Effect of weld clip design on thermally induced angular misalignment in laser welding based optoelectronic packaging

Thermally-induced angular misalignment of fiber collimators in the laser packaging of optical devices is studied experimentally and numerically in this study. A novel design of arch-shaped weld clips is proposed and tested; after sustaining 10 consecutive accelerated thermal cycles, the proposed clips have been demonstrated to significantly lower angular misalignment, from the original error of 0.023° for a traditional saddle-shaped weld clip, to an improved 0.01°. A non-linear thermal-mechanical coupled finite element analysis (FEA) has also been used to simulate the variation of thermal stresses, the distribution of residual stresses, as well as the accumulated angular misalignment in the package. The results of the simulation have been found to be in full agreement with the experimental measurements. The calculation further indicates that the saturated angular shift is 0.043° for the proposed weld clip, dramatically improved from the 0.065° angular shift for a conventional saddle-shaped clip. The major angular misalignments come from the redistribution of residual stresses in solidification shrinkage, as well as the thermal stresses induced by temperature fluctuation within the package.