MULTILAYER CERAMIC CAPACITORS/AXIAL & RADIAL LEADED
Multilayer ceramic capacitors are available in a
variety of physical sizes and configurations, including
leaded devices and surface mounted chips. Leaded
styles include molded and conformally coated parts
with axial and radial leads. However, the basic
capacitor element is similar for all styles. It is called a
chip and consists of formulated dielectric materials
which have been cast into thin layers, interspersed
with metal electrodes alternately exposed on opposite
edges of the laminated structure. The entire structure is
fired at high temperature to produce a monolithic
block which provides high capacitance values in a
small physical volume. After firing, conductive
terminations are applied to opposite ends of the chip to
make contact with the exposed electrodes.
Termination materials and methods vary depending on
the intended use.
TEMPERATURE CHARACTERISTICS
Ceramic dielectric materials can be formulated with
a wide range of characteristics. The EIA standard for
ceramic dielectric capacitors (RS-198) divides ceramic
dielectrics into the following classes:
Class III: General purpose capacitors, suitable
for by-pass coupling or other applications in which
dielectric losses, high insulation resistance and
stability of capacitance characteristics are of little or
no importance. Class III capacitors are similar to Class
II capacitors except for temperature characteristics,
Class I: Temperature compensating capacitors,
suitable for resonant circuit application or other appli-
cations where high Q and stability of capacitance char-
acteristics are required. Class I capacitors have
predictable temperature coefficients and are not
effected by voltage, frequency or time. They are made
from materials which are not ferro-electric, yielding
superior stability but low volumetric efficiency. Class I
capacitors are the most stable type available, but have
the lowest volumetric efficiency.
which are greater than
15%. Class III capacitors
have the highest volumetric efficiency and poorest
stability of any type.
KEMET leaded ceramic capacitors are offered in
the three most popular temperature characteristics:
C0G: Class I, with a temperature coefficient of 0
30 ppm per degree C over an operating
temperature range of - 55°C to + 125°C (Also
known as “NP0”).
X7R: Class II, with a maximum capacitance
change of 15% over an operating temperature
range of - 55°C to + 125°C.
Z5U: Class III, with a maximum capacitance
change of + 22% - 56% over an operating tem-
perature range of + 10°C to + 85°C.
Class II: Stable capacitors, suitable for bypass
or coupling applications or frequency discriminating
circuits where Q and stability of capacitance char-
acteristics are not of major importance. Class II
capacitors have temperature characteristics of 15%
or less. They are made from materials which are
ferro-electric, yielding higher volumetric efficiency but
less stability. Class II capacitors are affected by
temperature, voltage, frequency and time.
Specified electrical limits for these three temperature
characteristics are shown in Table 1.
SPECIFIED ELECTRICAL LIMITS
TEMPERATURE CHARACTERISTICS
PARAMETER
C0G
X7R
Z5U
Dissipation Factor: Measured at following conditions:
C0G — 1 kHz and 1 vrms if capacitance > 1000 pF
1 MHz and 1 vrms if capacitance ≤ 1000 pF
X7R — 1 kHz and 1 vrms* or if extended cap range 0.5 vrms
Z5U — 1 kHz and 0.5 vrms
0.15%
2.5%
4.0%
Dielectric Strength: 2.5 times rated DC voltage.
Pass Subsequent IR Test
Insulation Resistance (IR): At rated DC voltage,
whichever of the two is smaller
1,000 MΩ-µF
or 100 GΩ
1,000 MΩ-µF
or 100 GΩ
1,000 MΩ-µF
or 10 GΩ
Temperature Characteristics: Range, °C
Capacitance Change without
DC voltage
-55 to +125
30 ppm/°C
-55 to +125
15%
+10 to +85
+22%, -56%
0
* 1 MHz and 1 vrms if capacitance ≤ 100 pF on military product.
Table I
© KEMET Electronics Corporation, P.O. Box 5928, Greenville, S.C. 29606, (864) 963-6300
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