How does one determine when (if) a sodium permanganate bath is spent?? Problem: Our previously calibrated [Mil-class] etchback cycles for various epoxies are now requiring 2-3 cycles; sections show too much variability from .0005"-.0013"; lots of "gouging" into glass-rich regions with lowest etchback at the copper interface. Conditions are as follows: - All chemistries (solvent swell, permanganate, glass etch) are within vendor specs. - NaOH normality: 1.2-1.3 - NaMnO4 concentration: 60-70 g/l - MnO3 conc. 9 -12 g/l - S.G.: 1.13 - 180 gal tank with 500A continuous electrolytic regeneration - swell temp: 175 degF, permanganate temp: 185 degF Vendor's tech service won't touch this one - if you want to do chemical etchback "you're on your own"... Any ideas out there before I dump this bath? Thanks, Joe Felts PC World, Toronto *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************