Thermosetting Recipe
The programmed sequence of temperature and pressure applied over time during multilayer board fabrication defines the mechanical press cycle. Using a precise lamination press profile is critical for curing the prepreg sheets and bonding the copper layers into a single homogeneous panel. This thermal profile is customized for each resin system.
Resin Flow
The process begins with a rapid temperature ramp that lowers the viscosity of the epoxy resin, allowing it to flow and fill the gaps between the copper traces. During this low-viscosity window, the press applies a primary pressure, typically between two hundred and three hundred and fifty pounds per square inch, to expel air bubbles and consolidate the layers. If the pressure is applied too early, too much resin is squeezed out, resulting in dry spots and resin-starved areas.
If applied too late, the resin begins to cross-link and will not flow properly, leaving internal voids that cause delamination during subsequent reflow. The lamination press profile dictates the precise holding times at the peak temperature to ensure complete curing of the polymer chains.
Laminate Quality
Cooling must also be controlled to prevent build-up of internal thermal stress in the panel. Fast cooling rates can cause board warpage and twists that interfere with automated component placement. Following a structured cool-down curve ensures a flat, stable board that remains mechanically sound.
