Phil; We have been using a MacDermid Matte Tin Bath as both an etch resist before SMOBC and as a final solderable finish with a Nickel diffusion barrier. After about a year in opeation, the Tin is not as white and does not always pass a solder float solderability test. The bath itself has turned to a muddy brown appearance which MacDermid says is normal. Do you have any comments on Tin baths for a final finish? George Anderson [log in to unmask] >Paul. > >If I understand your process, you are only going to use tin as an etch resist >and strip it and go SMOBC > >A supplier down in Conn., MacDermid, sells a tin electroplate formulation >used mainly for your type of process and is one of the cheapest based on a >tin sulphate bath. You will find the tin stripping easier and faster than >the tin/lead. Obviously, after etching don't fuse it and don't use >solderbright. The plating is pretty normal and you can convert your tin/lead >process and pre-tin/lead pickle using the same process line and change the >acid predip accordingly. >The tin thickness minimum is about 0.0003 inch, but to be safe a 0.0005 is >often used. > >Your process removes all of the tin plating and you are not concerned with >whiskers, slivers and gray tin. If you are going to use the tin as a final >finish, put another note on technet and I can furnish additional information. > >Phil Hinton >[log in to unmask]