Flexible chips in paper • 02 Jun 2020
The Flexlines project has reached a new milestone. Very thin flexible chips can be integrated into paper gaming cards, tickets and official documents.
This spring, on may 28 and June 9, Flexlines organised 2 well attended webinars on flexible electronics. In both webinars, the Flexlines team shared their progress, challenges and solutions in all necessary areas.
The full webinar can be watched on this link
CONNECTING THE DOTS
Dieter, CEO of DSP Valley, kicked off the Webinar. He gave a brief overview of the Flexlines project and of the position of DSP Valley.
Fig 1: Dieter Therssen, DSP Valley, introducing the webinar
Dieter Therssen: “One of the objectives of the Flexlines project is the regional expansion of a flexible electronics pilot infrastructure. This means operationalisation of essential production investments and improvement of design and production processes, here in the Benelux region. Another objective is the set-up of a 'one-stop-shop' for the realisation of prototypes of flexible electronics applications. The realisation of a number of demonstrators counts as the first validation for the deployed design and manufacturing assets. They also count as showcases, to inform the ecosystem about the possibilities.”
DSP Valley conducts collaborative business development, connects businesses, helps them cultivate and consolidate projects. DSP Valley’s ecosystem consists of organisations -companies and academia- working on applications and/or enabling technologies. There are many interfaces between this ecosystem and the objectives of Flexlines, which leads to cross-pollination in different areas.
Flexlines addresses the entire physical realisation part of novel formable electronics and their embodiment in devices: design tools (modeling, simulation), design, fabrication steps, flexible electronics, integration in over-moulded assemblies. So Flexlines is one of the projects that is contributing technology for flexible electronics.
At the end of his presentation, Dieter highlighted a few other projects providing cascade funding for this technology.
Romano, program manager at imec, illustrated the main objective of the development of a One-Stop-Shop for flexible electronics in the Flexlines project.
Fig 2: Romano Hoofman, imec
Romano Hoofman: “We want to create a one-stop service, where academia and companies can realise their ideas and have them fabricated in flexible and cheap electronics technologies. In order to achieve this the technology will be further matured, compliant design process flow will be developed and we’re reaching out to customers for development of new applications. A customer that comes with a request is welcome at the one-stop-shop. Together with the customer the right design flow will be selected. When the design has been checked, the circuit will be manufactured and prototype testing and validating will follow. The last step is upscaling to volume, which is not part of the Flexlines pilotline, but will be facilitated through external fabs.”
Romano also explained to the audience that the EUROPRACTICE concept will also be used for flexible electronics. EUROPRACTICE was launched in 1995 to enhance European competitiveness in the global market offering of industrial technologies, which are not easily accessible for prototyping. EUROPRACTICE offers MPW (Multi Project Wafer) Prototyping to customers, in order to share the fabrication cost with several customers and therefore reducing the cost for each individual customer.
Romano: “Multi-customer project services will also be developed for flexible electronics, such that the fabrication cost can be lowered by sharing multiple customer prototypes on the same production run. “
Fig 3: A typical ecosystem
Flexlines utilises the already existing ecosystem where the one-stop-shop provides customer support for the offered services, such as access to design tools, design IP and fabrication.
Romano: “Typically we reach out to customers and as a result a customer might come up with an idea and he launches a request. The first thing we do is defining a supplier process flow. Once the design is ready, it needs to be checked. That will be done by imec. When the samples have been fabricated, they are shipped to the customer who tests and validates the product. And then the circle is complete.”
INFRASTRUCTURE AND INTEGRATION PROTOTYPING
Then the word was passed to Auke Jisk Kronemeijer, Program Manager & GEN1 TFT Pilot Line Manager at TNO/Holst Centre. He highlighted infrastructure, application and integration prototyping.
First Auke told the audience about oxide transistor arrays on plastic as a key enabler of flexible electronics. Then he presented the Holst Centre TFT Technology Platform. This platform embraces the GEN1 a-IGZO R&D pilot line for application prototyping: enabling flexible displays, flexible imagers, flexible circuitry, etc.
Pictures of the Holst Centre R&D Pilot Line Facilities were shown to the audience and Auke explained how the work has to be done in a ‘clean room’ because dust particles can damage the electronics.
Fig 4: Holst Centre R&D Pilot Line facilities
Subsequently, Auke presented several integration technologies. He mentioned printed electronics, soldering of hybrid structures, encapsulation, thermoforming and injection moulding and how to scale up to pilot fabrication.
As an example of application prototyping, Auke spoke of flexible AMOLED displays and their different components.
Fig 5: different components of flexible AMOLED displays
Then he went into more details on dual-gate self-aligned TFT performance (where dual-gate means it can be switched on and off using two ‘handles’), pixel/array realisation, delamination, etc.
Fig 6: Flexible AMOLED displays
Image sensor arrays have led to flexible X-ray detectors and large area fingerprint scanners. The technology is so sensitive that heartbeats can be visible on the screen of the fingerprint scanner. Near-infrared Vein detectors take it a step further. They can look deeper into the body than the fingerprint scanner that only looks at the fingerprints on the surface. The idea here is to identify the blood running through the veins. Like this, patterns of people’s veins can be measured.
Fig 7: Flexible X-Ray detectors
Fig 8: Large Area Fingerprint Scanners with integration of heart beat detection
Next Auke spoke about capacitive touchscreen tags, which have been published in Nature Electronics, and integration methods of integration of prototypes: inlay lamination, injection moulding, thermoforming, textile integration, ...For aforementioned chips, processes have been developed to transfer chips-on-plate to labels-on-roll. Integration of flexible electronics now is even possible in cards and paper.
After this, Auke explained more about several other integration technologies. Functional circuitry on PI is introduced in injection moulding, this takes everything a level higher. Thermoforming makes shape engineering possible. Auke also presented the TNO/Holst Centre approach of the challenge concerning simultaneous bending and stretching in multiple directions. Last but not least, the integration of stretchable circuitry has led to integration in textile.
Fig 9: integration in textiles
After Auke’s presentation, Mohit Dandekar, Research Assistant at the KU Leuven, explained the design challenges. He started with the benefits of thin-film electronics on plastic foil, being: low cost, very flexible and unbreakable. Thin-film electronics have endless possibilities for IoT (the Internet of Things), p.e. wearable health patches, smart shelves, user interaction applied in product branding, ‘everything-connected’ possibilities in gaming,…
Mohit Dandekar: “Large area electronics, IoT and wearables would really benefit from flexible electronics. When we compare production approaches of conventional silicon with thin film circuits and printing, we see that conventional silicon cannot be scaled to very large areas reliably and typical integrated chips are restricted to about few square centimetres. Meanwhile printing suffers from very low precision and lower performance. IGZO Thin film circuits made with silicon like processing can position themselves between the two. IGZO Thin Film Technology offers silicon like processing on plastic and can scale to several 100s of square centimetre area. It is faster than conventional a-Si thin film, cost effective and successful proof of designs have already been published.”
Fig 10: Mohit Dandekar, KU Leuven
Mohit gave an illustration of a unipolar TFT topology where dense flexible circuits are enabled by silicon circuits like processing. This brings along quite a lot design challenges. TFT properties have circuit robustness issues like device variability and bias stress variation. There are no validated simulation models, so the design flow actually is a designer’s issue. Circuit design techniques are still an area of active research. The limited amount of metal layers creates a design automation issue. Better device model and tool support are also on the agenda for research.
Fig 11: design platform