Optical technology detects tiny defects in thin films

25th November 2016

Enaie Azambuja

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Barrier coatings are vital to coated papers and flexible solar modules to protect against external influences that may impair quality. EU-funded scientists developed a metrology system for fast measurement of defects present in thin barrier films, aiding the manufacture of roll-to-roll barrier coatings in large volumes. Small defects in thin films used in products such as polymer-coated paper and low-cost, flexible PVs can decrease product quality and durability.

This also reduces yield and increases scrap levels, further affecting competitiveness. Exposure of such defective PV modules and polymer-coated paperboard barrier films to water vapour causes short circuits in electronics and the degradation of paper products.

In-line quality control inspection systems alleviate some of the burden, but there is often a trade-off between resolution and speed. Within the EU-funded project NANOMEND (Nanoscale defect detection, cleaning and repair for large area substrates), scientists developed innovative optical technology to better identify, clean and repair micro- and nanoscale defects without reducing production efficiency.

The newly developed instrument is a wavelength scanning interferometer that can make 3D measurements without mechanical movement of the optics by simply varying the wavelength of the light source in an interferometer set-up.

Analysis of measurement information is carried out in a matter of a few seconds. Micro- and nanoscale defects can be measured effectively in noisy environments because the interferometer has integrated environmental noise compensation. The wavelength scanning interferometer can be used to measure both smooth and structured surfaces.

NANOMEND established two pilot lines to showcase the new detection, cleaning and repair technology. The first was developed for extending the shelf life of foods in cartons, and the second for increasing efficiency and lifespan of flexible PVs.

The researchers also investigated the potential of a coating deposition technology called atomic layer deposition to produce ultra-barrier coatings and assess defects in holographic coatings for both flexible PVs and coated-paper packaging.

Enhanced defect detection and repair will improve the quality and lifetime of products employing large-area thin films, enhancing the competitive position of manufacturers. It will also reduce waste, decrease costs and translate to important benefits for the environment. New markets in smart packaging, flexible electronics and large-area lighting can be expected for the partner companies.