quantify & testing
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RF Testing of Materials
Teststrukturen für die Charakterisierung innovativer neuer Materialien und Schaltungstechnologien
New Materials – Novel Opportunities!

RF applications are conquering the world at a rapid pace. As a basis for all applications, the materials of the products itself as well as the surrounding systems have to fulfil certain RF requirements, too. Mostly, the electrical properties of such novel (to the RF industries and vice versa) materials are not known quite well. Applications such as parking-aids and automotive-cruise-control (ACC), e.g. at 24 GHz and/or 77/79 GHz, will perform badly, if the material properties of substrates, radomes, packages and covers are not taken into account at the product design phases.

Furthermore, there is also a tremendous interest from substrate vendors and PCB-manufacturing plants to extend the applications of their materials and their manufacturing processes beyond the current limits. Quality assessment and process optimization are their typical demand.

Engineers, involved in the development process of novel products, do have also a huge interest to understand the material behaviour and their properties and thus on how to use them for new, smart designs of their products.

IMST, a well known player in the areas of RF & microwaves, has established a full range service portfolio to cover this demands from manufacturers, developers and integrators for the characterization of RF materials.
Characterization of conductive layers and bulk materials
IMST with its accredited laboratories offers to the following services:
  • Characterisation of
    • Bulk materials: Substrates, dielectrics, ceramics, plastics, ...
    • Surfaces: Traces, conductive adhesives & films,…
  • Consulting regarding
    • RF materials,
    • Use and application,
    • Optimization of processes,
    • and
    • Measurement techniques.

Bulk materials, e.g. substrates, are determined by the electrical properties dielectric constant (permittivity, εr) and the loss tangent (tan(δε)), surfaces and their finish are characterized by frequency-dependent properties such as the conductivity/resistivity (κ) or the transmission line losses (a). The properties to be measured can be determined in a very broad parameter range:

  • Frequency Range: 10 MHz – 100 GHz
  • Temperature Range: -40°C - +85°C
  • Permittivity, εr: 1...100±0,01
  • Loss tangent, tan(δε): 0,1...0,001±0,001

Depending on the intended use of the materials to be characterized suitable test approaches will be chosen. Parameter values may be subject to changes, according to special application scenarios.An Overview about the services, examples and references can be found here for download (PDF 1MB).

Don’t hesitate to contact us for more information or any specific enquiries.


Methods for the determination of dielectrics and conductive materials:

Waveguide Methods:
The most classical method to determine the dielectric properties (relative dielectric constant, permittivity, εr; loss tangent, tan(δε)) utilizes cylindrical or rectangular waveguide resonators. At each frequency range of interest suitable resonator structures are required. Furthermore, the dimensions of the samples are mostly not easy to create (required dimensions, tolerances for the cylindrical samples, etc.).

However, utilizing transmission waveguide techniques instead of cavity based resonator structures the electrical properties can be easily determined with an appropriate accuracy. Cubical instead of cylindrical samples are also much easier to manufacture and thus, they reduce test costs drastically, compared to waveguide resonator techniques.

However, sometimes also this method is not suitable, because of the frequencies are too low and/or the material samples have unusual dimensions. E.g. at frequencies below 1 GHz samples should have dimensions of 0.2 m x 0.1 m x 0.4 m, which is quite unpractical.

Coupled resonators for low-frequency material determination
Coupled Resonators:
Using two, slightly different, coupled resonators, see fig., enables also a frequencies in the range of 100 MHz and 1 GHz the characterization of very thin dielectric samples, e.g. as low as 100 micrometer. The samples under test together with the parallel-plates of the electrodes are forming a capacitor which is quite sensitive to the electrical properties.


Surface Quality Determination – Ring-Resonators and Meander-Lines

Most of the losses of RF circuits are not caused by dielectrics but by the Ohmic losses of conductive layers and the RF-related skin-effect. They are not purely dependent on frequency, but also on the transmission, line geometries, surface roughness, layer materials, etc. Consequently, the characterization should heavily be dependent on the intended application scenario.

Ring-Resonators are a method to characterize the losses at the resonances of the resonators. This is a quite smalband approach. However, advantage can be gained from getting the dielectric properties of the substrate material at the same time.

Meander-Lines enable the measurement of the transmission line losses (attenuation) per unit length and thus they allow for the investigation of different effects such as skin-effect and layer configuration, etc.