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IPC7351-C Draft or Release date?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote dbrgn Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 6:03am
Sorry for digging out this thread. It's been 3 years since, does anyone know about the status of IPC7351-C? The only things I can find online are the "what's new" presentations by Tom H...
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 8:52am
I gave IPC the 7351C Draft over 3 years ago and the committee run by Karen McConnell is dragging their feet. I gave seminars on the updates and now it's really embarrassing. 

7351C hasn't even gone through the 1st 30-day ballot vote and when it does it will be rejected for multiple reasons. Then 30-days need to go by to fix all the issues and then another 30-day ballot vote and on and on. 

I continue to send updates of new data to the committee and they accept the updates but I don't see them in the master draft. 

All previous versions of 7351 were developed 100% behind closed doors in 3-day working sessions held several times a year by the main committee. Then, when we completed the draft it was shown to the sub-committee. This time around, the sub-committee meets once a month for an hour and all they do is argue and nothing meaningful gets accomplished. 

And the main thing is that 7351C was demoted from a "Standard" to a "Guideline", so there is no liability on IPC if it doesn't work. It's just a Guideline now so who cares anymore. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote dbrgn Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 10:07am
That's very sad to hear... I'm currently trying to build up a standard parts library for librepcb.org and the IPC7351C standard would be very relevant for that since a lot of thought and knowledge went into it. Your "what's new" slides that can be found through Google look quite promising.

The draft isn't public, right?
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 11:38am
The IPC-7351C draft is not public. Even the sub-committee members can't get an up-to-date copy of the draft. 

I'm not convinced that IPC is interested in releasing the new 7351C as the put a liaison on the committee that did not have any land pattern knowledge and couldn't contribute to it. 

Dieter Bergman, Gary Ferrari and Vern Solberg were the original architects of IPC-SM-782, which morphed into IPC-7351. Dieter passed away 3 1/2 years ago, Gary was the Vice Chairman and he hasn't attended any committee meetings for several years and Vern retired. 

Meeting once a month for an hour would take over 2 years to accomplish the same thing that we did in 3-days, when we created the original IPC-7351 (2004) and 7351A (2006) and 7351B (2009). 

The existing 7351B is 10 years old and obsolete due to advanced technology in manufacturing and packaging. 

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 12:01pm
Just for the recorded history, what is the difference between IPC-SM-782 and IPC-7351?

I worked on both committees and I’m familiar with all the differences, however, I joined the SM-782 Land Pattern committee in 1999 and there were no further. IPC had an on-line web-based SM-782 Calculator and Jeff Mellquist and I created a similar IPC-SM-782 calculator using Excel spreadsheets in 1999 & 2000 and shared it with IPC, Dieter Bergman and Gary Ferrari. Jeff and I used the same mathematical model to test our results against the online calculator and discovered some funny math that was going on in the SM-782 publication. For some reason that we don’t know, IPC left out important rounding calculations and left the readers to assume several key calculations. Jeff and I are mathematicians and we used the math that was printed in SM-782. We could not create a working calculator that accurately reproduced the on-line IPC calculator results because the entire IPC mathematical model for pad size and spacing was not printed in the standard. 

Note: 50% of the publication of in SM-782 were package and land pattern dimensions. This data was fabricated by the committee 10 years before I joined. I eventually discovered that none of that data was used by any component mfr. and the land pattern dimensions were created as a guideline and not a standard. i.e.: all of the dimensional data was a fictious fabrication (not real-world data). I proved that when I created the content for the new IPC Calculator, no manufacturer dimensions matched IPC-SM-782 package dimensions.

At the 2001 IPC APEX conference, Dieter and Gary handed me documents that they obtained from IEC in Europe that described a 3-Tier PCB library system. Jeff & I then created a 3-Teir calculator and abandoned the SM-782 calculator. Our comparison results between the new 3-Tier calculator and the old SM-782 calculator was that SM-782 land patterns were larger than Nominal but smaller than Most density levels.

IPC BOD created a Pin # for the creation of a new Standard called IPC-7351. Jeff and I flew back and forth to Chicago to meet with Dieter Bergman and John Perry to write the draft of 7351. Once a year Gary Ferrari attended our 3-day meeting. I created a Land Pattern Naming Convention that I contributed. I helped Dieter upgrade graphic images, tables and charts for 7351. Took the SM-782 and upgraded it to 7351, but the mathematical model stayed the same but with new Solder Joint goals for Toe, Heel and Side values. During this intensive upgrade, Dieter asked Jeff and me if we could create a software program that could be distributed with the new 7351 document and we agreed and signed an MOU with IPC. Then IPC removed the SM-782 on-line calculator from the internet.  

In 2004 PCB Libraries, Inc. was formed to distribute the new 7351 calculator, even though 7351 was not released yet. In 2005, IPC-7351 document was released, and the PCB Libraries LP Wizard Calculator came with the purchase of the new standard. The MOU between IPC and PCB Libraries lasted until October 2017 when out of the blue, IPC discontinued the MOU and that decision was based on a committee member from Mentor Graphics and Karen McConnell, the committee chair person, who claimed that the MOU broke the new IPC anti-trust law that states IPC will not promote any CAD vendor or PCB manufacturer. Even though PCB Libraries, Inc. supports every CAD tool in the electronics industry. The MOU agreement was canceled, and IPC no longer provides a free IPC Calculator with the sale of the 7351 standard publication. Gary Ferrari told IPC that their decision to end the MOU was a foolish mistake on their part.

During the creation of IPC-7351A Jeff Mellquist discovered a new bug in the IPC mathematical model that affected the “Heel” joint. Dieter Bergman’s excuse for this was that the Heel needed to be longer because it was an assumption that 70% of the solder joint strength was in the Heel. But this proved to be inaccurate because the longer Heel placed the pad under the package body. Then component manufacturers started to make the package stand-off very small, even 0.00 and the pad under the package didn’t make any sense. IPC upgraded the mathematical model to make the Heel shorter.

YTD 2018, the current committee has decided to remove the Fabrication and Assembly Tolerances in the upcoming release of 7351C. Leave them in the Calculator but turn the values to 0.00. This will have a minimal impact on the resulting land pattern as the pad sizes will be 0.01 – 0.04 mm smaller.

The bottom line is that IPC could never create a working calculator that produced repeatable reliable results until Jeff Mellquist and I created our calculator. Along the way, we discovered fuzzy math and inconsistency due to what we refer to as the Dieter fudge factor, where he twisted the math to create a result that he accepted. But we needed to create a calculator that provided consistent results without fudging the numbers. 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 05 Feb 2019 at 9:33am
The only information that is available for IPC-7351C is that it has been approved to be worked on. 


This web-page was updated last year to add Kristopher Moyer as the Co-Chair because Gary Ferrari is not participating in any of the meetings but IPC kept him on the committee as the Vice-Chair. 

Here is the status of all the IPC standards and guidelines and IPC-7351C needs to be moved to the "Ballot Draft" and then you know it's 4 - 6 months away from release. 


After IPC-7351C passes the Ballot Vote (which will take 3 months) then it has to go into Typesetting which will take at least 3 months or longer depending on how may standards are being Typeset at the time. 

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 10 Feb 2019 at 10:10am
It was already visible over the past couple of years that the decision makers at IPC are not aware of the importance of land pattern guidelines and also the PCB designers are getting less and less attention for the development of new IPC standards. 


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