Industrial + Specialty Printing

(May 2011) posted on Tue Jul 19, 2011

This article describes the current state of roll-fed electronics printing and discusses what we may expect to see in the near future.

By Deokkyun Yoon, Dong-Soo Kim

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The printed-electronics field is garnering attention from entrepreneurs, investors, and researchers around the world. This field of industry is multidisciplinary; as such, combined knowledge in machinery, materials, manufacturing process, and business is necessary to deliver the right product to the right market.
As the name suggests, printed electronics involves using a printing process in the manufacture of electronic devices and products. These processes include gravure, offset, flexography, inkjet, screen printing, and many more. Some technical challenges arise from the use of printing in producing electronics. We discuss them further on in this article.

At this stage of technological development, printing on either rigid or flexible substrates is considered a supplement to or replacement for traditional electronic-device-manufacturing processes. Table 1
summarizes the comparison between printed media—newspapers and magazines, for example—and printed electronics. The difference stems from the fact that printed media are used to convey information for people to process using their eyes, while printed electronic devices require machines to process electronic information; the level of required resolution and functionality make the difference.

Some of the widely used functional materials for printed electronics include nano/micro-size metal particles, semiconductive polymers, and dielectric materials. Due to the available and required readout resolution, feature sizes smaller than 20 μm need to be printed. Layer thickness and registration accuracy of printed products are closely related to quality control of electronic devices, and ink materials require a high level of quality. Overall, printing tolerance is much tighter in printed electronics.

Roll-to-roll printing
Roll-to-roll printing is considered the holy grail of manufacturing processes for production of flexible and large-area electronics. Substrate materials used in roll-to-roll printing are typically paper and plastic films. Metal foil is also widely used in solar-cell and energy-storage applications. Plastic films such as PET, PEN, and PC are commonly used for their low cost; however, the use of plastic film has involves some technical challenges that must be addressed.

Electronic devices, such as TFTs, solar cells, supercapacitors, thin-film batteries, RFID circuits and OLEDs, are produced continuously by various additive processes, such as flexography, gravure, offset, inkjet, and slot-die coating, in the order of square meters per second. This type of manufacturing process increases productivity by orders of magnitude when compared to the processes used in semiconductor fabrication, such as lithography for silicon wafers.