Definition
A polymer capacitor is a type of electrolytic capacitor that uses a solid conductive polymer as the electrolyte material for its electrode. The polymer replaces the liquid or solid manganese dioxide electrolytes found in conventional aluminum or tantalum electrolytic capacitors, providing low equivalent series resistance (ESR) and stable electrical performance.
Overview
Polymer capacitors are commonly manufactured in two main families: solid aluminum polymer electrolytic capacitors and solid tantalum polymer electrolytic capacitors. They are employed in a wide range of electronic applications, including power supplies, audio equipment, automotive electronics, and portable devices, where low ESR, high ripple‑current capability, and long operational life are required. The solid polymer electrolyte enables the capacitor to handle higher ripple currents and to exhibit improved temperature stability compared with traditional liquid‑electrolyte electrolytic capacitors.
Etymology/Origin
The term combines “polymer,” referring to high‑molecular‑weight organic compounds that can form conductive films (e.g., doped polyaniline or PEDOT), and “capacitor,” from the Latin capacitas meaning “capacity,” denoting an electrical component that stores charge. The designation “polymer capacitor” entered technical literature in the late 1990s as manufacturers introduced solid polymer electrolytes for electrolytic capacitors.
Characteristics
| Characteristic | Description |
|---|---|
| Electrolyte | Solid conductive polymer (e.g., PEDOT, polyaniline) replaces liquid electrolyte. |
| ESR | Typically 10–100 mΩ, markedly lower than comparable liquid‑electrolyte electrolytic capacitors. |
| Ripple‑current rating | Higher ripple‑current capability due to low ESR and uniform heat dissipation. |
| Temperature range | Usually –40 °C to +105 °C (some series up to +125 °C). |
| Lifetime | Long operational life; failure mechanisms are primarily related to dielectric breakdown rather than electrolyte drying. |
| Capacitance values | From a few microfarads to several hundred microfarads, depending on construction (aluminum vs. tantalum). |
| Form factor | Available in radial, axial, and surface‑mount device (SMD) packages. |
| Self‑healing | The solid polymer can redistribute charge locally, providing limited self‑healing after minor dielectric defects. |
Related Topics
- Electrolytic capacitor – a broader class of capacitors that use an electrolyte to achieve high capacitance values.
- Aluminum electrolytic capacitor – uses liquid or solid electrolyte with an aluminum foil electrode.
- Tantalum capacitor – utilizes tantalum metal as the anode; polymer electrolytes are used in solid‑tantalum variants.
- Solid‑state capacitor – a general term for capacitors employing solid electrolytes, including polymer and manganese dioxide types.
- Dielectric material – the insulating layer (often an oxide) that separates the capacitor’s plates.
- Equivalent series resistance (ESR) – a key parameter influencing capacitor performance in high‑frequency and high‑current applications.