Photopolymerazed sol-gel optical layers deposited on LTCC substrates

The paper presents novel method for obtaining thin optical layer with precisely assumed shape and size on the LTCC (Low Temperature Cofired Ceramics) substrates. Production of this kind of structures is a very difficult task due to high temperatures of the ceramic firing and roughness of material. Up to now, the easiest way was to use organic material e.g. epoxy-based negative photoresist SU8. Authors present new method, which can be simple, easy and provides high imaging of the pattern. Thanks to using sol-gel method it is possible to make thick layer with predicted parameters changed by sol composition. Unfortunately, most of popular dip-coating deposition methods are not suitable for strips and other defined structures. Authors decided to use photopolymerazed compound added to silica sol-gel composition. As a photoinitatior Irgacure 1800 from Ciba was used. This compound changed structure of the material and allowed to remove non-exposed to UV light parts of the materials. Obtained structures, process flow and examples of the applications are presented in the paper.