| In microelectronic packaging,solder joints not only assume the role of electrical interconnection,but also bear certain mechanical and thermal loads,and the failure of one solder joint may lead to the failure of the entire electronic component or even the device.Therefore,the choice of solder is critical to the reliability of electronic components.In this paper,lead-free solder Sn-1.0Ag-0.5Cu was used as the base alloy,and the effect of 0.5%Sb and 0.07%Ce element doping on the microstructure and properties of the solder was first investigated,and then the effect of rotating magnetic field on the microstructure and properties of SAC105-0.5Sb-0.07 Ce solder was studied.The main works are as follows.The effects of 0.5%Sb or 0.07%Ce doping on microstructure and properties of Sn-1.0Ag-0.5Cu lead-free solder were investigated.X-ray diffractometer(XRD)was adopted for phase analysis of the alloys.Optical microscopy(OM),scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)were employed to study the effect of the Sb or Ce doping on the microstructure of the solder.Then,the melting characteristics of solder alloys were characterized by differential scanning calorimeter(DSC),and the wettability of the solder alloys were estimated by the spread area and contact angle of the samples.Finally,the ultimate tensile strength(UTS),elongation(EL.%)and yield strength(YS)of solder alloys were measured by tensile testing machine.With the addition of Sb or Ce,the β-Sn and intermetallic compounds(IMC)of solders were refined and distributed more evenly.The pasty ranges of solders were reduced and thermal properties were improved.The contact angle was decreased and the wettability of the solder alloys was enhanced.With the addition of Sb,the ultimate tensile strength,elongation and yield strength of Sn-1.0Ag-0.5Cu increased by 15.3% 46.8%and 16.5%,respectively.The elongation of Sn-1.0Ag-0.5Cu increased by 56.5% due to Ce doping.The effect of the rotating magnetic field(RMF)on the microstructure and properties of Sn-1.0Ag-0.5Cu-0.5Sb-0.07 Ce alloy was investigated.The results showed that the size of β-Sn was refined and the distribution was more uniform,intermetallic compounds(IMCs)developed from long-strip-like or block shape to finely granular,and the layer spacing decreased after the application of a rotating magnetic field.The pasty range and the melting point of solder decreased slightly(from 5℃ to 4.7 ℃)with the RMF.Meanwhile,RMF processing led to an increase(about 13.4%)in the elongation(El.%)of alloy,and the mechanical properties of the solder were enhanced.The research serves as a helpful reference for the development of low-content lead-free solder,which provides a potential solution to the reliability problem of the lead-free joint. |
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