Wow. Thanks for the input. That seems like a big difference.
Doug
Jeff Loyer SI wrote:
Hi Doug,
FYI, my experience (and others') agrees with Gert's, that PCB "copper" isn't
pure. Our measured conductivities were:
2.1uohm-cm (4.76e7 ohm-m conductivity) for stripline
2.4uohm-cm for microstrip
Copper = 1.7uohm-cm (5.88e7 ohm-m)
We measured the temperature coefficient as 0.35%/degree C (interestingly
there was a difference between U.S. domestic and foreign vendors').
Coming from the copper foil vendors, IPC specs. ensure it is very "pure",
with conductivity specified. It appears the processing of the laminate
suppliers affects the conductivity significantly, though we've never
understood exactly what part of the process does that. I suspect treatments
diffuse into the copper, reducing its conductivity.
The data Ive seen indicates packages copper behaves more like copper.
Jeff Loyer
Signal Integrity Consulting
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Doug Brooks
Sent: Wednesday, July 1, 2015 8:44 PM
To: SI-LIST
Subject: [SI-LIST] Re: Resistivity of copper
Thank you all for your help.
Turns out I was on the wrong track! First, I have been under the assumption
that the resistivity curve was non-linear over this wide a range. Turns out
that the normal equation still works here. ( Rho-subT
= Rho-sub20*(1 + Alpha-sub20*(T-20)) This leads to about 5.3 or 5.1
depending on what assumptions you make. My 4.3 number, it turns out, was
irrelevant!
So, I apologize for the exercise. But thanks for the support.
Doug Brooks
Doug Brooks wrote:
I would like to know the resistivity of copper at 540 degrees C,------------------------------------------------------------------
assuming it is 1.72 * 10^-8 Ohm*m²/m at 20 degrees C. The temp
coefficient of resistivity is .00393 at 20 degrees C but using this I
get a result of around 5.31 at 540 degrees. But a problem I am solving
says it is closer to 4.30. I am having trouble resolving the difference.
Can anyone confirm the (approx.) 4.3 number for me?
Thanks for any help.
Doug Brooks
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