METHOD FOR PRODUCING AN INDUCTIVE COMPONENT AND INDUCTIVE COMPONENT

Abstract

In a method for producing an inductive component, a basic body, which includes a magnetic material, is sintered and subsequently comminuted. The comminuting has the effect of creating sintered particles, which are mixed with a binder to form at least one mixture. The at least one mixture and at least one coil are arranged in a mould and subsequently the binder is activated, so that the sintered particles form with the binder at least one magnetic core, which at least partially surrounds the at least one coil. The method allows easy and low-cost production of the inductive component with improved electromagnetic properties.

Claims

1. A method for producing an inductive component with the steps of: providing a basic body comprising a magnetic material, sintering the basic body, comminuting the sintered basic body to form sintered particles, producing at least one mixture from the sintered particles and a binder, arranging the at least one mixture and at least one coil in a mould, and activating the binder in the at least one mixture, so that the sintered particles form with the binder at least one magnetic core, which at least partially surrounds the at least one coil.

2. The method according to claim 1, wherein the magnetic material comprises at least one ferrite material.

3. The method according to claim 1, wherein the sintering is performed at a temperature T.sub.S, where: T.sub.S1000 C.

4. The method according to claim 1, wherein the sintered particles have a respective aspect ratio and, before producing the at least one mixture, the aspect ratios are at least partially reduced.

5. The method according to claim 1, wherein, before producing the at least one mixture, the sintered particles are worked by means of a ball mill.

6. The method according to claim 1, wherein, before producing the at least one mixture, the sintered particles are separated on the basis of at least one of the group comprising the particle form and the particle size.

7. The method according to claim 1, wherein at least 70% of the sintered particles used for producing the at least one mixture have a respective aspect ratio A, for which the following applies: 0.5A1.

8. The method according to claim 1, wherein at least 70% of the sintered particles used for producing the at least one mixture have a respective minimum dimension A.sub.min, for which the following applies: 10 mA.sub.min1000 m.

9. The method according to claim 1, wherein, before producing the at least one mixture, the sintered particles are separated into a first fraction with first sintered particles and into a second fraction with second sintered particles, which are different from the first sintered particles.

10. The method according to claim 1, wherein a first magnetic core is produced with first sintered particles, and wherein a second magnetic core is produced with second sintered particles, which differ from the first sintered particles.

11. The method according to claim 1, wherein the binder is activated by increasing at least one of the group comprising a temperature and by increasing a pressure.

12. The method according to claim 1, wherein the at least one mixture is produced in such a way that the following applies for a mass ratio m of the sintered particles to the binder: 75/25m99/1.

13. The method according claim 1, wherein the basic body is provided by pressing the magnetic material.

14. An inductive component comprising at least one coil, at least one magnetic core, which at least partially surrounds the at least one coil, wherein the at least one core is formed by means of sintered particles and a binder.

15. The inductive component according to claim 14, wherein a first magnetic core with first sintered particles at least partially surrounds the at least one coil, and wherein a second magnetic core with second sintered particles, which are different from the first sintered particles, at least partially surrounds the first magnetic core and the at least one coil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a sectional representation of an inductive component,

[0026] FIGS. 2A and 2B show a flow diagram with the steps for producing the inductive component according to FIG. 1,

[0027] FIG. 3 shows diagrams of the quality factor Q as a function of the time t and the frequency f, the upper diagram illustrating an inductive component comprising an iron alloy according to the prior art, the middle diagram illustrating an inductive component according to the invention with ferrite material comprising manganese and zinc and the lower diagram illustrating an inductive component according to the invention with ferrite material comprising nickel and zinc,

[0028] FIG. 4 shows diagrams of the AC voltage power loss PAC as a function of the time t and the frequency f, the upper diagram illustrating an inductive component comprising an iron alloy according to the prior art, the middle diagram illustrating an inductive component according to the invention with ferrite material comprising manganese and zinc and the lower diagram illustrating an inductive component according to the invention with ferrite material comprising nickel and zinc,

[0029] FIG. 5 shows a diagram of the quality factor Q as a function of the frequency f and the time t for an inductive component comprising an iron alloy according to the prior art, and

[0030] FIG. 6 shows a diagram of the quality factor Q as a function of the frequency f and the time t for an inductive component according to the invention with ferrite material comprising manganese and zinc.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031] An inductive component 1 comprises a coil 2, a first magnetic core 3 and a second magnetic core 4. The coil 2 is formed for example as a cylindrical coil. The coil 2 consists of an electrically conductive material. The coil 2 has terminal contacts 5, 6.

[0032] The first magnetic core 3 surrounds the coil 2. The first magnetic core 3 comprises first sintered particles P.sub.1, which are bonded to one another by means of a first binder B.sub.1. The second magnetic core 4 surrounds the first magnetic core 3 and the coil 2. The second magnetic core 4 comprises second sintered particles P.sub.2, which are bonded to one another by means of a second binder B.sub.2. The terminal contacts 5, 6 are led through the first magnetic core 3 and the second magnetic core 4 to the outside.

[0033] The first sintered particles P.sub.1 have in each case a minimum dimension A.sub.1min and a maximum dimension A.sub.1max. The first sintered particles P.sub.1 have a respective first aspect ratio A.sub.1, where: A.sub.1=A.sub.1min/A.sub.1max. At least 70%, in particular at least 80%, in particular at least 90%, and in particular at least 95%, of the first sintered particles P.sub.1 have a respective minimum dimension A.sub.1min, where: 500 mA.sub.1min1000 m, in particular 600 mA.sub.1min900 m, and in particular 700 mA.sub.1min800 m. At least 70%, in particular at least 80%, in particular at least 90%, and in particular at least 95%, of the first sintered particles P.sub.1 have a respective aspect ratio A.sub.1, where: 0.5A.sub.11, in particular 0.6A.sub.11, in particular 0.7A.sub.11, in particular 0.8A.sub.11, and in particular 0.9A.sub.11. Preferably, the following applies for the aspect ratio A.sub.1: 0.5A.sub.11, in particular 0.6A.sub.10.9, and in particular 0.7A.sub.10.8. The aspect ratio A.sub.1 may be chosen in dependence on the desired distribution of the magnetic flux. Advantageous properties are obtained with an aspect ratio of A.sub.10.75.

[0034] The second sintered particles P.sub.2 have in each case a minimum dimension A.sub.2min and a maximum dimension A.sub.2max. The second sintered particles P.sub.2 have a respective second aspect ratio A.sub.2, where: A.sub.2=A.sub.2min/A.sub.2max. At least 70%, in particular at least 80%, in particular at least 90% and in particular at least 95%, of the second sintered particles P.sub.2 have a respective minimum dimension A.sub.2min, where: 10 mA.sub.2min500 m, in particular 100 mA.sub.2min400 m, and in particular 200 mA.sub.2 min300 m. At least 70%, in particular at least 80%, in particular at least 90%, and in particular at least 95%, of the second sintered particles P.sub.2 have a respective aspect ratio A.sub.2, where: 0.5A.sub.21, in particular 0.6A.sub.21, in particular 0.7A.sub.21, in particular 0.8A.sub.21, and in particular 0.9A.sub.21. Preferably, the following applies for the aspect ratio A.sub.2: 0.5A.sub.21, in particular 0.6A.sub.20.9, and in particular 0.7A.sub.20.8. The aspect ratio A.sub.2 may be chosen in dependence on the desired distribution of the magnetic flux. Advantageous properties are obtained with an aspect ratio of A.sub.20.75.

[0035] The first sintered particles P.sub.1 and the second sintered particles P.sub.2 differ in their particle form or in their aspect ratio A.sub.1 or A.sub.2 and/or in their particle size or in their minimum dimension A.sub.1min or A.sub.2min, respectively.

[0036] The method for producing the inductive component 1 is described below on the basis of FIG. 2:

[0037] In a step S.sub.1, firstly starting materials R.sub.1 to R.sub.n are mixed with one another to form a starting material mixture R.sub.M. The starting materials R.sub.1 to R.sub.n are for example raw materials and/or waste materials, which are to be recycled or reprocessed. The starting materials R.sub.1 to R.sub.n comprise for example zinc oxide (ZnO), manganese oxide (MnO) and/or iron oxide.

[0038] The starting material mixture R.sub.M is activated and/or calcined in a step S2. In the calcining, a starting material mixture R.sub.M containing calcium and magnesium carbonate is heated to achieve dewatering and/or decomposition.

[0039] The activated raw material mixture R.sub.M forms a magnetic material M. The magnetic material M is for example in the form of powder and/or in the form of granules. The magnetic material M comprises at least one ferrite material, for example MnZn ferrite material and/or NiZn ferrite material.

[0040] The magnetic material M is pressed in a step S.sub.3 to form a basic body G. The basic body G is also referred to as a green body.

[0041] In a subsequent step S.sub.4, the basic body G is sintered. The sintering is performed at a temperature T.sub.S, where: T.sub.S1000 C., in particular T.sub.S1100 C., in particular T.sub.S1200 C. The sintered basic body is denoted by G.sub.S.

[0042] In a step S.sub.5, the sintered basic body G.sub.S is comminuted. The comminuting is performed for example by means of a crushing machine or comminuting machine (crusher). The comminuting creates sintered particles, which are denoted generally by P. The sintered particles P have in each case a minimum dimension A.sub.min and a maximum dimension A.sub.max, which define a respective aspect ratio A. The following applies for the respective aspect ratio: A=A.sub.min/A.sub.max. After the comminuting of the sintered basic body G.sub.S, the aspect ratios A of the sintered particles P widely diverge. In particular, when comminuting, sintered particles P with an elongated form, which have a respective small aspect ratio A, are also created. For the further processing of the sintered particles P, a form that corresponds substantially to a spherical form and/or a cuboidal form is desired.

[0043] In a step S.sub.6, the aspect ratios A of the sintered particles P are reduced. This means that the maximum dimension A.sub.max of the respective sintered particle P is brought closer to the minimum dimension A.sub.min. For this purpose, the sintered particles P are for example worked by means of a ball mill. The ball mill comprises a drum and metal balls arranged therein. The sintered particles P are introduced into the drum and, on the basis of a rotation of the drum, are worked by means of the metal balls, by further commination and/or friction, so that the aspect ratios A of the sintered particles P are at least partially reduced.

[0044] In a step S.sub.7, the sintered particles P are separated on the basis of their particle form and/or on the basis of their particle size. The sintered particles P are separated into a first fraction with first sintered particles P.sub.1 and a second fraction with second sintered particles P.sub.2. The first sintered particles P.sub.1 have the minimum dimension A.sub.1min and the maximum dimension A.sub.1max and also the aspect ratio A.sub.1, whereas the second sintered particles P.sub.2 have the minimum dimension A.sub.2 min, the maximum dimension A.sub.2max and the aspect ratio A.sub.2. The first fraction comprises coarser particles in comparison with the second fraction. Accordingly, the following applies for at least 70% of the sintered particles P.sub.1, P.sub.2: A.sub.1min>A.sub.2min and/or A.sub.1max>A.sub.2 min and/or A.sub.1min>A.sub.2max.

[0045] Sintered particles P segregated in step S.sub.7, belonging neither to the first fraction nor to the second fraction, can be returned and comminuted further in step S.sub.5 and/or worked further in step S.sub.6. This is illustrated in FIG. 2 by the dashed lines.

[0046] In a subsequent step S.sub.81, a first mixture X.sub.1 is produced from the first sintered particles P.sub.1 and the first binder B.sub.1. Correspondingly, in a step S.sub.82, a second mixture X.sub.2 is produced from the second sintered particles P.sub.2 and the second binder B.sub.2. The binders B.sub.1 and B.sub.2 may be the same or different. The binders B.sub.1, B.sub.2 are for example a polymer plastic and/or a resin.

[0047] The first mixture X.sub.1 has a mass ratio m.sub.1 of the mass m.sub.P1 of the first sintered particles P.sub.1 to the mass m.sub.B1 of the first binder B.sub.1. Consequently, the following applies for the mass ratio m:m.sub.1=m.sub.P1/m.sub.B1. Preferably, the following applies for the mass ratio m.sub.1: 75/25m.sub.199/1, in particular 80/20m.sub.198/2, and 85/15m.sub.195/5. The second mixture X.sub.2 has a mass ratio m.sub.2 of the mass m.sub.P2 of the second sintered particles P.sub.2 to the mass m.sub.B2 of the second binder B.sub.2. Consequently, the following applies for the mass ratio m.sub.2:m.sub.2=m.sub.P2/m.sub.B2. Preferably, the following applies for the mass ratio m.sub.2: 75/25m.sub.299/1, in particular 80/20m.sub.298/2, and 85/15m.sub.295/5. The mass ratio is denoted generally by m.

[0048] In a step S.sub.9, the first mixture X.sub.1 and the coil 2 are arranged in a first mould F.sub.1. Subsequently, the first binder B.sub.1 is activated, so that the first binder B.sub.1 bonds the first sintered particles P.sub.1 to form the first magnetic core 3. For activating the first binder B.sub.1, a pressure p.sub.1 on the first mixture X.sub.1 and/or a temperature T.sub.1 of the first mixture X.sub.1 is increased. After the curing of the first binder B.sub.1, the first magnetic core 3 with the coil 2 is demoulded.

[0049] In a subsequent step S.sub.10. the first magnetic core 3 is arranged with the coil 2 and the second mixture X.sub.2 in a second mould F.sub.2. Subsequently, the second binder B.sub.2 is activated, so that the second binder B.sub.2 bonds the second sintered particles P.sub.2 to form the second magnetic core 4. The second binder B.sub.2 is activated by increasing a pressure p.sub.2 on the second mixture X.sub.2 and/or by increasing a temperature T.sub.2 of the second mixture X.sub.2. After the curing of the second binder B.sub.2, the second core 4 with the first magnetic core 3 and the coil 2 is demoulded.

[0050] In a step S11, the inductive component 1 is provided by the demoulding.

[0051] FIG. 3 illustrates measurement curves for the quality factor Q (Q value) for frequencies f of 100 kHz, 500 kHz and 1 MHz over time t. The quality factor Q of the inductive components 1 according to the invention (cf. the middle and lower diagrams) is more constant over time t compared to the inductive component according to the prior art (cf. the upper diagram). In addition to the measurement curves, smoothed measurement curves, which are intended to make easier comparison with regard to the constancy of the quality factors Q possible, are illustrated in FIG. 3.

[0052] In a corresponding way, FIG. 4 illustrates measurement curves for the AC voltage power loss PAC for frequencies f of 400 kHz and 1.2 MHz over time t. The AC voltage power loss P.sub.AC of the inductive components 1 according to the invention (cf. the middle and lower diagrams) is more constant over time t in comparison with the inductive component according to the prior art (cf. the upper diagram). In addition to the measurement curves, smoothed measurement curves, which are intended to make easier comparison with regard to the constancy of the AC voltage power loss PAC possible, are illustrated in FIG. 4.

[0053] The components 1 according to the invention scarcely age thermally, and consequently ensure that the behaviour of an electrical circuit with the inductive components 1 according to the invention does not change as a result of parameters changing over time t, such as for example the quality factor Q or the AC voltage power loss PAC, and their function is not impaired. A comparison of the measurement curves in FIG. 5 with the measurement curves in FIG. 6 illustrates that the quality factor Q of the inductive component 1 according to the invention scarcely changes over time t and the components 1 according to the invention scarcely age thermally.

[0054] It generally applies that:

[0055] The inductive component 1 has at least one coil 2. Preferably, the inductive component 1 has precisely one coil or precisely two coils.

[0056] The sintered particles P created by comminuting the sintered basic body G.sub.S can be worked, separated and/or selected in any desired way. The sequence of the steps mentioned can be as desired here. Known filters and/or screens and/or separators can be used for the separating and/or selecting. The working, separating and/or selecting of the sintered particles P allow the electromagnetic properties of the inductive component 1 to be set in the desired way. In particular, the inductance, the saturation behaviour and/or the air gap can be set.

[0057] The activating of the binder B may be performed by cold pressing or hot pressing.

[0058] The magnetic material M, and consequently the at least one magnetic core 3, 4, preferably comprises at least one ferrite material. Ferrite material is available at low cost and easily. The use of ferrite material means that comparatively good electromagnetic properties of the inductive component 1 are achieved. In particular, the inductive component 1 has a high inductance, a desired saturation behaviour, low losses and/or can be operated at a high voltage. Such inductive components 1 can for example withstand a high potential test (AC HiPot test) at a voltage of 3 kVAC (3 mA, 3 sec).

[0059] The sintered particles are denoted generally by P. The aspect ratio is denoted generally by A. The minimum dimension is denoted generally by A.sub.min. The maximum dimension is denoted generally by A.sub.max.