Preparation,Performance And Soldering Study On A Sn1.0Ag0.5Cu Composite Solder Reinforced With Copper-Plated Zirconia

With the enhancement of environmental protection awareness and the rapid development of microelectronics packaging technology,Sn-Ag-Cu lead-free solder becomes one of the best alternative alloys for Sn-Lead solder due to its high comprehensive properties,showing a good development prospect.Nowadays,the solder joints of electronic products are becoming more and more small and complicated,which bear increasing pressure and are prone to failure.In order to meet the reliability requirement of high strength brazing joint for microelectronic connection in harsh environment,nano-scale reinforcing relative solder is widely paid attention to in lead-free solder alloy.Zirconia ceramic particles have stable properties and high strength.As reinforcement phase,it can improve the strength performance of solder well.It is the most promising reinforcement phase material at present.In this paper,the effect of surface Zirconia addition on microstructure and properties of Sn1.0Ag0.5Cu composite solder and soldered joint were studiedIn this paper,the electroless plating method was used to prepare copper-plated Zirconia（Cu-ZrO₂）reinforced phase.The low silver Sn1.0Ag0.5Cu filler metal alloy was taken as the research object.The Cu-ZrO₂reinforced Sn1.0Ag0.5Cu composite solder was prepared by powder metallurgy method.The microstructure and properties of Cu-ZrO₂reinforced Sn1.0Ag0.5Cu composite solder were studied.The effects of soldering process and solder composition on microstructure and mechanical properties of Cu-ZrO₂reinforced Sn1.0Ag0.5Cu composite solder/Cu soldering joint were investigated.The results show that the supported Cu-ZrO₂enhanced phase was prepared by electroless plating with hydrazine hydrate as reducing agent,and both of them have high adsorption capacity.The overall dispersibility of Cu-ZrO₂nanoparticles in composite solder is good after ball milling.The Sn1.0Ag0.5Cu solder alloy with good shape can be obtained under the powder metallurgy process of 140 MPa prepressing at220°C sintering for 2 h.Using Cu-ZrO₂as reinforcement phase,Cu-ZrO₂reinforced Sn1.0Ag0.5Cu composite solder was prepared by the above powder metallurgy process,and its microstructure and properties were tested.Adding proper amount of Cu-ZrO₂nanoparticles can refine Cu-ZrO₂and enhance the primaryβ-Sn grains in Sn1.0Ag0.5Cu composite solder and increase the proportion of eutectic microstructure.The addition of Cu-ZrO₂decreases the melting point of the composite solder and has little effect on the conductivity of the composite solder.The wettability of composite solder is improved obviously.The tensile strength of the composite filler metal reaches41.6 MPa when Cu-ZrO₂is added at 0.5 wt.%,which is 38.3%higher than that of Sn1.0Ag0.5Cu solder.The high strength Cu-ZrO₂reinforced Sn1.0Ag0.5Cu composite solder was obtained.The good wetting of Sn1.0Ag0.5Cu composite solder/Cu can be achieved by using Cu-ZrO₂with water-washed brazing agent,280℃and 0.5 wt.%Cu-ZrO₂addition,and the interface structure of IMC layer with uniform and compact morphology and small roughness is obtained.On the basis of wetting test,when the brazing time is 180 s and Cu-ZrO₂content is 0.5 wt.%,the Sn1.0Ag0.5Cu composite solder can be welded to Cu substrate with Cu-ZrO₂reinforced solder.The shear strength of the composite filler metal is 28.5MPa.Compared with Sn1.0Ag0.5Cu matrix solder,the shear strength is increased by41.8%,and the soldering joint with high strength can be obtained.With the increase of Cu-ZrO₂addition,the growth of interfacial IMC is obviously inhibited,and the thickness and roughness of IMC at the joint interface decrease.Cu-ZrO₂enhances the shear fracture path of Sn1.0Ag0.5Cu/Cu soldering joint from the IMC layer to the near soldering interface.The fracture mechanism also changed from the mixed fracture consisting of parabolic dimple and cleavage plane to the ductile fracture dominated by parabolic dimple.