try plasma etching with argon gas; this will preferentially etch grain
boundaries without much effect on the metal crystal itself.

> Bill Davis, Ph.D.
> Diamond Multimedia Systems
> Senior Scientist
> Tel. 408.325.7868
> Cell. 408.888.5650
> e-mail: [log in to unmask]
>
>


-----Original Message-----
From: Werner Engelmaier [mailto:[log in to unmask]]
Sent: Monday, May 24, 1999 1:34 PM
To: [log in to unmask]
Subject: Re: [TN] Copper grain size


In a message dated 5/24/99 10:12:01, [log in to unmask] writes:
>Hello Engelmaier!
>How does it change does it increase or decrease? Do you know
>any information about etchants to decorate grain boundaries.
>Thanks,
>Yasmeen

Hi Yasmeen,
The grains generally increase in size during annealing, but more
importantly
they change shape. Most commercial electrodeposited copper foil has a
columnar grain structure where the grains are packed columns running
through
the thickness of the foil; there also is a difference in the machine and
cross-machine directions. Rolled copper foil has a needle-like structure
with
the needles running in the rolling direction of the foil; this produces
large
(much larger than E-foil) differences in foil properties in the machine
and
cross-machine directions. Annealing will produce more uniform grain
structures.
For the appropriate etchants (they depend on what in the grain structure
you
want to emphasize) I need to send you to experts in this area. Since
your
internal lab does not seem to be experienced in this area, I would
suggest to
have the cross-sectioning, polishing and etching done by a commercial
laboratory. Any of the labs that are IPC members can be recommended (I
have
seen some rather bad results from some other labs); so pick one
conveniently
located to you out of the IPC membership directory.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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