Impedance Tolerance

Manufacturing Variable

Substrate thickness and dielectric constant variations are the primary factors affecting trace impedance during board fabrication. Etching accuracy directly controls the width and shape of the copper trace, meaning that over-etching reduces the cross-sectional area and raises the characteristic impedance. Consistent lamination pressure and controlled prepreg resin flow are also required to keep the trace height uniform across the entire board surface.

Transmission Impact

Signal reflection occurs when high-frequency pulses encounter impedance mismatches along a transmission line. If the impedance tolerance is exceeded, the resulting reflections can lead to rise-time degradation and increased bit error rates in high-speed digital circuits. Precise line modeling and automated coupon testing during manufacturing are used to verify compliance with these limits.