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IPC Adoption Justification

Printed From: PCB Libraries Forum
Category: PCB Footprint Expert
Forum Name: Questions & Answers
Forum Description: issues and technical support
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=1970
Printed Date: 18 Nov 2024 at 10:53pm


Topic: IPC Adoption Justification
Posted By: npassey
Subject: IPC Adoption Justification
Date Posted: 05 Oct 2016 at 10:17am
Hello,
 
Upper-level management needs convincing that moving ECAD library to IPC-7351 will positively affect Assembly Yield.  Does anyone have a link to a study showing this?

thanks,

-Nathan


Replies:
Posted By: Tom H
Date Posted: 05 Oct 2016 at 10:30am
We've been using IPC-7351 in all our land pattern calculator tools since 2004 and have about 250,000 users worldwide using a variety of IPC Calculators.

There must be millions of PCB's manufactured using IPC-7351 land patterns.

The IPC-7351 mathematical model is pristine because it compensates for the package and lead tolerances and fabrication and assembly tolerances.

For the past 12 years we have never heard a complaint that a IPC-7351 Calculator produced a bad land pattern.

The IPC-7351C guideline introduces new solder joint goals for micro-miniature packages as well as adjusting every Toe, Heel and Side fillet to compensate for the improvement in manufacturing technology. This new technology reduces the Toe solder joint and in turn opens up to 20% more PCB real-estate for part placement, via fanout and routing channels.

V2017 Library Expert Pro and Lite will be released on October 25th and it will default to the new IPC-7351C rules.



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Posted By: npassey
Date Posted: 05 Oct 2016 at 11:12am
Tom, 

Thanks for your response, and I already agree with all of that.  It doesn't answer my question though.

Posted By: Tom H
Date Posted: 05 Oct 2016 at 11:42am
Are you having assembly yield problems? And are Land Patterns the primary issue?



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Posted By: Matthew Lamkin
Date Posted: 19 Oct 2016 at 2:42am
The best answer for this would IMO generally come from internal sources, where your assembly problems lie.

To give an example, in a previous employment we made a board that was quite low tech, a simple pic etc. it has lots of assembly problems in solder balls, bad joint, capacitor cracking, oversized pads because they were not standardized, different pad codes for the same sized component etc.
We would get a lot of returns.

When I had to make a simple modification I actually redid the board entirely in IPC footprints which not only removed completely all the solder balls, better sized pads resulted in far far less capacitor cracking, it also enabled a far better placement because in general the components took up less space.
The number of returns was  reduced to very minimal numbers.

The reduction in returns alone quantified why it was best to use a standardized set of component dimensions.
Most major component manufacturers specify IPC-7351 component sizes now, the Footprint Expert makes creation of them so easy that IMO it's crazy to use anything else.
I'm so glad that I have not had to calculate heel/toe/pad sizes etc. for so many years, with the time saved it allows me to concentrate on actually laying the board out.

Again, this does not link to a "study" but is just actual experience of using standardized pad codes that improved efficiency and saved the company money - this I think is what counts more for most employers.

Posted By: npassey
Date Posted: 19 Oct 2016 at 10:04am
Matthew,
 
Thank you for your response.  This is a rough representation of the exact thing I'm searching for.  
 
If you could tell me that prior to your redo of the board using IPC footprints, there was a 31% failure in assembly, and after you made this update, there was a 6% failure rate in assembly, and the only difference made was the IPC footprints, then that's an example of concrete evidence.
 
Because IPC has been adopted so widely, so globally, I assume this type of experience is common.  I'm hoping someone somewhere did a controlled Before-After comparison on the assembly floor just like you describe, but including yield numbers.  Mostly because those numbers can be easily translated to Cost Savings, and that's sometimes one of the only languages upper management can speak. 
 
I hoped that if any data or studies like this were done and reported, their existence would be known here.  Maybe nothing concrete has been reported anywhere.
In the meantime, I'd like to use your "general description of an IPC-7351 success story" as an example in my justification.
 
thanks again,
 
-Nathan

Posted By: Matthew Lamkin
Date Posted: 20 Oct 2016 at 5:14am
Unfortunately I have not worked there for several years so would be unable to find figures (if they even existed) so it is mainly anecdotal.

I do however train many people in CAD software and have not come across any that disagree with using the 7351 footprints over the manufacturers recommended etc.

The repeatability, preciseness, ability to define the solder size rather than just blind faith that whoever wrote the datasheet knew what they were talking about etc. means that I am in control of the footprints but they are all produced to a standard that can be repeated, quantified, backed up by the IPC etc.

I will add that I am loosely connected to the Library Expert software now but I do not profit from it's sale and the above is from prior to my current employment.


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