Electrochemical Branching
Metallic copper dendrites migrate through the internal layers of a printed circuit board under the influence of an electrical bias and moisture. This phenomenon, known as conductive anodic filamentation, creates a bridge between adjacent conductors that were previously isolated. The pathway initiates at an anode and follows the glass fibre reinforcement interfaces within the epoxy resin.
Such failure modes happen when hygroscopic contaminants combine with voltage potential to break down the dielectric strength of the laminate material.
Laminate Sensitivity
High humidity levels accelerate the migration process by increasing the ionic mobility of copper ions between electrodes. Manufacturers manage this risk by choosing resin systems with high glass transition temperatures and superior adhesion properties between the resin and the glass weave. Testing protocols involve subjecting boards to elevated temperature and humidity while applying a constant electrical bias over long durations.
Failures often correlate with poor drilling quality or improper curing of the board material during fabrication.
Performance Threshold
Insulation resistance measurements catch the decline in dielectric performance before a total short circuit occurs. Engineers set limits for the drop in resistance during standardized damp heat testing to verify material compatibility with the intended operating environment. Current design rules mandate specific spacing distances between traces to reduce the potential gradient that drives the migration.
Design layouts that respect these spacing limits minimize the likelihood of filament formation throughout the service life of the electronic assembly.