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A water-cooled multi-die heat sink with parallel rectangular micro-channels was designed to satisfy the operational requirements of a multi-die processor. A shape optimization strategy based on the RSM (response surface method) was used to minimize pressure drop and die maximum case temperatures. The effects of the thermal interface materials and heat spreader between the dies and heat sink were captured by the numerical simulation. The optimization was performed for constant values of coolant flow rate and inlet temperature, as well as the power, location, and surface area of the dies. The influence of channel hydraulic diameter, Reynolds number, thermal entrance length, and total heat transfer surface area on the hydraulic and thermal performance of the heat sink was determined using CFD (computational fluid dynamics) simulations at RSM design points. A sensitivity analysis was performed to evaluate the effect of the design parameters on the response parameters. The optimum designs were achieved by minimizing a weighted objective function defined based on response parameters using JAYA algorithm. The results of weighted sum method were compared with Pareto based three objective optimization with a NSGA-II (non-dominated sorting GENETIC algorithm). Finally, a parametric study was performed to see the effect of the design parameters on the response parameters. 

Due to their lower pressure drop, impinging cold-plates are preferred over parallel flow cold-plates when there is no strict space limitation (i.e. when flow can enter perpendicular to the electronic board). Splitting the flow into two branches cuts the flow rate and path in half, which leads to lower pressure drop through the channels. A groove is used to direct the flow exiting the diffuser into the channels. The number of the geometric design parameters of the cold-plate will vary depending on the shape of the groove. In this research, the response surface method (RSM) was used to optimization the fin geometry of an impinging cold-plate with a trapezoidal cross section groove. The cold plate is used for warm water cooling of electronics. Three fin parameters (thickness, height, and gap) and three groove parameters were optimized to reach minimum values for hydraulic and thermal resistances at fixed values of coolant inlet temperature, coolant flow rate, and electronic chip power. 

Miniaturization of microelectronic components comes at a price of high heat flux density. By adopting liquid cooling, the rising demand of high heat flux devices can be met while the reliability of the microelectronic devices can also be improved to a greater extent. Liquid cooled cold plates are largely replacing air based heat sinks for electronics in data center applications, thanks to its large heat carrying capacity. A bench level study was carried out to characterize the thermohydraulic performance of two microchannel cold plates which uses warm DI water for cooling Multi Chip Server Modules (MCM). A laboratory built mock package housing mock dies and a heat spreader was employed while assessing the thermal performance of two different cold plate designs at varying coolant flow rate and temperature. The case temperature measured at the heat spreader for varying flow rates and input power were essential in identifying the convective resistance. The flow performance was evaluated by measuring the pressure drop across cold plate module at varying flow rates. Cold plate with the enhanced microchannel design yielded better results compared to a traditional parallel microchannel design. The study conducted at higher coolant temperatures yielded lower pressure drop values with no apparent change in the thermal behavior using different cold plates. The tests conducted after reversing the flow direction in microchannels provide an insight at the effect of neighboring dies on each other and reveal the importance of package specific cold plate designs for top performance. The experimental results were validated using a numerical model which are further optimized for improved geometric designs.