We use Scherring-Atotech high build chemistry for chemical copper and
their GS818 additive brightener system for electrolytic copper plating
for the last couple of years.
Right from the beginning we have been observing tiny nodules in the
through holes after doing 25 micron galvanic copper plating. No nodules
are observed at the the high build electroless stage when the built up
chemical copper is just 2 to 2.5 micron.
There have been lot of back and forth visits by the vendors application
staff and plus our own process engineers attempt to get over the
problems but none of which has met with any significant success.We have
tried out the following:
1 Thorough inspection of drilled holes and complete removal of epoxy
dust through high pressure reciprocating water jet cleaning at brushing
stage.
2 Transfering the electroless solution into another clean tank before
commencing electroless.
3 Continuous filteration of electroless copper bath at the rate of 2000
litres per hourmaintained.
4 Optimum temperature and concentration of various baths maintained by
periodic additions.
5 Close monitoring of brightener additions in electrolytic copper bath
as per ampere hour.
6 Current density lowered to 2 amps to 2.5 amps per decimetre square for
longer duration to eliminate the possibility of burning.
None of the above have yielded any significant improvement. Suggestions
invited.
Thanking in advance.
P. V. Khan
Chief Quality Manager
Linaks Microelectronics Ltd
e-mail: [log in to unmask]
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