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December 2000

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Thu, 14 Dec 2000 20:22:11 EST
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Wow!  Such a simple question has so many answers.
A wedge void occurs usually at the prepreg inner layer interface.
It is due to plating salts or desmear product being trapped at this interface
and
"poisoning" subsequent plating operations.

As for the cause:
1)  Uncured prepreg
2)  Too much resin "squeezed out" of the prepreg
3)  Drilling feeds and speeds not optimized (usually indicated by the
presence of nailheading)
4)  Too aggressive of a desmear or etchback chemistry
5)  Adhesion promoting properties of the inner layer foil being attacked more
aggessively by the desmear or etchback chemistries

These are just a few of the causes.

Unfortunately there are as many causes as you have steps in the process

Susan Mansilla
Technical Director
Robisan Lab

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