Roll-To-Roll Processing Becomes A Priority

May 10, 2007
Whenever flexible-display manufacturing is discussed, the term "roll-to-roll" processing often is invoked. Much like newspaper production, this process cost-effectively creates electronic devices on a roll of a large flexible substrate (see the figure)

Whenever flexible-display manufacturing is discussed, the term "roll-to-roll" processing often is invoked. Much like newspaper production, this process cost-effectively creates electronic devices on a roll of a large flexible substrate (see the figure). Circuits made with thin-film transistors (TFTs) and other devices can be easily patterned onto such substrates, which can be up to thousands of feet long and 10 to 20 feet wide. Some electronic devices can be patterned directly on the substrate, much like an inkjet printer deposits ink. For most semiconductors, though, the devices must be patterned using photolithography techniques.

Proponents of roll-to-roll processing argue that the large-scale manufacture of flexible displays may not be practical using batch processing methods of photolithography and vapor deposition. Yet when it comes to the feasibility of roll-to-roll processing, an equal number of skeptics instead favors modifying existing processing equipment, like those used for LCDs, to make cost-effective flexible displays.

"It's very reasonable to assume that as the LCD industry goes to generation-six processes and higher, they will retire some of their older lines. And those older lines, which will be fully depreciated, will be working toolsets, and they will be modified appropriately and adapted to a flexible display application," says Greg Raupp, director of the Flexible Display Center at Arizona State University, where government and industry funding is being funneled toward developing key manufacturing processes that will make flexible displays commercially viable. Raupp argues that we "might" potentially get lower-cost flexible displays using roll-to-roll processing, but it won't be the necessary higher-quality display possible using existing photolithographic and vapor-deposition techniques.

The final word on roll-to-roll processing has yet to be rendered, since it's a technology still in development with lots of activity going on. Novaled, for example, is working to make the manufacture of organic LEDs (OLEDs) practical. The company is developing what it calls a Rollex process for putting OLEDs on flexible substrates. Funded by the German government's Federal Ministry of Education and Research, the program is aimed at developing highly efficient, low-priced OLEDs.

About the Author

Roger Allan

Roger Allan is an electronics journalism veteran, and served as Electronic Design's Executive Editor for 15 of those years. He has covered just about every technology beat from semiconductors, components, packaging and power devices, to communications, test and measurement, automotive electronics, robotics, medical electronics, military electronics, robotics, and industrial electronics. His specialties include MEMS and nanoelectronics technologies. He is a contributor to the McGraw Hill Annual Encyclopedia of Science and Technology. He is also a Life Senior Member of the IEEE and holds a BSEE from New York University's School of Engineering and Science. Roger has worked for major electronics magazines besides Electronic Design, including the IEEE Spectrum, Electronics, EDN, Electronic Products, and the British New Scientist. He also has working experience in the electronics industry as a design engineer in filters, power supplies and control systems.

After his retirement from Electronic Design Magazine, He has been extensively contributing articles for Penton’s Electronic Design, Power Electronics Technology, Energy Efficiency and Technology (EE&T) and Microwaves RF Magazine, covering all of the aforementioned electronics segments as well as energy efficiency, harvesting and related technologies. He has also contributed articles to other electronics technology magazines worldwide.

He is a “jack of all trades and a master in leading-edge technologies” like MEMS, nanolectronics, autonomous vehicles, artificial intelligence, military electronics, biometrics, implantable medical devices, and energy harvesting and related technologies.

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