Hermetic housings are required for the vast majority of electronics used in RF microwave electronics to protect the gallium arsenide and silicon devices from the environment. A common housing style includes a metal ring frame that is brazed onto a metal or ceramic base. The housing is populated with electronic devices and circuits and then hermetically sealed with a thin metal lid. For high volume manufacturing, lids are often attached by a resistance weld using a seam seal process. The interior hermitic volume is sealed at or near one atmosphere internal pressure. Since the housing may be subjected to a substantial number of pressure cycles that can yield the lid material, a low cycle fatigue evaluation is required to establish the long-term reliability of the hermetic housing. Kovar is a common lid and housing material because of a good coefficient of thermal expansion match with glass, ceramic and other materials used in RF circuitry. Unfortunately only high cycle fatigue data is available for kovar. A method is proposed to generate an estimate of high cycle end of the low cycle fatigue response from the high cycle fatigue data. The proposed method is verified by comparing a predicted fatigue life with experimental results from hermetic housings subjected to pressure cycling.

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