Just a general inquiry on this cleaning issue: A while back when cleaning
alternatives was the subject of the day, the use of ultrasonics was one of
the viable candidates. Discussions always went like," ...ultrasonic
cleaning works great, but..." and then the stuff about possible part damage
scared everybody off. I always thought somebody would do a study
demonstrating liklihood of damage, or come up with a system that would be
safe for most parts, but the technology seems to just be sitting in the back
of the bus, not banned but not really used either. Are there actual
instances where responsible use of ultrasonics affected an assembly's
reliability?
Ralph Vaughan
> ----------
> From: Graham Naisbitt[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;Graham Naisbitt
> Sent: Wednesday, March 24, 1999 4:11 AM
> To: [log in to unmask]
> Subject: Re: [TN] RF PCMCIAs and Cleanliness
>
> Mike
>
> If this debate was 12 months old, I would have agreed with you 100%.
>
> However, if you are going to deal with BGA, MicroBGA, Flip-Chip and other
> COB packaging, then it becomes necessary to reduce the surface tension of
> the water to enable it to penetrate beneath such components. This means
> adding surfactants (wash chemistry) in the wash stage. Yes, I know that
> this
> renders a pure aqueous machine redundant, unless it is equipped with
> extended wet isolation and a separate wash stage.
>
> Removing OA residues particularly BGA is crucial when dealing with safety
> critical or high reliability devices. However, it is also crucial to
> ensure
> that the - dissolved or solubalised - contaminants are then adequately
> removed.
>
> As a suggestion to those who have concerns, make up (or I can help with) a
> coupon that includes the more difficult component types you are using or
> are
> proposing to use. Process them in parallel with your product and then run
> SIR testing using the latest methods - frequent monitoring and voltage
> gradient - if you have good results with pure OA or indeed no-clean, then
> no
> problem. You might also take a peek under some of them.
>
> From the evidence we have, I think you will need to adapt your process
> this
> way. Yeah! RMA could now be re-used - what goes around, comes around!
>
> Regards, Graham Naisbitt
>
> [log in to unmask]
>
> Concoat Ltd Phone: +44 1276 691100
> Alasan House Fax: +44 1276 691227
> Albany Park
> CAMBERLEY
> GU15 2PL UK
> -----Original Message-----
> From: McMonagle, Michael R. <[log in to unmask]>
> To: 'TechNet E-Mail Forum.' <[log in to unmask]>; 'Graham Naisbitt'
> <[log in to unmask]>
> Date: 23 March 1999 14:22
> Subject: RE: [TN] RF PCMCIAs and Cleanliness
>
>
> >Graham,
> > Thanks for the reference, it provides some interesting
> >information. However, it is based on cleaning RMA fluxes, not OAs. Most
> >non-military assembly processes are using OA chemistries with straight
> >aqueous processes, or have moved towards no-clean. A robust high
> >pressure inline aqueous cleaner should handle most all low-profile
> >components soldered with OA chemistries, without the use of wash
> >additives. However, each assembly must be evaluated on its own merits
> >and tested under production conditions to assure adequate cleanliness
> >for the specified end-use environment.
> >
> >Mike McMonagle
> >PCA Process Engineering Supervisor
> >K*Tec Electronics
> >1111 Gillingham Lane
> >Sugar Land, TX 77478
> >(281) 243-5639 Phone
> >(281) 243-5539 Fax
> >[log in to unmask]
> >
> >> -----Original Message-----
> >> From: Graham Naisbitt [SMTP:[log in to unmask]]
> >> Sent: Tuesday, March 23, 1999 6:34 AM
> >> To: [log in to unmask]
> >> Subject: Re: [TN] RF PCMCIAs and Cleanliness
> >>
> >> John
> >>
> >> It would appear that no-one answered your question. So if it is not
> >> too
> >> late...
> >>
> >> How clean is clean is a great big topic. There was an interesting
> >> article in
> >> the Feb 99 issue of Precision Cleaning magazine written by people at
> >> Lockheed Martin that covers this subject well. This is a USA journal
> >> and if
> >> you need details, ask me.
> >>
> >> They basically found that with low stand-off components, you MUST use
> >> wash
> >> chemistry to lower surface tension of the water to get it underneath
> >> AND
> >> remove the contaminant. However, it involves power - (wash pressure)
> >> as well
> >> as solvent power (wash chemistry).
> >>
> >> Regards, Graham Naisbitt
> >>
> >> [log in to unmask]
> >>
> >> Concoat Ltd Phone: +44 1276 691100
> >> Alasan House Fax: +44 1276 691227
> >> Albany Park
> >> CAMBERLEY
> >> GU15 2PL UK
> >> -----Original Message-----
> >> From: John Gulley <[log in to unmask]>
> >> To: [log in to unmask] <[log in to unmask]>
> >> Date: 12 March 1999 17:24
> >> Subject: [TN] RF PCMCIAs and Cleanliness
> >>
> >>
> >> >Address,
> >> >
> >> >We have an application where we are using OA Flux and Paste to
> >> process
> >> >RF PCMCIAs. The PCAs are thoroughly cleaned prior to test. I'm
> >> still
> >> >having test issues with RF PCMCIAs.
> >> >
> >> >If I remember correctly, I read an article that discussed cleanliness
> >> of
> >> >PCAs that are RF. If the PCA is not thoroughly cleaned, the organics
> >> >will wreak havoc on the RF tests. There are chemistries (saponifers)
> >> >available that will reliable remove the excess organics and provide
> >> >enough cleanliness to pass RF testing.
> >> >
> >> >CAN someone please provide some more light onto this issue or give me
> >> a
> >> >direction to pursue, e.g., contacts. Thanks.
> >> >
> >> >John
> >> >
> >> >
> >> >
> >> >
> >> >
> >>
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