Most common reason for innerlayer shorts I have seen is inadequate etching of the Copper.
The reasons for inadequate etching can be many, but include (when etching with ammoniacal etch) tarnished Copper before etch.
Can also include poor/inadequate developing, defoamer which did not rinse.
On the tarnished Copper cause, this can often be so subtle that the panel can pass AOI, and still have a short...!

Rudy Sedlak
RD Chemical Company

"Bhaskar.C.S" <[log in to unmask]> wrote:
What are the various reasons for getting internal shorts in Multilayer Pcb's?


REGARDS

D.VENKATESWARLU

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