PCB Libraries Forum : IPC-7251 https://www.PCBLibraries.com/forum/ Sat, 04 Apr 2026 02:32:04 +0000 Thu, 26 Nov 2015 10:44:23 +0000 http://blogs.law.harvard.edu/tech/rss Web Wiz Forums 12.07 360 https://www.PCBLibraries.com/forum/RSS_post_feed.asp?TID=1798 <![CDATA[PCB Libraries Forum]]> https://www.PCBLibraries.com/forum/forum_images/PCBLForumLogo.gif https://www.PCBLibraries.com/forum/ <![CDATA[IPC-7251 : Library Expert only uses &#034;Hole...]]> https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7370.html#7370 Author: Tom H
Subject: 1798
Posted: 26 Nov 2015 at 10:44am

Library Expert only uses "Hole Over Lead" from IPC. Everything else uses the PTH Reference Calculator located here -

http://www.pcblibraries.com/forum/ipc7351-smd-pth-reference-calculators_topic785.html

]]> Thu, 26 Nov 2015 10:44:23 +0000 https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7370.html#7370 <![CDATA[IPC-7251 : Thanks, but I still confused on...]]> https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7366.html#7366 Author: drj-bbe
Subject: 1798
Posted: 26 Nov 2015 at 12:59am

Thanks, but I still confused on below two calculation method for a pad:
 
IPC-2221B calculation formula is:
Land size, minimum = Hole size + 2*Min. annular ring(Min 0.05mm) + fabrication allowance
 
IPC-7351C calculation formula will be:
Pad diameter = Hole size + 2*Min. annular ring(Min 0.2mm), or = Hole size * pad-to-hole-ratio, whichever is larger.
 
But calculated result will be different between above two calculation method, IPC-7351C defined a proportional annular ring, IPC-2221B defined same size annular ring even though hole size go up, right?
 
This is for minimum pad design, the annular ring seems smaller than normal, is there suggestion for normal pad size?
 
]]> Thu, 26 Nov 2015 00:59:16 +0000 https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7366.html#7366 <![CDATA[IPC-7251 : Set all the Through-hole user...]]> https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7365.html#7365 Author: Tom H
Subject: 1798
Posted: 25 Nov 2015 at 8:55pm

Set all the Through-hole user preferences -

Preferences > Terminals > Through-hole

The current default settings are from IPC-2221 but will also be in IPC-7351C.

]]> Wed, 25 Nov 2015 20:55:09 +0000 https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7365.html#7365 <![CDATA[IPC-7251 : Thank you very much. I have other...]]> https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7364.html#7364 Author: drj-bbe
Subject: 1798
Posted: 25 Nov 2015 at 7:45pm

Thank you very much. I have other questions below:
 
The calculation formula below for pad diameter is different with IPC-2221B 9.1.1, how to set "pad to hole ratio" and "minimum annular ring"?
http://www.pcblibraries.com/forum/ipc7351-smd-pth-reference-calculators_topic785.html
 
The calculation of pad diameter in IPC-7351C will not consider "Standard fabrication allowance" which in IPC-2221B Table 9.1, right?
]]> Wed, 25 Nov 2015 19:45:49 +0000 https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7364.html#7364 <![CDATA[IPC-7251 : The IPC Land Pattern committeedecided...]]> https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7361.html#7361 Author: Tom H
Subject: 1798
Posted: 25 Nov 2015 at 5:48am

The IPC Land Pattern committee decided a year ago to merge IPC-7251 for through-hole into the new IPC-7351C.

You can download several documents here - http://www.pcblibraries.com/downloads
  • What's New in IPC-7351C
  • Surface Mount Component Families
  • Through-hole Component Families
]]> Wed, 25 Nov 2015 05:48:09 +0000 https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7361.html#7361 <![CDATA[IPC-7251 : Hi all: I cannot find IPC-7251...]]> https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7360.html#7360 Author: drj-bbe
Subject: 1798
Posted: 25 Nov 2015 at 2:33am

Hi all:
 
I cannot find IPC-7251 in IPC website, it haven't released?
What is the standard for through hole land calculation in Library Expert?
 
Thanks in advance.
]]> Wed, 25 Nov 2015 02:33:03 +0000 https://www.PCBLibraries.com/forum/ipc7251_topic1798_post7360.html#7360