ICT Technical Director Bill Wilkie has always excelled in locating interesting and unusual venues for the Institute of Circuit Technology Annual Symposium, and this year was no exception. For the 2015 event, the 41st, he chose the Black Country Living Museum, an open-air museum of rebuilt historic buildings in Dudley, in the West Midlands of England, home of the original Industrial Revolution.
From the smelting of iron with coal and the mechanisation of production with steam power, through the second industrial revolution that introduced mass production with electric power, followed by the digital revolution using electronics and information technology to automate production, we are now entering a fourth industrial revolution with development of the Internet of Things, a concept in which printed circuit boards are unseen, but fundamentally essential components.
Welcoming a full house of delegates, Bill Wilkie opened the proceedings by acknowledging the enormous contributions, spanning more than five years in office, of retiring ICT Chairman Professor Martin Goosey, and introducing newly elected chairman Dr. Andy Cobley.
The first technical presentation came from Dr. Darren Southee, formerly of Brunel University and currently programme director of product design and technology at Loughborough University. Speaking from a background of 15 years’ experience of printing electronic devices using unmodified printing presses, he described recent work supported by IeMRC at Loughborough aimed at broadening the integration of printed power sources with electronic systems, determining the feasibility of making rechargeable energy storage devices using mass produced printed electrodes, and producing a demonstrator. His team had characterised electrodes produced by offset lithographic printing and new examples produced by flexographic printing using commercially available inks, and investigated the scope to combine them with various electrolytes to construct a range of supercapacitors. A supercapacitor needed high-surface-area electrode material, its resistance needed to be as low as possible to achieve high power and its energy storage was strongly affected by the electrolyte’s electrochemical stability window. Trials with the new electrodes in 6-molar potassium hydroxide with a filter paper separator had given realistic electrical results, but there were issues regarding sealing and electrode wetting. A solid-state version had been developed by coating each electrode with a PVA gel and allowing it to dry, then gluing the two electrodes together using the same gel and allowing the assembly to partially dry before sealing. No additional separator was required. A stack of supercapacitors charged to 2.4 volts had been shown capable of powering a 1.6 volt LED for around 90 seconds. In a second demonstration, the printed electrodes were modified by adding an activated carbon layer and an ionic liquid was used as the electrolyte. The two electrodes were separated using filter paper and two supercapacitors were connected in series. In this combination, the supercapacitors could be charged to 6 volts, with a capacitance of around 0.5 Farad, and could light a wind-up torch for more than a minute.
Independent business consultant and ICT council member Francesca Stern gave her outlook on the UK PCB and electronics industry. Her figures indicated that the value of global electronics production, excluding components, grew from $1.4 trillion in 2013 to $1.5 trillion in 2014, the main growth coming from Asia, with low single-digit growth in Europe and North America and a 5% decline in Japan. Of a 2013 European total of $154 billion, the UK share was about $13 billion, with major sectors being instrumentation, radar and navigation and communications. Looking at UK PCB production, in pounds sterling to avoid distortion by exchange rate fluctuations, there had been a slight decline from £139 million in 2012 through £136 million in 2013 to £130 million in 2014, with the main market sectors being industrial and instrumentation 36%, military and government 21%, communications 12% and civil aerospace 10%. Net imports of PCBs into the UK had risen from £41 million in 2012, through £54 million in 2103 to £75 million in 2014. She believed that growth in PCB production in the UK would overall be zero in 2015, although it would appear as low single digit growth because of the shrinking number of fabricators. All regions had peaked on their current growth cycles and she expected the next surge to be in 2017–18.
Because of other commitments, Alun Morgan, chairman of the European Institute of Printed Circuits, was unable to attend the symposium and his paper on fire retardancy was presented by Professor Martin Goosey, who put his personal interpretation on certain points. He explained that flame retardants were chemicals which, when added to materials during or after manufacture, inhibited or suppressed the combustion process during heating, decomposition, ignition or flame spread. The presence of flame retardants in otherwise combustible materials had the effect either of preventing the fire from developing altogether or of slowing down the propagation of the fire and delaying the time to flashover so that people could escape. Annually in the EU there were more than 4,500 fatalities resulting from fires, accounting for 2% of all fatal injuries, and if occupants of a domestic dwelling fitted with working fire alarms were asleep upstairs when a fire started on the ground floor, they would have only about three minutes to escape.
Professor Goosey described the different classes of flame retardants and explained the physics and chemistry of how they worked. With specific reference to the halogenated flame retardant used in printed circuit laminates, the starting material was tetrabromobisphenol-A (TBBPA), which was chemically incorporated into epoxy resin during the manufacturing process. It was only when the resin was burned that bromine compounds were released by chemical breakdown, and inhibited the combustion process.
Unfortunately, there were widespread misconceptions about “halogens,” and their perceived toxicity. In fact, halogens such as chlorine and iodine were essential to life, and so far as the end-user was concerned, a halogenated PCB material was no more than a cross-linked polymer that would not burn! The toxicology of TBBPA had been exhaustively studied. No evidence of risk to human health had been observed and there was no clear scientific justification for restricting the use of halogenated flame retardants. TBBPA was one of the first substances to have been registered under the REACH regulations, and was not listed as a “substance of very high concern.” Neither was it listed as a restricted material under RoHS. However, the fact remained that major multinational OEMs such as Apple and Dell were committed to eliminating brominated flame retardants and PVC plastics form their products. Non-halogenated alternative reactive flame retardants for epoxy resin included the phosphorus compound dihydro-oxa-phosphaphenanthrene-oxide (DOPO), aluminium trihydrate and aluminium monohydrate (Boehmite). Halogen-free laminates tended to be more expensive and more difficult to drill. However, they generally had lower thermal expansion, longer T-260 and T-288 times and higher Td temperatures, so might be better suited for multiple reflow processes and able to withstand higher reflow temperatures.