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74 The PCB Magazine • May 2016 by Dr. Andrew Ballantyne and Prof. Karl Ryder uNIVERSITy oF lEICESTER Now in its second year, MACFEST is a col- laborative research project involving partners A-Gas Electronic Materials, C-Tech Innovation, MTG Research, the Institute of Circuit Technol- ogy, the University of Leicester and Merlin Cir- cuit Technology. Partly funded by Innovate UK (formerly the Technology Strategy Board), the aim of the project is the development of new "universal" PCB surface finishes which are suit- able for both solder reflow and gold wire bond- ing. This will help PCB manufacturers meet the performance demands for high value electronic systems, ensuring long term reliability, even in harsh environmental conditions. In addition, the use of deep eutectic solvents (DESs), a pat- ented technology of the University of Leicester, offers the ability to significantly reduce the en- vironmental impact of a number of PCB plating technologies, reducing the requirements for use of cyanide and toxic/corrosive acids in plating baths. DESs are a novel class of solvents similar to ionic liquids (ILs). Whereas ILs are composed exclusively of ions, DESs are liquids composed of a salt and complexing agent, commonly a tetraalkylammonium salt, such as choline chlo- ride, and a hydrogen bond donor (HBD), such as 1,2-ethanediol or urea [1] When mixed together the HBD binds to the anion, resulting in a large depression of the melting point. At Leicester we have used DESs in the development of immer- sion silver [2, 3] , electroless nickel-immersion gold (ENIG) [4] and hot air solder levelled electroless nickel (HASLEN) processes, each of which offer its own benefits over existing processes [5] from the reduced safety and environmental concerns mentioned above as well as, in some cases, the removal of existing failure mechanisms such as black pad. The MACFEST project is building on this previous work in the development of a new, state-of-the-art PCB surface finish for use in both reflow and wire bonding applications. Taking inspiration from the electroless nickel/ electroless palladium/immersion gold (ENEPIG) surface finish, we have developed a novel nick- Manufacturing Advanced Coatings for Future Electronic Systems artiCle

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