Study On IMC Growth And Ni Layer Consumption Of Three Kinds Of Solder Joints

With the rapid development of electronic packaging technology,the field of microelectronics constantly puts forward new requirements for solder joint reliability,too thick interface IMC will reduce the reliability of solder joints,so it is necessary to strictly control the thickness of interface IMC layer.The introduction of Ni layer can effectively delay the growth of IMC at the interface,avoid the formation of too thick IMC,and reduce the induction and propagation of IMC to the crack source.In this paper,SAC305,Sn58Bi and Sn5Sb solders are taken as the research objects.The growth of IMC and the consumption of Ni layer in the process of liquid heat preservation and solid-state aging are analyzed.At the same time,the shear properties of them are tested,and the influence of liquid heat preservation and solid-state aging on the shear strength of interface is analyzed.The growth of IMC and the consumption of Ni layer on the interface of three kinds of solders at different holding temperatures were studied.The results show that the interface IMC of SnBi/Ni solder joint grows in the mode of grain boundary diffusion at 180?with a growth index of 0.3584.The thickness of IMC layer is linear with holding time t^0.3584,and the consumption of Ni layer of SnBi/Ni solder joint is linear with holding time t^0.3568.With the increase of holding time,the growth rate and Ni consumption rate of IMC at the interface decrease gradually.The main reason is the formation of large Bi rich phase at the interface,which hinders the growth of IMC at the interface and delays the consumption of Ni layer.At 260?,the thickness of IMC layer and holding time t^0.3494are linear,while the consumption of Ni layer and holding time t^0.3294 are linear.At 280?,the thickness of IMC layer at the interface of Sn-5Sb/Ni solder joint has a linear relationship with the holding time t^0.5347,and the IMC grows in the mode of bulk diffusion.At the same time,it is found that the consumption of Ni layer of Sn-5Sb/Ni solder joint has a linear relationship with holding time t^0.4987.Among them,Cu and Bi elements in three kinds of solder will hinder the growth of IMC on the interface and delay the consumption of Ni layer,while Sb element has less effect.The growth of IMC and the consumption of Ni layer in the solid-state aging process of three kinds of solder joints were analyzed.The results showed that the growth of IMC in the three kinds of solder joints was mainly based on the bulk diffusion model,but the growth constants of IMC were different.The growth constants of Sn58Bi/Ni,SAC305/Ni and Sn5Sb/Ni were 5.42×10^-4?m²/h,5.97×10^-3?m²/h and 0.409?m²/h respectively.There is a linear relationship between the consumption of Ni layer and aging time t^0.5.The Ni layer consumption constants of Sn58Bi/Ni,SAC305/Ni and Sn5Sb/Ni are 2.75×10^-4?m²/h,5.64×10^-4?m²/h and 0.02?m²/h respectively.In order to further study the effect of liquid heat preservation and solid-state aging on the interface evolution of three kinds of solder joints.The shear properties of solder joints after liquid heat preservation and solid-state aging were tested.The results show that the shear strength of Sn58Bi/Ni,SAC305/Ni and Sn5Sb/Ni solder joints is affected by the holding time.When the holding time reaches 50min,the shear properties of Sn58Bi/Ni,SAC305/Ni and Sn5Sb/Ni solder joints decrease 21.52%,18.36%and 23.60%respectively.This is mainly due to the obvious coarsening of the internal structure of solder with the prolongation of liquid holding time,and the thickening of IMC layer at the interface will induce the generation of crack source and crack growth.In the process of solid-state aging,the shear properties of SAC305/Ni,Sn58Bi/Ni and Sn5Sb/Ni solder joints decreased with the increase of aging time.When the aging time was 672 h,the shear strength of Sn58Bi/Ni,SAC305/Ni and Sn5Sb/Ni solder joints decreased by18.24%,13.53%and 22.46%respectively.Due to the prolongation of aging time,a large number of cavities are produced in the solder joints,especially in the Sn5Sb/Ni solder joints which are aged in solid state at 180?,which produce obvious cracks at the interface between IMC and Cu substrate.With the increase of a large number of cavities and crack growth,the shear strength of three kinds of solder joints decreased under isothermal aging.