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Design for manufacturability (DFM) PCBs Test procedures

Kostas_P , 10-05-2017, 02:54 AM
Hi everyone,

I would like to ask what would be the procedures and tool required for testing high volume PCBs which include processors, FPGAs etc etc. I have read about a process called bed of nails fixtures which you can check for shorts, opens, resistance, capacitance, and other basic quantities which will show whether the assembly was correctly fabricated.

Thank you!
mairomaster , 10-05-2017, 04:15 AM
You have 2 options - either bed of nails or using a flaying probe service. The bed of nails could be a large initial investments but it's cheaper if you have many test points on the board and for large quantities of board. You should ideally speak to some test houses to get a better idea for your case.

If you are working on a design now and you are not quite sure what you will use for the testing, I would advice you to use test points with diameter of at lease 1mm (preferably bigger) and keep centre to centre distance between the test point of at least 2.54 mm. That will make the testing significantly easier and cheaper.
Kostas_P , 10-05-2017, 08:41 AM
Thank you Mairomaster!
robertferanec , 10-06-2017, 05:43 PM
What I have seen, usually companies use two methods for testing boards where you can run software:

1) testing where you place the board on spacers, you connect all connectors and run test software on the board
2) testing when bed of nails was used and you run test software

The first method doesn't need many special additional testing equipment (perspex or wooden board with simple breakout boards). However, this can not be used for huge quantities, because the process of connecting and disconnecting cables is sometimes slow and after some time it breaks and has to be replaced.

The second method was used for thousands of boards manufactured every month, however, the test equipment itself was expensive to create (it was a big box) and basically, to create the test equipment was a project itself. Google for "bed of nail test" and click on pictures, you will see the boxes, but could not find the one we were using (here I found some examples - I have never used this company and I do not know it, it is just for ilustration: http://www.test-x.com/ )
Kostas_P, 10-07-2017, 09:42 AM
Thank you very much Robert!!!
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