Inner Layer Alignment Metrics under Anisotropic Thermal Lamination Shrinkage
Anisotropic inner layer shrink requires asymmetric artwork scaling factors matching prepreg warp and fill glass weave thermal coefficients.
Artwork Compensation Factor
Scaling Ratio
Dimensional modification applied to photolithography tooling compensates for predictable material contraction and chemical etch undercut during printed circuit board fabrication. Process engineers apply an artwork compensation factor to master CAD artwork before plotting glass phototools or streaming digital vector files to direct imaging equipment. This adjustment fixes the target physical width of copper features after subtractive chemical etching.
Subtractive Etching
Chemical sprays dissolve exposed copper laterally while cutting vertically through the foil thickness. Applying an artwork compensation factor expands narrow trace geometries on photolithography tooling, offsetting the loss of copper beneath photoresist edges during alkaline etching. Heavy copper foils demand larger line adjustments than half-ounce foils.
Incorrect compensation results in out-of-tolerance signal impedance values.
Material Distortion
High pressure and elevated temperatures during multilayer lamination compress resin-glass cores, inducing permanent dimensional changes across substrate sheets. Engineering departments calculate artwork compensation factor values by measuring panel dimensional movement across historical production runs using precision optical coordinate measuring machines. Base material orientation influences shrinkage rate along x-axis and y-axis directions differently due to warp and weft yarn tension in the glass substrate.
Inadequate scaling values disrupt layer-to-layer registration accuracy across large panels. Automated optical inspection systems flag uncompensated line geometries as line-width defects prior to outer-layer lamination.