Datasheet

6
TANCAPTECHNOLOGYCO.,LTD.
ApplicationNotesforMultilayerCapacitors
1. EffectofTemperature
Both capacitance and dissipation are affected by variations in temperature. The maximum
capacitance change with temperature is defined by the temperature characteristic. However, this
onlydefinesa“box”boundedbythe upperandloweroperatingtemperaturesandtheminimumand
maximumcapacitancevalues.Withinthis“box”,thevariationwithtemperaturedependeduponthe
specificdielectricformulation.
Insulationresistancedecreaseswithtemperature.Typicaltheinsulationresistanceatmaximumrated
temperatureis10%ofthe25℃value.
2. EffectofVoltage
ClassⅠceramic capacitors are not affected by variations in applied AC or DC voltages. For Class Ⅱ
and Ⅲ ceramic capacitors, variations in voltage affect only the capacitance and dissipation factor.
TheapplicationofDCvoltagehigherthan5DCreducesboththecapacitanceanddissipationfactor.
The application of AC voltage up to 10‐20 Vac tend to increase both capacitance and dissipation
factor.AthigherACvoltage,bothcapacitanceanddissipationfactorbegintodecrease.
3. EffectofFrequency
Frequencyaff ectsbothcapacitanceanddissipationfactor.
The variation of impedance with frequency is an important consideration in the application of
multilayer ceramic capacitors. Tota l impedance of the capacitor is the vector of the capacitive
reactance, the inductive reactance, and the ESR. As frequency increases, the capacitive reactance
decreases. However, the series inductance (L) produces inductive reactance, which increases with
frequency. At some frequency, the impedance ceasesto be capacitive and becomes inductive. This
point is the self‐resonant frequency. At the self‐resonant frequency, the reactance is zero, and the
impedanceconsistsoftheESRonly.
Lead configuration and lead length have a significant impact on the series inductance. The lead
inductanceisapproximately10nH/inch,whichislargecomparedtotheinductanceofchip.Theeffect
of this additional inductance is a decrease in the self‐resonant frequency, and an increase in
impedanceintheinductiveregionabovetheself‐resonantfrequency.
4. EffectofTime
ThecapacitanceofClassⅡandⅢdielectricschangewithtimeaswellaswithtemperature,voltage
andfrequency.Thischangewithtime isknownas“aging”.Itiscausedbygradualrealignmentofthe
crystalline structure of the ceramic dielectric material as it is cooled below its Curie temperature,
which
 produces a loss of capacitance with time. The aging process is predictable and follows a
logarithmicdecay.TypicalagingratesforC0G,X7R,andZ5Udielectricsareasfollows:
C0G:None
X7R:1.0%perdecadeoftime
Z5U:5.0%perdecadeoftime
Y5V:6.0%perdecadeoftime
Theagingprocessisreversible.Ifthecapacitor is heatedtoatemperatureaboveitsCuriepoint for
someperiodoftime,de‐agingwilloccurandthecapacitorwillregainthecapacitancelostduringthe
agingprocess.Theamountofde‐agingdependsonboththeelevatedtemperatureandthe
lengthof
time at that temperature. Exposure to 150℃ for one‐half hour or 125℃ for two hour is usually
sufficienttoreturnthecapacitortoitsinitialvalue.