Thermal stresses in box-type laser packages

The effect of Au coating on thermally induced stresses in box-type semicond uctor laser packages was investigated by a finite-element method (FEM). The simulated results showed that Invar-Invar joints with Au coating have maxi mum stresses two times higher than joints without Au coating. This is due t o the different coefficients of the thermal expansion (CTE) between dissimi lar materials of Invar and Au, resulting in higher stresses. Maximum stress es were also found to be increased as the Au thickness increased. This effe ct is attributed to the increase in the thermal gradient in the welded regi on provided by the increased thermal conduction of the thicker Au coating l ayer. These results suggest that both the difference in CTE between dissimi lar materials and higher thermal conduction of Au coating layer have an imp ortant impact on thermally induced stresses for optoelectronic packages hav ing laser-welded Au coated materials.