Moisture absorption phenomena in green composite printed circuit board prototypes

This research developed the moisture-resistance of printed circuit board (PCB) laminate prototypes based on the non-toxic composite materials made from epoxidized linseed oil, melamine polyphosphate, and flax fibers. One of the key issues associated with using renewable base materials in composites is their sensitivity to moisture. A characterization of the properties of the dasiagreenpsila printed circuit boards developed in the present study showed that moisture absorption for untreated fiber laminates (4.87% vs. established limit Lt0.8% for FR4 boards over a 24 hour submersion period) compromised electrical resistance and decreased dielectric breakdown to an unacceptable level. A theoretical model was used to target methods for reducing moisture absorption. Based on this model, we found that reductions in fiber diffusivity and fiber volume fraction substantially reduce composite diffusivity. Through the use of chemical treatment, moisture absorption over a 24 hour time period was reduced from 4.87% to 1.15%, which improved electrical properties. At the end of this study, 15 of 18 PCB property requirements were met, while 3 moisture-critical property targets were narrowly missed.