Although MLCC is simple in function, it is widely used in electronic products such as smart phones. Once it fails, it will lead to circuit failure, abnormal function, and even safety problems such as product burning and explosion. The failure mode has to be subject to quality inspection and other related engineers' attention.
In many failure modes, capacitor leakage (low insulation resistance) is the most common type. The main reasons can be divided into internal factors in the manufacturing process and external factors in the production process.
The foreign matter inside the capacitor volatilizes the void formed during the sintering process. Cavities can cause short circuits between electrodes and potential electrical failure. If the cavity is large, it will not only reduce IR but also reduce the effective capacitance. When power is on, there may be local heating of the cavity due to leakage, which reduces the insulation performance of the ceramic medium and exacerbates leakage, thereby causing cracking, explosion, and combustion.
Sintering cracks are generally caused by rapid cooling during sintering and appear in the vertical direction of the electrode side.
Thermal shock mainly occurs during wave soldering, and the temperature changes abruptly, causing cracks between the internal electrodes of the capacitor. Generally, it is found through measurement that it is observed after grinding, usually a small crack, which needs to be confirmed by a magnifying glass, and in a few cases, it will be visible to the naked eye. Crack
Because the main component of MLCC is ceramic, in the process of placing components, sub-plates, screws, etc., it is likely that the capacitor is crushed and broken due to excessive mechanical stress, resulting in potential leakage failure. The crack at this time is generally oblique, cracking from the joint between the terminal and the ceramic body.