That green PCB board is tested with these 7 methods

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That green PCB board is tested with these 7 methods [Copy link]

The process of electronic hardware design includes hardware requirements, schematic design, PCB design, PCB manufacturing, UT and integrated testing, etc. Among them, in the PCB board processing and manufacturing link, in order to ensure the production quality of PCB boards, manufacturers usually use a variety of detection methods for different PCB defects during the production process. 7 Commonly used PCB board detection methods 1. Manual visual inspection of PCB boards Using a magnifying glass or a calibrated microscope, the operator visually inspects to determine whether the circuit board is qualified and when to perform correction operations. It is the most traditional detection method. However, due to the increase in PCB production, the reduction in the spacing between wires and the size of components on PCBs, this method is becoming increasingly unfeasible. Advantages: low budget cost and no test fixture. Disadvantages: human subjective errors, high long-term costs, discontinuous defect detection, difficulty in data collection, etc. 2. PCB board online testing Through the detection of electrical properties, manufacturing defects are found and analog, digital and mixed signal components are tested to ensure that they meet the specifications. There are several test methods such as bed of nails tester and flying probe tester. Advantages: low test cost per board, strong digital and functional test capabilities, fast and thorough short and open circuit testing, programming firmware, high defect coverage and easy programming, etc. Disadvantages: test fixtures are required, programming and debugging time, high cost of making fixtures, difficult to use, etc. 3. PCB board functional test Functional system testing is to use special test equipment in the middle stage and end of the production line to conduct comprehensive testing of the functional modules of the circuit board to confirm the quality of the circuit board. Functional testing can be said to be the earliest automatic testing principle. It is based on a specific board or a specific unit and can be completed with a variety of equipment. There are types such as final product testing, latest physical models and stacking tests. Functional testing usually does not provide in-depth data such as pin-level and component-level diagnosis for process improvement, and requires special equipment and specially designed test processes. Writing functional test programs is complicated, so it is not suitable for most circuit board production lines. 4. Automatic Optical Inspection Also known as automatic visual inspection, it is based on optical principles and uses a variety of technologies such as image analysis, computer and automatic control to detect and process defects encountered in production. It is a relatively new method to confirm manufacturing defects. AOI is usually used before and after reflow and before electrical testing to improve the pass rate of electrical processing or functional testing. The cost of correcting defects at this time is much lower than the cost after the final test, often reaching more than ten times. 5. Automatic X-ray Inspection It uses the different absorption rates of different materials to X-rays to see through the parts that need to be inspected and find defects. It is mainly used to detect ultra-fine pitch and ultra-high density circuit boards and defects such as bridging, chip loss, and misalignment generated during the assembly process. It can also use its tomography technology to detect internal defects of IC chips. It is currently the only method to test the welding quality of ball grid arrays and obscured solder balls. Advantages: It can detect BGA welding quality and embedded components without fixture costs. Disadvantages: Slow speed, high failure rate, difficulty in detecting rework solder joints, high cost and long program development time. 6. Laser Inspection System This is the latest development in PCB testing technology. It uses a laser beam to scan the printed circuit board, collect all measurement data, and compare the actual measurement value with the preset qualified limit value. This technology has been proven on light boards and is being considered for assembly board testing. The speed is fast enough for mass production lines. Advantages: fast output, no fixtures and visual non-covered access required. Disadvantages: high initial cost, many maintenance and use problems. 7. Dimension Inspection Use a two-dimensional image measuring instrument to measure hole position, length, width, position and other dimensions. Since PCB is a small, thin and soft product, contact measurement is easy to deform and cause inaccurate measurement. The two-dimensional image measuring instrument has become the best high-precision dimension measuring instrument. Different inspection methods have their own advantages and disadvantages. Manufacturers will choose the appropriate inspection method according to different PCB board types, complexity, defects and other specific conditions to ensure the quality of PCB boards. Interesting knowledge Some people say that they didn’t know that the green board was called PCB until they went to college. In fact, not all PCBs are green, there are also other colors such as black and purple. The green PCB board is because the surface of the board is coated with a "green oil layer", also known as a "solder mask layer", which is used to protect the circuit and prevent short circuits. (The above content is compiled from the Internet, the copyright belongs to the original author, if there is any infringement, please contact and delete.) Search for the WeChat applet [Kuaidian Academy] to learn front-end schematic design, PCB design and other courses for free.