微系统封装热问题探讨

Inquiry for Thermal Issues in Microsystems Packaging

电子机械系统微型化就是把不同功能的各种元器件封装到紧密空间,目的在于分析有关封装设计负载下降的方案。采用计算机程序配置发生器生成系统的热传递路径的几何构造和平面基板上热分布作为样本的方法,把这些构造的温度解决方案压缩进入快速估计公式中,使封装设计能够自由地进行相关的热传递分析。通过涉及到几何学方面复杂的传热路径的系统热传递分析,快速完成每个设计改变。结果表明系统微型化热设计,就是系统构造和整个向周围环境热损耗之间的耦合,就是热通过自然对流和辐射,从系统外壳上的一个区域向周围扩散。最后得出结论,外壳材料热传导性跨越的参数领域,以及系统的性能长度为系统级热传递领域,对系统的构造敏感。性能长度对塑料封装系统而言约为1 cm,对陶瓷及合金封装约为3~10 cm,在铜或铝金属包层系统为10~40 cm。

Miniaturization of electronic/ mechanical systems is achieved by packing different functional components into tight geometrically complex heat transfer paths. This paper proposes a concept that aims at reduction of analysis load on the packaging designer. The ways are used to generate possible geometric configurations of heat transfer paths in a systematic manner and the heat spreading on the planar substrate as an example. The temperature solutions for these configurations are compressed into fast estimate formulas that free the packaging designer from the need to perform involved. The results show that the miniaturization of system for the thermal design is the coupling between the system configuration and the overall heat dissipation to the environment. A model situation is considered where heat diffuses from a zone on the system shell and to the environment by natural convection andradiation. Therefore,the conclusion is made that in the parametric domain spanned by the thermal conductivity of shell material and the system＇s characteristic length there is a zone where the system-level heat transfer is sensitive to the system＇s configuration. Such characteristic length is around1 cm for systems encapsulated in plastics,3-10 cm for those in ceramic and alloy shells,and 10-40 cm in copper or aluminum clad systems.