Thickness Reduction
Structural compression of prepreg glass fabric and resin matrix along the normal axis determines final multilayer board laminate thickness. Hydraulic press pressure forces liquid resin into copper pattern topography while compressing softened prepreg glass plies together. Controlling z axis compaction governs layer-to-layer spacing, overall board thickness and characteristic impedance of internal signal traces.
The boundary of this physical compaction mechanism covers the lamination process step and excludes lateral panel shrink.
Lamination Kinetics
Higher press pressures and extended resin flow windows allow prepreg glass bundles to compress tighter, reducing dielectric spacing between copper layers. Insufficient compaction leaves micro-voids in internal resin areas, whereas excess compaction causes resin starvation and dielectric breakdown risk. Monitoring z axis compaction enables lamination engineers to predict final dielectric height within tight tolerances required for impedance-controlled trace stackups.
Optical measurement of microsection coupons verifies that actual ply thickness matches theoretical modeling parameters. Stackup calculation software incorporates compaction factors specific to resin content and glass style combinations. Uniform Z-axis compression across the entire panel prevents thickness variations that cause board twisting or warping during assembly reflow.
Impedance Verification
Microsection analysis measures finished dielectric spacing between reference planes to verify characteristic trace impedance calculations. Controlling Z-axis dimensions prevents signal reflection defects in high-speed digital transmission lines. Process adjustments tune press pressure profiles to hold target laminate thickness tolerances.
