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EIPC Technical Snapshots have become a monthly highlight, eagerly anticipated, enthusiastically supported, and with consistently outstanding quality of content. Introduced and moderated by EIPC board member Martyn Gaudion, managing director at Polar Instruments, the eighth in the series on May 19 featured a well-balanced selection of presentations with the collective focus of additive manufacturing in the electronics industry.
Professor Matti Mäntysalo
The opening presentation was delivered by Professor Matti Mäntysalo from the Faculty of Information Technology and Communication Sciences at Tampere University in Finland. His Laboratory for Electronics was engaged in the investigation of technologies and solutions related to sustainable materials, energy-autonomy, sensors, stretchable electronics, and hybrid system integration, and was exploring new device and circuit approaches based on printable organic and metal oxide semiconductors. He demonstrated how printed electronics techniques were enabling novel form factors, particularly in soft and stretchable devices. His designation, “soft electronics,” included conformable, deformable, and thin substrates, and in the field of health and wellbeing there was a requirement for ultra-thin, skin-like electronics for numerous wearable sensing applications.
Professor Mäntysalo’s roadmap forecast two phases of development beyond current commercially-available wearable devices, advancing through the
heterogeneous integration of various electronics, to fully-integrated highly sensitive stretchable nano-based devices.
After considering several state-of-the-art approaches and evaluating the features of different printing methods, his department had chosen techniques based on screen printing with a stretchable silver-polymer composite ink on 50 micron thermoplastic polyurethane film. This method was cost-effective for high-volume roll-to-roll production, whereas digital techniques were slower and more suitable for applications where ultimate precision was required.
He gave an example of a wireless, printed on-skin electrocardiogram sensor that could communicate via a smart-watch and a laptop or tablet, through cloud-based analysis tools to a front-end for data viewing, and could trigger alarms for abnormal heart rates. Another example was a printed on-skin amplifier with silver nano-paste conductors, dithienobenzodithiophene semiconductors, and poly (3-hexylthiophene) resistors, all integrated in a conformable parylene substrate.
Professor Mäntysalo believed that future developments would include biodegradable materials for single-use items, structural integration and 3D printing, integration of active functions, and integration of the energy supply.
Dr. Ashok Sridhar
The second presentation continued the theme of additive manufacturing, but turned from medical applications of printed electronics to trends in the automotive industry. Martyn Gaudion introduced Dr. Ashok Sridhar, senior business development manager at the Holst Centre in Eindhoven, the Netherlands, an independent research and innovation establishment with specialist expertise in wireless sensor technologies and flexible electronics, along with a tag line declaring, “The future belongs to those who create it.” Sridhar gave some thought-provoking insight into what could be achieved with printed electronics in next-generation automotive interiors, creating smart surfaces and using them as human-machine interfaces. “PCBs are too restrictive for future applications,” he said he briefly reviewed some of the principles of printed electronics.
The automotive dashboard would no longer be a dumb plastic structure if it could be transformed into a smart surface by seamlessly integrating electronics just beneath it, although because of its complex three-dimensional geometry, the electronics would need to conform to it. Holst Centre has taken electronics to the next level, making them flexible, stretchable, or permanently deformable into three-dimensional shapes, if necessary. By combining these building blocks with traditional electronic components in a smart manner, applications could be created with new form factors and enhanced design freedom.
How was it done? Sridhar explained that Holst Centre had made smart use of additive printing technologies, cost-effective and multifunctional, with a wide range of formulations and materials available, and taking advantage of the intrinsic flexibility and stretchability of polymer-based inks. And the choice of substrates ranged from rubbery materials like thermoplastic polyurethanes and silicones, smart plastics like polycarbonates, polymethyl methacrylates and polystyrenes, and even disposables like paper.
Complex multilayer circuit designs could be screen printed, with lines and spaces as fine as 30 microns. He showed photographs of a roll-to-roll printing line with fully integrated inkjet, multilayer rotary screen printing and photonic sintering, together with an assembly facility for hybrid integration, using photonic soldering to avoid thermal damage to substrates with conventional reflow.
Looking specifically at smart surfaces in automotive applications and how they could enable human-machine-interface and display functions, Sridhar demonstrated the operation of dashboard touch-controls, with optical and haptic feedback, and showed an example of an award-winning structural-electronics centre console. Manufacturing complexity was reduced, together with a reduction in weight and space, and aesthetics were considerably improved. He explained the manufacturing sequence used at the Holst Centre: roll-to-roll screen printing, followed by roll-to-roll component assembly, followed by high pressure thermoforming.
An innovation pioneered by Holst Centre was the world’s first thermoformed OLED display. The capability had also been established to produce printed large area sensors for automotive that could be incorporated into car seats for vital-signs monitoring, and it was clear that the expertise existed to enable and encourage the industry to develop and adopt a whole range of freeform electronics capabilities.
Additively Manufactured Electronics (AME) was the topic of the third presentation, from Chris Garden, EMEA sales director for Nano Dimension, headquartered in Israel.
Listing the benefits of additive manufacturing for electronics: accelerating time to market, protecting intellectual property, increasing design possibilities and improving efficiency, he saw AME technology as bridging the gap between traditional integrated circuits and traditional printed circuit boards, using what he termed “a digital factory in a box,” a digital process of using additive manufacturing technology for creating functional electronic circuits containing both dielectric and multilayer metal elements.
Describing the principles of operation of Nano Dimension’s DragonFly machine, Garden explained that it used two inkjet print-heads, simultaneously depositing conductor and insulator substrate, both materials being activated in real-time on-the-fly, as a fully additive process. The object was built up layer-by-layer, with conductive and dielectric layers. Through-holes and vias were printed from the bottom up, and solder mask and annotation could also be applied. The equipment was capable of producing complex multilayer PCBs up to 50 layers, as well as high-performance electronic devices (HiPEDs) with new design feasibilities. Manufacturing data was input as Gerber for two-dimensional and Solidworks for three-dimensional designs.
Customers included defence manufacturers, technology conglomerates and research institutions. It was clear from Garden’s presentation that AME technology was particularly suited to the fabrication of RF antennas and amplifiers, with the proven capability to print UHF and SHF signal transmission lines for applications with frequencies up to 6GHz. Its superior RF performance was attributed to lower losses due to lower parasitic capacitance and less skin effect, and the ability to design in the third dimension allowed complex 3D antennas to be produced. Garden showed many examples: tunable RF antennas, omnidirectional antennas, multimodal antennas and sphere phase array antennas. He cited case histories of successful cooperation with research institutes, aerospace, defence and medical companies, where AME technology had facilitated the construction of HiPED devices unattainable by traditional methods, as well as enabling fast proof-of-concept for new designs.
Martyn Gaudion commented that the brief journey through additive manufacturing taken during this Technical Snapshot webinar had illustrated the technology from several viewpoints, beginning with health, progressing through automotive, and then demonstrating how full 3D could take us right into the RF world and achieve things that weren’t imaginable with conventional printed circuits. The final speaker would bring us back into the real world of PCBs, but with an innovative approach to the deposition of solder mask.
Dr. Luca Gautero
For two decades, inkjet solder mask had remained an unfulfilled dream; the aspirations of many equipment and material suppliers had ended in disillusionment and disappointment. Only in the last couple of years has it become recognised as a mature technology, eagerly awaited by the industry. The final presentation came from Dr. Luca Gautero, product manager with SÜSS MicroTec Group in the Netherlands, who made a convincing case for his company to be considered the right partner for inkjet deposition of solder mask for PCB production.
Summarising the history of the SÜSS MicroTec organisation, Gautero explained that it had been founded in 1949 by Karl Süss, specialising in optical devices and high resolution photolithography and was now a leading supplier of equipment and process solutions for microstructuring applications in the semiconductor industry. The company was breaking new ground in additive printing with digital inkjet technology since acquiring PiXDRO in 2020, and had made significant innovations in solder mask application. Two fully automated machines were already running in production in Europe, and SÜSS had a further system working on a continuous improvement program at their in-house laboratory in Eindhoven.
They had cooperated with several material suppliers in order to ensure compatibility with a broad range of specialist solder mask inks and had chosen to use the FujiFilm Dimatix Samba G3L printhead, which they considered the most advanced technology currently available for accuracy and precision, with features that made it ideal for solder mask application. Its 2400 DPI resolution gave excellent pattern definition, a 2 picolitre drop-size enabling 75 micron line and space features, and its high print-speed capability made serious production throughput a reality. The JETx-SMP machine used six heads stacked together and featured on-the-fly raster image processing and a throughput of up to 60 panel-sides per hour.
Gautero recounted the clear advantages of inkjet over traditional imaging techniques. Specifically, as a true additive process, it placed solder mask only where it was needed and the JETx-SMP machine had the programmable capability to vary deposit thickness locally, according to the design requirement. The actual cross-section he used as illustration showed controlled thicknesses of 27 microns to 81microns on different features of the same sample.
In his conclusion, he remarked that inkjet solder mask technology had now been recognised and adopted worldwide. High-performance materials were commercially available and an optimum match between application and inkjet hardware had been established.
An active Q&A session followed the formal presentations, after which Gaudion closed the webinar, thanking presenters and participants, with special acknowledgement of the EIPC team’s smooth organisation of the event. The next Technical Snapshot is scheduled for June 16 on the topic of microvia reliability.