EFFECT OF THIN-FILM COATING OF AU ON JOINT STRENGTH IN INVAR-INVAR PACKAGES

The effect of a thin film coating of Au on the joint strength, weld wi dth, and penetration depth in laser welding techniques for Invar-Invar packages is investigated experimentally. It is found that the joint s trength, weld width, and penetration depth are strongly dependent on t he coating of Au thickness on the Invar material. The welded joints wi th thick Au coating show narrower weld width, shallower penetration, a nd hence less joint strength than those of the packages with thin Au c oating. The increase in both the thermal conductivity and the vapor vo lume in the welded joints as the coating of Au thickness increases are the possible mechanisms for the reduction. Detailed knowledge of the effect of thin film coatings of Au on the welded materials, which give s both the highest joint strength and good adhesion, is essential for practical design and fabrication of reliable optoelectronic packaging.