Method for producing a multilayer component

Abstract

A method can be used for producing a fully active stack. A stack has the sides A, B, C and D running along the stacking direction. The method includes combining and temporarily making contact with the internal electrodes that make contact with the respective side on one of the sides B or D, such that the internal electrodes that make contact with the respective side can be electrically driven selectively. The electrically driven internal electrodes are electrochemically coated on the sides A and C. The stack is singulated to form a fully active stack with the electrochemically coated internal electrodes on the sides A and C. A method for producing a multilayer component comprising the fully active stack and a fully active multilayer component producible according to the method are furthermore proposed.

Claims

1. A method for producing a fully active stack or a green precursor of the fully active stack, the method comprising: providing a sintered or unsintered stack having sides A, B, C and D running in each case in a stacking direction, the stack comprising a plurality of alternately successive ceramic dielectric layers and internal electrode layers, wherein the internal electrode layers are internal electrodes and are embodied in each case in a continuous fashion with respect to the sides A and C and are embodied in each case in a non-continuous fashion with respect to either the side B or the side D, such that one portion of the internal electrodes makes contact with the side B, but not with the side D, and another portion of the internal electrodes makes contact with the side D, but not with the side B; combining and temporarily contacting the internal electrodes that make contact with one of the side B or the side D via an external contact with temporary isozones, such that the internal electrodes that make contact with the side B or the side D are selectively electrically drivable; etching back at least one portion of the internal electrodes that make contact with the side B or the side D before electrochemically coating; electrochemically coating the internal electrodes that make contact with the side B or the side D on the sides A and C beyond an etching depth, wherein the electrochemically coating is effected by a plating technology; converting the electrochemical coating into an insulating oxide coating by electrochemical oxidation; and singulating the stack to form the fully active stack or the green precursor of the fully active stack with the coated internal electrodes on sides A and C, wherein the sides A and C correspond to the sides A and C, respectively, after the stack is singulated.

2. The method according claim 1, wherein the etching back comprises electrochemical machining.

3. The method according to claim 1, further comprising, after the electrochemical coating, covering uncoated internal electrodes with an insulating material.

4. The method according to claim 1, wherein a metal or a metal mixture that differs from metal of the internal electrode is used as an electrolytic coating material.

5. The method according to claim 1, wherein trenches that are not filled again after the etching-back are closed by sintering.

6. The method according to claim 1, wherein the electrochemical coating is carried out in an aqueous NaCl solution as electrolyte.

7. The method according to claim 1, wherein the internal electrode layers comprise silver, a silver alloy, or copper.

8. The method according to claim 1, further comprising applying external electrodes on the sides A and C of the fully active stack and contacting the electrochemically coated or uncoated internal electrodes, such that the external electrodes are electrically connected either to the electrochemically coated or to electrochemically uncoated internal electrode layers.

9. The method according to claim 8, further comprising sintering the fully active stack or the green precursor.

10. A method for producing a fully active stack or a green precursor of the fully active stack, the method comprising: providing a sintered or unsintered stack having sides A, B, C and D running in each case in a stacking direction, the stack comprising a plurality of alternately successive ceramic dielectric layers and internal electrode layers, wherein the internal electrode layers are internal electrodes and are embodied in each case in a continuous fashion with respect to the sides A and C and are embodied in each case in a non-continuous fashion with respect to either the side B or the side D, such that one portion of the internal electrodes makes contact with the side B, but not with the side D, and another portion of the internal electrodes makes contact with the side D, but not with the side B; combining and temporarily contacting the internal electrodes that make contact with one of the side B or the side D via an external contact with temporary isozones, such that the internal electrodes that make contact with the side B or the side D are selectively electrically drivable; etching back at least one portion of the internal electrodes that make contact with the side B or the side D before electrochemically coating; electrochemically coating the internal electrodes that make contact with the side B or the side D on the sides A and C, wherein the electrochemically coating is effected by a plating technology; converting the electrochemical coating into an insulating oxide coating by electrochemical oxidation; and singulating the stack to form the fully active stack or the green precursor of the fully active stack with the coated internal electrodes on sides A and C, wherein the sides A and C correspond to the sides A and C, respectively, after the stack is singulated.

11. The method according claim 10, wherein etching back comprises electrochemical machining.

12. The method according to claim 10, further comprising, after the electrochemically coating, covering uncoated internal electrodes with an insulating material.

13. The method according to claim 10, wherein a metal or a metal mixture that differs from the metal of the internal electrode is used as an electrolytic coating material.

14. The method according to claim 10, wherein trenches that are not filled again after the etching-back are closed by sintering.

15. The method according to claim 10, wherein the electrochemical coating is carried out in an aqueous NaCl solution as electrolyte.

16. The method according to claim 10, wherein the internal electrode layers comprise silver.

17. The method according to claim 10, wherein the internal electrode layers comprise a silver alloy.

18. The method according to claim 10, wherein the internal electrode layers comprise copper.

19. The method according to claim 10, further comprising applying external electrodes on the sides A and C of the fully active stack by contacting uncoated internal electrodes, such that the external electrodes are electrically connected to the uncoated internal electrodes.

20. The method according to claim 19, further comprising sintering the fully active stack or the green precursor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are illustrated by way of example in the accompanying schematic drawings, in which:

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

(3) FIG. 2 shows an electrolysis bath for electrochemically coating a piezo-stack;

(4) FIGS. 3A and 3B show the oxide layers applied on the internal electrodes;

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

(6) FIG. 5A shows a piezo-stack with applied electrolytic coating over the electrically driven internal electrodes;

(7) FIG. 5B shows a piezo-stack with additionally applied insulation material;

(8) FIG. 5C shows the piezo-stack after a further polishing step, such that the electrolytic coating is exposed;

(9) FIG. 6A shows a piezo-stack with internal electrodes etched back to form trenches;

(10) FIG. 6B shows a piezo-stack with trenches partly filled again by electrolytic coating;

(11) FIG. 6C shows the piezo-stack additionally coated with insulation material with the remaining trenches being filled;

(12) FIG. 6D shows the piezo-stack after an additional polishing step; and

(13) FIG. 6E shows the fully active piezo-stack finally provided with an external electrode.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(14) In a first exemplary embodiment, the process sequence is as follows.

(15) 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).

(16) 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.

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

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

(19) 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.

(20) Steps d) and e) can also be processed in the reverse order.

(21) 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).

(22) 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.

(23) In a second exemplary embodiment, the process is carried out as follows.

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

(25) 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).

(26) c) Method step b) is now repeated analogously for the side A.

(27) 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.

(28) 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.

(29) 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.

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

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

(32) 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.

(33) 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.

(34) d) Method steps b) and c) are now repeated analogously for the side A.

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

(36) 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.

(37) 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.

(38) In a fourth exemplary embodiment, the process sequence is as follows.

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

(40) 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.

(41) 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.

(42) d) Afterward, the electrolytic coating on the side C is oxidized by anodic oxidation.

(43) Particularly effective insulation can be produced in this way.

(44) e) Steps b) to d) are repeated analogously for the side A of the bar.

(45) f) The component is singulated.

(46) g) An external metallization is now applied on the sides A and C.

(47) Steps f) and g) can also be carried out in the reverse order.

(48) In a fifth exemplary embodiment, the process sequence is as follows.

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

(50) b) 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). 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).

(51) c) Afterward, the electrolytic coating is converted into an oxide coating by anodic oxidation.

(52) d) Method steps b) and c) are now repeated analogously for the side A.

(53) e) The component is singulated (FIG. 4).

(54) f) An external metallization is applied on the sides A and C.

(55) Steps e) and f) can also be processed in the reverse order.

(56) In a sixth exemplary embodiment, the process sequence is as follows.

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

(58) b) The piezo-stack (1) 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.

(59) 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 (1). At the now voltage-carrying internal electrodes (2) (anodes), the etched trenches (9) are filled again with conductive material.

(60) d) Method steps b) and c) are now repeated analogously for the side A.

(61) e) The green piezo-stack (1) is sintered, the non-filled trenches (9) being closed by sintering.

(62) f) The surfaces A and C of the piezo-stack (1) 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.

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