Learn effective AOI programming tips to catch defects in SMT boards, ensuring high-quality cold storage systems and reliable wire shelving solutions for your projects.
When people talk about AOI, they often say, “Just buy a good machine and you’re fine.”
Honestly, that’s not true.
If the AOI program is weak, even the best machine will miss defects. Or it will scream “NG” on every second board and drive your operators crazy.
In this article, we’ll walk through AOI programming tips that actually help you catch real defects on SMT boards. And we’ll tie it back to real hardware projects like cold storage room controllers and walk-in freezer control panels that sit behind your cold storage room multilayer wire shelving and walk-in refrigerated wire shelving.
If you build those systems with QIAO, you don’t want tombstoning or missing parts on the PCB hiding inside the freezer box. AOI is one big guard rail here.
AOI (Automated Optical Inspection) checks:
The camera can see all of that.
But the program tells AOI what is OK and what is defect.
So your job is not only “teach the board”.
Your job is to make the AOI think the same way as your quality engineer.
That matters a lot when the board controls freezer components or refrigeration units components inside a cold room.
First tip: give AOI a clean, solid “truth”.
If your “good” reference already has a little skew or poor wetting, the AOI will learn that bad habit. Later, real defects escape because they still look “kinda similar”.
Create a component library that includes:
And please, don’t just copy a random library from another plant.
For critical parts (MCU, drivers for compressor, fan controller, safety relay), spend extra time:
Library work is boring a bit, I know.
But it pays back every single day in less false calls.
This is where many teams mess up.
If thresholds are too tight, AOI will call “NG” for every small variation.
If too loose, real defects run away from you.
Use real rules, not “feeling”:
For example:
You can monitor:
If false call is crazy high, operators start to click “OK” without thinking.
Then even good AOI can’t save the line.
Where do you place AOI in the SMT line?
Answer: not only one place.
Before reflow, AOI can catch:
This is perfect for high-mix boards used in refrigeration control, where you have many part numbers. You fix placement before you “bake in” the problem.
After reflow, AOI checks:
For boards that manage cold room fans, defrost heaters, and door alarms on freezer wire shelving, bad solder can mean field failure and food waste.
You can use a combo like this:
| Step | AOI Position | Main Purpose | Typical Catches |
|---|---|---|---|
| 1 | Pre-reflow AOI | Catch placement + polarity issues | missing chip, flipped diode, wrong part |
| 2 | Post-reflow AOI | Catch solder-related defects | bridge, open joint, tombstone |
| 3 | Sampling recheck | Check recipe and false call trend | noisy program, drift in process |
This looks simple, but it covers most of the real world traps.
Below is a quick cheat sheet you can even print and stick near the AOI.
| Key AOI Setup Point | Why It Matters | Practical Tip in Real Line |
|---|---|---|
| Golden board + clean CAD | Defines what “good” really looks like | Approve golden board with QE before teaching |
| Strong component library | Reduces mis-match between packages and rules | Create special library for critical ICs |
| Clear polarity and text regions | Avoids reversed parts on diodes, electrolytics etc. | Use high-contrast silkscreen and marks |
| Sensible thresholds (not crazy tight) | Cuts false calls but still catches real defects | Tune on 30–50 boards, not just 1 sample |
| Pre + post reflow AOI combination | Catches both placement and soldering issues | Start with high-risk products first |
| Defect coding and feedback | Converts AOI alarms into real process actions | Use standard defect codes in MES or sheet |
| Regular recipe review | Keeps program aligned with process drift and ECN | Review every month or by lot change |
No need rocket science here.
Just follow the list and update it when your line changes.
AOI programming does not live alone.
The PCB layout can make AOI easy or almost impossible.
Some quick layout habits that help AOI a lot:
QIAO can offer DFM feedback so the control PCB works well with AOI and with your freezer cabinet design at the same time, including commercial refrigerator wire shelving and other cold storage room components.
If AOI only “kicks out bad boards”, you’re wasting half of the value.
Use AOI data to tune the process:
When you see more bridging on one pad design, maybe your paste aperture is off.
When missing parts always come from the same feeder, maybe that feeder needs deep maintenance, not just a quick blow of air.
