Invited Speakers

Kurt Schroder

NovaCentrix, USA

Photonic curing as a non-equilibrium heating process has been widely established as suitable for printed electronics applications such as drying and sintering metal-based electrically-conducting inks, annealing CIS photovoltaic materials, and processing other coatings on structures that cannot withstand the high thermal load of a conventional oven. Photonic curing is likely to continue to enable innovation in processing coated thin films for applications ranging from displays, sensors, energy storage, and other applications of flexible-hybrid electronics (FHE).  Importantly, new applications are being developed that take advantage of the advances in photonic curing tool capabilities. This talk will focus on a recent development called photonic soldering.

The development of flexible hybrid electronics requires an inexpensive, reliable and high throughput attachment technique for functional components onto printed circuits. The challenge faced with the current reflow technology is that many of the desired substrates cannot withstand the necessary temperatures required to reach the liquidus point of common solders. To overcome this limitation, conductive adhesive attachment techniques were developed but they lack the reliability of soldering. To circumvent the stated challenge posed by the substrates, a photonic soldering technique has been developed that takes advantage of the selective absorption of light to reach the liquidus temperature of conventional solders without significant heating of the underlying substrate. The short time the substrate spends at elevated temperatures may not be sufficient to damage the underlying substrate. This technique could work with conventional lead-free solders (e.g. SAC-305) and commercial packages (e.g. 402MM) or bare thinned dies on a variety of substrates, including PET, PEN as well as metallic foils.  The photonic soldering technique is feasible for integration into high throughput roll-to-roll or sheet-to-sheet setups in a compact package using significantly less energy as the time to solder is only a few seconds versus several minutes for conventional reflow technology.

Emre Ozer

Arm Research, Cambridge, UK

This paper proposes a framework for the design of bespoke machine learning (ML) processors on flexible substrates (e.g. plastic) to address an important need in flexible and wearable applications – a processing engine of the flexible electronics applications. The proposed framework automates the design of bespoke ML processors on flexible substrates to reduce development time, and therefore the time-to-market. 

Zheng Cui

Printable Electronics Research Center, Suzhou Institute of Nanotech and Nanobionics, Chinese Academy of Sciences, Suzhou, China

Low power electronics are typically achieved by CMOS circuits which require both p-type and n-type transistors. However, making CMOS electronics with solution type semiconductors has met great difficulties because no printable semiconductor materials are good at both p-type and n-type. In this paper, we demonstrated two approaches which enabled printable CMOS inverters with low static power consumption. One approach was to tune the polarity of as-printed p-type carbon nanotube (CNT) thin-film transistors (TFT) into n-type, so that a CMOS-like inverter can be constructed by two CNT-TFTs which has achieved low power consumption of 0.3 μW. Another approach was to combine a p-type CNT-TFT with a n-type metal oxide TFT to construct a CMOS inverter which demonstrated low power consumption of 0.4 μW. Both approaches were based on solution type inorganic semiconductor materials and therefore printable, which lay the foundation for printed low power electronic circuits.

Niko Münzenrieder

Sensor Technology Research Centre, University Of Sussex, UK

Conformable systems operated in close proximity to the human body, or fabricated on large-area plastic substrates enable new applications including smart implants, and electronic textiles. A unique requirement of flexible systems is the need to optimize their electrical and mechanical performance simultaneously. In particular, flexible sensor conditioning and transceiver circuits, insensitive to bending, are required. Thin-film transistors (TFTs) based on amorphous InGaZnO have the potential to enable such circuits. However, while InGaZnO TFTs can be fabricated on temperature sensitive plastic foils, provide carrier mobilities >10 cm2/Vs, and demonstrated functionality when bent to radii as small as 25 μm, they also suffer from certain limitations: First, only n-type devices are available which restricts the number of possible circuit topologies. Second, the electrical performance parameters shift when the TFTs are exposed to mechanical strain. Third, the use of flexible free-standing substrates requires fabrication tolerances complicating the realization of small features essential for fast transistors. Finally, a trade-off between the parasitic overlap capacitance and contact resistance is required as these parameters determine the TFT’s frequency performance, but cannot be minimized at the same time.

Here, the scaling behaviour of flexible InGaZnO TFT is modelled to enable the realization of optimized high-speed transistors. The model is validated using AC measurements of flexible TFTs with channel length down to 300 nm, and enabled the fabrication of TFTs with transit frequencies of 135 MHz, and maximum oscillation frequencies of 398 MHz. In a next step, circuit design principles and SPICE simulation models for the design of InGaZnO TFT circuits, considering electrical and mechanical effects, are presented. These led to various circuits such as fully flexible amplifiers with a gain-bandwidth-product >9 MHz.

Esma Ismailova

Department of Bioelectronics, Ecole Nationale Superieure des Mines de Saint Eitenne, CMP-EMSE, MOC

In the 21st century, consumers are rapidly gaining access to a novel suite of wearable electronic devices such as smart watches, glasses and garments. These technologies promise both comfort and ease of use, as well as an access to a wealth of health-related information. Advances in the field of electronic textiles, and recent achievements in organic electronics, have enabled the development of new flexible and conformable technologies that can perform the same sensing as current solid-state devices, for a fraction of the cost. Such progress relies on the subtle engineering of organic materials to model their properties in functional devices. The sustainable potential of using organic ionic and electronic conducting materials in wearable monitoring systems has yet to be demonstrated. In cutaneous applications, the use of such organic materials as electrodes lowers contact impedance with the skin resulting in higher quality recordings compared to metal–based electrodes. Combining these materials with textile structures reduces the mechanical mismatch at the interface with the skin, which enables the recording of electrophysiological activities for long time intervals with an enhanced signal to noise ratio. Traditional and non-traditional direct patterning techniques allow the selective deposition of organic materials onto different kind of fabrics. Therefore, the integration of organic electronics and the textile platform provides low-cost and tailored solutions in interfacing smart devices with the human body.