Electrical Parameter
The ratio of voltage to current for a signal propagating along a conductor embedded between two reference planes determines the signal integrity of transmission lines. Designers calculate the stripline characteristic impedance to avoid signal reflections. This electrical matching ensures clean pulse shapes in high-speed systems.
Geometry Dependency
The physical dimensions of the signal trace and the surrounding dielectric layers directly govern the electrical performance. Altering the width of the trace, the dielectric height between the reference planes, or the relative permittivity of the resin modifies the stripline characteristic impedance. Because the signal conductor is shielded by the planes, the resulting impedance is less sensitive to surface contaminants and solder mask variations than that of an equivalent microstrip trace, which makes it ideal for dense multilayer circuit boards.
Trace Verification
In-circuit test coupons are processed alongside production boards to verify circuit parameters. Using time-domain reflectometry to measure the stripline characteristic impedance of these coupons allows the fabricator to confirm that the lamination and etching processes stayed within the specified tolerance. A variation of more than ten percent from the target impedance indicates a defect in layer registration or dielectric thickness, which triggers a rejection of the entire panel.
