Tech Net Forum,

The following is a short clip revised from an original post to the SI List,
and a follow-up to the Designers Council List.

I have never received any responses to this post, or the question(s), other
then one response suggesting that I post it here.

I thought I had posted it here, but it appears that I did not, at least in
its present form.

Thanks,

JaMi Smith


Here follows a short and cleaned up, reposting of the questions:

***************************************************


1. What is the copper density of common electroless deposited copper, such
as that used in the initial plating of 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 thicknesses.

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.

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.

One other related new question that I have thought of, is this: Does the use
of electroless deposited copper, such as that used for the initial plating
of vias, but which also usually additionally plates the original bare copper
on the outer layers with a small amount of the same solution, form a barrier
(of any kind) between the original bare copper on the outer layers and any
additional plating (or "plating up") on the outer layers? Specifically, are
there any other chemicals, or anything else, that are used in the
"electroless" process, that will remain intact in that thin "electroless
layer", which may inhibit current flow between any original copper on the
outer layers and any new additional plating pn the outer layers?

Thanks,

JaMi Smith

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