In the Nov '95 issue of "SMT", pp.26-29, Ray P. Prasad wrote: "The critical surface finish requirement for boards is to ensure sufficient solder thickness. The general recommendation in the industry about maintaining at least 0.0003" (300 microinches) is essential for long-term solderability..." He goes on to talk about the dewetting effects of <0.0003" thick coatings and the benefits of 5um of tin and 7.5um of 60 Sn/40 Pb. He also deduces from a round-robin test conducted by the IPC that coating thickness alone is not all thats important, but also the quality of the coating. Ray P. Prasad is a "SMT" editorial advisory board member, engineer, author of "Surface Mount Technology: Principles and Practice", and founder of the Ray Prasad Consultancy Group. Contact him c/o "SMT" or (503)297-5898; fax:(503)297-0330. Understand, I am not suggesting that you call him. This is just the blurb from "SMT". (So much for the disclaimer -- I'm probably taking a big enough risk just quoting him...) I DO suggest getting "SMT" magazine. DonW...