Humidity, Bias (THB) Test
Humidity, Bias (THB)
testing is a reliability test designed to
metal corrosion, particularly that of the metallizations
on the die surface of the device.
which are enough to promote corrosion of metals in the presence of
is applied to the device to provide the potential differences needed to
trigger the corrosion process, as well as to drive mobile
contaminants to areas of concentration on the die.
testing employs the following stress conditions:
1000 hours at
85 deg C,
85% RH, with
bias applied to the
device. The bias applied is usually designed to simulate the bias
conditions of the device in its real-life application, maximizing
variations in the potential levels of the different metallization areas
on the die as much as possible.
Surface-mount devices are also
prior to THB testing. During THB proper, intermediate readpoints at 48H, 96H, 168H, and
500H are often used. This gives look-ahead reliability data as the
THB test progresses.
main drawback of THB is its long
duration, necessitating weeks before useable data are obtained.
Because of this, an alternative test, the HAST, has been developed. HAST uses more severe stress
conditions but can be completed in only 96 hours. Its shorter
duration is an advantage that makes it a more popular stress test in the
Examples of Temperature/Humidity Chambers
Test or PCT; Temperature
Heat Resistance Test (SHRT);
Reliability Modeling; Qualification
Package Failures; Die
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