Polymer Aluminum Electrolytic Capacitors Failures and Life

The main failure mode of the ECAS series is open mode due to aging (1).
We carry out sufficient debugging and screening in our process. Therefore, basically, the probability of a failure occurring is low and the characteristics are stable. Nevertheless, the possibility of a failure occurring is not zero. In addition, there is a possibility of short mode occurring under harsh conditions such as when a load exceeds the allowable limit is applied (2).

Failure Mode in Market is Open mode mainly.

Polymer aluminum electrolytic capacitors slowly degrade due to the usage conditions such as the ambient temperature and humidity.
Specifically, deterioration appears as a decrease in capacitance and an increase in ESR due to the electrochemical reaction of aluminum oxide (dielectric), which is an internal component, and organic components such as conductive polymers and carbon paste.

The decrease in capacitance and the increase in ESR due to aging are caused by the decrease in the active area of the electrode and the decrease in the contact area between layers due to the products generated by the electrochemical reaction, as shown in the figure below.

In this way, if we define the state in which the ESR or capacitance has degraded by a certain amount as the end of the life of the capacitor, we can also estimate the time until that life ends.
The temperature dependence is based on reaction kinetics, that is, the Arrhenius model. The voltage dependence is based on the Eyring model, which is an extension of the Arrhenius model.

Murata provides an original estimated life calculation tool based on this reliability logic.
This simulation makes it possible to predict the degree of capacitance/ESR degradation under the actual usage environment. That can then be applied to the design.