Multilayer Piezo Actuator Electrode Coating for Adhesion
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Solution Overview
Problem
Existing multilayer piezoelectric actuators face reliability issues due to poor adhesion and diffusion of conductive materials at high temperatures, leading to potential component failure under dynamic loads.
Innovation Solution
A multilayer coating comprising a current collector layer of silver-palladium and a diffusion barrier layer of titanium, applied between the internal electrode and the collective contact, ensures strong adhesion and prevents material diffusion into the ceramic matrix, while maintaining electrical conductivity and protecting against oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive adhesive is used to connect the collective contact to the internal electrodes, then the electrical connection is established, but the adhesion to the insulating layer is poor and contact resistance varies
Solution Approach 1:
The patent applies a composite multilayer structure consisting of a diffusion barrier layer (e.g., titanium, tantalum, or tungsten) combined with a conductive adhesive layer. This composite approach allows the diffusion barrier layer to provide strong adhesion to the insulating layer and prevent material diffusion, while the conductive adhesive layer ensures good electrical conductivity and contact with the internal electrodes. The combination resolves the contradiction by assigning different functions to different layers within the composite structure.
Solution Approach 2:
The diffusion barrier layer acts as an intermediary between the insulating layer and the conductive adhesive. It provides a stable interface that prevents direct contact between the conductive adhesive and the insulating layer, thereby preventing diffusion while maintaining adhesion. This intermediary layer resolves the contradiction by mediating between the adhesion requirement and the conductivity requirement.
2Strength
If a thin adhesion promoter layer is used to improve connection strength, then mechanical strength increases, but the layer diffuses into the ceramic matrix at high temperatures
Solution Approach 1:
The patent uses a composite structure where the diffusion barrier layer is specifically designed to be thermally stable and resistant to diffusion into the ceramic matrix. This layer is combined with other materials that provide adhesion and conductivity functions. The composite structure allows each layer to optimize its specific function without compromising the others, resolving the contradiction between mechanical strength and compositional stability.
Solution Approach 2:
The diffusion barrier layer is designed as a thin, sacrificial layer that prevents diffusion of the conductive adhesive into the insulating layer and ceramic matrix. Although it is thin and may eventually degrade, it performs its protective function effectively during the operational lifetime of the component, after which it can be replaced or the component serviced.
3Reliability
If the conductive adhesive layer is made thicker to improve current-carrying capacity, then electrical conductivity increases, but adhesion to the ceramic matrix deteriorates
Solution Approach 1:
The patent divides the conductive function across multiple layers: the diffusion barrier layer provides adhesion to the insulating layer and ceramic matrix, while a separate conductive adhesive layer provides current-carrying capacity. This composite structure allows the conductive adhesive layer to be sufficiently thick for electrical conductivity without compromising adhesion, as the diffusion barrier layer handles the adhesion function.
Solution Approach 2:
The patent segments the functional requirements into separate layers: adhesion function is assigned to the diffusion barrier layer, while conductivity function is assigned to the conductive adhesive layer. This segmentation allows each layer to be optimized for its specific function without the compromises required by a single-layer design, resolving the contradiction between thickness for conductivity and adhesion strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multilayer coating enhances adhesion, suppresses diffusion, and maintains electrical conductivity, reducing the risk of component failure and ensuring long-term durability even at high temperatures.
Implementation Method 1
a diffusion barrier layer as the second layer, which adjoins the insulation layer and the inner electrode borders
Implementation Method 2
DE 10 2007 058 873 A1 discloses a piezoelectric component with an outer electrode which has a vapor-phase deposition with a plurality of layers to which the outer electrode is applied
Data Source
Figure 1~2
Figure 3
AI summary
The invention describes a component (1) comprising a ceramic matrix (5) and at least one inner electrode (2), which is arranged in the ceramic matrix (5) and is exposed on a first surface (7). The component according to the invention also comprises at least one electrically conducting common contact (8), which is electrically connected to the inner electrode (2), and also an insulating layer (15) on a surface of the ceramic matrix (5), which is arranged between the body (5) and the common contact (8), wherein the insulating layer (15) has at least one opening (16), which exposes at least part of the inner electrode (2). Finally, the component has a further, electrically conducting layer (19), which is arranged between the inner electrode (2) and the common contact (8) and between the insulating layer (15) and the common contact (8). The component according to the invention is distinguished by the fact that the further layer (19) is formed as a multilayer (30) with at least two layers (30A, 30B), wherein the multilayer (30) comprises as the first layer (30A) a current collector layer, which is adjacent to the common contact (8), and as the second layer (30B) a diffusion barrier layer, which is adjacent to the insulating layer (15) and the inner electrode (2).