Effect of Au coating on joint strength in laser welding for Invar-Invar packages

The effect of Au coating on the joint strength, weld width, and penetration depth in laser welding technique for Invar-Invar packages is investigated experimentally. It is found that the joint strength, weld width, and penetration depth in the welded joints are strongly dependent on the Au thickness on the Invar material. The Invar-Invar joints with thick Au coating show narrower weld width, shallower penetration, and hence less joint strength than those of the package with thin Au coating. The increase in both the thermal conductivity and the vapor volume in the welded joints as the coating of Au thickness increases are the possible mechanisms for reduction of the weld width, penetration depth, and hence the joint strength. To the best of the authors' knowledge, this development of a new Invar-Invar package which combines the Au coating with laser welding technique has not been published yet.