Looking for suggestions on how to tweak soldermask process and/or immersion tin
process to decrease ionic contamination levels after immersion tin.

Soldermasks
     Hysol/Dexter SR-1000 - thermal cure
     Enthone DSR-3241(I) - thermal cure w/ no UV bump

Tin
     MSA based chemistry, 155F/15min
     Hot city water rinse 100F/2min
     2 x Cold DI rinse 2 min
     conveyorized double cascade DI rinse & dry

Ionic contamination levels measured w/ omegameter and Alpha ionograph
     after soldermask & before immersion tin = < 5 mg NaCl eq/in2
     after immersion tin = > 30 mg NaCl eq/in2

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