DE102005002925A1 - Piezoelectric transducer manufacture involves applying film section on surface area of base body, handling film section such that it adheres on surface of body, and passivating surface by insulating layer - Google Patents

Abstract

The method involves applying a prefabricated film section (2) consisting of an organic material on a surface area of a base body (1), where the surface area is arranged between an input part and an output part. The film section is handled in such a manner that the film section is holohedrally adhered on the surface of the base body. The surface of the base body is passivated by a breakdown resistant insulation layer. An independent claim is also included for a piezoelectric transducer provided with a base body.

Description

The The invention relates to a method for producing a piezoceramic Component. The invention further relates to a piezoelectric transformer.

A trained as multilayer varistor ceramic device with a passivated surface is from the document DE 199 31 056 A1 known.

task The present invention is a process for the preparation specify a puncture resistant piezoceramic device. A Another object of the present invention is to provide a puncture resistant specify piezoelectric transformer.

It is a method for producing a piezoelectric, preferably piezoceramic component with a full surface adhering to its body, preferably indicated by impact-resistant insulating layer.

Of the body in one embodiment a multilayer structure with at least two separate ones piezoelectric layers or areas.

Of the body is preferably made of a piezoceramic by sintering ceramic-containing layers educated. The ceramic-containing layers are shared with them arranged, preferably structured metal layers sintered.

The Component can be provided with galvanically separated parts be on the outside lying, arranged on a body surface Contacts of the device are connected. There is a danger of an electrical breakdown between exposed, with different electrical potentials connected electrodes different Component parts. To increase the breakdown voltage, can in particular, arranged between the exposed electrodes Area of the body surface by means of be passivated an impact-resistant insulating layer.

The In the process to be produced insulating layer can therefore in particular to increase serve the electrical breakdown strength of the device. In this case, the insulating layer has a significantly higher dielectric strength as the main body on. The dielectric strength of the ceramic is usually at about 2 to 4 kV / mm. The insulating layer preferably has a Dielectric strength of more than 5 or 10 kV / mm. The dielectric strength the insulating layer exceeds the Dielectric strength of the body preferably at least Factor 2.

It a film is provided which has at least one component, which z. B. after a certain treatment is able to wet the body surface. In one variant, a self-supporting film can be used. It be foil sections according to a for the produced insulating layer predetermined shape.

One Another advantage of covering the surface with an insulating layer lies in the fact that surface currents on the surface can be reduced the otherwise to a surface discharge between the to the main body to be connected lead electrical poles would. The surface discharge can greatly reduce the dielectric strength of the device.

Of the respective film section is applied to the body and positioned. The oriented film section is treated, with preference between the film portion and the body surface a strong adhesion bond arises. It is possible that the applied film section even before treatment on body adheres, with the adhesion between the main body and the film section is reinforced in the course of the treatment.

Is possible but also that the film section the surface of the body before the treatment is not wetted, with an adhesive force between the film and the body only during the treatment arises. In this case, the film section becomes in the treatment on the body by means of Holding fixtures firmly.

Of the Film section is before treatment and especially during application on the main body preferably deformable. In one variant, the untreated Film section flexible or at least partially plastic. Of the untreated film section preferably comprises a material which is in a B state. A material in B-state is partially networked, but capable of further networking. Of the B-state (in English B-stage) represents a preliminary stage in one variant to the thermoset. The film material is in this case to a Duroplast after a thermal treatment.

The sheet material preferably comprises several components, e.g. As a preferably polymerizable base material and a solvent. A solvent is understood as meaning organic solvents and also inorganic liquids including water.

The Basic material of the film is basically - if necessary after a suitable Treatment - to Wetting the body surface capable. The foil may in particular contain a plasticizer or a binder, the wetting of the body surface by the base material prevents the film. After the volatilization of the binder can the body surface with wetted the base material.

The Treatment of the film includes a targeted physical action on the film, preferably an irradiation or a thermal treatment, in particular heating. The targeted physical action includes in a preferred variant, a process step that comes with a power consumption connected is. The curing a solvent-containing Foil by volatilization of the solvent without power consumption is possible in principle. The volatilization of the solvent however, preferably accelerated by heating.

A Irradiation treatment z. B. by irradiation with infrared rays, visible rays, ultraviolet rays, X-rays or an electron beam is possible. This irradiation can be combined with ultrasound methods, wherein by the irradiation of the ultrasonic signals z. For example, the speed controlled by a chemical reaction such as polymerization in the film material can be.

The Heating the film section is at least up to a critical Temperature at which the film properties change such that between the film material and the surface of the body strong Adhesion forces occur. This can, for example, during melting of the film material, the Volatile from the adhesion preventing components. of the film material or during crosslinking the film material to be the case.

In In one variant, a film section is used whose melting point above the room temperature. The foil material can after the application of the film section on the body through Heating to melt. The molten material the film wets the underlying body surface. After cooling forms itself a hard insulating layer, which monolithically connected to the main body is. It is possible that the material structure before and after is the same, what an insulating layer made of a thermoplastic. It is also possible that the structure and thus physical properties of the film material change permanently after heating, what kind of an insulating layer of a thermoset applies.

The Treatment of the film section mainly causes that between the film material and the underlying surface of the the body particularly strong adhesion forces occur, wherein the film section over the entire surface on the surface of the basic body adheres and preferably monolithically connected to the body becomes.

The Handling the film section can also be a change the physical state of the film material - in particular curing, solidification or vitrification, polymerization or crosslinking - cause. In a thermal Treatment is the treatment temperature of the properties of the to be treated foil material as well as the effect to be achieved dependent. Polymerizing an organic component-containing film material can z. B. be accomplished at a temperature between 100 ° C and 300 ° C. at inorganic components on facing films, in particular glass-containing Slides can be a higher Treatment temperature z. B. between 400 ° C and 1000 ° C may be required.

Of the Advantage of a monolithically connected to the body insulating layer is that immediately adheres to the body surface and that it therefore no further adhesion layer for the adhesion mediation between the main body and the insulating layer is required.

Of the Film section preferably forms a hard, after treatment in a variant, a rigid or a glazed insulating layer. An insulating layer produced by the treatment of a film section can be through an over their entire surface uniform (constant) Layer thickness and in particular by a sharp, transverse in cross-section to the layer plane substantially rectangular profile or unrounded Outline edges. The layer thickness of the insulating layer can in a variant between 0.1 and 1 mm, z. B. 0.4 mm. The layer thickness however, is not limited to the range specified here.

The insulating cover can, for. For example, a crosslinked organic or inorganic polymer. An inorganic polymer may, for. B. be a silicone rubber. An inorganic polymer may have organic radicals. For forming an SiO ₂ layer as an insulating layer, an Si-based polymer, e.g. As silane or siloxane suitable.

The film can glass, plexiglass and / or white inorganic or organic substances, including hydrates. A hydrate can release water during the treatment and thus change its structure.

The Foil may be a mixture of ceramic and a glassy base material Material included. The base material can also be a mixture of a glassy material and organic components, e.g. B. organic Contain polymers.

The In one variant, foil can only contain organic components, z. B. contain an epoxy resin.

The Foil may comprise a B-stage material. The material in B-state may in particular contain the following monomers or dimers: monoepoxide, Dimethacrylate, phenylglycidyl ether (PGE) or methacrylated digicydyl ether of bisphenol A (up to GMA).

The Insulating layer can be a layer of polyurethane, Polyprolylene or polyester. An insulating layer with thermoplastic properties can z. As polystyrene or polymethyl methacrylate contain.

In A preferred variant of the method is a piezotransformer produced with a preferably ceramic body. First, will the main body with an input part and a through a separating layer of this provided galvanically isolated output part.

Of the Film section is at least one between the input part and the output part arranged surface region of the base body applied. The foil section can also be used in areas from external contacts of the transformer - input electrodes and output electrodes. The film section is preferably applied so that it in Cross section of the main body surrounds all sides.

Of the Film section can therefore be provided as a piece of pipe in a variant be whose inner circumference the outer circumference of the body in Is essentially the same. The film section can alternatively as Strip present, which is wound around the body. Is possible it too, on the area of the main body to be covered two concluding with each other, strip Apply film sections in such a way that they together the main body in Enclose cross section on all sides.

Of the Film section may be connected to an elastic carrier film, the removed after applying the film section on the body becomes.

It is z. Possible, a precursor device with several with their faces arranged facing each other to produce to be separated components. The precursor device has ie in the longitudinal direction successive component areas. On the carrier foil can several Film sections are generated, the center distance equal to the component length is. The film composite just described may be based on the precursor component with the foil sections to the individual component areas be applied. This is advantageously done in a single Process step. The carrier foil can later subtracted and the precursor device to be isolated.

It a piezoelectric transformer is provided, the one out Having an insulating layer produced a film section. The insulating layer encapsulates the surface area between the input part and the output part of the transformer.

In A preferred variant is a piezoceramic transformer specified in two preferably mechanically coupled to each other and galvanically separated parts - input part and output part - divided is. The galvanic separation of the two parts is through an intermediate arranged insulating separating layer, preferably a provided in the base body piezoelectric Layer attainable.

Of the Entrance part and the output part are along a longitudinal axis of the transformer arranged side by side and z. B. by a in the main body provided piezoelectric layers mechanically fixed together connected. An electrical input signal is in the input part of the piezoelectric transformer into mechanical vibrations of the the body Transformed the transformer. Due to the mechanical coupling the input part and the output part are both parts of the affected by mechanical vibration. The transformation of the electrical Energy in the mechanical energy is due to the inverse piezoelectric effect. In the output part, the mechanical Vibrations due to the direct piezoelectric effect back into an electrical Signal transformed.

The direct piezoelectric effect is understood to mean that a voltage drops in the body when deformations occur. Under the inverse piezoelectric effect is understood that the piezoelectric ceramic, which may need to be polarized for use of the device even when applying an electric field parallel or anti-parallel or in an angle to the polarization direction undergoes deformation.

The Dielectric strength of the transformer is mainly due to the Properties of the release layer determined. The electrical breakdown between exposed metal structures along the body surface should be prevented by the insulating layer.

One ceramic body is usually porous, taking his pores from the outside space Moisture, resulting in reduction of breakdown voltage of the piezotransformer leads. The homogeneous, preferably a smooth surface having insulating layer seals the otherwise rough surface of the body and prevents the accumulation of moisture, especially in terms of a electrical discharge critical isolation area of the transformer.

One for passivation of the surface used, originally semi-solid film section has one in the liquid state located to be applied insulating material, eg. B. a solution in the the component is immersed, the advantage that while the shape the insulating layer - d. H. their area as well as their layer thickness - by predetermined dimensions of the film section better controllable is. Also when spraying a liquid paint layer through a stencil it is difficult to over the entire circulation of the the body to achieve an insulating layer with a uniform thickness, since a liquid flows down and soups. In contrast, the thickness of one of a film section produced insulating layer predetermined by the thickness of the film portion and therefore remains even after the treatment of the film section in Essentially evenly.

in the The following is the invention with reference to embodiments and the associated figures explained in more detail. The Figures show diagrammatic and not true to scale representations different embodiments the invention. The same or equal parts are denoted by the same reference numerals designated. It show schematically

1 a detail of a view of a piezoelectric transformer with an insulating layer from above;

2 the piezoelectric transformer with an insulating layer produced from a tubular film section in cross section;

3 the piezoelectric transformer with an insulating layer produced from a strip-shaped film section in cross section;

4 the piezoelectric transformer with an insulating layer produced from two strip-shaped film sections in cross section;

5A a film portion disposed between two carrier sheets;

5B Applying the film portion connected to a carrier film to the piezoelectric transformer;

5C Peeling off the carrier film;

5D auschnittsweise the piezoelectric transformer with the insulating layer produced thereon.

1 shows a detail of a plan view of a piezoelectric transformer with a base body 1 which is in a longitudinal direction in an entrance part 11 , an output part 12 and an interposed release layer 13 is divided. The separation layer 13 ensures a galvanic separation and a mechanical coupling of the two transformer parts 11 . 12 ,

The entrance part 11 has external input electrodes 31 . 32 on. The starting part 12 has outer output electrodes 41 . 42 on. Preferably, inner electrodes, not shown here, are provided inside the main body, the z. B. are arranged transversely to a longitudinal axis of the transformer or, to the wave propagation direction. The internal electrodes are connected in a comb-like manner to the external electrodes of the corresponding transformer part, with internal electrodes connected to different potentials being arranged alternately.

The surface of the release layer 13 and to these adjacent areas of external electrodes 31 . 32 . 41 . 42 are through a treated foil section 2 covered. The foil section 2 forms one with the main body 1 monolithically bonded insulating layer, which arranged the underlying body surface and in particular the surface of the release layer 13 sealed.

In 2 to 4 an exemplary arrangement of the film section on the base body is shown in schematic cross section along the line AA '.

The foil section 2 in 2 is formed as a pipe section whose inner circumference with the outer periphery of the main body 1 is equal to. The tubular film section is applied to the base body 1 raised, aligned and then treated so that it is monolithically connected to the body and forms a protective, preferably hard insulating layer. A hard insulating layer has the advantage over a soft protective layer that it does not degrade the efficiency of the transformer.

In 3 is the foil section 2 formed as a strip which is wound around the main body circumference at least once. In 4 becomes the basic body 1 between two foil sections 21 . 22 positioned so that the film sections together completely surround the body circumference. The mutually facing ends of these film sections are firmly joined together during the treatment, wherein they preferably form a joint edge or flush with each other. The interface between the section ends may e.g. B. be sealed by the fact that the film material partially liquefied during treatment, wherein the section ends merge together. This also applies to the interface between the mutually facing ends of the same film section 2 in 3 to.

In 5A is a foil section 2 shown between two deformable carrier films 201 . 202 is arranged and in its original state z. B. may be gel-like. The foil section 2 and the carrier foils 201 . 202 form a film composite. The first carrier foil 201 is before applying the film section 2 deducted to the body. The foil section 2 can z. Example, be structured using photomasks such that its length to the outer periphery of the body 1 is adjusted and that its width is not smaller than the width of the separating layer 13 is. The composite of the films 2 and 202 is on the body surface to be covered with the film section 2 to the main body 1 applied what is in 5B is shown schematically. The material of the film section 2 wets the surface. Preferably, the adhesion force is between the film portion 2 and the body surface larger than the adhesion force between the film portion 2 and the carrier film 202 , In this case, the carrier film 202 before the treatment of the film section 2 subtracted from.

In a variant, first, the treatment of the film section 2 take place and the carrier film 202 be deducted afterwards. In a treatment by irradiation, the carrier film 202 be permeable to the rays used. The removal of the carrier film 202 is in 5C shown schematically.

The piezoelectric transformer after peeling off the carrier film 202 is in cross section in 3 shown. The top view of this transformer is in 5D presented. In this example, the insulating layer formed on the body of the device is thicker than the external electrodes of the device. The insulating layer can also be the same thickness or thinner than the outer electrodes 31 . 32 . 41 . 42 be.

Of the Film section can be structured in a variant such a resulting insulating layer covers the entire side surface of the Component including the outer electrodes - with the exception of to be kept free of contact areas - covered.

1

body

11

introductory

12

output portion

13

Interface

2

film section

21

first film section

22

second film section

31

32 input electrodes

41

42 output electrodes

20

film composite

201

202 carrier films

Claims (30)

Method for producing a piezoelectric component, comprising the steps: - applying at least one prefabricated film section ( 2 . 21 . 22 ) on at least a part of the surface of a basic body ( 1 ); - Treatment of the film section ( 2 . 21 . 22 ) such that it on the surface of the body ( 1 ) adheres to the entire surface. Method according to claim 1, wherein the basic body ( 1 ) as the main body of a piezotransformer with an input part ( 11 ) and an output part ( 12 ), wherein the film section ( 2 . 21 . 22 ) is applied at least to a arranged between the input part and the output part surface region of the base body. Method according to claim 1 or 2, wherein the film section ( 2 . 21 . 22 ) is formed as a strip. Method according to claim 3, wherein the foil section ( 2 . 21 . 22 ) around the main body ( 1 ) is wound. Method according to claim 3, wherein a first foil section ( 21 ) to a part of the basic body circumference and a second film section ( 22 ) so complementary to the first film section on the base body ( 1 ) is applied, that the ends of the two film sections mitein on the body finish flush. Method according to claim 1 or 2, wherein the film section ( 2 ) is produced as a pipe section, the inner circumference of the outer periphery of the body ( 1 ) is substantially the same. Method according to one of claims 1 to 6, wherein the film section ( 2 . 21 . 22 ) is deformable prior to treatment. Method according to one of claims 1 to 7, wherein the material of the film section is polymerizable and in the treatment is polymerized. Method according to one of claims 1 to 8, wherein the film section ( 2 . 21 . 22 ) contains an organic material. Method according to one of claims 1 to 8, wherein the film section ( 2 . 21 . 22 ) contains an inorganic material. The method of claim 10, wherein the film section contains a glassy material. Method according to one of claims 1 to 8, wherein the material of the film section contains an Si-based polymer. Method according to one of claims 10 to 12, wherein the material of the film section is inorganic. Method according to one of claims 1 to 13, wherein the material of the film section solidifies during the treatment. Method according to one of claims 1 to 14, wherein the material the film section is crosslinked in the treatment. Method according to one of claims 1 to 15, wherein the treatment heating the film section ( 2 . 21 . 22 ). Method according to one of claims 1 to 15, wherein the treatment irradiation of the film section ( 2 . 21 . 22 ). The method of claim 17, wherein the irradiation done with W-rays. The method of claim 17, wherein the irradiation with infrared rays. The method of claim 17, wherein the irradiation with x-rays he follows. Method according to one of claims 1 to 20, wherein the film section ( 2 . 21 . 22 ) is connected to an elastic carrier film, which after the application of the film section on the base body ( 1 ) is deducted. Method according to one of claims 1 to 21, wherein the film section ( 2 . 21 . 22 ) before treatment on the surface of the body ( 1 ), and wherein during the adhesion is strengthened so that the film connects monolithically with the surface of the body. Method according to one of claims 1 to 22, wherein the film section ( 2 . 21 . 22 ) contains a solvent which is removed during the treatment. Method according to one of claims 1 to 23, wherein the film section ( 2 . 21 . 22 ) Contains hydrates that give off water during the treatment. Piezoelectric transformer with a basic body ( 1 ), which has an input part ( 11 ) and an output part ( 12 ), wherein at least one between the input part ( 11 ) and the output part ( 12 ) arranged portion of the base body surface is covered by an insulating cover of thermoplastic or thermoset, with the base body ( 1 ) is monolithically connected. Transformer according to Claim 25, in which the basic body ( 1 ) contains a ceramic. A transformer according to claim 25 or 26, wherein the Layer thickness of the insulating cover over the entire surface of this Cover is constant. Transformer according to one of claims 25 to 27, wherein the insulating cover is a proportion of vitreous Material has. Transformer according to one of claims 25 to 28, wherein the insulating cover is tubular. Transformer according to one of claims 25 to 29, wherein the basic body ( 1 ) is porous, wherein the insulating cover has a smooth surface and the surface of the base body ( 1 ) sealed against the accumulation of moisture.