Lamination Step
Mechanical force application during the final stages of multilayer board construction ensures the bonding of individual circuit layers into a monolithic structure. Thermal cycles for sub-assembly pressing ensure the curing of the prepreg resin between copper layers. This step occurs after the internal layers have been etched and inspected but before the outer layers are processed.
It determines the final thickness and dielectric properties of the composite board. Precise control of the pressure cycle prevents the shifting of internal features.
Quality Control
Monitoring the temperature profile inside the press is necessary to achieve a complete chemical bond. If the pressure is too low, voids or delamination can occur during the subsequent soldering processes. High pressure can cause excessive resin flow, leading to thickness variations across the panel.
These variations affect the impedance of the transmission lines and can cause signal integrity problems in high speed applications. Automated logging of the press parameters allows the manufacturer to identify batches that deviate from the validated process.
Verification Output
Thickness measurements and micro sectioning are used to verify the quality of the pressing cycle. A uniform dielectric height across the panel indicates a successful lamination. Registration coupons at the corners of the panel show if any layer shifting occurred during the process.
