大尺寸LTCC器件在铝合金封装模块中的可靠性设计

Reliability design for soldering large-size LTCC component in microwave module with aluminum alloy package

在军用铝合金微波模块中焊接尺寸较大的LTCC器件时,由于热失配的存在,易出现应力过大甚至开裂。当采用陶瓷基板时问题更为突出。在此采用有限元分析方法研究了这类结构在温度循环过程中应力变化和分布的特点。研究结果表明,当采用陶瓷基板时,封装盒底厚度与其上各层结构(包括过渡层垫板,陶瓷基板和陶瓷元件)厚度的不合理匹配会导致陶瓷器件产生过高应力,可靠性降低。合理的设计应是减小过渡层垫板和陶瓷基板厚度,同时增加封装盒底厚度。

High stress and even failure problem, induced by thermal expansion mismatch, are usually observed in the soldered LTCC component in microwave module with aluminum alloy package, especially when ceramic substrate is used. The stress evolution and distribution of such structure were analyzed with finite element method. The results show that for ceramic substrate, too high stress primarily results from the mismatch of the thickness of package bottom and each architecture adhering to the bottom （such as stress transition layer, ceramic substrate and ceramic component）. Proper design strategy is to decrease in the thickness of stress transition layer and ceramic substrate, and increase in the thickness of package bottom.