Attention should be paid to the appearance inspection of the switching power supply adapter

　　Visual inspection of switching power supply:

　　The appearance inspection is mainly to analyze and inspect the appearance defects of the switching power supply products. The purpose of the appearance inspection is to record the physical dimensions, materials, design, structure and markings of PCBs, electronic parts and solder joints, determine the appearance of damage, and detect abnormalities and defects such as pollution. These problems are evidence of errors, overloads and operating errors caused by process manufacturing or application, and these information are likely to be related to failures.

　　Visual inspection is usually used for visual inspection, and 1.5~10 times magnifying glass or optical microscope can also be used. One of the functions of the visual inspection is to verify the consistency of the PCB, electronic parts and solder joints of the process failure with the standards and specifications; the second function of the visual inspection is to find the problem points that may cause the failure. For example, after the power adapter and charger are assembled for a period of time, the shell is cracked. It may be that the compatibility of the two raw materials of PC/ABS is not handled properly and is easy to crack. Good to eliminate internal stress. If there are foreign objects between the outer leads, the foreign objects may cause a short circuit between the leads. Mechanical damage on the PCB surface may cause the PCB trace to break and cause an open circuit.

　　Since the failure analysis of the switching power supply may require destructive analysis work such as slicing and de-encapsulation, the object of the appearance inspection no longer exists, so detailed records should be made during the appearance inspection, and it is best to take some pictures. As a preliminary inspection, you may lose valuable information if you arbitrarily handle the target before checking the appearance. As part of the visual inspection procedure, firstly, all its information marks should be recorded, that is, the names, models, specifications, batches, production dates and other information of PCB manufacturers and electronic parts manufacturers should be recorded in detail. Secondly, special attention should be paid to the inspection of the following aspects:

　　1. Mechanical damage: cracks, scratches, and defects from the pins, roots and sealing seams of the electronic parts; mechanical damage marks on the solder joints and the PCB surface.

　　2. Device sealing defects: from the joints of the pins of electronic components and glass, ceramics and plastics, as well as the adhesion parts and sealing seams of the roots.

　　3. Device pin coating defects: uneven coating, bubbles, pinholes and rust spots on the surface of electronic components.

　　4. Pollution or adhesions on the PCB surface: mainly from the PCB processing process.

　　5. Thermal damage or electrical damage of the device.

　　6. PCB delamination and bursting, etc.

　　7. The abnormality of the PCB surface treatment layer.

　　8. Whether the solder joints are remelted, cracked, or welded.

　　When designing the reliability of the switching power supply, it is necessary to put forward clear control requirements in the process documents for the production, storage, storage and transportation processes, and the suspicious parts must be further checked with measuring instruments that can obtain information and data. All important information is photographed and recorded with microscope and video equipment

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