Investigation On Microstructure And Mechanical Property Of In-Sn Based Composite Solder TLP Joints

The preparation of solder joints that can be used for high temperature service at relatively low temperatures is the development trend of modern electronic packaging and the focus of the semiconductor industry.The lower melting point of In-48Sn solder not only facilitates low-temperature packaging,but also reduces the manufacturing cost of solder joints.Reinforced particles are selected to regulate the structure of solder joints and the growth behavior of intermetallic compounds(IMC)within the solder joints to enhance solder joint stability.Transient Liquid Phase(TLP)packaging technology is used to prepare high-reliability package solder joints,with a view to achieving high-reliability package solder joints for high temperature and complex service environments.In this paper,In-Sn-xAg solder were prepared by TLP technology.The effects of different Ag contents(20,30,40,50,60,70wt.%)on the microstructure,IMC layer,shear properties and fracture morphology of the solder joints were studied,and the better Ag particle addition was obtained.The optimized solder composition was used to optimize the bonding process parameters(including pressure,temperature,and time).The reaction mechanisms of intermetallic compounds,growth behavior of Kirkendall void,and solder joint shear properties were studied.On the basis of the above research,the effect of adding Ni-CNTs content(0,0.01,0.03,0.05,0.07,0.1 wt.%),on the microstructure,interface and mechanical properties of the solder joint was discussed.Cu/In-Sn-50Ag-0.07(Ni-CNTs)/Ni solder joints were prepared on the basis of the optimal solder composition.The microstructure,IMC growth behavior and mechanical properties of the solder joints under the interaction of Cu-Ni substrate were studied.The microstructure and mechanical properties of In-Sn-xAg(x=20-70wt.%)Solder joints were studied and the shear fractures of the joints were analyzed.The results show that the thickness of the IMC at the solder joint interface with the addition of 50 wt.%Ag particles is the most moderate.The IMC in the interface diffusion reaction zone is the Cu3(In,Sn)phase.The IMC in the in situ reaction zone consists of high-melting Ag particles + Ag3In phase.With the increase of bonding time,the AgIn2 phase is completely replaced by the Ag3In phase.With the increase of Ag content,the shear strength of the solder joints increased first and then decreased,the Cu/In-Sn-50Ag/Cu solder joint shear strength reached a peak value of 18.3 MPa.The shear fracture mechanism of solder joints changed from ductile-brittle mixed fracture to brittle fracture.The effects of process parameters on microstructure evolution,IMC growth behavior and mechanical properties of In-Sn-50Ag composite solder joints have been studied.The results show that compact solder joints are obtained by the bonding pressure of 3 MPa,bonding temperature of 260? and bonding time of 10 min for Cu/In-Sn-50Ag/Cu solder joints.The thickness of Cu3(In,Sn)IMC layer increases first and then decreases slowly with the increase of bonding pressure,and the growth rate of IMC can be greatly promoted by properly increasing the pressure.With the bonding temperature increasing,the interface IMC changes from Cu11In9 phase to Cu6(In,Sn)5 phase,and finally Cu3(In,Sn)phase is formed.The in-situ reaction zone is composed of AgIn2 phase + Ag particles + Sn particles+?-In3Sn phase + In rich phase,and Ag9In4 phase + Ag particles are formed gradually with the increase of temperature.Ag3In phase + Ag particles are completely formed when the temperature exceeds 260?.The shear strength increased first and then decreased with the increase of pressure,temperature and time.The fracture mechanism of solder joint changed from brittle fracture to ductile fracture.The effect of Ni-CNTs content on the microstructure and mechanical properties of composite solder joints was studied.The results show that the diffusion coefficient of composite solder was reduced by adding Ni-CNTs,which effectively inhibited the growth of Cu3(In,Sn)IMC layer,and the Cu3(In,Sn)IMC layer changed from scallop structure to double-layer structure.The coarse Ag3In phase in the in-situ reaction zone is obviously refined.CNTs react with solder matrix to form Ni3Sn4 phase to form stable connection.With the Ni-CNTs content increasing,the shear strength of the solder joint increases first and then decreases,the shear strength of the solder joint reaches the peak value of 41.5 MPa when the content of Ni-CNTs exceeds 0.07 wt.%.The shear properties of the solder joints are enhanced by the dispersion strengthening and load transfer of Ni-CNTs,and the fracture mechanism changes from the ductile-brittle mixed fracture to the ductile fracture.The structure,IMC growth behavior and mechanical properties Cu/In-Sn-50Ag-0.07(Ni-CNTs)/Ni solder joint are studied.The results show that there are significant differences in growth rates and micro structure of intermetallic compounds on both sides due to Cu-Ni interaction during the bonding process of the Cu/In-Sn-50Ag-0.07(Ni-CNTs)/Ni system.Cu3(In,Sn)intermetallics on the Cu side changed from scallop like to seaweed like.The intermetallic compounds on the Ni side were transformed from loose stacking Ni3Sn4 phase to compacted(Cu,Ni)6Sn5 layer.The IMC micrographs between Cu/solder and Ni/solder are different due to the different Jackson factors.With the increase of bonding time,the shear strength of solder joints increased first and then decreased.The shear strength of solder joints reached the peak when the bonding time exceeds 60 minutes.The shear fracture mechanism of the solder joints is brittle fracture,and the fracture location gradually moves from Ni base metal side to Cu base metal side.