Institute of Circuit Technology Annual Symposium

Estimated reading time: 11 minutes

Dr. Andrew Ballantyne from University of Leicester presented a review of the applications of deep eutectic solvents in PCB surface finishing and electronics assembly, and an update of the MACFEST project. He explained that deep eutectic solvents are types of ionic liquids in which organic cations are combined with halide anions and complexing agents to make an anionic complex. The specific example used in his research work was composed of ethylene glycol and choline chloride in 2:1 molar ratio and known as Ethaline 200, which was relatively inexpensive and environmentally benign. Ethaline 200 had low vapour pressure and good thermal stability, and exhibited unusual solvation properties with metal salts. Its benefits had been demonstrated in metal nishing applications such as electropolishing, electroplating and immersion plating, as well as metal recycling and energy storage. It had also shown remarkable properties as a flux, enabling soldering direct to electroless nickel and other difficult-to-solder metal surfaces.

The MACFEST Project (www.macfest-project.co.uk), which was co-funded by Innovate UK, aimed at producing a “Universal Surface Finish” for electronics, capable of reflow soldering and wire bonding with gold, copper and aluminium. Required attributes were high reliability, good planarity and long shelf life. Deep eutectic solvent technology was being employed to improve functionality and to reduce safety and environment concerns. The first 15 months of the 24-month project had been completed.

Using a proprietary electroless nickel with an amorphous nodular structure and 8% phosphorus to form the base layer, immersion palladium had been deposited from Ethaline at 80°C to a thickness of 70–100 nanometres in 30 minutes. The palladium deposit had been over-plated with gold from a second Ethaline-based formulation at 50°C for 9–15 minutes. The source of gold could be either gold chloride or sodium gold thiosulphate, and bright uniform deposits had consistently been achieved from a chemistry free from acid and cyanide. This “ENIPIG”—electroless nickel, immersion palladium, immersion gold—finish had shown excellent solderability, with no evidence of “black pad” or “mud-cracking” effects on the nickel surface associated with acid attack when traditional aqueous chemistries were used.

The final speaker was ICT Chairman Dr. Andrew Cobley, from Coventry University, who reviewed current research projects in which the ICT was a collaborator. REPRIME and MACFEST had been discussed in earlier presentations, but two new projects were in their early stages.  

The first was Selective Electroless Catalysis in a Magnetic Field (surprisingly, no acronym!), led by Coventry University. The concept was to use a magnetic field to selectively catalyse a material prior to electroless plating, using a template of magnetised iron rods placed against the reverse face of a thin substrate to attract catalyst selectively to the opposite surface. Proof of concept was being funded by Higher Education Innovation Funding (HEIF). A patent had been filed, and a PhD student would be working full-time on the project from September 2016. Other sources of funding, for example Horizon 2020, were being explored.

Acronyms again! The second project, SYMETA—Synthesizing 3D Metamaterials for RF, microwave and THz applications—was being led by Loughborough University and funded by EPSRC. This project was looking at creating new materials for additive processes, to form substrates and conductive meta-atoms, and would take a radical new approach to high frequency circuit manufacture. Developing a more rational and sustainable use of materials would reduce waste, timescales and cost of manufacturing processes.

The main contribution of the ICT to these projects was as a dissemination partner, and the benefits of involvement were that the ICT could influence the direction of research and quickly inform its members of the latest R&D developments, as well as creating opportunities for ICT members to engage in and obtain funding for research.

Dr. Cobley wrapped up the proceedings, thanking speakers for sharing their knowledge and experience, delegates for their attention, Ventec Europe for their generous support, and Bill Wilkie for once again organising a splendid event. Delegates made the most of the networking opportunity, and an impressive number of motorcycle enthusiasts emerged from the group to spend a while admiring the exhibits in the museum before departing.

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

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