General Description
Basic Construction –
A multilayer ceramic (MLC) capaci-
tor is a monolithic block of ceramic containing two sets of
offset, interleaved planar electrodes that extend to two
opposite surfaces of the ceramic dielectric. This simple
structure requires a considerable amount of sophistication,
both in material and manufacture, to produce it in the quality
and quantities needed in today’s electronic equipment.
Ceramic Layer
Electrode
End Terminations
Terminated
Edge
Terminated
Edge
Margin
Electrodes
Multilayer Ceramic Capacitor
Figure 1
Formulations –
Multilayer ceramic capacitors are available
in both Class 1 and Class 2 formulations. Temperature
compensating formulation are Class 1 and temperature
stable and general application formulations are classified
as Class 2.
Class 1 –
Class 1 capacitors or temperature compensating
capacitors are usually made from mixtures of titanates
where barium titanate is normally not a major part of the
mix. They have predictable temperature coefficients and
in general, do not have an aging characteristic. Thus they
are the most stable capacitor available. The most popular
Class 1 multilayer ceramic capacitors are C0G (NP0)
temperature compensating capacitors (negative-positive
0 ppm/°C).
Class 2 –
EIA Class 2 capacitors typically are based on the
chemistry of barium titanate and provide a wide range of
capacitance values and temperature stability. The most
commonly used Class 2 dielectrics are X7R and Y5V. The
X7R provides intermediate capacitance values which vary
only ±15% over the temperature range of -55°C to 125°C. It
finds applications where stability over a wide temperature
range is required.
The Y5V provides the highest capacitance values and is
used in applications where limited temperature changes are
expected. The capacitance value for Y5V can vary from
22% to -82% over the -30°C to 85°C temperature range.
The Z5U dielectric is between X7R and Y5V in both stability
and capacitance range.
All Class 2 capacitors vary in capacitance value under the
influence of temperature, operating voltage (both AC and
DC), and frequency. For additional information on perfor-
mance changes with operating conditions, consult AVX’s
software, SpiCap.
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