TAP685010 datasheet(13/16 Pages) AVX

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MAY 2013

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SECTION 3:

RELIABILITY AND CALCULATION OF FAILURE RATE

3.1 STEADY-STATE

Tantalum Dielectric has essentially no wear out mechanism

and in certain circumstances is capable of limited self

healing, random failures can occur in operation. The failure

rate of Tantalum capacitors will decrease with time and not

increase as with other electrolytic capacitors and other

electronic components.

Figure 1. Tantalum reliability curve.

The useful life reliability of the Tantalum capacitor is affected

by three factors. The equation from which the failure rate can

be calculated is:

F = FU x FT x FR x FB

where

FU is a correction factor due to operating voltage/

voltage derating

FT is a correction factor due to operating

temperature

FR is a correction factor due to circuit series

resistance

FB is the basic failure rate level. For standard

leaded Tantalum product this is 1%/1000hours

Operating voltage/voltage derating

If a capacitor with a higher voltage rating than the maximum

line voltage is used, then the operating reliability will be

improved. This is known as voltage derating. The graph,

Figure 2, shows the relationship between voltage derating

(the ratio between applied and rated voltage) and the failure

rate. The graph gives the correction factor FU for any

operating voltage.

Voltage Correction Factor

Figure 2. Correction factor to failure rate F for voltage

derating of a typical component (60% con. level).

Operating temperature

If the operating temperature is below the rated temperature

for the capacitor then the operating reliability will be improved

as shown in Figure 3. This graph gives a correction factor FT

for any temperature of operation.

Temperature Correction Factor

Figure 3. Correction factor to failure rate F for ambient

temperature T for typical component (60% con. level).

100.0

10.0

1.0

0.1

0.0

90 100 110 120 130

Temperature (C)

Tantalum

1.0000

0.1000

0.0100

0.0010

0.0001

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Applied Voltage / Rated Voltage

Infinite Useful Life

Useful life reliability can be altered by voltage

derating, temperature or series resistance

Infant

Mortalities

TAP/TEP Technical Summary and

Application Guidelines

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