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I have a circuit board in production, primarily through-hole, to the tune of ~400 units per year. Each one is manually inspected and tested. The board has ten distinct voltage rails, four voltage feedback amps, three current feedback amps, a microprocessor with particular response characteristics, and a few other parts. That's a lot to check.

I'm considering building an automated test rig for all that. I think a PCB that feeds the appropriate input stimuli, observes the responses, and gives a go/no-go would save me a lot of time. I'm reasonably confident that this is done, commonly. However, the techniques used to do it are unknown to me.

I imagine a test rig with a circuit board of the same footprint as the unit under test (UUT). It would have a microprocessor, appropriate protection and scaling circuitry, and a large number of vertical pins sticking up from the board. Mount points would also stick up from the test rig for the UUT. When the UUT is mounted on top of the test rig, the bottom of the board makes contact with the vertical pins, allowing the test rig to feed stimuli to the UUT and observe responses.

This seems reasonable, and I have the idea I've seen something very much like this before. But the details elude me. What sorts of pins would be used on the bottom board? (Part numbers would be great!) Would I need to put specific kinds of test points on the UUT, or can I get away with just contacting the clipped pins protruding through the board? What other concerns might there be?

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The pins used for making the kind of test fixtures, which the O.P. is describing, are called: contact probes, or spring loaded pins, or pogo pins. They come in various sizes and with various shapes of tips. The choice of a tip depends on the type of test pad: via, flat pad, pin from a throughole component on the solder side.

Here's a datasheet of the pogo pin family as an example. This particular family is available on Mouser.

enter image description here

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The pins on the test rig would probably be pogo pins. Use that term to search on any suppliers website (mouser, digikey, etc).

Pogo pins come in various points, some are optimized to contact bare copper test points, others are optimized to make contact with via's.

But you mention you have a microcontroller on your on your product. Consider what you could check with a dedicated application on that controller, maybe with a little extra circuitry on your board.

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The test board arrangement referred to is commonly known as a Bed-of-Nails board.

The pins used are called pogo pins or spring-loaded test probes:

Pogo pin (source: eBay)

Pogo pins come in a variety of contact shapes:

Pogos

Yes, specific test points, and pogo pins in corresponding locations, would be good - else the pogo pins would simply press against random parts of the DUT, potentially causing shorts or meaningless readings.

If you mean "Do I need to shape my test points a certain way", then yes: Pogo pin contact points are often exposed pads on the DUT PCB, or exposed vias, depending on the manufacturing process preferences. Vias have the slight advantage of the pogo pin tips centering on the hole / dimple in the via, potentially providing better registration of contacts.

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Here is an example of test pads added to PCB for connecting the pogo pinsenter image description here

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Adafruit has a tutorial How to Make a Pogo Pin Test Jig which is quite informative. SparkFun also has an article on automated hardware testing jigs: PogoBeds: SparkFun Production and Testing.

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