There has been increasingly growing interest in recent years in the field of printed electronics (PE) and radio frequency identfication (RFID). IDTechEx’s estimates on the potential size of the overall PE market have ranged up to $57 billion by 2019, while it has placed the potential value of the RFID market as high as $25 billion by 2018.
For the RFID market to hit that figure, one of the key applications would be item level tagging. RFID has been thought of as a “smart” replacement for bar codes, which could be a tremendous asset for suppy chain management.
However, RFID has yet to take off as originally predicted, as the cost of an RFID tag has yet to come down to a figure that is sustainable for item level tagging. Still, RFID and conductive inks offer plenty of opportunities as new applications emerge.
“The RFID market developed in two waves so far,” said Dr. Wolfgang Mildner, managing director of PolyIC. “The first wave was that RFID was used in closed-loop applications and was still very expensive. The second wave was when RFID was standardized and EPC developed. That made RFID easier to use and less expensive. The third wave we anticipate is the wave that will be enabled through printed RFID technology.
“The conventional/standard RFID market is not PolyIC’s target market; however, we do look at it regularly,” Mr. Mildner added. “What PolyIC can say is that growth is not developing as fast as it was expected. However, we observe that there is increasing interest in RFID.”
“The market for RFID and conductive inks continues to grow, but less quickly than had been predicted,” said Neil Forsythe, new business development – security & sensors, coating effects business segment for Ciba Corporation. “In some cases, it seems projects in this area are now receiving less emphasis than previously. The development of silver conductive inks suffered from the high cost of the silver peaking at nearly $20 per ounce in early 2008.Now, even with lower, but climbing, silver pricing, the current economic climate means that the expectation for these sectors has lowered.”
Mr. Forsythe noted that despite the economic situation, key players in RFID and printed electronics are starting to derive real revenue, although it is still an area where investment in development now will not be fully repaid for some years to come.
“Electronic passports are now with us,” he noted. “It is just a matter of time before other ID documents and contactless cards become more widespread.”
“The HF antenna market has grown faster than UHF,” said Michelle Hearn, director of marketing, North American Inks, Sun Chemical. “This is driven by opportunities such as pharma, e-documents and passports and smart card. The UHF market requires significant tag cost reductions to drive adoption. Organic RFID is still several years away.”
Take. Watanabe, corporate communication, Toyo Ink Mfg. Co., Ltd., said that due to cost and environmental advantages, Toyo Ink believes that forming antenna patterns with conductive inks is likely to spread widely even in markets such as HF RFID, where etching is the established method for printing antennas, as well as UHF RFID, which is expected to expand even further.
“In the present RFID market, the widespread use of HF is growing and it has been adopted all over the world, primarily in the IC card sector due to its short coverage distance,” Mr. Watanabe noted. “ The etching method is predominantly used in forming antenna circuitry for RFID card applications, and the structure for volume production, product performance properties and cost is in place.
“Recently, with the adoption of UHF with its long coverage distance, the need on a global level to develop applications for IC tags for the logistics field has risen rapidly,” Mr. Watanabe added. “This is due in part to the quality of its read performance and data density that could not be obtained otherwise by traditional barcode management systems.”
Mr. Watanabe said that cost remains a critical factor.
“Essential to the proliferation of UHF RFID for IC tags is to determine in what ways the cost of quality IC tags that meet desired performance requirements can be reduced while minimizing its environmental impact during the production process,” Mr. Watanabe noted. “The key to resolving both these challenges lies in the formation of the antenna pattern by the printing method. Relative to conventional etching processes, the environmental footprint can be decreased. The printing method is effective not only in controlling costs as the technology is well-suited to complete dry process and mass production systems, but also there is no harmful waste generated during the chemical treatment process. The material needed to form an antenna pattern via the print process is a conductive ink.
“Patterning conductive layers with inks through an appropriate printing technique enables volume and stable production of desired antenna patterns, but does not generate the waste associated with the etching method,” Mr. Watanabe added. “This leads to substantial cost savings.”
“Printed electronics is nothing new,” said Subh Chatterjee, vice president of operations and managing member of IdeOn LLC. “People have been using the screen printing method to print inks made with conductive silver powder on ceramic and other high melting plastic substrates for years.”
Mr. Chatterjee said that the new opportunities are available for printing on flexible substrates, which would then be used for flexible displays, antennae (RFID), sensors, flex circuits, microwave susceptors, biomechanical devices etc.
“However, although there are a number of new market opportunities, the industry continues to approach them with old methods and techniques,” Mr. Chatterjee added. “For example, typical steps include (a) converting silver metal into silver powder, from micron to nano-size particles; (b) add ink vehicles to silver powder to make an ink with it; (c) print the ink with any of the traditional printing methods, i.e., offset, flexo, gravure, screen, inkjet etc.; and (d) heat the printed article at a high temperature to anneal all the silver particles together with an intent to get back the original electrical conductivity of metallic silver that one started with.
Mr. Chatterjee said their are many problems with this approach. “For example, the materials added to silver powder in formulating an ink get in the way of complete annealing of the silver particles, and the end conductivity of the printed article is not the same as metallic silver,” Mr. Chatterjee said. “Making a solvent-based ink results in VOC issues. High annealing temperature requires a high softening/non-distorting substrate. Moreover, once a conductive pathway, e.g., an antenna is printed, it needs to be functionalized by adding a computer chip, e.g., in fabricating a RFID tag. Placement of the chip must be precise, or it would be a source of additional wastes.
“Overall the current printing processes involve high energy and cost inputs and do not allow mass scale commercialization,” M.r Chatterjee concluded. “The net result is that everyone is sitting in a traffic jam on their way to the promised land. On top of that the road is littered with roadblocks called ‘patents’ which further slows down the progress, as everyone is approaching the problem more or less the same way. The only way to make progress and avail of the new opportunities is to identify a practical yet out of the box approach; an approach that would simply the process and bring the cost down for PE to enjoy mass production and industry growth, instead of remaining a ‘specialty.’”
Industry leaders say that they have seen countless interesting applications emerging in PE and RFID.
“PolyIC sees RFID as a basis which is widely used at the moment for logistics, for example,” said Mr. Mildner. “Logistics is a great application for RFID, with high growth rates. But printed RFID will open up new applications, for example, in the field of brand protection, and other applications were the value of the product can be raised because of printed RFID. This is not only about optimizing the costs. Examples for added value are RFID and advertisement or RFID and further functions integrated such as sensors.
“The possibilities are incredible,” Mr. Mildner added. “One example is intelligent packaging, where user interaction and information is possible.”
“The potential applications of PE are limitless,” said Mr. Chatterjee. “They can range from ‘simple circuitry for kids toys’ to ‘flexible displays’ to ‘talking packaging labels’ to ‘solar cells’ to ‘individuals wearing electroluminescent garments displaying promotional products.’However, the key to the success is reliability and cost. Until then we continue to debate about the dollar potential and missing the projections.”
“We see some opportunities for specialty conductive inks, for example, in the development of alternative formulations, not so much dependent on the fluctuations of the price of silver,” Mr. Forsythe said. “There will also be growth in flexo, gravure and digital.Overall, an optimized print process can provide real advantages over other technologies: faster production rate and potentially lower cost; good adhesion on multiple substrates including paper; more possibilities in the design, size and profile of the printed antenna; and environmental advantages as printing is an additive process as compared to the subtrative, more waste-generating method of etching into a copper layer.”
Ms. Hearn said that some intriguing applications range from security tagging, vehicle ID and smart packaging. “We have seen a lot of interest in the former through our Sun Chemical security and brand protection business,” she added.
Expertise in RFID and PE
Developing expertise in the highly challenging field of conductive inks is critical to become part of this expanding high-tech market.
Ms. Hearn said that Sun Chemical is uniquely positioned to help deliver value in the RFID market place by leveraging its well established fluid formulation and print applications expertise.
“In our corporate R&D center in Carlstadt, NJ, capabilities range from synthetic organic chemistry, fluid formulation and applications testing in a Class 10,000 clean room environment, and a commercial scale press room with inkjet, screen, flexo, gravure and offset presses,” Ms Hearn noted.
“Sun Chemical has launched several offerings under our SunTronic product line, a series of screen inks used for printed circuit boards (PCB), membrane switches, fascia panels, industrial labels, medical sensors and others in the printed electronics marketplace,” Ms. Hearn said. “Some of the offerings from the SunTronic product line include: Aqualine water-based flexo silver conductive inks for circuit boards and medical sensors; SunTronic 280 conductive silver inks for membrane touch switches, fascia panels and industrial labels; and SunTronic 680 UV dielectric inks for printable insulating layers between conductive tracks on membrane touch switches.”
“Ciba’s R&D capability and knowledge across a number of sectors means that we can work closely with customers and, in the right areas, work collaboratively,” Mr. Forsythe said. “Innovation is one of our key drivers,and we have extensive experience in developing partnerships in areas where we have expertise. Our traditional skills in pigments and particle dispersion printing are helpful in breaking into this newer area.”
“We believe firmly that, through the Toyo Ink Rexalpha series of conductive ink, we can contribute immensely in the realization of ultra-fine pattern formations, high throughput and vast cost savings in circuit and electrode printing for the electronics field,” Mr. Watanabe said. “Toyo Ink is a printing inks manufacturer with more than 100 years in business. We have leveraged our organic synthesis, particle design/dispersion and electronic materials technology to develop the Rexalpha conductive silver paste suitable for print patterning. Rexalpha not only exhibits exceptional electrical properties due to its unique particle design, but by incorporating Toyo Ink’s expertise in ink making, the product also offers a huge advantage in print productivity, which heavily contributes to production cost savings of its end-product, the IC tag.
“In addition to offering a heat-curable, screen-printable conductive ink as our standard issue, the Toyo Ink Group has also developed a product line that is suited to volume-production flexographic and gravure print processes,” Mr.Watanabe added. “With regard to conventional thermal-curable conductive inks, we have made much headway in attaining even shorter curing times at lower temperatures. We have also succeeded in engineering an instantly drying, UV-curable silver paste.”
“Prior to the UHF RFIDs being put on the market, the Toyo Ink Group works closely with each partner company in Japan from the development phase to the establishment of technical and product performance standards,” Mr. Watanabe said. “Although the UHF antenna market in Japan is projected to take off in 2009, we feel that our development efforts up to now give us a pivotal advantage in the field.”
Mr. Watanabe said that the special features of the Rexalpha conductive silver paste are consolidated in three points:
1. Low resistance of thin films: 3×10-5 Ω・cm or less with a layer 5-microns thick.
2. Low temperature and quick curing times: Curing and desired performance levels achieved in 5-10 minutes at 100-130℃.
3. Excellent print performance: Achieved unvarying viscosity and steady volume production through the heat-curable screen-print method.
“There may be many conductive silver paste manufacturers in this world, but Toyo Ink’s conductive silver paste exhibits superior results in the three performance areas mentioned above,” Mr. Watanabe said. “A variety of trial testing has already been conducted successfully in Japan, and we are now working to further business growth opportunities in regions such as North America, EU and other areas in Asia such as China.”
Mr. Chattterjee noted that IdeOn LLC’s founding principle is “continuation of ideas” (IdeOn) and identifying simple and practical solutions for complicated problems.
“For the PE market, IdeOn’s has identified a completely different, laser-based subtractive approach for manufacturing conductive patterns,” Mr. Chattterjee said. “The process starts with a metalized plastic film. The vacuum metallization is a well established economical, roll to roll process. Typically the metal is aluminum; however, any other metal or alloys can be deposited. The level of conductivity can be controlled by deposited film thickness. Onto such a metalized film appropriate computer chips can be placed in any given pattern.
“This film is then exposed to an IR laser (from the reverse side of the chip in order to create the contact pads for the chip) to trace and abate certain portion of the metal layer and create a desired conductive pattern,” Mr. Chatterjee continued. “Therefore, in one single step, an RFID antenna can be produced where the chip is attached to the required antenna geometry created by subtractive laser etching process. One can envision a roll to roll manufacturing process where a moving web with placed computer chips are being exposed to a bank of IR laser heads to mass produce RFID antenna or other conductive geometries useful for application in flexible displays to circuitry to solar cells etc.
“The process does not require expensive silver; does not involve printing inks; does not require thermal annealing process and hence is not limited by type of substrates used,” Mr. Chatterjee added. “The process also is flexible, that on the same line different conductive patterns can be traced based on computer input to the laser. In order to improve laser light sensitivity of the film or to improve sharp ablated lines and spaces, a layer of IR sensitive dye (or carbon black) can be introduced to the film during the extrusion process. However, during prototype development this did not turn out to be necessary. The created conductive articles can be die cut and/or laminated and quality controlled in-line, as required in obtaining a complete and functional conductive article. CO2 lasers are relatively cheap; metalized films are much more economical compared to silver inks and the overall process is relatively simple and inexpensive to make this an attractive alternate solution. The process has been validated by a laser company. IdeOn has filed for a patent (US2008120834 A1) on this. At present IdeOn is looking for a suitable partner to develop the process further for commercial success.”
Mr. Mildner said that to cope with the task “printed electronics,” physical, chemical and electro technical coherences have to be understood and developed further.
“To meet this challenge, PolyIC has built up a team of specialists from several fields of research (among others chemists, physicists, electrical and mechanical engineers), who work in interdisciplinary teams on materials, on the design of the electronic chips and optimize the printing process for the chip constantly,” said Mr. Mildner. “PolyIC has extraordinary competences in physics, in chemistry, and electronics and process engineering. With this combination, the print of electronics is made possible.”
Mr. Mildner pointed to the following key areas of study:
• Chemistry: “Printed electronics is based on soluble polymers which are electrical conducting or semiconducting,” he said. “These polymers can be printed or coated in form of a treated formulation similar to ink. Usually, the polymers are printed onto a polyester film. Our material specialists together with partners from the chemical industry work hard to pick the right polymers as well as the right film and to optimize them to make it possible to integrate them into a printing process.”
• Physics: “The design of electronic devices such as transistors, capacitors, diodes or rectifiers is developed, modeled and realized with physical means,” Mr. Mildner said. “Very important here is the coherence of chemistry with electrical and mechanical engineering. On the one hand, there is know-how in semi conductors from conventional electronics that can be used, on the other hand all designs and processes have to be adapted to the special requirements of polymer electronics.”
• Electronics engineering: “To build electronic circuits, you need conductive materials and moreover materials whose state of conductivity can be modified, e.g. by applying a voltage,” Mr. Mildner said. “In classical electronics, these tasks are performed by semi conductors such as silicon. After intensive research and development, nowadays polymers can be used to semiconduct and therefore, electronic devices can thus be realized from soluble polymers.”
• Process engineering: “To design printed electronics, technical expertise in mechanical and process engineering is very important as the requirements on resolution, cleanliness and homogeneity in contrast to regular printing processes is considerably higher,” Mr. Mildner said. “Therefore, existing processes are constantly optimized or new printing machines are build to be able to produce printed electronics in high quality and volume.”
Mr. Mildner said that there is great interest in printed electronics.
“Customers can see now that printed electronics comes from vision to reality,” Mr. Mildner said. “We see that the market for printed RFID will be stimulated through this. Printed electronics and thus printed RFID will be a long-term development. At the moment, more and more printed electronics products come onto the market, which shows a steady increase in growth. PolyIC also notices that more and more companies are starting to enter the printed electronics market, such as chemical companies who supply material, which helps to improve performance and functionality and will consequently stimulate the markets and applications.”