Packaging films made of plastic in particular are very popular in all areas of life, powerful and hard-wearing. Whether baked goods packaging, construction films, ice bags, packaging for dairy products, confectionery packaging or newspaper film, each of us has several copies at home. (wikipedia.org)
These plastic packagings are produced by film extrusion. Solid to viscous curable plastics are continuously pressed out of a die or die under pressure. Bodies with the cross-section of the opening, called extrudate, are produced in theoretically any length. (wikipedia.de)
Material selection and processing based on efficient quality assurance is of major importance. With regard to quality assurance in film production, the film thickness must first be checked.
Depending on the function of the layers, thicknesses ranging from a few nanometers to several hundred micrometers have to be measured. In the case of films with functional surfaces, it is also necessary to record and evaluate not only the thickness but also the topography of the film surfaces. The measurement of the soft film surface requires a non-contact sensor, which measures layer thickness and topography, as well as determining the surface roughness. The measuring method handles complex tasks:
· fast line measurements along the film strip as well as
· high-resolution 3D measurements to examine the fine structures of the film.
The FRT MicroProf® with optical sensors bridges the gap between information requirements and practicable measurement methods. The MicroProf® measuring tools are equipped with a confocal, chromatic distance sensor for applications with film thicknesses over 40 µm. The sensor measures the distance to the interfaces of the films with high resolution and determines the film thickness from the difference. For non-transparent films, the TTV system offers an optimal solution for determining the film thickness. The sample is measured from both sides at the same time, allowing the sample thickness, total thickness variation (TTV), 3D topography and roughness of the top and bottom sides to be determined.
Fast, non-contact topography and profile measurements are possible on highly reflective and mirroring surfaces as well as on highly absorbent and rough, jagged targets.
Optionally, a sensor can be used for the measurement of thin foils from 2 µm thickness, which evaluates the interference of the light reflecting on the upper and lower surfaces of the foil. A modified method allows topography measurements for the characterization of the foil surfaces. Both sensors can be combined in the MicroProf®. In addition, a reflectometer is used for the measurement of thin film systems. With the FTR sensor, layer thicknesses from 10 nm with a resolution of 1 nm can be determined.
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Topography of an extruded polymer film
Roughness profile of an extruded polymer film, Ra=0.157 µm
Film thickness mapping of a Si3N4 coating on a Si substrate
Film thickness measurement of a transparent foil, thickness distribution
Film thickness along the profile (black line), determination of the thickness variation
MicroProf® 200 - optical surface metrology tool