Cautions When Using Aluminum Dielectric Capacitors
[1] Using Aluminum
Electrolytic Capacitors
|
|
<1> |
DC
usage for aluminum electrolytic capacitors have polarity.
If the polarity is reversed, the electrical current across the capacitor
will be extreme. Thus, possibly causing shorts or damage to the capacitor.
Do not use a DC polarized aluminum electrolytic capacitor in circuits
where the polarity is unstable or unclear. Also note that the bipolar
aluminum electrolytic capacitors for DC usage cannot be used in AC
circuits.
|
|
<2> |
Do
not exceed the rated voltage.
Applying a voltage in excess to the rated voltage can cause an extremely
high leakage current. Thus, causing damage or destroying the capacitor.
Use caution when conditioning ripple currents to ensure that the peak
levels of the ripple voltage do not exceed the rated voltage.
|
|
<3> |
Do
not use in rapid charging/discharging circuits.
Performance would be hurt by generated heat within an aluminum electrolytic
capacitor used in a circuit that repeatedly and rapidly charges and
discharges the capacitor. This type of circuit could also destroy the
capacitor. Please inquire with your sales or service representative
regarding capacitors that can be rapidly charged and discharged for
use in such circuits.
|
|
<4> |
Do
not exceed the rated ripple current.
Applying a ripple current in excess of the rated ripple current can
cause excessive internal heating within the capacitor. Thus, shortening
the life span of the capacitor and, in extreme cases, destroying the
capacitor. In such a circuit, be sure to use a high-ripple electrolytic
capacitor.
|
|
<5> |
The
performance characteristics will vary depending on the temperature
classification. (Depending on the temperature)
Depending on the temperature, the performance characteristics of the
electrolytic capacitor will vary. These changes are temporary, The
initial performance characteristics will reappear once the capacitor
returns to a normal temperature (with the exception of damage to performance
caused by extended exposure to high temperatures). By using a capacitor
outside the guaranteed temperature range, this scenario could cause
increased leakage current, and could destroy the capacitor. Please
consider the following: the ambient temperature where the equipment
is used, the equipment's internal temperature, the heat radiated from
other components within the equipment, and the generated heat within
the capacitors caused by the ripple current, etc.
|
| |
(1) |
The
rated capacitance is generally indicated as the value at 20°C
and 120 Hz. The capacitance will be reduced at temperatures
higher and lower than 20°C.
|
| |
(2) |
The
tangent of the loss angle (tan  )
is indicated as the value at 20°C and 120 Hz. This value
will decrease at higher temperatures and increase at lower
temperatures.
|
| |
(3) |
The
leakage current will increase at high temperatures and decrease
at lower temperatures.
|
|
<6> |
The
performance is dependent on frequency.
Performance characteristics of the electrolytic capacitor depend on
the used frequency.
|
| |
(1) |
The
capacitance is expressed as the value at 20°C and 120 Hz.
The capacitance will be lower at higher frequencies.
|
| |
(2) |
The
tangent of the loss angle (tan )
is indicated at 20°C and 120 Hz. The tangent of the loss
angle will be higher at higher frequencies.
|
| |
(3) |
The
impedance is generally expressed as the value at 20°C and
100 KHz. The impedance will be higher at lower frequencies.
|
|
<7> |
Performance
is dependent on how the aluminum electrolytic capacitor's storage
conditions.
The leakage current in the aluminum electrolytic capacitor will increase
if the capacitor is stored for an extended period of time. For example,
in an unused state or after installation to some equipment. The effect
is more pronounced when the ambient temperature is higher. Note that
the leakage current is reduced by the application of a voltage. If
the leakage current has increased due to storage at room temperature
for two years or more (or for a shorter period of time at higher temperatures),
it may be necessary to recondition the capacitor by applying a voltage.
Additionally, it is necessary to consider the effects of the initial
increases in current when designing the equipment. When necessary,
a guard circuit should be provided in parallel.
|
|
<8> |
There
is no isolation between the capacitor case and the cathode
terminal.
The amount of resistance in the electrolyte between the electrolytic
capacitor case and the cathode terminal is unspecified.
|
|
<9> |
The
outer sleeves are susceptible to damage.
The outer sleeve that covers the capacitor may crack if exposed to
high temperatures. For example, after the capacitor is exposed to,
organic solvents. Generally the outer sleeves on aluminum electrolytic
capacitors are made from PVC. But, note that the PVC is used to facilitate
the labeling, not to provide electrical insulation.
|
|
<10> |
Consider
the effects of any unusual environmental conditions.
Corrosion may result if the aluminum electrolytic capacitor is placed
in an environment with high concentrations of halogen or halogen-compound
gas. This is the same as the corrosion that occurs when cleaning the
printed circuit boards. Please be wary of the halogen (or halogen-compound)
gas fumigation treatment that is performed when electronic equipment
is shipped overseas. This treatment must be taken into consideration.
|
|
<11> |
Match
the circuit board hole pitch.
The hole pitch in the printed circuit board should be designed to match
the lead pitch of the capacitors (the F dimension in the catalog).
Be aware that shorts, open circuits, increased leakage currents, etc.
can be caused by the stresses on the lead wires. Especially, if the
lead pitch does not match the hole pitch.
|
|
<12> |
Be
aware of necessary considerations regarding pressure vents.
|
| |
(1) |
In
pressure valves, a portion of the case, etc., is made thin
in order to prevent an explosion due to a buildup of internal
pressure. This pressure build-up occurs when an excessive load
is placed on the capacitor by the application's excessive voltage
or voltage with the incorrect polarity. Note that the capacitor
does not return to normal after the pressure vent has been
activated. Therefore, the capacitor must be replaced.
|
| |
(2) |
For
those components where the cases are equipped with pressure
vents, please allow a space above the pressure vent during
the design process. This must be done to avoid impediments
to the pressure vent's operation.
|
| |
|
Units:
mm
|
Capacitor
Diameter |
18
mm or less |
20
to 35 mm |
|
Space
above the pressure valve |
2.0
mm or more |
3.0
mm or more |
|
| <13> |
Avoid
short circuits on double-sided wiring boards.
|
| |
When
electrolytic capacitors are used on double-sided wiring boards,
caution must be taken to prevent the wiring pattern from passing
through the mounting location of the capacitors. Depending on
the selected mounting method, there is the danger that the capacitor
could cause a short circuit on the wiring board.
|
|
<14> |
Use
caution when connecting multiple capacitors.
|
| |
(1) |
The
balance of the electric current between the capacitors may
be lost when two or more capacitors are connected in parallel.
This will cause some of the capacitors to experience excessive
ripple current. The circuit design must ensure that there will
not be excessive ripple current in any of the capacitors
|
| |
(2) |
When
two or more capacitors are connected in series, the balance
of the voltages applied to the capacitors must be taken into
account. This precautionary step will ensure that the voltages
applied to each of the individual capacitors do not exceed
the rated voltages. Voltage divider resistors should be provided
in parallel with each of the capacitors. By taking leakage
current into account, the voltage divider resistor will prevent
the application from excessive voltage to any of the capacitors.
|
| |
(3) |
Calculate
the required voltage divider resistances when connecting capacitors
in series.
When two or more capacitors are connected in series, voltage divider
resistors are inserted in parallel to the capacitors in order to provide
voltage balancing. An example of the calculation of the voltage divider
resistances is given below:
(3.1) Circuit Design
When two or more capacitors (C1 and C2) are connected in series, the
equivalent circuit can be expressed as shown in the figure below.
|
| |
|
|
| |
|
RB
= the voltage divider resistance, where the following conditions
are assumed in the circuit:
|
| |
|
1.
V2 is the rated voltage (= V0), where V < V2.
2. V is a x V0 x 2.
V = 2aV0 (where a<1)
3. R2 = R1 x b (where b>1)
|
(Equation 1)
|
(3.2)
Deriving the Formula for Calculating RB
(3.2.1) The following equation is obtained by
finding the equilibrium conditions:
|
| |
|
 |
(Equation
2) |
|
| |
|
(3.2.2)
The following equations can be obtained by using the assumed
conditions:
(3.2.3) Substitute equations 1, 3, and 4' into equation
2:
|
| |
|
|
| |
|
2abV0(R1+RB) = V2{b(R1+RB)+bR1+RB}
2ab(R1+RB)(2bR1+(1+b)RB
As a result, the voltage divider resistance RB is given by the following
equation:
|
| |
|
  |
| |
|
(3.3) Example of Calculation
In this example we calculate the values of the voltage divider resistances
when two 400V 470(F (LC standard value: 1.88mA) capacitors are connected
in series:
|
| |
|
 |
| |
|
If we assume a=0.8, then 400(V) x 2 x 0.8 = 640(V) can be applied.
If we assume b=2, then R2=bR1=426(k ),
and LC=0.94(mA). The voltage divider resistance RB is as follows:
|
| |
|
 |
| |
(4) |
The
Regeneration Voltage
There is a phenomenon that causes the voltage between terminals to increase
after an aluminum electrolytic capacitor has been allowed to sit for
some time after first having been charged and then discharged by shorting
the terminals together. This voltage that occurs is known as the "regeneration
voltage." The mechanism by which this phenomenon occurs is as described
below.
When a voltage is applied to a dielectric there are electrical changes
within the actual dielectric. The electrical changes are due to the dielectric
effect where a charge that is the opposite of the voltage applied appears
on the surface of the dielectric. This phenomenon is known as the polarization
effect.
If a voltage has been applied, this polarization effect will cause the
capacitor to discharge until the terminal voltage reaches 0. Then, the
circuit between the terminals is opened, and an electric potential will
eventually appear between the terminals. This electric potential is the
regeneration voltage.
The regeneration voltage reaches a peak about 10 to 20 days after the
terminals are disconnected. After the peak period, the regeneration voltage
falls gradually. There is a tendency for the regeneration voltage to
be larger in larger capacitors (stand-alone capacitors).
After the regeneration voltage has been generated, there will be a spark
between the terminals if they are shorted. This may cause discomfort
to the assembly-line workers on or may damage low-voltage elements such
as CPUs and memory within the circuit. One way to prevent this is to
use a resistor between about 100 and 1000 ( to discharge the capacitor
before use.
|
[2] Mounting the Capacitors
|
|
<1> |
Cautions
When Mounting the Capacitors
|
| |
(1) |
Mount
the capacitors after checking the rated values (the rated capacitance
and the rated voltage).
|
| |
(2) |
Be
aware that there may be a regenerated voltage in the capacitor.
If this is the case, discharge the voltage through a resistor
that is about 1k.
|
| |
(3) |
Mount
the capacitor only after confirming its polarity.
|
| |
(4) |
Do
not drop the capacitor on the floor or on any other hard object.
Do not use any capacitor that has been dropped.
|
| |
(5) |
Do
not modify any capacitor before mounting.
|
|
<2> |
Use
caution so as to avoid applying any strong forces to the capacitor
itself, to its terminals, or to its lead wires.
|
| |
(1) |
Mount
the capacitor only after confirming the match between the terminal
pitch on the capacitor and the pitch of the holes in the printed
wiring board pattern.
|
| |
(2) |
The
stand-alone (snap-in) capacitors on the printed wiring board
should be pushed until they are tightly seated against the
substrate (i.e., they are not floating above the substrate).
|
| |
(3) |
If
using automatic insertion equipment, be certain the force,
with which the capacitor lead lines are clinched for fastening,
is not excessively strong.
|
| |
(4) |
Be
wary of shocks when performing the product checker and centering
operations on the automatic inserter vacuum chuck.
|
|
<3> |
Soldering
|
| |
(1) |
Do
not solder the capacitor by submerging the capacitor itself
in molten solder.
|
| |
(2) |
Insure
that the soldering conditions (the auxiliary heater, the soldering
temperature, the time over which the leads are in contact with
the molten solder) remain within the specification values from
the catalog or the purchase specifications.
|
| |
(3) |
Only
apply flux to the leads.
|
| |
(4) |
Shrinking
or cracking may result if the capacitor sleeve comes into direct
contact with a circuit board pattern or with the metal parts
(such as leads) of another component.
|
| |
(5) |
When
the capacitor sleeve is tightly sealed against the circuit
board itself, the sleeve will begin to heat by either the solder
being too hot or the soldering time being too long. This heat
will cause the sleeve to shrink or crack.
|
| |
(6) |
If
the capacitor is to be used over an extended period of time,
carefully control the characteristics of the solder to prevent
problems in contacts (such as the contacts between the capacitors
and the printed circuit board which could cause incorrect electrical
flow).
|
| <4> |
Handling
after Soldering
|
| |
(1) |
Be
sure not to tilt, invert, or twist the capacitor after it has
been soldered to the printed wiring board.
|
| |
(2) |
Do not carry the
printed circuit board by the capacitor after the capacitor
has been soldered to the printed circuit board.
|
| |
(3) |
Prevent shocks to
the capacitor after it has been soldered to the printed circuit
board. Use caution to prevent the capacitor from being struck
by a circuit board or by other components when circuit boards
are stacked.
|
|
<5> |
Post-solder
Clean
|
| |
(1) |
The
capacitor cannot be cleaned using any halogen-based solvent.
|
| |
(2) |
Only
those capacitors that are guaranteed for cleaning may be cleaned
using the procedures shown in (3) and (4).
|
| |
(3) |
Cleaning
procedure:
Solvent: Clean Through 710M, 750H, 750L; Pine Alpha ST-100S; TechnoCare
FRW-14 to 17; isopropyl alcohol
Cleaning conditions: The cleaning solution temperature is not to exceed
60°C. Also, the cleaning time of any or all of immersive cleaning,
immersive ultrasonic cleaning, and/or steam cleaning is not to exceed
5 minutes. After cleaning, there must be adequate water rinsing, then
the capacitor and the board are to be dried for at least 10 minutes
in a hot air flow. The temperature of the hot air flow most not exceed
the maximum use temperature. If the drying is inadequate, then the
sleeve may experience a secondary contraction, the seating may swell,
or other cosmetic defects may occur. When it comes to the cleaning-tolerant
capacitors, do not store them in a tightly sealed container after cleaning
or in an atmosphere subjected to fumes from the cleaning solution.
|
| |
(4) |
Cleaning
method using other cleaning solutions:
Cleaning agent: AK225 AES (Asahi Glass)
Cleaning conditions: No more than a total of 5 minutes in immersive
cleaning, immersive ultrasonic cleaning, or steam cleaning. For surface
mount chip products, no more than 2 minutes in these cleaning processes.
Note: When it comes to the Freon substitutes (AK225AES, etc.), efforts
should be made to avoid their usage. Due to global environmental issues,
there have been indications that their use will be prohibited in the
future.
|
|
<6> |
Bonding
Materials and Coating Materials
|
| |
(1) |
Do
not use bonding materials/coating materials that contain haloginated
solvents.
|
| |
(2) |
Do
not use bonding materials/coating materials that contain haloginated
solvents.
|
| |
(3) |
Be
sure all cleaning agents, etc. have been dried before using
any bonding or coating material.
|
| |
(4) |
Be
sure the bonding or coating material does not obstruct the
entire surface of the capacitor plug (on the lead side).
|
| |
(5) |
Follow
the stipulations in the catalog or the purchasing specifications
regarding the requirements for thermo hardening of the bonding
or coating material. (Contact your service representative if
there are no specified conditions.) When there is a mixture
of discrete components and chip components, processing according
to the thermo hardening conditions for the bonding material
for chips may cause the outer sleeve of the discrete components
to break, crack, shrink, etc.
|
[3] Other Notes and
Cautions
|
| <1> |
Do
not touch the capacitor terminals directly.
Touching the capacitor terminals may cause injuries such as electrical
shock or burns. Before using the capacitor, be sure to discharge the
capacitor through a 1k resistor
(after insuring that the resistor is adequate to handle the resistive
heating).
|
| <2> |
Avoid
shorting with conductive material between the capacitor leads.
Additionally, do not allow the capacitor to come into contact with a
conductive solution such as an acid solution or an alkali solution.
|
| <3> |
Perform
periodic inspections on those capacitors used in industrial equipment.
The inspections should include the following:
|
| |
(1) |
External
appearance: There is no obvious problems such as the vent being
open, leakage electrolyte, etc.
|
| |
(2) |
Electrical
performance: Leakage current, capacitance, tangent of the loss
angle, and items that are specified in the catalog or in the
purchasing specifications.
|
|
<4> |
Be
aware of the following for use in unlikely circumstances.
|
| |
(1) |
If
the capacitor vent used in an electrical product is triggered
and the gas is visible, immediately unplug the power cord or
turn off the main switch to the equipment.
|
| |
(2) |
When
the capacitor pressure release vent has been actuated, high
temperature gasses in excess of 100°C will be expelled
-- do not allow these gases to strike your face. If the jet
of gas strikes the eye or is inhaled, immediately rinse the
eye with water and/or gargle. Do not ingest the electrolyte
from the capacitor. If the electrolyte comes in contact with
skin, thoroughly wash the affected area with soap and water.
|
|
<5> |
Storage
Conditions
|
| |
(1) |
Store
the capacitor in a cool dry place, indoors with a temperature
between 5°C and 35°C and a relative humidity less than
75%.
|
| |
(2) |
When
the aluminum electrolytic capacitor is stored for an extended
period of time, the leakage current will tend to increase.
In particular, this tendency is more noticeable when the storage
temperature is high. Please note that applying a voltage can
reduce the leakage current. If the capacitor is stored for
an extended period of time (more than about two years after
manufacturing), condition the capacitor by applying a voltage.
|
| |
(3) |
Do
not store the capacitor in an environment where it will be
contacted directly by water, salt water, or oil.
|
| |
(4) |
Do
not store the capacitor in an environment where it will be
exposed to toxic gases (hydrogen sulfide, sulfurous acid gas,
nitrous acid gas, chlorine gas, ozone gas, ammonia gas, etc.).
|
| |
(5) |
Do
not store the capacitor in an environment where it will be
exposed to ultraviolet light or radiation.
|
|
<6> |
If
the capacitor is damaged, dispose of it using one of the following
methods:
|
| |
(1) |
If
the capacitor is to be incinerated, prevent explosion by either
drilling a hole in the case or by adequately pulverizing it
before incineration.
|
| |
(2) |
If
the capacitor will not be incinerated, send it to a special
industrial waste processing company for reclamation.
|
|
<7> |
Other
|
| |
When
using the capacitor, only do so after reading and understanding
both the information found in the catalog and in the following
publications:
Electronic Industries Association of Japan Technical Report EIAJ RCR-2367
(Cautions and Guidelines When Using Capacitors with Solid Aluminum and
Non-solid Electrolytes for Electronic Equipment)
|
|
V0