Effect of Pin-Shapes on Chip-Embedded Two-Phase Cooling

Increase in demand for high-performance computing for modern AI applications is driving the need for high-power heterogeneously integrated 2.5D and 3D packages that cannot be thermally managed by conventional air-cooling approaches. Novel liquid cooling solutions such as inter-chip two phase cooling, which utilizes two-phase flow boiling of dielectric fluid through microscale cavities while being compatible with device function, 3D chip stack interconnects, fabrication and assembly, is required. In this work, previously developed high fidelity Eulerian multiphase model was used to compare the chip-embedded two-phase cooling performance of five different types of micro-fin shapes. The simulation unit-structure model consisted of a 200 um wide by 120 um high fluid cavity with either round (80 um diameter) or square (80 um edge) or diamond (80 um edge) or triangular (half-diamond) or rectangular (80 um x 120 um) shaped fins on 200 um uniform planar pitch and a 50 um wide by 100 um long inlet flow restrictor. Results showed that for the same mass flow rate, the square and rectangular fins resulted in the lowest device temperatures while triangular fins resulted in the highest device temperatures. The round pins have higher thermal resistance compared to rectangular pins but at lower pressure drop. The square and rectangular fins have relatively larger pressure at the front edge on the pins which ensures a liquid film around the pins resulting in reduced super-heating of the pins and bottom surface compared to other pin shapes. The triangular and diamond shaped pins showed much higher pressure drops and intermittent dry-out regions resulting in higher device temperatures. If pressure drop is not a constraint, then rectangular fins are preferable.