What is polymer capacitor?

Polymer capacitor is a type of electrolytic capacitor that uses conductive polymer materials as electrolytes and belongs to a subdivision of solid-state electrolytic capacitors. Its core feature is that polymer can replace traditional liquid or gel electrolyte, significantly improving high-frequency performance, life and stability, and is widely used in high reliability electronic equipment.

Basic Structure and Principle

Electrode material:

Positive electrode: aluminum foil (polymer aluminum electrolytic capacitor) or tantalum metal (polymer tantalum capacitor).

Negative electrode: Conductive polymers (such as polypyrrole, polyaniline) or manganese dioxide (some tantalum capacitors).

Dielectric layer: The oxide film generated by anodic oxidation on the surface of the positive electrode (such as Al ₂ O3, Ta ₂ O ₅).

Encapsulation:

Aluminum shell or resin packaging (patch or direct insertion).

Working principle:

By conducting current through conductive polymers and using oxide film media to store charges, charging and discharging can be achieved.

core features

|Characteristics | Polymer Capacitors | Traditional Electrolytic Capacitors (Liquid)|

|Electrolyte | Solid conductive polymer | Liquid or gel electrolyte|

|ESR (Equivalent Series Resistance) | Extremely low (milliohm level) | High (ohm level)|

|High frequency performance | Excellent (suitable for MHz level high-frequency filtering) | Poor (only applicable to low frequencies)|

|Long lifespan (100000 hours+, no electrolyte drying) | Short lifespan (2-5 years, electrolyte evaporation failure)|

|Leakage current | Extremely low (nA level) | High (μ A level)|

|Temperature resistance | 55 ℃~125 ℃ (some models support higher temperatures) | Typically<105 ℃|

|Volume | Small (high capacity density) | Large (under the same capacity)|

|Safety | No leakage or explosion risk | Overpressure or reverse connection may cause explosion|

Main types

(1) Polymer aluminum electrolytic capacitor

Structure: Aluminum foil positive electrode+conductive polymer electrolyte.

Characteristics:

Capacity range: 1 μ F~1000 μ F, withstand voltage 6.3V~100V.

Cost lower than polymer tantalum capacitors, suitable for medium to high frequency filtering.

Application: Mainboard CPU power supply, graphics card power filtering, LED driver.

(2) Polymer tantalum capacitor

Structure: Tantalum powder sintered positive electrode+conductive polymer electrolyte.

Characteristics:

Capacity range: 0.1 μ F~470 μ F, withstand voltage 2.5V~35V.

Smaller size, excellent high-frequency performance, and strong surge resistance.

Applications: Smartphones, tablets, precision medical equipment.

(3) Hybrid polymer capacitor

Structure: Liquid electrolyte+polymer material mixture.

Characteristics:

Balancing lifespan and cost, ESR is slightly higher than that of pure polymer capacitors.

Application: Industrial power supply, automotive electronics (cost sensitive scenarios).

Typical application scenarios
Digital circuit power supply:

Provide low-noise power supply for chips such as CPU, GPU, FPGA, etc. (such as polymer capacitor arrays on motherboards).

High frequency filtering:

Switching power supply output filtering (replacing traditional electrolytic capacitors to reduce ripple).

Portable devices:

Mobile fast charging circuit, TWS headphone battery management (relying on small size and low ESR).

Automotive Electronics:

In car infotainment system, ADAS module (high temperature resistance, vibration resistance).

Industrial control:

Servo drive, PLC module (ensuring equipment reliability with long lifespan).

Key parameters for selection

|Parameter | Description|

|Rated voltage | Operating voltage should be ≤ 80% of the rated value (e.g. 16V capacitor used for ≤ 12.8V scenarios). |

|Capacity and ESR | Low ESR models are preferred for high-frequency scenarios (such as polymer tantalum capacitors with ESR as low as 10m Ω). |

|Temperature range | Automotive electronics require 40 ℃~125 ℃, while consumer electronics choose 25 ℃~85 ℃. |

|Expected lifespan | Choose models with a lifespan of 105 ℃ or 125 ℃ in high-temperature environments (lifespan>5000 hours). |

|Packaging form | Surface mount (SMD) is suitable for automated production, while plug-in (plug-in) is suitable for manual maintenance scenarios. |

Comparison of Polymer Capacitors vs. Other Capacitors

Precautions for use
Polarity requirement:

Strictly distinguish between positive and negative poles! Reverse connection may cause short circuit or permanent damage.

Voltage limit:

Avoid instantaneous surge voltage exceeding the rated value (can be protected by parallel TVS diodes).

Welding process:

The reflow soldering temperature of surface mount capacitors should be ≤ 260 ℃ to prevent high temperature damage to polymer materials.

Energy storage substitution:

Polymer capacitors have limited capacity, and high-capacity energy storage requires the use of electrolytic capacitors or supercapacitors.

Polymer capacitors have solved the high ESR, short lifespan, and leakage problems of traditional electrolytic capacitors through solid-state polymer electrolyte technology, becoming the preferred choice for modern high-density and high reliability circuit design. Its low ESR, high frequency response, and long lifespan characteristics are particularly prominent in digital power supply, portable devices, and automotive electronics. Despite the high cost, polymer capacitors have far more advantages than traditional solutions in scenarios with strict performance requirements. When selecting, special attention should be paid to voltage margin, ESR, and temperature adaptability to ensure precise matching with circuit requirements.