Sweeping- and multi-frequency systems do not eliminate the problem,
although they reduce the time that the resonance occurs; consequently,
the makers claim that the weakening of the bonds is lessened.

This would seem logical. I have not studied the structural strength of
the bonds, but I feel that even a short exposure to resonance could
work-harden the ends of the wire causing embrittlement. Perhaps a
metallurgist could advise?

My feeling is that it would be safer to apply the precautionary
principle until scientific studies prove the contrary.

Brian

Charles Caswell wrote:
> There are manuf. Of ultrasonic cleaning equipment that use a sweeped freq.
> which is supposed to eliminate the resonance problem. I would search the
> archives.
>
> -----Original Message-----
> From: Blair K. Hogg [mailto:[log in to unmask]]
> Sent: Monday, 18 April 2005 9:39 AM
> To: [log in to unmask]
> Subject: Re: [TN] Ultrasonics
>
> At a former employer we used resistor divider networks which had stamped
> leads soldered to the component. The component was made from resistive ink
> which was sliced in a serpentine pattern to create a high resistance. The
> legs of the device had three prongs that would straddle the device in an
> offset pattern. The manufacturer ultrasonically cleaned the parts after
> soldering, which caused the stress areas in the stamped legs to develop
> cracks and fail at a later date. Once the U/S cleaning was eliminated, the
> problem disappeared.
>
> Blair
>
>
>>>>[log in to unmask] 04/18/05 09:15AM >>>
>
> Technetters
>
> I seem to remember somewhere that ultrasonics shouldn't be used to clean
> populated PCB's. I have believed this to be due to damage inflicted to the
> wire bonds within IC's and Xtals.
>
> Is this the case can someone clarify what components (if any) cannot be
> cleaned using ultrasonics?
>
> Cheers
>
> Mark
>
>
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