Datasheet

5© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 • 864-963-6300 • www.kemet.com A4031_ALS30_31 • 3/24/2017
Screw Terminal Aluminum Electrolytic Capacitors – ALS30/31 Series, +85°C
Shelf Life
The capacitance, ESR and impedance of a capacitor will not change signicantly 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 specication under each product series for specic 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 specied limit. During re-aging a maximum charging current of twice the specied leakage
current or 5 mA (whichever is greater) is suggested.
Reliability
The reliability of a component can be dened 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 dene the level of stress involved (e.g. operating voltage, ripple
current, temperature and time). Finally, the meaning of satisfactory performance must be dened by specifying a set of
conditions which determine the end of life of the component.
Reliability as a function of time, R(t), is normally expressed as: R(t)=e-
λt
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% condence level for the various type codes. By convention, FIT is expressed as
1 x 10
-9
failures per hour. Failure rate is also expressed as a percentage of failures per 1,000 hours.
e.g., 100 FIT = 1 x 10
-7
failures per hour = 0.01%/1,000 hours
End of Life Denition
Catastrophic Failure: short circuit, open circuit or safety vent operation
Parametric Failure:
• Change in capacitance > ±10%
• Leakage current > specied limit
• ESR > 2 x initial ESR value