Automated Optical Inspection (AOI)

Automated optical inspection uses cameras to take photos of a printed circuit board and compares them against detailed schematics to ensure that there are no mistakes on the board. The board is lit from various angles and several pictures are taken and assembled together to build a complete profile of the board.

It is particularly useful for detecting issues early in printed circuit board manufacturing, such as scratches, nodules, stains, thinning solder, open circuits, and short circuits. AOI systems can also detect incorrect or missing components.

3D cameras have recently found use in AOI systems to provide even more reliable results. This is of the utmost importance to height-sensitive devices, as 2D camera systems rely on colored lighting and side-angle cameras to achieve these results.

AOI is able to detect the most common PCB faults in PCB supplier china, and is a ubiquitous system in PCB manufacturing. Often, AOI systems are deployed at several points throughout a facility to detect errors early. However, as these systems are designed around cameras, they are limited by what they can visually detect. 3D cameras have an advantage in that they can detect height differences, but they are unable to inspect hidden connections that are found in multilayered boards. For boards that are densely loaded, they may be unable to inspect components that are hidden or shadowed.

As a result of these drawbacks, AOI is not the only inspection method employed by most printed circuit board manufacturers. Especially in Class 3 PCB manufacturing, inspection must be flawless, leading to the development of additional inspection technology.

X-Ray Inspection (AXI)

With the advent of surface mount technology, or SMT, smaller components have led to more densely populated boards with over 20,000 solder connections. Solder connections on these boards are small enough that they can’t be inspected by AOI equipment. Further, multilayered boards contain components that cannot be visually detected from the surface.  X-ray inspection is able to provide a far more detailed picture of a printed circuit board than what can be done by simply examining its surface.

Printed circuit boards have the advantage of being made from much lighter elements than the solder connecting them. This allows for these details to appear with a high degree of clarity on X-ray inspections. X-rays pass directly through objects rather than relying on visible light – eliminating errors that might emerge from shadows or hidden components.

Why aren’t X-ray inspections used for all PCB inspection purposes? As it is a newer technology in the world of PCB manufacturing, it is expensive to purchase and use, making it unnecessary for lower class printed circuit boards that lack the complexity found in new chip packages. It requires experienced operators to use these machines, and the process can be extremely time consuming, leading to added expenses for customers.