CHARACTERIZATION OF PROTOTYPE HIGH TEMPERATURE LEAD-FREE SOLDERJOINTS FROM COPPER-NICKEL/TIN-ALLOY COMPOSITE PASTE PRODUCED BYLIQUID PHASE DIFFUSION BONDING

摘要

Initial research that produced model joints from a Cu-Ni/Sn-alloy powder composite to develop a "drop-in" replacement for the currently-used Pb-based high-temperature solder (Pb-5Sn, wt.%) provided enough evidence to support compounding of a paste prototype by our industrial partner. The prototype paste uses experimental gas-atomized Cu-10Ni, wt.%, powder that was blended with commercial SN100C (Sn-0.7Cu-0.05Ni+0.01Ge, wt.%) solder powder and compounded with a typical flux and solvent to form the paste. Joint porosity was investigated as a function of powder blend ratio. Test temperatures exceeding pure Sn melting were enabled by liquid-phase diffusion bonding (LPDB) of the composite solder components, creating a Ni-modified Cu_6Sn_5 matrix phase (T_m~525°C) that bonded the high-strength, highly-conductive filler of Cu-10Ni powder particles. Results of composite solderjoint tests began to explore highly-elevated maximum service temperatures of greater than 450°C.