Ling, J.H. (2008), "SUMEEP Sustainable Use of Materials for Electronic & Electrical Products Scientific & Technical Conference", Circuit World, Vol. 34 No. 2. https://doi.org/10.1108/cw.2008.21734bac.005Download as .RIS
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SUMEEP Sustainable Use of Materials for Electronic & Electrical Products Scientific & Technical Conference
Article Type: Exhibitions and conferences From: Circuit World, Volume 34, Issue 2.
March 2008Henry Ford College, Loughborough University
Professor Martin Goosey is the Technical Director of the IeMRC based at Loughborough University and he bade the delegates welcome. He described the IeMRC Mission, a £5 million support for academic research anywhere where most appropriate, with a strong industrial input involved in setting the research agenda. Currently, the IeMRC is supporting more than 30 projects, most of which have significant industrial input and a significant industrial potential. A key underlying theme of the IeMRC's work is sustainability. What is a definition of sustainability? It is “meeting the needs of the present generations without compromising the ability of future generations to meet their own”. Or “adopting a strategy and acting to meet the needs of the enterprise and its stakeholders to-day, whilst protecting the ability of others to do the same in the future”. There you have it.
L to R: Andy Abbot, Avtar Matharu, Gary Stevens and Martin Goosey
Electronics is not regarded as operating sustainably; it uses hazardous processes and materials, has short product life-cycles, creates waste during manufacture, and requires high energy in use, and there are end-of-life issues around waste materials, pollution, etc.
The latest producer responsibility legislation now includes a reference to sustainable use, and aims to divert end- of-life electronics for re-use, re-cycling and other forms of recovery, as the polluter pays, and the manufacturer has responsibility for end of life management. There is now a need to use greater amounts of recyclate; reduce or eliminate the use of hazardous materials; minimise waste, whilst using fewer resources. Some of the directives coming out of Brussels, with global import, include the:
The RoHS directive.
The EuP directive.
The REACh regulations.
The batteries and accumulators directive.
The packaging waste regulations.
The end of life vehicles directive.
Legislation is having a significant impact on the materials that can be used in electronics. The RoHS directive brought about the move to lead-free, and also limited several other materials including some metals such as chromium, cadmium and mercury. New materials were needed for lead- free, and there is pressure on the use of brominated flame retardants and other useful organics materials.
Martin gave some examples of materials for PCB lead-free where higher temperatures are needed for lead-free soldering; temperature compatibility and multiple solder cycles; the use of alternative curing agents to replace dicyandiamide with novolac resins; replacing TBBPA flame retardant in laminates, and the impact of bromine and nitrogen in PCBs. The influence of legislation on material choices means the removal of hazardous materials, and replacing them with more benign ones. However, the legislation has demanded a greater focus on sustainability, and electronics are treated as low-cost commodity items; they have a short life and are readily disposed of by the user, but less easily by the environment. Legislation is spreading globally China has its own RoHS, and takes it all very seriously. As do Japan, the USA, and the Far Eastern countries such as Taiwan. In Europe the Euro RoHS has a review of substances performed by the Oko Institute in Germany, and they have a list of 46 substances which have been drawn up for scrutiny, similar to those listed under the REACh programme. Summing up, Martin said that it has been proven that the removal of hazardous materials makes recycling easier, and there are emerging alternatives to hazardous materials, and electronic equipment is being converted to alterative uses.
Dr Andy Abbot from the University of Leicester talked about metals recovery using ionic liquids. Ionic liquids are solvent-free but full, very full, of ions. The use of ionic liquids is a simple principle, with a wide range of applications in uranium processing, batteries, metal plating, for example. One of the ingredients, Choline Chloride is biodegradable, and produced as a chicken feed additive, and it is very cheap. But is it is not liquid, at least not below 3008C, so they complex the material using an amide or alcohol, and produce two solids which can be mixed together and form a liquid by the endothermic reaction (ice + salt = liquid). They can make it in 300kg batches, and various metals can be converted to oxides by using ionic liquids; the tenable metal oxide solubility was described, offering a range of processes. Metals that tend to form linear or tetrahedral geometries tend to be soluble, added Andy. He cited the example of the 700ton a week of foundry dust containing lead, zinc, generated by a steel plant, and with the use of ionic liquids they can dissolve the dust, extract zinc, lead and cadmium, and they can be cemented. Turning to the electro-deposition of metals, the electroplating of metals, and the electroless deposition of metals, Andy said that metal polishing is a big business, and they now use ethylene glycol and choline chloride-based ionic liquids, as a drop in technology, to replace the traditional process, and the IONMET project was described. Chromium and chromium alloys are now available through ionic liquids and can give a mirror finish to aluminium. He mentioned the work done at PW Circuits who are evaluating an ionic liquid-based immersion silver finish, that is currently showing excellent results.
Avtar Matharu from the University of York talked about liquid crystal recovery and re-use. Liquid crystals are the Fourth State that sits between solid and liquid, hence liquid crystal. This material has an innate ability to react with an electrical field. Apply heat, and the intermediate matter becomes clear, and that is an LC. It was Professor George Gray of the University of Hull who invented the basis of the modern liquid crystal in 1972. Now they are everywhere in mobile phones, laptops screens, electro-optics, plus another less obvious world in photochromic temperature sensors, in fish tank thermometers and in bullet-proof vests made from Kevlar. Kevlar is in fact drawn as fibres from a liquid crystal. Liquid crystals are classified as non-hazardous, but they are persistent and volumes are growing and no one has measured the long-term effects of LCs in the environment. The Liquid Crystal Display industry is valued at $100 billion. About 100 million LCD TVs were sold in 2006/2007, and 48 million m2 of LCD glass were sold in 2007. Worldwide there are 185,994ton of LCD panels produced, of which 40 per cent are in Europe.
Indium tin-oxide is the transparent electric conductor on the glass, and in 2002 it was $100/kg, now it is $750/kg. The amount sold worldwide was 230 metric ton.
After all these statistics, exactly how an LCD was made was very entertainingly demonstrated.
Rapid assessment methods for flame retardants in engineering polymers were described by Professor Gary Stevens from the University of Surrey.
Legislation has driven a need for the rapid identification and qualification of plastic materials, extended to flame retardant certification and qualification. The quality qualification criteria controls the price of the plastic involved, especially end of life polymers where they are to be re-used. Universal probes for assessing plastic materials were described, as thermoplastics are rich in a spectral sense which makes identification easier. His company, Gnosys UK, have been carrying out a detailed evaluation of brominated flame retardants, working with ICL Industrial Plastics. Wide wavelength spectroscopic (WWS) methods work well at rapid polymer identification, colour index measurement and qualification. It is able to identify and quantify the brominated flame retardants down to 1.0 per cent. The Raman Spectra of Deca-BDE in ABS is 0.17 per cent accurate. WWS is also useful for the engineering family of plastics. What is needed is the molecular structure and the chemistry that is in a plastic and WWV is less sensitive the highly brominated flame retardants; it is Raman measurement that show clear discrimination and sensitivity to all BFRs including DecaBDE as well as to antimony trioxide. Raman-based multi variate statistical analysis can predict FR concentration to an accuracy of 0.1 per cent b.w or better. His company plans to develop a new portable Raman instrumentation for the rapid identification and measurement of BFRs and other related materials.
Dr Chris Hunt of the National Physical Laboratory spoke on the use of thermoplastic substrates materials and their significance with respect to the WEEE directive. WEEE legislation will impact design, as existing designs are not easily recycled, and new substrate systems will inevitably replace traditional FR4. At the moment there are few commercially available thermoplastic laminates available; those that do exist are reinforced with woven glass and therefore less attractive from a recycling point of view. Major laminate manufacturers are not working on alternative materials, so it may be that moulded substrates could be used. Dr Hunt discussed MIDs, which integrate electrical and mechanical functions. Subtractive PCBs were illustrated, based on what looks like a normal laminate but it was unfilled, i.e. homogenous. When considering MIDs, one has to think about CTE, about dielectric properties, the fabrication process, durability, processing advantages, and failure modes how to test for these? NPL are working on subtractive technology for recyclable electronics, and work includes putting test boards though dry heat damp heat, and thermal cycling. These test boards use polyetherimide as the substrate, formatted to take R0603, R1206 and SOIC. They have a 1oz copper ENIG surface finish. Testing has looked at reliability conditioning adhesion failure at the component/adhesive interface, and they found that even after 2,000h there were no significant failures in the vias, but the component/adhesive interface was less sure. So they have moved on to an additive approach, using conductive polymer inks. The process steps were described, as were the test methods. Further failures at the component/adhesive interface were noted. The direct write process was then described where the copper is applied to an inkjet-imaged catalyst on a reel-to-reel process, with immersion silver as a surface finish. Similar build to the others, but again whilst some failures were noted on the component/ adhesive interface, there was a significant improvement in damp heat resistance, and the system performs well under harsh testing. There is more to come here, one suspects.
David Harrison from Brunel University was convinced that sustainability and printed electronics can be spoken about together. Printed electronics are starting to meet many of the “needs” that exist to-day (Maslow's List) and his team have been working on the environmental impact and evaluation of additive circuitry, which is likely to be more benign for PCB production than traditional wet processing. The use of silver as a conductive ink seems to be standard but do we have enough? Is this a resource that we will have forever? No. So, how about aluminium? No, this is tricky. David took a look at resources, then on to the uses and applications of printed electronics which included printed solar cells; printed lighting; printed batteries; it is an innovative technology with some real applications.
Dr David Hutt , Loughborough University is working on integrated optical-electrical interconnect substrate manufacturing, known as the OPCB project. There are ten partners including Heriot-Watt University, Xyratex, Stevenage Circuits, BAE Systems, Cadence, Dow Corning, Renishaw, NPL, Exxelis, Xaar, RSoft, Loughborough University and UCL. Here, the aim is optical wave-guide construction within a printed circuit board. When moving large amounts of data within a system, or to another system, using high-speed copper connections, there can be cross-talk, interference, signal loss, plus some EMC issues. However, by using an optical wave guide, taking light, one wave guide can handle many signals at the same time, and the environmental benefit is you can compact more into less space, making a PCB more simplified to design and build. Less power is used in transmission, and low- power optical drives, integrating optical wave guides into a PCB along with some electrical connections, guarantee error free transmission, capable of handling 10Gb/s, which is a high bit- rate. Polymer waveguides are what they are looking at now, and the “wish list” includes low-optical loss, good adhesion to substrate; the ability to withstand manufacturing processes; have long- term reliability, and should be easily processed by a PCB manufacturer. A range of manufacturing techniques, including direct laser writing set up was described, showing cured wave guide structures, with mirrors used at corners or junctions. They can use laser ablation to form the channels into the core and cladding on the FR4, and then deposit a cladding layer. UV laser drilling is done at Stevenage Circuits, whilst at Loughborough they have an Excimer laser ablation process, which is good for making unusual shapes, and mirrors, perhaps. Another process is inkjet deposition, for the localised deposition of core or cladding material, but ink formulation, viscosity, surface tension, waveform development, all have to be considered with a variety of drying effects.
The final speaker of the day was Dr Andy Cobley of the University of Coventry. He spoke about the sonochemical modification of materials for electronics manufacture, or, as he preferred to call it “Lean, Green and Clean Manufacturing”.
L to R: David Hutt, Andy Cobley, Chris Hunt
The traditional “wet” surface modification, e.g. desmearing, of PCBs for adhesion of electroplating, is a system that has relatively long dwell times, usually are three-stage processes, high temperatures are employed, so there are high-energy costs and some pretty nasty chemistry. Hydrochloric acid is the worst culprit, with associated VOCs, carcinogens, corrosive chemistry all nasties, plus high-water usage. Can sonochemistry help? In a word yes.
It uses the effect of sound on the chemistry of a solution, creating acoustic cavitation.
Here, you have 200m/s velocity of water hitting a surface, generating a scrubbing action, and the movement of reactants to, and debris away from, the surface. They have run tests on a number of materials, operating at 40°C. They also looked at surface modification just using distilled water, and they determined the efficacy of the process. They have surface modified laminates such as Isola 370HR, Noryl HM4025 and Ceramic, using DI water.
Their partner company Prosonics have produced the “Prosonitron”, showing that scale up is feasible. Tests have shown that you can modify a surface with tap water, and the weight loss is significantly higher than with a HF etch, and adding a small amount of surfactant is beneficial to the process. Lean? Yes, it is a one-stage process. Green? Yes, it operates at lower temperatures, uses non-hazardous chemistry, at lower energy costs. Clean yes it is, emphatically.
Martin Goosey wrapped up the conference with a reminder that the IeMRC Annual Conference will take place on 4 July at The Henry Ford College, and over 200 people are expected to attend this significant and free event.
J.H. LingAssociate Editor