AOI is the abbreviation of  Automated Optical Inspection.  The main function of AOI to replace manual inspection for various defects in PCB. AOI plays an efficient, accurate, time-saving and cost-saving role in PCB line. The quality of Automated Optical Inspection (AOI) program directly decide the performance of AOI. Many client wan to know how to begin an AOI program. In this post we will present step by step.

ZhenHuaXing is the first and largest AOI manufacturer in China, which provide R&D, sales and after-sales service of AOI, SPI. Its products have been sold to all regions in China, and are exported to Europe, America, Japan, Middle East and India as well.

There is 6 steps to set up a new program in AOI:

1. Establish a New Program
2. Properties Setting
3. MARK setting
4. Edit Program
5. Debugging
6. Inspection

The first three steps are simple. For a experienced programmer, the first three steps of automated optical inspection program can be completed within three minutes. The fourth step of AOI program edit and the fifth step of  debugging are  difficult, which are key steps in the whole program set up in AOI. These two steps require more practice to be a qualified AOI engineer.

Step 1. Establish a New program

In this step you only click on ‘new’ and give a name to your new program.

Step 2 . Properties Setting

In this step, the you will set the size of PCB in AOI program.  It will be fulfilled automatically after you move the crossline to two corners of PCB. Then the program will generate the overview picture of PCB in test.

Step 3. Mark Setting

MARK setting has four main functions:

1. Check loaded PCB board is the corresponding to its program;

2. Check which side of PCB is inspecting (A/B side), automatically use corresponding program;

3. Check if the PCB board position is correct;

4. Inspect the deformation during the reflow oven.

In this step, you should locate two character positions on PCB. So, the program will found them on the PCB in the inspection.

Step 4. Edit program in Automated Optical Inspection Program

Program Editing have two methods, manual programming and CAD data programming. Both methods require standard registration of all components on the PCB.

Manual programming is a registration or linking standard for components on the PCB. The flexibility is not high. After the programming finish , we should check the program should be carefully. Because maybe there are missing components that are not registered.

CAD data programming must take CAD data before doing the program. Programmer only needs to register the corresponding component according the component number, which is more programmable. But, In the process of doing the program, the component frame drawn must be deleted in CAD data programming. The efficiency is reduced, and manual programming is not has such trouble.

Here, we recommended that CAD data programming, if there are more than 50 components on PCB.  if the components on the PCB below 50, we recommended manual programming.


5. Debugging

There are 3 main debugging modes:

  1. Auto-Learning Mode: The program learn a large number of standard PCB by statistical modeling. The speed of which is rapid and the performance is good.
  2. Error Pause Mode: The program will pause for each single inspected problem on PCB.  Engineer will debug error one by one.
  3. Auto-Positioning mode: the program will adjustment the component position automatically in allowed range, to get better learning results.

The basic steps of the debugging:

  1. After we optimize the lens, select the Auto-Positioning mode and let the program run three times.
  2. Select Auto-Learning Mode.  set learning limitation to 20 times, without Error Pause Mode and Auto-Positioning mode. Let the program run one time.
  3. Select the Error Pause Mode, without Auto-Learning Mode and Auto-Positioning mode. Let the program run one time.
  4. Load Second PCB board, increase the limit value to 40, and repeat the operation 2.
  5. Repeat operation 3.
  6. Load third PCB board, increase the limit value to 60, repeat the operation 2.
  7. Repeat operation 3.
  8. Load fourth PCB board, increase the limit value to 80, repeat operation 2.
  9. Repeat operation 3.
  10. Load fifth board and increase the limit value to 100. Repeat operation 2 and 3.
  11. Load Nth board and increase the limit value  to 20N. Repeat operation 2 and 3.
  12. Repeat operation 11 until the program become stable.


6. Inspection

Unselect the Error Pause Mode,  Auto-Learning Mode and Auto-Positioning mode. 

Click the start to begin Inspection.


Normally, there are  6 steps to finish an automated optical inspection program. 1.Establish a New Program. 2. Properties Setting. 3. MARK setting. 4. Edit Program. 5. Debugging and 6. Inspection. After these step we can run an AOI in our PCB assembly line.