In-Situ Free-Space Dielectric Testing of Unclad Substrates
Non-destructive free-space characterization evaluates bulk dielectric properties of raw unclad laminates without etched coupon waste or copper interface errors.
Temperature Coefficient Dielectric Constant
Thermal Drift
Mathematical values describing how the dielectric constant of a substrate changes per degree of temperature change govern the high-frequency stability of printed circuits. This parameter, known as the temperature coefficient dielectric constant, is expressed in parts per million per degree Celsius. It determines how much the resonant frequency and characteristic impedance of a microwave circuit will shift as the operating temperature rises.
Designers of aerospace and outdoor wireless systems rely on this parameter to ensure stable performance across extreme thermal ranges. A low value prevents frequency drift in phase-locked loops and resonant structures.
Impedance Stability
Internal thermal dissipation in high-power transmitters alters the electrical performance of the underlying substrate. If a board has a high temperature coefficient dielectric constant, the local heating from power components will alter the dielectric constant of the substrate. This shift changes the impedance of transmission lines, leading to detuning of filters and amplifiers.
Material Selection
Laboratory characterization of laminate materials involves measuring the capacitance of a test vehicle over a wide temperature range. This test measures the dielectric constant at distinct steps from below freezing to above the maximum operating limit. For demanding high-speed systems, a low temperature coefficient dielectric constant ensures that signal timing remains within specified tolerances.
This testing verifies that the material will perform reliably in the field.