Uniaxial ratcheting and fatigue behaviors of low-temperature sintered nano-scale silver paste at room and high temperatures

Uniaxial ratcheting and fatigue behaviors of low-temperature sintered silver films at room and high temperatures were studied experimentally and particular attention was paid to the influence of ratcheting to fatigue. The effects of stress amplitude, mean stress, stress rate, temperature, peak stress holding time and loading history on the ratcheting response of sintered silver films were analyzed, respectively. Firstly, it can be concluded that the ratcheting strain amplitude and ratcheting strain rate of the material increase with increasing stress amplitude or mean stress, correspondingly. Secondly, the experimental results indicate that ratcheting strain increases significantly with the increasing temperature and decreasing stress rate. Thirdly, the material was found having a strong memorization on loading history, the prior stress cycling with low stress amplitude or mean stress can greatly retard the strain accumulation under subsequent loading conditions. Fourthly, the strain accumulation with peak stress holding time is larger than that without hold time at high temperatures, but the ratcheting evolution with and without hold time is almost equal at room temperature. Finally, it was found that the fatigue failure of sintered silver paste is dominated by ratcheting response especially for high temperature and long peak stress holding time. The factors such as stress rate, temperature and peak stress holding time also have a significant influence on fatigue life since they all greatly affected ratcheting behavior of the material. (C) 2010 Elsevier B.V. All rights reserved.