Trials were also conducted in Plessey in the late 80s using an ICI u/s tank
and Arklone. The engineer concerned found that the standard packages used
were all OK after a total of 24 hours exposure. No functional degradation at
all, but, boy!, were they clean!
Unfortunately, the study was never published and the engineer himself passed
away a few years ago so I was never able to obtain confirmation in writing.
I am surprised that one of the larger suppliers of u/s cleaning equipment
has not undertaken a definitive study and published the results. Or have
they and I just missed it?
Regards
Eric Dawson
> -----Original Message-----
> From: Mike Fenner [SMTP:[log in to unmask]]
> Sent: Monday, October 29, 2001 10:26 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning paste when misaligned.
>
> Back in the days when F113 was the best thing since sliced bread there
> were several studies on bond wire integrity in ultrasonic cleaning. In
> this country by ICI (then supplying F113 cleaners under brand name
> Arklone, equivalent to Dupont Freon) and Marconi Stanmore in UK. Possibly
> also the UK National Physical Laboratory, although it might be that
> Marconi and NPL collaborated.
>
> Basically they concluded that there was possibly a problem with the then
> frequency used [40kHz], but this would really only affect poor quality
> wire bonds that would fail anyway. Modern units run at 70kHz and/or sweep
> the frequencies so eliminating the problem. This was all ages ago and my
> memory may be a little poor on the details, but the essentials are
> correct.
>
> Are we now saying that component sizes are now so reduced that there is a
> problem again?
>
> Best regards
>
> Mike Fenner
> Applications Engineer, European Operations
> Indium Corporation
> T: + 44 1908 580 400
> M: + 44 7810 526 317
> F: + 44 1908 580 411
> E: [log in to unmask]
> W: www.indium.com
> Leadfree: http://Pb-Free.com <http://pb-free.com/>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey
> Sent: Friday, October 26, 2001 7:15 PM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning paste when misaligned.
>
>
> I don't mean to cause any undue concern. The issue is fairly simple
> . . . You can break glass and ceramic with sound but it is not likely if
> you are careful. But ultrasonic cleaning can break wire bonds, and wires,
> this is especially true in controls, ceramic ICs and the like were the
> wires are not encapsulated and subject to vibration. There are
> technologies that are effective in reducing this type of damage. Hope this
> relieves your fear. If you are still concerned then you have some homework
> to do. What frequency and power does you cleaner work at. What is a
> construction of the packages in question . . . stuff like that.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Howard
> Watson
> Sent: Friday, October 26, 2001 11:46 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning paste when misaligned.
>
>
>
> Mike and Guy,
>
> We routinely clean the second side of misprint solder paste,
> but from what you are saying perhaps there could be a problem with
> damaging some components. The components that we clean in the ultrasonic
> cleaner are mostly flat chip package, C lead diodes, and some SOT-23 and
> SOIC. How do I verify which components can or cannot go in the cleaner?
> Is there any test data out there to support this issue? Though we clean
> very few misprints, I am a little concerned. Thanks for your help!
>
> Howard Watson
> Manufacturing Engineer
> AMETEK/Dixson
>
>
>
> "Barmuta, Mike" <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
>
> 10/26/01 09:02 AM
> Please respond to "TechNet E-Mail Forum."
>
>
>
> To: [log in to unmask]
> cc:
> Subject: Re: [TN] Cleaning paste when mis-aligned.
>
>
>
> Cathy: This should not be a problem for the bare (unloaded)
> PCB. However if
> you are doing a double sided reflow and misprint the
> second side you need
> to verify that the first side components are compatible with
> the ultrasonics
> you are using.
>
>
> Regards
>
> Michael Barmuta
>
> Staff Engineer
>
> Fluke Corp.
>
> Everett WA
>
> 425-446-6076
>
> -----Original Message-----
> From: Cathy Killen [mailto:[log in to unmask]]
> Sent: Friday, October 26, 2001 7:30 AM
> To: [log in to unmask]
> Subject: [TN] Cleaning paste when mis-aligned.
> Importance: High
>
>
> Hello All & the mountain dew man.
> Can a mis-printed PCB be washed in a ultrasonic bath to
> remove all paste
> particles?
> Is there any danger of damaging innerlayers of PCB?
>
> Thanks in advance.
>
> Cathy Killen
> Training Instructor
> Smtek Europe Ltd.
> The information contained in the E-mail is confidential. It
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> person is
> unauthorised.
> The views expressed in this E-mail are those of the author,
> and do not
> represent the views of Smtek Europe, its associates or
> subsidiaries, unless
> otherwise expressly indicated.
> Please note: It is your responsibility to scan this E-mail
> for viruses.
>
>
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