[SI-LIST] Re: Fw: Problem with Ni plated transmission line
- From: "Chris Schmolze" <schmolze@xxxxxxxxxxx>
- To: <kuchta@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 14 Mar 2003 13:17:16 -0600
Daniel,
Check the composition of your nickel plating bath. As Aubrey mentioned
the magnetic permeability of Ni can vary. If I recall properly, a
Japanese test socket manufacturer ( maybe Enplas or Yamaichi)had
disclosed in patents the relationship between the %P in electroless Ni
plating and skin depth of the rich P region and the effect of that
relationship to frequency. If you get the opportunity have your flex
supplier supply samples of identical microstips plated with both
2-5%(standard) and 20% phosphorus Ni. Make some S-parameter
measurements. You should gain back your bandwidth with the 20%P-Ni and
still reap the corrosion resistance and wear benefits of the Ni.
Regards,
Chris Schmolze
-----Original Message-----
From: Daniel Kuchta [mailto:kuchta@xxxxxxxxxx]=20
Sent: Friday, March 14, 2003 11:08 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Fw: Problem with Ni plated transmission line
>Did you make a x-section to verify your copper thickness ?
Yes, the line is about 6um thinner than expected: 14um vs 20um.
>Do you used electroless Ni-P ?
I believe so.
>And you are rigth you should have higher bandwidth witthout solder mask
I still think so too. My measured result doesn't agree so I'm looking
for a potential problem that someone may have encountered previously.
Daniel M. Kuchta
IBM T. J. Watson Research Center
1101 Kitchawan Rd. Rt. 134
Yorktown Heights NY 10598
914-945-1531 (voice)
914-945-4134 (fax)
kuchta@xxxxxxxxxx
----- Forwarded by Daniel Kuchta/Watson/IBM on 03/14/2003 12:05 PM -----
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| | "Jean Audet" |
| | <jaudet@xxxxxxxxx|
| | m> |
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| | 03/14/2003 10:47 |
| | AM |
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| To: Daniel Kuchta/Watson/IBM@IBMUS
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| cc:
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| Subject: Re: [SI-LIST] Problem with Ni plated transmission
line
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Daniel, the electroless plating need a copper surface preparation
(process
problem) and in some cases the Cu is too much etched and consequently
reduce the line thickness.. Did you make a x-section to verify your
copper thickness ? Maybe also during the etching process the copper line
have bee under etch (under the line) and also increasing the surface
roughness on the trace.
Also some electroless ni process contain magnetic Ni. Do you used
electroless Ni-P ?
And you are rigth you should have higher bandwidth witthout solder mask
Jean Audet
Electrical Analysis
InterConnect Products IMD
IBM Burlington
Tel: 802-769-0835, tie line: 446-0835
Tel: 450-534-6317, tie line: 552-6317
E-mail: jaudet@xxxxxxxxxx
Daniel Kuchta
<kuchta@xxxxxxxxx To:
si-list@xxxxxxxxxxxxx
m> cc:
Sent by: Subject: [SI-LIST]
Problem
with Ni plated transmission line
si-list-bounce@fr
eelists.org
03/14/2003 09:58
AM
Please respond to
kuchta
I have run into an unexpected problem with a Ni plated transmission
line.
I have fabricated 2 types of 100 Ohm differential transmission lines on
a flex circuit. They are both approximately 3mil width and 3 mil space.
The substrate is 3mil Dupont Pyralux.
The metallurgy on one pair is 1/2oz copper covered with PSR9000 solder
mask. The metallurgy on the other pair is 1/2 oz copper plated with 100u
in Electroless Ni and 10u in Electroless Au. The plated line is not
covered with solder mask.
The expected result was that the plated line would have higher bandwidth
since the solder mask has a loss tangent of 0.02.
The measured result is 20GHz for the covered lines and 7 GHz for the
plated lines! The plated lines appear to suffer from high conductor
losses.
The dc resistance of the lines is also different: 0.5 Ohm for the
unplated and 1.1 Ohm for the plated.
Does anyone have a similar experience with plated transmission lines?
Does anyone have an explanation for this effect?
Thanks
Daniel M. Kuchta
IBM T. J. Watson Research Center
1101 Kitchawan Rd. Rt. 134
Yorktown Heights NY 10598
914-945-1531 (voice)
914-945-4134 (fax)
kuchta@xxxxxxxxxx
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