摘要:
随着系统级封装（SIP）所容纳的电子元器件和集成密度迅速增加，传统的散热方法（热通孔、风冷散热等）越来越难以满足系统级封装的热管理需求。低温共烧陶瓷（LTCC）作为常见的封装基板材料之一，设计并研制了三种内嵌于LTCC基板的微流道，其中包括直排型、蛇型和螺旋型微流道（高度为0.3 mm，宽度分别为0.4, 0.5和0.8 mm）。通过数值仿真和红外热像仪测试相结合的方式分析了微流道网络结构、流体质量流量、雷诺数、材料热导率对内嵌微流道LTCC基板换热性能的影响，实验结果表明：当去离子水的流量为10 mL/min,热源等效功率为2 W/cm2时，直排型微流道的LTCC基板最高温度在3.1 kPa输入泵压差下能降低75.4 ℃，蛇型微流道的LTCC基板最高温度在85.8 kPa输入泵压差下能降低80.2 ℃，螺旋型微流道的LTCC基板最高温度在103.1 kPa输入泵压差下能降低86.7 ℃。在三种微流道中，直排型微流道具有最小的雷诺数，在相同的输入泵压差下有最好的散热性能。窄的直排型微流道（0.4 mm）在相同的流道排布密度和流体流量时比宽的微流道（0.8 mm）能多降低基板温度10 ℃。此外，提高封装材料的热导率有助于提高微流道的换热性能。
Abstract:
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.
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