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Date: | Thu, 17 Aug 95 13:40:49 CST |
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I have an upcoming high volume product that requires a very tight
tolerance on the bare PCB.
I need to locate the center of 3 non-plated holes of 2mm diameter to
+/- .004" X/Y tolerance to an etched feature.
The etched feature is square and is on one of the outside layers of
the board.
These holes are used to mechanically align a component to copper
features on the board.
Improper alignment will result in massive shorts or opens.
My questions are as follows:
1. For standard processing what tolerances are typical for NPTH to
etch feature registration on a PCB. My experience is that it is
somewhat greater than +/-.004" for standard processing.
2. Is there special automated equipment (or a process technique) that
is available for high volume production (i.e. more than 10K per month)
that can improve this tolerance? For example I have heard of optical
drilling equipment that can drill a hole with great precision relative
to an etch feature, much like a pick and place machine locates a SMT
part to a fidicual. I've "heard" of it, but never seen it or talked
to equipment manufacturers.
3. Is there any equipment out there that can measure this dimension?
(i.e. the center of a non-plated hole to the center of a square copper
pad).
I'd appreciate any insights or comments.
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