The Institute of Circuit Technology Tewkesbury Seminar, 1st March 2016

Estimated reading time: 8 minutes

The two-year STOWURC project, which had developed new effluent treatment processes using materials derived from crab shells had just reached a satisfactory conclusion, and demonstrated how a natural waste product from one industry could be utilised to treat waste from another industry by removing and recovering trace metals from PCB and metal finishing process effluents. Background to the project was that the seafood industry produced large quantities of shellfish waste, which was becoming increasingly expensive to dispose of. The potential value of crab shells was that they contained a compound called chitin, which was capable of absorbing metals, and one gram of shell could potentially absorb up to 250 milligrams of copper. A typical PCB factory effluent could still contain several parts per million of copper after normal effluent treatment, which required to be reduced to lower levels to satisfy discharge regulations, generally by the use of ion-exchange resins. Crab shells offered a readily-available natural alternative, and the project partners had comprehensively investigated and optimised the physical, chemical and economic parameters required to achieve a practicable and cost-effective effluent treatment process, which was currently running successfully at 100 kg pilot-plant scale in a large PCB factory. An additional application of crab shell materials was as the active component in spill kits and static drag-out bags, to treat spills and localised effluent issues, and this had also been successfully demonstrated. Full details of the project and further information may be found on the website^[1].

The two-year MACFEST project had set out to utilise the properties of ionic liquids to produce solderable finishes with improved joint reliability, and had just passed its half-way point. New ionic-liquid-based nickel-palladium-gold systems were being investigated and a process for the deposition of good quality palladium and gold coatings onto ‘aqueous’ electroless nickel has been developed. PCB test coupons were currently being prepared for evaluation, and would also be tested as part of a major SMART Group programme taking place over the coming few months. Potential benefits of coatings resulting from the MACFEST project would be a reduction of environmental impacts through the elimination of cyanide-based aqueous chemistries and a reduction in the amount of palladium consumed. The principal technical benefit would be the elimination of known reliability issues with nickel-palladium-gold finishes deposited from aqueous chemistry, particularly black pad effects, brittle joints and void formation. And the new coatings would meet the requirements of the industry and current IPC standards. Further information may be found on the MACFEST website^[2].

Project Manager and Research Fellow at Coventry University, Narinder Bains gave the final presentation, on the optimisation of process conditions for the maskless electrochemical patterning of materials, with particular reference the university’s collaboration in the MESMOPROC project, co-funded by the EU Eco-Innovation initiative.

The concept of electrochemical ‘maskless’ selective metallisation of materials had been established and demonstrated in the Enface process, where instead of a plating resist image being applied photolithographically to each workpiece then stripped off after a single operation, the image was applied to the anode and effectively re-used many times. With the selectively masked anode placed close to the workpiece, and using a low-acid, low-metal electrolyte and good agitation, the pattern on the anode could be replicated in metal deposited on the workpiece, enabling selective metallisation of microscale devices, components and printed circuit boards. A limitation of the process had been the difficulty in maintaining the intensity and uniformity of solution agitation when scaling up the electrochemical reactor.

In the MESMOPROC project, low frequency ultrasound was introduced to the system to enable high efficiency, focused agitation. The team at Coventry, with many years’ experience of ultrasonics applications, had modified the reactor to incorporate ultrasonic transducers and had studied the general effects of ultrasound on the electrochemical deposition process. The team had then studied the effects of ultrasound on deposit quality in low metal, low acid copper electrolytes with commercial electroplating additives. It had been demonstrated that low or no acid electrolyte formulations, together with very narrow anode-cathode spacing gave the best image reproduction and good deposit quality, although low frequency ultrasound tended to increase additive consumption. The overall conclusion was that ultrasound increased the limiting current density and opened up the process window.

The MESMOPROC process had been demonstrated and validated at pilot scale in a PCB shop and a specialist plating shop, and offered enhanced efficiency through a shorter and simpler process using fewer materials and less energy, with reduced waste generation and CO2 emissions. Further information may be found on the website^[3].

In his closing comments, Bill Wilkie acknowledged the generosity of Exception PCB Solutions in supporting the event, and reported that the membership of the Institute continued to increase, presently standing at over 350, with members drawn from over 100 companies. The seminar had once again brought together an enthusiastic group of industry professionals to further their technical knowledge and their awareness of business trends, and, equally importantly, to network with their peers.

I am grateful to Alun Morgan for allowing me to use his photographs.

References

1. www.stowurc.co.uk

2. www.macfest-project.co.uk

3. www.mesmoproc.eu 

Based in the U.K., I-Connect007 Technical Editor Pete Starkey has more than 30 years’ experience in the PCB industry and a background in process development, technical service and technical sales. Starkey is a fellow of the Institute of Technology, a member of the SMART Group Technical Committee, and an active supporter of the European Institute of Printed Circuits.

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