Polymer Cap
A conductive-polymer capacitor stores charge while using a conductive polymer in its cathode system. The cited Cornell Dubilier guide specifically documents solid-polymer aluminum capacitors; it is not a rating sheet for every polymer technology.
In the aluminum construction described by Cornell Dubilier, aluminum oxide is the dielectric and conductive polymer is the solid electrolyte. Its low resistivity supports low ESR. Solid construction does not mean unlimited life or no impedance change: use the selected series' endurance criteria and operating conditions.
In plain terms
An electrolytic with a solid-polymer cathode replacing the liquid — same bulk, lower ESR, way longer service life.
Why designers use it
- A selected low-ESR part can reduce ripple voltage and dissipation in a suitable power-supply design.
- Solid-polymer aluminum capacitors use a conductive polymer rather than the liquid electrolyte of a conventional wet aluminum capacitor.
Best for
- CPU/GPU VRM bulk
- Long-life industrial gear
- Low-ESR DC–DC output
Key specifications
- Technology: Identify the exact construction (The cited example is solid-polymer aluminum)
- Voltage: Follow the selected series' rating (Include ripple peaks and reverse-polarity limits)
- Ripple and ESR: Frequency and temperature-dependent (Use the manufacturer's tables and conditions)
- Lifetime: Specified test conditions required (No universal operating-life figure applies to the whole family)
When not to use it
- When voltage, ripple-current, temperature or lifetime requirements exceed the selected series' documented limits.
- When another capacitor technology better meets the required size, capacitance and cost.
Common mistakes
- Applying one derating rule to every polymer capacitor. Follow the selected series' voltage, ripple-current and temperature requirements.
- Allowing ripple peaks to exceed the rated voltage or reverse the capacitor's polarity.
- Treating different polymer-aluminum, polymer-tantalum and hybrid constructions as interchangeable.
Where you will find it
- Cornell Dubilier's guide compares its solid-polymer aluminum capacitors with wet aluminum and solid tantalum constructions.
- For a power-supply filter, select a specific capacitor from its voltage, ripple-current, impedance and endurance data instead of promising a fixed service life from the word polymer.
A short history
Conductive-polymer electrolytic capacitors offer another way to combine useful capacitance with low ESR. They are not simply ordinary aluminum electrolytics with an unlimited lifetime: voltage, temperature, ripple and reverse-polarity limits still apply. Select the documented polymer technology and series for the job.
Good to know
- Cornell Dubilier's cited solid-polymer aluminum guide permits operation at rated voltage and does not prescribe a universal 20% derating rule.
- The same guide warns that sufficient overvoltage or reverse voltage can cause a short-circuit failure. Polymer does not mean immune to misuse.