What do you know about Polymer Aluminum Electrolytic Capacitors ?

2024-12-28

Polymer Aluminum Electrolytic Capacitors, often abbreviated as Polymer Al Caps or simply Poly Caps, represent a significant advancement in the evolution of aluminum electrolytic capacitors.

Polymer Aluminum Electrolytic Capacitors are electrical components that utilize a conductive polymer material as the electrolyte, replacing the traditional liquid electrolyte found in standard aluminum electrolytic capacitors. This innovation offers several advantages, enhancing the overall performance and reliability of the capacitors.

Key Features

1. Low ESR and Impedance: The use of a conductive polymer as the electrolyte results in significantly lower Equivalent Series Resistance (ESR) and impedance compared to traditional aluminum electrolytic capacitors. This low ESR allows for better handling of ripple currents and improved transient response.

2. Temperature Stability: Polymer Aluminum Electrolytic Capacitors exhibit stable capacitance over a wide range of temperatures. This stability is due to the conductive polymer's ability to maintain its properties even when exposed to extreme temperature changes.

3. High Capacitance: These capacitors offer high capacitance values, making them suitable for applications requiring large amounts of energy storage.

4. Long Lifespan: The life expectancy of Polymer Aluminum Electrolytic Capacitors is significantly greater than that of traditional aluminum electrolytic capacitors, thanks to the stability and durability of the conductive polymer electrolyte.

5. Small Size: The compact design of these capacitors allows for increased flexibility in circuit design and can contribute to a reduction in the number of components and substrate area.

6. Environmental Benefits: The conductive polymer material used in these capacitors is often more environmentally friendly compared to traditional electrolytes.

Main Types of Capacitors

There are various other types of capacitors, such as film capacitors and niobium capacitors, but here we will describe aluminum electrolytic capacitors (polymer aluminum electrolytic capacitors), a type of capacitor produced by Hongda Capacitors Manufacturing, among others.

1. The Structure of an aluminum electrolytic capacitor

An aluminum electrolytic capacitor is a polarized capacitor that uses aluminum oxide film as a dielectric.

These capacitors are also classified according to whether the electrolyte is liquid or solid.

Aluminum foil is used for both the anode part and cathode part

• Anode: Conductor (aluminum) with a high-purity of 99.9% or more
• Cathode: Liquid or solid electrolyte closely adhered to the dielectric
• Dielectric: Oxide film adhered to the surface (aluminum: Al₂O₃)

The capacitance of a capacitor increases the wider the electrode area, the higher the dielectric constant, and the narrower the distance between the electrodes.

Aluminum is a special metal with a rectifying effect called a valve metal. Other metals with the performance of valve metal include tantalum and niobium. The dielectric constant of oxide film (Al₂O₃), which is a dielectric formed by anodic oxidation on the aluminum surface, is approximately 7 to 10. That means it is not necessarily higher than the dielectrics used in other capacitors. Nevertheless, forming a porous structure with a surface area expanded up to 350-fold by etching the aluminum surface with electrolysis realizes a large-capacity capacitor. Moreover, the withstanding voltage (rated voltage) of a capacitor depends on the thickness of the dielectric. On the other hand, the thicker the dielectric, the smaller the capacitance. Aluminum is characterized by a thin dielectric per 1 V of approximately 1.3 nm. Accordingly, it is suitable for designing high withstanding voltage and large-capacity capacitors.

Aluminum electrolytic capacitors are also classified by whether the electrolyte is a liquid or solid. Aluminum electrolytic capacitors with a liquid electrolyte are only the can type, which can hermetically seal in the liquid electrolyte (electrolytic solution). They are characterized by a large capacity and high withstand voltage.

Meanwhile, aluminum electrolytic capacitors with a solid electrolyte do not need to be hermetically sealed because they are a solid (conductive polymer). Therefore, there is a resin-molded surface-mounted type in addition to a can type. They are characterized by a large capacity and low product height. Furthermore, there is no risk of volatilization because it is a solid electrolyte. This means they are characterized by a long service life compared to capacitors with liquid electrolytes.

2. The Structure of  conductive polymer capacitors?

Conductive polymer capacitors refer to electrolytic capacitors that use a conductive polymer for the cathode.

This is the same for tantalum electrolytic capacitors and aluminum electrolytic capacitors. However, aluminum electrolytic capacitors use aluminum foil for the anode and conductive polymer for the cathode.

On the other hand, conductive polymer-type tantalum electrolytic capacitors use tantalum metal for the anode and conductive polymer for the cathode.

Conventional-type electrolytic capacitors use a liquid electrolyte (electrolytic solution) or MnO2 for the cathode. If we use conductive polymer for the cathode in place of those to make a conductive polymer capacitor, we can realize the following:

• low ESR,
• stable temperature characteristics,
• improved safety, and 4. longer service life.

In addition, the type of dielectric is basically determined by the type of valve metal used for the anode in the case of electrolytic capacitors. The dielectric constant, DC bias characteristics, and acoustic noise characteristics are then determined by that. In this way, we can obtain various characteristics by combining multiple types of materials for the anode, cathode, and dielectric. There are strong areas and weak areas depending on the material. Therefore, electronic device designers need to use them as appropriate when designing circuits.

Hongda Capacitors Manufacturing's polymer aluminum electrolytic capacitors

Hongda Capacitors's polymer aluminum electrolytic capacitors has the feature of low ESR, low impedance, and large scale. Furthermore, there is no DC bias characteristic of capacitance, and since temperature characteristics are also stable, it excels in the Ripple absorption, smoothness, and the transient response performance.

Therefore, it is suitable for smoothing of input-output current of various power supply circuits, and the backup use over the load change of the CPU circumference. This contributes to reduction of the number of parts, or reduction of substrate area.

Applications

Polymer Aluminum Electrolytic Capacitors are widely used in various electronic devices and circuits, including:

Motherboards

Power supplies

AC/DC converters

CPUs

DC/DC converters

Decoupling circuits

LCD monitors

Manufacturing Techniques

The production of Polymer Aluminum Electrolytic Capacitors involves replacing the liquid electrolyte with a solid polymer material. This can be achieved through different manufacturing techniques, such as stacking anode foils coated with conductive polymer, carbon paste, and silver paste together. The resulting capacitors are highly stable and exhibit excellent performance in various conditions.

Conclusion

In summary, Polymer Aluminum Electrolytic Capacitors offer a combination of advantages that make them an ideal choice for numerous applications. Their low ESR, high capacitance, temperature stability, and long lifespan make them superior to traditional aluminum electrolytic capacitors. With their compact design and environmental benefits, these capacitors are poised to continue playing a crucial role in the advancement of electronic technology.

Welcome to contact with Hongda Capacitors for more details.

Email: judy@hongdacap.com.hk

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