Corrosion failure analysis about package box of aluminum silicon alloy used for microwave module

A packaged microwave hybrid integrated circuit module is out of function when retested a few months later. The module using aluminium silicon alloy box with silver selectively plated in the inner surface, mainly passes through sealing by using epoxy resin bonding method and environment testing. Gray bubbling layers with full of white substances inner, are observed on the silver layer of aluminum silicon alloy box. The microstructure and chemical composition of the white substances and inner surface of gray bubbled layer are analysed by using SEM and EDX technology to investigate the failure mechanism of the package box. The results showed that the resin itself had certain moisture absorption, resulting in the poor humidity resistance of the package and micro-battery reaction between the plated silver layer and the aluminium silicon alloy in the packaged box. Micro-battery reaction resulted in spot corrosion of the aluminum silicon alloy material and generation of Al₂O₃ in the local performance. As time went on, a gray bubbling layer was formed by accumulation of resultant Al₂O₃. When the gray bubbling layer was large enough to rupture the bonding ribbon, the packaged microwave hybrid integrated circuit module was out of function. The improvement measures are also given in this paper. It can be concluded that micro-battery reaction between the plated silver layer and the aluminium silicon alloy under high humidity environment is the main failure cause of the package box of aluminum silicon alloy used for microwave module.