Doug,
I thought the purpose of inner layer oxide was to increase the bond between the copper and the epoxy.
The epoxy itself should protect the copper from corosion.  Have I been wrong all these years.  Why did I
do all those bond tests on oxides with different crystal structures?
Chuck Brummer

[log in to unmask] wrote:

> Rudy,
> One of the things I saw whilst at CSL was that we would sometimes see
> corrosion on inner layer traces when they were placed very close to the
> edge of a board.  If the panels had been scored rather than routed, as was
> the case, the mechanical flexing would open the edge of the laminate, or
> the rough edge would allow moisture ingress, such that the inner layers
> could corrode.  So one thing I would look at would be the flexibility of
> the oxide.  I would also look at how well oxide coated inner traces, placed
> near the edge of the board, resisted corrosion.  If you are convinced that
> the vendor has adequate inner layer cleanliness before lamination, then you
> might want to use some external contaminant source, such as salt spray/fog
> testing or some of the mixed flowing gas tests done at UL.  Susan Mansilla
> had a good test and would be dramatically faster and easier than the tests
> I suggest, but probably would not address the corrosion issues.
>
> The whole point of the inner layer oxide is protect the metal.
> a.  Does the oxide interfere with good plating in vias?
> b.  Does the oxide have sufficient flexibility to protect the metal in high
> G or high shock environments?
> c.  Does the oxide have sufficient chemical resistance to protect the metal
> against corrosive elements?
>
> Doug Pauls
> Rockwell Collins
>
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