Conductive Anodic Filament (CAF) has been increasingly concerns on printed circuit boards in the last few years. The major factors are current trend toward smaller size, lighter weights, thinner and higher performances that the density of PCB shall be designed with more closely spacing conductors, much smaller pitches and single-ply dielectrics such as mobile telephones, notebook computer and camcorder. In the other hand, some electrical applications must be exposed in extreme environment. For example, the safe necessity of automotive like engine control and brake control system. There cannot occur electrical shorts phenomenon, so the insulation resistance of material becomes very importance. These factors are pushing the demand for anti-CAF materials.
CAF is an electrochemical corrosion process that causes electrical shorts, when copper metal is dissolved at the anode and migrates to the cathode through the resin matrix/ glass fibers interface. CAF can occur between any two oppositely adjacent conductors when the conductors are in contact with the glass fibers. There are four ways that include hole-to-hole, line-to-line, hole-to-line and layer- to-layer. (See above diagram).