Prognostic Monitoring of Power QFN Packages With Silver Sintered Die-Attach Materials

Abstract

Prognostic monitoring of power quad flat no-lead (PQFN) packages with four distinct silver pastes, each varying in material composition (pure-Ag and resin-reinforced hybrid-Ag) and sintering processes (pressure-assisted and pressureless), was investigated in this study. The PQFN packages with silver sintered die-attach materials were subjected to thermal cycling tests ( $- 55~^{\circ } $ C to $150~^{\circ } $ C), and the performance degradation was evaluated based on the following metrics: 1) electrical on -state resistance $R_{\textrm {DSon}}$ monitored periodically at specific thermal cycling intervals and 2) transient thermal impedance $Z_{\textrm {th}}$ ( $t =0.1$ s) monitored online during thermal cycling. These measurements were further validated using acoustic microscopy imaging and cross-sectional inspection. The pressureless Ag-sintering material demonstrated comparable performance to pressure-assisted Ag-sintering, with a dense microstructure, and consistent electrical and stable thermal performance. Whereas the pressureless resin-reinforced hybrid-Ag material exhibited degradation with a relative increase of ~33% in $R_{\textrm {DSon}}$ , ~38% in $Z_{\textrm {th}}$ ( $t =0.1$ s), and ~67% delamination of the die-attach interface over 1000 cycles. These findings suggest that pressureless Ag-sintering may offer a viable alternative to pressure-assisted methods for lead (Pb)-free die-attachments, while resin-reinforced hybrid-Ag requires further development for improved thermomechanical reliability.