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Courtyard Excess Value For Non Standard Packages

Printed From: PCB Libraries Forum
Category: Libraries
Forum Name: Footprints / Land Patterns
Forum Description: [General or a CAD specific issues / discussions]
URL: http://www.PCBLibraries.com/forum/forum_posts.asp?TID=2509
Printed Date: 08 Mar 2021 at 6:16am


Topic: Courtyard Excess Value For Non Standard Packages
Posted By: Batiskaff
Subject: Courtyard Excess Value For Non Standard Packages
Date Posted: 03 Jul 2019 at 3:24am
What are the general recommendation for values of Courtyard to Body and Courtyard to Pad Excesses for non-standard packages?
For example:
https://media.digikey.com/pdf/Data%20Sheets/Cooper%20Bussmann%20PDFs/EM7117xx_Series.pdf" rel="nofollow - https://media.digikey.com/pdf/Data%20Sheets/Cooper%20Bussmann%20PDFs/EM7117xx_Series.pdf
https://www.cui.com/product/resource/pj-002a.pdf" rel="nofollow - https://www.cui.com/product/resource/pj-002a.pdf



Replies:
Posted By: Tom H
Date Posted: 03 Jul 2019 at 7:18am
Nominal Density Standard Components use a 0.20 mm courtyard excess. 

Unique Non-Standard packages us a 0.25 mm courtyard excess, but if any dimension L, W & H are over 10.00 mm then we make the courtyard 0.50 mm to make room for rework equipment. This is mostly connectors. 



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Posted By: Batiskaff
Date Posted: 03 Jul 2019 at 9:08am
Thank you Tom.


Posted By: 5not4
Date Posted: 11 Jul 2019 at 8:33am
Tom,
 
Is this for revision B or C? It seems to me most nominal courtyards in the B version are .25mm.


Posted By: Tom H
Date Posted: 11 Jul 2019 at 8:42am
Over the past 5 years, we have been using these Courtyard Excess values for "Standard Packages" that were tested by customers and reported great results. This has nothing to do with IPC. 
  1. Most = 0.40
  2. Nominal = 0.20
  3. Least = 0.10
The original IPC-7351B Courtyard Values were created in 2004 and are now 15 years old. 

New technology for Assembly machines has improved placement accuracy down to +/- 0.01 mm. 

There is no need for a 0.25 courtyard as it consumes too much PCB real-estate for densely populated layouts. 

Also, IPC-7351 has been downgraded from a "Standard" to a "Guideline" and is not to be taken literally. 

You must use your own common sense and advice from your assembly team to create your design rules. 




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