Decimal Precision in Physical Description

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   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

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AGONZ67 Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 30 Mar 2012 Status: Offline Points: 119	Post Options Post Reply Quote AGONZ67 Report Post Thanks(0) Quote Reply Topic: Decimal Precision in Physical Description 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



Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply 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.