Polymer Aluminum Electrolytic Capacitors Failure Mode

Polymer Al Capacitor

Main failure modes

ECAS series are carried out enough debug and screening in process.
Possibility of failure is low, and electrical characteristic is stable.

  • Accidental Failure : Short mode

    If more than allowable load (thermal stress / electric stress / mechanical stress) applied, rarely cause the breakdown of the dielectric layer and reach short circuit.

  • Wear-out Failure : Open mode

    Electrolyte (polymer) degrades under high temperature with the result that the Cap value deviates from the standard value, eventually leading to open mode.
    The ECAS series uses a conductive polymer, so it features a longer life than electrolyte-type conventional electrolytic capacitors that can experience dry-up failure. The ECAS series has a track record of problem-free use by many customers since its commercialization in 2000.

Failure Mode in Market

Failure Mode in Market is Open mode mainly.

Estimated life of wear-out failure

In the ECAS series, aging deterioration (decrease in capacitance, increase in ESR) occurs due to the electrochemical reaction of aluminum oxide (dielectric), which is an internal component, and organic components such as conductive polymers and carbon paste.

Figure 1. Change due to aging degradation of capacitance and ESR

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.

Figure 2. Relationship between time and active surface reduction (model)

ECAS series aging degradation (decrease in capacitance / increase in ESR) is a slow reaction over time due to the external environment and is predictable according to reaction kinetics.
The specific degree of deterioration is temperature-dependent or voltage-dependent. The temperature dependence is based on the reaction kinetics, that is, the Arrhenius model, and the voltage dependence is based on the Eyring model, which is an extension of the Arrhenius model.

Murata enabled the original degradation simulation based on this reliability logic.
By this deterioration simulation, it is possible to predict the degree of deterioration of capacitance / ESR under the actual usage environment and apply it in the design.
Please contact Murata for details.