Vibration-induced droplet cooling of microelectronic components

This paper describes a unique two-phase cooling method that includes a closed heat transfer cell, similar to a thermosyphon that can be used to cool microelectronic packages. The cooling method is based upon a Vibration-Induced Droplet Atomization, or VIDA, process that can generate small liquid droplets inside a closed cell and propel them onto a heated surface. The VIDA technique involves the violent break-up of a liquid film into a shower of droplets by vibrating a piezoelectric actuator and accelerating the liquid film at resonant conditions. The droplets continually coat the surface with a thin liquid film, which evaporates on the heated surface, and the vapor is condensed on the internal surfaces of the heat transfer cell. The condensed liquid is returned via gravity to the piezoelectric actuator where it is again atomized. VIDA heat transfer cells ranging in diameter from 12 to 41 mm, which generate spherical droplets between 50 and 100 μm, have been constructed. Test data described in this study include the operating characteristics of the VIDA cell as well as preliminary cooling capabilities for a small-scale cell that is suitable for cooling a desktop microprocessor. The VIDA process produces droplets of relatively uniform diameter, and the droplets have sufficient momentum to reach the remotely located heated source. Heat fluxes as high as 40 W/cm² have been measured when a chilled water jacket is used as the external heat removal device