7 ways to detect PCB board

In order to ensure the production quality and life of PCB, manufacturers have experienced a variety of inspection methods in the production development process, and each inspection method is mainly for different PCB defects of enterprises. circuit printing service Basically, it can be divided into two categories: electrical test analysis methods and visual test research methods.

Electrical testing typically measures the impedance characteristics between test points to detect all continuity (i.e. open and short circuits). Visual testing detects defects by visually examining the characteristics of electronic components and printed circuits. PCB fabrication company Electrical testing is more accurate when looking for short or open circuit defects. Visual testing makes it easier to spot incorrect gaps between conductors. Visual inspection is usually carried out early in the production process. Strive to find defects and fix them to ensure the highest product compliance rate.

Common PCB inspection methods are as follows:

1. Manual eye inspection of PCB board

Use a magnifying glass or calibrated microscope to visually inspect the operator and determine when we need students to perform analytical corrections. This is the most traditional method of inspection work. Its main advantage is that the initial cost is low, no need to pass the test fixture, but the main disadvantages are large subjective errors, high long-term development costs, china PCB discontinuous detection of defective products, and various difficulties in data information collection. At present, with the increase of printed circuit board production in China, the reduction of wire spacing and component volume, this teaching method research is becoming more and more impractical.

2. PCB board online test

Identify manufacturing defects through electrical performance testing and test analog, digital, and mixed-signal components to ensure they meet specification requirements. The test methods include needle bed tester, flying needle tester, etc. The main advantages are low cost per board test, powerful digital and functional testing capabilities, fast and thorough short and open circuit testing, programmable firmware, high defect coverage, and ease of programming. The main disadvantages are that the fixture needs to be tested, the programming and debugging time is long, the fixture manufacturing cost is high, and the use is difficult.

3. PCB board function test

Function management system analysis test is the use of special test equipment, in the middle stage and the end of the production line, the circuit board between the functional modules for comprehensive testing to confirm the quality of the circuit board. Function test method can be said to be the earliest automatic control test working principle in our country. It's based on a particular board or a particular unit, and we can choose to use a variety of teaching equipment to do it. Eventually there will be product testing, the latest physics learning model and stack testing. Functional testing usually does not provide more in-depth data (for example, pin position and component-level diagnostics) to improve the production process, but society needs a special equipment and a test program designed in some special environment. Writing functional test programs is complex, so it is not suitable for most circuit board production lines.

4. Automatic optical inspection

Also known as automatic appearance inspection, it is based on optical principles, using image analysis, computer and automatic control technology to detect and deal with defects encountered in production. This is a relatively new method for identifying manufacturing defects. Aoi solution is usually used before and after reflux and before electrical tests to improve consistency with electrical treatment or functional tests. At this point, the cost of fixing the defect is much lower than after the final test, often more than ten times the final test.

5. Automatic X-ray examination

According to the difference of X-ray absorptivity of different substances, the parts under test are checked and the defects are found. It is mainly used to detect defects in ultra-fine pitch and ultra-high density circuit boards, as well as defects such as bridging, chip defects, and poor alignment during assembly. It can also use tomography technology to detect internal defects in IC chips. This is the only way to test the quality of the ball grid array and the welding ball. The main advantage is that the welding quality of the BGA and the ability to embed components can be detected without the cost of fixtures. This is a relatively new test method, the effect is remarkable.

6. Laser detection system

This is the latest research and development of PCB test information technology. It uses a laser beam to scan the PCB, collect all the student measurement system data of the enterprise, and analyze and compare the actual measured value in China with the pre-set qualified limit value. The technician has been further validated on bare panels and is being considered for testing in assembly panels. This working speed is sufficient for the economic batch production line in our country. Its main method advantage is the fast output speed, does not form a fixed device and accessible vision, its main disadvantage is the high initial cost, as well as management maintenance and use of these issues.

7. Size check

The position, length, width and position of the hole were measured by using a two-dimensional image measuring instrument. Since PCB is a small, thin, soft product, contact measurement is easy to deform, resulting in inaccurate measurement. Two-dimensional image measuring instrument has become the best high-precision dimensional measuring instrument. The image measuring instrument can be programmed to realize automatic measurement, which not only has high measurement accuracy, but also greatly reduces the measurement time and improves the measurement efficiency.

In summary, among the seven detection technologies and methods, optical detection and X-ray detection are the most popular in the Chinese market.