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|Reliability of Electronics Assembled using SAC+Zn Solder Pastes|
|Keywords: solder, Zinc, reliability|
|A method of preparing SAC solder with addition of 1.0-1.5 wt.% Zn to Sn-3.8Ag-0.7Cu (SAC) solder alloy such that a standard solder paste reflow process results in good soldering is described. Solder-substrate couples were aged at 150 degC and 185 degC for 2000 h, and results on temperature cycling (-40 to + 180 C) and shear testing of solder joints is also described. The added Zn segregated to the interfacial IMCs so that Cu6Sn5 became (Cu,Zn)6Sn5 and (Cu,Ni)6Sn5 became (Ni,Cu,Zn)6Sn5. The reliability of assemblies utilizing Electroless Nickel Immersion Gold (ENIG) using the Zn enhanced solder is compared to that of standard SAC solder assemblies and it is found that the lower IMC growth rates of the Zn enhanced solder allow for reliable operation at temperatures up to 185 C.|
|Samjid Mannan, Professor of Materials Technology
King's College London