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Date: | Fri, 4 Aug 2006 09:21:47 EDT |
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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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