JP7471770B2 - Inductor and method for manufacturing the inductor - Google Patents

Description

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

Small electronic devices such as smartphones and tablet terminals use a variety of electronic components. One of these components is the inductor. Inductors are used, for example, in multi-phase DC-DC converters that supply power to CPUs (Central Processing Units).

There are various types of inductor structures, but the most widely used type is the wound type, which has a coil wound around a magnetic core.

JP 2003-168610 A

However, wound-type inductors are difficult to make thin because the volume occupied by the magnetic core is large, which is disadvantageous in miniaturizing electronic devices.

In one aspect, the present invention aims to make the inductor thinner.

According to one aspect, an inductor is provided which comprises a magnetic body containing magnetic powder and an insulating resin, a plurality of linear conductors whose surfaces are covered with an insulating layer and embedded in the magnetic body, a first electrode provided at one end of each of the conductors and a portion of which is exposed from the surface of the magnetic body, and a second electrode provided at the other end of each of the conductors and a portion of which is exposed from the surface of the magnetic body , wherein the conductors have an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and in a cross section cut in a direction perpendicular to the extension direction of the conductor and in the thickness direction of the conductor, a central portion of the side surface in the thickness direction protrudes laterally beyond the upper surface and the lower surface .

According to one aspect, it is possible to achieve a thinner inductor.

FIG. 2 is a plan view of a metal plate used in the first embodiment. 1A to 1C are cross-sectional views (part 1) of the inductor according to the first embodiment during manufacturing; 6 is a cross-sectional view (part 2) of the inductor according to the first embodiment during manufacturing; FIG. 5 is a cross-sectional view (part 3) of the inductor according to the first embodiment during manufacturing; FIG. 4 is a cross-sectional view (part 4) of the inductor according to the first embodiment during manufacturing; FIG. 5 is a cross-sectional view (part 5) of the inductor according to the first embodiment during manufacturing; FIG. 6 is a cross-sectional view (part 6) of the inductor according to the first embodiment during manufacturing; FIG. 1 is a plan view (part 1) of the inductor according to the first embodiment during manufacturing; FIG. FIG. 2 is a second plan view of the inductor according to the first embodiment during manufacturing; 11 is a plan view (part 3) of the inductor according to the first embodiment during manufacturing; FIG. FIG. 4 is a plan view (part 4) of the inductor according to the first embodiment during manufacturing; 5 is a plan view (part 5) of the inductor according to the first embodiment during manufacturing; FIG. FIG. 6 is a plan view (part 6) of the inductor according to the first embodiment during manufacturing; FIG. 7 is a plan view (part 7) of the inductor according to the first embodiment during manufacturing; 2 is a side view of the inductor according to the first embodiment as viewed from the first electrode side and the second electrode side. FIG. 1 is a perspective view of an inductor according to a first embodiment; 1A and 1B are plan views each showing a schematic diagram of a method of using an inductor. 1 is a cross-sectional view of an electronic device including an inductor according to a first embodiment. 1A to 1C are plan views (part 1) illustrating modified examples of the conductor in the inductor according to the first embodiment. FIG. 11 is a plan view (part 2) illustrating a modified example of the conductor in the inductor according to the first embodiment. FIG. 11 is a plan view (part 3) illustrating a modified example of the conductor in the inductor according to the first embodiment. 11A to 11C are cross-sectional views (part 1) of the inductor according to the second embodiment during manufacturing; 13 is a plan view (part 1) of an inductor according to a second embodiment during manufacturing; FIG. FIG. 13 is a second plan view of the inductor according to the second embodiment during manufacturing; FIG. 11 is a plan view (part 3) of the inductor according to the second embodiment during manufacturing; 13 is a cross-sectional view (part 2) of the inductor according to the second embodiment during manufacturing; FIG. 13 is a cross-sectional view (part 3) of the inductor according to the second embodiment during manufacturing; FIG. 13A to 13C are cross-sectional views of an inductor according to a first modified example of the second embodiment during its manufacture. 13A to 13C are cross-sectional views of an inductor according to a second modified example of the second embodiment during its manufacture. FIG. 11 is a cross-sectional view (part 1) of an inductor according to a second modification of the second embodiment. FIG. 13 is a second cross-sectional view of an inductor according to Modification 2 of the second embodiment. 11 is a cross-sectional view of an electronic device including an inductor according to a second embodiment.

Below, a description will be given of an embodiment of the invention with reference to the drawings. Note that in each drawing, the same components are given the same reference numerals, and duplicate descriptions may be omitted.

First Embodiment
The inductor according to this embodiment will be described in detail with reference to its manufacturing method.

Figure 1 is a plan view of the metal plate used in the first embodiment.

This metal plate 1 is, for example, a copper plate with a thickness of about 0.2 mm for a lead frame, and has multiple product regions R. Each product region R has multiple rectangular element regions C from which individual inductors will later be cut out. In this example, multiple element regions C are arranged in a grid pattern in one product region R.

The material of the metal plate 1 is not limited to copper, and a copper alloy may be used as the material of the metal plate 1. Furthermore, an Fe-Ni alloy such as alloy 42 may be used as the material of the metal plate 1.

In this embodiment, an inductor is formed in element region C of metal plate 1 as follows.

Figures 2 to 7 are cross-sectional views of the inductor according to the first embodiment during manufacturing, and Figures 8 to 14 are plan views thereof.

In addition, in Figures 2 to 7, the first cross section taken along line A-A in Figures 8 to 14 and the second cross section taken along line B-B are shown together.

First, as shown in FIG. 2(a) and FIG. 8, an island-shaped first resist layer 2 is formed on the front surface 1a of the metal plate 1, and the back surface 1b of the metal plate 1 is covered with a second resist layer 3.

Next, as shown in FIG. 2(b), while using each of the resist layers 2 and 3 as a mask, the metal plate 1 in the portion not covered by the first resist layer 2 is wet etched to a depth halfway through its thickness. As a result, the island-shaped first terminal 1x and second terminal 1y are formed at a distance from each other on the metal plate 1 under the first resist layer 2, and the thickness t of the metal plate 1 other than the terminals 1x and 1y is reduced to about 0.1 mm.

Then, each resist layer 2 and 3 is removed.

Figure 9 is a plan view of the metal plate 1 after the resist layers 2 and 3 have been removed.

As shown in FIG. 9, the first terminal 1x and the second terminal 1y are arranged at intervals along the edge of the rectangular element region C. Each of the terminals 1x and 1y is a square with a side length W1 of about 0.2 mm.

Next, as shown in Figures 3(a) and 10, a third resist layer 6 is formed on the front surface 1a of the metal plate 1, and a fourth resist layer 7 is formed on the rear surface 1b in a portion opposite the third resist layer 6.

As shown in FIG. 10, the third resist layer 6 extends in a serpentine manner from the first terminal 1x to the second terminal 1y.

Next, as shown in FIG. 3(b), the metal plate 1 is patterned by wet etching from both sides of the metal plate 1 using each of the resist layers 6 and 7 as a mask, thereby forming multiple conductors 1w on the metal plate 1.

The wet etching proceeds isotropically, so that the conductor 1w has a roughly rectangular shape with the center of the side surface protruding to the side and flat top and bottom surfaces, as shown in the dotted circle.

In addition, instead of wet etching, the metal plate 1 may be patterned by die punching or laser processing.

Furthermore, the upper surfaces of the first terminal 1x and the second terminal 1y are arranged to protrude from the surface of the conductor 1w.

Then, each resist layer 6, 7 is removed.

Figure 11 is a plan view of the metal plate 1 after the resist layers 6 and 7 have been removed in this manner.

As shown in FIG. 11, a frame 1d is provided in the element region C, and multiple conductors 1w are supported by the frame 1d. Each conductor 1w is made of a linear metal plate that meanders along the same extension direction D, and has a first terminal 1x at one end and a second terminal 1y at the other end.

Furthermore, each conductor 1w has a meandering portion 1e and a straight portion 1f. Of these, the straight portion 1f extends along the extension direction D. Also, the meandering portion 1e is provided so as to bend left and right from the straight portion 1f in a plan view. Note that the straight portion 1f may be omitted, and each conductor 1w may be formed only with the meandering portion 1e.

The width W2 of each conductor 1w is not particularly limited, but in this example, the width W2 is approximately 0.1 mm.

Next, as shown in FIG. 4(a), an insulating layer 9 of epoxy resin with a dielectric constant of about 1.8 is formed on the surface of the conductor 1w and each of the terminals 1x and 1y to a thickness of about 10 μm by electrocoating, and the surfaces of the conductor 1w and each of the terminals 1x and 1y are covered with the insulating layer 9.

The material of the insulating layer 9 is not limited to epoxy resin, and other insulating resins such as polyimide resin may be used as the material.

Next, as shown in FIG. 4(b), the metal plate 1 is placed between the lower die 15 and the upper die 16 of the hot press machine, and the metal plate 1 is filled with powder 18 made by kneading magnetic powder 18a and insulating resin 18b. Note that the powder 18 under the metal plate 1 may be preformed into a plate shape before this process, and the metal plate 1 may be placed on top of it.

The insulating resin 18b is a binder (bonding material), and may be, for example, a thermosetting resin or a thermoplastic resin such as epoxy resin, polyimide resin, phenolic resin, or acrylic resin. Furthermore, the material of the magnetic powder 18a is not particularly limited, and a powder of a soft magnetic material may be used as the magnetic powder 18a. Examples of such magnetic powder 18a include powders of carbonyl iron powder, ferrite, and permalloy.

Then, while heating the powder 18 in this state to about 160°C, a pressure of about 200 MPa is applied to the powder 18 from each of the lower die 15 and the upper die 16, and the powder 18 is molded under high pressure into a flat plate-shaped magnetic material 19.

The magnetic body 19 thus formed contains both magnetic powder 18a and insulating resin 18b.

In addition, as shown in the dotted circle in FIG. 3(b), in this example, the side surface of the conductor 1w protrudes laterally, increasing the contact area between the conductor 1w and the magnetic body 19 and improving the adhesion between the conductor 1w and the magnetic body 19.

In this example, the magnetic body 19 is formed by high-pressure molding of the powder 18, but the method of forming the magnetic body 19 is not limited to this. For example, a laminate may be made by sandwiching the metal plate 1 between two magnetic films, and the laminate may be heated to about 100°C in a vacuum while being pressed at a pressure of about 0.8 MPa to turn the magnetic film into the magnetic body 19. An example of such a magnetic film is a film made by molding a magnetic material made by kneading carbonyl iron powder with an insulating resin as a binder into a sheet. In this case, after forming the magnetic body 19 as described above, the binder may be thermally cured by performing a heat treatment at a heating temperature of about 180°C for about one hour.

The insulating resin to be used as the binder is not particularly limited. For example, thermosetting resins and thermoplastic resins such as epoxy resin, polyimide resin, phenolic resin, and acrylic resin can be used as the insulating resin.

Furthermore, the powder to be kneaded into the magnetic film is not limited to the carbonyl iron powder described above, and powder of a soft magnetic material such as ferrite or permalloy can be kneaded into the magnetic film.

Then, as shown in Figures 5(a) and 12, the metal plate 1 is removed from between the lower mold 15 and the upper mold 16. Note that in Figure 12, the insulating layer 9 has been omitted to avoid complicating the illustration. This also applies to Figures 13 and 14 described below.

Next, as shown in FIG. 5(b) and FIG. 13, the surface 19a of the magnetic body 19 is polished by brush polishing or blasting to remove the insulating layer 9 and the magnetic body 19 from above each terminal 1x, 1y, thereby exposing a portion of each terminal 1x, 1y on the surface 19a of the magnetic body 19.

In this embodiment, the metal plate 1 is etched halfway to form the terminals 1x and 1y as shown in FIG. 2(b), resulting in a structure in which the terminals 1x and 1y protrude above the conductor 1w, making it easier to expose the terminals 1x and 1y from the top surface of the magnetic body 19.

Next, as shown in FIG. 6(a), a fifth resist layer 21 having openings 21a and 21b overlapping with the terminals 1x and 1y is formed on the front surface 19a of the magnetic body 19. At the same time, a sixth resist layer 22 is formed on the back surface 19b of the magnetic body 19, and the back surface 19b is covered with the sixth resist layer 22.

Then, as shown in FIG. 6(b), by supplying electricity to the metal plate 1, a nickel layer and a tin layer are formed in this order as a metal plating layer 23 on the surface of each terminal 1x, 1y in the portion exposed from each opening 21a, 21b by electrolytic plating.

As a result, the first electrode 24 is formed by the first terminal 1x and the metal plating layer 23, and the second electrode 25 is formed by the second terminal 1y and the metal plating layer 23.

The thickness of the metal plating layer 23 is not particularly limited; for example, the nickel layer can be formed to a thickness of about 2 μm, and the tin layer can be formed to a thickness of about 5 μm.

In addition to functioning as an anti-oxidation layer for each of the terminals 1x and 1y, the metal plating layer 23 also has the function of improving the wettability of the solder in each of the electrodes 24 and 25. Examples of the metal plating layer 23 having such a function include a laminated film in which a nickel layer and a gold layer are laminated in this order, and a laminated film in which a silver layer and a tin layer are laminated in this order.

Then, as shown in FIG. 7(a), the fifth resist layer 21 and the sixth resist layer 22 are removed.

Then, as shown in FIG. 7(b) and FIG. 14, the metal plate 1 and the magnetic body 19 are cut along the cutting line S to complete the basic structure of the inductor 30 according to this embodiment.

As shown in FIG. 14, the magnetic body 19 is a square (rectangular) with a side length of about 2.5 mm in plan view, and its surface 19a has a first edge 19x and a second edge 19y that face each other. A plurality of first electrodes 24 are exposed at the first edge 19x, and a plurality of second electrodes 25 are exposed at the second edge 19y.

Each conductor 1w is made of metal plate 1 and is formed to extend in one direction from the first edge 19x to the second edge 19y. Furthermore, each conductor 1w is arranged to meander in a plan view, which increases the inductance of each conductor 1w compared to when each conductor 1w is linear.

Although the magnetic body 19 has a certain degree of electrical conductivity, in this embodiment, the surface of the conductor 1w is covered with an insulating layer 9 (see FIG. 7(b)), so that the magnetic body 19 can prevent the conductors 1w from electrically shorting out.

In addition, in this example, the connection portion 1p between the straight portion 1f of the conductor 1w and the first electrode 24 tapers toward the first electrode 24. Similarly, the connection portion 1q between the straight portion 1f and the second electrode 25 tapers toward the second electrode 25. Therefore, after the inductor 30 is mounted on a circuit board (not shown), the mechanical stress applied to these connection portions 1p, 1q is alleviated, preventing cracks from occurring in each connection portion 1p, 1q, thereby improving the reliability of the inductor 30.

Figure 15(a) is a side view of the inductor 30 as viewed from the first electrode 24 side, and Figure 15(b) is a side view of the inductor 30 as viewed from the second electrode 25 side.

As shown in Figures 15(a) and (b), the side surfaces of terminals 1x and 1y that form each electrode 24 and 25 are exposed on the side surface of the inductor 30.

Figure 16 is a perspective view of the inductor 30.

As shown in FIG. 16, the inductor 30 has a flat or rectangular appearance suitable for surface mounting, and has multiple conductors 1w embedded in a magnetic body 19. The inductance of each conductor 1w can be adjusted by the magnetic permeability of the magnetic body 19, the shape of the conductors 1w, etc.

In this embodiment, by forming each conductor 1w from the metal plate 1 as described above and molding the magnetic body 19 into a flat plate, the thickness T of the inductor 30 can be reduced to approximately 0.3 mm, which contributes to the miniaturization of electronic devices equipped with the inductor 30.

In addition, as in the examples of Figures 14 and 16, by making the meandering shapes of multiple conductors 1w coincident, even if the spacing between adjacent conductors 1w is narrowed, contact between adjacent conductors 1w can be prevented. This makes it possible to narrow the spacing between adjacent conductors 1w, thereby enabling further miniaturization of the inductor 30.

Figures 17(a) and (b) are plan views that show a schematic diagram of how the inductor 30 can be used.

In the example of FIG. 17(a), multiple conductors 1w of the inductor 30 are connected in parallel with wiring 29. This reduces the overall resistance of the inductor 30, and allows the inductor 30 to be used in high-current applications such as a power supply circuit that supplies power to a CPU.

As shown in the example of FIG. 17(b), wiring 29 may be individually connected to each of the multiple conductors 1w, and each conductor 1w may be used independently.

Figure 18 is a cross-sectional view of an electronic device equipped with this inductor 30.

This electronic device 40 is, for example, a multiphase DC-DC converter for supplying power to a CPU, and includes an inductor 30 and a circuit board 33.

The circuit board 33 has an insulating layer 31 and electrode pads 32 formed thereon. A solder resist layer 34 having openings 34a that overlap the electrode pads 32 is formed on the insulating layer 31, and the electrodes 24, 25 of the inductor 30 are connected to the electrode pads 32 through the openings 34a via solder 36.

At this time, in this embodiment, the surface and side of the first electrode 24 are exposed to the surface of the magnetic body 19, and the surface and side of the second electrode 25 are also exposed to the surface of the magnetic body 19. Therefore, the solder 36 creeps up from the surface of each electrode 24, 25 to the side of each electrode 24, 25, forming a solder meniscus. This increases the bonding area between each electrode 24, 25 and the solder 36, increases the bonding strength between each electrode 24, 25 and the electrode pad 32, and ultimately improves the reliability of the electronic device 40.

Furthermore, in this embodiment, the inductor 30 is made thinner as described above, so the entire electronic device 40 can also be made smaller.

In addition, by embedding multiple conductors 1w in one magnetic body 19 as in this example, it becomes easier to reduce the mounting area compared to mounting each conductor 1w individually on the circuit board 33, and further miniaturization of the electronic device 40 can be achieved.

<Modification of the First Embodiment>
In the modified example of the first embodiment, a modified conductor constituting the inductor is shown. Note that in the modified example of the first embodiment, the description of the same components as those in the embodiment already described may be omitted.

Figure 19(a) is a plan view of an inductor with one conductor. Also, Figure 19(b) is a plan view of an inductor with two conductors. Also, Figure 19(c) is a plan view of an inductor with three conductors.

For example, in the first embodiment, the number of conductors 1w provided in the inductor 30 is four, but the number of conductors 1w may be one, two, or three, as shown in the plan views of Figures 19(a) to (c), or five or more conductors 1w may be provided in the inductor 30.

Furthermore, in the first embodiment, the conductor 1w is made to meander between each of the electrodes 24, 25, but the inductance of each conductor 1w may be reduced by forming the conductor 1w in a straight line between each of the electrodes 24, 25 as shown in the plan view of FIG. 20(a).

Also, as shown in the plan view of FIG. 20(b), a meandering conductor 1w and a straight conductor 1w may be mixed in one inductor 30. This makes it possible to obtain an inductor 30 having multiple conductors 1w with different inductances, thereby expanding the range of uses for the inductor 30.

Furthermore, as shown in the plan view of Figure 21, multiple conductors 1w with different meandering shapes may be provided.

The modified examples described with reference to Figures 19 to 21 can be applied not only to inductor 30, but also to inductors 30A, 30B, 30C, 30D, and 30E described below.

Second Embodiment
In the second embodiment, an example in which the heights of the first electrode and the second electrode are made higher than those in the first embodiment will be described. Note that in the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

The first electrode and the second electrode appear only in the first cross section and not in the second cross section, so in the second embodiment, the following explanation will be given with reference to the plan view and the cross-sectional view showing the first cross section along line A-A as appropriate.

First, a metal plate 20 having the same planar shape as the metal plate 1 shown in FIG. 1 is prepared, and the same process as that described in the first embodiment with reference to the cross-sectional view of FIG. 2 and the plan view of FIG. 8 is carried out on the metal plate 20, and then the resist layers 2 and 3 are removed. As a result, as shown in the cross-sectional view of FIG. 22(a), a plurality of third terminals 20x and fourth terminals 20y protruding from the surface 20a are formed on the metal plate 20. Note that the plan view corresponding to FIG. 22(a) is the same as FIG. 9. The material and thickness of the metal plate 20 can be the same as those of the metal plate 1, for example.

Next, as shown in the cross-sectional view of FIG. 22(b) and the plan view of FIG. 23, a seventh resist layer 300 is formed on the front surface 20a of the metal plate 20. Specifically, the seventh resist layer 300 is formed on the front surface 20a of the metal plate 20 so as to cover the third terminal 20x and the fourth terminal 20y, as well as the portion of the front surface 20a of the metal plate 20 that is more peripheral than the third terminal 20x and the fourth terminal 20y. In addition, an eighth resist layer 310 is formed at a position that overlaps with the seventh resist layer 300 in a plan view on the rear surface 20b of the metal plate 20.

Next, as shown in the cross-sectional view of FIG. 22(c), the metal plate 20 is patterned by wet etching from both sides of the metal plate 20 using the resist layers 300 and 310 as masks. Note that instead of wet etching, the metal plate 20 may be patterned by die punching or laser processing.

Next, by removing each resist layer 300, 310, a plurality of third terminals 20x and fourth terminals 20y supported by the frame body 20d are formed in the element region C as shown in the plan view of FIG. 24. As in the first embodiment, each of the third terminals 20x and fourth terminals 20y is arranged at intervals along the edge of the rectangular element region C. Also, the third terminals 20x and fourth terminals 20y are, for example, square-shaped with a side length W3 of about 0.2 mm. Also, for example, the thickness of the frame body 20d is about 0.1 mm, and the thickness of the third terminals 20x and fourth terminals 20y is about 0.2 mm (the same as the thickness of the metal plate 20 before etching).

Next, a metal plate 10 having the same planar shape as the metal plate 1 shown in FIG. 1 is prepared, and instead of carrying out the process described in the first embodiment with reference to the cross-sectional view of FIG. 2, a process similar to the process described with reference to the cross-sectional view of FIG. 3 and the plan views of FIG. 8 to FIG. 11 is carried out. As a result, a structure is produced in which multiple conductors 10w are supported by a frame body 10d provided in the element region C, as shown in the plan view of FIG. 25.

Each conductor 10w is made of a linear metal plate that meanders along the same extension direction D, and has a first terminal 10x at one end and a second terminal 10y at the other end. Each conductor 10w is further provided with a meandering portion 10e and a straight portion 10f. Of these, the straight portion 10f extends along the extension direction D. The meandering portion 10e is provided so as to bend left and right from the straight portion 10f in a plan view. Note that the straight portion 10f may be omitted, and each conductor 10w may be formed only with the meandering portion 10e.

The boundary between the conductor 10w and the first terminal 10x can be formed, for example, so that it tapers from the conductor 10w side toward the first terminal 10x side. Similarly, the boundary between the conductor 10w and the second terminal 10y can be formed, for example, so that it tapers from the conductor 10w side toward the second terminal 10y side.

The width W4 of each first terminal 10x and each second terminal 10y is not particularly limited, but for example, the width W4 can be about 0.2 mm. The width W5 of each conductor 10w is not particularly limited, but for example, the width W5 can be about 0.1 mm. Unlike the first embodiment, the frame body 10d and the multiple conductors 10w are not thinned, and the first terminal 10x and the second terminal 10y and the frame body 10d and the multiple conductors 10w have the same thickness (for example, about 0.2 mm).

Next, as shown in the cross-sectional view of FIG. 26(a), the structure shown in FIG. 24 is stacked on the structure shown in FIG. 25, and the two are bonded together. The third terminal 20x and the fourth terminal 20y are protrusions bonded to one surface of the flat conductor 10w. For example, diffusion bonding or soldering can be used to bond the two. A conductive paste (for example, silver paste) may be used instead of solder. Diffusion bonding is a method in which the two are brought into close contact with each other, and pressure is applied to the extent that plastic deformation is minimized at a temperature condition below the melting point of both, and the two are bonded using the diffusion of atoms that occurs between the bonding surfaces of the two. Diffusion bonding can be performed, for example, by heating and pressurizing in a vacuum atmosphere.

Next, as shown in the cross-sectional view of FIG. 26(b), similar to FIG. 4(a) of the first embodiment, the structure shown in FIG. 25 and the structure shown in FIG. 24 are covered with an insulating layer 9 except for the joint surfaces. Specifically, an insulating layer 9 made of epoxy resin with a dielectric constant of about 1.8 is formed to a thickness of about 10 μm by electrochemical coating on the exposed surfaces of the frame body 10d, the first terminal 10x, the second terminal 10y, the conductor 10w, the frame body 20d, the third terminal 20x, and the fourth terminal 20y. Note that the material of the insulating layer 9 is not limited to epoxy resin, and other insulating resins such as polyimide resin may be used as the material.

Next, as shown in the cross-sectional view of FIG. 26(c), similar to the first embodiment shown in FIG. 4(b) and FIG. 5(a), a magnetic body 19 is formed to cover the insulating layer 9 on the front side and the insulating layer 9 on the back side of the structure shown in FIG. 26(b). As in the first embodiment, the magnetic body 19 contains both magnetic powder and insulating resin.

Next, as shown in the cross-sectional view of FIG. 27(a), similar to FIG. 5(b) and FIG. 13 of the first embodiment, the surface 19a of the magnetic body 19 is polished by brush polishing or blasting to remove the insulating layer 9 and the magnetic body 19 from above the third terminal 20x and the fourth terminal 20y. As a result, a part (upper surface) of the third terminal 20x and the fourth terminal 20y is exposed on the surface 19a of the magnetic body 19.

In this embodiment, the metal plate 20 is etched halfway to form the third terminal 20x and the fourth terminal 20y, as shown in FIG. 22(a). This results in a structure in which the third terminal 20x and the fourth terminal 20y protrude from the frame body 20d, making it easier to expose the third terminal 20x and the fourth terminal 20y from the surface 19a of the magnetic body 19.

Next, as shown in the cross-sectional view of FIG. 27(b), similar to FIG. 6(a) to FIG. 7(a) of the first embodiment, a nickel layer and a tin layer are formed in this order as a metal plating layer 23 on the upper surfaces of the third terminal 20x and the fourth terminal 20y by electrolytic plating. As a result, the first electrode 24A is formed by the first terminal 10x, the third terminal 20x, and the metal plating layer 23, and the second electrode 25A is formed by the second terminal 10y, the fourth terminal 20y, and the metal plating layer 23.

The thickness of the metal plating layer 23 is not particularly limited; for example, the nickel layer can be formed to a thickness of about 2 μm, and the tin layer can be formed to a thickness of about 5 μm.

In addition to functioning as an anti-oxidation layer for the third terminal 20x and the fourth terminal 20y, the metal plating layer 23 also has the function of improving the wettability of the solder in each electrode 24A, 25A. Examples of the metal plating layer 23 having such a function include a laminated film in which a nickel layer and a gold layer are laminated in this order, and a laminated film in which a silver layer and a tin layer are laminated in this order.

Next, the structure shown in FIG. 27(b) is cut along the cutting line S to complete the basic structure of the inductor 30A according to this embodiment, which is shown in the cross-sectional view of FIG. 27(c). As in FIG. 14 and FIG. 16, the inductor 30A is, for example, a square (rectangular) shape with a side length of about 2.5 mm in a plan view, with the side of the first electrode 24A exposed on one of the opposing sides of the inductor 30A and the side of the second electrode 25A exposed on the other.

Inductor 30A has the following effect in addition to the effect of inductor 30. That is, in inductor 30, the height of the portion of first electrode 24 and second electrode 25 protruding from conductor 10w (height of the portion excluding metal plating layer 23) is about half the thickness of metal plate 1 (e.g., 0.1 mm). In contrast, in inductor 30A, the height H1 of the portion of first electrode 24A and second electrode 25A protruding from conductor 10w (height of the portion excluding metal plating layer 23) can be the same as the thickness of metal plate 20 (e.g., 0.2 mm).

In this way, in inductor 30A, the height of the protruding parts of each electrode is higher than in inductor 30, so the magnetic body 19 located on the conductor 10w can be made thicker. As a result, the inductance of inductor 30A can be made higher than that of inductor 30. For example, if the height of the protruding parts of each electrode is increased by 0.1 mm, the inductance can be increased by about 20%.

In addition, since the structure and dimensions of conductor 10w itself do not need to be changed from conductor 1w, the increase in DC resistance due to the increased height of the protrusions of each electrode is slight.

In addition, in inductor 30A, by adjusting the height of the protruding parts of each electrode, the thickness of the magnetic body 19 provided on the upper side of conductor 1w and the thickness of the magnetic body 19 provided on the lower side of conductor 1w can both be made uniformly thick, thereby making it possible to increase the inductance. This also makes it easier to adjust the inductance of inductor 30A. Furthermore, since magnetic body 19 can be provided evenly above and below conductor 1w, warping of inductor 30A can be prevented.

<Modification 1 of the second embodiment>
In the first modification of the second embodiment, an example is shown in which the heights of the first terminal and the second terminal are made even higher than those in the second embodiment. Note that in the first modification of the second embodiment, the description of the same components as those in the already described embodiment may be omitted.

First, the structure shown in FIG. 11 is fabricated in the same manner as in the first embodiment. Then, the structure shown in FIG. 24 is fabricated in the same manner as in the second embodiment. Then, as shown in the cross-sectional view of FIG. 28(a), the structure shown in FIG. 24 is stacked on the structure shown in FIG. 11, and the two are bonded together. For example, methods such as diffusion bonding or soldering can be used to bond the two together.

Note that each of the first terminals 1x and second terminals 1y is an example of a first protrusion that is continuously and integrally formed with the conductor 1w, and each of the third terminals 20x and fourth terminals 20y is an example of a conductive second protrusion that is joined onto the first protrusion. Here, "continuously and integrally formed" means that the metal material is patterned by wet etching, die punching, laser processing, etc., and is not a structure in which two or more conductors are joined.

Next, steps similar to those described with reference to the cross-sectional views of Figures 26(b) to 27(c) of the second embodiment are carried out to complete the basic structure of the inductor 30B according to this embodiment shown in the cross-sectional view of Figure 28(b). The first terminal 1x, the third terminal 20x, and the metal plating layer 23 form a first electrode 24B, and the second terminal 1y, the fourth terminal 20y, and the metal plating layer 23 form a second electrode 25B.

Similar to Figures 14 and 16, the inductor 30B is, for example, a square (rectangular) shape with a side length of about 2.5 mm in a plan view, and the side of the first electrode 24B is exposed on one of the opposing sides of the inductor 30B, and the side of the second electrode 25B is exposed on the other.

In inductor 30B, in addition to the effects of inductor 30A, the following effects are achieved. That is, in inductor 30A (see FIG. 27(c)), the height H1 (height of the part excluding the metal plating layer 23) of the part of first electrode 24A and second electrode 25A protruding from conductor 10w is approximately the same as the thickness of metal plate 20 (e.g., 0.2 mm). In contrast, in inductor 30B, the height H2 (height of the part excluding the metal plating layer 23) of the part of first electrode 24B and second electrode 25B protruding from conductor 1w can be approximately half the thickness of metal plate 1 plus the thickness of metal plate 20 (e.g., H2 = approximately 0.3 mm).

In this way, in inductor 30B, the height of the protruding parts of each electrode is higher than in inductor 30A, so the magnetic body 19 located on the conductor 1w can be made thicker. As a result, the inductance of inductor 30B can be made even greater than that of inductor 30A.

<Modification 2 of the second embodiment>
In the second modification of the second embodiment, an example is shown in which the first electrode and the second electrode have protruding portions protruding from the surface of the magnetic body. Note that in the second modification of the second embodiment, the description of the same components as those in the embodiment already described may be omitted.

First, the structure shown in FIG. 26(b) is fabricated in the same manner as in the second embodiment. In this case, the thickness of the metal plate 20 may be made thicker than in the second embodiment. This allows the protrusion amount from the surface of the conductor 10w to be increased in the multiple third terminals 20x and the fourth terminals 20y.

Next, as shown in the cross-sectional view of FIG. 29(a), the structure shown in FIG. 26(b) is placed between the lower die 15 and upper die 16 of the hot press machine. Then, in the same manner as in FIG. 4(b) of the first embodiment, magnetic bodies 19 are formed on the front and back sides of the structure shown in FIG. 26(b), and the structure is removed from between the lower die 15 and upper die 16.

In this embodiment, the upper mold 16 is formed with recesses 16x into which the tip sides of the third terminal 20x and the fourth terminal 20y are inserted. Therefore, in the structure removed from between the lower mold 15 and the upper mold 16, the tip sides of the third terminal 20x and the fourth terminal 20y protrude from the surface 19a of the magnetic body 19. At this point, the parts of the third terminal 20x and the fourth terminal 20y protruding from the surface 19a of the magnetic body 19 on the tip side are covered with the insulating layer 9.

29(b), the surface of the insulating layer 9 that covers the portions of the third terminal 20x and the fourth terminal 20y that protrude from the surface 19a of the magnetic body 19 on the tip side is polished and removed by brush polishing or blasting. As a result, the tip sides of the third terminal 20x and the fourth terminal 20y that protrude from the surface 19a of the magnetic body 19 are exposed from the insulating layer 9.

Next, a metal plating layer 23 is formed on the surfaces (part of the side surface and the top surface) of the third terminal 20x and the fourth terminal 20y protruding from the surface 19a of the magnetic body 19 in the same manner as in FIGS. 6(a) to 7(a) of the first embodiment, and then the inductor 30C according to this embodiment is completed as shown in the cross-sectional view of FIG. 29(c). The first terminal 10x, the third terminal 20x, and the metal plating layer 23 form a first electrode 24C, and the second terminal 10y, the fourth terminal 20y, and the metal plating layer 23 form a second electrode 25C.

As in Figures 14 and 16, the inductor 30C is, for example, a square (rectangular) shape with a side length of about 2.5 mm in a plan view, and the side of the first electrode 24C is exposed on one of the opposing sides of the inductor 30C, and the side of the second electrode 25C is exposed on the other. In addition, the metal plating layer 23 of the first electrode 24C and the metal plating layer 23 of the second electrode 25C are exposed to the outside of the inductor 30C. The metal plating layer 23 is formed on the upper surfaces and side surfaces of the third terminal 20x and the fourth terminal 20y that are exposed from the magnetic body 19, except for the portions exposed on the side surfaces of the inductor 30C.

In the above steps, it is also possible to form the inductor 30D shown in FIG. 30 by using the structure shown in FIG. 28(a) instead of the structure shown in FIG. 26(b). The first terminal 1x, the third terminal 20x, and the metal plating layer 23 form a first electrode 24D, and the second terminal 1y, the fourth terminal 20y, and the metal plating layer 23 form a second electrode 25D.

As in Figures 14 and 16, the inductor 30D is, for example, a square (rectangular) shape with a side length of about 2.5 mm in a plan view, and the side of the first electrode 24D is exposed on one of the opposing sides of the inductor 30D, and the side of the second electrode 25D is exposed on the other. In addition, the metal plating layer 23 of the first electrode 24D and the metal plating layer 23 of the second electrode 25D are exposed to the outside of the inductor 30D. The metal plating layer 23 is formed on the upper surfaces and side surfaces of the third terminal 20x and the fourth terminal 20y that are exposed from the magnetic body 19, except for the portions exposed on the side surfaces of the inductor 30D.

In inductor 30D, the height of the protruding parts of each electrode is higher than in inductor 30C, so the magnetic body 19 located on the conductor 10w can be made thicker. As a result, the inductance of inductor 30D can be made larger than that of inductor 30C.

Also, as shown in FIG. 31, the first electrode and the second electrode may be made to protrude from the surface of the magnetic body by joining separate parts.

Figure 31 illustrates an inductor according to the second modification of the second embodiment, where Figure 31(a) is a cross-sectional view showing the first cross section, and Figure 31(b) is a perspective view.

The inductor 30E shown in FIG. 31 is, for example, a structure in which a metal post 28 is bonded to the first terminal 1x and the second terminal 1y, which are protruding parts protruding from the conductor 1w of the structure shown in FIG. 11, and a metal plating layer 23 is formed on the end surface of the metal post 28. The metal post 28 is a conductive raised part that increases the amount of protrusion from the surface of the conductor 1w, and can be formed using, for example, copper or a copper alloy. For example, a method such as diffusion bonding or soldering can be used to bond the first terminal 1x and the second terminal 1y to the metal post 28. A conductive paste (for example, silver paste) may be used instead of solder. The metal post 28 is, for example, a cylinder, but may also be a square pillar. The height of the metal post 28 can be set to any value as necessary. The metal post 28 may be bonded to the third terminal 20x and the fourth terminal 20y shown in FIG. 27(c) or FIG. 28(b).

By having the first electrode and the second electrode protrude from the surface of the magnetic body, as in inductors 30C, 30D, and 30E, a semiconductor chip or passive components can be placed in the space that is created when inductor 30C, 30D, or 30E is mounted on a wiring board. Examples of passive components include resistors and capacitors.

For example, in the electronic device 50 shown in FIG. 32, an inductor 30E is mounted on a circuit board 51. The metal plating layers 23 of the first electrode 24E and the second electrode 25E of the inductor 30E are electrically connected to electrode pads 52 formed on the circuit board 51 by solder or the like. In the space on the circuit board 51 created by mounting the inductor 30E on the circuit board 51, a semiconductor chip 53 is mounted by flip-chip mounting or the like and sealed with molded resin 54. Instead of or in addition to the semiconductor chip 53, an active component such as a capacitor may be mounted in the space on the circuit board 51.

In this way, by arranging a semiconductor chip or passive components in the space created when an inductance with a first electrode and a second electrode protruding from the surface of a magnetic body is mounted on a wiring board, the area of the wiring board can be reduced. In addition, because the first electrode and the second electrode are long, heat generated by the inductance can be efficiently dissipated via the first electrode and the second electrode.

Although the preferred embodiments have been described above in detail, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

1, 10, 20...metal plate, 1a, 20a...surface, 1b, 20b...back, 1d, 10d, 20d...frame, 1e, 10e...serpentine portion, 1f, 10f...straight portion, 1x, 10x...first terminal, 1y, 10y...second terminal, 1w, 10w...conductor, 1p, 1q...connection portion, 2...first resist layer, 3...second resist layer, 6...third resist layer, 7...fourth resist layer, 9...insulating layer, 15...lower mold, 16...upper mold, 18...powder, 18a...magnetic powder, 18b...insulating resin, 19...magnetic material, 19a...surface, 19x...first edge portion, 19y...second edge part, 20x...third terminal, 20y...fourth terminal, 21...fifth resist layer, 22...sixth resist layer, 23...metal plating layer, 24, 24A, 24B, 24C, 24D, 24E...first electrode, 25, 25A, 25B, 25C, 25D, 25E...second electrode, 28...metal post, 29...wiring, 30, 30A, 30B, 30C, 30D, 30E...inductor, 31...insulating layer, 32, 52...electrode pad, 33, 51...circuit board, 34...solder resist layer, 34a...opening, 40, 50...electronic device, 53...semiconductor chip, 54...molding resin

Claims (15)

A magnetic material containing magnetic powder and an insulating resin;
A plurality of linear conductors, the surface of which is covered with an insulating layer and embedded in the magnetic body;
a first electrode provided at one end of each of the conductors and partly exposed from a surface of the magnetic body;
a second electrode provided at the other end of each of the conductors and partially exposed from the surface of the magnetic body;
having
The conductor has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and in a cross section cut in a direction perpendicular to the extension direction of the conductor and in the thickness direction of the conductor, the central portion of the side surface in the thickness direction protrudes laterally beyond the upper surface and the lower surface . The inductor according to claim 1 , wherein the conductor is meandering in a plan view. The inductor according to claim 1 , wherein the conductor is linear in a plan view. 4. The inductor according to claim 1, wherein the conductor is made of a metal plate. 5. The inductor according to claim 1, wherein the first electrode and the second electrode have conductive protrusions protruding from a surface of the conductor. The inductor according to claim 5 , wherein the protrusion is integrally formed continuously with the conductor. One surface of the conductor is flat,
6. The inductor according to claim 5 , wherein the protrusion is another conductor joined to one surface of the conductor. 6. The inductor according to claim 5, wherein the protrusion includes a first protrusion integrally formed with the conductor and a conductive second protrusion joined onto the first protrusion. 9. The inductor according to claim 5 , wherein the protrusion protrudes from a surface of the magnetic body. 10. The inductor according to claim 5, wherein a conductive raised portion is joined onto the protruding portion, the raised portion increasing the amount of protrusion from the surface of the conductor. forming a plurality of linear conductors each having a first electrode at one end and a second electrode at the other end;
forming an insulating layer on a surface of each of the conductors;
a step of embedding each of the conductors, the insulating layer being formed on a surface thereof, in a magnetic body containing magnetic powder and an insulating resin;
exposing a portion of each of the first electrode and the second electrode from a surface of the magnetic body in each of the conductors;
having
The step of forming the conductor includes a step of patterning a metal plate by etching from both sides to form the conductor;
A method for manufacturing an inductor, in which the conductor after etching has an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface, and in a cross section cut in a direction perpendicular to the extension direction of the conductor and in the thickness direction of the conductor, the central portion of the side surface in the thickness direction protrudes laterally beyond the upper surface and the lower surface . The step of forming the conductor includes a step of patterning a metal plate by etching from both sides to form the conductor;
12. The method for manufacturing an inductor according to claim 11 , wherein the conductor after etching has a shape in which a central portion of a side surface protrudes laterally. 13. The method for manufacturing an inductor according to claim 11 , wherein the step of forming the conductor comprises a step of patterning a metal plate to form the conductor. The step of forming a conductor includes:
14. The method for manufacturing an inductor according to claim 13, further comprising a step of thinning the metal plate except for portions of the metal plate corresponding to the first electrode and the second electrode , prior to the step of patterning the metal plate. 15. The method for manufacturing an inductor according to claim 11 , further comprising the step of bonding another conductor onto the first electrode and bonding another conductor onto the second electrode.

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