CFD study of flow boiling in silicon microgaps with staggered pin fins for the 3D-stacking of ICs

Flow boiling in surface-enhanced microgaps represents a promising thermal control method for the removal of relatively high heat fluxes in applications such as three-dimensional (3D) integration of microelectronics. Although a few experimental investigations have reported encouraging results for these types of cooling layers, the computational fluid dynamics (CFD) analysis of the involved physics has lagged behind due to a number of challenges. In the present study, a phase-change model is used with the Volume of Fluid (VOF) method for interface tracking to analyze the transient flow regime evolution due to boiling in a microgap with circular pin fins for area enhancement, where the simultaneous heat conduction is solved in the silicon medium. High-Performance Computing (HPC) is used for investigating two-phase flow and heat transfer in a relatively dense array of pin fins of 150 μm diameter populating a 175 μm height microgap, which is 10 mm long. The dielectric refrigerant R245fa is used as the coolant due to its negligible electrical conductivity, desirable for inter-tier cooling. Results provide useful insight on how the vapor phase is generated and distributed as a function of the axial direction, as well as the implication on heat transfer and resulting surface temperatures to identify trends and required conditions for the reliable operation in potential microelectronic applications.