Lead Width on Axial Through Hole

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

   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".

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
jameshead Members Profile Send Private Message Find Members Posts Add to Buddy List Expert User Joined: 20 Mar 2012 Location: Oxfordshire, UK Status: Offline Points: 576	Post Options Post Reply Quote jameshead Report Post Thanks(0) Quote Reply Topic: Lead Width on Axial Through Hole Posted: 07 Mar 2013 at 2:40am
	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".



Jeff.M Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 16 May 2012 Location: San Diego Status: Offline Points: 477	Post Options Post Reply Quote Jeff.M Report Post Thanks(0) Quote Reply Posted: 07 Mar 2013 at 9:11am
	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.

jameshead Members Profile Send Private Message Find Members Posts Add to Buddy List Expert User Joined: 20 Mar 2012 Location: Oxfordshire, UK Status: Offline Points: 576	Post Options Post Reply Quote jameshead Report Post Thanks(0) Quote Reply Posted: 07 Mar 2013 at 9:14am
	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.

jameshead Members Profile Send Private Message Find Members Posts Add to Buddy List Expert User Joined: 20 Mar 2012 Location: Oxfordshire, UK Status: Offline Points: 576	Post Options Post Reply Quote jameshead Report Post Thanks(0) Quote Reply Posted: 11 Mar 2013 at 7:33am
	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 Example: DIOAD800W52L600D150B Diodes, Non Polarized Axial Diameter; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50 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.

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: 15 Mar 2013 at 8:24pm
	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"

Naveed Khan Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 12 Mar 2013 Location: India Status: Offline Points: 20	Post Options Post Reply Quote Naveed Khan Report Post Thanks(0) Quote Reply Posted: 18 Mar 2013 at 1:52am
	Hi Tom, How to calculate pitch for axial lead components? IF mounted horizontally and vertically?

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: 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...

jameshead Members Profile Send Private Message Find Members Posts Add to Buddy List Expert User Joined: 20 Mar 2012 Location: Oxfordshire, UK Status: Offline Points: 576	Post Options Post Reply Quote jameshead Report Post Thanks(0) Quote Reply Posted: 20 Mar 2013 at 8:41am
	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)

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(1) Quote Reply Posted: 20 Mar 2013 at 12:31pm
	I agree that we need to clarify Wmax for hole calculation and Wnom for Footprint Name.