Phil, 

I've no direct experience of failures definitely attributed to
ultrasonic cleaning, but I'd refer you to 'Reliability and Yield 
problems of Wirebonding in Microelectronics' Harman, G. 
ISBN: 0-930815-25-4 available from ISHM. 

There is a discussion on this issue, in the book, with references.

>From my perspective, dealing with PEMs, the key message is that 
cleaning frequencies >100kHz are unlikely to cause any damage.

regards

Olly



> From [log in to unmask] Fri Jun  6 19:24:55 1997
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> Date: Fri, 6 Jun 1997 14:23:14 -0400 (EDT)
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> Subject: Ultrasonic Cleaning
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> I have a argument going on ultrasonic cleaning of PWA's with different types
> of component.
> 
> Several opinions have come up: 
> (1) Never ultrasonic clean if you have hybrids with wire bond connections.
> (2) Hybrids are OK to clean in an ultrasonic if an encapsulant is used.
> (3) Hybrids are OK to clean if they supplier follows standard wire bond
> requirements.
> (4) Do any of the above rules apply to multichip modules.
> (5) Do Ball Grid Array fall in any of the above categorties.
> 
> Phil Hinton 
> [log in to unmask]    
> 
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