Crack formation mechanism in laser-welded Au-coated Invar materials for semiconductor laser packaging

Crack formation mechanism in laser-welded Au-coated Invar materials for sem iconductor laser packaging is investigated experimentally and numerically. Experimental results obtained from metallography, scanning electron microsc ope (SEM), SEM mapping, and energy dispersive spectrometer (EDS) line profi le show that high concentration of Au composition accumulate near the crack region. The cause of Au accumulation may come from the segregation of Au a long the crack region. A finite-element method (FEM) is performed on the ca lculation of thermal stresses during spot-welding for An-coated Invar mater ials. Numerical results show that the high tensile stresses of the Au segre gation layer generated by rapid solidification shrinkage is:: the possible cause for crack formation. Both experimental and numerical results suggest that the crack formation mechanism investigated experimentally and numerica lly. Experimental results obtained from metallography, scanning electron mi croscope (SEM), SEM mapping, and energy dispersive spectrometer (EDS) numer ical results suggest that the crack formation mechanism in laser-welded Au- coated optoelectronic materials is directly related to the combined effects of the Au segregation and high tensile stresses induced by the strain shri nkage during the final stage of solidification.