A Comprehensive Guide to Capacitors

1. Introduction

Capacitors play an essential role in electrical and electronic circuits, along with resistors and inductors. Their ability to store electrical charges makes them crucial for power management, noise suppression, DC voltage biasing, and signal filtering. Capacitors also provide rapid charge and discharge cycles, making them a suitable alternative for energy storage (such as batteries). They are commonly found in industrial applications, including power factor correction (PFC), motor operation, and consumer appliances. This guide covers three types of capacitors from Panasonic:

• Conductive polymer electrolytic capacitors,
• Aluminum electrolytic capacitors, and
• Film capacitors.

2. Conductive Polymer Electrolytic Capacitors

Conductive polymer electrolytic capacitors have ultra-low equivalent series resistance (ESR) and remain stable at high frequencies. They offer superior electrical performance by utilizing conductive polymer as the electrolyte. These capacitors also have longer operational lifespans compared to conventional aluminum electrolytic capacitors. Their unique construction makes them durable and ideal for applications requiring stable voltage regulation and high ripple current endurance.

Panasonic offers various conductive polymer capacitors meeting various industrial requirements, including SP-Cap, POSCAP, OS-CON, and Hybrid capacitors.

• SP-Cap (Aluminum Polymer, Multilayer): Figure 1a shows a rectangular-shaped, aluminum electrolytic capacitor that uses a polymer as its electrolyte. SP-Cap is primarily used as input and output Capacitors for DC/DC converters due to its ultra-low ESR and low Equivalent Series Inductance (ESL), a long-life span, a compact size, a low profile, and high stability. It is suitable in final products such as servers, AC adapters, embedded boards, and SSDs.

• POSCAP (Tantalum Polymer): These capacitors have a sintered tantalum anode and a proprietary high-conductivity polymer cathode (Figure 1B). Tantalum Polymer capacitors can simultaneously maintain low Equivalent Series Resistance (ESR) with stable capacitance at high frequencies and temperatures. 
  Panasonic's advanced Tantalum-Polymer Capacitor technology delivers some of the lowest ESR levels and excellent performance in high-frequency applications. POSCAP capacitors come in a range of compact package sizes, ensuring a small PCB footprint with high volumetric efficiency.
  Additionally, POSCAP capacitors offer high reliability and exceptional heat resistance, making them an ideal choice for digital, high-frequency devices and more.

• OS-CON (Aluminum Polymer, Wound): These Solid Electrolyte Aluminum OS-CON Capacitors use aluminum and a highly conductive polymer material (Shown in Figure 1C) to offer low ESR, excellent noise reduction, superior frequency characteristics, and ripple current capabilities. Additionally, it has a long lifespan, with minimal ESR variation, even at low temperatures due to its solid electrolyte. It supports up to 7.5A ripple current and withstands voltages up to 100V. These capacitors are available in surface-mount and through-hole types. They are commonly used in power electronics, industrial automation, and computing applications.

• Hybrid Capacitors (Aluminum Hybrid Polymer/Electrolyte): Hybrid Capacitors are known for their stable electric characteristics at high frequencies while maximizing reliability. The electrolyte consists of conductive polymer and electrolytic liquid (shown in Figure 1d) and has high endurance, low ESR, high tolerance for ripple currents, inrush currents, and elevated temperature. These Hybrid Capacitors are compact, allowing significant board space savings. Its "hybrid electrolyte" is used in a wide range of automotive and industrial applications such as BMS, ECUs, LED headlights, and ADAS systems.

Key Features of Conductive Polymer Electrolytic Capacitors

• Very low ESR and high-frequency characteristics
• Stable characteristics independent of temperature and voltage
• Higher safety than general tantalum electrolytic capacitors

FAQs:

• What are aluminum electrolytic capacitors used for?
  Aluminum electrolytic capacitors are commonly used for power supply filtering, energy storage, and DC-link applications in power electronics due to their high capacitance values and voltage ratings.
• What are the disadvantages of aluminum electrolytic capacitors?
  They typically have a higher ESR than polymer capacitors. They are also prone to degradation over time due to electrolyte evaporation and have a limited lifespan in high-temperature environments.
• What is the lifespan of an aluminum electrolytic capacitor?
  The lifespan of an aluminum electrolytic capacitor depends on operating conditions, including rated voltage and temperature. It generally ranges from 1,000 to 10,000 hours or even more.
• How do aluminum electrolytic capacitors fail?
  Failures in electrolytic capacitors can occur due to electrolyte drying out. Excessive ripple current also causes overheating, and dielectric breakdown can lead to short circuits or leakage.

Featured Products

3. Aluminum Electrolytic Capacitors

Aluminum capacitors are polarized electrolytic components where an aluminum oxide film forms the dielectric on the etched surface of an aluminum foil anode, while an electrolyte liquid serves as the cathode, as shown in Figure 2. This structure increases the electrode surface area through etching, enabling compact designs with high capacitance and reliability.

Aluminum electrolytic capacitors have higher equivalent series resistance (ESR) than ceramic or film capacitors. However, advances in materials and design have improved ESR performance, making today’s generation of aluminum electrolytic capacitors suitable for power supply filtering, motor drives, and industrial applications. A rise in ESR can also affect the component's lifespan. Panasonic offers a wide range of aluminum electrolytic capacitors, including general-purpose, OS-CON (polymer-based), and hybrid variants, catering to diverse application requirements.

• General-Purpose Aluminum Electrolytic Capacitors: These capacitors use traditional aluminum electrolytes (Figure 2A). They provide a balance between high capacitance, miniaturization, and low ESR. General-purpose aluminum electrolytic capacitors offer high reliability, long lifespan, low impedance, and industry-leading high ripple current. They are commonly used in automotive electronics, industrial power supplies, and LED drivers.

• Conductive Polymer Aluminum Solid Capacitors (OS-CON): These capacitors use a high-conductivity polymer electrolyte instead of a liquid (Figure 2B), providing ultra-low ESR, excellent noise reduction, and superior frequency characteristics. OS-CON capacitors offer a longer lifespan, and due to the presence of a solid electrolyte, there is minimal impact on ESR variation, even at low temperatures. They are ideal for applications such as LED backlighting, industrial automation, and DC-DC converters in servers and base stations.

• Hybrid Aluminum Electrolytic Capacitors: These capacitors make use of hybrid electrolytes consisting of a conductive polymer and electrolytic liquid, as shown in Figure 2C. This helps them to achieve low ESR, withstand high voltages, and high reliability. Their high ripple current capability, superior thermal endurance, and vibration resistance (including anti-vibration models) make them well-suited for automotive, industrial, and high-power applications. With a compact design, they enable miniaturization while keeping performance.

FAQs

• What is the difference between polymer and electrolytic capacitors?
  Traditional or standard aluminum electrolytic capacitors use a liquid electrolyte, while polymer capacitors use a solid conductive polymer. Polymer capacitors offer lower ESR, higher ripple current tolerance, and greater stability over temperature fluctuations, but they may have lower voltage ratings than standard electrolytic capacitors.
• Can a polymer capacitor substitute for an electrolytic capacitor?
  Only under certain conditions, but not always. The voltage and capacitance ratings may differ between the two types of capacitors. This holds true even though polymer capacitors offer better performance in ESR and frequency characteristics. If you continue with the substitution, ensure that the new capacitor meets the voltage, capacitance, and ripple current requirements of the application.

• What are the disadvantages of polymer capacitors?
  Polymer capacitors are often more expensive than traditional electrolytic capacitors, even when they have the same capacitance and voltage. The lower voltage ratings of polymer capacitors also make them unsuitable for high-voltage applications. Additionally, exposure to moisture can lead to desorption, package cracking, dielectric damage, and increased ESR degradation.
• How long do polymer capacitors last?
  Typically, they have a longer lifespan than liquid electrolytic capacitors. Some Panasonic OS-CON series capacitor models are ideal for long-term industrial applications as they can last up to 20,000 hours at 105°C.

Featured Products

4. Film Capacitors

Film capacitors are a highly reliable capacitor that uses an insulating plastic film as the dielectric material. These capacitors are primarily made of PP (polypropylene), PET (polyethylene terephthalate), PPS (polyphenylene sulfide), and PEN (polyethylene naphthalate) as dielectric materials. They offer higher insulation resistance than ceramic and aluminum electrolytic capacitors, along with a greater ability to keep stored electricity. Characterized by excellent volumetric efficiency, high reliability, high insulation resistance, and low ESR and ESL, they are commonly used in high-frequency applications, power factor correction, and start-run motor circuits.

Additionally, film capacitors experience lower energy loss during charging and discharging compared to other capacitor types. PP-based film capacitors not only operate with minimal losses but also maintain their efficiency despite temperature fluctuations.

The primary cause of deterioration in film capacitors is electrode oxidation. Panasonic has enhanced moisture resistance through "encapsulation technology" and "weatherproof technology." Encapsulation technology minimizes moisture penetration into the internal element by optimizing exterior case materials, filling resin, and high humidity-resistant metallic coatings. Weatherproof technology further prevents electrode erosion by utilizing highly moisture-resistant evaporated metal and advanced processing techniques for internal electrodes, as illustrated in Figure 3.

Panasonic offers a wide lineup of film capacitors to meet diverse application requirements in electronic equipment, automotive, industrial and infrastructure, and AC motor use. The company enhances capacitor longevity and reliability in harsh environmental conditions by integrating advanced manufacturing techniques, such as segmented metalized film technology and encapsulation methods.

1) Film Capacitors for Electronic Equipment Use:
These capacitors are used in power supplies, consumer electronics, and industrial systems. Panasonic provides a wide selection of film capacitors (Electronic Equipment Use), including radial lead-type products for mid/high voltage and high frequency, as well as power supply noise suppressors. For low or mid-range voltage, surface mount-type products are used.

• Radial Lead-Type Capacitors (ECWFA, ECWFD, ECWFE Series):
  • Designed specifically for high-voltage and high-frequency applications
  • Safety-enhanced design featuring Panasonic's original vapor deposition pattern technology
  • Integrated fuse function to prevent catastrophic failures
• Surface Mount-Type Capacitors (ECHU(X), ECWU(X) Series):
  • Improved electrode structure to prevent chip standing during reflow soldering
  • Enhanced adhesion to suppress electrode oxidation, improving long-term reliability

2) Film Capacitors for Automotive, Industrial, and Infrastructure Use:
These capacitors are engineered for high-voltage and high-current applications, used as smoothing, snubbers, and noise suppressors in xEV and industrial inverters.

• AEC-Q200 compliant for automotive applications
• High resistance to moisture and environmental stress
• Built-in safety features using proprietary vapor deposition technology

3) Film Capacitors for AC Motor Use:
Designed specifically for motor-running applications, the PMF series capacitors improve power factor efficiency in motor-running circuits of household appliances such as air conditioners, refrigerators, and washing machines.

• Integrated fuse function ensuring higher safety
• Certified to global safety standards (UL, CSA, JIS, EN60252-1)
• Enclosure designed for long lifespan and flame resistance

Fuse Function Technology:Unlike traditional aluminum electrolytic capacitors, which open upon failure, film capacitors tend to short-circuit, posing a potential hazard. To mitigate this risk, Panasonic has developed a fuse function for its film capacitors by incorporating fragile layers of vapor-deposited aluminum slits at various points in the dielectric material. These slits localize failures, as shown in Figure 4, limiting damage to only a few sections of the capacitor. If too many of these areas fail rapidly, the capacitor will open in a fail-safe manner.

How it Works:

• If a local breakdown occurs due to high stress, only the affected segment becomes an open circuit, preventing further damage.
• The capacitor continues to function, and permanent failure (such as fire or smoke) is averted.
• This self-healing function also increases the capacitor's functional lifespan, making fuse function technology ideal for xEV inverters, industrial power systems, renewable energy converters, and other high-stress applications.

FAQ

• What is a film capacitor used for?
  Film capacitors, known for their excellent stability, reliability, and low-loss operation, are used in high-frequency circuits, power factor correction, motor-running applications, noise suppression, industrial inverters, and automotive electronics.
• Are film capacitors better than electrolytics?
  Film capacitors offer higher insulation resistance, better stability, and longer lifespans compared to electrolytic capacitors. However, electrolytic capacitors provide higher capacitance per volume, making them more suitable for bulk energy storage.
• Are film capacitors suitable for audio applications?
  Yes, film capacitors are ideal for high-end audio systems and signal processing due to their low distortion, minimal loss, and excellent high-frequency response.
• What are the disadvantages of film capacitors?
  Compared to ceramic capacitors, film capacitors are larger in size and more expensive for high-capacitance values. They also have limited availability in extremely high capacitance ranges and may suffer catastrophic failure under demanding conditions.

Featured Products

About the Sponsor

Equipping, enabling, inspiring: About Panasonic Industry Europe A common purpose: as part of Panasonic Corporation’s global business, people at Panasonic Industry strive for continuous innovation and share the company’s mission and vision - shaping the future for the better. To take engineering to the next level, Panasonic Industry researches, produces and supplies technologies for a vast range of industries. For more information, click here