Insulated wire and manufacturing method thereof, and inductor and manufacturing method thereof

Abstract

The invention provides an insulated wire which comprises a base material and an insulating layer wrapping the base material, the base material is made of a conductive material, the insulating layer is made of an inorganic insulating material, and the porosity of the insulating layer is not higher than 20%. The insulated wire provided by the invention has good electrical insulation characteristic and high temperature resistance, and is suitable for forming a single-turn or multi-turn coil so as to be used for manufacturing an integrated compression molding inductor. The invention also provides a method for manufacturing the insulated wire, an integrated compression molding inductor manufactured by using the insulated wire, and a method for manufacturing the integrated compression molding inductor.

Description

Technical Field

[0001] The present invention relates to insulated wires, methods for manufacturing insulated wires, inductors, and methods for manufacturing inductors. Background Art

[0002] As one of the indispensable passive components in electronic circuits, the basic function of an inductor is to convert electrical energy into magnetic energy and store it. The operating mechanism of an inductor is based on the following principle: when an alternating current passes through a wire, an alternating magnetic field is generated inside and around the wire. An inductor has the characteristic of "passing direct current and blocking alternating current", that is, it allows direct current to pass through smoothly while presenting impedance to alternating current, thereby realizing various functions such as filtering, stabilizing current, and suppressing electromagnetic interference. Due to these characteristics, inductors are widely used in many fields such as mobile communication, automotive manufacturing, industrial control, medical devices, and aerospace. Currently, the inductor industry is developing towards miniaturization, high frequency, high power, integration, etc.

[0003] Among conventional inductors, the most common is the wound inductor. Taking a light storage block combination magnetic core as an example, the magnetic core is composed of a magnetic column and a magnetic yoke, and the coil is usually wound around the magnetic column. To ensure that the inductor meets the "three-proof" (waterproof, salt spray-proof, and mildew-proof) standards and to ensure the effective heat dissipation of the magnetic core and prevent performance degradation or damage caused by overheating, a common practice is to pot these combined block magnetic cores in an aluminum shell with a colloid. This process can not only significantly improve the thermal management efficiency of the inductor but also provide additional electrical insulation, reducing electromagnetic interference between different components, thereby ensuring the electrical performance of the inductor. In addition to the above advantages, the combined potted inductor also has the following disadvantages: (1) The combined potted inductor has a high cost, including the costs of potting materials, aluminum shells, and potting processes; (2) The use of potting materials increases the overall volume and weight of the inductor, which is not conducive to the high power density of power electronic devices; (3) The potting process requires precise control to ensure that there are no air bubbles remaining, otherwise it will affect the performance of the inductor. Therefore, there is still much room for improvement in the power density, cost control, etc. of the combined potted inductor. In addition, factors such as the fluidity and viscosity of the potting material need to be considered to ensure a good filling effect. A one-piece compression molding technical solution has been proposed, in which the magnetic core and the coil are pressed together to form a one-piece compression molding inductor, so that the coil is coated or embedded inside the magnetic core and still meets the electrical performance and temperature rise requirements. This one-piece compression molding inductor does not require an aluminum shell and potting glue, significantly reducing the labor and material costs, and at the same time improving the temperature rise grade of the inductor.

[0004] When manufacturing an integrally molded inductor with a high compression density, a bare wire can be used for molding. However, this approach limits the number of turns of the coil in the integrally molded inductor. Currently, the coils of integrally molded inductors are all single-turn coils. If a multi-turn coil is molded, it is impossible to ensure the inter-turn insulation of the coil, which easily leads to a short circuit between the turns of the coil, thereby affecting the normal function of the integrally molded inductor.

[0005] To solve the problem of inter-turn short circuit of the coil of the integrally molded inductor, it is necessary to coat the outer surface of the wire with an insulating layer formed by an insulating material, so that a coil formed by multi-turn wires can be used.

[0006] During the manufacturing process of the integrally molded inductor, a powder molding process needs to be adopted. The powder molding process usually requires heat treatment at a high temperature above 600 °C (for example, above 700 °C) to restore the material structure to achieve the best electromagnetic performance. However, conventional insulating materials usually use polyimide. The temperature resistance range of this material is usually only 220 °C to 260 °C. The wire coated with this insulating material cannot withstand the high-temperature environment during the manufacturing process of the integrally molded inductor. When the temperature is too high, the polyimide insulating layer will lose its electrical insulation performance, thus bringing a significant electrical insulation risk.

[0007] Chinese invention patent CN111234693B discloses a high-temperature resistant insulating polyimide enameled wire paint and its preparation method. By optimizing the component ratios (such as polyamide acid salt, maleic resin, and nano-silica) and the preparation process (including dissolution, precipitation, use of dehydrating agents and catalysts, etc.), an enameled wire paint with strong adhesion, not easy to wrinkle, and rapid drying is prepared. Although this enameled wire paint has good heat resistance, it can only withstand a temperature of 400 °C. Considering that the heat treatment temperature of the integrally compression-molded inductor is as high as 600 °C or even above 700 °C, its heat resistance still has certain limitations. Chinese invention patent CN104900390B describes a manufacturing method of a new type of high-density integrally compression-molded inductor. Since the integrally compression-molded inductor uses enameled wire, its structure needs to be formed in the mold cavity of the injection mold, and the treatment of ferromagnetic powder requires two steps and cannot directly perform one-step pressing and high-temperature heat treatment, making the manufacturing process of the inductor relatively complex and increasing the time cost. Chinese invention patent application CN105940470A discloses an inductor and its preparation method. This method uses a mixture of an organic binder and an inorganic insulating material to be coated on the surface of the wire, and after forming the inductor, heat treatment is carried out at a heating temperature above 600 °C. After heating, the organic binder volatilizes, and the inorganic insulating material wraps on the surface of the wire. However, since the coating layer is a mixture of organic and inorganic substances, after high-temperature heat treatment, the porosity of the inorganic coating remaining on the surface of the wire is high, the thickness and uniformity are difficult to control, and the bonding strength between the inorganic coating and the wire is insufficient. Summary of the Invention

[0008] To solve the problem of inter-turn short circuit of the coil during the manufacturing process of the integrally compression-molded inductor, the present invention provides an improved insulating wire, which has good electrical insulation characteristics and high temperature resistance, is suitable for forming single-turn or multi-turn coils, and is used for manufacturing integrally compression-molded inductors. The present invention also provides a method for manufacturing the insulating wire, an integrally compression-molded inductor made of the insulating wire, and a method for manufacturing the integrally compression-molded inductor.

[0009] Specifically, the present invention provides an insulating wire, the insulating wire comprising: a base material formed of a conductive material; and an insulating layer coating the base material, the insulating layer being formed of an inorganic insulating material, wherein the porosity of the insulating layer is not higher than 20%.

[0010] In one embodiment, the insulated wire further includes a transition layer disposed between the substrate and the insulating layer such that the substrate is coated with the transition layer and the transition layer is coated with the insulating layer, wherein the lattice constant of the transition layer is between the lattice constant of the substrate and the lattice constant of the insulating layer, and / or the thermal expansion coefficient of the transition layer is between the thermal expansion coefficient of the substrate and the thermal expansion coefficient of the insulating layer.

[0011] In one embodiment, the insulated wire further includes a protective layer that coats the insulating layer, wherein the protective layer is formed of a material having a layered crystal structure.

[0012] In one embodiment, the transition layer is formed of one or more of the following materials: nickel, titanium, chromium, iron, aluminum, and nickel-aluminum alloy.

[0013] In one embodiment, the protective layer is formed of one or more of the following materials: hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS 2 )

[0014] In one embodiment, the substrate is formed of copper, the insulating layer is formed of aluminum oxide (Al 2 O 3 ), the transition layer is formed of nickel, and the protective layer is formed of hexagonal boron nitride (h-BN), and wherein the thickness of the insulating layer is between 1 μm and 100 μm, the thickness of the transition layer is between 10 nm and 800 nm, and the thickness of the protective layer is between 1 μm and 50 μm.

[0015] In one embodiment, the substrate is formed of copper, the insulating layer is formed of aluminum nitride (AlN), the transition layer includes a first transition layer and a second transition layer, the first transition layer is formed of nickel and the second transition layer is formed of nickel-aluminum alloy, and the protective layer is formed of molybdenum disulfide (MoS 2 ), and wherein the thickness of the insulating layer is between 1 μm and 100 μm, the thickness of the first transition layer is between 10 nm and 500 nm, the thickness of the second transition layer is between 10 nm and 500 nm, and the thickness of the protective layer is between 1 μm and 50 μm.

[0016] In one embodiment, the inorganic insulating material includes one or more of the following compounds: metal oxides, non-metal oxides, metal nitrides, non-metal nitrides, carbides, and silicates.

[0017] In one embodiment, the inorganic insulating material includes one or more of the following compounds: silicon nitride (Si 3 N 4) Aluminum nitride (AlN), silicon carbide (SiC), aluminum oxide (Al 2 O 3 ), zirconia toughened alumina (ZTA), boron nitride (BN), magnesium oxide (MgO), yttrium oxide (Y 2 O 3 ), sodium silicate (Na 2 O·nSiO 2 ), potassium sulfate (K 2 SiO 3 ), lithium sulfate (Li 2 SiO 3 ), silicon dioxide (SiO 2 ), copper oxide (CuO), zinc oxide (ZnO), zirconium dioxide (ZrO 2 ), diamond-like carbide (DLC) and aluminum chromium nitride (AlCrN).

[0018] The present invention also provides a method for manufacturing an insulated wire, the insulated wire comprising a base material and an insulating layer, the method comprising the steps of: forming the base material from a conductive material; and directly applying the insulating layer on the base material by a magnetron sputtering process such that the insulating layer coats the base material, wherein the insulating layer is formed from an inorganic insulating material and wherein the porosity of the insulating layer is not higher than 20%.

[0019] In one embodiment, the method further comprises the step of: applying a protective layer on the insulating layer by a plasma enhanced chemical vapor deposition process such that the protective layer coats the insulating layer, wherein the protective layer is formed from a material having a layered crystal structure.

[0020] The present invention also provides a method for manufacturing an insulated wire, the insulated wire comprising a base material, a transition layer and an insulating layer, the method comprising the steps of: forming the base material from a conductive material; applying the transition layer on the base material by an electroplating process such that the transition layer coats the base material; and directly applying the insulating layer on the transition layer by a magnetron sputtering process such that the insulating layer coats the transition layer, wherein the insulating layer is formed from an inorganic insulating material and wherein the porosity of the insulating layer is not higher than 20%.

[0021] In one embodiment, the method further comprises the step of: applying a protective layer on the insulating layer by a plasma enhanced chemical vapor deposition process such that the protective layer coats the insulating layer, wherein the protective layer is formed from a material having a layered crystal structure.

[0022] The present invention also provides an inductor, which includes: a housing; a first pin and a second pin, the first pin and the second pin being disposed on an outer surface of the housing; and a compression molded part, the compression molded part being received in the housing, the compression molded part including a magnetic core and a coil, the magnetic core being formed by pressing soft magnetic powder, the coil being wound by an insulating wire according to the present invention and embedded in the magnetic core, the coil including opposite first and second ends, a first end of the coil extending out of the magnetic core to be electrically connected to the first pin, and a second end of the coil extending out of the magnetic core to be electrically connected to the second pin.

[0023] In one embodiment, the number of turns of the coil is between 2 and 200.

[0024] The present invention also provides a method for manufacturing an inductor, the method including the following steps: providing an insulating wire according to the present invention; using a winding device to wind the insulating wire into a single-turn or multi-turn coil; laying soft magnetic powder in a mold and embedding the coil in the soft magnetic powder; integrally pressing and molding the soft magnetic powder and the insulating wire to obtain a compression molded part; subjecting the compression molded part to a heat treatment with a maximum temperature between 650 °C and 1000 °C; loading the compression molded part into a housing, and electrically connecting a first end of the coil to a first pin on the housing and electrically connecting a second end of the coil to a second pin on the housing.

[0025] In one embodiment, the method further includes the following step: after subjecting the compression molded part to the heat treatment and before loading the compression molded part into the housing, immersing the compression molded part in an impregnating liquid to improve its structural strength.

[0026] In one embodiment, the number of turns of the coil is between 2 and 200.

[0027] The technical solution of the present invention can at least bring the following advantages:

[0028] 1. The insulated wire with an inorganic insulating layer according to the present invention has the advantage that an inorganic material capable of maintaining stability in a high-temperature environment is selected as the insulating material, effectively overcoming the problem that conventional organic insulating materials are prone to carbonization or volatilization under high-temperature conditions, thereby improving the performance of the insulated wire under high-temperature working conditions. In addition, the inorganic material has excellent electrical insulation performance, can effectively prevent current leakage, and provides a better electrical isolation effect in high-voltage and high-frequency applications. Particularly importantly, the inorganic insulating layer endows the insulated wire with better environmental tolerance, including corrosion resistance and anti-aging properties, enabling the insulated wire with an inorganic insulating layer according to the present invention to be applied in more severe environments. The present invention proposes to apply an inorganic insulating layer on a substrate through a magnetron sputtering process. The obtained inorganic insulating layer has a low porosity, a high density, and excellent bonding strength, and can maintain its physical properties and stable chemical properties even under high-temperature conditions.

[0029] 2. The integrally compression-molded inductor made of the insulated wire with an inorganic insulating layer according to the present invention achieves a smaller volume and a lighter weight compared to conventional wound inductors, which is crucial for products pursuing miniaturized and lightweight designs.

[0030] 3. The insulated wire according to the present invention can fully ensure the inter-turn insulation between multiple turns of coils in a complex and high-temperature powder pressing process environment. Therefore, in the design of a small integrally compression-molded inductor, in addition to using a single-turn coil, a multi-turn coil can also be used, overcoming the disadvantages and deficiencies in the prior art that only a single-turn coil can be used to manufacture a small integrally compression-molded inductor.

[0031] 4. A reasonable multi-turn coil design can significantly improve the heat dissipation performance, thereby effectively reducing the risk of performance degradation or damage caused by overheating. The coils of conventional inductors are wound outside the magnetic core. If more stringent heat dissipation technical requirements need to be met, potting treatment is usually required. The coils wound with the insulated wire with an inorganic insulating layer according to the present invention and directly embedded inside the magnetic core do not require additional potting processes and are easy to realize automated production. This not only helps to improve production efficiency and reduce costs, but also enables the wire and the magnetic core to be directly in contact with air, thereby greatly enhancing the heat dissipation effect.

[0032] It should be noted that the embodiments of the present disclosure have been described with reference to different topics. In particular, some embodiments have been described with reference to apparatus-type claims, while other embodiments have been described with reference to method-type claims. However, those skilled in the art will understand from the above and the following descriptions that, unless otherwise indicated, any combination between features related to different topics, especially any combination between the features of apparatus-type claims and the features of method-type claims, is also considered to be disclosed by this application in addition to any combination of features belonging to one type of topic. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other aspects of the present disclosure will be apparent from and will be explained with reference to the examples of the embodiments described hereinafter. The present disclosure will be described in more detail below with reference to the examples of the embodiments, but the present disclosure is not limited to these embodiments.

[0034] Figure 1 is a schematic diagram of a combined potted inductor of the prior art;

[0035] Figure 2 is a partial cross-sectional schematic diagram of an insulated wire according to an embodiment of the present invention;

[0036] Figure 3 is a partial cross-sectional schematic diagram of an insulated wire according to another embodiment of the present invention;

[0037] Figure 4A is an external view schematic diagram of an integrally molded inductor according to an embodiment of the present invention;

[0038] Figure 4B is an internal perspective schematic diagram of an integrally molded inductor according to an embodiment of the present invention;

[0039] Figure 5 is a flowchart of a method for manufacturing an inductor according to an embodiment of the present invention.

[0040] The illustrations in the drawings are schematic. Note that in different figures, similar or identical elements are provided with the same reference numerals. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The following detailed description in conjunction with the accompanying drawings is intended as a description of the currently preferred embodiments of the device according to the present disclosure, and is not intended to represent the only forms in which the device of the present disclosure can be constructed or utilized. This specification sets forth the features and steps of embodiments for constructing and using the device of the present disclosure in connection with the illustrated embodiments. However, it should be understood that the same or equivalent functions and structures can be achieved by different embodiments, which are also intended to be included within the spirit and scope of the present disclosure. As indicated elsewhere herein, like reference numerals are intended to indicate like or similar elements or features.

[0042] Figure 1 is a schematic diagram of a combined potted inductor of the prior art. As Figure 1 shown, the combined potted inductor includes a housing 10, a magnetic core 20, pins 30, and a coil 40. The housing 10 is typically made of aluminum. The housing 10 surrounds the magnetic core 20 and the coil 40. The pins 30 are disposed on the outer surface of the housing 10 and are electrically connected to the coil 40. The coil 40 is wound around a magnetic post (not shown) of the magnetic core 20 located inside the housing 10. To ensure compliance with the "three-proof" (waterproof, salt spray resistant, and mold resistant) standards and to ensure effective heat dissipation of the magnetic core 20, preventing performance degradation or damage caused by overheating, the magnetic core 20 is potted in the housing 10 with a colloid.

[0043] Figure 2 is a partial cross-sectional schematic diagram of an insulated wire 100 according to an embodiment of the present invention. The insulated wire 100 according to the present invention can be formed into a single turn or multiple turns of a coil by winding. It should be understood that unless otherwise clearly described, the "insulation" referred to by the present invention for a wire generally refers to electrical insulation.

[0044] As Figure 2 shown, the insulated wire 100 may include a base material 110 and an insulating layer 120 that coats the base material 110. It should be understood that Figure 2 only a partial cross-section of the insulated wire 100 according to the present invention is shown. The base material 110 has an elongated shape, and the insulating layer 120 coats the base material 110 in the circumferential direction of the base material 110. It should be understood that unless otherwise clearly described, the meaning of "coating" referred to by the present invention includes direct coating and indirect coating, that is, there may or may not be one or more other layers between the coating layer and the coated layer.

[0045] The substrate 110 can be formed of a conductive material, which can include, but is not limited to, copper and aluminum. In one embodiment, the substrate 110 can be formed of copper. In one embodiment, the substrate 110 can be formed of aluminum. In one embodiment, the substrate 110 can include a core portion and a coating layer surrounding the core portion, wherein the core portion can be formed of aluminum and the coating layer can be formed of copper. In one embodiment, the cross-section of the substrate 110 can be circular, rectangular, oval or polygonal.

[0046] The insulating layer 120 is electrically insulating and can be formed of an inorganic insulating material.

[0047] In one embodiment, the inorganic insulating material can include one or more of the following compounds: metal oxides, non-metal oxides, metal nitrides, non-metal nitrides, carbides and silicates. In a specific embodiment, the inorganic insulating material can include one or more of the following compounds: silicon nitride (Si 3 N 4 ), aluminum nitride (AlN), silicon carbide (SiC), aluminum oxide (Al 2 O 3 ), zirconia toughened alumina (ZTA), boron nitride (BN), magnesium oxide (MgO), yttrium oxide (Y 2 O 3 ), sodium silicate (Na 2 O·nSiO 2 ), potassium sulfate (K 2 SiO 3 ), lithium sulfate (Li 2 SiO 3 ), silicon dioxide (SiO 2 ), copper oxide (CuO), zinc oxide (ZnO), zirconia (ZrO 2 ), diamond-like carbide (DLC) and aluminum chromium nitride (AlCrN).

[0048] The insulating layer 120 according to the present invention does not include organic substances. Moreover, the insulating layer 120 according to the present invention is directly applied to the substrate 110 such that during the process of applying the insulating layer 120 to the substrate 110, at any time and in any state, the insulating layer 120 does not include organic substances.

[0049] In one embodiment, the insulating layer 120 can be directly applied to the substrate 110 by a magnetron sputtering process.

[0050] Figure 3FIG. 0 is a partial cross-sectional schematic view of an insulated wire 200 according to another embodiment of the present invention. The insulated wire 200 is different from the insulated wire 100 in that, in addition to including a base material formed of a conductive material and an insulating layer formed of an inorganic insulating material, it further includes a transition layer and / or a protective layer. The insulated wire 200 according to the present invention can be formed into a single-turn or multi-turn coil by winding.

[0051] As Figure 3 shown, the insulated wire 200 may include a base material 210 and an insulating layer 220 covering the base material 210.

[0052] Similar to the base material 110 of the insulated wire 100, the base material 210 of the insulated wire 200 can be formed of a conductive material, and the conductive material may include, but is not limited to, copper and aluminum. In one embodiment, the base material 210 may be formed of copper. In one embodiment, the base material 210 may be formed of aluminum. In one embodiment, the base material 210 may include a core portion and a covering layer surrounding the core portion, wherein the core portion may be formed of aluminum and the covering layer may be formed of copper. In one embodiment, the cross-section of the base material 210 may be circular, rectangular, oval or polygonal.

[0053] Similar to the insulating layer 110 of the insulated wire 100, the insulating layer 220 of the insulated wire 200 is electrically insulating and can be formed of the inorganic insulating material described above.

[0054] The insulating layers 120 and 220 according to the present invention serve as the main electrical insulation. Under the condition of ensuring sufficient electrical insulation characteristics, the insulating layers 120 and 220 preferably should have a sufficiently high thermal conductivity. The high thermal conductivity can improve the heat transfer efficiency, timely export the internal heat, and is beneficial to improving the product performance. The insulation strength of the insulating layers 120 and 220 is preferably not less than 10 kV / mm (at 25 °C), and the thermal conductivity is preferably not less than 1.5 W / (m·K). The insulating layer preferably should ensure sufficient plasticity, toughness and bonding force with adjacent material layers to ensure that it will not crack or peel off during bending or deformation, so as to maintain its electrical insulation performance. The peeling strength of the insulating layers 120 and 220 from the adjacent layers is preferably not less than 50 N / cm 2 . After the insulated wires 100 and 200 are wound into coils, when subjected to a 10 V withstand voltage test, the insulation resistance is preferably not less than 20 kΩ.

[0055] As Figure 3As shown, optionally, the insulated wire 200 may further include a transition layer 230. The transition layer 230 is disposed between the substrate 210 and the insulating layer 220 such that the substrate 210 is coated by the transition layer 230 and the transition layer 230 is coated by the insulating layer 220. The main function of the transition layer 230 is to neutralize the difference in material properties between the substrate 210 and the insulating layer 220, so that the change gradient of the material properties between the substrate 210 and the insulating layer 220 can be slowed down by a gradual transition. The material of the transition layer 230 should have good adhesion to the adjacent layers (i.e., the substrate 210 and the insulating layer 220), and its peel strength is preferably not less than 50 N / cm 2 . The lattice constants between the substrate 210 and the transition layer 230 and between the transition layer 230 and the insulating layer 220 should be substantially matched to reduce the distortion at the interface, and the lattice mismatch is preferably not higher than 10%. The difference in the coefficient of thermal expansion between the transition layer 230 and the adjacent layers should be controlled within a certain range. When the difference in the coefficient of thermal expansion (CTE) between the transition layer 230 and the adjacent layers is large, the temperature change during the inductor manufacturing process will cause mismatched stresses between different layers, which may lead to delamination or peeling of different layers. For metal and ceramic materials, the difference in the coefficient of thermal expansion is preferably not greater than 50 ppm / °C. If the coefficients of thermal expansion of two layers are α1 and α2 respectively, then the difference in the coefficient of thermal expansion between the two layers can be expressed as: ∣α1 - α2∣ < Δα_max, and preferably it should satisfy: Δα_max ≤ 50 ppm / °C.

[0056] In one embodiment, the lattice constant of the transition layer 230 may be between the lattice constant of the substrate 210 and the lattice constant of the insulating layer 220, and / or the coefficient of thermal expansion (CTE) of the transition layer 230 may be between the coefficient of thermal expansion of the substrate 210 and the coefficient of thermal expansion of the insulating layer 220.

[0057] In one embodiment, the transition layer 230 may be formed of one or more of the following materials: nickel, titanium, chromium, iron, aluminum, and nickel-aluminum alloy.

[0058] The insulating layer 220 according to the present invention does not include organic matter. Moreover, the insulating layer 220 according to the present invention is directly applied to the transition layer 230 such that during the process of applying the insulating layer 220 to the transition layer 230, at any moment and in any state, the insulating layer 220 does not include organic matter.

[0059] In one embodiment, the transition layer 230 may be applied to the substrate 210 by an electroplating process, and then the insulating layer 220 may be directly applied to the transition layer 230 by a magnetron sputtering process.

[0060] As described above, in the present invention, an insulating layer can be directly applied, for example, by a magnetron sputtering process, such as directly applying the insulating layer onto a substrate or an intermediate layer. The porosity of the insulating layer according to the present invention is not higher than 20%, and can be, for example, between 0.2% and 20%, between 0.5% and 18%, between 1% and 16%, between 2% and 14%, between 3% and 12%, between 4% and 10%, between 5% and 8%, or between 6% and 7%. The porosity of the insulating layer can be measured by, for example, a conventional drainage method. Additionally, the porosity of the insulating layer can also be measured by a microscopic counting method, and the specific method is as follows: The surface of the insulating layer is appropriately treated to improve the surface flatness, and then observed under a microscope for holes, counted by grid method, and then the porosity is analyzed or calculated.

[0061] The insulating layer according to the present invention is substantially different from the insulating layers in the prior art. In the prior art, an organic binder and an inorganic insulating material are mixed and then coated on the surface of a wire. After forming an inductor, it is heated to volatilize the organic binder, and the inorganic insulating material wraps around the surface of the wire. The obtained insulating layer has a loose texture, many holes, and poor thickness uniformity. Limited by the process, the porosity of the insulating layer obtained in this way is at least 30% - 50% or even greater. Through experimental observation, the insulating layer obtained in this way has a large number of holes visible to the naked eye and many through-holes. The insulating layer obtained in this way has a measured resistance usually less than 1 GΩ at 1000 V. Additionally, in the prior art, there will be partial residues in the volatilization or decomposition of the organic binder at high temperatures. That is to say, part of the organic matter volatilizes into gas, resulting in more holes, and another part of the organic matter decomposes when heated to form carbon and remains in the insulating layer, thus inevitably leading to a deterioration of the electrical insulation performance of the insulating layer. In such a high porosity and the presence of residual carbon elements, the thickness of the insulating layer usually needs to be above 1 mm to achieve the desired electrical insulation performance.

[0062] The porosity of the insulating layer according to the present invention is significantly lower than that of the insulating layers in the prior art. In other words, the density of the insulating layer according to the present invention is significantly higher than that of the insulating layers in the prior art. The porosity of the insulating layer according to the present invention can be not higher than 20%, or even close to zero. Additionally, the thickness of the insulating layer according to the present invention is more uniform. The insulating layer according to the present invention (such as made of aluminum nitride) can achieve a resistance of 10 GΩ at a thickness of 1 μm under the same test conditions. Moreover, the insulating layer according to the present invention does not contain organic matter. The insulating layer according to the present invention is directly applied, such that during the process of applying the insulating layer, at any moment and in any state, the insulating layer does not contain any organic matter. Additionally, due to the significantly reduced porosity of the insulating layer according to the present invention, the density is significantly increased, resulting in a corresponding significant increase in hardness and strength.

[0063] Compared with the insulating layer material itself, the holes in the insulating layer are more easily electrically broken down. Therefore, the more holes there are, the worse the electrical insulation performance of the insulating layer, and a thicker insulating layer is required to achieve the same electrical insulation performance. Under the same material and thickness, an insulating layer with a higher porosity has worse electrical insulation performance than an insulating layer with a lower porosity. In the present invention, by making the porosity of the insulating layer significantly smaller or even close to zero, the same insulation can be achieved with a thinner insulating layer.

[0064] On the other hand, for an inductor, the less non-magnetic material, the better. Excessive non-magnetic material is not conducive to the inductance of the inductor. Since the inorganic insulating material used for the insulating layer is a non-magnetic material, by significantly reducing the porosity of the insulating layer in the present invention, the insulating layer can be made thinner, thereby greatly reducing the non-magnetic material in the inductor.

[0065] As Figure 3 shown, optionally, the insulated wire 200 may further include a protective layer 240. The protective layer 240 covers the insulating layer 220. The protective layer 240 functions to reduce friction, protect the insulating layer 220, and provide a lubricating effect, and is mainly used to reduce the shear damage to the coil during the pressing process of manufacturing the inductor. The protective layer 240 is subjected to the combined action of the compressive stress and shear stress of the powder during the pressing process. Therefore, a material with a lower coefficient of friction should be selected, and its dynamic coefficient of friction is preferably not higher than 0.5 (i.e., μ ≤ 0.5). In one embodiment, the protective layer 240 is formed of a material having a layered crystal structure. Such materials usually have excellent lubricating properties, such as hexagonal boron nitride (h-BN), molybdenum disulfide (MoS 2 ) etc.

[0066] It should be understood that Figure 3 only a partial cross-section of the insulated wire 200 according to the present invention is shown. The base material 210 has an elongated shape. The transition layer 230 covers the base material 210 in the circumferential direction of the base material 210. The insulating layer 220 covers the transition layer 230 in the circumferential direction of the transition layer 230, and the protective layer 240 (if any) covers the insulating layer 220 in the circumferential direction of the insulating layer 220.

[0067] Although Figure 3 both the transition layer 230 and the protective layer 240 are shown simultaneously, in other embodiments, there may be only the transition layer 230 without the protective layer 240, or there may be only the protective layer 240 without the transition layer 230.

[0068] In one embodiment, the protective layer 240 can be applied to the insulating layer 220 by a plasma enhanced chemical vapor deposition (PECVD) process.

[0069] In some embodiments, the transition layer 230 and / or the protective layer 240 may further include auxiliary functional materials, which serve the purpose of repairing damaged coatings after heat treatment. The auxiliary functional materials may include, for example, silica (SiO 2 ) microcapsules, hexagonal boron nitride nanoparticles (h-BN), etc.

[0070] In one embodiment, copper wires with a rectangular cross-section (e.g., width of 8 mm and thickness of 0.5 mm) may be used as the substrates 110, 210. The substrates 110, 210 are ultrasonically cleaned using acetone and isopropyl alcohol to remove surface grease and impurities, ensuring a clean surface. Then, plasma cleaning is used to make the surfaces of the substrates 110, 210 sufficiently flat and shiny. The surface roughness (Ra) of the treated substrates 110, 210 is 0.013 μm.

[0071] In one embodiment, nickel may be selected as the material for the transition layer 230 to improve the bonding strength between the transition layer 230 and the substrate 210. The transition layer 230 can be prepared by an electroplating process. Nickel sulfate can be used as the main salt: 250 g / L, the pH value of the electroplating solution is 4, the temperature is 50 °C, and the current density is 3 A / dm 2 , to prepare a nickel transition layer 230 with a thickness of 1 μm. Then, the surface of the transition layer 230 is treated in the same surface treatment manner as the substrates 110, 210, such that the surface roughness (Ra) of the transition layer 230 is 0.01 μm.

[0072] In one embodiment, silicon nitride may be selected as the material for the insulating layers 120, 220. The insulating layers 120, 220 can be prepared by a magnetron sputtering process. A silicon nitride target with a purity of 99.99% can be used, the sputtering power is 100 W, and continuous sputtering is carried out for 30 minutes in a nitrogen environment. The prepared insulating layers 120, 220 have a thickness of approximately 0.5 μm, and then they can be cleaned with acetone.

[0073] In one embodiment, hexagonal boron nitride may be selected as the material for the protective layer 240. The protective layer 240 can be prepared by a plasma-enhanced chemical vapor deposition (PECVD) process. The NH 3 flow rate can be 100 sccm, the B 2 H 6 flow rate can be 10 sccm, the temperature of the substrate can be 400 °C, and deposition is carried out for 30 minutes. The prepared protective layer 240 has a thickness of approximately 1 μm.

[0074] Through the above three-layer coating process, a composite layer structure with excellent performance is formed on the substrate. The first layer is a nickel transition layer, which improves the bonding strength between the substrate and the subsequent layers. The second layer is a silicon nitride insulating layer, which provides good insulation and wear resistance. The third layer is a hexagonal boron nitride protective layer, which further enhances the lubricity and high-temperature resistance of the entire insulated wire.

[0075] In one embodiment, the substrate 210 of the insulated wire 200 can be formed of copper. The insulating layer 220 of the insulated wire 200 can be formed of aluminum oxide (Al 2 O 3 ). The thickness of the insulating layer 220 formed of aluminum oxide can be between 1 μm and 100 μm, preferably between 20 μm and 80 μm, such as 30 μm, 40 μm, 50 μm, 60 μm or 70 μm. Aluminum oxide has excellent electrical insulation performance, and its resistivity can reach 10 16 Ω·m or more. At the same time, aluminum oxide has self-healing ability after damage, and it is an ideal electrical insulation material. The transition layer 230 of the insulated wire 200 can be formed of nickel. The thickness of the transition layer 230 formed of nickel can be between 10 nm and 800 nm, preferably between 50 nm and 600 nm, such as 100 nm, 200 nm, 300 nm, 400 nm or 500 nm. The transition layer 230 formed of nickel improves the bonding strength between the substrate 210 formed of copper and the insulating layer 220 formed of aluminum oxide. The protective layer 240 of the insulated wire 200 can be formed of hexagonal boron nitride (h-BN), for example, using a powdery hexagonal boron nitride material with a powder particle diameter not exceeding 5 μm. The protective layer formed of hexagonal boron nitride is used to reduce the overall surface friction coefficient of the coating, thereby reducing the friction force received. The thickness can be between 1 μm and 50 μm, preferably between 5 μm and 40 μm, such as 10 μm, 20 μm or 30 μm.

[0076] In another embodiment, the substrate 210 of the insulated wire 200 can be formed of copper. The insulating layer 220 of the insulated wire 200 can be formed of aluminum nitride (AlN). The thickness of the insulating layer 220 formed of aluminum nitride can be between 1 μm and 100 μm, preferably between 20 μm and 80 μm, such as 30 μm, 40 μm, 50 μm, 60 μm or 70 μm. Aluminum nitride has excellent electrical insulation performance, and its electrical insulation performance is close to that of aluminum oxide. Its resistivity can reach 10 16Above Ω·m. Aluminum nitride has excellent thermal conductivity, with a thermal conductivity as high as about 320 W / m·K, which is beneficial to the timely dissipation of heat generated by the inductor. The transition layer 230 of the insulated wire 200 may include a first transition layer and a second transition layer. Among them, the first transition layer may be formed of nickel and the second transition layer may be formed of nickel-aluminum alloy. The thickness of the first transition layer formed of nickel may be between 10 nm and 500 nm, preferably between 50 nm and 400 nm, such as 100 nm, 200 nm or 300 nm. The thickness of the second transition layer formed of nickel-aluminum alloy may be between 10 nm and 500 nm, preferably between 50 nm and 400 nm, such as 100 nm, 200 nm or 300 nm. The first and second transition layers formed of nickel and nickel-aluminum alloy further improve the bonding force between the base material 210 formed of copper and the insulating layer 220 formed of aluminum nitride. The protective layer 240 of the insulated wire 200 may be formed of molybdenum disulfide (MoS 2 ), for example, using a powdered molybdenum disulfide material, and the diameter of the powder particles does not exceed 5 μm. The protective layer formed of molybdenum disulfide is used to reduce the overall surface friction coefficient of the coating, thereby reducing the friction force received. The thickness may be between 1 μm and 50 μm, preferably between 5 μm and 40 μm, such as 10 μm, 20 μm or 30 μm.

[0077] In the present invention, the thickness of each layer can be selected within a suitable range based on a comprehensive consideration of material properties, process conditions, and actual functions.

[0078] The thickness of the insulating layer can be judged and selected according to its electrical insulation performance. The experimental results show that for inorganic insulating materials (such as aluminum nitride, alumina), at least 1 μm of uniform coating is required to obtain a certain degree of insulation. At the same time, considering reasons such as process instability, substrate surface quality, and pressing force, an insulating layer less than 1 μm may be uneven in local or irregular places, resulting in a reduction in resistance. On the other hand, on the premise of ensuring insulation, the thickness of the insulating layer should not be too large to avoid excessive content of non-magnetic materials. Therefore, a thickness range of 20 μm to 100 μm is a more ideal range.

[0079] The thickness selection of the transition layer should consider that different transition layer materials are suitable for different process methods and should completely cover the substrate. For electroplating processes, a transition layer thickness of 10 nm to 800 nm is a feasible range. On the other hand, the thickness of the transition layer should not be too large to avoid excessive content of non-magnetic materials. Therefore, a thickness range of 100 nm to 200 nm is a more ideal range.

[0080] The protective layer mainly improves the surface friction and may fall off during wear, so it needs to have a certain thickness. On the other hand, as a non-magnetic material, it is preferably as thin as possible. Therefore, a thickness of 1 μm to 50 μm can better improve the surface roughness without being too thick.

[0081] The insulated wire according to the present invention includes at least an insulating layer outside the substrate, and may further include other functional coatings, such as a transition layer and / or a protective layer. To ensure the overall mechanical properties and electrical insulation, the overall porosity of the prepared inorganic insulating layer should not be higher than 20%, the friction coefficient of the protective layer is preferably not higher than 0.5 (i.e., μ ≤ 0.5), the hardness > 50 HV, the film layer on the wire surface is evenly covered, and there are no obvious cracks or damages. The insulation strength is not lower than 10 kV / mm, and the thermal conductivity is not lower than 1.5 W / (m·K).

[0082] The present invention proposes to directly apply an inorganic insulating layer (preferably with a thickness not exceeding 100 μm, preferably not exceeding 50 μm, preferably not exceeding 20 μm) on the surface of the wire to replace the conventional polyimide film layer. This inorganic insulating layer has a low porosity, high density, and excellent bonding force, and can maintain its physical properties and stable chemical properties even under high-temperature conditions. Further, to ensure the bonding force between the substrate, insulating layer, and optionally the transition layer and / or protective layer of the wire, the surface roughness (Ra) of the surface of the substrate and each layer is preferably not greater than 0.3 μm. The insulated wire according to the present invention can fully guarantee the inter-turn insulation between multiple-turn coils in a complex and high-temperature process environment of powder pressing.

[0083] According to an embodiment of the present invention, there is provided a method for manufacturing an insulated wire, the insulated wire including a substrate and an insulating layer, the method including the following steps: forming the substrate from a conductive material; and directly applying the insulating layer on the substrate by a magnetron sputtering process such that the insulating layer coats the substrate, wherein the insulating layer is formed of an inorganic insulating material, and wherein the porosity of the insulating layer is not higher than 20%. In a further embodiment, the method may further include: applying a protective layer on the insulating layer by a plasma-enhanced chemical vapor deposition process such that the protective layer coats the insulating layer, wherein the protective layer is formed of a material having a layered crystal structure.

[0084] According to an embodiment of the present invention, there is provided a method for manufacturing an insulated wire, the insulated wire including a base material, a transition layer, and an insulating layer, the method comprising the steps of: forming the base material from a conductive material; applying the transition layer on the base material by an electroplating process such that the transition layer coats the base material; and directly applying the insulating layer on the transition layer by a magnetron sputtering process such that the insulating layer coats the transition layer, wherein the insulating layer is formed of an inorganic insulating material, and wherein the porosity of the insulating layer is not higher than 20%. In a further embodiment, the method may further comprise: applying a protective layer on the insulating layer by a plasma enhanced chemical vapor deposition process such that the protective layer coats the insulating layer, wherein the protective layer is formed of a material having a layered crystal structure.

[0085] Figure 4A is an external schematic view of an integrally molded inductor 300 according to an embodiment of the present invention, and Figure 4B is an internal perspective schematic view of an integrally molded inductor 300 according to an embodiment of the present invention to show the various components inside the inductor 300.

[0086] As Figure 4A and Figure 4B shown, the inductor 300 may include a housing 310, a first pin 330a and a second pin 330b, and a molded part 320. The first pin 330a and the second pin 330b may be provided on the outer surface of the housing 310. The molded part 320 may be received within the housing 310. The molded part 320 may include a magnetic core 340 and a coil 350. The magnetic core 340 may be formed by pressing soft magnetic powder. The coil 350 may be wound from the insulated wires 100, 200 according to the present invention and embedded in the magnetic core 340. The coil 350 may be embedded in the magnetic core 340 formed of soft magnetic powder, and then the molded part 320 may be formed via an integrally molding process. The molded part 320 may be subjected to a heat treatment with a maximum temperature between 650 °C and 1000 °C (for example, between 650 °C and 950 °C, or between 700 °C and 900 °C, or between 750 °C and 850 °C, or between 700 °C and 750 °C). For example, the heat treatment process may include the following two heat treatments. In the first heat treatment, first, from room temperature, it is heated to 300 °C in a nitrogen atmosphere, which takes 120 minutes; then, from 300 °C, it is heated to 710 °C, which takes 120 minutes; then, it is held at 710 °C for 30 minutes; then, it is cooled naturally in air. In the second heat treatment, first, from room temperature, it is heated to 300 °C in an air atmosphere, which takes 120 minutes; then, it is held for 30 minutes; then, it is cooled naturally in air.

[0087] The heat-treated compacted part 320 can be immersed in an impregnating liquid to improve its structural strength.

[0088] The coil 350 can include opposite first end 350a and second end 350b. The first end 350a of the coil 350 can extend from the magnetic core 340 to be electrically connected to the first pin 330a and the second end 350b of the coil 350 can extend from the magnetic core 340 to be electrically connected to the second pin 330b.

[0089] The cross-sectional shape of the insulated wire of the coil 350 shown in FIG. 4b is rectangular. In other embodiments, the cross-sectional shape of the insulated wire of the coil 350 can be other shapes, such as circular, oval, polygonal.

[0090] In one embodiment, the number of turns of the coil 330 can be between 2 and 200, such as between 3 and 100 or between 4 and 50, and can be, for example, 5, 6, 8, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180.

[0091] In one embodiment, the spacing between the turns of the coil 330 can be between 0.1 mm and 5 mm.

[0092] In one embodiment, the first pin 330a and the second pin 330b can be located on opposite sides of the housing 310.

[0093] Figure 5 is a flowchart of a method 400 for manufacturing an inductor according to an embodiment of the present invention.

[0094] In step 410, an insulated wire is provided, which can be the insulated wire 100 or the insulated wire 200 described above.

[0095] In step 420, the insulated wire is wound into a single-turn or multi-turn coil using a winding device.

[0096] In step 430, soft magnetic powder is laid in a mold, and the coil is embedded in the soft magnetic powder.

[0097] In step 440, the soft magnetic powder and the insulated wire are integrally compacted to obtain a compacted part.

[0098] In step 450, the compacted part is subjected to a heat treatment with a maximum temperature between 650 °C and 1000 °C (such as between 650 °C and 950 °C, or between 700 °C and 900 °C, or between 750 °C and 850 °C, or between 700 °C and 750 °C). This heat treatment process can fully release the performance loss of the powder caused by pressing.

[0099] Optionally, in step 460, the compression molded part can be immersed in an impregnating liquid to improve its structural strength. The impregnating liquid is mainly composed of epoxy resin. The specific process is to immerse the integrally compression molded and heat-treated compression molded part in the impregnating liquid and perform vacuum pumping. Due to the powder compression molding, there are inevitably small pores in the compression molded part. The gas in the pores can be discharged through vacuum, so that the impregnating liquid can enter these pores and solidify, thereby strengthening the structural strength.

[0100] In step 470, the compression molded part is installed in the housing, the first end of the coil is electrically connected to the first pin on the housing, and the second end of the coil is electrically connected to the second pin on the housing.

[0101] The method 400 according to the present invention may not include step 460. In this case, it can directly proceed from step 450 to step 470.

[0102] In one embodiment, the insulated wire is a copper wire with a rectangular cross-section having a width of about 8 mm and a thickness of about 0.5 mm. The insulated wire is wound into a double-column circular coil. The outer diameter of the double-column circular coil is about 35 mm, the spacing between turns is about 3 mm, and the lead-out length at both ends is about 15 mm. The outer dimensions of the obtained inductor are about 80 mm × 50 mm × 100 mm. Taking a 30 kW photovoltaic inverter inductor as an example, its magnetic core is made of iron-silicon-aluminum material with an initial magnetic permeability of 60μ (i.e., 60 times the magnetic permeability of vacuum). After combining the yoke and the magnetic column, a coil is wound around the magnetic column to make an inductor, and then this inductor is encapsulated with potting glue into an aluminum housing. Under the 500V working condition, after testing, the average temperature is 96.29°C and the highest temperature is 109.8°C. In contrast, under the same test conditions, the test results of the integrally compression molded inductor according to the present invention show that the average temperature is 68.72°C and the highest temperature is 77.84°C, achieving an average temperature reduction of about 28%.

[0103] In another embodiment, the insulated wire is a copper wire with a rectangular cross-section having a width of about 1 mm and a thickness of about 0.5 mm. The insulated wire is wound into a single-column coil with an outer diameter of about 6.5 mm and a spacing between turns of about 0.33 mm. The outer dimensions of the obtained inductor are about 7 mm × 6.6 mm × 4.8 mm. The inductance of the integrally compression molded inductor in this embodiment is 3.3 μH and the resistance is 2.2 mΩ. The integrally compression molded inductor manufactured by the method of the present invention not only significantly reduces the volume of the inductor, but also reduces the magnetic leakage phenomenon. This inductor is very suitable for application in complex electronic circuits with high integration and dense component arrangement, and can effectively save space and improve the overall performance of the circuit.

[0104] In one embodiment, a conventional polyimide film-coated wire and an insulating wire according to the present invention are respectively used to fabricate an integrally molded inductor. The size of the integrally molded inductor is 5mm×6mm×7mm. The thermal conductivity of polyimide is 0.15 W / (m·K), and the thermal conductivity of silicon nitride is 18.4 W / (m·K).

[0105] The insulating wire according to the present invention has a silicon nitride insulating layer with an insulation strength of up to 100 kV / mm and can still maintain excellent electrical insulation at high temperatures. The insulation strength of a conventional polyimide insulating layer is 180 kV / mm, and the operating temperature range is 200°C - 300°C. The withstand voltage level of this small inductor is 50V, and the thickness of its insulating layer is calculated respectively according to the following formula.

[0106] Insulating layer thickness = withstand voltage level ÷ insulation strength

[0107] After calculation, the thickness of the polyimide insulating layer is 0.27 μm, and the thickness of the silicon nitride insulating layer is 0.5 μm. The thicknesses of the two are at a relatively close level in the same order of magnitude, but the silicon nitride insulating layer has a wider temperature application range and a higher thermal conductivity, greatly broadening its application scenarios.

[0108] The silicon nitride insulating layer has a higher heat conduction efficiency, which can quickly transfer the heat generated by inductance loss to the surface of the inductor for heat dissipation. At the same time, the silicon nitride insulating layer can support a wider operating temperature. Combining its higher heat conduction efficiency and excellent electrical insulation performance, the integrally molded inductor according to the present invention can meet higher performance requirements.

[0109] The present invention proposes an insulating wire based on an inorganic insulating layer, which utilizes the thermal stability and insulation of inorganic substances at high temperatures to achieve inter-turn insulation of multi-turn coils in a complex high-temperature process environment of powder pressing.

[0110] The present invention proposes a method for manufacturing an insulating wire, which directly applies an inorganic insulating layer on a substrate through a magnetron sputtering process. The obtained inorganic insulating layer has a low porosity, a high density, and excellent bonding force, and can maintain its physical properties and stable chemical properties even under high-temperature conditions. The insulating wire according to the present invention can fully ensure the inter-turn insulation between multi-turn coils in a complex and high-temperature process environment of powder pressing.

[0111] The present invention proposes a high-performance integrally molded inductor based on the integration of a coil formed by the above-mentioned insulating wire and soft magnetic powder. The withstand voltage level of such an inductor is between 10V and 5kV. Compared with conventional inductors, this integrally molded inductor significantly reduces the volume, weight, and cost.

[0112] The present invention also provides a method for manufacturing the above integrally molded inductor. The above insulating wire is wound to form a single-turn or multi-turn coil, and the coil is embedded in the insulated soft magnetic powder and integrally molded therewith. The inter-turn spacing of the coil can be small enough while ensuring the insulation between multi-turn coils. Preferably, the inter-turn spacing of the coil prepared by this method is not greater than 50% of the length H of the inductor in the axial direction of the coil, and the length of the lead is preferably between 50% and 100% of the length H of the inductor. The winding shape of the coil can be circular, elliptical, square, racetrack-shaped, etc. The above wound insulating coil is embedded in the granulated coated soft magnetic powder and positioned through the coil pins and the mold, and integrally molded under high pressure. The pressing temperature can be between 0°C and 400°C, and the pressing force can be between 5t / cm 2 - 30 t / cm 2 between.

[0113] The technical solution of the present invention can at least bring the following advantages:

[0114] 1. The insulating wire with an inorganic insulating layer according to the present invention has the advantage of selecting an inorganic substance that can remain stable in a high-temperature environment as the insulating material, effectively overcoming the problem that conventional organic insulating materials are prone to carbonization or volatilization under high-temperature conditions, thereby improving the use performance of the insulating wire under high-temperature working conditions. In addition, inorganic substances have excellent electrical insulation performance, can effectively prevent current leakage, and provide better electrical isolation effects in high-voltage and high-frequency applications. Particularly importantly, the inorganic insulating layer endows the insulating wire with better environmental tolerance, including corrosion resistance and anti-aging properties, enabling the insulating wire with an inorganic insulating layer according to the present invention to be applied in more severe environments. The present invention proposes to directly apply an inorganic insulating layer on the substrate through a magnetron sputtering process. The obtained inorganic insulating layer has a low porosity, a high density, and excellent bonding strength, and can maintain its physical properties and stable chemical properties even under high-temperature conditions.

[0115] 2. The integrally molded inductor made of the insulating wire with an inorganic insulating layer according to the present invention has a smaller volume and lighter weight compared with conventional wound inductors, which is crucial for products pursuing miniaturized and lightweight designs.

[0116] 3. The insulating wire according to the present invention can fully ensure the inter-turn insulation between multi-turn coils in the complex and high-temperature process environment of powder pressing. Therefore, in the design of small integrally molded inductors, in addition to using single-turn coils, multi-turn coils can also be used, overcoming the disadvantages and deficiencies of only using single-turn coils to manufacture small integrally molded inductors in the prior art.

[0117] 4. A reasonable multi-turn coil design can significantly improve the heat dissipation performance, thereby effectively reducing the risk of performance degradation or damage caused by overheating. In a conventional inductor, the coil is wound around the outside of the magnetic core. If more stringent heat dissipation technical requirements need to be met, potting treatment is usually required. For the coil wound with the insulated wire having an inorganic insulating layer of the present invention and directly embedded inside the magnetic core, no additional potting process is needed, and it is easy to achieve automated production. This not only helps to improve production efficiency and reduce costs, but also enables the wire and the magnetic core to be in direct contact with air, thus greatly enhancing the heat dissipation effect.

[0118] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. In addition, elements described in connection with different embodiments may be combined. It should also be noted that the reference signs in the claims should not be construed as limiting the scope of the claims.

[0119] It should be understood that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to cover all such changes, modifications and variations that fall within the spirit and scope of the appended claims.

[0120] Throughout the specification and the following claims, unless the context requires otherwise, the word "comprising" and its variations such as "comprises" and "comprising" shall be understood to imply the inclusion of the stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0121] Any reference in this specification to any prior publication (or information derived therefrom) or to any known matter is not and should not be taken as an admission or acknowledgment or any form of suggestion that the prior publication (or information derived therefrom) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1. An insulated wire, comprising: a substrate formed of a conductive material; and An insulating layer covering the substrate is formed of an inorganic insulating material, wherein the porosity of the insulating layer is not higher than 20%.

2. The insulated wire according to claim 1, further comprising a transition layer, wherein the transition layer is disposed between the substrate and the insulating layer, so that the substrate is covered by the transition layer and the transition layer is covered by the insulating layer, wherein: The lattice constant of the transition layer is between the lattice constant of the substrate and the lattice constant of the insulating layer, and / or the thermal expansion coefficient of the transition layer is between the thermal expansion coefficient of the substrate and the thermal expansion coefficient of the insulating layer.

3. The insulated wire according to claim 1 or 2, further comprising a protective layer, wherein the protective layer covers the insulating layer, The protective layer is formed of a material having a layered crystal structure.

4. The insulated conductor according to claim 2, wherein: The transition layer is formed of one or more of the following materials: nickel, titanium, chromium, iron, aluminum and nickel-aluminum alloy.

5. The insulated conductor according to claim 3, wherein: The protective layer is formed of one or more of the following materials: hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2).

6. The insulated conductor according to claim 3, wherein: The substrate is formed of copper, the insulating layer is formed of aluminum oxide (Al2O3), the transition layer is formed of nickel, and the protective layer is formed of hexagonal boron nitride (h-BN), and wherein the thickness of the insulating layer is between 1 μm and 100 μm, the thickness of the transition layer is between 10 nm and 800 nm, and the thickness of the protective layer is between 1 μm and 50 μm.

7. The insulated conductor according to claim 3, wherein: The substrate is formed of copper, the insulating layer is formed of aluminum nitride (AlN), the transition layer includes a first transition layer and a second transition layer, the first transition layer is formed of nickel and the second transition layer is formed of a nickel-aluminum alloy, and the protective layer is formed of molybdenum disulfide (MoS2), and wherein the thickness of the insulating layer is between 1 μm and 100 μm, the thickness of the first transition layer is between 10 nm and 500 nm, the thickness of the second transition layer is between 10 nm and 500 nm, and the thickness of the protective layer is between 1 μm and 50 μm.

8. The insulated conductor according to claim 1, wherein: The inorganic insulating material includes one or more of the following compounds: metal oxides, non-metal oxides, metal nitrides, non-metal nitrides, carbides and silicates.

9. The insulated conductor according to claim 1, wherein: The inorganic insulating material includes one or more of the following compounds: silicon nitride (Si3N4), aluminum nitride (AlN), silicon carbide (SiC), aluminum oxide (Al2O3), zirconium oxide toughened alumina (ZTA), boron nitride (BN), magnesium oxide (MgO), yttrium oxide (Y2O3), sodium silicate (Na2O·nSiO2), potassium sulfate (K2SiO3), lithium sulfate (Li2SiO3), silicon dioxide (SiO2), copper oxide (CuO), zinc oxide (ZnO), zirconium dioxide (ZrO2), diamond-like carbide (DLC) and aluminum chromium nitride (AlCrN).

10. A method for manufacturing an insulated wire, the insulated wire comprising a substrate and an insulating layer, the method comprising the following steps: forming the substrate from a conductive material; as well as The insulating layer is directly applied on the substrate by a magnetron sputtering process, so that the insulating layer covers the substrate, wherein the insulating layer is formed of an inorganic insulating material, and wherein the porosity of the insulating layer is not higher than 20%.

11. The method according to claim 10, further comprising the steps of: A protective layer is applied on the insulating layer by a plasma enhanced chemical vapor deposition process, so that the protective layer covers the insulating layer, wherein the protective layer is formed of a material having a layered crystal structure.

12. A method for manufacturing an insulated conductor, the insulated conductor comprising a substrate, a transition layer and an insulating layer, the method comprising the following steps: forming the substrate from a conductive material; Applying the transition layer on the substrate by an electroplating process so that the transition layer covers the substrate; as well as The insulating layer is directly applied on the transition layer by a magnetron sputtering process, so that the insulating layer covers the transition layer, wherein the insulating layer is formed of an inorganic insulating material, and wherein the porosity of the insulating layer is not higher than 20%.

13. The method according to claim 12, further comprising the steps of: A protective layer is applied on the insulating layer by a plasma enhanced chemical vapor deposition process, so that the protective layer covers the insulating layer, wherein the protective layer is formed of a material having a layered crystal structure.

14. An inductor, comprising: shell; a first pin and a second pin, wherein the first pin and the second pin are disposed on an outer surface of the housing; as well as A pressed part, which is accommodated in the shell, and includes a magnetic core and a coil, wherein the magnetic core is formed by pressing soft magnetic powder, the coil is wound by an insulated wire according to any one of claims 1 to 9 and is embedded in the magnetic core, the coil includes a first end and a second end opposite to each other, the first end of the coil extends from the magnetic core to be electrically connected to the first pin, and the second end of the coil extends from the magnetic core to be electrically connected to the second pin.

15. The inductor according to claim 14, wherein The number of turns of the coil is between 2 and 200.

16. A method for manufacturing an inductor, comprising the steps of: Providing an insulated wire according to any one of claims 1 to 9; Using a winding device to wind the insulated wire into a single-turn or multi-turn coil; Laying soft magnetic powder in a mold and embedding the coil in the soft magnetic powder; Pressing the soft magnetic powder and the insulated wire into an integral part to obtain a pressed part; subjecting the pressed part to a heat treatment at a maximum temperature between 650° C. and 1000° C.; The press-formed part is enclosed in a housing, and a first end of the coil is electrically connected to a first pin on the housing and a second end of the coil is electrically connected to a second pin on the housing.

17. The method according to claim 16, further comprising the step of immersing the press-formed part in an impregnation liquid to improve its structural strength after subjecting the press-formed part to heat treatment and before housing the press-formed part in a housing.

18. The method according to claim 16, wherein: The number of turns of the coil is between 2 and 200.

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