Nano-Ag Particles Affect The Melting Characteristics, Solderability And Reliability Of Sn3.0Ag0.5Cu Solder

Nowdays,the development of electronic packaging tends to the high integration,high power consumption and low packaging size,which requires higher weldability and reliability of solder.In recently years,the research and development of nano composite solder with high weldability and high reliability has become one of the topics in the research about electronic packaing solder.Due to the application of nano-composite solder is still in its infacy,there are few researches on the preparation,storage,welding,service and recovery of composite solder.In this paper,starting from the preparation of composite solder paste,the problems of nano phase escape,bubble formation and growth,solidaifaction and nucleation of solder joints,thermal properties and wettability of solder are studied,and so as to study the weldability and reliability of the composite solder.In this paper,SAC3005/?0.01-0.5?Ag composite solder paste were prepared by mixing and blending,then the composite solder alloy and composite solder joints were prepared.The phase diagram and solid solubility was calculated by Thermo-Calc software.Electronic density balance was used to test and analyze the influence of nano-Ag particle content on the density about composite solder alloy.XRD,SEM and metallographic microscope were used to observe and analyze the influences of nano-Ag particle on structure,distribution,morphology and size of solder joint matrix and interface layer.DSC was used to test and analyze the influence of nano-Ag particle on the thermal properties about the solder alloy.The weldability tester was used to test and analyze the influence of nano-Ag particle on the weladability of solder alloy.The influence of nano-Ag particle on the qualification rate of solder joints and the bubble growth was analyzed by the nondestructive flaw detector.And influence of nano-Ag particle on the nucleation and growth of solder joints microstructure was emphatically analyzed.The results indicate that:?1?During welding,the nano-Ag particle will be partially alloyed and converted into Ag₃Sn phase.When the nano-Ag particle are combined with?-Sn phase,the transition layer with width of 2-5 nm is easy to appear at the grain boundary of nano-Ag particle/?-Sn,and the atomic ratio of Ag:Sn in the transition layer is close to 3.?2?The higher the addition of nano-Ag particle,the lower the percentage of nano-Ag particle escaping from the solder joint.The addition of nano-Ag particle may aggravate the phenomenon of“solder bead splashing”.?3?After aged at 100?for more than 150h,the bubbles of solder joint no longer grow.Nano-Ag particle can not hinder the growth of the bubbles from solder joint,but promote the growth of the bubbles.?4?After adding nano-Ag particle,the?-Sn lattice of the solder joint has distorted.While the addition amount is 0.1 wt%,themicrostructure of the solder joint matrix and interface layer is refined and the growth rate is reduced,and the refinement effect is most obvious.The undercooling of the solder alloy decreased first and then increased.While the addition amount is 0.1wt%,the undercooling required for the solder alloy solidification was the lowest,and the matrix microstructure grow in an equiaxed manner.The weldability of the solder increases with the addition of nano-Ag particle.When the addition amout is 0.5 wt%,the weldability of the composite solder is best.