Incorrect part numbers

April-01-2016 23:13:37
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Deciphering manufacturer part numbers can be a painful and error prone experience. But ensuring you have the correct part number when it matters doesn't have to be so hard.

This is a minefield of potential problems. It inevitably involves a scan through the datasheet to the part number coding key, which for some parts can leave you with a lot to think about (anything from case size to pin pitch, plating finish, height dimensions and a whole load more).

Hurrah! You determine your part number, add it to your library definition and forget about it...

Next thing you know your contract manufacturer is calling you up. These calls are generally not courtesy calls, and the phrase you are likely to hear uttered down the telephone will be something like “We can’t seem to source the part you have specified, the usual suppliers are telling us this is non-stock and isn’t available”. Or perhaps “We’ve got a problem on the assembly line – the part we have received is a QFN, and it looks like the design is using a TSSOP package for that device”. Or maybe even “The part number we’ve got in the BOM is not an orderable part”.

So what went wrong?

Well in the first case, sure the part number may be correct, but perhaps you didn’t check availability with the usual channels. Or perhaps you did, but that was 6 weeks ago, and now there is not only no stock, but you find out this is a build to order part stocked of the back of a larger customer order. Oh dear.

The second case is just one of those things. Everything is correct in the design, and of course you intended to specify the TSSOP part… but somehow the QFN part number made it into the BOM. Hmmm. Ah, that extra little “N” at the end of the 12 digit part number, how did that get there? Ok, let’s order the correct part… what, not in stock? Delayed delivery for another week because you’ve missed your build slot?

In the third case, it is quite common for only the core part of a part number to be present, short of those critical few characters that make it a fully qualified, orderable part. In these situations, the procurement person or contract manufacturer will have to revert back to the engineer to clarify the required part number. More time lost.

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