Conformal Coated Guide
www.vishay.com
Vishay Sprague
Guide for Conformal Coated Tantalum Capacitors
INTRODUCTION
Tantalum electrolytic capacitors are the preferred choice in
applications where volumetric efficiency, stable electrical
parameters, high reliability, and long service life are primary
considerations. The stability and resistance to elevated
temperatures of the tantalum / tantalum oxide / manganese
dioxide system make solid tantalum capacitors an
appropriate choice for today's surface mount assembly
technology.
Vishay Sprague has been a pioneer and leader in this field,
producing a large variety of tantalum capacitor types for
consumer, industrial, automotive, military, and aerospace
electronic applications.
Tantalum is not found in its pure state. Rather, it is
commonly found in a number of oxide minerals, often in
combination with Columbium ore. This combination is
known as “tantalite” when its contents are more than
one-half tantalum. Important sources of tantalite include
Australia, Brazil, Canada, China, and several African
countries. Synthetic tantalite concentrates produced from
tin slags in Thailand, Malaysia, and Brazil are also a
significant raw material for tantalum production.
Electronic applications, and particularly capacitors,
consume the largest share of world tantalum production.
Other important applications for tantalum include cutting
tools (tantalum carbide), high temperature super alloys,
chemical processing equipment, medical implants, and
military ordnance.
Vishay Sprague is a major user of tantalum materials in the
form of powder and wire for capacitor elements and rod and
sheet for high temperature vacuum processing.
Rating for rating, tantalum capacitors tend to have as much
as three times better capacitance / volume efficiency than
aluminum electrolytic capacitors. An approximation of the
capacitance / volume efficiency of other types of capacitors
may be inferred from the following table, which shows the
dielectric constant ranges of the various materials used in
each type. Note that tantalum pentoxide has a dielectric
constant of 26, some three times greater than that of
aluminum oxide. This, in addition to the fact that extremely
thin films can be deposited during the electrolytic process
mentioned earlier, makes the tantalum capacitor extremely
efficient with respect to the number of microfarads available
per unit volume. The capacitance of any capacitor is
determined by the surface area of the two conducting
plates, the distance between the plates, and the dielectric
constant of the insulating material between the plates.
COMPARISON OF CAPACITOR
DIELECTRIC CONSTANTS
DIELECTRIC
Air or vacuum
Paper
Plastic
Mineral oil
Silicone oil
Quartz
Glass
Porcelain
e
DIELECTRIC CONSTANT
1.0
2.0 to 6.0
2.1 to 6.0
2.2 to 2.3
2.7 to 2.8
3.8 to 4.4
4.8 to 8.0
5.1 to 5.9
5.4 to 8.7
8.4
26
12 to 400K
THE BASICS OF TANTALUM CAPACITORS
Most metals form crystalline oxides which are
non-protecting, such as rust on iron or black oxide on
copper. A few metals form dense, stable, tightly adhering,
electrically insulating oxides. These are the so-called “valve”
metals and include titanium, zirconium, niobium, tantalum,
hafnium, and aluminum. Only a few of these permit the
accurate control of oxide thickness by electrochemical
means. Of these, the most valuable for the electronics
industry are aluminum and tantalum.
Capacitors are basic to all kinds of electrical equipment,
from radios and television sets to missile controls and
automobile ignitions. Their function is to store an electrical
charge for later use.
Capacitors consist of two conducting surfaces, usually
metal plates, whose function is to conduct electricity. They
are separated by an insulating material or dielectric. The
dielectric used in all tantalum electrolytic capacitors is
tantalum pentoxide.
Tantalum pentoxide compound possesses high-dielectric
strength and a high-dielectric constant. As capacitors are
being manufactured, a film of tantalum pentoxide is applied
to their electrodes by means of an electrolytic process. The
film is applied in various thicknesses and at various voltages
and although transparent to begin with, it takes on different
colors as light refracts through it. This coloring occurs on the
tantalum electrodes of all types of tantalum capacitors.
Revision: 11-Oct-2018
Mica
Aluminum oxide
Tantalum pentoxide
Ceramic
In the tantalum electrolytic capacitor, the distance between
the plates is very small since it is only the thickness of the
tantalum pentoxide film. As the dielectric constant of the
tantalum pentoxide is high, the capacitance of a tantalum
capacitor is high if the area of the plates is large:
eA
C
=
------
-
t
where
C = capacitance
e = dielectric constant
A = surface area of the dielectric
t = thickness of the dielectric
Tantalum capacitors contain either liquid or solid
electrolytes. In solid electrolyte capacitors, a dry material
(manganese dioxide) forms the cathode plate. A tantalum
lead is embedded in or welded to the pellet, which is in turn
connected to a termination or lead wire. The drawings show
the construction details of the surface mount types of
tantalum capacitors shown in this catalog.
Document Number: 40150
1
For technical questions, contact:
tantalum@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
Conformal Coated Guide
www.vishay.com
SOLID ELECTROLYTE TANTALUM CAPACITORS
Solid electrolyte capacitors contain manganese dioxide,
which is formed on the tantalum pentoxide dielectric layer
by impregnating the pellet with a solution of manganous
nitrate. The pellet is then heated in an oven, and the
manganous nitrate is converted to manganese dioxide.
The pellet is next coated with graphite, followed by a layer
of metallic silver, which provides a conductive surface
between the pellet and the can in which it will be enclosed.
After assembly, the capacitors are tested and inspected to
assure long life and reliability. It offers excellent reliability
and high stability for consumer and commercial electronics
with the added feature of low cost.
Surface mount designs of “Solid Tantalum” capacitors use
lead frames or lead frameless designs as shown in the
accompanying drawings.
Vishay Sprague
TYPE 194D
SnPb or Gold Plated Ni Cathode
End Cap Termination
Encapsulation
SnPb or Gold Plated Ni Anode
End Cap Termination
Cathode
Backfill
Conductive Silver
Epoxy Adhesive
Sintered Tantalum
Pellet
MnO
2
/Carbon/
Silver Coating
Sponge Teflon
Anode Backfill
TANTALUM CAPACITORS FOR ALL DESIGN
CONSIDERATIONS
Solid electrolyte designs are the least expensive for a given
rating and are used in many applications where their very
small size for a given unit of capacitance is of importance.
They will typically withstand up to about 10 % of the rated
DC working voltage in a reverse direction. Also important
are their good low temperature performance characteristics
and freedom from corrosive electrolytes.
Vishay Sprague patented the original solid electrolyte
capacitors and was the first to market them in 1956. Vishay
Sprague has the broadest line of tantalum capacitors and
has continued its position of leadership in this field. Data
sheets covering the various types and styles of Vishay
Sprague capacitors for consumer and entertainment
electronics, industry, and military applications are available
where detailed performance characteristics must be
specified.
TYPE T96
Intermediate
Cathode
Silver
Fuse
Cathode Termination
(Silver + Ni/Sn or
Ni/SnPb Plating)
Encapsulation
MnO
2
/Carbon/
Silver Coating
TYPE 195D, 572D, 591D, 592D / W, 594D,
595D, 695D, T95, 14002
Cathode Termination
(Silver + Ni/Sn/Plating)
Epoxy Tower/
Sponge Teflon
Anode Termination
(Silver + Ni/Sn or
Sintered Tantalum
Ni/SnPb Plating)
Pellet
TYPE T98
Encapsulation
Anode Termination
(Silver + Ni/Sn/Plating)
Intermediate
Cathode
Silver
Fuse
MnO
2
/Carbon/Silver
Coating
Sintered Tantalum
Pellet Sponge Teflon/Epoxy Tower
TYPE 597D / T97 / 13008
Cathode Termination
(Silver + Ni/Sn/Plating)
Encapsulation
Anode Termination
(Silver + Ni/Sn/Plating)
Cathode Termination
(Silver + Ni/Sn or
Ni/SnPb Plating)
Encapsulation
Anode Termination
(Silver + Ni/Sn or Sintered Tantalum
Ni/SnPb Plating)
Pellet
MnO
2
/Carbon/
Silver Coating
Epoxy Tower/
Sponge Teflon
MnO
2
/Carbon/Silver
Coating
Sintered Tantalum
Pellet
Silver Epoxy
Sponge Teflon/Epoxy Tower
Revision: 11-Oct-2018
Document Number: 40150
2
For technical questions, contact:
tantalum@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT
www.vishay.com/doc?91000
PCB Design
京公网安备 11010802033920号
EEWORLD
