An AOI system conducts an inspection using several light sources and one or more still or video cameras. The light sources light up the board from various angles. The cameras then take still images or video of the board, compiling them to create a complete picture of the unit. The system then compares the images it captures with information about what the board should look like taken from design specifications or an approved completed unit.

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What are the features about Automated Optical Inspection on PCB during manufacturing?

Pros

·  Non-contact test method.

·  AOI accurately detects a specific category of programmed defects on PCBs (bad solder joints and missing parts).

Cons

·  AOI only catches PCB defects and doesn’t catch defects with difficult to classify failure modes such as glue or seal defects.

·  Defect detection capabilities are not flexible, each change must be programmed.

·  AOI does not discover new detects, it only detects defects that are preprogrammed.

·  Teams don’t have access to data from AOI systems.

·  Teams often can’t program new defect tests into AOI systems remotely.

·  AOI does not provide value in development.

What is the Automated Optical Inspection on PCB?

Positional accuracy: With the size of components decrease, the positional accuracy of both inspection equipment and manufacturing are increasingly important. And AOI system should have sub-pixel accuracy as a rule-of-thumb, which make sure the there is enough accurate for the system to detect the small deviations in position that can result in a 01005 defect.

Low cost: AOI test can improve the pass rate of PCB so that reduce the PCB cost.

Multiple inspection objects: AOI test not only works well used in PCBs, but also for PCB assembly. As to PCB, it checks the defects, for example, shorts, opens and insufficient solder. However, for PCB assembly, it inspects some questions, such as component soldering, polarity and values.

Programmable lighting: It’s important for lighting to achieve the desired results in any machine vision application. Considering the constantly changing environment of electronics fabrication, it’s impossible to find one light source that can detect all defect conditions. So a dynamic light is so important to make sure the component and PCB configurations have the widest defect coverage. As the cost reduction of light-emitting diodes, AOI test can configure light arrays that are highly customizable within the inspection software. What’s more, AOI test can flexibly increase the contract of image so that make it easy to identify a multitude of defect conditions with multiple colors at different angles. Programming lighting is an invaluable tool to make sure the widest range of detect detection.

Network capable software: One important function of any AOI system is data collection and retrieval. The data can be in the form of a text output, image collection, database, or a combination of several formats. Collecting the data is a basic function of most AOI systems, but, retrieving the information is often more complex and depends on the configuration of the manufacturing line.

Good Flexibility: AOI can be used in any stage of fabrication process based on the needs and cost tolerance capacity. And the reason why it’s better to do AOI test after reflow soldering is that most of defects are the result of failure in the soldering process so that reduce corresponding cost and increase inspection efficiency. As well as it can modify immediately the fabrication or assembly parameters to manufacture correctly the subsequent products.

Why to process Automated Optical Inspection on PCB?

It's almost impossible for current electronic devices to work without a circuit board. A PCB plays a critical role in electrical connection between components such as integrated circuits (ICs) that are assembled on bare boards applied in different electronic devices ranging from relatively simple equipment such as electronic watches, calculators, handheld computers, electronic communication equipment to advanced electronic devices like military, medical or aerospace products.

Due to the rapid progress of modern technologies and people's continuous higher demands for electronic devices, modern circuits have to be much more complicated than what they were just a few years ago. Furthermore, the introduction of Surface Mount Technology (SMT) leads circuit boards to develop towards miniaturization and high density. Nowadays, even an ordinary printed circuit board contains lots of solder joints and layers. Moreover, component size keeps gradually shrinking so that the massive application of 0402 and 0201 components leads to urgent necessity to ensure that correct components are applied with correct polarity and values.

When it comes to inspection methods for PCBs and PCBAs, manual inspection did make sense for a period of time. Nevertheless, it is hardly accepted for inspection of modern circuit boards since it fails to inspect their internal issues or defects.

Current market strongly calls for a reliable and fast inspection method, which is why AOI (Automated Optical Inspection) becomes so significantly important before products leave manufacturing house and function in customers' projects or devices. Moreover, AOI test enables a reduction of cost and to make issues exposed in the early phase.

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