Lou,
     
     Every chemical vendor probably has an oxide treatment that they would 
     recommend for solder mask adhesion.  Usually, they recommend 
     red/bronze oxide versions.  But, like your 33% less filling oxide, 
     they do require time, process control, etc.
     
     Equipment manufacturers would recommend scrubbing as being sufficient 
     for solder mask adhesion, with pumice being the preferred option.  A 
     "good" pumice scrubber carries a significant price tag.  Also, some 
     pumice scrubbers tend to self destruct.(Keep in mind price versus 
     cost, you get what you pay for, etc.)
     
     As a former chemical salesman, I recommend going with a proprietary  
     oxide treatment.  (Enthone-OMI, MacDermid, Shipley, etc.)  However, I 
     would also get inputs from your LPI vendor on his recommendations. 
     (LPIs should not present a particular adhesion problem IF your boards 
     are clean prior to the solder mask process.)
        
     As a former quality manager, I recommend pumice scrubbing of the 
     copper surfaces prior to solder mask application. It seems to be more 
     consistent and less of a headache for the lab guys.  (I've never been 
     a maintenance guy though, so take this with a grain of salt.)   
     
     As a current engineer working with buyers of circuit boards, I don't 
     care as long as the solder mask stays on the board.  Solder mask 
     adhesion has not been an issue with the board shops we use.  
     
     In summary: Weigh the options, pick the vendor (equipment or chemical) 
     you trust to support you the best, and go for it.
     
     Regards,
     Jamie Baumgart
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