Dear Werner,

Thank you very much for your input, this sounds like a tough defect to
find!

What about what could happen within a via on the bare board?

I seen voids but usually not detectable by ET as it was to small in surface
proportion.

What about annular rings that were non-plated (the bubble effect /
entrapped gas bubbles), partial or complete, do we have some ET information
on those?
On blind or buried vias?

Meilleures salutations
Very Best Regards
Rol@nd

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, June 05, 2006 1:11 PM
To: [log in to unmask]
Subject: Re: [TN] Cracks in Holes / Barrel rupture total or partial

Hi Roland,
There was some work done by IBM [I think in Minneapolis] in the late 80's.
I
showed that a full barrel crack needed to have at least a 90% physical
separation before a significant resistance increase could be measured. That
is why
testing for barrel cracks is done in situ, or after the test a some
elevated
temperature. At room temperature barrel cracks are essentially electrically
invisible; perhaps signal degradation could be found with high-frequency
signals.

Werner

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