Absorption and diffusion of water in printed circuit boards

When exposed to harsh and humid environments, electronic systems can show electrochemical corrosion. One of the possible defects is Conductive Anodic Filament (CAF). This defect needs the presence of humidity. Though the moisture uptake of printed circuit boards has been studied thoroughly, a complete understanding of the diffusion processes and paths in printed circuit boards has not yet been achieved. This work deals with the anisotropy of moisture diffusion in the laminate. According to this purpose samples have been produced and tested. The results show a different absorption behavior according to sample type and base material as well as to storage temperature and humidity. The diffusion constants can be extracted from the measured mass changes of the samples. Since the different sample designs allow diffusion only in specific directions, a determination of the anisotropy is feasible. Furthermore, information on the storage location of the moisture in printed circuit boards can be gained. Therefore, samples have been produced to investigate the absorption behavior of different components of printed circuit boards such as resin and glass weave.