Press Force
Automated control systems regulate the amount of force applied to a multilayer stack throughout the heating and cooling phases of lamination. The hydraulic pressure profile ensures that air is evacuated before the resin begins its liquid flow phase. This sequence prevents the formation of voids while maintaining the correct final thickness of the board.
Lamination Sequence
Low pressure initially allows the prepreg to soften and expel trapped gases or moisture. Once the material reaches a specific viscosity, the hydraulic pressure profile increases to force the resin into the gaps between copper traces. This timing is necessary because applying high force too early might squeeze too much resin out of the stack.
A secondary high pressure stage often follows to maintain flatness as the resin undergoes chemical crosslinking.
Force Consistency
Variations in the force applied can lead to uneven dielectric spacing or thickness deviations across the panel. Monitoring the hydraulic pressure profile helps identify mechanical issues in the press or imbalances in the stack distribution. Consistent force application is required to meet IPC Class 3 standards for high reliability electronics.
Final board thickness and copper bond strength are the primary metrics for evaluating the success of the pressure cycle.
