Development of the micro capillary pumped loop for electronic cooling

Electronic devices have been minimized but the performance of those is becoming better and better. Therefore it is needed to develop new cooling methods suitable for a thin packaging structure with high thermal density. The thin flat plate type micro CPL(capillary pumped loop) with the thickness less than 2 mm was developed in this study. The proposed micro CPL has two staged grooves in evaporator instead of poles for preventing backflows of the vapor bubble and the simpler structure than that of a micro CPL with the poles. Also a large vapor space from the evaporator to the condenser was constructed in the middle plate therefore flow resistance of the vapor could be reduced. The micro CPL was fabricated using MEMS technology. The micro CPL was composed of lower, middle and upper substrates. The lower substrate was made of silicon and the middle and upper substrates are made of Pyrex glass for visualization. Through a preliminary test it was checked that there was no leakage at the adhesion interface between lower and middle or upper substrates and at the bonding interface between lower substrate and fill tube. Although the experimental studies for the micro CPL have been poor till now, we have obtained the reasonable experimental results in this study. The performance test result has showed 8.5 W of the heat transfer rate for the micro CPL and we could observe the operating characteristics of circulating or evaporating and condensing by visualization. Pure distilled water was used as the working fluid.