Capacitance Monitoring While Flex Testing

The common printed circuit board (PCB) built of G10 or FR4 glass epoxy materials will easily bend under moderate forces. Almost all processes involved in populating these boards can involve bending the board many times unknowingly. High stresses transmitted to small areas of the board are of greatest concern. Manufacturing efficiencies improved by processing small PCBs as a group of multiple circuits within a singular “mother board.” Depanellization, where the individual circuit boards are isolated from the “mother board,” is one area where extremely high stress forces can be transmitted to the boards near the edges being cut. “Snap together” methods of assembly are also prone to creating these localized stress areas. The boards may be placed in a holder between process stages, where the outside edges are held and the board is allowed to droop in the middle. The board may be fitted into a cabinet or slot with a force that causes bending near an edge. Communication cables may be mechanically attached to an unsupported edge, translating all forces applied to the cable back to the board. These are just a few of the more common areas where board flexing can occur in assembly. These may be compounded if the board is later worked on in repair especially by an impatient technician with a rubber hammer.