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Date: | Tue, 7 Oct 1997 12:50:01 EDT |
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TO: I4235700 IBMMAIL new address for ipc technet 25.6.96
FROM: DSTEWART EX2 D.Stewart - Product Development Manager.
DATE: 7 October 1997
SUBJECT: YTECHNET? IMMERSION AU, NPTH DEPOSITS
David, what you are seeing is ENAu depositing onto the palladium
residues from the original electroless copper process, left in the
holes after etch and tin strip. If your boards are soldermasked
prior to ENAu, the temperature of stoving 'fixes' this palladium
deposit and it cannot be 'poisoned' by the preactivation stages of
the ENAu line. We had to do all over ENAu for a long time because
of this problem, but by working with our chemistry supplier, we no
longer have an issue. The reason why you don't see it on the
drilled after plate holes is because they never had palladium in to
start with.
Dougal Stewart
Viasystems, Selkirk
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