Dynamic Spreading Behavior And Interfacial Reaction Of Sn-Ag-Cu-RE-Ni Lead-Free Solder On The Surface Of Copper Under Ultrasonic Vibration

Ultrasonic assisted soldering has attracted much attention because it can improve the wettability of different materials and achieve high quality welding.In the process of soldering,only solder spreading and wetting substrate can form reliable solder joint,which requires accurate analysis of solder spreading process to explore the wetting mechanism of solder,so as to improve the wettability of solder and then obtain high quality soldering joint.With the rapid development of microelectronic connection,the development of new micro-connection methods for lead-free solder to meet the harsh environmental requirements has become a research hotspot in this field.On the basis of studying the dynamic spreading process and physical phenomena of pure Sn solder under ultrasonic action,the influence of ultrasonic technology and materials on the spreading wetting behavior and bonding interface oxide of Sn-Ag-CuRE-Ni lead-free solder on copper surface under ultrasonic action is studied,the optimum wetting parameters of solder spreading wetting parameters are determined,the wetting mechanism and breaking mechanism of oxide film under ultrasonic action are discussed,and Sn-Ag-Cu-RE-Ni lead-free soldering process under ultrasonic action It provides theoretical and experimental basis for the development and application of ultrasonic assisted soldering in microelectronic connection industry.The results show that a multi-angle real-time ultrasonic-assisted solder dynamic spreading and soldering test device is designed to solve the problem of sample offset caused by ultrasonic high-frequency vibration,improve the accuracy and reliability of high-speed camera shooting information,and different sources of information from different angles of view shooting.The device has the characteristics of multi-angle realtime observation,anti-vibration offset,reliable data information,wide application range and simple operation.Dynamic spreading process of Sn-Ag-Cu-RE-Ni lead-free solder on copper surface under ultrasonic action is divided into three stages: collapse deformation,"extendedback" and in situ oscillation,accompanied by obvious "ripple" and "atomization" physical phenomena.Ultrasonic technology and materials affect the dynamic spreading process of solder by affecting "ripple" and "atomization",especially the collapse deformation and "expansion-back" stage of dynamic spreading process.Under the ultrasonic power 70 W? ultrasonic time 3 s and soldering temperature 270?,the NiGNSs enhancement with the addition amount of 0.05 wt.% is best when spreading and wetting the composite solder.Under the action of ultrasound Sn-Ag-Cu-RE-Ni there are three stages: micro-fracture,fracture and exfoliation of oxide film,crushing and dissolving of oxide film.Ultrasonic process and material affect the breaking effect of interfacial oxide film.A physical model of spreading and wetting of Sn-Ag-Cu-RE-Ni lead-free solder on copper surface was established under ultrasonic action.The optimum process parameters of Sn-Ag-Cu-RE-Ni lead-free solder/Cu spreading and wetting under ultrasonication can be realized.The maximum shear strength of Sn2.5Ag0.7Cu0.1RE0.05 Ni solder/Cu soldering joint is 27.5 MPa,which is29.1% higher than that without ultrasonic;the Ni-GNSs enhancement with 0.05 wt.%;the maximum shear strength of composite solder/Cu soldering joint is 32.6 MPa,18.5%higher than that without adding Ni-GNSs.With the increase of ultrasonic power,the average thickness of IMC layer of solder/Cu soldering interface decreases,the roughness decreases first and then rises,the shear strength of the corresponding joint increases first and then decreases.The shear fracture path is transferred from the transition zone composed of soldering seam region and interface IMC layer to soldering seam zone.The shear fracture mechanism is gradually changed from brittle fracture dominated by soldering seam and IMC layer cleavage to ductile-brittle mixed fracture composed of a small amount of soldering joint cleavage.With the increase of Ni-GNSs addition,the average thickness and roughness of the IMC layer of Ni-GNSs reinforced composite solder/Cu soldering interface decreased first and then increased,and the shear strength of the corresponding joint increased first and then decreased.The fracture mechanism of the joint was gradually changed from dimple-brittle mixed fracture composed of dimple and a small amount of crack cleavage.