An optimum approach for reduction of fiber alignment shift of fiber-solder-ferrule joints in laser module packaging

The results of experimental and numerical investigations leading to an optimum approach for the reduction of fiber alignment shift of fiber-solder-ferrule (FSF) joints in laser module packaging under temperature cycling test is presented. Using a novel image capture camera system as a monitor probe and the Sn-based solders as bonding materials, we have achieved the minimum fiber eccentric offsets of 8 and 20 mum in FSF joints with the PbSn and AuSn solders, respectively. After a 500-temperature cycling test, the fiber alignment shifts for these small initial fiber eccentric offsets of FSF joints were found to be 0.7 and 0.3 mum with the PbSn and AuSn solders, respectively. The measured fiber shifts were in good agreement with the numerical results of the finite-element method (FEM) analysis when both the residual stresses and the creep deformation within the solder were considered. This study have demonstrated that by soldering the fiber near to the center of the ferrule, and hence minimizing the fiber eccentric offset, the fiber alignment shifts of FSF joints in laser diode module packaging under temperature cycling test can be reduced significantly.