Fiber alignment shifts of fiber-solder-ferrule joints in butterfly laser packaging: measurement and finite-element-method analysis

Abstract

The fiber alignment shifts of fiber-solder-ferrule (FSF) joints in butterfly laser module packaging under temperature cycle testing are studied experimentally and numerically. 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 20mm in FSF joints with the PbSn and AuSn solders, respectively. The measured results showed that the fiber alignment shifts of FSF joints with the hard AuSn solder exhibited shifts two times less than that with the soft PbSn solder. The experimental measurements of fiber alignment shifts were in good agreement with the numerical calculations of the finite-element method (FEM) analysis. The major fiber shift formation mechanisms of FSF joints in temperature cycling may come from the localized plastic solder yielding introduced by the local thermal stress variation, the redistribution of the residual stresses, and the stress relaxation of the creep deformation within the solder.