Innovations: Cheap, Submicron Circuit Printing

Tanaka Kikinzoku Kogyo has developed a new means of printing circuitry onto a substrate that it promises is cheaper and easier than any other option available, while also making an order-of-magnitude leap in diminishing line widths to 0.8 micron.

There are several interrelated reasons touchscreens are still not common outside of smartphones, including manufacturing cost, manufacturing ease, the difficulty of making flexible screens and the difficulty of making screens that are smaller than smartphone screens. While Tanaka KK's process is still essentially a lab process, the technique promises to make touchscreens practical for just about any device. As a practical matter, being able to add touchscreens at a reasonable cost has the potential to provide a significant boost to any number of Internet-of-Things (IoT) devices, including wearables. And of course, cheaper more flexible screens could also reduce the overall bill of materials (BOM) on smartphones, possibly making them more durable as well.

The company just announced the process at Semicon West. Tested on 12-inch square flexible substrates, the process still needs to be refined to make it suitable for large-scale commercial production. The first, most obvious application is touchscreens, but Tanaka KK hopes that as more companies become aware the process is available, other applications might be discovered.

The company calls the technology surface photo-reactive nano metal printing (SuPR-NaP). The process uses a UV source and mask to expose the "ink" (essentially, this means it uses a common light source and a stencil to create circuit patterns). Other approaches rely on expensive specialized pieces of equipment such as lithography, sputtering or etching systems. Those technologies typically require 11 or 12 processing steps; Tanaka's requires five. Also in contrast to rival techniques, it can be performed at atmosphere, so it doesn't require processing in a specially pressurized chamber, and at normal temperatures -- requiring only a cure at 120 degrees C.

Tanaka says its process creates durable circuitry. It has stress-tested circuits printed on flexible substrates, and Tanaka told Light Reading the substrate typically fails before the circuitry does.

Want to know more about communications ICs? Check out our comms chips channel here on Light Reading.

The ability to scale down to submicron linewidths is significant, the company explained. While there had been increasing expectation that printable metal mesh wiring would become useful in touchscreen applications, the problem was that hardly any light could pass through the metal areas, making it necessary to achieve "delicate fabrication of electronic circuit patterns with wires that are invisible to the eye, on the order of a few microns wide."

The company expects that its process will likely lead to expanding use of touch sensors because it is applicable even to very small touch panels (for wearables, for example).

Tanaka KK is the manufacturing arm of Tanaka Precious Metals. Tanaka Precious Metals plans to begin sampling the technology starting in January, and expects that full-scale commercial production might begin in 2018.

The process was developed with the collaboration of Yamagata University, the Flexible Electronics Research Center of the National Institute of Advanced Industrial Science and Technology (AIST) and the University of Tokyo.

Separately, Tanaka announced the acquisition of Metalor Technologies International, which is based in Switzerland.

— Brian Santo, Senior Editor, Components, T&M, Light Reading

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