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Decimal Precision in Physical Description

Printed From: PCB Libraries Forum
Category: PCB Footprint Expert
Forum Name: Questions & Answers
Forum Description: issues and technical support
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=298
Printed Date: 06 Oct 2024 at 10:34am


Topic: Decimal Precision in Physical Description
Posted By: AGONZ67
Subject: Decimal Precision in Physical Description
Date Posted: 25 May 2012 at 1:21pm
I have noticed in the physical description field most dimensions are two places past the decimal, ie 3.20 x 1.60 x1.40, but there are several that are carried out to three places. This only refers to the description field as the examples shown below. IPC Standard is two places past the decimal point and include trailing zeros

PLCC127P1244X1244X457-28 Plastic Leaded Chip Carrier (PLCC), 1.27mm pitch;square,7 pin X 7 pin,12.445mm L X 12.445mm W X 4.57mm H body

TO254P1054X203-4 Transistor Outline (TO, DPAK),2.54 pitch;;3 pin,10.54mm L X 9.395mm W X 2.03mm Hbody

LEDDFN120X77X40-4 LED, Dual Flat No-Lead (DFN 4 Pins), 0.75mm pitch;4 pin,1.20mm L X 0.775mm W X 0.40mm H body
DIOMELF3515   Diode, Metal Electrode Face (MELF);3.50mm L X 1.525mm Dia
 
RESMELF3515   Resistor, Metal Electrode Face (MELF);3.50mm L X 1.525mm Dia
 
 


Replies:
Posted By: Tom H
Date Posted: 21 Oct 2012 at 2:46pm
If the package is originally a Inch Based part, the millimeter values are sometimes carried out 3 places to the right of the decimal point.
 
Eventually all packages will be metric based parts and this will automatically correct itself.
 


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