Study on the reliability of nano-silver-coated tin solder joints for flip chips

Abstract

The nano-silver-coated tin (Sn@Ag) paste was modeled using the method of the Anand unified viscoplastic constitutive model and elastic model. After thermal cyclic loading, the plastic strain of the solder joints increased cumulatively, while the maximum equivalent stress remained basically stable. The simulation results show that the maximum displacement occurs at the solder joint at the farthest end from the center of the chip, which is a dangerous solder joint. Using the finite element method and EPRI (the American Electric Power Research Institute) estimation method, the fatigue life of the nano-silver-coated tin solder joint is predicted to be 616 weeks, which is significantly higher than that of the nano-silver solder joint. It is indicated that adding a certain amount of nano-tin to the nano-silver paste to form a core–shell structure can improve the shear strength of the solder joint and reduce the plastic strain, thereby significantly improving the reliability of the solder joint. It is proved by experiments that the nano-silver paste is feasible for flip–chip interconnection. The research on this topic provides experimental reference and theoretical basis for the application of a new generation of interconnection materials in power devices and promotes the development and application of microelectronic packaging technology.

Keywords

• flip chip
• nano-silver-coated tin
• fatigue life