6

© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com

P0102_ASB • 4/6/2016

Multilayer Piezoelectric Actuators – ASB Series Metal Sealed 85°C

Reliability

The majority of failure modes on multilayer piezoelectric actuators are short-circuits due to degraded insulation. Although the cause of

degradation of insulation has not been clarified, it has been found that the failure rate varies greatly between static uses (DC voltage

application) and dynamic uses (pulse voltage application). Like other electrical components, piezoelectric actuators can be affected by

humidity as well as applied voltage and ambient temperature. KEMET has added the metal sealed piezoelectric actuators featuring high

reliability by eliminating the effects of the ambient atmosphere.

This section describes reliability guidelines for static and dynamic usage of the metal sealed type actuators. Reliability of our multilayer

piezoelectric actuators is represented by MTTF (mean time to failure) in case of static usage. The number of repetitions is considered to

represent the reliability in the case of dynamic usage.

DC Voltage Application

MTTFr of the metal sealed type under the actual operating conditions is calculated from the reference MTTFs and the acceleration

factor as it is in the case of the resin coated type. However, since the internal element is sealed from the atmosphere, it is not affected

by the atmospheric humidity. Therefore, equation (1) below is used.

(1) MTTFr = MTTFs × A

MTTFr : Estimated value

MTTFs : Reference value (= 36,000 hours)

A

2

V

A

(85 -Tr)/10

T

The following calculation is made for the case of use at 25°C, and 150 V.

= 36,000 X 0.44 X 11.3

≈ 179,000 hours (20.4 years)

Pulse Voltage Application

Similarly to the resin coated type, it is extremely difficult to estimate reliability for the metal sealed type products by using an equation.

In KEMET’s testing on the ASB170C801NP0, there was no failure confirmed up to 1,000 hours (equivalent to 100 million pulses applied)

under the conditions below:

Temperature: 85 ±2°C

Humidity: 90 to 95% RH

Load: 200 N to 500 N (20 kgf to 50 kgf)

Drive voltage waveform: rectangular wave, 30 Hz, 0 to 100 V, duty ratio at 30%