General Technical Information
www.vishay.com
Vishay Roederstein
Film Capacitors
FILM CAPACITORS
Plastic film capacitors are generally subdivided into film/foil
capacitors and metalized film capacitors.
RFI suppression capacitors are the most effective way to
reduce RF energy interference. As its impedance decrease
with frequency, it acts as a short-circuit for high-frequencies
between the mains terminals and/or between the mains
terminals and the ground.
Capacitors for applications between the mains terminals are
called X Class capacitors. Capacitors for applications
between the terminals and the ground are called Y Class
capacitors.
X-Capacitors
For the suppression of symmetrical interference voltage.
Capacitors with unlimited capacitance for use where their
failure will not lead to the danger of electrical shock on
human beings and animals. The capacitor must present a
safe end of life behavior.
Y-Capacitors
Capacitors for suppression of asymmetrical interference
voltage, and are located between a live wire and a metal
case which may be touched. High electrical and mechanical
reliability to prevent short-circuits in the capacitors. The
capacitance value is limited, in order to reduce the AC
current flowing through the capacitor. By following these
technical requirements, it is intended that its failure will not
lead to the risk of electrical shock, making the device with Y
capacitor (in conjunction with other protective measures)
safe to human beings and animals.
For
detailed
information,
www.vishay.com/doc?28153.
we
refer
to
FILM / FOIL CAPACITORS
Film / foil capacitors basically consist of two metal foil
electrodes that are separated by an insulating plastic film
also called dielectric. The terminals are connected to the
end-faces of the electrodes by means of welding or
soldering.
Main features:
High insulation resistance, excellent current carrying and
pulse handling capability and a good capacitance stability.
METALIZED FILM CAPACITORS
The electrodes of metalized film capacitors consist of an
extremely thin metal layer (0.02 μm to 0.1 μm) that is vacuum
deposited either onto the dielectric film or onto a carrier film.
The opposing and extended metalized film layers of the
wound capacitor element are connected to one another by
flame spraying different metals to the end-faces. The metal
spraying process is also known as schooping. The terminals
are connected to the end-faces by means of welding or
soldering. For the production of metalized film capacitors
Vishay film capacitors uses the conventionally wound film.
Main features:
High volume efficiency, self-healing properties
SPECIAL DESIGN CAPACITORS
For high current applications Vishay film capacitors is also
able to offer special designs such as capacitors with a heavy
edge metalization or a double sided metalization as well as
combinations that have a film/foil and a metalized film
design in one unit. For high voltage applications it is
furthermore possible to offer designs with dual and multiple
sections. Depending on the design these capacitors provide
low losses, high current and pulse carrying capabilities, high
voltages, small dimensions and good self-healing
properties.
SELF-HEALING
Self-healing, also known as clearing, is the removal of a
defect caused by pinholes, film flaws or external voltage
transients. The heat generated by the arcing during a
breakdown, evaporates the extremely thin metalization of
the film around the point of failure, thereby removing and
isolating the short circuit conditions. On Segmented Film
Technology Capacitors, the self healing effect is more
controlled. The film metalization is made by forming a
pattern of segments, which are connected to each other by
micro fuses. This limits the healing current and limits the
self-healing effect to a well defined section of the film.
The self-healing process requires only μW of power and a
defect is normally isolated in less than 10 μs. Extensive and
continuous self-healing (e.g. at misapplications) will
gradually decrease the capacitance value.
RFI SUPPRESSION CAPACITORS
There are two main sources of Radio Frequency
Interference (RFI). Devices that due to their construction
produce RF energy, such as oscillators, radio and TV
receivers; and devices that produce a wide spectrum of
frequency, due to rapid variations in electrical current
intensity, such as switch mode power supplies.
Interference from source to receiver is spread in three ways:
• Along wiring
• By coupling
• By radiation
Revision: 17-May-17
Document Number: 26033
1
For technical questions, contact:
dc-film@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
General Technical Information
www.vishay.com
DIELECTRIC MATERIALS
The electrical characteristics of plastic film capacitors are to
a great extent dictated by the properties of their dielectric
materials. Vishay film capacitors uses the following film
materials in their production:
POLYETHYLENE
TEREPHTALATE
POLYESTER FILM (PET)
FILM
OR
Vishay Roederstein
stability. The temperature coefficient of the material is
negative. Polypropylene capacitors are typically used in AC
and pulse applications at high frequencies and in DC-Link
capacitors. They are further used in switched mode power
supplies, electronic ballasts and snubber applications, in
frequency discrimination and filter circuits as well as in
energy storage, and sample and hold applications.
Polyester film offers a high dielectric constant, and a high
dielectric strength. It has further excellent self-healing
properties and good temperature stability. The temperature
coefficient of the material is positive. Polyester capacitors
are regarded as “general purpose capacitors”. They provide
the best volume efficiency of all film capacitors at moderate
cost and are preferably used for DC applications such as
decoupling, blocking, bypassing and noise suppressions.
POLYPROPYLENE FILM (PP)
Polypropylene film has superior electrical characteristics.
The film features very low dielectric losses, a high insulation
resistance, a low dielectric absorption, and a very high
dielectric strength. The film provides furthermore an
excellent moisture resistance and a very good long-term
DIELECTRIC PROPERTIES
(TYPICAL VALUES)
PARAMETER
Relative dielectric constant
DF at 1 kHz (tan
δ
in %)
IR (MΩ x μF)
Dielectric absorption (%)
Capacitance drift -
ΔC/C
(%)
Moisture absorption (%)
Maximum temperature (°C)
TC (ppm/°C)
PET
3.2
0.5
25 000
0.2
1.5
0.4
125
+ 400, ± 200
PP
2.2
0.02
100 000
0.05
0.5
0.01
100
- 200, ± 100
CAPACITANCE
Capacitance change at 1 kHz as function of temperature
(typical curve)
Capacitance change as a function of frequency
at room temperature (typical curve)
DISSIPATION FACTOR
Dissipation factor as function of temperature
(typical curve)
Dissipation factor as a function of frequency
at room temperature (typical curve)
Revision: 17-May-17
Document Number: 26033
2
For technical questions, contact:
dc-film@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
General Technical Information
www.vishay.com
INSULATION RESISTANCE
Vishay Roederstein
Notes
• Dielectrics according to IEC 60062:
KT = Polyethylene terephthalate (PET)
KP = Polypropylene (PP)
KI = Polyphenylene sulfide (PPS)
KN = Polyethylene naphtalate (PEN)
• Polyethylene terephthalate (PETP) and polyethylene naphtalate
(PEN) films are generally used in general purpose capacitors for
applications typically with small bias DC voltages and/or small
AC voltages at low frequencies.
• Polyethylene terephthalate (PETP) has as its most important
property, high capacitance per volume due to its high dielectric
constant and availability in thin gauges.
• Polyethylene naphtalate (PEN) is used when a higher
temperature resistance is required compared to PET.
• Polyphenylene sulfide (KI) film can be used in applications where
high temperature is needed eventually in combination with low
dissipation factor.
• Polypropylene (KP) films are used in high frequency or high
voltage applications due to their very low dissipation factor and
high dielectric strength. These films are used in AC and pulse
capacitors and interference suppression capacitors for mains
applications.
• Typical properties as functions of temperature or frequency are
illustrated in the following chapters: “Capacitance”, “Dissipation
factor”, and “Insulation resistance”.
Insulation resistance as a function of temperature
(typical curve)
DEFINITIONS
The following definitions apply to both film/foil capacitors
and metalized film capacitors.
RATED VOLTAGE (U
R
)
The rated voltage is the voltage for which the capacitor is
designed. It is defined as the maximum DC (U
R
) or AC (U
RAC
)
voltage or the pulse voltage that may continuously be
applied to the terminals of a capacitor up to an operating
temperature of + 85 °C. The rated voltage is dependent
upon the property of the dielectric material, the film
thickness and the operating temperature. Above + 85 °C,
but without exceeding the maximum temperature, the rated
voltage has to be derated in accordance to the dielectric
material used.
TEST VOLTAGE OR DIELECTRIC STRENGTH
The test voltage of a capacitor is higher than the rated DC
voltage and may only be applied for a limited time. The
dielectric strength is measured between the electrodes with
a test voltage of 1.5 x U
NDC
for 10 s, at metalized film
capacitors and of 2 x U
NDC
at film/foil capacitors for typically
2 s. The occurrence of self-healing or clearing-effects during
the application of the test voltage is permitted for metalized
film capacitors.
AC VOLTAGE
The AC voltage ratings refer to clean sinusoidal voltages
without transients. The capacitors must not, therefore, be
operated in mains applications (e.g. across the line). This
applies also to capacitors that are rated with AC voltages
≥
250 V
AC
. Capacitors especially designed for mains
operations (X and Y capacitors) are listed as “RFI
Capacitors”. For operations in the higher frequency range,
the applied AC voltage has to be derated. The derated AC
voltages are provided in the graphs “Permissible AC Voltage
Versus Frequency” on the capacitor datasheet. The
calculations of the graphs are based on the assumption that
the temperature rise measured on the surface of the
capacitor under working conditions does not exceed 10 °C.
P
=
U
RMS
x
ω
x C x tan
δ
P - Dissipation power (W)
ω
- Angular frequency (rads/s)
C - Capacitance (F)
tan
δ
- Dissipation factor at frequency (f)
2
P x 1000
P x 1000
ΔT
=
-----------------------
=
-----------------------
-
-
Ax
α
G
ΔT
- Temperature rise (°C)
A - Surface area of the capacitor (cm
2
)
α
- Heat transfer coeff. [mW/(°C x cm
2
)]
(α = 0.96 for plastic boxes with a smooth surface)
G - Component heat conductivity (displayed in datasheet)
Heat coefficient for the capacitor is presented in datasheet
for
ΔT
calculation.
For critical applications, please forward your voltage and
current waveforms (worst case conditions) for our capacitor
proposal.
MAXIMUM APPLICABLE PEAK TO PEAK RIPPLE
VOLTAGE
When an AC voltage is superimposed to a DC voltage, the
sum of both the DC voltage (U
DC
) and the peak value of the
AC voltage (U
pk
) must not exceed the rated DC voltage (U
R
)
of the capacitor.
U
R
≥
U
DC
+ U
pk
PULSE VOLTAGE
The RMS value of a pulse voltage (U
RMS(pulse)
) must not
exceed the rated AC voltage U
RAC
.
U
RAC
≥
U
RMS
(
pulse
)
The peak value of the pulse voltage (U
pk
) must not exceed
the rated DC voltage.
U
R
≥
U
pk
NOMINAL CAPACITANCE (C
N
)
The nominal capacitance is defined as the capacitive part of
an equivalent series circuit consisting of capacitance and
equivalent series resistance (ESR). C
N
is the capacitance for
which the capacitor is designed. It's value is typically
measured at a frequency of 1 kHz ± 20 %, at voltage of
0.03 x U
RDC
(max. 5 V
AC
) and a temperature of 20 °C.
The capacitance tolerance indicates the acceptable
deviation from the rated capacitance at 20 °C. Since the
dielectric constant of plastic film is frequency dependent,
the capacitance value will decrease with increasing
frequency. High relative humidity may increase the
capacitance value. Capacitance changes due to moisture
are reversible.
Revision: 17-May-17
Document Number: 26033
3
For technical questions, contact:
dc-film@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
General Technical Information
www.vishay.com
CAPACITANCE DRIFT (LONG TERM STABILITY)
In addition to reversible changes the capacitance of a
capacitor is also subject to irreversible changes also known
as capacitance drift. The capacitance drift is dependent
upon the dielectric material. The drift decreases gradually
over the time. Frequent and extreme temperature changes
may accelerate the process.
TEMPERATURE COEFFICIENT (TC)
The temperature coefficient is the average capacitance
change over a specified temperature range. It indicates how
much the capacitance changes referred to 20 °C, if the
temperature changes by 1 °C. The TC is typically expressed
in ppm/°C (parts per million per °C). Depending upon the
dielectric material the TC can either be positive, or negative.
C
2
- C
1
TC =
---------------------------------------
-
C
20
x
(
T
1
- T
2
)
C
1
- Capacitance at temperature T
1
C
2
- Capacitance at temperature T
2
C
20
- Reference capacitance at 20 °C ± 2 °C
DISSIPATION FACTOR (tan
δ)
The dissipation factor (tan
δ)
is the ratio of the ESR to the
capacitive reactance X
C
(series capacitance) or the active
power to the reactive power at a sinusoidal voltage of a
specified frequency.
ESR
Vishay Roederstein
INSULATION RESISTANCE (R
is
) AND TIME CONSTANT (τ)
The R
is
is the ratio of an applied DC voltage to the resulting
leakage current (flowing through the dielectric and over its
body surface) after the initial charging current has ceased.
The R
is
is typically measured after one minute. ± 5 s at 20 °C
and a relative humidity of 50 % ± 2 %.
U
DC
R
is
=
-------------
( Ω )
-
I
leack
The insulation resistance is determined by the property and
the quality of the dielectric material and the capacitor's
construction. The R
is
decreases with increasing
temperature. A high relative humidity may decrease the
insulation resistance. R
is
changes due to moisture are
reversible. The R
is
is shown as time constant (τ). It is the
product of insulation resistance and capacitance and is
expressed in seconds.
τ
=
R
is
x C
INDUCTANCE (L)
The inductance of a capacitor depends upon the geometric
design of the capacitor element and the length and the
thickness of the contacting terminals. All Vishay film
capacitors have an extended metalized film or foil
construction and exhibit thus a very low inductance. The
inductance of radial leaded capacitor types are typically
measured with 2 mm long lead wires. Typical values are less
than 1.0 nH per mm of lead length.
RESONANT FREQUENCY (f
r
)
The resonant frequency is a function of the capacitance
and the inductance of a capacitor. At resonant frequency
the capacitive reactance equals the inductive reactance
(l/ωC =
ωL).
At its lowest point of the resonant curve only the
ohmic value is effective, this means the impedance equals
the ESR. Above the resonate frequency the inductive part of
the capacitor prevails.
IMPEDANCE (Z)
The impedance Z is the magnitude of the vectorial sum of
ESR and the capacitive reactance X
C
in an equivalent series
circuit under consideration of the series inductance L.
Z
=
2
l
2
ESR +
ωL
-
--------
ωC
X
C
δ
The tan
δ
reflects the polarization losses of the dielectric film
and the losses caused by the contact resistance (terminals
- schooping - electrodes) of the capacitor. Parallel losses
can, due to the high insulation resistance of film capacitors,
be neglected. The tan
δ
is temperature and frequency
dependent.
ESR
tan
δ
=
-----------
-
X
C
The reciprocal value of tan
δ
is also known as Q-factor.
1
Q
=
------------
-
tan
δ
EQUIVALENT SERIES RESISTANCE (ESR)
The ESR is the ohmic part of an equivalent series circuit. Its
value assumes all losses to be represented by a single
resistance in series with the idealized capacitor.
R
pol
L
R
S
The impedance is typically measured on capacitors (radial
types) having 2 mm long leads.
DIELECTRIC ABSORPTION (DA)
The DA depends upon the dielectric material and is a
measure of the reluctance of a dielectric to discharge
completely. After a fully charged capacitor is discharged the
residual charge (recovery voltage) is expressed as a
percentage of the initial charge. DA measurements are
normally performed in accordance to IEC 60384-1.
U
1
DA
=
100 x
------
(
%
)
-
U
2
U
1
- Recovery Voltage
U
2
- Charging Voltage
R
is
The ESR comprises the polarization losses of the dielectric
material (R
pol
), the losses caused by the resistance of the
leads, termination and electrodes (R
s
) and the insulation
resistance (R
is
).
tan
δ
ESR
=
--------------
-
ω
xC
Revision: 17-May-17
AMBIENT TEMPERATURE (T
amb
)
The ambient temperature is the temperature in the
immediate surrounding of the capacitor. It is identical to the
surface temperature of an unloaded capacitor. At pulse or
AC load operations the surface temperature may, due to an
internal temperature increase, rise above the ambient
temperature.
Document Number: 26033
4
For technical questions, contact:
dc-film@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
General Technical Information
www.vishay.com
MAXIMUM TEMPERATURE (T
max.
)
The maximum temperature or upper category temperature
is the highest temperature at which a capacitor may still be
operated. At pulse or AC load operations, the sum of the
ambient temperature (T
amb
) and the temperature increase
(ΔT) caused by the load conditions, must not exceed the
maximum temperature (T
max.
).
T
max.
≥
T
amb
+
ΔT
CLIMATIC CATEGORY
The climatic category indicates the climatic conditions
which the capacitor may be operated. According to
IEC 60068-1 the climatic category is expressed by a three
group coding e.g. 55/100/56.
- The first group indicates the lower category temperature
(- 55 °C).
- The second group the upper category temperature
(+ 100 °C).
- The third group indicates the number of days (56) which
the capacitor can withstand within specified limits if
exposed to a relative humidity of 95 % and a temperature
of + 40 °C.
(IEC 60068-1)
PULSE RISE TIME (du/dt)
The pulse rise time indicates the ability of a capacitor to
withstand fast voltage changes and hence high current
peaks. The du/dt value, expressed in volts per μs (V/μs),
represents the steepest voltage gradient of the pulse (rise or
fall time). Its value is dependent upon the properties of the
dielectric material, the film thickness and the capacitor's
construction. If the applied pulse (U
pulse
) voltage is lower
than the rated voltage (U
R
) higher pulse rise times are
permitted.
U
R
du
⁄
dt
(max.)
=
(
du
⁄
dt
)
x
----------------
-
U
pulse
du/dt = Datasheet value.
The pulse rise time (du/dt) is tested with values that are 5 to
10 times above the datasheet value.
For film/foil capacitors the applied pulse rise time (du/dt) is
not limited. At higher repetition frequencies, however, the
heat generated in the capacitor during the pulse operation
must not rise by more than 10 °C.
PULSE LOAD AND CURRENT HANDLING CAPABILITY
The pulse load and current handling capability is the load of
a non-sinusoidal AC voltage that may be applied to a
capacitor. To prevent the capacitor from overheating the
following operating parameters have to be considered:
Vishay Roederstein
- Maximum pulse voltage (U
pulse
)
- Pulse shape
- Pulse rise or fall time (du/dt)
- Repetition frequency of the pulse
- Ambient temperature
- Heat dissipation (cooling)
The maximum pulse current depends upon the capacitance
and the permissible du/dt value.
I
max.
=
(
du
⁄
dt
)
x C (A)
For high voltage and high current pulse loads Vishay film
capacitors offers also a series of special capacitors. For
example capacitors with a heavy-edge or a double-sided
metallization and capacitors that combine a film/foil and a
metalized film design in one unit.
For critical applications, please forward your voltage and
current waveforms (worst case conditions) for our
capacitor proposal.
CORONA STARTING VOLTAGE
The corona starting voltage is defined as detectable
electrical discharges resulting from the ionization of air on
the surface or between the capacitor layers. Its value is
dependent upon the internal design of the capacitor
element, the dielectric material, and the thickness of the film.
The usage of series wound capacitors increases the corona
voltage level.
NON-FLAMMABILITY
Non-flammability of capacitors is accomplished by the
usage of flame-retardant materials. Non-flammability is
periodically checked according to IEC 60384-1 and IEC
60695-2-2. All plastic case materials used comply with
UL-class 94 V-0.
GENERAL TEST CONDITIONS
Unless otherwise specified, all electrical data refer to an
ambient temperature of + 23 °C, an atmospheric pressure of
86 kPa to 106 kPa and a relative humidity of 45 % to 75 %.
For arbitration cases measurements at 20 °C and a relative
humidity of 50 % ± 2 % are mandatory.
SOLDERING CONDITIONS
Regarding the resistance to soldering heat and the
solderability, our products comply with “IEC 60384-1” and the
additional type specifications.
For all capacitors, we refer to the paragraph “Soldering
Conditions” in the type specifications.
For more detail, we refer to the document “Soldering
Guidelines for Film Capacitors”:
www.vishay.com/doc?28171
MAXIMUM
PERMITTED
BURNING TIME (s)
3
10
30
CATEGORY OF
FLAMMABILITY
A
B
C
SEVERITIES FLAME EXPOSURE TIME (s) FOR
CAPACITOR VOLUME (V) (mm
3
)
V = 250 250 < V = 500
500
≤
V = 1750 V > 1750
15
20
60
120
10
5
20
10
30
20
60
30
ADDITIONAL REQUIREMENTS
Burning droplets or glowing
parts falling down shall not ignite
the tissue paper.
Revision: 17-May-17
Document Number: 26033
5
For technical questions, contact:
dc-film@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
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