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© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com

A4031_ALS30_31 • 4/3/2014

Screw Terminal Aluminum Electrolytic Capacitors – ALS30/31 Series, +85°C

Shelf Life

The capacitance, ESR and impedance of a capacitor will not change significantly after extended storage periods, however the leakage

current will very slowly increase. KEMET products are particularly stable and allow a shelf life in excess of three years at 40°C. See

sectional specification under each product series for specific data.

Re-age (Reforming) Procedure

Apply the rated voltage to the capacitor at room temperature for a period of one hour, or until the leakage current has fallen to a steady

value below the specified limit. During re-aging a maximum charging current of twice the specified leakage current or 5 mA (whichever

is greater) is suggested.

Reliability

The reliability of a component can be defined as the probability that it will perform satisfactorily under a given set of conditions for a

given length of time.

In practice, it is impossible to predict with absolute certainty how any individual component will perform; thus, we must utilize probability

theory. It is also necessary to clearly define the level of stress involved (e.g. operating voltage, ripple current, temperature and time).

Finally, the meaning of satisfactory performance must be defined by specifying a set of conditions which determine the end of life of the

component.

where R(t) is the probability that the component will perform satisfactorily for time t, and λ is the failure rate.

Failure Rate

The failure rate is the number of components failing per unit time. The failure rate of most electronic components follows the

characteristic pattern:

• Early failures are removed during the manufacturing process.

• The operational life is characterized by a constant failure rate.

• The wear out period is characterized by a rapidly increasing failure rate.

failures per hour. Failure rate is also expressed as a percentage of failures per 1,000 hours.

End of Life Definition

Catastrophic Failure: short circuit, open circuit or safety vent operation

Parametric Failure:

• Change in capacitance > ±10%

• Leakage current > specified limit

• ESR > 2 x initial ESR value