Lead Width on Axial Through Hole
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=875
Printed Date: 06 Oct 2024 at 12:20pm
Topic: Lead Width on Axial Through Hole
Posted By: jameshead
Subject: Lead Width on Axial Through Hole
Date Posted: 07 Mar 2013 at 2:40am
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The PDF for IPC-7251 states: W = Maximum Lead Width (or Component Lead Diameter) In Through Hole > Axial though users have to enter both Min and Max values for b and the calculated footprint name uses the nominal value for b, for W, and not Maximum Lead Width as I expected. IPC-2222 says "no greater than 0.7 mm (level A) over minimum lead diameter" so I guess that's why FPX has a mandatory field for a Min value for b in Axial (?) but if I'm creating a footprint in a program like FPX I am more concerned with the maximum lead diameter and the "No less than 0.25 mm over maxium lead diameter". |
Replies:
Posted By: Jeff.M
Date Posted: 07 Mar 2013 at 9:11am
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A maximum value is required to calculate the hole. A minimum value is required to get the nominal value which is used in the footprint name.
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Posted By: jameshead
Date Posted: 07 Mar 2013 at 9:14am
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Hi Jeff, thanks for the reply. My observation is that the PDF guide for IPC-7251 says: W = Maximum Lead Width (or Component Lead Diameter) So, W should be taking the maximum and not the nominal dimension. |
Posted By: jameshead
Date Posted: 11 Mar 2013 at 7:33am
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This behavour in FPX hasn't changed in the v47 Beta today. The PDF guide for IPC-7251 naming says: Diodes, Axial Diameter Horizontal Mounting .......................................DIOAD + Lead Spacing + W Lead Width + L Body Length + D Body Diameter And on page 3: W = Maximum Lead Width (or Component Lead Diameter) The way I read this was that W is always the Maximum whether it's the lead width or component lead diameter, but Jeff's saying W is nominal. |
Posted By: Tom H
Date Posted: 15 Mar 2013 at 8:24pm
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The Calculator requires Maximum to determine the hole size per IPC-7251 (which is currently on the table by IPC for review for release (finally)). The component dimensions require the Minimum so the Calculator can determine the value for the Footprint name. Every value in the Footprint Name is a "Nominal" component package dimension with one exception - "Height" |
Posted By: Naveed Khan
Date Posted: 18 Mar 2013 at 1:52am
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Hi Tom, How to calculate pitch for axial lead components? IF mounted horizontally and vertically? |
Posted By: Tom H
Date Posted: 18 Mar 2013 at 6:27am
The PCB Footprint Expert has a "Utilities" button in the Main Toolbar. Select the "Axial Leadform Calculator" option and this menu will appear -  I hope this helps... |
Posted By: jameshead
Date Posted: 20 Mar 2013 at 8:41am
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I understand but I think the PDF for the PCB Libraries Footprint Naming Convention for Standard TH Components on page 3 confuses users since it says: W = Maximum Lead Width (or Component Lead Diameter) |
Posted By: Tom H
Date Posted: 20 Mar 2013 at 12:31pm
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I agree that we need to clarify Wmax for hole calculation and Wnom for Footprint Name. |