05041A820KA79A Datasheet, PDF (4/48 Pages) AVX Corporation – Multilayer Ceramic Chip Capacitor

General Description
Effects of Voltage – Variations in voltage have little affect
on Class 1 dielectric but does effect the capacitance and
dissipation factor of Class 2 dielectrics. The application of
DC voltage reduces both the capacitance and dissipation
factor while the application of an AC voltage within a rea-
sonable range tends to increase both capacitance and dis-
sipation factor readings. If a high enough AC voltage is
applied, eventually it will reduce capacitance just as a DC
voltage will. Figure 2 shows the effects of AC voltage.
Cap. Change vs. A.C. Volts
AVX X7R T.C.
50
40
30
20
10
0
12.5
25
37.5
50
Figure 2
Volts AC at 1.0 KHz
Capacitor specifications specify the AC voltage at which to
measure (normally 0.5 or 1 VAC) and application of the
wrong voltage can cause spurious readings. Figure 3 gives
the voltage coefficient of dissipation factor for various AC
voltages at 1 kilohertz. Applications of different frequencies
will affect the percentage changes versus voltages.
D.F. vs. A.C. Measurement Volts
AVX X7R T.C.
10.0
Curve 1 - 100 VDC Rated Capacitor
8.0 Curve 2 - 50 VDC Rated Capacitor
Curve 3 - 25 VDC Rated Capacitor
6.0
Curve 3
Curve 2
4.0
2.0
Curve 1
0
.5
1.0 1.5
2.0
2.5
AC Measurement Volts at 1.0 KHz
Figure 3
The effect of the application of DC voltage is shown in
Figure 4. The voltage coefficient is more pronounced for
higher K dielectrics. These figures are shown for room tem-
perature conditions. The combination characteristic known
as voltage temperature limits which shows the effects of
rated voltage over the operating temperature range is
shown in Figure 5 for the military BX characteristic.
2.5
0
-2.5
-5
-7.5
-10
Figure 4
Cap. Change vs. D.C. Volts
AVX X7R T.C.
25%
50%
75%
Percent Rated Volts
100%
Typical Cap. Change vs. Temperature
AVX X7R T.C.
+20
+10
OVDC
0
-10
RVDC
-20
-30
-55 -35 -15 +5 +25 +45 +65 +85 +105 +125
Figure 5
Temperature Degrees Centigrade
Effects of Time – Class 2 ceramic capacitors change
capacitance and dissipation factor with time as well as tem-
perature, voltage and frequency. This change with time is
known as aging. Aging is caused by a gradual re-alignment
of the crystalline structure of the ceramic and produces an
exponential loss in capacitance and decrease in dissipation
factor versus time. A typical curve of aging rate for semi-
stable ceramics is shown in Figure 6.
If a Class 2 ceramic capacitor that has been sitting on the
shelf for a period of time, is heated above its curie point,
(125°C for 4 hours or 150°C for ¹â„2 hour will suffice) the part
will de-age and return to its initial capacitance and dissipa-
tion factor readings. Because the capacitance changes
rapidly, immediately after de-aging, the basic capacitance
measurements are normally referred to a time period some-
time after the de-aging process. Various manufacturers use
different time bases but the most popular one is one day or
twenty-four hours after “last heat.” Change in the aging
curve can be caused by the application of voltage and other
stresses. The possible changes in capacitance due to de-
aging by heating the unit explain why capacitance changes
are allowed after test, such as temperature cycling, mois-
ture resistance, etc., in MIL specs. The application of high
voltages such as dielectric withstanding voltages also tends
2