KEMET®
APPLICATION NOTES FOR TANTALUM CAPACITORS
125
120
their accompanying Qualified Products Lists should be
consulted for details.
1.2
3
10
For Series not covered by military specifications, and
internal sampling program is operated by KEMET Quality
1.1
2
10
110
100
Assurance. The confidence level chosen for reporting the
85°C
1.0
0.9
0.8
1
10
data is 60%. However, the cost of sampling each batch
produced is overwhelmingly prohibitive, and no claim is
made concerning knowledge of failure rate for any partic-
ular lot shipped. It is demonstrated that average failure
rate for all commercial Series is between .1 and 1%/Khr at
standard conditions and 60% confidence after 2,000
hours’ testing, +85°C, and rated voltage and ≤ 1 ohm total
series resistance.
Rating
1.0
90
85
80
-1
10
10
10
10
10
10
10
10
-2
-3
-4
-5
-6
-7
-8
0.7
125°C
Rating
0.67
Connect the temperature and
17. SURGE CURRENT
applied voltage ratio of
70
60
50
40
0.6
0.5
0.4
0.3
0.2
interest with a straight edge.
The multiplier of failure rate is
given at the intersection of this
line with the model scale.
All conventional reliability testing is conducted under
steady-state DC voltage. Experience indicates that AC rip-
ple, within the limits prescribed, has little effect on failure
rate. Heavy surge currents are possible in some applica-
tions, however. Circuit impedance may be very low (below
the standard 0.1 ohm/volt) or there may be driving induc-
tance to cause voltage “ringing.” Surge current may
appear during turn-on of equipment, for example.
Failure rate under current-surge conditions may not
be predictable from conventional life test data. A surge cur-
rent test is utilized to ensure against a high frequency of
such failures, and a description is available free of charge.
The test has been adopted for all capacitors under
MIL-C-39003/06/09/10 and KEMET’s GR500 specifica-
tions.
Given T & V1 Read Failure
1
Rate Multiplier F1
Given T, & F2
Read Reguired Voltage V2
Given F3 & V3
Read Allowable Temp T3
30
25
T
V 0.1
F
Figure 12.
Reliability Nomograph
Circuit Impedance
(ohms/volt)
Failure Rate Improvement
(multiplying factors)
18. ENVIRONMENTAL CONSIDERATION
It is not possible to foresee all the conditions to which
capacitors may be subjected. Following is a list of stan-
dard tests which every Series will survive. Data may be
available (upon request) under more severe stresses for
certain Series.
0.1
0.2
0.4
0.6
1.0
.8
.6
.4
.3
0.8
1.0
.2
• LIFE TEST 85°C OR 125°C, 2000 Hours: When sub-
jected to 2000 hours at 85°C at full rated DC voltage, or
125°C at 2/3 of 85°C voltage, the capacitor shall meet
the following requirements when tested at 25°C:
2.0
3 or greater
.1
.07
TABLE 3 Relationship of Failure Rate to Impedance
Voltage “de-rating” is a common and useful approach
to improved reliability. It can be pursued too far, however,
when it leads to installation of higher voltage capacitors of
much larger size. Inherent failure rate is roughly propor-
tional to CV1.6, where C is capacitance and V is rated volt-
age. The effect becomes particularly noticeable above 50-
volt ratings. It is possible to lose more via higher inherent
failure rate than is gained by voltage derating.
The DCL shall be within 1.25 times the initial DCL
limit.
Capacitance shall be within ±10% of the initial mea-
sured value.
The DF shall not exceed the initial limit.
• SHELF LIFE +85°, 2000 hours. Post test of capacitor
shall meet the following requirements when tested at
25°C:
The relationships shown are more useful when the
failure rate has been statistically determined for a given
group of capacitors.
Failure rate is statistically determined for each pro-
duction batch of KEMET High Reliability capacitors, as
described in Specification GR500 Catalog F2956. As
noted above, not all capacitance/voltage rate values are
inherently equal in failure rate. GR500 capacitors are
processed and subjected to 100% reliability testing as a
homogeneous group of one capacitance/voltage value.
Failure rate under standard conditions is available from 1
to 0.001% Khr, depending upon the capacitance/voltage
value.
Several Series are qualified under U.S. military spec-
ification MIL-C-39003. Failure rates as low as 0.001%/Khr
are available for all capacitance/voltage values in given
groups under this test program. The specifications and
The DCL shall be within 1.5 times the initial DCL
limit.
Capacitance shall be within ±10% of the initial mea-
sured value.
The DF shall not exceed 1.5 times the initial limit.
• LEAD STRENGTH MIL-STD-202 Method 211: Pull test
will be performed as in MIL-STD-202, Method 211. The
following details and exceptions shall apply.
a. Test condition letter—A
b. The body of the capacitor will be securely clamped
during test.
80
KEMET Electronics Corporation, P.O. Box 5928, Greenville, S.C. 29606 (864) 963-6300
KEMET [ KEMET CORPORATION ]
