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Date: | Thu, 02 Jan 97 14:53:00 CST |
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This may sound like splitting hairs, but I think there is some confusion
(maybe only on my part) about whether the finished or the drilled hole
size should be used. In the example below, if the .020 diameter is the
nominal finished hole size and the hole is drilled .025 diameter, the
aspect ratio based on the drilled hole would be 2.4 to 1. IPC-T-50E
defines aspect ratio as "The ratio of the length or depth of a hole to
its preplated diameter". I assume this means that the drilled hole size,
not the finished hole size, should be used.
>From the designers' viewpoint, using the finished hole size would be more
convenient, since this is what is usually specified. The drilled hole
size is up to the fabricator.
Nick Wander
Printed Circuit Engineering
Unisys Corporation
Roseville, MN
[log in to unmask]
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From: David Bergman[SMTP:[log in to unmask]]
Sent: Tuesday, December 31, 1996 10:05 PM
To: Isaac Stringer
Cc: [log in to unmask]
Subject: Re: Aspect Ratios
Sure,
Aspect ratio is the thickness dimension of the PWB divided by the
diameter dimension of the plated thru hole. So an 0.060 inch thick pwb
with a 0.020 inch diameter pth would have an hole aspect ratio of 3 to 1.
Regards
__________________________________________________
David W. Bergman, V.P. of Technical Programs
IPC
2215 Sanders Road
Northbrook, IL 60062-6135
847-509-9700 x340 Phone
847-509-9798 Fax
email [log in to unmask]
www http://www.ipc.org
faxback support 800-646-0089
---------------------------------------------------
On Tue, 31 Dec 1996, Isaac Stringer wrote:
> Greetings:
>
> Would someone be so kind as to explain 'aspect ratios' in a way
> that will make sense to someone who understands hole sizes and
> trace width/space?
>
> Thank you!
>
> Isaac Stringer
> KML Engineering Corp.
> [log in to unmask]
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