Aluminum Electrolytic Capacitors
1. Aluminum Electrolytic Capacitors Overview
Aluminum electrolytic capacitors are composed of an aluminum cylinder as the negative electrode, a liquid electrolyte is injected into the inside, and an oxidized aluminum strip is inserted as the positive electrode. Its medium is an aluminum oxide (Al₂O₃) film formed on the surface of the anode aluminum foil. The surface area of the electrode is increased by an electrochemical etching process to increase the capacitance. During operation, electric field energy storage is achieved through the dielectric effect of the oxide film, and the electrolyte participates in the conduction as the actual cathode during the charging and discharging process.
2. How Aluminum Electrolytic Capacitors are Made?
Materials:
The anode uses high-purity etched aluminum foil, and the cathode uses electrolyte or conductive polymer materials.
The electrolyte includes liquid electrolyte (traditional type) or solid/solid-liquid mixed materials (new type).
Process:
Etching aluminum foil to increase the surface area → Anodic oxidation to form a dielectric layer → Winding the anode/cathode foil and electrolytic paper → Injecting electrolyte and encapsulating.
3. What are the Main Classification of Aluminum Electrolytic Capacitors?
1) By Electrolyte Type:
Liquid Electrolytic Capacitor: low cost, large capacity, but high leakage current and short life.
Solid Electrolytic Capacitor: conductive polymer, excellent high-frequency characteristics and long life.
Solid-liquid Hybrid Capacitor: combining the advantages of liquid and solid, high temperature resistant and in line with automotive standards.
2) By packaging form:
Lead type (radial/axial), SMD, bolt type, etc..
4. What are the Core Characteristics of Aluminum Electrolytic Capacitors?
Advantages:
High capacity per unit volume (large CV value), suitable for large capacity demand scenarios.
Low cost, widely used in power filtering and low-frequency circuits.
Limitations:
There are problems such as large leakage current, high-temperature sensitivity (-40℃~125℃), and large equivalent series resistance (ESR).
Polarity-sensitive, reverse voltage can easily lead to failure.
5. What are Aluminum Electrolytic Capacitors Used for?
Power Circuit: used for post-rectification filtering, energy storage, and voltage smoothing.
Industrial Equipment: Energy buffering in motor drives and inverters.
Consumer Electronics: Low-frequency signal processing in audio equipment and LED driver power supplies.
Automotive Electronics: On-board chargers, battery management systems (mainly solid-liquid hybrids).
6. Precautions for Using Aluminum Electrolytic Capacitors
Strictly follow the polarity markings to avoid reverse connection.
The operating voltage must be lower than 80% of the rated voltage to prevent dielectric breakdown.
In high-temperature environments, 105℃ or 125℃ specifications must be selected to extend life.
7. Technological Development of Aluminum Electrolytic Capacitors
In recent years, aluminum electrolytic capacitors have developed towards high frequency and high reliability:
Solid State: Conductive polymers are used to reduce ESR and improve frequency response.
Hybrid: Solid-liquid hybrid electrolytes take into account temperature stability and capacity density, and are suitable for new energy vehicles.
Miniaturization: SMD technology promotes its application in compact electronic devices.
Aluminum Electrolytic Capacitors FAQs
1) Will reverse voltage damage aluminum electrolytic capacitors?
Aluminum electrolytic capacitors have clear positive and negative polarities. Reverse voltage application will damage the internal oxide film medium, which may cause a sharp increase in leakage current, heating, or even explosion. Therefore, the polarity marking must be strictly followed when using it.
2) What are the main application scenarios of aluminum electrolytic capacitors?
Its characteristics are large capacity and low cost, but large leakage and poor high-frequency characteristics. Therefore, it is mostly used in circuits such as power supply filtering, low-frequency coupling, or bypass, and is not suitable for high-frequency or precision signal processing scenarios.
3) What are the alternatives to aluminum electrolytic capacitors?
Solid-state multilayer polymer capacitors (MLPC) are a new alternative that uses conductive polymers as electrolytes, has lower equivalent resistance and longer life, and is suitable for high-precision circuits.
4) What are the specifications of chip aluminum electrolytic capacitors?
Size: Common metric specifications include Φ4×5.5mm, Φ5×5.5mm, etc., and the maximum can reach Φ10×12mm.
Capacity and Voltage: Capacity range 0.1μF～1000μF, voltage covers 4V～100V, meeting different circuit requirements.
5) How to deal with the leakage current problem of aluminum electrolytic capacitors?
Due to the characteristics of its liquid electrolyte, the leakage current is large. When designing, it is necessary to reserve redundant capacity or select low-leakage current models to improve stability.