Prepreg

Thermal Window

Heating rates during the initial ramp phase dictate how viscosity drops before crosslinking reactions lock the molecular structure permanently. Excessive heat application causes premature gelation, trapping volatiles inside dielectric layers and creating internal blisters that fail automated optical inspection. Conversely, sluggish thermal delivery permits resin to escape past tooling pins, leaving dry spots with inadequate dielectric thickness beneath surface mount pads.

Standard automated optical inspection systems catch surface anomalies, while microsection analysis reveals internal resin starvation after thermal stress exposure.

Dielectric Boundary

Interlayer insulation thickness depends strictly upon initial resin weight and glass style selection within the uncured composite. Production engineers calculate resin volume fractions to maintain controlled impedance values across high frequency signal traces routed through inner layers. Operating frequencies demand strict thickness tolerances because variations alter propagation delays and cause signal degradation across differential pairs.

Post lamination thickness checks confirm compliance with customer stackup specifications before drilling operations commence.