Hi Guy-

Matte ImSn stinks as a solderable surface. I'd basically rather leave the
boards bare copper and do a quick wash with citric acid followed by a
thorough cleaning rather than work with ImSn. It's just "eyewash" since its
main attraction is preventing bare copper from turning brown. (ImAg is a
wonderful surface finish, but it can turn brown/yellow/purple if it gets
near any sulfur (still solders good, though!.)

Plated Sn would probably be OK as a surface finish, and as I'm certain
you're aware, is one of the primary processes used as an etch resist for
processing outer layers when using alkaline ammoniacal etchant. BUT, it will
certainly grow whiskers unless you can get the Pb percent up to a reasonable
level. The shinier the surface finish, the faster the whiskers sprout.

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Thursday, March 05, 2015 8:51 PM
To: [log in to unmask]
Subject: [TN] bright electroplated tin, versus immersion matte tin

Can anyone give me a nutshell difference between immersion tin for a solder
finish and electroplated tin? 
Advantages, disadvantages as a surface finish more than the chemical and
plating process differences. 
Thanks,
Guy





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