IPC Land Pattern Vs Manufacturer's Recommendation

Randy: Seems you have a long way to go to DFM. To your strategy: - proof that in the case of wrong landpattern design the IPC would have been the better choice - count money ( what�s the cost of redesigns due to bad landpatterns ) - establish at least the process of checking the landpatterns of new devices for manufactureability - offer your help in the design process - at least make it a process step to check designs before they leave your house. In my old company it took a year until they accepted that fiducials are necessary and what do you think happened after I left? Yes you�re right, they skipped them because they were just doing it for me and not for easier assembly and their CM had the same struggle I had before.

Again, proof that it saves money and that it costs only a little to check manufacturer�s recommendation against IPC.

Good luck

Wolfgang

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Randy,

I have been with my present company about 14 months and my first and ongoing task is to improve 1st time yield rates at ATE.

Upon examination of the failures (14 months ago)there were cases of IC legs being physically wider than the pads on the board. This was due to a lack of info at CAD stage and the guys were only doing what a)the CAD package library had and / or b) what the manufacturer stated.

I have since definitely found both sources to be lacking. After one week I purchased a copy of IPC-782. GET IT NOW !

The differences were astounding.

Now every new design goes through a PCB only (not product) proto, pre-prod and general production release with an emphasis on land patterns and how the PCB performs using existing processes.

We have cut our rework down by an enormous amount and consequently the first time pass rate has improved dramatically. It wasn't rocket science. It just needed someone like me with nothing better to do.

Regards,

Chris May.

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Randy: My druthers on sources for SMT land patterns, in decreasing preference order are: 1 Manufacturers' recommendations. The problem with manfacturers' recommendations is that someone must make the effort to obtain them, document, and use them. Otherwise you end-up wth the very undesirable third choise. 2 SM-782. SM-782, while a very useful, is negotiated by committee and so, is conservative and may have little to do with peculiarities of a specific component. Further, SM-782 hasn't been up-dated in years and excludes array packages. 3 Some place else. We could write a book on horror stories about pads from this source, couldn't we?

Jim Blankenhorn (SMTPlus) has developed, publishes, and maintains a good set of land patterns.

Someone, Earl maybe, mentioned something about this recently. It may be worthwhile checking back to see what was said.

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