Study On Reinforced Snbi Composite Solder With Nanosized SiC Particles By Ultrasonic And Its Soldering Performance

Electronic packaging technology is developing to high-density and miniaturization direction.Due to the toxicity of the Sn-Pb solder,it has been banned widely.It has become a hot research topic and an urgent problem to be solved to find a Pb-free solder with high performance,which can replace tin-lead alloy.Sn Bi eutectic solder as a low melting point alternative to the traditional Sn-based solder,with low cost,compatible with traditional SMT equipment and processes,can be used for low temperature welding.However,the high content of Bi in the Sn Bi eutectic solder leads to the failure of the joint after welding,such as hard and brittle failure.How to improve the mechanical properties of the soldering joint and improve the reliability of long-term service has become urgent problems to be solved.The key issue in this project,a composite soldering filler metal preform was prepared by doping nano-SiC particles by ultrasonic assisted mechanical mixing and cold pressing.The effect of the nano-SiC particle content and the power parameters of ultrasonic-assisted hot press reflow on the soldering performance of the composite soldering filler metal was discussed.The subject of nano-SiC particles enhanced Sn Bi solder microstructure was analyzed and characterized.The results show that with the content of nano-SiC particles increasing,the average phase size of the Sn Bi solder alloy first decreases and then increases with the increase of the content of nano-SiC particles in the range of 0.2 wt.% To 0.8 wt.%.The heat input can effectively promote the uniform distribution of nano-SiC particles.After the ultrasonic vibration is applied,the heat input inside the soldering filler metal is increased under the effect of acoustic flow and cavitation to accelerate the thermal motion of the particles inside the soldering filler metal and prevent the density of SiC and Sn Bi The difference between the floating and reunion caused by the great difference increases the wettability of the composite solder after the nano-SiC particles and the micro-sized Sn Bi particles are mixed,and makes the nano-SiC disperse and disperse after the composite solder melts and cools down.When the ultrasonic wave is 500 W,the dispersion effect of nano-SiC is optimal.When the nano-SiC content reaches 0.6 wt.%,The average phase size of ?-Sn phase in the eutectic structure reaches the minimum 0.49 ?m.The results of DSC analysis,micro Vickers hardness test,joint shear strength test and fracture surface morphology of Sn Bi composite soldering filler metal reinforced by nano-SiC particles show that the melting point decreases obviously with the increase of nano-SiC content,But the decline is within 1 ?,little effect on the solder melting point.After hot reflow and ultrasonic reflow process,the hardness of joints of Sn Bi composite solder alloy with different content of nano-SiC particles changed significantly.After hot pressing and refluxing,the hardness decreased by about 50%.The hardness of the samples remained unchanged after ultrasonic reflux,and thehardness of some samples increased slightly.When the content of nano-SiC particles reaches 0.6 wt.%,The shear strength reaches 33.15 MPa,which is 99.1% higher than the shear strength of the original Sn Bi eutectic solder 16.65 MPa.When the nano-SiC particles content exceeds 0.6 wt.%.The shear strength of the composite solder joints showed a downward trend.Fracture morphology are mainly intergranular fracture and transgranular fracture.