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Scaffalatura metallica refrigerata walk-in

Suggerimenti per la programmazione Aoi per catturare efficacemente i difetti

Imparate a conoscere gli efficaci consigli di programmazione AOI per individuare i difetti nelle schede SMT, garantendo sistemi di stoccaggio a freddo di alta qualità e soluzioni di scaffalature metalliche affidabili per i vostri progetti.

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 Scaffalature metalliche multistrato per celle frigorifere e scaffalature refrigerate walk-in in filo metallico.

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 Programming For SMT Assembly

AOI (Automated Optical Inspection) checks:

  • missing parts
  • wrong polarity
  • solder bridges
  • tombstoning
  • skewed or twisted chips

The camera can see all of that.
But the program tells AOI what is OK e 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 componenti del congelatore o componenti per unità di refrigerazione inside a cold room.

Scaffalatura metallica refrigerata walk-in

AOI Reference Data And Component Library

First tip: give AOI a clean, solid “truth”.

Use a golden board and CAD data

  • Start from CAD + BOM: correct X/Y, rotation, designators.
  • Utilizzare un tavola d'oro that’s really good. No rework, no scratch, no half-baked solder.
  • Let the machine learn the good image from that board.

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”.

Build and maintain the component library

Create a component library that includes:

  • package size and outline
  • pin count
  • polarity mark (dot, notch, chamfer)
  • expected solder joint area

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:

  • zoom in
  • define clear pads
  • define polarity region
  • check a few boards from different lots

Library work is boring a bit, I know.
But it pays back every single day in less false calls.


AOI Thresholds And Defect Criteria

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”:

  • follow IPC class: Class 2 vs Class 3 have different acceptance limits
  • define what is “major defect” (safety, function) and “minor defect” (cosmetic)
  • set tighter limits on safety-related parts (over-temperature protection, door sensor input, etc.)

Ad esempio:

  • allow small position drift on a big resistor
  • but be strict on polarity and offset for the compressor driver IC

Use data, not only eyeballs

You can monitor:

  • false call rate (too many fake alarms = program too nervous)
  • escape defects (customer or final QC finds what AOI missed)
  • first pass yield (FPY) after AOI

If false call is crazy high, operators start to click “OK” without thinking.
Then even good AOI can’t save the line.

Scaffalatura metallica refrigerata walk-in

Pre-Reflow And Post-Reflow AOI Inspection

Where do you place AOI in the SMT line?
Answer: not only one place.

Pre-reflow AOI

Before reflow, AOI can catch:

  • missing component
  • wrong value / wrong part
  • polarity mistakes
  • gross skew

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.

Post-reflow AOI

After reflow, AOI checks:

  • solder bridges
  • insufficient solder
  • open joints
  • tombstoning / lifted leads

For boards that manage cold room fans, defrost heaters, and door alarms on scaffalatura metallica per congelatore, bad solder can mean field failure and food waste.

Simple AOI inspection strategy

You can use a combo like this:

PassoAOI PositionMain PurposeTypical Catches
1Pre-reflow AOICatch placement + polarity issuesmissing chip, flipped diode, wrong part
2Post-reflow AOICatch solder-related defectsbridge, open joint, tombstone
3Sampling recheckCheck recipe and false call trendnoisy program, drift in process

This looks simple, but it covers most of the real world traps.

Scaffalatura metallica refrigerata walk-in

AOI Programming Checklist Table

Below is a quick cheat sheet you can even print and stick near the AOI.

Key AOI Setup PointPerché è importantePractical Tip in Real Line
Golden board + clean CADDefines what “good” really looks likeApprove golden board with QE before teaching
Strong component libraryReduces mis-match between packages and rulesCreate special library for critical ICs
Clear polarity and text regionsAvoids reversed parts on diodes, electrolytics etc.Use high-contrast silkscreen and marks
Sensible thresholds (not crazy tight)Cuts false calls but still catches real defectsTune on 30–50 boards, not just 1 sample
Pre + post reflow AOI combinationCatches both placement and soldering issuesStart with high-risk products first
Defect coding and feedbackConverts AOI alarms into real process actionsUse standard defect codes in MES or sheet
Regular recipe reviewKeeps program aligned with process drift and ECNReview every month or by lot change

No need rocket science here.
Just follow the list and update it when your line changes.


Make PCB Layout AOI Friendly

AOI programming does not live alone.
Il PCB layout can make AOI easy or almost impossible.

Some quick layout habits that help AOI a lot:

  • add fiducial marks with clear copper pads
  • keep tall parts away from tiny chips they will shadow
  • align polarity marks all in one main direction, not random
  • keep text readable and not under parts

QIAO can offer DFM feedback so the control PCB works well with AOI and with your freezer cabinet design at the same time, including scaffalature a filo per frigoriferi commerciali and other Componenti della cella frigorifera.


Turn AOI Results Into Process Control

If AOI only “kicks out bad boards”, you’re wasting half of the value.

Use AOI data to tune the process:

  • track where defects happen most (which feeder, which side, which product family)
  • look at solder-related defects vs paste printer settings
  • check if defects spike after changeover or stencil cleaning

When you see more ponte on one pad design, maybe your paste aperture is off.
Quando missing parts always come from the same feeder, maybe that feeder needs deep maintenance, not just a quick blow of air.

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