| With the continuous development of electronic equipment in the direction of miniaturization and light weight,how to improve the interface performance between the IC chip and the PCB substrate has attracted increasing attention.During the service of electronic equipment,the solder establishes a bridge between various components so that electronic signal IC chips can be exchanged with each other,thereby maintaining the normal operation of electronic products.Therefore,research of high-performance solder has become a hot research topic in the field of electronic packaging.At present,the commonly used solder in the international community is high-silver Sn-Ag-Cu solder,which has good spreading properties,electrical conductivity and thermal stability.The poor adhesion between the two leads to the formation of large pieces of Ag3Sn IMCs at the solder joints during the solidification process of the solder,which reduces the reliability of the solder joints,which limits the promotion of the solder in the field of electronic packaging.Therefore,optimizing the composition ratio of low-Ag Sn-Ag-Cu solder and improving the performance of soldered joints strength has become one of the current research hotspots.In this paper,the solidification theory of alloy was adopted,and different contents of Zn(x=0,0.1,0.4,0.7,1.0,2.0wt.%)were added to low Ag Sn-0.5Ag-0.7Cu(SAC(0507))by metallurgical smelting.The effect of Sn-0.5Ag-0.7Cu solder physical properties and soldering performance were researched,so as replace the high Ag Sn-Ag-Cu solder.Through a comparative analysis of the microstructure,thermal behavior,wetting properties,electrical conductivity,and solder joint mechanical properties of SAC(0507)-xZn solder alloy,the effect mechanism of Zn element on Sn-0.5Ag-0.7Cu solder alloy were effectively researched.The research shows that the proper amount of Zn element can effectively improve the overall performance of the solder alloy.When the Zn content is 0.4wt.%,the Ag3Sn IMCs and Cu6Sn5 IMCs in the solder were evenly distributed on the primary ?-Sn substrate.Both the tensile strength and shear strength reached the maximum.However,with the further addition of Zn content,the SAC(0507)brazing alloy appeared large blocks of Cu-Zn IMCs,resulting in a sharp decline in the overall performance of the SAC(0507)brazing filler metal.Based on the above studies,SAC(0507)-0wt.%Zn/Cu,SAC(0507)-0.4wt.%Zn/Cu,and SAC(0507)-1.0wt.%Zn/Cu brazed joints were subjected to aging experiments under different conditions.Research shown that the morphology of the IMCs layer changes with the aging temperature and time.When the Zn content is 0wt.%And 0.4wt.%,The interface layer gradually changes from the original single layer Cu6Sn5 to Cu6Sn5+Cu3Sn.When the Zn content was 1.0wt.%,Cu5Zn8 at the SAC(0507)/Cu solder joint gradually decomposes,and continuous Cu6Sn5 was generated on the Cu substrate side.The diffusion rate and diffusion activation energy in the SAC(0507)-0wt.%Zn/Cu and SAC(0507)-0.4wt.%Zn/Cu IMC layers were calculated.The mechanism of the effect of Zn on the IMCs layer at the SAC(0507)/Cu interface was further explained.During the aging process,Zn element inhibited the growth rate of IMCs(D0wt.%>D0.4wt.%)and increased the diffusion activation energy(Q0wt.%<Q0.4wt.%).Therefore,the increase of the thickness of the bonding interface layer during the aging process is suppressed. |
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