In-situ observation of microscale crack-tip strain field evolution in underfill with different toughening agents via SEM-DIC coupled method

In this study, a digital image correlation (DIC) based strain mapping technology was combined with scanning electron microscope (SEM) to track the crack-tip strain field evolution with sub-micron spatial resolution and sub-nanometer displacement accuracy. The crack-tip strain field evolution at a microscale was established on single edge notch bend (SENB) testing through a miniature loading platform in SEM. The SEM-DIC coupled method were used to investigate the effect of filler and toughening agent on the crack-tip strain field evolution of underfill.