JP7477263B2 - Inductor and manufacturing method thereof - Google Patents

Description

The present invention relates to an inductor and a method for manufacturing the same.

Traditionally, inductors are known to be installed in electronic devices and used as passive elements such as voltage conversion components.

One such inductor that has been proposed is one that includes an internal conductor such as copper and a chip body made of a magnetic material in which the internal conductor is embedded (see, for example, Patent Document 1 below). In the inductor of Patent Document 1, both end faces of the internal conductor and both end faces of the chip body are formed flush with each other.

Japanese Patent Application Laid-Open No. 10-144526

However, before an inductor is installed in an electronic device, it is necessary to contact both end faces of the internal conductor with a probe (test terminal) or the like to evaluate the inductor's magnetic properties, such as its inductance, and/or to test whether the internal conductor is conductive.

However, in the inductor of Patent Document 1, at least one end face of the internal conductor and one end face of the chip body are formed flush with each other, making it difficult to directly contact the one end face of the internal conductor with a probe, which makes it impossible to carry out the above-mentioned evaluation and inspection.

Even if the probe can be brought into contact with one end surface of the internal conductor, the electrical connection between the probe and the internal conductor is likely to be poor, which can cause the above-mentioned evaluation and inspection to become unreliable.

On the other hand, there is also a demand to manufacture inductance at low cost.

The present invention provides an inductor and a method for manufacturing the same that allows for easy and reliable evaluation of magnetic properties and wiring continuity testing while also enabling the inductor to be manufactured at low cost.

The present invention (1) includes a method for manufacturing an inductor, comprising a first step of preparing a wiring, a second step of forming a magnetic layer from a magnetic composition containing magnetic particles so as to cover the outer circumferential surface of the intermediate portion of the wiring and to expose the end of the wiring from the magnetic layer within a range of 2 mm or more and less than 100 mm, and a third step of removing the end of the wiring.

In this inductor manufacturing method, in the second step, the magnetic layer is formed so that the ends of the wiring are exposed from the magnetic layer by 2 mm or more. This allows the terminals to be easily contacted with the ends of the wiring, ensuring a reliable electrical connection between the terminals and the wiring. This makes it easy to evaluate the magnetic properties and to perform a continuity test of the wiring.

In addition, in the second step, the magnetic layer is formed so that the ends of the wiring are exposed from the magnetic layer at less than 100 mm, and in the third step, the ends of the wiring are removed, so the length of the ends to be removed can be kept to less than 100 mm. This makes it possible to reduce the amount of wiring to be removed, and as a result, inductors can be manufactured at low cost.

Therefore, this manufacturing method allows for easy and reliable evaluation of magnetic properties and wiring continuity testing while manufacturing inductors at low cost.

The present invention (2) includes the method for manufacturing an inductor described in (1), in which the length of the wiring in the thickness direction of the inductor is 1000 μm or less.

The thickness direction length of the wiring inductor is short, less than 1000 μm, so a thin inductor can be manufactured.

On the other hand, in a method for manufacturing a thin inductor, if the end face of the wiring and the end face of the magnetic layer are flush, as in the inductor of Patent Document 1, it becomes even more difficult to contact the end of the terminal thereafter.

However, as described above, in the second step, the magnetic layer is formed so that the ends of the wiring are exposed from the magnetic layer over a range of 2 mm or more. Therefore, even if the thickness direction length of the wiring in the inductor is short, such as 1000 μm or less, the terminal can be easily brought into contact with the ends of the wiring.

This allows the terminals to easily contact the ends of the wiring while still producing a thin inductor.

The present invention (3) includes the method for manufacturing an inductor described in (1) or (2), in which, in the second step, both ends of the wiring are exposed from the magnetic layer.

In the second step, both ends of the wiring are exposed from the magnetic layer, so that after the second step, each of the two terminals can be easily brought into contact with each of the two ends of the wiring, ensuring a reliable electrical connection between the two terminals and the wiring.

The present invention (4) includes the method for manufacturing an inductor according to any one of (1) to (3), in which in the first step, the wiring is prepared, the wiring comprising a conductor and an insulating layer covering the outer surface of the conductor, and further includes a fourth step, which is performed after the second step and before the third step, of exposing the conductor from the insulating layer at the end of the wiring.

In the first step, wiring is prepared that includes a conductor and an insulating layer that covers the outer surface of the conductor, so that the insulating layer can prevent short circuits between the conductor and the magnetic layer.

In addition, in the fourth step, the conductor at the end of the wiring is exposed from the insulating layer, so that the terminal can be easily contacted with the conductor at the end of the wiring, ensuring a reliable electrical connection between the terminal and the conductor.

The present invention (5) includes an inductor comprising a plurality of wirings and a magnetic layer covering an intermediate portion of each of the plurality of wirings, the magnetic layer containing magnetic particles, and each end of the plurality of wirings being exposed from the magnetic layer within a range of 2 mm or more and less than 100 mm.

In this inductor, the ends of each of the multiple wirings are exposed from the magnetic layer by 2 mm or more. This allows the terminals to be easily brought into contact with the ends of the wiring, ensuring a reliable electrical connection between the terminals and the wiring. This allows for easy and reliable evaluation of the magnetic properties of the inductor and other components, as well as wiring continuity testing.

In addition, since the ends of each of the multiple wirings are exposed from the magnetic layer within a range of less than 100 mm, the inductors are manufactured by cutting the inductors into individual pieces corresponding to each of the multiple wirings so as to remove the ends, thereby reducing the amount of wiring that is removed, and as a result, multiple inductors can be manufactured at low cost.

The inductor and manufacturing method of the present invention allow for easy and reliable evaluation of magnetic properties and wiring continuity testing while manufacturing the inductor at low cost.

Figures 1A to 1D show manufacturing process diagrams of a first embodiment of a manufacturing method for an inductor of the present invention. Figures 1A to 1B show a first process, with Figure 1A being a plan view and Figure 1B being a front view as viewed in the direction of the arrow in Figure 1A. Figures 1C to 1D show a second process, with Figure 1C being a plan view and Figure 1D being a front view. Fig. 2 shows the manufacturing process of the first embodiment, following Fig. 1D. Fig. 2E to Fig. 2F show the fourth step and the evaluation inspection step, with Fig. 2E showing a plan view and Fig. 2F showing a front view. Fig. 2G to Fig. 2H show the third step, with Fig. 2G showing a plan view of the inductor and Fig. 2H showing a front view of the inductor. FIG. 3 shows a flow chart of a manufacturing method of the first embodiment shown in FIGS. 1A to 2H. Figures 4A to 4C are examples of detailed oblique process views of the second process shown in Figures 1C to 1D, where Figure 4A shows the process of preparing wiring and a first magnetic sheet, Figure 4B shows the process of pressing the first magnetic sheet onto the wiring and the process of preparing a second magnetic sheet and a third magnetic sheet , and Figure 4C shows the process of pressing the second magnetic sheet and the third magnetic sheet onto the first magnetic sheet and wiring to form a magnetic sheet. FIG. 5 is a perspective view illustrating the evaluation and inspection process shown in FIGS. 2E to 2F. FIG. 6 is a perspective view illustrating a modified example of the evaluation and inspection process of the first embodiment shown in FIG. FIG. 7 shows a perspective view of a modified example of the inductor of the first embodiment shown in FIGS. 1C and 1D. FIG. 8 shows an inductor in a modification of the third step of the first embodiment shown in FIG. 2G and a plan view of the inductor. FIG. 9 shows an inductor in a modification of the third step of the first embodiment shown in FIG. 2G and a plan view of the inductor. FIG. 10 shows an inductor in a modification of the third step of the first embodiment shown in FIG. 2G and a plan view of the inductor. 11A and 11B are plan views of modified examples of the third step of the first embodiment shown in FIG. 2G, with FIG. 11A showing a modified example in which the magnetic layer is not cut but the wiring is cut, and FIG. 11B showing a modified example in which the magnetic layer and the wiring are cut. FIG. 12 is a plan view illustrating a third step of the second embodiment of the inductor manufacturing method of the present invention. FIG. 13 is a plan view illustrating a third step of the third embodiment of the inductor manufacturing method of the present invention.

A first embodiment of the inductor manufacturing method of the present invention and the inductor obtained thereby will be described with reference to Figures 1A to 5.

First Embodiment
As shown in FIGS. 1A to 2H, in the method for manufacturing an inductor 1, an inductor 30 including a plurality of wirings 2 and a magnetic layer 3 covering the wirings 2 is manufactured, and then a plurality of inductors 1 are manufactured from the inductor 30.

Specifically, the manufacturing method of the inductor 1 includes a first step of preparing the wiring 2, a second step of forming the magnetic layer 3 so as to cover the middle portion 10 of the wiring 2 and expose the first end 8 and second end 9 of the wiring 2 from the magnetic layer 3, and a third step of removing the first end 8 and second end 9 of the wiring 2. In this manufacturing method, the first step, the second step, and the third step are carried out in order as shown in FIG. 3.

This manufacturing method further includes a fourth step, which occurs after the second step and before the third step, of exposing the conductor 6 from the insulating layer 7 at the first end 8 and the second end 9 of the wiring 2, and an evaluation and inspection step, which occurs after the fourth step and before the third step, of evaluating the inductance of the multiple inductors 1 and inspecting the continuity of the multiple wirings 2. In other words, in this manufacturing method, the first step, second step, fourth step, evaluation and inspection step, and third step are performed in this order, as shown in FIG. 3.

As shown in Figures 1A and 1B, in the first step, a plurality of wirings 2 are prepared. The plurality of wirings 2 includes, for example, a first wiring 4 and a second wiring 5.

The first wiring 4 comprises a conductive wire 6 and an insulating layer 7 covering it.

The conductor 6 extends long in the direction of electrical current flow and has, for example, a generally U-shape in plan view. Specifically, in the first step, the first wiring 4 is placed on a horizontal stand (not shown) so that it has a generally U-shape in plan view, causing the conductor 6 to have the above-mentioned shape in plan view. The conductor 6 has a generally circular shape in cross section that shares a central axis with the first wiring 4.

The material of the conductor 6 is a metal conductor such as copper, silver, gold, aluminum, nickel, or an alloy of these, preferably copper. The conductor 6 may have a single-layer structure or a multi-layer structure in which the surface of a core conductor (e.g., copper) is plated (e.g., nickel) or the like.

The radius R1 of the conductor 6 is the distance from the center of the conductor 6 to the first outer surface 12, and is, for example, 25 μm or more, preferably 50 μm or more, and, for example, 2000 μm or less, preferably 250 μm or less.

The insulating layer 7 is a layer for protecting the conductor 6 from chemicals and water and for preventing short-circuiting of the conductor 6. The insulating layer 7 is arranged so as to cover the entire first outer surface 12, which is an example of the outer surface of the conductor 6.

The insulating layer 7 has a generally circular cross-sectional shape that shares a central axis (center) with the first wiring 4.

Materials for the insulating layer 7 include, for example, insulating resins such as polyvinyl formal, polyester, polyesterimide, polyamide (including nylon), polyimide, polyamideimide, and polyurethane. These may be used alone or in combination of two or more types. The insulating layer 7 may be composed of a single layer or multiple layers.

The thickness T1 of the insulating layer 7 is the distance from the first outer surface 12 of the conductor 6 to the second outer surface 13, which is an example of the outer surface of the first wiring 4 (wiring 2), and is approximately uniform in the radial direction of the wiring 2 at any position in the circumferential direction, and is, for example, 1 μm or more, preferably 3 μm or more, and, for example, 100 μm or less, preferably 50 μm or less.

The radius R2 of the first wiring 4 is the sum (R1+T1) of the radius R1 of the conductor 6 and the thickness T1 of the insulating layer 7, specifically, the length R2 from the center of the first wiring 4 to the second outer peripheral surface 13. The radius R2 of the first wiring 4 is, for example, 25 μm or more, preferably 50 μm or more, and, for example, 2000 μm or less, preferably 250 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less.

The diameter D of the first wiring 4 (corresponding to the thickness of the first wiring 4 in the inductor 1) is twice the radius R2 of the first wiring 4 described above (2 x R2), and specifically, for example, is 50 μm or more, preferably 100 μm or more, and for example, is 4000 μm or less, preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 400 μm or less, and particularly preferably 300 μm or less.

If the radius R2 and/or diameter D of the first wiring 4 is equal to or greater than the lower limit described above, an excellent inductance can be obtained. If the radius and/or diameter of the first wiring 4 is equal to or less than the upper limit described above, a thin inductor 1 can be obtained.

As shown in FIG. 1A, the first wiring 4 has a first end 8 and a second end 9 disposed at both ends in the direction of current flow, and an intermediate portion 10 located midway in the direction of current flow (between them).

The first end 8 and the second end 9 are used, for example, as electrical contacts (terminal portions) in the evaluation and inspection process described below.

The intermediate portion 10 connects the first end 8 and the second end 9 in the current flow direction. The intermediate portion 10 has a curved portion 11 that has, for example, a roughly semicircular arc shape in a plan view at the center in the current flow direction. The intermediate portion 10 also has a first connecting portion 19 that is connected (continuous) to the first end 8, and a second connecting portion 29 that is connected (continuous) to the second end 9.

The first connecting portion 19 is disposed and formed in a straight line with the first end portion 8 in a plan view. In addition, although the first connecting portion 19 is not depicted in Figures 1A to 1B, in a cross section along the direction of electrical flow, the first connecting portion 19 is disposed and formed in a straight line with the first end portion 8. One end of the first connecting portion 19 is connected to the first end portion 8, and the other end of the first connecting portion 19 is connected to one end of the curved portion 11.

The second connecting portion 29 is arranged and formed in a straight line with the second end portion 9 in a plan view. Although the second connecting portion 29 is not depicted in Figures 1A to 1B, the second connecting portion 29 is arranged and formed in a straight line with the second end portion 9 in a cross section along the direction of electrical flow. One end of the second connecting portion 29 is connected to the second end portion 9, and the other end of the second connecting portion 29 is connected to the other end of the curved portion 11.

The intermediate portion 10 is the entire portion of the wiring 2 excluding the first end portion 8 and the second end portion 9. In addition, the intermediate portion 10 has a planar area of each of the plurality of wirings 2 of, for example, 60% or more, preferably 80% or more, and for example, 99% or less, preferably 95% or less.

The center-to-center distance L2 between the first end 8 and the second end 9 in cross-sectional view (or front view) is, for example, 20 μm or more, preferably 50 μm or more, and, for example, 3000 μm or less, preferably 2000 μm or less.

The second wiring 5 has the same shape, structure and material as the first wiring 4.

The center-to-center distance L1 between the second end 9 of the first wiring 4 and the first end 8 of the second wiring 5 is, for example, 20 μm or more, preferably 50 μm or more, and is, for example, 3000 μm or less, preferably 2000 μm or less.

As shown in Figures 1C and 1D, in the second step, the magnetic layer 3 is formed so as to cover the second outer surface 13 of the middle portion 10 of the wiring 2 and to expose the first end 8 and second end 9 of the wiring 2.

In the second step, the magnetic layer 3 is formed from a magnetic composition containing magnetic particles. Specifically, the magnetic composition contains magnetic particles and a binder.

The magnetic material constituting the magnetic particles can be, for example, a soft magnetic material or a hard magnetic material. From the viewpoint of inductance, a soft magnetic material is preferable.

Examples of soft magnetic bodies include single metal bodies that contain one type of metal element in a pure substance state, and alloy bodies that are eutectic bodies (mixtures) of one or more types of metal elements (first metal elements) and one or more types of metal elements (second metal elements) and/or non-metal elements (carbon, nitrogen, silicon, phosphorus, etc.). These can be used alone or in combination.

An example of a single metal body is a metal element consisting of only one type of metal element (first metal element). The first metal element is appropriately selected from among metal elements that can be contained as the first metal element in a soft magnetic body, such as iron (Fe), cobalt (Co), nickel (Ni), and others.

The single metal body may be, for example, a form including a core containing only one type of metal element and a surface layer containing an inorganic and/or organic substance that modifies a part or all of the surface of the core, such as an organometallic compound containing a first metal element or a form in which an inorganic metal compound is decomposed (e.g., thermally decomposed). More specifically, the latter form may include iron powder (sometimes called carbonyl iron powder) obtained by thermally decomposing an organoiron compound (specifically, carbonyl iron) containing iron as the first metal element. The position of the layer containing an inorganic and/or organic substance that modifies the part containing only one type of metal element is not limited to the surface as described above. The organometallic compound or inorganic metal compound from which the single metal body can be obtained is not particularly limited, and may be appropriately selected from known or commonly used organometallic compounds or inorganic metal compounds from which a single metal body of a soft magnetic material can be obtained.

The alloy body is a eutectic of one or more metal elements (first metal elements) and one or more metal elements (second metal elements) and/or nonmetallic elements (carbon, nitrogen, silicon, phosphorus, etc.), and is not particularly limited as long as it can be used as an alloy body of a soft magnetic material.

The first metal element is an essential element in the alloy body, and examples of the element include iron (Fe), cobalt (Co), and nickel (Ni). If the first metal element is Fe, the alloy body is an Fe-based alloy; if the first metal element is Co, the alloy body is a Co-based alloy; and if the first metal element is Ni, the alloy body is a Ni-based alloy.

The second metal element is an element (secondary component) secondarily contained in the alloy body, and is a metal element that is compatible (eutectic) with the first metal element, and examples of such elements include iron (Fe) (when the first metal element is other than Fe), cobalt (Co) (when the first metal element is other than Co), nickel (Ni) (when the first metal element is other than Ni), chromium (Cr), aluminum (Al), silicon (Si), copper (Cu), silver (Ag), manganese (Mn), calcium (Ca), barium (Al), and the like. These include Ba, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), ruthenium (Ru), rhodium (Rh), zinc (Zn), gallium (Ga), indium (In), germanium (Ge), tin (Sn), lead (Pb), scandium (Sc), yttrium (Y), strontium (Sr), and various rare earth elements. These can be used alone or in combination of two or more.

Nonmetallic elements are elements (secondary components) secondarily contained in the alloy body, and are nonmetallic elements that are compatible (eutectic) with the first metallic element, such as boron (B), carbon (C), nitrogen (N), silicon (Si), phosphorus (P), and sulfur (S). These can be used alone or in combination of two or more types.

Examples of alloy bodies, such as Fe-based alloys, include magnetic stainless steel (Fe-Cr-Al-Si alloy) (including electromagnetic stainless steel), Sendust (Fe-Si-Al alloy) (including super Sendust), Permalloy (Fe-Ni alloy), Fe-Ni-Mo alloy, Fe-Ni-Mo-Cu alloy, Fe-Ni-Co alloy, Fe-Cr alloy, Fe-Cr-Al alloy, Fe-Ni-Cr alloy, Fe-Ni-Cr-Si alloy, silicon copper (Fe-Cu-Si alloy), Fe-Si alloy, Fe-Si-B (-Cu-Nb) alloy, Fe-B-Si-Cr alloy, Fe-S Examples include i-Cr-Ni alloys, Fe-Si-Cr alloys, Fe-Si-Al-Ni-Cr alloys, Fe-Ni-Si-Co alloys, Fe-N alloys, Fe-C alloys, Fe-B alloys, Fe-P alloys, ferrites (including stainless steel ferrites, as well as soft ferrites such as Mn-Mg ferrites, Mn-Zn ferrites, Ni-Zn ferrites, Ni-Zn-Cu ferrites, Cu-Zn ferrites, and Cu-Mg-Zn ferrites), permendur (Fe-Co alloys), Fe-Co-V alloys, and Fe-based amorphous alloys.

Examples of alloy bodies, such as Co-based alloys, include Co-Ta-Zr and cobalt (Co)-based amorphous alloys.

An example of an alloy body, a Ni-based alloy, is, for example, a Ni-Cr alloy.

Of these soft magnetic materials, from the viewpoint of magnetic properties, an alloy body is preferable, an Fe-based alloy is more preferable, and sendust (Fe-Si-Al alloy) is even more preferable. In addition, as the soft magnetic material, a single metal body is preferable, a single metal body containing iron element in a pure substance state is more preferable, and iron alone or iron powder (carbonyl iron powder) is even more preferable.

The volume percentage of the magnetic particles in the magnetic composition is, for example, 40 volume% or more, preferably 50 volume% or more, more preferably 60 volume% or more, and, for example, 95 volume% or less, preferably 90 volume% or less.

The shape of the magnetic particles is not particularly limited, and examples include anisotropic shapes such as flat (plate-like) and needle-like, as well as non-anisotropic shapes such as spherical. From the viewpoint of orientation, anisotropic shapes are preferred, and more preferably, flat shapes are preferred from the viewpoint of good relative magnetic permeability in the plane direction (two dimensions).

The flattening ratio (flatness) of the flat magnetic particles is, for example, 8 or more, preferably 15 or more, and, for example, 500 or less, preferably 450 or less. The flattening ratio is calculated, for example, as the aspect ratio obtained by dividing the average particle diameter (average length) (described later) of the flat magnetic particles by the average thickness of the flat magnetic particles.

The flat magnetic particles have an average particle diameter (average length) of, for example, 3.5 μm or more, preferably 10 μm or more, and for example, 200 μm or less, preferably 150 μm or less. If the flat magnetic particles are flat, their average thickness is, for example, 0.1 μm or more, preferably 0.2 μm or more, and for example, 3.0 μm or less, preferably 2.5 μm or less.

The average particle size of the non-anisotropic magnetic particles is, for example, 0.1 μm or more, preferably 0.5 μm or more, and, for example, 200 μm or less, preferably 150 μm or less.

Examples of binders include resins, such as thermosetting resins such as epoxy resins and phenolic resins, and thermoplastic resins such as acrylic resins. These can be used alone or in combination.

Preferably, a combination of a thermosetting resin and a thermoplastic resin is used, and more preferably, a combination of an acrylic resin, an epoxy resin, and a phenolic resin is used.

Additives such as thermosetting catalysts, inorganic particles (excluding magnetic particles), organic particles, and crosslinking agents can also be added to the magnetic composition as needed.

The proportion of binder and additives in the magnetic composition is the remainder of that of the magnetic particles described above.

Details of the magnetic composition are described, for example, in JP 2014-165363 A.

In the second step, the magnetic sheet 20 is first prepared from the magnetic composition described above, for example in the form of a substantially rectangular sheet. The magnetic sheet 20 has one side and the other side that are opposed in the thickness direction, parallel to each other, and flat. The magnetic sheet 20 is preferably prepared by first preparing a varnish of the magnetic composition, applying it to a release sheet (not shown) to prepare an A-stage sheet, and then heating it to prepare a B-stage sheet.

Then, the second outer surface 13 of each of the intermediate portions 10 (intermediate portions 10 including curved portions 11) of the multiple wirings 2 is covered with the magnetic sheet 20. Preferably, the intermediate portions 10 of each of the multiple wirings 2 are embedded in the magnetic sheet 20 of the B-stage sheet. Alternatively, the intermediate portions 10 of each of the multiple wirings 2 are embedded in the magnetic sheet 20 of the B-stage sheet. The magnetic sheet 20 in which the intermediate portions 10 are embedded forms the magnetic layer 3.

More specifically, in the second step, as shown in Figures 4A to 4B, a magnetic sheet 20 is prepared (manufactured) that includes a first magnetic sheet 21, a second magnetic sheet 22, and a third magnetic sheet 23, each of which is independent of the other. The planar shapes of the first magnetic sheet 21, the second magnetic sheet 22, and the third magnetic sheet 23 are the same as the magnetic sheet 20 described above. In addition, the planar dimensions of the first magnetic sheet 21, the second magnetic sheet 22, and the third magnetic sheet 23 are the same as one another.

As shown in FIG. 4A, a plurality of wirings 2 are separately placed on a horizontal stand (not shown) in the above-mentioned arrangement. Specifically, the first end 8 and the second end 9 of each of the plurality of wirings 2 are arranged so as to overlap when projected in the adjoining direction.

As shown in FIG. 4B, the middle portion 10 of each of the multiple wirings 2 is then covered with a first magnetic sheet 21 (preferably a first magnetic sheet 21 in B stage). More specifically, the first magnetic sheet 21 is pressed from one side in the thickness direction toward the middle portion 10. As a result, the entire second outer peripheral surface 13 of the middle portion 10 (except for the other edge in the thickness direction) is covered with the first magnetic sheet 21. Note that the first magnetic sheet 21 after pressing is still in B stage, for example, when the magnetic composition contains a thermosetting resin.

When viewed from the front (or in cross section), the first magnetic sheet 21 has a curved surface on one side in the thickness direction that corresponds to the wiring 2.

As shown in FIG. 4C, the second magnetic sheet 22 and the third magnetic sheet 23 (preferably the second magnetic sheet 22 and the third magnetic sheet 23 in the B stage, respectively, when the magnetic composition contains a thermosetting resin) are then placed on one side and the other side in the thickness direction of the intermediate portion 10 and the first magnetic sheet 21, respectively, and the second magnetic sheet 22 and the third magnetic sheet 23 are pressed against the intermediate portion 10 and the first magnetic sheet 21. Note that, after pressing, the second magnetic sheet 22 and the third magnetic sheet 23 are both still in the B stage, for example, when the magnetic composition contains a thermosetting resin.

In this way, the magnetic sheet 20, which includes the second magnetic sheet 22, the first magnetic sheet 21, and the third magnetic sheet 23 in order from one side to the other side in the thickness direction, is formed so as to cover the second outer peripheral surface 13 of the multiple wirings 2. Note that, as shown in FIG. 4C, the boundaries between the second magnetic sheet 22, the first magnetic sheet 21, and the third magnetic sheet 23 are clearly drawn, but for example, in the magnetic sheet 20, which is a laminated sheet of the second magnetic sheet 22, the first magnetic sheet 21, and the third magnetic sheet 23, the boundaries may not be clear, and more specifically, the boundaries may not be confirmed, as shown in FIG. 1D.

One side of the magnetic sheet 20 in the thickness direction has a flat surface.

On the other hand, the first end 8 and the second end 9 of each of the multiple wirings 2 are exposed from the magnetic sheet 20. Specifically, the first end 8 and the second end 9 protrude from one end face (tip face) 16 of the four peripheral end faces of the magnetic sheet 20.

As shown in FIG. 1C, the length L of each of the first end 8 and the second end 9 exposed from the magnetic sheet 20 is in the range of 2 mm or more and less than 100 mm.

If the length L is less than 2 mm, as shown in Figures 2E and 5, in the evaluation and inspection process (described below), the terminal 25 (described below) cannot be easily brought into contact with the first end 8 and the second end 9 of the wiring 2, making the electrical connection between the terminal 25 and the wiring 2 uncertain. Therefore, it is not possible to easily and reliably evaluate the magnetic properties of the inductor 1 and to perform a continuity test of the wiring 2.

On the other hand, if the length L is 100 mm or more, as shown in FIG. 2G, when considering removing the first end 8 and the second end 9 of the wiring 2 in the third step (described later), the length L of the first end 8 and the second end 9 to be removed cannot be suppressed to a range of less than 100 mm. Therefore, the amount of wiring to be removed cannot be suppressed, and therefore the yield of the wiring 2 decreases, and as a result, the inductor 1 cannot be manufactured at low cost.

In more detail, the range of length L is preferably 3 mm or more, more preferably 4 mm or more, even more preferably 5 mm or more, and even more preferably 10 mm or more, and is preferably 99 mm or less, more preferably 95 mm or less, even more preferably 75 mm or less, particularly preferably 50 mm or less, most preferably 40 mm or less, and even more preferably 25 mm or less.

After that, if the magnetic sheet 20 is still in B stage, it will be changed to C stage.

As shown in Figures 1C and 1D, this forms a magnetic layer 3 made of a magnetic sheet 20 so as to expose the first end 8 and second end 9 of each of the multiple wirings 2 and to cover the middle portion 10 of each of the multiple wirings 2.

By this second step, an inductor 30 is obtained that includes a plurality of wirings 2 and a magnetic layer 3 that forms the intermediate portion 10 of each of the plurality of wirings 2. In this inductor 30, the magnetic layer 2 contains magnetic particles, and the first end 8 and the second end 9 of each of the plurality of wirings 2 are exposed from the magnetic layer 3 in a direction perpendicular to the thickness direction of the magnetic layer 3 within a range of 2 mm or more and less than 100 mm.

As shown in Figures 2G and 2H, this inductor 30 is an assembly sheet for obtaining the inductor 1 described below, and is not the inductor 1 itself, but includes a first end 8 and a second end 9 in addition to multiple inductors 1. The inductor 30 is a device that can be distributed independently and is industrially applicable.

The thickness of the inductor 30 is the same as the thickness of the magnetic layer 3, specifically, for example, 5000 μm or less, preferably 1000 μm or less, and for example, 100 μm or more.

As shown in FIG. 2F, in the fourth step, the conductor 6 is exposed from the insulating layer 7 at the first end 8 and the second end 9 of each of the multiple wirings 2.

For example, the insulating layer 7 that faces one end of the first outer peripheral surface 12 of the conductor 6 in the thickness direction is removed at the first end 8 and the second end 9 by laser processing in which laser light is irradiated from one side in the thickness direction, thereby exposing one end of the first outer peripheral surface 12 of the conductor 6 in the thickness direction from the insulating layer 7.

Alternatively, one thickness-wise end of the first outer surface 12 of the conductor 6 can be exposed from the insulating layer 7 by polishing.

The evaluation and inspection process involves, for example, evaluating the inductance of multiple inductors 1 and testing the continuity of multiple wirings 2.

Specifically, a pair of terminals 25 are disposed on one side in the thickness direction of the first end 8 and the second end 9, and the other side in the thickness direction of the pair of terminals 25 is brought into contact with the first outer surface 12 of the conductor 6 exposed from the insulating layer 7 at the first end 8 and the second end 9.

The shape of the terminal 25 is not particularly limited, and examples include an approximately cylindrical shape with a relatively wide flat surface on the other end surface in the thickness direction, or a needle shape that extends long in the thickness direction of the inductor 30. From the viewpoints of convenience and ensuring a wide contact area with the conductor 6, an approximately cylindrical shape is preferred.

The terminal 25 is connected to an inspection device (specifically, an LCR meter, a vector network analyzer, an impedance analyzer, etc.) via a connection wire (not shown).

In evaluating inductance, impedance is measured while applying a weak current to a pair of terminals 25, and the measured value is substituted into a theoretical formula to calculate the inductance determined by one wiring 2 and the magnetic layer 3 around it.

In the continuity test of wiring 2, the resistance between a pair of terminals 25 is measured to check whether wiring 2 has continuity.

As shown in Figures 2G to 2H, in the third step, the first end 8 and the second end 9 of the wiring 2 are removed.

Specifically, the inductor 30 is cut so as to correspond to each of the multiple wirings 2 and be separated from the first end 8 and the second end 9, thereby obtaining the inductor 1.

At this time, rather than just removing the exposed first end 8 and second end 9, the inside of the magnetic layer 3 is also cut away.

For example, the wiring 2 and the magnetic layer 3 are cut so that a first cutting line 26 is formed on the inside of the peripheral end face of the magnetic layer 3 in a plan view, and the magnetic layer 3 is cut so that a second cutting line 27 is formed that passes between the adjacent first wiring 4 and second wiring 5. For example, dicing, laser processing, punching, etc. are used for the above cutting.

This results in multiple inductors 1 each having one wiring 2, covering the entire second outer peripheral surface 13 in the flow direction, and one magnetic layer 3. In other words, the inductor 1 is separated (cut out) from the inductor 30 so that the first end 8 and the second end 9 remain in the inductor 30. In other words, the inductor 1 is obtained by removing the first end 8 and the second end 9. Note that this inductor 1 preferably has only one wiring 2 and one magnetic layer 3.

The inductor 1 has, for example, a rectangular flat plate shape, and specifically has multiple (four) flat peripheral end surfaces. The inductor 1 does not include a first end 8 and a second end 9. The inductor 1 is a device that can be distributed independently and is industrially applicable.

At one end surface 18 of the four peripheral end surfaces of this inductor 1, the end surface of the wiring 2 and the end surface of the magnetic layer 3 are formed flush with each other.

The thickness of the inductor 1 is the same as the thickness of the magnetic layer 3 described above.

In the manufacturing method of this inductor 1, as shown in Figures 1C to 1D, in the second step, the magnetic layer 3 is formed so that the first end 8 and the second end 9 of the wiring 2 are exposed from the magnetic layer 3 by 2 mm or more. Therefore, as shown in Figures 2E to 2F, in the evaluation and inspection step after the second step, the terminal 25 can be easily brought into contact with the first end 8 and the second end 9 of the wiring 2, and the electrical connection between the terminal 25 and the wiring 2 is reliable. Therefore, the inductance of the inductors 1 and 30 can be evaluated, and the continuity test of the wiring 2 can be easily and reliably performed.

More specifically, since the first end 8 and the second end 9 of the wiring 2 are exposed from the magnetic layer 3 by 2 mm or more, terminals 25 having various shapes can be brought into contact with the conductor 6. As shown in Figs. 2F and 5, for example, not only a needle-shaped terminal 25 (solid line) with a sharp tip at the other end in the thickness direction, but also a terminal 25 (virtual line) having a roughly cylindrical shape can be brought into contact with the conductor 6. Therefore, regardless of the shape and/or size of the terminal 25, contact between the terminal 25 and the wiring 2 can be easily and reliably achieved. In other words, there is a high degree of freedom in the terminals 25 that can be used, and therefore inspection and evaluation using the terminals 25 are easy.

Conversely, if the first end 8 and the second end 9 of the wiring 2 are exposed from the magnetic layer 3 by less than 2 mm, it is possible to contact the needle-shaped terminal 25 (solid line) with the conductor 6, but it is difficult to contact the approximately cylindrical terminal 25 (virtual line) with the conductor 6.

As shown in Figures 1C and 1D, in the second step, the magnetic layer 3 is formed so that the first end 8 and the second end 9 of the wiring 2 are exposed from the magnetic layer 3 by less than 100 mm, and as shown in Figures 2G and 2H, in the third step, the first end 8 and the second end 9 of the wiring 2 are removed, so that the length L of the first end 8 and the second end 9 to be removed can be suppressed to a range of less than 100 mm. This makes it possible to suppress the amount (or length) of the wiring 2 to be removed, which results in an excellent yield of the wiring 2 and, as a result, allows the inductor 1 to be manufactured at low cost.

Therefore, this manufacturing method makes it possible to easily and reliably evaluate the inductance of the inductor 1 and perform a continuity test of the wiring 2, while manufacturing the inductor 1 at low cost.

In addition, with this manufacturing method, when the diameter D of the wiring 2 is small, such as 1000 μm or less, a thin inductor 1 can be manufactured.

On the other hand, in a method for manufacturing a thin inductor 1, if the end face of the wiring 2 and one end face 16 of the magnetic layer 3 are flush with each other, as in the inductor of Patent Document 1, it becomes even more difficult for the terminal 25 to subsequently contact the end face of the wiring 2.

However, in this first embodiment, as described above, in the second step, the magnetic layer 3 is formed so that the first end 8 and the second end 9 of the wiring 2 are exposed from the magnetic layer 3 over a range of 2 mm or more. Therefore, even if the diameter D of the wiring 2 is small, such as 500 μm or less, the terminal 25 can be easily brought into contact with the first end 8 and the second end 9.

This allows the terminal 25 to easily come into contact with the first end 8 and the second end 9 of the wiring 2, while still allowing the manufacture of a thin inductor 1.

In addition, as shown in FIG. 1C, in the second step of this first embodiment, the first end 8 and the second end 9 of the wiring 2 are exposed from the magnetic layer 3. Therefore, after the second step, in the evaluation inspection step shown in FIG. 2E, each of the two terminals 25 can be easily brought into contact with each of the first end 8 and the second end 9 of the wiring 2, and the electrical connection between the two terminals 25 and the wiring 2 is reliable.

As shown in FIG. 1B, in the first step of this first embodiment, a wiring 2 is prepared that includes a conductor 6 and an insulating layer 7 that covers the first outer surface 12 of the conductor 6. However, as shown in FIG. 2F and FIG. 5, in the fourth step, the conductor 6 is exposed from the insulating layer 7 at the first end 8 and the second end 9 of the wiring 2. This allows the terminal 25 to easily contact the conductor 6 at the first end 8 and the second end 9 of the wiring 2, and ensures a reliable electrical connection between the terminal 25 and the conductor 6.

In the inductor 30 of the first embodiment shown in Figures 1C to 1D, the first end 8 and second end 9 of each of the multiple wirings 2 are exposed from the magnetic layer 3 by 2 mm or more. Therefore, as shown in Figures 2E to 2F, the terminal 25 can be easily brought into contact with the first end 8 and second end 9 of the wiring 2, and the electrical connection between the terminal 25 and the wiring 2 is reliable. Therefore, the inductance of the inductor 1 can be evaluated and the continuity of the wiring 2 can be easily and reliably tested.

In addition, since the first end 8 and second end 9 of each of the multiple wirings 2 are exposed from the magnetic layer 3 within a range of less than 100 mm, even if the inductor 30 is divided into individual pieces corresponding to each of the multiple wirings 2 so as to remove the first end 8 and second end 9, and the inductor 1 is manufactured, the amount of wiring removed can be reduced, and as a result, multiple inductors 1 can be manufactured at low cost.

In the following modified examples, the same reference numerals are used for the same components and steps as those in the first embodiment, and detailed descriptions thereof will be omitted. In addition, each modified example can achieve the same effects as those in the first embodiment, unless otherwise specified. Furthermore, the first embodiment and the modified examples can be appropriately combined.

As shown in Figures 2E and 5, in the fourth step of the first embodiment, the insulating layer 7 that faces one end in the thickness direction of the first outer peripheral surface 12 of the conductor 6 at the first end 8 and the second end 9 is removed to expose one end in the thickness direction of the first outer peripheral surface 12 of the conductor 6 from the insulating layer 7.

As shown in FIG. 6, in this modified example, the insulating layer 7 facing the entire first outer surface 12 of the conductor 6 can be removed to expose the entire first outer surface 12 of the conductor 6 from the insulating layer 7. In other words, in the fourth step, the entire insulating layer 7 at the first end 8 and the second end 9 can be removed.

Also, as shown in FIG. 1C, in the first embodiment, in the second step (inductor 30), both the first end 8 and the second end 9 are exposed from the magnetic layer 3. However, although not shown, it is also possible to expose only one of the first end 8 and the second end 9 from the magnetic layer 3.

As shown in FIG. 5, the cross-sectional shape of the wiring 2 (or the front view shape of the first end 8 and the second end 9) is approximately circular, but in a modified example, it is approximately rectangular as shown in FIG. 7. Specifically, in the inductor 30, each of the first end 8 and the second end 9 has an approximately box shape.

The thickness T2 of the wiring 2 in this modified example is the same as the diameter D of the wiring 2 in the first embodiment.

In addition, in this modified example, the corners of the wiring 2 in a cross-sectional view (e.g., corners formed by one side in the thickness direction and both outer sides in the adjacent direction (the direction in which the first wiring 4 and the second wiring 5 are adjacent)) can also have a curved shape, for example.

As shown in Figures 4A to 4C, in the first embodiment, the magnetic layer 3 is formed as a laminated sheet of three magnetic sheets (first magnetic sheet 21, second magnetic sheet 22, and third magnetic sheet 23), but the number is not limited and may be one, two, or four or more.

In the second step of the first embodiment, the wiring 2 is covered with the magnetic sheet 20 (magnetic layer 3) formed into a sheet shape, but it is also possible to form the magnetic layer 3 by, for example, applying a varnish of a magnetic composition to the wiring 2 and then forming the magnetic composition into a sheet shape.

As shown in FIG. 2G, in the third step of one embodiment, the intermediate portion 10 of the wiring 2 that is embedded in the magnetic layer 3 is cut. In other words, the inductor 30 is cut so that the first cutting line 26 is formed.

However, in this modified example, as shown in FIG. 8, it is also possible to cut the portion of the wiring 2 that is not embedded in the magnetic layer 3 (specifically, the boundary portion between the wiring 2 and the intermediate portion 10). The wiring 2 is cut so that a third cutting line 28 is formed along the end face of the inductor 30.

As shown in FIG. 2G, in the third step of one embodiment, the magnetic layer 3 is cut so as to separate the multiple wirings 2, i.e., so as to form the second cutting lines 27.

As shown in FIG. 9, in the modified example, the multiple wirings 2 are not separated into individual pieces, that is, the magnetic layer 3 is cut so that the second cutting lines 27 are not formed. The inductor 1 obtained by the third process has multiple wirings 2.

In the modified example shown in Figure 9, the magnetic layer 3 and wiring 2 are cut.

However, in a modified example, as shown in FIG. 10, it is also possible to cut only the wiring 2 without cutting the magnetic layer 3. The wiring 2 is cut so that the third cutting line 28 is formed.

In one embodiment, an inductor 30 is fabricated that includes multiple wirings 2, as shown in FIG. 1C.

However, as shown in Figures 11A and 11B, in a modified example, an inductor preparation sheet 15 having one wiring 2 can be produced.

As shown in FIG. 11A, in the third step, the wiring 2 and the magnetic layer 3 are cut so as to form a first cutting line 26.

Alternatively, as shown in FIG. 11B, in the third step, the wiring 2 is cut so as to form a third cutting line 28.

In one embodiment, the evaluation and inspection process involves both evaluating the inductance of the inductor 1 and inspecting the continuity of the wiring 2, but it is also possible to perform only one of them.

The proportion of magnetic particles in the magnetic layer 3 may be uniform throughout the magnetic layer 3, or may increase or decrease with increasing distance from each wiring 2. To manufacture an inductor 1 in which the proportion of magnetic particles in the magnetic layer 3 increases with increasing distance from the wiring 2, for example, as shown in FIG. 4B, the proportion of magnetic particles in the second magnetic sheet 22 and the proportion of magnetic particles in the third magnetic sheet 23 are set higher than the proportion of magnetic particles in the first magnetic sheet 21.

Second Embodiment
In the second embodiment described below, the same reference numerals are used for the same components and steps as those in the first embodiment and its modified examples, and detailed descriptions thereof will be omitted. In addition, the second embodiment can achieve the same effects as those in the first embodiment and its modified examples, unless otherwise specified. Furthermore, the first embodiment, its modified examples, and the second embodiment can be appropriately combined.

In the first embodiment, the wiring 2 shown in FIG. 1A and prepared in the first step (see FIG. 1A), and the wiring 2 in the inductor 30 shown in FIG. 1C and fabricated in the second step (FIG. 1C) have a generally U-shaped shape in plan view.

However, the planar shape of wiring 2 is not limited to the above.

For example, as shown in FIG. 12, in the second embodiment, the wiring 2 has a generally zigzag shape in plan view.

The intermediate portion 10 of the wiring 2 also has a generally zigzag shape in plan view, and more specifically, has bent portions 14 that are bent in plan view. A plurality of bent portions 14 are arranged at intervals in the intermediate portion 10 in the direction of electrical flow.

In the inductor 30, the first end 8 and the second end 9 are exposed from each of the four peripheral end faces of the magnetic layer 3, one end face (front end face) 16 and the other end face (rear end face) 17 which face each other with a gap between them.

Third Embodiment
In the following third embodiment, the same reference numerals are used for the same members and steps as those in the first embodiment, its modified example, and the second embodiment, and detailed description thereof will be omitted. In addition, the third embodiment can achieve the same effects as those in the first embodiment, its modified example, and the second embodiment, unless otherwise specified. Furthermore, the first embodiment, its modified example, the second embodiment, and the third embodiment can be appropriately combined.

As shown in FIG. 1C, in the first embodiment, the entire flow direction of the midsection 10 of the inductor 30 is embedded in the magnetic layer 3.

As shown in FIG. 13, in the third embodiment, a portion of the flow direction in the intermediate portion 10 can be exposed from the magnetic layer 3.

Specifically, in the inductor 30, the curved portion 11, which corresponds to the approximate center portion 18 in the flow direction of the intermediate portion 10 (wiring 2), is exposed from the other end surface 17 of the magnetic layer 3.

In the evaluation inspection process, the terminal 25 is not brought into contact with the curved portion 11, but is brought into contact with the first end 8 and the second end 9.

In the third step, the first end 8 and the second end 9 are removed, while the wiring 2 and the magnetic layer 3 are cut so that the curved portion 11 remains. In other words, the curved portion 11 is attached to the inductor 1.

This results in an inductor 1 having a magnetic layer 3, a curved portion 11 exposed from the magnetic layer 3, and a wiring 2 having a portion embedded in the magnetic layer 3 (the portion of the intermediate portion 10 other than the curved portion 11).

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is in no way limited to the examples and comparative examples. Furthermore, the specific numerical values of the compounding ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding compounding ratio (content ratio), physical property value, parameter, etc. described in the above "Form for carrying out the invention".

Example 1
As shown in FIGS. 1A to 2D, the first and second steps were carried out in order to obtain the inductor 30 shown in FIGS. 1C and 1D.

As shown in Figures 1A and 1B, in the first step, multiple wirings 2 with a diameter D of 220 μm (radius R2 of 110 μm) were prepared. In more detail, multiple wirings 2 each having a conductor 6 with a radius R1 of 100 μm and an insulating layer 7 with a thickness T1 of 10 μm were prepared and placed on a horizontal stand (not shown) so that they were U-shaped in plan view.

Separately, the middle portion 10 of the conductor 6 was covered with a magnetic sheet 20 (more specifically, a laminated sheet of a first magnetic sheet 21, a second magnetic sheet 22, and a third magnetic sheet 23 (see Figures 4A to 4C) containing magnetic particles and a binder. The magnetic sheet 20 was formed into a sheet shape so that the first end portion 8 and the second end portion 9 were exposed.

As shown in FIG. 1C, the length L of each of the first end 8 and the second end 9 was 10 mm.

As shown in Figures 2E to 2H, the fourth and third steps were then carried out in sequence to obtain inductor 1.

Example 2 to Comparative Example 2
Inductor 30 was produced in the same manner as in Example 1, except that the length L was changed according to the description in Table 1, and then inductor 1 was obtained.

[Ease of testing in the testing and evaluation process]
The inductors 30 of the examples and comparative examples were evaluated for inspectability during manufacture according to the following criteria. The results are shown in Table 1.
Both the needle-shaped terminal 25 having a diameter of 5 mm and the cylindrical terminal 25 having a diameter of 5 mm were able to come into contact with the first end 8 and the second end 9, the inductance of the inductor 1 was able to be measured, and a continuity test of the wiring 2 was able to be performed.
△ The needle-shaped terminal 25 with a diameter of 5 mm was able to come into contact with the first end 8 and the second end 9, and was able to measure the inductance of the inductor 1 and perform a continuity test of the wiring 2. However, the cylindrical terminal 25 with a diameter of 5 mm was not able to come into contact with the first end 8 and the second end 9, and was unable to measure the inductance of the inductor 1 and was also unable to perform a continuity test of the wiring 2.
× Neither the needle-shaped terminal 25 having a diameter of 5 mm nor the cylindrical terminal 25 having a diameter of 5 mm could come into contact with the first end 8 and the second end 9, so the inductance of the inductor 1 could not be measured, and no continuity test of the wiring 2 could be performed.

[Manufacturing costs]
The amount of the first end 8 and the second end 9 removed in the fourth step of each example and each comparative example was measured, and the manufacturing cost was evaluated according to the following criteria. The results are shown in Table 1.
○: The length L of each of the first end 8 and the second end 9 of the wiring 2 is 40 mm or less. △: The length L of each of the first end 8 and the second end 9 of the wiring 2 is more than 40 mm and less than 100 mm. ×: The length L of each of the first end 8 and the second end 9 of the wiring 2 is 100 mm or more.

Reference Signs List 1 Inductor 2 Wiring 3 Magnetic layer 6 Conductor 7 Insulating layer 8 First end 9 Second end 10 Midway portion 13 Second outer peripheral surface 30 Inductor L Length of end D Diameter T2 of wiring with approximately circular cross section Thickness of wiring with approximately rectangular cross section

Claims (4)

A first step of preparing wiring having a conductor and an insulating layer covering the conductor, the insulating layer being made of an insulating resin;
a second step of forming a magnetic layer from a magnetic composition containing magnetic particles so as to cover the outer peripheral surface of the intermediate portion of the wiring and to expose the end portion of the wiring from the magnetic layer within a range of 2 mm or more and less than 100 mm;
an evaluation and inspection process in which a terminal connected to an inspection device is brought into contact with an outer peripheral surface of an end of the wiring and the wiring is inspected using the inspection device; and
A method for manufacturing an inductor, comprising a third step of removing the end of the wiring after the evaluation and inspection step. The method for manufacturing an inductor according to claim 1, characterized in that the length of the wiring in the thickness direction of the inductor is 1000 μm or less. The method for manufacturing an inductor according to claim 1 or 2, characterized in that in the second step, both ends of the wiring are exposed from the magnetic layer. In the first step, the wiring is prepared, the wiring including a conductor and an insulating layer covering an outer peripheral surface of the conductor;
4. The method for manufacturing an inductor according to claim 1, further comprising a fourth step, after the second step and before the third step, of exposing the conductor from the insulating layer at the end of the wiring.

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