| Along with the electronic products constantly updated,the third generation of semiconductor started to be widely used in high temperature electronic packaging.Therefore it was an urgent demand for developing the novel tin based solder with the high temperature resistant and high strength properties.The research content of this article was mainly divided into two aspects:One was the composition design of Sn-Sb based lead-free solder.The composition of the Sn-Sb based alloy was determined by means of orthogonal experimental design.Meanwhile,the weldability and soldering technology of SnSbCuNiAg/Cu solder joint were analyzed.Another was to study the modification method of tin based lead-free solder by the addition of Cu nanoparticles,in order to further provide theory basis of the improved comprehensive performance of Sn-Sb based alloy.The influence of alloy elements on melting characteristics of Sn-Sb alloy were studied through a lot of experiments.The melting temperature,wettability and thermal conductivity were referred as the evaluation indicators,the composition of Sn-Sb based lead-free solders were made primary and optimum choice.After adding different content of Ag,Cu,Ni alloy elements as well as the high melting point of alloy into Sn-Sb alloy,the melting temperature were 221-242?.The three kinds of Sn-Sb based solders were selected as Sn-5Sb-0.5Cu-0.1Ni-0.1Ag,Sn-5Sb-1Cu-0.1Ni-0.1Ag,Sn-5Sb-0.5Cu-0.1Ni-0.5Ag.The microstructure of the SnSbCuNiAg/Cu solder joints were analyzed.With soldering from 10 s to 90 s at 280?,the thickness of interfacial IMC layer increased.With Cu and Ag content increasing,the growth exponent of IMC changed.When soldering 30 s at 280?,the shear strength for three kinds of Sn-Sb based solder joints reached the maximum value.The Sn-5Sb-0.5Cu-0.1Ni-0.5Ag/Cu solder joint had the highest shear strength.It increased by 36.4%compared with SAC305.When soldering 10 s to 90 s at 280?,the shear failure mode transformed from ductile fracture to ductile-brittle fracture.The hardness of three kinds of SnSbCuNiAg bulk solders were higher than SAC305.To refine the microstructure of solder,and further improve the mechanical properties of solder joints,the modification method of the tin based solder paste was studied by adding copper nanoparticles.It was found that 0.1-1.0 wt%nanoCu doped into SACBN solder had no appreciable influence on melting temperature of the composite solder.The addition of Cu nanoparticles refined the microstructure of bulk solder.After reflow and aging,the addition of 0.1 wt%-1.0 wt%Cu nanoparticles suppressed the growth of intermetallic compound layer at the interface.After the addition of 1.0 nanoCu,the interfacial IMC grains size of composite solder joint increased slightly compared with the pure solder joint.In addition,solder joints containing Cu nanoparticles displayed higher microhardness.However,the existing porosity in the solder joint exerted a negative effect on microhardness and shear strength.The mechanism of porosity formation was analyzed.Meanwhile,the effect of nanoCu content on the porosity was studied.Porosity increased markedly with increasing Cu nanoparticles proportion. |
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