Development of Combined Cooler with Additively Manufactured Planar Magnetics

There are strong incentives to reduce the size of advanced power electronics, such as high-frequency converters. Reduced system size often lowers parasitic losses, system weight, and system cost. Two items significantly limiting such reductions in size, however, are the following: 1) the dimension of magnetic devices such as transformers; and 2) the size of the cooling system, including heat sinks, required to dissipate the heat generated in the transformer windings. This paper will present an advanced transformer configuration that allows for significant volume reduction by using additive manufacturing (AM) to deposit planar transformer windings on a thermally conductive combined-core-and-coil (C3) cooler substrate. The candidate material of the C3 cooler is ceramic, as it needs to be electrically insulating but thermally conductive. The C3 cooler is additively manufactured using selective laser sintering (SLS) technology, so as to have channels for liquid cooling inside. Windings are deposited on this cooler substrate by syringe printing and sintering of nano-silver (nano-Ag) and other conductive pastes, making the design flexible and sustainable. These planar transformer windings spiral with 45° angles between each straight segment. A minimum spacing of 0.45 mm between the windings has been achieved without shorting. This paper will also detail the effect of the sintering process times and temperatures on electrical resistivity and adhesive bonding strength. Microstructural evolution in the sintered paste will also be addressed.