I strongly reccomend that you get a sample part from the manufacturer and
measure it yourself.  Also if their documentation is confilcting, a call
wouldn't hurt.

Mike
-----Original Message-----
From: TSListServer [mailto:[EMAIL PROTECTED]]On
Behalf Of Duane Hague
Sent: Saturday, March 03, 2001 3:58 PM
To: Multiple recipients of list proteledausers
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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