One of the often overlooked issues with surface mount is the physical strain the parts are under and it's variation when the board flexes. The leads on through hole parts have some amount of flex, where SMT terminals don't. Additionally, due to the closeness of the part to the board a small amount of flex can put tremendous pressure on the part - affecting it's properties.

If memory serves there was some mention of this in an Analog Devices app note for their ADXL202 accelerometer, it specified a minimum solder thickness between the component and the board to ease this issue  (but they might have been more concerned about thermal expansion issues - same problem, different cause)

-Denny



> The capacitor's a 0.33uF 0603 SMT part. I'd have thought that was too
> large a value to be much influenced by small changes in contact length
> so I'm not sure if that confirms or refutes your theory.
> 
> I just had a look at the PCB layout. It's no great surprise it's
> emitting EMI - the designer doesn't seem to have paid any special
> attention to careful layout at all.
> 
> Cheers,
> Zik
> 

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