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In order to ensure the production quality of PCB boards, we need to conduct certain tests on the quality and performance of PCBs. This article will share with you the methods of testing the quality of PCBs.
In order to ensure the production quality of PCB boards, we need to conduct certain tests on the quality and performance of PCBs. Each inspection method is aimed at different PCB board defects, and can basically be divided into the following types.
1. Manually inspect the PCB board visually
Use a magnifying glass or a calibrated microscope to determine whether the circuit board is qualified through the operator's visual inspection, and to determine when a correction operation is required.
This is the most traditional inspection method. Its main advantages are low initial cost and no test fixture, but the main disadvantages are subjective human error, high long-term cost, discontinuous defect detection, and difficulty in data collection. Currently, due to the increase in PCB production and the shrinking of the wire spacing and component volume on the PCB, this method is becoming increasingly infeasible.
2. PCB board online test
Identify manufacturing defects through electrical performance testing, and test analog, digital, and mixed-signal components to ensure they meet specifications. There are several test methods, such as the bed of needle tester and flying probe tester.
The main advantages are the low test cost of each board, powerful digital and functional test functions, fast and thorough short-circuit and open-circuit tests, programming firmware, high defect coverage, and easy programming. The main disadvantages are the need to test fixtures, programming and debugging time, fixture manufacturing costs, and difficulty to use.
3. PCB board function test
Functional system testing is a comprehensive test of circuit board functional modules using special test equipment at the intermediate stage and at the end of the production line 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 done using various devices.
There are final product testing, the latest physical model, and stack testing. Functional testing usually does not provide in-depth data (for example, pin location and component-level diagnostics) to improve the process, but requires special equipment and specially designed test procedures. Writing functional test programs is very complicated, so it is not suitable for most circuit board production lines.
4. Automatic optical inspection
It is also called automatic appearance inspection. It is based on optical principles and comprehensively uses image analysis, computer, and automatic control technology to detect and deal with defects encountered in production. This is a relatively new method of identifying 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. At this time, the cost of correcting the defect is much lower than the cost after the final test, usually more than ten times.
5. Automatic X-ray inspection
Use the difference in X-ray absorption of different substances to inspect the parts to be tested and find defects. It is mainly used to detect defects in ultra-fine pitch and ultra-high-density circuit boards, as well as bridges, missing chips, poor alignment, and other defects generated during the assembly process. It can also use tomography to detect internal defects in IC chips.
This is the only way to test the soldering quality of ball grid arrays and solder balls. The main advantage is the ability to check the quality of BGA soldering and embedded components without the need to spend fixtures. This is a relatively new test method with significant results.
6. Laser detection system
This is the latest development of PCB testing technology. It scans the printed board with a laser beam, collects all measurement data, and compares the actual measurement value with the preset qualified limit value. This technology has been verified on bare boards and is being considered for assembly board testing.
This speed is sufficient for mass production lines. Fast output, no fixtures, and barrier-free visual access are its main advantages; high initial cost, maintenance, and use problems are its main disadvantages.
7. Dimension check
Use a two-dimensional image measuring instrument to measure the position, length and width, position, and other dimensions of the hole. Since the PCB is a small, thin and soft product, it is easy to deform in contact measurement, resulting in an inaccurate measurement.
The two-dimensional image measuring instrument has become the best high-precision dimension measuring instrument. The image measuring instrument can realize automatic measurement after programming, which not only has high measurement accuracy but also greatly shortens the measurement time and improves the measurement efficiency.
Visual inspection is usually carried out early in the PCB production process. It can try to find defects and repair them to ensure the highest product pass rate. Electrical testing usually measures the impedance characteristics between test points to detect all continuity (ie, open circuit and short circuit), which will be more accurate in detection.
Choosing a suitable inspection method will be more efficient and accurate for detecting the quality of printed circuit boards. If you want to know more about this, please contact us for a comprehensive solution.
As a professional PCB product manufacturer, we have won praise and trust from many customers with our excellent R&D technology and high-quality products. We have a professional production team and strict quality inspection system, which can test and inspect all aspects of product quality. At the same time, we will provide thoughtful one-stop service and effective solution technology according to the actual needs of customers. If you are interested in our printed circuit boards, please contact us immediately!