The paper “Capacitor Degradation and Failure Mechanisms: Exploring Different Causes Across Technologies” was presented by Frank Puhane, Würth Elektronik eiSos GmbH & Co.KG, Waldenburg, Germany at the 5th PCNS Passive Components Networking Symposium 9-12th September 2025, Seville, Spain as paper No. 2.7.
This paper was selected and awarded by TPC Technical Program Committee as the:
OUTSTANDING PAPER AWARD
Introduction
This article presents a comprehensive study of how various capacitor types age, degrade, and eventually fail. Capacitors are a crucial yet failure-prone component in power supply and electronic systems. The paper clearly distinguishes between capacitor degradation (wear-out) and total failure, and it explores how environmental, electrical, and material factors influence both phenomena across technologies such as aluminum electrolytic capacitors, aluminum polymer, hybrid polymer, metallized film capacitors, multilayer ceramic capacitors (MLCCs), and supercapacitors (EDLCs).
Key Points
- Degradation vs. Failure: Degradation involves gradual performance loss (capacitance and ESR), while failure may be sudden and is quantified through metrics like FIT and MTBF.
- Technology-Specific Mechanisms: Each capacitor type has unique failure drivers—temperature, voltage stress, humidity, and mechanical stress influence them differently.
- Environmental Impact: High temperature, humidity, and applied voltage accelerate aging in most capacitors, while MLCCs are particularly susceptible to mechanical cracking.
- Reliability Modeling: Traditional FIT/MTBF metrics do not accurately represent individual component lifetime; separate lifetime estimation models are needed.
- Case Studies: Practical experiments on electrolytic, polymer, film capacitors, MLCCs, and supercapacitors illustrate correlations between environmental stress, weight loss, ESR increase, and capacitance drop.
Extended Summary
The article begins by clarifying the difference between capacitor degradation—a progressive reduction in performance—and total failure. While FIT and MTBF provide statistical reliability measures, they often overestimate practical lifetime because they do not predict when a capacitor can no longer fulfill its functional role in a circuit.
The paper thoroughly examines various capacitor technologies. Metallized film capacitors are sensitive to temperature, humidity, and AC voltage, with electrochemical corrosion being the critical failure mechanism under harsh conditions. Lifetime modeling often uses Arrhenius or Eyring laws, but parameters vary significantly among manufacturers. Aluminum electrolytic capacitors primarily degrade through electrolyte evaporation accelerated by high temperatures. Their lifetime is commonly modeled with Arrhenius-based formulas incorporating temperature, voltage, and ripple current effects. Aluminum polymer and hybrid polymer capacitors avoid electrolyte dry-out but are sensitive to humidity, which increases ESR over time, while capacitance remains stable.
Multilayer ceramic capacitors (MLCCs) have undergone major changes with the adoption of base-metal electrodes and miniaturization. BME MLCCs are prone to insulation resistance degradation due to oxygen vacancy electromigration and are very sensitive to mechanical stress. High CV density and thin dielectrics make them more vulnerable to cracking, which may lead to long-term reliability issues. Supercapacitors (EDLCs) show degradation under prolonged voltage stress due to slow faradaic reactions and electrolyte aging. Long-term endurance tests demonstrate that ESR and capacitance loss occur in two phases, with the initial period showing the fastest changes.
The article also includes case studies that quantify how environmental and operational conditions affect performance over time. For electrolytic capacitors, weight loss correlates with capacitance reduction under high-temperature endurance tests. Polymer and hybrid capacitors show ESR increases under 85°C/85% RH stress without significant capacitance loss. Metallized film capacitors exposed to 85°C/85% RH with AC voltage reveal rapid early capacitance drop, while THB-rated variants fare better. MLCCs demonstrate long-term voltage-dependent capacitance drift, and supercapacitors exhibit extended lifetimes under room-temperature, rated-voltage conditions with gradual performance decay.
Finally, the authors emphasize that lifetime estimation should be tailored to each capacitor type and application. FIT/MTBF provides statistical reliability for large populations but does not define practical end-of-life. Predictive methods incorporating environmental and operational factors—potentially enhanced with physics-based machine learning—are increasingly valuable for real-world reliability assurance.
Conclusion
The study highlights that capacitor lifetime and failure depend heavily on technology, environmental stress, and operating conditions. Accurate lifetime prediction requires distinguishing between statistical failure rates and practical end-of-life behavior. By analyzing degradation mechanisms, accelerated tests, and long-term studies across different capacitor technologies, the paper provides clear guidance for engineers designing high-reliability systems. Incorporating advanced modeling and predictive approaches can help in mitigating failures, extending service life, and improving the reliability of electronic systems where capacitors remain critical components.
