
KEMET Electronics Corporation, P.O. Box 5928, Greenville, SC 29606 (864) 963-6300
13.Power Dissipation
The power dissipation of this device is defined by
the allowable ripple current rating as listed in the part
number reference tables. These ratings reflect an
internal temperature rise of +50°C at the +85°C ambi-
ent temperature with 40 kHz ripple life currents as
specified in MIL-PRF-39006. These currents are
established at these conditions, with the adjusted DC
bias applied during the test.
The permissible AC currents applied to these
devices at conditions other than those defined for the
Ripple Life Test can be derived from the following table.
This table is listed as Table II, in MIL-PRF-39006/22F.
The following rules apply to the ripple capability of these
devices:
1. At +125°C, the rated voltage decreases to 2/3 of the
+85°C rated.
2. The positive peak of the applied AC ripple voltage plus
the DC bias cannot exceed the rated voltage of the
device, and the DC bias minus the negative peak of
the AC voltage cannot exceed the maximum allow-
able reverse voltage of the device.
3. The ripple current ratings within the part number tables
represents a maximum allowable internal tempera-
ture rise of +50°C at 40 kHz, and at an ambient tem-
perature of +85°C, and complying to rules 1 and 2.
4. The maximum allowable temperature rise decreases
linearly, to a +10°C rise at +125°C.
5. The ESR decreases with increasing frequency, and the
internal temperature rise is proportional the ESR of
the device.
6. The "% of +85°C Rated Voltage" defines the DC bias
level for the device.
14.Long-Term Stability
When stabilized for measurement at standard con-
ditions, capacitance will typically change within
+10% -20% during a 10,000 hour life test +85°C.
Dissipation factor data from 10,000 hour life tests at
+85°C show that post limits (at standard conditions) are
within 20% (max) of initial value at the conclusion of these
tests.
Leakage current is more variable than capacitance or
DF; in fact, leakage current typically exhibits a logarithmic
dependence in several respects. MIL-PRF-39006 permits
leakage current (measured at standard conditions) to rise
by 25% at 85°C over 10,000 hour life tests.
15.Failure Mode
Capacitor failure may be induced by exceeding the
rated conditions of forward DC voltage, reverse DC volt-
age, surge voltage, surge current, power dissipation, or
temperature. As with any practical device, these capaci-
tors also possess an inherent, although low, failure rate
when operated within the rated condition.
One failure mode is by short-circuit. Minor para-
metric drifts (see Section 14 “Long Term Stability”)
are of no consequence in circuits suitable for wet tanta-
lum capacitors. Catastrophic failure occurs as an ava-
lanche in DC leakage current over a short (millisecond)
time span. The failed capacitor, while called “short-cir-
cuited”, may exhibit a DC resistance of 10 to 10
4
ohm.
If a failed capacitor is in an unprotected low-imped-
ance circuit, continued flow of current through the capac-
itor may obviously produce severe overheating. The
short-circuit failure may thereby be converted to an
open-circuit failure. If the circuit does not open promptly,
the over-heated capacitor may damage the circuit board
or nearby components. Protection against such occur-
rence is obtained by current-limiting devices or fuses
provided by the circuit design.
Fortunately, the inherent failure rate of KEMET wet
tantalum capacitors is low, and this failure rate may be
further improved by circuit design. Statistical failure rates
are provided for wet tantalum capacitors.
16.Reliability Prediction
The failure rate is dependent upon three important
application conditions; DC voltage, ambient tempera-
ture, and circuit impedance. Additional effects are
attributable to the capacitance of the device and atmos-
pheric and mechanical exposure of the assembled cir-
cuit. The 1000 multiplier at the end converts the failure
rate to parts-per-billion piece-hours. A prediction of the
failure rate can be made using these application condi-
tions and the formulas and tables listed in MIL-HDBK-
217F (Notice 2).
6
Frequency of
applied ripple
current
120 Hz
800 Hz
1kHz
10 kHz
40 kHz
100 kHz
Ambient
Temp (°C)
Temp (°C)
Temp (°C)
Temp (°C)
Temp (°C)
Temp (°C)
=55°
85°
105°
125°
=55°
85°
105°
125°
=55°
85°
105°
125°
=55°
85°
105°
125°
=55°
85°
105°
125°
=55°
85°
105°
125°
% of
+85°C
Rated
Voltage
100%
0.60
0.39
--
--
0.71
0.43
--
--
0.72
0.45
--
--
0.88
0.55
--
--
1.00
0.63
--
--
1.10
0.69
--
--
90%
0.60
0.46
--
--
0.71
0.55
--
--
0.72
0.55
--
--
0.88
0.67
--
--
1.00
0.77
--
--
1.10
0.85
--
--
80%
0.60
0.52
0.35
--
0.71
0.62
0.42
--
0.72
0.62
0.42
--
0.88
0.76
0.52
--
1.00
0.87
0.59
--
1.10
0.96
0.65
--
70%
0.60
0.58
0.44
--
0.71
0.69
0.52
--
0.72
0.70
0.52
--
0.88
0.85
0.64
--
1.00
0.97
0.73
--
1.10
1.07
0.80
--
+66.67%
0.60
0.60
0.46
0.27
0.71
0.71
0.55
0.32
0.72
0.72
0.55
0.32
0.88
0.88
0.68
0.40
1.00
1.00
0.77
0.32
1.10
1.10
0.85
0.50
Permissible AC Currents