CA1155189A - Encapsulated capacitor with minimum anode impedance - Google Patents

Encapsulated capacitor with minimum anode impedance

Info

Publication number
CA1155189A
CA1155189A CA000371129A CA371129A CA1155189A CA 1155189 A CA1155189 A CA 1155189A CA 000371129 A CA000371129 A CA 000371129A CA 371129 A CA371129 A CA 371129A CA 1155189 A CA1155189 A CA 1155189A
Authority
CA
Canada
Prior art keywords
anode
capacitor
capacitor according
cathode
termination means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000371129A
Other languages
French (fr)
Inventor
William D. Davies
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Emhart Industries Inc
Original Assignee
Emhart Industries Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Emhart Industries Inc filed Critical Emhart Industries Inc
Application granted granted Critical
Publication of CA1155189A publication Critical patent/CA1155189A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004Details
    • H01G9/04Electrodes or formation of dielectric layers thereon
    • H01G9/048Electrodes or formation of dielectric layers thereon characterised by their structure
    • H01G9/052Sintered electrodes

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Fixed Capacitors And Capacitor Manufacturing Machines (AREA)

Abstract

ENCAPSULATED CAPACITOR WITH
MINIMUM ANODE IMPEDANCE

Abstract of Disclosure Superior capacitor characteristics are achieved by providing a capacitor body having a solid porous anode of film forming metal which is characterized by a multiplicity of microscopic inter-communicating voids and permeated by at least one channel to reduce the quantity of metal in the anode with a cathode substantially surrounding the anode. A protective layer of an epoxy resin, silicone resins and rubbers, phenoxy resins, or phenolic resins encapsulate the body.

Description

1155~89 BACKGROUND OF THE INVENTION
.. . ... _ .
Generally speaking, the present invention pertains to a capacitor comprising a body including a solid porous anode of film forming metal characterized by a multiplicity of microscopic intercommunicating voids and permeated by at least one channel to reduce the quantity of metal in the anode, and cathode means substantially surrounding the anodei a protective layer of material taken from the class consisting essentially of epoxy resins, silicone resins and rubbers, phenoxy resins, and phenolic resins encapsulating the body; anode termination means extending from an internal portion of the anode; and cathode termination means extending from the cathode means at an outer surface of the body.
The present invention relates to an electrical capacitor of the electrolytic type having a porous sintered anode of a particular geometrical shape and wherein the anode as well as other elements of the capacitor are encapsulated in a protective layer of resin.
It is known in the tantalum capacitor art that superior electrical characteristics can be achieved when the anode ~s designed in such a manner as to reduce tc a minimum the distance between any point within the anode and an external surface where contact to the electrolyte may be provided. In this way, the effects of electrolyte resistance within the anode are minimized resulting in an improved dissipation factor and a greater stability of capacitance over a wide range of frequencies.
For example, there is described in U. S. patent 3,345, 545, issued October 3, 1967 a solid electrolytic tantalum capacitor having various anode shapes providing better electrical characteristics.
It is also known in the tantalum capacitor art to encapsulate the capacitor elements in a protective layer of resin helps protect the capacitor from harmful effects of the environment, including moisture and other contaminents and to help protect the capacitor from abusive handling. The encapsulant also provides a smooth regular appearance for the capacitor. For example, there is described in U. S. patent B ~

4,049,904 issued August 2, 1977, a tantalum capacitor that is encapsulated in an overcoating layer of resin.

~i~ .~, ,.....
-la-~155189 Prior to the present invention, the two enumerated features have not been combined primarily because of the anticipated fabrication difficulties of covering the different anode configurations with the encapsulant.
FEATURES OR OBJECTS OF THE INVENTION
Accordingly, it is a feature of the present invention to provide a capacitor having a solid porous anode having a configuration which provides better electrical characteristics and which is encapsulated in a protective coating of a resin. Another feature of the invention is to provide such a capacitor wherein the anode is permeated by at least one channel to reduce the quantity of metal in the anode. Another feature of the invention is to provide such a capacitor wherein the anode is a cylinder having a central bore therein. Yet another feature of the invention is the provision of such a capacitor wherein the bore is at least partially filled with the resin. Another feature of the invention is the provision of such a capac,itor wherein the anode has a cross section which is in the form of a four leaf clover. Still another feature of the invention is the provislon of such a capacitor wherein the anode termination means extends from an internal portion of the anode and the cathode termination means extends along an outer most surface of the anode. These and other features of the invention will becnme apparent from the following description taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE _RAWINGS
Figure 1 is a cross section of one embodiment of the invention illustrating its features.
Figure 2 is a cross section taken along the line 2-2 of Figure 1.
Figure 3 is a cross section of another embodiment of the invention.
Figure 4 is a cross section taken along the line 4-4 of Figure 3.

llS5189 DETAILED DESCRIPTION OF THE INVENTION
Referring now to Figures 1 and 2, which illustrate one embodiment of the invention, a capacitor 10 includes a body 12 that is encapsulated in a protective layer 14, anode termination means 16 and cathode termination means 18. Body 12 includes a sintered porous anode 20 fabricated of a film forming metal and having a multiplicity of inter-communicating voids. Although not shown in detail, but as is well known in the art, body 12 also includes an appropriate dielectric oxide film and a solid electrolyte or conducting layer which together act as a cathode means for the capacitor.
Suitable materials for anode 12 are generally selected from the metals aluminum, titanium, tantalum, niobium or zirconium, and preferably tantalum. The conducting layers generally comprise a layer of manganese dioxide film next to the dielectric oxide film and one or more layers of graphite, solder, silver or other conducting materials.
The protective layer 14 should be composed of a material that is electrically insulative, has good resistance to mechanical shock, is able to withstand elevated temperatures, is relatively impervious to moisture and other contaminants in the atmosphere, is relatively inexpensivej and is able to be applied to capacit~rs by techniques such as dipping, molding, brushing, spraying and the like. Examples of such materials are epoxy resins, silicone resins and rubbers, phenoxy resins and phenolic resins.
In accordance with the present invention, porous anode 20 of body 12 takes a form which provides a minimum distance between any point within the anode and the surface where contact with the electrolyte is made, which is generally accomplished by permeating the solid anode with a channel to reduce the quantity of metal in the anode and the body is then encapsulated in the protective layer 14. In Figures 1 and
2, the anode takes the shape of a cylinder 22 having a centrally ~55~89 disposed bore 24. Anode termination means 16 extends from the internal portion 26 of the anode in an area about midway between the bore 24 and the outer surface of the cylinder. Cathode termination means 18 is in electrical contact with the cathode means of the capacitor at the outer surface of body 12. As shown, bore 24 is at least partially filled with the material of protective layer 14.
In the embodiment of capacitor 10' shown in Figures 3 and 4, anode 20' takes on the form of a four leaf clover 21 as viewed in cross section in Figure 3. Such structure provides for greater quantities of removed metal so as to further minimize the effects of electrolyte resistance.
In this embodiment, anode termination means 16' extends from the center of the anbde while the cathode termination means 18' extends from the outer surface of body 12' at the body's greatest diameter.
A number of capacitors fabricated according to the embodiment of Figures 1 and 2 were tested and compared with capacitors fabricated with a solid rectangular anode. Both types of capacitors were encapsulated by dipping into an epoxy r,esin. The results are tabulated in Table I.
TABLE I
120 Hz 1000 Hz lOOK Hz Cap % DF Cap % DF ER5 in ohms 227 4.5 220 2~.0 .106 Solid 231 4.0 225 26.9 .090 Anode 229 4.5' 222 28.6 .098 231 4.0 224 26.2 .095 229 4.8 221 30.6 .107 234 1.5 233 9.2 .060 Anode of 227 1.7 225 9.0 .058 Figures 238 1.7 237 9.4 .060 1 and 2 234 1.5 233 8.9 .058 ' 223 1.5 222 7.9 .055 A number of capacitors fabricated in accordance with the embodiment of Figures 3 and 4 were tested and compared with capacitors with the solid rectangular anode of Table I. Again, both types of capacitors were encapsulated by dipping into an epoxy resin. The results are shown in Table II.
TABLE II
120 Hz 1000 Hz lOOK Hz Cap % DF Cap % DF ERS in ohms 218 1.5 217 9.5 .056 217 1.3 215 8.4 .044 216 1.3 214 8.3 .045 216 1.3 215 7.7 .045 221 1.9 218 8.4 .044 214 1.9 212 8.1 .044 212 1.3 211 8.2 .045 216 1.3 215 8.5 .053 Referring to both Tables, the term % DF stands for Dissipation Factor which is a measure of power loss due to internal resistance.
The lower the number the better is the performance of the capacitor.
The term ERS, which is a standard measurement at high frequencies, stands for Equivalent Series Resistance and is a measure of the resistance of the capacitor. Again, the lower the number the better is the performance of the capacitor.
Examination of the tables clearly shows the better results obt~in when using the anodes of the invention as compared to a standard solid rectangular anode.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A capacitor comprising:
a) a body including a solid porous anode of film forming metal characterized by a multiplicity of microscopic intercommunicating voids and permeated by at least one channel to reduce the quantity of metal in said anode, and cathode means substantially surrounding said anode, b) a protective layer of material taken from the class consisting essentially of epoxy resins, silicone resins and rubbers, phenoxy resins, and phenolic resins encapsulating said body, c) anode termination means extending from an internal portion of said anode, and d) cathode termination means extending from said cathode means at an outer surface of said body.
2. A capacitor according to claim 1 wherein said solid porous anode is a cylinder having a central bore therein.
3. A capacitor according to claim 2 wherein said bore is at least partially filled with said resin.
4. A capacitor according to claim 2 wherein said anode termination means extends longitudinally from said cylinder in an area about midway between said bore and an outer surface of said anode.
5. A capacitor according to claim 1 wherein said solid porous anode has a cross-section which is in the form of a clover leaf.
6. A capacitor according to claim 5 wherein said anode termination means extends from the center of said cross section.
7. A capacitor according to claim 6 wherein said cathode termination means extends from an outermost surface of the clover leaf cross section.
CA000371129A 1980-06-16 1981-02-18 Encapsulated capacitor with minimum anode impedance Expired CA1155189A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US15963180A 1980-06-16 1980-06-16
US06/159,631 1980-06-16

Publications (1)

Publication Number Publication Date
CA1155189A true CA1155189A (en) 1983-10-11

Family

ID=22573330

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000371129A Expired CA1155189A (en) 1980-06-16 1981-02-18 Encapsulated capacitor with minimum anode impedance

Country Status (4)

Country Link
JP (1) JPS5713733A (en)
CA (1) CA1155189A (en)
DE (1) DE3111580A1 (en)
GB (1) GB2077997A (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59200411A (en) * 1983-04-27 1984-11-13 日本電気株式会社 Tantalum electrolytic condenser anode element
JPS60153461A (en) * 1984-01-20 1985-08-12 Yanmar Diesel Engine Co Ltd Air-fuel ratio controller for gas engine
NL8501584A (en) * 1985-06-03 1987-01-02 Philips Nv DRY ELECTROLYTIC CAPACITOR.
US9275799B2 (en) 2011-12-20 2016-03-01 Avx Corporation Wet electrolytic capacitor containing an improved anode
US9324503B2 (en) 2013-03-15 2016-04-26 Avx Corporation Solid electrolytic capacitor

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1083632A (en) * 1952-06-26 1955-01-11 Heraeus Gmbh W C Electrolytic capacitor
US4068291A (en) * 1976-04-12 1978-01-10 Sprague Electric Company Solid electrolyte capacitor with improved cathode lead
DE2631776C3 (en) * 1976-07-15 1979-06-13 Standard Elektrik Lorenz Ag, 7000 Stuttgart Electrolytic capacitor
US4107762A (en) * 1977-05-16 1978-08-15 Sprague Electric Company Solid electrolyte capacitor package with an exothermically-alloyable fuse

Also Published As

Publication number Publication date
JPS5713733A (en) 1982-01-23
DE3111580A1 (en) 1982-04-08
GB2077997A (en) 1981-12-23

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