I have to agree with Jeffery and Susan. A degree of roughness is normal and
solder leveling smoothes the hole so you would not notice it typically. Any
of the electroless processes will tend to make moderate roughness visible.
That being said, it is still a matter of degree of roughness that is of
concern.
Your question was "Does this impact on current carrying capacity?" The
answer to that question is that, if the copper plating is within your
thickness specification, then the roughness of itself will not impact
current carrying capacities.
Macroscopically (say 50X) the back lit hole with an electroless finish
should look rough but round, maybe nodular or striated, but defiantly not
like a "star shaped cookie cutter center" with spikes, posts, or flakes of
copper sticking in from the edge of the PTH. Be concerned if the minimum
hole size is violated.
I believe that microsectioning in this case is prudent. Measure the
thickness of the copper in the thinnest part of the hole and expect it to
measure greater than .0008". Next, look for gouges in the barrel of the
hole caused by drilling or etchback and expect them to be .001" or less.
Drill gouges are not usually an issue, even if they are large (.002"), but
they usually are not greater than .001" either. If you find very large
drill gouging or very thin plating a flag should go up and a MRB review is
in order.
The picture posted looks normal.
Paul Reid
PWB Interconnect Solutions
-----Original Message-----
From: Jeffrey Bush [mailto:[log in to unmask]]
Sent: Monday, January 24, 2005 9:21 AM
To: [log in to unmask]
Subject: Re: [TN] Silver plated barrel? does it reduce current carrying
ability?
This is actually how a copper plated barrel looks. Some what rough
drilling, but not an issue unless there are voids in the plating.
Immersion coating like tin and silver are thin and will represent the
barrel topography. Solder levels the barrel and masks the topography of
the walls.
Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice: 802.257.4571.21 Fax: 802.257.0011
http://www.vtcircuits.com
-----Original Message-----
From: Matthew Lamkin [mailto:[log in to unmask]]
Sent: Monday, January 24, 2005 6:44 AM
To: [log in to unmask]
Subject: [TN] Silver plated barrel? does it reduce current carrying
ability?
I have just noticed the barrels on some boards that we now get silver
plated instead of tin plated so as to be lead free.
I can clearly see the laminate strands through this hole and many others
on the boards.
What difference is this from an ordinary tin plated hole?
looking at older boards, I can see nice shiny & flat holes & no ridges.
Is there something wrong with the holes that have been silver plated or
would they look like this anyway?
What impact does this have on the current carrying ability of a plated
hole?
I have managed to get a picture taken of one hole to indicate what I'm
on about.
http://www.ukxboxgamers.co.uk/BARRELL.jpg
Thankyou,
Matthew Lamkin.
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