Electronics Assembly

Contributors: Nate
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Inspection and Testing

Automated optical inspection machine

The next step is optical inspection. Optical inspection catches any problems with parts (wrong resistor, missing cap, etc.). The AOI (automated optical inspection) machine is fast. You watched the video, right? That’s very close to real time. The AOI uses a series of high-power cameras at different angles to see different parts of the solder connections (sometimes called fillets). Good and bad solder fillets reflect light differently so the AOI using different color LEDs to illuminate and inspect every connection, with great accuracy, at high speed. It’s pretty sweet.

Do you need optical inspection for your board? Probably not. We didn’t get one until we were doing 30,000+ boards a month when it was becoming harder and harder to catch all the errors.

Solder jumper on IC

Can you see the problem?

We run the majority of boards through our automated optical inspection (AOI) machine. Optical inspection checks to make sure all of the correct components are on the board, in the right places, with correct solder fillets and no solder jumpers between adjacent pins.

Pogo pin test jig

Once the board has been inspected it is tested to make sure it does what it is supposed to do.

Imagine if it takes 15 seconds to test a board. What if you have to test 10 boards? That’s about 3 minutes. What about 1500? That’s over 6 hours of mind numbing testing. We spend a tremendous amount of time making our test procedures and programming as quick as possible.

To speed up this process, our technicians use a test fixture, sometimes called a pogo bed to allow for quick testing. Pogo pins use a spring loaded head to create a temporary electrical connection to the various points on the board for power and data. Once the board or panel is loaded onto the pogo bed we run various tests to make sure the board is fully electrically functional. This may include testing the voltage output of regulators, expected voltages on certain pins and sending various commands to the board under test to make sure it responds correctly. On boards that require programming or calibration, additional steps are taken to load code and verify the output.

Larger facilities may use flying probe or bed of nails fixtures to test every connection on a board for continuity before powering the board. These larger fixtures are good for more complex, expensive products but can frequently run into the tens of thousands of dollars to create.