Capacitance degradation of metallized film capacitors under 85℃/85% RH

Atmospheric corrosion is one of the key factors affecting the working reliability of metallized film capacitors (MFCs) in a harsh environment (e.g., high temperature and humidity). When corrosion occurs, the electrodes, which are layers of nano-scaled Zn-Al alloy, will be oxidized, leading to capacitance loss. To study the characteristics of capacitance degradation evolution process of MFCs, an accelerated aging test was carried out at 85 ℃ and 85% RH. with 8 types of MFC specimens, the electrode composition of which is in a range from 2 wt.%Al/98 wt.%Zn to 100 wt.%Al. The results indicates the capacitance loss rate is reduced over time. Also, as aluminum content increases, the capacitance degradation is inhibited, especially when aluminum content is in 2-20 wt.% .