[SI-LIST] Re: Microstrip Trace under Nickel
- From: "Geoff Stokes" <GStokes@xxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 12 May 2006 10:12:06 +0100
Thanks Yuriy
I have only to add some practical observations which may be obvious to
many. Your very useful figures show that right through the frequency
range of 1KHz to 1 GHz (and beyond actually), the resistive part
outweighs the inductive part by a factor of several thousand or more.
Also, the larger permeability of nickel makes the resistive (real) part
much larger due to the reduced skin depth compared to copper, much
larger than the effect of the increased resistivity alone.
[Skin depth is 1/(sqrt(pi*conductivity*frequency*mu*muzero)) from which
we see skin depth goes in proportion to the square root of resistivity
and inversely as the square root of magnetic permeability.]
This means that nickel on its own will show some significant signal loss
in the region of roughly 100 MHz into the GHz range. However this is
not the practical case. In microstrip, the nickel plating may sit on
top of relatively thick copper, with gold (often 1 to 5 micron) on top.
In microstrip, due to the skin effect, most of the high frequency
current flows on the lower surface of the signal conductor in the copper
where the electromagnetic field in the dielectric is strongest. What
little current flows in the nickel is further attenuated (but not a
great amount) by the skin effect in the gold on top. Therefore the loss
is not great and many RF and high-speed digital (or analogue) circuits
can be built this way unless the application is highly critical.
I am wondering, may I ask, are you the same Mr Shlepnev well-known to
many RF engineers for your good work on the method of lines used in
Eagleware EMPower? For some people this could be an alternative to the
relatively high cost solutions from Ansoft (HFSS) and CST (Microwave
Studio), and still provide improved accuracy over quasi-static analysis.
Thanks again
Geoff Stokes
Systems Engineer
Zetex Semiconductors plc
Zetex Technology Park
Chadderton
Oldham
OL9 9LL
UK
=20
+44-161-622-4857
www.zetex.com
www.zetex.cn
=20
=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Yuriy Shlepnev
Sent: 10 May 2006 19:41
To: ryan.satrom@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Microstrip Trace under Nickel
Ryan,
The internal impedance of a trace or slab is obviously going to be
higher
for nickel. But, it might have little effect on the total inductance
p.u.l.
and on the characteristic impedance of a transmission line overall.
Though,
the resistive losses in such line are going to increase considerably.
Also,
take a closer look at the imaginary part of the characteristic
impedance.
Here are internal resistance and inductance p.u.l. for a single
rectangular
conductor 5 mil by 1.4 mil made of nickel:=20
f=3D1 KHz; R=3D15.16 Ohm/m; L=3D1.6 nHn/m (trace thickness is about 0.2 skin
depths - almost DC solution);
f=3D1 MHz; R=3D44.31 Ohm/m; L=3D0.627 nHn/m (trace thickness is about 6 skin
depths);
f=3D1 GHz; R=3D1244 Ohm/m; L=3D0.019 nHn/m (trace thickness is about 209 sk=
in
depths).
Copper conductor resistance and inductance p.u.l. for comparison:
f=3D1 KHz; R=3D3.82 Ohm/m; L=3D2.72 fHn/m (DC solution);
f=3D1 MHz; R=3D3.82 Ohm/m; L=3D2.71 fHn/m (trace thickness is about 0.5 skin
depths);
f=3D1 GHz; R=3D26.66 Ohm/m; L=3D0.4 fHn/m (trace thickness is about 17 skin
depths);
Bulk resistivity of nickel is assumed to be 6.85e-8 Ohm-m, and relative
permeability is 600, resistivity of copper 5.8e-8 Ohm-m.
It is easy to do the same estimations for a gold-plated nickel trace for
instance.
Yuriy Shlepnev
Simberian Inc.=20
shlepnev@xxxxxxxxxxxxx=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of ryansatrom
Sent: Wednesday, May 10, 2006 7:08 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Microstrip Trace under Nickel
Hello All-
I have been concerned with a microstrip trace traveling under a slab of
nickel. There is only a .020" gap between the trace and the nickel. I
have
done simulations in HFSS to confirm that the Nickel has minimal effect
on
the impedance.
However, it brought up an interesting discussion point that i don't
really
understand:
How does the magnetic properties of a material effect Signal Integrity?
I understand that some traces are made out of nickel. But they are
typically plated with enough gold that any signal in the MHz and higher
will
only travel in the gold due to skin effect.
Nickel has a relative PERMEABILITY of about 600. Does this effect
anything?
Thanks for any help on this.
Regards
Ryan Satrom
Everett Charles Technologies
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:=20=20=20=20=20
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
=20=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:=20=20=20=20=20
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
=20=20
_________________________________________________________
Zetex Semiconductors - Solutions for an analog world.
http://www.zetex.com
http://www.zetex.cn
E-MAILS are susceptible to interference. You should not assume that
the contents originated from the sender or the Zetex Group or that they=20
have been accurately reproduced from their original form.
Zetex accepts no responsibility for information, errors or omissions in
this e-mail nor for its use or misuse nor for any act committed or
omitted in connection with this communication.
If in doubt, please verify the authenticity with the sender.
_________________________________________________________
=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
