Pool Boiling Enhancement via Surface Engineering for Thermal Management

Due to the escalating demands for computational power, coupled with a continuous reduction in the size of electronic packaging, thermal management for electronic devices has become increasingly critical in recent years. Ensuring that the temperature of electronic chips remains below a certain threshold is essential, since overheating can result in a decline in performance and chip breakdowns. To address the intensive cooling needs of heat-emitting chips, a variety of devices and methods have been explored, such as heat pipes, vapor chambers, pool boiling, spray cooling, and jet impingement cooling. Tailoring thermal and chemical characteristics of the target heated surface is one of the key factors in enhancing heat removal efficiency. This study highlights the critical role of employing advanced surface engineering techniques which particularly focuses on the integration of a novel semi-layered microporous copper structure, developed in conformity with a multi-level micro-cubic pin fin silicon substrate. The semi-layered microporous copper structure is fabricated using polystyrene sphere as the template to assist the electrodeposition of copper, with a low current density being employed to ensure meticulous fabrication. The initial gradient of the muti-level substrate is defined using silicon dioxide as the mask, setting the depth to encapsulate the PS template effectively. This foundational layer is crucial for confining the PS template securely in place. The second gradient is defined using photoresist as the mask to etch micro pin fin structures into the substrate, aimed at enhancing the adhesion between the substrate and the PS template and expand the heat exchange area. This meticulous structuring prevents the template from detaching during large-scale electroplating operations, ensuring the integrity of the micro fabrication process. The semi-layered microporous copper and the multi-level micro-cubic pin fin silicon substrate are both strategically designed to augment nucleation sites and enlarge the heat exchange surface area during the boiling heat transfer process within a pool boiling system. Further enhanced by the jet flow disturbances aimed directly at the heat transfer surface, facilitating rapid bubble removal and liquid replenishment, which contributes to delaying the onset of dry out. By employing Novec 649 as the coolant under a jet flow rate of 2.5L/min, we've reached a critical heat flux of 90/Wcm2 on a semi-layered microporous copper structure over a large heated area of 1.5 x 1.5 cm. This research provides valuable knowledge that can inform the development of highly effective surface engineering designs in high heat flux management systems.