[SI-LIST] Re: Copper atom density

I apologize for letting this email sit unfinished in my "Drafts" Folder for well
over a month now, as I had to attend to something else important that had come 
up
while I was in the middle of writing this response to the above "Subject" 
thread,
and I simply saved it to my "Drafts" Folder, and forgot to get back to complete 
and
send my reply in a timely manner. Therefore please excuse the out of context 
post,
but I felt it was important enough to finish up and reply to.

I specifically wanted to follow up and expand on Doug Brooks question, earlier 
in
the thread (which can be seen below).

This was originally intended to respond to a thread that ran from 11/16 thru 
11/19.

* * * * * * * * * *

Let's please dispense with the esoteric and with the egos . . .

The real question(s) behind the density issue as it really applies to the
manufacture of today's Printed Circuit Boards (as I see it), is as follows:

1. What is the copper density of common electroless deposited copper, such as 
that
used in plating vias, and more specifically, what is it's conductivity - bottom
line, what is the current carrying capacity - as related to say solid copper bar
stock.

2. What is the copper density of common electro plated copper, such as that 
used in
plating vias, and more specifically, what is it's conductivity - bottom line, 
what
is the current carrying capacity - as related to say solid copper bar stock.

3. What is the copper density of common electro plated copper, such as that 
used in
pattern plating on either internal or external layers, and more specifically, 
what
is it's conductivity - bottom line, what is the current carrying capacity - as
related to say solid copper bar stock.

4. What is the copper density of common rolled sheet copper, such as that used 
as
the basis of normal planes and layers, and more specifically, what is it's
conductivity - bottom line, what is the current carrying capacity - as related 
to
say solid copper bar stock.

These 4 different scenarios present 4 possibly different densities of copper,
commonly used in the manufacture of today's PCB's. These 4 possibly different
densities of copper, also appear to result in possibly having different 
densities
per specific thickness'.

If these densities are in fact different, then there are possibly differences 
in how
the different types of copper react to an etchant, and there most certainly are
probably also differences in both current carrying capacities, as well as
differences in thermal conductivity.

This is an issue that I have tried to get answers to for many many years, but 
which
I have never succeeded in getting answers to, and which I have never seen 
discussed
in any publications that I have read, nor in any of the "lists" that I 
subscribe to,
notwithstanding that this is not the first time I have asked these questions.

This discussion in this "thread" seems to be very close to answering some of the
questions  that I have set forth above, so I would ask whether or not any of the
participants of this "thread" can in fact address these questions, as I feel 
that
these questions, while never (to my knowledge) posed before, do in fact address 
the
quality of the manufacture of modern PCB's, especially as we move to smaller and
smaller trace widths and features, on thinner and thinner substrates.

Finally, I would pose yet one more question, albeit possibly a little complex, 
which
is directly relevant to this "List", and that is this: What, if any, effect or
impact, do the 4 different types of copper discussed above, with their possibly
different copper densities, especially with reference to the specific 
"thickness" of
that type (or composite type) of copper, have in determining the specific
capacitance, and thus impedance, of specific structures, made up of these 
different
types of copper ?

One additional question that may additionally have a very minor bearing on the
questions posed above, is that of whether or not any of these possibly different
densities respond differently to thermal expansion and / or current carrying
situations ?

Or, are all of the densities the same, and am I just asking dumb questions ?

Thanks,

JaMi Smith

* * * * * * * * * *

----- Original Message -----
From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>
To: <esayre3@xxxxxxxx>; <doug@xxxxxxxxxx>
Cc: <si-list@xxxxxxxxxxxxx>
Sent: Saturday, November 19, 2005 8:35 AM
Subject: [SI-LIST] Re: Copper atom density


> Hear Hear! Inquring minds want to know.
> Can you say what kind of research you're doing??
>
> Best Regards
> Charles Grasso
> Senior Compliance Engineer
> Echostar Communications Corp.
> Tel: 303-706-5467
> Fax: 303-799-6222
> Cell: 303-204-2974
> Pager/Short Message: 3032042974@xxxxxxxx
> Email: charles.grasso@xxxxxxxxxxxx;
> Email Alternate: chasgrasso@xxxxxxxx
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Ed Sayre III
> Sent: Wednesday, November 16, 2005 1:17 PM
> To: doug@xxxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Copper atom density
>
> Doug,
>    I you are dealing with single crystalline copper then the volume is
> an=20
> algebraic expression based on the atomic unit cell.  This is derived
> from=20
> the crystal orientation (ie face centered cubic, body centered cubic,=20
> Diamond...etc)
>    The thing is that copper is not single crystalline in a typical=20
> conductor, so I would guess that the density is a bit lower.  I would=20
> recommend you pull out the old "CRC Handbook of Chemistry and Physics".
> I=20
> think this will answer all your questions.  Also the text by "Ramo,=20
> Whinnery and Van Duzer"  may also have some material constants as
> applied=20
> to Electromagnetics
>
>   I am curious, why do you need this??? Critical currents density?
>
> Regards
> -Ed
>
>
> At 12:01 PM 11/16/2005 -0800, Doug Brooks wrote:
> >I am interested in determining the density of copper atoms per unit
> >cross sectional area, i.e. the average number of atoms at the cross
> >sectional area of a conductor.
> >It is given by various sources that the volumetric density of copper is
>
> >between
> >8.37 10^28  and
> >8.5   10^28  atoms/meter^3
> >
> >Is it as simple as taking the 2/3 root of this number (19.3
> >10^18/meter^2)? That seems logical but not necessarily realistic. I
> >think there is a better answer but I'm not sure how to approach it.
> >
> >Doug Brooks
> >
> >_______________________________________________________________________
> _____-
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