1996 Dec 03 1
Philips Components
Electrolytic Capacitors General Introduction
TRANSLATION OF TECHNICAL TERMS
SOME IMPORTANT TERMS DES TERMES IMPORTANTES EINIGE WICHTIGE BEGRIFFE
Ambient temperature (Tamb) température ambiante Umgebungstemperatur
Assessment level niveau d'assurance Gütebestätigungsstufe
Axial terminations sorties axiales axiale Anschlußdrähte
Capacitance capacité Kapazität
Charge charge laden
Climatic category catégorie climatique Klimakategorie
Dimensions dimensions Maße
Discharge décharge entladen
Dissipation factor (tan δ) tangente de l`angle de pertes Verlustfaktor
Endurance endurance Dauerspannungsprüfung
Equivalent series resistance (ESR) résistance série équivalente äquivalenter Serienwiderstand
Equivalent series inductance (ESL) inductance série équivalente äquivalente Serieninduktivität
Failure rate taux de fiabilité Ausfallrate
Frequency (f) fréquence Frequenz
General purpose grade usage général allgemeine Anforderungen
Impedance (Z) impédance Scheinwiderstand, Impedanz
Leadless sans fils unbedrahtet
Leakage current (Il) courant de fuite Reststrom
Long life grade longue durée de vie erhöhte Anforderungen
Method méthode Verfahren
Mounting montage Montage
No visible damage aucun dommage keine sichtbaren Schäden
Open circuit circuit ouvert Unterbrechung
Piercing diagram dessin de montage Bohrungsraster
Rated capacitance (CR) capacité nominale Nennkapazitat
Rated voltage (UR) tension nominale Nennspannung
Recovery reprise Nachbehandlung
Forming voltage (UF) tension de formation Formierspannung
Requirements exigences Anforderungen
Reverse voltage (Urev) tension inverse Umpolspannung
Ripple current (IR) courant ondulé überlagerter Wechselstrom
Short circuit court-circuit Kurzschluß
Surface mounting device (SMD) composant pour montage en surface oberflächenmontierbares Bauelement
Surge voltage (US) surtension Spitzenspannung
Terminations sorties Anschlüsse
Useful life durée de vie Brauchbarkeitsdauer
Visual examination examen visuel Sichtkontrolle
1996 Dec 03 2
Philips Components
Electrolytic Capacitors General Introduction
CAPACITOR PRINCIPLES
The essential property of a capacitor is to store electrical
charge. The amount of electrical charge (Q) in the
capacitor (C) is proportional to the applied voltage (U). The
relationship of these parameters is:
Q=C×U
where:
Q = charge in coulombs (C)
C = capacitance in farads (F)
U = voltage in volts (V).
The value of capacitance is directly proportional to the
(anode) surface area and inversely proportional to the
thickness of the dieletric layer, thus:
where:
εO= absolute permittivity (8.85 ×10−12 F/m)
εr= relative dielectric constant (dimensionless)
A = surface area (m2)
d = thickness of the dielectric (oxide layer in electrolytic
capacitors) (m).
CεOεrA
d
----
××=
Energy content of a capacitor
The energy content of a capacitor is given by:
WE1
2
--- CU
2
××=
handbook, halfpage
MBC552
A
cathode
dielectric
d
εr
C
anode
Fig.1 Equivalent circuit of an ideal capacitor.
NON-POLAR
handbook, full pagewidth
dielectric layer cathode
electrolyte current supply
aluminium foil
anode
aluminium foil
(highly etched)
electrolyte absorbing paper
(spacer)
Al2O3Al2O3
CCA422
Fig.2 Equivalent circuit of an electrolytic capacitor.
d
book, halfpage
C
MBC551
Rins
ESR
RESL
L
POLAR
Anode electrode: valve effect metal: aluminium
Dielectric: Al2O3
Cathode electrode, solid or non-solid electrolyte depending on technology
non-solid: wet electrolyte, spacer and aluminium foil
solid: solid electrolyte (e.g. manganese dioxide), graphite and silver epoxy.
1996 Dec 03 3
Philips Components
Electrolytic Capacitors General Introduction
ELECTRICAL BEHAVIOUR
CHARACTERISTICS OF ELECTROLYTIC CAPACITORS VARY WITH TEMPERATURE, TIME AND APPLIED
VOLTAGE.
Fig.3 Typical variation of electrical parameters as a function of frequency, ambient temperature, voltage and time.
handbook, full pagewidth
MBC545 - 1
frequency
C
frequency
Tan δ
frequency
Z
ESR
temperature
leakage
current
load time
leakage
current
voltage
leakage
current
temperature
failure
rate
% rated voltage
failure
rate
temperature
ripple
current
capability
Z
ESR
temperature
ESR
C
25 C
o
C/C0
Z/Z0
ESR/
ESR0Z
life time
C
Tan δ
ESR
ZTan δ
ESR/Z
C
frequency
ripple
current
capability
1996 Dec 03 4
Philips Components
Electrolytic Capacitors General Introduction
CONSTRUCTION
Examples
dt
h
Aluminium can
Rubber sealing
Aluminium
connection part
Insulating
sleeve
Anode and cathode lead,
tin plated
Wound cell, consisting of:
- Aluminium foil anode
with aluminium oxide
dielectric
- Paper spacer impreg-
nated with electrolyte
- Aluminium foil cathode
MSB819
Fig.4 Non-solid Aluminium, radial.
Fig.5 Non-solid Aluminium, axial.
handbook, full pagewidth
Anode lead
Aluminium foil anode
with aluminium
oxide dielectric
Cathode tab foil
welded to the bottom
of the can Aluminium
foil cathode
Blue insulating
sleeve
Cathode lead
Aluminium can
Sealing disc
Paper spacer
impregnated
with electrolyte
CCA419
1996 Dec 03 5
Philips Components
Electrolytic Capacitors General Introduction
Fig.6 Power non-solid Aluminium, snap-in.
handbook, full pagewidth
Snap-in connections
for fast assembly
Non-porous, teflon-coated
hard paper disc and rubber
insert for optimum seal
Wound cell:
Aluminium foil anode with
aluminium oxide dielectric
Paper space impregnated
with electrolyte
Aluminium foil cathode
Aluminium can
Solvent-resistant shrink
sleeve gives high
insulation resistance
High-quality low-resistance
laser weld between
connections and anode/cathode.
This means low ESR and ESL
Special design so that insertion
forces on the connections
do not stress the
windings mechanically
CCA420
a
ndbook, full pagewidth
Epoxy resin Cone-shaped flange
Anode lead
Etched aluminium
covered with Al2O3
(dielectric)
Cathode connection:
Silver epoxy on graphite
and manganese dioxide
Cathode lead
CCA421
Fig.7 Solid Aluminium (SAL), radial.
1996 Dec 03 6
Philips Components
Electrolytic Capacitors General Introduction
DEFINITIONS OF ELECTRICAL PARAMETERS
Capacitance
AC CAPACITANCE OF AN ELECTROLYTIC CAPACITOR
The capacitance of an equivalent circuit, having
capacitance, resistance and inductance in series,
measured with alternating current of approximately
sinusoidal waveform at a specified frequency; refer to
Fig.8.
Standard measuring frequencies for electrolytic capacitors
are 100 or 120 Hz.
DC CAPACITANCE OF AN ELECTROLYTIC CAPACITOR
(FOR TIMING CIRCUITS)
DC capacitance is given by the amount of charge which is
stored in the capacitor at the rated voltage (UR).
DC capacitance is measured by a single discharge of the
capacitor under defined conditions. Measuring procedures
are described in
“DIN 41328, sheet 4”
(withdrawn).
At any given time, the DC capacitance is higher than the
AC capacitance.
handbook, halfpage
VAC CESR ESL
MBC549
Fig.8 AC equivalent circuit of an electrolytic capacitor.
Fig.9 DC equivalent circuit of an electrolytic capacitor.
handbook, halfpage
MBC578
CDC
Rleak
ESR
RATED CAPACITANCE (CR)
The capacitance value for which the capacitor has been
designed and which is usually indicated upon it.
Preferred values of rated capacitance and their decimal
multiples are preferably chosen from the E3 series of
“IEC Publication 63”
.
TOLERANCE ON RATED CAPACITANCE
Preferred values of tolerances on rated capacitance are:
−20/+20%, −10/+50%, −10/+30% and −10/+10%.
These values depend on the relevant series.
Voltage
RATED VOLTAGE (UR)
The maximum direct voltage, or peak value of pulse
voltage which may be applied continuously to a capacitor
at any temperature between the lower category
temperature and the rated temperature.
CATEGORY VOLTAGE (UC)
The maximum voltage which may be applied continuously
to a capacitor at its upper category temperature.
TEMPERATURE DERATED VOLTAGE
The temperature derated voltage is the maximum voltage
that may be applied continuously to a capacitor, for any
temperature between the rated temperature and the upper
category temperature.
RIPPLE VOLTAGE (URPL)
An alternating voltage may be applied, provided that the
peak voltage resulting from the alternating voltage, when
superimposed on the direct voltage, does not exceed the
value of rated direct voltage or fall under 0 V and that the
ripple current is not exceeded.
REVERSE VOLTAGE (UREV)
The maximum voltage applied in the reverse polarity
direction to the capacitor terminations.
SURGE VOLTAGE (US)
The maximum instantaneous voltage which may be
applied to the terminations of the capacitor for a specified
time at any temperature within the category temperature
range.
1996 Dec 03 7
Philips Components
Electrolytic Capacitors General Introduction
Temperature
CATEGORY TEMPERATURE RANGE
The range of ambient temperatures for which the capacitor
has been designed to operate continuously: this is defined
by the temperature limits of the appropriate category.
RATED TEMPERATURE
The maximum ambient temperature at which the rated
voltage may be continuously applied.
MINIMUM STORAGE TEMPERATURE
The minimum permissible ambient temperature which the
capacitor shall withstand in the non-operating condition,
without damage.
Resistance/Reactance
EQUIVALENT SERIES RESISTANCE (ESR)
The ESR of an equivalent circuit having capacitance,
inductance and resistance in series measured with
alternating current of approximately sinusoidal waveform
at a specified frequency; refer to Fig.8.
EQUIVALENT SERIES INDUCTANCE (ESL)
The ESL of an equivalent circuit having capacitance,
resistance and inductance in series measured with
alternating current of approximately sinusoidal waveform
at a specified frequency; refer to Fig.8.
DISSIPATION FACTOR,(TANGENT OF LOSS ANGLE; tan δ)
The power loss of the capacitor divided by the reactive
power of the capacitor at a sinusoidal voltage of specified
frequency:
tan δ= ESR ×2πfC (approximation formula).
IMPEDANCE (Z)
The impedance (Ζ) of an electrolytic capacitor is given by
capacitance, ESR and ESL in accordance with the
following equation (see Fig.10):
Z ESR22π
f
ESL 1
2π
f
C
--------------
–
+2
=
Current
LEAKAGE CURRENT (IL)
Leakage current flows through a capacitor when a DC
voltage is applied in correct polarity. It is dependent on
voltage, temperature and time.
Leakage current for acceptance test (I
L5
)
In accordance with international standards
(“IEC 384-4”
,
and
“CECC 30300”)
the leakage current (IL5)after
5 minutes application of rated voltage at 20 °C, is
considered as an acceptance requirement.
The leakage current requirements for the majority of
Philips electrolytic capacitors, are lower than specified in
“IEC 384-4”
or
“CECC 30300”
.
If, for example, after prolonged storage and/or storage at
excessive temperature (>40 °C), the leakage current at the
first measurement does not meet the requirements,
pre-conditioning shall be carried out in accordance with
“CECC 30300 subclause 4.1”
.
Leakage current at delivery (I
L1
or I
L2
)
In addition to IL5, the leakage current after 1 minute
application of rated voltage (IL1) is specified in most of the
detail specifications.
For some series this value is specified after
2 minutes (IL2).
Operational leakage current (I
OP
)
After continuous operation (1 hour or longer) the leakage
current will normally decrease to less than 20% of the
5 minute value (IL5).
The operational leakage current depends on applied
voltage and ambient temperature; see Tables 1 and 2.
Leakage current after storage with no voltage applied
(shelf life)
If non-solid electrolytic capacitors are stored above room
temperature for long periods of time, the oxide layer may
react with the electrolyte, causing increased leakage
current when switched on for the first time after storage.
1996 Dec 03 8
Philips Components
Electrolytic Capacitors General Introduction
Table 1 Typical multiplier of operational leakage current as a function of ambient temperature (as far as allowed for
the corresponding series)
Table 2 Typical multiplier of operational leakage current as a function of applied voltage
SYMBOL MULTIPLIER
Tamb (°C) −55 −40 −25 0 20 45 65 85 105 125
IOP/IL<0.5 0.5 0.6 0.8 1 1.5 2.5 4 7 10
SYMBOL MULTIPLIER
U/UR<0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
IOP/IL0.1 0.15 0.2 0.3 0.4 0.5 0.65 0.8 1
Ripple current (IR)
Any pulsating voltage (or ripple voltage superimposed on
DC bias) across a capacitor results in an alternating
current through the capacitor.
Because of ohmic and dielectric losses in the capacitor,
this alternating current produces an increase of
temperature in the capacitor cell.
The heat generation depends on frequency and waveform
of the alternating current.
The maximum RMS value of this alternating current, which
is permitted to pass through the capacitor during its entire
specified useful life (at defined frequency and defined
ambient temperature), is called rated ripple current (IR).
The rated ripple current is specified in the relevant detail
specifications at 100 or 120 Hz (in special cases at
100 kHz) and at upper category temperature.
Usually the rated ripple current will cause a temperature
increase of the capacitor's surface of approximately 3 or
5 K (dependent on series) compared with ambient
temperature. A further temperature increase of 3 or 5 K
will be found in the core of the capacitor.
Fig.10 Vector diagram showing the AC parameters
of a capacitor.
handbook, halfpage
MBC550
δZ
ESR
1
2πf C
2πf L
This temperature rise is the result of the balance between
heat generated by electric losses:
P=I
R
2
ESR
and the carried off heat by radiation, convection and
conduction:
P=∆Τ × Α × β
IR can be determined by the equation:
where:
∆Τ = difference of temperature between ambient and
case surface
A = geometric surface area of the capacitor
β= specific heat conductivity.
The heat, generated by ripple current, is an important
factor of influence for non-solid electrolytic capacitors for
calculating the useful life under certain circumstances.
In the detail specifications this factor is considered in the
so-called ‘life-time nomograms’ (‘Multiplier of useful life’
graph) as a ratio between actual ripple current (IA) and
rated ripple current (IR), drawn on the vertical axis.
Care should be taken to ensure that the actual ripple
current remains inside the graph at any time of the entire
useful life. If this cannot be realized, it is more appropriate
to choose a capacitor with a higher rated voltage or higher
capacitance, than originally required by the application.
The internal losses and the resultant ripple current
capability of electrolytic capacitors are frequency
dependent. Therefore, a relevant frequency conversion
table (‘Multiplier of ripple current as a function of
frequency’) is stated in the detail specifications.
IR∆TAβ××
ESR
---------------------------=
1996 Dec 03 9
Philips Components
Electrolytic Capacitors General Introduction
CALCULATION OF THE APPLICABLE RMS RIPPLE CURRENT
Non-sinusoidal ripple currents (if not accessible by direct
measurement) have to be analyzed into a number of
sinusoidal ripple currents by means of Fourier-analysis;
the vectorial sum of the currents thus found may not
exceed the applicable ripple current.
For some frequently occurring waveforms, approximation
formulae are stated in Fig.11 for calculating the
corresponding RMS value.
STORAGE
No pre-condition will be necessary for Philips electrolytic
capacitors, when stored under standard atmospheric
conditions
(“IEC 68-1, clause 5.3.1”)
for the following
periods of time:
2 to 3 years for non-solid 85 °C types
4 years for non-solid 105 °C types
10 years for non-solid 125 °C types
20 years for solid types.
Fig.11 Approximation formulae for RMS values of
non-sinusoidal ripple currents.
handbook, halfpage
CCA416
A
t2
t1T
t2t
A
t2
t1Tt
t0T
A
t
t
A
t0T
WAVE FORM RMS VALUE
A3 t12 t2
3 T
t0
2 TA
t0
TA
3 TA t 1 t 2
After these periods, the leakage current for acceptance
test shall not exceed twice the specified IL5 requirement.
To ensure good solderability and quality of taping, for all
types and prior to mounting, the storage time shall not
exceed 2-3 years. This means for example: 2 years
storage time between manufacture and arrival at the
customer, plus 1 year in customer storage.
OPERATIONAL CONDITIONS
Charge-discharge proof
This term means the capability of capacitors to withstand
frequent switching operations without significant change of
capacitance.
Philips Al-electrolytic capacitors are charge-discharge
proof in accordance with
“IEC 384-4”
and
“CECC 30300 subclause 4.20”:
unless otherwise
specified, 106 switching operations (RC = 0.1 s) shall not
cause a capacitance change of more than 10%.
Non-frequent charging and discharging, without a series
resistor, will not damage the capacitor.
If a capacitor is charged and discharged continuously
several times per minute, the charge and discharge
currents have to be considered as ripple currents flowing
through the capacitor. The RMS value of these currents
should be determined and the resultant value must not
exceed the applicable limit.
Endurance test
In
“IEC 384-4”
or
“CECC 30300”
the criteria for the
acceptable drift of electrical parameters after the
endurance test at UR and upper category temperature are
defined.
Test duration and conditions per series are stated in the
relevant detail specification.
The endurance test does not provide information about the
useful life of a capacitor, as no failure percentage is
defined for this investigation.
Useful life
Useful life (other names: load life, life time or typical life
time) is that period of time, during which a given failure
percentage may occur, under well defined conditions and
requirements. Useful life data are usually calculated with a
confidence level of 60%.
1996 Dec 03 10
Philips Components
Electrolytic Capacitors General Introduction
High quality of materials and controlled manufacturing
processes provided, the useful life of non-solid electrolytic
capacitors is solely determined by evaporation of
electrolyte through the sealing.
Figure 12 shows the principal electrical consequences of
this electrolyte loss: increasing impedance and decreasing
capacitance at the end of useful life, for different non-solid
(general purpose, long life and 125 °C types) and solid
(SAL-) electrolytic capacitors.
The influence of temperature on useful life is indicated by
the so-called ‘10 K-rule’ under the horizontal axis of the
graph. The ‘10 K-rule’ means approximately, that double
the life time can be expected per 10 K temperature
decrease; this principle is derived from the well known law
of Arrhenius about acceleration of reaction processes.
The exact temperature dependence of useful life for a
particular range is given in the corresponding detail
specification in the ‘life-time nomogram’ (‘Multiplier of
useful life’ graph in the detail specifications). Detailed
performance requirements, on which the definition ‘useful
life’ is based, are also stated in the relevant detail
specifications.
Exceeding those requirements shall not necessarily
induce a malfunction of the equipment involved. The
performance requirements offer advice on the choice of
components and design of the circuitry.
Fig.12 Principal trend of electrical parameters during useful life of different electrolytic capacitors.
C0= initial value of capacitance.
ZD= specified limit of impedance.
h
andbook, full pagewidth
CCA417
life time at specified ambient temperature
100
100
Z/ZD
(%)
2000 h/85 C
o
4000 h/75 C
o
8000 h/65 C
o
5 years / 40 C
o
10K - rule 8000 h/85 C
o
16000 h/75 C
o
32000 h/65 C
o
20 years / 40 C
o
30000 h/85 C
o
60000 h/75 C
o
120000 h/65 C
o
50 years / 40 C
o
GP - types LL - types
SAL - capacitors
GP - types LL - types
125 C types
o
typ. useful life of
125 C - types
(extra long - life types)
o
SAL - capacitors
typ. useful life
of general -
purpose types
typ. useful life
of long - life
types
C/C0
(%)
∆
125 C types
o
1996 Dec 03 11
Philips Components
Electrolytic Capacitors General Introduction
CALCULATION OF USEFUL LIFE BY MEANS OF ‘LIFE-TIME
NOMOGRAMS’
Based on the Arrhenius law and on experience for some
decades, a nomogram is specified in the detail
specification for each range, where the influence of
ambient temperature and ripple current on the expected
useful life is shown. Ripple currents at other frequencies
than specified must be corrected using the frequency
conversion tables in the relevant detail specification.
The ratio of ripple current (IA/IR) is plotted on the vertical
axis and the ambient temperature (Tamb) on the horizontal.
At the intersection of these two operational conditions the
appropriate multiplier (correction factor) for useful life can
be read. The useful life under certain conditions shall be
calculated by multiplying (or dividing respectively) the
specified useful life, with the resultant correction factor.
The useful life determined by this procedure is normally
valid for applications without forced cooling. Under certain
conditions and with additional cooling, the useful life may
be considerably extended.
Fig.13 Typical example of a life-time nomogram: useful life as a function of ambient temperature
and ripple current load.
handbook, full pagewidth
3.3
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.5
0.0
3.1
40 50 60 70 80 90 100
Tamb (C)
o
MBC579
lifetime multiplier
Axial and radial 85 C - types.
I = actual ripple current at specified conditions.
I = rated ripple current, multiplied with the frequency correction
factor (see relevant tables in the detail specifications).
A
R
o
70
50
20
6.0
4.0
2.0
1.5
1.0
30
15
10
3.0
IA
R
I
Axial and radial 85 °C types.
1996 Dec 03 12
Philips Components
Electrolytic Capacitors General Introduction
Fig.14 Typical example of a life-time nomogram: useful life as a function of ambient temperature and
ripple current load.
handbook, full pagewidth
3.8
3.7
3.6
3.5
3.4
3.3
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.5
0.0
3.1
40 50 60 70 80 90 100 110
MBC580
lifetime multiplier
Tamb (C)
o
Axial and radial 105 C - types.
I = actual ripple current at specified conditions.
I = rated ripple current, multiplied with the frequency correction
factor (see relevant tables in the detail specifications).
A
R
o
200
100
60
20
6.0
4.0
2.0
1.5
1.0
30
12
8.0
150
3.0
IA
R
I
Axial and radial 105 °C types.
1996 Dec 03 13
Philips Components
Electrolytic Capacitors General Introduction
EXAMPLES FOR THE USE OF ‘LIFE-TIME NOMOGRAMS’
Example 1
Temperature in (operating) equipment is 45 °C.
Ripple current load is exactly the rated value (thus:
IA/IR= 1).
Which useful life can be expected (without pause and
storage times):
1. for a capacitor with a specified useful life of
2000 hours at 85 °C?
2. for a capacitor with a specified useful life of
2000 hours at 105 °C?
Solution:
The corresponding life-time multiplier may be found at the
intersection between the vertical ‘45 °C’-line and the
horizontal ‘1’-line. For the 85 °C type this is ‘30’ (see
Fig.13) and for the 105 °C type it is ‘90’ (see Fig.14).
Resulting useful life is thus:
1. for 85 °C type: 30 ×2000 hours = 60000 hours or
about 7 years
2. for 105 °C type: 90 ×2000 hours = 180000 hours or
about 20 years.
Example 2
Which life time requirement has to be fulfilled by the
capacitors, if the equipment life shall be 10 years (approx.
100000 hours), consisting of 1000 hours at 75 °C+
9000 hours at 65 °C + 90000 hours at 40 °C? No ripple
current applied (thus: IA/IR= 0).
Solution:
The mentioned life-times shall be converted to specified
85 °C or 105 °C life-times, i.e. they have to be divided
through the correction factors found at the intersection of
the respective operational conditions (see Table 4).
The required life-time can be fulfilled by types with a
specified useful life of:
1. >2970 hours at 85 °C i.e. a 3000 hours/85 °C type, or
2. >935 hours at 105 °C i.e. a 1000 hours/105 °C type.
Example 3
Which internal temperature may occur in the equipment,
if the actual ripple current at 10 kHz is 3 times higher than
specified for a 16 V-type and the load limit may not be
exceeded?
Solution:
The ripple current must first be converted from 10 kHz to
100 Hz by using the conversion table (see typical
example, Table 3). This shows that the conversion factor
for a 16 V-type is 1.2.
IA/IR= 3 at 10 kHz and must be divided by 1.2, resulting in
IA/IR= 2.5 at 100 Hz.
The load limit is defined by the diagonal line ‘multiplier 1’ in
the relevant nomogram.
This means here: the vertical line on the intersection of
IA/IR= 2.5 and the multiplier 1-line shows the maximum
permitted internal temperature:
1. for 85 °C types this is max. 59 °C
2. for 105 °C types this is max. 79 °C.
The corresponding life-time in this case is equal to the
specified useful life.
Table 3 Typical example of a frequency conversion table (IR/IRO) as a function of frequency;
IRO = ripple current at 100 Hz
FREQUENCY
(Hz) IR MULTIPLIER
UR=6.3 to 25 V UR=35 and 40 V UR=50 and 63 V
50 0.95 0.85 0.80
100 1.00 1.00 1.00
300 1.07 1.20 1.25
1000 1.12 1.30 1.40
3000 1.15 1.35 1.50
≥10000 1.20 1.40 1.60
1996 Dec 03 14
Philips Components
Electrolytic Capacitors General Introduction
Table 4 Life-time calculation in “Example 2”
LIFE CONDITIONS 85 °C TYPES (see Fig.13) 105 °C TYPES (see Fig.14)
1000 hours at 75 °C 1000/2.9 = 345 hours 1000/8 = 125 hours
9000 hours at 65 °C 9000/6 = 1500 hours 9000/20 = 450 hours
90000 hours at 40 °C 90000/80 = 1125 hours 90000/250 = 360 hours
sum for 85 °C=2970 hours sum for 105 °C=935 hours
FAILURE RATE (λ)
The failure rate is defined by the number of components
failing within a unit of time, related to the total quantity of
components observed:
or
λnumber of failures (statistical upper limit 60%)
total number of components duration×
-------------------------------------------------------------------------------------------------------------------------
=
λfailure percentage (%)
100 duration×
-----------------------------------------------------------
=
however, for an individual component it is not
longer than the specified useful life.
The failure rate (λ) is generally expressed in so-called ‘fit’
(failure intime) = 10−9/hours with an upper confidence
level (UCL) of 60%. It is calculated from results of
periodical tests in the quality laboratories or derived from
field observations respectively.
Usually the failure rate during time shows the well known
‘bathtub’ curve (see Fig.15).
MTBF 1
λ
---
=
Fig.15 Failure rate (λ) as a function of time (‘bathtub’ curve).
a) Initial failure period (‘infant mortality’).
b) Random failure period (= useful life period).
c) Wear-out failure period.
handbook, full pagewidth
MBC547
factory customer
failure
rate
(λ)
(a) (b) (c)
time (t)
1996 Dec 03 15
Philips Components
Electrolytic Capacitors General Introduction
There are 3 periods in a typical capacitor life cycle:
1. Initial failure period, showing a rapidly decreasing
failure rate. During production of Philips electrolytic
capacitors, initial failures are removed after re-forming
(which is a short burn-in); all capacitors shipped, have
passed burn-in.
2. Random failure period, showing a low and constant
failure rate. This period is identical with ‘useful life’.
The sum total of all (drift and accident) failures during
this period, related to the total number of observed
capacitors, is called ‘failure percentage’. Both are
specified in the detail specification of the relevant
series.
3. Wear-out failure period, showing an increasing failure
rate due to gradual deterioration.
Since the failure rate mainly depends on two stress factors
(temperature and applied voltage), it is usually specified
under reference conditions, which are: Tamb =40°C and
U = 0.5 UR.
For other operational conditions, λ has to be converted
correspondingly with the aid of Figs 16 and 17, failure
rates as a function of stress factors (T and U/UR) for
non-solid and SAL electrolytic capacitors.
CLIMATIC CATEGORY
For each capacitor range the climatic category in
accordance with
“IEC 68-1”
is stated in the relevant detail
specification. The climatic category consists of three digit
groups; example given in Table 5.
Fig.16 Conversion factors for failure rate (λ) as a function of ambient temperature (Tamb) and
voltage ratio (U/UR) for non-solid electrolytic capacitors.
handbook, 4 columns
020
CCA418
100 Tamb (°C)
10
1
failure rate
multiplying
factor
40 60 80
10−2
102
4.102
120 140
U/UR =
0.9
0.8
0.7
0.6
0.5
0.4
0.3
1
0.2/0.1
1996 Dec 03 16
Philips Components
Electrolytic Capacitors General Introduction
Table 5 Example of climatic categories
Example: 40 / 085 / 56
40 lower category temperature (here: −40 °C)
085 upper category temperature (here: +85 °C)
56 duration of test ‘damp heat, steady state’ (here: 56 days)
Fig.17 Conversion factors for failure rate (λ) as a function of ambient temperature (Tamb) and
voltage ratio (U/UR) for SAL electrolytic capacitors.
handbook, full pagewidth
150050
CCA425
100
1
failure rate
multiplying
factor
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2/0.1
1
102
10
10−1
U/UR =
Tamb (°C)
1996 Dec 03 17
Philips Components
Electrolytic Capacitors General Introduction
Table 6 Maximum humidity condition indication for the application class
CODE
LETTER
RELATIVE AIR HUMIDITY
YEARLY
AVERAGE 30 DAYS
PER YEAR OCCASIONALLY DEWING
C≤95% 100% 100% permitted
D≤80% 100% 90% permitted
E≤75% 95% 85% slightly/rarely
F≤75% 95% 85% not permitted
APPLICATION CLASS
Although the German standard
“DIN 40040”
has been
withdrawn, it is still widely used in industrial specifications
for the definition of climatic working conditions. The
application class consists of 3 code letters which have the
following meanings.
Code letter meanings
MOUNTING
Mounting position of non-solid Al-electrolytic
capacitors
Snap-in and printed wiring (PW) as well as solder lug (SL)
power electrolytic capacitors, in addition to the larger case
sizes of axial and radial types, are normally equipped with
pressure relief in the aluminium case. These and all
smaller case size types, may be mounted in any position.
Screw-terminal power electrolytic capacitors have a
pressure relief in the sealing disc. These types shall be
mounted so that no emissions of electrolyte or vapour may
reach either the conductors under voltage, or other parts
of the printed circuit board. Vertical (pressure relief up) or
horizontal (pressure relief on the upper side) mounting
position is recommended.
Design rules for ‘capacitor batteries’
MECHANICAL
Philips power electrolytic capacitors are mainly used in
power supply applications under high ripple current load.
In these circumstances, the capacitors must be mounted
with a distance of ≥15 mm from each other, in order to
1st letter: lower category temperature
F: −55 °C; G: −40 °C; H: −25 °C
2nd letter: upper category temperature
P: +85 °C; M: +100 (+105) °C; K: +125 °C
3rd letter: maximum humidity conditions (see Table 6)
allow sufficient air circulation and to prevent mutual
radiation.
Likewise, if axial or radial types are subject to high ripple
load, they shall be mounted with sufficient distance (e.g.
≥10 mm) from each other for good convection.
ELECTRICAL
Parallel connection
Al-electrolytic capacitors may be connected in parallel, but
for safety reasons, large sizes should be individually
guarded against sudden energy discharge of the whole
battery due to a defective specimen.
With smaller batteries, this safeguarding is sufficiently
ensured by current limiting resistors.
Series connection
Al-electrolytic capacitors may be connected in series, but
when doing so it should be noted that the voltage
distribution will be according to their leakage currents. This
phenomenon may induce irregularities in voltage load and
cause maximum ratings to be exceeded; this could have
drastic consequences, especially with high voltage
capacitors.
Series-connected electrolytic capacitors should therefore
be, either supplied by galvanically separated voltage
sources or the voltages shall be proportionally distributed
by balancing resistors.
The balancing resistors can be dimensioned in
accordance with the following approximation formula:
Rsym (in kΩ) = 10000/CR (in µF)
Combined series/parallel connection
The above mentioned rules for both series and parallel
connection are accordingly valid for any combination of
these two cases.
1996 Dec 03 18
Philips Components
Electrolytic Capacitors General Introduction
MARKING
Philips electrolytic capacitors are identified in accordance with
“IEC”
rules. When sufficient space is available,
capacitors are marked with the following details:
Rated capacitance in µF (the ‘µ’ sign represents the position of the decimal point)
Rated voltage in V
Tolerance on rated capacitance if necessary, as a letter code in accordance with
“IEC 62”
, e.g.
T for −10/+50%
M for ±20%
K for ±10%
Q for −10/+30%
A for tolerance according to detail specification
Group number 3-digit part of the catalogue number, e.g. 036 for RSP series
Name of manufacturer PHILIPS or PH or P
Date code abbreviation in 2 digits (
(“IEC 62”)
, e.g.
1st digit 2nd digit
C = 1992 1 = January
D = 1993 2 = February
E = 1994 ...
F = 1995 9 = September
H = 1996 O = October
J = 1997 N = November
K = 1998 D = December
example:
F5 = produced in 1995, May
production date may also be stated as year/week code
example: 9525 = produced in 1995, 25th week
Date code may also be stamped in the case.
Factory code indicating the factory of origin
Polarity identification strip, band or negative symbol (“−” sign) to indicate the negative terminal and/or a
“+” sign to identify the positive terminal.
