Hi Brian
Can you share with me the title of your book? I am very interested.
Also, would this abrasive implanted contamination affect wire bonding? I
would imagine that the effect of these particles imbedded into the gold
would interfere with proper bonding of the wire (especially if the
substrate is Teflon filled with ceramic filler).
Thanks in advance
Pete
> -----Original Message-----
> From: Brian Ellis [SMTP:[log in to unmask]]
> Sent: Tuesday, February 29, 2000 5:54 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] 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 out of date!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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