Wave soldering bumping process incorporating electroless nickel UBM

The Si/Ti/Cu/electroless nickel/solder bump was produced incorporating wave soldering without flux. The most suitable wave soldering condition for depositing solder is presented. The material interactions occurring during wave soldering, afterwards reflow, and extended heat treatment were found to produce Ni/sub 3/Sn/sub 2/, Ni/sub 3/Sn/sub 4/, and Ni/sub 4/Sn compounds between solder and electroless nickel deposit. The thickness of electroless nickel deposit required for being the barrier layer of the solder bump was investigated by reflow process.