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SECTION 4 - FAILURE RATE ACCELERATION DUE TO T
J
•
Table 2 indicates the relative failure rate as a function of junction temperature
based on the assumption that the Arrhenius relationship is valid and that the
average activation energy is 0.6eV. T
J
=
5SoC
is used as the reference
temperature.
It should be noted that different device manufacturers' assumptions
may vary from those upon which the acceleration factors in Table 1 are based.
Additional design margin is recommended if T
J
is above 10soe.
Also, a more thorough
analysis should be done if the designer's system causes T
J
to exceed 10SoC for any
length of time.
TABLE 2 -
FAILURE RATE AS A FUNCTION OF T
J
RECOMMENDATIONS
T
J
ACCELERAT I ON
F~rrOltS
Relative to 55 C Incremental
Good
55°C
1 .00
1 .8
Operating
65°C
1. 87
1.87
Range
7SoC
3.39
1.7S
85°C
5.92
1.70
95°C
10.04
1.65
Acceptable for lOSoC
16.56
Intermittant
l150e
26.62
1 .61
Operation
Not
Recommended
l250e
41.78
1 .57
Example:
The MTBF (mean time to failure) for a device with T
J
=
55°C
will on the average be 3.39 times longer than the MTBF for
o
the same device with T
J
=
75
c .
23
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