Our drive power supply is often used, and chip capacitors often fail. Especially mass-produced power supplies. Here are a few common reasons for your failure, and how to avoid them.

1. During the mounting process of the chip capacitor, if the pressure of the nozzle head of the chip mounter is too large, it is easy to deform and lead to cracks; this situation is relatively rare, but once a problem occurs, a large proportion of the batch will fail. .

2. The chip capacitor is too close to the edge of the PCB, which will cause the capacitor to be broken internally after being stressed.

Solution: Improve the layout so that the capacitors are parallel to the edge or as far away as possible; use mechanical splitting; deepen the micro-cutting depth to 1/3; add slots to facilitate splitting.

In fact, adding slotting is the most reliable method. When slotting, pay attention. If the chip capacitor is too close to the edge, and there is not enough space for slotting, then you slot on the other side. The same effect, pay attention to the slot width It should not be too small. If it is too small, the supplier will not be able to process it. Generally, it is at least 1mm.

3. The chip capacitor pad is connected to the nearby large solder joint. It is subjected to thermal expansion thrust during welding, and shrinks during solidification to generate tensile force, which is easy to cause cracks in the capacitor.

Sometimes, it is convenient to put a chip capacitor in the large electrolysis to go to high frequency, and put another chip resistor to discharge.

In this way, the chip capacitor has the possibility of failure, too close to the large electrolysis. This problem can be avoided by swapping the position of the chip capacitor and the chip power.

4. Thermal shock during the welding process and the deformation of the substrate after welding can easily lead to cracks: during the wave soldering process of the capacitor, insufficient preheating temperature, insufficient time or excessive welding temperature may easily lead to cracks.

5. In the process of manual repair welding, the tip of the soldering iron is in direct contact with the ceramic body of the capacitor, and the capacity causes cracks. The deformation of the substrate after welding (such as splitting, installation, etc.) is also prone to cracks.

The above is the failure in the production process, and we also need to pay attention when we choose the voltage and capacitance of the chip capacitor:

1. When using a large capacitance value (uF level) such as VCC capacitor, try to choose a large foreign brand such as TDK capacitor or increase the withstand voltage value of domestic capacitor by one level.

2. Try not to use high-voltage and large-capacity chip capacitors, such as capacitors above 100V/100nF.

In general, as long as we pay attention to design and production, most of the chip capacitor failures can be avoided.