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Footprints naming convention: IPC-7351 vs. Expert
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zentekfr View Drop Down
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    Posted: 06 Jan 2022 at 12:00am
Hello everyone.

Can some of you please clarify the differences between the two "Footprint Naming Convention" options available in Footprint Expert 2021.21?
I mean "PCB Libraries" vs. "IPC-7351B".

After having taken a quick look at the two different explanation documents, I can't say it's crystal clear because I can't precisely spot the differences Ermm

From a forum post by Tom, I think I understand that the custom "PCB Libraries" naming has been created to de-duplicate some names:
Quote
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.

Is it the only reason?
What about the naming scheme in IPC-7351C?

Thanks! Wink
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Tom H View Drop Down
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Points: 5716 		Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jan 2022 at 8:42am
PCB Footprint Expert added the IPC-7351C footprint naming convention 4 years ago as soon as it was created. 

2 years ago IPC contacted us and asked us to remove IPC-7351C from out program and our website because they were getting too many people asking when 7351C was going to be released. 

So, we changed IPC-7351C to PCB Libraries on request from IPC. 

No one knows when or even if 7351C will ever be released. I think they stopped the development meetings due to lack of interest. IPC downgraded 7351 from a Standard to a Guideline. 
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zentekfr View Drop Down
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Points: 83 		Post Options Post Options   Thanks (0) Thanks(0)   Quote zentekfr Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jan 2022 at 1:49pm
Thanks Tom.
I also read the documentation about Console options ("Chapter 1 Footprint Expert Console Options") and this is explained, so this is clear now.

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The PCB Libraries option is an updated Naming Convention that was submitted by PCB Libraries, Inc. to IPC 4 years ago and intended for the IPC-7351C release. The IPC-7351C land pattern sub-committee voted to approve it, but last year the committee leaders decided to revert back to the legacy IPC-7351B naming convention.
The main differences between the 2 naming conventions is that IPC-7351B produced mass duplication of land pattern names because it did not contain Thermal Tab sizes, Terminal Lead sizes, BGA ball sizes and it was not 100% symmetrical. PCB Libraries naming convention eliminated duplication of land pattern names.
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Tom H View Drop Down
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Points: 5716 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jan 2022 at 2:04pm
I'm not 100% sure that the updated and improved 7351C Land Pattern Naming Convention was reverted back to 7351B. 

I do know that the preliminary 7351C draft was worked on for 3 years and eventually discarded because Dieter Bergman the architect passed away and the committee couldn't wrap their head around the massive changes to completely rewrite and upgrade 7351C for today's technology. 

The chairman Karen McConnell made the decision to revert back to the IPC-7351B and start IPC-7351C from scratch. There hasn't been a 7351C meeting in months because the committee decided that the missing Through-hole guidelines were more important to complete and release in the new IPC-7352 publication that went for final review last September. I do not know what the status of that document. 
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