The Research Of Sn-Zn System Without Ag Lead-free Solder

Along with the implementation of the comprehensive prohibition law of world industry developed countries for containing Pb solder of the production and use on electronic field,the research and development of the lead-free solder has launched vigorously.Up to day,among the solders that,Sn-Cu solder has good mechanical properties and price advantage,so it is considered to the most potential substitutes for Sn-Pb solder.The purpose of this research is to develop good property and low cost lead-free solder.Therefore,the Sn-0.7Cu solder alloy was investigated in the paper by the addition of Bi,Ce and Ni,to get a better solder Sn-0.7Cu.In the research,the microstructure of the alloys and solder interface are observed, and some properties including melting,wetting,mechanical properties,shearing are tested.The relationships between the characteristic of the solder alloy and the concentration of Bi,Ce and Ni are further analyzed theoretically. The results show that:Bi is an effective alloying element for the melting temperature and wettabilities in Sn-0.7Cu alloy.The melting is depressed and wettabilities is increased follow Bi content is increased,when Bi content is 5%,the melting temperature is 220℃.Bi is an effective element in increasing the tensile strength,but the ductility has a sharp drop at the same time.When the Bi content increases,the rupture mechanism shows a transition from toughness to brittle.Rare earth Ce element was investigated in Sn-0.7Cu-3Bi solder;the adding of rare earth Ce element can be helpful to reduce the intermetallic compound in solders.Adding the rare earth element Ce is the best to depress the growth of the intermetallic compound Ce is not an effective alloying element for the melting temperature when Ce content is not above 0.1%.Below 0.05%with the addition of Ce,the wetting and the tensile strength are better.Above 0.05%,they are worse.The addition of Ni element has no remarkable effect on the melting point of Sn-0.7Cu-3Bi-0.05Ce.The wettability and ductility are increased follow Ni content is increased.The tensile strength is increased when Ni content is not above 0.05%,they are worse when 0.1%.For this research,the best content of the lead-free solder is Sn-0.7Cu-3Bi-0.05Ce-0.1Ni;it has best mechanical properties and wetting properties for these solders.The shear strength of Sn-0.7Cu-3Bi-0.05Ce-0.1Ni is better than Sn-3.0Ag-0.5Cu,but Sn-0.7Cu-3Bi-0.05Ce-0.1Ni is a little worse about the wettability.