The Stirring Soldering Study Of Nano-Ni Enhanced Sn-Cu-Ag Hypoeutectic Solder

Eutectic and hypoeutectic Sn-Ag-Cu alloy is recognized as the most likely toreplace Sn-Pb alloy solder.This kind of solder is good at mechanical properties andwettability, however, the impact resistance of the solder joint is bad and easy tobecome brittle; especially, the solder with high silver increases the cost of thepackaging. The Sn-Ag-Cu hypoeutectic solders with low silver (wAg=0.1%~1.0%)are gradually drawing more concern from the electronics assembly industry, owing tothat low silver can reduce more than80percent of the solder cost, and the impactresistance is better, smaller tendency to be embrittled. In general, there are still somequestions of the hypoeutectic Sn-Ag-Cu solder. Such as poor mechanical property,serious oxidation being derived from higher soldering temperature (above260℃),and non-wetting, and so on.This paper takes Sn-0.68Cu-0.45Ag solder as the research object; the wettabilityof solder was improved by adding Nano-Ni particles; in order to reduce the oxidation,low-temperature soldering process (soldering between the solid phase region andliquid phase region) was used. In addition, the microstructure and the mechanicalproperties of Low-silver Solder joints was improved by Mechanical Stirring, Theresults showed:(1) There were no obvious mismatches between Nano-Ni (orNi3Sn4)and β-Sn.Both Nano-Ni and Ni3Sn4were regarded as Non-spontaneous nucleation core of β-Sn.They could only form the coherency interface with β-Sn, so that the starting-meltingtemperature of Low-silver Solder was brought down.(2) Nano-Ni particles added into Low-silver Solder, can improve the wettabilityand the filler capacities, making the composite solder soldering joint less defects thanthe Low-silver Solders’. Mechanical Stirring could remove surface oxidation film ofthe substrate, meanwhile, also broke dendritic structure and accelerated the diffusionof elements, and promoted the reaction between the Nano-Ni and the Cu6Sn5. Theheat issued from the reaction and loose holes (CuxNi1-x)6Sn5both promoted thegrowth interfacial IMC.(3) The interface IMC of the Low-silver Solder joint assisted by soldering fluxappeared Dissolve-ripple shape, and were made of Cu6Sn5, however, because ofStirring heat flux, the IMC of stirring-joint was hackly shape. when Nano-Ni particl-es were added into solder, the heat from reaction of nano Ni and Cu6Sn5wouldmutually counteract with Stirring heat flow, so that IMC changed from hackly shapeto straightness.In addition, which was made of the composition of Cu6Sn5, Cu3Sn andHole-shape (CuxNi1-x)6Sn5.(4) The IMC thickness of composite solder joint was significantly higher thanthe low silver brazing joint.The tensile strength. Under the same auxiliary weldingtechnology, shear strength of composite solder joint showed higher than the low silverbrazing joint. When Mechanical Stirring was imposed basis on soldering fluxauxiliary, the tensile strength and shear strength were increased by32%and24%respectively, compared with the matrix solder joint. (5) The Mechanical Stirring soldering process would be able to realize the jointbetween the Nano-Ni particles reinforced composite solder and aluminum matrixcomposites.