I N F L U E N C E O F A L L O Y I N G E L E M E N T S O N S N- 9 Z N S O L D E R B R A Z E D W I T H 6 0 6 1a L U M I N U M A L L O Y

Solder as an ancient way of welding is widely used.With the toxicity of Pb and national ban Pb legislative actions were implemented, traditional Sn-Pb alloys solder is limited.Sn-Zn lead-free solder has the potential to be replace traditional solder because of its low melting point and cost, advanced mechanical properties and Sn-Zn based lead-free solder because of the low melting point and cost, good mechanical properties is expected to replace the traditional solder. However, poor performances in oxidation resistance and wettability resistance limited its applications.In order to ameliorate the disadvantages of Sn-Zn lead-free solder.By adding elements of Cu and RE method was adopted to the Sn-9Zn alloy,and investigate of existing form and evolution mechanism.The results indicate that the exist of copper improve the the solder microstructure and copper are dispersed in the matrix. The form of the second phase consist of copper and zinc make it harder for zinc phase to grow up and be oxided. XRD results indicate that Cu Zn,Cu6Sn5 and Cu5Zn8 exists in the solder,but adding mass fraction of Cu with resulting compound is not proportional relationship,which slowly increase while it add greater than0.7%.Addition of Cu does not exist as the single phase, but the formation of low melting compound.In the analysis of welded joint, it is found that zinc enrichment phase in solder and spherical aluminum solid solution in dissolving diffusion zone shows a trend of growing up after the first decreases and copper content of 0.2% is a cut-off point. When welding joint have a good condition, solder of 0.3% copper have a best performance that the shear strength increased by 1.5 times. Fracture present a ductile fracture, and the source of fracture is zinc enrichment phase. It is thus concluded that copper zinc solid solution forming the second phase improve the strength of solder.The addition of La-Ce elements that utilize solution aging methods in Sn-9Zn alloy solder can improve the solder micro-structure, zinc enrichment phase was refined and the cluster speed of copper enrichment phase was reduced. All these make it harder for Cu6Sn5 to form. In fact that the addition of RE have little effect on zinc enrichment phase, but make a difference in reducing the diffusion of aluminum to solder and increasing the diffusion of solder to aluminum contribute to the adsorption between solder and aluminum.XRD diffraction analysis results indicate that the diffraction peaks is offset, in order to lattice Sn element has changed.It is found that the shear strength increase 11% with an optimal 0.2% Re in tensile tests. With the increase of RE from 0.1% to 0.2%, Fracture surfaces appear ductile fracture. A large amount of β-Sn produced in 0.4% RE because of Solder oxidation.