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A Brief Discussion on the Working Principle of aoi Optical Inspection Instruments to Reduce Labor Costs

A Brief Discussion on the Working Principle of aoi Optical Inspection Instruments to Reduce Labor Costs A Brief Discussion on the Working Principle of aoi Optical Inspection Instruments to Reduce Labor CostsTo effectively control the quality of smt soldering and reduce labor costs, it is necessary to make good use of the automated aoi optical inspection instrument. To use the automated aoi optical inspection instrument well, one must understand its working principle. Only in this way can one know the reasons behind it when dealing with actual defect detection. aoi inspection equipment is a branch of artificial intelligence automation, and its principle is to imitate the process of manual inspection of smt soldering quality. By using artificial light sources instead of natural light and optical lenses instead of human eyes, images of components or solder joints are obtained through optical lens photography. Then, after processing and analysis by a computer, the defects and faults of soldering are compared and judged by imitating the human brain. But machines are machines. Under the current circumstances, they cannot be as flexible and adaptable as humans. This is why we need to understand the working principle of the automated aoi optical inspection instrument: by mastering the aoi principle, we can better play the role of aoi quality inspection. This will enhance product quality and reduce labor costs. ​A Brief Discussion on the Working Principle of aoi Optical Inspection Instruments to Reduce Labor CostsThe general process of aoi inspection is the same, mostly through graphic recognition methods. The standard digital images stored in the AOI system are compared with the actual detected images to obtain the detection results. For instance, when inspecting a certain solder joint, a standard digital image is established based on a complete solder joint and compared with the actual measured image. Whether the inspection result is passed or not depends on the standard image, resolution and the inspection program used. Various algorithms are used in graphic recognition, such as calculating the ratio of black to white, color, composition, averaging, summation, difference, plane, and corner. ​The light irradiation of aoi inspection equipment can be divided into two types: white light and colored light. White light uses 256 levels of gray scale, while colored light uses red, green, and blue light. When the light shines on the surface of the solder/components, it is then reflected into the lens, generating a three-dimensional display of a two-dimensional image to reflect the height and color difference of the solder joints/components. People judge and recognize objects based on the amount of light reflected back. A large amount of reflected light indicates brightness, while a small amount indicates darkness. AOI works on the same principle as human judgment. ​aoi inspection equipment can be classified into single-lens and multi-lens types in terms of the number of lenses. This is merely one option for the implementation of technical solutions. It is hard to say which method is definitely better, as a single lens can also obtain excellent inspection images when illuminated from different angles by multiple light sources. Especially for the relatively rough surface of lead-free welding, which can produce weld points of different shapes, easily form bubbles, and have the characteristics of one end of the part lifting up, the new aoi inspection equipment has also undergone adaptive hardware and algorithm updates. ​

How is the AOI automatic optical inspection system applied in the production of printed circuits

How is the AOI automatic optical inspection system applied in the production of printed circuits After nearly 112 years of efforts, the automatic optical inspection system (AOI) has finally been successfully applied to the printed circuit board (PCB) production line. During this period, the number of AOI suppliers has increased sharply, and various AOI technologies have also made considerable progress. At present, from simple camera systems to complex 3-D X-ray inspection systems, many suppliers have almost been able to provide AOI equipment that can be applied to all automatic production lines. Over the past decade, the performance of solder paste printers and SMT placement machines has been improved, which has enhanced the speed, accuracy and reliability of product assembly. The yield rate of large manufacturers has thus been improved. The increasing number of SMT-packaged components provided by component manufacturers has also driven the development of automation in printed circuit board assembly lines. The automatic placement of SMT components can almost completely eliminate the errors that may occur during manual assembly on the production line. In the PCB manufacturing industry, the miniaturization and denaturization of components have always been the development trend. This has prompted manufacturers to install AOI equipment on their production lines. Because it is no longer possible to conduct reliable and consistent detection of densely distributed components and keep accurate detection records by relying on manual labor. AOI, on the other hand, can conduct repeated and precise inspections, and the storage and release of inspection results can also be digitized. In many cases, the inspection and adjustment of the solder paste printer and assembly process by process engineers can ensure that the solder paste contamination rate (spatter rate) on the production line is only a few parts per million (ppm). For a high-output/low-mixing production line, the typical solder paste contamination rate is between 20 parts per million and 150 parts per million. Practical experience has shown that it is difficult to detect the contamination of each and every type of solder paste merely by sampling and testing printed circuit board samples. Only by conducting 100% inspection on all circuit boards can a greater inspection coverage be guaranteed, thereby achieving statistical process control (SPC). To a large extent, only a very small portion of specific types of solder paste contamination actually exist, and the generation of these solder paste contaminants can be linked to certain specific production equipment. In many cases, you can also attribute the occurrence of a solder paste contamination to a specific device. However, for some variables, such as component offset (due to the self-correction effect during the reflow process), it is impossible to trace back to a specific production step. Therefore, in order to detect all solder paste contamination, it is necessary to conduct 100% inspection on each production step on the production line. However, in reality, due to economic considerations, PCB manufacturers cannot test each circuit board after each process is completed. Therefore, process engineers and quality control managers must carefully consider how to strike the best balance between investment in inspection and the benefits brought by increased production. Generally speaking, as shown in Figure 1, you can effectively apply AOI after any one of the four production steps in a production line. The following paragraphs will respectively introduce the application of AOI after four different production steps on the SMT PCB production line. We can roughly divide AOI into two categories: problem prevention and problem detection. In the following description, the inspection after solder paste printing, (surface mount) device placement and component placement can be classified as problem prevention, while the last step - inspection after reflow soldering - can be classified as problem detection, because inspection at this step cannot prevent the occurrence of defects. ◆ After solder paste printing: To a large extent, defective soldering stems from defective solder paste printing. At this stage, you can easily and economically remove the soldering defects on the PCB. Most 2-D detection systems can monitor solder paste offset and skew, insufficient solder paste areas, as well as solder splashes and short circuits. The 3-D system can also measure the amount of solder. After the placement of (chip) devices: The detection at this stage can detect missing components, displacement, skew of (chip) devices and directional faults of (chip) devices. This detection system can also check the solder paste on the pads used to connect close-pitch and ball grid array (BGA) components.◆ After component mounting: After the equipment mounts components onto the PCB, the detection system can check for missing, offset and skewed components on the PCB, and also detect errors in component polarity. After reflow soldering: At the end of the production line, the detection system can check for missing, offset and skew of components, as well as defects in all polarity aspects. The system must also detect the correctness of solder joints as well as defects such as insufficient solder paste, short circuits during soldering and lifted feet. If necessary, you can also add the optical Character Recognition (OCR) and optical Character verification (OCV) methods for detection in steps 2, 3 and 4. Engineers and manufacturers' discussions on the pros and cons of different detection methods are always endless. In fact, the main criteria for selection should focus on the type of components and processes, the fault spectrum, and the requirements for product reliability. If many BGA, chip-scale packaging (CSP), or flip-chip components are used, the detection system needs to be applied to the first and second steps to maximize its effectiveness. In addition, conducting inspections after the fourth stage can effectively identify defects in low-end consumer goods. For PCBS used in aerospace, medical and safety products (automotive airbags), due to the extremely strict quality requirements, it may be necessary to conduct inspections in many places on the production line, especially after the second and fourth steps. For this type of PCB, X-rays can be selected for inspection. If the AOI used on the production line is to be evaluated, it is necessary to distinguish between systems that can only perform detection and those that can perform measurement. Detection systems that can only look for defects such as missing components and incorrect placement cannot provide tools for process control, so they cannot be used to improve the production process of PCBS. Engineers still have to adjust the production process manually. However, these detection systems are both fast and inexpensive. On the other hand, the measurement system can provide accurate data for each component, which is of great significance for measuring production process parameters. These systems are more expensive than detection systems, but when you integrate them with SPC software, the measurement system can provide the information necessary to improve the production process. Overall, it is not comprehensive for people to evaluate the quality of a detection system merely based on its accuracy rate of error reporting, that is, the ratio of true errors (accurate error reporting) to false alarms (false error reporting). If a measurement system is to be evaluated, it is also necessary to rely on the assessment results of the accuracy of the measurement system within a smaller tolerance range. Statistical Process controlFinally, if you want to effectively use the data from the AOI system to help you control the production process, thereby enabling your company to achieve higher output and greater profits, you must master the following information:Accurate measurement dataReproducible and repeatable measurement◆ Close to the measurement of events in time and spaceAs well as the real-time measurement process and all the information related to the production processInstalling an AOI system during the printing or mounting process can help you eliminate other process variables accumulated during the production process. Assuming that you measure whether the components have shifted positions after reflow soldering, the data you collect cannot reflect the accuracy of the mounting process. You should measure the results both after mounting and after reflow soldering. But this information is almost useless for controlling the device mounting. Given the trend of monitoring development, installing an AOI system near the process you must monitor can quickly correct a parameter that is about to enter the next step. At the same time, close-range detection can also reduce the number of non-compliant PCBS before the detection process.Although most AOI users in the electronics industry still only focus on post-soldering inspection, the future trend of miniaturization of components and PCBS will require more effective closed-loop process control. AOI systems that can provide effective detection and measurement solutions will attract more and more users, and engineers will also consider the investment in such systems to be more worthwhile. For all customers, AOI will continue to play an important role in improving product production lines and increasing the yield of finished products.

Analysis of the Differences between Online Testers and Automatic Visual Inspection Instruments

Analysis of the Differences between Online Testers and Automatic Visual Inspection Instruments I. Preface Recently, many friends have had such a question: "Our company hopes to introduce a set of automatic circuit board testing equipment, but we don't know how to choose between the online tester and the automatic visual inspection instrument?" . When answering these friends' questions, the author deeply felt that these friends in the electronics field lack sufficient information when facing new testing technologies. At the same time, it is also believed that some key issues should be clarified. Therefore, this article attempts to explain these two methods of circuit board testing. Second, cost differences: In terms of cost, it should include two items: equipment procurement cost and subsequent usage cost. Online testing instruments and automatic visual inspection instruments each have different advantages in these two aspects of cost. In terms of equipment procurement costs, generally speaking, online testers have a price advantage. The price of an automatic visual inspection instrument is several to dozens of times that of an online testing instrument. Relatively speaking, if there are people within the enterprise who can program and debug the automatic visual inspection instrument, the usage cost will be relatively low. The online tester also has inevitable costs such as needle discs and probes in use, and its usage cost is higher than that of the automatic visual inspection instrument. The total cost depends on the actual situation. Each enterprise has different circumstances and cannot be generalized. Third, differences in testing speed: In terms of testing speed, online testers using needle discs have obvious advantages. To achieve the same number of tests, several automatic visual inspection instruments are needed to be equivalent to one online testing instrument. This situation varies as the size of the circuit board to be tested increases. Take the computer motherboard as an example. Using a relatively new online tester, the testing time is approximately 10 seconds. However, it usually takes several minutes to use an automatic visual inspection instrument. Four. Differences in test Coverage In terms of test coverage, 稆 each has its own advantages. The automatic visual inspection instrument performs relatively well in the "visible" part, while the online test instrument performs better in terms of electrical characteristics. The relevant projects are as follows in Table 1. The project online tester and automatic visual inspection instrument can measure the open circuit and short circuit of the circuit base plate, but cannot measure the open circuit and short circuit of solder. Most of them can be measured. Some components, due to their special properties, cannot be tested. For integrated circuit boards such as PLCC or PGA, BGA, etc., the open/short circuit of pins cannot be tested, but most of the missing components can be tested. Some components cannot be tested due to the characteristics of the circuits. If a large capacitor is connected in parallel with a small capacitor, the values of the small capacitor cannot be measured, and the values of the measurable components have deviations or defects. If the measurable and non-measurable components are installed incorrectly, most of them can be measured. Some components cannot be tested due to the characteristics of the circuits. If a large capacitor is connected in parallel with a small capacitor, the small capacitor cannot be measured while the majority can. There is something measurable. Some components cannot be tested because they have no external markings. If a capacitor is attached, it cannot be measured. The defect of the integrated circuit bracket is measurable and unmeasurable. The post-production cracking of surface mount components during reflow soldering is measurable and unmeasurable. The tombstones produced by the 砀 of surface mount components during reflow soldering are measurable and measurable. The polarity of electrolytic capacitors is measurable, but due to the long required testing time, The common users do not test the false solder parts, the empty solder parts, the surface mount devices that are not fully loaded, and whether they are tested or not V. Differences in Accuracy: In terms of accuracy, both devices depend on the debugging of the program. However, the online tester also requires the cooperation of a needle bed, which poses a certain degree of complexity. On the other hand, the difficulty of program debugging for automatic visual inspection equipment is relatively high. Therefore, in terms of accuracy and misjudgment rate, these two types of equipment must be judged automatically by the user through actual use. Six. Differences in Application Scope Generally speaking, online testers are suitable for circuit boards with reliable measurement points. If the pin cannot be inserted due to the circuit board wiring, the online tester will be in a predicament where it has no place to be put to use. Secondly, online testers are suitable for products with large quantities. Due to the certain cost of the needle size, if the output of the product is too small, the average cost of the needle bed that each circuit board has to bear will be too high, which is not cost-effective from an economic perspective. The automatic visual measuring instrument is not restricted by the needle bed, but due to its relatively slow testing speed, it is not suitable for mass-produced products. Additionally, the relatively high purchase cost makes it unsuitable for products with lower profits. Therefore, the automatic visual inspection instrument is suitable for a small number of diverse products. On the one hand, it can save the cost of the needle bed; on the other hand, the slow speed does not pose a pressure on the testing of a small number of products. Vii. Conclusion. Online testing instruments and automatic visual inspection instruments each have their own advantages and disadvantages, and their application scopes are also different. In some respects, it can even play a complementary role. If a choice must be made, then taking all the above aspects into consideration, a correct decision should be achievable.

The basic principles of AOI

The basic principles of AOI The basic principle of AOIThe principle of image comparison, the principle of AOI statistical modeling, and optical principles The principle of image comparisonThe principle of image comparison: The image is captured by a CCD camera and then processed. Through specialized intelligent application software (which converts information such as pixel distribution, brightness and color into digital signals), it is transformed into the information we need. The AOI system testing process mainly determines whether the component is okay by comparing the image of the component to be tested with the standard image, including the component's size, Angle, offset, brightness, color and position, etc. The principle of AOI statistical modelingAOI statistical modeling enhances the system's ability to recognize OK and NG images by learning a series of OK templates, observing image changes, and combining the visual biases seen in all OK images to identify the features of component shape changes and possible future changes. During the process of learning the OK template, the following three problems are mainly solved: What should the shape of Component A look like?That is, the size, shape, color and surface pattern of the components, etc. What changes will occur to component B?That is, the variation rules of the natural size, shape, color and surface pattern of the components. How much will the shape of component C change? That is, the extent to which the size, shape, color, surface pattern, etc. of the components change is reasonable. The final result is a standard model for testing that integrates the above elements and lies between OK and NG

Analysis of PCB design layout rate and design efficiency techniques

Analysis of PCB design layout rate and design efficiency techniques Introduction: In PCB routing design, there is a complete set of methods to improve the layout rate. Here, we provide effective techniques for enhancing the layout rate and design efficiency of PCB design. These not only save the project development cycle for customers but also ensure the quality of the design product to the greatest extent. Determine the number of layers of the PCB The size of the circuit board and the number of wiring layers need to be determined at the initial stage of the design. If the design requires the use of high-density ball grid array (BGA) components, the minimum number of wiring layers needed for the wiring of these devices must be taken into consideration. The number of wiring layers and the stacking method will directly affect the wiring and impedance of the printed line. The size of the board helps determine the layering method and the width of the printing line, achieving the desired design effect. For many years, people have always believed that the fewer layers a circuit board has, the lower its cost will be. However, there are many other factors that affect the manufacturing cost of circuit boards. In recent years, the cost differences among multi-layer boards have been significantly reduced. When starting the design, it is best to use a large number of circuit layers and ensure that the copper coating is evenly distributed to avoid discovering a small number of signals that do not meet the defined rules and space requirements near the end of the design, thus being forced to add new layers. Careful planning before design will reduce a lot of trouble in wiring. 2. Design rules and restrictions The automatic wiring tool itself has no idea what it should do. To complete the wiring task, the wiring tools need to operate under the correct rules and constraints. Different signal lines have different wiring requirements. All signal lines with special requirements should be classified, and the classification varies with different designs. Each signal class should have a priority. The higher the priority, the stricter the rules. The rules involve the width of printed lines, the maximum number of vias, parallelism, the mutual influence between signal lines, and layer restrictions. These rules have a significant impact on the performance of routing tools. Carefully considering the design requirements is an important step towards successful wiring.

What are the differences between AOI automatic optical inspection equipment and X-RAY inspection equipment in SMT assemb

What are the differences between AOI automatic optical inspection equipment and X-RAY inspection equipment in SMT assembly and DIP through-hole production? What are the differences between AOI automatic optical inspection equipment and X-RAY inspection equipment in SMT assembly and DIP through-hole production?AOI is the abbreviation of Automatic Optical Inspection in English. Its basic principle is to check whether the SMT surface mount and DIP through-hole component mounting and soldering are correct, whether the position is good, and whether there are defects such as missed mounting and reverse alignment through the reflection of red, green and blue light. It is an automated inspection device.AOI (Automated Optical Inspection) is an automatic optical inspection instrument and equipment applied on the Surface mount Technology (SMT) production line. It can effectively detect the printing quality, mounting quality and solder joint quality. By using AOI automatic optical inspection instruments as tools to reduce defects, errors can be identified and eliminated in the early stage of the assembly process to achieve good process control. Early detection of defects will prevent defective products from being sent to the assembly stage of subsequent processes. AOI automatic optical inspection instruments will reduce repair costs and avoid scrapping non-repairable circuit boards. The implementation objective of the AOI automatic optical inspection instrument: Final quality: Usually placed at the very end of the SMT production line, it is used to check for product defects in SMT. Process control: Placed respectively after the printing machine and the surface mount technology (SMT) placement machine, it is used to inspect defects in the SMT process and provide feedback data.Inspection content: Solder paste defects, including presence or absence, deviation, insufficient solder, excessive solder, open circuit, short circuit, contamination, etc. Part defects, including missing parts, offset, skew, standing upright, standing sideways, overturned parts, reversed polarity, wrong parts, damage, etc. Solder joint defects, including insufficient solder, excessive solder, and continuous solder, etc. Advantages and features of X-RAY non-destructive ray inspection equipment X-RAY non-destructive ray inspection equipment is an X-ray fluoroscopy machine. Its principle is to utilize the characteristic that X-rays can penetrate non-metallic substancesIt adopts a structure combining a high-resolution enhanced screen and a sealed micro-focus X-ray tube. Through non-destructive X-ray fluoroscopy inspection, clear internal images of the product can be observed in real time. Check whether the lower parts of components such as BGA are soldered well and whether there are any short circuits, etc. The rapid development of high-density packaging technology has also posed new challenges to testing technology. To meet the challenges, new testing technologies are constantly emerging, and X-ray inspection technology is one of them. It can effectively control the welding and assembly quality of BGA. Nowadays, X-ray inspection systems are not only used in laboratory failure analysis, but have also been specially designed for PCB assembly in production environments and the semiconductor industry, providing high-resolution X-ray systems. The implementation goals of AXI non-destructive testing machine and X-ray optical inspection instrument: X-RAY non-destructive testing machines and X-Ray inspection machines provide non-destructive testing solutions for industries such as PCBA, SMT assembly, semiconductor devices, batteries, automotive electronics, solar energy, LED packaging, hardware parts, and wheels. Measurement range of X-ray inspection instrument: It is suitable for inspecting various types of SMT chips, electronic wafers, semiconductor chips,BGA, CSP, SMT, THT, Flip Chip and other components, etc. Welding/packaging inspection X_RAY(whether the structure, solder joints, and solder lines are de-soldered, poorly soldered, missed soldered, wrongly soldered, etc.). The application fields of X-RAY inspection equipment1. BGA soldering inspection (bridging, open circuit, cold soldering voids, etc.2. The connection conditions of ultra-fine parts such as system LSI (broken wires, solder joints)3. Semiconductor inspection of IC packaging, rectifier Bridges, resistors, capacitors, connectors, etc4. Inspection of PCBA soldering conditions5. Internal structure inspection of hardware components, electric heating tubes, pearls, heat sinks and lithium batteries, etc What are the differences between AOI automatic optical inspection equipment and X-RAY inspection equipment in SMT assembly and DIP through-hole production? The current application and the transformation process of effective quality control methods in the SMT patch processing industry. The traditional quality control methods for SMT patch soldering production and processing all relied on manual visual inspection (referred to as visual inspection). Next, microscopic optical technology is introduced, and optical magnification technology is used for the quality inspection of industrial circuit boards. Later, it was found that the application of this technology was increasingly unable to keep up with the needs of industrial development. During this period, the AOI optical inspection instrument emerged. In China, after more than ten years of development in optical inspection technology, AOI has become an indispensable quality inspection device for PCBA surface mount technology production and processing. The AOI automatic optical inspection instrument has effectively solved the thorny problem of manual appearance inspection of flexible circuit boards, significantly reducing the labor cost for inspection and lowering costs. With the increasingly fierce market competition, terminal electronic product manufacturers are putting forward more and more strict requirements for the quality assurance of PCBA, among which the quality of the pads used for soldering chips is particularly strict. At present, for the appearance inspection of the gold surface of PCBA pads, many domestic enterprises still adopt the method of manual visual inspection, which has disadvantages such as low efficiency, poor reliability and low inspection quality. Due to the continuous rise in labor costs, the density of circuit integration will become increasingly higher, and manual visual inspection will inevitably be gradually phased out by machine vision inspection. The detection technology of AOI automatic optical inspection instruments is becoming increasingly intelligent, gradually growing and extending in the form of quality robots. Under the premise that the performance of AOI automatic optical inspection instruments is constantly improving and their integration capabilities are getting stronger and stronger, AOI automatic optical inspection instruments bring customers not only inspection but also a powerful tool for quality traceability and quality assurance. While we are constantly developing new products to enhance performance, we are also conducting research on AOI applications. We not only aim to teach our customers how to use AOI but also encourage them to make good use of it. We firmly believe that as long as it is flexibly applied, the prospects of visual AOI are immeasurable and the value it brings to customers is also tremendous.

AOI has a good detection rate for SMT component defects with relatively concentrated colors

AOI has a good detection rate for SMT component defects with relatively concentrated colors AOI has a good detection rate for SMT component defects with relatively concentrated colorsThe RGB color mode is a color standard in the industrial field. It acquires different colors by changing the three color channels of red (R), green (G), and blue (B) and their superposition on each other. RGB represents the colors of the red, green and blue channels, basically covering all the colors that human vision can perceive. It is also one of the most widely used color systems at present.AOI has a good detection rate for SMT component defects with relatively concentrated colorsThe RGB color mode uses the RGB model to assign an intensity value within the range of 0 to 255 to the RGB component of each pixel in the image. An RGB image only uses three colors, which can be mixed in different proportions to present 16,777,216 (255 * 255 * 255) colors on the screen.As shown in the following figureColor name: Red value (red) Green value (Green) Blue value (BlueBlack 0 0 0Blue 0 0 255Green 0 255 0Cyan 0 255 255Red 255 0 0Magenta 255 0 255Yellow 255 255 0White 255 255 255 The above colors are the commonly used basic colors. During AOI inspection, the color of each pixel in the component image captured by the camera is composed of three different values of RGB. By calculating the variation range of each value of RGB, the variation range of the component can be detected.In terms of the characteristics of color analysis and data analysis: AOI has a good detection rate for defects with relatively concentrated colors in SMT components, such as missing or incorrect parts of capacitors and ics, and its programming and debugging are also very simple.

AOI-OCR algorithm

AOI-OCR algorithm The OCR algorithm, namely the character recognition algorithm, is an effective image processing algorithm specifically for character recognition and detection. The OCR algorithm is divided into two parts. Firstly, sufficient samples (8) need to be trained to generate a standard character library for character recognition. Secondly, call up the produced standard character library to recognize the character to be tested and determine whether the character to be tested complies with the standard. The OCR algorithm is generally applied in the identification of important components, such as BGA, QFP, SOP, etc.