Ralph,
I do not have a copy to hand but, I remember that IVF in Sweden did a
detailed report about this issue some 8 years ago. Maybe Per-Erik
Tegehall is looking in??
The conclusion was that using the right frequency made little or no
difference with immersion up to around 8 hours or something. Kinda prolonged
cleaning regime that would be! The other issue is that some of the newer
solvents require substantially more USC power to achieve cavitation.
I also recall from the British CFC Elimination Project run by Colin Lea of
our NPL, that there was no appreciable difference in cleaning results
between high pressure spraying and USC - spraying (which in those days
employed far lower pump power than today) just got the vote.
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: Vaughan, Ralph H <[log in to unmask]>
To: 'TechNet E-Mail Forum.' <[log in to unmask]>; 'Graham Naisbitt'
<[log in to unmask]>
Date: 24 March 1999 16:22
Subject: RE: [TN] RF PCMCIAs and Cleanliness
>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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