Printable Electronics - Work in Progress
By Tom Kerchiss, RK Print Coat Instruments
IMost printers and converting practitioners would admit that until quite recently they knew next to nothing about printed electronics. They neither knew what the term printable electronics, often vaguely referred to as disruptive technologies actually meant and were not sure of its relevance to them and the market they operated in or around.
It must be said that information only slowly filtered through, and any insight gleaned tended to be sparse and often disjointed as many of the research and development programs took place under conditions of close commercial security with many of the players in the market, the global branded organisations having much to lose if products and concepts were introduced too early and onto a market that was not ready for them. Many printers and converters, if they thought about it at all, viewed the electronics sector and its links to packaging, automotive and supply chain distribution, medical diagnostics and very much more beside as a very specialist market.
Over time this has begun to change; the possibilities afforded by printable electronics and its links with industry as a whole holds out great promise with many new projects, products and new applications either out in the market or on the horizon.
The drive in printable electronics, circuits and indeed all components is towards ‘ever-thinner’ products. Products such as flexible screens; roll up and go devices, intelligent and active packaging; interactive books, fit bit watches and pictures or screens that a consumer purchases to hang on a wall and which can be changed according to mood or programmed to cycle through a range of scenes are being created with printable electronics. As substrates become thinner in order that they can be integrated in with existing and innovative new manufacturing and product concepts, so the need arises for low cost, flexible, lightweight technology that can sense, store information securely and transmit data.
Before moving too far ahead lets just telescope in on ‘printed electronics,’ and take a snap shot look at process developments. Inorganic semi-conductor fabrication up until comparative quite recent times required the deposition of slabs of semi-conductive film followed by the lithographic impression of the device structure that the chip producer wanted and at the same time the removal of unwanted elements via physical and chemical etching. But this has changed; new processes and techniques are superseding traditional methods of chip production.
The ability to create and employ organic polymers has redefined many of the process parameters ushering in the ability to provide devices for products for the energy market such as photovoltaic solar cells. Print technologies, including flexo, inkjet and gravure can be used with the new generation conductive flexible polymeric materials.
As printed electronics no longer needs to rely on additive film growth to control crystal and formation of the electronic structure, developers theoretically have a greater degree of choice with regard to substrate and design configuration. This was not the case in the not too distant past, when developers were restricted by material and by the lattice matching of a semi conductor material or building block.
Newer flexible substrates can often now be matched to specific and targeted product requirements such as thin curved and conformable surfaces. Ultra thin and unlike traditional semi conductors that used thin wire to form circuits new generation materials are often printed using conductive inks and can be integrated discretely into product spaces that take up the minimum of real estate. This makes them ideal for anti-counterfeiting products; active, intelligent or so-called smart packaging purposes.
The dynamics with regard to printing electronics and associated processes has altered somewhat and now positions mainstream print processes more centre stage. For example, many of the components that are integrated in with products must be technically functional as well as graphically or visually appealing. Often, as in the case of flexible circuitry and membrane switches, the printed image requires dimensional stability, not only in image length and width, but in ink deposition as well. Flexography is a process that is economical and offers excellent print resolution possibilities.
Controlling process variables, developing new products and determining what will work and what will not occupies the minds of many engaged in printable electronics and integration in with more familiar lines of products such as printed packaging. Many issues centre on ink and coating manufacture, compatibility issues and deposition. The latter, the smooth coating of ink in thin or discrete and accurate layers is critical.
Concern about ink deposit thickness is not unique to the electronic printing specialist. Packaging converters and others know that print thickness controls colour density. Printers/converters, those who manufacture backlit displays for instance, must lay down a consistent thickness of transparent ink or coating in order to achieve the visual objectives. The difference between success and failure is one of degree. The light transmission properties must be consistent and repeatable from batch to batch. Colour must match exactly because the translucent properties of the ink transmit light to within a specified degree of tolerance.
A strong collaboration between printer/converters, research departments, consumable providers and customers is a must. Collaborative efforts involve considerable trialling, product evaluation, monitoring and experimentation, especially when products are in the early days of development. Many variables impact on performance and on meeting objectives. These include but are not limited to: ink characteristics, ink-drying time, colour matching; degree of print accuracy; material waste; image length and width.
Quality control, product development tools and systems that enable users to colour match; determine printability requirements such as durability, flexibility, chemical resistance, rub resistance and to evaluate how various process and material elements interact or react are useful.
RK Print Coat Instruments sample preparation or colour communication devices such as the FlexiProof 100, FlexiProof UV and FlexiProof LED UV are used for a wide range of quality control and product development processes associated with the production and use of flexographic inks. The FlexiProof UV and FlexiProof LED UV incorporate a miniaturised UV curing system allowing for printing and curing to be under taken seamlessly. The LED version is ideal for heat sensitive applications.
A scaled down but component critically exact version of a conventional flexo press, the FlexiProof, an award winning concept can be used to undertake product trials without necessarily having to rely on a production press. This saves on material waste, speeds productivity and helps identify issues off press before they become costly and time consuming on press. Colour matching can be undertaken quickly and samples provided for a customer to approve and sign off.
A flag ship system; one that has already been manufactured and supplied for printable electronics and similar high tech sectors is the customer bespoke VCM coater.
The VCM or Versatile Converting Machine is suitable for research and development and for pilot and production purposes and is being used for a wide range of industrial purposes. Apart from printable electronic applications it is also being used for security and hologram; for latent imaging; medical diagnostics; fuel cell and battery; for polymeric semi-conductor production and for solar reflective films and for other demanding applications.
Sturdily constructed its framework enables it to accommodate wider and heavier substrates to be processed while still enabling considerable flexibility to expand or modify the system as developments or applications change. This is particularly important in fast moving product development sectors such as electronics.
The VCM offers customers a broad range of coating options; print technologies; laminating options, i.e., wet or dry as well as a number of customer selectable drying/curing options.
RK Print Coat Instruments Ltd
Litlington, Royston, Hertfordshire SG8 0QZ
www.rkprint.com sales@rkprint.com
Source: RK Print Coat Instruments Ltd
