Multilayer component and use of external electrodes

Description

[0001] The invention relates to a multilayer component, in particular a ceramic multilayer component. The invention further relates to the use of external electrodes for a multilayer component.

[0002] For many multilayer components, it is critical for performance that the positive and negative polarities on the multilayer component are correctly connected to the corresponding polarities of the control. This is generally the case when ordering states must be created in the ceramic to ensure the performance of the multilayer component. A typical example is the polarization process step in PZT (lead zirconate titanate) multilayer components, which involves the alignment of domains under the influence of an electric field. For such multilayer components, the polarity assignment established in the manufacturing chain must remain known in subsequent process steps.

[0003] US 2016 / 056366 A1 shows a ceramic multilayer structure with a first C-shaped outer electrode that completely covers an outer side of the multilayer structure and partially overlaps a top and a bottom side of the multilayer structure, and a second L-shaped outer electrode that completely covers a second outer surface and partially covers a bottom side of the multilayer structure. DE 102009029571 A1 shows a piezo actuator, on one outer side of which a first outer electrode and a connecting electrode are arranged.

[0004] From US 2013 / 241360 A1, a piezoelectric multilayer component is known in which an outer electrode has a notch to indicate the polarity.

[0005] For example, it is known to print a label with the correct polarity or to apply a chamfer to the multilayer component with the correct polarity.

[0006] One object to be achieved is to provide an improved multilayer component and the use of improved external electrodes for a multilayer component. This object is achieved by the electronic component according to claim 1 and the use according to claim 8.

[0007] According to one aspect, a multilayer component is specified. The multilayer component has a base body. The base body has a plurality of alternating ceramic layers and internal electrodes. The ceramic layers comprise, for example, an Nd-doped PZT material. The internal electrodes comprise, for example, silver and / or palladium. The internal electrodes are arranged, for example, at a distance of 0.1 mm to 0.8 mm, for example, 0.4 mm + / - 0.05 mm, from one another. The distance corresponds approximately to the thickness of the ceramic layers.

[0008] The component has at least two external electrodes for electrically contacting the internal electrodes. For example, the multilayer component has at least a first internal electrode electrically connected to a first external electrode and a second internal electrode electrically connected to a second external electrode.

[0009] The outer electrodes are arranged, for example, in layers on opposite side surfaces of the base body. In particular, the outer electrodes can be formed as sputtered layers. The outer electrodes can be made of chromium, nickel, and silver. For example, the outer electrodes have a CrNiAg layer structure.

[0010] The multilayer component has exactly two external electrodes arranged on opposite side surfaces of the base body.

[0011] The two outer electrodes have different polarities. During the manufacture of the multilayer component, the ceramic layers are polarized by applying an electrical voltage between the outer electrodes. This polarization determines the electrical connection of the multilayer component during operation. In particular, one of the outer electrodes is designed as the positive outer electrode and one as the negative outer electrode.

[0012] The outer electrodes have a different arrangement on an outer surface of the base body to indicate the different polarity assignments. Additionally, the outer electrodes can have a different geometric shape and / or a different size.

[0013] In particular, the outer electrodes are designed in such a way that their top views cannot be converted into one another by rotation.

[0014] The different designs of the outer electrodes serve to identify the different polarities of the outer electrodes. In the process chain, the application of the outer electrodes always takes place before the process step of creating the order in the ceramic, as this requires controllable inner electrodes. If this process step is carried out in the correct position relative to the existing polarity markings, the polarity of the multilayer component can always be subsequently detected.

[0015] The external electrodes always present on the multilayer component allow for simple and cost-effective marking of polarity. The external electrodes are assigned an additional function. Additional effort for applying a polarity marking is eliminated, as the external electrode must be applied in every case. Correct assembly of the multilayer component, particularly the correct electrical connection of the external electrodes, is ensured in a simple and cost-effective manner. This provides a cost-effective, simple, and user-friendly multilayer component.

[0016] According to one embodiment, the first outer electrode has a smaller area than the second outer electrode, or vice versa. In particular, the outer electrodes have different areas for polarity marking. It is crucial that at least one of the outer electrodes is enlarged in size beyond the amount required for the actual function of the respective outer electrode. The other outer electrode can have an area or dimension that is precisely required for the actual function of the outer electrode. This allows the polarity of the outer electrodes to be easily differentiated.

[0017] According to one embodiment, the outer electrodes each have a width in a direction perpendicular to a stacking direction of the ceramic layers. The width of the first outer electrode is smaller than the width of the second outer electrode. The reverse case is also conceivable, with the width of the second outer electrode being smaller than the width of the first outer electrode.

[0018] The outer electrodes each have a height in a direction parallel to a stacking direction of the ceramic layers. The height of the first outer electrode can be greater than the height of the second outer electrode, or vice versa.

[0019] In one embodiment, the outer electrodes have the same height but different widths. In one embodiment, the outer electrodes have the same width but different heights.

[0020] According to one embodiment, the first outer electrode has a rectangular shape and the second outer electrode has a round shape or vice versa.

[0021] According to one embodiment, the multilayer component has broken rotational symmetry. The base body has opposing side surfaces, with one of the external electrodes being offset from an edge delimiting the respective side surface. The multilayer component is, for example, asymmetrical with respect to a rotation of 180° around a vertical axis that runs in the stacking direction of the multilayer component.

[0022] According to one embodiment, the multilayer component is designed as a piezo multilayer actuator, as a multilayer pressure sensor or as a ceramic capacitor.

[0023] The pressure sensor is designed, for example, as an NCS sensor (needle closing sensor), which monitors the closing of a valve needle of a fuel injector. The pressure sensor is designed, for example, such that when pressure is applied to an upper side and / or a lower side of the base body, an electrical signal can be tapped at the outer electrodes. The upper side and lower side are the sides that close off the base body at the top and bottom in the stacking direction of the layers. The outer electrodes are preferably arranged on side surfaces that do not form the upper side or the lower side of the stack. In particular, the side surfaces are arranged perpendicular to the upper side and lower side.

[0024] According to a further aspect, the use of external electrodes is described. The external electrodes preferably correspond to the external electrodes described above. All features described in connection with the external electrodes and the multilayer component also apply to the use, and vice versa.

[0025] The external electrodes described above are used for a multilayer component as described above. The external electrodes are used to identify the different polarities of the external electrodes, in particular for polarity marking on the multilayer component. The external electrodes have a different arrangement on a base body of the multilayer component for polarity marking. The external electrodes thus have an additional function that allows the polarity on the multilayer component to be identified in a simple and cost-effective manner.

[0026] The invention is explained in more detail below with reference to exemplary embodiments and the associated figures.

[0027] The drawings described below are not to be considered to scale. Rather, individual dimensions may be enlarged, reduced, or distorted for clarity.

[0028] Elements that are identical or that perform the same function are designated by the same reference symbols. Figure 1 shows a schematic sectional view of a multilayer component according to the prior art, Figure 2a shows a perspective view of a multilayer component according to a first embodiment, Figure 2b shows a plan view of the multilayer component according to Figure 2a , Figure 3a shows a perspective view of a multilayer component according to a comparative example which does not fall under the subject matter of the protection sought. Figure 3b shows a perspective view of the multilayer component rotated by 180° according to Figure 3a , Figure 4a shows a perspective view of a multilayer component according to a further embodiment, Figure 4b shows a perspective view of the multilayer component rotated by 180° according to Figure 4a .

[0029] The Figure 1 shows a schematic sectional view of a multilayer component according to the prior art.

[0030] The multilayer component 1 comprises a base body 1a. The base body 1a comprises a plurality of ceramic layers 2. In particular, the ceramic layers 2 are piezoceramic layers. The ceramic layers 2 comprise, for example, an Nd-doped PZT material.

[0031] Internal electrodes 3a, 3b are arranged between the ceramic layers 2. The internal electrodes 3a, 3b comprise, for example, an alloy of silver and palladium.

[0032] The internal electrodes 3a, 3b serve to electrically control the ceramic layers 2. The ceramic layers 2 and the internal electrodes 3a, 3b are arranged one above the other to form a stack. A plurality of internal electrodes 3a, 3b each extend alternately out of the base body 1a at a side surface 6 of the base body 1a. In particular, internal electrodes 3a, 3b assigned to different polarities extend to the surface of the base body 1a on opposite side surfaces 6 of the base body 1a.

[0033] The multilayer component 1 has two external electrodes 4a, 4b arranged on opposite side surfaces 6 of the base body 1a. The external electrodes 4a, 4b can be formed as fired metallic layers. The external electrodes 4a, 4b are preferably formed as sputtered layers. For example, the external electrodes 4a, 4b can have a sputtered layer made of CrNiAg. The internal electrodes 3a, 3b are electrically conductively connected alternately in the stacking direction to one of the external electrodes 4a, 4b and are electrically insulated from the other external electrode 4b, 4a. The external electrodes 4a, 4b thus connect the internal electrodes 3a, 3b and enable their joint control.

[0034] The multilayer component 1 can, for example, comprise a piezoelectric multilayer actuator, a multilayer pressure sensor, or a ceramic capacitor. The ceramic layers 2 represent the actual functional element of the multilayer component 1. When an electrical voltage is applied to the internal electrodes 3a, 3b, they realize capacitance, mechanical displacement, or sensor signal output, depending on the type of multilayer component 1.

[0035] During the production of the multilayer component 1, the ceramic layers 2 are polarized by applying an electrical voltage between the external electrodes 4a, 4b. During polarization of the multilayer component 1, for example, the first external electrode 4a is connected to a negative pole of a voltage source and the second external electrode 4b to a positive pole of a voltage source. Accordingly, the first external electrode 4a can be referred to as the negative electrode / negative external electrode and the second external electrode 4b as the positive electrode / positive external electrode. Of course, the reverse assignment is also possible. Thus, the second external electrode 4b can be referred to as the negative electrode / negative external electrode and the first external electrode 4a as the positive electrode / positive external electrode.

[0036] For the electrical performance of the multilayer component 1, it is essential that the positive and negative polarities on the multilayer component 1 are correctly connected to the corresponding polarities of the control. Figures 2a to 4b therefore deal with embodiments by which the polarity on the multilayer component 1 can be characterized. Figures 2a to 4b The underlying multilayer component 1 essentially corresponds to the multilayer component 1 according to the Figure 1 with the exception of the shape, dimensions and / or arrangement of the external electrodes 4a, 4b.

[0037] Figure 2a shows a perspective view of a multilayer component according to a first embodiment. Figure 2b shows a top view of the multilayer component according to Figure 2a .

[0038] In this embodiment, both outer electrodes 4a, 4b have a rectangular shape. However, other geometric shapes for the outer electrodes 4a, 4b are also conceivable, for example, a circular shape.

[0039] Different dimensions of the external electrodes 4a, 4b are used for polarity marking on the multilayer component 1. In this exemplary embodiment, the first external electrode 4a has a width b1 that is smaller than the width b2 of the second external electrode 4b. The width of the external electrodes 4a, 4b refers to the extent of the external electrodes 4a, 4b that extends in a direction perpendicular to a stacking direction of the ceramic layers 2. For example, the width b1 of the first external electrode 4a is half the width b2 of the second external electrode. In this exemplary embodiment, the first external electrode 4a refers to the negative external electrode, and the second external electrode 4b corresponds to the positive external electrode 4b.

[0040] The height h1 of the first outer electrode 4a is also greater than the height h2 of the second outer electrode 4b. The height h1, h2 of the outer electrodes 4a, 4b refers to the extent of the outer electrodes 4a, 4b in a direction parallel to a stacking direction of the ceramic layers 2. Overall, the first outer electrode 4a has a smaller area than the second outer electrode 4b. For example, the area of ​​the first outer electrode 4a is 0.4 to 0.7 times the area of ​​the second outer electrode. For example, the area of ​​the first outer electrode 4a is half the area of ​​the second outer electrode.

[0041] Of course, the polarity assignment can also be reversed, i.e., for example, the width b1 of the negative outer electrode 4a can be greater than the width b2 of the positive outer electrode 4b. The height h1 of the negative outer electrode 4a can be smaller than the height h2 of the positive outer electrode 4b. The area of ​​the negative outer electrode 4a can be larger than the area of ​​the positive outer electrode 4b. What is crucial is that at least one of the outer electrodes 4a, 4b is enlarged in its dimensions beyond the amount required for the actual function of the respective outer electrode 4a, 4b (the reliable electrical supply to the inner electrodes 3a, 3b).

[0042] In addition, in this exemplary embodiment, the rotational symmetry of the multilayer component 1 is broken. In particular, the first external electrode 4a is not arranged centrally on a side surface 6 of the base body 1a. Rather, the first external electrode 4a is arranged offset towards an edge 6a delimiting the side surface 6. In other words, in a plan view of the side surface 6 in question, the first external electrode 4a is shifted to the left in the direction of the edge 6a of the side surface. Of course, the shifting of the external electrode 4a in a different direction is also conceivable. In a plan view of the side surface 6 in question, the first external electrode 4a can be shifted to the left, right, up or down in the direction of an edge 6a of the side surface 6.

[0043] The second outer electrode 4b, however, is arranged centrally on an opposite side surface 6. The polarity of the outer electrodes 4a, 4b can also be identified by the different arrangement of the outer electrodes 4, 4b on the respective outer surface. Thus, the negative outer electrode 4a is shifted toward an edge 6a, while the positive outer electrode 4b is arranged rotationally symmetrically on the center of the side surface 6.

[0044] Of course, the reverse case (central negative outer electrode 4a and offset positive outer electrode 4b) is also possible. Due to the different arrangement of the outer electrodes 4a, 4b on the respective side surface 6, the rotational symmetry of the multilayer component 1 is broken (see also the Figures 4a and 4b ). After rotation of the multilayer component 1 by 180° around a vertical axis v (see Figures 3a and 3b) the first outer electrode 4a is shifted to the right towards the edge 6a of the side surface (not explicitly shown).

[0045] The two outer electrodes 4a, 4b can alternatively or additionally have different geometric shapes for polarity identification (not explicitly shown). For example, the first outer electrode 4a can be circular and the second outer electrode 4b can be rectangular, or vice versa. Other shapes are also conceivable for the outer electrodes 4a, 4b, for example, a trapezoidal shape. In the case of polarity identification purely by geometric shape, it is important that the two outer electrodes 4a, 4b have a different geometric shape.

[0046] Figure 3a shows a perspective view of a multilayer component according to a comparative example, which does not fall under the subject matter of the protection sought. Figure 3bshows a perspective view of the multilayer component rotated by 180° according to the Figure 3a .

[0047] In this exemplary embodiment, the first outer electrode 4a also has a width b1 that is smaller than the width b2 of the second outer electrode 4b. The first outer electrode 4a has a height h1 that is greater than the height h2 of the second outer electrode 4b. Overall, the first outer electrode 4a has a smaller area than the second outer electrode 4b. In this way, the polarity of the two outer electrodes 4a, 4b can be easily marked and thus differentiated.

[0048] However, the width b1 of the first outer electrode 4a is smaller than the width b1 of the first outer electrode 4a according to the Figures 2a, 2b. In other words, the first outer electrode 4a is particularly narrow in this embodiment. The height h1 of the first outer electrode 4a is greater than the height h1 of the first outer electrode 4a according to the Figures 2a, 2b In other words, the first outer electrode 4a is particularly long in this embodiment. For example, the first outer electrode 4a in this embodiment has a surface area that is precisely the size required for the actual function of the outer electrode.

[0049] The width b2 of the second outer electrode 4b, however, is greater than the width b2 of the second outer electrode 4b according to the Figures 2a, 2b . The height h2 of the second outer electrode 4b is smaller than the height h2 of the second outer electrode 4b according to the Figures 2a, 2b. Thus, many different dimensions or areas are conceivable for the respective outer electrodes 4a, 4b, as long as the respective outer electrode 4a, 4b has a minimum dimension that is necessary for the actual function of the outer electrode 4a, 4b, namely the electrical supply of the inner electrodes 3a, 3b.

[0050] Furthermore, in contrast to the embodiment according to the Figures 2a and 2b Here, the rotational symmetry of the multilayer component 1 is not broken. In particular, both the first outer electrode 4a and the second outer electrode 4b are arranged centrally on opposite side surfaces 6 of the base body 1a. After rotation of the multilayer component 1 by 180° (indicated by arrow 5) about the vertical axis v, both outer electrodes 4a, 4b are consequently still arranged centrally on the respective side surface 6.

[0051] Figure 4ashows a perspective view of a multilayer component according to a further embodiment. Figure 4b shows a perspective view of the multilayer component rotated by 180° according to Figure 4a .

[0052] In contrast to the Figures 3a and 3b In the embodiment shown, the rotational symmetry of the multilayer component 1 is according to the Figures 4a and 4b broken. In particular, the first outer electrode 4a is not arranged centrally on a side surface 6 of the base body 1a, but is offset from an edge 6a delimiting the side surface 6. In a top view of the relevant side surface 6, the first outer electrode 4a is shifted to the right in the direction of the edge 6a of the side surface 6.

[0053] The second outer electrode 4b is arranged centrally on an opposite side surface 6. The polarity of the outer electrodes 4a, 4b can be identified by the different arrangement of the outer electrodes 4, 4b on the respective outer surface.

[0054] All other features of the multilayer component 1 according to the Figures 4a and 4b correspond to those related to the Figures 3a and 3b described characteristics. List of reference symbols

[0055] 1Multilayer component 2Ceramic layer 3a, 3bInner electrode 4a, 4bOuter electrode 5Arrow 6Side surface 6aEdge b1, b2Width h1, h2Height vVertical axis

Claims

1. Multilayer component (1) comprising - a main body (1a) having a multiplicity of alternately arranged ceramic layers (2) and inner electrodes (3a, 3b), - a first outer electrode (4a) and a second outer electrode (4b) for electrically contacting the inner electrodes (3a, 3b), wherein the two outer electrodes (4a, 4b) have a different polarity assignment and wherein the outer electrodes (4a, 4b) have a different arrangement at an outer surface of the main body (1a) for identifying the different polarity assignment, wherein the multilayer component (1) comprises exactly two outer electrodes (4a, 4b) arranged on opposite side surfaces (6) of the main body (1a), wherein each of the outer electrodes (4a, 4b) is spaced apart from the edges of the respective side surface (6), wherein the first outer electrode (4a) is arranged offset towards an edge (6a) delimiting the side surface (6), and therefore not centrally on the side surface of the main body (1a), and wherein the second outer electrode (4b) is arranged centrally on the opposite side surface.

2. Multilayer component (1) according to Claim 1, wherein the first outer electrode (4a) has a smaller area than the second outer electrode (4b).

3. Multilayer component (1) according to either of the preceding claims, wherein the first outer electrode (4a) has a rectangular shape and wherein the second outer electrode (4b) has a round shape, or vice versa.

4. Multilayer component (1) according to any of Claims 1 to 3, wherein the multilayer component (1) has a broken rotational symmetry.

5. Multilayer component (1) according to any of the preceding claims, wherein the multilayer component (1) is configured as a piezo-multilayer actuator or as a multilayer pressure sensor.

6. Multilayer component (1) according to any of the preceding claims, wherein the outer electrodes (4a, 4b) each have a width (b1, b2) in a direction perpendicular to a stacking direction of the ceramic layers (2), and a height (h1, h2) in a direction parallel to a stacking direction of the ceramic layers (2), wherein the width (b1) of the first outer electrode (4a) is smaller than the width (b2) of the second outer electrode (4b) and / or wherein the height (h1) of the first outer electrode (4a) is greater than the height (h2) of the second outer electrode (4b).

7. Multilayer component (1) according to any of the preceding claims, wherein the outer electrodes (4a, 4b) have a different geometric shape and / or a different size.

8. Use of outer electrodes (4a, 4b) for identifying the different polarity assignment of the outer electrodes (4a, 4b) of a multilayer component (1) according to any of Claims 1 to 7.

9. Use according to Claim 8, wherein the outer electrodes (4a, 4b) have a different geometric shape and / or a different size.