David Savastano, Editor08.18.10
One of the major decisions for manufacturers of printed electronics (PE) is what process best suits their application. There are a number of choices, all of which have their advantages and disadvantages. The use of inkjet is increasing in the field of printed electronics, thanks to the advantages of the process as well as the advances being made by suppliers.
Stan Farnsworth, vice president of marketing for NovaCentrix, said that variability and the ability to print without contact on thin film substrates are critical advantages for inkjet.
“The interest in inkjet is being driven by its variability,” Farnsworth said. “For example, companies want to be able to run multiple types of jobs without having to replace screens. We have seen interest in jetting medical sensors, and there are examples of inkjet being used in display and PV materials. Inkjet is being looked at for non-contact production of solar cell connectors, as it can protect thin film PV substrates.”
Bill Buskirk, president of ImTech, a specialist in engineering digital inks and systems, noted that he has seen a lot of interest in inkjet for printed electronics, and that inkjet is already successfully being utilized in areas such as color filters for LCDs.
“Inkjet is non-impact, which is important since fragile substrates can’t run through standard deposition processes, and as an additive process, it is more ecologically friendly,” Buskirk said. “Where inkjet is advantageous is where there is variability in patterns. For example, RFID antennas have no variability, and it is not clear that the digital process is the best choice. However, if you want each antenna to be tuned differently or have a digital identification placed on each antenna, then the digital process makes sense.”
Mathias Borella, sales and business development manager for Ceradrop, sees inkjet as a classic example of a disruptive technology for printed electronics.
“Inkjet printing can be classified as a ‘disruptive technology’ (as defined by J. L. Bower and C. M. Christensen: ‘An innovation that eventually overturn the existing dominant technology in the market’) and following that, inkjet micromanufacturing is suitably addressed for ‘disruptive components,” Borrella said. “I mean this technology is more adapted to manufacture new products and new concepts like manufacturing existing products by a different way. The digital aspect of the technology allow to imagine more freely new design, the flexibility of the process allow to easily shaping many new materials (notably nanomaterials and polymers in solution).”
“One of the bigger drivers for inkjet in micromanufacturing in general and PE in particular is its digital aspect,” Borella added. “Inkjet printing offers a full digital process flow that provides a wide flexibility in terms of design and in terms of materials.”
“Inkjet is certainly becoming more prevalent in the field of printed electronics,” said Dr. Neil Chilton, technical director, Printed Electronics Ltd. (PEL). “Inkjet is part of the equation, but it is not the whole story; we still use screen print and lithography for some of our applications. Inkjet is really learning its role. For example, it is not cost effective to use inkjet for RFID, which is better suited to gravure or offset, but if you want to interconnect electronic devices or print onto conformable shapes such as curves, that can’t be done with gravure. Also, set up lead time is virtually nil when using inkjet.”
Joel Yocom, business development manager, Conductive Inkjet Technology/Inkjet Flex (CIT), said that the interest in inkjet is extremely high and diverse.
“We have a portfolio of customers that are pursuing this technology from an extremely wide variety of applications,” Yocom added. “The issue isn’t the amount of interest but the degree to which suppliers have actual working production technologies. To date inkjet printing has been high on hype and low on delivery. We’ve changed that equation.”
“There is a great amount of interest in inkjet for PE,” said Dr. Tim Phillips, marketing manager for Xennia. “We get enquiries pretty much daily.”
“We continue to have high demand for our research and development platforms as customers develop next generation PE processes around our print solution,” Mike O'Reilly, Aerosol Jet product management for Optomec, Inc., said.
“Design engineers are expressing real interest in finding solutions to the drawbacks and limitations of traditional photolithography methods for applications like circuits and PCBs,” said Steve Liker, business manager, Trident. “Design engineers need to be able to more quickly and efficiently produce and debug custom and short run projects to meet product development schedules. Design engineers are eager for an on-demand, digital alternative to the lengthy photolithography development process. Additionally, in an increasingly competitive market, design engineers want to reduce the inefficiency and waste of subtractive removal screen printing.
“As a digital additive process inkjet is well suited to overcome these challenges,” Liker added. “Recent outstanding lab performance has demonstrated that inkjet can consistently meet each of these challenges and perform with great precision. In the future, inkjet should become the predominant technique for printed electronics.”
Advantages of Inkjet in PE
When it comes to PE, inkjet offers numerous advantages. It is an additive process. As a non-contact process, inkjet works well with low cost substrates. The ability to produce digital images is also a key benefit.
“The drivers for inkjet are the need for digital images, non-contact process and the use of flexible and low cost substrates,” Dr. Chilton said. “The sweet spot for inkjet is the 100 micron track and gap, which inkjet can print at a slightly better throughput than screenprinting. Gravure and offset are probably better suited for sub 50 micron work. For inkjet, the key is to select projects that need to be processed digitally, where the image changes every time.”
“Inkjet is a non-contact technique for printing,” said Yocom. “That matters a lot if the substrate is fragile or sensitive. Silicon, as used in photovoltaics, is particularly sensitive to contact pressure. Glass to a lesser degree is also.
“Inkjet is the only true digital printing process,” Yocom noted. “As a veteran of the flexible circuit industry, there is nothing I hate worse than tooling. Building it is only the first part of the pain. Once you have it there is a need to store it, inventory it, maintain revision control and rebuild it once it wears. Inkjet avoids all of that. Further, digital means that changing images is effortless. Any PE technology that features some degree of customization will be drawn to inkjet.
“Inkjet is a purely additive technology that creates a very small environmental footprint. Even the print and plate technology developed by CIT produces solid copper traces with a significantly reduced discharge stream to alternative approaches,” Yocom said. “Inkjet lends itself to roll-to-roll processing. Unlike print methods that use plates or patterns, inkjet is a continuous and seamless print technology. That means that length is irrelevant. CIT is routinely building 6’ to 15’ circuits for a variety of applications without any significant increase in effort.”
“In this frame and at mean terms, inkjet has a great interest for high added value components,” Borella added. “I think about the MLCC (multilayer ceramic capacitor) market, where inkjet adds customization for components and the possibility to highly increase the performance. I think about specific MEMS market like sensors and actuators where inkjets allow the use of a wide range of new materials and gives access to the third dimension. OLED and PLED technologies are also a good example of a disruptive technology where inkjet technology has a good position.
“The main advantage is the digital aspect of the technology that removes all necessary hardware for the manufacturing process,” Borella said. “It reduces the cost and increases the flexibility. It also reduces the delivery time, to work on small batches and provides the possibility to answer to variable data jobs. The additive approach is also a relevant advantage, notably for multilayer process. The easy way to manage many different materials (ink media) also increases the process versatility.
Time savings are also a key benefit. Liker noted that inkjet offers considerable time savings when compared to alternative technologies like screen printing, and speeds product development schedules as it is much easier to do custom one-off products in product development stages, thus reducing time to market and making it much easier to do short runs.
Inkjet also leads to greater efficiency and reduced waste. “Materials used in printed electronic applications are quite expensive,” Liker said. “Using an additive inkjet process rather than a subtractive screen printing technique leads to considerable cost savings.”
Dr. Mickaël Barret, R&D manager for Ardeje, noted that inkjet printing extends design and integration capabilities, offers flexibility and adaptability in the manufacturing process and reduced time-to-market.
“Inkjet printing technology has advantages in the lab but also in production,” Dr. Barret said. “One is cost-efficiency, but the most is that inkjet is an additive non-contact digital printing process.”
Dr. Barret noted that PE is an additive process utilizing direct writing, which reduces the number of process steps and lowers material consumption, allowing for digital patterning, rapid design change and adaptation for customization and the ability to move from small to large surface with a similar cost per square meter. As inkjet is a non-contact and low-temperature process, it is applicable to a wide range of substrates and multi-layer devices, and inkjet offers a reduced initial investments and running cost compared to roll-to-roll printing technologies.
“Aerosol Jet is a cost effective alternative to photolithography steps used in the display market, as an effective replacement for wirebond and an inexpensive alternative to TSV technology for 3DIC packaging, and providing performance and cost advantages for crystalline silicon solar wafers over traditional screen print processes,” O’Reilly said.
There are some drawbacks to inkjet that are being worked on by suppliers.
“Following users’ feedback, the main current limitation is the minimum features size,” Borella said. “Users are looking for details in the range of 10 µm, and the state of the art is around 30 µm. But we are close to go ahead, and users are working on surface functionalization to increase the minimum features and printhead manufacturers are working on smaller drop size.”
“As inkjet technology is further developed for printed electronics, new opportunities will become more obvious and widespread,” Buskirk said. “One of the big issues on the table is inkjet’s current carrying capability. Inkjet drops are put down in very thin layers that don’t have high conductivity. Another challenge is the size of lines and spaces. Inkjet is somewhat limited; it can’t put down lines and spaces as small as photolithographic processes.”
Yocom noted that there are two types of inkjet printing: fixed and scanning.
“In a fixed setting, the heads stay in one place and the target substrate moves underneath the heads,” said Yocom. “In a scanning inkjet, like the desktop ones we are used to, the head moves. If you are moving the head and manage it correctly, you can create very fine features. Unfortunately, this is a very slow process. Reports of very small features done by inkjet are done by scanning and don’t have the potential to ever be a viable production process.
“In a production setting, the only way to get economical throughput is to fix the heads in location and move the substrate underneath it,” Yocom added. “By doing this, print speeds of 20-30 meters per minute and higher are achievable but the resolution is limited. In the CIT process, for example, we use 360 dots per inch (dpi) print heads and can routinely resolve 200 micron images. Speed limits resolution but increases the economics dramatically.”
“The advantages are additive, non-contact, precise deposition quantities, the fact that the technology is applicable to rigid and flexible substrates, and its ability to print short runs cost effectively,” Phillips said. “The disadvantages are minimum feature size (currently around 40 microns – almost everyone would like less) and availability of suitable inks.”
“Some of the limitations are that not all materials (inks) are readily available for production scaling, and that certain applications, i.e. semiconductor manufacturing, do not lend themselves well to current state-of-the-art printing capabilities,” O’Reilly said.
Liker noted that there are limited materials for jetting, and said that printhead manufacturers are developing very inert, stainless steel printheads capable of printing much more aggressive materials. Whereas normal inkjet printheads would have a lifespan of only weeks when depositing aggressive printable electronic materials, the latest generation of inert, stainless steel inkjet printheads offer a lifespan of up to a year in these same applications.
“Inkjet is still largely in the phase of demonstrating lab and development feasibility,” Liker added. “It will take another five to 10 years for full production capability to become a reality.”
Key Opportunities for Inkjet in PE
While the use of inkjet in PE has grown, particularly in the lab, inkjet production has also shown growth. In particular, displays are being produced through inkjet. Dr. Barret emphasized OPV, OLED, printed electronics circuits and systems as key areas of opportunities. O’Reilly sees opportunities in the capacitive touch screen markets, 3DIC multi-chip packaging markets and crystalline silicon solar markets.
According to Phillips, the key applications are PV, displays and RFID, and probably also wearable electronics.
“Probably the best examples of inkjet in production now are in displays,” Phillips said. “There are several major companies that use inkjet as part of the manufacturing process for LCD and other displays.”
“Historically, the main industrial product where inkjet printing is playing a key role is the display market through Asian manufacturers,” Borella said.
“Inkjet is well-suited to PCB applications including the formation of traces, contacts, and electrical components such as semiconductors, resistors and capacitors,” Liker said. “Inkjet also has potential for dispensing solder for making precision electrical connections.”
“Inkjet is a truly additive process,” Dr. Chilton noted. “One example is a circuit which requires an interconnect placed by a non-impact process. For low cost displays such as electroluminescent (EL), inkjet can print high-resolution images. Inkjet is also ideal for adding biologically active materials such as antibiotics or painkillers built in a bandage, as it is a very precise additive process.”
Brand security and anti-counterfeiting applications are also ideal for inkjet.
“One of the advantages of inkjet is its highly precise drop placement,” Dr. Chilton noted. “For a security application a tiny hidden 2D barcode containing a lot of information can be placed covertly or coupled with overt security features, and a company can put down individual drops of different materials.”
Yocom said that CIT’s emphasis on inkjet for PE has created resonance, particularly in areas that CIT’s technology is focused, notably low power applications where its thin copper fits well. These include RFID antennas, heaters, sensors, LED lighting and capacitive touch sensors.
“For RFID antennas, all UHF antennas and some HF ones fit nicely,” Yocom said. “The cost advantage of our roll-to-roll processing play well here and it seems like it’s finally gaining serious acceptance in the market. In heaters, low temperature and low cost heating elements are being incorporated into products they wouldn’t work with previously. Sensors are a large area that is difficult to summarize. For example, we have two customers working with pressure sensitive foams and grids of our substrate to create insoles, grips and other devices.
“In LED lighting, the latest generation of surface mount LEDs are small footprint, low power devices going into new places,” Yocom added. “That requires a solderable, low cost substrate. We have the added advantage of being insensitive to length and are now shipping 6’ to 15’ circuits routinely. These are also becoming a hot topic for anybody doing graphic overlays because they can add functionality behind a 4-color top layer. In terms of capacitive touch sensors, they are more sensitive and simpler than dome switches, and have traditionally been used in high-end appliances but are becoming more common in a wider variety of applications. Again, these require a low cost copper-based substrate.”
Combining these different opportunities can yield even more unique products.
“Now this is where it gets the most interesting,” Yocom added. “The real power and potential of PE is the ability to create products that haven’t even been thought of yet. Our substrate has the low cost and the high degree of flexibility to allow customers to put all of this functionality in a single place.”
Working Closely with Customers
Companies throughout the inkjet supply chain are positioning themselves to help their customers move froward in the field of printed electronics.
NovaCentrix’s expertise comes in both the inkjet and post-processing fields. In July 2010, its Metalon ICI conductive ink was selected by R&D Magazine as a recipient of the 2010 R&D 100 Award in the Materials category. Metalon ICI conductive ink is a low-cost nano CuO-based ink for printed electronics applications that converts to highly electrically-conductive Cu thin-film after printing and post-processing. In 2009, NovaCentrix was awarded an R&D 100 for the PulseForge 3100 tools, which dry, cure, sinter or anneal high temperature materials on low temperature substrates such as plastic and paper.
“Our Metalon inks are prominent in inkjet, and it is a really nice technology platform,” Farnsworth said. “We are really excited by what we see in inkjet, and we are working closely with printers to integrate all elements of inkjet, as most of what we do is created with production in mind. Companies need to select the right combination of inkjet inks, printheads, chassis, substrates and post-processing, such as sintering and curing. The good news is that there has been process in each area.
“The attributes of inkjet are very appealing, and it needs to be integrated into production, which a handful of companies have already successfully accomplished,” Farnsworth added. “Post-processing can open doors for inkjet in printed electronics.”
Borella noted that Ceradrop provides an exclusive approach to the process, by offering a real manufacturing tool to customers as well as strong customer service.
“First of all, our printer is developed by material science and component science engineers, not by people coming from the graphics field,” Borella said. “That makes a huge difference. We provide to our customers a real manufacturing tool. Users can work directly from their CAD file to define and simulate the printing job. We remove the classical use of image file (like bitmap or tiff) as a file source. It allows us to give a high level of freedom in the definition of the printing job.
“Currently, users have to design their component to be compatible with inkjet printing,” Borella added. “With our approach, the process adapts itself to the design, and it completely changes the possibilities of the technology. Moreover, our team integrates chemistries and is able to formulate ink on demand. Our customers are never alone in this important aspect of the process. We also have in our premise three machines with process engineers dedicated to process development for our customer. We also completely integrate the third dimension in our process.”
Dr. Barret said that Ardeje’s knowledge and resources could help customers at all process development steps, from feasability to industrial solutions.
“Optomec offers a wide array of integration options to our customers,” O’Reilly said. “These range from supplying automation offerings to partnering with leading, market specific, automation vendors.”
Phillips said that Xennia is well positioned to help customers, with a store of IP based on 14 years of development, and a set of products ready for customers to use, from development scale inkjet printers, high precision systems for accurate applications, through to production scale systems and modules for customers to build their own systems. He added that Xennia also has developed many inks and processes for customers.
Liker said that Trident stands out due to its product design and jettable material expertise.
“Many providers of inkjet technology for printable electronic applications have simply adapted existing commercially available graphic printers for use in printable electronic applications,” Liker said. “They have replaced the ink with aggressive jettable printable electronic materials. Due to the aggressive nature of jettable printable electronic materials, this has not always provided reliable performance.
“Rather than adopting existing inkjet technology for printable electronics applications, Trident has specifically designed inkjet technology to meet the needs of printable electronic applications,” Liker added. “Trident is unique in it has expertise in both inkjet printhead technology and ink development capabilities. Trident works closely with material providers to produce inkjettable printable electronics materials.”
Yocom said that CIT has a unique market position and strategy, as the PE manufacturer is already in production. “Our first roll-to-roll production line is operational in our Cambridge, England facility,” Yocom said. “We are focused on contract manufacturing of circuit materials for our diverse customer base. We also built the printer ourselves and would supply the printer and plating line to customers if they wanted to build the material themselves.
“What we expect to happen is that some minority of our customers, say 25%, will develop enough demand for it to make sense to bring this capability internal,” Yocom added. “Our contract manufacturing is intended to enable this process to occur. Review samples, build prototypes rapidly, introduce the first product to the market, build demand, purchase equipment and add the capability internally……make more money. That’s the cycle we expect.”
Expectations for Inkjet in Printed Electronics
What, then, are the overall expectations for inkjet in printed electronics? Borella said that the first step is to be realistic in what inkjet can actually do.
“For me, the main limitation to inkjet development is due to a bad first approach of the process,” Borella said. “We call that ‘the ctrl P fantasy.’ The first idea was to simply take a desktop printer, replace the blue ink by a functional material and print a component.
“Now, the user starts to understand that it will be never so simple,” Borella added. “Inkjet printing for micromanufacturing has to be aboard like a standard manufacturing process. The technology needs advanced and dedicated tools allowing to fully manage and understand all the process steps. Low cost does not mean no cost. We currently have crossed this step and the technology is leaving the laboratory. Industrial actors now have to make their own R&D on their products, which is the only route to production.”
“Optomec expects that the move from the lab to fab will commence shortly in key markets as cost drivers within those markets will force manufacturers to look at lower cost production alternatives,” O’Reilly said. “PE has the promise of meeting these lower costs on both the equipment and material usage fronts.”
“Expectations are in the near term, relatively low level activity with many companies doing development but relatively few in production,” Dr. Phillips said. “In the long term, the market will be huge, but then people have been saying that for years.”
Liker said that in the near term, inkjet technologies will increasingly demonstrate lab and development feasibility for additional printed electronics applications.
“Over the next five to 10 years, this demonstrated lab and development feasibility will evolve into development and pilot production capability,” Liker said. “Within the next 20 years, inkjet will become the dominant production technique for PCB formation. There will also be significant advances in jettable material development. Currently, conductive inks have demonstrated feasibility and will find increased commercial use in lab-based insulators, dielectrics and capacitors in the near-term. There has also been some recent success with non-oxidizing jettable copper ink. These materials will play a larger role in printable electronic applications in the years ahead.”
Buskirk is optimistic about the opportunities for inkjet in printed electronics, and for ImTech’s ability to help further inkjet’s potential.
“I’m pretty bullish on inkjet’s future in printed electronics,” Buskirk said. “There is a lot of progress being made, and ImTech is perfectly positioned. We are working with many different printhead technologies on numerous applications. We are partnering with leading companies in the printed electronics field, and are utilizing our material and systems expertise to put together the tools to help evaluate the technology and fabricate devices.”
“Inkjet is still very early in terms of development,” Farnsworth concluded. “One challenge is that inkjet deposition is so thin, and as a result, the total resistance is not as high as screen. There is a different processing methodology from inkjet, which can put down layers 300 to 400 nanometers thick, and screen, which is 10 to 20 microns thick. Now that we understand it, it makes sense. Companies need to select the right combination of inkjet inks, printheads, chassis, substrates and post-processing, such as sintering and curing. The good news is that there has been progress in each area.”
Photo courtesy of Ceradrop. |
“The interest in inkjet is being driven by its variability,” Farnsworth said. “For example, companies want to be able to run multiple types of jobs without having to replace screens. We have seen interest in jetting medical sensors, and there are examples of inkjet being used in display and PV materials. Inkjet is being looked at for non-contact production of solar cell connectors, as it can protect thin film PV substrates.”
Bill Buskirk, president of ImTech, a specialist in engineering digital inks and systems, noted that he has seen a lot of interest in inkjet for printed electronics, and that inkjet is already successfully being utilized in areas such as color filters for LCDs.
“Inkjet is non-impact, which is important since fragile substrates can’t run through standard deposition processes, and as an additive process, it is more ecologically friendly,” Buskirk said. “Where inkjet is advantageous is where there is variability in patterns. For example, RFID antennas have no variability, and it is not clear that the digital process is the best choice. However, if you want each antenna to be tuned differently or have a digital identification placed on each antenna, then the digital process makes sense.”
Mathias Borella, sales and business development manager for Ceradrop, sees inkjet as a classic example of a disruptive technology for printed electronics.
“Inkjet printing can be classified as a ‘disruptive technology’ (as defined by J. L. Bower and C. M. Christensen: ‘An innovation that eventually overturn the existing dominant technology in the market’) and following that, inkjet micromanufacturing is suitably addressed for ‘disruptive components,” Borrella said. “I mean this technology is more adapted to manufacture new products and new concepts like manufacturing existing products by a different way. The digital aspect of the technology allow to imagine more freely new design, the flexibility of the process allow to easily shaping many new materials (notably nanomaterials and polymers in solution).”
“One of the bigger drivers for inkjet in micromanufacturing in general and PE in particular is its digital aspect,” Borella added. “Inkjet printing offers a full digital process flow that provides a wide flexibility in terms of design and in terms of materials.”
“Inkjet is certainly becoming more prevalent in the field of printed electronics,” said Dr. Neil Chilton, technical director, Printed Electronics Ltd. (PEL). “Inkjet is part of the equation, but it is not the whole story; we still use screen print and lithography for some of our applications. Inkjet is really learning its role. For example, it is not cost effective to use inkjet for RFID, which is better suited to gravure or offset, but if you want to interconnect electronic devices or print onto conformable shapes such as curves, that can’t be done with gravure. Also, set up lead time is virtually nil when using inkjet.”
Joel Yocom, business development manager, Conductive Inkjet Technology/Inkjet Flex (CIT), said that the interest in inkjet is extremely high and diverse.
“We have a portfolio of customers that are pursuing this technology from an extremely wide variety of applications,” Yocom added. “The issue isn’t the amount of interest but the degree to which suppliers have actual working production technologies. To date inkjet printing has been high on hype and low on delivery. We’ve changed that equation.”
“There is a great amount of interest in inkjet for PE,” said Dr. Tim Phillips, marketing manager for Xennia. “We get enquiries pretty much daily.”
“We continue to have high demand for our research and development platforms as customers develop next generation PE processes around our print solution,” Mike O'Reilly, Aerosol Jet product management for Optomec, Inc., said.
Photo courtesy of Ceradrop. |
“As a digital additive process inkjet is well suited to overcome these challenges,” Liker added. “Recent outstanding lab performance has demonstrated that inkjet can consistently meet each of these challenges and perform with great precision. In the future, inkjet should become the predominant technique for printed electronics.”
Advantages of Inkjet in PE
When it comes to PE, inkjet offers numerous advantages. It is an additive process. As a non-contact process, inkjet works well with low cost substrates. The ability to produce digital images is also a key benefit.
“The drivers for inkjet are the need for digital images, non-contact process and the use of flexible and low cost substrates,” Dr. Chilton said. “The sweet spot for inkjet is the 100 micron track and gap, which inkjet can print at a slightly better throughput than screenprinting. Gravure and offset are probably better suited for sub 50 micron work. For inkjet, the key is to select projects that need to be processed digitally, where the image changes every time.”
“Inkjet is a non-contact technique for printing,” said Yocom. “That matters a lot if the substrate is fragile or sensitive. Silicon, as used in photovoltaics, is particularly sensitive to contact pressure. Glass to a lesser degree is also.
“Inkjet is the only true digital printing process,” Yocom noted. “As a veteran of the flexible circuit industry, there is nothing I hate worse than tooling. Building it is only the first part of the pain. Once you have it there is a need to store it, inventory it, maintain revision control and rebuild it once it wears. Inkjet avoids all of that. Further, digital means that changing images is effortless. Any PE technology that features some degree of customization will be drawn to inkjet.
“Inkjet is a purely additive technology that creates a very small environmental footprint. Even the print and plate technology developed by CIT produces solid copper traces with a significantly reduced discharge stream to alternative approaches,” Yocom said. “Inkjet lends itself to roll-to-roll processing. Unlike print methods that use plates or patterns, inkjet is a continuous and seamless print technology. That means that length is irrelevant. CIT is routinely building 6’ to 15’ circuits for a variety of applications without any significant increase in effort.”
“In this frame and at mean terms, inkjet has a great interest for high added value components,” Borella added. “I think about the MLCC (multilayer ceramic capacitor) market, where inkjet adds customization for components and the possibility to highly increase the performance. I think about specific MEMS market like sensors and actuators where inkjets allow the use of a wide range of new materials and gives access to the third dimension. OLED and PLED technologies are also a good example of a disruptive technology where inkjet technology has a good position.
“The main advantage is the digital aspect of the technology that removes all necessary hardware for the manufacturing process,” Borella said. “It reduces the cost and increases the flexibility. It also reduces the delivery time, to work on small batches and provides the possibility to answer to variable data jobs. The additive approach is also a relevant advantage, notably for multilayer process. The easy way to manage many different materials (ink media) also increases the process versatility.
Time savings are also a key benefit. Liker noted that inkjet offers considerable time savings when compared to alternative technologies like screen printing, and speeds product development schedules as it is much easier to do custom one-off products in product development stages, thus reducing time to market and making it much easier to do short runs.
Inkjet also leads to greater efficiency and reduced waste. “Materials used in printed electronic applications are quite expensive,” Liker said. “Using an additive inkjet process rather than a subtractive screen printing technique leads to considerable cost savings.”
Dr. Mickaël Barret, R&D manager for Ardeje, noted that inkjet printing extends design and integration capabilities, offers flexibility and adaptability in the manufacturing process and reduced time-to-market.
“Inkjet printing technology has advantages in the lab but also in production,” Dr. Barret said. “One is cost-efficiency, but the most is that inkjet is an additive non-contact digital printing process.”
Dr. Barret noted that PE is an additive process utilizing direct writing, which reduces the number of process steps and lowers material consumption, allowing for digital patterning, rapid design change and adaptation for customization and the ability to move from small to large surface with a similar cost per square meter. As inkjet is a non-contact and low-temperature process, it is applicable to a wide range of substrates and multi-layer devices, and inkjet offers a reduced initial investments and running cost compared to roll-to-roll printing technologies.
“Aerosol Jet is a cost effective alternative to photolithography steps used in the display market, as an effective replacement for wirebond and an inexpensive alternative to TSV technology for 3DIC packaging, and providing performance and cost advantages for crystalline silicon solar wafers over traditional screen print processes,” O’Reilly said.
There are some drawbacks to inkjet that are being worked on by suppliers.
“Following users’ feedback, the main current limitation is the minimum features size,” Borella said. “Users are looking for details in the range of 10 µm, and the state of the art is around 30 µm. But we are close to go ahead, and users are working on surface functionalization to increase the minimum features and printhead manufacturers are working on smaller drop size.”
“As inkjet technology is further developed for printed electronics, new opportunities will become more obvious and widespread,” Buskirk said. “One of the big issues on the table is inkjet’s current carrying capability. Inkjet drops are put down in very thin layers that don’t have high conductivity. Another challenge is the size of lines and spaces. Inkjet is somewhat limited; it can’t put down lines and spaces as small as photolithographic processes.”
Yocom noted that there are two types of inkjet printing: fixed and scanning.
“In a fixed setting, the heads stay in one place and the target substrate moves underneath the heads,” said Yocom. “In a scanning inkjet, like the desktop ones we are used to, the head moves. If you are moving the head and manage it correctly, you can create very fine features. Unfortunately, this is a very slow process. Reports of very small features done by inkjet are done by scanning and don’t have the potential to ever be a viable production process.
“In a production setting, the only way to get economical throughput is to fix the heads in location and move the substrate underneath it,” Yocom added. “By doing this, print speeds of 20-30 meters per minute and higher are achievable but the resolution is limited. In the CIT process, for example, we use 360 dots per inch (dpi) print heads and can routinely resolve 200 micron images. Speed limits resolution but increases the economics dramatically.”
“The advantages are additive, non-contact, precise deposition quantities, the fact that the technology is applicable to rigid and flexible substrates, and its ability to print short runs cost effectively,” Phillips said. “The disadvantages are minimum feature size (currently around 40 microns – almost everyone would like less) and availability of suitable inks.”
“Some of the limitations are that not all materials (inks) are readily available for production scaling, and that certain applications, i.e. semiconductor manufacturing, do not lend themselves well to current state-of-the-art printing capabilities,” O’Reilly said.
Liker noted that there are limited materials for jetting, and said that printhead manufacturers are developing very inert, stainless steel printheads capable of printing much more aggressive materials. Whereas normal inkjet printheads would have a lifespan of only weeks when depositing aggressive printable electronic materials, the latest generation of inert, stainless steel inkjet printheads offer a lifespan of up to a year in these same applications.
“Inkjet is still largely in the phase of demonstrating lab and development feasibility,” Liker added. “It will take another five to 10 years for full production capability to become a reality.”
Key Opportunities for Inkjet in PE
While the use of inkjet in PE has grown, particularly in the lab, inkjet production has also shown growth. In particular, displays are being produced through inkjet. Dr. Barret emphasized OPV, OLED, printed electronics circuits and systems as key areas of opportunities. O’Reilly sees opportunities in the capacitive touch screen markets, 3DIC multi-chip packaging markets and crystalline silicon solar markets.
According to Phillips, the key applications are PV, displays and RFID, and probably also wearable electronics.
“Probably the best examples of inkjet in production now are in displays,” Phillips said. “There are several major companies that use inkjet as part of the manufacturing process for LCD and other displays.”
“Historically, the main industrial product where inkjet printing is playing a key role is the display market through Asian manufacturers,” Borella said.
“Inkjet is well-suited to PCB applications including the formation of traces, contacts, and electrical components such as semiconductors, resistors and capacitors,” Liker said. “Inkjet also has potential for dispensing solder for making precision electrical connections.”
“Inkjet is a truly additive process,” Dr. Chilton noted. “One example is a circuit which requires an interconnect placed by a non-impact process. For low cost displays such as electroluminescent (EL), inkjet can print high-resolution images. Inkjet is also ideal for adding biologically active materials such as antibiotics or painkillers built in a bandage, as it is a very precise additive process.”
Brand security and anti-counterfeiting applications are also ideal for inkjet.
“One of the advantages of inkjet is its highly precise drop placement,” Dr. Chilton noted. “For a security application a tiny hidden 2D barcode containing a lot of information can be placed covertly or coupled with overt security features, and a company can put down individual drops of different materials.”
Yocom said that CIT’s emphasis on inkjet for PE has created resonance, particularly in areas that CIT’s technology is focused, notably low power applications where its thin copper fits well. These include RFID antennas, heaters, sensors, LED lighting and capacitive touch sensors.
“For RFID antennas, all UHF antennas and some HF ones fit nicely,” Yocom said. “The cost advantage of our roll-to-roll processing play well here and it seems like it’s finally gaining serious acceptance in the market. In heaters, low temperature and low cost heating elements are being incorporated into products they wouldn’t work with previously. Sensors are a large area that is difficult to summarize. For example, we have two customers working with pressure sensitive foams and grids of our substrate to create insoles, grips and other devices.
“In LED lighting, the latest generation of surface mount LEDs are small footprint, low power devices going into new places,” Yocom added. “That requires a solderable, low cost substrate. We have the added advantage of being insensitive to length and are now shipping 6’ to 15’ circuits routinely. These are also becoming a hot topic for anybody doing graphic overlays because they can add functionality behind a 4-color top layer. In terms of capacitive touch sensors, they are more sensitive and simpler than dome switches, and have traditionally been used in high-end appliances but are becoming more common in a wider variety of applications. Again, these require a low cost copper-based substrate.”
Combining these different opportunities can yield even more unique products.
“Now this is where it gets the most interesting,” Yocom added. “The real power and potential of PE is the ability to create products that haven’t even been thought of yet. Our substrate has the low cost and the high degree of flexibility to allow customers to put all of this functionality in a single place.”
Working Closely with Customers
Companies throughout the inkjet supply chain are positioning themselves to help their customers move froward in the field of printed electronics.
NovaCentrix’s expertise comes in both the inkjet and post-processing fields. In July 2010, its Metalon ICI conductive ink was selected by R&D Magazine as a recipient of the 2010 R&D 100 Award in the Materials category. Metalon ICI conductive ink is a low-cost nano CuO-based ink for printed electronics applications that converts to highly electrically-conductive Cu thin-film after printing and post-processing. In 2009, NovaCentrix was awarded an R&D 100 for the PulseForge 3100 tools, which dry, cure, sinter or anneal high temperature materials on low temperature substrates such as plastic and paper.
“Our Metalon inks are prominent in inkjet, and it is a really nice technology platform,” Farnsworth said. “We are really excited by what we see in inkjet, and we are working closely with printers to integrate all elements of inkjet, as most of what we do is created with production in mind. Companies need to select the right combination of inkjet inks, printheads, chassis, substrates and post-processing, such as sintering and curing. The good news is that there has been process in each area.
“The attributes of inkjet are very appealing, and it needs to be integrated into production, which a handful of companies have already successfully accomplished,” Farnsworth added. “Post-processing can open doors for inkjet in printed electronics.”
Borella noted that Ceradrop provides an exclusive approach to the process, by offering a real manufacturing tool to customers as well as strong customer service.
“First of all, our printer is developed by material science and component science engineers, not by people coming from the graphics field,” Borella said. “That makes a huge difference. We provide to our customers a real manufacturing tool. Users can work directly from their CAD file to define and simulate the printing job. We remove the classical use of image file (like bitmap or tiff) as a file source. It allows us to give a high level of freedom in the definition of the printing job.
“Currently, users have to design their component to be compatible with inkjet printing,” Borella added. “With our approach, the process adapts itself to the design, and it completely changes the possibilities of the technology. Moreover, our team integrates chemistries and is able to formulate ink on demand. Our customers are never alone in this important aspect of the process. We also have in our premise three machines with process engineers dedicated to process development for our customer. We also completely integrate the third dimension in our process.”
Dr. Barret said that Ardeje’s knowledge and resources could help customers at all process development steps, from feasability to industrial solutions.
“Optomec offers a wide array of integration options to our customers,” O’Reilly said. “These range from supplying automation offerings to partnering with leading, market specific, automation vendors.”
Phillips said that Xennia is well positioned to help customers, with a store of IP based on 14 years of development, and a set of products ready for customers to use, from development scale inkjet printers, high precision systems for accurate applications, through to production scale systems and modules for customers to build their own systems. He added that Xennia also has developed many inks and processes for customers.
Liker said that Trident stands out due to its product design and jettable material expertise.
“Many providers of inkjet technology for printable electronic applications have simply adapted existing commercially available graphic printers for use in printable electronic applications,” Liker said. “They have replaced the ink with aggressive jettable printable electronic materials. Due to the aggressive nature of jettable printable electronic materials, this has not always provided reliable performance.
“Rather than adopting existing inkjet technology for printable electronics applications, Trident has specifically designed inkjet technology to meet the needs of printable electronic applications,” Liker added. “Trident is unique in it has expertise in both inkjet printhead technology and ink development capabilities. Trident works closely with material providers to produce inkjettable printable electronics materials.”
Yocom said that CIT has a unique market position and strategy, as the PE manufacturer is already in production. “Our first roll-to-roll production line is operational in our Cambridge, England facility,” Yocom said. “We are focused on contract manufacturing of circuit materials for our diverse customer base. We also built the printer ourselves and would supply the printer and plating line to customers if they wanted to build the material themselves.
“What we expect to happen is that some minority of our customers, say 25%, will develop enough demand for it to make sense to bring this capability internal,” Yocom added. “Our contract manufacturing is intended to enable this process to occur. Review samples, build prototypes rapidly, introduce the first product to the market, build demand, purchase equipment and add the capability internally……make more money. That’s the cycle we expect.”
Expectations for Inkjet in Printed Electronics
What, then, are the overall expectations for inkjet in printed electronics? Borella said that the first step is to be realistic in what inkjet can actually do.
“For me, the main limitation to inkjet development is due to a bad first approach of the process,” Borella said. “We call that ‘the ctrl P fantasy.’ The first idea was to simply take a desktop printer, replace the blue ink by a functional material and print a component.
“Now, the user starts to understand that it will be never so simple,” Borella added. “Inkjet printing for micromanufacturing has to be aboard like a standard manufacturing process. The technology needs advanced and dedicated tools allowing to fully manage and understand all the process steps. Low cost does not mean no cost. We currently have crossed this step and the technology is leaving the laboratory. Industrial actors now have to make their own R&D on their products, which is the only route to production.”
“Optomec expects that the move from the lab to fab will commence shortly in key markets as cost drivers within those markets will force manufacturers to look at lower cost production alternatives,” O’Reilly said. “PE has the promise of meeting these lower costs on both the equipment and material usage fronts.”
“Expectations are in the near term, relatively low level activity with many companies doing development but relatively few in production,” Dr. Phillips said. “In the long term, the market will be huge, but then people have been saying that for years.”
Liker said that in the near term, inkjet technologies will increasingly demonstrate lab and development feasibility for additional printed electronics applications.
“Over the next five to 10 years, this demonstrated lab and development feasibility will evolve into development and pilot production capability,” Liker said. “Within the next 20 years, inkjet will become the dominant production technique for PCB formation. There will also be significant advances in jettable material development. Currently, conductive inks have demonstrated feasibility and will find increased commercial use in lab-based insulators, dielectrics and capacitors in the near-term. There has also been some recent success with non-oxidizing jettable copper ink. These materials will play a larger role in printable electronic applications in the years ahead.”
Buskirk is optimistic about the opportunities for inkjet in printed electronics, and for ImTech’s ability to help further inkjet’s potential.
“I’m pretty bullish on inkjet’s future in printed electronics,” Buskirk said. “There is a lot of progress being made, and ImTech is perfectly positioned. We are working with many different printhead technologies on numerous applications. We are partnering with leading companies in the printed electronics field, and are utilizing our material and systems expertise to put together the tools to help evaluate the technology and fabricate devices.”
“Inkjet is still very early in terms of development,” Farnsworth concluded. “One challenge is that inkjet deposition is so thin, and as a result, the total resistance is not as high as screen. There is a different processing methodology from inkjet, which can put down layers 300 to 400 nanometers thick, and screen, which is 10 to 20 microns thick. Now that we understand it, it makes sense. Companies need to select the right combination of inkjet inks, printheads, chassis, substrates and post-processing, such as sintering and curing. The good news is that there has been progress in each area.”