Finite Element Analysis and Experimental Investigation of Die-Attach Fillet Influence on the Reliability of Epoxy-Based Pressure-Less Sintered Silver Joints

This work investigated the impact of die-attach fillet geometry on the reliability of epoxy-based pressure-less sintered silver joints. Three types of sintered silver samples (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Ag}-{0}, \text{Ag}-{1}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Ag}-{2}$</tex>) with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${0 \%}, {1 \%}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${2 \%}$</tex> epoxy content were prepared and characterized. Nanoindentation tests combined with inverse calculations were used to determine their elasto-plastic behavior. Fillet formation was influenced by organic solvent composition, dispense volume, and placement pressure, resulting in three geometries: rounded, triangular, and rounded rectangular. Finite element analysis was employed to simulate stress distribution and equivalent thermal strain under thermal cycling conditions (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-55^{\circ} \mathrm{C}$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$150^{\circ} \mathrm{C}$</tex>). The simulation results were validated experimentally through shear strength testing and microstructural characterization using scanning electron microscopy (SEM). The findings highlight the significant role of fillet geometry, climbing height, and die-attach thickness in stress distribution and failure mechanisms, providing valuable insights into optimizing the die-attach process to enhance joint reliability in power electronics applications.