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| Created: 07/27/2004 |
Product: Ceramic |
| Updated: 11/09/2005 |
Categories: Materials, Product Offerings
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What is the “low voltage failure mode” and does it apply to military ceramics? |
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Description :
What is the “low voltage failure mode” and does it apply to military ceramics?
Answer :
The "low voltage failure mechanism" has been the subject of much discussion over the years, but KEMET has not seen this failure mechanism in our ceramic capacitors. The primary method of checking for low voltage failure mechanism was the development of the low voltage humidity test, wherein low voltage is applied through high impedance in a humid environment, followed by insulation resistance checks, again at low voltage and high impedance. The test has long been formalized in the military chip specification, MIL-PRF-55681, as part of the group C test schedule. There is no corresponding test in MIL-PRF-39014, the leaded military specification.
However, the ceramic chips we use in MIL-PRF-55681 are manufactured using the same dielectric and electrode materials as those in MIL-PRF-39014. Additionally, the dielectric thicknesses follow the same guidelines for the 50 volt ratings. Thus, the low voltage humidity data collected for MIL-PRF-55681 could be used to predict MIL-PRF-39014 performance.
To date, we have never experienced a failure in the MIL-PRF-55681 due to the low voltage humidity phenomenon, so we are skeptical about the possibility of "low voltage failure mechanism" for military ceramic products. It is true that high capacitance (high layer count), coupled with low voltage (thinner dielectric), can make parts more susceptible to failure on life testing, but this does not convince us of the existence of any special physical phenomena such as "low voltage failure mechanism".
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