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Reply To: | TechNet E-Mail Forum. |
Date: | Wed, 13 Feb 2002 07:58:56 -0800 |
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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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