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100 DESIGN007 MAGAZINE I OCTOBER 2019 tages and disadvantages as well. It's not prac- tical to compare all of the bullet points for both technologies; instead, we should consid- er whether the process is capable of building key parts at an acceptable cost. Once we pass the cost test, we can determine if there are any critical issues with the technologies. It is easy to determine which technology to employ, since both have measurable perfor- mance at each milestone. Usually, the con- ductivity for thick-film circuits is two or three orders lower than copper-etched circuits, so there is no argument against using copper foil circuits. Since silver ink conductors have mi- gration issues, thick-film circuits require spe- cial constructions to guarantee reliable insu- lation. Progress and innovation over the last 20 years alone have changed the process of generating fine lines with thick-film circuits. Volume manufacturers can produce 50-micron lines and spaces on plastic films. Thick-film circuits have the equivalent fine-line capabili- ties as thin copper foil circuits. However, there is still a gap between reliable technology and process yields. A thick-film printing process can generate low-cost via holes for double-sided circuits and multi-layer circuits. This could be an alterna- tive process for additional layers. Traditional etching processes require an appropriate flex- ible copper-clad laminate as the starting mate- rial. On the other hand, a thick-film process is available for all kinds of plastic films, and elas- tic materials are available for wearable devices. Generally, copper foil circuits are designed to have enough heat resistance for soldering, but most thick-film circuits do not have a high heat resistance due to the organic matrix of the conductive inks. One advantage of the thick- film process is the ability to create operative layers for functional devices, such as flexible sensors, photovoltaic cells, batteries, displays, and more. This is achieved from a simple print- ing process assuming the appropriate inks are available. A traditional etching process has lit- tle to no capabilities for functional materials. The actual designs for flexible devices cou- pled with the manufacturing processes are not simple. If you have the ability to use a tradi- tional etching process, this is a safe bet. How- ever, if the construction is not possible using the etching process, you should consider the thick-film printing process with appropriate ink materials. Headlines 1. Mitsubishi Electric (electric and electronic company in Japan) Developed a multi-cell GaN-HEMT with dia- mond substrate for industrial uses that makes power efficiency 10% higher, reducing the temperature increase to one-sixth. 2. NEDO (R&D organization) Will start field testing of a biomass power generator in October. Bamboo is available as the main fuel material. 3. Taiwan Pucka (flexible circuit manufacturer in Taiwan) Established the hybrid process of polymer thick-film and copper plating. The new pro- cess significantly reduces the conductor resis- tance in the circuits. 4. Toshiba Memory (semiconductor manufacturer in Japan) Expects a big loss in 2019. Plans to buy SSD business of Lite-On in Taiwan. 5. Murata (device supplier in Japan) Had an open house at the newly built bat- tery manufacturing Koriyama plant, which will be the core facility of the battery business. Progress and innovation over the last 20 years alone have changed the process of generating fine lines with thick-film circuits.

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