Advanced Testing Methods in PCB Manufacturing: Ensuring Quality Through Innovation and Precision

In order to ensure the production quality of electronic circuit boards, circuit board manufacturers use a variety of testing methods in the production process, each testing method for different electronic circuit board defects. For example, manual inspection, flying pin test, AOI inspection equipment, etc. These tests can be basically divided into electrical testing and visual testing. Let's take a look.

1. Manual visual inspection

The operator uses a magnifying glass or calibrated microscope to observe and determine whether the board is qualified, which is the most traditional testing method. Its main advantages are low cost and no need for test fixtures. However, this method is prone to subjective errors, higher long-term costs, discontinuous defects are difficult to find, and data collection is more difficult. With the increase in PCB production and the reduction in wire spacing and component size, this method is gradually being phased out.

2. In-Line Testing

The electrical properties of PCB boards are examined by means of needle-bed testers and flying probe testers, etc., to find out manufacturing defects as well as to test analog, digital and mixed-signal components to ensure their conformity. Advantages include low test cost per board, high digital and functional test capability, fast and thorough short and open circuit testing, programmed firmware, high defect coverage, and ease of programming.2 oz copper thickness in mm However, this type of test requires test fixtures, programming and debugging time, higher cost of making fixtures and more difficult to use. Shenzhen Qinji Electronics factory can save test fixtures for customers to provide customers with subsequent PCB orders for hassle-free production and testing.

3. Functional test

Functional test can be said to be one of the earliest automatic testing principles. It is based on specific boards or specific units and can be accomplished using a variety of equipment. In the middle stage and at the end of the production line, the board's functional modules are thoroughly tested using specialized test equipment to confirm the board's goodness. There are types of functional system testing such as final product testing, up-to-date physical modeling and stacked testing. However, these types of tests typically do not provide in-depth data such as foot-level and component-level diagnostics for process improvement, and require specialized equipment and specially designed test procedures. Writing functional test programs is complex and therefore not applicable to most board production lines.

4. Automated Optical Inspection

Automatic Optical Inspection is based on optical principles and uses a combination of technologies such as image analysis, computers and automatic control to detect and process defects encountered in production.plated through hole vs via It 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 at the electrical processing or functional testing stage. The cost of correcting defects at this point is far less than if they were performed after final testing, and can often be as much as ten times greater.

5. Automated X-ray Inspection

Automated X-ray inspection is mainly used to detect ultra-fine pitch and ultra-high density circuit boards, as well as the assembly process generated during the bridging, lost pieces, poor alignment and other defects. In addition, it can also be used to detect internal defects of IC chips using its chromatographic imaging technology. It utilizes the difference in the absorption rate of different substances to X-rays to see through the parts that need to be inspected in order to find defects. Currently, automated X-ray inspection is the only method to test the soldering quality of ball grid arrays (BGAs) and obscured solder balls. This method is capable of detecting BGA solder quality and embedded components without the cost of fixtures; however, it is slower, has a higher failure rate, is difficult to detect reworked solder joints, is more costly, and requires a longer program development time. This is a newer inspection method and is subject to further research.

6. Laser inspection system

Laser inspection system is the latest development in PCB testing technology. It utilizes a laser beam to scan the printed circuit board, collects all the measured data, and compares the actual measured values with the preset qualified limit values. This technology has been proven on bare boards and is being considered for assembly board testing. It is fast enough to be used in batch production lines. Advantages include fast output, no fixturing required, and visual non-obscuring access; major disadvantages are high initial cost and more maintenance and usage problems.

7. Dimensional Inspection

Since PCBs are small, thin and soft types of products, contact measurements are prone to deformation, resulting in inaccurate measurements. Therefore, the quadratic image measuring instrument has become the best high-precision dimensional measurement instrument. This method utilizes a quadratic image measuring instrument to measure dimensions such as hole position, length and width, and positional degree. The image measuring instrument of SIRI Measurement is able to realize fully automatic measurement through programming, which not only has high measurement accuracy, but also can greatly shorten the measurement time and improve the measurement efficiency.

Dimensional Inspection Laser inspection system X-ray Inspection

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