Ceramic Multi-Layer Component and Method for Producing a Ceramic Multi-Layer Component

Abstract

A ceramic multi-layer component and a method for producing a ceramic multi-layer component are disclosed. In an embodiment a ceramic multi-layer component includes a stack with ceramic layers and electrode layers arranged between them, wherein the ceramic layers and the electrode layers are arranged above one another along a stacking direction, wherein at least one first electrode layer extends along a first main extension direction from a first end region to a second end region of the first electrode layer, and wherein the at least one first electrode layer has a current-carrying capacity that decreases along the first main extension direction.

Claims

1-20. (canceled)

21. A ceramic multi-layer component, comprising a stack with ceramic layers and electrode layers arranged between them, wherein the ceramic layers and the electrode layers are arranged above one another along a stacking direction (S), wherein at least one first electrode layer extends along a main extension direction (H) from a first end region to a second end region of the first electrode layer, wherein the at least one electrode layer has a current-carrying capacity that decreases along the main extension direction.

22. The multi-layer component as claimed in claim 1, wherein the at least one electrode layer has a specific electrical conductivity that decreases along the main extension direction.

23. The multi-layer component as claimed in claim 1, wherein the at least one first electrode layer comprises a mixture of at least one first material with a first specific electrical conductivity and a second material with a second specific electrical conductivity that is lower than the first electrical conductivity, and the ratio (R) of the first material to the second material becomes smaller along the main extension direction.

24. The multi-layer component as claimed in claim 3, wherein the ratio decreases continuously in at least one partial region.

25. The multi-layer component as claimed in claim 3, wherein the ratio decreases in a stepwise manner in at least one partial region.

26. The multi-layer component as claimed in claim 3, wherein the first material comprises a metal.

27. The multi-layer component as claimed in claim 3, wherein the second material is electrically conductive.

28. The multi-layer component as claimed in claim 7, wherein the second material comprises a metal.

29. The multi-layer component as claimed in claim 3, wherein the first and/or second material is selected from Ni, Cu, Ag, Pd.

30. The multi-layer component as claimed in claim 3, wherein the second material is electrically insulating.

31. The multi-layer component as claimed in claim 10, wherein the second material comprises a ceramic material.

32. The multi-layer component as claimed in claim 1, wherein the at least one first electrode layer has a center of mass (C) that is located closer to the first end region than to the second end region.

33. The multi-layer component as claimed in claim 12, wherein the at least one first electrode layer has a greater thickness and/or a greater width at the first end region than at the second end region.

34. The multi-layer component as claimed in claim 13, wherein the thickness and/or the width of the at least one first electrode layer decreases in a stepwise manner in at least one partial region.

35. The multi-layer component as claimed in claim 13, wherein the thickness and/or the width of the at least one first electrode layer decreases in a continuous manner in at least one partial region.

36. The multi-layer component as claimed in claim 1, wherein the at least one first electrode layer comprises openings that extend into the electrode layer in the stacking direction.

37. The multi-layer component as claimed in claim 16, wherein the openings exhibit an occupancy density that increases along the main extension direction.

38. The multi-layer component as claimed in claim 1, wherein the stack has outer surfaces that bound the stack in directions perpendicular to the stacking direction, wherein the at least one first electrode layer adjoins the first end region at a first outer surface and wherein a first outer electrode that contacts the at least one first electrode layer electrically is arranged at the first outer surface.

39. The multi-layer component as claimed in claim 1, wherein at least one second electrode layer extends along a main extension direction (H) from a first end region to a second end region of the second electrode layer, wherein a second outer electrode that contacts the at least one second electrode layer electrically is arranged at a second outer surface that is different from the first outer surface, wherein the at least one second electrode layer adjoins the first end region at the second outer surface and wherein the at least one second electrode layer and the at least one first electrode layer are of the same design.

40. A method for the manufacture of a ceramic multi-layer component as claimed in claim 1, wherein the at least one first electrode layer is manufactured by means of multi-layer screen printing, by means of inhomogeneous screen printing, or by means of inkjet printing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further advantages, advantageous forms of embodiment and developments emerge from the exemplary embodiments described below in connection with the figures.

[0029] FIG. 1 shows a schematic illustration of a ceramic multi-layer component according to a first exemplary embodiment;

[0030] FIGS. 2A to 2D show schematic illustrations of multi-layer components according to further exemplary embodiments;

[0031] FIGS. 3A and 3B show schematic illustrations of multi-layer components according to further exemplary embodiments;

[0032] FIGS. 4A and 4B show schematic illustrations of multi-layer components according to further exemplary embodiments; and

[0033] FIGS. 5A and 5B show schematic illustrations of compositions of an electrode layer of a multi-layer component according to further exemplary embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0034] In the embodiments and figures, identical, similar or identically acting elements are provided in each case with the same reference numerals. The elements illustrated and their size ratios to one another should not be regarded as being to scale, but rather individual elements, such as for example layers, components, devices and regions, may have been made exaggeratedly large to illustrate them better and/or to aid comprehension.

[0035] The following figures each show exemplary embodiments of a ceramic multi-layer component 100 that is designed, purely by way of example, as an overvoltage protection element, in particular as what is known as a multi-layer overvoltage protection element. As an alternative to this, embodiments of the ceramic multi-layer components as, for example, thermal sensors, are possible through an appropriate selection of the ceramic material.

[0036] A schematic sectional view of an exemplary embodiment of the ceramic multi-layer component 100 that comprises a primary body formed of a stack 1 with ceramic layers 2 and electrode layers 3, 4 that are arranged above one another along a stacking direction S is shown in FIG. 1. The stack 1 furthermore comprises external surfaces that bound the stack 1 in directions perpendicular to the stacking direction S. The opposing external surfaces 5, 6 can be recognized in FIG. 1. The external surfaces 9, 10 are in addition recognizable in the following FIGS. 2A to 2D and 4A. The multi-layer component 100 can, for example, have a rectangular cross-section when viewed along the stacking direction S, so that the stack 1 accordingly comprises four external surfaces and can be designed as a cuboid. The stack 1 ends in the stacking direction with a lower side and an upper side.

[0037] The multi-layer component 100 is, as described above, designed, purely by way of example, as an overvoltage protection element, in particular as a multi-layer overvoltage protection element, in which at least the ceramic layers 2 that are arranged in the stacking direction S between the electrode layers 3, 4 comprise or consist of a varistor material. The stack 1 can finish in the stacking direction S with ceramic layers 2 that can also comprise a varistor material or, alternatively, a dielectric material. The electrode layers 3, 4 can preferably comprise or consist of one or a plurality of metals selected, for example, from Ni, Cu, Ag and Pd.

[0038] The ceramic layers 2 and the electrode layers 3, 4 can be manufactured of corresponding pastes, for example in the form of green tapes, applied to one another and sintered together in order to manufacture the ceramic multi-layer component 100. Printing methods such as, for example, screen printing or inkjet printing, using masks where appropriate, by means of which the pastes can be applied with the desired materials in the form of sintering particles mixed with binders, can for example be used for this purpose. Layer boundaries between the ceramic layers 2 are indicated in FIG. 1 by means of the dashed lines, which indicate the respective applied layers, and which are no longer present in the finished multi-layer component 100 as a result of the sintering process. Methods such as multi-layer screen printing, inhomogeneous screen printing and/or 3D inkjet printing can also be used, particularly in respect of the electrode layers 3, 4. The ceramic layers 2 can, for example, have a thickness, i.e. an extension along the stacking direction S, of between 1 m and 200 m. The electrode layers 3, 4 can, for example, have a thickness between 0.1 m and 10 m.

[0039] Outer electrodes can be attached to at least one or a plurality of external surfaces, by means of which electrode layers 3, 4 arranged in the stack can be contacted. A first outer electrode 7 and a second outer electrode 8, which can be embodied as one or a plurality of layers, are applied in the illustrated exemplary embodiments on the outer surfaces 5, 6 that can be recognized in FIG. 1, which are also referred to below as the first outer surface 5 and the second outer surface 6. The outer electrodes 7, 8 can comprise one or a plurality of metals selected from Cu, Cr, Ni, Ag and Au, for example. The outer electrodes 7, 8 can, for example, be vapor-deposited or sputtered. The outer electrodes 7, 8 can preferably have layer sequences with layers of Cr/Cu/Au or Cr/Cu/Ag or Cr/Ni/Ag or Cr/Ni/Ag. The outer electrodes 7, 8 are preferably in direct contact with the electrode layer 3 that can also be referred to below as the first electrode layer 3, or with the electrode layers 4 that can also be referred to below as the second electrode layers 4, so that the electrode layers 3, 4 are contacted electrically by the outer electrodes 7, 8.

[0040] The multi-layer component 100 is drawn in FIG. 1 with, purely by way of example, a first electrode layer 3 and with two second electrode layers 4. As an alternative to this it is also possible for more than one first electrode layer 3, as well as only one or more than two second electrode layers 4 to be present, which can preferably be separated from one another by ceramic layers 2 in the stacking direction S, applied in alternation on top of one another. The ceramic multi-layer component boo can thus comprise at least one first electrode layer 3 and at least one second electrode layer 4.

[0041] The at least one first electrode layer 3 extends from a first end region 31 that adjoins the first external surface 5 and the first external electrode 7, along a main extension direction H to a second end region 32, while the second electrode layers 4 correspondingly extend from a first end region 41 that adjoins the second external surface 6 and the second external electrode 8, along a main extension direction H, parallel to and aligned opposite to the main extension direction H, to a second end region 42. The first end regions 31, 41 can, in particular, form supply zones via which, when the ceramic multi-layer component 100 is in operation, an electrical current can be fed into the electrode layers or drawn out of the electrode layers, depending on the current direction. A corresponding, purely exemplary, current flow is indicated in FIG. 1 by means of the arrows between the first electrode layer 3 and the second electrode layers 4. Since the current injected into the first electrode layer 3 can continuously dissipate into the ceramic along the main extension direction H, the current intensity decreases with increasing distance to the supply zone formed by the first end region 31 in the first electrode layer 3. The at least one first electrode layer 3 is therefore designed such that it has a current-carrying capacity that reduces along the main extension direction H. The at least one first electrode layer 3 can accordingly withstand a higher maximum current at the first end region 31 than at the second end region 32. Exemplary embodiments for corresponding embodiments of the at least one first electrode layer 3 are shown in the following figures. The second electrode layers 4 can preferably have the same design as the first electrode layer 3. In the case of a plurality of first electrode layers, these can also preferably be of the same design.

[0042] FIGS. 2A to 2D show sectional illustrations through a multi-layer component wo like that of FIG. 1 along a sectional plane that extends perpendicularly to the stacking direction through the at least one first electrode layer 3. In the exemplary embodiments illustrated, the at least one first electrode layer 3 has a center of mass C that is located closer to the first end region 31 than to the second end region 32, the position of the center of mass C being only indicated schematically in the figures. The at least one first electrode layer 3 furthermore has a geometrical center along the main extension direction H, as indicated by the dashed line, which divides the at least one first electrode layer 3 along the main extension direction H into two equally long halves. As seen from the geometrical center, the center of mass C thus lies in the half that adjoins the first end region 31. The at least one first electrode layer 3 accordingly comprises more material, in particular more electrically conductive material in the half that faces toward the first end region 31 than in the half that faces toward the second end region 32. In this way it is possible to ensure that the current-carrying capacity is greater in the first end region 31 than in the second end region 32.

[0043] In the exemplary embodiments of FIGS. 2A to 2D the position of the center of mass C described has the effect that the at least one first electrode layer 3 has a greater width at the first end region 31 than at the second end region 32. This means that the width of the at least one first electrode layer 3 measured in a direction perpendicular to the stacking direction S and perpendicular to the main extension direction H decreases along the main extension direction H. The width in at least one partial region can, for example, decrease continuously. A first electrode layer 3 is shown in FIG. 2A, whose width becomes smaller in a linear and continuous manner over the entire length of the main extension direction H. The first electrode layer 3 can, as shown, be of trapezoidal design for this purpose. The width of the at least one first electrode layer 3 can furthermore decrease stepwise in at least one partial region. In the exemplary embodiment shown in FIG. 2B, the width of the first electrode layer 3 decreases for example in one step, or in the exemplary embodiment shown in FIG. 2C in a plurality of steps. As shown in FIG. 2D, the reduction in width is not only restricted to electrode layers shaped as polygons, but can also include surfaces with edges that are not straight lines. Mask-based printing methods, or inkjet printing methods can for example be used to manufacture the electrode layer shapes illustrated.

[0044] In the exemplary embodiments of FIGS. 3A and 3B, the at least one first electrode layer 3 has a greater thickness at the first end region 31 than at the second end region 32. As in the preceding exemplary embodiments, it can be ensured that the center of mass C is closer to the first end region 31 than to the second end region 32. The thickness of the at least one first electrode layer 3, as is shown in FIGS. 3A and 3B, can for example decrease stepwise in at least one partial region. The thickness of the first electrode layer 3 can, for example, decrease in one step, as is shown in FIG. 3A, or in a plurality of steps, as is shown in FIG. 3B. To manufacture a thickness that decreases in a stepwise manner, a multi-layer screen printing method can, for example, be used. A varying thickness can be manufactured here through the multiple printing of appropriate surface regions. An inhomogeneous screen printing method in which the material throughput can be adjusted through a density and/or size of cavities of a screen, can furthermore also be used. A 3D inkjet printing method can also be used. A continuously reducing thickness can in particular be manufactured by means of the latter method. The electrode layers illustrated in FIGS. 3A and 3B can, when viewed along the stacking direction S, for example have a rectangular cross-section, or a cross-section described in connection with the preceding figures with a decreasing width.

[0045] Exemplary embodiments of the ceramic multi-layer component 100 with the at least one first electrode layer 3 that comprises openings 11 that extend in the stacking direction S into the at least one first electrode layer 3, and particularly preferably extend through the at least one first electrode layer 3, are shown in FIGS. 4A and 4B. The openings 11 can be filled with the material of the adjoining ceramic layers 2 or also with a different ceramic material, for example a dielectric ceramic material. As is shown in FIG. 4A, the openings 11 have an occupancy density that increases along the main extension direction H, so that the at least one first electrode layer 3 has more openings near to the second end region 32 than near to the first end region 31, whereby again a shift in the center of mass C in the direction of the first end region 31 is achieved. The number and arrangement of the openings 11 shown in FIG. 4A is to be understood as purely exemplary. It can also be possible for the diameter of the openings to become greater with increasing distance from the first end region 31.

[0046] As is shown in FIG. 4B, the openings 11 can also be combined with a varying thickness, as described in connection with the exemplary embodiments of FIGS. 3A and 3B. In addition to this, an alternative or additional combination with a varying width, as described in connection with the exemplary embodiments of FIGS. 2A to 2D, is also possible. As explained above and shown in FIG. 4B, first and second electrode layers 3, 4 can in particular be of the same design.

[0047] As is described in the preceding exemplary embodiments, the electrode layers of the multi-layer component can have a shape that tapers along the main extension direction in terms of the width and/or the thickness, as well as, alternatively or in addition, openings with an occupancy density that becomes greater, or an opening diameter that becomes larger, along the main extension direction to reduce the electrode layer material, whereby an efficient consumption of material can be achieved. The geometrical design of the electrode layers can in particular be done in such a way that the local current density within the electrode layers, depending on the usual operating conditions to be expected, preferably remains constant, and always below a critical level, in spite of the current-carrying capacity becoming smaller along the main extension direction.

[0048] Alternatively or in addition to the geometrical variations described, the at least one first electrode layer can have a specific electrical conductivity that decreases along the main extension direction, whereby again a current-carrying capacity that becomes smaller along the main extension direction can be achieved. In particular, the at least one first electrode layer can have a higher specific electrical conductivity in the first end region than in the second end region. This can be achieved in that the at least one first electrode layer comprises a mixture with or consisting of at least one first material with a first specific electrical conductivity and a second material with a second specific electrical conductivity, wherein the second specific electrical conductivity is lower than the first specific electrical conductivity, and the ratio of the first material to the second material becomes smaller along the main extension direction. The at least one first electrode layer accordingly comprises a higher proportion of the first material as compared with the second material in the first end region than in the second end region. The at least one first electrode layer can here be free from the second material in the first end region and/or be free from the first material in the second end region. As an alternative to this, the first and the second material can be contained together in the at least one first electrode layer in the first end region and/or in the second end region. The varying mixture with or consisting of the first and second material can, for example, be achieved through a locally varying proportion of sintering particles with or consisting of the first material and through a locally varying proportion of sintering particles with or consisting of the second material in the green tape applied for the manufacture of the at least one first electrode layer. A 3D inkjet printing method can preferably be used to manufacture a varying ratio between the first and second material.

[0049] As is shown in FIGS. 5A and 5B, the ratio R of the first material to the second material correspondingly decreases in at least one partial region of the at least one first electrode layer along the main extension direction H. The drop in the ratio R between the first and second material can, as is indicated in FIG. 5A, occur in a stepwise manner, i.e., as shown, in a single step or alternatively also in multiple steps. The drop in the ratio R can furthermore for example also be continuous, as is indicated in FIG. 5B.

[0050] The first material can, particularly preferably, be a metal, in particular one or a plurality of metals selected from Ni, Cu, Ag and Pd. The second material can, like the first material, be electrically conductive and also comprise a metal, for example one or a plurality of the metals mentioned above, but in a composition such that the second material exhibits a lower specific electrical conductivity than the first material. The second material can, furthermore, also be electrically insulating, and can for example comprise or consist of an electrically insulating ceramic material such as, for example, silicon dioxide and/or aluminum oxide.

[0051] The features and embodiments described in connection with the figures can also be combined with one another according to further embodiments, even if not all such combinations are explicitly described. Furthermore, the embodiments described in connection with the figures can alternatively or additionally have further features according to the description in the general part.

[0052] The invention is not limited by the description based on the embodiments to these embodiments. Rather, the invention includes each new feature and each combination of features, which includes in particular each combination of features in the patent claims, even if this feature or this combination itself is not explicitly explained in the patent claims or embodiments.