Thank you for answering my previous question regarding selective solder
stripping. I wonder if I can take this a little further. I kind understand
chemical reaction with Nitric based system, and just curious about what is
really going on with H2O2/NaF chemistry (Oxidize/disolve solder into metal
ion, what is funtion of NaF?). Could you also give the recommendation for
surface preparation of Soldermask (selective solder boards with Cu, Solder,
even gold on the surface )?
-----Original Message-----
From: <Rudy Sedlak> <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Monday, February 15, 1999 10:06 AM
Subject: Re: [TN] Tin Stripping; Immersion Tin
>Oh, yeah, about stripping immersion Tin.
>
>You can strip immersion Tin the same way you strip plated Tin, and there
are
>two basic systems in use, a Nitric/Ferric based system, and a
>Peroxide/Bifluoride based system.
>
>The Peroxide Bifluoride based system is "cleaner", in that all the Tin
>actually goes into solution, however it is heavily chelated.
>
>The Nitric/Ferric system is slower, and the Tin goes into true solution
only
>when it is fresh, it then is dispersed as the oxide in the solution. This
>system is sometimes chelated, depending on your vendor.
>
>The Peroxide Biflouride system inherently does not attack the Copper to a
>great extent. The Nitric/Ferric system attacks Copper a lot, but usually
>contains anti-tarnish type ingredients to minimize that.
>
>If either system were left on the board permenantly, the
Peroxide/Biflouride
>system probably has less tendency to continue attack.
>
>Rudy Sedlak
>RD Chemical Company
>
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