As the carrier of various components and the hub of circuit signal transmission, PCB has become the most important and critical part of electronic information products, and its quality and reliability level determine the quality and reliability of the whole equipment. With the miniaturization of electronic information products and the environmental requirements of lead-free and halogen-free, PCB has also developed in the direction of high density, high Tg and environmental protection. However, due to cost and technical reasons, PCB has a large number of failure problems in the production and application process, and therefore caused a lot of quality disputes. In order to find out the cause of the failure in order to find a solution to the problem and distinguish the responsibility, it is necessary to carry out failure analysis on the failure cases.

　　To obtain the exact cause or mechanism of PCB failure or failure, it is necessary to follow the basic principles and analysis process, otherwise valuable failure information may be missed, resulting in the analysis can not continue or may get wrong conclusions. The general basic process is that the failure location and failure mode must first be determined based on the failure phenomenon through information collection, functional testing, electrical performance testing and simple appearance inspection, that is, failure location or fault location. For simple PCB or PCBA, the failure site is easy to determine, but for more complex BGA or MCM packaged devices or substrates, the defect is not easy to observe through a microscope, and it is not easy to determine at this time, you need to use other means to determine. Then it is necessary to analyze the failure mechanism, that is, the use of various physical and chemical means to analyze the mechanism that causes PCB failure or defects, such as virtual welding, pollution, mechanical damage, wet stress, medium corrosion, fatigue damage, CAF or ion migration, stress overload and so on. Then there is the failure cause analysis, that is, based on the failure mechanism and process process analysis, to find the cause of the failure mechanism, and carry out test verification when necessary. In general, test verification should be carried out as far as possible, and the accurate cause of induced failure can be found through test verification. This provides a targeted basis for further improvement. Finally, according to the test data, facts and conclusions obtained in the analysis process, the failure analysis report is prepared, requiring the report to be clear, logical and well-organized, and avoid imagination.