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

A4031_ALS30_31 • 8/30/2016

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.

The failures in time (FIT) are given with a 60% confidence level for the various type codes. By convention, FIT is expressed as

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