Stackup Bonding
Fabricating a high-density circuit board involves the permanent bonding of multiple etched layers. Through the application of heat and pressure in a vacuum press, multilayer lamination turns a stack of cores and prepreg into a single monolithic structure. The resin in the prepreg melts and flows to encapsulate the copper traces before hardening.
This process creates the internal structure required for complex signal routing.
Pressure Distribution
Uniform force is required across the entire panel to prevent air bubbles and thickness variations. During multilayer lamination, the press must maintain a specific ramp rate for both temperature and pressure to ensure the resin flows correctly. If the pressure is applied too late, the resin may cure before it has filled all the voids.
If it is applied too early, too much resin might be squeezed out of the edges. Sophisticated press plates and padding materials help distribute the load evenly over the delicate copper features. High-quality lamination requires precise synchronization between the heat and the load application.
Registration Accuracy
Internal layers must remain aligned to each other within very tight tolerances for through-hole drilling. Any shifting during multilayer lamination results in broken connections or short circuits. Modern factories use X-ray systems to verify the registration of internal features after the bond is complete.
