The new PI technology adds two steps to this standard process: After the thick film structures have dried on the substrate, a photomask with the desired final structure is positioned above. UV radiation is then applied to the substrate. Where the photomask has structural openings, the UV light penetrates the layer and cures the polymer it contains. At those points where the mask covers the layer, the polymers remain unchanged. This is followed by a wet chemical development process on an aqueous basis. This removes the areas of the layer that were covered by the mask. The thick film adheres to all other areas. This means that the previously 50 micrometer wide structures can be reduced to the desired 20 µm by this process; the final structure is determined by the photomask. Now it goes back to the usual process in which the substrate is sintered. The two additional process steps each take only 15 to 30 seconds and can therefore be easily integrated into the production process.
Tailor-made thick-film pastes are necessary for the PI technology to function properly: These are composed in such a way that they cure reliably under UV lighting but remain unaffected by daylight. A costly “Yellow Room” (as in semiconductor technology) is therefore not necessary. The specific process expertise lies in the precise coordination of the components of the pastes. In the case of metallization pastes, these are powdered metals (silver, gold or alloys), of which the later structures are to consist, the UV-curing polymer and other additives. Developers are currently working on platinum and resistance pastes. The corresponding production facilities are already being developed - the Italian company Aurel is involved here.
IKTS will be presenting their developments at the Productronica trade fair from 12 to 15 November 2019 in Munich (Hall B2, Stand 228).
Further information: https://www.ikts.fraunhofer.de/en.html