ZINC OXIDE VARISTORS Introduction

Zinc Oxide Varistors
Reliability
PRODUCT QUALITY ASSURANCE
AVX has a Quality System that complies with the ISO &
CECC quality requirements.
All products are tested and released by the quality department
based on the compliance to established customer
specifications. Critical raw materials are inspected for dimensional,
electrical and physical properties prior to releasing to
the production floor.
Routine checks are carried out at crucial processes. The
finished products are submitted to Quality Control for inspection
on electrical, dimensional, physical & visual conformance
to relevant specifications, based on established AQLs.
The average outgoing quality level is < 10ppm on AVX
varistors. The low ppm value is applicable for total functional
failures, i.e. short circuit and open circuit.
RELIABILITY
AVX varistors are subjected to reliability tests stated in page
37 (per CECC 42000).
Life test is conducted to determine the life time of varistors.
The test conditions used are stated in page 00. The varistors
are subjected to these conditions for a minimum period of
1000 hours.
Failure in time (FIT) is computed for all tested parts based on
Arrhenius equation. The definition of failure is a shift in the
nominal voltage exceeding ± 10%. The FIT calculation is
computed in units of 10 -9 /h.
Figures below give the FIT for low and high voltage varistors.
The FIT values at various stresses are extrapolated based
on Arrhenius equation.
FIT (Failure in Time)
100,000
10,000
1,000
100
0.8 V RMS
0.7 V RMS
FIT OF VARISTORS (Vrms > 40 V)
1.0 V RMS
0.9 V RMS
10
1
40 60 80
Temperature (°C)
100 120
FIT OF VARISTORS (Vrms