Effect of laser welding sequence on WIAD in packaging of dual-in-line laser modules

The tolerance of aligning a single mode fiber to a laser in a fiber pigtailed laser diode module is extremely tight, a sub micron misalignment can often lead to a significant reduction in the power coupled into the fiber. Among various fiber-optic assembly approaches, laser welding is the one with submicron accuracy and is most conducive to process automation. However, the solidification and materials shrinkage during the laser welding process lead to a relative movement of the pre-aligned components: the welding-induced-alignment-distortion (WIAD). The WIAD is a serious issue and may significantly affect the packaging yield. Our previous investigation has demonstrated that an elimination or minimization of the WIAD in a butterfly laser module package is possible if laser welding process: the welding sequence, can be optimized. In this work, by means of numerical method of finite element analysis (FEA), the influence of the laser welding sequence on the WIAD in a dual-in-line package (DIP) is investigated using a realistic physics based laser-materials interaction model. The model combines the spatial and temporal characteristics of the laser beam and the thermophysical properties of the material. It is found that the influence of the welding sequence on the WIAD in packaging of the DIP could not be neglected, the WIAD can be minimized by the proper design of the welding process, for both of the butterfly and DIP packaging.