Micro pore structure dependence on pressured-type sintered silver tensile mechanical properties

Abstract

Sintered silver (s-Ag) material is expected as a next-generation die-attach material in wide-band gap device packaging owing to its high thermal conductivity. However, micro pore structure is inevitably included into the die layer even with pressure assist, which gives rise to complicated thermal reliability of the packaging. Toward reliable packaging design with s-Ag die-attach, this study focuses on micro pore structure dependence on pressured-type s-Ag tensile mechanical properties. Only nano-sized silver paste was sintered under 60MPa process pressure at 300℃ for 10min (Type A). To control micro pore structure, two types of annealing process was performed after sintering: 350℃ annealing for 30min (Type A’) and 120min (Type A’’). From cross sectional scanning electron microscopy (SEM), mean local porosity rate (p) was 2.4%, 3.2%, and 4.0% for Type A, A’, and A’’, respectively. Quasi-static tensile tests were performed at room temperature (RT), 100℃, and 150℃, where all types of s-Ag showed brittle to ductile transition around 100℃ and ductile behavior at each temperature depended on its initial micro pore structure.