Laser welding for hermetic sealing of large MIC package

A comparison of different methods for producing MIC (microwave integrated circuit) package sealing shows that laser technology provides the best results with regard to hermetic welding, especially with high-conductivity materials. A pulsed YAG:Nd laser is most suitable for numerous high-conductivity materials. For an MIC package, aluminum appeared to be excellent, owing to its mechanical, thermal, and electrical properties. Several approaches have been tested for cover-housing interface to achieve hermetic welds in aluminum structures. Realization of the cover with a high-silicon-content aluminum was found to be particularly advantageous. Welding was performed by directly joining the cover to the aluminum case without any interposed material. This solution is the simplest for large cases (>20 cm/sup 3/) of different shapes. The laser brazing of RF coaxial feedthroughs in filling holes of an aluminum case was also investigated.<>