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Ceramic Capacitors(MLCCs)

Design and Characteristics

© 2017 KEMET Corporation

Ceramic Chip Capacitors


Design


C = Design CapacitanceK = Dielectric ConstantA = Overlap Aread = Ceramic Thicknessn = Number of Electrodes

Electrodes

Ceramic

Termination

Ceramic Capacitor Structure

+-

Capacitances in parallel are additive

CT=C1+C2+C3+….Cn

C = e0KA(n-1)d


Multilayer Ceramic Capacitor (MLCC)Typical Construction

Ceramic Dielectric

Internal Electrode (Ni for BME, Ag/Pd for PME)

Termination (External Electrode, Cu for BME, Ag for PME)

Plated Sn finish for Solderability

Barrier Layer (Plated Ni)


Dielectric Technology

C0GPME & BME

200oC

U2J

BME

X8R

BME

X8L

BME

X7RPME & BME

175oC

X5R

BME

Y5V

BME

Z5U

BME

BP

PME

C0G @ Rated V

BX

PME

X7R +15/25% @

Rated V

BR

PME

X7R & +15/-40% @ Rated V

Commercial & Automotive Grade Dielectric Materials

Military & Hi-Rel Dielectric Materials


Trend in BME MLCC Technology: Dielectric Thickness and Layers Count Progression

0.1 µF/50V (PME)(12 µm layers, n= 30 )

1.0 µF/25V (PME)(8 µm layers, n=100 )

2000- 4.7 µF/16V(225 4 µm layers)

10 µF/6V(300 3 µm layers)

22 µF/6V(500 1.8 µm layers)

47 µF/4V(600 1 µm layers)Class 2 1206 (EIA)

1988 Today


• RoHS and Non-RoHS• Extensive Dielectric Portfolio• Bulk Capacitance• High Voltage • High Temperature • SMD & Through-Hole• Non Standard Sizes and Configurations• A full range of termination materials

and finishes

• Arc Prevention • Flex Mitigation• ESD • Noise Reduction• Pulse Capable• High Shock & Vibration• Integrated Technology• Specialized Testing/ Screening• Encapsulation

Ceramic Engineered Solutions


Characteristics


Relative Capacitance vs. Temperature

C0G (NP0)

Temperature

‘K’

Mag

nit

ude

X7R

X5R

Z5U

Y5V

‘Room’ Ambient

U2J


Alpha Symbol

Significant Figure of

Temp Coefficient

ppm/ºC

Numerical Symbol

Multiplier to significant

figure

Alpha Symbol

Tolerance of Temp

Coefficient± ppm/ºC

C 0 0 -1 G 30

B 0.3 1 -10 H 60

L 0.8 2 -100 J 120

A 0.9 3 -1000 K 250

M 1.0 4 -10000 L 500

P 1.5 5 +1 M 1000

R 2.2 6 +10 N 2500

S 3.3 7 +100

T 4.7 8 +1000

U 7.5 9 +10000

Dielectric ClassificationClass I (Per EIA – 198)

Class I Dielectrics: (Example: C0G)

Temperature Range: -55ºC to +125ºCC0G provides highest temperature stability


Alpha Symbol

Low Temperature

(ºC)

Numerical Symbol

High Temperature

(ºC)

Alpha Symbol

Max cap change over temp. range

(%)

Z +10 2 +45 A ±1.0

Y -30 4 +65 B ±1.5

X -55 5 +85 C ±2.2

6 +105 D ±3.3

7 +125 E ±4.7

8 +150 F ±7.5

9 +200 P ±10

R ±15

S ±22

* L +15 to - 40

T +22 to - 33

U +22 to - 56

V +22 to - 82

Dielectric ClassificationClass II and III (per EIA-198)

CL

AS

S III

CL

AS

S II

* Industry Classification (Non EIA-198)


Voltage Coefficient (Class II and III)1210 vs 0805, X7R, 10uF, 6.3V

-60%

-50%

-40%

-30%

-20%

-10%

0%

10%

0 1 2 3 4 5 6

Cap

acit

an

ce

Ch

an

ge

Applied DC Bias (VDC)

Capacitance Change vs. DC Bias

Rated 6.3V

1210

0805


Voltage Coefficient (Class II and III)DC Bias

BaTiO3 above 130oC

• Cubic

• No Dipole

BaTiO3 below 130oC

• Tetragonal

• Creates Dipole

Face Centered Cubic Crystal Structure


Voltage Coefficient (Class II and III)

0V DC+V

-VDomains


Voltage Coefficient (Class II and III)Piezoelectricity and Electrostriction

- -

- - - -

+ + + +

+ +

Mechanical Distortion


Barium Titanate crystal cartridges

Piezoelectricity and ElectrostrictionClass II and III Only

Ceramic Chip

Piezoelectricity

Mechanical forces can create electrical signals. Electrostriction

Electrical forces can create mechanical distortion.


Class 2 BaTiO3

Ferroelectric

VAC

Ferroelectric dipoles in domains align with the AC Field

Domain wall heating & Signal distortion

Class 1 CaZrO3

Paraelectric

Paraelectric dipoles align with AC field

No domains, so No Domain wall heating & Reduced signal distortion

VAC

AC Coupling and Signal Distortion X7R vs. C0G


Aging of Class 2 and

Class 3 Capacitors


X7R Aging Rate1.5% per Decade Hour (Limit)

-14-12-10-8-6-4-202468

101214

1 10 100 1,000 10,000 100,000

Time Post Heat

Per

cent

age

Nom

inal

Ref

eren

ce

8,77

7 H

r=

1 Y

r

87,7

70 H

r =

10 Y

r

https://ec.kemet.com/design-tools/aging-calculator-for-ceramics


Common Failure Modes


Typical Crack SignaturesMLCC Cross-Sections

The major sources MLCC of cracks are:– Mechanical damage (impact)

• Aggressive pick and place

• Physical mishandling

– Thermal shock (parallel plate crack)• Extreme temperature cycling

• Hand soldering• Do not touch electrodes while hand soldering!

– Flex or Bend stress • Occurs after mounted to board

• Common for larger chips (>0805)

Mechanical Damage

Flex Crack

Thermal Shock Crack

Failure is not always immediate!Failure mode is not always deterministic!


Flex Cracks

https://ec.kemet.com/knowledge/flexible-termination-reliability-in-harsh-environments

https://ec.kemet.com/q-and-a/what-is-failure-mode-for-ceramic-capacitors


Flex Mitigation TechnologySelect the Right Level of Protection for Your Application

Level 0: NO Crack Protection

Standard MLCC

Target Applications: Non-Critical

Fail-Short Condition

Up to 2mm flex bend capability

Level I: Basic Level of Crack Protection

Floating Electrode or Open-Mode

Target Applications: Semi - Critical

Fail-Open Condition

Up to 2mm flex bend capability

Level III: High Level of Crack Protection

Floating Electrodeplus Flexible Termination

Target Applications: Safety Critical

Combines cascading electrode design with tear-away, termination technology. Provides for a high level of protection from thermal stress cracks, pick-and-place damage, and board flex stress

Fail-Open Condition

Up to 5mm flex bend capability.

Level II: IntermediateLevel of Crack Protection

Flexible Termination

Target Applications: Critical

Flexible termination provides for a high level of protection from thermal stress cracks, pick-and-place damage, and board flex stress

Fail-short Condition

Up to 5mm flex bend capability.

Flex Crack


Capacitors for RF Applications


RF Capacitor BasicsSome Key Parameters

C0G ppm / oC levelX7R % level

Effective Series ResistanceESR• The resistance of the capacitor which includes resistance due to the dielectric as well as electrodes.

Quality FactorQ• Quantifies the amount of energy stored versus how much is dissipated as heat. It represents the efficiency of the capacitors. Higher Q’s are

needed for RF capacitors to limit power dissipation.

Series Resonant FrequencySRF• Shows where the total impedance is no longer capacitive and begins an upward trend (becomes inductive). Higher SRF = better RF capacitor,

since some applications require the designer to stay well below the SRF.

Temperature Coefficient of CapacitanceTCC• Determines how much the capacitance values will shift at different temperatures. RF capacitors need to be very stable over a broad

temperature range.


What is an RF Capacitor?

An RF capacitor is a capacitor whose “characteristics” are favorable at RF frequencies.

Characteristic RF Capacitor Requirements

ESR (Effective Series Resistance) RF Capacitors are designed to have the lowest possible ESR. This allows for minimal power loss at RF frequencies.

Q (Quality Factor) RF Capacitors are designed to have a high Q.

SRF (Series Resonant Frequencies) RF Capacitors are designed to have high SRF allowing for a higher operating frequency range.

TCC (Temperature Coefficient of Capacitance)

The dielectric is chosen to have a minimal capacitance shift across its entire operating temperature range.

So, for RF capacitors, materials are chosen and the design is optimized so that thecapacitors’ characteristics are well suited at the higher frequencies.


RF Capacitor Construction

Design Characteristic

Dielectric Low-loss dielectrics are chosen to reduce ESR. Typically, these are C0G dielectrics which also provide temperature stability (TCC) performance.

Electrodes Electrode materials are chosen to provide the lowest ESR and ESL over a broad frequency range. This means we stay away from ferrous materials such as nickel.

Construction / Physical Geometry

Physical geometry plays an important role in resistance and inductance of the capacitor. Long and narrow capacitors will have a higher ESR and ESL than a short and wide capacitor.

Long/Narrow vs. Short/Wide


RF CapacitorsWhy Copper BME?

Ag-PME

Pd-PME

Ni-BME

Cu-BME

0

3

6

9

12

15

Ele

ctr

ica

l Re

sist

ance

Ω-c

m

Electrode Material

Electrical Resistance

05

10152025303540

150 300 600 1200

Pow

er D

issi

patio

n m

W

Frequency

Power Dissipation vs. Frequency

Ni BME Cu BME

Copper BME = Lower ESR = Better power dissipation = Ideal for High Frequency applications

Application Power and Frequency Capabilities

Base Station / Power AmpC0603-C2225<10W Power

<100MHz Frequency

CBR06, CBR08>10W Power

>100MHz Frequency

Mobile PhoneC0201, C0402

<1W Power<100MHz Frequency

CBR02, CBR04>10W Power

>100MHz Frequency

COMMERCIAL RF & MICROWAVE


KEMET CBR RF CapacitorsConstruction

Base Metal, Copper Electrodes

Plated Tin Finish

Ceramic Dielectric

Plated Nickel Barrier Layer

Copper External ElectrodeCopper Internal Electrode

31

Thank You!

wilmer companioni - kemet workshop -- ceramic ......&odvv %d7l2)huurhohfwulf 9...

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