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July 2004

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Subject:
From:
Franklin <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 12 Jul 2004 12:22:20 -0500
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Doubt such a document exists... Hole size is dependant on may factors,
especially once it reaches assembly.

Depending up the fabricators process a specific hole size, for example a
finished 0.035" hole may be drilled at 0.040" - 0.042" to allow for plating
and solder (HASL).

Now lets say they allowed the panel to remain in the copper plate tank for
an extra 10 minutes, this may add an additional 0.5 mil (0.0005) to the hole
wall, then the air knives during HASL are ever-so-slightly out of adjustment
and the allow for additional solder to remain in the holes...this has closed
the hole to 1 to 2 mils below nominal...so you see you cannot correlate a
given hole size (including allowable tolerances) to a specific pin
size...only a range...

Keep in mind also that if a given hole is 0.035" mils exactly...only a
0.034" pin (or less) will go in it (without causing damage)...

Franklin

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