Offline AOI EKT-VT-680

 There are a number of vendors offering automated optical detection systems (AOI) for detecting PCB components, so choosing a “appropriate” supplier becomes a challenging and potentially far-reaching task. Among them, the biggest difficulty is keeping a keen eye on the dizzying number of AOI suppliers, who use different technical terms when describing their products and advertise what they call special features in advertisements, great deal of confusion and creating problems for potential users, especially those who intend to buy AOI systems  customers who undertake important testing tasks.

the most important question for users is: which system is most suitable for the current production status? several basic factors can be simply considered regarding this issue: will the AOI system be integrated into the production line (used online) or used as the so-called “AOI solution “(used alone) or is the detection process included in the production process? these questions can be answered without testing any product.

 More important is the flexibility of the system to test programming, defect identification or misjudgment rate. The answers to these questions can only be derived from first-hand information about device testing. If a AOI system is tried, the following procedure must be performed:

Select a typical PCB to develop a test program.Check the debugging process.Detect the defect-free and defective PCB produced by the user himself

Of course, even if you have completed the basic check, there is still too much work to do, so users must further narrow the scope. Therefore, it is necessary to determine further preselection criteria, such as analyzing the system configuration. camera modules in the system must be given great attention because this is the key module that determines any AOI system performance.

Choose Fish Eye View or High Precision Picture

As we all know, for the detection work of high performance IC and solder joints in recent years, camera-based systems have become acceptable standard configuration beyond scanner-based systems, because telecentric lenses can achieve higher image resolution and less distortion under more flexible illumination and configuration conditions.

A larger field of vision (FOV) is required in order to meet the requirements of modern production for detection speed without loss of image quality. Five-million pixel cameras for industrial use can cover nearly 20 cm2 in a high-resolution photo.

As the system records an image through a telecentre lens, its extremely high resolution and very low distortion will truly reflect every part of the detected area, which can not only significantly reduce the workload of the debugging and detection program, but also reduce the misstatement rate, especially for higher components, multiple pins and very small pin spacing IC.. This characteristic of the detection system provides decisive benefits

It must be emphasized that the telecentric lens is a remarkable innovation, especially for the 5m pixel camera. With EKT company’s nine-series detection systems, a line of telecentric optical modules can capture high-quality images of 42 mm×42 mm of the detected area. on the one hand, this is the basis for providing finer element position information —— independent of its height; on the other hand, it is also critical for the actual detection performance.

The brighter the better

As important as the quality of the optical module is the light source control. selecting the appropriate light source means higher PCB defect detection rate. In addition, flexible illumination is also necessary to detect a large number of different types of electronic components and find their various defects. Because of its inherent high stability and brightness, the LED of various shapes and colors has been widely used and become a standard configuration in recent years.

Light sources have a variety of configurations, such as:

A ring-shaped vertical light source configured above, mostly around the lens :• useful for checking the presence of components and identifying crescent solder joint shapes • disadvantage is often misjudged when used to detect defects between IC pins due to the presence of flux and solder joint marks.

 Angle-configured light source, multi-directional multi-incidence angle configuration :• suitable for detecting welding short circuit, reducing misjudgment rate • able to display laser signs with high contrast, which is a prerequisite for effective use of real OCR( optical character recognition) functions and polarity detection

 A variety of color light sources :• can display color polarity markers with high contrast, distinguish elements from PCB background • improve defect detection rate and reduce misjudgment rate.

 Also, for different PCB materials and different color components, the brightness control in the specific detection task is also necessary. because the arrangement and combination of light sources are varied, a large number of parameters need to be provided for faster and easier management of detection tasks, and AOI software must make the process as simple as possible.

In EKT 9 series of AOI systems, a special set of light sources enables the welding short circuit to be correctly detected even in minimal pin spacing and is not affected by contamination that flux and solder joint marking may cause. the user can select light sources of different colors in order to safely detect the wrong polarity (e.g. color markers).

Flexibility should not be just a catchphrase

A flexible set of system configurations not only refers to software and its parameter management, but also includes the possibility of integrating other modules. Due to the various assembly methods encountered in the production environment, the additional detection module is very helpful to improve the defect coverage. for example, camera systems with angular viewpoints make it possible to detect some key elements (such as solder joints and short circuits of PLCC and SOJ elements).

 Summary

However, other factors, such as after-sales service and technical support, should be given taken into account because they are very beneficial to the operator and ultimately determine the satisfaction of the user. AOI users of the system should benefit from future development to get the best return on investment.

AOI system selection requires a series of work, as users have to examine many indicators. In addition to detailed requirements for a specific production environment and product range, the components installed and used in the system will also highlight additional requirements for system performance and features. users should pay special attention to the image acquisition module and the light source module, because they are the key to ensure that the system has a high degree of flexibility in the face of multiple PCB types. A set of effective and user-friendly database management software can greatly save time when compiling new PCB programs, which is necessary for a variety of detection objects.

Of course, users will have to test each alternative system separately before the final decision. After completing the pre-selection as described above, users should assess their programming and testing performance on alternative systems with their own PCB products.

 No one would think it’s easy to choose the right AOI system —— but when you’ ve identified those really important indicators, you’ll find that all roads lead not to rome, but to a suitable testing system supplier.