Analysis of the dynamic phenomena during lamination of multilayer printed circuit board by the measurement of pressure distribution

A pressure-distribution sensor with 81 pressure detectors in a 9×9 array was developed to study dynamic phenomena during the lamination of multilayer printed circuit boards (MLPCBs). The pressure detector is a parallel plate structure instrumented with strain gauges. The array of detectors allows the exact multipoint measurement of the dynamic pressure behavior under conditions of high pressure and high temperature. Experiments with the sensor show that the pressure is distributed so that the maximum pressure is located at the center of the mold. As curing progresses, the pressure gradient from the edges to the center increases, with a commensurate increase in the pressure level at the center of the mold. The final thickness of the cured MLPCB correlates well with the pressure distribution during the initial state of curing. Theoretical models that explain this behavior have been developed. The behavior of the laminate during the initial stage of curing can be represented by viscous fluid flow, and the cured laminate can be treated as a solid mass. The thickness variation in the cured MLPCB expresses the magnitude of the springback of the laminate, which is approximately proportional to the pressure distribution during the initial stage of curing