EP0184645B1 - Chip varistor and production process - Google Patents

Chip varistor and production process Download PDF

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Publication number
EP0184645B1
EP0184645B1 EP85113401A EP85113401A EP0184645B1 EP 0184645 B1 EP0184645 B1 EP 0184645B1 EP 85113401 A EP85113401 A EP 85113401A EP 85113401 A EP85113401 A EP 85113401A EP 0184645 B1 EP0184645 B1 EP 0184645B1
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Prior art keywords
varistor
chip
squaredlike
squared
metallic
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German (de)
French (fr)
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EP0184645A3 (en
EP0184645A2 (en
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Peter Brogl
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C Conradty Nuernberg GmbH and Co KG
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C Conradty Nuernberg GmbH and Co KG
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01CRESISTORS
    • H01C7/00Non-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
    • H01C7/10Non-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
    • H01C7/102Varistor boundary, e.g. surface layers

Definitions

  • the invention relates to a chip varistor, consisting of a cuboid body, which is formed at least in part from varistor material and has at least two metallized connection surfaces on two opposite square ends, and a method for its production.
  • Higher energy absorption values can be achieved by increasing the volume of the varistor, for example the entire body can be formed from varistor material. If the same contacting is used as in the known chip varistors, then there is a flashover on the varistor surface with higher pulse currents.
  • This spark formation between the metallized connection surfaces at the ends of the cuboid body, which has dimensions of 8 x 4 x 2 mm, for example, is due to the fact that the contacting formed by the metallized connection surfaces favors a current flow on the surface of the varistor, while the inside of the varistor remains practically de-energized. At higher voltages or pulse currents from about 20 A, there are arcing on the top and bottom sides of the varistor.
  • the object of the invention is therefore to design the chip varistor of the type mentioned in such a way that it has a sufficient volume in order to obtain the required energy absorption capacity and also offers security against sliding sparks on its surface and also offers the possibility of its Make tension adjustable with constant dimensions of its top and bottom sides.
  • the upper and lower sides of the cuboid body adjoining the cuboid ends are provided with a metallization which has an interruption, the metallization of most of the upper side only with the metallized connecting surface of the one cuboid end and the metallization of the most of the underside is only electrically conductively connected to the metallized connection surface of the other cuboid end.
  • the current flow direction is rotated by 90 ° so that current or voltage flashovers are only possible in the area of the interruption of the metallization.
  • the adjustability of the varistor voltage is made possible in a simple manner by choosing different dimensions for the thickness of the cuboid body, which is denoted by H in the exemplary embodiment.
  • each strip-shaped recess can be delimited by two parallel edges which are parallel to the edges of the upper and lower edges. Underside, extend transversely to the longitudinal direction of the cuboid body.
  • the surface of the varistor material in the region of the strip-shaped recesses can be provided with grooves which are incorporated into the varistor material and extend in the direction of the strip-shaped recesses.
  • the cuboid body as a laminated body, consisting of alternating layers of varistor material and electrically highly conductive material running parallel to its top and bottom sides, the latter layer in turn alternating with one and the other metallized Cuboid ends are electrically connected.
  • a method is used, according to which a cuboid body is made of varistor material and is completely metallized on its surfaces, whereupon at least one metallization each on the opposite top and bottom sides of the cuboid body recessing groove is incorporated and then the body is cut transversely to its longitudinal axis into individual longitudinal pieces which form the actual cuboid bodies, so that their longitudinal axis runs in the direction of the transverse axis of the original cuboid body and their transverse axis in the direction of the longitudinal axis of the original cuboid body.
  • variable is used to denote voltage-dependent resistors which generally consist of sintered silicon carbide or zinc oxide with admixtures of other materials in the form of disks or rods and are used above all in communications engineering. Their voltage dependence is based on a variable contact resistance between the individual crystals.
  • the chip varistor shown in FIG. 1 is a cuboid body 1. Its dimensions are, for example, 2 x 1.25 x 0.5 mm (length, width, height) to, for example, 8 x 4 x 4 mm. It consists of an oxide-ceramic resistance material and is provided on the cuboid ends 2, 3 with metallized connection surfaces 8, 9, which completely cover the cuboid ends, and also on its top side 4 and its underside 5 with a metallization 6, 7 (FIG. 2).
  • the metallization of the upper side 4 is electrically conductively connected to the metallized connection surface 9 of one cuboid end 3, while the metallization 7 of the underside 5 is only electrically conductively connected to the metallized connection surface 8 of the other cuboid end 2.
  • This means that the metallization is interrupted both on the upper side 4 and on the underside 5, this interruption, as can be seen in FIGS. 1 and 2, in each case forms a strip-shaped recess 10, 11 in the metallized surface which extends up to Surface of the varistor material ranges, which is generally designated 19.
  • the strip-shaped recesses 10, 11 are delimited by two parallel edges 12, 13 which extend parallel to the edges of its upper and lower sides lying in the transverse direction of the body.
  • the chip varistor Due to this design of the chip varistor, its voltage can be set at home with a constant “base area” of the cuboid body by changing the overall height H (FIG. 2), that is to say during the manufacture of the chip varistor. This means that the voltage can be adjusted depending on the component height. It has been found through experiments that the width d of the strip-shaped recesses 10, 11 must be approximately 1.5 times the height H, since after this design, owing to the overlap of the electrodes (metallized surfaces), the current flow direction compared to only one of the the front-side cuboid ends contacted chip varistor is rotated by 90 °, the possibility of current or voltage flashovers is only given in the area of the strip-shaped recess.
  • FIG. 5 shows another embodiment of the chip varistor, in which the cuboid body is designed as a laminated body 16, consisting of a plurality of alternating layers of varistor material 17 and electrically highly conductive material 18 that run parallel to the top and bottom sides.
  • the conductive material layers 18 are in turn alternately electrically connected to one and the other metallized cuboid ends 2a and 3a.
  • a method is used to produce a chip varistor of the type shown in FIGS. 3 and 4, the steps of which are explained below with reference to FIGS. 6a, 6b and 6c.
  • the surface of the chip varistor thus produced is, with the exception of the contact areas, i.e. the front ends, covered with a protective layer.
  • the contact areas can be reinforced, for example, by nickel plating and tinning.

Abstract

1. Chip-varistor comprising a squaredlike body consisting at least partly of varistor material and provided with at least two metallic connecting areas at two opposing ends of the squared body, characterized in that the upper end lower surfaces (4, 5) of the squaredlike body (1) joining the ends of the squared body are provided with a metalic layer comprising an interruption (10, 11) so that the metallic layer (6) of the greater part of the upper surface (4) is electrically attached only to the metallic connecting area (8) of the one end (2) of the squared body and the metallic layer (7) of the greater part of the lower surface (5) only to the metallic connecting area (9) of the other end (3) of the squared body.

Description

Die Erfindung betrifft einen Chip-Varistor, bestehend aus einem quaderförmigen Körper, der wenigstens zum Teil aus Varistormaterial gebildet ist und wenigstens zwei metallisierte Anschlussflächen an zwei gegenüberliegenden Quaderenden aufweist, sowie ein Verfahren zu seiner Herstellung.The invention relates to a chip varistor, consisting of a cuboid body, which is formed at least in part from varistor material and has at least two metallized connection surfaces on two opposite square ends, and a method for its production.

Bekannte Chip-Varistoren dieser Art (Prospekt der Firma National Matsushita Electric «Transient/Surge Absorbers» 1983/84), sogenannte «Glaze-Varistors», weisen aufgrund des relativ kleinen Volumens der Varistorschicht nur ein geringes Energieabsorptionsvermögen auf. Sie sind deshalb für die übliche Varistoranwendung im Überspannungsschutz nicht geeignet. Darüber hinaus besteht bei Impulsbelastung bei diesen bekannten Varistoren die Gefahr der Gleitfunkenbildung auf der Oberfläche der Varistorschicht, also Widerstandsschicht, die auf einem Keramiksubstrat aufgebracht ist.Known chip varistors of this type (brochure from National Matsushita Electric “Transient / Surge Absorbers” 1983/84), so-called “glaze varistors”, have only a low energy absorption capacity due to the relatively small volume of the varistor layer. They are therefore not suitable for the usual varistor application in surge protection. In addition, when these known varistors are subjected to impulses, there is a risk of sliding spark formation on the surface of the varistor layer, that is to say a resistance layer which is applied to a ceramic substrate.

Höhere Energieabsorptionswerte lassen sich durch eine Vergrösserung des Varistorvolumens erreichen, zum Beispiel kann der ganze Körper aus Varistormaterial gebildet werden. Verwendet man die gleiche Kontaktierung wie bei den bekannten Chip-Varistoren, so kommt es bei höheren Impulsströmen zu Überschlägen auf der Varistoroberfläche. Diese Funkenbildung zwischen den metallisierten Anschlussflächen an den Enden des quaderförmigen Körpers, der beispielsweise Abmessungen von 8 x 4 x 2 mm aufweist, ist darauf zurückzuführen, dass die Kontaktierung, die durch die metallisierten Anschlussflächen gebildet wird, einen Stromfluss auf der Oberfläche des Varistors begünstigt, während das Innere des Varistors praktisch stromfrei bleibt. Bei höheren Spannungen bzw. Impulsströmen ab etwa 20 A kommt es deshalb zu Überschlägen auf den Ober- und Unterseiten des Varistors. Diese Wirkung kann zwar durch eine Stirnflächenkontaktierung vermieden werden, bei der nur die einander gegenüberliegenden, endseitigen Stirnflächen des quaderförmigen Körpers mit einer Metallisierung versehen werden und nicht zumindest teilweise auch die Ober- und Unterseite dieses Körpers, jedoch hat diese Stirnflächenkontaktierung den Nachteil, dass sie die Lötbarkeit der Varistorelemente stark einschränkt und damit ihre Brauchbarkeit grundsätzlich in Frage stellt. Darüber hinaus lässt sich bei derartigen Chip-Varistoren die Varistorspannung nur über die Bauelementlänge einstellen, was dazu führt, dass eine Vielzahl von unterschiedlichen Längenabmessungen hergestellt und bevorratet werden müssen, um unterschiedliche Spannungen zu realisieren.Higher energy absorption values can be achieved by increasing the volume of the varistor, for example the entire body can be formed from varistor material. If the same contacting is used as in the known chip varistors, then there is a flashover on the varistor surface with higher pulse currents. This spark formation between the metallized connection surfaces at the ends of the cuboid body, which has dimensions of 8 x 4 x 2 mm, for example, is due to the fact that the contacting formed by the metallized connection surfaces favors a current flow on the surface of the varistor, while the inside of the varistor remains practically de-energized. At higher voltages or pulse currents from about 20 A, there are arcing on the top and bottom sides of the varistor. This effect can be avoided by contacting the end face, in which only the opposite end faces of the cuboid body are provided with a metallization and not at least partially the top and bottom of this body, but this end face contact has the disadvantage that it The ability of the varistor elements to be soldered is severely restricted, thereby fundamentally questioning their usability. In addition, with such chip varistors, the varistor voltage can only be set over the component length, which means that a large number of different length dimensions have to be produced and stored in order to realize different voltages.

Die Aufgabe der Erfindung besteht deshalb darin, den Chip-Varistor der genannten Art so auszubilden, dass er sowohl ein ausreichendes Volumen aufweist, um das geforderte Energieabsorptionsvermögen zu erhalten, als auch Sicherheit gegen Gleitfunken auf seiner Oberfläche bietet und darüber hinaus die Möglichkeit bietet, seine Spannung bei konstanten Abmessungen seiner Ober- und Unterseiten einstellbar zu machen.The object of the invention is therefore to design the chip varistor of the type mentioned in such a way that it has a sufficient volume in order to obtain the required energy absorption capacity and also offers security against sliding sparks on its surface and also offers the possibility of its Make tension adjustable with constant dimensions of its top and bottom sides.

Darüber hinaus soll für einen derartigen Varistor ein Herstellungsverfahren entwickelt werden, das den bisher bekannten insbesondere in wirtschaftlicher Hinsicht überlegen ist.In addition, a manufacturing method is to be developed for such a varistor, which is superior to the previously known ones, particularly in economic terms.

Diese Aufgabe wird erfindungsgemäss dadurch gelöst, dass die sich an die Quaderenden anschliessenden Ober- und Unterseiten des quaderförmigen Körpers mit einer eine Unterbrechung aufweisenden Metallisierung versehen sind, wobei die Metallisierung des grössten Teils der Oberseite nur mit der metallisierten Anschlussfläche des einen Quaderendes und die Metallisierung des grössten Teils der Unterseite nur mit der metallisierten Anschlussfläche des anderen Quaderendes elektrisch leitend verbunden ist.This object is achieved according to the invention in that the upper and lower sides of the cuboid body adjoining the cuboid ends are provided with a metallization which has an interruption, the metallization of most of the upper side only with the metallized connecting surface of the one cuboid end and the metallization of the most of the underside is only electrically conductively connected to the metallized connection surface of the other cuboid end.

Durch diese Konstruktion ist infolge Überlappung der Elektroden die Stromflussrichtung um 90° gedreht, so dass Strom- bzw. Spannungsüberschläge nur noch im Bereich der Unterbrechung der Metallisierung möglich sind. Die Einstellbarkeit der Varistorspannung wird in einfacher Weise dadurch ermöglicht, dass für die Dicke des quaderförmigen Körpers, die im Ausführungsbeispiel mit H bezeichnet ist, verschiedene Abmessungen gewählt werden.As a result of this overlap of the electrodes, the current flow direction is rotated by 90 ° so that current or voltage flashovers are only possible in the area of the interruption of the metallization. The adjustability of the varistor voltage is made possible in a simple manner by choosing different dimensions for the thickness of the cuboid body, which is denoted by H in the exemplary embodiment.

Gemäss einer weiteren Ausgestaltung der Erfindung kann jede streifenförmige Aussparung durch zwei parallele Ränder begrenzt sein, die sich parallel zu den Rändern der Ober- u. Unterseiten, quer zur Längsrichtung der quaderförmigen Körpers erstrecken.According to a further embodiment of the invention, each strip-shaped recess can be delimited by two parallel edges which are parallel to the edges of the upper and lower edges. Underside, extend transversely to the longitudinal direction of the cuboid body.

Zur weiteren Verbesserung der Überschlagsfestigkeit lässt sich gemäss einer weiteren Ausgestaltung des Erfindungsvorschlags die Oberfläche des Varistormaterials im Bereich der streifenförmigen Aussparungen mit Nuten versehen, die in das Varistormaterial eingearbeitet sind und sich in Richtung der streifenförmigen Aussparungen erstrecken.To further improve the flashover resistance, according to a further embodiment of the proposal of the invention, the surface of the varistor material in the region of the strip-shaped recesses can be provided with grooves which are incorporated into the varistor material and extend in the direction of the strip-shaped recesses.

Darüber hinaus hat es sich als vorteilhaft erwiesen, den quaderförmigen Körper als Schichtkörper auszubilden, bestehend aus parallel zu seinen Ober- und Unterseiten verlaufenden, einander abwechselnden Schichten aus Varistormaterial und elektrisch gut leitfähigem Material, wobei letztgenannte Schicht wiederum abwechselnd mit dem einen und dem anderen metallisierten Quaderende elektrisch verbunden sind.In addition, it has proven to be advantageous to design the cuboid body as a laminated body, consisting of alternating layers of varistor material and electrically highly conductive material running parallel to its top and bottom sides, the latter layer in turn alternating with one and the other metallized Cuboid ends are electrically connected.

Zur Herstellung von Chip-Varistoren nach einem der Ansprüche 1 bis 5 dient ein Verfahren, gemäss dem ein quaderförmiger Körper aus Varistormaterial hergestellt und auf seinen Oberflächen vollständig metallisiert wird, woraufhin in die einander gegenüberliegenden Ober- und Unterseiten des quaderförmigen Körpers wenigstens je eine die Metallisierung aussparende Nut eingearbeitet wird und danach der Körper quer zu seiner Längsachse in einzelne Längsstücke zerschnitten wird, die die eigentlichen quaderförmigen Körper bilden, so dass deren Längsachse in Richtung der Querachse des ursprünglichen quaderförmigen Körpers verläuft und deren Querachse in Richtung der Längsachse des ursprünglichen quaderförmigen Körpers.For the production of chip varistors according to one of claims 1 to 5, a method is used, according to which a cuboid body is made of varistor material and is completely metallized on its surfaces, whereupon at least one metallization each on the opposite top and bottom sides of the cuboid body recessing groove is incorporated and then the body is cut transversely to its longitudinal axis into individual longitudinal pieces which form the actual cuboid bodies, so that their longitudinal axis runs in the direction of the transverse axis of the original cuboid body and their transverse axis in the direction of the longitudinal axis of the original cuboid body.

Die Erfindung wird nachfolgend anhand der in der Zeichnung dargestellten Ausführungsbeispiele näher erläutert. In der Zeichnung zeigen:

  • Figur 1 eine perspektivische Ansicht des quaderförmigen Körpers eines Chip-Varistors, dessen gegenüberliegende Enden vollständig und dessen gegenüberliegende Ober- und Unterseiten teilweise metallisiert sind,
  • Figur 2 eine schematische Seitenansicht des Varistors von Fig. 1 in Richtung des Pfeils A in Fig. 1,
  • Figur 3 eine perspektivische Ansicht einer anderen Ausführungsform des Chip-Varistors,
  • Figur 4 eine der Fig. 2 entsprechende schematische Seitenansicht des Chip-Varistors von Fig. 3,
  • Figur 5 eine längsgeschnittene Seitenansicht eines Vielschicht-Varistors mit den Merkmalen der Erfindung, und
  • Figur 6a, b und c schematische Darstellungen der aufeinanderfolgenden Herstellungsschritte des quaderförmigen Körpers, aus dem der Chip-Varistor aufgebaut ist.
The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing. The drawing shows:
  • Figure 1 is a perspective view of the cuboid body of a chip varistor, its opposite ends completely and its ge opposite top and bottom sides are partially metallized,
  • FIG. 2 shows a schematic side view of the varistor from FIG. 1 in the direction of arrow A in FIG. 1,
  • FIG. 3 shows a perspective view of another embodiment of the chip varistor,
  • FIG. 4 shows a schematic side view corresponding to FIG. 2 of the chip varistor from FIG. 3,
  • Figure 5 is a longitudinal sectional side view of a multilayer varistor with the features of the invention, and
  • 6a, b and c show schematic representations of the successive manufacturing steps of the cuboid body from which the chip varistor is constructed.

Mit «Varistor» werden bekanntlich spannungsabhängige Widerstände bezeichnet, die in aller Regel aus gesintertem Siliziumkarbid oder Zinkoxid mit Beimengungen anderer Stoffe in Scheiben- oder Stabform bestehen und vor allem in der Nachrichtentechnik Anwendung finden. Ihre Spannungsabhängigkeit beruht auf einem veränderlichen Kontaktwiderstand zwischen den einzelnen Kristallen.As is known, “varistor” is used to denote voltage-dependent resistors which generally consist of sintered silicon carbide or zinc oxide with admixtures of other materials in the form of disks or rods and are used above all in communications engineering. Their voltage dependence is based on a variable contact resistance between the individual crystals.

Der in Fig. 1 dargestellte Chip-Varistor ist ein quaderförmiger Körper 1. Seine Abmessungen betragen beispielsweise 2 x 1,25 x 0,5 mm (Länge, Breite, Höhe) bis beispielsweise 8 x 4 x 4 mm. Er besteht aus einem oxydkeramischen Widerstandsmaterial und ist an den Quaderenden 2, 3 mit metallisierten Anschlussflächen 8, 9 versehen, die die Quaderenden vollständig abdecken, und auf seiner Oberseite 4 sowie seiner Unterseite 5 ebenfalls mit einer Metallisierung 6, 7 (Fig. 2). Die Metallisierung der Oberseite 4 ist mit der metallisierten Anschlussfläche 9 des einen Quaderendes 3 elektrisch leitend verbunden, während die Metallisierung 7 der Unterseite 5 nur mit der metallisierten Anschlussfläche 8 des anderen Quaderendes 2 elektrisch leitend in Verbindung steht. Dies bedeutet, sowohl auf der Oberseite 4 als auch auf der Unterseite 5 ist die Metallisierung unterbrochen, wobei diese Unterbrechung, wie den Fig. 1 und 2 entnommen werden kann, jeweils eine streifenförmige Aussparung 10, 11 in der metallisierten Fläche bildet, die bis zur Oberfläche des Varistormaterials reicht, das allgemein mit 19 bezeichnet ist.The chip varistor shown in FIG. 1 is a cuboid body 1. Its dimensions are, for example, 2 x 1.25 x 0.5 mm (length, width, height) to, for example, 8 x 4 x 4 mm. It consists of an oxide-ceramic resistance material and is provided on the cuboid ends 2, 3 with metallized connection surfaces 8, 9, which completely cover the cuboid ends, and also on its top side 4 and its underside 5 with a metallization 6, 7 (FIG. 2). The metallization of the upper side 4 is electrically conductively connected to the metallized connection surface 9 of one cuboid end 3, while the metallization 7 of the underside 5 is only electrically conductively connected to the metallized connection surface 8 of the other cuboid end 2. This means that the metallization is interrupted both on the upper side 4 and on the underside 5, this interruption, as can be seen in FIGS. 1 and 2, in each case forms a strip-shaped recess 10, 11 in the metallized surface which extends up to Surface of the varistor material ranges, which is generally designated 19.

Die streifenförmigen Aussparungen 10, 11 sind durch zwei parallele Ränder 12, 13 begrenzt, die sich parallel zu den in Querrichtung des Körpers liegenden Rändern seiner Ober- und Unterseiten erstrecken.The strip-shaped recesses 10, 11 are delimited by two parallel edges 12, 13 which extend parallel to the edges of its upper and lower sides lying in the transverse direction of the body.

Durch diese Bauform des Chip-Varistors lässt sich seine Spannung bei konstanter «Grundfläche» des quaderförmigen Körpers durch Änderung der Bauhöhe H (Fig. 2) von Hause aus, also bei der Herstellung des Chip-Varistors, festlegen. Somit ist die Einstellbarkeit der Spannung in Abhängigkeit von der Bauteilhöhe gegeben. Durch Versuche wurde gefunden, dass die Breite d der streifenförmigen Aussparungen 10, 11 etwa das 1, 5-fache der Höhe H sein muss, da, nachdem durch diese Bauform aufgrund der Überlappung der Elektroden (metallisierte Oberflächen) die Stromflussrichtung gegenüber einer nur an den stirnseitigen Quaderenden kontaktierten Chip-Varistor um 90° gedreht ist, die Möglichkeit von Strom- bzw. Spannungsüberschlägen nur noch im Bereich der streifenförmigen Aussparung gegeben ist.Due to this design of the chip varistor, its voltage can be set at home with a constant “base area” of the cuboid body by changing the overall height H (FIG. 2), that is to say during the manufacture of the chip varistor. This means that the voltage can be adjusted depending on the component height. It has been found through experiments that the width d of the strip-shaped recesses 10, 11 must be approximately 1.5 times the height H, since after this design, owing to the overlap of the electrodes (metallized surfaces), the current flow direction compared to only one of the the front-side cuboid ends contacted chip varistor is rotated by 90 °, the possibility of current or voltage flashovers is only given in the area of the strip-shaped recess.

Da die Bedingung d > 1,5 H bei höheren Varistorspannungen zu kleinen Elektrodenflächen führt und damit zu geringem Energieabsorptionsvermögen, wird vorzugsweise, wie aus den Fig. 3 und 4 ersichtlich, im Bereich der streifenförmigen Aussparungen 10, 11 der Ober- und Unterseiten des Chip-Varistors zwischen den Elektroden wenigstens eine Nut 14, 15 angebracht, durch die bei grossen Werten von H der Wert für d vergrössert wird, da der Stromfluss zwischen den Elektroden und damit die Überschlagsweite nicht durch die Luftstrecke gemessen wird, sondern über die Varistor-Oberflächenmaterialstrecke zwischen den benachbarten Elektroden und diese Materialstrecke gegenüber dem blossen Abstand d um die zweifache Höhe der Nutseiten vergrössert ist.Since the condition d> 1.5 H at higher varistor voltages leads to small electrode areas and thus to low energy absorption capacity, it is preferred, as can be seen from FIGS. 3 and 4, in the area of the strip-shaped recesses 10, 11 of the top and bottom sides of the chip -Varistor between the electrodes at least one groove 14, 15 through which the value for d is increased at large values of H, since the current flow between the electrodes and thus the rollover distance is not measured through the air gap, but via the varistor surface material path between the adjacent electrodes and this material path is increased by twice the height of the groove sides compared to the mere distance d.

Es versteht sich, dass bei niedrigen Varistorspannungen und kleinen Bauteilhöhen H diese Nut überflüssig ist.It goes without saying that this groove is superfluous for low varistor voltages and small component heights H.

In Fig. 5 ist eine andere Ausführungsform des Chip-Varistors dargestellt, bei der der quaderförmige Körper als Schichtkörper 16 ausgebildet ist, bestehend aus mehreren parallel zu den Ober- und Unterseiten verlaufenden, einander abwechselnden Schichten aus Varistormaterial 17 und elektrisch gut leitfähigem Material 18.FIG. 5 shows another embodiment of the chip varistor, in which the cuboid body is designed as a laminated body 16, consisting of a plurality of alternating layers of varistor material 17 and electrically highly conductive material 18 that run parallel to the top and bottom sides.

Die leitfähigen Materialschichten 18 sind wiederum abwechselnd mit dem einen und dem anderen metallisierten Quaderende 2a bzw. 3a elektrisch verbunden.The conductive material layers 18 are in turn alternately electrically connected to one and the other metallized cuboid ends 2a and 3a.

Durch Anwendung einer solchen Schichttechnik, die zu dem in Fig. 5 gezeigten Vielschicht-Chip-Varistor führt, lässt sich das Energieabsorptionsvermögen noch wesentlich steigern, allerdings auf Kosten eines doch erheblich höheren Herstellungsaufwandes.The use of such a layer technique, which leads to the multilayer chip varistor shown in FIG. 5, allows the energy absorption capacity to be increased significantly, but at the cost of a considerably higher production outlay.

Zur Herstellung eines Chip-Varistors der in den Fig. 3 und 4 gezeigten Art dient ein Verfahren, dessen Schritte im folgenden anhand der Figuren 6a, 6b und 6c erläutert werden.A method is used to produce a chip varistor of the type shown in FIGS. 3 and 4, the steps of which are explained below with reference to FIGS. 6a, 6b and 6c.

Zunächst werden grössere Platten oder Stangen aus Varistormaterial zu Körpern der in Fig. 6a gezeigten Art gepresst, gesintert und eventuell zersägt. Daraufhin wird dieser Körper auf seiner gesamten Oberfläche mit Silber kontaktiert, also metallisiert. Danach werden in Längsachsenrichtung des stangenförmigen Körpers in seine Ober- und Unterseiten Nuten oder rillenförmige Vertiefungen der bei 14 und 15 in Fig. 3 gezeigten Art eingefräst oder eingesägt, die tiefer sind als die Metallisierungsschicht und die die Aufgabe haben, die Überschlagsfestigkeit zu verbessern (Fig. 6b). Anschliessend werden von diesem stangenförmigen oder quaderförmigen Körper quer zu seiner Längsachse in Fig. 6c mit 20 bezeichnete Stücke abgeschnitten, die die in Fig. 3 dargestellten Chip-Varistoren bilden, deren Seitenflächen 21 (22) demnach nicht metallisiert sind, im Gegensatz zu den stirnseitigen Enden. Die Längsachse dieser Chip-Varistoren entspricht somit der Querachse des ursprünglich hergestellten quaderförmigen Körpers, der in die einzelnen Chips zerteilt wird.First, larger plates or rods made of varistor material are pressed into bodies of the type shown in FIG. 6a, sintered and possibly sawn. This body is then contacted with silver over its entire surface, that is, metallized. Thereafter, in the longitudinal axis direction of the rod-shaped body, grooves or groove-shaped depressions of the type shown at 14 and 15 in FIG 6b). 6c, pieces are then cut from this rod-shaped or cuboid body transversely to its longitudinal axis in FIG. 6c, which form the chip varistors shown in FIG. 3, the side surfaces 21 (22) of which are accordingly not metallized, in contrast to the end faces End up. The longitudinal axis of these chip varistors thus corresponds to the transverse axis of the cuboid body originally produced, which is divided into the individual chips.

Die Oberfläche des so hergestellten Chip-Varistors wird mit Ausnahme der Kontaktflächen, d.h. der stirnseitigen Enden, mit einer Schutzschicht überzogen. Die Kontaktflächen können beispielsweise durch Vernickeln und Verzinnen verstärkt werden.The surface of the chip varistor thus produced is, with the exception of the contact areas, i.e. the front ends, covered with a protective layer. The contact areas can be reinforced, for example, by nickel plating and tinning.

Claims (6)

1. Chip-varistor comprising a squaredlike body consisting at least partly of varistor material and provided with at least two metallic connecting areas at two opposing ends of the squared body, characterized in that the upper and lower surfaces (4, 5) of the squaredlike body (1) joining the ends of the squared body are provided with a metallic layer comprising an interruption (10, 11) so that the metallic layer (6) of the greater part of the upper surface (4) is electrically attached only to the metallic connecting area (8) of the one end (2) of the squared body and the metallic layer (7) of the greater part of the lowersurface (5) only to the metallic connecting area (9) of the other end (3) of the squared body.
2. Chip-varistor according to claim 1, characterized in that the interruption (10, 11) of the metallic area (6, 7) on the upper surface (4) and the lower surface (5), respectively, of the squaredlike body (1) is formed by at least one striplike recess.
3. Chip-varistor according to claim 1, characterized in that the striplike recess is limited by two parallel edges (12, 13) extending parallel to the edges of the upper- and lower surfaces (4, 5).
4. Chip-varistor according to claim 1 or 2, characterized in that the surface of the varistor material is provided in the area of the interruption (10, 11 ) of the metallic layer with at least one groove (14, 15) extending over the whole length of the striplike recess (10, 11).
5. Chip-varistor according to one of the claims 1 through 3, characterized in that the squaredlike body (1) is configured as sandwich body (16), consisting of alternating layers of varistor material (17) and electrically well conductive material (18) extending parallel to its upper and lower surfaces, wherein the electrically well conductive layers of material are alternatingly electrically conductive attached to the metallic connecting areas of the other end (2a, 3a) of the squared body.
6. Process of maufacturing the chip-varistors according to one of the claims 1 through 5, characterized in that
a) a squaredlike body of varistor material is manufactured and its surface is completely covered by a metal,
b) at least one longitudinally extending recess is manufactured into the opposing upper and lower surfaces of the squaredlike body, interrupting the metallic layer,
c) the squaredlike body is cut in cross direction to its longitudinal axis into single pieces of its length, the upper and lower surfaces of which are in the direction of the original longitudinal direction of the squared body shorter than in the direction of the original cross direction of the squared body.
EP85113401A 1984-12-14 1985-10-22 Chip varistor and production process Expired EP0184645B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85113401T ATE40765T1 (en) 1984-12-14 1985-10-22 CHIP VARISTOR AND PROCESS FOR ITS MANUFACTURE.

Applications Claiming Priority (2)

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DE19843445698 DE3445698A1 (en) 1984-12-14 1984-12-14 CHIP VARISTOR AND METHOD FOR THE PRODUCTION THEREOF
DE3445698 1984-12-14

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EP0184645A2 EP0184645A2 (en) 1986-06-18
EP0184645A3 EP0184645A3 (en) 1987-01-28
EP0184645B1 true EP0184645B1 (en) 1989-02-08

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EP85113401A Expired EP0184645B1 (en) 1984-12-14 1985-10-22 Chip varistor and production process

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AT (1) ATE40765T1 (en)
DE (1) DE3445698A1 (en)

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DE102006033691A1 (en) * 2006-07-20 2008-01-31 Epcos Ag Resistive element with PTC properties and high electrical and thermal conductivity

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US5973588A (en) * 1990-06-26 1999-10-26 Ecco Limited Multilayer varistor with pin receiving apertures
US6183685B1 (en) 1990-06-26 2001-02-06 Littlefuse Inc. Varistor manufacturing method
DE4029681A1 (en) * 1990-09-19 1992-04-02 Siemens Ag Metal electrode face type ceramic component - has end caps in contact with outer electrode having gaps in top and bottom surfaces

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DE102006033691A1 (en) * 2006-07-20 2008-01-31 Epcos Ag Resistive element with PTC properties and high electrical and thermal conductivity
US7902958B2 (en) 2006-07-20 2011-03-08 Epcos Ag Resistor element with PTC properties and high electrical and thermal conductivity

Also Published As

Publication number Publication date
DE3445698C2 (en) 1991-01-03
EP0184645A3 (en) 1987-01-28
DE3445698A1 (en) 1986-06-26
EP0184645A2 (en) 1986-06-18
ATE40765T1 (en) 1989-02-15

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