Looks like you missed part of what Ian was saying there...

Let me try to expand on that:
It could have been
a) skipped by electroless Cu plating and therefore not 
electrolytically plated at all.
b) If it was first plated fine by electroless and then successfully 
electrolytic plated. It could then be etched out down to base 
dielectric if there was skip in the etch resist plating.

In either case it would show a bare dielectric in the hole wall. They 
will have different copper shape leading into the void though 
depending on source of the missing copper.

Once more with feeling: A picture is worth a thousand words. Of a 
cross-section that is...


At 01:18 PM 3/23/2012, [log in to unmask] wrote:
>It is a base dielectric material.  The plating portion of the wet 
>process begins with an electroless Cu bath.
>
>
>
>----- Forwarded Message -----
>From: Ian Hanna <[log in to unmask]>
>To: "[log in to unmask]" <[log in to unmask]>
>Sent: Friday, March 23, 2012 12:47 PM
>Subject: Re: [TN] plating void
>
>do you mean base dielectric material, or base copper material -- an 
>electrolytic  copper plating void will still leave the base copper 
>intact  if it is caused by a bubble -- what is the shape of the 
>edges, is it tapered or rounded -- is the void in the centre of the 
>hole or towards the outside? any photos? could be electroless copper 
>void electrolytic copper void tin void dry-film residue
>From:  "[log in to unmask]" <[log in to unmask]>
>To:  <[log in to unmask]>
>Date:  23/03/2012 03:41 PM
>Subject:  [TN] plating void
>Sent by:  TechNet <[log in to unmask]>
>
>________________________________
>I'm looking for input on the following plating defect.
>
>I observe a plating void that occurs on a Cu plated feature with 
>ENIG finish.    The void goes down to the base material.  The defect 
>is typically .002 diameter.  The feature size is .010 across.  The 
>parts run on a manual plating line and hang on a small plating rack.
>
>The plating engineer believes the root cause of the void is a bubble 
>on the part during plating.  The action plan includes implementing 
>stronger vibration on the part in the plating bath.
>
>I have two questions.
>1.  How much vibration is typically needed to avoid developing a 
>bubble on a part during plating?
>2.  For this plating void defect, is it possible that Ni corrosion 
>or other reliability concerns would eventually develop if defective 
>parts escaped?
>
>Thank you,
>
>Mark Julstrom
>
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