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Draft IPC-7351C

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Category: General
Forum Name: General Discussion
Forum Description: general topics not related to other forums
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=2052
Printed Date: 21 Dec 2024 at 8:21pm


Topic: Draft IPC-7351C
Posted By: ransonjd
Subject: Draft IPC-7351C
Date Posted: 06 Jan 2017 at 7:43am
Is there any way to obtain/buy the draft version of IPC-7351C? 

While PCB Libraries serves most of my footprint generation needs, there are some footprints with odd body shapes that I make by hand. 

I would like to use the same set of rules that PCB Libraries is automatically applying to the rest of my library.

I hope this isn't a bother, but this is the only place I know to ask. Are there any updates to the status of IPC-7351C?

Best regards,
John



Replies:
Posted By: Tom H
Date Posted: 30 Sep 2017 at 8:34pm
There is no news, at this time, on IPC-7351C progress. 

Right now the status category is "Proposal" and there is no release date scheduled (yet), no committee meetings are scheduled with an agenda and there is no set date to vote on the existing working draft (that only committee members have access to). 



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Posted By: Tom H
Date Posted: 28 Dec 2019 at 12:30pm

Why is IPC-7351C not released yet?

During the creation of the first draft, the main committee met face to face for 3-days several times a year and large sections of the draft were worked on by individual members and sent to IPC for update. It wasn’t until the main draft was completed that the sub-committee was invited to webcasts to review the new standard.


When IPC-7351 was first drafted, there was a main committee of dedicated people:

Dieter Bergman (IPC Leader in Standards Technology) – Deceased

Vern Solberg (Technical Consultant Specializing in SMT) – Left the Committee

Gary Ferrari (Ex Vice Chairman)  – Left the Committee

Rainer Taube (FED Director of Standardization) – Left the Committee

John Perry (IPC Liaison) – Left the Committee

Karen McConnell (Current Chairman) – In the process of retiring

Tom Hausherr (President & CEO of PCB Libraries, Inc.) – Still on the 1-13 Land pattern Committee since 1999

Tom, Rainer and Dieter met at IPC headquarters the week of July 14, 2014 for 3 days. We decided to rewrite 7351C into a new updated format because prior updates to IPC-7351 were simply added to the end and Dieter wanted a fresh new rewrite that organized all the component families into special groups according to pin quantity. We wanted to add color to all the graphic images because all previous versions were printed in Black & White. Update the naming convention to include Thermal Pad Sizes and Terminal Lead Sizes which impacted the resulting land pattern. We wanted to add the Zero Orientation “Pin 1 Lower Left” to match the original IPC-SM-782 land pattern standard and the new IEC 61188-7 standard for Pin 1 location. Introduce Rounded Rectangle pad shape and add additional component families. All of these issues were discussed and organized into an outline that clearly described the work that was required for the 7351C rewrite.


Tom left IPC on Thursday July 17, 2014 with the framework and a to do list from Dieter Bergman. Less than one week later, Dieter Bergman passed away on Wednesday July 23, 2014. Using Dieter’s instructions, Tom went to work on 7351C and spent over 1,000 hours to create the original 109-page 7351C draft that was submitted to IPC in June 2015. The sub-committee then met via 1-hour webcasts. The original comments were to change some images and content and Tom went back to the draft for another 6 months to make the updates proposed by the sub-committee. Tom submitted draft 2 of 7351C in May 2016 to IPC. The sub-committee reconvened for 1-hour webcasts for the next 3 years. A recent decision by IPC was made to scrap Tom and Dieter’s 7351C draft and start over from scratch using the IPC-7351B as the base starting point.


A revision to an IPC standard must be drafted, reviewed and approved by a base group of the sub-committee who attends the webcast meetings. Then the final draft is sent out to the entire sub-committee to vote on the revision details. All changes are highlighted so the sub-committee knows all the data that was updated. Since the main sub-committee group does not participate in the regular webcasts, when the final draft goes out, it’s the first time they have seen it. They are given 30 days to vote on the changes. During the voting process, every member has the opportunity to question the changes and submit alternate changes. The draft then goes back to the base sub-committee to address all the questions and additional changes. After the base subcommittee adds the additional comments and recommendations to the standard, a new final draft is created and sent back out for another 30-day committee vote. Normally, this final draft gets approved and then the draft is sent to a typesetter to officially organize the draft into a document that is ready to publish. This process can take up to 3 months or longer depending on the scope of the changes.


Basically, it takes almost a half year to go to publication after the first draft is sent to a sub-committee vote. The IPC-7351C draft is still in committee and sending it out for vote is not on the calendar schedule yet.



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Posted By: tgross
Date Posted: 12 Jul 2021 at 3:25pm
Originally posted by Tom H Tom H wrote:

Tom left IPC on Thursday July 17, 2014 with the framework and a to do list from Dieter Bergman. Less than one week later, Dieter Bergman passed away on Wednesday July 23, 2014. Using Dieter’s instructions, Tom went to work on 7351C and spent over 1,000 hours to create the original 109-page 7351C draft that was submitted to IPC in June 2015. The sub-committee then met via 1-hour webcasts. The original comments were to change some images and content and Tom went back to the draft for another 6 months to make the updates proposed by the sub-committee. Tom submitted draft 2 of 7351C in May 2016 to IPC. The sub-committee reconvened for 1-hour webcasts for the next 3 years. A recent decision by IPC was made to scrap Tom and Dieter’s 7351C draft and start over from scratch using the IPC-7351B as the base starting point.


Tom,


Have there been any changes since this update on 2019-12-28? If not, is there somebody you would recommend writing to to get things moving on approving your draft?


Unfortunately I'm just a lowely professional PCB designer rather than somebody who has any real pull, but I'm sure I (or anyone) could at least show that there is demand for a new update to 7351. We have already been using thermal pads in the name, different silkscreen outlines, and rounded rectangle pads in our work for a year (as described in  http://www.pce-oc.org/archive/What_is_New_in_IPC-7351C_03_11_2015.pdf" rel="nofollow - http://www.pce-oc.org/archive/What_is_New_in_IPC-7351C_03_11_2015.pdf https://docs.google.com/viewer?url=http%3A%2F%2Fwww.pce-oc.org%2Farchive%2FWhat_is_New_in_IPC-7351C_03_11_2015.pdf&embedded=true&chrome=false&dov=1" rel="nofollow"> ) and would love for it to finally be official.


So, let me know who I or anyone can talk to, so we can hopefully help get things moving.


Side note - I am 100% in favor of completely removing any reference to mils from the spec. With 95% of SMT parts giving their dimensions in mm, I don't think there are many people who still do their footprints in mil (even though they might route with them, and it's worth removing them to reduce unnecessary clutter in the spec.


Thanks,

Trevor



Posted By: Tom H
Date Posted: 12 Jul 2021 at 3:36pm
IPC is hosting "IPC SummerCon" in Milwaukee, WI next month and there will be a standards meeting on IPC-7351C. 

I missed the last 2 webcast meetings due to interruptions (full schedule). 

But even if IPC completes their editing of the 11 year old 7351B, it will take several months to get it through ballot vote and several more months to typeset. So we're looking at a 2022 release. 

Even when they do release it, it's not going to be much different than 7351B. The "What's New in IPC-7351C" went to the wayside. IPC dumped it. 

If you want some good standard data on Thermal Pads, buy the IPC-7093A for BTC package technology. It was released 2 months ago. I worked on that committee 3 years ago. Good stuff. 



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Posted By: tgross
Date Posted: 12 Jul 2021 at 3:43pm
Thanks for the quick reply Tom, and for the tips. Sorry to hear that your hard work went to waste, if there's something we could do to get it back on track I'm sure lots of people would be happy to help.


Posted By: cioma
Date Posted: 13 Jul 2021 at 1:17am
Well, I think Tom's and other's work brought us the fruit of Library Expert which in my view is becoming an industry standard tool.


Posted By: Tom H
Date Posted: 13 Jul 2021 at 8:53am
We took the IPC-7351 as a base standard for the mathematical model for auto-generation of a solder pattern from package dimensions. We also used the 7351 solder joint goals from 2005 - 2011. 

But after taking the IPC-J-STD-001 training class, we quickly realized that the solder joint goals in the 7351 were hand me downs from the 1980's and J-STD-001 contradicts 7351 solder joint goals. So we incorporated Toe, Heel and Side goals to align with J-STD-001 and called that "Incremental Pad Stacks". Example: the toe value of a Gull Wing lead should not be any longer than the terminal lead thickness. This varies with each pin pitch, so one Toe value is not the best solution for every Gull Wing terminal. 

We used the original 7351 land pattern naming convention and started collecting millions of package dimensions, only to find out that the original naming convention created massive duplication producing the the land pattern name for packages with similar but different dimensions and tolerances. So we created the extended naming convention which removed duplication and created a new naming convention for connectors and non-standard packages. 

We used the original 7351B Zero Component Orientation where pin 1 was Upper Left. Then IEC produced the IEC 61188-7 world standard for Zero Component Orientation with Pin in the Lower Left. This makes perfect sense as the length of the package and solder pattern should be long in the X direction to follow the PCB layouts that are normally long in the X direction because all the paper sizes are long in the X direction. And the IPC-SM-782 standard from 1987 - 2005 had Pin 1 in the lower left and IPC-7351 changed it for no logical reason. 

Our suite of tools incorporates the best standards from the global industry and common sense. 



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