Temperature Effects on Capacitors
Temperature has a significant influence on the electrical characteristics, performance and lifetime of capacitors. High temperatures accelerate ageing, increase leakage current and shorten service life, while extremely low temperatures can reduce capacitance and increase Equivalent Series Resistance (ESR). Understanding how temperature affects different capacitor technologies helps engineers and technicians select the right capacitor for reliable long-term operation.
Why Temperature Matters
Every capacitor is designed to operate within a specified temperature range. Outside this range, its electrical characteristics may change significantly, reducing performance and reliability.
Manufacturers specify both the operating temperature range and the maximum rated temperature in the capacitor datasheet.
Effects of High Temperature
| Effect | Description |
|---|---|
| Higher Leakage Current | The dielectric becomes less effective, allowing more current to flow. |
| Higher Internal Pressure | Electrolytic capacitors may generate gas internally. |
| Electrolyte Drying | The electrolyte gradually evaporates, especially in aluminium electrolytic capacitors. |
| Shorter Lifetime | Ageing accelerates rapidly at elevated temperatures. |
| Higher ESR | As the capacitor ages, ESR increases and filtering performance decreases. |
Effects of Low Temperature
| Effect | Description |
|---|---|
| Higher ESR | Electrolytes become less conductive. |
| Reduced Capacitance | Some dielectric materials lose capacitance at low temperatures. |
| Slower Charging | Higher ESR limits charging current. |
| Poor Ripple Performance | Power supply filtering becomes less effective. |
| Reduced Efficiency | Higher internal losses occur. |
Temperature Ratings
| Typical Rating | Common Applications |
|---|---|
| 70°C | Older consumer electronics. |
| 85°C | General-purpose electronics. |
| 105°C | Power supplies, industrial equipment and automotive electronics. |
| 125°C | Automotive and harsh industrial environments. |
Typical Operating Temperature Ranges
| Capacitor Type | Typical Temperature Range |
|---|---|
| Ceramic | -55°C to +125°C |
| Polypropylene Film | -55°C to +105°C |
| Polyester Film | -55°C to +125°C |
| Aluminium Electrolytic | -40°C to +105°C |
| Tantalum | -55°C to +125°C |
| Supercapacitor | -40°C to +65°C (typical) |
Temperature and Capacitor Lifetime
Electrolytic capacitors are particularly sensitive to temperature. A common engineering guideline is that reducing the operating temperature by approximately 10°C can significantly extend the service life of many aluminium electrolytic capacitors.
Conversely, operating continuously at high temperatures accelerates ageing and reduces reliability.
Temperature Stability by Capacitor Type
| Capacitor Type | Temperature Stability |
|---|---|
| Silver Mica | Excellent |
| C0G / NP0 Ceramic | Excellent |
| Polypropylene Film | Excellent |
| Polyester Film | Good |
| X7R Ceramic | Moderate |
| Electrolytic | Moderate |
Reducing Temperature Stress
- Use capacitors with a higher temperature rating.
- Keep capacitors away from heat sinks and power resistors.
- Provide adequate airflow.
- Choose low-ESR capacitors for high ripple-current applications.
- Avoid operating continuously at the maximum rated temperature.
- Select high-quality components for demanding applications.
Common Temperature-Related Failures
| Failure | Likely Cause |
|---|---|
| Bulging electrolytic capacitor. | Overheating and internal gas generation. |
| Capacitance loss. | Electrolyte drying or dielectric ageing. |
| High ESR. | Long-term operation at elevated temperatures. |
| Electrolyte leakage. | Seal failure caused by heat. |
| Reduced filtering. | Combined increase in ESR and capacitance loss. |
Real-World Examples
| Equipment | Temperature Consideration |
|---|---|
| Computer Power Supply | Use 105°C low-ESR electrolytic capacitors. |
| Car Audio Amplifier | Must tolerate high ambient temperatures. |
| Solar Inverter | High operating temperatures require long-life capacitors. |
| LED Driver | Heat management greatly affects capacitor life. |
| Industrial Controller | Designed for continuous operation in harsh environments. |
Key Points
- Temperature significantly affects capacitor performance and lifetime.
- High temperatures increase leakage current and accelerate ageing.
- Low temperatures can increase ESR and reduce capacitance.
- 105°C capacitors are preferred for power electronics and demanding applications.
- Good thermal management greatly improves long-term reliability.