Resin Saturation
Woven E glass reinforcement acts as the mechanical skeleton for printed circuit board substrates by establishing dimensional stability and dielectric uniformity across thermal excursions. 7628 glass fabric delivers a balanced warp and fill count that optimizes resin pick up during the prepreg manufacturing stage. Excess resin creates thick insulating layers while insufficient resin leaves dry spots prone to electrical shorting.
Automated optical inspection systems scan the treated cloth for foreign debris and broken filaments before the material enters the treating tower. Calibrated squeeze rollers control the resin content to strict mass percentages so that the resulting dielectric constant remains predictable during subsequent lamination cycles.
Thermal Deformation
Multilayer lamination presses apply heat and high pressure to bond copper foil and prepreg stacks into rigid panels. 7628 glass fabric restrains resin flow during this pressing cycle to prevent core thickness variation across the board area. Thermal expansion mismatches between the copper circuitry and the glass epoxy matrix generate shear stresses that can cause barrel cracking in plated through holes.
Automated X-ray inspection equipment measures hole wall integrity and registration accuracy after reflow soldering to verify that the reinforcement withstood the thermal shock. Low twist yarn configurations reduce yarn pattern print through on outer layers, preserving fine line impedance control for high frequency signal traces.
Mechanical Routing
Post etch panel separation requires specialized carbide routers to machine board outlines and internal cutouts without inducing delamination or fiber pullout. 7628 glass fabric exhibits high tensile strength along both principal axes, which prevents dimensional warping when mechanical stress is applied during CNC machining. Spindle speed and feed rate parameters must match the density of the woven glass bundle to avoid thermal degradation of the epoxy binder at the cut edge.
Automated coordinate measuring machines verify edge profile tolerances and hole locations against CAD data before electrical testing validates circuit continuity.
