Constitutive, creep, and fatigue behavior of sintered Ag for finite element simulation of mechanical reliability: a critical review

Due to the miniaturization development in the electronic packaging industry and the significant thermal management requirement for high-power electronic devices, the sintered Ag has become one of the promising die-attach materials. Nevertheless, the mechanical reliability of the sintered Ag is still undergoing intensive examinations and investigations by both academy and industry. In this paper, the research progress is reviewed by focusing on the tensile, creep, and fatigue properties of sintered Ag in recent years to facilitate finite element (FE) simulations of mechanical reliability. The purpose is to obtain the mechanical reliability of the sintered Ag at a low cost by combining FE simulation. Firstly, to understand the constitutive behavior and quantify the mechanical properties as the basis of FE analysis, the stress–strain curves of the sintered Ag are adopted from tensile tests subjected to varying strain rates and temperatures. As the high temperature is the most influential factor in the service condition of die-attach materials, the relationship between constitutive parameters and temperatures is summarized. To quantify the creep behavior of packaging structures in the long-term service state, the constitutive models for creep under shear strain are addressed and the steady-state creep strain rate is emphasized. The influence of temperature and applied shear stress on creep strain rate is revealed. Regarding the effect of sintering condition on creep deformation, it is further explained that a higher applied pressure during the sintering process improves the initial shear strength of Ag lap joints and thus enhance the creep resistance against shear deformation. Finally, the fatigue behavior with damage accumulation under cyclic shear loading is reviewed by focusing on the evolutions of ratcheting response and hysteresis loop. To complement the FE predictions of mechanical reliability, the empirical damage models and fatigue life models are discussed to achieve a concise understanding of the mechanical reliability of sintered Ag under coupled thermo-mechanical loading.