Posted for Bob Hamilton by Denny Fritz - MacDermid, Inc.

"Lead-free compatible" high-Tg (170-180 C) materials mostly  contain
phenolics now.   The resistance of these laminates to  desmear chemistries
is substantially higher than the dicy-cured high-Tg  materials they replace,
which means the desmear cycles need to be  re-evaluated.  You can't just
drop them into existing processes and  expect nothing to go wrong.   If the
desmear cycle has not been  re-optimized, the fabricator will be faced with
poor hole wall topography,  and possibly unremoved smear.  In either case,
plating adhesion will  suffer.

Therefore, the fabricator should examine this aspect of the  process.  Given
that getting any topography at all is generally harder  with these
laminates, and that the higher lead-free assembly temperatures put  more
stress on the barrel, it also makes sense to move to the latest  low-stress
electroless copper systems.  That change alone can be the  difference
between winning and losing the adhesion war.

Robert  Hamilton
Technical Director
Americas


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