Dielectric Thickness Uniformity

Impedance Consistency

Fluctuations in prepreg thickness alter the spatial capacitance between signal traces and reference planes. Uncontrolled resin flow during lamination causes localized thinning near dense copper features, creating impedance discontinuities along long transmission lines. Automated optical inspection and microsectioning confirm that thickness variations stay within tight manufacturing limits.

Lamination Tolerance

Pressing cycles during multilayer board stackup fabrication require balanced hydraulic pressure and controlled heating rates to yield uniform dielectric cores. Variations in resin content or glass cloth weave produce localized thickness gradients, altering the propagation delay of high speed differential pairs. Designers compensate by specifying core materials with low resin flow and tight thickness tolerances for high frequency applications.

Microsection measurements verify layer spacing across panel edges and center zones to ensure compliance with IPC standards.