T0247 Datasheet, PDF (26/35 Pages) International Rectifier – Fit Rate / Equivalent Device Hours

TEMPERATURE & HUMIDITY (THB)
Test circuit
Conditions
Bias:
Vce = 100% of maximum rated
V_(BR)CES up to 500V: 500V for
all devices with rated V_(BR)CES
DUT
greater than 500V *
Temperature:
85°C
D
Relative Humidity: 85%
Duration:
2000 Hours nominal
Test points:
168, 500, 1000,
1500, 2000 Hours nominal.
DC
BIAS
* Devices manufactured since week
code 9640 the applied bias: V_(BR)CES =
Vmax or 100v which ever the lesser
D = Diode for CoPack devices only
Purpose
Temperature and Humidity bias testing for non-hermetic packages is to subject the
devices to extremes of temperature and humidity to examine the ability of the
package to withstand the deleterious effect of the humid environment.
Failure Modes
There are two primary failure modes which have been observed. The first failure
mode comes about as a result of the ingression of water molecules into the active
area on the surface of the die. Once sufficient water has accumulated in the region
of the electric field termination structure on the die, the perturbation of that field
begins to degrade the breakdown characteristics of the device.
The second failure mode that has been observed is due to cathodic corrosion of the
aluminum emitter bonding pad. As with first failure mode, water will ingress to the top
of the die. There, in the presence of applied bias, an electric current through the few
monolayers of water will begin to cause the bond pad to dissolve. Eventually. the
corrosion will proceed to the point where the current capability of the device is
increased and become unstable.
The dominance of either of these failure modes is basically determined by the
amount of bias present during test. Under low bias conditions, the corrosion
proceeds slowly, so the first failure mode will proceed very rapidly and the device will
fail due to on-resistance before the breakdown characteristics can degrade.
Sensitive Parameters
V_(BR)CES,V_CE(on)