Is one side of the component connected to a voltage or ground plane? It could be that the copper in the plane is taking heat away from the pad. One solution is to separate the pad from the plane by use of a small short trace. 

Also, if one pad has a large trace connecting to it, and one has a small trace, the large trace can also take heat away. One way to solve this is to neck down the trace right next to the pad. 

Blair

>>> [log in to unmask] 06/08/05 08:09AM >>>
Technetters,

I have several SMT board styles which give me some trouble with 0306
capacitor tombstones, and through many attempts to reduce the number of
these defects, I have found a condition that I can not seem to attribute
a cause to. I have found that across a board, all the tombstones tend to
lift in the same direction (for components in the same orientation).

I have looked at the build process, but different board styles result in
tombstones in different directions, so I believe the cause to be board
related. I have looked at solder mask registration (misregistration
occurs in various directions), power/ground plane connections by pad
(changes from location to location), and solder bumps due to HASL
(wicked pads have similar results), and nothing has led me to a root
cause.

Any ideas???

Thanks,
Ben Gumpert




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