Paul
Thanks
Brian writes one helluva lot more than he engineers, now. The reason for the apparent
inversion is that the contamination AFTER cleaning is more important than before!!!
Please remember the Bible was a result of divine inspiration. I think my work was more
from the devil. :-) However, please admit it is the best bedside reading book you have
ever come across: sends you to sleep within one minute of opening it.
BTW, sent Pete similar details privately before I read your post.
Brian
Paul Klasek wrote:
> Pete , i'd hate to see somebody like Brian guilty on grounds of Netics,
> just finished the bible sized thing (reads in similar way) :
>
> Cleaning and contamination of electronics components and assemblies
> B.N.Ellis
> ISBN 0 901150 20 7
> Electrochemical Publications, code EP06
> http://www.elchempub.com
> [log in to unmask]
>
> pk
>
> PS
> title sequence would sound better starting with Contamination and cleaning
> ....;
> just shows Brian is fair dinkum engineer and not just another eloquent tech.
> writer .
>
> -----Original Message-----
> From: Pete Nemcik [mailto:[log in to unmask]]
> Sent: Tuesday, 7 March 2000 6:53
> To: [log in to unmask]
> Subject: Re: [TN] Surface prep before soldermask
>
> 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 out of date!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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