Isothermal aging effect on SAC interconnects of various Ag contents: Nonlinear simulations

Abstract

The mechanical behavior of the tin (Sn)–silver (Ag)–copper (Cu) (SAC) lead-free solders is strongly influenced by the isothermal aging due to the evolution of the microstructure and mechanical properties. This study aims to examine the influence of pre-isothermal aging at 100°C on the mechanical behavior of different SACN05 alloys with different silver content including N=1,2,3N=1,\hspace{.25em}2,\hspace{.25em}3 and 4% by applying nonlinear finite element analysis. The mechanical properties, including elastic and inelastic properties, of the SAC systems with various Ag percentages are gathered from the literature and incorporated in thorough thermomechanical simulations. In addition to the unaged solders condition, two aging periods, 6 and 12 months, are studied. The computational results showed that the mechanical response of pre-aged SACN05 solders is significantly influenced by the aging duration and silver content. Specifically, interconnects with higher Ag percentage are shown to be more resistive to aging and expected to have lower thermally induced inelastic deformations, strains, and strain energies. Therefore, better thermal fatigue performance and improved failure resistance is potentially expected. However, the pre-isothermally aged SACN05 solders generally exhibit lower resistance to the accumulations of inelastic strains and strain energies. Thus, it is probable that pre-aged SACN05 solders will demonstrate deterioration in thermal fatigue performance compared to unaged interconnects. Nonetheless, the aged SAC solder systems could be an innovative solution for designing electronic devices regularly exposed to shock and impact loading as the aging process significantly reduces the brittleness of the SnAgCu alloys.

Keywords

• sac alloys
• isothermal aging
• finite element simulations
• thermal fatigue