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Round off in footprint expert calculator

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=3415
Printed Date: 06 Oct 2024 at 10:21am


Topic: Round off in footprint expert calculator
Posted By: eaglor
Subject: Round off in footprint expert calculator
Date Posted: 28 Aug 2024 at 10:20am
Hi All

I am using the Footprint Expert SMD Reference Calculator.xlsx. 

I have a question about the round off when calculating the footprint pad size and spacing. 

Why does it round the C(Center to Center Spacing) and X value, not the ZMax and GMin value? 

Is it compliant with IPC7351B standard?

Thanks


Replies:
Posted By: Tom H
Date Posted: 28 Aug 2024 at 10:39am
You should download and install the V24.10 Footprint Expert Calculator to get better results. 

http://www.pcblibraries.com/downloads" rel="nofollow - www.pcblibraries.com/downloads



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Posted By: eaglor
Date Posted: 28 Aug 2024 at 10:41am
Hi Tom,

Thanks, Does the "V24.10" round the ZMax and GMin value, not the C and X value?

Posted By: eaglor
Date Posted: 28 Aug 2024 at 10:44am
I am comparing the formula difference between Altium Designer and Footprint Export, just want to know which one is better? which value should be round to compliant with the B standard. 

Posted By: Tom H
Date Posted: 28 Aug 2024 at 1:41pm
Altium uses the original 2005 IPC-7351 release. 

V24.11 Footprint Expert uses a combination of these standards and guidelines:
  • IPC-7351B (Mathematical model)
  • IPC-7352 (Pad Stack naming convention)
  • IPC J-STD-001 (Solder Joint Goals)
  • IEC 61188-7 (Zero component orientation) 
  • IPC-7093A (Solder mask defined thermal pads)



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Posted By: Tom H
Date Posted: 28 Aug 2024 at 1:46pm
After calculation of a footprint, select the Footprint panel > Calculation Details. 



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