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,

Product Development Engineer
Zener Electric Pty Ltd

Ph: +61 2 9795 3600
Fax: +61 2 9795 3611

-----Original Message-----
From: Duane Hague <[EMAIL PROTECTED]>
To: Multiple recipients of list proteledausers
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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