The Influence of Mechanical Property on the Heat-Cycle Reliability of Sintered Silver Die Attach

This paper investigates how the mechanical properties of sintered silver (s-Ag) influence its heat-cycle reliability as a die attach material. The uniaxial tensile test at room temperature (RT) provides the stress-strain (S-S) curve of three s-Ag films with the same porosity rate (p) of 5%. The fatigue test with repeated stress impressment is performed at RT to obtain the so-called S-N curve, showing how an imposed stress changes the number of cycles to facture (tft). The imposed stress nearly linearly correlates with log $_{10} t_{ft}$. The thermal shock test (TST) is used to estimate how s-Ag deteriorates as a die-attach with the temperature cycle pattern of $-60^{\circ}\mathrm{C}$ to $60^{\circ}\mathrm{C}$ (Test I) and RT to $150^{\circ}\mathrm{C}($ Test II). Scanning acoustic tomography (SAT) reveals that degradation occurs in Test II in stark contrast to no significant degradation in Test I, while scanning electron micrograph (SEM) observe cracks even in Test I but the difference in the crack structure. Finally, finite-element-modeling simulation is used to estimate strain in Test I. The reference to the observed S-S and S-N reveals that tftis in the same order of magnitude to the lifetime of TST defines as the time to crack appearing in TST.