薄膜电容器的容量大小取决于薄膜金属层面积的大小，所以容量的下降主要就是金属镀层受外界因素影响，面积减少而产生的。

　　The capacity of thin film capacitor depends on the area of metal layer, so the decrease of capacity is mainly caused by the reduction of metal coating area affected by external factors.

　　在电容器制作过程中，膜层之间存在微量的空气，且较难完全消除。电容器工作时，空气在电场作用下，有可能被电离。空气电离后产生臭氧，臭氧是一种不稳定的气体，常温下自行分解为氧，是一种强氧化剂，低浓度下可瞬间完成氧化作用。

　　In the process of capacitor fabrication, there is a trace of air between the films, which is difficult to eliminate completely. When the capacitor works, the air may be ionized under the action of electric field. Ozone is a kind of unstable gas, which can decompose into oxygen at room temperature. It is a strong oxidant, and it can complete oxidation instantly at low concentration.

　　金属化薄膜的金属镀层（成份为Zn/Al）遇到臭氧分解的氧后立即氧化，生成透明不导电的金属氧化物ZnO和Al2O3，实际表现为板面积减小，电容器容量下降。因此消除或减少膜层间的空气，可以减缓电容量衰减。

　　The metal coating (Zn / Al) of the metallized film will be oxidized immediately when it meets the oxygen decomposed by ozone, resulting in transparent and non-conductive metal oxides ZnO and Al2O3. The actual performance is that the plate area decreases and the capacitor capacity decreases. Therefore, eliminating or reducing the air between the films can slow down the capacitance attenuation.

　　当膜层间的空气被外界水份侵入时，空气的击穿电位会降低，加快空气电离，产生大量的臭氧，氧化金属化薄膜的金属镀层，电容器的容量会迅速下降。

　　When the air between the film layers is invaded by external water, the breakdown potential of the air will be reduced, which will accelerate the air ionization and produce a large amount of ozone. The capacitance of the capacitor will decrease rapidly when the metal coating of the metallized film is oxidized.