SDK Develops Conductive Ink for Screen Printing of Film Circuits
―Contributing to Performance Improvement of Electronic Devices―
Showa Denko K.K.
May 28, 2015
Showa Denko (SDK) (TOKYO:4004) has developed an electro-conductive silver ink that can form thin film electronic circuits through screen printing.
In recent years, in order to attain higher performance, many electronic devices adopt multilayered circuit boards, and the need for thin film electronic circuits is increasing. However, conventional electro-conductive inks contain not only particles of metals including silver, but also polymers to increase viscosity of inks, and solvents. Therefore, in order to maintain necessary viscosity of electro-conductive inks and simultaneously attain required electro-conductivity even after the formation of thin film circuits, it is necessary for ink manufacturers to minimize the amount of nonconductive polymers used, and increase density of metal particles in inks. Moreover, since screen printing, which is the mainstream method in the field of printed electronics, mimeographs electro-conductive inks oozing from backside of stencils, certain volume of ink is required to penetrate mesh on the stencils. Therefore, the membranous ink after screen printing tends to be thicker than those formed by other methods of printing.
This time, SDK successfully improved its proprietary compositions of polymers and solvents, and developed silver ink that secures enough electro-conductivity and viscosity even in the form of thin film, without increasing density of precious silver particles. Electric circuits printed with this new ink can form thin film of less than 1 micrometer* in thickness through simple after-treatment process to vaporize and dry solvents out with heat.
Though this new ink can attain enough electro-conductivity even through the simple after-printing-treatment process with heat, the parallel use of Photonic CuringTM** process technology, which SDK has already introduced, enables this new ink to attain higher electro-conductivity through very short processing time. In addition, SDK has developed undercoating and overcoating agents optimized for the new ink. These coating agents can further enhance adhesive strength of the ink, while maintaining its electro-conductivity.
SDK will have a lineup of silver inks with a variety of grades that can form film circuits with various thicknesses ranging from thin-type (1 micrometer) to thick-type (30 micrometers and over), and start shipment of sample inks and related materials in June 2015***.
Printed electronics technology, which forms electronic circuits applying printing technology, is expected to be increasingly used as it enables substantial simplification of manufacturing processes. While pursuing downsizing and weight saving of electronic devices, their manufacturers desire technical development to achieve not only further thinning but also further narrowing of electronic circuits. Through application and sophistication of the technologies mentioned above, SDK will aim to develop technologies to realize circuit with width of 5 micrometers or less for screen printing and other printing methods.
SDK will exhibit the new silver ink at “JPCA Show 2015” which is to be held at Tokyo Big Sight from June 3 to 5, 2015.
- *1 micrometer (µm) = one thousandth of millimeter
- **SDK’s news release on April 11, 2011: “SDK Develops Printable Conductive Inks for Electronics”
- ***This product is under development, and the specifications indicated here are subject to change.
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