I don't think many people or companies relish the thought of all those
toluene vapors going into the air, or their noses. Sounds like good results
though.

Timothy Reeves
ECD Circuit Board Division
13626 South Freeman Road
Mulino, OR 97042
[log in to unmask]
(503) 829-9108 (800) 228-8198  FAX (503) 829-5482


> ----------
> From:         Brian Ellis
> Sent:         Tuesday, February 29, 2000 2:54
> Subject:      Re: Surface prep before soldermask
> 
> Adeodato
> 
> It is about a hundred years since I did this, so what I say is certainly
> out of date! Our preferred method was to clean the board with a good hot
> (55°C) agitated DI water wash with 10% IPA, followed by a single DI
> rinse at 85°C, followed by a 30°C dilute sodium persulfate (not
> ammonium) etch to remove c. 2 um of copper followed by 3 DI rinses.
> Oxide-free drying was done by successive pure IPA (to remove the gross
> water) and toluene displacement, followed by placing in a walk-in oven
> with filtered air at 30°C for 5 hours minimum.. This produced a residual
> ionic contamination of < 0,3 ug/cm2 eq. NaCl, where the then MIL-P-55110
> suggested a max of about 1,3-1,5 ug/cm2 eq. NaCl depending on your
> interpretation. Solderability was excellent. We did this with both dry
> film and liquid screened masks. Do NOT use abrasives or brushing of any
> sort: you smear epoxy onto the copper and implant abrasives into the
> copper, causing a certain dewetting (see my book for full details).
> 
> Brian
> 
> 
> Adeodato Vigano wrote:
> 
> >  TechNet,I would like to hear the Forum's opinions about pre-cleaning
> > before soldermask (both Dry Film and LPI), in particular about the
> > methods based on chemical rather than mechanical action.We are
> > evaluating an "oxide replacement" chemistry versus different microetch
> > chem-clean systems.  The microetch would be our preference because
> > running thick panels through our oxide replacement equipment may
> > result in damage to the line, of course we are getting good results
> > from the oxide replacement chemistry but we are not getting consistent
> > results from the chem-cleaning process.Also I would like to know what
> > other PCB manufacturers are doing when they are not using mechanical
> > scrubbing methods.Any suggestions regarding chemistry and/or process
> > parameters would be greatly appreciated.Thanks in advanceadeodato
> > viganocompunetics, inc.  -  pcb divisionphone: 412.858.6115fax:
> > 412.858.8060email: [log in to unmask]
> 

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