WO2019076601A1

WO2019076601A1 - Passive electrical component comprising an insulating layer

Info

Publication number: WO2019076601A1
Application number: PCT/EP2018/076241
Authority: WO
Inventors: Ralph Wilken; Franz-Josef Wöstmann
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung eingetragener Verein
Priority date: 2017-10-17
Filing date: 2018-09-27
Publication date: 2019-04-25
Also published as: DE102018101183A1

Abstract

The invention relates to a method for producing a passive electrical component, which has an insulating layer on its surface, and to a passive electrical component that is produced or can be produced according to said method.

Description

Passive electrical component with insulating layer

The present invention relates to a method for producing a passive electrical component, which has an insulating layer on its surface, and a passive electrical component produced or producible by this method.

In the course of the introduction and spread of electromobility, the lightweight construction of electric motors is gaining in importance. Therefore, it is necessary to form passive components such as coils, coils, conductors, chokes, resistors and switches of aluminum or an aluminum alloy or an alloy containing aluminum. Passive electrical components for use in electric motors usually have to be provided with an insulating layer that satisfies both high electrical (high dielectric strength) and high mechanical requirements (low abrasion, strong adhesion to the body of the component). According to the prior art, suitable for this purpose are insulating wet paints, insulating powder paints, anodizing films and plasma polymer coatings or combinations thereof, in each case after the production of the component in one or more downstream, time-consuming and costly steps (optionally with pre- and post-treatments such as curing in the case of paints), the insulating layer forming materials must be applied to the surface of the component. DE 103 14 700 A1 discloses a method for producing surface-modified workpieces made of aluminum or aluminum alloys. The method comprises treating the workpiece to be modified with at least one modifying agent to obtain the surface-modified workpiece, the provided workpiece to be modified having a temperature of 80 to 550 ° C and the at least one modifying agent a temperature of 15 to 80 ° C having. As modifying agents, metal salts of an element of one of the subgroups IV to VI or of the main groups I, II, III or IV of the PSE (preferably in aqueous solution), CAB flux, potassium aluminum hexafluoride, ammonium fluoride, potassium fluoride, sodium or potassium silicate, Sodium or potassium borate, sodium or potassium aluminate, water, and an aqueous solution containing ammonia, or amines, or organic acid or its salts. The surface modification should be a chemical conversion, ie formation of a conversion layer and / or formation or reinforcement of a boehmite layer or aluminum oxide layer. DE 103 14 700 A1 contains no information on the composition, thickness and the insulating properties of the boehmite layer or aluminum oxide layer thus formed.

US 2002/0053461 A1 discloses the preparation of an insulating layer on an aluminum coil by oxidation in an aqueous solution, wherein the oxidation is preferably carried out at a temperature of 20 ° C to 120 ° C. US 8,754,735 B2 discloses the formation of an insulating layer on aluminum by anodic oxidation.

WO 2016/022871 A1 discloses an aluminum-containing electrical conductor having an insulating layer containing at least one oxide of a metal other than aluminum (e.g., titanium dioxide) and resistant to high temperatures. The insulating layer is prepared by deposition from a bath containing an aqueous solution of a precursor.

US Pat. No. 5,091,609 A discloses an electrical conductor having a conductor core whose outer surface is covered by aluminum or an aluminum alloy, an anodic oxide layer disposed thereon and a further oxide layer deposited thereon by a sol-gel method or pyrolysis of a salt of an organic oxide Acid is generated. The object of the present invention is to provide a method for producing a passive electrical component, which has on its surface an insulating layer with high dielectric strength.

This object is achieved by a method for producing a passive electrical component having an insulating layer on its surface. The method according to the invention comprises the steps

Producing or providing a base body for the passive electrical component, wherein the prepared or provided base body of aluminum or an aluminum alloy or an aluminum-containing alloy is formed and has a temperature in the range of 300 ° C to 630 ° C.

Contacting the surface of the body having a temperature ranging from 300 ° C to 630 ° C with an oxidizing agent having a standard potential higher than 1 V and a temperature in the range of 15 ° C to 150 ° C.

In the method according to the invention, by contacting the surface of the body having a temperature in the range of 300 ° C. to 630 ° C. with an oxidizing agent on the surface of the base body, aluminum is oxidized by the oxidizing agent to aluminum oxide, thus forming an insulating layer containing aluminum oxide. If the surface of the base provided or provided has a thin oxide layer (spontaneously formed, for example, by contact with atmospheric oxygen and / or moisture) prior to contact with the oxidizing agent, it is reinforced, i. her thickness is increasing.

In order to promote the formation of aluminum oxide, according to the invention relatively strong oxidizing agents are used, namely oxidizing agents with a standard potential higher than 1 V, preferably 1.2 V or higher, more preferably 1.5 V or higher. Among the modifying agents specifically disclosed in DE 103 14 700 A1, insofar as they are oxidizing at all over aluminum, are no strong oxidizing agents as defined herein.

Due to the high temperature of the base body in the inventive method (in the range of 300 ° C to 630 ° C, preferably 400 ° C to 600 ° C, more preferably 500 ° C to 550 ° C), the redox reaction between aluminum and the oxidizing agent be - accelerates and allows the rapid formation of a relatively thick layer in which aluminum is oxidized to alumina. In other words, the oxidation of aluminum to alumina proceeds very rapidly from the surface of the body to the bottom due to the high temperature of the body. Preferably, the inventive method is carried out immediately after the preparation of the base body, wherein the base body due to in his Herstellungspro- zess (eg by casting or a heat treatment process) registered heat a temperature in the range of 300 ° C to 630 ° C, preferably 400 ° C to 600 ° C, more preferably 500 ° C to 550 ° C, having. Such a procedure is advantageous in terms of energy because, on the one hand, the temperature of the base body required for the method according to the invention is generated without additional energy expenditure by the heat necessarily introduced during the production of the base body, and on the other hand, for conventional methods of oxidation of aluminum such as Anodizing or coating with an insulating varnish required cooling of the base body avoided.

In the method according to the invention, the base body having a temperature in the range from 300 ° C. to 630 ° C., preferably 400 ° C. to 600 ° C., particularly preferably 500 ° C. to 550 ° C., is brought into contact with an oxidizing agent which is heated before the Contact with the base body has a temperature in the range of 15 ° C to 150 ° C, in some variants preferably 20 ° C to 99 ° C. Due to the large difference in temperature between the base body and the oxidizing agent, after the base body is brought into contact with the oxidizing agent, rapid cooling of the base body takes place, so that coarse grain formation in the base body is advantageously suppressed or at least reduced. The temperature of the base body and the temperature of the oxidation agent are preferably matched to one another such that the component after contacting the surface of the base body with the oxidizing agent has a temperature of more than 100 ° C., preferably more than 150 ° C., particularly preferably up to 200 ° C has. As a result, a dehydration of the insulating layer is achieved, so that the formation of boehmite (aluminum oxide hydroxide) is limited to aluminum oxide. The formation of alumina is preferred over boehmite because alumina has better insulating properties. The base body to be provided or to be provided for the method according to the invention advantageously already essentially has the shape of the passive electrical component to be produced, preferably selected from the group consisting of coils, helices, conductors, chokes, resistors, and switches. The basic body is preferably prepared by a process selected from the group consisting of

Casting a melt of aluminum or an aluminum alloy or an aluminum-containing alloy

Forming a blank

- Combination of casting and forming

Joining semi-finished products

Selective Laser Sintering (SLS)

Selective laser melting

3D printing of metal powder,

- electron beam melting

Metal powder injection with subsequent sintering process.

The corresponding methods are known to the person skilled in the art.

An aluminum alloy is understood according to the invention to mean an alloy whose main constituent is aluminum, i. the aluminum content is at least 50%, based on the total mass of the alloy. Under an aluminum-containing alloy is understood according to the invention an alloy with a lower aluminum content.

The joining of semi-finished products takes place for example by welding and / or soldering.

The combination of casting and forming usually involves the production of a blank, e.g. a blank in the form of a coil by a casting process and its subsequent forming, e.g. to adjust the geometry (height, width) of the coil in the desired manner.

Particularly preferably, the preparation of the base body for the process according to the invention is carried out by casting a melt of aluminum or an aluminum alloy or an alloy containing aluminum in a mold. The casting process may also be carried out with a partially liquid alloy (known to those skilled in the art as thixocasting).

The casting process takes place, for example, in die-casting, low-pressure casting or precision casting, the corresponding technologies are known in the art. In a preferred variant of the method according to the invention, the surface of a temperature in the range of 300 ° C to 630 ° C, preferably 400 ° C to 600 ° C, more preferably 500 ° C to 550 ° C, comprising the base body with a solution of the oxidizing agent contacted in a solvent or with an aerosol or vapor formed from a solution of the oxidizing agent in a solvent, the solution, the aerosol or the steam having a temperature in the range of 15 ° C to 150 ° C, in some variants preferred 20 ° C to 99 ° C.

In this preferred variant of the process according to the invention, the oxidizing agent is selected from the group consisting of permanganates, perborates, peroxycarboxylic acids, percarbonates, peroxides and salts of halo-oxygen acids. The choice of solvent is made by those skilled in the art considering the solubility of the oxidizing agent in the solvent, the evaporation temperature of the solvent and the wetting behavior of the resulting solution against the surface of the body having a temperature in the range of 300 ° C to 630 ° C the oxidizing agent is to be brought into contact. Preferred solvents for the oxidizing agent are water, molten salts and solutions of crown ethers in organic solvents such as alcohols and aromatics, e.g. Toluene. The concentration of the oxidizing agent in the solution is preferably 1% to 40% of its saturation concentration at the use temperature of the solution, more preferably 5% to 30% of its saturation concentration, more preferably 7.5% to 20% of its saturation concentration, most preferably 10% of its Saturation concentration, in each case at the operating temperature of the solution.

One or more further constituents selected from the group consisting of surfactants, glycol, glycerol, polyethylene glycol, polypropylene glycol, electrically nonconductive particles, pigments and metal salts may be added to the solution of the oxidizing agent. Surfactants serve to support the wetting of the wall surface of the surface of the body. Suitable surfactants are known to the person skilled in the art. The addition of glycol, glycerol, polyethylene glycol and / or polypropylene glycol is particularly useful when using water as a solvent, because this retards the formation of water vapor. This is advantageous because the formation of water vapor directly on the surface of the base body could hinder the contact between the solution of the oxidizing agent and the component surface to be coated (Leidenfrost ^'s phenomenon).

If one or more constituents selected from the group consisting of electrically nonconductive particles, pigments and metal salts are added to the solution of the oxidizing agent, an insulating layer is formed in the process according to the invention on the surface of the main body, which contains these other constituents in addition to aluminum oxide. Thus, in addition to the dielectric properties of the insulating layer, the method according to the invention may advantageously also provide further properties, e.g. the color of the insulating layer to be influenced. Preferred electrically non-conductive particles are i.a. PTFE particles, mica and benetonites. Preferred pigments are inorganic color pigments, i.a. Iron oxide, zirconium silicate, bismuth, chromate pigments and manganese dioxide. Corresponding pigments are known to the person skilled in the art. Preferred metal salts are coloring metal salts. Corresponding metal salts, e.g. Cr (II) salts, bismuth vanadate, ZrSiO 4, Cd salts and Mn salts are known to the person skilled in the art.

By incorporated in the insulating layer coloring metal salts or pigments, the insulating layer is given a coloring or shading. This may be used to characterize the layer thickness of the insulating layer, as a quality assurance measure, or as component marking (e.g., as an indication that an insulating layer is present, or for the assignment to a particular batch or type of component or customer).

For contacting the surface of the base body with a solution of the oxidizing agent in a solvent or with an aerosol formed from a solution of the oxidizing agent in a solvent, various techniques known to those skilled in the art are available, for example

the main body is immersed in a solution of the oxidizing agent,

the body is flooded or rinsed with a solution of the oxidizing agent, the main body is impregnated with a solution of the oxidizing agent, the main body is brought into contact with an aerosol of a solution of the oxidizing agent.

The amount of oxidizing agent acting on the surface of the body determines the amount of alumina and boehmite formed in the process of the invention, and thus the thickness of the insulating layer formed. The person skilled in the art adjusts the amount of oxidizing agent acting on the surface of the main body via the concentration of the oxidizing agent in the solution and / or via the application rate of the solution. When immersed in a solution of the oxidizing agent, the application rate of the solution of the oxidizing agent depends on the rate of removal of the immersed base body from the solution, as well as on the temperature and viscosity of the solution.

When coating with an aerosol of a solution of the oxidizing agent, the applied amount of aerosol (duration of spraying) and the concentration of the solution decide on the thickness of the insulating layer formed. Methods and tools (atomizers) for the production of an aerosol are known in the art. Preferably, the droplets of the aerosol droplet diameter in the range of 0, 1 μιη and 1 mm, preferably in the range of 1 μιη to 300 μιη, more preferably in the range of 5 μιη to 50 μιη.

In certain cases, it is preferable for the main body to be exposed to an electric field during the contacting with the aerosol of the solution of the oxidizing agent. Here, the same principle is used as in electrostatic painting, ie the base body to be brought into contact with the aerosol is at earth potential (grounded) and the aerosol is negatively charged by means of a spray electrode relative to the grounded body. This accelerates the movement of the aerosol droplets onto the surface of the main body. This effect occurs until the resulting by reaction of the oxidant contained in the aerosol with the aluminum on the surface of the body insulating layer has reached such a thickness that due to their insulating effect, the aerosol droplets are no longer accelerated, and so their movement to the surface of the body comes to a halt. It is therefore a self-limiting process. According to the invention, however, it is not excluded to terminate the aerosol deposition before the self-limiting effect occurs, in particular if the field strength in the aerosol deposition is higher than the desired dielectric strength of the insulating layer. A circulation of the aerosol is useful to ensure the most uniform contact of the workpiece with the aerosol.

If necessary, after forming the insulating layer, the component surface is washed to remove residues of the solution of the oxidizing agent. This is particularly useful when the solution of the oxidizing agent contains components from the group consisting of surfactants, glycol, glycerol, polyethylene glycol and polypropylene glycol.

The surface of the base body is preferably brought into contact with a solution of the oxidizing agent in a solvent or with an aerosol formed from a solution of the oxidizing agent in a solvent at a pressure in the range from 80 kPa to 1500 kPa, particularly preferably 100 kPa to 500 kPa. Particularly preferred is a process control with respect to the atmospheric pressure (standard pressure) increased pressure. Increasing the pressure above the atmospheric pressure raises the boiling point of the solvent. Upon contact with the solution of the oxidizing agent, the surface of the body is cooled to the evaporation temperature of the solvent. A high evaporation temperature of the solvent is therefore advantageous, because the higher the evaporation temperature of the solvent, the higher the temperature of the main body in the reaction with the oxidizing agent, and the more favored in particular with aqueous solutions of the oxidizing agent, the formation of alumina over the Formation of boehmite (aluminum oxide hydroxide). The formation of alumina is preferred over boehmite because alumina has better insulating properties.

In a preferred alternative variant of the process according to the invention, the surface of a body in the range of 300 ° C to 630 ° C, preferably 400 ° C to 600 ° C, particularly preferably 500 ° C to 550 ° C, having a gaseous oxidant brought into contact. Ozone is preferably used as the gaseous oxidizing agent. In order to increase the reactivity of the ozone, irradiation of the gas or of the workpiece with UV or vacuum UV radiation can simultaneously be carried out.

If necessary, after forming the alumina-containing insulating layer, the method of the invention comprises one or more further steps selected from the group consisting of

Applying an insulating wet paint, an insulating powder coating and / or a potting compound on the insulating layer Wrapping in insulating paper, in insulating foil and / or in a shrink tube

Depositing a plasma polymer layer on the insulating layer

Annealing of the component, preferably at a temperature in the range of> 50 ° C to 250 ° C, preferably from 100 ° C to 200 ° C, more preferably 130 ° C to 160 ° C. By the first three steps, a further insulating layer is produced on the insulating layer produced by the method according to the invention, so that the dielectric strength of the component is further increased. By annealing the component, boehmite present in the insulating layer produced by the method according to the invention is converted into aluminum oxide, so that the proportion of aluminum oxide in the insulating layer is further increased and the proportion of boehmite is further reduced.

The subject matter of the present invention is also a passive electrical component produced and / or producible by the method according to the invention described above.

An inventively produced or producible passive electrical component comprises

- A base body made of aluminum or an aluminum alloy or an aluminum-containing alloy

an insulating layer on the surface of the base body,

wherein in this insulating layer the mass ratio of alumina to boehmite is greater than 5,

wherein this insulating layer has a thickness of 1 μιη or more.

A passive electrical component according to the invention comprises a base body made of aluminum or of an aluminum alloy or of an aluminum-containing alloy and an insulating layer on the surface of the base body. This means that the component has a basic body of aluminum or of an aluminum alloy or of an aluminum-containing alloy as well as an insulating layer on the surface of the main body. This insulating layer contains alumina and optionally one or more components from the group consisting of boehmite and other aluminum compounds. In the said insulating layer, the mass ratio of aluminum oxide to boehmite is greater than 5. The condition defined here with regard to the mass ratio of aluminum oxide to boehmite is according to the invention in a region of at least 1 μm thickness extending from the component surface into the interior of the component (measured perpendicular to the component surface) fulfilled. Preferably, the mass ratio of the proportions of aluminum oxide and boehmite in the insulating layer is greater than 6, more preferably greater than 7, particularly preferably> 10.

According to the invention, it is not excluded that aluminum oxide is also present in a region further away from the component surface (that is to say below the insulating layer defined above).

At least 90% of the surface of the passive electrical component according to the invention are covered by the above-defined insulating layer, preferably at least 95% of the surface of the passive electrical component according to the invention, particularly preferably at least 99% of the surface of the passive electrical component according to the invention.

The mass ratio of the proportions of aluminum oxide and boehmite in the insulating layer is determined by means of X-ray diffraction (XRD) with an incident angle of 70 ° relative to the surface normal. The resulting diffraction pattern is adjusted by the diffraction patterns of the various modifications of the alumina, boehmite and aluminum, optionally further crystal modifications of non-alumina oxides (e.g., manganese dioxide) through a best-fit routine, and from this the mass ratio of alumina to boehmite is determined.

In addition to aluminum oxide and possibly boehmite and other aluminum compounds, the insulating layer may contain reaction products formed by reduction of the oxidizing agent, e.g. in the case of potassium permanganate as reducing agent, compounds of manganese (in a lower oxidation state than in potassium permanganate) and compounds of potassium.

In addition to aluminum oxide (and optionally boehmite, further aluminum compounds and reaction products formed by reduction of the oxidizing agent), the insulating layer may contain one or more of the following constituents:

pigments

metal salts

electrically non-conductive particles.

If present, said components are incorporated in the alumina-containing insulating layer. Preferred electrically non-conductive particles include PTFE Particles, mica and bentonites. Preferred pigments are inorganic color pigments, including iron oxide, zirconium silicate, bismuth, chromate pigments and manganese dioxide. Corresponding pigments are known to the person skilled in the art. Preferred metal salts are coloring metal salts. Corresponding metal salts, for example Cr (III) salts, bismuth vanadate, ZrSiC, Cd salts and Mn salts are known to the person skilled in the art.

By incorporated in the insulating layer coloring metal salts or pigments, the insulating layer is given a coloring or shading. This can be used to characterize the layer thickness of the insulating layer, as a quality assurance measure or component identification (eg as an indication that an insulating layer is present, or for the Zu-order to a particular batch or to a particular type of components or to a specific customer) , In the insulating layer embedded electrically non-conductive particles enhance the insulating effect.

The elemental composition of the insulating layer, and thus the content of aluminum and oxygen, can be determined by means of energy-dispersive X-ray spectroscopy EDX, wherein the expert selects the acceleration voltage so that the information depth is as large as the minimum thickness (1 μιη) of the insulating layer.

Optionally, X-ray photoelectron spectroscopy can also be used. In order to be able to record the element composition in lower layers (> 10 nm), the skilled person uses depth profiling (sputtering). When determining the composition of the elements, the skilled person takes into account any preferential sputtering which may occur.

If different elemental compositions are determined by different methods, the value determined by EDX is decisive.

The thickness of the insulating layer is determined non-destructively by means of the eddy current method according to DIN EN ISO 2360, for example by means of a leptoscope from Karl Deutsch Prüf- und Messgerätebau GmbH + Co. KG, Wuppertal (Germany). Alternatively, the thickness of the insulating layer formed on the surface of the component on a cryogenic fracture surface can be determined by means of scanning electron microscopy.

The passive electrical component according to the invention is for example selected from the group consisting of coils, coils, conductors, chokes, resistors, and switches. A passive electrical component according to the invention may have one or more form elements from the group consisting of undercuts, bores and channels. Particularly preferably, the passive electrical component according to the invention is a coil.

Preferably, the insulating layer has a thickness in the range of 10 μιη to 100 μιη. Within this thickness, the mass ratio of alumina to boehmite is greater than 5, preferably greater than 6, more preferably greater than 7, particularly preferably> 10.

Preferably, the insulating layer has a dielectric strength of 40 V / μιη or more, measured according to DIN EN 60243-1 and DIN EN 60243-2 for a current of up to 3 mA maximum. Particularly preferably, the insulating layer has a thickness of 10 μιη or more, and is puncture resistant to a voltage of 400 V or more, more preferably 2500 V or more.

The insulating layer also improves the corrosion resistance and aging resistance of the passive electrical component. Preference is given to passive electrical components according to the invention, in which the dielectric strength of the insulating layer drops by less than 20% after 1000 hours at a temperature in the range from -80.degree. C. to 300.degree.

In certain embodiments, a passive electrical component according to the invention comprises a further layer arranged on the surface of the insulating layer containing one or more materials selected from the group consisting of insulating lacquer layers, plasma polymers, insulating papers, insulating films, heat-shrinkable tubing and casting compounds. Materials and methods for making such layers are known to those skilled in the art.

The invention will be explained in more detail by way of examples. Example 1 :

A passive electrical component in the form of a die-cast aluminum conductor (rotor aluminum) measuring 10 mm x 10 mm x 100 mm is removed from the die at 550 ° C and transferred to a sealable chamber. The chamber is provided with a lining acting as a dielectric (3 cm thick PTFE plates). The component is earthed with a suitable clamping device at the points which are provided as contacting points for use as an electrical conductor, and therefore should not receive an insulating layer. The chamber is closed and a pressure of 500 kPa is set in the chamber by means of a compressor.

An electrostatic coating plant is an aqueous solution containing 0, 1 mol / l KMnC and 0.3 mol / l glycerol supplied. The atomizing nozzle (rotary atomizer) of the paint shop is introduced with an electrically insulating passage in the chamber. By applying a voltage of 45 kV to the atomizer (current 8 μΑ), the aerosol is charged. By turning the aluminum conductor in the chamber, the surface is evenly exposed to the aerosol. After spraying, the chamber is relaxed and removed the component. It has a temperature of 150 ° C at this time. After cooling, the component is cleaned with water and acetone to remove excess glycerine and KMnC from the surface. The thickness of the insulating layer formed on the surface of the component is determined on a cryogenic fracture surface by scanning electron microscopy at 10 different locations. The layer thickness was 2.8 μιη ± 0.3 μιη. The elemental composition of the insulating layer in the region of a thickness of 1 μm determined by means of EDX is as follows: Al (28 at%), O (53 at%), Mn (14 at%), C (5 at%) and traces of K. The dielectric strength is 180 V measured according to DIN EN 60243-1 and DIN EN 60243-2 up to a maximum current flow of 3 mA. The mass ratio of alumina to boehmite was determined by X-ray diffraction (XRD) using an angle of incidence of 70 ° with respect to the surface normal to 15 ± 3.

Example 2 In a sealable chamber, a tank is filled with an aqueous solution containing 0.1 mol / l KMnO4 and 0.3 mol / l glycerol. A passive electrical component in the form of a die-cast aluminum conductor (rotor aluminum) measuring 10 mm x 10 mm x 100 mm is removed from the die at 550 ° C and transferred to the chamber. The chamber is closed and a pressure of 500 kPa is set in the chamber by means of a compressor. The component is then immersed in the solution in the basin. After 5 minutes, the component is removed from the solution, the chamber relaxed and removed the component. It has a temperature of 140 ° C at this time. After cooling, the component is cleaned with water and acetone to remove excess glycerine and KMnC from the surface.

The thickness of the insulating layer formed on the surface of the component is determined on a cryogenic fracture surface by scanning electron microscopy at 10 different locations. The layer thickness was 3.5 μιη ± 0.2 μιη. The elemental composition of the insulating layer in the region of a thickness of 1 μm determined by means of EDX is as follows: Al (29 at%), O (56 at%), Mn (11 at%), C (4 at%) and traces of K. The dielectric strength is 195 V measured according to DIN EN 60243-1 and DIN EN 60243-2 up to a maximum current flow of 3 mA. The mass ratio of alumina to boehmite was determined by X-ray diffraction (XRD) using an angle of incidence of 70 ° with respect to the surface normal to 10 ± 2.

Claims

claims

A method of making a passive electrical component, comprising the steps

2. The method of claim 1, wherein the passive electrical component is selected from the group consisting of coils, coils, conductors, chokes, resistors, and switches.

3. The method of claim 1 or 2, wherein the base body is prepared by a method selected from the group consisting of

Casting a melt of aluminum or an aluminum alloy or an aluminum-containing alloy

Forming a blank

Combination of casting and forming

Joining semi-finished products

Selective laser sintering

Selective laser melting

3D printing of metal powder

electron beam melting

Metal powder injection with subsequent sintering.

4. The method according to any one of the preceding claims, wherein the component after Inkontaktbrin- gene of the surface of the body with the oxidizing agent has a temperature of more than 100 ° C, preferably more than 150 ° C, particularly preferably up to 200 ° C.

5. The method according to any one of the preceding claims, wherein the surface of the base body is brought into contact with a solution of the oxidizing agent in a solvent or with an aerosol formed from a solution of the oxidizing agent in a solvent.

6. The method according to any one of the preceding claims, wherein the surface of the base body at a pressure in the range of 80 kPa to 1500 kPa with a solution of the

Oxidant is brought into contact in a solvent or with an aerosol formed from a solution of the oxidizing agent in a solvent.

7. The method according to claim 5 or 6, wherein the base body is exposed during the contacting with the solution of the oxidizing agent or with the aerosol of the solution of the oxidizing agent to an electric field.

8. The method according to any one of claims 5 to 7, wherein the oxidizing agent is selected from the group consisting of permanganates, perborates, peroxycarboxylic acids, percarbonates, peroxides and salts of halo-oxygen acids.

9. A process according to any one of claims 5 to 8, wherein one or more ingredients selected from the group consisting of surfactants, glycol, glycerin, polyethylene glycol, polypropylene glycol, electrically non-conductive particles, pigments and metal salts are added to the solution of the oxidizing agent are.

10. The method according to any one of claims 1 to 4, wherein the oxidizing agent is gaseous, wherein the gaseous oxidizing agent is preferably ozone.

1 1. Passive electrical component

full

a basic body made of aluminum or an aluminum alloy or an aluminum-containing alloy

an insulating layer on the surface of the base body,

wherein said insulating layer has a thickness of 1 μιη or more and / or

preparable by a method according to one of claims 1 to 10.

12. Passive electrical component according to claim 1 1, wherein the passive electrical component is selected from the group consisting of coils, coils, conductors, chokes, resistors, and switches.

13. Passive electrical component according to claim 1 1 or 12, wherein the passive electrical component comprises one or more mold elements from the group consisting of undercuts, bores and channels.

14. Passive electrical component according to one of claims 1 1 to 13, wherein the insulating layer has a dielectric strength of 40 V / μιη or more, measured according to DIN EN 60243-1 and DIN EN 60243-2 up to a maximum current flow of 3 mA

15. Passive electrical component according to one of claims 1 1 to 14, wherein the insulating layer contains one or more of the following constituents:

pigments

metal salts

electrically non-conductive particles.