Automatic optical inspection of assemblies

Automatic Optical Inspection (AOI) is a versatile process for quality control in electronics production. Leesys offers its customers a wide portfolio, whether electronic or optical inspection, including X-ray inspection.


Automatic Optical Inspection

Conventional Automatic Optical Inspection (AOI) and AOI systems are used to control the production of printed circuit boards and electronic assemblies (assembled circuit boards).

The following test methods are used at Leesys:

3D – AOI - for paste printing:

Checking the correct execution of solder paste printing

2D - AOI – for the evaluation of the assembled components before or after the soldering process:
Checking the presence, position, polarity of components

3D – X-ray inspection:

Checking the correct soldering (for example also under the components) + Checking the presence and position of components

InCircuitTest for assembled circuit boards:

The data accuracy of the installed components is measured by a multitude of test points.

Functional test of assembled circuit boards:
Checking the function of more complex circuit parts
Device test (function test):
Checking the function of the completely assembled device

BurnIn + function test:
Devices or assemblies are exposed to different temperatures (positive, negative). Subsequently, it is checked whether the function is still guaranteed.

Laser marking incl. check reading:
After marking, the readability is checked.

The following systems are used for this purpose:

  • Inline test systems for functional testing of devices
  • Combined assembly/test lines
  • Semi-automatic module test systems with PXI and RF testing technology
  • Functional test systems that can be adapted to customer requirements
  • Inline test systems for functional testing of assemblies


The electrical test is carried out via test needles and by contacting the interfaces. LEDs and displays are tested optically, while keys are tested by pneumatic plungers. All modules are equipped with a DMC to guarantee the traceability.
At Leesys, all assemblies undergo an automatic optical inspection as standard.
The tests are carried out automatically in the corresponding systems. The results and the execution of the checkpoint are reported to the central traceability system. Our highest claim is to find all manufacturing and component defects in order to ensure the high delivery quality of Leesys at all times.