Guidelines For Using Aluminum Electrolytic Capacitors

When using Aluminum Electrolytic Capacitors, please observe the following points to ensure optimum capacitor performance and long life.

1. DC electrolytic capacitors are polarized.

Make sure of the polarity which is marked on the body of the capacitor.  Application of the reversed voltage may cause a short circuit or damage to the capacitor.  Use bipolar capacitors when the polarity is not determined or unknown.  Note that DC electrolytic capacitors CAN NOT be used for AC application.

2. Bipolar capacitors

These capacitors are used only in pulse circuits as well as polarity reverse circuits, but not applicable in pure AC or high ripple current. 

3. Do not apply voltage greater than the rated voltage

If a voltage exceeding the rated voltage is applied, the leakage current will increase, which will damage the capacitor.  Recommended working voltage is 70% - 80% of rated voltage.  Using capacitors at recommended working voltage prolongs capacitor life.

4. Do not allow excessive ripple current through the capacitor

The flow of ripple current greater than the permissible (rated) value will cause heating of the capacitor, which may decrease the capacitance and damage the capacitor.

Ripple current through the capacitor must be at or below the allowable level, generally not more than 80% of the rated current.

5. Use specially designed capacitors for the circuits where charge and discharge are frequently repeated.

In circuits subjected to rapid charge and discharge cycles, a capacitor may be damaged and its life may be shortened by capacitance decrease at higher temperature.  

6.       6.    Operating temperature range.

The characteristics of capacitors change with the operating temperature.  The capacitance and leakage current increase and dissipation factor will decrease at higher temperatures. Usage at lower temperature will ensure longer life.

7.       7.    Temperature vs. Life.

The expected life of a capacitor is related to its ambient temperature. Generally, if the ambient temperature is reduced 10^o C, life is doubled at rated voltage.  Here is the formula:

L₂₌ L_{1 x} 2   T₁ ?T₂    L_{1 ?}Life at rated temperature   L₂- Life at actual temperature

                      T_{1 ?}Rated used temperature    T_2- Actual used temperature

8.       8.    Check operating frequency.

Electrolytics usually have their capacitance measured at 100 Hz. or 120 Hz.  However, remember that capacitance decreases and dissipation factor increase as the applied frequency becomes higher.

9.       9.    Capacitor Storage

Long periods of storage have virtually no effect on a capacitor’s capacitance and dissipation factor. However, such periods can increase leakage current and decrease the capacitors withstand voltage. Apply rated DC voltage treatment to the capacitors which have been stored for a long time.

10.   The capacitor case is not insulated from the cathode terminal.

The capacitor’s case and cathode terminal connect through the electrolyte. If the case is to be completely insulated, that insulation must be at the capacitor’s mounting point.

11.    11.  Do not apply excessive force to the terminals and leads.

An excessively strong force applied to the terminals and lead wires may cause leads to break or terminals to separate and, in turn, cause the internal contact to fail.

12.    12.   Cleaning of the circuit board after solder dipping.

Clean circuit boards to remove flux or other extraneous matter.  To ensure protection for the sleeve, its marking, and the capacitor's sealing materials, the capacitor should never be washed or cleaned by halogenous agents or solvents such as trichlorethylene, xylene, acetone, etc. 

Recommended cleaning solvents;  Methanol, isopropanol ethanol, isobutanol, petroleumether, propanol and/ or commercial detergents.

13.    13.   Be cautious of the temperature and duration when soldering.

Soldering irons should be kept away from vinyl-insulated sleeves of capacitor.  When the capacitor is dipped in a solder bath, use at less than 260^o C and 10 seconds to avoid damaging the capacitor.

14.    14.  Hole positions on the circuit board.

When designing a circuit board, space the through-holes equal to the space between the capacitor's lead wires. If the spacing is either greater than or less than the capacitor's leads, mounting will apply stress to the leads, causing short circuits, broken circuits, and increased current.

Also, through-holes on the circuit board as well as lead holes of post-process parts can result in solder splashing onto the vinyl sleeve causing damage.  Consider hole positions carefully.