The same is true for inspecting component presence, but for solder-joint detection these
technologies are in their infancy at present. The shape of different components’ solder-joints
is complex and the specular surface also makes the task even more difficult. There have been
a number of research efforts, optical 3D shape measurement technologies, based on several
technologies as shown in Fig.2. Some of these researches can be found in the following studies
[181-198]. Also some companies are in the development phase such as Koh-Young Technology
[180]. So the evaluation of these geometries is as yet more difficult, but with the development
of optical metrology there will be more AOI machines with measuring capability.
11. Further developments, the future of AOI
AOI systems are following the worldwide trends i.e. multi-task integration, adaptivity, speed,
etc. There are already appliances that integrate optical inspection with repair functions: Ersa’s
AOI+R solution or optical and X-ray inspection together. Some suppliers have AOI+AXI or
Viscom’s AOXI (simultaneous inspection). Another possible area of development is the
inspection speed. Faster image capturing (with larger FOV, faster camera positioning etc),
parallel inspection of two PWBs are some possible ways for this to be done.
The other important area is adaptivity. Mainly adaptive illumination is the future of AOI
systems. It would help to drastically reduce pseudo-failures rates and eliminate slip-through
failures.
A third area is image processing. 3D inspection, neural networks, fuzzy systems, intelligent
algorithms which will help to increase the efficiency and reliability of these systems.
12. Conclusion
Inspection systems are widely used to determine the quality of electronics modules after
assembly sequences. Nowadays this is usually the automatic, non-contact and non-destructive
process, such as automatic optical inspection (AOI), supplemented with automatic X-ray
inspection (AXI) if necessary. These appliances inspect the ready or the incomplete printed
wiring boards to determine the quality of it's given property in any technological sequence,
such as paste printing, component placement or soldering. The rapid development of elec‐
tronics module assembly manufacturing requiring parallel development of test procedures.
The automatic optical inspection is potential multi-disciplinary research area, because from
image acquiring, (illumination, the detection of the reflected light etc.) through image proc‐
essing, to the evaluation each area can be optimized to reach to goal, that the qualification of
the inspected object in the field of interest (FOI) by the used appliance, matches the specifica‐
tions as stated. Most manufacturers agree that, from a strategic point of view, the optical
inspection after soldering should not be ignored. As a consequence, this is the most important
part of an AOI inspection. The quality of solder joints is determined from geometric and optical
properties of the solder meniscus. These parameters determine the reflection properties of the
Materials Science - Advanced Topics
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