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rbuck
USA
63 Posts |
 Posted - 26 Jun 2009 : 02:21:45
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This has probably been asked before but I searched all 6 pages of the PCB forum and don't see it mentioned.
Is there any published standard for SMT pads? The manufacturers all have suggested pad layouts for their parts but I have noticed different manufacturers may have different suggestions for pads. For instance if I look at a suggested layout for an 0603 part from two different manufacturers, the pad sizes are often times different.
And the pad sizes for 0402, 0603, and 1206 parts in the Easy-PC libraries do not match any suggested layouts I can find.
I have seen references to something called IPC-7351A standard but can't seem to find the actual document.
Ray |
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Peter Johnson
United Kingdom
498 Posts |
Posted - 06 Jul 2009 : 13:17:40
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I'm not sure what the current standard is, but it used to be IPC SM-782, before it was renamed. That's the ANSI standard. Of course, there's more than one standards body, so I believe there's a JEDEC standard as well. Again, I don't know the number.
One thing they all have in common is an exorbitant price tag, as it's by selling copies of these standards that standard agencies are able to fund their busuness. That also means that you won't find anything other than small extracts being offered for free download, unfortunately. In any case, for a given part there may be as many as 3 different recommended pad sizes, depending on the type of manufacturing process being used. It's not simple any more!
The pad sizes in the standard library did match the IPC SM-782 standard extant at the time of creation - but that was well ove 10 years ago, and things have got a lot smaller since then. |
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pedro444
United Kingdom
25 Posts |
Posted - 06 Jul 2009 : 15:28:11
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Have a look at www.PCBMatrix.com They have a free downloadable land pattern viewer "LP Viewer" which gives the JEDEC outlines (and what manufacturers actually call the outlines) for over 3000 components.
We found that the only thing you can seem to rely on is the JEDEC number.
The best thing about standards is there are so many to choose from.
Best Regards
Pedro |
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olga
United Kingdom
107 Posts |
Posted - 07 Jul 2009 : 10:10:35
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quote:
Originally posted by pedro444
The best thing about standards is there are so many to choose from
I used to have a quote from an Orcad manual pinned up by my desk:
"Create Netlist: Creates a file that lists the logical interconnections between signals & pins in one of more than thirty standard formats."  !
Best wishes,
Olga. |
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Topic |
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SMT Pad Standards