Bob Arciolla asked
- About two weeks ago I questioned whether clipping leads (and possible
fractured joints) was a problem if there was a good fillet on the component
side of the board. The main input I received back is that there is a chance
of corrousion to the leads. Last week I asked if this would still be a
problem if the PCB was totally encapsulated and a vacuum pulled on the
units. Any input?????
- Reply:  Bob, lots of words were generated by your question.  My vote would
be that the fractured solder connection will have a much greater impact on
reliability than the exposed lead end (possible corrosion).  Masking the
problem of fractured leads with conformal coating, encapsulant or embedment
compound will do just that, mask the problem.  Depending on the nature of the
structure being encapsulated, the encapsulation may in fact mature the
failures more quickly than if the unit were not encapsulated.  Check the
thermal coefficient of expansion of the encapsulant and determine how much
movement, mechanical force, the encapsulant will exert on the assembly
(including fractured connections) when the product goes into service in it's
intended use environment (what sort of temperature cycles/extremes are
anticipated).  
Hope the above clarifies my original intent (fractured solder connections are
bad medicine).  Regards, Jim Moffitt, Technical Director, Electronics
Training Advantage