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This paper introduces a non-destructive microwave-based detection method which was developed with respect to the detection of internal defects in composite insulators. The test equipment comprised a microwave-generating Gunn oscillator (frequency 24 GHz) combined with an open-ended rectangular waveguide as emitting and receiving sensor operating in the near-field (stand-off distance < 5 mm). The...
Adhesives in electronic packages contain numerous pores and cavities of various size-scales. Moisture diffuses into these voids. During reflow soldering, the simultaneous action of thermal stresses and moisture-induced internal pressure drives both pre-existing and newly nucleated voids to grow and coalesce, causing adhesive failure. In this work, a nonuniform initial porosity distribution in the...
IC packages exposed to humid environment are susceptible to thin film adhesive failures during reflow soldering. Under reflow temperatures, moisture trapped in the micropores of the polymeric adhesives vaporizes and induces vapor pressure within these voids, accelerating failure via void growth. In this work, a computational discrete void approach is adopted to study the rate-dependent void growth...
The numerous pores and cavities present in adhesive underfills increase the susceptibility of microelectronic packages to type II cracking. This work focuses on the effects of softening-rehardening and pressure-sensitivity on adhesive failure. An axisymmetric unit-cell study is first performed to ascertain the failure mechanisms in a softening-rehardening polymer. Results show that shear banding is...
Adhesives in electronic packages contain numerous pores and cavities of various size-scales. Moisture diffuses into these voids. During reflow soldering, the simultaneous action of thermal stresses and moisture-induced internal pressure drives both pre-existing and newly nucleated voids to grow and coalesce, causing adhesive failure. In this work, a non-uniform initial porosity distribution in the...
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