How do you do the 1st sample inspection?

Just to be clear:

* First Article inspection is the qualifying of new product/processes and changes. Automotive PPAP approval is a good example.

* First Piece inspection is the first off when a process is started.

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At an EMS I used to work for, our process for first article inspection was to have a human technician do a point to point comparison between the BOM and the PCB. They would verify component part #s were correct per the location, correct polarity and solder joint quality. It was labor intensive and highly prone to error.

By first article inspection, I'm talking about a brand new board that's never been built on the SMT line before. Once we had a known good board, we could program our AOI to inspect boards from future runs. In the automotive world, we have AOI, ICT, functional tests etc. We do lots of test runs before the final PPAP and customer approval processes so any errors or mistakes have been found and fixed before that point. This is very capital and material intensive as we build hundreds of PCBs that will never be sold long before we go into production.

The problem with any sort of automated test (AOI, ICT, etc.) is that it requires a known good PCB to test and debug the program. This in turn requires a PCB to be build and verified as "good". It's hard to get away with having a human verify a board at some point in the process, by extension is hard to get away from the risk of human error.

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Here, there are two possibilities - either it is a new board to us (ie built elsewhere previously) or it is a new product for the company requesting the build. If new to us only, ask for a sample PCB.

You will need CAD data for pick & place machines, plus a parts placement diagram and circuit drawing.

As an AOI operator, I will often place each part from the customer BOM, whilst the P&P technician will use the CAD data. That often shows up any discrepancies between BOM and CAD.

One PCB will be built, which I can then AOI to check for placement & polarity. After that, another technician will check the PCB by eye, using the BOM, and comparing with the circuit and parts placement diagrams.

If this is a totally new PCB for the customer, we will usually only build - say - 5 PCB's and send them to the customer for test and verification before buidling the bulk.

If it is not totally new, and we have a sample PCB, we will follow the above procedure, but complete the order once AOI and visual inspections are complete and satisfactory.

It is not unknown for the silk screen to be wrong, CAD or BOM to be wrong, and so on, so use as many different methods of checking as you can.

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