Josh Koffman wrote:
>
> Perhaps if we could get a device that could emit a focused beam of
> energy at the resonant frequency of copper...

Ultrasonics? The resonant frequency would be based on the thickness of
the copper, its stiffness,  adhesion to the substrate and the stiffness
of the substrate. Although, it should be possible to tune the freq on
the fly by observing the reaction of the board. Or maybe find a common
center frequency and then xmit a bunch of freqs around it. Focusing the
sound would be difficult, but if the transducer is close enough to the
board it shouldn't be a problem.

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