By RYAN HILL
Conventional printing processes, such as gravure, may be able to revolutionize the way electronics are manufactured. The trend in the electronics industry is towards smaller products, lower prices, and more reliable products (Pudas, 2004). Traditional semiconductor electronics require a circuit board in order to function. To date, most circuit boards have chips, transistors, and other components that are soldered to a sheet of fiberglass.(How Stuff Works, n.d.). The ultimate goal is to increase electronic manufacturing speeds, reduce the number of manufacturing steps, and create products that are considerably smaller than those on the market today for a fraction of their current cost (M2, 2004). Gravure printing may benefit from the electronic industry’s demands. The hope is that conventional and existing high-speed printing processes can use conductive ink to print on various substrates to replace traditional circuit boards, wires, and batteries (Svensson, 2003).
Statement of the problem
To determine the feasibility of printing electronics with gravure.
Review of published material from trade journals, magazines, and company Web sites.
There has been much industry buzz about radio frequency identification (RFID) in recent years concerning retailers such as Wal-Mart. RFID is a type of smart label that could eventually replace the Universal Product Code (UPC). UPCs are printed on consumer products worldwide for inventory management purposes (Kepler, 2004). In its simplest form, an RFID tag will consist of three main parts: a supporting substrate, a microprocessor containing information about the product, and a metal antenna (Kepler, 2004). A computer that serves as a reader will be able to decode the data transmitted from the tag’s antenna to identify and count the product. Ink manufacturing companies, such as Flint Group’s Precisia LLC, currently produce conductive inks formulated for gravure and other print processes to make the antennas for RFID tags (Precisia, 2004). Precisia’s Silver Gravure ink is available in both water- and solvent-based formulas to be placed into traditional printing lines to manufacture RFID antennas and other printable electronic devices (Precisia, 2004).
There are numerous advantages for RFID tags over UPC labels since they operate on radio frequencies. For example, the RFID tag does not have to be in the reader’s line of sight as does a conventional UPC code and scanner, multiple tags can be read simultaneously, and tags can contain large amounts of data about the item they identify (Kepler, 2004). The biggest advantage is that RFID tags are read automatically and do not have to be scanned individually by hand—a process which is prone to error (Donoghue, 2004). Wal-Mart, the world’s largest retailer, mandated that its top one-hundred suppliers must place RFID tags on pallets and cases by January 1, 2005 (Kepler, 2004). It will expect full compliance from the remaining suppliers by 2006 (Hines, 2004). Annually, Wal-Mart receives about one billion cases and pallets from its top companies and expects them to voluntarily comply with the mandate (Kepler, 2004). According to a report, 10 percent of Wal-Mart’s costs are related to supply-chain issues such as storing, transporting, and tracking inventory. With RFID, the costs can be reduced 3-4 percent, thus saving the company $1.3-$1.5 billion annually (Kepler, 2004). Target, Best Buy, Albertsons, the United States Department of Defense, and several European retailers will also place mandates on their suppliers to implement RFID technology similar to Wal-Mart (Power Paper Ltd., 2004).
Wal-Mart might be pushing its luck with the January deadline less than two months away. Industry analysts state that large-scale RFID technology is still too immature to implement and will cost each supplier up to $9 million to comply (Donoghue, 2004). Also, Wal-Mart’s initial plan will require about one billion tags. As of this date, there is no tag manufacturer that can supply this amount (Kepler, 2004). Another hamper is the cost of the tags themselves. Wal-Mart’s goal is to get the per-unit cost down below five cents and pass the cost onto consumers. Currently, the tags are between thirty to fifty cents apiece (Kepler, 2004). This price is not feasible to individually tag lower-cost consumer products. Only supply chain operations are currently being addressed, such as placing tags on pallets entering the warehouse.
Gravure printing technology may help lower the price of RFID tags. The hope is that the antennas will be mass produced using conventional high-speed printing processes, such as gravure, with conductive inks available from suppliers such as Precisia, T-Ink, Dow Chemical, Cabot, and others. Printing RFID antennas instead of manufacturing the tags using traditional methods will cut costs as much as fifty percent (Burke, 2004). This will make individual item tagging economically feasible. Thus, with every item in a store or facility tagged with radio-frequency chips, extremely detailed inventory management data can be collected and used accordingly. According to Wal-Mart’s RFID strategy manager, however, individual product tagging may still be ten to fifteen years away (Donoghue, 2004).
Just this November, Power Paper, an Israeli company, released a research paper detailing an improved version of the RFID tag. The difference is that it is an active tag. It has a power source supplied by a battery printed directly onto a substrate along with the other necessary RFID components (Power Paper Ltd., 2004). According to Power Paper, the printed battery enables more accurate scans and greater distances can be achieved between the tagged item and scanning equipment (Power Paper Ltd., 2004).
Another type of printed electronic device under development is organic lightemitting devices (OLEDs). Simply put, OLEDs consist of three layers: an anode substrate and light-emitting and cathode layers (Tuomikoski, 2004). This technology may be used for devices that require small LCD-like screens such as cell phones and small computer screens. VTT Technical Research Centre of Finland is one company developing the technology. It has been developing a flexible OLED using roll-to-roll gravure technology to print onto plastic and paper. According to VTT’s report, “OLEDs have attracted a lot of attention, mainly due to their simplicity of fabrication, low operating voltage and power consumption, high brightness, very thin structure, mechanical flexibility, light weight, and full-color range in visible wavelengths.” (Tuomikoski, 2004). VTT states that OLED technology may lead to roll-up displays and disposable electronics. However, according to a European printing industry report, VTT has been experiencing difficulty with the technology (Birkenshaw, 2004).
Other Printable Electronics in Development
In addition to OLED technology, VTT has also developed a sensor using gravure printing that reacts to hormones, microbes, and toxins for use in the medical field. In it, biotechnology and nanotechnology are combined with traditional gravure printing techniques (Tuomikoski, 2004). Cypak, a corporation based in Sweden, has developed a paperboard computer with 32 Kbytes of memory and smart pharmaceutical packages that alert the patient and doctor to dosage usage (Cypak, n.d.). T-Ink, a competitor to Precisia, has developed a toy product line currently sold at Toys ’R Us that uses its brand of conductive ink. T-ink also has an entire product line of gravure ink which may be formulated to any color, is flexible, nontoxic, and washable for use in other electronic applications (T-ink, n.d.).
The Gravure Printing Process for Electronics
The same setup to print electronics is required to print normal ink on paper. The gravure printing process uses a copper cylinder with a steel coating for strength. Cells are engraved on the surface in different depths and widths usually using either an electromechanical or laser process. These cells are then flooded with ink and any excess is removed with a doctor blade that comes into contact with the outside of the cylinder. The cells are then transferred to a substrate under pressure to create an impression. For certain types of printable electronics, an offset gravure process will most likely have to be used since there is too much pressure with the standard process to print on rigid substrates or glass (Birkenshaw, 2004).
Advantages of Gravure for Printing Electronics
Gravure offset has significant advantages over other competing print processes when it comes to transferring conductive ink to a substrate. Its advantages are well known even to traditional printing environments. Gravure excels with speed, laying down variable ink film thickness, long press runs, and the simplicity of the process involved to transfer ink onto a substrate. Other important factors include gravure offset’s ability to transfer large areas of ink at high speeds with nominal distortion (Pudas, 2004), and the ability to produce the world’s smallest precision object (Kepler, 2004). Conductive inks have already been successfully printed onto alumina, glass, and metal substrates using the offset gravure method (Pudas, 2004). Researchers have also proven that gravure can offer a cost-effective manufacturing method for electronic circuitry (Pudas, 2004).
The other printing processes—screen printing, ink jet, flexography, and lithography—have certain short comings when compared to gravure. For example, screen printing has more of a limited resolution due to the mesh screen the ink paste is pressed through. Ink jet technology lacks the ability to print a variable film thickness and currently its resolution is too low for printing electronics. Both processes also lack gravure’s speed. Flexography produces a squashed-ink appearance around outside edges of solids, lines, and type, which might be a drawback for using the process for some applications. However, the design of the shape of circuitry conductors can be compensated accordingly to pose no problem for printing electronics. Lithography’s largest drawback is the lack of a thick ink film. Theoretically, it is a better choice than the other processes to print electronics because it produces flat ink films (Birkenshaw, 2004).
Disadvantages of Gravure for Printing Electronics
The main drawback for gravure is that more tests need to be conducted to evaluate its suitability to print electronic devices. To this date, other printing processes have been evaluated more thoroughly (Birkenshaw, 2004). Current research has noted, however, that better blankets and conductive inks are still needed for optimum performance (Pudas, 2003). Offset blankets are also required for delicate substrates. A common problem with gravure printing also becomes more apparent with conductive inks. A small portion of ink will remain in the etched wells in the cylinder and dry. The solution to solve this problem is a Self-Cleaning Gravure (SCG) process to prevent ink blockage in the wells (Pudas, 2004). Gas or solvents are pumped to the bottom of the ink wells under the doctored ink to lower the viscosity. As a result, ink flows better, even from extremely narrow grooves. Implementing SCG does not affect the length for print runs and nominally affects overall production costs (Pudas, 2004).
Printed electronics are continuing to be developed and improved upon. The lure of low production costs and high speeds for manufacturing electronics should benefit the gravure printing industry. Gravure stands to benefit as new emerging technologies such as OLEDs and other printed display devices evolve into consumer items and more companies that produce conductive inks are formed. RFID tags are one of the most sought-after items to produce using a printing process. These radio frequency tags could one day replace the bar code printed on every consumer item sold worldwide. Currently, however, RFID is still an experimental technology that, for better or worse, Wal-Mart actively pushed with a deadline of January 1, 2005, for its top one-hundred suppliers. Gravure is in a position to benefit from this emerging technological trend because of its ability to lay down thick areas of ink in a precise manner, and, more importantly, some of its differences from other competing print processes.
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