Roll-to-roll processing

In the field of electronic devices, roll-to-roll processing, also known as web processing,^[1] reel-to-reel processing or R2R,^[2] is the process of creating electronic devices on a roll of flexible plastic, metal foil, or flexible glass.^[3] In other fields predating this use, it can refer to any process of applying coating, printing, or performing other processes starting with a roll of a flexible material and re-reeling after the process to create an output roll. These processes, and others such as sheeting, can be grouped together under the general term converting . When the rolls of material have been coated, laminated or printed they can be subsequently slit to their finished size on a slitter rewinder.

Large circuits made with thin-film transistors and other devices can be patterned onto these large substrates, which can be up to a few metres wide and 50 km (31 mi) long.^{[citation needed ]} Some of the devices can be patterned directly, much like an inkjet printer deposits ink. For most semiconductors, however, the devices must be patterned using photolithography techniques.

Roll-to-roll processing of large-area electronic devices reduces manufacturing cost.^{[4] [2]} Most notable would be solar cells, which are still prohibitively expensive for most markets due to the high cost per unit area of traditional bulk (mono- or polycrystalline) silicon manufacturing. Other applications could arise which take advantage of the flexible nature of the substrates, such as electronics embedded into clothing, large-area flexible displays, and roll-up portable displays.

• Inorganic LED - Flexible LED is commonly made into 25, 50, 100 m, or even longer strips using a roll-to-roll process. A long neon LED tube is using such a long flexible strip and encapsulated with PVC or silicone diffusing encapsulation.
• Organic LED (OLED) - OLED for foldable phone screen is adopting roll-to-roll processing technology.

A crucial issue for a roll-to-roll thin-film cell production system is the deposition rate of the microcrystalline layer, and this can be tackled using four approaches:^[5]

• very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD)
• microwave (MW)-PECVD
• hot wire chemical vapour deposition (hot-wire CVD)
• the use of ultrasonic nozzles in an in-line process

Roll-to-roll processing has been used in the manufacture of electrochemical devices such as batteries,^[6] supercapacitors,^[7] fuel cells,^{[8] [9]} and water electrolyzers.^[10] Here, the roll-to-roll processing is utilized for electrode manufacturing and is the key to reducing manufacturing cost^[11] through stable production of electrodes on various film substrates such as metal foils, membranes, diffusion media, and separators.

• Amorphous silicon
• Low cost solar cell
• Printed electronics
• Roll slitting
• Rolling (metalworking)
• Thin film solar cell
• Web manufacturing
• Tape automated bonding, TAB

• Electronics manufacturing
• Semiconductors
• Engineering stubs

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