Datasheet

16© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 • 864-963-6300 • www.kemet.com A4070_A765 • 1/9/2018
Surface Mount Conductive Polymer Aluminum Solid Electrolytic Capacitors
A765 105°C
Product Safety continued
4. Unsafe Use
Most failures are of a passive nature and do not represent a safety hazard. A hazard may, however, arise if this failure causes
a dangerous malfunction of the equipment in which the capacitor is employed. Circuits should be designed to fail safe under
the normal modes of failure.
The usual failure mode is an increase in leakage current or short circuit. Other possible modes are decrease of capacitance,
increase in dissipation factor (and impedance) or an open circuit. Capacitors should be used in a well-ventilated enclosure or
cabinet.
5. Mounting
Care should be taken when mounting by clamp so that any safety vent in the can is not covered.
6. Fumigation
In many countries throughout the world it is now common practice to fumigate shipments of products in order to control
insect infestation, particularly when wooden packaging is used. Currently, methyl bromide is widely used as a fumigant,
which can penetrate cardboard packing and polymer bags and, therefore, come into direct contact with equipment or
components contained within.
If aluminum electrolytic capacitors become exposed to methyl bromide, then corrosion may occur, depending upon the
concentration and exposure time to the chemical.
This failure mode can affect all types of KEMET aluminum electrolytic capacitors. Methyl bromide can penetrate the seals of
aluminum electrolytic capacitors and cause internal corrosion of the anode connection, resulting in the component becoming
open circuit. The rate of corrosion will depend upon the level of exposure to methyl bromide as well as the subsequent
operating conditions, such as voltage and temperature. It may take months or, in some cases, several years before the
component becomes open circuit.
7. Dielectric Absorption
A phenomenon known as the dielectric absorption can cause aluminum electrolytic capacitors to recharge themselves. The
phenomenon is well known but impossible to predict with any great accuracy, so potentially any electrolytic product could be
affected. Thus, a capacitor that has been charged and then completely discharged, will appear to recharge itself if left open
circuit; this will manifest itself as a small voltage across the terminals of the capacitor. Generally, the voltages seen are less
than 20 VDC, however, higher voltages have on occasion been reported.
In order to avoid any problems caused by this voltage, KEMET recommends that capacitors be discharged before connecting
to the terminals.