Study On Micstructure And Properties Of Sn Solder/solder Joint Based On Carbon Nanotubes/Ag Nanoparticles

With the continuous rise of high-tech industries and the development of the electronic information industry in the direction of integration and diversification,electronic packaging technology has gradually entered people’s field of vision.Sn-Pb solder has been the material of choice for soldering electronic components for a long time due to the good wettability of Pb.But the Pb is very toxic,which limits the use of Sn-Pb solders.Therefore,researchers have developed many new lead-free solders:Sn-Bi,Sn-Ag,Sn-Cu,Sn-Ag-Cu.Pure Sn solder is often used in the transient liquid phase bonding of electronic packaging,but the melting point of pure Sn solder(234.4°C)is relatively high,and it is easy to cause thermal damage to the circuit board during the soldering process.This experiment is based on pure Sn solder,by adding carbon nanotubes(CNTs)and nano-Ag particles to study the melting characteristics,wettability,mechanical properties,and reliability of pure Sn solder.The experimental results are as follows:(1)Adding CNTs and nano Ag particles does not significantly improve the melting point of pure Sn solder.The melting point of Sn-0.075 CNTs composite solder is higher than that of pure Sn solder when CNTs is added at 0.075 wt.%.The temperature is lowered by about 6℃,and the preparation after adding nano-Ag particles does not have much effect on the melting characteristics of Sn-0.075CNTs-x Ag.(2)Adding an appropriate amount of CNTs can effectively improve the wettability of pure Sn solder.With the addition of CNTs,the wetting area of the Sn-x CNTs solder shows a trend of first increasing and then decreasing,and when the addition amount of CNTs is 0.075 wt.%,the spreading area of the solder reaches the maximum,which is64.2mm2,The spreading area of the pure Sn solder is increased by about 16.7%,that is,the wettability of the composite solder is the best when the addition amount of CNTs is0.075 wt.%.With the increase in the amount of nano Ag particles,the spreading area of the Sn-0.075 CNTs composite solder also shows a trend of first increasing and then decreasing,and when the amount of nano Ag particles is 0.10 wt.%,the solder shown the best wetting performance.(3)After an appropriate amount of CNTs were added into the solder,the number of dimples in the fracture of the composite solder joints increased significantly,showing obvious ductile fracture,and the shear force of the solder joints also increased first and then decreased with the addition of CNTs Trend.The number of dimples in the solder joint is the largest,and the shear stress is the largest at 25 MPa when the amount of CNTs added is 0.075 wt.%,which is about 32.7% higher than the shear stress of the solder joint of pure Sn solder.The mechanical properties of the solder joints are the best when the addition amount of CNTs is 0.075 wt.%.With the increase of nano-Ag particles,the shear force of the Sn-0.075 CNTs composite solder also shows a trend of first increasing and then decreasing,and when the amount of nano-Ag particles is0.10 wt.%,the mechanics of the solder The best performance.(4)With the addition of CNTs,the thickness of the IMC layer between Sn-x CNTs/Cu shows a trend of first decreasing and then increasing,and when the addition amount of CNTs is 0.075 wt.%,the thickness of the IMC layer is the thinnest and the IMC layer is relatively flat and uniform.The increase of nano-Ag particles can effectively inhibit the production of Cu6Sn5 compound,and when the addition amount of nano-Ag particles is 0.10 wt.%,the thickness of the IMC layer at the solder joint interface is the thinnest.(5)With the addition of CNTs,the acicular phase inside the solder joint gradually disappears,and the microstructure is gradually refined.When the addition amount of CNTs is 0.075 wt.%,the coarse structure inside the solder joint has basically disappeared and strengthened.The phase is evenly distributed inside the solder joint.Adding an appropriate amount of Ag nanoparticles can significantly refine the microstructure of Sn-0.075CNTs/Cu solder joints,thereby improving the performance of Sn-0.075 CNTs.(6)CNTs can effectively inhibit the growth of Cu3 Sn.The number of Kerkendall voids in the Sn-x CNTs solder system is also less than that of the pure Sn solder system after multiple thermal aging and reflow.After aging,the activation energy of Sn-0.075CNTs/Cu system is 33.256KJ/mol,and the activation energy of Sn-0.075CNTs/Cu system is 58.19KJ/mol.With the gradual increase of the thermal cycle time,the thickness of the IMC layer between Sn-0.075CNTs/Cu-0.1Ag/Cu gradually increases,and the size of Cu6Sn5 grains also increases with the increase of the thermal cycle time.With the increase of time,Sn-0.075CNTs-0.1Ag /Cu solder joints gradually produces Kirkendall holes and crack sources inside the solder joints,the microstructure of the solder joints gradually coarsens,and the reliability of the Sn-0.075CNTs-0.1Ag /Cu solder joints decreases.