Chip capacitor (multi-layer chip ceramic capacitor) is a common component with a relatively large amount at present, the production of chip capacitors in terms of NPO, X7R, Z5U, Y5V and other different specifications, different specifications have different uses. In the process of use, we often encounter a variety of problems, which brings us no small impact. This paper mainly focuses on the situation of chip capacitor failure, analyzes its causes and countermeasures, and hopes to help you solve such problems more quickly and effectively.
The most common failure mode of chip ceramic capacitors is fracture, which is determined by the brittleness of the chip ceramic capacitor's own medium. Since the chip ceramic capacitor is welded directly to the circuit board, it can directly withstand various mechanical stresses from the circuit board, and the lead ceramic capacitor can absorb mechanical stresses from the circuit board through the pin. Therefore, for chip ceramic capacitors, mechanical stress caused by different coefficient of thermal expansion or circuit board bending will be the most important factor of chip ceramic capacitor fracture.
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After mechanical fracture of ceramic chip capacitor, the electrode insulation distance at the fracture will be lower than the breakdown voltage, which will cause arc discharge between two or more electrodes and completely damage the ceramic chip capacitor. The profile microstructure of ceramic chip capacitor due to discharge between electrodes after mechanical fracture is shown as follows:
The above figure shows the profile microstructure of ceramic chip capacitor due to discharge between electrodes after mechanical fracture. The main methods to prevent mechanical fracture of ceramic chip capacitor are: reduce the bending of the circuit board as much as possible, reduce the stress of ceramic chip capacitor on the circuit board, and reduce the mechanical stress caused by the difference between the thermal expansion coefficient of ceramic chip capacitor and the circuit board. How to reduce the stress of the ceramic chip capacitor on the circuit board will be described separately below, and will not be repeated here. The mechanical stress caused by reducing the difference in the coefficient of thermal expansion between ceramic chip capacitors and circuit boards can be slowed down by choosing capacitors with small package sizes, such as aluminum-based circuit boards should be packed below 1810 as far as possible, and if the capacitance is not enough, multiple parallel methods or laminated methods can be used to solve the problem. It can also be solved by ceramic capacitors in the form of packages with pins.