Russ,

There's not enough info!

1. How thick are the laminates?
2. Is there glass weave in it and if so what kind?
3. How many layers?
4. Is this a flex or "semi rigid" board?
5. Are the shorts "horizontal" or "vertical" or both?
6. Are the shorts confined to the "inner" layers or the surface and if
so which ones?
7. How thick is the foil?
8. What kind of etching and rinse/cleaning chemistry are you using?
9. How high is high? Is there an ohms "range" these reading are confined to?

This is just for starters.

BTW Omega meters are NOT to be used to determine if you have ionic
contamination.
Only to used used to detect variations in conductivity from one
"batch/production run" to another.

Polyimide is well known as a moisture absorbent. I suspect this will be
a factor in your problem.

David A. Douthit
Manager
LoCan LLC



Russell Burdick wrote:

> Here's a question for all you electrical fans...( ha, ha, ha, not
> those type
> of shorts)
>
> We are getting high resistance shorting on multilayer polyimide only
> boards.
> Inner layers test out with no problem. Immediately after outer layer etch
> there are the shorts. Omega meter testing shows no ionic contamination at
> this stage. Baking prior to ET reduces the number of shorts, although
> after
> a few days the shorts are back. Construction of board is foil copper at
> lamination, not cap-core.
>
> As usual, any and all help is greatly appreciated.
>
> Russ
>
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