Precision Optical Packaging of V-grooved Fiber Array by Lead-free Solders

 

Sheng-Quan Ou, Gu Xu, Yuhuan Xu, and K. N. Tu

Department of Materials Science and Engineering, UCLA

Los Angeles, CA 90095-1595

 

Abstract:

 

Wet-etched V-grooves along the [110] direction on (001) silicon wafers have been used in high precision alignment of fibers in optical-electronic devices packaging. Currently, epoxy is used to bond fibers to V-grooved chips, but it lacks long-term stability and reliability due to epoxy aging. In this work, we studied a novel method of bonding fibers to V-grooved chips by metallic soldering. Multi-layered metallic thin films were deposited on the surfaces of both fibers and V-grooved chips by e-beam evaporation. These metal thin films play a bridge role, producing good adhesion between the solder and the glassy surfaces of the fiber and the V-grooves. Three types of multi-layered metallic film coatings, Ti/Au, Ti/Cu/Au, and Ti/Ni/Au, were experimented. A lead-free solder, eutectic 43Sn57Bi (in wt %) having a melting point of 139C, was selected to bond the fibers and the V-grooved chips. Mechanical and optical tests show that the precision packaging by soldering has met the reliability in the required working-temperature range from 40 C to 85 C. Also, the metallic solder bonding is hermetic and can isolate the optical device from ambient environment.