Message
I
think the quote you are looking for is Paragraph 9.2.6 of
IPC-2221.
"9.2.6 Aspect Ratio The aspect ratio of
plated-through holes plays an important part in the ability of the manufacturer
to provide sufficient plating within the plated through
hole."
What
the aspect ratio is however is not included in the statement. The calculation I
prefer to use is maximum board thickness to
minimum drilled hole size, i.e. an 62mil overall PCB has a
maximum thickness of 69mil, so that a 20mil nominal finished hole
could be drilled at 20mil and have a ratio
of ~2:7.
Thomas,
During the design of a PCB the total thickness will
guide you as to what is the smallest size drill you can use to ensure that
adequate plating is placed on the barrel of a PTH. This is the
DOCUMENT that I have been searching for.ie ASPECT RATIO. If
this guideline is violated there is a potential for LOW plating in the
barrel. I recall the document. However I need to make
a QUOTE to it. Therefore, I need to review the page and verse once
again.
victor,
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