CA1078935A - Electrical device containing a silicone resin - Google Patents
Electrical device containing a silicone resinInfo
- Publication number
- CA1078935A CA1078935A CA268,774A CA268774A CA1078935A CA 1078935 A CA1078935 A CA 1078935A CA 268774 A CA268774 A CA 268774A CA 1078935 A CA1078935 A CA 1078935A
- Authority
- CA
- Canada
- Prior art keywords
- housing
- electrical component
- oxide film
- over
- electrical
- 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
Links
- 229920002050 silicone resin Polymers 0.000 title claims abstract description 13
- 239000003990 capacitor Substances 0.000 claims abstract description 49
- 239000000463 material Substances 0.000 claims abstract description 23
- 229920001296 polysiloxane Polymers 0.000 claims abstract description 22
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052751 metal Inorganic materials 0.000 claims description 26
- 239000002184 metal Substances 0.000 claims description 26
- 239000002966 varnish Substances 0.000 claims description 11
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 8
- 239000007784 solid electrolyte Substances 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 5
- 239000004065 semiconductor Substances 0.000 claims description 5
- 239000004020 conductor Substances 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims 1
- 238000010521 absorption reaction Methods 0.000 abstract description 13
- 229910052715 tantalum Inorganic materials 0.000 abstract description 3
- 239000007787 solid Substances 0.000 abstract 1
- 238000000576 coating method Methods 0.000 description 6
- 230000002411 adverse Effects 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- 229910000679 solder Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 239000008393 encapsulating agent Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000010981 drying operation Methods 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 239000000806 elastomer Substances 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000004922 lacquer Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 125000000962 organic group Chemical group 0.000 description 1
- 125000005375 organosiloxane group Chemical group 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/15—Solid electrolytic capacitors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/08—Housing; Encapsulation
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
Abstract
AN ELECTRICAL DEVICE CONTAINING A SILICONE RESIN
ABSTRACT OF THE DISCLOSURE
An electrical device includes a housing, an electrical component within the housing and a material containing silicone over the electrical component. The silicone material helps to reduce harmful moisture absorption by the electrical component during the manufacture of the device and during use of the device. In a preferred embodiment, the electrical component is a solid tantalum capacitor and the material contains a silicone resin.
ABSTRACT OF THE DISCLOSURE
An electrical device includes a housing, an electrical component within the housing and a material containing silicone over the electrical component. The silicone material helps to reduce harmful moisture absorption by the electrical component during the manufacture of the device and during use of the device. In a preferred embodiment, the electrical component is a solid tantalum capacitor and the material contains a silicone resin.
Description
1~7~3.S
The present invention relates to electrical devices and more specifically, to means for reducing moisture absorption in electrical -~
devices which may adversely affect electrical characteristics of the device.
While the present invention may be adaptable to a wide variety of electrical devices such as batteries, resistors and the like, it is particularly adaptable and will be discussed hereafter with reference to high capacitance, low voltage solid electrolyte dielectric oxide film-forming metal capacitors which are enclosed in a housing. It should be understood that although the present invention is primarily discussed ; with reference to such capacitors, the invention is not thereby so limited.
High capacitance, low voltage solid electrolyte dielectric oxide film-forming capacitors generally comprise a housing, an anode within the housing, the anode of dielectric oxide film-forming metal, - such as tantalum, aluminum, niobium and the like, and various layers or coatings over the anode. The housing is usually a metal housing with an appropriate hermetic end seal. The layers over the anode include a dielectric oxide film over the film-forming metal anode, a semi-con-ducting layer such as manganese dioxide over the dielectric oxide film and an electrically conducting layer or layers containing materials such as silver, carbon, copper and the like over the semi-conducting layer.
One major problem in the manufacture of the above type of capacitor is absorption of moisture from the air by the layered anode, especially by the semi-conducting layer over the anode, before the layered anode is sealed within the housing. Semi-conducting materials such as manganese dioxide are generally somewhat hygroscopic and are therefore quite difficult to dry and to keep dry. The absorption of moisture by the layered anode may manifest itself in the operation of the completed capacitor as a high dissipation factor (DF) and undesirably large 1~7~93S
changes in capacitance with changes in temperature (~C). Generally, the specification maximum for ~C between 25C and 85C in these types of capacitors is 8%. Present efforts to minimize moisture absorption in these type capacitors include drying the layered anode prior to sealing it within the housing. However, the drying operation is many times not entirely effective or it is not feasible to seal the dried anodes within the housing immediately after drying in mass production type operation.
In either situation, the finished capacitor may absorb and therefore contain detrimental amounts of moisture which may adversely affect the electrical characteristics of the capacitor.
In addition, a housing with an associated end seal containing an anode may not be hermetic or may lose its hermeticity after a period of use due to rough handling, vibrat;on or the like. The loss of herme-ticity may allow the ingress of moisture from the ambient atmosphere into the housing and thereby harmfully affect the electrical charac-teristics of the capacitor.
The above problem of moisture absorption is generally not encountered in the manufacture of solid electrolyte dielectric oxide film-forming metal capacitors which are encapsulated in a thermoplastic or thermosetting resin by a molding or dipping operation. Usually the heat used to cure the encapsulant is sufficient to remove substantially all of the entrained moisture and the cured encapsulant has good resis-tance to moisture penetration thereafter.
It is therefore a feature of the present invention to provide a means for minimizing moisture absorption in electrical devices, especially in high capacitance, low voltage solid electrolyte dielectric oxide film-forming metal capacitors which are contained within a hous-ing. Another feature of the present invention is to utilize a material containing silicone as a means to minimize moisture absorption in elec-trical devices. Yet another feature is that electrical devices, such as 1()';'~93S
capacitors, utilizing the present invention may have improved electrical properties such as lowered dissipation factor and less change in capa-citance with changes in temperature. Another feature of the invention is that the use of a material containing silicone to minimize moisture absorption in certain electrical devices may not adversely affect the solderability of that portion of the device treated with material con-taining silicone. These and various other features of the invention as well as many specific advantages will be more fully apparent from a detailed consideration of the remainder of this disclosure including the examples and the appended claims in conjunction with the accompanying drawing in which is shown a cross-sectional view of a typical high capacitance, low voltage solid electrolyte dielectric oxide film-forming metal capacitor.
Generally, the present invention comprehends an electrical device comprising housing means, electrical component means within the housing means and material containing silicone over the electrical component means and methods for making the same. In a preferred embodi-ment, the electrical component means is a solid electrolyte, dielectric oxide film-forming metal capacitor and the material contains silicone resin.
One important function of the material containing silicone over the electrical component means is to help minimize the absorption of moisture by the electrical component means during the manufacture of the electrical device and also during the life of the electrical device and thereby improve the electrical characteristics of the device.
For the purposes of the present invention, materials contain-ing silicone resins are preferred to help minimize the absorption of moisture by an electrical component means of an electrical device.
These resins may be filled or unfilled. Of particular adaptability to the present invention are silicone varnishes and lacquers, an 1l)7~3S
example of which is the varnish sold under the ~egistered Trademark "Dow Corning 997" varnish by Dow Corning Corp. of Midland, Michigan, U.S.A. These type silicone resins are most preferred.
` The term silicone resin as used herein comprehends a particular class of organo-siloxane polymers known generally as silicones.
Silicones have a polymer structure made of alternating silicon and oxygen atoms, typically with the silicon atoms having one or more organic ~; side groups attached, generally phenyl, methyl or vinyl units.
Silicones can be classified as fluids, elastomers and resins, their ultimate physical form being determined by molecular weight, extent of cross link;ng between polymeric chains and the type and number of organic groups attached to the silicon atoms.
The material containing silicone may be applied to the electrical component means by a variety of methods. Preferably, the material containing silicone is in a liquid state before application and is then cured or dried after application to the electrical component means.
Suitable methods of application may include brushing, painting, dipping and the like.
The thickness of the material containing silicone over the electrical component means is not believed to be critical. Of course, the thickness should be great enough to provide protection against the absorption of moisture by the electrical component means but not so great as to adversely affect any joining operation of the electrical component means to another member, such as the soldering of an external termination means to the electrical component means.
According to the above features from a broad aspect, the present invention provides an electrical device comprising housing means, electrical component means within the housing means, the electrical component means including electrode means of dielectric oxide film-forming metal, dielectric oxide film over the electrode means, semiconducting material over the ~ -4-.~ , .
.
~ielectric oxide film, electrically conductive material over the semiconducting materia1, and material containing non-elastomeric silicone over the electrically conductive material.
The invention can be more clearly understood by reference to the drawing which illustrates a preferred embodiment of the invention.
The drawing shows a cross-sectional view of a solid electrolyte, dielectric oxide film-forming metal capacitor 10. The capacitor 10 includes cylindrical shaped metal housing 12 and hermetic type and seal 14 closing the open end of the housing. End seal 14 includes an annular metal -4a-.,~,.~, 11~7~3S
portion 16, metallic tube 18, and glass mass 20 joined to the metal portion and to the tube. The seal 14 is joined to the housing 12 by means such as solder 22. While the end seal 14 is shown as a glass-to-; metal type seal, the seal forms no part of the present invention and the seal could be selected from a wide variety of other end seal designs known in the art.
Located with the housing 12 is a film-forming metal anode electrode 24 formed by the pressing and sintering of metal powder such as tantalum powder. Over the anode 24 is a dielectric oxide film (not shown) of the film-forming metal. Over the dielectric oxide film is a semi-conducting layer 26 containing manganese dioxide. Over layer 26 is one or more electrically conductive layers 28 containing a metal such as silver or a finely divided material such as carbon. Over layer 28 is a layer 30 of material containing silicone resin according to the present invention which helps to minimize moisture absorption by the layers beneath layer 30, especially by the semi-conducting layer 26. The layered anode 24 is maintained in place within the housing 12 by anode riser means 32 projecting through the end seal 14 and joined thereto by solder 34 joined to the walls of the housing 12 and layer 20. Cathode termination means 37 attached to housing 12 and anode riser means 32 provide external electrical connection for the capacitor 10.
Suprisingly, it has been found that the layer 30 containing silicone resin over the conductive layer 28 may not inhibit the soldera-bility of the conductive layer and may even enhance the solderability of the conductive layer when solder 34 is used to join the layered anode 24 to the housing 12.
It should be realized that the relative thicknesses of layers 26, 28 and 30 are exaggerated in the drawing for purposes of clarity and do not accurately reflect the relative thicknesses of these layers in an actual capacitor.
Capacitors of the type described above using the concepts of . .
~07893S
the present invention exhibit improved electrical characteristics such as lowered change in capacitance with temperature and lowered dissipa-tion factor. The change in capacitance during changes in temperature is ; significantly lower with capacitors incorporating the present invention than with conventional capacitors. Capacitors of the present invention also have a lower dissipation factor and comparable DC leakage current values. These improved electrical characteristics are illustrated in the following example. It should be understood that the example is given for the purposes of illustration only and the example is not intended to limit the invention as has heretofore been described.
EXAMPLE
Forty pellet-like tantalum anodes for use in electrolytic capacitors are processed conventionally up to and including the applica-tion and curing of a conductive silver layer over the anodes. The anodes are designed for a nominal capacitance of 220 uf at 10 volts.
Twenty of the anodes are then dipped in a silicone type varnish sold under Registered Trademark "Dow Corning 997" by Dow-Corning Inc., Midland, Michigan, U.S.A. and then the resultant varnish coating is allowed to dry at room temperature for about ten to fifteen minutes.
The varnished anodes are placed in a drying oven for about two hours at about 175 to 185C to remove any entrained moisture in the anodes and to cure the applied silicone varnish coating. The other twenty anodes are placed in another oven and dried also.
Ten of the anodes with a varnish coating and ten dried un-varnished anodes are soldered in metal housings and the housing sealed.
Each of the resultant capacitors is then tested for capacitance (C) and dissipation factor (DF) at about 25C and for capacitance at about 85C
with a 10 volt, 100 hz unbiased applied source. Capacitance is measured in microfarads (uf). The percentage change in capacitance (%1~C) between the two temperatures is then calculated. The results of the tests are as follows, 107~93S
Unvarnished Varnished C %DF C %~C C DF C ,O~C
237 4.3 253 6.7 234 2.4 240 2.6 233 5.2 257 10.3 239 2.4 246 2.9 244 5.2 269 10.2 223 2.1 229 2.7 246 4.6 258 4.9 229 2.3 236 3.0 223 3.7 234 5.3 231 2.1 237 2.6 231 3.9 244 5.6 227 2.7 223 2.6 232 3.7 245 5.6 219 2.3 226 3.2 229 3.6 243 6.1 222 2.3 229 3.2 223 3.7 236 5.8 229 2.6 236 3.1 221 3.6 233 5.4 230 2.5 237 3.0 Ave. 4.15 6.59 2.37 2.89 As the above table indicates, the capacitors with silicone varnish coatings of the present invention generally have a significantly lower dissipation factor and less change in capacitance with change in temperature than do the unvarnished capacitors. The average DF for the ten varnished capacitors is approximately half that for the unvarnished capacitors. The average percentage change in capacitance with tempera-ture for the varnished capacitors is significantly less than half that for the unvarnished capacitors.
To further illustrate the benefits of the present invention, the remaining ten anodes with a varnish coating and ten anodes without varnish are also soldered in metal housings. Before sealing the hous-ings, the unvarnished anodes are left open in ambient air for about ten minutes. The housings containing the varnished anodes were left open for about twenty-four hours before sealing. The resultant capacitors are then tested as before and the results are as follows;
107~935 Unvarnished Varnished 25-- 85 l 25 85 I
C DF C%~C I C DF C ,'~C
242 5.2 265 9.5 234 2.6 241 3.0 240 6.5 26811.6 239 2.6 246 2.9 247 6.3 269 8.9 223 2.2 229 2.7 250 5.5 269 7.1 229 2.6 236 3.1 227 4.8 246 8.3 231 2.2 238 3.0 236 4.8 252 6.8 228 3.0 239 3.5 238 4.8 254 7.6 221 2.7 229 3.6 235 4.7 253 7.6 224 2.7 232 3.6 228 4.9 248 8.8 231 2.8 239 3.5 225 4.6 224 8.4 231 2.5 239 3.5 I
Ave. 5.22 8.46 I 2.59 3.24 Again the change in capacitance with temperature and dissipa-tion factor for the capacitors with varnished anodes are significantly less than those capacitors without varnished anodes. The average DF for the varnished capacitors is approximately half that for the unvarnished capacitors. The percentage change in capacitance with temperature for the varnished capacitors is significantly less than half that for the unvarnished capacitors. Also of significance is a comparison of the average values for DF and % AC for the varnished capacitors in this group and the varnished capacitors of the previous group which shows very little difference in average values even after the one group had been exposed to the atmosphere for about 24 hrs. In contrast, a com-parison of these values for the unvarnished capacitors of this group and the previous group shows a marked increase in both DF and % ~C after an exposure to the atmosphere of only about ten minutes. Thus by utilizing the concepts of the present invention, the encapsulation of film-forming metal capacitors within a housing becomes a much less critical step in the manufacturing process in addition to yielding capacitors having better electrical characteristics.
While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually . . :
1~)7893S
departing from the spirit and scope of the invention as defined in the appended claims.
The present invention relates to electrical devices and more specifically, to means for reducing moisture absorption in electrical -~
devices which may adversely affect electrical characteristics of the device.
While the present invention may be adaptable to a wide variety of electrical devices such as batteries, resistors and the like, it is particularly adaptable and will be discussed hereafter with reference to high capacitance, low voltage solid electrolyte dielectric oxide film-forming metal capacitors which are enclosed in a housing. It should be understood that although the present invention is primarily discussed ; with reference to such capacitors, the invention is not thereby so limited.
High capacitance, low voltage solid electrolyte dielectric oxide film-forming capacitors generally comprise a housing, an anode within the housing, the anode of dielectric oxide film-forming metal, - such as tantalum, aluminum, niobium and the like, and various layers or coatings over the anode. The housing is usually a metal housing with an appropriate hermetic end seal. The layers over the anode include a dielectric oxide film over the film-forming metal anode, a semi-con-ducting layer such as manganese dioxide over the dielectric oxide film and an electrically conducting layer or layers containing materials such as silver, carbon, copper and the like over the semi-conducting layer.
One major problem in the manufacture of the above type of capacitor is absorption of moisture from the air by the layered anode, especially by the semi-conducting layer over the anode, before the layered anode is sealed within the housing. Semi-conducting materials such as manganese dioxide are generally somewhat hygroscopic and are therefore quite difficult to dry and to keep dry. The absorption of moisture by the layered anode may manifest itself in the operation of the completed capacitor as a high dissipation factor (DF) and undesirably large 1~7~93S
changes in capacitance with changes in temperature (~C). Generally, the specification maximum for ~C between 25C and 85C in these types of capacitors is 8%. Present efforts to minimize moisture absorption in these type capacitors include drying the layered anode prior to sealing it within the housing. However, the drying operation is many times not entirely effective or it is not feasible to seal the dried anodes within the housing immediately after drying in mass production type operation.
In either situation, the finished capacitor may absorb and therefore contain detrimental amounts of moisture which may adversely affect the electrical characteristics of the capacitor.
In addition, a housing with an associated end seal containing an anode may not be hermetic or may lose its hermeticity after a period of use due to rough handling, vibrat;on or the like. The loss of herme-ticity may allow the ingress of moisture from the ambient atmosphere into the housing and thereby harmfully affect the electrical charac-teristics of the capacitor.
The above problem of moisture absorption is generally not encountered in the manufacture of solid electrolyte dielectric oxide film-forming metal capacitors which are encapsulated in a thermoplastic or thermosetting resin by a molding or dipping operation. Usually the heat used to cure the encapsulant is sufficient to remove substantially all of the entrained moisture and the cured encapsulant has good resis-tance to moisture penetration thereafter.
It is therefore a feature of the present invention to provide a means for minimizing moisture absorption in electrical devices, especially in high capacitance, low voltage solid electrolyte dielectric oxide film-forming metal capacitors which are contained within a hous-ing. Another feature of the present invention is to utilize a material containing silicone as a means to minimize moisture absorption in elec-trical devices. Yet another feature is that electrical devices, such as 1()';'~93S
capacitors, utilizing the present invention may have improved electrical properties such as lowered dissipation factor and less change in capa-citance with changes in temperature. Another feature of the invention is that the use of a material containing silicone to minimize moisture absorption in certain electrical devices may not adversely affect the solderability of that portion of the device treated with material con-taining silicone. These and various other features of the invention as well as many specific advantages will be more fully apparent from a detailed consideration of the remainder of this disclosure including the examples and the appended claims in conjunction with the accompanying drawing in which is shown a cross-sectional view of a typical high capacitance, low voltage solid electrolyte dielectric oxide film-forming metal capacitor.
Generally, the present invention comprehends an electrical device comprising housing means, electrical component means within the housing means and material containing silicone over the electrical component means and methods for making the same. In a preferred embodi-ment, the electrical component means is a solid electrolyte, dielectric oxide film-forming metal capacitor and the material contains silicone resin.
One important function of the material containing silicone over the electrical component means is to help minimize the absorption of moisture by the electrical component means during the manufacture of the electrical device and also during the life of the electrical device and thereby improve the electrical characteristics of the device.
For the purposes of the present invention, materials contain-ing silicone resins are preferred to help minimize the absorption of moisture by an electrical component means of an electrical device.
These resins may be filled or unfilled. Of particular adaptability to the present invention are silicone varnishes and lacquers, an 1l)7~3S
example of which is the varnish sold under the ~egistered Trademark "Dow Corning 997" varnish by Dow Corning Corp. of Midland, Michigan, U.S.A. These type silicone resins are most preferred.
` The term silicone resin as used herein comprehends a particular class of organo-siloxane polymers known generally as silicones.
Silicones have a polymer structure made of alternating silicon and oxygen atoms, typically with the silicon atoms having one or more organic ~; side groups attached, generally phenyl, methyl or vinyl units.
Silicones can be classified as fluids, elastomers and resins, their ultimate physical form being determined by molecular weight, extent of cross link;ng between polymeric chains and the type and number of organic groups attached to the silicon atoms.
The material containing silicone may be applied to the electrical component means by a variety of methods. Preferably, the material containing silicone is in a liquid state before application and is then cured or dried after application to the electrical component means.
Suitable methods of application may include brushing, painting, dipping and the like.
The thickness of the material containing silicone over the electrical component means is not believed to be critical. Of course, the thickness should be great enough to provide protection against the absorption of moisture by the electrical component means but not so great as to adversely affect any joining operation of the electrical component means to another member, such as the soldering of an external termination means to the electrical component means.
According to the above features from a broad aspect, the present invention provides an electrical device comprising housing means, electrical component means within the housing means, the electrical component means including electrode means of dielectric oxide film-forming metal, dielectric oxide film over the electrode means, semiconducting material over the ~ -4-.~ , .
.
~ielectric oxide film, electrically conductive material over the semiconducting materia1, and material containing non-elastomeric silicone over the electrically conductive material.
The invention can be more clearly understood by reference to the drawing which illustrates a preferred embodiment of the invention.
The drawing shows a cross-sectional view of a solid electrolyte, dielectric oxide film-forming metal capacitor 10. The capacitor 10 includes cylindrical shaped metal housing 12 and hermetic type and seal 14 closing the open end of the housing. End seal 14 includes an annular metal -4a-.,~,.~, 11~7~3S
portion 16, metallic tube 18, and glass mass 20 joined to the metal portion and to the tube. The seal 14 is joined to the housing 12 by means such as solder 22. While the end seal 14 is shown as a glass-to-; metal type seal, the seal forms no part of the present invention and the seal could be selected from a wide variety of other end seal designs known in the art.
Located with the housing 12 is a film-forming metal anode electrode 24 formed by the pressing and sintering of metal powder such as tantalum powder. Over the anode 24 is a dielectric oxide film (not shown) of the film-forming metal. Over the dielectric oxide film is a semi-conducting layer 26 containing manganese dioxide. Over layer 26 is one or more electrically conductive layers 28 containing a metal such as silver or a finely divided material such as carbon. Over layer 28 is a layer 30 of material containing silicone resin according to the present invention which helps to minimize moisture absorption by the layers beneath layer 30, especially by the semi-conducting layer 26. The layered anode 24 is maintained in place within the housing 12 by anode riser means 32 projecting through the end seal 14 and joined thereto by solder 34 joined to the walls of the housing 12 and layer 20. Cathode termination means 37 attached to housing 12 and anode riser means 32 provide external electrical connection for the capacitor 10.
Suprisingly, it has been found that the layer 30 containing silicone resin over the conductive layer 28 may not inhibit the soldera-bility of the conductive layer and may even enhance the solderability of the conductive layer when solder 34 is used to join the layered anode 24 to the housing 12.
It should be realized that the relative thicknesses of layers 26, 28 and 30 are exaggerated in the drawing for purposes of clarity and do not accurately reflect the relative thicknesses of these layers in an actual capacitor.
Capacitors of the type described above using the concepts of . .
~07893S
the present invention exhibit improved electrical characteristics such as lowered change in capacitance with temperature and lowered dissipa-tion factor. The change in capacitance during changes in temperature is ; significantly lower with capacitors incorporating the present invention than with conventional capacitors. Capacitors of the present invention also have a lower dissipation factor and comparable DC leakage current values. These improved electrical characteristics are illustrated in the following example. It should be understood that the example is given for the purposes of illustration only and the example is not intended to limit the invention as has heretofore been described.
EXAMPLE
Forty pellet-like tantalum anodes for use in electrolytic capacitors are processed conventionally up to and including the applica-tion and curing of a conductive silver layer over the anodes. The anodes are designed for a nominal capacitance of 220 uf at 10 volts.
Twenty of the anodes are then dipped in a silicone type varnish sold under Registered Trademark "Dow Corning 997" by Dow-Corning Inc., Midland, Michigan, U.S.A. and then the resultant varnish coating is allowed to dry at room temperature for about ten to fifteen minutes.
The varnished anodes are placed in a drying oven for about two hours at about 175 to 185C to remove any entrained moisture in the anodes and to cure the applied silicone varnish coating. The other twenty anodes are placed in another oven and dried also.
Ten of the anodes with a varnish coating and ten dried un-varnished anodes are soldered in metal housings and the housing sealed.
Each of the resultant capacitors is then tested for capacitance (C) and dissipation factor (DF) at about 25C and for capacitance at about 85C
with a 10 volt, 100 hz unbiased applied source. Capacitance is measured in microfarads (uf). The percentage change in capacitance (%1~C) between the two temperatures is then calculated. The results of the tests are as follows, 107~93S
Unvarnished Varnished C %DF C %~C C DF C ,O~C
237 4.3 253 6.7 234 2.4 240 2.6 233 5.2 257 10.3 239 2.4 246 2.9 244 5.2 269 10.2 223 2.1 229 2.7 246 4.6 258 4.9 229 2.3 236 3.0 223 3.7 234 5.3 231 2.1 237 2.6 231 3.9 244 5.6 227 2.7 223 2.6 232 3.7 245 5.6 219 2.3 226 3.2 229 3.6 243 6.1 222 2.3 229 3.2 223 3.7 236 5.8 229 2.6 236 3.1 221 3.6 233 5.4 230 2.5 237 3.0 Ave. 4.15 6.59 2.37 2.89 As the above table indicates, the capacitors with silicone varnish coatings of the present invention generally have a significantly lower dissipation factor and less change in capacitance with change in temperature than do the unvarnished capacitors. The average DF for the ten varnished capacitors is approximately half that for the unvarnished capacitors. The average percentage change in capacitance with tempera-ture for the varnished capacitors is significantly less than half that for the unvarnished capacitors.
To further illustrate the benefits of the present invention, the remaining ten anodes with a varnish coating and ten anodes without varnish are also soldered in metal housings. Before sealing the hous-ings, the unvarnished anodes are left open in ambient air for about ten minutes. The housings containing the varnished anodes were left open for about twenty-four hours before sealing. The resultant capacitors are then tested as before and the results are as follows;
107~935 Unvarnished Varnished 25-- 85 l 25 85 I
C DF C%~C I C DF C ,'~C
242 5.2 265 9.5 234 2.6 241 3.0 240 6.5 26811.6 239 2.6 246 2.9 247 6.3 269 8.9 223 2.2 229 2.7 250 5.5 269 7.1 229 2.6 236 3.1 227 4.8 246 8.3 231 2.2 238 3.0 236 4.8 252 6.8 228 3.0 239 3.5 238 4.8 254 7.6 221 2.7 229 3.6 235 4.7 253 7.6 224 2.7 232 3.6 228 4.9 248 8.8 231 2.8 239 3.5 225 4.6 224 8.4 231 2.5 239 3.5 I
Ave. 5.22 8.46 I 2.59 3.24 Again the change in capacitance with temperature and dissipa-tion factor for the capacitors with varnished anodes are significantly less than those capacitors without varnished anodes. The average DF for the varnished capacitors is approximately half that for the unvarnished capacitors. The percentage change in capacitance with temperature for the varnished capacitors is significantly less than half that for the unvarnished capacitors. Also of significance is a comparison of the average values for DF and % AC for the varnished capacitors in this group and the varnished capacitors of the previous group which shows very little difference in average values even after the one group had been exposed to the atmosphere for about 24 hrs. In contrast, a com-parison of these values for the unvarnished capacitors of this group and the previous group shows a marked increase in both DF and % ~C after an exposure to the atmosphere of only about ten minutes. Thus by utilizing the concepts of the present invention, the encapsulation of film-forming metal capacitors within a housing becomes a much less critical step in the manufacturing process in addition to yielding capacitors having better electrical characteristics.
While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually . . :
1~)7893S
departing from the spirit and scope of the invention as defined in the appended claims.
Claims (8)
1. An electrical device comprising housing means, electrical component means within the housing means, the electrical component means including electrode means of dielectric oxide film-forming metal, dielec-tric oxide film over the electrode means, semi-conducting material over the dielectric oxide film, electrically conductive material over the semi-conducting material, and material containing non-elastomeric silicone over the electrically conductive material.
2. The electrical device of claim 1 wherein the material containing non-elastomeric silicone includes silicone resin.
3. The electrical device of claim 2 wherein the device is a capacitor.
4. The capacitor of claim 3 wherein the electrode means is a sintered mass of dielectric oxide film-forming metal powder including tantalum powder, the semi-conducting material includes manganese dioxide, and the housing is of metal containing material.
5. The electrical device of claim 2 wherein the material containing silicone resin includes silicone type varnish.
6. A method of decreasing the change in capacitance with a change in temperature in a dielectric oxide film-forming metal capacitor contained within a housing comprising applying a material containing silicone resin to the capacitor.
7. A method of making the device of claim 1 comprising the steps of providing electrical component means, applying material containing silicone over the electrical component means and placing the electrical component means within a housing.
8. The method of claim 7 wherein the electrical component means is a solid electrolyte film forming metal capacitor and the ma-terial contains silicone resin.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US64661976A | 1976-01-05 | 1976-01-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078935A true CA1078935A (en) | 1980-06-03 |
Family
ID=24593779
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA268,774A Expired CA1078935A (en) | 1976-01-05 | 1976-12-29 | Electrical device containing a silicone resin |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1078935A (en) |
| DE (1) | DE2700331A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105304336A (en) * | 2015-11-04 | 2016-02-03 | 中国振华（集团）新云电子元器件有限责任公司 | Full-sealed tantalum capacitor |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19846936C1 (en) * | 1998-10-12 | 2000-03-30 | Siemens Matsushita Components | Tantalum electrolytic condenser for use in SMD elements has the increase in residual current under undesirable conditions prevented by inclusion of filler particles in moisture protection layer |
-
1976
- 1976-12-29 CA CA268,774A patent/CA1078935A/en not_active Expired
-
1977
- 1977-01-05 DE DE19772700331 patent/DE2700331A1/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105304336A (en) * | 2015-11-04 | 2016-02-03 | 中国振华（集团）新云电子元器件有限责任公司 | Full-sealed tantalum capacitor |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2700331A1 (en) | 1977-07-21 |
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