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IPC7351-C Draft or Release date?

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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 24 Sep 2019 at 10:34am
It may be Kris Moyer. Did he just go on IPC's payroll last month? 

Thank you for joining the sub-committee. They need some help with the 7351C. It's been dragging along for the past 5 years and the pace needs to be picked up to update the 9 year old standard. 

I'm still on the committee, but not attending the webcasts because over 50% of them in the past year have been canceled for one reason or another. 

There are 80 sub-committee members and only a small fraction attend the webcast meetings. Now they're looking for new members who are fresh and can jump start the progress. 

I spent over 2 years and 1,000 hours redesigning 7351C per Dieter Bergman's and Rainer Taube's recommendations. All new graphic images, new naming convention, new solder joint goals, new format, added through-hole technology. Now, it has officially been shelved to start over from scratch. 

Good luck.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2019 at 2:53pm
If they are going to start over on the Land Pattern Standard I wish they would take a different approach than the current "three density levels" scheme.
In my mind, for any particular solder joint there will be some theoretical "optimum" dimension that will be the strongest and most reliable. Adding extra paste or pad dimensions beyond this theoretical optimum would be diminishing returns and few would ever want to go bigger.
But MANY designers will want to go smaller, even to the point where the pad area is the same size as the lead area (like power pads under no-lead devices for example. Same size to same size used to be called "lap soldering", but I'm getting off the point I wanted to make. 

I think the IPC should only list TWO parameters for any particular lead style - OPTIMUM and MINIMUM. 
Unless I'm missing something, it seems obvious that any size pad that falls between those two extremes will be acceptable, and would be much easier to check than the current system. The three-tier system was interesting, and filled a need for high-density design, but doesn't make as much sense to me as a two-tier optimum/minimum scheme.
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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 27 Sep 2019 at 7:14am
I agree and the Japanese standards groups also agree that the Nominal Density level can pass all shock, vibration, stress and thermal cycle testing as the Most Density level. 

They ran these tests 6 years ago and reported their findings to Dieter Bergman. Dieter went to Japan to see the results of all the tests and came back to the states and held a conference call webcast. 

Dieter told all of us that there is no real need for the Most Density level except if you intend to manually solder the components to the PC board. 

Dieter made a suggestion to eliminate the Most Density level but the committee chairperson disagreed and recommended leaving it in the 7351 standard but commenting the suggested use for the Most Density level (hand soldering). 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tgross Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2021 at 3:54pm
It's been a bit over a year, does anybody know if there have been any updates? 

I'm hoping that IPC reverses course and accepts Tom's changes, I have been using many of the guidelines in this Powerpoint for a while: 


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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2021 at 5:25pm
IPC-7351C was originated at IPC headquarters with Dieter and Rainer Taube in mid July 2014. The original concept was to not add on to the existing standard, but to rewrite it in a highly organized fashion so that PCB designers and Librarians could easily read it and understand it. 

The main reason for the 100% rewrite was because the IPC-7351, 7351A and 7351B were just adding new terminal leads, new component families and new concepts randomly. It was a haphazard document that had no rhythm or order. 

Dieter and Rainer had been working on the concept of 7351C for over a year before discussing it with me. Then when we got together in person, the entire structure for the new 7351C was already laid out. We met every day for a week for 12 hour work days to accomplish writing the framework. 

One of the concepts was to relocate all assembly information from the 7351 to a new standard IPC-7070 to clean up 7351C. IPC-7070 was supposed to be written in lock step with 7351C so that chapter 1, 2, 3, 4, 5, 6, etc. matched 100%. The IPC-7070 was supposed to be the assembly aspect of the land pattern document. 

It took me over a year to rewrite 7351C and add all the new information, but in the meantime, Dieter passed away and Rainer who was the chairman for IPC-7070 quit. I submitted the 1st draft to the subcommittee in late 2015. They made several comments of changes that should be made to improve the flow and the graphics. It took me 6 more months to update their requests and in the spring of 2016 I submitted the final draft, which I still have. It included everything in the mentioned PowerPoint presentation and much more. 

The subcommittee started the review and we had bi-weekly webcasts to go over every chapter. We did this process for the next 2 years. But it was slow, because there were no more face to face meetings where you really accomplish a lot in a week. 

Unfortunately for the global electronics industry, the chairman Karen McConnell made a decision in late 2018 to scrap our version of 7351C and drop the IPC-7070 because they could not get any volunteers to replace Rainer Taube. 

Karen's decision was to revert back to the IPC-7351B and simply add and remove data and that is what 7351C is today. 

So I took all the new updated solder joint goals, naming convention, component families and terminal lead data and put it in PCB Libraries, Inc. Library Expert in 2018. And I created all the documentation to support Library Expert and put it here - www.pcblibraries.com/downloads ;

The next step was to totally rewrite Library Expert 100% and create the next generation of land pattern calculation and rename the software V2021 Footprint Expert. The new rewrite is in Beta test right now and will be officially released in the next couple weeks. 

The main problem now is that since IPC abandoned our 7351C draft, PCB Libraries, Inc. had to take over the copyright for all the support documentation for "Footprint Expert" as we lost to connection between IPC-7351C and Footprint Expert. IPC made PCB Libraries, Inc drop all reference to IPC-7351C from our website and our literature and we went separate ways. 

Now the big secret is, will IPC-7351C ever be released? No one knows because Karen McConnell stepped down from being Chairman and Gary Ferrari stepped down from being the Vice Chairman and new people took over. The newbees had no idea of the work we did over the past 20 years to create the original standard. 

When and if IPC-7351C is released, it will look similar to the 11 year old IPC-7351B and all the updates we created will not be in the new release. The committee is even changing the mathematical model for pad stack calculations, but no one knows if it will be accepted by the industry. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote dbrgn Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2021 at 1:37am
Tom, since you put so much work into this: Could your IPC-7351C draft be published under a free license (e.g. CC-BY) and a new name, and with a clear process to integrate community / user feedback into future versions?

It may not have the IPC name on it anymore, but it would be a coherent standard with clear guidelines that others could refer to. (And you could keep the door open for IPC, so they could reconsider if they wanted to.)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2021 at 9:20am
IPC-7351C chapters 1 - 4 are identical to to IPC-7351B so we would need to leave that alone. These chapters are very old and taken from the 1987 IPC-SM-782 and explain the mathematical model for land pattern calculation. But the math model is intended for public knowledge and we created an Excel spreadsheet reference calculator to prove that it works. It's available for free download on www.pcblibraries.com/downloads

But Chapter 5 on Surface Mounted component families and Chapter 6 on Through-hole component families and Chapter 7 on land pattern naming convention are free community documents located on www.pcblibraries.com/downloads 

So the main changes to the original 7351C are available for free download and maybe they need to be located on another website for the entire electronics industry to access. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote cioma Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2021 at 11:01am
Well, IMHO, Library Expert has become a de-facto industry standard.
Many thanks for your efforts, Tom!

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Tom H View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2021 at 11:11am
Thanks for the kind words. We're trying to organize chaos. 

We're hoping that the new rewrite V2021 Footprint Expert lasts until the end of my life and beyond. 

We've been averaging 100 new customer registrations worldwide on our website every week for many years. We now support over 170 different countries. 

Life is good when you dedicate your life to a project that others can benefit from. 

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