Investigation of weld cracking in Nd:yttrium–aluminum–garnet keyhole spot welding of materials used in optoelectronic packaging

The welding of a problematic optical device weld joint between dissimilar materials is investigated in depth. The original material combination of cold rolled steel 1010 with 6 μm of gold coating and 304 L produced consistent weld cracking. The CRS1010 material was fixed, however the other component was open to material selection. The materials tested were 304 L stainless steel, kovar, invar, and Carpenter high permeability 49 alloy. The effect of these different materials, laser pulse parameters, level of weld constraint, and thickness of gold plating on the CRS component are investigated to determine the key crack initiator. The results indicated that gold thickness is the key factor in the cracking mechanism, however weld volume and the level of weld constraint are also significant, with material selection a secondary factor. The use of pulse shaping had no effect on alleviating or reducing the extent of cracking.