Manufacturing Process And Thermal Performance Analysis Of Ultra-thin Vapor Chamber

Performance degradation of the electronic components causing by high heat flux is becoming increasingly significant, with the microminiaturization and performance improvement of these components. Phase-change heat transfer devices are now widely applied on high-heat-flux components due to the high heat transfer efficiency. Vapor chambers(VCs), kind of phase-change heat transfer devices that can dissipate heat in two-dimension direction, have been gradually applied on high-performance components. Ultra-thin vapor chambers, which are thinner and with better performance, are required for the limited space in the electronic devices.Ultra-thin vapor chambers with 2.5 mm thickness and with two different wick structures were designed and optimized. Multi-artery powder-mesh composite sintered structre was employed as the wick structure at the evaporator zone. Copper mesh structure(namely, CMVC) and copper foam structure(namely, CFVC) were used as the wick structure at the condenser zone. Porosities of different wick structures were measured and the micromorphology and sintered state were observed by scanning electron microscope(SEM). The manufacturing processes of ultra-thin vapor chamber were investigated and optimized. A process route was established and several specific process parameters were normalized.Fluid motion within the wick structure was analyzed. Capillary performance of different wick structures was quantified, which showed that the copper foam wick exhibited the best capillary performance. Phase-change heat transfer mechanism within the vapor chamber was analyzed, simplified model of thermal resistance was established and calculated. The spreading resistnace exhibited the dominating factor(approximately 90%) in determining the overall thermal resistance. Theoretical thermal resistances of CMVC and CFVC were 0.238 K/W and 0.239 K/W, respectively. A water-cooled experimental device was designed and set up to evaluate the heat transfer performance of vapor chambers comprehensively. The heat transport capacity of the water-cooled module was verified via calculation and simulation.Samples with 3 charging ratios were fabricated for CMVCs and CFVCs and were tested by circulating water with 2 differnet temperatures, to investigate the effects of technological parameters on the heat transfer performance. Results show that performance improvement occurs while employing circulating water with high temperature, whereas the surface temperature of the heat source can also increase. The sample with a charging ratio of 95% performs the best amonst CFVCs, with a critical heat flux(CHF) over 180 W/cm2 and thermal resistance of 0.152 K/W. The sample with a charging ratio of 105% with CHF of 90 W/cm2 performs the best amonst CMVCs, but the advatages are slight compared to that with 90% charging ratio. In general, CFVCs perform better than CMVCs. Temperature uniformity of vapor chambers under low heat flux and natural convection condition were also measured by infrared thermal imaging(IRTI). Steady temperature increase and start-up time extension occurs in this condition, despite of the good temperature uniformity.