Hi Bogert,

I would call and talk to someone at CAE Ultrasonics, I feel they have been
one of the industry leaders in developing safe ultrasonic cleaning for
electronics. Go to:

http://www.caeultrasonics.com/

Another company that has been actively producing systems to clean electronic
assemblies is Crest Ultrasonics. Go to:

http://www.crest-ultrasonics.com/home.html

I think it's like you said, back in the past, ultrasonic cleaning was
discouraged, and for good reason back then. Most ultrasonic transducers
produced the ultrasonic energy at lower frequencies and stayed at a single
frequency. Lower frequencies generate larger cavitation bubbles and excite a
part into resonance which causes the damage that everyone worried about.

Nowdays, the technology has advanced far from what it was years ago, and
transducers are made to transmit ultrasonic energy at the higher frequencies,
and with what is called non-uniform sweep rates that vary the frequencies
slightly so that resonances can't form and so that there won't be "Hot spots"
forming in certain areas of the cleaning tanks..ie: corners,etc.

Here's another link that you're probably familiar with, of the IPC-TM-650
test to determine the sensitivity of electronic assemblies to ultrasonic
cleaning, that personally, I think is a hold-over from the old days when
ultrasonics (at the time) wasn't a good thing:

http://www.ipc.org/html/2.6.9.1.pdf

I work at a contract assembly company, and have tried to feel out some of our
customers as to what their opnions are regarding ultrasonic cleaning, and
it's a tough sell...even with all the advancements that have been made with
the technology. Being able to use ultrasonics would solve a lot of issues
that I (we) face in cleaning, and I feel would provide superior results to
many methods and chemistries that are in place now...but you have to change a
lot of perceptions that were set in stone years ago.

I really think there's a lot of misplaced concern with the technology as it
stands currently...but that's only my opinion.

-Steve Gregory-


> 10/18/2001
>
> Anyone out there have any information on using ultrasonics for cleaning of
> a daughter-board PWA that has BGA soldered in place.  I recall in the old
> military days, ultrasonic cleaning was a no-no because of fear of
> destroying electrical bonds within individual parts.  I know times have
> changed and some folks allow use of ultrasonics.  J-STD-001 allows it
> subject to the supplier proving documentation that there will be no
> mechanical damage or electrical problems.  What ultrasonic cleaning process
> paramaters do we need to control?  Any specific process details would be
> appreciated.  Any good technical reference documents would also help.
> Please respond to Les Bogert  <A HREF="mailto:[log in to unmask]">[log in to unmask]</A>.
>