The Institute of Circuit Technology Autumn Seminar
An ancient monument dating back more than 500 years stands proudly on the green in the village of Meriden with a plaque stating that, by tradition, it marks the centre of England. But more recently, GPS technology argues that the true geographical centre is 11 miles north! Either way, Meriden has been established as a popular Midlands venue for Institute of Circuit Technology (ICT) meetings. On September 19, a multitude of Fellows, Members, and Associates gathered for the Institute’s autumn seminar, which was organised and hosted by ICT Technical Director Bill Wilkie. The agenda included five informative technical presentations, describing current research and development on significant topics relevant to the industry.
Sophia Danilova, a Ph.D. student worker from the Research Centre for Manufacturing and Materials Engineering at Coventry University, discussed the importance of selective metallisation in the electronics sector. Her presentation titled entitled “Selective Electroless Copper Plating on a Non-Conductive Substrate Via Magnetic Field Application” included a discussion of PCBs, moulded interconnect devices, microelectronics, printed electronics, wearable technology, and radio-frequency identification devices.
It had been estimated that 30–40% of the total manufacturing cost of an electronic device was due to photolithography, a time-consuming, multi-step process with high material wastage due to coating the entire surface with photoresist before exposure and development to create a resist pattern. Patterning by magnetic field was being investigated as a lower-cost alternative with shorter processing time. The objective was to selectively deposit a catalyst and then to build the conductor pattern by electroless copper deposition.
The first step was to prepare a suitable magnetic catalyst. Initial attempts to combine silver and iron powders by ball-milling resulted in particle sizes that were too large for accurate patterning. Iron-palladium nano-particles supplied by the specialists at the Jožef Stefan Institute in Slovenia were found to be unsuitable for the application. Wet chemical synthesis of a composite of silver and iron oxide using arginine as reducing agent gave promising results, and wet chemical synthesis of a composite of silver with silica and iron oxide using tin as a reducing agent gave particles with a regular distribution of magnetic and catalytic sites.
The conditions for magnetic deposition of a catalyst had been optimised in terms of time and pH as determined by the uniformity of electroless copper coverage. Magnetic templates were designed using finite element method magnetics (FEMM) software for the simulation of magnetic field distribution. Copper patterns with micron-scale features had been successfully produced by electroless plating, and the research had progressed from idea to proof of concept. The main goal of future work was to selectively deposit copper in sub-micron patterns by creating mono-dispersed magnetic nanoparticles, continuing work on template modelling using 3D simulation software and the optimisation of catalyst and copper plating conditions.
Professor and ICT Chairman Andy Cobley from Coventry University gave a two-part presentation, including an update on the MATUROLIFE project in which the university was a partner and an introduction to the ReCollect project in which the Institute was a partner. The Horizon 2020 funded MATUROLIFE project was in its 20th month out of 36, and Cobley reported its progress in the areas of design, materials, electronics integration, and prototype manufacturing. The consortium of 20 partners from nine European countries brought a creative and artistic design together with materials science and electronic manufacturing to produce innovative assistive technology co-created with older adults across Europe to support independent ageing and well-being.
Fundamental to the concept of smart textiles was a practical metallisation process, and extensive work had been carried out to compare different catalysts for the electroless copper plating of polyester, nylon, and cotton fibres. A copper-nanoparticle formulation had given better results than standard colloidal palladium, based on the conductivity of the electroless deposit. By adding polyethylene glycol to adjust viscosity, an inkjet-printable version of this formulation had been produced which had been used to produce high-resolution images on fine polyester fabric. Various organic post-treatments were evaluated for the protection of conductive tracks against perspiration and repeated washing.
Cobley also showed examples of the integration of electronics by embedding smart textiles into a range of clothing, furniture, and footwear solutions. Concept prototypes had been manufactured, and opportunities for industrial scalability were explored. And in the second part of his presentation, Cobley introduced the ReCollect project funded by Innovate U.K., in which ICT had undertaken to support the stimulation and dissemination of U.K. industry feedback on the developments.
It had been estimated that the annual world demand for FR-4 glass-epoxy circuit boards was approaching 20 billion square metres, of which about 15% was single- and double-sided. It was not practical to salvage the fibreglass and epoxy-resin components at end of life. Generally, recycling was limited to shredding and incinerating to recover precious metals. The ReCollect project proposed an alternative route to managing end-of-life circuit boards by removing glass-epoxy materials from the supply chain and establishing an efficient manufacturing process for non-toxic, recyclable, composite laminates.
One of the project partners had already demonstrated the feasibility of reinforcing water-soluble materials with natural fibres to use as substrates for single- and double-sided PCBs. The primary aim of the project was to demonstrate the feasibility of producing this material in high volumes within the U.K. and show that it could match the performance of CEM 1 and FR-4. The secondary aim was to investigate means of chemically protecting the material from existing aqueous processes used in PCB manufacturing. Another of the project partners was developing a novel process for the continuous production of sheet material. The overall market opportunity was substantial, although there would inevitably be a need to overcome the expected inertia in transitioning from a long-standing existing technology.
Recognised for many years in the printed circuit industry for his outstanding contribution to science and technology—both academically and practically—as well as for his environmental awareness and commitment, Professor Martin Goosey drew delegates’ attention to the finite supply of key raw materials to the electronics industry. Particularly, he emphasised the scarcity of platinum-group metals (PGMs), the growing global demand, and the importance of recovering and recycling these materials to bridge the increasing gap between supply and demand.
Goosey had a long-standing interest in recovering materials from PCBs and waste electrical and electronic equipment (WEEE). Indeed, I remember him chairing the Environmental Working Group of the Printed Circuit Interconnection Federation, studying opportunities for PCB recycling over twenty years ago. More recently, changes in technology have been driving the demand for critical raw materials. Examples include the move from CRT towards LCD and OLED displays, the replacement of incandescent lighting with LED, the evolution of battery technology from nickel-cadmium through nickel-metal-hydride to lithium-ion, and the transition of vehicle propulsion systems from the internal combustion engine to battery power.
Europe had been estimated to have the highest annual demand of PGMs in the world—40 tonnes, worth over 1100 million Euros—and globally, there was currently an annual shortfall of about 20 tonnes between demand and what could be supplied from primary sources. And the shortfall was forecast to continue to grow. End-of-life recycling became even more relevant, especially considering that the concentration of PGMs could be at least 100 times greater in electronics wastes than in natural ores. The traditional method was to shred the waste and burn it; there was an urgent need to develop viable methods for recovering valuable materials at end of life.
Further, Goosey gave an introduction to the PLATIRUS Project—Recovery of Critical Raw Materials from WEEE—funded by the European Commission as part of the Horizon 2020 Research and Innovation programme. His company, Env-Aqua Solutions Ltd., was one of 12 partners representing industry, research, and academic organisations across the value chain. The objective of the PLATIRUS Project was to help bridge the supply-demand gap of PGMs in Europe by developing and introducing novel secondary raw materials to the recovery supply chains of automotive catalysts, mining, and electronic wastes. The project aimed to develop a miniaturised recovery process for platinum-group metals based on selection and optimisation of a cost-effective combination of advanced hydro-metallurgy, iono-metallurgy, supercritical CO2 extraction, solvo-metallurgy, pyro-metallurgy, hydro-metallurgy, and electro-winning technologies, and to upscale the process to industrially relevant levels.
Apart from the obvious advantages of bridging the supply-demand gap and reducing Europe’s dependence on global PGM supply chains, the PLATIRUS Project offered potential benefits in reducing energy costs and environmental impacts as well as providing solutions requiring lower capital investment than centralised refineries and maximising the exploitation of local waste sources. The work of the PLATIRUS Project was due to be completed and the final report published in October 2020.
Frank Ferdinandi, director of Azurion Technology described an environmentally friendly surface finish for PCBs, which was effectively an ultra-thin fluorochemical conformal nano-coating deposited and polymerised in-situ by a plasma process. Where the coating was deposited on copper, it offered long-term protection against oxidation, but the copper remained solderable by standard techniques. Elsewhere on the PCB, it provided a durable waterproof finish. Ferdinandi showed samples of boards coated more than 10 years previously, using an early version of the finish. The copper remained bright and tarnish-free, but still easily solderable. There had been a programme of continuous development, and the current finish represented the third iteration.
Ferdinandi explained that the new technology outperformed existing surface finishes in key areas and provided major advantages for PCB protection and post-processing. Its functional benefits included excellent long-term protection against oxidation together with a solder-through capability compatible with current reflow processes for lead-free and leaded solders. After soldering, its non-wetting properties across the complete surface gave circuits increased resistance to aggressive environments, resulting in longer product life with no rework issues. A major environmental benefit was that since no water was used, the effluent associated with traditional surface coating processes was eliminated and health and safety issues were significantly reduced. Plasma deposition was carried out in a single chamber, and in-situ cleaning was possible. The system could be semi-automated for high throughput.
Solderability, solder joint reliability, and electrical properties had been extensively studied and compared favourably with immersion silver, HASL, OSP, ENIG, electroplated nickel-gold, and immersion tin. Although previous commercialisation programmes had shown only limited success, there was currently renewed interest—particularly from China—where the opportunity to reduce water consumption was especially attractive.
The team behind Rainbow Technology Systems introduced a specialised surface-cleaning technology to the printed circuit manufacturing industry over 30 years ago. Their system of contact sheet-cleaning and web-cleaning solutions, based on rubber pick-up rollers lifting minute particles from surfaces and transferring them to an adhesive roll, became the industry standard. David Westwood, Rainbow’s sales and marketing manager, explained how this proven technology maintained its relevance and impact in the advancement and development of ultra-fine-line circuitry.
Aided by a series of animations, and frequently wielding a small hand-held pick-up roller and a pad of adhesive sheets for dramatic effect, Westwood demonstrated the potential effect of dust-related imaging defects on manufacturing yield. His illustration of typical dust and debris on a design of the 1980s with 300-micron track and gap included particles varying in size, including 75–100 microns, 50 microns, 25–30 microns, and down to 15 microns. At this level of design rule, even if the efficiency of cleaning was only 98%, any issues associated with the remaining 2% could be touched in by a skilled operator with a steady hand. It’s not so for current designs with track and gap trending towards 15–20 microns!
The KSM Superclean division of Rainbow Technology Systems had stayed ahead of the technology and was confident that contact cleaning remained the most effective method of removing debris from surfaces. Roller and adhesive technologies had been developed that enabled greater efficiency of cleaning to 99.9% at finer particle sizes down to the 0.5–3-micron critical levels. Harder rollers were available with precision surface finishes, silicone-free, and static-dissipating. And the adhesive rolls were based on clean-room film materials. Westwood believed that contact cleaning would continue to be the most effective means for the permanent removal of surface debris as design technology progressed from fine-line to ultra-fine line.
Cobley brought the seminar proceedings to a close, thanking the audience for their attention and the presenters for generously sharing their knowledge. A special thanks went to Bill Wilkie for another superbly organised learning and networking event.