Understanding Capacitors: Key Terms and Definitions
3D Capacitor Arrays
Arrays of capacitors printed in three dimensions to maximize space efficiency.
3D-Printed Capacitors
Capacitors manufactured using additive manufacturing techniques.
Additive Manufacturing
3D printing methods to produce capacitor components with complex geometries.
AI-Integrated Systems
Capacitors designed for AI-driven energy management in smart grids and EVs.
Annealing
Heat treatment to relieve stress in films and improve dielectric performance.
Anodization
A process to create a dielectric layer on aluminum or tantalum for electrolytic capacitors.
BDS
Shorthand for Broadband Dielectric Spectroscopy. See related terms.
Biaxial Orientation
A post-processing technique used to reduce the thickness of film, improve film thickness uniformity, and improve breakdown strength. A thick film is fed into an oven and stretched in both the machine and transverse direction. The process can be done either sequentially or simultaneously. Typically biaxial orientation is carried out at a temperature above Tg but below melting. This is a common technique employed to make state of the art polypropylene or PET capacitor films.
Bioinspired Dielectrics
Materials mimicking biological structures for enhanced performance.
Bobbin
An individual roll of film, either metallized or raw film, that has been slit down to a thinner width from the master production roll.
Bosch Test
A breakdown test whereby a continuous roll of film is passed over a voltage source and the number of breakdown events at a prescribed electric field is recorded. This is used as a quality control for capacitor film. An area of one square meter is typically set for the amount of film under test.
Breakdown
Failure of a material due to a voltage stress. Breakdown of a thin film typically results in vaporization of the polymer at the failure point, resulting in a pinhole in the film that can be anywhere from tens to hundreds of microns in diameter.
Breakdown Strength
The maximum electric field a dielectric material can withstand without breaking down.
Breakdown Voltage
The voltage at which a material experiences electrical breakdown.
Broadband Dielectric Spectroscopy
Capacitance, dielectric constant, and dissipation factor as a function of broad frequency range, typically from Hz to MHz. PNF's internal capabilities enable testing from 30 Hz to 300 kHz. If higher and lower frequencies need to be measured, PNF typically outsources measurement to Case Western Reserve University.
Calendering
Compressing films to achieve uniform thickness and surface smoothness.
Capacitance
The ability of an electrical component to to collect and store energy in the form of an electric charge. The Farad is the unit of measure.
Capacitor
A device used to store electrical energy in an electric field.
Capacitor Manufacturer
Companies specializing in producing capacitors for various applications.
Capacitor Winder
A machine used for winding capacitor films during manufacturing.
Ceramic Dielectric
Used in multilayer ceramic capacitors (MLCCs) for its high dielectric constant.
Chill Roll
A cooling cylinder used in film extrusion to set the film's properties.
Clear Margin
During fabrication of metallized film capacitors, a pair of metallized film bobbins are wound together to make the initial capacitor cell. The metallized film bobbins will both have a heavy edge and clear margin, and exist in a matched pair geometry such that during winding the heavy edge from one bobbin winds over the clear margin from the other bobbin. The clear margin refers to one side of a metallized film that does not have a metal coating. This ensures that the device does not short when terminal electrodes are added during end spray.
Coefficient of Friction
The coefficient of friction (COF) is a surface property of a capacitor film. It is a measurement of ease or difficulty with which a capacitor film can be dragged across another surface. Typically, COF is quoted on either a film-to-film basis, or a film-to-metal basis. There are two main types of COF - static, and dynamic. The static COF is the COF at the onset of movement for the film being measured, whereas the dynamic COF is measured during the course of movement. A low dynamic film-to-film COF (~ 0.4 and below) is typically indicative of a film that should have no issues with the capacitor winding step, whereas a high dynamic film-to-film COF (0.6 and above) is suggestive that the film may 'catch' or wrinkle during winding. In extreme cases, high COF can cause film to tear during winding or during flattening of the winding in the case of flat-pack capacitor geometries.
Coefficient of Thermal Expansion (CTE)
How much a material expands with temperature changes.
Coefficient of Variation (cov%)
A statistical measure of the dispersion of data relative to its mean.
Coextrusion
Simultaneous extrusion of multiple materials to create a layered film.
Composition
The material makeup of a capacitor or its dielectric.
Conversion
The process of altering a full width 'as extruded' roll of PNF film into a new format suitable for part manufacture. For capacitor films, conversion always includes slitting and rewinding to individual bobbins of film, but often also includes metallization of the film.
Corona Treatment
A surface modification technique to improve adhesion of metallization layers.
Cryogenic Capacitors
Capacitors designed to operate at extremely low temperatures, such as in superconducting systems.
Curing
A capacitor manufacturing step centered on thermal treatment of capacitor windings prior to application of end spray. The curing process is typically performed slightly below Tg of the source film and used to induce a small amount of shrinkage that forces entrapped air from the winding. Typically a 24 hr process.
DC Link Capacitor
Capacitors that stabilize voltage in DC circuits, common in EVs and power grids.
DC-DC Converter Capacitors
Used in converters to smooth voltage and reduce ripple.
Design for Manufacturability (DFM)
Ensuring capacitor designs are optimized for efficient production.
Df
Dissipation factor; indicates energy loss in a dielectric.
Dielectric
An insulating material used to store electric charge in a capacitor.
Dielectric Coating
Applying a dielectric material to enhance electrical properties.
Dielectric Constant (Dk)
Material constant of proportionality between applied electric field and internal electric field. The higher the dielectric constant the higher the stored energy for a capacitor film. The refractive index of a material is found by taking the square root of the dielectric constant. Also known as the relative permittivity.
Dielectric Loss
Energy lost as heat in the dielectric material.
Dielectric Spectroscopy
Evaluating dielectric properties across a frequency range for quality assurance.
Dissipation Factor
Ratio of energy lost to energy stored in a capacitor.
Dissipation Factor (Df)
A measure of energy lost as heat in the dielectric material.
Dk
Symbol for dielectric constant.
Downgauging
Reducing the thickness of capacitor film for improved efficiency.
Dynamic Voltage Restorer (DVR)
Capacitor-based system to protect sensitive equipment from voltage sags.
Electric Field
A field produced by electric charges, affecting capacitors' energy storage.
Electric Field (E)
A force field created by electric charges, influencing capacitor performance.
Electrolytic Capacitor
A capacitor that uses an electrolyte as one of its conducting layers, ideal for high capacitance.
Elongation at Break
A measure of the average percentage elongation of a film at the point at which it breaks. Typically measured for both machine and transverse directions.
Emerging Applications and Future Capacitor Trends
Encapsulation
Sealing capacitors with insulating materials to protect against environmental damage.
End Spray
A metallic coating applied to capacitor ends to facilitate electrical connections.
Energy Density
The amount of energy stored per unit volume or mass of a capacitor.
Energy Efficiency
The ratio of stored energy to energy lost in a capacitor.
Energy Storage Module
Large-scale capacitor banks for renewable energy and grid applications.
Epoxy Coating
A protective layer applied to capacitors for insulation and mechanical protection.
Equivalent Series Resistance (ESR)
The resistive component of a capacitor, affecting efficiency.
ESR (Equivalent Series Resistance)
The resistive losses in a capacitor, impacting efficiency.
ESR Measurement
Evaluating the equivalent series resistance of a capacitor to assess efficiency.
Etched Foil
Foil with increased surface area to enhance capacitance in electrolytic capacitors.
EV
Electric vehicle; a key application for advanced capacitors.
EV Drive Train Capacitor
Capacitors used in electric vehicle drive systems to handle high-power demands.
Extrusion
Process by which PNF creates thin films. Polymer resin pellets are melted and flow through a coat-hanger die which spreads the melt onto a chill roll to quench and solidify the melt into a film.
Fast-Charging Capacitor
Capacitors designed to handle high currents during EV fast charging.
Feedblock
Shapes and combines multiple materials as part of an extrusion line to make different types of film. Each material or combination of materials can have a different feedblock
Film
A thin layer of material used as the dielectric in capacitors.
Film/Foil Capacitor
A capacitor fabricated with sheets of raw film (no metallization) wound against a thin foil of aluminum. These capacitors are typically impregnated with oil to suppress surface discharges that can lead to catastrophic failure of the device. Film/Foil capacitors are typically designed for high voltage and often contain multiple capacitor subunits that are wired either in series or parallel (or both) to achieve a desired voltage and current rating.
Finite Element Analysis (FEA)
Simulation technique to model electrical, thermal, and mechanical behavior in capacitors.
Flyback Converter
Power supply topology that uses capacitors for energy storage and transfer.
Forming Voltage
The voltage applied to form the dielectric layer in electrolytic capacitors.
Fusion Energy Capacitors
High-energy capacitors for fusion reactor pulsed power applications.
Fusion Energy Storage
Advanced capacitors for storing energy in fusion reactors for pulsed power.
Glass Dielectric
A dielectric material used in high-temperature capacitors.
Glass Transition Temperature (Tg)
The temperature range where the polymer substrate changes from a rigid glassy material to a soft (not melted) material. The Tg of a material or nanolayer film can be determined by DSC and/or DMA.
Graphene Electrode
Using graphene as an electrode material for its high conductivity and surface area.
Grid Energy Storage
Large-scale capacitor systems for renewable energy integration and grid stabilization.
Grid-Tied Capacitor
Capacitors used in power grids for voltage stabilization and reactive power compensation.
Harmonic Filtering
Capacitors used to reduce harmonics in AC systems for improved efficiency.
Heavy Edge
A thicker metallized film edge for improved mechanical and electrical properties.
Hierarchical Structure
A multi-level structural arrangement within materials to enhance performance.
High-Energy Density
Capacitors capable of storing large amounts of energy in compact sizes.
High-Frequency Capacitors
Designed for power electronics in fast-switching applications.
High-Pot Test
Testing capacitors with high voltage to ensure insulation integrity.
High-Speed Slitting
Cutting films at high speeds with minimal edge defects.
HT-BDS
High-temperature Breakdown Dielectric Strength.
Hybrid Capacitor
Combines features of electrostatic and electrolytic capacitors for EV applications.
Hybrid Electrolytic Capacitor
Combines the benefits of solid and liquid electrolytes for improved performance.
Hybrid Power Factor Correction
Using capacitors to improve the power factor in mixed AC/DC systems.
Hysteresis
Energy loss in a dielectric material due to cyclic polarization.
Impedance Measurement
Measuring resistance to AC currents over a range of frequencies.
Insulation Resistance
The resistance to current leakage through a dielectric.
Integration
Combining components or processes into a unified system.
Inverter Capacitor
Capacitors that smooth voltage in EV motor control inverters.
Laser Ablation
Precision removal of material to create fine features or correct imperfections.
Laser Cutter
Precision equipment used to cut capacitor films.
Layer Structure
The arrangement of layers in a capacitor's dielectric or electrodes.
Layering
Stacking or layering films to achieve the desired dielectric thickness.
LCR Meter
Instrument to measure inductance (L), capacitance (C), and resistance (R).
Lead Attachment
Process of connecting leads to capacitor terminals.
Leakage Current
The unwanted flow of current through a capacitor's dielectric.
Life Cycle Assessment (LCA)
Evaluating the environmental impact of capacitor production and disposal.
Lifetime
The expected operational lifespan of a capacitor.
LT-BDS
Low-temperature Breakdown Dielectric Strength.
Machine Direction
The direction of material flow during film production.
Mechanical Fatigue
Weakening of capacitor materials due to repeated mechanical stress.
Metallization
A process to apply a thin metal layer to capacitor film.
Metallized Film
Film coated with a thin metal layer to serve as electrodes in capacitors.
Metallized Film Capacitor
A capacitor type that uses metallized film as electrodes.
Microperforation
Creating tiny holes in dielectric film to control properties like self-healing or insulation.
Nanocomposite Dielectric
Dielectrics engineered with nanoparticles to improve performance.
Onboard Charger Capacitor
Used in EV charging systems to filter and stabilize voltage.
Paper Dielectric
Insulating paper impregnated with oil for improved dielectric properties.
Partial Discharge Testing
Detecting small electrical discharges that indicate dielectric defects.
Polymer Electrolyte
Conductive polymer used in some electrolytic capacitors.
Polypropylene Film
A common dielectric material in film capacitors, prized for low loss and high dielectric strength.
Power Conditioning
Using capacitors to stabilize and filter power in high-voltage systems.
Power Conversion
The process of converting electrical energy into usable forms, often using capacitors.
Power-to-X Applications
Capacitors enabling energy conversion, such as power-to-gas or power-to-heat systems.
Process Template
A predefined method or protocol for manufacturing processes.
Prototyping
Creating initial models or samples of capacitors for testing.
Pulldown Breakdown
Breakdown occurring when voltage is rapidly decreased.
Pulsed Power
High-power, short-duration energy delivery systems using capacitors.
Qualification
Testing and certifying capacitors for specific applications.
Quantum Dielectric
Advanced materials that leverage quantum effects for higher capacitance.
Reek
Undesirable byproducts during capacitor production.
Resistance
Opposition to electrical current in a material.
Resonant Circuit
Circuits using capacitors and inductors to oscillate at specific frequencies.
Ripple Current
The AC current that a capacitor can handle without overheating.
Roll-to-Roll Processing
Continuous production method for capacitor films, enhancing efficiency.
RT-BDS
Room-temperature Breakdown Dielectric Strength.
Self-Healing
The ability of metallized film capacitors to repair damage by vaporizing defects.
Shrinkage
A measurement of how much a capacitor film contracts in either the transverse or machine direction as a function of temperature and time. Most manufacturers of dry metallized film capacitors will cure windings at a temperature slightly below the Tg of the polymer to cause ~ 1% shrinkage of the film in the winding. This step helps to compact the winding and force out any entrapped air. From a capacitor operational standpoint - high shrinkage (2% or higher) can sometimes cause the film in the winding to separate from the end spray, resulting in failure of the part. Therefore, quantifying shrinkage effects at the film level is important for forecasting operational temperature ratings in resultant capacitors.
Slip
The movement of one layer of material over another during production.
Slitting
Cutting capacitor film into precise widths for winding.
Snubber Capacitor
Used to reduce voltage spikes and protect switching components in power electronics.
Snubber Circuit
A circuit with capacitors to protect switches and semiconductors from voltage spikes.
Solid Electrolytic Capacitor
Uses a solid polymer or ceramic electrolyte for better stability and reliability.
Solid-State Capacitors
Capacitors with solid dielectric materials for higher stability and efficiency.
Space Factor
A rough measure of the surface roughness of a film. Space Factor is important for film/foil capacitors where oil is used to coat individual layers of the dielectric film. The surface roughness is required in order to wick oil for complete coverage of the film.
Sputter Coater
Equipment for applying thin films via sputtering.
Static VAR Compensator (SVC)
Capacitor banks used for reactive power compensation in power grids.
Step Stress Test - Temperature
Gradual increase in temperature to test capacitor limits.
Step Stress Test - Voltage
Gradual increase in voltage to determine capacitor breakdown limits.
Step-Stress Testing
Gradually increasing voltage or temperature to determine capacitor limits.
Step-Stress Voltage Test
Gradually increasing voltage to find breakdown points of a capacitor.
Stretching
A generic catch-all term typically used for biaxial orientation of thin films.
Supercapacitors
High-capacitance devices used in energy storage and fast charge-discharge applications.
Surge Protection
Capacitors designed to absorb voltage spikes in high-voltage systems.
Switch-Mode Power Supply (SMPS)
A system that uses capacitors for energy storage and voltage regulation.
Takeoff
The point where capacitor film leaves the production line.
Tensile Strength
The maximum stress a material can withstand without breaking.
Tensile Testing
Measuring the mechanical strength of films under tension.
Tension
The force applied to stretch or hold a material during processing.
Thermal Conductivity
A material's ability to conduct heat, important for managing heat in capacitors.
Thermal Cycling
Repeated heating and cooling to test reliability under temperature changes.
Thermal Evaporation
Depositing thin metal films on a dielectric by heating the metal in a vacuum.
Thermal Runaway
A failure mode where excessive heat leads to capacitor breakdown.
Thermal Simulation
Modeling heat dissipation to optimize capacitor thermal management.
Thickness
The measure of a material's depth, often crucial in film capacitors.
Transverse Direction
The direction perpendicular to the machine direction during film production.
Ultra-High Energy Density Capacitors
Next-generation capacitors with exceptional energy storage capabilities.
Uniformity (Composition)
Consistency in the material composition of a capacitor.
Uniformity (Thickness)
Consistency in the thickness of capacitor film.
Vacuum Lamination
Bonding layers of dielectric under vacuum to ensure uniformity and minimize defects.
Vacuum Sputtering
Depositing thin metal layers on film under vacuum conditions.
Vacuum-Deposited Metal
Thin metallic layers applied to capacitor films for improved conductivity.
Vertical Integration
Controlling multiple production stages within a single company.
Voltage
Electrical potential difference between two points.
Voltage Rating
The maximum voltage a capacitor can withstand during operation.
Voltage Stabilization
Maintaining consistent voltage levels in power grids or electronic systems.
Weibull Alpha
A scale parameter in Weibull distribution indicating characteristic life.
Weibull Analysis
Statistical analysis of failure data to predict reliability and performance.
Weibull Beta
A shape parameter in Weibull distribution indicating failure rate trends.
Weibull Distribution
The Weibull Distribution is a continuous probability distribution used to analyse life data, model failure times and access product reliability. It is commonly used for analysis of capacitor film to better understand distribution of failure modes and predict device performance.
Wet Electrolytic Capacitor
A capacitor with a liquid electrolyte, providing high capacitance but prone to leakage.
Winding
Process of rolling capacitor film into a cylindrical or oval shape.
Wireless Charging Capacitors
Used in inductive or resonant wireless charging systems.
X-Ray Inspection
Non-destructive examination of internal capacitor structures.
Young's Modulus
A measure of material stiffness, indicating resistance to deformation.