What affects power semiconductor reliability?
Excessive operating voltage can cause power semiconductor failures because the devices may have small spacing between their internal elements. An even worse condition for a power semiconductor is to have high voltage and high current present simultaneously. A few nanoseconds at an excessive voltage or excessive current can cause a failure. Most power semiconductor data sheets specify the maximum voltage that can be applied under all conditions. The military has shown very clearly that operating semiconductors at 20% below their voltage rating improves their reliability substantially.
