Stereolithographically fabricated aluminum nitride microchannel substrates for integrated power electronics cooling

The presence of multiple thermally resistive layers in power electronics packages diminishes the enhanced convective benefit of high-performance microchannel cold plates. One improvement reported here is the development of stereolithographically defined aluminum nitride (AlN) microchannel integrated coldplates as substrates for power electronics packages. High-resolution fabrication of green ceramic parts using a standard stereolithography machine has been enabled by the development of photosensitive ceramic materials. Complex microchannel integrated AlN substrates with simplified fluid connections have been produced with 2-3 mm channel height and channel width down to 200 mum. This structure bypasses the majority of the traditional thermal stack, bringing the coolant closer to the heat source. The substrates were packaged and tested with 4 mm Silicon Carbide pin diodes as heat sources at pressure drops from < 1 kPa up to 70 kPa (10 psi) and power levels exceeding 80 W (500 W/cm²). Measured total thermal stack resistivity on best performing devices was about 0.1 K-cm²/W at 70 kPa (-10 psi) and 0.14 K-cm²/W at 5 kPa (-0.7 psi). Paths for further performance improvement, broadening of fabrication possibilities, and transition to real-world systems are briefly discussed.