Duane,
I have also been in this situation.
Check the manufacturers data sheet.
Somewhere in the fine print should be a statement along the lines of
"Controlling dimension : inches" or "Controlling dimension : millimetres"
Of course the wording may differ between manufacturers but it indicates
which set of dimensions are "accurate" and which are "approximate".
Best Regards,
LINDEN DOYLE
Product Development Engineer
Zener Electric Pty Ltd
[EMAIL PROTECTED]
Ph: +61 2 9795 3600
Fax: +61 2 9795 3611
-----Original Message-----
From: Duane Hague <[EMAIL PROTECTED]>
To: Multiple recipients of list proteledausers
<[EMAIL PROTECTED]>
Date: Sunday, 4 March 2001 11:17
Subject: [PROTEL EDA USERS]: Confused Newbie on Footprints
>Here is hoping that some knowledgeable "old hand" could point me in the
>right direction. Or have I just stumbled into the rabbit hole? I am now
>starting to understand the problems with footprint libraries and why "you
>do your own" but am very confused about one area of detail. Any help would
>be greatly appreciated. It appears to me that no one is very consistent
>about the use of metric/"english" measurements in their package definitions
>(specifically with reference to pin pitch). For example, on QFPs the same
>manufacturer will refer to a part as having a 25 "mill" (0.025 inch) pin
>pitch and then provide a package drawing in metric showing a pitch of 0.65
>millimeters "Typical" (and the other dimensions on the drawing indicate
>that the original was in "inches" and then converted to metric). Since "25
>mill" is actually 0.635 millimeters; after about ten linear pin pads, the
>pin is no longer on the pad. Which reference measurement does one use? Do
>different manufacturers use different meanings when talking about pin
>pitch? Are there some hidden "rules" about this to confuse newbies? Is
>this a problem only for older parts? Or does this whole question
>demonstrate how ignorant I am???? Any wisdom would be welcome. Cheap
>shots will be evaluated on their humor level.
>
>Thanks in advance,
>Duane Hague
>
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