Electronics Goes Green 2004

Citation

Goosey, M. (2005), "Electronics Goes Green 2004", Circuit World, Vol. 31 No. 2. https://doi.org/10.1108/cw.2005.21731bac.003

Electronics Goes Green 2004

Electronics Goes Green 2004+

Keywords: Electronics industry, Trade fairs, Printed circuits

From 6th to 8th September, the Estrel Hotel and Conference Centre in Berlin played host to approximately 500 people who attended the Electronics Goes Green 2004+ Joint International Conference and Exhibition. (Plate 3). The theme for the conference was “Driving Forces for Future Electronics” and the programme was of sufficient size and breadth that there were seven parallel sessions running for most of the conference. These were dedicated to a wide range of topics covering the full spectrum of environmental issues pertinent to the electronics industry. Key areas covered in detail included the WEEE and RoHS Directives, the draft REACH regulations, lead-free electronics, ecodesign, metals and plastic recycling, as well as new materials. In this latter category there was coverage of new flame retardants and new materials for printed circuit boards (PCBs). In a short review of this type it is not possible to give more than a brief overview of just some of the presentations and I have, therefore, focussed on the papers that I believe will be of most interest to readers of Circuit World. However, for those wishing to obtain more details of all the papers presented, the 1,086 page hardback book of proceedings has been published by the Fraunhofer Institute (Reichel et al., 2004).

Plate 3 The opening session

One of the more interesting papers on PCB materials was presented by Martin Moller of the Oko Institute in Freiburg, Germany, and this covered the development of new thermoplastic PCBs for future electronics. The presentation detailed the work carried out in a multi-partner project to develop more environmentally acceptable alternatives to the traditional thermosetting materials such as FR4. Conventional materials are mostly not recyclable and contain hazardous materials such as derivatives of tetrabromobisphenol A. Although these materials are still acceptable, there are growing fears that increasingly stringent future legislation may require the development of new materials and processes. This seven partner project, which included the PCB fabricator, Wurth, had set out to develop a PCB fabrication process based on the use of high temperature thermoplastic materials which could be fabricated using a continuous manufacturing process rather than the batch process employed for current materials. The substrate material developed had a sandwich structure with a foamed centre and was said to be compatible with conventional PCB processing chemistries. A key novel feature of the substrate had been the development of a processes for foaming the polyetherimide (PEI) used in the centre section. This had a closed cell structure with the cells displaying a diameter of approximately 50 m. Various metallization routes had been developed including both a semi-additive processes and a fully additive method based on the use of a catalytic primer. Through-hole plating had also been achieved. The new substrate had been evaluated in assembly trials with both conventional and lead-free solders and the higher temperatures required for the lead-free process did not cause any problems. Because the centre part of the substrate was foamed, weight savings of 30 per cent had been achieved and the dielectric constant was only 2.1. Also, as the PEI was inherently flame retardant, no additional flame retardant additives were required. A number of circuit types had been manufactured including ones for automotive and TV applications. Work had also been carried out on liquid crystal polymer (LCP) substrates and multilayer structures had been fabricated. The use of LCP films opened up the possibility of using a reel-to-reel process. An example of a double sided circuit was also described which could be folded on itself 32 times to give a more compact multilayer structure. The processes had high temperature operational capabilities and metal adhesion levels of 2N/mm had been achieved. Also, the boards could show an overall ecological performance increase of up to 50 per cent compared to conventional laminate- based processes.

The paper by Mr H. Nagele of the German company Tecnaro, covered work that had been carried out to date to develop renewable resources for PCB laminates. The concept here was to make PCB substrates using natural materials. Lignin was used to replace the conventional thermosetting resins and natural fibres, such as flax, hemp and sisal, were alternatives to conventional glass fibres. Additional natural additives were also used as processing aids during the substrate moulding process. In early samples that had been produced some of the laminate property requirements had been achieved, but it had not been possible to meet the required metal peel strengths, chemical resistance and flame retardancy levels, or the moisture and thermal stability requirements. However, newer versions had been produced that had sufficient chemical stability to survive the metal plating process. An ecologically acceptable halogen-free flame retardant system had also been introduced which used a less than 10 per cent loading to achieve the required flame retardancy properties. Work was still needed to increase the peel strength and to decrease the water absorption of the substrates but as the project was only at the halfway stage, further work was planned to introduce woven fabric materials and a thermosetting resin component. It will be interesting to learn how much more progress has been made by the end of the project.

Another session that was of specific relevance to the PCB industry was the one covering new flame retardant materials. There were four papers detailing a wide range of topics specific to the electronics industry. Cefn Blundell of, what was until recently, Akzo Nobel, gave a paper on a new highly efficient flame retardant curing agent for epoxy resins. The material described was phosphorus-based and sought to overcome some of what were increasingly perceived to be the disadvantages of bromine-based flame retardants such as tetrabromobisphenol A. Because of these concerns with brominated materials, phosphorus containing flame retardants were of increasing interest to formulators and they were said to be generally compatible with epoxy resin systems. These materials tended to work by a different type of mechanism to their brominated analogues; they retard volatilisation of combustible polymer fragments, leading to charring. Phosphorus containing species are also potent free radical scavengers. Traditional phosphorus-based flame retardants could cost more than their brominated counterparts, as well as exhibiting hydrolytic stability issues and acting as plasticizers agents for polymers. The materials described here were a new type of reactive flame retardant with a molecular weight range of 1,000-1,400 and a phosphorus content of around 17-18 per cent. Thermal decomposition did not start until around 320°C and thus, they were compatible with the higher soldering temperatures encountered in lead-free assembly.

The other three presentations in this section also covered a number of different aspects of flame retardant development. Sebastian Harold of Clariant covered a new generation of environmentally friendly flame retardants that were suitable for use with the polyamides and epoxides that find wide application in the electronics industry. The Exolit materials described were both non-toxic and non- bioaccumulative systems based on metal phosphonate chemistry with additional synergists. They did not contain any halogens, heavy metals or red phosphorus. Exolit OP930 was suitable for PCB laminate and semiconductor encapsulant applications; it was used a fine grained powder additive and behaved like a conventional filler. With a decomposition onset temperature of 330°C it was ideal for applications in FR4 type laminates and was compatible with lead-free processing.

Susan Landry of Albermarle Corporation presented a paper in which she covered sustainability concerns for flame retarded plastics used in electrical and electronic equipment applications. Susan stated that, in a study carried out in Minnesota, high impact polystyrene (HIPS) from over 8,000 televisions was collected to give around 24,000 kg of material, most of which was flame retarded with decabromodiphenylether. The possibilities for recycling brominated HIPS had been investigated by monitoring the physical properties of the material as it was put through five injection moulding cycles. The results indicated that recycling could be achieved with no significant degradation of key properties. Recycling of HIPS flame retarded with a phosphorus-based material was also investigated. In this case there were some issues and some important properties were shown to be degraded. For example, impact strength dropped significantly and melt flow increased. Various blends of virgin material and recyclate were also studied and it was found that the more recyclate used the greater was the effect on properties.

The final paper of the flame retardants session was given by Kirsten Lichtenvort of the Technical University of Berlin. Kerstin gave a review of a multi-partner project that had assessed the environmental and economic implications of a shift to halogen-free printed wiring boards. This work had been carried out as part of the “grEEEn” project and results had indicated that moving to halogen-free laminates was likely to have cost implications in a number of processing areas including desmear, pressing and drilling. A slight increase in environmental burden had also been found when manufacturing PCBs with halogen-free laminates. Overall cost increases of between zero and ten euros per panel could currently be expected, although the figure would diminish as halogen-free laminate production increased and prices dropped.

Yoshito Kita of Osaka University gave a fascinating presentation on the dissolution of gold from PCBs using a bioleaching process. This process used the bacterium Chromobacterium Violaceum to recover the gold. Under the appropriate conditions these bacteria can both generate and destroy cyanide. Initially, the cyanide generated is used to bring the gold from the PCB into solution and at a later stage the cyanide is converted to ethanoic acid. Details of a study to optimise the conditions used in this process were given and it was also found that oxygen levels in the solution had an important influence on the process. Under suitable conditions both copper and nickel could also be dissolved.

There were also a large number of presentations covering various aspects of the move to lead-free assembly. An interesting paper from Michael Lantzach discussed the beneficial impact of using small quantities of nickel in tin-copper alloys. Tin-copper alloys are increasingly popular because they can be almost half the cost of their tin-silver-copper alternatives, whilst still offering low drossing and outstanding solderability retention, even after 6 months of storage. Because nickel and copper are very similar elements with the same close packed hexagonal structures they can exchange atoms relatively easily. In the tin-copper alloy the nickel helps to reduce copper dissolution into the solder and it also helps to give the solder a smoother surface.

The conference concluded with a series of special keynote presentations that attempted to predict future trends in the electronics industry. For example, Jurgen Wolf of the Fraunhofer Institute/ IZM in Berlin, gave a very interesting presentation on the ITRS Roadmap for future semiconductor technologies. The ITRS roadmap covered 15 different technology areas including interconnect. Jurgen compared the parallel trends towards the integration of electronics via “System in a Package” (SIP) and “System on a Chip” approaches. Both routes would enable “board-sized” products to be reduced to a single package and the big drivers were to be found in cellular wireless and digital camera applications. Packages containing four or five stacked die were already in volume production and very soon packages with seven stacked die would be available. By 2010, SIP would have more than 2,000 I/Os and up to nine stacked die. Key challenges included the integration of both active and passive devices into the substrate and a project called IPAD was underway to develop this technology further. Another key challenge was to close the gap between semiconductor interconnection dimensions and the next level of substrate interconnections.

This report has only been able to give a brief overview of just some of the wide range of papers presented at EGG2004+. There were many other interesting reports on a wide range of other topics including, for example, the WEEE, RoHS, EuP and REACH legislation. Full details of these and other presentations can be found in the proceedings.

In summary this was an excellent conference which covered a diverse range of environmental topics of importance to the electronics industry. The organisers are to be congratulated for the quality of the presentations, as well as for the conference itself, which in all aspects was an extremely well panned and successful event.

Martin Goosey

ReferenceReichel, H., Griese, H. and Potter, H. (Eds) (2004), “Electronics Goes Green 2004+”, Proceedings of the Joint International Congress and Exhibition, 6-8 September 2004, ISBN 3-8167-6624-2, Fraunhofer IRB Verlag, Stuttgart.