Reliability prediction for semiconductor devices is a very important tool in each stage of
product life, from design to application by user.
Naturally, to make reliability predictions in addition to the knowledge of the functional
characteristic of the equipment, it’s mandatory to know the reliability of the component
used.
Temperature is one of the main factors affecting the reliability of semiconductor devices.
Failure rate increases rapidly with the junction temperature following the Arrhenius law:
Lambda=Aexp(-Ea/KTj)
where:
A is a constant;
Ea is activation energy depending on failure mode (0.44 for infant mortality and 0.7 for
random failure);
K is Boltzman constant;
Tj is the junction temperature.
FIT (failure in time) computation is made by derating the data collected from
accelerated test (generally operating life test performed at Tj max) to normal operating
condition using the above law.
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Regarding Life time, we can make the following hypothesis about field
working profile:
OPERATION: 5 h/day at Tj=80degC (junction temperature)
STAND BY: 19 h/day at Tj=50degC (junction temperature)
Days per year: 365
Hours per day: 24
In this case, by Arrenhius law, we can estimate a LIFE TIME = approx 21
years.
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