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Now in its second year, MACFEST is a collaborative research project involving partners A-Gas Electronic Materials, C-Tech Innovation, MTG Research, the Institute of Circuit Technology, the University of Leicester and Merlin Circuit 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 suitable for both solder reflow and gold wire bonding. 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 patented technology of the University of Leicester, offers the ability to significantly reduce the environmental 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 chloride, and a hydrogen bond donor (HBD), such as 1,2-ethanediol or urea 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 immersion silver[2, 3], electroless nickel-immersion gold (ENIG) and hot air solder levelled electroless nickel (HASLEN) processes, each of which offer its own benefits over existing processes 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.
Editor's Note: This article originally appeared in the May 2016 issue of The PCB Magazine.