Degradation mechanisms of embedded cooling systems for high heat flux power electronics: Particle erosion of silicon and silicon carbide

Embedded cooling systems have enabled higher volumetric heat removal rates at the chip and package levels, permitting advanced power electronic devices to operate closer to their inherent electrical limits. By embedding microchannels directly into the chip or substrate, higher local and global heat fluxes can be reached as the heat removal takes place in close proximity to the source. As this emerging technology finds its way into aerospace, military and commercial applications, reliability will be of utmost importance. This paper will address the fundamental reliability concerns and degradation mechanisms associated with embedded cooling systems, specifically those pertaining to particle erosion. This mechanism has the potential to hinder the active cooling of the electronics by altering the microfluidic geometries and by subsequently restricting or blocking fluid paths due to the increased particle concentration in the fluid. A slurry erosion jet-impingement testing apparatus was constructed to investigate how factors such as particle size, particle concentration, impingement angle and velocity affect the erosion of single crystal silicon and silicon carbide. The test setup is capable of handling velocities up to 60 m/s, particle sizes ranging from the nanometer scale to tens of micrometers, impingement angles from 10 to 90 degrees, and is chemically compatible with a variety of working fluids including deionized water and propylene and ethylene glycols. The main goal of this research is to identify threshold velocities and threshold particle sizes under which no erosion will occur. Additionally, a procedure to develop a new model has been proposed which considers factors that current particle erosion models do not consider such as particle concentration and fluid viscosity.