Hi Steve,
The root cause of tombstoning is the presence of fillets on the chip
components.
Historically, they were needed because chip components were almost always
wavesoldered.
If you reflow solder CCs, you do not need the fillets.
Reducing the fillet size by making the pads smaller--both narrower and
shorter--reduces tombstoning.
Tombstoning is worse for LF-solders than for SnPb.
The surest way of eliminating tombstoning entirely is by eliminating the
fillets--make the pads the same size as the metallization on the CC underside [or
just slightly larger]. No more tombstoning, no more CC cracking and more
reliable solder joints as well because you wind up with more solder joint height.

Werner

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