Multilayer silver-tin transient liquid phase bonds: Constitutive modeling summary

• The constitutive models of the AgSn transient liquid phase (AgSn-TLP) bonds are summarized and discussed. • The constitutive models include elastic properties, isotropic hardening plasticity, steady-state creep and Anand viscoplasticity. • Nonlinear simulations revealed that the AgSn-TLP bonds have high damage resistance properties compared to other die attach materials. Transient liquid phase (TLP) bonding technology is one promising joining technique in power electronics as it offers superior thermal, electrical and mechanical characteristics. Multilayer silver-tin (AgSn) foils are common TLP joining configuration because of their improved thermal stability and high melting temperature. In fact, the accurate estimation of the elastic and inelastic mechanical properties of the silver-tin TLP bonds is essential for precise evaluations of the bond's stresses and strains using finite element simulations. This paper aims to summarize the various material constitutive models of the AgSn-TLP interconnects developed by the author and their co-workers over the years. Particularly, the elastic, time-independent, steady-state creep and viscoelasticity mechanical properties are introduced. Additionally, this research incorporates comprehensive finite element analysis (FEA) study to evaluate the mechanical response of the silver-tin TLP die attachment due to thermal and thermomechanical loadings in comparison to other common die attach systems of power modules. The simulation results revealed that the AgSn transient liquid phase bonds have superior resistance to the accumulation of inelastic strains and inelastic strain energy suggesting their high potential of improved fatigue life due to thermomechanical loadings.