Experimental study in thermal expansion devices of phase-change material coupled to vapor chamber with gradient wettability wick

With the rapid development of electronics and communication technology, the applications of high-performance chips and large-scale integrated circuits have become more and more widespread. Most electronic devices have low heat generation in standby mode but large heat generation during operation, and the instantaneous temperature rise is fast. The problems of resistance to thermal shock and heat dissipation have become the bottleneck of the development of electronic technology. Phase-change thermal control technology uses phase change materials to control the temperature of electronic devices with short-term high output power. It has the advantages of reliable performance, economical and energy saving. The temperature uniformity of the bottom surface is conducive to heat expansion in the interior of the phase change material, which is promoting to the phase ratio with the finite volume phase change material. In this article, a kind of novel thermal expansion device coupled PCM (paraffin OP50E) heat sinks with vapor chambers was proposed, which were applied with gradient wettability capillary wick. The copper microcolumns clusters as the capillary wicks in these vapor chambers were grown by electroplating on copper substrate plates covered with photolithography masks using the progressive current method. By changing the characteristic scales of the microcolumn clusters from 100 μm to 10 μm, the gradient capillary pressure direction was concentrated from the periphery to the middle, and the surface wettabilities of the capillary wicks were changed from hydrophilic to superhydrophilic. From the analysis of the experimental results, the vapor chambers with gradient wettability wicks can shorten the thermal response time of the thermal expansion device by 81.7 %, and at the same time, reduce the temperature at the center of the heat source with a heat flux of 40 W/cm2 by 6.8 °C, which can be applied to effectively control the central heat source temperature of the pulsed short-time electronic device.