[SI-LIST] Re: Resistivity of PCB's?
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Wed, 3 Oct 2012 18:23:45 -0400
Jeff
here's a couple of questions.
How can a person researching the modeling of copper surface roughness not
be concerned about the actual resistivity of the metal they are modeling?
How can a person performing measurement to modeling comparisons of
interconnect models not be concerned about resistivity?
Blows your mind considering that the error in copper conductivity is around
25%, doesn't it?
On Wed, Oct 3, 2012 at 6:19 PM, Scott McMorrow <scott@xxxxxxxxxxxxx> wrote:
> BTW, conductivity of Cu in packages is even lower. Pair that with traces
> that are 27 um wide, and you have lots of loss.
>
>
>
> On Wed, Oct 3, 2012 at 6:02 PM, Loyer, Jeff <jeff.loyer@xxxxxxxxx> wrote:
>
>> Thanks guys for your input.
>>
>> My measurements seem to agree w/ Scott's - that a conductivity of about
>> 4.6 S/m is average for stripline, a little lower (4.2 S/m) for microstrip,
>> far from the 5.88 S/m of pure copper.
>>
>> Temperature coefficient gets more interesting - stripline follows that of
>> pure copper, ~0.4%/deg C, but microstrip is about half of that.
>>
>> I think our assumption that PCB conductors are pure copper may be flawed.
>>
>> Any idea why there are no papers published on this? It seems like
>> something that would have been studied ad-nauseum, but if you look at all
>> the modeling tools available, they all follow the "pure copper" (or
>> annealed copper) assumption. Blows me away that such a fundamental
>> characteristic hasn't been nailed down. I would think this would be
>> especially true for power delivery folks.
>>
>> Likewise, any idea why folks haven't insisted on conductivity and
>> conductivity temp. coefficient being specified on data sheets?
>>
>> Thanks for your time/insights,
>> Jeff Loyer
>> (253) 371-8093
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>> On Behalf Of steve weir
>> Sent: Tuesday, October 02, 2012 6:00 PM
>> To: si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] Re: Resistivity of PCB's?
>>
>> I have measured trace resistances for many years and gotten good
>> correlation. If you are measuring outer traces and you want close
>> correlation you may need to consider surface finish and if your traces are
>> skinny: etch profile. I also have done a fair number of tests on
>> temperature coefficient over the past 30 years and 0.00393 for Cu still
>> works well for -50C to 150C. Over wider ranges a second order
>> polynomial gives a better fit. That is generally unnecessary for any
>> ordinary applications. A strain gage that has to go down hole in an oil
>> well is a different matter.
>>
>>
>> Steve.
>>
>> On 10/2/2012 2:22 PM, Loyer, Jeff wrote:
>> > Just to make sure I'm not missing the obvious, does anyone have data
>> from measuring the actual resistivity of PCB traces? I think we typically
>> use a value of 1.7uohm-cm (conductivity = 5.88e7 S/m), assuming it's the
>> same as copper, but that's not what I'm seeing when I perform actual
>> measurements.
>> > Likewise, do you know of any studies done on the actual resistivity
>> temperature coefficient? Again, I believe most people use 0.4%/degree C,
>> but I'm not sure that's correct. I would love to see what others have
>> found.
>> >
>> > Thanks,
>> > Jeff Loyer
>> >
>> >
>> > ------------------------------------------------------------------
>> > 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 forum is accessible at:
>> > http://tech.groups.yahoo.com/group/si-list
>> >
>> > List archives are viewable at:
>> > //www.freelists.org/archives/si-list
>> >
>> > Old (prior to June 6, 2001) list archives are viewable at:
>> > http://www.qsl.net/wb6tpu
>> >
>> >
>> >
>>
>>
>> --
>> Steve Weir
>> IPBLOX, LLC
>> 150 N. Center St. #211
>> Reno, NV 89501
>> www.ipblox.com
>>
>> (775) 299-4236 Business
>> (866) 675-4630 Toll-free
>> (707) 780-1951 Fax
>>
>> All contents Copyright (c)2012 IPBLOX, LLC. All Rights Reserved.
>> This e-mail may contain confidential material.
>> If you are not the intended recipient, please destroy all records and
>> notify the sender.
>>
>> ------------------------------------------------------------------
>> 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 forum is accessible at:
>> http://tech.groups.yahoo.com/group/si-list
>>
>> List archives are viewable at:
>> //www.freelists.org/archives/si-list
>>
>> Old (prior to June 6, 2001) list archives are viewable at:
>> http://www.qsl.net/wb6tpu
>>
>>
>>
>
>
> --
>
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> (401) 284-1827 Business
> (401) 284-1840 Fax
>
> http://www.teraspeed.com
>
> Teraspeed® is the registered service mark of
> Teraspeed Consulting Group LLC
>
>
>
--
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
------------------------------------------------------------------
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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
