A study of moisture diffusion in plastic packaging

Abstract

Plastic packaging is the most widely used package for nonmilitary applications where hermeticity is not required because plastic materials are cheaper than ceramic materials. Some surface-mount plastic packages may be moisture sensitive. For example, if they contain moisture above a threshold limit and are subjected to reflow soldering temperatures, crack and even popcorning may happen because of the vapor pressure and lead to the failure of plasticpackaged components.Absorbed moisture affects the thermomechanical properties of epoxy materials. It reduces the glass transition temperature (T g ), the modulus, and the strength, especially at high temperature. 1 Moisture diffusion through epoxy is the cause of corrosion of metals in electronic packaging. It has been reported that the dominant reason of flip-chip on-board electronic failure was corrosion of the Al pad in a moist environment. 2 The moisture inside the package also can change the electric properties of materials. Tong monitored moisture diffusion in epoxy based on the principle that the absorbed moisture increased the dielectric constant of epoxy materials. 3

The stable hydrogen and oxygen isotope variation of water stored in polyethylene terephthalate (PET) bottles

“…Few studies have, however, described the solvent‐polymer physical interactions in a water‐PET system. The sorption‐desorption and diffusion of water vapor into PET vary with relative humidity, polymer crystallinity and temperature 1, 10–13. The diffusivity of water in PET membranes varies from 2.11 × 10 −9 to 12.61 × 10 −9 cm 2 s −1 for thicknesses between 22 and 205 µm, while the equilibrium water uptake varies from 0.50 to 0.95% by weight for the same range of thickness 14.…”

Copper/Epoxy Joints in Printed Circuit Boards: Manufacturing and Interfacial Failure Mechanisms

“…Moisture adsorption is one of the major reliability concerns in plastic packaging and PCBs because many failure mechanisms are believed to arise from the diffusion of water or water vapor during manufacturing, storage or operation [96,97,98]. The degrading effects of moisture lead to adhesion loss, hygroscopic swelling and vapor pressure formation at the interface when accelerated stress tests and solder reflow processes are performed.…”

Effect of hygro-thermo-mechanical stress on reliability of stacked die package

“…With the increment of moisture concentration, more water molecules would bond with the epoxy resins through hydrogen bonding in the micro holes. The bonding water molecules and polymers would reduce the adhesive strength at the interface between die and epoxy materials in the package [10]. As a result, moisture induced failures such as die cracks, popcorn and delamination during reflow process may occur at the interface between bottom die and bottom die-attach.…”