Press Sequence
Heat and pressure applications drive the fusion of multiple layers of circuitry into a single rigid board structure. The lamination cycle coordinates the melting of prepreg resin with the mechanical evacuation of air to prevent internal voids. It involves specific stages of ramping temperatures to optimize the viscosity of the bonding material before it reaches the full cure stage.
Proper execution ensures that the stack has consistent thickness and electrical properties throughout the panel.
Thermal Ramp
Operators configure the equipment to raise the temperature of the stack at a controlled rate of five to eight degrees per minute. During this window, the lamination cycle allows the epoxy to liquify and flow into the empty spaces between the copper traces. High pressure is applied once the resin reaches its minimum viscosity point to force out any trapped volatiles.
This timing prevents early hardening, which would lock in bubbles, or excessive flow, which would starve the board of necessary insulation. After the pressure peaks, the system holds the temperature at the curing point for approximately ninety minutes to finish the chemical reaction.
Cooling Control
Gradual cooling at the end of the process reduces the internal stresses built up between the copper layers and the substrate. Rapid cooling would cause warping or bowing of the thin glass fiber mats inside the finished circuit.
