.. 4
D. CAPACITANCE ................................................................................................... 5
E. FACTORS AFFECTING CAPACITANCE ...................................................... 5
F. DIELECTRIC BEHAVIOR ................................................................................. 7
G. DIELECTRIC PROPERTIES ......................................................................... 13
H. FERROELECTRIC CERAMICS .................................................................... 20
I. LINEAR DIELECTRICS ................................................................................... 24
J. CLASSES OF DIELECTRICS ......................................................................... 25
K. TEST PARAMETERS AND ELECTRICAL PROPERTIES...................... 29
L. INDUSTRY TEST STANDARDS ..................................................................... 35
M. HIGH RELIABILITY TESTING .................................................................... 37
N. VISUAL STANDARDS FOR CHIP CAPACITORS ..................................... 40
O. CHIP USER GUIDELINES ............................................................................... 46
NOVACAP
TECHNICAL BROCHURE 2
A. INTRODUCTION
Ceramic chip capacitors are multilayer polycrystalline ceramic and metal composites, complex in
their structure, behavior and application.
The purpose of the
NOVACAP
technical brochure is to provide the user of the product with basic
information on the nature and properties of chip capacitors, their dielectric behavior, product classi-
fications, test and quality standards, and information relevant to their applications. This fourth
edition of the brochure contains new material pertaining to some of these topics, and has been
prepared to satisfy the current changes in technology affecting the industry.
A. Galliath
Andre P. Galliath, Ph.D..
President
NOVACAP
NOVACAP
TECHNICAL BROCHURE 3
B. CAPACITOR APPLICATIONS
Ceramic capacitor technology covers a wide range of product types, based on a multitude of dielec-
tric materials and physical configurations, yet all are basically storage devices for electric energy
which find use in varied applications in the electronic industry, and include the following:
Discharge of Stored Energy:
This, the most basic of applications for a capacitor, involves
the generation of a current pulse by discharge of a capacitor in the circuit.
Blockage of Direct Current:
Capacitors, once charged, act as high impedance elements and
thereby block the direct current in a specified portion of a circuit.
Coupling of Circuit Components:
In an AC circuit, a capacitor charges and discharges with
opposing polarity of the input signal, and thus allows alternating current to appear on either
side of the component, so that sections of a circuit can be coupled. The current does not
flow physically through the capacitor, as the dielectric is an insulator; continuous current
surges are the result of the change in voltage across the capacitor.
By-Passing of an AC Signal:
By virtue of the ability of a capacitor to block direct current
and yet permit the passage of alternating current, the device can be used in parallel with
another circuit element to allow AC to by-pass the element without passing the DC por-
tion of the signal.
Frequency Discrimination:
An input signal of mixed frequencies can be segregated by the use
of a capacitor which is nonresponsive (by virtue of its capacitance value) to the low fre-
quency portion of the signal. For capacitors in an AC circuit, the current flow increases
with frequency. Also, the capacitance reactance, i.e. the resistance to flow of alternating
current, is inversely proportional to the capacitance value. A device selected to display
relatively minor opposition to current flow for the high frequency portion of the signal, while
offering greater opposition to the lower frequency current, can thus be used to discriminate
and filter out the desired frequency range.
Transient Voltage and Arc Suppression:
Capacitors are utilized to stabilize circuits by re-
moval of undesired transient voltage surges, and to eliminate arcing of contact points. The
capacitor absorbs the energy generated by these voltage surges.
NOVACAP
TECHNICAL BROCHURE 4
C. THE BASIC CAPACITOR
The basic model of a capacitor is a single plate device consisting of two conductors, or electrodes,
separated by a dielectric material, as illustrated in Figure C-1. The dielectric must be an insulator
material, the properties of which largely determine the electrical behavior of the device.
The dielectrics are characterized by their ability to store electrical charge (the dielectric constant)
and their intrinsic responses to an electric field, namely capacitance change, loss characteristics,
insulation resistance, dielectric strength, as well as the aging rate and the temperature dependence of
these properties.
In general, capacitors utilize such dielectrics as air, (with a dielectric constant almost identical to a
vacuum, and defined as 1) or naturally occurring dielectrics, such as mica, with a dielectric constant
(K) of 4-8, or prepared materials, such as the ceramic groups, with K values ranging from K=9 to as
high as K=18,000, as illustrated in Table C-1. Of the ceramic materials, those based on the titanates
Vacuum:
1.0
Air:
1.004
Mylar:
3
Paper:
4-6
Mica:
4-8
Glass:
3.7-19
Alumina (Al
2
O
3
):
9
Titania (TiO
2
):
85-170, (varies with crystal axis)
Barium Titanate (BaTiO
3
):
1500
Formulated ceramics
with discrete characteristics: 20-18,000
TABLE C-1
DIELECTRIC CONSTANTS FOR VARIOUS MATERIALS
FIGURE C-1
SINGLE PLATE CAPACITOR
electrode
dielectric
NOVACAP
TECHNICAL BROCHURE 5
and niobates as the major constituent display the highest dielectric constant, can be formulated with suit-
able electrical characteristics, and are thus the basis of chip capacitor technology. All processes and other
materials used in the manufacture of chip capacitors are oriented towards optimization of the electrical
properties of these dielectrics.
D. CAPACITANCE
The principal characteristic of a capacitor is that it can store an electric charge (Q), which is directly
proportional to the capacitance value (C) and the voltage applied (V).
Q = CV
The charging current I is therefore defined as
I = dQ/dt = CdV/dt.
The value of capacitance is defined as one Farad when the voltage across the capacitor is one volt,
and a charging current of one ampere flows for one second.
C = Q/V = Coulomb/Volt = Farad
Because the Farad is a very large unit of measurement, and is not encountered in practical applica-
tions, fractions of the Farad are commonly used, namely:
picofarad (pF)
= 10
-12
Farad
nanofarad (nF)
= 10
-9
Farad
microfarad (mF)
= 10
-6
Farad
E. FACTORS AFFECTING CAPACITANCE
For any given voltage the capacitance value of the single plate device of Figure C-1 is directly
proportional to the geometry and dielectric constant of the device:
C = KA/f(t)
NOVACAP
TECHNICAL BROCHURE 6
K = dielectric constant
A = area of electrode
t = thickness of dielectric
f = conversion factor
In the English system of units, f=4.452, and using dimensions in inches for A and t, the capacitance
value is expressed in picofarads (pF). For example: for a device as in Figure C-1, with a 1.0 X 1.0"
area, .056" dielectric thickness, and a dielectric constant of 2500,
C = 2500 (1.0)(1.0)/4.452 (.056) = 10,027 pF
utilizing the Metric System, the conversion factor is f= 11.31, and dimensions are in centimeters.
C = 2500 (2.54)(2.54)/11.31 (.1422) = 10,028 pF.
As is evident from the above relationship of capacitance to geometry, greater capacitance can be
achieved by increasing the electrode area while decreasing the dielectric thickness. As it is physi-
cally impractical to increase area in a single plate device with thinner dielectric, the concept of
stacking capacitors in a parallel array was conceived to produce a physically sound device with more
capacitance per unit volume, as illustrated in Figure E -1.
In this multilayer configuration, the area A is increased by virtue of many electrodes in parallel
arrangement, in a construction permitting very thin dielectric thickness between opposing elec-
trodes, such that the capacitance C is enlarged by the factor N (number of dielectric layers) and
reduced dielectric thickness t, where A is now the area of overlap of opposing electrodes:
FIGURE E-1
MULTILAYER CAPACITOR
terminal
electrode (internal)
ceramic dielectric
NOVACAP
TECHNICAL BROCHURE 7
C = KAN/4.4452(t)
The capacitance value previously obtained for the inch square by 056" single plate device can now
be produced with the same dielectric in a multilayer unit of only .050 x .050 x .040" dimensions
and thirty (30) dielectric layers of thickness .001" (where A, the electrode overlap, is .030 x .020").
C = 2500 (.030) (.020) 30/4.452 (.001) = 10,107 pf
This example, in effect, shows that multilayer construction can deliver the same capacitance in a
volume 700 times smaller than that of the single plate device. Chip capacitors are therefore designed
and manufactured to maximize the volumetric efficiency of capacitance, by optimizing the geometry
and by the selection of dielectric formulations with high dielectric constant and general electrical
properties, namely good insulation resistance and dielectric strength, which permit very thin layer
construction.
F. DIELECTRIC BEHAVIOR
Dielectric behavior occurs in all insulators - solids, liquids and gases, yet it is not yet fully under-
sto