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Using Aluminum Electrolytic Capacitors

1DC 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.

2Do 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.

3Do 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.

4Do 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.

5The 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. 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. 2.The tangent of the loss angle (tan δ) is indicated as the value at 20°C and 120 Hz. This value will decrease at higher temperatures and increase at lower temperatures.
  3. 3.The leakage current will increase at high temperatures and decrease at lower temperatures.

6The performance is dependent on frequency.

Performance characteristics of the electrolytic capacitor depend on the used frequency.

  1. 1.The capacitance is expressed as the value at 20°C and 120 Hz. The capacitance will be lower at higher frequencies.
  2. 2.The tangent of the loss angle (tan δ) is indicated at 20°C and 120 Hz. The tangent of the loss angle will be higher at higher frequencies.
  3. 3.The impedance is generally expressed as the value at 20°C and 100 KHz. The impedance will be higher at lower frequencies.

7Performance 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.

8There 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.

9The 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.

10Consider 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.

11Match 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.

12Be aware of necessary considerations regarding pressure vents.

  1. 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. 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

13Avoid 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.

14Use caution when connecting multiple capacitors.

  1. 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. 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. 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:
    1. (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. 1.V2 is the rated voltage (= V0), where V < V2.
      2. 2.V is a x V0 x 2.
        V = 2aV0 (where a < 1)
      3. 3.R2 = R1 x b (where b > 1)(Equation 1)
    2. (3-2)Deriving the Formula for Calculating RB
      1. (3.2.1) The following equation is obtained by finding the equilibrium conditions:
        (Equation 2)
      2. (3.2.2) The following equations can be obtained by using the assumed conditions:
        V2≦VO(Equation 3)
        V1=V-V2(Equation 4)
        =2aVO-V2(Equation 4')
      3. (3.2.3) Substitute equations 1, 3, and 4' into equation 2:

        As a result, the voltage divider resistance RB is given by the following equation:
    3. (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(kΩ), and LC=0.94(mA). The voltage divider resistance RB is as follows:
  4. 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.

Mounting the Capacitors

1Cautions When Mounting the Capacitors

  1. 1.Mount the capacitors after checking the rated values (the rated capacitance and the rated voltage).
  2. 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 1kΩ.
  3. 3.Mount the capacitor only after confirming its polarity.
  4. 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. 5.Do not modify any capacitor before mounting.

2Use caution so as to avoid applying any strong forces to the capacitor itself, to its terminals, or to its lead wires.

  1. 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. 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. 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. 4.Be wary of shocks when performing the product checker and centering operations on the automatic inserter vacuum chuck.


  1. 1.Do not solder the capacitor by submerging the capacitor itself in molten solder.
  2. 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. 3.Only apply flux to the leads.
  4. 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. 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. 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).

4Handling after Soldering

  1. 1.Be sure not to tilt, invert, or twist the capacitor after it has been soldered to the printed wiring board.
  2. 2.Do not carry the printed circuit board by the capacitor after the capacitor has been soldered to the printed circuit board.
  3. 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.

5Post-solder Clean

  1. 1.The capacitor cannot be cleaned using any halogen-based solvent.
  2. 2.Only those capacitors that are guaranteed for cleaning may be cleaned using the procedures shown in (3) and (4).
  3. 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. 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.

6Bonding Materials and Coating Materials

  1. 1.Do not use bonding materials/coating materials that contain haloginated solvents.
  2. 2.Do not use bonding materials/coating materials that contain haloginated solvents.
  3. 3.Be sure all cleaning agents, etc. have been dried before using any bonding or coating material.
  4. 4.Be sure the bonding or coating material does not obstruct the entire surface of the capacitor plug (on the lead side).
  5. 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.

Other Notes and Cautions

1Do 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 1kΩ resistor (after insuring that the resistor is adequate to handle the resistive heating).

2Avoid 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.

3Perform periodic inspections on those capacitors used in industrial equipment.

The inspections should include the following:

  1. 1.External appearance: There is no obvious problems such as the vent being open, leakage electrolyte, etc.
  2. 2.Electrical performance: Leakage current, capacitance, tangent of the loss angle, and items that are specified in the catalog or in the purchasing specifications.

4Be aware of the following for use in unlikely circumstances.

  1. 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. 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.

5Storage Conditions

  1. 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. 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. 3.Do not store the capacitor in an environment where it will be contacted directly by water, salt water, or oil.
  4. 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. 5.Do not store the capacitor in an environment where it will be exposed to ultraviolet light or radiation.

6If the capacitor is damaged, dispose of it using one of the following methods:

  1. 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. 2.If the capacitor will not be incinerated, send it to a special industrial waste processing company for reclamation.


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)