Numerical and analytical evaluation of resin flow during PCB pressing cycles
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This paper presents a novel method to evaluate and subsequently optimize the production cycle of printed circuit boards (PCBs). The critical process step is pressing glass fiber epoxy prepregs with PCB core layers on which conductive copper micropatterns are present [1]. During pressing, the gaps in the copper structures are filled with resin from the prepreg. This requires an increased temperature to make the resin flowable and at the same time to start the curing reaction so that the resin is fully cured at the end of the pressing cycle. The amount of pressure and temperature required depends primarily on the materials used, but also on the type of present copper micropatterns. An algorithm developed in Python scans a binary image of such a PCB copper micropattern layer and identifies particularly critical areas in advance (see Figure 1). Another Python script is used to automatically create CAD geometries of the critical areas, which can be implemented for press simulations in the commercial finite element software 3DTimon (CompositePress module, Toray, Japan). The fluid-structure interaction between resin, fibers, and copper micropatterns is considered using the EULER method in 3DTimon. The combination of analytical models for calculating the resulting layer thickness after the pressing process and the localized analysis of potential weak points using simulation is a powerful tool for PCB manufacturers.
