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From: | |
Date: | 4 Nov 96 12:16 CST |
Content-Type: | text/plain |
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I've got a set of questions for the distinguished body.
It regards to specifying the finished diameters of non-plated holes on
PCBs.
1. What is the tightest finished hole size tolerance I can
reasonably specify for volume production. Is this a function of hole
size.
2. I have a standard table of drill bit sizes. Does the PCB
industry have custom drill bit sizes or are these all in the
standards? If there are custom sizes are these published anywhere?
3. For a given drill bit size, what will be the nominal finished
hole size drilling in a typical FR-4,.062" thick PCB?
4. Is there a table of the different values of nominal FINISHED
holes sizes for non-plated through holes.
My problem is that often I need to specify tight tolerance holes and I
need to know the "sweet spots" of finished hole sizes for these holes.
For example I might desire to specify a hole .093" +/- .001", not
knowing that there is no drill size near this size. Or if there is a
drill size, I might not know that if I drill at a given size the
finished hole shrinks slightly. I need to understand this to
understand the "sweet spots" for tight tolerance hole sizes.
I'd appreciate any feedback.
Thanks,
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