Different tolerances

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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. 

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? Maybe, but it seems that the package Heights are all over the map. When 3D STEP modeling comes into play, having the perfect height becomes important if the PCB enclosure is tight. 

The new version of IPC-7351C has been downgraded from a "Standard" to a "Guideline". So there is no strict standard on footprint names. And we believe that 3D STEP model names, origins and rotations should match the footprint name. And, all the dimensions are nominal except for height.

My vision of the future is that the IPC-7351 Naming Convention will eventually be phased out. Some of the names are already too long. A high pin count BGA could be as long as 40 characters. And the world standard for computer science names should not exceed 20 characters. 

This forum is open to discussions for anyone to openly discuss any topic. The standard needs to be challenged to insure that it's the best solution for the electronics industry. May the best ideas and concepts eventually win acceptance as the defacto standard. 

You can download the latest version of the Library Expert Naming Convention here. We tried to cover all the options. 
http://www.pcblibraries.com/products/fpx/userguide/default.asp?ch=5

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Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 6033	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 26 Mar 2015 at 1:52pm
	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. 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? Maybe, but it seems that the package Heights are all over the map. When 3D STEP modeling comes into play, having the perfect height becomes important if the PCB enclosure is tight. The new version of IPC-7351C has been downgraded from a "Standard" to a "Guideline". So there is no strict standard on footprint names. And we believe that 3D STEP model names, origins and rotations should match the footprint name. And, all the dimensions are nominal except for height. My vision of the future is that the IPC-7351 Naming Convention will eventually be phased out. Some of the names are already too long. A high pin count BGA could be as long as 40 characters. And the world standard for computer science names should not exceed 20 characters. This forum is open to discussions for anyone to openly discuss any topic. The standard needs to be challenged to insure that it's the best solution for the electronics industry. May the best ideas and concepts eventually win acceptance as the defacto standard. You can download the latest version of the Library Expert Naming Convention here. We tried to cover all the options. http://www.pcblibraries.com/products/fpx/userguide/default.asp?ch=5
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Maarten Verhage Members Profile Send Private Message Find Members Posts Add to Buddy List Active User Joined: 27 Jul 2012 Location: Netherlands Status: Offline Points: 27	Post Options Post Reply Quote Maarten Verhage Report Post Thanks(0) Quote Reply Posted: 26 Mar 2015 at 11:43am
	Hello everybody, I do agree with fiaduu. Many many footprints are completely the same for different part numbers. I don't expect PCB designers like the approach of MfrName_MfrPartNumber. Having just a different speed grade for an FPGA requires to have a different footprint? I don't think many PCB designers will follow through. Maybe an addition can be made to the current IPC-7351 naming convention. Or maybe using an unique package description provided by a manufacturer. For example Lattice_PQFP208, if they can guarantee that once a 208 pins PQFP package is specified on their devices it is exactly that package. Otherwise THEY have to make a new unique name and STICK to that once and forever and tell the customers you promised to do that. That was my personal opinion. I hope PCB libraries allows discussions like this on this forum. Most of the times it is purely used for questions to PCB Libraries. Best regards, Maarten Verhage

JJonas Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 21 Apr 2014 Status: Offline Points: 113	Post Options Post Reply Quote JJonas Report Post Thanks(0) Quote Reply Posted: 26 Mar 2015 at 11:11am
	Thank you for this insight. New naming convention will solve my reported issue, however, it will introduce two new inconveniences - duplication of footprints and inability to distinguish for which package a footprint is designed for. But I guess that is a trade-off. What about Step files, will IPC-7351C recommend using the same naming convention (MfrName_MfrPartNumber)? It looks like the old naming convention is still good, because tolerances have no importance (dimensions are nominal)?

Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 6033	Post Options Post Reply Quote Tom H Report Post Thanks(1) Quote Reply Posted: 24 Mar 2015 at 11:03am
	You are absolutely correct. The IPC-7351 Land Pattern Naming Convention is starting to fall apart. We recommend a new naming convention - MfrName_MfrPartNumber This ties a component package directly to the Mfr. Part Number regardless of the component package tolerances. I meet with IPC at their headquarters the week of April 27th and this topic is on the agenda as we update the IPC-7351C Guideline. Yes, I said "Guideline". IPC-7351C will not be considered a "Standard" anymore. We voted unanimously on that at the IPC APEX meeting last month.
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JJonas Members Profile Send Private Message Find Members Posts Add to Buddy List Advanced User Joined: 21 Apr 2014 Status: Offline Points: 113	Post Options Post Reply Quote JJonas Report Post Thanks(1) Quote Reply Posted: 24 Mar 2015 at 10:55am
	In the picture below you can see two footprints that have the exact same name, but they look different. That is because one has smaller tolerances than another. How do you deal with this issue (e. g. if you want to have these two footprints in your library)? It looks like standard footprint naming convention is not detailed enough.