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
-----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.
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