Thanks for the response.

We have random failures on assemblies that have been
heated up, only on one batch of boards.
The guy doing the cross-section implied that he found this
almost by accident. By recommending a "referee" sample
are you saying we should we see the same thing in the
same spot on a different board (from the same lot)?

I'm curious how you could accept this condition on planes
and not suspect that there would be trace layers with the
same condition.

I'm not disputing what you say, just trying to understand...

Jack


On 2/7/08, Kerry Bode <[log in to unmask]> wrote:
>
> Jack,
>
> This condition is most likely to occur when the board fabricator was
> processing the inner layer. The resist coating used for imaging may have
> had an air pocket at that location causing a lifted resist condition.
> Then during the etching process the chemical etch solution undercut the
> resist. From my prospective this is an anomaly and is classified as an
> etch down condition. If the remainder of the sections do not exhibit the
> condition, a referee cross-section of the same serial number would
> acceptable. Based on the cross-section photo it appears to be a ground
> or power layer, if so IPC specification allowance for this condition.
>
> Regards
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
> Sent: Thursday, February 07, 2008 8:33 AM
> To: [log in to unmask]
> Subject: [TN] FAB: Thin Trace Failures
>
> Has anyone ever seen a cross-section like this?
>
> http://www.frontdoor.biz/PCBportal/opentrace.jpg
>
> (ignore the words on the pic, just a guess)
>
> Can you point me in the right direction for cause?
>
> thanks,
> Jack
>
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