Dissemination Seminar: Results from Applied Research Projects in the Surface Engineering and Printed Circuit Sectors Surface Engineering Association, Federation House, Vyse Street, Birmingham 29 June 2012

Circuit World

ISSN: 0305-6120

Article publication date: 16 November 2012



Goosey, M. (2012), "Dissemination Seminar: Results from Applied Research Projects in the Surface Engineering and Printed Circuit Sectors Surface Engineering Association, Federation House, Vyse Street, Birmingham 29 June 2012", Circuit World, Vol. 38 No. 4. https://doi.org/10.1108/cw.2012.21738daa.014



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Copyright © 2012, Emerald Group Publishing Limited

Dissemination Seminar: Results from Applied Research Projects in the Surface Engineering and Printed Circuit Sectors Surface Engineering Association, Federation House, Vyse Street, Birmingham 29 June 2012

Article Type: Exhibitions and conferences From: Circuit World, Volume 38, Issue 4

Hosted by the Surface Engineering Association (SEA) at its excellent conference facility in Birmingham’s Jewellery Quarter, this seminar had been organised to provide a dissemination platform for nine UK and European multi-partner projects that were each addressing different, but related topics of interest and relevance to both the printed circuit board and surface engineering sectors.

David Elliot, Chief Executive of the SEA, opened the seminar by welcoming the delegates to Federation House and then immediately invited the first speaker to the rostrum.

The opening technical presentation of the event was given by Karl Ryder from Leicester University, who gave an update on surface finishing processes in ionic liquid electrolytes. Karl began by discussing some of the motivations for using ionic liquids and key advantages included environmental benefits and the ability to comply with increasingly stringent legislation. Example, ionic liquids were then described and their novel properties outlined; they typically had very low vapour pressures, good thermal stabilities, unusual solvent properties and wide potential windows for processes. They had been known for almost 100 years, but it was only in the last ten years or so that there had been growing interest in their use in PCB and surface finishing applications. Eutectic-based ionic liquids formed using choline chloride, a very low cost component that was used as an animal feed, were then described. One such example was made by mixing choline chloride and ethylene glycol or, as Karl stated, by mixing “chicken feed” with “antifreeze”. Chromium plating had been performed using choline chloride-based ionic liquids and a pilot plant built by C-Tech Innovation was shown. The process had been developed for hard, decorative and black chromium deposits and good current efficiencies had been achieved. The process used a less toxic source of chromium with no acid and the deposits had excellent corrosion resistance and hardnesses up to 1,500 HV after thermal treatment. Karl also described an aluminium plating process. A 40 l demonstration unit had been built that included a nitrogen gas blanket. Both bright and matt aluminium finishes were possible and these also exhibited excellent corrosion resistance. Work on electropolishing of stainless steel using ionic liquids was also reported. The choline chloride-ethylene glycol-based process offered low toxicity and high current efficiencies. A pilot plant had also been built for this process and it had operated for three years using the same electrolyte. As part of the IONMET project (www.ionmet.eu), an immersion silver process for PCBs was developed and scaled up to an 800 l ionic liquid production demonstration scale. In addition, immersion gold coatings for PCB applications had also been demonstrated as part of the ASPIS FP7 project. Another ionic liquid technology that had emerged from the IONMET project was related to zinc rechargeable batteries that used a choline chloride ionic liquid-based electrolyte. The advantages included low toxicity, light weight, low cost and high power density. This work was undertaken in the PolyZion project (www.polyzion.eu). Karl then discussed zinc-tin alloy corrosion resistant coatings from ionic liquids and examples made by Promet were shown. He concluded by summarising the potential benefits of eutectic-based ionic liquids.

Andy Cobley from Coventry University then presented the results of his work on ultrasonically (U/S) enhanced surface modification processes in a project that had originally been funded by the IeMRC and that had been taken forward to a European Eco-Innovation project called Susonence (www.susonence.eu). Andy began by outlining the hazardous nature of traditional wet chemical surface modification methods used in the PCB and surface engineering sectors. Sonochemistry was described as the effect of sound on the chemistry of a solution and it could be used to offer alternative processes to the more traditional ones. Advantage was taken of acoustic cavitation, along with so-called microjetting/microstreaming. Micro-jetting could be used to clean and mechanically attack a surface and, at the extreme local temperatures generated, chemical reactions via free radicals could also be utilised. By using this approach, it was possible to reduce operating temperatures, reduce the use of aggressive chemicals and generate less waste. The approach had been used on ceramic, thermoplastic and thermosetting polymer surfaces. In some cases the use of U/S enabled surface modification in water alone and examples of circuit board laminates treated in this way were shown. The optimum ultrasonic frequency was found to be 20 kHz and the ultrasonic power density had also been optimised, along with a number of other factors such as sample to probe distance. The success of the initial IeMRC project lead to the nine month TSB funded “HEPPROC” feasibility study which focused on the PCB desmear process. In this work it had been possible to reduce the operating temperature of the process by 20°C and to use half strength permanganate chemistry. Printed circuit boards had been produced using the process which had comparable reliability to those processed through the standard desmear process. This work was now being taken further towards industrial implementation in the Susonence project which was building five units for installation at factories in France and the Czech Republic.

After a networking coffee break Stuart Dalrymple from C-Tech Innovation discussed energy efficiency support for the surface engineering and PCB sectors that had been developed in the recently completed Surf Energy multi-partner collaborative “Intelligent Energy Europe” project (www.surfenergy.eu). The project had developed a free toolkit for use in the PCB and surface engineering sectors which provided a “path to energy efficiency”. Stuart then proceeded to demonstrate the toolkit by working through each of the individual stages which began with the set-up of an environmental management system. The next stage involved energy auditing and he described the five phases of the audit process. Key performance indicators needed to be identified before moving on to the interactive benchmarking tool part of the process. The benchmarking was performed on line and enabled a comparison to be made in terms of performance relative to others and industry standards. If costs were above the benchmark, a potential “savings” figure was indicated. A more detailed part of the toolkit was a downloadable spreadsheet that could be used by companies for monitoring their performance. The spreadsheet had three parts for recording past, current and future desired performance. By inputting this data, it was possible to obtain information on the potential savings that could be made. The toolkit also provided a pathway to energy efficiency via technology intelligence and road-mapping. This was based on intelligence that had been gathered on technologies, knowhow and other measures with the potential to reduce energy consumption. The toolkit also contained detailed best practice guides for both PCB and surface finishing activities and was available in nine European languages.

The final part of the morning was focussed on the results of two projects concerned with new technologies for nickel recovery. The first presentation was given by Rod Kellner of Env-Aqua Solutions who detailed work on the European Commission supported Ecometre project (www.ecometre.eu) which had developed new electrocoagulation and electrowinning technology. The process had integrated three existing technologies which combined electrocoagulation, acid extraction and electrowinning for metal recovery. This enabled nickel from different sources, such as filter cake, waste streams and spent chemistry, to be recovered. Rod then discussed the electrocoagulation process and how it was utilised in the Ecometre approach. Sacrificial metal electrodes were used to donate coagulant ions leading to in situ floc formation. The process was current driven and controlled and the floc could be settled, skimmed or filtered depending on the application. No liquid chemicals were used. The process had been developed to have high coagulant dosing efficiency, reduced downstream chemical requirements, quick and easy electrode replacement, reduced energy consumption and a plant availability of around 98 per cent. The pilot plant that had been developed and installed at Promet in Paris was shown and its operation explained.

Paul Fitzpatrick of C-Tech Innovation then presented the work that had been carried out on the UK Technology Strategy Board supported Reconif project. The Reconif approach had used ionic liquids for the selective extraction and recovery of nickel. Paul gave some background information on ionic liquids and explained how a “task specific” ionic liquid had been selected for the targeted approach that matched the ionic liquid against the target metal profile and the waste source to be treated, i.e. the presence of other metals. The best match was then optimised for solubility and separation capability. Paul gave an overview of the complete Reconif process which was designed to treat nickel containing filter cake or battery waste. Ligands were used to bind the target metal selectively. The complex was then broken down to free the nickel ions, which were taken into an aqueous phase that enabled subsequent electrowinning using a Chemelec cell. The ionic liquids operated in a closed loop part of the process and sourcing them from China had enabled their cost to be significantly reduced. The operation of the pilot plant was described and examples of the nickel recovered were shown. There was around 100 tonnes of nickel available in the UK per annum that was suitable for recovery using the Reconif approach and significantly greater quantities throughout Europe. The project was due to end later this year and an LCA was currently being undertaken to assess the true benefits of the process.

The afternoon session began with a talk by Martin Goosey on the FP7 Aspis project (www.aspis-pcb.eu). Aspis was short for “Advanced Surface Protection for Improved Reliability PCB Systems” and the project’s objective was to enhance the performance of the nickel-gold solderable finishes used in PCB assembly. The key objectives of the project were to; investigate fundamental failure modes and mechanisms of ENIG coatings, develop an ENIG screening tool, develop improved coating methods and materials (both aqueous and ionic liquid-based) and to verify the compatibility of any new technology developed with assembly methods and practices. In the first part of the project a large amount of fundamental research had been undertaken to gain a better understanding of the key factors influencing the reliability of assembled circuit boards employing nickel-gold solderable finishes. A large number of variables were known to have an influence on the occurrence of problems such as “black pad” and these included the pre-treatment of the copper before nickel deposition, the formulation of the electroless nickel chemistry used, the deposition conditions, and the presence of copper ions in the immersion gold solution. Martin then described some of the longer range research that had been undertaken in the project by Karl Ryder’s team Leicester University. Gold had been successfully deposited onto nickel using an ionic-liquid-based immersion process. A variety of gold salts had been used and some of the deposits gave much smoother coatings than those obtained from conventional aqueous processes. Another part of the project required the development of a non-destructive test method for circuit boards and Martin highlighted the challenges in developing a suitable process that could successfully detect potential issues at one specific region (the solder circuit board interface) inside an assembly comprising a multilayer circuit board populated with a range of surface mount components including flip chip devices. There had been numerous dissemination activities for the project and Martin concluded by giving examples of the publications and presentations that had been made on the project and he gave references to the Aspis web site and to two papers that gave more detailed information.

David Hall from C-Tech Innovation then presented details of a “Research for SMEs” project called Nanocoat (www.nanocoat-project.eu), which had a focus on new aluminium anodisation techniques. The aim was to produce uniform nanostructured anodised aluminium oxide coatings and to develop improved functionality and new coating applications for products in surface engineering. David then gave an overview of the Nanocoat process, which actually had two anodising steps, and he described the scale-up activities that C-Tech had undertaken. Eductors were employed to provide energy efficient agitation and heat removal from the process tank and computational fluid dynamics (CFD) was used to help with the equipment design and educator location. Testing had been performed on samples prepared using the Nanocoat process and improvements achieved in a number of key mechanical properties. Structural analysis had shown that the Nanocoat process gave uniform nanostructural coatings. Industrial applications were being tested and a life cycle assessment was being undertaken.

Karl Ryder then returned to give a presentation on the electropolishing of aerospace alloys in new sustainable ionic liquid electrolytes. The work had been supported by the Royal Society and had the intention of developing electropolishing processes for super alloys using ionic liquids. The alloys being studied had very complex metallurgies and were typically grown as single crystals. The aim was to remove scale on the surface of these single crystal castings by electropolishing and work had been conducted on turbine blades using the pilot plant at Leicester University. Karl highlighted the mechanisms for the formation of scale on the surface of these metals during casting. The scale had successfully been removed using ionic liquids and the changes occurring during the process had been characterised. Results indicated that the alloy composition had not been affected by the electropolishing process and that the surface roughness had been greatly reduced. Examples of electropolished turbine blades were shown and the scale had clearly been removed. Etch rate characterisation work had also been undertaken and AFM data used to assess etch rates. Karl concluded by confirming that electropolishing was effective in removing nickel-based surface scales on turbine blades.

Andy Cobley also returned to give a second presentation, which was entitled ultrasonically enabled immersion and electroless metallisation and he detailed work carried out on the three year IeMRC funded “ULTIEmet” project. The aim had been to enhance the performance of electroless nickel, electroless copper and immersion silver and immersion gold processes. The first part of the project had focussed on electroless copper processes. Andy described the process stages involved and explained the palladium catalysed deposition of copper. Initial studies had been carried out to assess the effect of ultrasound on the stability of the plating bath. The stability varied with U/S frequency and at several frequencies the baths became unstable with the copper being precipitated from solution. This was thought to be due to destruction of the EDTA that was used to complex the copper. Plating rates were then evaluated using a commercial EDTA-based copper bath with an agitation frequency of 40 kHz. Not surprisingly, plating rates increased with increasing temperatures and the use of U/S gave only a further slight improvement, which was disappointing. One suggestion was that the U/S was scrubbing some of the catalyst from the surface and this had subsequently been confirmed by XPS analysis. However, if a delay time was introduced before the U/S was applied, the plating rate was found to increase. A 7 min delay before introducing the U/S led to a significant increase in plating rates at 40°C, giving a rate that was higher than that using standard agitation at 45°C. Deposit morphology had also been studied and this had shown that fine grained deposits had been achieved.

At the end of an intense programme of nine presentations David Elliot made the concluding remarks and thanked all the speakers before closing what had been a very useful, interesting and well attended seminar.

Martin Goosey

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