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Ceramic Capacitors(MLCCs)
Design and Characteristics
© 2017 KEMET Corporation
Ceramic Chip Capacitors
© 2017 KEMET Corporation
Design
© 2017 KEMET Corporation
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
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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)
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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
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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
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• 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
© 2017 KEMET Corporation
Characteristics
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Relative Capacitance vs. Temperature
C0G (NP0)
Temperature
‘K’
Mag
nit
ude
X7R
X5R
Z5U
Y5V
‘Room’ Ambient
U2J
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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
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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)
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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
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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
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Voltage Coefficient (Class II and III)
0V DC+V
-VDomains
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Voltage Coefficient (Class II and III)Piezoelectricity and Electrostriction
- -
- - - -
+ + + +
+ +
Mechanical Distortion
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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.
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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
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Aging of Class 2 and
Class 3 Capacitors
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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
© 2017 KEMET Corporation
Common Failure Modes
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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!
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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
© 2017 KEMET Corporation
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
© 2017 KEMET Corporation
Capacitors for RF Applications
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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.
© 2017 KEMET Corporation
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.
© 2017 KEMET Corporation
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
© 2017 KEMET Corporation
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
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KEMET CBR RF CapacitorsConstruction
Base Metal, Copper Electrodes
Plated Tin Finish
Ceramic Dielectric
Plated Nickel Barrier Layer
Copper External ElectrodeCopper Internal Electrode
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