The Study Of SnAgCu Nano Solder Paste

Sn3.0Ag0.5Cu lead-free solder paste has good thermos-mechanical properties,tensile strength,shear strength,yield strength and creep strength?It is considered to be one of the most promising alternatives to replace the traditionally used Sn-Pb solder.Howerer,this alloy composition possesses some weakness es,mainly as a result of its higher melting temperature compared to the eutectic Sn–Pb solders.The higher melting temperature leads to a series of challenges to the heat resistance of electronic package components and substrate materials.In this study,nanoparticles of Sn3.0Ag0.5Cu lead-free solder alloy were prepared by chemical reduction with Na BH₄ as a reducing agent.The size control of Sn3.0Ag0.5Cu nanoparticles and the theoretical analysis under different precursor species and synthesis conditions were focused.Finally its melting point and welding performance were studied.Study results are as follows:1.Effect of synthesis parameters on nanometer Sn3.0Ag0.5Cu nanoparticlesNanoparticles Sn3.0Ag0.5Cu lead-free solder alloy were successfully synthesized by chemical reduction.The effect of surfactant on the nanoparticles size and size distribution was studied.The result reveals that the larger ratio of the surfactant to the p recursor resulted in smaller particle size.Due to the capping effect caused by the surfactant molecules coordinating with the nanoclusters,a larger surfactant would restrict the growth of the nanoparticles until the surfactant concentration reached its critical micelle concentration?cmc?.Meanwhile,the effect of reaction temperature on nanoparticles size and size distribution was studied.The result shows that the lower reaction temperature resulted in smaller particle size.The higher reaction temperature leads to larger driving force which resulted in the more agglomeration.Finally we studied the effect of precursor's dropping speed on nanoparticles.The results shows that the particle size increased as decreasing the reduction adding rate,which can be explained by the competitive growth of the primary particles and second particles.2.Effect of precursor species Sn3.0Ag0.5Cu nanoparticlesThe study shows that different precursors have a significant effect on the morphology and size of nanoparticles.Compared three Sn's precursors,the nanoparticles synthesized by stannous acetate have the smallest particle size and the narrowest distribution.The nanoparticles synthesized by cupric acetate monohydrate among the three Cu precursors have the widest particle size distribution and the largest average particle size,which is improper for the synthesis of the Sn Ag Cu nanoparticules.The effect of C u SO₄·5H₂O and Cu?NO₃?₂·3H₂O used as Cu precursor shows little different.3.The study of Sn3.0Ag0.5Cu nanoparticles'size-dependent melting temperatureThe DSC result shows that the melting temperatures of Sn nanoparticles had strong size-dependent tendency.With the decrease in particle size,the melting temperature is significantly reduced and is generally lower than that of commercially available solder pastes.When the reaction temperature is 0?and the surface active agent is 3.0g,the melting point of the nanometer alloy is 199.1?,which is 18?lower than that of the commercial solder paste.The melting point of Sn3.0Ag0.5Cu nanoparticles can be predicted by Gibbs-Thomson equation.4.The study of Sn3.0Ag0.5Cu nanoparticles soldering propert y.The Sn Ag Cu nano solder paste was prepared by mixing nano-Sn3.0Ag0.5Cu alloy particles with an imported flux,and the soldering experiment was carried out.The results show that with applying pressure,the Sn Ag Cu nano solder paste prepared in this experi ment has successfully realized the interconnection between copper plates,and its tensile strength is 21.5MPa³4.3MPa,which shows excellent welding performance.