RE: [SI-LIST] : Proposal: Rs correlation/collaboration for W-Elem

Dave Hoover (dhoover@mccurdy.com)
Wed, 4 Aug 1999 08:22:40 -0700

The copper foil profiles are on one side of the etch=20
(opposite drum side). The copper foil is manufactured by=20
plating to a large slow turning highly polished steel drum.=20
The side towards the drum is very smooth. The side away=20
from the drum gets plated with parameters to produce those=20
profiles.

As the copper weight goes down (like from 1 oz to=20
1/2 oz) the size of the dendrites (topology) decreases. Those
teeth are mainly used for adhesion purposes. Yes, it does make
a difference in electrical performance. (e.g., in the case of
distributed plane capacitance it is more favorable to have the
two drum sides facing each other). The microwave PTFE based
substrates offer a RA (rolled annealed) copper that is very
expensive but evidently has favorable electrical performance
characteristics. (RA foil has greatly reduced peel strengths)
At very high RF frequencies there also may be some differences=20
between copper foil suppliers from the actual grain sizes=20
(boundaries) of the copper foil. Not sure where that really=20
starts showing up. Unless the product is way up in frequency,
I think that surface finish selection would be more critical=20
than copper dendrites. (i.e., HASL vs Imm Gold vs White Tin or Ag)=20

Just my $.02

Dave Hoover=20

-----Original Message-----
From: John, Hans-Joerg [mailto:Hans-Joerg.John@pdb.siemens.de]
Sent: Wednesday, August 04, 1999 12:21 AM
To: 'si-list@silab.eng.sun.com'
Subject: AW: [SI-LIST] : Proposal: Rs correlation/collaboration for
W-Elem ents

Hello Vadim,

in ANSI/IPC-MF-150F (Metal Foil for Printed Wiring Applications) you =
find
information regarding the foil profile. There are three types: =
Standard, Low
Profile and Very Low Profile. In paragraph 3.4.5 of this standard =
numbers
are given for the different types:

Low Profile: < 10.2 micron
Very Low Profile: < 5.1 micron

For the Standard type no values are specified!

Additional you can find the resistivity of the copper foil as a =
function of
the thickness!! This results from the different influence of the =
profile for
my opinion.

Best regards

Hans-Joerg

---------------------------------------------------
Dr.-Ing. Hans-Joerg John phone: +49 5251 820 347=09
Siemens AG fax: +49 5251 820 349=09
ICP CS PS DH4 =09
EMC and Signal Integrity Design Support
mailto:hans-joerg.john@pdb.siemens.de

Heinz-Nixdorf-Ring 1 =09
D-33106 Paderborn
Germany

> -----Urspr=FCngliche Nachricht-----
> Von: Heyfitch, Vadim [SMTP:vadim.heyfitch@intel.com]
> Gesendet am: Mittwoch, 4. August 1999 03:58
> An: 'si-list@silab.eng.sun.com'
> Betreff: RE: [SI-LIST] : Proposal: Rs correlation/collaboration for
> W-Elem ents
>=20
>=20
> Such measurements should allow us to nail down the surface roughness
> parameter that is required by field solvers. Rs is rather sensitive =
to
> this
> parameter making it into a good fudge factor. (At 1GHz, skin depth is
> about
> 2 micron. Does anyone know how this compares to typical Cu etch
> roughness?)
>=20
> Vadim
>=20
>=20

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