Spray the coating with what??
John
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of R Sedlak
Sent: Friday, April 22, 2005 1:09 PM
To: [log in to unmask]
Subject: Re: [TN] Dry film soldermask
Mr. Burdick:
I have sold a lot of the old traditional black oxide chemistry to Hewlett
Packard, back in the days when they were making their own PCB's, for use
under dryfilm soldermask. HP had some pretty stringent standards for
soldermask adhesion, and the only way they could achieve those standards was
to use black oxide under the soldermask. And they achieved these standards
easily when the oxide was on the board. They claimed the only way they
could get the mask off the board was to destroy the board...
Now, for the fascinating second chapter on this... it turns out that if you
spray the old traditional black oxide chemistry, the deposit lightens up
tremendously, so much so that it becomes essentially invisible... YET, there
is no loss in mask adhesion. (I don't understand this either!) The guys at
HP referred to this as the "Emporers Oxide", because only the faithful could
see the oxide.
(We had some folks who did not believe we were putting anything down on the
surface at all, and they tried running some panels through the pre-clean
before oxide, and skipped the oxide, and the mask peeled off as easy as tape
from a board)
I may even have some brochures about this process still kicking around, and
would be happy to send you one, if you would like.
Rudy Sedlak
RD Chemical Company
Russell Burdick <[log in to unmask]> wrote:
Sorry to bust in with a "real" question....
Has anyone experience with using the black oxide replacement chemistry as a
pre-clean for dry film soldermask? The mask is Dupont Vacryl(sp?). The
chemistries are usually refered to as alternative etch or differential etch
as generic terms. Vendors offer Cobrabond and Bondfilm and Multibond as
process names.
I have experience using these chemistries with Liquid photoimagable
soldermasks, but the dry stuff is not in my toolkit.
Thanks in advance,
Russ
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