>> " Unplated holes have to be drilled after the plating process
because the plating process will plate any exposed PCB surface."
If you have exposed PCB surfaces (i.e. copper) inside a non-plated hole
you should check your design. There shoudn't be any exposed copper
(top/bottom or plane edges in a non-plated hole). The rest of the
comments are correct in that non-plated holes add cost via extra steps
to the PCB fabrication.
However, most pre-processing of gerber files nowadays is automated. I
have tried to sneak non-plated holes through a 'special of the day'
process with mixed results. Sometimes it works, sometimes they come
back with 6mil annular rings and plated.
For those who don't know, an annular ring (circle of copper) is required
to produce a plated-thru hole. The landings provide anchors for the
plated barrel to adhere to. Without them the barrel may not form
correctly, or may just fall out at a later time.
Also, drill sizes are adjusted differently for plated and non-plated
holes. Plated holes are over-drilled, and the plated process brings the
hole back down to the designed size. Non-plated holes are drilled at
the desired size. PCB house don't want to deal with this problem unless
they are getting paid to do it so they *may* turn all non-plated holes
into plated.
The following houses have definitely turned non-plated holes into plated
by adding an annular ring (contrary to the previous poster). And they
did not tell me about it before doing it.
sfcircuits.com
pcbfabexpress.com
The following house did it at no extra cost even though the
specifications said they would not.
ultimatepcb.com
On 5/28/2010 9:03 PM, David Kelly wrote:
On May 28, 2010, at 4:33 PM, Jon Varteresian wrote:
> Without seeing the actual gerbers I can't be 100% sure but more than
> likely his fab house added that annular ring in order to make it a
> plated hole. unplated holes cost more for some reason (probably the
> stencil costs) so board houses take your unplated holes and add a small
> annular ring in order to plate them. The lower prototype 'specials'
> usually don't allow unplated holes.
Unplated holes have to be drilled after the plating process because
the plating process will plate any exposed PCB surface. Or if drilled
with the other holes the unplated holes must be masked manually to
prevent plating, and unmasked manually after. Either way it costs more
than a plated hole.
I seriously doubt the PCB shop added an annular ring as that is just
more labor.
--
David Kelly N4HHE, [email protected] <mailto:dkelly%40HiWAAY.net>
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Whom computers would destroy, they must first drive mad.
