AOI quality control
Over the years, the process of manufacturing and assembling PCBs has undergone significant changes. Thanks to the huge popularity of this type of service, not only the scale of production has increased, but also the boards themselves, which are subject to increasing miniaturization. As a result, it also became necessary to change the way of checking their quality, which would allow quick and accurate detection of any damage or errors. That is why, at our company, we offer AOI quality control, which combines high performance with precision.
AOI quality inspection – what does it consist of?
Automatic Optical Inspection (AOI) is one of the most accurate and effective tools for production quality control. It helps detect errors such as soldering defects or improper positioning of components on the board.
Automatic optical inspection is one of the most accurate and effective tools for quality control.
Because of the large and, above all, rapid development in the semiconductor industry, not only the prices of the services performed, but also the product itself have changed. PCBs (Printed Circuit Boards) are getting smaller and smaller, but with the change in size, the number of integrated circuits and the density of components have increased while the distance between components has decreased. As a result, even the slightest error can lead to damage to the device. This is why previous production quality testing methods have had to transform.
Previously, for much smaller-scale productions, manual inspection was used, which involved testing random samples from a given production batch. However, the highly complex layout of the wafers and the sheer volume of production made it necessary to automate quality control.
AOI inspection – how it works
The most important component of the AOI device is the system designed for image recording. The PCB passes through the AOI camera, which carefully scans its surface. Using the resulting images, it is possible to compare the result with the uploaded reference data. This allows the algorithms to find any inconsistencies and errors, such as misplaced components, soldering errors or path errors. The device generates a special report that not only contains data on the detected errors, but also images of the errors, their location and degree of criticality. PCBs in which an error is detected are then categorized or redirected for repair accordingly. When operators finish working on the faulty board, it is run through the device again to confirm that it conforms to the reference data.
AOI devices – image inspection and programming
AOI devices often make use of various types of illumination, which allows precise inspection of the component under test. In order to obtain the most precise image, the intensity, color and angle of the light must be configured with the requirements of the specific product being inspected.
An important role is also played by the image recording system, which can be built with one or several cameras. The choice of recorder itself depends on the requirements of the project. Usually one of two solutions is used. The first involves continuous image recording – similar to a video camera, while the second records individual frames – similar to a camera.
To be sure of the effectiveness of the AOI system, it must be subjected to a proper configuration. Then we can count on the device being as accurate as possible. Often a so-called reference plate is used, which is recorded by the system. Based on the received parameters, the device creates a reference model, to which it compares the recorded image during production control. In the case of several product variants, each of them must be provided. An equally popular method is to use an algorithm that is uploaded to the AOI system. Then the device generates a correct model of the wafer and compares the objects being checked with the supplied algorithm.
AOI – why is it worth it?
Quality control is an integral part of any manufacturing process. It not only ensures the highest quality of manufactured equipment, but also minimizes additional costs associated with the appearance of defective batches – thanks to the use of the AOI system, any errors are not only detected, but also categorized. It is also worth noting the high throughput of this type of solution, which ensures checking a certain number of samples in the shortest possible time.
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