Application of Diffusion Brazing in Stockage of Vacuum Electronic Devices

The vacuum electronic device is the key components widely used in the fields of radar, navigation, electronic warfare and so on. Multi-brazing process is adopted in the manufacturing, and the leakage is easy to happen at many parts, such as brazed seams and base materials of tube shell, leading breakage of the devices. But now the brazing filler metal used in the stockage of vacuum electronic devices is very seldom. For the safe of vacuum electronic devices, stockage temperature must be lower than the brazing temperature. Gallium is liquid at room temperature, and has a lower vapor pressure. The Ga-based alloy can diffuse with the high melting point metal, and then form heat-resistance and a good sealing performance of solid-state alloys. In this study three kinds of Ga-based alloys used for the stockage were developed. The diffusion brazing for the stockage on three materials with defect, such as OFHC, kovar and Ag-Cu brazed seams was carried out. The influence factors such as parent materials, brazing filler metal and brazing temperature on the stockage quality were discussed. The results indicated that parent materials, brazing filler metals and brazing temperature had obvious influences on stockage. For OFHC and Ag-Cu filler with defects, the stockage effects were better than kovar. The effect of Ga-In-Cu alloy was the best because the compact diffusion layer was formed between the stockage brazing materials and base materials. As the brazing temperature went up, the diffusion layer formed between stockage material and OFHC, kovar became obviously thicker, the stockage effect got better. For Ag-Cu brazing seams, the stockage effect was satisfactory at 500 ℃, erosion will happen at the higher temperature.