Effects of Ag content on microstructure evolution, intermetallic compound (IMC) and mechanical behaviour of SAC solder joints

SnAgCu (SAC) solder joints are widely used in electronic industry as alternative to lead free solder. The microstructure of the solder joint plays an important role in enhancing the mechanical properties of the solder joint, thus the electronic devices will have a longer lifetime. This paper studies the effects of silver (Ag) percentage on the microstructure and intermetallic compound (IMC) in Sn-Ag-Cu solder, and how the addition of Ag impacts the mechanical concepts of SAC solder joints. SAC solder joints were examined as a function of Ag3Sn precipitates (in terms of the number and size of the precipitates) and intermetallic compounds (IMCs). The microstructure morphology of the SAC samples was analyzed by using a scanning electron microscope (SEM) with back scattering mode. A quantitative analysis of number of Ag3Sn was performed for all SAC samples. The results showed that when the amount of the Ag content increased, that led to an increase in the number of Ag3Sn precipitates with an increase the eutectic area but does not affect the growth of IMC. The mechanical properties of SAC samples were enhanced significantly by increasing the Ag content.