EIPC 50th Anniversary Conference Day 2: The Past, the Present and the Future, Pt. 1
The sun was shining in Dusseldorf as delegates returned to the conference room for the second day of the EIPC 50th Anniversary Conference. There were very few empty chairs—even those who had enjoyed a late networking session in the hotel bar had taken their seats as Paul Waldner opened the proceedings with Session 5, on a theme of future PCB design, material and processes for the PCB supply chain.
Waldner introduced Micha Perlman, senior marketing manager at Orbotech, to give a presentation on digital solutions for automotive PCB production. He commented that advances in automotive electronics presented a new driving experience, considering developments in connectivity, autonomous operation, safety, infotainment, comfort and environmental friendliness. Automotive data was growing rapidly, with cameras, sonar, GPS, radar and lidar. It was forecast that an autonomous vehicle would generate 4000 Gb of data per day, and connectivity via 5G was a 
fundamental enabler for the future for vehicle-to-infrastructure and vehicle-to-vehicle interaction. As a consequence, the large communications providers would be joining the automotive supply chain.
Automotive electronics would place new demands on the PCB industry: HDI was predicted to grow from zero to over 15% of the total HDI market by 2020, more complex multilayer boards would be required for engine control units, boards microwave and radio frequency radar would need SLP technology, high power systems would require heavy copper, and flex and flex-rigid harnesses would replace conventional wiring. And at all times, safety and reliability would remain the number 1 priority.
How did a leading supplier of imaging and inspection equipment respond to these requirements? Perlman described a whole range of digital solutions to meet the demands of the automotive industry: direct digital imaging, triple vision AOI with integrated 2D metrology, full production traceability, defect distribution visualisation, and a full suite of IoT and Industry 4.0 solutions for data tracking, big data analysis and data visibility.
“You already recognize the winner at the start—A supply chain without wastage.” Speaking from the position of a distributor with a 40-year history of supplying laminates, pre-pregs, foils and ancillary materials to the European PCB industry, Gerd Appelt, with responsibility for sales and technical service at Göttle GmbH, focused on customer satisfaction and optimisation of the supply chain.
With the rapid introduction of new products into the market, managers were always looking for opportunities, and making a wrong decision could be very costly. Appelt referred to a series of opportunities missed by bad decisions, notably Decca Records turning down the Beatles, Nokia missing the smartphone market, and Kodak trusting in film and not capitalising on the digital camera. Of the twelve companies in the original Dow Jones Index from 1896, only General Electric was left.
“90% of the potential of your supply chain is not active now!” he commented, and asked, “Are you working with the right partners? Size doesn‘t matter—potential does!” He remarked that Steve Jobs had been looking for HD video capability for the iPhone, and found the solution in a small German company. At the other end of the scale, the news headlines announced that Apple is moving on from Intel because Intel wasn’t moving anywhere!
Appelt advocated keeping time to market to a minimum, to be successful, and optimisation of supplier services and product quality. New applications needed tight cooperation along the whole supply chain and in the case of specialised laminates it was an advantage if the supplier could provide a range of material options. The Internet of Things was enabling Industry 4.0 and the world was moving towards Smart everything: smart city, smart energy, the connected car, smart agriculture, connected health, smart retail, smart supply chain and smart home. Industry 4.0 was already reality in the laminate manufacturing industry. And there was more to come in the future ... “Business is changing,” he said as he concluded with an example of a teddy bear that could tell bedtime stories.
Jonathan Weldon, principal investigator in DuPont’s Circuit and Industrial Technologies group, gave a scintillating presentation on flexible materials for 5G. He began by defining the market needs of 5G technology and asking the question “Where does flex fit in?”
The evolution of 5G technology was creating increased demand for high frequency circuit materials with low relative permittivity and loss tangent to achieve low latency, low loss and highest antenna gain, for applications including mobile handsets, base stations, smart devices, small cells and beam formers, and hybrid substrates. The critical frequencies were sub-6GHz, and the millimetre-wave frequencies 28GHz and 39GHz, and typical examples of the functional components required were digital-to-analogue and analogue-to-digital converters, filters, mixers and circulators, digital/analogue/hybrid beam formers, antenna feedlines and arrays. The important characteristics of materials for these functions were frequency and phase stability, loss performance and processability.
The use of flex material was still primarily driven by packaging needs, the separation of analogue, digital and antenna components, and the elimination of cables and connectors. Its electrical benefits were the absence of glass, and therefore of skew and phase issues, and its low permittivity and loss tangent.
Traditional all-polyimide-based flexible copper-clad laminates have been predominant in the flex circuit market but had been perceived as having some undesirable properties and limited performance at millimetre-wave frequencies. An alternative material was liquid crystal polymer LCP, which has very low moisture absorption and had been considered a better choice for high frequencies, but it has its limitations: its bulk material properties did not directly correlate to circuit performance and its mechanical properties could limit processability and yield.
Weldon had set out to compare all-polyimide with LCP to determine its viability for 5G applications and to ascertain when and where polyimide and LCP could be used to maximize system performance. He concluded that LCP and all-polyimide laminates were both suitable for millimetre wave applications up to 40GHz, and their bulk dielectric properties did not account for their performance in flexible laminates. Copper roughness and type—rolled annealed versus electrodeposited—had a dramatic effect on high-frequency performance.
It had been observed that both all-polyimide and LCP flexible laminates exhibited degraded performance after environmental ageing, and further work was necessary to explain this effect. For the future, a new flexible laminate was required with low relative permittivity and loss tangent, together with a smooth high-conductivity conductor.
“The future belongs to those who create it” is the tag-line of the Holst Centre, an independent R&D centre based in Netherlands that develops technologies for wireless autonomous sensor technologies and flexible electronics. Jaap Lombaers and Corné Rentrop took a new approach to hybrid integration of electronics and delivered an inspirational presentation on large-area printed electronics becoming curved, flexible, stretchable and three-dimensional.
When they referred to the shape of things to come, the emphasis was definitely on shape and they demonstrated that wherever there was a surface, whether flat or three-dimensional, and whether it was in a car, a house, a hand-held device, a health-care device or an item of sports apparel, it was potentially a smart functional surface with electronics unobtrusively integrated into it.
Lombaers likened himself to a chef in a kitchen, asking “What kind of cooking is needed?” and “What can we serve today?” in the context of being able to prepare a whole range of dishes from a few basic ingredients.
He explained that hybrid integration of printed electronics offered savings in weight and space, as well as flexibility, bendability, stretchability and wearability. Devices could be easily integrated into anything and any product surface could become a user interface. Devices would be more robust and with a longer lifetime, contain less material, be less expensive and easily manufactured using new manufacturing concepts. Hybrid printed electronics could be combined with traditional electronics and were available in various form factors. They were applicable in various market sectors: for example, packaging, wearables, medical, Smart building—the possibilities were infinite.
Rentrop compared rigid and flexible PCBs, produced through conventional process routes on relatively expensive substrates using photoimaging, plating and etching processes, with printed electronics circuitry, and discussed printing techniques and materials. Various well-established printing techniques were available: inkjet, flat-bed screen, rotary screen and flexo-gravure for example, and a wide range of plastic foil substrates: polyethylene terephthalate, polyethylene naphthenate, thermoplastic polyurethane foils or even paper. These could be processed roll-to-roll if necessary, at speeds up to 60 metres per minute, and it was possible to print multiple layers. Metal inks were used, typically nano-particle silver, sintered by photonics or near-infrared. An example of industry-proven capability was a dry thickness of 5−8 microns with conductivity 10−20% of that of bulk silver and 150-micron feature size and pitch. On a laboratory scale, conductivity 20−40% of that of bulk silver and feature size and pitch as fine as 20 microns had been achieved at 5−8 microns dry thickness. Thin-film transistors had been produced, as well as stretchable circuits using either stretchable inks or meander patterns. The largest circuit they had made was 300 metres long, roll-to-roll assembled with 2000 LEDs.
Lombaers showed many practical examples of printed sensors and integrated displays in apparel, fashion and sportswear, some of which could be self-powered by energy harvesting. Rentrop demonstrated how 3D electronics, including discrete components, could be created by printing and thermoforming, and discussed in-mould electronics: “There’s no PCB any more, the component becomes the PCB.” And the opportunities for combining printed electronics with 3D printing techniques were endless.
Back to normality—the optimisation of SMT component land dimensions to achieve the most effective and reliable solder joint geometry—as Rainer Taube of Taube Electronic discussed “The Proportional Land Dimensioning Concept” and reported the results of the Proportional Verification Project carried out by FED, the Fachverband Elektronik-Design.
Taube explained that since the introduction of surface mount technology, the development of component packages has progressed rapidly, but IPC and IEC calculation standards for component land dimensions were still largely based on the component packaging conventions of the 1980s and 1990s. This led to problems in design and assembly and could also affect the reliability of the solder joints. As component terminations became progressively smaller, a new method was required for calculating the dimensions of surface-mount pads on PCBs, and this was reflected in the FED’s approach to a proportional land dimensioning concept.
The concept recognised two classes of terminations: those with facing wettable areas and those with a combination of facing and vertical wettable areas. Land dimensions were defined by solder joint requirements, terminal type, terminal size and terminal height in the case of those with vertical wettable areas. Advantages were that land dimensions were defined and easily scalable for future components, leading to smoother assembly and higher reliability. In many cases additional design space was created. The only disadvantage was that there were no longer any generic footprints. The concept had been extensively tested and proven over a wide range of component package types and dimensions through the FED’s Proportional Verification Project.
The continuation of this article will be published tomorrow.
EIPC 50th Anniversary Conference Day 1: The Past, the Present and the Future, Pt. 1
1EIPC 50th Anniversary Conference Day 1: The Past, the Present and the Future, Pt. 2
