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Switching power supply surface physical inspection
time2006/03/06
- The physical inspection of the surface of the switching power supply is an important basis for the troubleshooting of the switching power supply. At the same time, the appearance of the switching power supply components, circuit boards, solder joints, etc. Switching power supply defect faults are generally caused by errors in the process of manufacturing, resulting in a switching power supply that does not work properly, and there are often physical defects in the switching power supply.
Then the surface physical inspection can generally be checked by a magnifying glass or by visual inspection. The surface inspection is mainly based on the failure of the switching power supply. For example, the power adapter and the charger are assembled for a period of time and the casing has cracks. The compatibility of the two raw materials of /ABS is not well treated, it is easy to crack, or the process, the internal stress is not well eliminated during the processing of the product. If there is foreign matter between the outer leads, the foreign matter may cause a short circuit between the leads. Mechanical damage on the surface of the PCB may result in an open circuit caused by a broken PCB trace.
After the switching power supply fails, it usually needs to do the destructive work such as slicing and de-encapsulation. At this time, the visual inspection is no longer used. Therefore, the physical inspection of the surface of the switching power supply is very important. In addition to recording the basic information, it is also necessary to pay attention to various aspects:
1. Mechanical damage: cracks, scratches, flaws in the pins, roots, and package seals of electronic parts; mechanical damage on solder joints and PCB surfaces.
2. Device sealing defects: the junction of the leads from the electronic components with the glass, ceramic and plastic, as well as the adhesion of the root and the sealing seam.
3. Device lead plating defects: uneven coating from the surface of electronic components, bubbles, pinholes and rust spots.
4. Contamination or adhesion on the surface of the PCB: mainly from the processing of the PCB.
5. Thermal damage or electrical damage to the device.
6. Layering and bursting of PCBs, etc.
7. Abnormality of the PCB surface treatment layer.
8. Whether there are remelting and cracking, solder joints, etc. at the solder joints.
At the beginning of designing the switching power supply, the rationality of the design of the switching power supply should be reconfirmed, and the requirements should be clearly specified in the production, transportation and storage. The abnormal parts should be inspected and recorded.