Method for applying an electrode onto a composite material

Abstract

The invention relates to a method for applying an electrode (28) onto a sensor-based or actuator-based composite material (22), in particular piezocomposite ceramics, for contacting sensors or actuators (24) integrated in the composite material (22): The method comprises providing the composite material (22) and applying the electrode (28) onto the composite material (22) by means of a thermal coating method.

Description

[0001]2024.101 Method for applying an electrode to a composite material Description The invention relates to the application of an electrode to a sensory or actuator composite material, in particular a piezocomposite ceramic, for the production of a waterborne sound transducer for a sonar system. Currently, the electrodes are implemented, for example, using conductive silver adhesive, wet-chemical deposition processes, or PVD coating (physical vapor deposition). However, all known methods have the disadvantage that the reliability of the coating when adhering to the piezocomposite ceramic is not guaranteed. For example, the PVD coating has proven to be not very homogeneous. Furthermore, the PVD coating lacks robustness and thus durability, since the adhesion to the composite material is not ideal.Although the application of silver conductive adhesive has reduced these problems, the application process is not easily automated. The object of the present invention is therefore to create an improved concept for applying electrodes to a sensory and / or actuatory composite material. This object is achieved by the subject matter of the independent patent claims. Further advantageous embodiments are the subject matter of the dependent patent claims. Exemplary embodiments show a method for applying an electrode to a sensory and / or actuatory composite material, in particular a piezo composite ceramic, for contacting sensors and / or actuators integrated into the composite material. A composite material comprises, for example, a matrix material and the sensors / actuators, wherein the sensors / actuators are encapsulated in the matrix material. The matrix material can therefore also be referred to as a potting compound.However, the sensors / actuators are exposed on both sides of the surfaces (particularly opposite surfaces) of the matrix material. The sensors / actuators preferably have a rod shape. A plastic, such as polyurethane or epoxy resin, is particularly suitable as a matrix material, which fills the gaps between the sensors / actuators. A material that can utilize the piezoelectric effect, in particular a piezoceramic, such as lead zirconate titanate (PZT), is suitable as sensors / actuators. The method can then comprise the production or simply the provision of the manufactured composite material. The electrode is then applied to one surface of the composite material, in particular the matrix material and the sensors / actuators, using a thermal coating process. The electrode contacts one side of the sensors / actuators that are exposed on the surface.The composite material preferably has a further electrode on the other (in particular opposite) surface. The further electrode contacts the other side of the sensors / actuators exposed on the other surface. The further electrode is preferably also applied using the thermal coating process, preferably using the same thermal coating process. The idea is therefore to use a thermal coating process to apply the electrode(s) to the composite material for contacting the sensors / actuators. Thermal coating processes are characterized by the fact that they produce a very robust coating and can apply the electrodes in an automated process. In exemplary embodiments, metal arc spraying is used as the thermal coating process.In studies, metal arc spraying has proven to be a very good thermal coating process for applying the electrode to the composite material in terms of cost, automation capability, and electrode durability. Metal arc spraying makes it possible to produce a very homogeneous electrode that also bonds very well with the composite material. In metal arc spraying, a (direct) voltage is applied to two metal wires in a hot air environment, particularly one with temperatures of several hundred degrees. The metal wires are brought together at the tip. Due to the brief drop in resistance shortly before or at the time the wire tips touch, the wire heats up most strongly at the tips and becomes liquid. The liquid metal is shot onto the composite material, e.g., using a process gas (e.g., compressed air).There, the liquid metal cools very quickly, contracts, and interlocks with the surface of the composite material. If the process is repeated continuously, the entire surface can be coated with the liquid metal, forming a closed electrode from the solidified metal. In further embodiments, zinc is used as the electrode material. It is also possible for the electrode material to comprise zinc, in particular predominantly, and not consist entirely of zinc. Thus, a zinc alloy can also be used. Furthermore, it is also possible to use other metals that are good electrical conductors. Furthermore, zinc and other metals have the advantage over silver conductive adhesive that the electrical contact of the electrodes, in particular a wire, can be soldered to the electrode.This can be done at any time after the electrodes have been applied, allowing maximum flexibility in the production process. When using silver conductive adhesive, the contact must be immersed in the liquid silver conductive adhesive. The application of the electrode(s) and their contacting must therefore take place simultaneously or in very short succession, or silver conductive adhesive must be applied again in a subsequent process step to establish the contact. Examples also show that the surface of the composite material to which the electrode is applied is chemically or mechanically pretreated to enable better adhesion of the electrode to the composite material. Chemicals used for pretreatment are referred to as primers, primers, or adhesion promoters. Mechanical pretreatment is carried out, in particular, by means of a blasting process.Plastic beads are preferably used for blasting. Conventional blasting materials, such as corundum, are very hard and can damage the sensors / actuators, especially piezocomposite ceramics. Furthermore, the risk of compression of the composite material, particularly the matrix material, is reduced when using plastic beads 2024.101 compared to known hard blasting materials. Irradiation with hard materials such as corundum, on the other hand, can lead to compression (or compaction) of the composite material, which undesirably changes the acoustic properties of the composite material used as a waterborne sound transducer. In further embodiments, the composite material has a curvature. The electrode is applied to the inside of the composite material using the thermal coating process.The PVD coating exhibits the greatest deficiencies in coating quality, particularly on steep flanks of the curve, for example, near the front edges of a hollow hemisphere. However, using the thermal coating process, in particular metal arc spraying, the electrode can be applied to the steep flanks with consistent quality. Similarly, a water-borne sound transducer is made of a composite material comprising sensory or actuator rods and a potting compound arranged between the rods. The rods are electrically connected to one another on at least one side of the composite material by means of an electrode, wherein the electrode is applied to the composite material using a thermal coating process. Preferably, one electrode is applied to each side of the composite material.Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. They show: Fig. 1: a schematic plan view of a flat composite material with an electrode applied thereto; Fig. 2: a schematic sectional view of a curved composite material with an electrode on each of the two surfaces where the sensors / actuators are exposed. 2024.101 Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it should be noted that identical, functionally equivalent, or equivalent elements, objects, and / or structures are provided with the same reference numerals in the different figures, so that the description of these elements presented in different exemplary embodiments is interchangeable or can be applied to one another. Fig. 1 shows a water-borne sound transducer 20 with a composite material 22.The composite material 22 comprises sensory and / or actuator rods 24 and a potting compound 26 arranged between the rods, which is also referred to as a matrix material. The rods 24 are electrically connected to one another at least on one side (here, the top side) of the composite material 22 by means of an electrode 28, wherein the electrode 28 is applied to the composite material 22 by means of a thermal coating process. The lower electrode is not shown. The waterborne sound transducer 20 in Fig. 1 is a planar waterborne sound transducer. Fig. 2 discloses a curved waterborne sound transducer 20 in the form of a hollow hemisphere in a schematic sectional view. Here, both electrodes 28, 28' for contacting the sensory / actuator rods 24 are visible. At least the inner electrode 28 is applied to the inner surface of the composite material by means of the thermal coating process.The outer electrode 28 can also be applied to the outer surface of the composite material using the thermal coating process. However, existing known processes, such as PVD coating, achieve better results on the outer surface than on the inner surface, so that it is also possible in principle to apply this electrode using a known process, such as PVD coating. The surfaces to which the electrode is not to be applied, in particular the end faces, can be covered with a suitable mask. The disclosed (water) sound transducers are designed for use underwater, in particular in the sea. The sound transducers can convert water sound into an electrical signal (e.g., voltage or current) corresponding to the sound pressure, the water sound signal. Furthermore, it is possible for the sound transducers to convert an applied electrical voltage into water sound.The sound transducers can therefore be used as underwater sound receivers and / or as underwater sound transmitters. The sound transducers can have a piezoelectric material, such as a piezoceramic, as their sensor material. The sound transducers can be used for (active and / or passive) sonar (sound navigation and ranging). The sound transducers are preferably not suitable for medical applications or are not used for medical applications. Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step.Analogously, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device. The embodiments described above are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein. 2024.101 List of reference numerals: 20 Waterborne sound transducer 22 Composite material 24 Sensory / actuator rods 26 Matrix material 28 Electrode.

Claims

2024.101 Patent Claims 1. A method for applying an electrode (28) to a sensory or actuator composite material (22), in particular a piezocomposite ceramic, for contacting sensors or actuators (24) integrated in the composite material (22), comprising the following steps: - Providing the composite material (22); - Applying the electrode (28) to the composite material (22) by means of a thermal coating process.

2. A method according to claim 1, wherein metal arc spraying is used as the thermal coating process.

3. A method according to one of the preceding claims, wherein zinc is used as the electrode material or wherein the electrode material, in particular predominantly, comprises zinc.

4. A method according to one of the preceding claims, wherein a surface of the composite material (22) to which the electrode (28) is applied is chemically pretreated to enable better adhesion of the electrode (28). 5.Method according to one of the preceding claims, wherein a surface of the composite material to which the electrode is applied is pretreated mechanically, in particular by means of a blasting process, in order to enable better adhesion of the electrode (28).

6. Method according to claim 5, wherein plastic beads are used for blasting.

7. Method according to one of the preceding claims, wherein the composite material (22) has a curvature, wherein the electrode (28) is applied to an inner side of the composite material (22).

8. Water-borne sound transducer (20) having the following features:. 2024.101- a composite material (22) comprising sensory or actuator rods (24) and a potting compound (26) arranged between the rods (24),- wherein the rods (24) are electrically connected to one another at least on one side of the composite material by means of an electrode (28);- wherein the electrode (28) is applied to the composite material (22) by means of a thermal coating process.

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