Multilayer Component

Abstract

A multilayer component is disclosed. In an embodiment, a multilayer component includes a fully active stack comprising a plurality of dielectric layers, internal electrodes and two external electrodes arranged on opposite sides of the stack, wherein at least one portion of the internal electrode layers are coated.

Claims

1. A fully active multilayer component comprising: a fully active stack comprising: a plurality of dielectric layers; internal electrodes; and two external electrodes arranged on opposite sides of the stack, wherein at least one portion of the internal electrodes are electrochemically coated, wherein the two external electrodes are electrically connected in each case either to the electrochemically coated or to the electrochemically uncoated internal electrodes, and wherein the electrical connection to a portion of the internal electrodes either is interrupted by an oxide layer on the internal electrodes or is produced by an electrolytic coating of the internal electrodes.

2. The multilayer component according to claim 1, wherein the oxide layer contains a metal which differs from the metal contained in the internal electrodes.

3. The multilayer component according to claim 2, wherein the metal of the oxide layer is more electronegative than the metal of the internal electrodes.

4. The multilayer component according to claim 1, wherein the electrical connection of the external electrodes to a portion of the internal electrodes is produced by an electrolytic coating of the internal electrodes and the electrical connection of the external electrodes to the rest of the internal electrodes is interrupted by a narrow isozone composed of ceramic having a width of 50 to 200 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Exemplary embodiments of the invention are illustrated by way of example in the accompanying schematic drawings, in which:

[0026] FIG. 1 shows a perspective side view of a piezo-stack having the sides A, B, C and D along the stacking direction;

[0027] FIG. 2 shows an electrolysis bath for electrochemically coating a piezo-stack;

[0028] FIGS. 3A and 3B show the oxide layers applied on the internal electrodes;

[0029] FIG. 4 shows a singulated fully active piezo-stack having the sides A, B, C and D along the stacking direction;

[0030] FIG. 5A shows a piezo-stack with applied electrolytic coating over the electrically driven internal electrodes;

[0031] FIG. 5B shows a piezo-stack with additionally applied insulation material;

[0032] FIG. 5C shows the piezo-stack after a further polishing step, such that the electrolytic coating is exposed;

[0033] FIG. 6A shows a piezo-stack with internal electrodes etched back to form trenches;

[0034] FIG. 6B shows a piezo-stack with trenches partly filled again by electrolytic coating;

[0035] FIG. 6C shows the piezo-stack additionally coated with insulation material with the remaining trenches being filled;

[0036] FIG. 6D shows the piezo-stack after an additional polishing step; and

[0037] FIG. 6E shows the fully active piezo-stack finally provided with an external electrode.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0038] In a first exemplary embodiment, the process sequence is as follows.

[0039] a) A sintered piezo-stack (1) having the sides A, B, C and D along the stacking direction is provided. The piezo-stack has (temporary) isozones and external contact-connections (3), such that every second internal electrode (2) on the side B can be electrically driven via the external contact-connection (3) and every second internal electrode (2) can be electrically driven via the corresponding external contact-connection (3, not shown), on the side D (see, e.g., FIG. 1).

[0040] b) The piezo-stack (1) is dipped on one side (side C) into an electrolyte solution (6) (FIG. 2), (positive) voltage is applied to the piezo-stack (1) at the external contact-connection (3) of the side B, negative voltage is applied to the counterelectrode (5), and energization takes place for a few minutes. An oxide layer (4) forms at the voltage-carrying internal electrodes (2) of the piezo-stack (1) (see, e.g., FIG. 2, FIG. 3A and FIG. 3B). The principle of anodic oxidation is used in this case.

[0041] c) Method step b) is carried out analogously for the side A of the piezo-stack (1).

[0042] d) The piezo-stack (1) with the coated internal electrodes (2, 2) is singulated to form fully active piezo-stacks (12) (FIG. 4).

[0043] e) External electrodes (11) are applied on the sides A and C by metallization with conductive adhesive or metallization paste, said external electrodes, in each case on the corresponding side, making electrical contact with the internal electrodes not provided with an oxide layer, i.e., internal electrodes (2) on side A and respectively internal electrode (2) on side C.

[0044] Steps d) and e) can also be processed in the reverse order.

[0045] In one variant of the first exemplary embodiment, an aqueous NaCl solution is used as electrolyte and an electrical AC voltage is applied between the piezo-stack (1) via the internal electrodes (2) driven by the external contact-connection (3) and the counterelectrode (5). In this variant, the internal electrodes consist of silver or a silver alloy, e.g. AgPd, as a result of which a silver oxide layer grows on the voltage-carrying electrodes (see, e.g., BAEWA, W. Oxidation von Silber durch Wechselstrom von 50 HZ in wssriger Natriumchloridlsung [Oxidation of silver by AC current at 50 HZ in aqueous sodium chloride solution] in Werkstoffe and Korrosion, volume 22, edition 2, page 143 et seq., issue February 1971).

[0046] In a further variant of the first exemplary embodiment, the internal electrodes (2, 2) to be coated are firstly removed 1 to 10 m, preferably 1 to 5 m, into the depth by the principle of electrochemical machining, as a result of which electrochemically etched-back trenches (9) arise. Afterward, the process of anodic oxidation is carried out, if appropriate by changing the electrolyte. As a result, an oxide layer is obtained which extends further into the component depth and thus ensures better insulation.

[0047] In a second exemplary embodiment, the process is carried out as follows.

[0048] a) A sintered piezo-stack (1) having lateral (temporary) isozones and external contact-connections (3) is provided (FIG. 1).

[0049] b) The side C of the component is dipped into a plating technology coating basin, and negative potential is applied to the internal electrodes (2) via the external contact-connection (3) on the side B of the piezo-stack (1). A metal layer several m thick (typically 10 to 20 m) is deposited (process of plating technology) at the now voltage-carrying internal electrodes (2) (cathodes).

[0050] c) Method step b) is now repeated analogously for the side A.

[0051] d) The structured surface of the piezo-stack (1) (see, e.g., FIG. 5A) is now smoothed with insulation material (8) (see, e.g., FIG. 5B). Glass or organic lacquer is preferably used as insulation material.

[0052] e) The surfaces A and C of the bar are polished, such that the plated outwardly situated electrodes (7) are sufficiently free and suitable for a further metallization (e.g., spattering, regrinding, etc.). The more deeply situated electrodes still remain insulated from the surface as a result of this cleaning step.

[0053] f) An external metallization is now applied on sides A and C and the piezo-stack is singulated to form fully active piezo-stacks and processed further.

[0054] In a third exemplary embodiment, the process sequence is as follows (see, e.g., FIGS. 6A to 6E).

[0055] a) A sintered piezo-stack (1) having lateral (temporary) isozones and external contact-connections (3) is provided (FIG. 1).

[0056] b) The piezo-stack (1) is dipped on one side (side C) into a suitable electrolyte solution (FIG. 2), (positive) voltage is applied to the piezo-stack (1) at the internal electrodes (2) via the external contact-connection (3) on the side B and, at the same time, to the internal electrodes (2) via the external electrode (3) (not shown) on the side D, negative voltage is applied to the counterelectrode (5), and energization takes place for a few minutes. All the electrodes are thereby etched back by 1 to 10 m, preferably 1 to 5 m, by means of the principle of electrochemical machining.

[0057] c) Afterward, the side C of the piezo-stack (1) is dipped into a plating technology coating basin and negative potential is applied to the internal electrodes (2) via the external contact-connection (3) on the side B of the piezo-stack (1). At the now voltage-carrying internal electrodes (2) (cathodes), the etched trenches (9) are filled again with conductive material.

[0058] d) Method steps b) and c) are now repeated analogously for the side A.

[0059] e) The trenches (9) are now filled with insulating material (e.g., glazed, or sealed with organic lacquer).

[0060] f) The surfaces A and C of the piezo-stack (1) are cleaned in such a way that surfaces of the outwardly situated electrodes are sufficiently free and suitable for a further metallization (e.g., sputtering, regrinding, etc.). The more deeply situated electrodes still remain insulated from the surface as a result of this cleaning step.

[0061] g) An external metallization is now applied on the sides A and C, and the piezo-stack (1) is singulated to form fully active piezo-stacks (12) and processed further.

[0062] In a fourth exemplary embodiment, the process sequence is as follows.

[0063] a) A sintered piezo-stack (1) having lateral (temporary) isozones and external contact-connections (3) is provided (FIG. 1).

[0064] b) The piezo-stack (1) is dipped by the side C into an electrolysis bath and voltage is applied to the internal electrodes (2) via the external contact-connection (3) on the side B, and etching back 1 to 10 m, preferably 1 to 5 m, is effected according to the principle of electrochemical etching-back.

[0065] c) Afterward, the side C of the component is dipped into a plating technology coating basin, and negative voltage is applied to the internal electrodes (2) via the external contact-connection (3) on the side B of the piezo-stack (1). A metal layer several m thick is deposited (process of plating technology), preferably beyond the etching channel, at the now voltage-carrying internal electrodes (2) (cathodes). A material that differs from the material of the internal electrode (2) is preferably used here. With further preference, a metal or a metal mixture that is more electronegative than the metal of the internal electrode is used. By way of example, aluminum can be used.

[0066] d) Afterward, the electrolytic coating on the side C is oxidized by anodic oxidation. Particularly effective insulation can be produced in this way.

[0067] e) Steps b) to d) are repeated analogously for the side A of the bar.

[0068] f) The component is singulated.

[0069] g) An external metallization is now applied on the sides A and C.

[0070] Steps f) and g) can also be carried out in the reverse order.

[0071] In a fifth exemplary embodiment, the process sequence is as follows.

[0072] a) A sintered piezo-stack (i) having lateral (temporary) isozones and external contact-connections (3) is provided (FIG. 1).

[0073] b) The side C of the piezo-stack (i) is dipped into a plating technology coating basin and negative potential is applied to the internal electrodes (2) via the external contact-connection (3) on the side B of the piezo-stack (i). A metal layer several m thick (typically 10 to 20 m) is deposited (process of plating technology) at the now voltage-carrying internal electrodes (2) (cathodes).

[0074] c) Afterward, the electrolytic coating is converted into an oxide coating by anodic oxidation.

[0075] d) Method steps b) and c) are now repeated analogously for the side A.

[0076] e) The component is singulated (FIG. 4).

[0077] f) An external metallization is applied on the sides A and C.

[0078] Steps e) and f) can also be processed in the reverse order.

[0079] In a sixth exemplary embodiment, the process sequence is as follows.

[0080] a) A green piezo-stack (i) having lateral (temporary) isozones and external contact-connections (3) is provided (FIG. 1).

[0081] b) The piezo-stack (i) is dipped on one side (side C) into a suitable electrolyte solution, and (positive) voltage is applied to the internal electrodes (2) via the external contact-connection (3) on the sides B and D and positive voltage is applied to the counterelectrode, and energization takes place for a few minutes. As a result, all the internal electrodes (2, 2) are etched back according to the principle of electrochemical machining.

[0082] c) Afterward, the side C of the component is dipped into a plating technology coating basin, and positive potential is applied to the internal electrodes (2) via the external contact-connection (3) of the piezo-stack (i). At the now voltage-carrying internal electrodes (2) (anodes), the etched trenches (9) are filled again with conductive material.

[0083] d) Method steps b) and c) are now repeated analogously for the side A.

[0084] e) The green piezo-stack (i) is sintered, the non-filled trenches (9) being closed by sintering.

[0085] f) The surfaces A and C of the piezo-stack (i) are cleaned, such that the surfaces of the plated internal electrodes (2) are sufficiently free and suitable for a further metallization (e.g., sputtering, regrinding, etc.). The more deeply situated internal electrodes (2) still remain insulated from the surface as a result of this cleaning step.

[0086] g) An external metallization is now applied on the sides A and C, and the sintered piezo-stack (i) is singulated to form fully active piezo-stacks (12) and processed further.