Flow boiling of HFE-7100 for cooling Multi-Chip modules using manifold microchannels

Abstract

Two-phase manifold microchannel heat sinks have gained significant interest for their efficient use of the coolant’s latent heat. Despite this, manifold microchannel flow boiling heat transfer has not yet been applied to wide-bandgap semiconductor power modules with multiple chips, primarily due to the complexity of the process and challenges related to electrical insulation. This study introduces a novel embedded manifold microchannel design that ensures uniform mass flow distribution, tailored for the thermal management of multi-chip power modules. The microchannels were laser-etched onto direct bonded copper (DBC) to reduce thermal resistance while maintaining electrical insulation. Thermal test vehicles (TTVs) for multi-chip power modules, featuring two different microchannel widths, were assembled using silver sintering. Experimental tests were then conducted using HFE-7100 as the coolant to evaluate two-phase heat dissipation performance. Results indicate that during flow boiling heat transfer, the temperature difference between chips in a power module strongly correlates with the exit quality. A higher coolant mass flow rate significantly reduces temperature variation between chips, particularly under high chip heat flux. At a coolant mass flow rate of 9 g/s, with a chip heat flux of 357 W/cm² and total heat dissipation of 536 W, the minimum thermal resistance reached 0.15 cm²∙K/W, yielding a COP of 1391. With a slight sacrifice in thermal resistance, 0.17 cm²∙K/W and 0.20 cm²∙K/W were achieved at mass flow rates of 6 g/s and 3 g/s, respectively. Correspondingly, the COPs reached 2179 and 6749. This research offers valuable insights for applying flow boiling heat transfer with dielectric coolants to cool multi-chip power modules.