Overview
IEC 63616:2025 specifies a non‑destructive method for measuring the conductivity of metal thin films at microwave and millimeter‑wave frequencies using a balanced‑type circular disk resonator (BCDR). The method evaluates either a free metal foil used with a substrate or the interfacial conductivity of a metal layer formed on a dielectric substrate. By exploiting higher‑order TM modes of a single BCDR, IEC 63616 enables broadband conductivity measurements with one resonator over the frequency band specified in the standard (10 GHz to 170 GHz).
Key topics and technical requirements
- Measurement principle
- Uses a balanced‑type circular disk resonator (BCDR) composed of a thin metallic disk sandwiched between matched low‑loss dielectric sheets and parallel conductor plates.
- Conductivity is derived from resonant frequency and unloaded Q‑factor comparisons between a reference BCDR and the BCDR containing the sample.
- Modes and bandwidth
- Higher‑order TM modes of the BCDR provide a broadband measurement capability from a single physical resonator.
- Instrumentation
- A vector network analyzer (VNA) is recommended (scalar analyzers acceptable) to measure S21 transmission, determine resonant frequencies and Q‑factors, and apply complex‑plane circle fitting for accuracy.
- Careful control of coupling (under‑coupled ports), IF bandwidth, and frequency sampling density (≤ 1/10 of FWHM) is required.
- Practical limits and constraints
- The standard identifies cutoff constraints (coaxial line cutoff, excitation hole cutoff, radial radiation cutoff) that limit the maximum usable frequency.
- Reference foils with known conductivity are required for relative measurements; surface roughness and skin‑depth effects should be considered.
- Procedures
- Includes apparatus preparation, VNA calibration, measurement steps for metal foils and metal‑clad substrate samples, and periodic resonator checkup.
Applications and users
IEC 63616:2025 is targeted to professionals and organizations involved in high‑frequency materials metrology and RF component manufacturing:
- Material scientists and thin‑film researchers characterizing metal layers for RF/mmWave performance.
- RF/microwave engineers validating conductor losses in advanced substrates and foil materials for antennas, filters, and interconnects.
- Metrology institutes and test labs performing traceable conductivity measurements at microwave/millimeter‑wave frequencies.
- Manufacturers of metal foils, PCB/clad materials, and deposition processes needing non‑destructive conductivity evaluation.
Keywords: IEC 63616:2025, conductivity measurement, metal thin films, microwave, millimeter‑wave, balanced‑type circular disk resonator, BCDR, vector network analyzer, interfacial conductivity, broadband measurements.
Related standards
- IEC 61788‑7 - referenced as a conventional dielectric resonator method for comparison.
- IEC Electropedia and IEC publications for terminology and measurement best practices (see IEC webstore for the full document).