WO2001090026A2 - Ceramic component and the use thereof - Google Patents

Ceramic component and the use thereof Download PDF

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Publication number
WO2001090026A2
WO2001090026A2 PCT/DE2001/002002 DE0102002W WO0190026A2 WO 2001090026 A2 WO2001090026 A2 WO 2001090026A2 DE 0102002 W DE0102002 W DE 0102002W WO 0190026 A2 WO0190026 A2 WO 0190026A2
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WO
WIPO (PCT)
Prior art keywords
ceramic
base body
ceramic component
contact layer
component according
Prior art date
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PCT/DE2001/002002
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German (de)
French (fr)
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WO2001090026A3 (en
Inventor
Hermann GRÜNBICHLER
Peter Grobbauer
Adalbert Feltz
Original Assignee
Epcos Ag
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Publication date
Application filed by Epcos Ag filed Critical Epcos Ag
Priority to AU2001276258A priority Critical patent/AU2001276258A1/en
Priority to EP01953769A priority patent/EP1286934A2/en
Publication of WO2001090026A2 publication Critical patent/WO2001090026A2/en
Publication of WO2001090026A3 publication Critical patent/WO2001090026A3/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/52—Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
    • C04B41/81—Coating or impregnation
    • C04B41/89—Coating or impregnation for obtaining at least two superposed coatings having different compositions
    • 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
    • H01C7/02—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 having positive temperature coefficient
    • H01C7/022—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 having positive temperature coefficient mainly consisting of non-metallic substances
    • H01C7/023—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 having positive temperature coefficient mainly consisting of non-metallic substances containing oxides or oxidic compounds, e.g. ferrites
    • H01C7/025—Perovskites, e.g. titanates
    • 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
    • H01C7/115—Titanium dioxide- or titanate type
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00844—Uses not provided for elsewhere in C04B2111/00 for electronic applications

Definitions

  • the invention relates to a ceramic component with a protective layer.
  • the invention relates to the use of the ceramic component.
  • Ceramic components are known which are used as varistors, which have high thermal stability and whose base body contains a mixture of metal oxides. Components of this type are usually soldered on boards in surface mounting and serve to protect the voltage of various electronic components in electrical devices and apparatuses of electrical engineering.
  • SMD capability surface mounting of the components is achieved by contacting the base body by baking a silver paste on the base body and then galvanizing the silver paste in one
  • Nickel and tin bath The outermost tin contact layer guarantees the SMD capability.
  • the contact layers are applied in the acid baths known from standard electroplating, which attack the ceramic component chemically.
  • a protective layer prevents acid attack on parts of the surface of the ceramic component that are not to be coated with the contact layer.
  • the known ceramic materials have the disadvantage that they have a high lead content.
  • the lead can easily penetrate into the interior of the ceramic base body and adversely affect the electrical characteristics of the ceramic component.
  • the non-environmentally friendly and toxic lead accumulates in the sintering furnace necessary for the production of ceramic components.
  • the aim of the present invention is therefore a ceramic
  • the invention provides a ceramic component with a
  • the specified ceramic materials can optionally contain other conventional constituents in small amounts that do not impair the desired properties.
  • the ceramic materials mentioned here represent modifications of the known PZT, PLZT and PLZST ceramics. They are characterized in that the lead from the known ceramics is at least partially replaced by bismuth. As a result, the ceramic materials have the advantage that they have a low lead content. Furthermore, the ceramic materials have the advantage that they are chemically resistant to the acid baths used in standard electroplating.
  • the ceramics mentioned are further characterized in that the entire lead content is not replaced by bismuth, but that cation gaps remain in the perovskite structure.
  • ⁇ formally marks a blank.
  • the modified formula (t ⁇ 1, v> 0) corresponding to the PLZST ceramic is: (Pb / La) 1 _ 3x Bi 2x ⁇ x (Zr, Sn, Ti) 0 3 .
  • the amount of materials contains a ceramic material with the general formula:
  • Bi / Ba a / b, where n is an integer and where: a) 1 ⁇ n ⁇ 5 b) 0 ⁇ b and a / b> 0.5.
  • the ceramic materials specified here can optionally contain other conventional constituents in small amounts, which do not impair the desired properties.
  • Ceramic materials have the advantage that they contain no lead and that they are chemically resistant to the acid baths used in the electroplating process.
  • the amount of materials contains a ceramic material with a pyrochlore structure, which can contain a rare earth metal SE, with the general formula: Bi 2 - Z SE Z (TijL_ x _y, Zr x , Sny) 2 ° 7 , where applies: O ⁇ z ⁇ l, O ⁇ x ⁇ l; O ⁇ y ⁇ l.
  • the specified ceramic materials can optionally contain other conventional constituents in small amounts that do not impair the desired properties.
  • Ceramic materials have the advantage that, owing to their resistance to the acid baths used in electroplating, they are suitable as a protective layer for ceramic components and that they contain no lead.
  • Such materials with a pyrochlore structure would be, for example
  • SE stands for an element of rare earths (e.g. lanthanum, praseodymium, samarium, gadolinium).
  • the ceramic component according to the invention has the advantage that, because of the protective layer, the ceramic base body is not chemically attacked by the galvanic application of the contact layer.
  • the ceramic component has the advantage that the electrical properties of the ceramic due to the low lead content of the protective layer
  • the ceramic component can not be changed by lead penetrating into the ceramic base body. Furthermore, the ceramic component has the advantage that, due to the low lead content of its protective layer, it is particularly environmentally friendly and less toxic.
  • a ceramic component is particularly advantageous in which there is a starting layer for the electroplating process between the base body and the contact layer.
  • the starting layer for the electroplating process has the advantage that the electroplating takes place in a clearly limited space, since the metal in the electroplating process only layer and does not deposit on the remaining surface of the base body.
  • the starting layer has the advantage that, because of its good electrical conductivity, which is necessary for the electroplating, it ensures good contacting of the ceramic base body of the component.
  • a ceramic component is particularly advantageous in which the contact layer is suitable for surface mounting the component. Due to the suitability of the contact layer for surface mounting (SMD capability), the entire component is suitable for surface mounting. With the help of surface mounting, a highly rationalized, automated assembly process of the components on a printed circuit board is possible.
  • a contact layer made of tin, for example, can be used as a particularly advantageous contact layer.
  • a ceramic component in which the starting layer is produced by a silver baking paste on the base body is particularly advantageous.
  • the silver baking paste has the advantage that it ensures good adhesion to the ceramic. This has a positive influence on the mechanical stability of the ceramic component.
  • a ceramic component is particularly advantageous, the base body of which has a contact layer on two opposite sides, which are contacted with electrically conductive electrodes located in the interior of the base body, the electrodes being arranged such that they measure the ohmic resistance measured between the contact layers reduce the component.
  • the electrodes in the interior of the base body have the advantage that they reduce the relatively high ohmic resistance of the ceramic to such an extent that the ceramic component has an electrical resistance which is adapted to the particular use of the component.
  • the ohmic resistance of the ceramic component can be flexibly adapted to the intended area of use of the component by suitable design of the conductive electrodes.
  • Palladium or silver is advantageously used as the material for the conductive electrodes. These two precious metals have the advantage that they can be sintered in air, which means that a special sintering atmosphere can be created.
  • the invention also provides a ceramic component in which the base body is a zinc oxide ceramic doped with aluminum, cobalt and manganese oxide.
  • a ceramic component has the advantage that it can be used as a varistor due to the special material properties of the base body.
  • Such components are important as voltage protection of electronic circuits on circuit boards in computer technology and communication technology as well as in electrical devices and apparatus of electrical engineering.
  • the SMD capability is an important prerequisite, so that the component according to the invention with its SMD capability, which is easy to obtain due to the protective layer, can be used particularly advantageously.
  • Figure 1 shows an example of a ceramic component according to the invention in a schematic perspective view.
  • FIG. 2 shows the ceramic component from FIG. 1 in a schematic longitudinal section.
  • FIG. 3 shows the area of the contact layer of the component from FIG. 2.
  • FIG. 1 shows a ceramic component according to the invention, which has a base body 1, on which a first contact layer 2 and a second contact layer 3 are arranged.
  • the two contact layers 2, 3 are galvanically applied tin layers. With the help of these tin layers, the component can be attached to a printed circuit board in SMD mounting.
  • FIG. 2 shows the ceramic component from FIG. 1 with a ceramic base body 1, which can be, for example, a doped zinc oxide ceramic.
  • a first contact layer 2 and a second contact layer 3 are applied to two opposite sides of the base body 1. These contact layers 2, 3 give the component its SMD capability.
  • a protective layer 4 made of one of the specified ceramic materials .
  • electrodes 6 which consist of a mixture of silver and palladium and which reduce the ohmic resistance of the component.
  • the component shown in FIG. 2 can be a varistor, which is manufactured according to the method described below:
  • the raw material mixture processed into a slip and processed into ceramic green foils.
  • Ceramic green foils are processed in a screen printing process using a precious metal paste suitable for sintering with the ceramic, with which the green foils are printed. This precious metal paste represents the electrodes 6.
  • the printed green foils are stacked, laminated and separated by cutting, from which green parts of a certain miniaturized design of multilayer varistors, essentially given by the geometric dimensions, result.
  • protective ceramic foils made of a ceramic material according to the invention are used as the base and cover foil, which have a high electrical resistance, are chemically stable with respect to the electroplating baths to be used later and are adapted in their sintering behavior to the varistor ceramic.
  • the green parts are printed on the respective cut sides with a screen printing paste consisting of the same passivating material.
  • a screen printing paste consisting of the same passivating material.
  • green parts are sintered and then provided with a metal paste consisting of silver or a silver-containing alloy on the end faces in the area of the emerging electrodes 6 in a dipping process.
  • the silver or the silver-containing alloy is then burned in in a separate process step, as a result of which contact is made with the electrodes 6 of the component.
  • This passivation layer also forms the starting layer 5 of the electroplating, which, as shown in FIG. 3, is located between the base body 1 and the second contact layer 3.
  • the baked metal paste is then electroplated with a nickel and tin layer to produce the contact layers 2, 3, as a result of which the component's SMD capability is established.
  • the passivation layers prevent the caustic partial dissolution of the varistor ceramic and, moreover, the deposition of nickel or tin on the ceramic surface between the end faces of the components.
  • a ceramic material according to the following formula: Big 4Pto 4 ⁇ 0 2 (T Zr 0 6 5 '- 0 3 5) ° 3 USAGE ⁇ be det.
  • the symbol ⁇ formally denotes an empty space.
  • Preparation technique mixed oxide technique with two conversions (once at 750 ° C and once at 950 ° C) followed by fine grinding.
  • Suitable raw materials for manufac Development of this compound are Bi 0 3 , Pb 3 0 4 , Zr0 2 and Ti0 2 .
  • the varistors are coated with the protective layer 4 before the components are sintered.
  • the coating itself can be carried out using conventional methods, for example by pasting the powder with an organic binding agent and solvent and then screen printing.
  • the protective layer 4 densifies to a large extent free of tension and pores, so that the surfaces printed with the protective layer 4 are sealed and protect against the acid attack of an electroplating bath.
  • the protective layer can fulfill its protective function, it must have a layer thickness between 20 and 50 ⁇ m.
  • the substances Bi 2 ZrTi ⁇ (bismuth zirconate / titanate) and Bi 2 SnTi ⁇ (bismuth stannate / titanate) are used.
  • This material can also be produced using the “mixed oxide” technique — similar to embodiment 1 — with conversion and subsequent fine grinding.
  • the protective layer 4 is again applied to the component by screen printing a paste.
  • protective layers 4 which are approximately twice as thick are required for these materials in order to prevent the acid attack of the electroplating. After sintering, voltage-free and dense protective layers 4 are formed, which do not have any influence on the electrical characteristics of the varistor.
  • the protective layer 4 according to exemplary embodiment 1 has somewhat better chemical stability compared to the acids used in electroplating than the protective layer 4 according to exemplary embodiment 2.
  • the influencing of the electrical characteristic values was again in the case of a ceramic material in accordance with exemplary embodiment 2, it was considerably cheaper than in the case of exemplary embodiment 1.
  • the evaporation of lead oxide was likewise substantially more favorable in the case of a ceramic material in accordance with exemplary embodiment 2. The reason for this is the obvious absolute freedom from lead of the protective layer 4 according to exemplary embodiment 2.
  • the invention is not limited to the exemplary embodiments shown, but is defined in its most general form by claim 1.

Abstract

The invention relates to a ceramic component (e.g. a varistor) comprising a protective layer (4) made of ceramic materials, which contain small amounts of lead and which are based on perovskite structures, whereby the lead is completely or partially replaced by bismuth. Titanates are also considered which comprise a structure of phases of the Aurivillius type, whereby no lead whatsoever is present. Additionally considered are compounds which have pyrochlore structures and which contain bismuth and, optionally, an element of the rare earths. The ceramic component is resistant against the acids used during the electrodeposition of the contact layers (SMD capability) due to the provision of the protective layer (4) that contains small amounts of lead.

Description

Beschreibungdescription
Keramisches Bauelement und dessen VerwendungCeramic component and its use
Die Erfindung betrifft ein keramisches Bauelement mit einer Schutzschicht. Darüber hinaus betrifft die Erfindung die Verwendung des keramischen Bauelements.The invention relates to a ceramic component with a protective layer. In addition, the invention relates to the use of the ceramic component.
Es sind keramische Bauelemente bekannt, die als Varistoren verwendet werden, die eine hohe thermische Stabilität aufweisen und deren Grundkörper eine Mischung aus Metalloxiden enthält. Derartige Bauelemente werden üblicherweise in Oberflächenmontage auf Platinen gelötet und dienen dem Spannungs- schutz verschiedener elektronischer Komponenten in elektri- sehen Geräten und Apparaten der Elektrotechnik.Ceramic components are known which are used as varistors, which have high thermal stability and whose base body contains a mixture of metal oxides. Components of this type are usually soldered on boards in surface mounting and serve to protect the voltage of various electronic components in electrical devices and apparatuses of electrical engineering.
Die Möglichkeit der Oberflächenmontage (SMD-Fähigkeit) der Bauelemente wird erreicht durch Kontaktierung des Grundkörpers mittels Einbrennen einer Silberpaste auf dem Grundkörper und anschließendes Galvanisieren der Silberpaste in einemThe possibility of surface mounting (SMD capability) of the components is achieved by contacting the base body by baking a silver paste on the base body and then galvanizing the silver paste in one
Nickel- und Zinnbad. Die äußerste Zinn-Kontaktschicht garantiert dabei die SMD-Fähigkeit . Das Aufbringen der Kontaktschichten geschieht dabei in den aus der Standardgalvanik bekannten Säurebädern, die das keramische Bauelement chemisch angreifen. Durch eine Schutzschicht wird ein Säureangriff auf nicht mit der KontaktSchicht zu beschichtenden Teilen der Oberfläche des keramischen Bauelements verhindert .Nickel and tin bath. The outermost tin contact layer guarantees the SMD capability. The contact layers are applied in the acid baths known from standard electroplating, which attack the ceramic component chemically. A protective layer prevents acid attack on parts of the surface of the ceramic component that are not to be coated with the contact layer.
Es sind als Schutzschichten verwendete keramische Materialien der eingangs genannten Art bekannt, die auf dem Perowskit-Ceramic materials of the type mentioned at the outset, which are used as protective layers and which are based on the perovskite
Strukturtyp basieren und Blei enthalten. Beispiele hierfür sind Pb(Zr,Ti)03 (PZT-Keramik) , (Pb, La) (Zr, Ti) 03 (PLZT- Keramik) oder (Pb,La) (Zr, Sn,Ti) 03 (PLZST-Keramik) . Diese Ke- ramiken werden als Schutzschichten für keramische Bauelemente verwendet, auf deren Oberfläche Kontaktschichten galvanisch aufgebrachte werden sollen.Structure type based and contain lead. Examples include Pb (Zr, Ti) 0 3 (PZT ceramic), (Pb, La) (Zr, Ti) 0 3 (PLZT ceramic) or (Pb, La) (Zr, Sn, Ti) 0 3 ( PLZST ceramics). This key Ramics are used as protective layers for ceramic components, on the surface of which contact layers are to be applied galvanically.
Die bekannten keramischen Materialien haben den Nachteil, daß sie einen hohen Bleigehalt aufweisen. Das Blei kann leicht in das Innere des keramischen Grundkörpers eindringen und die elektrischen Kennwerte des keramischen Bauelements negativ beeinflussen. Darüber hinaus reichert sich das nicht umweit- freundliche und giftige Blei im für die Herstellung keramischer Bauelemente notwendigen Sinterofen an.The known ceramic materials have the disadvantage that they have a high lead content. The lead can easily penetrate into the interior of the ceramic base body and adversely affect the electrical characteristics of the ceramic component. In addition, the non-environmentally friendly and toxic lead accumulates in the sintering furnace necessary for the production of ceramic components.
Es sind ferner aus DE 196 34 498 C2 Schutzumhüllungen für keramische Bauelemente bekannt, die aus zwei unterschiedlichen Materialien bestehen. Diese Schutzumhüllungen haben den Nachteil, daß aufgrund der Notwendigkeit von zwei verschiedenen Materialien eine aufwendige Vorgehensweise zur Herstellung dieser Schichten notwendig ist.From DE 196 34 498 C2 protective coverings for ceramic components are known which consist of two different materials. These protective casings have the disadvantage that, because of the need for two different materials, a complex procedure for producing these layers is necessary.
Ziel der vorliegenden Erfindung ist es daher, ein keramischesThe aim of the present invention is therefore a ceramic
Bauelement mit einer Schutzschicht aus einem Material anzugeben, das einen niedrigen Bleigehalt aufweist und das als Schutz vor den Säurebädern der Standardgalvanik geeignet ist.Specify component with a protective layer made of a material that has a low lead content and is suitable as protection against the acid baths of standard electroplating.
Dieses Ziel wird erfindungsgemäß durch ein keramisches Bauelement nach Anspruch 1 erreicht . Weitere Ausgestaltungen der Erfindung sowie die Verwendung des keramischen Bauelements sind den weiteren Ansprüchen zu entnehmen.This goal is achieved according to the invention by a ceramic component according to claim 1. Further refinements of the invention and the use of the ceramic component can be found in the further claims.
Die Erfindung gibt ein keramisches Bauelement mit einemThe invention provides a ceramic component with a
Grundkörper an, dessen Oberfläche teilweise mit einer galvanisch aufgebrachten Kontaktschicht bedeckt ist und dessen von der Kontaktschicht freie Teil seiner Oberfläche mit einer Schutzschicht aus einem keramischen Material bedeckt ist. Dabei ist das Material der Schutzschicht ausgewählt aus einer Menge von Materialien, die ein keramisches Material mit Perowskitstruktur mit der allgemeinen Formel : ABO3 enthält wobei die A-Plätze mit den Metallen Bi und Pb und/oder La und die B-Plätze mit den Metallen Zr und/oder Ti und/oder Sn mit folgenden Verhältnissen besetzt sind: a) Pb/La = t/l-t b) (Pb + La)/Bi = l-3x/2x c) Zr/Sn/Ti = u/v/w, und wobei gilt :Base body, the surface of which is partially covered with a galvanically applied contact layer and whose part of the surface free of the contact layer is covered with a Protective layer is covered from a ceramic material. The material of the protective layer is selected from a set of materials which contains a ceramic material with a perovskite structure with the general formula: ABO3, where the A sites with the metals Bi and Pb and / or La and the B sites with the metals Zr and / or Ti and / or Sn are occupied with the following ratios: a) Pb / La = t / lt b) (Pb + La) / Bi = l-3x / 2x c) Zr / Sn / Ti = u / v / w, and where:
0 < t ≤ 1; 0 < 3x < 1; 0 < V < 1 ; 0 ≤ u < 1 ; 0 ≤ w < 1.0 <t ≤ 1; 0 <3x <1; 0 <V <1; 0 ≤ u <1; 0 ≤ w <1.
Die angegebenen keramischen Materialien können gegebenenfalls weitere übliche Bestandteile in geringen Mengen enthalten, die die gewünschten Eigenschaften nicht beeinträchtigen.The specified ceramic materials can optionally contain other conventional constituents in small amounts that do not impair the desired properties.
Die hier genannten keramischen Materialien stellen Modifikationen der bekannten PZT-, PLZT- und PLZST-Keramiken dar. Sie zeichnen sich dadurch aus, daß das Blei aus den bekannten Keramiken wenigstens teilweise durch Wismut ersetzt ist. Dadurch haben die keramischen Materialien den Vorteil, daß sie einen niedrigen Bleigehalt aufweisen. Ferner haben die keramischen Materialien den Vorteil, daß sie gegenüber den in der Standardgalvanik benutzten Säurebädern chemisch resistent sind.The ceramic materials mentioned here represent modifications of the known PZT, PLZT and PLZST ceramics. They are characterized in that the lead from the known ceramics is at least partially replaced by bismuth. As a result, the ceramic materials have the advantage that they have a low lead content. Furthermore, the ceramic materials have the advantage that they are chemically resistant to the acid baths used in standard electroplating.
Die genannten Keramiken sind ferner dadurch gekennzeichnet, daß nicht der ganze Bleigehalt durch Wismut ersetzt wird, sondern zudem noch Kationenlücken in der Perowskitstruktur zurückbleiben. So lautet beispielsweise die allgemeine Formel für eine modifizierte PZT-Keramik (t = 1, v = 0) : Pb1_3XBi2xΔx(Zr,Ti)03. Dabei kennzeichnet Δ formal eine Leerstelle. Die entsprechende allgemeine Formel für eine modifizierte PLZT-Keramik (t ≠ 1, v = 0) lautet: (Pb,La)1_3xBi2xΔx(Zr,Ti)03. Die der PLZST-Keramik entsprechende modifizierte Formel (t < 1, v > 0) lautet: (Pb/La)1_3xBi2xΔx(Zr,Sn,Ti)03.The ceramics mentioned are further characterized in that the entire lead content is not replaced by bismuth, but that cation gaps remain in the perovskite structure. For example, the general formula for a modified PZT ceramic (t = 1, v = 0) is: Pb 1 _3 X Bi 2x Δ x (Zr, Ti) 0 3 . Δ formally marks a blank. The corresponding general formula for a modified PLZT ceramic (t ≠ 1, v = 0) is: (Pb, La) 1 _ 3x Bi 2x Δ x (Zr, Ti) 0 3 . The modified formula (t <1, v> 0) corresponding to the PLZST ceramic is: (Pb / La) 1 _ 3x Bi 2x Δ x (Zr, Sn, Ti) 0 3 .
Ferner enthält die Menge von Materialien ein keramisches Ma- terial mit der allgemeinen Formel:Furthermore, the amount of materials contains a ceramic material with the general formula:
Bi03 (ATi03)n/ bei der A für Bi oder für Bi und Ba in einem MengenverhältnisBi0 3 (ATi0 3 ) n / at A for Bi or for Bi and Ba in a ratio
Bi/Ba = a/b steht, bei der n ganzzahlig ist und bei der gilt: a) 1 < n < 5 b) 0 < b und a/b > 0,5.Bi / Ba = a / b, where n is an integer and where: a) 1 <n <5 b) 0 <b and a / b> 0.5.
Die hier angegebenen keramischen Materialien können gegebenenfalls weitere übliche Bestandteile in geringen Mengen enthalten, die die gewünschten Eigenschaften nicht beeinträchti- gen.The ceramic materials specified here can optionally contain other conventional constituents in small amounts, which do not impair the desired properties.
Diese keramischen Materialien haben den Vorteil, daß sie kein Blei enthalten und daß sie chemisch resistent sind gegenüber den im galvanischen Beschichtungsprozeß verwendeten Säurebä- dem. Speziell kommen beispielsweise die folgenden Keramiken in Betracht: Bi4Ti30ι2 (n = 3),
Figure imgf000005_0001
(n = 4) oder Ba Bi4Ti5018 (n = 5) .These ceramic materials have the advantage that they contain no lead and that they are chemically resistant to the acid baths used in the electroplating process. The following ceramics are particularly suitable, for example: Bi 4 Ti 3 0ι 2 ( n = 3),
Figure imgf000005_0001
(n = 4) or Ba Bi 4 Ti 5 0 18 (n = 5).
Darüber hinaus enthält die Menge von Materialien ein kerami- sches Material mit Pyrochlorstruktur, das ein Seltenes Erdmetall SE enthalten kann, mit der allgemeinen Formel: Bi2--ZSEZ (TijL_x_y, Zrx,Sny) 2°7, wobei gilt: O ≤ z ≤ l, O ≤ x ≤ l; O ≤ y ≤ l. Die angegebenen keramischen Materialien können gegebenenfalls weitere übliche Bestandteile in geringen Mengen enthalten, die die gewünschten Eigenschaften nicht beeinträchtigen.In addition, the amount of materials contains a ceramic material with a pyrochlore structure, which can contain a rare earth metal SE, with the general formula: Bi 2 - Z SE Z (TijL_ x _y, Zr x , Sny) 2 ° 7 , where applies: O ≤ z ≤ l, O ≤ x ≤ l; O ≤ y ≤ l. The specified ceramic materials can optionally contain other conventional constituents in small amounts that do not impair the desired properties.
Diese keramischen Materialien haben den Vorteil, daß sie aufgrund ihrer Resistenz gegenüber den bei der Galvanik verwendeten Säurebädern als Schutzschicht für keramische Bauelemente geeignet sind und daß sie kein Blei enthalten. Solche Ma- terialien mit Pyrochlorstruktur wären beispielsweiseThese ceramic materials have the advantage that, owing to their resistance to the acid baths used in electroplating, they are suitable as a protective layer for ceramic components and that they contain no lead. Such materials with a pyrochlore structure would be, for example
Bi2_zSEz (τil-x-y/Zr »Sny) 2°7' wobei SE für ein Element der seltenen Erden (z.B. Lanthan, Praseodym, Samarium, Gadolinium) steht .Bi 2 _z SE z (τ i l -xy / Zr » Sn y) 2 ° 7 'where SE stands for an element of rare earths (e.g. lanthanum, praseodymium, samarium, gadolinium).
Das erfindungsgemäße keramische Bauelement hat den Vorteil, daß wegen der Schutzschicht der keramische Grundkörper durch das galvanische Aufbringen der Kontaktschicht chemisch nicht angegriffen wird. Darüber hinaus hat das keramische Bauelement den Vorteil, daß aufgrund des niedrigen Bleigehalts der Schutzschicht die elektrischen Eigenschaften des keramischenThe ceramic component according to the invention has the advantage that, because of the protective layer, the ceramic base body is not chemically attacked by the galvanic application of the contact layer. In addition, the ceramic component has the advantage that the electrical properties of the ceramic due to the low lead content of the protective layer
Bauelements nicht durch in den keramischen Grundkörper eindringendes Blei verändert werden. Ferner hat das keramische Bauelement den Vorteil, daß es aufgrund des niedrigen Bleigehalts seiner Schutzschicht besonders umweltfreundlich und we- nig giftig ist.Component can not be changed by lead penetrating into the ceramic base body. Furthermore, the ceramic component has the advantage that, due to the low lead content of its protective layer, it is particularly environmentally friendly and less toxic.
Es ist darüber hinaus ein keramisches Bauelement besonders vorteilhaft, bei dem sich zwischen dem Grundkörper und der Kontaktschicht eine Startschicht für den Galvanikprozeß be- findet. Die StartSchicht für den Galvanikprozeß hat den Vorteil, daß die Galvanik eindeutig räumlich begrenzt stattfindet, da sich das Metall im Galvanikprozeß nur auf der Start- schicht und nicht auf der restlichen Oberfläche des Grundkörpers abscheidet .In addition, a ceramic component is particularly advantageous in which there is a starting layer for the electroplating process between the base body and the contact layer. The starting layer for the electroplating process has the advantage that the electroplating takes place in a clearly limited space, since the metal in the electroplating process only layer and does not deposit on the remaining surface of the base body.
Ferner hat die Startschicht den Vorteil, daß sie aufgrund ih- rer für die Galvanik notwendigen guten elektrischen Leitfähigkeit für eine gute Kontaktierung des keramischen Grundkörpers des Bauelementes sorgt .Furthermore, the starting layer has the advantage that, because of its good electrical conductivity, which is necessary for the electroplating, it ensures good contacting of the ceramic base body of the component.
Ferner ist ein keramisches Bauelement besonders vorteilhaft, bei dem die Kontaktschicht für die Oberflächenmontage des Bauelements geeignet ist. Aufgrund der Eignung der Kontaktschicht für die Oberflächenmontage (SMD-Fähigkeit) ist das ganze Bauelement für die Oberflächenmontage geeignet. Mit Hilfe der Oberflächenmontage ist ein stark rationalisierter, automatisierter Bestückvorgang der Bauelemente auf einer Leiterplatte möglich. Als besonders vorteilhafte Kontaktschicht kann beispielsweise eine aus Zinn bestehenden Kontaktschicht verwendet werden.Furthermore, a ceramic component is particularly advantageous in which the contact layer is suitable for surface mounting the component. Due to the suitability of the contact layer for surface mounting (SMD capability), the entire component is suitable for surface mounting. With the help of surface mounting, a highly rationalized, automated assembly process of the components on a printed circuit board is possible. A contact layer made of tin, for example, can be used as a particularly advantageous contact layer.
Ferner ist ein keramisches Bauelement besonders vorteilhaft, bei dem die Startschicht durch eine Silber-Einbrennpaste auf dem Grundkörper hergestellt ist. Die Silber-Einbrennpaste hat den Vorteil, daß sie eine gute Haftung auf der Keramik gewährleistet. Dadurch wird die mechanische Stabilität des ke- ramischen Bauelements positiv beeinflußt.Furthermore, a ceramic component in which the starting layer is produced by a silver baking paste on the base body is particularly advantageous. The silver baking paste has the advantage that it ensures good adhesion to the ceramic. This has a positive influence on the mechanical stability of the ceramic component.
Darüber hinaus ist ein keramisches Bauelement besonders vorteilhaft, dessen Grundkörper auf zwei gegenüberliegenden Seiten je eine Kontaktschicht aufweist, die mit im Inneren des Grundkörpers befindlichen, elektrisch leitfähigen Elektroden kontaktiert sind, wobei die Elektroden so angeordnet sind, daß sie den zwischen den Kontaktschichten gemessenen ohmschen Widerstand des Bauelements reduzieren. Die Elektroden im Inneren des Grundkörpers haben den Vorteil, daß sie den relativ hohen ohmschen Widerstand der Keramik so weit reduzieren, daß das keramische Bauelement einen an die jeweilige Verwendung des Bauelements angepaßten elektrischen Widerstand aufweist. Durch geeignete Gestaltung der leitfähigen Elektroden kann der ohmsche Widerstand der keramischen Bauelements flexibel an den jeweils vorgesehenen Einsatzbereich des Bauelements angepaßt werden.In addition, a ceramic component is particularly advantageous, the base body of which has a contact layer on two opposite sides, which are contacted with electrically conductive electrodes located in the interior of the base body, the electrodes being arranged such that they measure the ohmic resistance measured between the contact layers reduce the component. The electrodes in the interior of the base body have the advantage that they reduce the relatively high ohmic resistance of the ceramic to such an extent that the ceramic component has an electrical resistance which is adapted to the particular use of the component. The ohmic resistance of the ceramic component can be flexibly adapted to the intended area of use of the component by suitable design of the conductive electrodes.
Als Material für die leitfähigen Elektroden kommt vorteilhafterweise Palladium oder Silber zum Einsatz. Diese beiden Edelmetalle haben den Vorteil, daß sie an Luft gesintert werden können, wodurch auf eine spezielle Sinteratmosphäre ver- ziehtet werden kann.Palladium or silver is advantageously used as the material for the conductive electrodes. These two precious metals have the advantage that they can be sintered in air, which means that a special sintering atmosphere can be created.
Ferner gibt die Erfindung ein keramisches Bauelement an, bei dem der Grundkörper eine mit Aluminium-, Kobalt- und Manganoxid dotierte Zinkoxidkeramik ist. Ein solches keramisches Bauelement hat den Vorteil, daß es aufgrund der speziellen Materialeigenschaft des Grundkörpers als Varistor verwendet werden kann. Derartige Bauelemente sind als Spannungsschütz von elektronischen Schaltungen auf Platinen in der Computertechnik und Kommunikationstechnik sowie in elektrischen Gerä- ten und Apparaturen der Elektrotechnik von Bedeutung.The invention also provides a ceramic component in which the base body is a zinc oxide ceramic doped with aluminum, cobalt and manganese oxide. Such a ceramic component has the advantage that it can be used as a varistor due to the special material properties of the base body. Such components are important as voltage protection of electronic circuits on circuit boards in computer technology and communication technology as well as in electrical devices and apparatus of electrical engineering.
Bei diesen Anwendungen ist die SMD-Fähigkeit eine wichtige Voraussetzung, so daß das erfindungsgemäße Bauelement mit seiner aufgrund der Schutzschicht leicht zu erlangenden SMD- Fähigkeit besonders vorteilhaft verwendet werden kann.In these applications, the SMD capability is an important prerequisite, so that the component according to the invention with its SMD capability, which is easy to obtain due to the protective layer, can be used particularly advantageously.
Im folgenden wird die Erfindung anhand von Ausführungsbei- spielen und den dazugehörigen Figuren näher erläutert . Figur 1 zeigt beispielhaft ein erfindungsgemäßes keramisches Bauelement in schematisch-perspektivischer Darstellung.The invention is explained in more detail below with the aid of exemplary embodiments and the associated figures. Figure 1 shows an example of a ceramic component according to the invention in a schematic perspective view.
Figur 2 zeigt das keramische Bauelement aus Figur 1 im schematischen Längsschnitt.FIG. 2 shows the ceramic component from FIG. 1 in a schematic longitudinal section.
Figur 3 zeigt den Bereich der Kontaktschicht des Bauele- ments aus Figur 2.FIG. 3 shows the area of the contact layer of the component from FIG. 2.
Figur 1 zeigt ein erfindungsgemäßes keramisches Bauelement, das einen Grundkörper 1 aufweist, an dem eine erste Kontaktschicht 2 und eine zweite Kontaktschicht 3 angeordnet ist. Die beiden Kontaktschichten 2, 3 sind galvanisch aufgebrachte Zinnschichten. Mit Hilfe dieser Zinnschichten kann das Bauelement in SMD-Montage auf einer Leiterplatte befestigt werden.FIG. 1 shows a ceramic component according to the invention, which has a base body 1, on which a first contact layer 2 and a second contact layer 3 are arranged. The two contact layers 2, 3 are galvanically applied tin layers. With the help of these tin layers, the component can be attached to a printed circuit board in SMD mounting.
Figur 2 zeigt das keramische Bauelement aus Figur 1 mit einem keramischen Grundkδrper 1, der beispielsweise eine dotierte Zinkoxidkeramik sein kann. An zwei gegenüberliegenden Seiten des Grundkörpers 1 ist eine erste Kontaktschicht 2 und eine zweite Kontaktschicht 3 aufgebracht. Diese Kontaktschichten 2, 3 verleihen dem Bauelement seine SMD-Fähigkeit. Zum Schutz des Grundkörpers 1 vor den während der Aufbringung der Kontaktschichten 2, 3 auf den Grundkörper 1 einwirkenden Säuren im Galvanikbad ist der von den Kontaktschichten 2, 3 freie Teil der Oberfläche des Grundkörpers 1 mit einer Schutz- schicht 4 aus einem der angegebenen Keramikmaterialien bedeckt . Im Innern des Grundkörpers 1 befinden sich Elektroden 6, die aus einer Mischung aus Silber und Palladium bestehen und die den ohmschen Widerstand des Bauelements verringern.FIG. 2 shows the ceramic component from FIG. 1 with a ceramic base body 1, which can be, for example, a doped zinc oxide ceramic. A first contact layer 2 and a second contact layer 3 are applied to two opposite sides of the base body 1. These contact layers 2, 3 give the component its SMD capability. To protect the base body 1 from the acids in the electroplating bath which act on the base body 1 during the application of the contact layers 2, 3, the part of the surface of the base body 1 free of the contact layers 2, 3 is covered with a protective layer 4 made of one of the specified ceramic materials , Inside the base body 1 there are electrodes 6 which consist of a mixture of silver and palladium and which reduce the ohmic resistance of the component.
Das in Figur 2 dargestellte Bauelement kann ein Varistor sein, der gemäß dem im folgenden beschriebenen Verfahren hergestellt wird:The component shown in FIG. 2 can be a varistor, which is manufactured according to the method described below:
Ausgehend von einer mit Aluminium-, Kobalt- und Manganoxid dotierten Zinkoxidkeramik, deren Gefügeausbildung im nachfolgenden Sinterprozeß durch weitere Zusätze, vor allem Bi20 Sb 03, Si02, NiO und Cr203 sowie etwas Borsäure gesteuert wird, wird die Rohstoffmischung zu einem Schlicker aufbereitet und zu keramischen Grünfolien verarbeitet. Die Verarbei- tung zu keramischen Grünfolien geschieht in einem Siebdruckverfahren mit einer zur gemeinsamen Sinterung mit der Keramik geeigneten Edelmetallpaste, mit der die Grünfolien bedruckt werden. Diese Edelmetallpaste stellt die Elektroden 6 dar.Starting from a zinc oxide ceramic doped with aluminum, cobalt and manganese oxide, the structure of which is controlled in the subsequent sintering process by further additives, especially Bi 2 0 Sb 0 3 , Si0 2 , NiO and Cr 2 0 3 as well as some boric acid, the raw material mixture processed into a slip and processed into ceramic green foils. Ceramic green foils are processed in a screen printing process using a precious metal paste suitable for sintering with the ceramic, with which the green foils are printed. This precious metal paste represents the electrodes 6.
Die bedruckten Grünfolien werden gestapelt, laminiert und durch Schneiden vereinzelt, woraus Grünteile einer bestimmten, im wesentlichen durch die geometrischen Abmessungen gegebenen, miniaturisierten Bauform von Vielschichtvaristoren entstehen. Bei diesem Prozeß werden als Basis- und Deckfolie schutzgebende Keramikfolien (Schutzschichten 4) aus einem erfindungsgemäßen keramischen Material angewendet, die einen hohen elektrischen Widerstand aufweisen, gegenüber den später anzuwendenden Galvanikbädern chemisch stabil und in ihrem Sinterverhalten an die Varistorkeramik angepaßt sind.The printed green foils are stacked, laminated and separated by cutting, from which green parts of a certain miniaturized design of multilayer varistors, essentially given by the geometric dimensions, result. In this process protective ceramic foils (protective layers 4) made of a ceramic material according to the invention are used as the base and cover foil, which have a high electrical resistance, are chemically stable with respect to the electroplating baths to be used later and are adapted in their sintering behavior to the varistor ceramic.
Nach dem Schneiden werden die Grünteile an den jeweiligen Schnittseiten mit einer Siebdruckpaste, bestehend aus dem gleichen passivierenden Material bedruckt . Die so aufgebauten Grünteile werden nach dem sorgfältigen Entbindern (Entfernen von Kohlenstoffresten) gesintert und anschließend an den Stirnseiten im Bereich der austretenden Elektroden 6 im Tauchverfahren mit einer Metallpaste, bestehend aus Silber oder einer silberhaltigen Legierung, versehen. Das Silber beziehungsweise die silberhaltige Legierung wird anschließend in einem gesonderten Prozeßschritt eingebrannt, wodurch der Kontakt zu den Elektroden 6 des Bauelements hergestellt wird.After cutting, the green parts are printed on the respective cut sides with a screen printing paste consisting of the same passivating material. The so constructed After careful debinding (removal of carbon residues), green parts are sintered and then provided with a metal paste consisting of silver or a silver-containing alloy on the end faces in the area of the emerging electrodes 6 in a dipping process. The silver or the silver-containing alloy is then burned in in a separate process step, as a result of which contact is made with the electrodes 6 of the component.
Diese Passivierungsschicht bildet gleichzeitig die Startschicht 5 der Galvanik, die, wie in Figur 3 dargestellt, sich zwischen dem Grundkörper 1 und der zweiten Kontaktschicht 3 befindet. Anschließend wird die eingebrannte Metallpaste mit einer Nickel- .und Zinnschicht zur Herstellung der Kontakt- schichten 2, 3 galvanisch überzogen, wodurch die SMD- Fähigkeit des Bauelements hergestellt wird. Die Passivie- rungsschichten verhindern die ätzende partielle Auflösung der Varistorkeramik und darüber hinaus die Abscheidung von Nickel oder Zinn auf der Keramikoberfläche zwischen den Stirnseiten der Bauelemente.This passivation layer also forms the starting layer 5 of the electroplating, which, as shown in FIG. 3, is located between the base body 1 and the second contact layer 3. The baked metal paste is then electroplated with a nickel and tin layer to produce the contact layers 2, 3, as a result of which the component's SMD capability is established. The passivation layers prevent the caustic partial dissolution of the varistor ceramic and, moreover, the deposition of nickel or tin on the ceramic surface between the end faces of the components.
Die in dem genannten Prozeß verwendeten Schutzschichten werden im folgenden anhand von zwei Ausführungsbeispielen näher erläutert :The protective layers used in the process mentioned are explained in more detail below using two exemplary embodiments:
In einem ersten Beispiel kann ein keramisches Material gemäß der folgenden Formel: Big 4Pto 4 Δ 0 2 (Zr 0 65T:'-0 35) °3 verwen¬ det werden. Das Symbol Δ bezeichnet formal eine Leerstelle.In a first example, a ceramic material, according to the following formula: Big 4Pto 4 Δ 0 2 (T Zr 0 6 5 '- 0 3 5) ° 3 USAGE ¬ be det. The symbol Δ formally denotes an empty space.
Die Herstellung dieses Keramikpulvers kann in klassischerThe production of this ceramic powder can be classic
Präparationstechnik (Mixed Oxide-Technik) mit zweimaligem Umsetzen (einmal bei 750°C und einmal bei 950°C) und anschließender Feinmahlung erfolgen. Geeignete Rohstoffe zur Herstel- lung dieser Verbindung sind Bi 03, Pb304, Zr02 und Ti02. Die Beschichtung der Varistoren mit der Schutzschicht 4 erfolgt vor dem Sintern der Bauelemente. Die Beschichtung selbst kann mit gängigen Verfahren erfolgen, so zum Beispiel durch Anpa- sten des Pulvers mit einem organischen Binde- und Lösungsmittel und anschließendem Siebdruck.Preparation technique (mixed oxide technique) with two conversions (once at 750 ° C and once at 950 ° C) followed by fine grinding. Suitable raw materials for manufac Development of this compound are Bi 0 3 , Pb 3 0 4 , Zr0 2 and Ti0 2 . The varistors are coated with the protective layer 4 before the components are sintered. The coating itself can be carried out using conventional methods, for example by pasting the powder with an organic binding agent and solvent and then screen printing.
Beim Sintern verdichtet die Schutzschicht 4 weitgehend span- nungs- und porenfrei, so daß die mit der Schutzschicht 4 be- druckten Flächen dicht sind und vor dem Säureangriff eines Galvanikbades schützen. Durch die Reduktion des Bleianteils auf die Hälfte gegenüber der die Basis für diese Verbindung bildenden PZT-Keramik ist die negative Beeinflussung der elektrischen Kennwerte des Varistors weitgehend vermieden.During sintering, the protective layer 4 densifies to a large extent free of tension and pores, so that the surfaces printed with the protective layer 4 are sealed and protect against the acid attack of an electroplating bath. By reducing the proportion of lead to half compared to the PZT ceramic that forms the basis for this connection, the negative influence on the electrical characteristics of the varistor is largely avoided.
Weiterhin ist der Bleiabdampf beim Sintern und die Anreicherung von Bleioxid im Sinterofen deutlich verringert. Die Reduzierung des Bleianteils ist somit auch aus ökologischer Sicht ein bedeutender Schritt. Damit die Schutzschicht ihre Schutzfunktion erfüllen kann, muß sie eine Schichtdicke zwischen 20 und 50 μm aufweisen.Furthermore, the lead vapor during sintering and the accumulation of lead oxide in the sintering furnace are significantly reduced. The reduction of the lead content is therefore also an important step from an ecological perspective. So that the protective layer can fulfill its protective function, it must have a layer thickness between 20 and 50 μm.
In einem zweiten Ausführungsbeispiel kommen die Substanzen Bi2ZrTiθ (Wismut-Zirkonat/-Titanat) und Bi2SnTiθ (Wismut- Stannat/-Titanat) zum Einsatz.In a second exemplary embodiment, the substances Bi 2 ZrTiθ (bismuth zirconate / titanate) and Bi 2 SnTiθ (bismuth stannate / titanate) are used.
Die Herstellung dieses Materials kann ebenfalls in der "Mixed-Oxide" -Technik - ähnlich dem Ausführungsbeispiel 1 - mit Umsatz und anschließender Feinmahlung erfolgen. Die Auf- bringung der Schutzschicht 4 auf dem Bauelement erfolgt wiederum durch Siebdruck einer Paste. Gegenüber dem Ausführungsbeispiel 1 sind bei diesen Materialien etwa doppelt so dicke Schutzschichten 4 erforderlich, um den Säureangriff der Galvanik abzuhalten. Nach dem Sintern entstehen spannungsfreie und dichte Schutzschichten 4, die zu keinerlei Beeinflussung der elektrischen Kennwerte des Varistors führen.This material can also be produced using the “mixed oxide” technique — similar to embodiment 1 — with conversion and subsequent fine grinding. The protective layer 4 is again applied to the component by screen printing a paste. Compared to the exemplary embodiment 1, protective layers 4 which are approximately twice as thick are required for these materials in order to prevent the acid attack of the electroplating. After sintering, voltage-free and dense protective layers 4 are formed, which do not have any influence on the electrical characteristics of the varistor.
In einem experimentellen Vergleich der beiden Ausführungsbei- spiele wurde festgestellt, daß die Schutzschicht 4 gemäß Aus- fuhrungsbeispiel 1 eine etwas bessere chemische Stabilität gegenüber den bei der Galvanik verwendeten Säuren aufweist, als die Schutzschicht 4 gemäß Ausführungsbeispiel 2. Die Beeinflussung der elektrischen Kennwerte wiederum war bei einem keramischen Material gemäß Ausführungsbeispiel 2 wesentlich günstiger als gemäß dem Ausfuhrungsbeispiel 1. Das Abdampfen von Bleioxid war ebenfalls bei einem keramischen Material gemäß Ausführungsbeispiel 2 wesentlich günstiger. Der Grund dafür ist die offensichtliche absolute Bleifreiheit der Schutzschicht 4 gemäß Ausfuhrungsbeispiel 2.In an experimental comparison of the two exemplary embodiments, it was found that the protective layer 4 according to exemplary embodiment 1 has somewhat better chemical stability compared to the acids used in electroplating than the protective layer 4 according to exemplary embodiment 2. The influencing of the electrical characteristic values was again in the case of a ceramic material in accordance with exemplary embodiment 2, it was considerably cheaper than in the case of exemplary embodiment 1. The evaporation of lead oxide was likewise substantially more favorable in the case of a ceramic material in accordance with exemplary embodiment 2. The reason for this is the obvious absolute freedom from lead of the protective layer 4 according to exemplary embodiment 2.
Die Erfindung beschränkt sich nicht auf die beispielhaft gezeigten Ausführungsformen, sondern wird in ihrer allgemeinsten Form durch die Anspruch 1 definiert . The invention is not limited to the exemplary embodiments shown, but is defined in its most general form by claim 1.

Claims

Patentansprüche claims
Keramisches Bauelement mit einem Grundkörper (1) , dessen Oberfläche teilweise mit einer galvanisch aufgebrachten Kontaktschicht (2, 3) bedeckt ist und dessen von der Kontaktschicht freie Teil seiner Oberfläche mit einer Schutzschicht (4) aus einem keramischen Material besteht, das ein oder mehrere Elemente einer Menge von Materialien enthält, wobei die Menge folgende Elemente enthält:Ceramic component with a base body (1), the surface of which is partially covered with a galvanically applied contact layer (2, 3) and the part of its surface free of the contact layer with a protective layer (4) made of a ceramic material which comprises one or more elements contains a set of materials, the set containing the following elements:
ein keramisches Material mit Perowskitstruktur mit der allgemeinen Formel: AB03 , bei dem die A-Plätze mit den Metallen Bi und Pb und/oder La und die B-Plätze mit den Metallen Zr und/oder Ti und/oder Sn mit folgenden Verhältnissen besetzt sind: a) Pb/La = t/l-t b) (Pb + La)/Bi = l-3x/2x c) Zr/Sn/Ti = u/v/w, und bei der gilt: 0 < t ≤ 1; 0 < 3x < 1; 0 ≤ V < 1; 0 < u < 1 ; 0 ≤ w < 1,a ceramic material with a perovskite structure with the general formula: AB0 3 , in which the A sites are occupied by the metals Bi and Pb and / or La and the B sites by the metals Zr and / or Ti and / or Sn with the following ratios are: a) Pb / La = t / lt b) (Pb + La) / Bi = l-3x / 2x c) Zr / Sn / Ti = u / v / w, and the following applies: 0 <t ≤ 1 ; 0 <3x <1; 0 ≤ V <1; 0 <u <1; 0 ≤ w <1,
ein keramisches Material mit der allgemeinen Formel: Bi03 (ATi03)n, bei dem A für Bi oder für Bi und Ba in einem Mengenverhältnis Bi/Ba = a/b steht, bei der n ganzzahlig ist und bei der gilt : a) 1 < n < 5 b) 0 < b und a/b > 0,5, unda ceramic material with the general formula: Bi0 3 (ATi0 3 ) n , in which A stands for Bi or for Bi and Ba in a ratio Bi / Ba = a / b, in which n is an integer and in which: a) 1 <n <5 b) 0 <b and a / b> 0.5, and
ein keramisches Material mit Pyrochlorstruktur, das ein Seltenes Erdmetall SE enthalten kann, mit der allgemeinen Formel : Bi2 _ zSEz (Tiι _x_y, Zrx, Sny) 2°1 , wobei gilt : O ≤ z ≤ l , O ≤ x ≤ l ; O ≤ y ≤ l .a ceramic material with pyrochlore structure, which can contain a rare earth metal SE, with the general Formula: Bi 2 _ z SE z (Tiι _ x _y, Zr x , Sny) 2 ° 1, where: O ≤ z ≤ l, O ≤ x ≤ l; O ≤ y ≤ l.
2. Keramisches Bauelement nach Anspruch 1, bei dem sich zwischen dem Grundkörper (1) und der Kon- taktschicht (2, 3) eine Startschicht (5) für den Galvanikprozeß befindet.2. Ceramic component according to claim 1, in which there is a starting layer (5) for the electroplating process between the base body (1) and the contact layer (2, 3).
3. Keramisches Bauelement nach einem der Ansprüche 1 oder 2, bei dem die Kontaktschicht (2, 3) für die Oberflächenmontage des Bauelements geeignet ist.3. Ceramic component according to one of claims 1 or 2, wherein the contact layer (2, 3) is suitable for surface mounting of the component.
4. Keramisches Bauelement nach einem der Ansprüche 1 bis 3, bei dem die Kontaktschicht (2, 3) aus Zinn besteht.4. Ceramic component according to one of claims 1 to 3, wherein the contact layer (2, 3) consists of tin.
5. Keramisches Bauelement nach einem der Ansprüche 2 bis 4, bei dem die Startschicht (5) durch Auftragen einer Silber-Einbrennpaste auf den Grundkörper (1) hergestellt ist.5. Ceramic component according to one of claims 2 to 4, in which the starting layer (5) is produced by applying a silver baking paste to the base body (1).
6. Keramisches Bauelement nach einem der Ansprüche 1 bis 5, dessen Grundkörper (1) auf zwei gegenüberliegenden Seiten je eine Kontaktschicht (2, 3) aufweist, die mit im Innern des Grundkörpers (1) befindlichen, elektrisch leitfähigen Elektroden (6) kontaktiert sind, wobei die Elektroden (6) so angeordnet sind, daß sie den zwischen den Kontaktschichten (2, 3) gemessenen ohmschen Widerstand des Bauelements reduzieren.6. Ceramic component according to one of claims 1 to 5, the base body (1) on two opposite sides each having a contact layer (2, 3) which are in contact with the inside of the base body (1) located, electrically conductive electrodes (6) The electrodes (6) are arranged in such a way that they reduce the ohmic resistance of the component measured between the contact layers (2, 3).
7. Keramisches Bauelement nach einem der Ansprüche 1 bis 6, bei dem der Grundkörper (1) eine mit Aluminium-, Kobalt- und Manganoxid dotierte Zinkoxidkeramik ist. erwendung eines keramischen Bauelements nach Anspruch 7 als Varistor. 7. Ceramic component according to one of claims 1 to 6, in which the base body (1) is a zinc oxide ceramic doped with aluminum, cobalt and manganese oxide. Use of a ceramic component according to claim 7 as a varistor.
PCT/DE2001/002002 2000-05-26 2001-05-25 Ceramic component and the use thereof WO2001090026A2 (en)

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CN114716241A (en) * 2021-12-29 2022-07-08 西南科技大学 High-voltage ceramic dielectric material and preparation method and application thereof

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DE102007020783A1 (en) 2007-05-03 2008-11-06 Epcos Ag Electrical multilayer component
DE102007031510A1 (en) 2007-07-06 2009-01-08 Epcos Ag Electrical multilayer component
DE102015120640A1 (en) 2015-11-27 2017-06-01 Epcos Ag Multi-layer component and method for producing a multilayer component
DE102020122299B3 (en) 2020-08-26 2022-02-03 Tdk Electronics Ag Multilayer varistor and method for producing a multilayer varistor

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CN107068311A (en) * 2016-10-12 2017-08-18 江西兴勤电子有限公司 Low-temperature sintered voltage-sensitive resistor without antimony component and preparation method thereof
CN107068311B (en) * 2016-10-12 2018-10-16 江西兴勤电子有限公司 Low-temperature sintered voltage-sensitive resistor without antimony component and preparation method thereof
CN114716241A (en) * 2021-12-29 2022-07-08 西南科技大学 High-voltage ceramic dielectric material and preparation method and application thereof

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WO2001090026A3 (en) 2002-06-27
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DE10026258B4 (en) 2004-03-25
AU2001276258A1 (en) 2001-12-03

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