I am wondering if anyone has a good method of marking rejects on internal layers of PCB's such that they are detectable on the external layers.  We are a flex-circuit manufacturer and this has not been a problem on lower layer counts, but more opaque materials make internal marking hard to detect.  Keep in mind that these rejects are not always opens or shorts, but may be pattern width or spacing violations.

Any help would be appreciated

Dave Kell
Product Assurance

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