Development And Properties Of Nanoparticle Reinforced SnCu Solder

With the rapid development of electronic packaging technology and the popularization of lead-free solder,higher requirements have been placed on the reliability of solder joints,leading to the development of new lead-free solders becoming one of the hot research directions in the field of electronic package soldering.In this paper,SnCu solder is selected as the matrix solder,a composite solder containing nano-SnO₂ particles and Ag particles was prepared by ultrasonic-assisted melting and mechanical stirring.The microstructure,melting properties of the composite solder,and the growth behavior of the IMC layer at the interface of the brazed joint and its influencing mechanism were studied,and the shear strength of the brazed joint was also explored.Comparing the composite solder obtained by the mechanical stirring method and the ultrasonic-assisted melting method,it is found that the microstructure of the solder obtained by the ultrasonic-assisted method is fine,β-Sn is equiaxed,and the melting point and the solid-liquid temperature intervalΔT are significantly reduced;With the increase of the content of nano-SnO₂,the microstructure of the composite solder gradually refines and then coarsens,and the enhanced phase SnO₂ particles have little effect on the melting point of the solder;The growth of intermetallic compound layer was inhibited by SnO₂ nanoparticles.The thickness of the IMCs at the interface of 1.0wt.%SnO₂ joints is significantly thinner than that of Sn0.6Cu/Cu,which is a reduction of 10.4%,reducing from 5.29μm to 4.74μm.Adding SnO₂ nanoparticles and applying ultrasound can significantly improve the shear strength of brazed joints.It was found that with the increase of Ag content,the microstructure of the composite solder was gradually refined.When the Ag content is 2.0 wt.%,the size of the Sn phase was the smallest.Micron Ag had a significant effect on the melting point of SnCu solder,and the melting point of composite solder could be reduced by 9.3℃.When 1.0 wt.%SnO₂ was added to the SAC206 solder,The effect of compound enhancement on grain refinement and inhibition of interfacial IMCs growth is better.In this study,the shear strength of Sn0.6Cu brazing alloy was 18.5 MPa,which was22.5%higher than the 15.1 MPa of Sn0.7Cu brazing alloy prepared by smelting method.Under the thermal insulation condition,the shear strength of SAC206-1.0SnO₂ reached a maximum value of 26.39 MPa,an increase of 42%,taking the shear strength of Sn0.6Cu solder as 18.5 MPa.After 30 s of ultrasound,the shear strength of Sn0.6Cu-2.0Ag reached a maximum value of 35.18 MPa,which was 1.9 times higher than that of Sn0.6Cu-2.0Ag.Under the same filler metal condition,the shear strength of brazed joints after applying 30 s ultrasonic is higher than that of joints under thermal insulation condition.Through fracture analysis,the fracture mainly occurred at the interface between the solder and the base plate without ultrasonic action,and was affected by the thickness of intermetallic compound layer.After the application of ultrasound for 30 s,the fracture mainly occurred in the filler metal matrix,which was affected by the microstructure of the filler metal matrix in the brazing joint.