The IPC-7351C executive and sub-committee is meeting every 2 weeks until IPC APEX on March 15. Last meeting we reviewed and discussed Silkscreen Legend Polarity Markings - http://www.pcblibraries.com/forum/polarity-marking-silkscreen-legend_topic1816.html" rel="nofollow - Download Here

The next meeting is Tuesday and we'll start reviewing the new SMD Proportional Pad Stacks which will replace the existing 3-Tier Density system. However, Library Expert will continue to support IPC-7351B through 2016 until everyone migrates to the new, much more accurate mathematical model to land pattern automation.

At IPC APEX on March 15 we will meet in Las Vegas to vote on the final draft and then it will go into the final Ballot for 30-day review by everyone on the committee. If everyone agrees then it will go directly to print. If there are disagreements, they will have to be resolved and a new 30-day voting Ballot will go out. This process will continue until everyone agrees and then it will go into print (PDF only due to all the color images).

I came across this thread but it doesn't appear 7351C is available for purchase yet.

Has something stalled the release process, or is it still cycling through 30 day reviews?

Yes, IPC-7351C is stalled due to the solder joint goal tables and a solution for micro-miniature components.

You can download V2016.08 Library Expert Pro pre-release and test it out. It has our recommendations for incremental pitch solder joint goals - http://www.pcblibraries.com/downloads%20" rel="nofollow - www.pcblibraries.com/downloads

IPC-7351C has not been submitted for 30-day committee vote yet, but it's expected to happen this year.

I'm on the 1-13 Land pattern Committee and we do have meetings every 2 weeks.

IPC has made a decision on focusing on Through-hole technology and breaking it out of the IPC-7351B and creating an Addendum for IPC-7351B. So all progress has stopped on the Surface Mount since the beginning of September.

If you downloaded every piece of documentation on our website, you would have much of the IPC-7351C standard as far as component families, solder goal tables and naming convention. It's not going to change very much. http://www.pcblibraries.com/downloads" rel="nofollow - www.pcblibraries.com/downloads

IPC will not release the official IPC-7351C until next fall. Now that Dieter Bergman is gone and Gary Ferrari is near retirement, there's a lot of bureaucracy and progress is slower than an ant walking through peanut butter.

However, we introduced IPC-7351C technology a year ago and many companies are using it and having great results.

If you really want to know the status of IPC-7351C, contact IPC.

Due to manufacturing machine accuracy and advanced technology the Courtyard Excess for IPC-7351C is now -

IPC-7351B is -

We will release V2017.01 today or tomorrow and it will be fully loaded with IPC-7351C. I do not believe there will be any changes as it already went through committee approval.

The Manufacturing Zone is the additional space between Courtyards that your assembly shop needs. You cannot determine the Manufacturing Zone without the Assembly manager's assistance.

Hi Tom,

Thanks for that info.  That matches my understanding after reading through the B revision and the info on the C revision from your site.

The good news is that I can - within reason - do what is necessary to determine the appropriate manufacturing zone(s) for our equipment.  The bad news is that I don't know how best to do it.  Of course I know the stated placement positional capability for our P&P equipment but that is something like 30 microns, which is nearly an order of magnitude better than the 0.2mm between-component-spacing which would result from using the IPC 0.1 mm least courtyard dimensions and zero manufacturing zones.

I was thinking of setting the manufacturing zones all to zero, which will result in components being spaced based on their courtyard dimensions only - e.g. 0.2 mm for small chip parts.  We build mainly small hand-held PCBs that we design so we already use the IPC-7351B "Least" footprints and courtyards.  Presently each layout person uses their "best judgment" to further space components apart from one another for manufacturing - typically resulting in between 0.3 mm and 0.5 mm between small chip parts.  We haven't had any problems that I'm aware of at 0.3 mm spacing, but I'm having a tough time convincing others that we might go even closer.   I'd like to enforce using the manufacturing zones so that we can be more uniform when deciding on components placement, but I'm not sure where to start to determine the manufacturing zones. 

Based on your experience do you foresee problems placing small chip parts with 0.2 mm separation using the IPC-7351C Least footprints?  Is that just crazy?

What would you do if you were in my shoes to determine the manufacturing zones for our equipment?  Are there test boards available that help in determining the minimum manufacturing zones?

Thanks again for your help and advice.

Doug

Today's assembly equipment has a tolerance of +/- 0.01, which is very accurate.

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. 

That's very sad to hear... I'm currently trying to build up a standard parts library for http://librepcb.org/" rel="nofollow - 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?

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. 

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. 

http://www.ipc.org/committeedetail.aspx?Committee=1-13 " rel="nofollow - http://www.ipc.org/committeedetail.aspx?Committee=1-13 

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. 

http://www.ipc.org/Status.aspx?utm_source=outlook&utm_medium=email&utm_content=071514&utm_campaign=status " rel="nofollow - http://www.ipc.org/Status.aspx?utm_source=outlook&utm_medium=email&utm_content=071514&utm_campaign=status 

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. 

Tom, I want to bring up a general comment about the naming convention. I mention it here, because you're the one who really got the naming convention started and is still talking about it.

I like to have the freedom to add additional information to the IPC name. Especially with IPC-7351B, I like to augment the IPC-7351B name with a prefix showing the common or manufacturer’s acronym followed immediately by the signal pin count. E.g: 
VSSOP8_SOP50P310x90-8N

This helps me search on and find similar footprint types in my PCB library files. I would want the freedom to add information like that to the 7351C name, as well. 

I want to recommend to IPC that they allow for some freedom on the part of the user to add such information. How would I go about doing that? Should I try to get on a committee?

IPC always had a PCB design liaison but went for the last year without one. They either quit or were fired. Now, IPC just hired a new PCB design liaison and maybe that's why they want to start from scratch. 

Do not expect the new IPC-7351C to be as robust as the original version. It most likely will be IPC-7351B with minimal changes. 

I don't agree with this decision and I think IPC is making a huge mistake. The 7351 Land Pattern Guideline is the foundation for all the other standards, but I do not think IPC realizes this basic principle. 

I think I will, because I would like to do something about this.

I agree, the land patterns are the most basic standard of the IPC PCB design standards. It was through them that I first became aware of the existence of IPC over 30 years ago.

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.

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). 

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: 

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

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. 

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 - http://www.pcblibraries.com/downloads " rel="nofollow - 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. 

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.)

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 http://www.pcblibraries.com/downloads " rel="nofollow - 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. 

Well, IMHO, Library Expert has become a de-facto industry standard.

Many thanks for your efforts, Tom!

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.