CAF, conductive anodic filament, is an internal failure in which copper migrates along the boundary between glass fibers and resin, driven by voltage, humidity and ionic contamination, until it forms a conductive path between plated holes or conductors. It typically appears between closely spaced holes that share a glass bundle under constant bias. CAF-resistant laminates, wider hole-to-hole spacing and clean drilling reduce the risk, and it is a major concern in high-voltage and automotive designs.
Field shorts between adjacent vias at 48 V, the sections show CAF along the glass, move to a CAF-resistant laminate.
Also heard as
- conductive anodic filament
Related terms
Laminate
Sheet of reinforced resin, usually clad with copper foil, that rigid printed circuit boards are built from.
PTH
Plated through-hole: a drilled hole whose walls are copper-plated to connect every layer it passes through.
Whisker
Hair-like crystal of tin that grows spontaneously from a tin-plated surface and can short nearby conductors.