EP0351004B1 - Non-linear voltage-dependent resistor - Google Patents
Non-linear voltage-dependent resistor Download PDFInfo
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- EP0351004B1 EP0351004B1 EP89201797A EP89201797A EP0351004B1 EP 0351004 B1 EP0351004 B1 EP 0351004B1 EP 89201797 A EP89201797 A EP 89201797A EP 89201797 A EP89201797 A EP 89201797A EP 0351004 B1 EP0351004 B1 EP 0351004B1
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- Prior art keywords
- layer
- resistance material
- zinc oxide
- dependent resistor
- doped
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/105—Varistor cores
- H01C7/108—Metal oxide
- H01C7/112—ZnO type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/30—Apparatus or processes specially adapted for manufacturing resistors adapted for baking
Definitions
- the invention relates to a nonlinear voltage-dependent resistor with a ceramic sintered body made of resistance material based on at least one alkaline earth metal, rare earth metal and iron group metal present as an oxide and with at least one of the metals from the group aluminum, gallium and / or indium doped zinc oxide and with electrodes attached to the opposing main surfaces of the sintered body.
- the invention further relates to a method for producing such a resistor.
- Varistors are used in many ways to protect electrical systems, devices and expensive components against overvoltages and voltage peaks.
- the operating voltages of varistors are in the order of 3 V to 3000 V.
- low-voltage varistors are increasingly required, whose response voltage U A is below approximately 30 V and the highest possible Have values for the non-linearity coefficient ⁇ .
- Varistors based on zinc oxide have relatively good non-linearity coefficients ⁇ in the range from 20 to 60.
- varistors based on zinc oxide with about 3 to 10 mol% of metal oxide additives such as Mg0, Ca0, La203, Pr203, Cr203, Co304 as doping.
- metal oxide additives such as Mg0, Ca0, La203, Pr203, Cr203, Co304 as doping.
- the interior of the polycrystalline Zn0 grains becomes low-resistance and high-resistance barriers form at the grain boundaries.
- the contact resistance between two grains is relatively high at voltages ⁇ 3.2 V, but decreases at voltages> 3.2 V with increasing voltage by several orders of magnitude.
- DE-OS 33 23 579 discloses varistors with sintered bodies based on zinc oxide doped with rare earth metal, cobalt, boron, alkaline earth metal and with at least one of the metals aluminum, gallium and / or indium.
- DE-PS 33 24 732 discloses varistors with sintered bodies based on rare earth metal, cobalt, alkaline earth metal, alkali metal, chromium, boron and zinc oxide doped with at least one of the metals aluminum, gallium and / or indium. Both the varistors known from DE-OS 33 23 579 and from DE-PS 33 24 732 only show useful values for the non-linearity coefficient ⁇ at response voltages U A above 100 V with ⁇ > 30.
- the usual way of producing low-voltage varistors based on doped zinc oxide is to use coarse-grained resistance material.
- Sintered bodies made of doped zinc oxide with a relatively coarse grain structure with grain sizes> 100 ⁇ m are obtained, for example, if material of the system Zn0-Bi203 is doped with about 0.3 to about 1 mol% Ti02.
- Ti02 forms a low-melting eutectic with Bi203 during sintering, which promotes the grain growth of polycrystalline Zn0.
- a disadvantage, however, is that relatively long, rod-shaped ZnO crystallites often form, which make it very difficult to control the microstructure of the ceramic structure.
- the invention has for its object to provide varistors and in particular low-voltage varistors that reproducibly low values for the response voltage U A in the range 30 V in addition to values for the non-linearity coefficient ⁇ > 30 and show methods for their production.
- the sintered body has a multilayer structure with at least one layer sequence consisting of a layer of resistance material on a carrier layer based on zinc oxide, which has a higher electrical conductivity than the resistance material.
- a cover layer based on zinc oxide, which has a higher electrical conductivity than the resistor material, is applied to the layer of resistor material.
- the invention is based on the knowledge that the response voltage U A in the case of varistors based on zinc oxide with dopants forming high-resistance grain boundaries is essentially determined by the number of grain boundaries that the current I must pass between the electrodes. If relatively thin layers of resistance material are present, the number of grain boundaries can be kept within relatively narrow limits.
- the invention is also the based on further knowledge that, in addition, a particularly uniform grain growth can be achieved in a relatively thin layer of resistance material if the layer of resistance material is covered in as large a surface area as possible by layers of a material which has a grain growth similar to that of the resistance material during the sintering process which, however, does not affect the resistance properties of the finished varistor.
- Nonlinear voltage-dependent resistors with average response voltages U A ⁇ 20 V are already obtained if the varistor has only one layer sequence made of a layer of resistance material on a carrier layer. If a cover layer is also provided, the layer of resistance material is covered in an even larger surface area by material with a similar sintering behavior, but with higher electrical conductivity, varistors with reproducible values for the response voltage U A ⁇ 10 V with improved values for the non-linearity coefficient ⁇ receive.
- the resistor material consists of 0.01 to 3.0 atom% praseodymium, 1.0 to 3.0 atom% cobalt, calcium to 1.0 atom% and 10 to 100 ppm aluminum doped zinc oxide, preferably from zinc atom doped with 0.5 atom% praseodymium, 2 atom% cobalt, 0.5 atom% calcium and 60 ppm aluminum.
- the material for the carrier layer (s) and for the cover layer is doped with aluminum; the material for the backing layer (s) and the covering layer is preferred doped with 30 to 100 ppm aluminum, in particular with 60 ppm aluminum.
- the electrodes are applied as layer electrodes without wire connections, preferably made predominantly of silver. This enables the varistors according to the invention to be used as SMD components.
- the layer (s) made of resistance material have a thickness in the range from 65 to 250 ⁇ m and the carrier layer (s) and the cover layer each have a thickness in the range from 250 to 600 ⁇ m .
- a method for producing a nonlinear voltage-dependent resistor with a ceramic sintered body based on zinc oxide as the resistance material which contains at least one alkaline earth metal, rare earth metal and iron group metal as well as at least one of the metals from the group aluminum, gallium and / or indium is endowed and with electrodes attached to the opposite main surfaces of the sintered body is characterized in that a multilayer sintered body is produced with at least one layer sequence consisting of a layer of resistance material on a carrier layer based on zinc oxide, which has a higher electrical conductivity than the resistance material.
- dry powder mixtures of the resistance material and the material for the carrier layer (s) and the cover layer are produced and these powder mixtures are compressed and deformed in accordance with the desired layer sequence and the desired layer thickness under pressure in such a way that that the powder mixtures are individually compacted one after the other in accordance with the layers to be produced and deformed in the process.
- the layers of the powder mixtures are preferably compressed at a pressure in the range from 8.107 to 1.8.108 Pa. It is advantageous to vary the pressure for pressing the individual layers of powder mixtures from layer to layer in such a way that the carrier layer is compressed at the highest pressure, the layer of resistance material is then compressed at a lower pressure, and the cover layer is compressed again when the pressure is reduced again. In this way it is ensured that there are relatively sharply delimited transitions between the individual layer layers, that is to say that material of the subsequent layer (s) is not pressed into the layer below, forming an undesirably deep boundary layer.
- the layer structure of the varistors according to the invention can of course also be produced by means of other manufacturing processes. E.g. it is also possible to use liquid slurries of the layer materials which are cast or layer structures can be produced from higher-viscosity masses by rolling or extrusion.
- the green shaped bodies pressed from the powder mixtures are sintered in air at a temperature in the range from 1260 to 1300 ° C. at a heating rate of ⁇ 10 ° C./min, the sintering of the shaped bodies preferably being carried out in this way is that the maximum sintering temperature is maintained for a period of 0 to 240 min before the cooling process is initiated.
- the level of the sintering temperature and also the duration of the maximum sintering temperature (holding time at maximum temperature) influence the grain growth in the layers in the sintered body and thus the values for the response voltage U A.
- FIGS. 1a and 1b each show a multi-layer varistor 1 with a layer 3 made of resistance material and a carrier layer 5 (FIG. 1a) and a cover layer 7 (FIG. 1b) and metal layer electrodes 9, 11 made of a silver-based contact material.
- the varistors according to FIGS. 1a and 1b represent only examples of several possible embodiments.
- Low-voltage varistors with good electrical properties can also be made from one Layer sequence made up of a multiplicity of layers 3 of resistance material, each on a carrier layer 5 and with a cover layer 7; the electrodes 9, 11 are then applied to the lower surface of the lowermost carrier layer 5 and to the upper surface of the cover layer 7 (compare principle in FIG. 1b).
- Zinc oxide was doped with 0.5 atom% praseodymium, 2 atom% cobalt, 0.5 atom% calcium and 60 ppm aluminum as the resistance material (designated IV in the tables below).
- aqueous solution 0.023 g Al (N03) 3.9H20 in a ball mill. The slip is then dried at a temperature of 100 ° C.
- Zinc oxide was doped with 60 ppm aluminum as the material for the carrier layer (s) 5 and the cover layer 7 (referred to as material A in the tables below).
- material A the material for the carrier layer (s) 5 and the cover layer 7
- 81.38 g of Zn0 are mixed with an aqueous solution of 0.023 g of Al (N03) 3.9H20 in a ball mill.
- the slip is then dried at a temperature of 100 ° C.
- Multi-layer varistors were manufactured as follows: The material A and the resistance material IV are combined with one another and sintered together, as shown in the schematic representations of FIGS. 1a and 1b. A summary of the combinations carried out is shown in Table 1 below.
- the combination of carrier layer / cover layer and layer of resistance material was carried out in the following way: 0.15 g of powder of material A (prepared according to the examples given above) were placed in a cylindrical steel die with a diameter of 9 mm under pressure mechanically compressed from 1.8.108 Pa.
- the resistance material (material IV) (produced according to the example given above) was then coated in amounts of 0.025 g to 0.1 g onto the pre-compressed substrate and pressed together with this under a pressure of 1.3.108 Pa.
- the pressed green moldings were then sintered in air at temperatures in the range from 1260 to 1300 ° C and with holding times of the maximum temperature in the range from 0 to 120 min at a heating rate of ⁇ 10 ° C / min.
- Table 2 The results of the electrical measurements are shown in Table 2 below.
- the values for the layer thickness given here refer to the resistance layer.
- Table 1 Sample No. Carrier layer / top layer Quantity Mat.
- A Resistance layer quantity Mat. IV
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Description
Die Erfindung betrifft einen nichtlinearen spannungsabhängigen Widerstand mit einem keramischen Sinterkörper aus Widerstandsmaterial auf Basis von mit mindestens je einem als Oxid vorliegenden Erdalkalimetall, Seltenerdmetall und Metall der Eisengruppe sowie mit mindestens einem der Metalle aus der Gruppe Aluminium, Gallium und/oder Indium dotiertem Zinkoxid und mit auf den einander gegenüberliegenden Hauptflächen des Sinterkörpers angebrachten Elektroden.
Die Erfindung bezieht sich weiter auf ein Verfahren zur Herstellung eines derartigen Widerstandes.The invention relates to a nonlinear voltage-dependent resistor with a ceramic sintered body made of resistance material based on at least one alkaline earth metal, rare earth metal and iron group metal present as an oxide and with at least one of the metals from the group aluminum, gallium and / or indium doped zinc oxide and with electrodes attached to the opposing main surfaces of the sintered body.
The invention further relates to a method for producing such a resistor.
Nichtlineare spannungsabhängige Widerstände (im folgenden auch als Varistoren bezeichnet) sind Widerstände, deren elektrischer Widerstand bei konstanter Temperatur oberhalb einer Ansprechspannung UA mit steigender Spannung sehr stark abnimmt. Dieses Verhalten kann durch die folgende Formel näherungsweise beschrieben werden:
worin bedeuten:
- I =
- Strom durch den Varistor
- V =
- Spannungsabfall am Varistor
- C =
- geometrieabhängige Konstante; sie gibt das Verhältnis Spannung an; in praktischen Fällen kann
Strom ¹/α
dieses Verhältnis einen Wert zwischen 15 und einigen 1000 annehmen. - α =
- Stromindex, Nichtlinearitätsfaktor oder Regelfaktor; er ist materialabhängig und ist ein Maß für die Steilheit der Strom-Spannungs-Kennlinie; typische Werte liegen im Bereich von 30 bis 80.
in which mean:
- I =
- Current through the varistor
- V =
- Voltage drop at the varistor
- C =
- geometry-dependent constant; it indicates the relationship tension ; in practical cases
Current ¹ / α
this ratio has a value between 15 and several 1000. - α =
- Current index, non-linearity factor or control factor; it depends on the material and is a measure of the steepness of the current-voltage characteristic; typical values are in the range from 30 to 80.
Varistoren werden vielseitig eingesetzt zum Schutz von elektrischen Anlagen, Geräten und teuren Bauelementen gegen Überspannungen und Spannungspitzen. Die Betriebsspannungen von Varistoren liegen in der Größenordnung von 3 V bis 3000 V. Zum Schutz von empfindlichen elektronischen Bauelementen, wie integrierte Schaltungen, Dioden oder Transistoren, werden in zunehmendem Umfang Niederspannungsvaristoren benötigt, deren Ansprechspannung UA unter etwa 30 V liegt und die möglichst hohe Werte für den Nichtlinearitätskoeffizienten α aufweisen.
Je größer der Wert für den Nichtlinearitätskoeffizienten α ist, desto besser ist die Wirkung als Überspannungsbegrenzer und um so geringer ist die Leistungsaufnahme des Varistors. Varistoren auf Basis von Zinkoxid weisen relativ gute Nichtlinearitätskoeffizienten α im Bereich von 20 bis 60 auf.Varistors are used in many ways to protect electrical systems, devices and expensive components against overvoltages and voltage peaks. The operating voltages of varistors are in the order of 3 V to 3000 V. To protect sensitive electronic components, such as integrated circuits, diodes or transistors, low-voltage varistors are increasingly required, whose response voltage U A is below approximately 30 V and the highest possible Have values for the non-linearity coefficient α.
The larger the value for the non-linearity coefficient α, the better the effect as a surge limiter and the lower the power consumption of the varistor. Varistors based on zinc oxide have relatively good non-linearity coefficients α in the range from 20 to 60.
Bekannt sind (z.B. aus DE-PS 29 52 884 oder Jap.J.Appl. Phys. 16 (1977), Seiten 1361 bis 1368) Varistoren auf Zinkoxid-Basis mit etwa 3 bis 10 Mol.% Metalloxidzusätzen wie z.B. Mg0, Ca0, La₂0₃, Pr₂0₃, Cr₂0₃, Co₃0₄ als Dotierung. Als Folge der Dotierung wird das Innere der polykristallinen Zn0-Körner niederohmig und an den Korngrenzen bilden sich hochohmige Barrieren aus. Der Übergangswiderstand zwischen zwei Körnern ist bei Spannungen < 3,2 V relativ hoch, nimmt jedoch bei Spannungen > 3,2 V mit zunehmender Spannung um mehrere Größenordnungen ab.Are known (for example from DE-PS 29 52 884 or Jap.J.Appl. Phys. 16 (1977), pages 1361 to 1368) varistors based on zinc oxide with about 3 to 10 mol% of metal oxide additives such as Mg0, Ca0, La₂0₃, Pr₂0₃, Cr₂0₃, Co₃0₄ as doping. As a result of the doping, the interior of the polycrystalline Zn0 grains becomes low-resistance and high-resistance barriers form at the grain boundaries. The contact resistance between two grains is relatively high at voltages <3.2 V, but decreases at voltages> 3.2 V with increasing voltage by several orders of magnitude.
Aus DE-OS 33 23 579 sind Varistoren mit Sinterkörpern auf Basis von mit Seltenerdmetall, Kobalt, Bor, Erdalkalimetall und mit mindestens einem der Metalle Aluminium, Gallium und/oder Indium dotiertem Zinkoxid bekannt. Aus DE-PS 33 24 732 sind Varistoren mit Sinterkörpern auf Basis von mit Seltenerdmetall, Kobalt, Erdalkalimetall, Alkalimetall, Chrom, Bor und mit mindestens einem der Metalle Aluminium, Gallium und/oder Indium dotiertem Zinkoxid bekannt.
Sowohl die aus DE-OS 33 23 579 als auch die aus DE-PS 33 24 732 bekannten Varistoren zeigen erst bei Ansprechspannungen UA über 100 V mit α > 30 brauchbare Werte für den Nichtlinearitätskoeffizienten α. Bei Ansprechspannungen UA unter 100 V liegen die Werte für α mit dem Bereich von 7 bis 22 zu niedrig hinsichtlich effektiver Überspannungsbegrenzung und Leistungsaufnahme der Varistoren. Überdies hat eine Bor-Dotierung Flußmittelwirkung und führt zur Ausbildung von flüssigen Phasen im Sinterkörper während des Sinterprozesses, was unerwünscht ist, wenn Diffusionsprozesse während des Sinterns vermieden werden müssen.DE-OS 33 23 579 discloses varistors with sintered bodies based on zinc oxide doped with rare earth metal, cobalt, boron, alkaline earth metal and with at least one of the metals aluminum, gallium and / or indium. DE-PS 33 24 732 discloses varistors with sintered bodies based on rare earth metal, cobalt, alkaline earth metal, alkali metal, chromium, boron and zinc oxide doped with at least one of the metals aluminum, gallium and / or indium.
Both the varistors known from DE-OS 33 23 579 and from DE-PS 33 24 732 only show useful values for the non-linearity coefficient α at response voltages U A above 100 V with α> 30. At response voltages U A below 100 V, the values for α with the range from 7 to 22 are too low with regard to effective overvoltage limitation and power consumption of the varistors. In addition, boron doping has a flux effect and leads to the formation of liquid phases in the sintered body during the sintering process, which is undesirable if diffusion processes have to be avoided during sintering.
Der bisher übliche Weg zur Herstellung von Niederspannungsvaristoren auf Basis von dotiertem Zinkoxid ist, grobkörniges Widerstandsmaterial einzusetzen.
Sinterkörper aus dotiertem Zinkoxid mit einem relativ groben Korngefüge mit Korngrößen > 100 µm werden z.B. erhalten, wenn Material des Systems Zn0-Bi₂0₃ mit etwa 0,3 bis etwa 1 Mol% Ti0₂ dotiert wird. Ti0₂ bildet mit Bi₂0₃ beim Sintern ein niedrigschmelzendes Eutektikum, das das Kornwachstum von polykristallinem Zn0 fördert. Nachteilig ist jedoch, daß sich hierbei häufig relativ lange, stabförmige Zn0-Kristallite ausbilden, die eine Kontrolle der Mikrostruktur des keramischen Gefüges sehr erschweren.The usual way of producing low-voltage varistors based on doped zinc oxide is to use coarse-grained resistance material.
Sintered bodies made of doped zinc oxide with a relatively coarse grain structure with grain sizes> 100 µm are obtained, for example, if material of the system Zn0-Bi₂0₃ is doped with about 0.3 to about 1 mol% Ti0₂. Ti0₂ forms a low-melting eutectic with Bi₂0₃ during sintering, which promotes the grain growth of polycrystalline Zn0. A disadvantage, however, is that relatively long, rod-shaped ZnO crystallites often form, which make it very difficult to control the microstructure of the ceramic structure.
Die stets sehr breiten und fast immer inhomogenen Kornverteilungen in einem mit Ti0₂-dotierten Widerstandsmaterial aus dem System Zn0-Bi₂0₃ machen die Herstellung von Varistoren mit reproduzierbaren Ansprechspannungen UA < 30 V nahezu unmöglich.The always very wide and almost always inhomogeneous grain distributions in a Ti0₂-doped resistance material from the Zn0-Bi₂0₃ system make the production of varistors with reproducible response voltages U A <30 V almost impossible.
Der Erfindung liegt die Aufgabe zugrunde, Varistoren und insbesondere Niederspannungsvaristoren zu schaffen, die reproduzierbar niedrige Werte für die Ansprechspannung UA im Bereich 
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß der Sinterkörper mehrschichtig aufgebaut ist mit mindestens einer Schichtenfolge bestehend aus einer Schicht aus Widerstandsmaterial auf einer Trägerschicht auf Basis von Zinkoxid, das eine gegenüber dem Widerstandsmaterial höhere elektrische Leitfähigkeit hat.This object is achieved in that the sintered body has a multilayer structure with at least one layer sequence consisting of a layer of resistance material on a carrier layer based on zinc oxide, which has a higher electrical conductivity than the resistance material.
Nach einer bevorzugten Ausbildung des nichtlinearen spannungsabhängigen Widerstandes gemäß der Erfindung ist auf der Schicht aus Widerstandsmaterial eine Deckschicht auf Basis von Zinkoxid, das eine gegenüber dem Widerstandsmaterial höhere elektrische Leitfähigkeit hat, angebracht.According to a preferred embodiment of the nonlinear voltage-dependent resistor according to the invention, a cover layer based on zinc oxide, which has a higher electrical conductivity than the resistor material, is applied to the layer of resistor material.
Der Erfindung liegt die Erkenntnis zugrunde, daß die Ansprechspannung UA bei Varistoren auf Basis von Zinkoxid mit hochohmige Korngrenzen bildenden Dotierungen im wesentlichen durch die Zahl der Korngrenzen, die der Strom I zwischen die Elektroden passieren muß, bestimmt wird. Wenn relativ dünne Schichten aus Widerstandsmaterial vorliegen, kann die Zahl der Korngrenzen in relativ engen Grenzen gehalten werden. Der Erfindung liegt außerdem die weitere Erkenntnis zugrunde, daß darüberhinaus ein besonders gleichmäßiges Kornwachstum in einer relativ dünnen Schicht aus Widerstandsmaterial erreicht werden kann, wenn die Schicht aus Widerstandsmaterial in einem möglichst großen Oberflächenbereich abgedeckt ist von Schichten aus einem Material, das beim Sinterprozeß ein ähnliches Kornwachstum aufweist, wie das Widerstandsmaterial, das jedoch die Widerstandseigenschaften des fertigen Varistors nicht beeinflußt. Nichtlineare spannungsabhängige Widerstände mit mittleren Ansprechspannungen UA ≈ 20 V werden bereits erhalten, wenn der Varistor nur eine Schichtenfolge aus einer Schicht aus Widerstandsmaterial auf einer Trägerschicht aufweist. Wird außerdem noch eine Deckschicht vorgesehen, wird die Schicht aus Widerstandsmaterial also in einem noch größeren Oberflächenbereich von Material ähnlichen Sinterverhaltens, jedoch höherer elektrischer Leitfähigkeit abgedeckt, werden Varistoren mit reproduzierbaren Werten für die Ansprechspannung UA ≦ 10 V bei noch verbesserten Werten für den Nichtlinearitätskoeffizienten α erhalten.The invention is based on the knowledge that the response voltage U A in the case of varistors based on zinc oxide with dopants forming high-resistance grain boundaries is essentially determined by the number of grain boundaries that the current I must pass between the electrodes. If relatively thin layers of resistance material are present, the number of grain boundaries can be kept within relatively narrow limits. The invention is also the based on further knowledge that, in addition, a particularly uniform grain growth can be achieved in a relatively thin layer of resistance material if the layer of resistance material is covered in as large a surface area as possible by layers of a material which has a grain growth similar to that of the resistance material during the sintering process which, however, does not affect the resistance properties of the finished varistor. Nonlinear voltage-dependent resistors with average response voltages U A ≈ 20 V are already obtained if the varistor has only one layer sequence made of a layer of resistance material on a carrier layer. If a cover layer is also provided, the layer of resistance material is covered in an even larger surface area by material with a similar sintering behavior, but with higher electrical conductivity, varistors with reproducible values for the response voltage U A ≦ 10 V with improved values for the non-linearity coefficient α receive.
Nach vorteilhaften Ausgestaltungen des nichtlinearen spannungsabhängigen Widerstandes gemäß der Erfindung besteht das Widerstandsmaterial aus mit 0,01 bis 3,0 Atom% Praseodym, 1,0 bis 3,0 Atom% Kobalt, Calcium bis 1,0 Atom% und 10 bis 100 ppm Aluminium dotiertem Zinkoxid, vorzugsweise aus mit 0,5 Atom% Praseodym, 2 Atom% Kobalt, 0,5 Atom% Calcium und 60 ppm Aluminium dotiertem Zinkoxid.According to advantageous embodiments of the non-linear voltage-dependent resistor according to the invention, the resistor material consists of 0.01 to 3.0 atom% praseodymium, 1.0 to 3.0 atom% cobalt, calcium to 1.0 atom% and 10 to 100 ppm aluminum doped zinc oxide, preferably from zinc atom doped with 0.5 atom% praseodymium, 2 atom% cobalt, 0.5 atom% calcium and 60 ppm aluminum.
Nach weiteren vorteilhaften Ausbildungen des nichtlinearen spannungsabhängigen Widerstandes gemäß der Erfindung ist das Material für die Trägerschicht(en) und für die Deckschicht mit Aluminium dotiert; vorzugsweise ist das Material für die Trägerschicht(en) und die Deckschicht mit 30 bis 100 ppm Aluminium, insbesondere mit 60 ppm Aluminium dotiert. Hierdurch wird dem Material für die Trägerschicht(en) und für die Deckschicht eine gegenüber dem Widerstandsmaterial höhere elektrische Leitfähigkeit erteilt und aufgrund des sehr ähnlichen Hauptbestandteils des Materials für die Widerstandsschicht bzw. für die Trägerschicht(en) und die Deckschicht (Zinkoxid) wird in allen Schichten ein Korngefüge mit Körnern gleicher Größenordnung erreicht.According to further advantageous developments of the nonlinear voltage-dependent resistor according to the invention, the material for the carrier layer (s) and for the cover layer is doped with aluminum; the material for the backing layer (s) and the covering layer is preferred doped with 30 to 100 ppm aluminum, in particular with 60 ppm aluminum. This gives the material for the support layer (s) and for the cover layer a higher electrical conductivity than the resistance material and due to the very similar main constituent of the material for the resistance layer or for the support layer (s) and the cover layer (zinc oxide) in all Layers a grain structure with grains of the same order of magnitude is achieved.
Nach weiteren vorteilhaften Ausgestaltungen des nichtlinearen spannungsabhängigen Widerstandes gemäß der Erfindung sind die Elektroden als Schichtelektroden ohne Drahtanschlüsse, vorzugsweise aus überwiegend Silber, angebracht. Dies ermöglicht einen Einsatz der erfindungsgemäßen Varistoren als SMD-Bauelemente.According to further advantageous configurations of the nonlinear voltage-dependent resistor according to the invention, the electrodes are applied as layer electrodes without wire connections, preferably made predominantly of silver. This enables the varistors according to the invention to be used as SMD components.
Nach weiteren vorteilhaften Ausbildungen des nichtlinearen spannungsabhängigen Widerstandes gemäß der Erfindung hat(haben) die Schicht(en) aus Widerstandsmaterial eine Dicke im Bereich von 65 bis 250 µm und die Trägerschicht(en) und die Deckschicht jeweils eine Dicke im Bereich von 250 bis 600 µm.
Hieraus ergibt sich der Vorteil, daß Varistoren relativ kleiner Abmessungen gefertigt werden können, was in bezug auf die fortschreitende Mikrominiaturisierung von elektronischen Schaltungen nicht ohne Bedeutung ist.According to further advantageous embodiments of the nonlinear voltage-dependent resistor according to the invention, the layer (s) made of resistance material have a thickness in the range from 65 to 250 μm and the carrier layer (s) and the cover layer each have a thickness in the range from 250 to 600 μm .
This results in the advantage that varistors of relatively small dimensions can be produced, which is not without significance with regard to the progressive microminiaturization of electronic circuits.
Ein Verfahren zur Herstellung eines nichtlinearen spannungsabhängigen Widerstandes mit einem keramischen Sinterkörper auf Basis von Zinkoxid als Widerstandsmaterial, das mit mindestens je einem als Oxid vorliegenden Erdalkalimetall, Seltenerdmetall und Metall der Eisengruppe sowie mit mindestens einem der Metalle aus der Gruppe Aluminium, Gallium und/oder Indium dotiert ist und mit auf den einander gegenüberliegenden Hauptflächen des Sinterkörpers angebrachten Elektroden ist dadurch gekennzeichnet, daß ein mehrschichtiger Sinterkörper hergestellt wird mit mindestens einer Schichtenfolge bestehend aus einer Schicht aus Widerstandsmaterial auf einer Trägerschicht auf Basis von Zinkoxid, das eine gegenüber dem Widerstandsmaterial höhere elektrische Leitfähigkeit hat.A method for producing a nonlinear voltage-dependent resistor with a ceramic sintered body based on zinc oxide as the resistance material, which contains at least one alkaline earth metal, rare earth metal and iron group metal as well as at least one of the metals from the group aluminum, gallium and / or indium is endowed and with electrodes attached to the opposite main surfaces of the sintered body is characterized in that a multilayer sintered body is produced with at least one layer sequence consisting of a layer of resistance material on a carrier layer based on zinc oxide, which has a higher electrical conductivity than the resistance material.
Nach einer vorteilhaften Weiterbildung des Verfahrens gemäß der Erfindung werden trockene Pulvermischungen des Widerstandsmaterials und des Materials für die Trägerschicht(en) und die Deckschicht hergestellt und diese Pulvermischungen werden entsprechend der gewünschten Schichtenfolge und der gewünschten Schichtdicke in einer Matrize unter Druck verdichtet und verformt, derart, daß die Pulvermischungen einzeln jeweils lagenweise entsprechend den herzustellenden Schichten nacheinander verdichtet und dabei verformt werden.According to an advantageous further development of the method according to the invention, dry powder mixtures of the resistance material and the material for the carrier layer (s) and the cover layer are produced and these powder mixtures are compressed and deformed in accordance with the desired layer sequence and the desired layer thickness under pressure in such a way that that the powder mixtures are individually compacted one after the other in accordance with the layers to be produced and deformed in the process.
Vorzugsweise werden die Lagen aus den Pulvermischungen bei einem Druck im Bereich von 8.10⁷ bis 1,8.10⁸ Pa verdichtet. Es ist vorteilhaft, den Druck zum Verpressen der einzelnen Lagen aus Pulvermischungen von Lage zu Lage zu variieren, derart, daß die Trägerschicht bei höchstem Druck, die Schicht aus Widerstandsmaterial anschließend bei niedrigerem Druck und die Deckschicht bei nochmals erniedrigtem Druck verdichtet und dabei verformt werden. Auf diese Weise wird sichergestellt, daß sich relativ scharf begrenzte Übergänge zwischen den einzelnen Schichtlagen ergeben, daß also nicht Material der nachfolgenden Schicht(en) in die darunterliegende Schicht unter Ausbildung einer unerwünscht tiefen Grenzschicht eingepreßt wird.The layers of the powder mixtures are preferably compressed at a pressure in the range from 8.10⁷ to 1.8.10⁸ Pa. It is advantageous to vary the pressure for pressing the individual layers of powder mixtures from layer to layer in such a way that the carrier layer is compressed at the highest pressure, the layer of resistance material is then compressed at a lower pressure, and the cover layer is compressed again when the pressure is reduced again. In this way it is ensured that there are relatively sharply delimited transitions between the individual layer layers, that is to say that material of the subsequent layer (s) is not pressed into the layer below, forming an undesirably deep boundary layer.
Die Schichtstruktur der erfindungsgemäßen Varistoren kann selbstverständlich auch mittels anderer Fertigungsprozesse hergestellt werden. Z.B. sind auch flüssige Schlicker der Schichtmaterialien einsetzbar, die vergossen werden oder es können aus höherviskosen Massen Schichtstrukturen durch Walzen oder Strangpressen hergestellt werden.The layer structure of the varistors according to the invention can of course also be produced by means of other manufacturing processes. E.g. it is also possible to use liquid slurries of the layer materials which are cast or layer structures can be produced from higher-viscosity masses by rolling or extrusion.
Nach weiteren vorteilhaften Ausgestaltungen des Verfahrens nach der Erfindung werden die aus den Pulvermischungen verpreßten grünen Formkörper bei einer Temperatur im Bereich von 1260 bis 1300 °C an Luft bei einer Aufheizgeschwindigkeit von ≈ 10 °C/min gesintert, wobei die Sinterung der Formkörper vorzugsweise so geführt wird, daß die maximale Sintertemperatur über eine Dauer von 0 bis 240 min gehalten wird, ehe der Abkühlungsprozeß eingeleitet wird. Die Höhe der Sintertemperatur und auch die Dauer der maximalen Sintertemperatur (Haltezeit bei Maximaltemperatur) beeinflussen das Kornwachstum in den Schichten im Sinterkörper und damit die Werte für die Ansprechspannung UA.According to further advantageous refinements of the method according to the invention, the green shaped bodies pressed from the powder mixtures are sintered in air at a temperature in the range from 1260 to 1300 ° C. at a heating rate of ≈ 10 ° C./min, the sintering of the shaped bodies preferably being carried out in this way is that the maximum sintering temperature is maintained for a period of 0 to 240 min before the cooling process is initiated. The level of the sintering temperature and also the duration of the maximum sintering temperature (holding time at maximum temperature) influence the grain growth in the layers in the sintered body and thus the values for the response voltage U A.
Anhand der Zeichnung werden Ausführungsbeispiele der Erfindung beschrieben und ihre Wirkungsweise erläutert.
Es zeigen:
- Fig. 1a,1b
- Mehrschichtige Varistoren gemäß der Erfindung im Schnitt.
Show it:
- 1a, 1b
- Multi-layer varistors according to the invention in section.
Die Figuren 1a und 1b zeigen jeweils einen mehrschichtigen Varistor 1 mit einer Schicht 3 aus Widerstandsmaterial und einer Trägerschicht 5 (Figur 1a) sowie einer Deckschicht 7 (Figur 1b) und Metallschicht-Elektroden 9, 11 aus einem Kontaktwerkstoff auf Silber-Basis. Die Varistoren gemäß den Figuren 1a und 1b stellen nur Beispiele von mehreren möglichen Ausführungsformen dar. Niederspannungsvaristoren mit guten elektrischen Eigenschaften können auch aus einer Schichtenfolge aus einer Vielzahl von Schichten 3 aus Widerstandsmaterial auf jeweils einer Trägerschicht 5 und mit einer Deckschicht 7 aufgebaut sein; die Elektroden 9,11 werden dann auf der unteren Fläche der untersten Trägerschicht 5 und auf der oberen Fläche der Deckschicht 7 angebracht (vergleiche Prinzip Figur 1b).FIGS. 1a and 1b each show a
Als Widerstandsmaterial (in den nachfolgenden Tabellen mit IV bezeichnet) wurde Zinkoxid mit 0,5 Atom% Praseodym, 2 Atom% Kobalt, 0,5 Atom% Calcium und 60 ppm Aluminium dotiert. Dazu werden 79,1 g Zn0, 0,851 Pr₆0₁₁, 1,499 g Co0, und 0,5 g CaCO₃ mit einer wässerigen Lösung von 0,023 g Al(N0₃)₃.9H₂0 in einer Kugelmühle gemischt. Der Schlicker wird anschließend bei einer Temperatur von 100 °C getrocknet.Zinc oxide was doped with 0.5 atom% praseodymium, 2 atom% cobalt, 0.5 atom% calcium and 60 ppm aluminum as the resistance material (designated IV in the tables below). For this purpose, 79.1 g Zn0, 0.851 Pr₆0₁₁, 1.499 g Co0, and 0.5 g CaCO₃ are mixed with an aqueous solution of 0.023 g Al (N0₃) ₃.9H₂0 in a ball mill. The slip is then dried at a temperature of 100 ° C.
Als Material für die Trägerschicht(en) 5 und die Deckschicht 7 (in den nachfolgenden Tabellen als Material A bezeichnet) wurde Zinkoxid mit 60 ppm Aluminium dotiert. Dazu werden 81,38 g Zn0 mit einer wässerigen Lösung von 0,023 g Al(N0₃)₃.9H₂0 in einer Kugelmühle gemischt. Der Schlicker wird anschließend bei einer Temperatur von 100 °C getrocknet.Zinc oxide was doped with 60 ppm aluminum as the material for the carrier layer (s) 5 and the cover layer 7 (referred to as material A in the tables below). For this purpose, 81.38 g of Zn0 are mixed with an aqueous solution of 0.023 g of Al (N0₃) ₃.9H₂0 in a ball mill. The slip is then dried at a temperature of 100 ° C.
Mehrschichtvaristoren wurden wie folgt hergestellt:
Das Material A und das Widerstandsmaterial IV werden, wie in den schematischen Darstellungen der Figuren 1a und 1b gezeigt, miteinander kombiniert und zusammengesintert. Eine Zusammenstellung von durchgeführten Kombinationen zeigt die nachfolgende Tabelle 1. Die Kombination von Trägerschicht/Deckschicht- und Schicht aus Widerstandsmaterial wurde auf folgende Weise durchgeführt:
0,15 g Pulver des Materials A (hergestellt gemäß den oben angeführten Beispielen) wurden in einer zylindrischen Stahlmatrize eines Durchmessers von 9 mm unter einem Druck von 1,8.10⁸ Pa mechanisch verdichtet. Anschließend wurde das Widerstandsmaterial (Material IV) (hergestellt gemäß dem oben angeführten Beispiel) in Mengen von 0,025 g bis 0,1 g auf das vorverdichtete Substrat geschichtet und mit diesem unter einem Druck von 1,3.10⁸ Pa zusammengepreßt. Im Fall der Herstellung von Dreischichtvaristoren (Sandwich) wurde auf die verpreßte Schicht aus Widerstandsmaterial (Material IV) erneut 0,15 g Pulver des Materials A geschichtet und dieses bei einem Druck von 8.10⁷ Pa in der zylindrischen Matrize an die Schicht aus Widerstandsmaterial (Material IV) angepreßt.Multi-layer varistors were manufactured as follows:
The material A and the resistance material IV are combined with one another and sintered together, as shown in the schematic representations of FIGS. 1a and 1b. A summary of the combinations carried out is shown in Table 1 below. The combination of carrier layer / cover layer and layer of resistance material was carried out in the following way:
0.15 g of powder of material A (prepared according to the examples given above) were placed in a cylindrical steel die with a diameter of 9 mm under pressure mechanically compressed from 1.8.10⁸ Pa. The resistance material (material IV) (produced according to the example given above) was then coated in amounts of 0.025 g to 0.1 g onto the pre-compressed substrate and pressed together with this under a pressure of 1.3.10⁸ Pa. In the case of the production of three-layer varistors (sandwich), 0.15 g of powder of material A was again layered on the pressed layer of resistance material (material IV) and this was pressed at a pressure of 8.10⁷ Pa in the cylindrical die onto the layer of resistance material (material IV) pressed.
Die verpreßten grünen Formkörper wurden anschließend bei Temperaturen im Bereich von 1260 bis 1300 °C und bei Haltezeiten der Maximaltemperatur im Bereich von 0 bis 120 min bei einer Aufheizgeschwindigkeit von ≈ 10 °C/min an Luft gesintert.The pressed green moldings were then sintered in air at temperatures in the range from 1260 to 1300 ° C and with holding times of the maximum temperature in the range from 0 to 120 min at a heating rate of ≈ 10 ° C / min.
Die Ergebnisse der elektrischen Messungen zeigt die nachfolgende Tabelle 2. Die hier angegebenen Werte für die Schichtdicke beziehen sich auf die Widerstandsschicht.
Claims (26)
- A non-linear voltage-dependent resistor having a ceramic sintered body based on zinc oxide as a resistance material which is doped with at least one alkaline earth metal, at least one rare earth metal and at least one metal of the iron group present as oxides as well as with at least one of the metals of the group aluminium, gallium and/or indium, and having electrodes which are provided on the major surfaces of the sintered body which are located opposite to each other, characterized in that the sintered body (1) has several layers with at least one laminated structure of one layer (3) of resistance material on a carrier layer (5) based on zinc oxide which has a higher electric conductivity as compared with the resistance material.
- A voltage-dependent resistor as claimed in Claim 1, characterized in that a coating layer (7) based on zinc oxide having a higher electrical conductivity as compared with the resistance material is provided on the layer (3) of resistance material.
- A non-linear voltage-dependent resistor as claimed in Claims 1 and 2, characterized in that the resistance material consists of zinc oxide doped with 0.01 to 3.0 at.% praseodymium, 1.0 to 3.0 at.% cobalt, O to 1.0 at.% calcium and 10 to 100 ppm aluminium.
- A non-linear voltage-dependent resistor as claimed in Claim 3, characterized in that the resistance material consists of zinc oxide doped with 0.5 at. % praseodymium, 2 at. % cobalt, 0.5 at. % calcium and 60 ppm aluminium.
- A non-linear voltage-dependent resistor as claimed in any of the Claims 1 to 4, characterized in that the material for the at least one carrier layer (5) and for the coating layer (7) is doped with aluminium.
- A non-linear voltage-dependent resistor as claimed in Claim 5, characterized in that the material for the at least one carrier layer (5) and the coating layer (7) is doped with 30 to 100 ppm aluminium.
- A non-linear voltage-dependent resistor as claimed in Claim 6, characterized in that the material for the at least one carrier layer (5) and the coating layer (7) is doped with 60 ppm aluminium.
- A non-linear voltage-dependent resistor as claimed in any of the Claims 1 to 7, characterized in that the electrodes (9, 11) are provided as laminar electrodes.
- A non-linear voltage-dependent resistor as claimed in Claim 8, characterized in that the electrodes (9, 11) consist predominantly of silver.
- A non-linear voltage-dependent resistor as claimed in any of the Claims 1 to 9, characterized in that the at least one layer (3) of resistance material has a thickness in the range from 65 to 250µm.
- A non-linear voltage-dependent resistor as claimed in any of the Claims 1 to 9, characterized in that the at least one carrier layer (5) and the coating layer (7) each have a thickness in the range from 250 to 600µm.
- A method of manufacturing a non-linear voltage-dependent resistor having a ceramic sintered body based on zinc oxide as a resistance material which is doped with at least one alkaline earth metal, at least one rare earth metal and at least one metal of the iron group present as oxides and is doped with at least one of the metals of the group formed by aluminium, gallium and/or indium, and having electrodes provided on the major surfaces of the sintered body which are located opposite to each other, in particular as claimed in Claims 1 to 11, characterized in that a multi-layer sintered body (1) is manufactured having at least a laminated structure of one layer (3) of resistance material on a carrier layer (5) based on zinc oxide which has a higher electrical conductivity as compared with the resistance material.
- A method as claimed in Claim 12, characterized in that a coating layer (7) based on zinc oxide which has a higher electrical conductivity as compared with the resistance material is provided on the layer (3) of resistance material.
- A method as claimed in Claims 12 and 13, characterized in that zinc oxide having a doping of 0.01 to 3.0 at. % praseodymium, 1.0 to 3.0 at. % cobalt, O to 1.0 at. % calcium and 10 to 100 ppm aluminium is used as a resistance material.
- A method as claimed in Claim 14, characterized in that zinc oxide having a doping of 0.5 at. % praseodymium, 2 at. % cobalt, 0.5 at. % calcium and 60 ppm aluminium is used as a resistance material.
- A method as claimed in any of the Claims 13 to 15, characterized in that aluminium-doped zinc oxide is used as a material for the at least one carrier layer (5) and the coating layer (7).
- A method as claimed in Claim 16, characterized in that zinc oxide doped with 30 to 100 ppm aluminium is used as a material for the at least one carrier layer (5) and the coating layer (7).
- A method as claimed in Claim 17, characterized in that zinc oxide doped with 60 ppm aluminium is used.
- A method as claimed in any of the Claims 12 to 18, characterized in that dry powder mixtures of the resistance material and of the material for the at least one carrier layer (5) and the coating layer (7) are manufactured and these powder mixtures are densified and deformed in a mould under pressure in accordance with the desired layer structure and the desired layer thickness, in such a manner that the powder mixtures are individually densified and deformed in layers one after the other in accordance with the layers to be manufactured.
- A method as claimed in Claim 19, characterized in that the layers of the powder mixtures are densified at a pressure in the range from 8 x 10⁷ to 1,8 x 10⁸ Pa.
- A method as claimed in any of the Claims 12 to 20, characterized in that the green bodies obtained by compressing the powder mixtures are sintered at a temperature in the range from 1260 to 1300°C in air at a heating rate of ≈10°C per minute.
- A method as claimed in Claim 21, characterized in that the sintering of the moulded body is carried out so that the maximum sintering temperature is maintained for O to 240 minutes before the cooling process is started.
- A method as claimed in any of the Claims 12 to 22, characterized in that the at least one layer (3) of resistance material is manufactured in a thickness in the range from 65 to 250µm.
- A method as claimed in any of the Claims 12 to 22, characterized in that the at least one carrier layer (5) and the coating layer (7) is manufactured in a thickness in the range from 250 to 600µm.
- A method as claimed in any of the Claims 12 to 24, characterized in that metal layer electrodes (9, 11) are provided on the oppositely located major surfaces of the sintered body (1).
- A method as claimed in Claim 25, characterized in that a contact material on the basis of silver is used for the electrodes (9, 11).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3823698A DE3823698A1 (en) | 1988-07-13 | 1988-07-13 | NON-LINEAR VOLTAGE RESISTANCE |
| DE3823698 | 1988-07-13 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0351004A2 EP0351004A2 (en) | 1990-01-17 |
| EP0351004A3 EP0351004A3 (en) | 1990-03-21 |
| EP0351004B1 true EP0351004B1 (en) | 1993-10-06 |
Family
ID=6358567
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP89201797A Expired - Lifetime EP0351004B1 (en) | 1988-07-13 | 1989-07-07 | Non-linear voltage-dependent resistor |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5008646A (en) |
| EP (1) | EP0351004B1 (en) |
| JP (1) | JPH0266901A (en) |
| KR (1) | KR0142574B1 (en) |
| DE (2) | DE3823698A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0509582B1 (en) * | 1991-04-16 | 1996-09-04 | Koninklijke Philips Electronics N.V. | SMD-resistor |
| US5167537A (en) * | 1991-05-10 | 1992-12-01 | Amphenol Corporation | High density mlv contact assembly |
| US5699035A (en) * | 1991-12-13 | 1997-12-16 | Symetrix Corporation | ZnO thin-film varistors and method of making the same |
| DE4142523A1 (en) * | 1991-12-21 | 1993-06-24 | Asea Brown Boveri | RESISTANCE WITH PTC BEHAVIOR |
| JPH05275958A (en) * | 1992-03-25 | 1993-10-22 | Murata Mfg Co Ltd | Noise filter |
| EP0578046B1 (en) * | 1992-07-10 | 1996-11-06 | Asahi Glass Company Ltd. | Transparent conductive film, and target and material for vapor deposition to be used for its production |
| WO1994009499A1 (en) * | 1992-10-09 | 1994-04-28 | Tdk Corporation | Resistance element with nonlinear voltage dependence and process for producing the same |
| AU6627394A (en) * | 1993-04-28 | 1994-11-21 | Mark Mitchnick | Conductive polymers |
| US5441726A (en) * | 1993-04-28 | 1995-08-15 | Sunsmart, Inc. | Topical ultra-violet radiation protectants |
| US5391432A (en) * | 1993-04-28 | 1995-02-21 | Mitchnick; Mark | Antistatic fibers |
| EP0649150B1 (en) * | 1993-10-15 | 1998-06-24 | Abb Research Ltd. | Composite material |
| EP0771465B1 (en) * | 1994-07-14 | 2002-11-13 | Surgx Corporation | Method of making single and multi-layer variable voltage protection devices |
| JP3293403B2 (en) * | 1995-05-08 | 2002-06-17 | 松下電器産業株式会社 | Lateral high resistance agent for zinc oxide varistor, zinc oxide varistor using the same, and method of manufacturing the same |
| JP3223830B2 (en) * | 1997-02-17 | 2001-10-29 | 株式会社村田製作所 | Varistor element manufacturing method |
| US6519129B1 (en) * | 1999-11-02 | 2003-02-11 | Cooper Industries, Inc. | Surge arrester module with bonded component stack |
| DE10056283A1 (en) * | 2000-11-14 | 2002-06-13 | Infineon Technologies Ag | Artificial neuron for artificial neural network, has transistor with several inputs connected to first transistor input in parallel via resistance elements containing material ensuring a varistor effect |
| US7015786B2 (en) * | 2001-08-29 | 2006-03-21 | Mcgraw-Edison Company | Mechanical reinforcement to improve high current, short duration withstand of a monolithic disk or bonded disk stack |
| KR100441863B1 (en) * | 2002-03-28 | 2004-07-27 | 주식회사 에이피케이 | Fabrication of praseodymium-based zinc oxide varistors |
| JP4123957B2 (en) * | 2003-02-10 | 2008-07-23 | 株式会社村田製作所 | Voltage dependent resistor |
| US7436283B2 (en) * | 2003-11-20 | 2008-10-14 | Cooper Technologies Company | Mechanical reinforcement structure for fuses |
| US8117739B2 (en) * | 2004-01-23 | 2012-02-21 | Cooper Technologies Company | Manufacturing process for surge arrester module using pre-impregnated composite |
| US7075406B2 (en) * | 2004-03-16 | 2006-07-11 | Cooper Technologies Company | Station class surge arrester |
| US7633737B2 (en) * | 2004-04-29 | 2009-12-15 | Cooper Technologies Company | Liquid immersed surge arrester |
| JP4893371B2 (en) * | 2007-03-02 | 2012-03-07 | Ｔｄｋ株式会社 | Varistor element |
| JP5304772B2 (en) * | 2010-12-06 | 2013-10-02 | Ｔｄｋ株式会社 | Chip varistor and method of manufacturing chip varistor |
| JP5375810B2 (en) * | 2010-12-06 | 2013-12-25 | Ｔｄｋ株式会社 | Chip varistor |
| EP3178098A4 (en) * | 2014-08-08 | 2018-06-06 | Dongguan Littelfuse Electronics, Co., Ltd. | Varistor having multilayer coating and fabrication method |
| US11894166B2 (en) | 2022-01-05 | 2024-02-06 | Richards Mfg. Co., A New Jersey Limited Partnership | Manufacturing process for surge arrestor module using compaction bladder system |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3928242A (en) * | 1973-11-19 | 1975-12-23 | Gen Electric | Metal oxide varistor with discrete bodies of metallic material therein and method for the manufacture thereof |
| JPS5385400A (en) * | 1977-01-06 | 1978-07-27 | Tdk Corp | Porcelain composite for voltage non-linear resistor |
| JPS57164502A (en) * | 1981-04-03 | 1982-10-09 | Hitachi Ltd | Voltage nonlinear resistor and method of producing same |
| US4400683A (en) * | 1981-09-18 | 1983-08-23 | Matsushita Electric Industrial Co., Ltd. | Voltage-dependent resistor |
| US4477793A (en) * | 1982-06-30 | 1984-10-16 | Fuji Electric Co., Ltd. | Zinc oxide non-linear resistor |
| US4908597A (en) * | 1987-04-28 | 1990-03-13 | Christopher Sutton | Circuit module for multi-pin connector |
-
1988
- 1988-07-13 DE DE3823698A patent/DE3823698A1/en not_active Withdrawn
-
1989
- 1989-06-26 US US07/371,866 patent/US5008646A/en not_active Expired - Fee Related
- 1989-07-07 EP EP89201797A patent/EP0351004B1/en not_active Expired - Lifetime
- 1989-07-07 DE DE89201797T patent/DE58905814D1/en not_active Expired - Fee Related
- 1989-07-10 JP JP1175754A patent/JPH0266901A/en active Pending
- 1989-07-11 KR KR1019890009832A patent/KR0142574B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0351004A3 (en) | 1990-03-21 |
| JPH0266901A (en) | 1990-03-07 |
| KR900002353A (en) | 1990-02-28 |
| EP0351004A2 (en) | 1990-01-17 |
| DE3823698A1 (en) | 1990-01-18 |
| US5008646A (en) | 1991-04-16 |
| KR0142574B1 (en) | 1998-08-17 |
| DE58905814D1 (en) | 1993-11-11 |
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