Fracture and damage investigations enhancing the thermo-mechanical reliability of plastic packages

摘要

Polymeric materials are widely used in electronic packages as encapsulant materials, stress reducing layers in chip-scale pack-ages and flip-chip assemblies, as part of redistribution layers and substrates. They prevent electronic packages from being exposed to harsh environments or act with their electric/dielectric qualities. Unfortunately polymerics have a much higher thermal expansion coefficient compared to that of silicon or ceramics. They show a mainly viscoelastic behavior, a glass transition temperature which is occasionally inside the temperature range concerned and in addition, all material coefficients highly depend on the temperature. These special qualities in combination with various kinds of inhomogeneities and shape-owed stress singularities lead to interface delaminations, chip cracking and fatigue of solder joints and in contrast to the goal of their usage, to a thermo-mechanical reliability lower than expected.