David,
Your supplier, if they do stressed sections on each lot, should see this
before they ship. My guess is smear, which occurs during drilling, and
should be removed by a chemical or plasma desmear process. Ask for
cross-section mounts from these lots and see if you observe any
separation.
Good Luck,
Rick Howieson
General Technology Corp.

>-----Original Message-----
>From:  Smith, David V. [SMTP:[log in to unmask]]
>Sent:  Wednesday, April 19, 2000 3:34 PM
>To:    [log in to unmask]
>Subject:       [TN] PCB question
>
>A question for the PCB gurus:
>
>We have been receiving boards from a supplier that are exhibiting
>separations at the interface between plated hole wall and internal layers
>(a.k.a. interplane separations, post separations, interconnect defects) in
>cross-section, after thermal stress. Specifically, the separations are
>occurring between the electroless copper and electrolytic copper. Horizontal
>cross-sectioning reveals that the location of the separations is consistent
>from hole to hole. For example, in a grouping of holes viewed in horizontal
>cross-section, the majority of holes will show the separation extending from
>the 6 o'clock position to the 11 o'clock position. Any suggestions on what
>process/processes the vendor should look to for troubleshooting?
>
>Thanks,
>David Smith
>Benchmark Electronics
>
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