ON PARAMETRIC ANALYSIS OF COLD SPRAY OF METALLIC COATING ONTO CERAMIC SUBSTRATES USING CERAMIC DAMAGE EVOLUTION APPROACH

Power electronics packaging plays a key role in the translation from robust mechanical systems, to more efficient electronic systems. One of the current power modules challenges is the direct bond copper process used to fabricate ceramic substrates. These substrates suffer high residual stresses from the high temperatures needed to bond metals to ceramics, which in combination with dissimilar coefficients of thermal expansion, lowers the reliability of electronics when thermally cycled. Substrate thickness is limited by the thermal excursion during the process, thus inhibiting high voltage (>20kV) operation due to low breakdown voltages. Cold spray has the potential to reduce stresses due to its low-temperature process nature. A thick, controllable coating of conducting metal can be obtained owing that bonding depends mostly on mechanical interlocking, eliminating the need to melt the materials. Cold spray on ceramics has not been widely studied and is an open research area due to the complexity of bonding soft metals to hard ceramics, known to be brittle with no plasticity at low temperatures. This work provides a parameter selection map resulting from parametric modeling of the process. Experiments were run to validate the numerical model on different substrate surfaces, deposition angles, standoff distances, and nozzle geometry.