Teflon fluoroplastics enable high measuring accuracy in triaxial cable applications

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  • Very good electrical properties due combination of two Teflon fluoroplastic grades
  • Highly conductive PTFE film for banding
  • Copolymer of tetrafluoroethylene and hexafluoropropylene for insulation and sheathings

The Chemours Company announced that HEW-Kabel, Wipperfürth, Germany uses Teflon fluoroplastics from Chemours for triaxial cables used in measuring devices featuring very high measuring accuracy in the nanometer range.

Very good electrical properties due combination of two Teflon fluoroplastic grades

Capacitive sensors from Micro-Epsilon, Ortenburg, Germany, are designed for contactless path, distance and position measurements, and ensure very high accuracy and stability. So that the measurements are not impaired by outside influences, use is made of special triaxial cables from HEW-Kabel. Due to their structure and the combination of two Teflon fluoroplastic types, these cables have very good electrical properties such as extremely low noise voltage. They thus contribute to the high measuring accuracy of up to 0.2 nm, a figure that corresponds approximately to the diameter of a cesium atom. Typical fields of application include the automation industry, in particular semi-conductor technology and photolithography.

Highly conductive PTFE film for banding

A special characteristic of these cables is the banding. HEW-Kabel has developed its own highly conductive PTFE film for this because conventional films available on the market did not have the necessary quality in combination with high conductivity. The base material used is Teflon 669N X from Chemours. The main reasons for choosing this material were its good compounding and processing properties. The material also has good mechanical properties even with high contents of conductive additives, and can be stripped mechanically.

Copolymer of tetrafluoroethylene and hexafluoropropylene for insulation and sheathings

For the insulation and sheathings, HEW-Kabel uses Teflon FEP 100 X fluoroplastic, a melt-extrudable copolymer of tetrafluoroethylene and hexafluoropropylene. The material is free of additives, has very high chemical resistance and temperature stability, good electrical properties and relatively low permittivity. It also has low outgassing, which is particularly important for applications in a vacuum or clean room. Due to the good processing properties of this Teflon grade, insulating and dielectric layers with low wall thicknesses and very small diameters can be produced.

Extremely low flammability

Both of the Teflon also have extremely low flammability. The triaxial cables produced from them are classified to UL 444 in the highest fire protection category of CMP (CMP = communication plenum). They are noted for their very high flame retardancy and low fume/smoke development.

Application: measuring devices featuring very high measuring accuracy

One example of an application for the capacitive sensors from Micro-Epsilon is a system for measuring the thickness of silicon wafers for the production of photovoltaic cells or semi-conductors. The wafers are measured for their wedgeness and flatness. After sawing, the wafers are subjected to a complex machining stage to attain optimum planarity. With semi-conductor wafers with a thickness of e.g. 900 µm, the flatness must be in the range of below 5 nm. During the course of the various processing steps from lapping and etching through to polishing, the wafers have to be examined several times.



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