QPE Blog: Automated optical inspection: checking PCB assembly quality after reflow

Once components have been placed and the PCB has passed through reflow soldering, the next step is to check the assembly for visible manufacturing defects.

At QPE, our Automated Optical Inspection (AOI) system uses high-resolution cameras to inspect each PCB against programmed criteria based on the manufacturing data. This provides a consistent way to check the assembly before it progresses to further inspection and testing.

What does AOI check?

AOI examines visible features of the populated board, helping identify potential issues such as:

• Missing or incorrectly positioned components.

• Incorrect component orientation or polarity, where identifiable.

• Visible solder bridges.

• Visible solder joint irregularities.

  
  

These checks help establish whether the assembly matches the expected build. Potential defects flagged by the system can then be reviewed and investigated.

Identifying an issue at this stage gives the team an opportunity to address it before the assembly moves further through production.

Consistent inspection across production builds

AOI applies the same programmed inspection criteria to each board of a given assembly type. This repeatability is particularly useful across production runs, where consistent checks help maintain control of assembly quality.

The findings can also provide useful feedback on the manufacturing process. Repeated defects may indicate an issue that needs investigation in printing, placement or soldering.

Inspection therefore supports both the assessment of individual boards and the ongoing control of the processes used to manufacture them.

Where AOI fits in the quality process

AOI is designed to assess features that the cameras can see. Hidden solder joints and the electrical function of an assembly require other inspection or testing methods.

For this reason, AOI forms part of a wider quality process. It works alongside further checks selected to suit the assembly and its requirements, helping build confidence in the finished product.

What this means for customers

For QPE’s customers, AOI supports consistent inspection, early identification of visible defects and a reduced risk of those defects progressing to later production stages.

It also provides valuable feedback to help our team maintain a repeatable manufacturing process.

From solder paste printing and component placement to reflow and inspection, each stage contributes to the quality of the finished assembly. AOI helps us check the results of those preceding stages before the board moves on.

Want to discuss inspection and testing for your PCB assemblies? Contact QPE to talk through your requirements.

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