6 Steps to Verifying a Part you Didn’t Make

Saving time on your projects is what pre-populated parts libraries are all about, and they’re great at it.  But doing these quick checks will keep you confident that using parts you didn’t make are what you expect them to be.Ever heard your boss, or someone else in your industry mention the line “do a sanity check”?  I’ve also heard the term “do a smoke test”, or “run a warm/fuzzy test”.  To me, the “sanity check” line is a bit dramatic and implies your mental well-being is at stake, but in hardware design, these tests can mean the difference between being mildly upset over a part not being entered correctly in the library and losing hours of work or potentially thousands of dollars in fabrication costs.In an interview with Circuits Central’s Hooman Javdan, a contract manufacturer and PCB assembler of more than 5000 designs, he mentioned that selecting the wrong part or providing the wrong footprint for a specific application can mean hours lost and hundreds of dollars in remanufacturing cost overruns.

So before committing blindly to a complex part that you found already existing in your part library and doing a quick “cha-ching” in your head, it’s valuable to slow down and take a second look to make sure the part you’re selecting is really the part you think it is.  If the part attributes were properly populated and there is a URL to the data sheet, open it up and make sure it matches the data sheet of the part you’re hoping to use.  You’ll want to check both the schematic and the footprint against this data sheet next.  The good news is that a sanity check on a footprint can be done very fast with a bit of practice.

Some things you can quickly check on the schematic:

1) That the number of pins matches the number of pins on the data sheet.

2) That the names correctly match the pin designations in the data sheet.

With the footprint, you need to check the mechanical details against the data sheet.

3) Use your hardware design tool’s measurement tool to measure the package outline and compare that to the size of the device in the data sheet.

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4) The pad pitch or the pin pitch needs to match the data sheet too so measure those as well.

Note, ‘pitch’ means centre-to-centre spacing between adjacent pads and/or pins.

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5) Measure the pad size, both length and width and ensure they seem reasonably larger than the pads on the part you’re using.

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6) Make sure the pin numbers match, and that pin #1 is in the position you expect it to be.

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If you have any other details you like to check as part of your ‘Sanity Check’ let us at Upverter know!  We’d love to hear from you.

These might seem like mundane details to check, but in the event that the part you’re using in your design software doesn’t exactly match the part you’re using in fabrication, checking these details means you likely won’t run into any issues anyways. If you can do these really fast checks that cover ~90% of the aspects of a part, you might spend a few minutes to save hours and sleep better at night with a warm/fuzzy feeling in a smoke-free environment, thus preserving your sanity.

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