CA1143866A - Sinterless zinc oxide varistor devices - Google Patents
Sinterless zinc oxide varistor devicesInfo
- Publication number
- CA1143866A CA1143866A CA000330905A CA330905A CA1143866A CA 1143866 A CA1143866 A CA 1143866A CA 000330905 A CA000330905 A CA 000330905A CA 330905 A CA330905 A CA 330905A CA 1143866 A CA1143866 A CA 1143866A
- Authority
- CA
- Canada
- Prior art keywords
- varistor
- substrate
- oxide
- zinc oxide
- sinterless
- 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
Abstract
SINTERLESS ZINC OXIDE VARISTOR DEVICES
Abstract of the Disclosure Sinterless zinc oxide varistor devices are prepared in one embodiment by flame spraying premixed zinc oxide and additive metal oxide powders onto a refractory sub-strate. The coated substrate is then treated by an abrasive removal process to form a trimmable resistor.
A further embodiment comprises the use of a plasma spray process wherein carbonates and nitrates of the varistor constituents are oxidized in situ by entrainment within an oxygen gas stream and directing the plasma upon a rotating substrate. Ultra pure zinc oxide varistor devices having excellent electrical properties can be prepared in this manner.
Abstract of the Disclosure Sinterless zinc oxide varistor devices are prepared in one embodiment by flame spraying premixed zinc oxide and additive metal oxide powders onto a refractory sub-strate. The coated substrate is then treated by an abrasive removal process to form a trimmable resistor.
A further embodiment comprises the use of a plasma spray process wherein carbonates and nitrates of the varistor constituents are oxidized in situ by entrainment within an oxygen gas stream and directing the plasma upon a rotating substrate. Ultra pure zinc oxide varistor devices having excellent electrical properties can be prepared in this manner.
Description
~ 66 5D3711 SINTERLESS ~INC OXIDE ~ARISTOR DEVICES
. . .
Background o~ the Invention Zinc oxide ~aris~ors of the tY~pe used with surge arrester devices are currently prepared by batch mixing and ball milling techniques wherein the zinc oxide powder is combined with certain additive metal compounds for pressing and sintering into solid discs . After sintering the discs are then coated ~ith a layer of conductive metal to provide electrodes to the discs. Pressing and sintering the discs into pr~scribed cylindrical configura-tions requires a yood deal of preparation time and contributes to the overall varistor costsO
The electrical properties of the varistors, for example, the exponent n and resistance R must be uniform from batch to batch to ensure uniformity of electrical character-istics æmong the variou varistors. Removing -the varistors having unacceptably low exponent values causes a decrease in the material's operating eficiency since defective varistor discs quite often must be discarded. Methods for currently reclaiming rejected ~inc oxide varistor discs require that the discs be completely reprocessed including costly re-pressing and resintering operations.
The purpose of this invention is to provide means for forming inexpensive ~inc oxide varistor electrical elements from rejected varistor discs in one embodiment and for form-ing high purity zinc oxide varistor discs from high purity starting materials in another embodiment~
;;.
.. . .. .
~ ~ ~3~6 5D3717 Brief Description of the DraWings ~ IGURE 1 is a side view of a flame spray coating apparatus for use within the invention;
FIGURE 2 is a top perspective view of one embodiment of a sinterless zinc oxide varistor manufactured by the methods of the invention;
FIGURE 3 is a top perspective view of the varistor of FIGURE 2 in the fo.rm of a trimmable resistor;
FIGURE 4 is a top perspective view of a zinc oxide Yaristor fuse device;
FIGURE 5 is a front perspective view of a high purity zinc oxide varistor manufackured by a plasma spray tech-ni~ue; and FIGURE 6 is a side view of a plasma spray apparatus for manufac~uring the varistor of FIGURE 5.
Description of the Preferred Embodiment FIGURE 1 shows a flame spraying apparatus 14 of the type utilizing a high tempexature flame 15 and a special nozzle 16 wherein an oxyhydrogen gas flame is used for the purpose of directing the pOWder stream 13 onto the surface of substrate 11. The metal oxide varistor components 13' are propelled by combustible gases through pipe 19 and tubing 17 up into manifold ~J where they become heated upon further passage through nozzle 16 and flame 15. The heated powder stream 13 is caused to impinge upon a rotating -25 tubular substrate 11 such that the powder 13' within con-tainer 18 forms an oxide coating 12. The oxide coating tightly adheres to the substrate by becoming fused thereon ~ 3~ SD3717 in the deposition pxocess. ~ coated substrate 10 conkaining an oxide coating 12 is shown in FIG~RE 2 wherein the sub-strate 11 also contains a ~etal coating 20 at each end of the substrate to provide electrical access with the oxide coating. The substrate 11 comprises a refractory tubing.
The refractory matertal can compri'se a silica or alumina compound or a ceramic or porcelain material. The metal coating generally compxises alumin~m metal deposited by the same flame spray techni~ues as for the oxide coating 12. The metal coating can be applied directly on top of the oxide coating or upon the substrate contingent with the oxide materialO
FIGURE 3 contains a coated substrate 10 similar to the coated substrate of FIGURE 2 with part of the oxide layer removed b~ an abrasive grit blasting technique so that the remaining oxide 12 exhibits a continuous long filament of very thin cross section. The embodiment of FIGURE 3 comprises a trimmable non-linear resistor device having a very high resistance value ~nd containing elec-trodes at each end formed by the metal coa~ing 20.
A varistor fuse device is provided by the coated substrate 10 of FIGURE 4 wherein the oxide material 12 is deposited upon a flat substrate 8 and contains a region 9 o~ reduced thickness. The metal coating 20 at each end of the coated substrate provides electrodes to the device and the reduced thickness 9 is designed to melt and break contact between the electrodes when the power capacity of the device is exceeded. The embodiment of FIGURE 4 therefore 3~6~
combines non-linear resis~ive properties due to the operating characteristics of the oxide coating 12 with a fusible feature to protect sensitive circuit elements from conditions of ex-cess current as well as excess voltage.
S The flame spray apparatus of FIGURE 1 is particula~ly use~ul for reclaiming the zinc oxide powder ~rom rejected YaristOrs. The varistors are crushed, pulverized, and classi-fied through a 200 mesh sieve to provide pinhole free, tightly adherent coatings upon ~lame deposition.
A sinterless zinc oxide varistor 21 having exceptional electrical properties is shown in FIGURE 5 and consists o a highly pure zinc oxide disc con~aining a deposited metal coating 20 at both ends for providing electrical cOntact with the zinc oxide material. A ceramic collar 22 is provided lS around the periphery of the varistor in order to prevent varistor current from transferring in the vicinity of the periphery rathex than through the bulk cross section of the varistor. The highly purified zinc oxide composition is achieved by the vapor deposition process depicted in FIGURE
6. The highly puriied materials are obtained by in situ oxidation of the nitrates or carbonates of the constituen s.
Other materials such as oxalates, acetates and other anions of organic acids, which thermally decompose to their oxides, can also be employed. The zinc oxide precursor comprises zinc nitrate and other materials such as bismuth, titanium, magnesium and cobalt are provided by either their respective carbonates or nitrates. In order to ensure sufficient oxygen ... , .,.. ,,,. ~ .
~4~;6 to completely oxidize the carbonates and nitrates of the constituents, the materials, in powder form, are entrained within a stream.of pure oxygen. In order to energize the plasma discharge an ionizable and inert gas, such as argon, is also transported through the plasma nozzle 16 along with the powder constituents. A first tube 28 is connected with a source of highly purified oxygen gas, a second tube 2g i~
connected with a highly puri~ied ta~k of argon and a third tube 30 is connected to a containex having the mixed oxide precursors. The mixing between the oxygen and the precursor materials occurs within the manifold 25 and the mixed oxygen, argon and precursor materials transmit through nozzle 16 wherein a plasma carries the powder 13 to a rotating support 24. The powder precursor materials can be directly entrained lS within tha oxygen gas by passing the oxygen gas through the container and forcing the precursor powders through manifold 25 and nozzle 16. The varistor 21 is built up upon the rotating support 24 of the coating table assembly 23. The height and diameter of the varistor can accurately be gaged by the speed of rotation in the direction of the indicating arrow, the location of the nozzle relative to the rotating support and both the flow rate and concentration of the precursor powder. The coating table comprises the rotating support which is connected by gears or puIies to shaft 27 of motor 26 and is supported upon a base member 28. When ultrapure zinc o~i.de varistors are desired the precursor - materials can be formed from ultrapure liquid compounds ~hich :
~ 6 5D3717 react with the oxygen en-training gas to form the respective oxides insitue. The zinc oxide precursor would then be a zinc chloride solu~ion and the bismuth precursor, for example, would comprise bismuth trichloride.
When formlng ultrapure zinc oxide varistor material having exceptionally good electric:al characteristics the plasma spray technique of FIGURE 6 is preferred. When relatively ine~pensive æinc oxide varistors or varistor devices are ~o be manufactured the flame spray technique of FIGURE 1 is preferLed since the flame process does not readily lead to ultrapure materials.
One o~ the advantages of the method of the instant invention is the ability to make non-linear resistors by calcining the chemical constituents consisting of ~inc oxide and various additives without first having to sinter, the constituents., This is a valuable feature since calcining can be achieved in air by heating at relatively low tempera-tures compared to the higher sintering temperatures. In some instances partial calcining can be achieved during the actual flame spray process.
The method of the instant invention also allows varistors to be manufactured having pred~termined and carefully controlled resistance values. Zinc oxide materials having very high resistance for example can be combined with materials having low resistance values to provide any inter-mediate range of desired resistance ~o the varistor devices.
Although the methods of the invention are disclosed for ~;
~ 1~3~66 5D3717 manu~acturing zinc oxide varistors ~or surge arres~er applications this is by way of example only. The varistors manufactured by the method~ of the invention find applica-tion wherever 2inc oxide var.istors may be employed.
.' - .
. . .
Background o~ the Invention Zinc oxide ~aris~ors of the tY~pe used with surge arrester devices are currently prepared by batch mixing and ball milling techniques wherein the zinc oxide powder is combined with certain additive metal compounds for pressing and sintering into solid discs . After sintering the discs are then coated ~ith a layer of conductive metal to provide electrodes to the discs. Pressing and sintering the discs into pr~scribed cylindrical configura-tions requires a yood deal of preparation time and contributes to the overall varistor costsO
The electrical properties of the varistors, for example, the exponent n and resistance R must be uniform from batch to batch to ensure uniformity of electrical character-istics æmong the variou varistors. Removing -the varistors having unacceptably low exponent values causes a decrease in the material's operating eficiency since defective varistor discs quite often must be discarded. Methods for currently reclaiming rejected ~inc oxide varistor discs require that the discs be completely reprocessed including costly re-pressing and resintering operations.
The purpose of this invention is to provide means for forming inexpensive ~inc oxide varistor electrical elements from rejected varistor discs in one embodiment and for form-ing high purity zinc oxide varistor discs from high purity starting materials in another embodiment~
;;.
.. . .. .
~ ~ ~3~6 5D3717 Brief Description of the DraWings ~ IGURE 1 is a side view of a flame spray coating apparatus for use within the invention;
FIGURE 2 is a top perspective view of one embodiment of a sinterless zinc oxide varistor manufactured by the methods of the invention;
FIGURE 3 is a top perspective view of the varistor of FIGURE 2 in the fo.rm of a trimmable resistor;
FIGURE 4 is a top perspective view of a zinc oxide Yaristor fuse device;
FIGURE 5 is a front perspective view of a high purity zinc oxide varistor manufackured by a plasma spray tech-ni~ue; and FIGURE 6 is a side view of a plasma spray apparatus for manufac~uring the varistor of FIGURE 5.
Description of the Preferred Embodiment FIGURE 1 shows a flame spraying apparatus 14 of the type utilizing a high tempexature flame 15 and a special nozzle 16 wherein an oxyhydrogen gas flame is used for the purpose of directing the pOWder stream 13 onto the surface of substrate 11. The metal oxide varistor components 13' are propelled by combustible gases through pipe 19 and tubing 17 up into manifold ~J where they become heated upon further passage through nozzle 16 and flame 15. The heated powder stream 13 is caused to impinge upon a rotating -25 tubular substrate 11 such that the powder 13' within con-tainer 18 forms an oxide coating 12. The oxide coating tightly adheres to the substrate by becoming fused thereon ~ 3~ SD3717 in the deposition pxocess. ~ coated substrate 10 conkaining an oxide coating 12 is shown in FIG~RE 2 wherein the sub-strate 11 also contains a ~etal coating 20 at each end of the substrate to provide electrical access with the oxide coating. The substrate 11 comprises a refractory tubing.
The refractory matertal can compri'se a silica or alumina compound or a ceramic or porcelain material. The metal coating generally compxises alumin~m metal deposited by the same flame spray techni~ues as for the oxide coating 12. The metal coating can be applied directly on top of the oxide coating or upon the substrate contingent with the oxide materialO
FIGURE 3 contains a coated substrate 10 similar to the coated substrate of FIGURE 2 with part of the oxide layer removed b~ an abrasive grit blasting technique so that the remaining oxide 12 exhibits a continuous long filament of very thin cross section. The embodiment of FIGURE 3 comprises a trimmable non-linear resistor device having a very high resistance value ~nd containing elec-trodes at each end formed by the metal coa~ing 20.
A varistor fuse device is provided by the coated substrate 10 of FIGURE 4 wherein the oxide material 12 is deposited upon a flat substrate 8 and contains a region 9 o~ reduced thickness. The metal coating 20 at each end of the coated substrate provides electrodes to the device and the reduced thickness 9 is designed to melt and break contact between the electrodes when the power capacity of the device is exceeded. The embodiment of FIGURE 4 therefore 3~6~
combines non-linear resis~ive properties due to the operating characteristics of the oxide coating 12 with a fusible feature to protect sensitive circuit elements from conditions of ex-cess current as well as excess voltage.
S The flame spray apparatus of FIGURE 1 is particula~ly use~ul for reclaiming the zinc oxide powder ~rom rejected YaristOrs. The varistors are crushed, pulverized, and classi-fied through a 200 mesh sieve to provide pinhole free, tightly adherent coatings upon ~lame deposition.
A sinterless zinc oxide varistor 21 having exceptional electrical properties is shown in FIGURE 5 and consists o a highly pure zinc oxide disc con~aining a deposited metal coating 20 at both ends for providing electrical cOntact with the zinc oxide material. A ceramic collar 22 is provided lS around the periphery of the varistor in order to prevent varistor current from transferring in the vicinity of the periphery rathex than through the bulk cross section of the varistor. The highly purified zinc oxide composition is achieved by the vapor deposition process depicted in FIGURE
6. The highly puriied materials are obtained by in situ oxidation of the nitrates or carbonates of the constituen s.
Other materials such as oxalates, acetates and other anions of organic acids, which thermally decompose to their oxides, can also be employed. The zinc oxide precursor comprises zinc nitrate and other materials such as bismuth, titanium, magnesium and cobalt are provided by either their respective carbonates or nitrates. In order to ensure sufficient oxygen ... , .,.. ,,,. ~ .
~4~;6 to completely oxidize the carbonates and nitrates of the constituents, the materials, in powder form, are entrained within a stream.of pure oxygen. In order to energize the plasma discharge an ionizable and inert gas, such as argon, is also transported through the plasma nozzle 16 along with the powder constituents. A first tube 28 is connected with a source of highly purified oxygen gas, a second tube 2g i~
connected with a highly puri~ied ta~k of argon and a third tube 30 is connected to a containex having the mixed oxide precursors. The mixing between the oxygen and the precursor materials occurs within the manifold 25 and the mixed oxygen, argon and precursor materials transmit through nozzle 16 wherein a plasma carries the powder 13 to a rotating support 24. The powder precursor materials can be directly entrained lS within tha oxygen gas by passing the oxygen gas through the container and forcing the precursor powders through manifold 25 and nozzle 16. The varistor 21 is built up upon the rotating support 24 of the coating table assembly 23. The height and diameter of the varistor can accurately be gaged by the speed of rotation in the direction of the indicating arrow, the location of the nozzle relative to the rotating support and both the flow rate and concentration of the precursor powder. The coating table comprises the rotating support which is connected by gears or puIies to shaft 27 of motor 26 and is supported upon a base member 28. When ultrapure zinc o~i.de varistors are desired the precursor - materials can be formed from ultrapure liquid compounds ~hich :
~ 6 5D3717 react with the oxygen en-training gas to form the respective oxides insitue. The zinc oxide precursor would then be a zinc chloride solu~ion and the bismuth precursor, for example, would comprise bismuth trichloride.
When formlng ultrapure zinc oxide varistor material having exceptionally good electric:al characteristics the plasma spray technique of FIGURE 6 is preferred. When relatively ine~pensive æinc oxide varistors or varistor devices are ~o be manufactured the flame spray technique of FIGURE 1 is preferLed since the flame process does not readily lead to ultrapure materials.
One o~ the advantages of the method of the instant invention is the ability to make non-linear resistors by calcining the chemical constituents consisting of ~inc oxide and various additives without first having to sinter, the constituents., This is a valuable feature since calcining can be achieved in air by heating at relatively low tempera-tures compared to the higher sintering temperatures. In some instances partial calcining can be achieved during the actual flame spray process.
The method of the instant invention also allows varistors to be manufactured having pred~termined and carefully controlled resistance values. Zinc oxide materials having very high resistance for example can be combined with materials having low resistance values to provide any inter-mediate range of desired resistance ~o the varistor devices.
Although the methods of the invention are disclosed for ~;
~ 1~3~66 5D3717 manu~acturing zinc oxide varistors ~or surge arres~er applications this is by way of example only. The varistors manufactured by the method~ of the invention find applica-tion wherever 2inc oxide var.istors may be employed.
.' - .
Claims (10)
1. A method for manufacturing sinterless zinc oxide varistor devices comprising the steps of:
providing a mixture of zinc oxide powder and additive metal oxide powders;
subjecting the mixture to a high temperature flame for heating and fusing the oxides;
providing an oxygen containing gas stream for directing the oxide powders through the flame;
directing the fused oxides upon the surface of an electrically insulating aluminum oxide substrate to form the varistor material on the substrate; and providing at least one metal electrode layer on the varistor material.
providing a mixture of zinc oxide powder and additive metal oxide powders;
subjecting the mixture to a high temperature flame for heating and fusing the oxides;
providing an oxygen containing gas stream for directing the oxide powders through the flame;
directing the fused oxides upon the surface of an electrically insulating aluminum oxide substrate to form the varistor material on the substrate; and providing at least one metal electrode layer on the varistor material.
2. The method of claim 1 wherein the additive metal oxides include bismuth.
3. The method of claim 1 wherein the metal electrode comprises aluminum.
4. The method of claim 1 wherein the substrate comprises a tubular member.
5. The method of claim 1 including the step of removing a portion of the metal oxide coating to provide a trimmable non-linear resistor.
6. The method of claim 1 wherein the substrate comprises a planar surface and wherein -the metal oxide layer has a region of reduced cross section for providing a fusible varistor.
7. A method for forming high purity sinterless varistor materials comprising the steps of:
providing zinc and bismuth chloride varistor precursor materials;
8 ' entraining the chlorides in an oxygen containing gas stream;
adding an inert gas to the oxygen containing gas stream;
directing the entrained chlorides through a plasma torch for heating the chlorides to form zinc and bismuth oxide powders and fusing the powders; and directing the fused powders upon the surface of an electrically insulating aluminum oxide substrate to form a varistor body.
providing zinc and bismuth chloride varistor precursor materials;
8 ' entraining the chlorides in an oxygen containing gas stream;
adding an inert gas to the oxygen containing gas stream;
directing the entrained chlorides through a plasma torch for heating the chlorides to form zinc and bismuth oxide powders and fusing the powders; and directing the fused powders upon the surface of an electrically insulating aluminum oxide substrate to form a varistor body.
8. The method of claim 7 including the step of rotating the substrate in order to generate a cylinder of the varistor material.
9. A method of forming a sinterless zinc oxide varistor comprising the steps of :
providing a tubular insulating aluminum oxide substrate;
mixing a plurality of metal carbonates with zinc nitrates to form the varistor precursor mixture;
introducing an air stream to the precursor mixture to entrain the mixture and to form a continuous stream of airborn particles;
directing the entrained particles through a high temperature flame for fusing the particles upon the substrate;
applying a layer of aluminum at both ends of the substrate to provide a pair of electrodes; and removing part of the oxide layer to form a thin spiral of oxide material around the substrate.
providing a tubular insulating aluminum oxide substrate;
mixing a plurality of metal carbonates with zinc nitrates to form the varistor precursor mixture;
introducing an air stream to the precursor mixture to entrain the mixture and to form a continuous stream of airborn particles;
directing the entrained particles through a high temperature flame for fusing the particles upon the substrate;
applying a layer of aluminum at both ends of the substrate to provide a pair of electrodes; and removing part of the oxide layer to form a thin spiral of oxide material around the substrate.
10. A method of manufacturing sinterless zinc oxide coated substrates comprising steps of:
providing one of the group selected from, 1) a mixture of zinc oxide powder and additive metal oxide powders entrained in an oxygen containing gas stream or, 2) a mixture of powdered zinc oxide precursors and powdered additive metal oxide precursors entrained in an oxygen and insert gas containing gas stream;
subjecting the mixture to a high temperature flame;
and, directing the resultant fused oxides upon the surface of an electrically insulating aluminum oxide substrate to form a layer of varistor material on said substrate.
providing one of the group selected from, 1) a mixture of zinc oxide powder and additive metal oxide powders entrained in an oxygen containing gas stream or, 2) a mixture of powdered zinc oxide precursors and powdered additive metal oxide precursors entrained in an oxygen and insert gas containing gas stream;
subjecting the mixture to a high temperature flame;
and, directing the resultant fused oxides upon the surface of an electrically insulating aluminum oxide substrate to form a layer of varistor material on said substrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000330905A CA1143866A (en) | 1979-06-29 | 1979-06-29 | Sinterless zinc oxide varistor devices |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000330905A CA1143866A (en) | 1979-06-29 | 1979-06-29 | Sinterless zinc oxide varistor devices |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143866A true CA1143866A (en) | 1983-03-29 |
Family
ID=4114586
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000330905A Expired CA1143866A (en) | 1979-06-29 | 1979-06-29 | Sinterless zinc oxide varistor devices |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1143866A (en) |
-
1979
- 1979-06-29 CA CA000330905A patent/CA1143866A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US1922221A (en) | Resistance material | |
| JPH0252409B2 (en) | ||
| WO2014174984A1 (en) | Silver-bismuth powder, conductive paste and conductive film | |
| US3252831A (en) | Electrical resistor and method of producing the same | |
| US4198443A (en) | Sinterless zinc oxide varistor devices | |
| KR100204255B1 (en) | Chip type ceramic element and method of manufature thereof | |
| US5964918A (en) | Process for preparing metal powder | |
| EP2642492A1 (en) | Conductive fine powder, conductive paste and electronic component | |
| JP6804286B2 (en) | Silver alloy powder and its manufacturing method | |
| CA1143866A (en) | Sinterless zinc oxide varistor devices | |
| CN1051862C (en) | Paste for high temperature sintering | |
| US4349496A (en) | Method for fabricating free-standing thick-film varistors | |
| EP0834369B1 (en) | Process for preparing metal powder | |
| JPH11186006A (en) | Nonlinear resistor | |
| KR100201160B1 (en) | Resistance material composition, resistive paste, and resistor | |
| WO2021187353A1 (en) | Zinc oxide element | |
| EP1993108B1 (en) | Material composition having a core-shell microstructure used for a varisator | |
| KR920005155B1 (en) | Zno-varistor making method | |
| JPH0541307A (en) | Manufacturing method of potential nonlinear resistor | |
| CN113782251A (en) | Electrode paste, electrode thick film and preparation method thereof | |
| JP2695639B2 (en) | Method of manufacturing voltage non-linear resistor | |
| JP2634838B2 (en) | Method of manufacturing voltage non-linear resistor | |
| JP2002289409A (en) | Ceramic element, its manufacturing method, and lightening arrestor using the element | |
| JP2000182808A (en) | Nonlinear resistance member | |
| JPH01222404A (en) | Manufacture of voltage dependent non-linear resistor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |