The visualized investigation of a silicon based built-in heat pipe micropillar wick structure

Abstract

With the drastically development of the power electronics in the new energy industry, the compact Multi Chip Module packages for the high power density devices became the future tendency. The wick structures inside the flat plate heat pipe, as the key element, have to be fully investigated. The flat plate heat pipe research was toward visualization, micro scaling, multi heat sources, and so on. In here, a thin silicon based plate heat pipe (0.85 mm thick) was constructed with the integrated 250 μm height square micropillar array wick structure. The wick structure was fabricated directly in the silicon substrate (0.35 mm thick) by the dry etching process. Since only 100 μm silicon substrate between the heat resource and the cooling structures, the heat dissipation efficiency could be remarkable strengthen. The silicon microfabrication process is compatible with the standard IC process. This integrated cooling structure could be suitable for many high-power transistor packages. Facilitated with the glass cover transparency, not only the vapor-liquid interfaces could be distinguished, but also the water liquid phase temperature could be measured by the Raman spectral shifting. The Volume of Fluid two-phase flow transient model was established to evaluate the self-adaptability of the micropillar array wick structure. The structure showed a good response for the two heat resources’ power fluctuation. By the nature logarithm linear fitting of the heating power and the heating frequency, the maximum heat dissipation power (21 ± 2 W) of the heat pipe under the stable operation state could be estimated.