Capacitance Measurement

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Capacitance Measurement

Apr. 2012

All Rights Reserved, Copyright Samsung Electro-Mechanics Co., Ltd.


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CONTENTS Confidential

1. Introduction

2. LCR meters and Measurement Principle

2-1. LCR meters

2-2. Measurement Theory

- .

3. Characteristics of MLCC

- . empera ure arac er s cs

3-2. DC Bias Characteristics3-3. AC Voltage Characteristics

3-4. Aging Characteristics


3-5. DC Bias Aging Characteristics


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1. Introduction Confidential

A capacitor is an electrical device that can store energy in the electric field between a pair of closely spaced

conducting plates. Capacitance value means the measure of how much charge a capacitor can store at a certain

vo age. apac ance o s ou e measure un er appropr a e measur ng con ons suc as empera ure,

voltage (AC/DC), and frequency. Especially, when you measure a high dielectric MLCC (Class II: X7R, X6S, X5R,

Y5V) by LCR meter, you may be careful to obtain a reasonable capacitance using specified measurement conditions.

Before measurement, the equipment should be used with correct meter setting and have the capability required for

accura e capac ance measuremen . e ac ua measuremen con ons o capac ance o ass an s are

shown in tables below. The temperature used for these conditions is 25 degree.

Nominal Capacitance Frequency Voltage(AC) Voltage(DC)

1,000pF 1MHz 10% 0.5~5Vrms No Bias

,> 1,000pF 1KHz 10%

CLASS II

Nominal Capacitance Frequency Voltage(AC) Voltage(DC)

10uF 1KHz 10% 1.0 0.2Vrms No Bias

* 10uF 1KHz 10% 0.5 0.1Vrms


> 10uF 120Hz 20% 0.5 0.1Vrms

* Exceptions: Please check the specification on the web site


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2-1. LCR meters Confidential

LCR meters are used for measurement of the capacitance and dissipation factor of MLCCs.

Typical LCR meters are shown in Table including 4288A, 4268A, 4284A, and E4980A by Agilent Technologies Corp.

LCR Meter Overview Application

4288A

1kHz/1MHz

High-speed sorting tests of ceramic

capacitors.

Class I

Class II

Meteru

4268A

120Hz/1kHz

Constant test level for high value ceramic

capacitor tests.

Class II

Capacitance

Meter*Auto level control (ALC)

4284A Wide frequency Range Class I

LCR Meter4284A : 20Hz to 1 MHz

E4980A : 20Hz to 2 MHz

Auto level control (ALC)

Class II

Option 001.

power and DC bias enhancement (+/- 40V)

E4980A

Precision

LCR Meter


ALC: The automatic level control (ALC) feature adjusts the voltage across the DUT to the same level as the signal voltage level

setting. By this feature, you can maintain a constant level of voltage of measurement signals applied to the DUT. Technical overview is available at www.agilent.com


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2-2. Measurement Theory Confidential

When the AC voltage (V) is applied to the DUT and the AC current (I) is flowing through the DUT, the impedance

(|Z|) can be calculated according to the Ohms raw (|Z|=V/I). The measurement circuit depends on the frequency.

So, there are two methods (Auto Balance Bridge and RF I-V). It also depends on the type of fixture.

DUT

I

V

R: ResistanceAV

Source Voltage Current

X: Reactance

IZI: Absolute value of impedance

: Phase of impedance

o age

I

V

Z

Fig. Circuit model



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2-2. Measurement Theory Confidential

Energy loss is zero in the ideal capacitor. But, real capacitor has dielectric loss and electrode loss by the parasitic

resistance. Loss of ca acitor is shown b the dela in of hase an le between AC volta e and current.

DF (Dissipation Factor) is described as tan. Here, means delayed phase angle.

XESRZ

j

Inductive

(High freq.)

CLXc

cc

1

X

Z

ESR

ZXZESR

1

sin,cos

Capacitive

XQESR

-

Real (R).


Fig . Impedance characteristics of general Capacitor


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2-3. ALC (Automatic Level Control) Function Confidential

The automatic level control (ALC) feature adjusts the voltage across the DUT to the same level as the signal

voltage level setting. By this feature, you can maintain a constant level of voltage of measurement signals applied

to the DUT. The ALC feature uses a monitorable feedback circuit to iterate a feedback loop as shown in figure.

The feedback loop consists of level measurement and level change. The time is required for level adjustment.

Feedback loo

DUT

V

Source

RHIGH LOW

o age


Fig. Circuit model from Users Guide provided by Agilent Technologies


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2-3. ALC Function Confidential

The automatic level control (ALC) feature adjusts the voltage across the DUT to the same level as the signal

voltage level setting. When ALC function is off, the capacitance was measured as ~43F and when ALC function

~, . .

and off was ~6 F. However, we cant see the difference at AC voltage of 0.5V when looking at the figure of

capacitance change. Therefore, the correct capacitance value can be obtained by using ALC function.

40

ALC (on)

ALC (off)50.0

55.0

0

20

(%)

35.0

40.0

45.0

ap(uF)

-40

-20

20.0

25.0

30.0C

ALC (on)

ALC (off)

Fig. Capacitance of 0603 X5R 47F with AC voltage Fig. Capacitance change of 0603 X5R 47F with AC voltage

. . .

AC voltage(V)

. . .

AC voltage(V)


for ALC on and off (Agilent 4284A, 120Hz) for ALC on and off (Agilent 4284A, 120Hz)


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3-1. Temperature Characteristics Temp vs.CConfidential

Temperature coefficient of capacitance (TCC) can be described as the change of capacitance dependent on

temperature in MLCCs. There are several TCC categories found in Class I and II. TCC of Class I and II MLCCs are

shown in figure. Class I MLCCs are composed of paraelectric material and show simple TCC behaviors. It has a

near var a on n capac ance w empera ure. e c ange n capac ance w empera ure s expresse near y

as parts per million per degree centigrade (PPM/).

Class II MLCCs such as X5R and X7R show irregular and high change in capacitance with temperature. This is due

to the ferroelectric nature of the dielectric material of barium titanate (BaTiO3). The change in capacitance with

empera ure s expresse as a percen c ange over a spec e empera ure range. or examp e, means a

the capacitance can change by +/-15% across a temperature range of -55 to 125.

40% C

Table. Temperature characteristics of Class I and II MLCCs

Class

Temperature

Coefficient

Dielectric

Constant

Operating

Tem erature

Capacitance

Chan e20

+85 oC

+125oC

+22%+105oC

Class I C0G 6 ~ 400 -55 ~ +125 0 30ppm/

X5R -55 ~ +85 15%

--- C0G

Class II1,000 ~

20,000

X6S -55 ~ +105 22%

X7R -55 ~ +125 15%

Y5V -30 ~ +85 -82 ~ +22%-20

X7RX5R-15%

-22%

All Rights Reserved, Copyright Samsung Electro-Mechanics Co., Ltd.-40

Fig. Capacitance change of X5R, X7R, Y5V, C0G with temperature


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3-2. DC Bias characteristics DC bias vs. CConfidential

DC bias is an important electrical parameter affecting the capacitance of MLCCs. DC bias characteristics can be

described as the phenomena of capacitance loss in Class II with increasing DC voltage. This behavior is dependent

on the dielectric formulation, microstructure, and internal construction of MLCC as well as DC voltage load.

ass s are ase on a 3 w erroe ec r c po es an as m s e po e movemen s resu ng n

reduction of the dielectric constant and capacitance.

The DC bias characteristics of C0G, X5R, X7R, and Y5V MLCCs are shown in figure. Class I MLCC, C0G shows the

stable capacitance value because of its paraelectric structure without dipoles although its relative dielectric constant

.]

s or ers o magn u e ower an ass suc as , , an . n case o , s ows e mos severe

degradation despite of the highest dielectric constant. X5R/X7R have high dielectric constants which are preferred

for high capacitance applications.

X5R / X7R

C0G

ange[a

rb

citancec

10 20 30 40 50

DC voltage [V]

Cap


Fig. Capacitance change of X5R, X7R, Y5V, C0G with DC voltage

(HP 4284A, 25oC, 1.0Vrms, 1kHz (X7R, Y5V) / 1MHz (C0G))


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AC voltage vs. C3-3. AC voltage characteristics Confidential

AC voltage characteristics can be described as the phenomena of capacitance change in Class II with increasing

AC voltage. Class I MLCCs composed of paraelectric material do not show this phenomenon. The AC voltage

c arac er s cs o ass s are s own n gure. n ass s, s ows e more severe c ange w

AC voltage than X5R/X7R. This is due to the non-linear characteristics in voltage-polarization curve of ferroelectric

materials. Thus, the slope in the curve increases and the capacitance increases as AC voltage increases.

40 40

0

(%) 0

(%)

-

-20

-

-20

0.0 0.5 1.0

AC voltage(V)

0.0 0.5 1.0

AC voltage(V)


. , .

with AC voltage (Agilent 4284A, 1kHz)

. , .

with AC voltage (Agilent 4284A, 120Hz)


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3-4. Aging Characteristics Time vs. CConfidential

Aging is a time dependent phenomenon encountered in Class II MLCCs. Class I MLCCs do not show agingdue to the paraelectric nature of the composed material. However, Class II MLCCs such as X5R, X7R, and

Y5V have ferroelectric dielectrics based on BaTiO3 and the capacitance is decreased logarithmically over time.

Figure shows the aging behavior of Class I and II MLCCs with different temperature characteristics. Aging rate

increases with dielectric constant of the material. C0G shows a constant capacitance value independent of

time due to its paraelectric characteristics while Y5V the highest capacitance value and X5R/X7R have an

intermediate aging rate. Aging is intrinsically reversible. The capacitance can be recovered after heattreatment. MLCCs can be returned to ferroelectric structure by heating above the Curie point (at least 1 hr at

Ct = C0 (1 - k log10 t)Ct = Capacitance value, t hours after the start of aging

C0= Initial capacitance value, k = Aging constant, t = Aging time

150) and cooling to room temperature.

C0G

X7R/X5Rgrate[%

]

C0G

X7R/X5R-10 Slope (k) 2~5%

Y5V

picalagin

Y5V

-20

-30

Slope (k) 5%~

1 2 3

Time [log10t hr]

4 50 1 2 3

Time [log10t hr]

T

4 5

-40


Fig. Typical aging rate of X7R/X5R, Y5V, C0G with aging timeDe-aging : Decreased capacitance is recovered after heat treatment ( above 150)


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3-5. DC Bias Aging Characteristics DC bias, Time vs. CConfidential

In order to increase the capacitance density of MLCCs, the dielectric layer thickness should be reduced and thismeans the increase in the electric field applied to dielectric layers. The aging characteristics under DC biasbecomes more important in the high-end products with ultra thin dielectric layers. DC bias aging characteristics

observed in the working condition. The effective capacitance can be described as the capacitance observed inworking condition. The effective capacitance is more important than the nominal capacitance because thenominal capacitance is dependent on DC-bias, temperature and time. Better effective capacitance can be

obtained by the improvement of DC-bias and aging characteristics.

34

34

30

32

ce(uF)

ce(F)

32

30

24

26

Capacita

Capacitan

26

24

1 10 100 1000 1000020

Time (hr)

20

1 10 100 1000 10000

Time (hr)


Fig. Capacitance of 0805 X5R47uF, 6.3V with time in the measurement condition of85, 1.2V(DC) (E4980A, 1kHz)


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Capacitance Measurement

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