Heat transfer performance of microchannels in LTCC substrate

With the obvious increase of integrating capacity and density in System-in-Package (SIP), it is more and more difficult for traditional cooling methods (e.g., thermal vias through substrate, air cooling) to meet the cooling requirements of high power application. Liquid cooling microchannels integrated into LTCC packaging substrate have been demonstrated as a competitive packaging substrate for SIP of high power applications. In this paper, heat transfer performance of microchannels embedded in LTCC packaging substrate for electronic cooling application is investigated. Proprietary process is selected to make LTCC microchannel samples. Three kinds of microchannels are designed and samples are fabricated, including serpentine, spiral and parallel microchannels. The effects of channel pattern, Reynolds numbers, flow rate and thermal conductivity of substrate on heat transfer performance of LTCC substrate are experimentally measured and simulated with commercial software COMSOL multi-physics. The heat transfer performance in term of maximum working temperature drop is measured with infrared thermometer. With the deionized water flow rate of 10 mL/min and equivalent power source of 2 W/cm2, parallel microchannel cuts the substrate temperature by 75.4 ℃ under inlet pressure drop of 3.1 kPa, serpentine microchannel by 80.2 ℃ under inlet pressure drop of 85.8 kPa, spiral microchannel by 86.7 ℃ under inlet pressure drop of 103.1 kPa. Among the three microchannel patterns, parallel microchannel has the smallest Reynolds numbers and the best cooling performance under the same inlet pressure drop. Narrow parallel microchannel (channel width 0.4 mm) with the same channel density and flow rate can cut substrate working temperature 10 ℃ more than the relatively wide microchannel (channel width 0.8 mm). Simulation results indicate that thermal conductivity of LTCC packaging substrate can enhance heat transfer performance by 13%. Results show microchannels embedded in LTCC substrate are suitable for thermal management of high power system.