“ Improve Your Designs with Large Capacitance Value
Multi-Layer Ceramic Chip ( MLCC ) Capacitors ”
by George M. Harayda, Akira Omi, and Axel Yamamoto, Panasonic
termination of the MLCC assembly. Each of those two sets of
electrodes is terminated with a tin plated metallization.
Introduction
This paper explores how recent advances in ceramic material
and package technologies have now increased the choices for
a designer when selecting the best capacitor for by-passing,
de-coupling, filtering, and non-critical timing circuitry.
These technology improvements have made it possible to add
more capacitance ( 1 µF & greater ) into smaller case sizes
( 1210 down to 0402 ) while maintaining the largest possible
operating voltage ( 6.3 up to 50 V ), improving the electrical
performance, and lowering the cost of MLCC Capacitors.
d
A
No longer is a designer restricted to SMT - Chip Aluminum
Electrolytic ( ‘wet’ or ‘solid-polymer’ ) or Chip Tantalum
( ‘solid-polymer’ or ‘low ESR’ ). The superior equivalent
series resistance (ESR) and equivalent series inductance (ESL)
/ impedance and reliability of MLCCs can now be found in the
higher capacitance values.
The capacitance value of a basic multi-layer capacitor is
determined by the following:
C =
C = nominal capacitance value
K = dielectric constant
n = number of layers ( n + 1 electrodes )
A = area of electrode overlap
d = distance between each layer ( dielectric thickness )
Larger Capacitance values are made possible by :
Larger Dielectric Constant Values
Increased number of layers
Larger Electrode Areas
Thinner layers of dielectric *
* Note: As the dielectric layer gets thinner,
the Maximum Operating Voltage decreases.
Equivalent Circuit Model of a MLC Capacitor
‘Ideal’ Capacitors have only a capacitance property and
therefore have no power loss. ‘Real-world’ capacitors, on the
other hand, have intrinsic resistive and inductive parasitic
elements which cause power loss. These losses can be
characterized by Equivalent Series Resistance (ESR),
Equivalent Series Inductance (ESL). The nominal
capacitance value is represented by the element (C) and its
Insulation Resistance and inherent leakage current is
represented by the element (Rp). Lower intrinsic losses result
in a higher capacitor quality factor (Q), a higher SelfResonance Frequency (SRF), less self-heating, and better
performance more closely approaching an ideal capacitor.
Ceramic Material Technology Advances
The recent state-of-the-industry ceramic material technology
advances for MLCC Capacitors include;
Rp
ESR
(d)
where :
These improved MLCC mechanical and electrical attributes
will enable you to make your electronic products smaller, with
less weight, better electrical performance, and at a lower cost;
thereby making your products more competitive.
Multi-Layer Ceramic Capacitor Basics
(K) (n) (A)
finer size ceramic grains
thinner dielectric-sheets
thinner inner-electrodes
o
and faster speed stacking processes
ESL
Electrode
Dielectric
C
Electrode
The basic structure of a Multi-Layer Ceramic Chip ( MLCC )
Capacitor is comprised of two sets of inter-leaved electrodes.
Each set of inter-leaved electrodes is connected to one end
Dielectric
Page 1 of 5
( ~ 0.5 µ m )
( ~ 2.0 µ m )
( ~ 1.4 µ m )
o
o
o
making possible 800 layers, resulting in a
100 µF / 6.3 V / X5R MLCC Capacitor in 1210 Case Size !
MLCC Metallization Technology Advances
Base Metal Electrodes ( BME )
Not only are advances in ceramic material technology
important, but also is that of the choice of metal used for the
electrode metallization. To cope with escalating costs, many
suppliers have converted from palladium-based precious metal
electrodes ( PME ), such as Palladium ( Pd ) or Silver
Palladium ( Ag-Pd ) to that of nickel base metal electrodes
(BME ). This conversion is primarily applied to MLCCs with
Class II dielectrics such as X5R, X7R, and Y5V and some
Class I C0G ( a.k.a. NP0 ) dielectrics which are not intended
for high reliability applications.
Lead-free Terminations & Solder Assembly to PCBs
Board-Area & Volumetric Efficiency
MLLCs have a physical volumetric advantage over some other
capacitor technology candidates. For example, refer to the
following table :
Ratio
Please note that Class II type dielectric Ceramic Capacitors
have a normal 'aging' behavior characteristic. That is, the
capacitance value of the capacitor decreases with time from its
value when the capacitor was first manufactured.
From that date, the capacitance value begins to decrease at a
logarithmic rate defined by:
Ct = C48 ( 1 - k log10 t )
where :
Ct = Capacitance Value, t hours after the start of 'aging'
C48 = Capacitance Value, 48 hours after its manufacture
k = aging constant ( capacitance decrease per decade-hour )
t = time, in hours, from the start of 'aging'
Ceramic’s Capacitance Change ( % ) versus Time ( hours )
In accordance to the world-wide trend to reduce the quantity
of lead within electronic products, these Large Capacitance
Value MLCCs have lead-free end-terminations of plated Tin.
Higher temperatures are usually needed for assembling /
attaching components onto Printed Circuit Boards ( PCBs )
with lead-free solders. Compared with the Tin / Lead eutectic
( 63% Sn / 37% Pb, respectively ) which has a maximum
temperature of approximately 185 oC, a lead-free solder may
require a temperature as high as 250 oC.
There are no problems exposing MLCCs to this higher
temperature as is the possible case with other technologies.
Chip Tantalum
Low ESR ( A-size )
10 µF, 10 V
3.2 x 1.6 x 1.6 mm
~ 2.6 to 1
‘Aging’ / ‘De-aging’ Behavior of Class II dielectric MLCCs
The capacitance value is typically guaranteed by suppliers for
up to t = 1000 hours after being manufactured.
Ceramic Package Technology Advances
MLCC
( 0805 )
10 µF, 6.3 V, X5R
2.0 x 1.25 x 1.25 mm
( Reference Volume)
MLCC Capacitor Application Notes
Polymer Al Lytic
( ‘solid’-type )
10 µF, 6.3 V
7.3 x 4.3 x 1.8mm
~ 18 to 1
Low Height / Profile Case Sizes
While MLCCs are commonly used in the standard EIA Case
Sizes, they are also available in low-profile versions to fit your
‘tight’ clearance needs. For example, while the L x W x H of
the standard 0805 (2012 metric) is 2.0 x 1.25 x 1.25 mm; a
0805 version having a height of only 0.85 mm is also
available.
Reverse-Geometry / Low Inductance ( ESL ) Type
Reverse-geometry / wide-width packages make it possible to
reduce the equivalent series inductance by approximately a
factor of two.
The reverse-geometry construction accomplishes this by
making the capacitor’s terminations physically wider, using
what normally would be the length ( L ) dimension of a 0805
package as the terminations. ( see below )
Reverse Geometry
0508 EIA Case Size ( L x W)
Page 2 of 5
C0G
X5R / X7R
Y5V
48
100
1,000
10,000
100,000 Hours
The capacitance value can be restored ( a.k.a. ‘de-aged’ ) by
exposing the component to elevated temperatures approaching
its Curie Temperature ( approximately 120 oC ). This ‘deaging’ can occur during the component’s solder-assembly onto
the PCB, during life or temperature cycle testing, or by
'
baking ' at 150 oC for about 1 hour.
Piezo-electric Effect Considerations
The base structure of the ceramic dielectrics are crystalline in
nature. Mechanical shock or vibration through the PCB can
induce noise into the electronic circuitry via the MLCC.
Mechanical displacement can also be triggered by sharply
rising voltages which can create a ‘ringing’ or ‘oscillatory
noise’ signals onto the line. Therefore, due to these potential
piezoelectric effects, take note when using MLCCs in higher
voltage audio or lower frequency applications.
Assembly Considerations
Try to eliminate board flex as much as possible since it can
cause mechanical strain on the MLCCs potentially causing a
crack, and with the incursion of moisture, could result in a
‘short’ as its subsequent failure mode. A prudent design
practice is to place MLCCs as close to the edge of the PCB as
possible to minimize the stress being applied to them.
Handling Considerations
The non-polarized electrodes of MLCCs make for worry-free
handling and for easier assembly onto Printed Circuit Boards.
Electrolytic capacitor technologies, on the other hand, have a
polarity. Therefore, reverse-attachment, even temporarily, can
result in instant failure of the capacitor, degradation of its lifetime, or worst yet, a latent failure in the field.
MLCC Capacitor Application Notes ( continued )
Operating Voltage - De-rating
Comparison of ESL versus Case Size
Ceramic Capacitors do not have to be de-rated as do Chip
Tantalum Capacitors, either the low ESR or polymer types.
The suggested de-rating of the polymer type is 80% while the
de-rating of the low-ESR type can require between 30 – 70%.
3.5
3.0
0402
Inductance (nH)
2.5
Comparison of Capacitance Value vs. Applied DC Voltage
The capacitance change versus applied bias voltage is another
consideration when choosing the capacitor technology.
0603
0805
2.0
1206
1210
1.5
1812
0508
1.0
0612
The following graph shows the relative capacitance change as
a function of the representative dielectric material types, Class
I type ( C0G ) and Class II types ( X5R / X7R & Y5V ).
0.5
0.0
0
10000
20000
30000
40000
50000
Frequency (kHz)
C0G
0%
-20 %
X5R / X7R
-40 %
-60 %
-80 %
Y5V
0 5 10 15 20 25 30 35 40 45 50 V DC Bias
From the Class II types X5R / X7R , 1 µF, 6.3, 10, 16, 25, &
50 V shown below, it can be noted that the larger case sizes
have less capacitance change versus the applied DC voltage.
This is due to thinner layers and higher dielectric materials.
Please note that while choosing smaller case sizes to help
reduce PCB size, it may be at the expense of a performance
trade-off. Generally speaking regarding large capacitance
value MLCCs, the ESR gets worst as the case size gets smaller
while the ESL gets better. You should consider this trade-off
when making your case size decision. One option is the use of
a reverse-geometry package as a way of getting a compromise
between ESR & ESL performance out of a smaller package.
Please also take into account the effect Case Size and
Capacitance Values have on the ripple current capability of
MLCCs and the temperature rise due to its self-heating.
Comparison of Temperature Rise due to Ripple Current
Capacitance Value Change versus DC Bias Voltage
1 µ F in various Case Sizes / Voltage Ratings
versus MLCC Case Size
1.0
Ripple current - Temperature rise
1206 / 50 V
at 100kHz
70
0.8
0805 / 10 V 1206 / 16 V
60
Temperature rise (degC)
0603 / 6.3 V
1206 / 25 V
0.6
0805 / 16 V
0603 / 10 V
0805 / 16 V
Low Profile
0.4
0402 / 6.3 V
0.2
0603 / 16 V
0805 / 25 V
50
40
30
20
0805/10uF
1206/10uF
10
1210/10uF
0
0
5
10
15
20
0.0
25 V ( Bias Voltage )
2.0
4.0
6.0
8.0
10.0
Ripple current (Arms)
Comparison of ESR versus Case Size
Comparison of Temperature Rise due to Ripple Current
As seen below with this example of a 1 µF capacitance value,
larger case sizes also have the advantage having less ESR
versus MLCC Capacitance Value
Ripple current - Temperature rise
at 100kHz
70
ESR - Frequency
1000
60
Temperature rise (degC)
0402/1uF
0603
100
0805
1206
ESR (ohm)
10
1210
1
50
40
30
1206/4.7uF
1206/10uF
20
1206/22uF
0.1
10
0.01
0
0.0
2.0
4.0
6.0
Ripple current (Arms)
0.001
0.1
1
10
100
1000
10000
100000
Frequency (kHz)
Page 3 of 5
8.0
10.0
12.0
MLCC Performance Characteristics versus
Chip Tantalum and other Capacitor Technologies
The table below is a guide of the main considerations when
determining the most appropriate capacitor for your
application.
MLCC
Tantalum Tantalum Aluminum
( X5R, X7R ) ( Low ESR ) Polymer
Polymer
4 - 35 V
2 - 25 V
2 - 16 V
Operating Voltage
6.3 - 50 V
30 - 70 %
80%
100%
Voltage De-Rating
100%
330
F
1,000
F
470 µF
Capacitance Value ( max )
220 µF
µ
µ
Fair
Good
Very Good
ESR / Impedance ( Z )
Excellent
Good
Good
Good
ESL ( Equivalent Series Inductance )
Excellent
Fair
Good
Very Good
Capacitance vs Frequency
Excellent
Excellent
Excellent
Excellent
Capacitance vs Temperature
Good
Excellent
Excellent
Excellent
Capacitance vs DC Bias
Fair
Fair
Good
Very Good
Ripple Current / Self-Heating
Excellent
Has Polarity Has Polarity Has Polarity
Special Handling due to Polarity
None
Fair
Good
Excellent
Safety Performance
Excellent
Good
Good
Good
Volumetric Efficiency
Excellent
Excellent
Fair
Good
Cost
Excellent
The lower Equivalent Series Resistance ( ESR ) and
Impedance ( Z ) of MLCC capacitors versus other candidates - especially at the higher frequencies in the 100 KHz to 1
MHz range -- provides a performance advantage for your bypassing and de-coupling needs.
MLCCs have less temperature rise due to Ripple Current
When used in ‘smoothing’ circuit applications, MLCCs offer
significant advantages over Tantalum Capacitors. Reduced
ESR results in lower component operating temperature than
other capacitor solutions making it and your product more
reliable.
As you may note from above, MLCCs offer many advantages
over that of capacitors of other technologies.
Of those many advantages, MLCCs have a distinct electrical
performance advantages when it comes to lower ESR, ESL,
and Impedance ( Z ), especially at the higher frequencies.
MLCC capacitors are one of the main alternatives to that of
chip tantalum capacitor technology. The following graphs
illustrate the performance advantage of MLCC capacitors.
MLCCs have lower Equivalent Series Resistance ( ESR )
MLCCs have lower Equivalent Series Inductance ( ESL )
Improved ESL, especially at higher frequencies, reduces the
harmonic content of ripple current and high frequency noise.
MLCCs have lower Impedance ( Z )
It is suggested to carefully review the above parameters when
evaluating the candidates for your power supply design.
The following information focuses upon how these electrical
performance characteristics relate to relate to the applications.
Page 4 of 5
Applications of MLCCs
Of the various capacitor technologies, ceramic capacitors have
the dominant usage, approximately 80%. Of the single-layer
( primarily for the higher voltages ) and multi-layer ceramic
capacitors, the majority usage is of multi-layer construction.
A candidate for the input capacitor of a typical DC to DC
Converter might be 50 V / 1 µF in 1210 Case Size while the
output capacitors might be 6.3 V 22 / 47 / or 100 µF in either
a 1210 or 1206 Case Size.
The ubiquitous MLCCs are found in all types of electronic
products Those products include Communications ( Telecom
& Datacom ), Computers & Peripherals, and Industrial types.
Regarding ESR, it is prudent to account that the impedance at
100 Hz may be from 10 to 1,000 times higher than that at 100
KHz. The ESR also changes from component to component,
as well as increases with temperature.
Computer & Peripheral Products
The ESL of a MLCC capacitor does not effect its impedance
until over its Self Resonant Frequency ( SRF ), usually beyond
1 MHz and higher. Please take into account that the ESL
parasitic increases with temperature.
The need for lower ESR & ESL continues to increase in highfrequency, lower working-voltage, and higher current
applications. This is occurring in the computer market
segment, especially with its higher clock speeds of 3 GHz and
higher. They are also for Laptop & Tablet Personal
Computers, PC Cards, PDAs, Hard Disk Drives, Electronic
Games, and MP3 Audio Players.
Examples of applicable MLCCs are: 25 V / 4.7 µF or 2.2 µF
in 0805 Case Sizes. Others include; 6.3 V / 22 µF in a 1206
Case Size or 6.3 V / 47 or 100 µF in a 1210 Case Size.
The Future of Multi-Layer Ceramic Capacitors
As you have seen, advances in ceramic material and package
technology has allowed the development of more and more
capacitance within a given package size.
As a result, the chart below lists the presently available and
planned Values, Case Sizes, Rated Voltages from one of the
major suppliers of MLCC Capacitors.( X5R unless otherwise noted )
Communication Products
The small / low profile parts are especially suited for handheld / mobile communication ( voice & data ) products such as
Wireless Accessories ( WLAN / Bluetooth ).
Case Size
Rated
( EIA )
Voltage
0402
0603
Examples of applicable MLCCs are: 6.3 V / 1 µF in 0402
Case Size. Others include; 6.3 V / 4.7 µF in a 0603 Case Size
or 6.3 V / 10 µF in a 0805 Case Size having height of 0.95
mm max or an array comprised of two 1 µF capacitors in a
0405 Case Size package.
0805
1206
MLCCs offer lower Impedance and ESR needed for the 100 –
500 KHz frequencies of today’s Switch Mode Power Supplies
such as DC – DC Converters. The performance advantage is
so great that lower capacitance values provide better
decoupling than higher values in other dielectrics.
Ideal Application for Large Capacitance Value MLCCs
Input Capacitor
Output Capacitors
VDC Outputs
VDC Input
Switched-Mode
Power Supply
12 V
5V
DC to DC
Converter
3.3, 2.5 V
In power supply design, the parasitic elements of the
capacitors used can have a significant effect upon the
operation of the electronic circuitry. The most important are
the capacitor’s ESR and ESL. Important to note is that these
parasitic elements are not constant with time, temperature, or
frequency and should be accounted for in your design.
6.3 V
0.5
V
V
V
V
V
V
V
V
V
V
V
0.8
0.8
0.8
0.8
1.25
1.25
1.25
1.25
1.25
1.6
1.15
1.6
1.6
1.6
16
10
6.3
4
25
16
10
6.3
4
25
16
V
10
6.3 V
Industrial Products: DC to DC Converter Example
1210
Height
(mm)
50
25
V
V
16
V
10
V
6.3 V
1 µF
2.2 µF
4.7 µF
10 µF
22 µF
47 µF
100 µF
Available in 2003
Available in 2003
Available in 2003
X7R
X7R
X7R
Available in 2003
Available in 2003
Available in 2003
2.0
2
2.5
2.0
2.5
2.0
2.5
2.5
Look for larger capacitance values becoming available as
ceramic technology improves.
Two major application trends effecting electronic circuitry are
continuing. One of the trends is a reduction of Operating
Voltages ( down from 15, 12, 5, 3.3, 2.5, 1.0, 0.8, and lower )
with accompanying higher currents. Another trend is a
reduction in product size.
The component size reduction with regard to MLCC
components is happening in two major ways. As seen, one
way is that individual larger capacitance values are being put
into a given package size. Another way is the development of
a higher degree of integration by putting two or four large
capacitance values ( array ) into a single package to increase
its placement density and efficiency.
Ceramic technology is ideally poised to take advantage of
these trends as well as that of Integrated Passives, MLCC +
other components within a package, and Integral Passives,
MLCCs + embedded components within a ceramic substrate.
Panasonic Industrial Company / Product Management Division, Two Panasonic Way, M/S: 7H-2, Secaucus, NJ 07094 USA
Page 5 of 5
Publication # PG33.07/03/03