Pressure Application
Incremental increases in the compressive force applied by hydraulic press platens during the lamination cycle optimize the resin distribution in multi-layer boards. Platen pressure ramping controls the rate at which the resin is squeezed between layers as the prepreg material transitions from a solid to a liquid state. This parameter is adjusted based on the board’s complexity, the copper weight and the glass style used in the prepreg.
It prevents resin starvation in dense trace areas.
Flow Optimization
The timing and rate of the pressure ramp must be aligned with the resin’s viscosity curve to ensure a void-free laminate. In the early stages of the cycle, low pressure is applied to allow the prepreg resin to melt and wet the surfaces without being forced out of the laminate prematurely. As the temperature rises and the resin viscosity decreases, the pressure is ramped up to its maximum value to force the liquid resin into the spaces between the copper traces and to drive out any trapped air pockets.
If the pressure is increased too quickly, the resin will squeeze out of the panel, leaving dry spots.
Laminate Flattness
Uniform pressure ramping reduces internal stresses within the board panel, which minimizes warp and twist. This physical stability is necessary for high-speed automated placement machines that require flat surfaces to place small components. Balanced pressure application ensures that the board remains flat through subsequent thermal cycles.
