Pete
I must have skipped over the original message. I thought it was looking for
a book. Repeat what you want to bond to and I bounce back some ideas.
Carey
-----Original Message-----
From: Pete Nemcik <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, March 07, 2000 5:49 AM
Subject: Re: [TN] Surface prep before soldermask
Many thanks, Brian, and apologies to everybody. I meant to send the
original to Brian only. I always realize my screw-up right AFTER I hit
the send button!!!
Pete
> -----Original Message-----
> From: Brian Ellis [SMTP:[log in to unmask]]
> Sent: Tuesday, March 07, 2000 4:38 AM
> To: [log in to unmask]
> Subject: Re: [TN] Surface prep before soldermask
>
> Pete
>
> Lest I be accused of spamming, I'll send you the title by a private
> e-mail. Although I
> have no experience of the problem, I could well imagine that it may be
> difficult to
> weld a gold or aluminium wire onto an implanted carborundum particle
> from a brushing
> process :-) However, as the particles are much smaller than the weld
> diameter, it may
> be that you would not notice the reduction of pull strength. However,
> as the
> carborundum is less malleable than the gold plating, it may be that
> there would be a
> mechanical effect whereby the pressure on the metal-to-metal parts
> would be reduced
> while that of the metal-to-inclusion would increase, but this is off
> the top of my
> head. I don't think that the substrate material would have a
> significant effect.
>
> Brian
>
> Pete Nemcik wrote:
>
> > 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 out of date!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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