Types of Wound Film Capacitors

A Capacitor is passive electronic device, second in use only to that of a resistor. Capacitors can be found in virtually all electronic devices. Simply put, a capacitor is two electrodes (conductors) separated by a dielectric(insulator). In this case, the insulator would be air, and the electrode could be any conductive material, such as aluminum or copper. When a voltage potential is applied to the electrodes, an electric field is present in the dielectric, which in turn stores energy. The measured amount of stored energy is the capacitance. The amount of capacitance is directly proportional to the area of the electrodes, and inversely proportional to the distance between the electrodes. The capacitance is also proportional to the dielectric constant (k) of the insulator, whereas air is 1.00 and polyester is 3.2, therefore at the same distance between the plates, polyester would have 3.2x the
capacitance. The higher the “k” of a particular dielectric, the higher the capacitance for the same given area and distance between the electrodes

A wound film Capacitor is just that, where two or more films/electrodes are spirally wound on a mandrel to a predetermined number of turns, length, or capacitance value. The mandrel is then ejected from the winding, which is
then further processed depending on the style and/or application of that particular part. Wound Film Capacitors can be further broke down into three basic categories:
Metalized Electrode
Discrete Foil Electrode
Hybrid electrode

Metalized Electrode Capacitor or commonly know as Metalized Film Capacitor, consists of a thin layer of metal, typically aluminum, zinc, or an alloy of aluminum/zinc, which has been previously deposited onto the dielectric. The metal is vacuum deposited onto a master roll of film typically using resistive evaporation (aluminum) or heated crucibles (zinc). Special masking, either mechanical or print transfer is used to make the unmetalized margins. The master roll is then slit into narrower “bobbins” which are used on specialized “winders” to manufacture the wound film capacitors.

The metalization thickness is typically around 200 Ä (Angstroms) or .0000008” thick. When compared to a discrete foil of .00022” thick, the volumetric efficiency (energy density) of a metalized electrode is far greater than that of a discrete foil. Ancillary vacuum technologies exist that allow designed variations of the metalized surface for specific applications. For example, a heavy region is possible where the termination will be attached, thus allowing for higher current capabilities. It is also possible to print patterns onto the dielectric surface, giving specific metal patterns. These patterns are used for high stress and/or high energy applications.
 

Another major energy density advantage of a metalized electrode is the ability of the film to “self heal” or “clear”. That is, when the voltage is sufficient to break down the dielectric so that there is a direct conducting path from electrode to electrode, (effectively shorting the plates) a small portion of the stored energy in the capacitor discharges into the “short” and creates a super heated area, thus vaporizing the metal away from the break down (pin hole), giving a “clearing site” or margin area without metal. This phenomenon allows for higher stress to the dielectric without failure. A similarly rated discrete film/foil unit would be 2x to 3x larger than the metalized film counter part.

Film Capacitor
Photo	Description	Vishay SPRAGUE	Kemet	Pilkor	TDK/EPCOS
	CL21 Series Metallized Polyester Capacitors	MKT368 Series MKT467 Series MKT468 Series	***	PCMP 384 389 Series PCMT 365-367 Series PCMT 369, 468, 368 Series	B32520-B32529 Series B32591-32594 Series B32593-32594 Series
	CL21B Series Box Type Metallized Polyester Film Capacitor	MKT371 Series MKT372 Series MKT373 Series MKT373M Series	R66 Series R60 Series F611 Series F612 Series	***	***
	CBB21B Series Box Type Metallized Polypropylene film Capacitor	MKP385（DC） Series KP1836（AC）Series	F461 Series F464 Series PMR-205 Series	***	***
	X2 Series X2 Metallized Polypropylene Film Capacitor	MKP3382 Series MKP3384 Series MKP3392 Series	R46 Series PHE840M Series PHE850 Series PMR-209 Series	PCX2 337 Series PCX2 339 Series	B32921C/D-B32928C/D Series B81 130 Series

 

Polyester Capacitors are one of the most widely used film capacitors. Capacitor grade Polyester film is available in a wide variety of thicknesses, ranging from 0.5 um up to 20 um. Combining the thin film with the relatively high dielectric constant (k) of 3.2, high energy densities are possible. However, Polyester is considered a high loss film and typically not used in applications that require high current or high frequency.

CL23 Mini Box Metallized Polyester Film

CL19 CL20 Axial Lead, Metallized Polyester Capacitor

CL21 Met Polyester Capacitor

 

Polypropylene Capacitors are second in use only to Polyester. Capacitor grade Polypropylene is available in thicknesses ranging from 3 um to 15 um. The electrical characteristics of Polypropylene film exhibits many advantages, such as high break down strength, low moisture absorption, low loss factors, and capacitance stability throughout the temperature range. It is ideally suited for high frequency and/or high current applications. The disadvantages of Polypropylene are the relatively low dielectric constant (k) of 2.2 and low maximum temperature of 105 C.

UF Capacitors offer below Polypropylene Capacitors

X2 Metallized Polypropylene Film Capacitor

X2 Metallized Polypropylene Film Capacitor-THB Series

CBB23B Box Type Metallized Polypropylene Film Capacitor

MPX Series Premium Metallized Polypropylene Film Capacitors, Axial Lead Audio Capacitors

CBB81 High Voltage Metallied Polypropylene Capacitor

CBB21 Metallized Polypropylene Capacitors

 

Film Capacitor
Photo	Description	Vishay SPRAGUE	Kemet	Pilkor	TDK/EPCOS
	CBB81 Series High Voltage Metallized  Polypropylene Capacitor	***	***	***	B32685-B32678 Series
	CL19 CL20 CL23 CBB19 CBB20 Axial Lead Met Polyester Film Capacitors	MKT370 Series	C4G Series F5A Series F5B Series F5D Series	***	***
	X2 Metallized Polypropylene Film Capacitor	MKP3382 Series MKP3384 Series MKP3392 Series	R46 Series PHE840M Series PHE850 Series PMR-209 Series	PCX2 337 Series PCX2 339 Series	B32921C/D-B32928C/D Series B81 130 Series

 

CAPACITOR APPLICATIONS
General applications include but not limited to:
Blocking                          Coupling                          Bypass
Filtering                           Timing                              Smoothing
Pulse Coupling                  Snubber Energy              Discharge
Commutating                     Motor run                          Motor Start
Decoupling                      EMI Suppression            RFI Suppression

Below is representative application:
Laser                            Audio                         Rangefinders
Strobe                          Ignition                        Lighting
Power supply                 Aircraft Lighting              Speed Controls
Avionics                       Electronic Filter              AC Drives
Inverters                       UPS                            Induction Heating

UF Capacitors manufactures a broad spectrum of reliable wound film capacitors suitable for a wide variety of applications. Many of the catalog standards and/or custom capacitors can meet the most stringent requirement of the customer.

Our market position is to replace first tier brands like TDK/EPCOS, Panasonic, Vishay, Kemet, PIkor etc with equivalent quality, but much better price and fast lead time. After 27 years development, UF capacitors has become a very famous electronic parts manufacturer and electronic parts supplier. Now UF capacitors Group and UF Capacitors include 4 manufacturer sites in China, and export our electronic components to USA, Canada, Brazil, Argentina, Mexico, South Africa, Tunisia, New Zealand, Australia, Germany, Italy, France, UK, Poland, Bulgaria, Spain, Portugal, Russia, Belarus, Ukraine, Korea, Vietnam, Singapore, Malaysia, Indonesia, India, Philippine,Thailand. Currently UF capacitors supply our various capacitors to famous international companies like GE, Philips, Honeywell, Bosch and so on. Cost down with reliable quality is KEY important than ever.To achieve this, the KEY point is to pick up the right Chinese supplier.  UF capacitors could support you to make this happen for metallized Plastic Film Capacitors. Could you please send us emails and RFQ. We can help you for cost down and solve your shortage problem.