PCB Capacitor and Resistor Failure Analysis

金鉴实验室邵工

PCB Capacitor and Resistor Failure Analysis [Copy link]

Disassemble the NG1 lamp power supply, test the MOS switch tube on the board, and find that the DS pin is short-circuited. After removing it from the board, test DS and it is normal, so other circuits on the power supply board are short-circuited. From the appearance, it can be observed that the varistor has exploded. After removing the varistor, the MOSFET switch tube DS on the power supply is no longer short-circuited, so it is caused by the short-circuited varistor. Test other components and find that the capacitor has a serious reduction in capacity, and the fuse, transformer, etc. of the power supply are normal. After removing the varistor and powering on the test, the power supply can light up the light source.

When disassembling the failed capacitor NG1, it was found that the aluminum film inside was melted. When the aluminum film was unfolded and compared with the aluminum films of other conventional CBB capacitors, the color of the aluminum film of the failed NG1 capacitor was darker.

Metallographic sectioning + argon ion grinding sectioning analysis of the failed capacitor NG2 revealed that the aluminum film inside the capacitor had melted under SEM. Since the C1 capacitors of the samples tested all failed to varying degrees, it is recommended that the power supply manufacturer confirm the capacitors of the same batch and strengthen the reliability inspection of the power supply.

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Is the melting of aluminum film caused by high pressure?

金鉴实验室邵工

qwqwqw2088 posted on 2021-6-3 12:57 Is the melting of aluminum film caused by high pressure?

When disassembling the NG1 capacitor, it was found that the aluminum film inside was melted. When the aluminum film was unfolded and compared with the aluminum film of other conventional CBB capacitors, the color of the aluminum film of the failed NG1 capacitor was black, which was inferred to be oxidized. When the NG2 capacitor was sliced metallographically, the aluminum film inside the capacitor was observed to be melted under SEM .

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Jinjian Laboratory Engineer Shao published on 2021-6-4 10:53 After disassembling the NG1 capacitor, it was found that the aluminum film inside was molten. The aluminum film was compared with other conventional CBB capacitor aluminum films. The color of the aluminum film of the failed NG1 capacitor was black, ...

The analysis makes sense