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Different tolerances
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Tom H View Drop Down
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    Posted: 07 Apr 2015 at 8:16am
That's a good idea.
 
All IPC Calculator parts have the mfr. abr. at the end of the land pattern name.
 
All Unique parts that use the mfr. recommended pattern have the mfr. abr. at the beginning of the land pattern name.
 
This way when you look at the land pattern name you know instantly if it's IPC-7351C calculation or mfr. recommended pattern.
 
We're looking at adding common sense to the land pattern name.
 
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Points: 576 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jameshead Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2015 at 8:06am
I just want to add something - when I'm outputting my centroid data for the assembler with the footprint name I am telling them importantly that it's a standard land pattern so they know the appropriate rotation (for us, Level A).

For the assembler, they might only be interested in the SOIC127P600X...-3N bit and if it was at the front of the land pattern name it's easier for them to see.

If they see something different at the front then it's a bit more of a red flag to say "hang on, this is a non-standard footprint - lets double check everything".

Just a thought.  It would be interesting to get some feedback from assemblers and auto-insertion programmers.
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Points: 576 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jameshead Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2015 at 7:51am
Thanks Tom, I downloaded the latest copy from Dr Munie this morning.  Last Friday and Monday were a bank holiday here in the UK.

The Manufacturer_Manufacturer'sPartNumber naming is very sensible for non-standard parts and I can see the sense in extending it to standard footprints.

I find it neater when viewing a list of land patterns in the CAD Tool's libraries to have ALL the same standard land patterns listed together though - and then easier to manipulate.

In terms of looking at a standard land pattern name and "processing" the name in my head:

I'm more interested in seeing if it's a standard land pattern, then what type it is, then what size it is, and to be honest I'm not bothered who the manufacturer is until the end.

If that makes sense!

I just wanted to add my tuppence halfpenny worth.

If the agreement is to do it the other way around then that's what I'll do.
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Tom H View Drop Down
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Points: 6029 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2015 at 7:37am
We already thought of putting the manufacturer abbreviation as the Suffix, however, we're trying to have a universal naming convention that fits all parts created in FP Designer for Unique packages and connectors. Their naming convention is MfrNameAbvr_MfrPartNumber.
We want ALL parts to sort by the component manufacturer abbreviation regardless if it is a Standard Part or a Non-standard Part or a Connector.
 
Did you download the latest IPC-7351C Naming Convention Proposal -
 
You are suggesting that all "Standard" parts have the mfr. abbreviation as the land pattern name suffix and all "Non-standard" parts have the mfr. abbreviation as the land pattern name prefix.
 
Or do you have a suggestion for the non-standard land pattern names?
 
Or is this what you prefer? The 1-13 land pattern subcommittee will have to vote on this.
 
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Points: 576 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jameshead Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2015 at 12:59am
Originally posted by Tom H Tom H wrote:

Bottom Line is that regardless if the package is standard or unique, all Footprint Names will sort on the Mfr. Abbreviation and no longer sort by the component family abbreviation.


For a standard naming land pattern having the manufacturer abbreviation as a suffix instead of a prefix would be better in my view, in sorting footprints in a library.

When I'm looking for a standard footprint in a list I would prefer to see:

SON80P400X400X80-9N-TI
SON80P400X400X80-9N-AD

So all the SON80Ps are grouped together.

It kind of leads on better as the footprint name tells me from the beginning that it's a standard package, the size, then at the end that it's a Texas Instruments or Analog Devices variant.
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Tom H View Drop Down
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Points: 6029 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 30 Mar 2015 at 1:52pm
The new recommended IPC-7351C Land Pattern Naming Convention is only used for component families recognized in the IPC Standard and the Calculator.
 
All unique packages and connectors created using FP Designer will use the MfrName_MfrPartNumber Naming Convention.
 
And all complex one-of-a-kind packages will also use the MfrName_MfrPartNumber Naming Convention.
 
Bottom Line is that regardless if the package is standard or unique, all Footprint Names will sort on the Mfr. Abbreviation and no longer sort by the component family abbreviation.
 
Something that the IPC-7351C subcommittee must approve.
 
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Maarten Verhage View Drop Down
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Hi Tom,

Good to hear about that. I'm glad to see you seem to be willing to reconsider the initial idea of MfrName_MfrPartNumber.

This discussion started with dealing with the different tolerances in the packages and the unique names for that. I think with the new idea it is important that the component manufacturers stick to their tolerances for the IPC-7351 Naming Convention names.

I was wondering do you talk with component manufacturers about this? Would it be likely they are willing to commit to the new standard/guideline and promise not to mess with the tolerances or other dimensional data that might result in the same IPC-7351 footprint name but having different packages?

About the IRF part you showed us. I would be trying to find another part that would give me this functionality rather than this overly complicated non-standard one. But it is great you also support packages like these in your software.

Best regards,
Maarten Verhage
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Tom H View Drop Down
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Update: I discussed the Land Pattern Naming Convention concerns in our weekly IPC-7351C development meeting today. Everyone on the executive committee agrees the short comings of the existing Naming Convention.
 
One of the members from Germany recommended that we use an abbreviation of the Mfr. Name as a prefix followed by a hyphen.
 
Example: TI-QFN50P350X350X100-19_15T205X205
 
This is the Texas Instruments QFN for the RHL case code.
 
We have already collected every mfr. name and assigned an abbreviation and we'll be submitting it to the 1-13 Land Pattern subcommittee for review and comment. I'll let you know if this is accepted into the standard, but I personally approve it as it extends the life of the current naming convention.
 
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Tom H View Drop Down
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Points: 6029 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 2015 at 1:01pm

The character limitation was brought up in an IPC standards development meeting. I don't have the records of that meeting, but it was injected into the discussion by Dieter Bergman last year when we were reviewing an alternate Land Pattern Name solution. I'm not sure if he was referring to Cadence Allegro or some other CAD tool limits for both Land Pattern and Pad Stack names.

When using the mfr. recommended pattern for unique packages, there is no guidance on a 3-Tier Density Level system. In this example of an International Rectifier footprint that is only 6 mm x 5 mm, see this datasheet pages 44 - 49 details on the pad, paste and solder mask sizes and locations. This FPX file for Library Expert took 4 hours to create and we sell it on www.pcblibraries.com/POD for a couple credits.
 
 
 
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Originally posted by Tom H Tom H wrote:

Let's put this in perspective. There are approximately 500,000 different component packages in the industry today and there will be more next year.
 
When the IPC-7351 Naming Convention was created 12 years ago it was good for about 70% of all component packages. But as time goes by, component manufacturers continue to produce unique one-of-a-kind packages as to corner the market for their new IC that has multiple functions like Bluetooth, GPS, CPU processing, audio/video, etc. and you can remove 100 parts from your BOM and reduce the layer count by 4 - 6 layers if you single source this device. Are you going to do that? I think you might. So in 2015, the IPC-7351 Naming Convention is good for about 50% of all packages but quickly dropping.
 
Most connectors are unique packages. Even the simplest USB connectors are produced with unique packages where the manufacturer is trying to corner the market with their connector. Connectors make up about 35 - 40% of all packages. And if most of them are unique, you can't use the IPC-7351 Naming Convention.
I think we need to separate unique and standard packages. For unique packages, I believe your suggested naming convention (MfrName_MfrPartNumber) is good. However, I still like the old naming convention for standard packages. I have just checked that there are ~1100 0603 resistors from Vishay on DigiKey and about the same number of 0603 resistors from Panasonic. MfrName_MfrPartNumber naming convention would not be very suitable for these parts because of extremely large number of duplicated footprints.

One way of solving my reported issue with tolerances would be using maximum dimensions in footprint names, not nominal. This way we could continue using current naming convention for standard packages.

Originally posted by Tom H Tom H wrote:

Chip resistor packages by Panasonic might have a single package that maps to a couple thousand part numbers and this is good for the IPC-7351 Naming Convention. But what about multiple sourcing with AVX and Vishay? Do their 0603 package dimensions match Panasonic?
From my observations, most of the time no. And that is an issue - usually you need to create universal footprints for such simple components as resistors or capacitors. Personally, I would like to see a capability to combine several footprints into one universal within Library Expert. I have to do it manually now and it is a big time wasting activity.

Originally posted by Tom H Tom H wrote:

When 3D STEP modeling comes into play, having the perfect height becomes important if the PCB enclosure is tight.
I agree, but height is currently specified within Step file's name, for example CAPC2012X80. For this reason, I see no issues using current naming convention for Step files that do not involve unique packages.

Originally posted by Tom H Tom H wrote:

And the world standard for computer science names should not exceed 20 characters.
Could you please provide a reference to this requirement?
 
Originally posted by Tom H Tom H wrote:

You can download the latest version of the Library Expert Naming Convention here. We tried to cover all the options.
Why don't you recommend adding Environment part to unique land patterns, i. e. MfrName_MfrPartNumber_Environment?
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