Process Variable
Control of heat and pressure during the bonding of multilayer circuit boards ensures the resin flows correctly to fill all internal voids. The lamination pressing parameters include the ramp rate of the temperature and the specific pressure applied at different stages of the cycle. Proper management of these variables prevents the formation of air bubbles and ensures a uniform thickness across the entire panel.
Technicians use data loggers to monitor the conditions inside the press in real time.
Heat Application
Thermal energy triggers the chemical reaction that cures the epoxy or polyimide resin into a solid matrix. Adjusting the lamination pressing parameters to match the specific resin system is necessary to achieve the target glass transition temperature. If the temperature rises too quickly, the resin may flow out of the edges of the panel before it can bond the layers together.
A steady soak at the curing temperature ensures that the polymer chains crosslink fully for maximum structural integrity.
Dimensional Control
Physical force applied during the cooling phase prevents the board from warping as the different materials contract at different rates. Incorrect lamination pressing parameters can lead to registration errors where the internal pads no longer align with the drilled holes. Precise control over the pressure profile helps to minimize the internal stress that builds up during the transition from a liquid to a solid state.
Finished panels are inspected for flatness and thickness uniformity to verify that the pressing cycle was successful. This stage is the final opportunity to set the mechanical properties of the multilayer stack.
