Voltage References

humidity independently of each other, thus we are able to set
different combinations of temperature and relative humidity.
The most frequently used combination is 130°C with 85% RH.
This has been related to THB (85°C, 85% RH) by an
acceleration factor of 20 (minimum). The ability to keep the
relative humidity variable constant for different temperatures
is the most appealing factor of the HAST test because it
reduces the determination of the acceleration factor to a single
Arrhenius type of relationship. Motorola has been phasing
over to HAST testing since 1985.
Temperature, Humidity and Bias (THB): This test
measures the moisture resistance of plastic encapsulated
packages. It detects corrosion type failure mechanisms due to
free and bounded ionic contaminants that may have entered
MOTOROLA LINEAR/INTERFACE ICs DEVICE DATA
14-9
the package during the manufacturing processes, or they may
be bound in the materials of the integrated circuit packaging
system and activated by moisture and the applied electrical
fields. Conditions are per JEDEC-STD-22, Method 102 (85°C,
85% RH), with bias applied. The duration is for 1008 hours,
with a 504 hour interim readout. The acceleration factor
between THB (85°C, 85% RH with bias) and the 30°C, 90%
RH is typically 40 to 50 times, depending on the type of
corrosion mechanism, electrical field and packaging system.
Analysis Procedure: Devices failing to meet the electrical
criteria after being subjected to an accelerated environment
type test(s) are verified and characterized electrically, then
they are submitted for root cause failure analysis and
corrective action for continuous improvement.
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