Thermomechanical Stress Analysis of Packaging Options for VCSEL Arrays

This work was conducted to examine the mechanical stress occurring within Vertical Cavity Surface Emitting Lasers (VCSEL) due to packaging deformation under Continuous Wave (CW) operation. The modeling of a VCSEL device in this thesis utilized finite element analysis methodology to examine the viability and optimization of packaging options from a mechanical standpoint. Previous works have analyzed the resulting thermal stress within a single VCSEL structure, or from the standpoint of optical alignment. However, little to no work has been conducted to examine VCSEL arrays and device packaging from a mechanical stress perspective. This thesis demonstrates the resulting stress within the VCSEL array device at temperature extremes necessary for qualification in industry. Stress is found to be below documented fracture levels for two sub-mount packaging arrangements. The second sub-mount design includes copper through vias and proved to increase the overall stress in the package. Analysis of a VCSEL device bonded directly to a printed circuit board (PCB) found the use of plated through vias within the PCB to most viable. While package deformation induced larger stresses than previous designs, the VCSEL die and solder connections remained below fracture and shear failure levels. This thesis further demonstrates the most significant and cost effective method to reduce stress in any packaging variation is through depositing solder onto the sub-mount rather than the VCSEL di