kV (in MV and HV applications) and this requires using cooling fluid with high electrical resistivity.  Deionized water (with very low conductivity of ~ 0.5 µS) is often used as the cooling fluid for such applications. Deionized water is very corrosive and special attention to materials selection is required. In such cases, highly corrosion resistant aluminum (EN AW 6082) or stainless steel tubes are used.
As part of a development of new IGCT based converter, a new water cooled heatsink for 38-68 mm press-pack IGCT’s was developed.  The development process included mechanical and thermal optimization to achieve the required target values for thermal resistance, pressure drop, and structural strength. CFD (Computational Fluid Dynamics) simulations were used in the optimization process for accurate flow and thermal analysis and prediction of the heatsink performances (thermal resistance and pressure drop curves).