Trapped in PCB inspection for dozens of days​​

[calleypcba]

Here's the thing I learned from a recent rush job:​​ the board was tiny and packed with components—BGAs mixed with 0201s. When the first prototypes came back, I was totally stuck at the testing stage.
After talking to engineers from a few manufacturers, I realized I’d been thinking about it all wrong. I kept trying to choose between flying probe and test fixtures, but that was too narrow. ​​Reliable testing is like diagnosing an illness, you need multiple checks, not just one.​​
For example: Start with ​​AOI, then move to ​​flying probe testing​​, like a quick ECG for the board, checking for shorts or open circuits, perfect for low-volume validation. Finish with ​​FCT, a full simulation of real-world operation. Only when it passes all functional tests is the board truly good to go.
Honestly, you don’t need to be an expert in every testing method, it’s too complicated. The key is to find a reliable manufacturer with comprehensive equipment. When I handed the board over to the engineers at ​​kingshengpcba.com, their advice was practical: With a dense board like this, AOI and X-Ray are must-haves. Use flying probe for connectivity during low-volume runs, and FCT for final validation. When you scale up, switch to fixtures to reduce cost.
Just like that, the path became clear.

[Shub]

That’s a great breakdown of the process. A lot of people get stuck thinking there’s only one “right” testing method, when in reality dense boards almost always need a combination of AOI, X-Ray, flying probe, and FCT to really catch everything.

Your example is spot-on BGAs + 0201s are a nightmare if you rely on only one inspection method. AOI catches obvious solder issues, X-Ray is essential for hidden joints under BGAs, flying probe is perfect for early runs, and FCT is really the only way to confirm that the whole system behaves the way it should.

And you’re right about finding a manufacturer with the right equipment. A lot of small shops can do assembly, but very few can provide all stages of testing reliably.

Thanks for sharing your experience it’s a good reminder that testing strategy matters just as much as PCB design in tight, high-density builds.