Prepreg Resin Flow Mechanics in Multilayer PCB Lamination
Prepreg resin flow during vacuum lamination requires balancing platen ramp rates against copper fill volume to eliminate internal clearance microvoids.
Woven Glass Fabric
Structural Base
Interlocking yarn bundles made of fine glass filaments provide the primary mechanical reinforcement and structural stiffness for printed circuit board laminates. This woven glass fabric holds the cured epoxy resin together, giving the board its strength and preventing electrical shorts under thermal stress. The density of the weave controls the dimensional stability of the board.
Fibers of this type form the physical backbone of the dielectric substrate.
Resin Absorption
Absorption of liquid epoxy into the spaces between glass bundles is necessary to create a uniform dielectric layer. When woven glass fabric is used, variations in the weave density create paths of high and low resin concentration across the board. This non-uniformity can cause differences in the dielectric constant, affecting the speed of high-frequency signals.
Choosing tight, uniform weaves minimizes these material variations.
Drilling Integrity
Resistance of glass fibres to drilling forces affects the quality of through-holes drilled for component mounting and layer connection. If woven glass fabric has a coarse weave, the drill bit can deflect as it hits the tough glass bundles, leading to off-center holes and pad damage. Using fine-weave glass fabrics reduces tool wear and prevents internal fracturing along the fiber paths.
These fabrics are checked for moisture absorption before lamination to ensure that the finished board does not suffer from conductive anodic filament growth during field operation.