Behavior Simulation Of New Lead-free Solder Joints Under Thermal Electric Coupling

With the prohibition of production and use of lead-containing filler metals in various countries,SnAgCu filler metals have excellent properties and are considered as excellent materials to replace lead-containing filler metals.In the field of electronic packaging,the welding structure size of microelectronic chip becomes smaller and smaller,which leads to the increase of current density in the model,which makes the integrated circuit temperature rise obviously,and eventually leads to the phenomenon of electric migration.Electromigration phenomenon generally occurs in the electronic components of the welding structure,solder joints of the cathode produce holes,holes affect the stability of the components,lead to welding structure circuit or open circuit,the phenomenon such as cracks,holes increase since the phenomenon of electromigration,current density and temperature gradually increased,and will in turn exacerbated electromigration phenomenon,eventually lead to distortion of components,and even damaged.So it is necessary to study the electromigration of SnAgCu solder joints.In this paper,the effects of different contents of Ni on the properties of the brazing joints of low Silver SnAgCu system brazing alloy sn2.5Ag0.7Cu0.1Re with trace rare earth elements were studied.The conclusion is that the appropriate Amount of Ni will increase the shear strength of the brazing joints.When the concentration of Ni is 0.1%,The shear strength of solder welded joint is the largest and the mechanical properties are the best.The addition of Ni has little effect on the melting characteristics of solder,which is beneficial to welding.The service life of welded joints can be increased by adding different Ni elements,and the service life of welded joints can be increased obviously when the content of Ni element is 0.05% and 1%.At present,there are many researches on electromigration test of SnAgCu leadfree solder,but there are few simulations on numerical simulation analysis of solder joint model.Therefore,in this paper,SnAgCu filler metal SAC305 is used for COMSOL simulation study of lead-free solder joint,and the single-cylinder,three-hole,three-hole,sandwich solder joint model commonly used in microelectronics packaging field is constructed for numerical simulation.The following conclusions are drawn :（1）the solder joint temperature will be higher than the plate,which will lead to the deformation of the welding model.The increase of input voltage will increase the current density,space charge density,temperature and stress at the solder joint welding,which will easily lead to the phenomenon of electric migration,and even cause the failure of components.（2）When the spherical cavity is formed and the radius increases with the occurrence of electrical migration,the resistance value of the welding model will increase accordingly,resulting in component distortion,which is consistent with the test results of others.（3）If the component originally has holes,the holes will affect the current flow and distribution.When there are multiple holes,the current density on the left side of the first hole is greater than that on the left side of all the holes behind,because the holes hinder the current.（4）more Cu column welded structure maximize illustrates the current density in the solder ball and closest to the electric potential input Cu on either side of the plate,welding ball up and down on both sides of the current density with distance and the distance of the input voltage decreasing,current crowding in turn reduced,current produced by the joule heat is reduced,in turn solder ball temperature decreasing.Therefore,the first welding ball is easy to fail under the pressure of current and temperature.（5）The maximum current density of the sandwich welding model is located at the current inflow and outflo w at the contact point between the welding ball and the Cu plate,where there is current crowding.Extremely dangerous,a new welding structure composed of two sandwich welding structures of the same size,the current density of the current outflow point i n the welding ball is half of the current outflow point of a single sandwich structure.The current density of fixed points in the welding structure is N 1/1 of a welding model under the condition of the same input voltage,and N is the number of welding structures.Adjust the input parameters of the circuit,otherwise a single solder joint is extremely prone to failure.