Analysis of decline of silicon-aluminum alloy cavity air tightness

In this paper, based on the results of SEM and EDS analysis, there are two main reasons for Silicon-aluminum alloy cavity leakage. First, silicon-aluminum alloy material is unqualified; second, it produces cracks and pores during laser welding defects. In the test, silicon-aluminum alloy material is manufactured by powder metallurgy. It is pressure-type is not dense. In the uneven distribution of silicon particles can appear stress concentration, and the substrate itself do not close with the combination of silicon, in the material porosity increased, there may be no or only a few of the aluminum substrate distribution, but also for aluminum ductility is better than silicon ductility, lead to formation and extension of cracks. It is difficult to meet the electronic packaging air tightness. In the process of laser welding, the water on the surface of aluminum silicon alloy or not removed the film decompose to produce hydrogen under the instantaneous heat input of laser. Due to the hydrogen solubility in the solid and liquid aluminum vary widely, when laser welding molten pool start cooling, hydrogen solubility in the aluminum decrescent fast and hydrogen precipitate. Along the edge of the fusion many porosity, crack, and a certain extent coarsening the weld microstructure, which lead to a fall in the microwave cavity air tightness.