Effect of fabrication parameters on capillary pumping performance of multi-scale composite porous wicks for loop heat pipe

In this study, a new multi-scale composite porous wick (MCPW) is proposed for the loop heat pipe to guarantee the thermal reliability of the microelectronics packages. The MCPW, which is featured with the nanostructures distributed on the sintered copper powders, can effectively enhance the capillary performance through modifying the properties of the copper powders. In this study, a number of MCPWs were developed by the sintering and alloying-dealloying treatment. Based on the infrared radiation (IR) thermal imaging method, the capillary rate-of-rise tests were used to the evaluate the capillary pumping performance, and the effects of the porous substrate and nanostructures were investigated in detail. The results indicated that morphologies of the copper powders, including powder size and powder type, would influence the capillary performance. The larger powder size and irregular type were better for liquid rise. Meanwhile, nanostructures on the powder surface played a dominant role in forming the hydrophilic surface on the copper powders, which could achieve the higher capillary height and rising velocity of working fluid for the wick. The optimum choice for the nanostructures formation was NaOH solution under the corrosive time 24 h.