JP2024079257A - Insulated Conductor - Google Patents

Abstract

[Problem] To provide an insulating coated conductor having high heat resistance. [Solution] The insulating coated conductor has a metal conductor part containing Cu and an insulating layer covering the metal conductor part. The insulating layer contains Si, Ti, and oxygen, and the ratio of the Ti content to the total content of Si and Ti in the insulating layer is 2.5 at % or more and 50 at % or less. [Selected Figure] Figure 1

Description

This disclosure relates to a conductor having an insulating coating.

In electronic components such as inductors, transformers, and choke coils, conductors with insulating coatings are used as the coil material. In such electronic components, the insulating coating of the conductors plays a role in ensuring insulation between the windings of the coil. Conventional electronic components generally use conductors with insulating coatings containing resins such as polyamide-imide resin, polyimide resin, epoxy resin, or urethane resin. For example, Patent Document 1 discloses a conductor with an insulating coating containing epoxy resin, and Patent Document 2 discloses a conductor with an insulating coating containing copolymer polyamide resin.

Patent No. 2890280 Japanese Patent Application Laid-Open No. 3-089414

This disclosure provides an insulated conductor with high heat resistance.

The insulating coated conductor according to the first aspect of the present disclosure comprises:
A metal conductor portion including Cu and an insulating layer covering the metal conductor portion,
the insulating layer includes Si, Ti and oxygen;
The ratio of the Ti content to the total content of Si and Ti in the insulating layer is 2.5 at % or more and 50 at % or less.

The insulating layer may have an average thickness of 1 μm or more and 220 μm or less.

The insulating coated conductor according to the second aspect of the present disclosure comprises:
A metal conductor portion containing Cu and an inorganic insulating layer covering the metal conductor portion,
the inorganic insulating layer includes an oxide containing Si and Ti,
The ratio of the Ti content to the total content of Si and Ti in the inorganic insulating layer is 2.5 at % or more and 50 at % or less.

The inorganic insulating layer may have an average thickness of 1 μm or more and 200 μm or less.

FIG. 1 is a cross-sectional view showing an insulated conductor according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view showing an insulation-covered conductor having an inorganic insulating layer after firing. FIG. 3 is a perspective view showing an example of a coil using the insulating coated conductor wire shown in FIGS. 1 and 2. In FIG. Fig. 4 is a cross-sectional view showing an example of an electronic component including the coil shown in Fig. 3. Fig. 5 is a cross-sectional view showing a modified example of an insulating coated conductor. FIG. 5A is a cross-sectional view showing a modified example of an insulating coated conductor. FIG. 5B is a cross-sectional view showing another modified example of the insulation-coated conductor. FIG. 6 is a perspective view showing an example of a coil using the insulating coated conductor shown in FIG. 5A.

An embodiment of the present disclosure will be described below with reference to the drawings. The embodiment of the present disclosure described below is an example for explaining the present disclosure. Various components relating to the embodiment of the present disclosure, such as numerical values, shapes, materials, and manufacturing processes, can be modified or changed within the scope that does not cause technical problems. Furthermore, the shapes, etc. shown in the drawings of the present disclosure do not necessarily match the actual shapes, etc. This is because the shapes, etc. may be modified for the purpose of explanation.

The insulated conductor 2 of this embodiment is a wire having a metal conductor portion 6 and an insulating layer 8 covering the metal conductor portion 6. The cross-sectional shape of the insulated conductor 2 is not particularly limited, and the insulated conductor 2 may have a circular, elliptical, rectangular, square, or other polygonal cross-sectional shape. For example, in the round-wire-shaped insulated conductor 2 shown in Figures 1 and 2, the metal conductor portion 6 has a circular cross-sectional shape. Note that both Figures 1 and 2 illustrate a cross section perpendicular to the longitudinal direction (Y-axis direction) of the insulated conductor 2, and the X-axis, Y-axis, and Z-axis in each figure are mutually perpendicular.

In the case of a round-shaped insulated conductor 2 as shown in Figures 1 and 2, for example, the average diameter D of the metal conductor portion 6 is preferably 0.1 mm or more and 1.5 mm or less. Note that this range of the average diameter D is an example of a suitable dimensional range when the insulated conductor 2 is applied to a coil such as an inductor, and the dimensions of the metal conductor portion 6 are not necessarily limited to the above dimensional range regardless of the application.

The metal conductor portion 6 is a portion through which current flows and plays a central role in the insulated conductor 2. Therefore, the metal conductor portion 6 is composed of metal components and contains at least Cu. For example, the metal conductor portion 6 may be pure copper or a copper alloy. The detailed composition of the metal conductor portion 6 is not particularly limited, but it is preferable that Cu is the main component that occupies at least 50 wt% of the metal conductor portion 6, and it is more preferable that the content of Cu in the metal conductor portion 6 is 70 wt% or more. When the metal conductor portion 6 is a copper alloy, in addition to Cu, the metal conductor portion 6 may contain one or more elements selected from Ag, Ni, Al, Zn, Be, Sn, Mn, and the like. The composition of the metal conductor portion 6 can be analyzed, for example, by energy dispersive X-ray analysis (EDS) or wavelength dispersive X-ray analysis (WDS).

The insulating layer 8 is a coating made of an insulating material that covers the metal conductor portion 6. The coverage of the insulating layer 8 with respect to the surface of the metal conductor portion 6 is preferably 90% or more, and more preferably 100%. The coverage can be calculated by observing a cross section perpendicular to the longitudinal direction of the insulating coated conductor 2. The insulating layer 8 is located on the outermost side of the insulating coated conductor 2, and the surface of the insulating layer 8 forms the outermost surface 2s of the insulating coated conductor 2.

The average thickness T _Ave of the insulating layer 8 is not particularly limited. When the insulating coated conductor 2 is applied to a coil such as an inductor, the average thickness T _Ave of the insulating layer 8 is preferably 1 μm or more and 220 μm or less, and more preferably 1 μm or more and 200 μm or less. In a coil such as an inductor, by setting the average thickness T _Ave in the above range, it is possible to suppress an increase in leakage flux while maintaining a high insulation resistance between the windings. The variation in the thickness t of the insulating layer 8 is preferably within a range of ±10% of the average thickness T _Ave , and more preferably within a range of ±5% of the average thickness T _Ave. In other words, the tolerance of the thickness t of the insulating layer 8 is preferably within a range of ±10%, and more preferably within a range of ±5%.

When calculating the average thickness T _Ave of the insulating layer 8, it is preferable to analyze at least 10 cross sections of the insulation-coated conductor 2, and it is preferable to measure the thickness t of the insulating layer 8 at 10 or more cross sections. Furthermore, the maximum thickness t _MAX and minimum thickness t _MIN of the insulating layer 8 are identified by the measurements, and the tolerance (%) of the thickness t of the insulating layer 8 can be calculated based on T _Ave , t _MAX and t _MIN . Specifically, the deviation of t _MAX from T _Ave (t _MAX - T _Ave ) and the deviation of t _MIN from T _Ave (t _MIN - T _Ave ) are calculated, and the deviation with the larger absolute value is divided by T _Ave to calculate the thickness tolerance. That is, "F1 = (|t _MAX - T _Ave |/T _Ave ) x 100" and "F2 = (|t _MIN - T _Ave |/T _Ave ) x 100" are calculated, and the larger of F1 and F2 is adopted as the tolerance (%) of the thickness t.

The insulating layer 8 contains at least Si, Ti, and oxygen. The ratio of the Ti content to the total content of Si and Ti in the insulating layer 8 (Ti/(Si+Ti)) is 2.5 at% or more and 50 at% or less, more preferably 5.0 at% or more and 40 at% or less, and even more preferably 7.5 at% or more and 25 at% or less. As described above, by setting the Ti/(Si+Ti) ratio in the insulating layer 8 to 2.5 at% or more and 50 at% or less, the variation in the thickness of the insulating layer 8 can be reduced and high heat resistance can be obtained.

The insulating layer 8 is preferably formed by a sol-gel method. When the insulating layer 8 is formed by the sol-gel method, the specifications (dimensions, material, etc.) of the metal conductor portion 6 do not change before and after firing, but the state of the insulating layer 8 changes. In this embodiment, the insulating layer 8 before firing is called the "unfired insulating layer 8A", and the insulating layer 8 after firing is called the "inorganic insulating layer 8B". Both the unfired insulating layer 8A and the inorganic insulating layer 8B satisfy 2.5 at% ≦ (Ti/(Si+Ti)) ≦ 50 at%, but the unfired insulating layer 8A is a coating containing an organic substance, whereas the inorganic insulating layer 8B is an oxide coating that does not substantially contain an organic substance. Below, an example of a method for forming the insulating layer 8 and the characteristics of the unfired insulating layer 8A and the inorganic insulating layer 8B are described in detail.

When forming the insulating layer 8 using the sol-gel method, first, liquid Si source and Ti source are mixed together to prepare a coating liquid.

The Si source used in the coating liquid is not particularly limited, but it is preferable to use, for example, an alkoxysilane. Examples of alkoxysilanes include monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, and tetraalkoxysilanes. Examples of monoalkoxysilanes include trimethylmethoxysilane, trimethylethoxysilane, and trimethyl(phenoxy)silane. Examples of dialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, t-butylmethyldimethoxysilane, and t-butylmethyldiethoxysilane. Examples of trialkoxysilanes include trimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, n-propyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, and phenyltrimethoxysilane. Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetraisopropoxysilane. As the Si source, one type of alkoxysilane may be used, or two or more types of alkoxysilanes may be used in combination.

The Ti source used in the coating liquid is not particularly limited, but it is preferable to use, for example, titanium alkoxide or titanium chelate. Examples of titanium alkoxides include titanium tetramethoxide, titanium tetraethoxide, titanium tetra-n-propoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, etc. Examples of titanium chelates include titanium acetylacetonate, titanium tetraacetylacetonate, titanium ethylacetoacetate, titanium octylene glycolate, titanium ethylacetoacetate, titanium lactate ammonium salt, titanium lactate, titanium triethanolamine, etc. As the Ti source, one type of titanium alkoxide or titanium chelate may be used, or two or more types of titanium alkoxides and/or titanium chelates may be used.

The Ti/(Si+Ti) ratio in the insulating layer 8 may be controlled by the compounding ratio of the Si source and the Ti source in the coating liquid. In order to adjust the viscosity of the coating liquid, an organic solvent may be added to the coating liquid as appropriate in addition to the Si source and the Ti source. In this case, the organic solvent used is not particularly limited. For example, ethanol, n-propyl alcohol, isopropyl alcohol, acetone, or methyl ethyl ketone may be used as the organic solvent.

Next, the unsintered insulating layer 8A is formed by a dip coating method using the above coating liquid. Specifically, in the dip coating method, a wire consisting of only the metal conductor portion 6 is immersed in the above coating liquid, and then the wire is removed from the coating liquid and dried. As the wire consisting of only the metal conductor portion 6 before being immersed in the coating liquid, a wire manufactured by a known method may be prepared. In addition, the process of immersing the wire in the coating liquid may be performed multiple times. The thickness tA of the unsintered insulating layer 8A can be controlled by the immersion time in the coating liquid and the number of immersions in the coating liquid. For example, the immersion time in the coating liquid each time may be 1 second to 300 seconds, and the number of immersions in the coating liquid may be 1 to 10 times.

When the immersion process is performed multiple times, a drying process may be performed after each immersion, and the conditions for the drying process are not particularly limited. For example, the drying temperature for each process may be set to 50°C or higher and lower than 300°C, and the thermal drying time for each process may be set to 0.5 to 3 hours.

By the above dip coating method, an unsintered insulating layer 8A is formed on the surface of the metal conductor portion 6. Note that the method for forming the unsintered insulating layer 8A is not limited to the dip coating method, and other forming methods such as spray coating may also be used.

After the drying process, the unfired insulating layer 8A (Figure 1) is a coating of a dry gel that contains organic matter such as polymeric compounds derived from Si and Ti sources. It is believed that the molecular structure of the organic matter contained in the unfired insulating layer 8A varies depending on the type of Si and Ti sources used in the coating liquid and the degree of drying. Structural analysis of the organic matter contained in the unfired insulating layer 8A can be difficult, and the molecular structure is not particularly limited, but the organic matter of the unfired insulating layer 8A contains at least Si and Ti. In addition, the organic matter of the unfired insulating layer 8A contains C (carbon), H (hydrogen), and O (oxygen), which are common constituent elements of organic matter.

Here, "organic material containing Si and Ti" means an organic compound containing bonds via Si and bonds via Ti in the molecular chain. Examples of bonds via Si include Si-O, Si-H, Si-OH, and Si-OR (R is an organic functional group). Similarly, examples of bonds via Ti include Ti-O, Ti-H, Ti-OH, and Ti-OR. As mentioned above, structural analysis of the organic material in the unfired insulating layer 8A is not easy, so there are no particular limitations on the bonds via Si and the bonds via Ti, but it is believed that at least Si-O and Ti-O are contained in the organic material in the unfired insulating layer 8A.

The unsintered insulating layer 8A may contain oxides produced by the decomposition of a part of the organic material. In other words, the unsintered insulating layer 8A may be a composite material containing an organic material and an inorganic material. Examples of oxides produced by the decomposition of the organic material include SiO ₂ , TiO ₂ , and Si-Ti-O (complex oxide containing Si and Ti).

As described above, Si and Ti are considered to be present in the skeleton of the polymer compound in the unsintered insulating layer 8A, and some of the Si and Ti may be present as oxides. The Ti/(Si+Ti) ratio in the unsintered insulating layer 8A is 2.5 at% to 50 at%, more preferably 5.0 at% to 40 at%, and even more preferably 7.5 at% to 25 at%.

The Si content (at %), Ti content (at %), and Ti/(Si+Ti) ratio in the unsintered insulating layer 8A can be calculated, for example, by point analysis using EDS or WDS. It is preferable to perform EDS or WDS point analysis at least 10 points and calculate the average value. If the total of the elements detected by point analysis is 100 at%, the total content of Si and Ti in the unsintered insulating layer 8A is not necessarily limited, but is preferably, for example, 1 at% or more and 10 at% or less.

The unsintered insulating layer 8A contains C and H, but these elements are lost during the firing process described below. The content ratio RO of the elements lost during firing among the elements contained in the unsintered insulating layer 8A is preferably 75 wt% or more and 90 wt% or less. The content ratio RO in the unsintered insulating layer 8A may be calculated using a thermogravimetric and differential thermal analyzer (TG-DTA). Specifically, in the analysis using TG-DTA, a measurement sample taken from the insulating coated conductor 2 having the unsintered insulating layer 8A is heated to 700°C at a constant heating rate. The content ratio RO of the elements lost during firing may be calculated from the weight change of the measurement sample at this time.

The unsintered insulating layer 8A may contain one or more elements selected from B, Al, Zn, P, Ta, Nb, Bi, Ba, Ca, V, Ge, and Te. These elements may be intentionally added to the coating liquid, or may be contained in the unsintered insulating layer 8A as impurities.

The average thickness T1 _Ave of the unsintered insulating layer 8A is not necessarily limited, but is preferably 1.5 μm or more and 220 μm or less. The tolerance of the thickness tA of the unsintered insulating layer 8A is preferably within a range of ±10%, and more preferably within a range of ±5%.

The insulating coated conductor 2 having the unsintered insulating layer 8A is heat-treated (sintered) under predetermined conditions to sinter the unsintered insulating layer 8A, thereby obtaining an insulating coated conductor 2 having an inorganic insulating layer 8B as shown in FIG. 2. The conditions for the heat treatment are not particularly limited, but for example, it is preferable to set the holding temperature to 300°C or higher and 900°C or lower (more preferably 500°C or higher and 900°C or lower), and the temperature holding time to 0.5 hours or higher and 10 hours or lower. The heat treatment may also be performed in an inert atmosphere such as nitrogen.

The unfired insulating layer 8A contains organic matter containing Si and Ti, and the organic matter is decomposed and oxidized by the heat treatment, forming a coating of oxide containing Si and Ti. That is, the Si and Ti in the organic matter remain in the inorganic insulating layer 8B and become oxides. On the other hand, most of the elements derived from the organic matter, such as carbon and hydrogen, contained in the unfired insulating layer 8A are vaporized and disappear during the process of oxidation and/or phase change of the unfired insulating layer 8A. For example, the carbon in the unfired insulating layer 8A becomes _CO2 gas and disappears from the insulating layer. Also, the hydrogen in the unfired insulating layer 8A becomes water vapor ( _H2O ) and disappears from the insulating layer.

As described above, it is preferable that the inorganic insulating layer 8B after firing contains at least an oxide containing Si and Ti, and is substantially free of organic matter. The content (remaining amount) of organic matter in the inorganic insulating layer 8B can be analyzed using TG-DTA. Specifically, in the analysis using TG-DTA, a measurement sample taken from an insulating coated conductor 2 having an inorganic insulating layer 8B is heated to 700°C at a constant heating rate. The content of organic matter can then be calculated from the weight change of the measurement sample in the temperature range of 300°C to 700°C. For example, if the rate of change in sample weight in the temperature range from 300°C to 700°C based on the sample weight at 300°C is within the range of ±3% (i.e., within the range of -3% or more and +3% or less), the inorganic insulating layer 8B may be determined to be "substantially free of organic matter."

The Ti/(Si+Ti) ratio in the insulating layer 8 hardly changes before and after firing, so the Ti/(Si+Ti) ratio in the inorganic insulating layer 8B is 2.5 at% or more and 50 at% or less, more preferably 5.0 at% or more and 40 at% or less, and even more preferably 7.5 at% or more and 25 at% or less.

The inorganic insulating layer 8B may also contain elements other than Si, Ti, and oxygen. Examples of the other elements include B, Al, Zn, P, Ta, Nb, Bi, Ba, Ca, V, Ge, and Te. If the total content of elements excluding oxygen contained in the inorganic insulating layer 8B is 100 at%, the total content of Si and Ti in the inorganic insulating layer 8B is preferably 70 at% or more, and more preferably 80 at% or more.

The Si content (at %), Ti content (at %), and Ti/(Si+Ti) ratio in the inorganic insulating layer 8B can be calculated by point analysis using EDS or WDS, similar to the analysis of the unsintered insulating layer 8A. It is preferable to perform EDS or WDS point analysis at at least 10 points and calculate the average value.

In addition, it is preferable that the inorganic insulating layer 8B is a coating having high density and homogeneity, rather than a state in which granular and/or fibrous substances are accumulated. For example, in the inorganic insulating layer 8B, it is preferable that Si and Ti are distributed uniformly without being locally unevenly distributed, and it is preferable that the locations where Si exists and the locations where Ti exists overlap. The distribution of Si and Ti in the inorganic insulating layer 8B can be confirmed, for example, by mapping analysis using EDS or WDS. In the mapping image obtained by this analysis, the concentration of the measurement target element (Si, Ti) is expressed as a brightness corresponding to the integrated intensity of the detection peak (the peak of the characteristic X-ray detected at each measurement point), and it can be visually confirmed whether the measurement target element is unevenly distributed or not. In addition, the brightness or integrated intensity data obtained by the mapping analysis is used as a population, and the distribution of the measurement target element can be quantitatively evaluated by calculating the average value, standard deviation, and coefficient of variation (standard deviation/average value) of the population. For example, in inorganic insulating layer 8B, it is preferable that the coefficient of variation of the Si distribution and the coefficient of variation of the Ti distribution are both 0.5 or less.

As described above, in the inorganic insulating layer 8B, it is preferable that the oxide containing Si and Ti is the main phase, and the main phase is uniformly dispersed. For example, the area ratio of the main phase in the inorganic insulating layer 8B is preferably 80% or more, more preferably 90% or more. In other words, in the cross section of the inorganic insulating layer 8B, the total area ratio of other phases other than the main phase is preferably 20% or less, more preferably 10% or less. The other phases include oxides having a composition different from that of the oxide containing Si and Ti, residual carbon, etc. The above-mentioned area ratios may be calculated by analyzing the cross section of the inorganic insulating layer 8B with a SEM, an optical microscope, etc., and the field of view during the cross section analysis may be, for example, 100 x 100 μm ² to 500 x 500 μm ² .

The average thickness T2 _Ave of the inorganic insulating layer 8B is not necessarily limited, but is preferably 1 μm or more and 200 μm or less. The tolerance of the thickness tB of the unsintered insulating layer 8A is preferably within a range of ±10%, and more preferably within a range of ±5%.

The application of the insulated conductor wire 2 is not particularly limited, but the insulated conductor wire 2 is particularly suitable for use as a coil for electronic components such as inductors, transformers, and choke coils. For example, FIG. 3 is a perspective view illustrating a coil 20 made of the insulated conductor wire 2.

The coil 20 in FIG. 3 has a structure in which the insulating coated conductor wire 2 is wound in a spiral shape along the Z-axis. The coil 20 in FIG. 3 employs an aligned multi-layer winding method, but the winding method of the insulating coated conductor wire 2 is not particularly limited. For example, a winding method such as one-layer aligned winding, uneven winding, diagonal winding, or space winding may be employed. The number of turns of the insulating coated conductor wire 2 in the coil 20 is not particularly limited and may be appropriately determined according to the desired coil characteristics. For example, the number of turns of the insulating coated conductor wire 2 may be 0.5 turns to 100 turns. Furthermore, when the insulating coated conductor wire 2 is wound in multiple layers, the number of layers of the winding is not particularly limited and may be, for example, 2 to 10 layers.

In the coil 20, the ends 2e1 and 2e2 of the insulating conductor 2 are each pulled out from the winding portion toward the outside in the X-axis direction. External terminals (not shown) can be connected to the ends 2e1 and 2e2, and the ends 2e1 and 2e2 may have an area where the insulating layer 8 is partially removed to expose the metal conductor portion 6. The shape and pull-out direction of the ends 2e1 and 2e2 are not particularly limited.

When manufacturing the coil 20, the insulating layer 8 may be formed and then the insulating conductor 2 may be wound in a predetermined manner. Alternatively, a wire consisting of only the metal conductor portion 6 may be wound into a coil shape, and then an unfired insulating layer 8A may be formed on the surface of the metal conductor portion 6 by a dip coating method or the like. When the insulating layer 8 is formed and then the insulating conductor 2 is wound, the insulating conductor 2 may be wound before the insulating layer 8 is fired, or the insulating conductor 2 may be wound after the insulating layer 8 is fired. In other words, the insulating conductor 2 having the unfired insulating layer 8A may be wound to form a coil shape, or the insulating conductor 2 having the fired inorganic insulating layer 8B may be wound to form a coil shape.

The coil 20 as shown in FIG. 3 may be incorporated into a circuit as an air-core coil, or may be used in combination with a magnetic core. When the coil 20 is applied to an electronic component having a magnetic core, the coil 20 may be formed by winding the insulating coated conductor 2 around a bobbin made of a non-magnetic material, and the bobbin and the magnetic core may be combined. The magnetic core may be inserted into the inner peripheral wall of the coil 20, or the coil 20 may be formed by winding the insulating coated conductor 2 around the outer surface of the magnetic core. Furthermore, the coil 20 may be used by being embedded inside a powder magnetic core containing magnetic powder and resin. In particular, since the insulating coated conductor 2 has high heat resistance, the coil 20 can be embedded inside a magnetic core made of a sintered body. For example, FIG. 4 is a cross-sectional view showing an example of an electronic component including the coil 20.

The electronic component 100 shown in FIG. 4 has a magnetic core 40, a coil 20 inside the magnetic core, and an external terminal (not shown). The magnetic core 40 is a sintered body of magnetic powder and does not contain a resin component such as epoxy resin, phenol resin, or silicone resin. The shape and dimensions of the magnetic core 40 are not particularly limited. The magnetic powder of the magnetic core 40 is also not particularly limited, and it is preferable to use soft magnetic metal powder, for example. Examples of soft magnetic metal powder include Fe-Ni alloy powder, Fe-Si alloy powder, Fe-Si-Cr alloy powder, Fe-Co alloy powder, Fe-Si-Al alloy powder, Fe-based amorphous alloy powder, and Fe-based nanocrystalline alloy powder. The grain size of the magnetic powder is not particularly limited, and the average grain size of the magnetic powder may be, for example, 1 μm or more and 100 μm or less.

When the magnetic powder is composed of soft magnetic metal particles as described above, the surface of each soft magnetic metal particle may be formed with an insulating coating, such as a coating formed by oxidation of the metal surface or a coating layer containing an inorganic compound. In this case, adjacent soft magnetic metal particles are in contact with each other via an insulating coating, or are joined via a grain boundary phase containing Si-based oxides. In other words, no organic components such as resins are present between the particles. The average thickness of the insulating coating formed on the surface of the soft magnetic metal particles is not particularly limited, and may be, for example, 5 nm or more and 200 nm or less.

The magnetic powder of the magnetic core 40 may be a mixed powder containing two or more types of particle groups with different particle compositions and/or particle sizes. For example, a magnetic powder may be used that is a mixture of Fe-Si alloy particles with a particle size of 25 μm or more and pure Fe particles with a particle size of less than 5 μm.

In the electronic component 100, the coil 20 is present inside the magnetic core 40 made of a sintered body, and the coil 20 is covered with sintered magnetic powder. In this way, when the coil 20 is present inside the sintered body, the insulating layer 8 in the insulating coated conductor 2 exists as an inorganic insulating layer 8B after sintering.

Furthermore, the ends 2e1 and 2e2 of the insulated conductor 2 that constitutes the coil 20 are each drawn from inside the magnetic core 40 to the outer surface of the magnetic core 40 and are electrically connected to an external terminal present on the outer surface of the magnetic core 40. At the connection portions of the ends 2e1 and 2e2 and the external terminals, the inorganic insulating layer 8B has been locally removed, and the metal conductor portion 6 and the external terminals are in direct contact.

The manufacturing method of the electronic component 100 is not particularly limited. For example, the magnetic core 40 may be manufactured by press molding. First, the coil 20 is placed in the cavity of a molding die. Then, a composite material made by mixing magnetic powder and a binder is filled into the cavity, and a predetermined pressure is applied to the cavity. The compact with the coil 20 embedded therein is then fired to obtain the magnetic core 40 as a sintered body including the coil 20. The firing conditions are not particularly limited as long as they are set to conditions under which the magnetic powder can be sintered. For example, the firing temperature may be set to 500°C or higher and 900°C or lower, and the firing time may be 0.5 to 10 hours. Note that a binder removal process may be performed before firing.

In addition, in the manufacture of the electronic component 100, the coil 20 having the inorganic insulating layer 8B may be embedded in the molded body. Alternatively, the coil 20 having the unsintered insulating layer 8A may be embedded in the molded body, and the unsintered insulating layer 8A may be fired simultaneously with the firing of the magnetic core 40. From the viewpoint of production efficiency, it is preferable to fire the insulating layer 8 when firing the magnetic core 40, as in the latter case.

Here, magnetic cores made of sintered bodies generally have a higher density than powder cores containing magnetic powder and resin. Therefore, magnetic cores made of sintered bodies almost always have a higher magnetic permeability than powder cores containing magnetic powder and resin.

However, when a coil is formed from a conventional conductor having an insulating coating containing a resin (for example, polyamide-imide resin, polyimide resin, epoxy resin, or urethane resin), the insulating coating on the coil surface is burned when the magnetic core is sintered as described above. Alternatively, the resin in the insulating coating on the coil surface is carbonized, and the electrical resistance of the insulating coating is significantly reduced. As a result, the insulation between the conductors in the coil is impaired, and the inductance is reduced. In contrast, when a coil 20 made of an insulating conductor 2 is used, the insulating layer 8 becomes an inorganic insulating layer 8B having high heat resistance during the sintering process of the magnetic core 40, so that the insulation between the windings in the coil 20 can be maintained even after the magnetic core 40 is sintered. In other words, the electronic component 100 has both a "magnetic core 40 made of a sintered body having high magnetic permeability" and a "coil 20 that maintains the insulation between the windings". As a result, the electronic component 100 can obtain a higher inductance than an electronic component made of a powder magnetic core containing magnetic powder and resin.

(Summary of the embodiment)
The insulating coated conductor 2 of the present embodiment has a metal conductor portion 6 containing Cu, and an insulating layer 8 covering the metal conductor portion 6. The insulating layer 8 contains Si, Ti, and oxygen, and the ratio of the Ti content to the total content of Si and Ti in the insulating layer 8 (Ti/(Si+Ti)) is 2.5 at % or more and 50 at % or less.

The insulating layer 8 is formed by the sol-gel method, and Ti/(Si+Ti) hardly changes before and after firing. In other words, the insulated conductor 2 after firing the insulating layer 8 has a metal conductor portion 6 containing Cu and an inorganic insulating layer 8B covering the metal conductor portion 6. The inorganic insulating layer 8B contains an oxide containing Si and Ti, and the ratio of the Ti content to the total content of Si and Ti in the inorganic insulating layer 8B (Ti/(Si+Ti)) is 2.5 at% or more and 50 at% or less.

By having the insulating layer 8 (8A, 8B) satisfy 2.5 at%≦(Ti/(Si+Ti))≦50 at%, the uniformity of the insulating layer 8 can be improved. Also, by having the insulating layer 8 (8A, 8B) satisfy 2.5 at%≦(Ti/(Si+Ti))≦50 at%, the insulating layer 8 can obtain high insulation resistance even after heating at high temperatures of 500°C or higher. In other words, by having the insulating layer 8 (8A, 8B) that satisfies a specified Ti/(Si+Ti), the insulating coated conductor 2 can obtain high heat resistance.

In the insulation coated conductor 2, the average thickness T _Ave of the insulation layer 8 is preferably 1 μm or more and 220 μm or less. In particular, the average thickness T2 _Ave of the inorganic insulating layer 8B after firing is preferably 1 μm or more and 200 μm or less. By satisfying the above average thickness, the heat resistance of the insulation coated conductor 2 is further improved. Furthermore, when the insulation coated conductor 2 is applied to a coil such as an inductor, by satisfying the above average thickness, the space factor of the conductor (metal conductor portion 6) can be sufficiently secured in the coil cross section. As a result, a decrease in inductance due to an increase in leakage flux can be suppressed.

Although the embodiments of the present disclosure have been described above, the present disclosure is in no way limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present disclosure.

For example, as mentioned above, the cross-sectional shape of the insulated conductor is not particularly limited, and may be substantially rectangular, such as the rectangular insulated conductor 2α shown in FIG. 5A. In the case of rectangular wire such as the insulated conductor 2α, the width Wx (long width) in the X-axis direction of the metal conductor portion 6 is preferably, for example, 0.1 mm or more and 2.5 mm or less, and the width Wz (short width) in the Z-axis direction of the metal conductor portion 6 is preferably, for example, 0.1 mm or more and 1.0 mm or less. The above dimensions are within a suitable range when the insulated conductor 2α is applied to a coil such as an inductor, and the dimensions of the metal conductor portion 6 in the rectangular wire are not particularly limited regardless of the application.

The coil 20α shown in FIG. 6 is an example of a coil using the rectangular insulating coated conductor 2α shown in FIG. 5A. As shown in FIG. 6, the coil 20α uses an edgewise method, and the insulating coated conductor 2α is wound along the Z axis so that the direction of the long width (Wx shown in FIG. 5A) intersects with the Z axis (winding axis). The winding method when using the rectangular insulating coated conductor 2α is not limited to FIG. 6, and the flatwise method may be used. In the case of the flatwise method, the insulating coated conductor 2α is wound so that the direction of the long width (Wx shown in FIG. 5A) coincides with the Z axis (winding axis). Even when using the rectangular insulating coated conductor 2α, the number of turns of the insulating coated conductor 2α is not particularly limited and may be determined appropriately according to the desired coil characteristics.

The metal conductor portion 6 may have two or more regions with different compositions. For example, the metal conductor portion 6 may have a main body portion 6a and a metal coating layer 6b, as in the case of the insulating coated conductor 2β shown in FIG. 5B. In FIG. 5B, the insulating coated conductor 2β is a round wire having a circular cross-sectional shape, but even in the case of a rectangular wire as shown in FIG. 5A, the metal conductor portion 6 may have a main body portion 6a and a metal coating layer 6b. The metal coating layer 6b is a layer made of a metal component that covers the main body portion 6a, and may be formed by a plating method or a vapor deposition method. The metal coating layer 6b may have a structure in which two or more types of plating layers are laminated. In addition, when the metal conductor portion 6 has the metal coating layer 6b, the insulating layer 8 covers the surface of the metal coating layer 6b and is located on the outermost side of the insulating coated conductor 2β. By forming the metal coating layer 6b between the main body portion 6a of the metal conductor portion 6 and the insulating layer 8, the flexibility of the insulating coated conductor 2β may be improved.

In the case of the insulated conductor 2β shown in FIG. 5B, Cu may be contained in either the main body 6a or the metal coating layer 6b, or in both the main body 6a and the metal coating layer 6b. For example, the main body 6a may be made of pure copper or a copper alloy (i.e., the main component of the main body 6a is Cu), and a metal coating layer 6b containing one or more selected from Ni, Cr, Al, Ag, and Zn may be formed on the surface of the main body 6a. Alternatively, the main body 6a may be made of pure Al or an Al alloy, and a metal coating layer 6b containing Cu may be formed on the surface of the main body 6a (so-called copper-coated aluminum wire).

The average thickness of the metal coating layer 6b is not particularly limited and may be, for example, 10 μm or more and 150 μm or less. Furthermore, the main body portion 6a may have dimensions similar to the average diameter D in FIG. 1 or the widths Wx and Wz in FIG. 5A.

The present disclosure will be explained below in more detail with reference to examples, but the present disclosure is not limited to these examples.

(Experiment 1)
In experiment 1, the insulated conductors of samples A1 to A17 were manufactured by the following procedure. First, trimethoxysilane, which is a Si source, and titanium tetra-n-butoxide, which is a Ti source, were prepared, and a coating liquid was prepared using these raw materials. Specifically, for samples A2 to A16, the compounding ratio of the Si source and the Ti source was controlled so that the Ti/(Si+Ti) ratio in the insulating layer was the value shown in Table 1. In addition, only the Si source was added to the coating liquid of sample A1, and only the Ti source was added to the coating liquid of sample A17.

Next, a Cu wire having an average diameter D of 500 μm was prepared, and the Cu wire was immersed in the above coating liquid for 30 seconds and allowed to stand. The Cu wire was then removed from the coating liquid and dried. In the drying process, the holding temperature was set to 100°C, and the temperature holding time was set to 30 minutes. This immersion in the coating liquid and drying process were repeated three times to obtain an insulating coated conductor having an insulating layer (unfired insulating layer). The following evaluations were performed on the insulating coated conductor of each sample before firing.

Measurement of the average thickness and thickness tolerance of the insulating layer <br/> The cross section of the insulating coated conductor was observed with a scanning electron microscope (SEM) to measure the thickness tA of the unsintered insulating layer present on the surface of the Cu wire. Ten cross sections of each sample of the insulating coated conductor were analyzed, and the thickness tA of the unsintered insulating layer was measured at ten points on each cross section. From the data on the thickness tA obtained by the measurement, the average thickness T1 _Ave , the maximum thickness t1 _MAX , and the minimum thickness t1 _MIN were calculated. In addition, "F1 = (|t1 _MAX - T1 _Ave |/T1 _Ave ) x 100" and "F2 = (|t1 _MIN - T1 _Ave |/T1 _Ave ) x 100" were calculated, and the larger of F1 and F2 was adopted as the tolerance (%) of the thickness tA.

Regarding the uniformity of the thickness of the insulating layer, samples with a thickness tolerance within ±10% were judged to be good, and samples with a thickness tolerance within ±5% were judged to be particularly good.

Insulation layer component analysis During cross-sectional analysis by SEM, point analysis was performed by EDS to measure the Si content (at%) and Ti content (at%) contained in the unfired insulation layer. The point analysis was performed at least at 10 points, and the Si and Ti contents were calculated as average values. Based on the measurement results, the ratio of the Ti content to the total content of Si and Ti in the unfired insulation layer (Ti/(Si+Ti)) was calculated.

Measurement of insulation resistance by insulating layer After coating, the insulation resistance (Ω) of the insulating layer before firing (unfired insulating layer) was measured using an HP high resistance meter 4339B. For this measurement, the unfired insulating layer equivalent to 1/2 of the surface was locally removed. Then, one of the measuring terminals was pressed against the part where the unfired insulating layer was removed (i.e., the part where the Cu metal conductor part was exposed) and the other terminal was pressed against the surface of the unfired insulating layer to measure the insulation resistance. The insulation resistance of the unfired insulating layer was judged to be 1 x 10 ⁷ Ω or more as passing. Note that "ND" in the insulation resistance column of Table 1 means that the insulation resistance was less than 1 x 10 ³ Ω and the insulation resistance could not be measured.

<Firing of insulating layer>
In the above evaluation before firing, for the samples (samples A5 to A17) for which the insulation resistance could be measured, the insulation-covered conductor was subjected to a heat treatment (firing treatment) in order to sinter the insulating layer. In the heat treatment, the holding temperature was set to 700° C., and the temperature holding time was set to 1 hour. The heat treatment sintered the insulating layer, and an insulation-covered conductor having an inorganic insulating layer was obtained.

For the insulated conductors of each sample after firing, the average thickness and thickness tolerance of the inorganic insulating layer were measured, the components of the inorganic insulating layer were analyzed, and the insulation resistance of the inorganic insulating layer was measured using the same methods as before firing. In addition, the appearance of the inorganic insulating layer formed after firing was inspected to check for the presence or absence of cracks in the inorganic insulating layer.

The heat resistance of the insulated conductor was evaluated based on the insulation resistance (Ω) of the inorganic insulating layer after firing and the results of an appearance inspection of the inorganic insulating layer. Specifically, if no cracks were present and the insulation resistance was 1× ¹⁰ Ω or more, it was judged to have "good heat resistance," and if no cracks were present and the insulation resistance was 1× ¹⁰ Ω or more, it was judged to have "particularly good heat resistance."

The evaluation results of Experiment 1 are shown in Table 1.

In the comparative samples A1 to A4, it was confirmed that oxide particles had accumulated on the surface of the Cu metal conductor, and no continuous coating had been formed. Therefore, the thickness of the coating layer was not measured for samples A1 to A4. In samples A1 to A4, the resistance value measured on the deposit surface was almost the same as the resistance value of the metal conductor (Cu wire), and a coating with sufficient resistance was not formed.

Furthermore, in the comparative examples, samples A12 to A17, the tolerance of the thickness of the insulating layer was large, and uniformity could not be ensured. As a result, in samples A12 to A17, the thermal stress generated during firing became non-uniform, and cracks occurred in parts of the inorganic insulating layer. In other words, the insulating coated conductors of samples A12 to A17 did not provide sufficient heat resistance.

On the other hand, in the case of the working examples, Samples A5 to A11, the thickness tolerance was within ±5% of the average thickness both before and after firing, and it was confirmed that a highly uniform insulating layer was formed. Furthermore, Samples A5 to A11 were able to maintain high insulation resistance even after heat treatment at 700°C, and the occurrence of cracks was also suppressed. These results prove that high heat resistance can be obtained by having an insulating layer that satisfies 2.5 at% ≦ Ti/(Si + Ti) ≦ 50 at% for an insulated conductor.

(Experiment 2)
In Experiment 2, ten types of insulation-coated conductors with different average thicknesses of the unsintered insulating layer were manufactured. For Samples B1 to B9 in Experiment 2, the same coating liquid as for Sample A6 in Experiment 1 was used, and the Ti/(Si+Ti) ratio was controlled to 5.2 at %. The average thickness of the unsintered insulating layer in each sample was controlled based on the number of times the coating process was repeated so as to obtain the values shown in Table 2. The manufacturing conditions in Experiment 2 other than those mentioned above were the same as in Experiment 1, and each sample in Experiment 2 was evaluated in the same manner as in Experiment 1. The evaluation results of Experiment 2 are shown in Table 2.

The results in Table 2 show that by setting the average thickness of the unsintered insulating layer to 1 μm or more and 220 μm or less (in other words, by setting the average thickness of the inorganic insulating layer to 1 μm or more and 200 μm or less), an inorganic insulating layer with uniform and high insulating properties can be obtained.

2, 2α, 2β: Insulated conductor 2s: Outermost surface 2e1, 2e2: End 6: Metal conductor 6a: Main body 6b: Metal coating layer 8: Insulating layer 8A: Unfired insulating layer 8B: Inorganic insulating layer 20, 20α: Coil 100: Electronic component 40: Magnetic core

Claims (4)

A metal conductor portion including Cu and an insulating layer covering the metal conductor portion,
the insulating layer includes Si, Ti, and oxygen;
The ratio of the Ti content to the total content of Si and Ti in the insulating layer is 2.5 at % or more and 50 at % or less. The insulated conductor according to claim 1, wherein the average thickness of the insulating layer is 1 μm or more and 220 μm or less. A metal conductor portion containing Cu and an inorganic insulating layer covering the metal conductor portion,
the inorganic insulating layer includes an oxide containing Si and Ti,
The ratio of the Ti content to the total content of Si and Ti in the inorganic insulating layer is 2.5 at % or more and 50 at % or less. The insulated conductor according to claim 3, wherein the average thickness of the inorganic insulating layer is 1 μm or more and 200 μm or less.

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