Ryan,

Some quirks?

    a.. Pay special attention to the heating and circulation of the tin bath. While this is true of most heated plating solutions, it appears to be more critical with the immersion tin. What poor heating/circulation will cause of course, is very poor appearance and solderability
    b.. Use an enhanced hardener with your solder mask. The normal hardener doesn't seem to cut it. It results in solder mask peeling and flaking around pads and clearance areas.
    c.. Perform a final cure after immersion tin. The immersion tin attacks the solder mask similar to immersion gold, this added cure prevents any peeling or flaking of the solder mask after immersion tin.
We currently use Dexter's FST, of course we had to modify their recommended process a great deal in order to get it to work properly for us. Since we were able to resolve our biggest pain in the bu**, solder mask adhesion, we have had great success.

We'd be glad to do some qualification samples for you, if you're interested, just let me know.

Franklin D Asbell
Network Circuits, Inc.
Irving, Texas
972-313-1400