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Date: | Sat, 04 May 96 08:15:07 EST |
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Kevin,
The definition of wedge voiding that I'm familiar with is a defect
located at the plated through hole where the oxided layer meets
perpendicular to the plated barrel of the hole. (I have never heard
of the ends <or tails> of nailheading called that before)
--[===| |===]--
| | | |
======|< >|===== ========<| |
| | ^Oxided | |
======|< >|===== InnerLayer
| | Wedge void @ PTH interface
--[===| |===]--
On this <crude> 4 lyr diagram
the "<" and ">" would indicate where the
wedge void could be.
An improperly drilled hole may produce a small gap at that location
as attempted to depict above.
During <acidic> wet processing solution works it way up the innerlayer
oxided copper area surrounding the drilled hole and can dissolve oxide
<hence pink ring but lets leave that one alone>. If the size of the
gap <or wedge> is sufficient to trap air bubbles or chemistries, there
would not be ample coverage for proper copper plated through holes.
Cross section analysis could produce circumferential voiding or copper
plated through hole thickness less than .0008" <isolated>.
Are others calling the <absence of> ends of the nailheading not taking
plating wedge voids?
Groovy
______________________________ Reply Separator _________________________________
Subject: Re: Fab-Re: More nailheading
Author: [log in to unmask] at SMTPLINK-HADCO
Date: 5/4/96 2:42 AM
Dear Phil:
As you indicated, the potential for circumferential voiding exists in any direct
plating process that would remove the underlying copper from the conductive
deposit. This condition is commonly referred to as wedge voiding, as it exhibits
itself as a wedge shaped defect in cross sectional examinations. Further, this
condition manifests itself typically on the oxide treated surface of the foil
only.
Actual production using palladium based direct plating systems can occasionally
exhibit this defect, but the liklihood is not very great. Further, because
palladium systems can modify the process sequence to incorporate microetching
prior to conditioning, the chance of the defect occuring is further reduced.
Finally, substituting double treat foil for oxide treated foil will eliminate
the chance of wedge voiding in all but the most severe cases.
Kevin H. Baranowski
Atotech USA Inc.
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