阅读说明：本技术 线圈部件及其制造方法 (Coil component and method for manufacturing same ) 是由 生石正之 于 2021-04-15 设计创作，主要内容包括：本发明提供能够缓和应力并且线圈的位置稳定而且能够抑制因腐蚀性气体引起的线圈的电阻率的增大的线圈部件及其制造方法。线圈部件具备：本体；和线圈,其设置于上述本体内,上述本体具有层叠起来的多个磁性层,上述线圈具有层叠起来的多个线圈布线,上述磁性层和上述线圈布线在一个方向上交替地层叠,上述线圈布线的上述一个方向上一侧的第1面与位于上述线圈布线的上述一个方向上一侧的一个上述磁性层接触,在上述线圈布线的上述一个方向上另一侧的第2面与位于上述线圈布线的上述一个方向上另一侧的另一个上述磁性层之间具有空隙部,在上述线圈布线的上述第2面的至少局部存在磁性膜。(The invention provides a coil component and a manufacturing method thereof, wherein the coil component can relieve stress, stabilize the position of a coil and inhibit the increase of the resistivity of the coil caused by corrosive gas. A coil component is provided with: a body; and a coil provided in the body, the body having a plurality of laminated magnetic layers, the coil having a plurality of laminated coil wires, the magnetic layers and the coil wires being alternately laminated in one direction, a 1 st surface of one side of the coil wires in the one direction being in contact with one of the magnetic layers located on one side of the coil wires in the one direction, a gap portion being provided between a 2 nd surface of the other side of the coil wires in the one direction and the other of the magnetic layers located on the other side of the coil wires in the one direction, and a magnetic film being provided at least partially on the 2 nd surface of the coil wires.)

1. A coil component, comprising:

a body; and

a coil disposed within the body,

the body has a plurality of magnetic layers stacked,

the coil has a plurality of coil wires laminated,

the magnetic layers and the coil wiring are alternately laminated in one direction,

a 1 st face on one side in the one direction of the coil wiring is in contact with one of the magnetic layers on one side in the one direction of the coil wiring,

a gap portion is provided between a 2 nd surface on the other side in the one direction of the coil wiring and the other magnetic layer on the other side in the one direction of the coil wiring,

a magnetic film is present at least partially on the 2 nd surface of the coil wiring.

2. The coil component of claim 1,

when the thickness of the magnetic film is a and the thickness of the other magnetic layer is b,

a/(a + b) ≦ 0.1 · (equation 1).

3. The coil component of claim 1 or 2,

the thickness of the magnetic film is 1 [ mu ] m or less.

4. The coil component according to any one of claims 1 to 3,

the ratio of the area of the 2 nd surface of the coil wiring covered with the magnetic film is 50% or more and 100% or less with respect to the area of the 2 nd surface of the coil wiring.

5. The coil component according to any one of claims 1 to 4,

the thickness of the void is 0.5 to 8.0 [ mu ] m.

6. A method for manufacturing a coil component, comprising:

a preparation step of preparing an unfired magnetic layer containing a magnetic material and a binder in an amount that increases from a 1 st main surface toward a 2 nd main surface except for at least the 1 st main surface;

a laminating step of laminating two of the unfired magnetic layers with an unfired coil wire interposed therebetween so that the unfired coil wire is in contact with a 2 nd main surface of the unfired magnetic layer and a 1 st main surface of another unfired magnetic layer; and

and a firing step of firing the one unfired magnetic layer, the other unfired magnetic layer, and the unfired coil wiring so that the one fired magnetic layer is in contact with the coil wiring after firing, and a void portion is formed between the other fired magnetic layer and the coil wiring after firing, and a magnetic film is formed at least partially on a surface of the coil wiring after firing on the side of the void portion.

7. The coil component manufacturing method as claimed in claim 6,

in the preparation step, the unfired magnetic layer includes a surface layer region including the 1 st main surface and a minimum layer region adjacent to the surface layer region and having a minimum amount of the binder, and the amount of the binder in the surface layer region is larger than the amount of the binder in the minimum layer region.

8. The coil component manufacturing method as claimed in claim 7,

in the firing step, at least a part of the surface layer region of the other unfired magnetic layer is torn from the other part of the other unfired magnetic layer and is adhered to the unfired coil wiring, and the part of the other unfired magnetic layer adhered to the unfired coil wiring is fired to form the magnetic film.

Technical Field

The present invention relates to a coil component and a method for manufacturing the same.

Background

As a conventional coil component, there is a structure described in japanese patent application laid-open No. 11-219821 (patent document 1). The coil component includes a body and a coil provided in the body. The body includes a plurality of magnetic layers and the coil includes a plurality of conductor layers. The magnetic layers and the conductor layers are alternately laminated. In order to relax the stress between the conductor layer and the magnetic layer, a void portion is provided over the entire periphery of the conductor layer.

Patent document 1: japanese laid-open patent publication No. 11-219821

However, in a conventional coil component, a conductor layer forming a coil and a magnetic layer are not in direct contact with each other, and the position of the coil may be unstable in such a coil component. Further, there is a possibility that defects (cracks, and the like) of the main body are caused by some reason, and when corrosive gas (sulfide gas) enters the gap portion, the conductor layer is corroded by the corrosive gas, and the specific resistance (Rdc) of the coil increases.

Disclosure of Invention

Accordingly, the present disclosure is directed to provide a coil component and a method of manufacturing the same, in which stress can be relaxed, a position of a coil is stable, and increase in resistivity of the coil due to a corrosive gas can be suppressed.

In order to solve the above problem, a coil component according to an aspect of the present disclosure includes:

a body; and

a coil disposed in the body,

the body has a plurality of magnetic layers stacked,

the coil has a plurality of coil wires laminated,

the magnetic layers and the coil wiring are alternately laminated in one direction,

a 1 st surface on one side in the one direction of the coil wiring is in contact with one of the magnetic layers on one side in the one direction of the coil wiring,

a gap portion is provided between the 2 nd surface on the other side in the one direction of the coil wiring and the other magnetic layer on the other side in the one direction of the coil wiring,

a magnetic film is present at least partially on the 2 nd surface of the coil wiring.

Here, the magnetic film may be a sheet-like film, a dot-like film such as a circular film, a single film, or a plurality of films separated from each other.

According to the above aspect, the gap portion is provided between the 2 nd surface of the coil wiring and the other magnetic layer, thereby relaxing the stress between the coil wiring and the magnetic layer. Further, since the 1 st surface of the coil wire is in contact with one magnetic layer, the position of the coil wire is more stable than a case where a gap portion is present over the entire circumference of the coil wire. Further, since the magnetic film is present at least in part on the 2 nd surface of the coil wiring, when corrosive gas enters the gap portion for some reason, corrosion of the coil wiring due to the corrosive gas can be prevented, and an increase in the specific resistance of the coil can be suppressed.

In one embodiment of the coil component, preferably, when the thickness of the magnetic film is a and the thickness of the other magnetic layer is b, a/(a + b) ≦ 0.1 · (equation 1) holds.

Here, the thickness of the magnetic film and the thickness of the other magnetic layer refer to thicknesses at a center line in a width direction of the coil wiring in a cross section orthogonal to the extending direction of the coil wiring.

According to the above embodiment, the thickness of the magnetic film can be made thin, and therefore, a further stress relaxation effect can be obtained.

In one embodiment of the coil component, the magnetic film preferably has a thickness of 1 μm or less.

According to the above embodiment, the thickness of the magnetic film can be made thin, and therefore, a further stress relaxation effect can be obtained.

In one embodiment of the coil member, a ratio of an area of the 2 nd surface of the coil wiring covered with the magnetic film is preferably 50% or more and 100% or less with respect to an area of the 2 nd surface of the coil wiring.

According to the above embodiment, corrosion of the coil wiring due to the corrosive gas can be prevented.

In one embodiment of the coil component, the thickness of the void portion is preferably 0.5 μm or more and 8.0 μm or less.

Here, the thickness of the void portion is a thickness at a center line in a width direction of the coil wire in a cross section orthogonal to the extending direction of the coil wire.

According to the above embodiment, the thickness of the void portion can sufficiently exhibit the stress relaxation effect, and the thickness of the void portion is within a specific range, so that a high impedance value (inductance value) of the coil component can be ensured.

In one embodiment of the method for manufacturing a coil component, the method includes:

a preparation step of preparing an unfired magnetic layer containing a magnetic material and a binder in an amount that increases from a 1 st main surface toward a 2 nd main surface except for at least the 1 st main surface;

a laminating step of laminating two of the unfired magnetic layers with an unfired coil wire interposed therebetween so that the unfired coil wire is in contact with a 2 nd main surface of one of the unfired magnetic layers and a 1 st main surface of the other unfired magnetic layer; and

and a firing step of firing the one unfired magnetic layer, the other unfired magnetic layer, and the unfired coil wire, bringing the fired one magnetic layer of the one unfired magnetic layer into contact with the fired coil wire of the unfired coil wire, forming a gap between the fired other magnetic layer of the other unfired magnetic layer and the coil wire, and forming a magnetic film at least partially on a surface of the coil wire on the side of the gap.

Here, the unfired magnetic layer is made of, for example, a magnetic sheet or a magnetic paste. The unfired coil wiring is made of, for example, a conductor paste.

According to the above embodiment, by using the unfired magnetic layer having the uneven amount of the binder, it is possible to form the magnetic film at least partially on the surface of the coil wiring on the side of the void portion while bringing one magnetic layer into contact with the coil wiring and forming the void portion between the other magnetic layer and the coil wiring. Therefore, the stress is relaxed, and the position of the coil is stabilized. Further, it is possible to easily manufacture a coil component that can prevent corrosion of coil wiring due to a corrosive gas and suppress an increase in the specific resistance of a coil when the corrosive gas enters a void portion for some reason.

In one embodiment of the method of manufacturing a coil component, in the preparation step, the unfired magnetic layer preferably includes a surface layer region including the 1 st main surface and a minimum layer region adjacent to the surface layer region and having a minimum amount of the binder, and the amount of the binder in the surface layer region is larger than the amount of the binder in the minimum layer region.

Here, the surface layer region is a layer-shaped region in a range of 1 μm or less from the 1 st main surface in the thickness direction. The minimum layer region means a layered region in which the amount of the binder in the unfired magnetic layer is minimum.

According to the above embodiment, the amount of the binder in the surface layer region is larger than the amount of the binder in the minimum layer region, and therefore, the binder in the surface layer region contributes to the bonding between the surface layer region of the unfired magnetic layer and the unfired coil wire at the time of degreasing in the firing process. In addition, since the amount of the binder in the minimum layer region is the smallest, the strength of the minimum layer region is the weakest, and tearing of the unfired magnetic layer can occur in the minimum layer region upon degreasing in the firing process.

In one embodiment of the method for manufacturing a coil component, in the firing step, at least a part of the surface region of the other unfired magnetic layer is torn from the other part of the other unfired magnetic layer and is adhered to the unfired coil wiring, and a part of the other unfired magnetic layer adhered to the unfired coil wiring is fired to form the magnetic film.

According to the above embodiment, since the magnetic film is formed from at least a part of the surface layer region of the other unfired magnetic layer, the magnetic film can be easily formed.

According to the coil component and the manufacturing method thereof of the aspect of the present disclosure, stress can be relaxed, the position of the coil can be stabilized, and increase in the resistivity of the coil due to the corrosive gas can be suppressed.

Drawings

Fig. 1 is a perspective view showing an embodiment of a coil component.

Fig. 2 is an X-X sectional view of the coil component of fig. 1.

Fig. 3 is an exploded plan view of the coil component.

Fig. 4 is an enlarged cross-sectional view of the periphery of the coil wiring.

Fig. 5 is a sectional view showing a method of manufacturing a coil component.

Fig. 6 is a graph showing a relationship between a position of the unfired magnetic layer in the T direction and an amount of the binder contained in the unfired magnetic layer.

Fig. 7A is a sectional view showing a method of manufacturing a coil component.

Fig. 7B is a sectional view showing a method of manufacturing the coil component.

Fig. 7C is a sectional view showing a method of manufacturing the coil component.

Fig. 8 is a schematic view based on an image showing the state of the magnetic layer, the magnetic film, and the coil wiring after firing.

Description of the reference numerals

A coil component; 10.. a body; a magnetic layer; an unfired magnetic layer; 1 st major face; a 2 nd major face; 1 st end face; a 2 nd end face; a side surface; a coil; coil routing; 1 st face; no. 2 nd side; unfired coil wiring; 1 st external electrode; 2 nd external electrode; a void portion; 61.. No. 1 lead-out conductor layer; no. 2 lead-out conductor layer; 71.. a magnetic film; z0... surface layer region; z1.. minimal layer area.

Detailed Description

Hereinafter, a coil component and a method for manufacturing the same according to an embodiment of the present disclosure will be described in more detail with reference to the illustrated embodiments. In addition, some of the drawings include schematic ones, and there are cases where actual sizes and ratios are not reflected.

(embodiment mode)

Fig. 1 is a perspective view showing an embodiment of a coil component. Fig. 2 is an X-X sectional view of fig. 1, and is an LT sectional view passing through the center in the W direction. Fig. 3 is an exploded plan view of the coil component, and a view along the T direction is shown from the lower drawing to the upper drawing. In addition, the L direction is the longitudinal direction of the coil component 1, the W direction is the width direction of the coil component 1, and the T direction is the height direction of the coil component 1. Hereinafter, the positive direction in the T direction is also referred to as the upper side, and the negative direction in the T direction is also referred to as the lower side.

As shown in fig. 1, 2, and 3, the coil component 1 includes a main body 10, a coil 20 provided inside the main body 10, and a 1 st external electrode 31 and a 2 nd external electrode 32 provided on a surface of the main body 10 and electrically connected to the coil 20.

The coil component 1 is electrically connected to wiring of a circuit board not shown via the 1 st and 2 nd external electrodes 31 and 32. The coil component 1 is used as a noise removal filter, for example, and is used in electronic devices such as a personal computer, a DVD player, a digital camera, a TV, a mobile phone, and an automotive electronic system.

The body 10 is formed in a substantially rectangular parallelepiped shape. The surface of the body 10 has a 1 st end surface 15, a 2 nd end surface 16 located on the opposite side of the 1 st end surface 15, and four side surfaces 17 located between the 1 st end surface 15 and the 2 nd end surface 16. The 1 st end face 15 and the 2 nd end face 16 are opposed to each other in the L direction.

The body 10 includes a plurality of magnetic layers 11. The magnetic layers 11 are stacked in the T direction. The magnetic layer 11 is made of a magnetic material such as a Ni — Cu — Zn ferrite material. The thickness of the magnetic layer 11 is, for example, 5 μm or more and 30 μm or less. In addition, the body 10 may also partially include a nonmagnetic layer.

The 1 st external electrode 31 covers the entire 1 st end surface 15 of the body 10 and the end portion of the side surface 17 of the body 10 on the 1 st end surface 15 side. The 2 nd external electrode 32 covers the entire 2 nd end surface 16 of the main body 10 and the end portion of the side surface 17 of the main body 10 on the 2 nd end surface 16 side. The 1 st external electrode 31 is electrically connected to the 1 st end of the coil 20, and the 2 nd external electrode 32 is electrically connected to the 2 nd end of the coil 20. The 1 st external electrode 31 may have an L shape formed across the 1 st end face 15 and the one side face 17, and the 2 nd external electrode 32 may have an L shape formed across the 2 nd end face 16 and the one side face 17.

The coil 20 is spirally wound along the T direction. The coil 20 is made of a conductive material such as Ag or Cu. The coil 20 includes a plurality of coil wires 21 and a plurality of extraction conductor layers 61 and 62.

The two 1 st lead conductor layers 61, the plurality of coil wires 21, and the two 2 nd lead conductor layers 62 are arranged in this order in the T direction and are electrically connected in this order via a via conductor. The plurality of coil wirings 21 are sequentially connected in the T direction, and form a spiral along the T direction. The 1 st lead conductor layer 61 is exposed from the 1 st end face 15 of the body 10 and connected to the 1 st external electrode 31, and the 2 nd lead conductor layer 62 is exposed from the 2 nd end face 16 of the body 10 and connected to the 2 nd external electrode 32. The number of layers of the 1 st and 2 nd extraction conductor layers 61 and 62 is not particularly limited, and may be 1 layer, for example.

The coil wiring 21 is formed in a shape wound with less than 1 turn on a plane. The lead conductor layers 61 and 62 are formed in a linear shape. The thickness of the coil wiring 21 is, for example, 10 μm or more and 40 μm or less. The thicknesses of the 1 st and 2 nd extraction conductor layers 61 and 62 are, for example, 30 μm, but may be thinner than the thickness of the coil wiring 21.

The coil wiring 21 is sandwiched between the two magnetic layers 11. In other words, the coil wiring 21 and the magnetic layer 11 are alternately laminated in one direction. In this embodiment, one direction is the T direction. Since the coil wiring 21 is sandwiched between the two magnetic layers 11, the shape of the coil wiring 21 becomes elliptical in a cross section of the coil wiring 21 orthogonal to the extending direction (winding direction).

The 1 st and 2 nd lead conductor layers 61 and 62 are provided on different layers from the coil wiring 21. The 1 st and 2 nd extraction conductor layers 61 and 62 are sandwiched between the two magnetic layers 11, respectively.

Fig. 4 is an enlarged cross-sectional view of the periphery of the coil wiring 21 of fig. 2. As shown in fig. 2 and 4, a void 51 exists in the body 10. The void 51 is located between the magnetic layer 11 and the coil wiring 21. Specifically, the coil wiring 21 has a 1 st surface 21a on one side in one direction and a 2 nd surface 21b on the other side in one direction. In this embodiment, one side in one direction refers to a positive direction of the T direction (in other words, an upper side), and the other side in one direction refers to a negative direction of the T direction (in other words, a lower side). The 1 st surface 21a is an upper surface, and the 2 nd surface 21b is a lower surface. At least a part of the 1 st surface 21a of the coil wiring 21 is in contact with one (upper) magnetic layer 11 located above the coil wiring 21. A gap 51 is provided between at least a part of the 2 nd surface 21b of the coil wiring 21 and the other (lower) magnetic layer 11 located below the coil wiring 21.

By providing the void portion 51 between the 2 nd surface 21b of the coil wire 21 and the magnetic layer 11 on the lower side in this manner, stress due to a difference in thermal expansion coefficient between the coil wire 21 and the magnetic layer 11 can be suppressed, deterioration in inductance (impedance value) due to internal stress can be eliminated, and a high impedance value (inductance value) can be secured. Further, since the 1 st surface 21a of the coil wire 21 is in contact with the upper magnetic layer 11, the position of the coil wire 21 is stable and a high impedance value (inductance value) can be secured as compared with the case where the void portion 51 is present over the entire circumference of the coil wire 21.

As shown in fig. 4, a magnetic film 71 is present at least in part on the 2 nd surface 21b of the coil wiring 21. The magnetic film 71 is exposed at the gap 51. The thickness of the magnetic film 71 is thinner than that of the magnetic layer 11. The material of the magnetic film 71 is the same as that of the magnetic layer 11. The magnetic film 71 is in the form of a sheet and covers the entire 2 nd surface 21b of the coil wiring 21. The magnetic film 71 may be a sheet-like film, a dot-like film such as a circular film, a single film, or a plurality of films separated from each other. The magnetic film 71 may cover a part of the 2 nd surface 21b of the coil wiring 21.

Since the magnetic film 71 is present on the 2 nd surface 21b of the coil wire 21 in this way, when corrosive gas enters the gap 51 for some reason, corrosion of the coil wire 21 by the corrosive gas can be prevented, and an increase in the specific resistance of the coil 20 can be suppressed.

Since the thickness of the magnetic film 71 is smaller than the thickness of the magnetic layer 11, the gap 51 is close to the coil wiring 21, and a sufficient stress relaxation effect is obtained. In contrast, when the gap is located at the center between the coil wirings adjacent in the lamination direction, the stress relaxation effect by the gap is insufficient.

Preferably, when the thickness of the magnetic film 71 is a and the thickness of the lower magnetic layer 11 is b, a/(a + b) ≦ 0.1 · (equation 1) holds. Accordingly, the thickness of the magnetic film 71 can be made thin, and thus a further stress relaxation effect can be obtained.

Here, the thickness a of the magnetic film 71 and the thickness b of the magnetic layer 11 refer to thicknesses at a center line M in a width direction (W direction) of the coil wiring 21 in a cross section of the coil wiring 21 orthogonal to the extending direction. Specifically, a cross section (referred to as a measurement surface) of the LT surface of the coil member passing through the center of the coil member in the W direction is observed. The cross section of the LT plane as the measurement plane is obtained by polishing the sample in the W direction by a polishing machine to a depth at which the substantially central portion in the W direction is exposed. In the obtained cross section, a Scanning Electron Microscope (SEM) photograph was taken. In the measurement plane, the thicknesses of the magnetic film and the magnetic layer are measured at the center line in the width direction of the coil wiring.

The thickness a of the magnetic film 71 is preferably 1 μm or less. Accordingly, the thickness of the magnetic film 71 can be made thin, and thus a further stress relaxation effect can be obtained. This stress relaxation effect is almost equivalent to a structure in which the thickness a of the magnetic film 71 is zero, in other words, the void 51 is adjacent to the coil wiring 21 without passing through the magnetic film 71.

The ratio of the area of the 2 nd surface 21b of the coil wiring 21 covered with the magnetic film 71 (also referred to as coverage) is preferably 50% to 100%, more preferably 80% to 100%, with respect to the area of the 2 nd surface 21b of the coil wiring 21. Therefore, if the coverage is 100%, corrosion of the coil wire 21 by the corrosive gas can be reliably prevented, but even if the coverage is about 50%, corrosion can be prevented to some extent.

Here, a method of measuring the coverage will be described. The coverage can be obtained by taking a 5000-fold image of the surface of the coil wiring 21 on the side of the magnetic film 71 as viewed from the direction orthogonal to the 2 nd surface 21b by SEM within a specific range (for example, 15 μm × 25 μm), and analyzing the SEM image by using image analysis software (for example, asahi co., ltd., a (registered trademark)) to determine the ratio of the area of the magnetic film 71 to the total value of the area of the 2 nd surface 21b of the coil wiring 21 exposed to the gap portion 51 and the area of the magnetic film 71.

The thickness t of the void 51 is preferably 0.5 μm or more and 8.0 μm or less. Here, the thickness t of the void 51 is a thickness at a center line M in a width direction (W direction) of the coil wire 21 in a cross section of the coil wire 21 orthogonal to the extending direction. Specifically, the thickness t of the void 51 is measured by the same method as the method for measuring the thicknesses of the magnetic film and the magnetic layer as described above.

By providing the thickness of the void 51 as described above, not only the effect of stress relaxation is sufficiently exhibited, but also a high impedance value (inductance value) of the coil component 1 can be ensured because the thickness of the void 51 is within a specific range.

Specifically, the stress relaxation effect is obtained in the entire temperature range of the operating temperature range (-40 to 150 ℃) of the coil member 1. On the other hand, when the thickness t of the void portion 51 is less than 0.5 μm, if the use temperature range is 150 ℃, a portion where the thickness of the void portion 51 becomes locally zero occurs due to the difference in thermal expansion coefficient between the magnetic layer 11 and the coil wiring 21, and the stress relaxation effect is deteriorated, thereby degrading the characteristics (impedance value and inductance value). On the other hand, when the thickness of the void portion 51 exceeds 8.0 μm, good initial characteristics (high impedance value and inductance value) cannot be obtained. In other words, the magnetic flux generated by the coil 20 is concentrated in the vicinity of the coil wiring 21, and therefore, higher impedance values and inductance values can be obtained with the magnetic layer 11 in the vicinity of the coil wiring 21.

Next, a method for manufacturing the coil component 1 will be described with reference to fig. 5 and 7A to 7C. Fig. 5 and 7A to 7C show LT cross sections of the coil wiring 21 orthogonal to the extending direction.

First, as shown in fig. 5, an unfired magnetic layer 111 including a magnetic material and a binder is prepared. This is referred to as a preparation step. The unfired magnetic layer 111 is in a state before firing of the magnetic layer 11. The unfired magnetic layer 111 is made of, for example, a magnetic sheet or a magnetic paste.

The magnetic material is not particularly limited, and for example, Fe-containing magnetic material can be used₂O₃ZnO, CuO and NiO. The magnetic material may further comprise an additive. Examples of the additive include Mn₃O₄、Co₃O₄、SnO₂、Bi₂O₃、SiO₂。

The binder is, for example, any of PVB (polyvinyl butyral), PVA (polyvinyl alcohol), polyvinyl acetate, polyethylene, acrylic, polyurethane, polyvinyl chloride, or polystyrene.

The unfired magnetic layer 111 includes a 1 st main surface 111a on the upper side and a 2 nd main surface 111b on the lower side. The amount of the binder contained in the unfired magnetic layer 111 is increased continuously or stepwise from the 1 st main surface 111a toward the 2 nd main surface 111b, except for at least the 1 st main surface 111a. In fig. 5, the adhesive is indicated by a dotted line for convenience, and the amount of the dotted line indicates the amount of the adhesive.

Specifically, the unfired magnetic layer 111 includes: a surface layer region Z0 including the 1 st main face 111a, and a minimum layer region Z1 adjacent to the surface layer region Z0 and having the smallest amount of adhesive. The amount of adhesive in surface layer region Z0 is greater than the amount of adhesive in minimum layer region Z1. Here, the surface layer region Z0 is a layer region in the range of 1 μm or less from the 1 st main surface 111a in the thickness direction in the T direction. The minimum layer area Z1 refers to a layered area in which the amount of binder in the unfired magnetic layer 111 is minimum.

Fig. 6 shows the relationship between the position of the unfired magnetic layer 111 in the T direction (thickness direction) and the amount of the binder contained in the unfired magnetic layer 111. In fig. 6, the positions in the T direction are T1 to T8 in order from the 2 nd main surface 111b to the 1 st main surface 111a. The position of T1 is defined as the 2 nd main surface 111b, and the position of T8 is defined as the 1 st main surface 111a. The location of T8 is contained in surface layer region Z0 and the location of T7 is contained in minimum layer region Z1.

As shown in fig. 6, the amount of adhesive decreases from the position of T1 toward the position of T7, except for the position of T8. At the location of T7, the amount of adhesive is minimal. From the position of T2 toward the position of T6, the amount of adhesive decreases linearly. At the position of T1, the amount of adhesive was sharply increased compared to the position of T2. At the position of T8, the amount of adhesive increased as compared with the position of T7, becoming the amount of adhesive to the same extent as at the position of T4.

By making the concentration of the binder (resin) in the unfired magnetic layer 111 different in this way, strength can be given to the inside of the unfired magnetic layer 111 during degreasing. In other words, the strength is strong when the amount of the binder is large (the binder concentration is high), and the strength is weak when the amount of the binder is small (the binder concentration is low).

Here, an example of a method of segregating the binder in the unfired magnetic layer 111 will be described.

When a ceramic green sheet as the unfired magnetic layer 111 is formed on the support, the binder is moved downward by gravity, and a large amount of the binder is distributed on the lower surface (the 2 nd main surface 111b) side of the green sheet in contact with the support. Further, by setting the forming speed of the green sheet to be low and setting the drying temperature of the green sheet to be low, the binder is present more on the support side. Further, by drying the upper surface (1 st main surface 111a) of the green sheet faster than the inside of the green sheet, the amount of the binder at the upper surface of the green sheet can be made larger than the amount of the binder at the area inside the green sheet by a predetermined distance from the upper surface. In this way, the binder in the unfired magnetic layer 111 is controlled and segregated.

As another method for segregating the binder, a slurry containing a fluorine-modified resin is applied to the carrier film to form a ceramic green sheet. This makes it easy for the fluorine-modified resin in the ceramic green sheet to migrate to the side of the carrier film having the same polar group, thereby causing a so-called interfacial segregation phenomenon.

As another method for segregating the binder, a steric dispersant is used. As the dispersant, a steric type dispersant such as an allyl ether polymer is used. Thus, since the binder is light, it segregates upward, and the concentration of the binder varies in the thickness direction.

Then, the two unfired magnetic layers 111 are laminated with the unfired coil wire 121 interposed therebetween. This is referred to as a lamination process. The unfired coil wire 121 is in a state before firing of the coil wire 21. The unfired coil wiring 121 is made of, for example, a conductor paste. Specifically, as shown in fig. 7A, the unfired coil wire 121 is laminated on the 1 st main surface 111a of the unfired magnetic layer 111 on the lower side, and as shown in fig. 7B, the unfired magnetic layer 111 on the upper side is laminated on the unfired magnetic layer 111 on the lower side and the unfired coil wire 121. Thus, the unfired coil wire 121 is brought into contact with the 2 nd main surface 111b of the upper unfired magnetic layer 111 and the 1 st main surface 111a of the lower unfired magnetic layer 111. Then, the unfired coil wire 121 and the unfired magnetic layer 111 are sequentially laminated, and this is repeated a plurality of times to form a laminated block. Thereafter, the laminated block is singulated.

Thereafter, the unfired magnetic layer 111 and the unfired coil wire 121 are fired, and as shown in fig. 4, the fired upper magnetic layer 11 of the upper unfired magnetic layer 111 is brought into contact with the fired coil wire 21 of the unfired coil wire 121, a gap 51 is formed between the fired lower magnetic layer 11 of the lower unfired magnetic layer 111 and the coil wire 21, and the magnetic film 71 is formed at least partially on the surface (the 2 nd surface 21b) of the coil wire 21 on the side of the gap 51. This is called a firing process.

Specifically, as shown in fig. 7C, at least a part of the surface layer region Z0 of the lower unfired magnetic layer 111 is torn from the other part of the lower unfired magnetic layer 111 and adheres to the unfired coil wire 121. For example, the unfired magnetic layer 111 is broken at an interface C shown by a two-dot chain line between the surface layer region Z0 and the minimum layer region Z1.

Here, the breaking (tearing) of the unfired magnetic layer 111 in the firing step will be described. The amount of the binder of the surface layer region Z0 is larger than that of the minimum layer region Z1, and therefore, the binder of the surface layer region Z0 contributes to the bonding between the surface layer region Z0 of the unfired magnetic layer 111 and the unfired coil wiring 121 at the time of degreasing in the firing process. In this way, during degreasing in the firing process, the unfired coil wire 121 is shrunk while bonding between the 1 st main surface 111a of the unfired magnetic layer 111 and the unfired coil wire 121 is exhibited. In this way, the amount of the binder of the minimum layer area Z1 is minimum, and therefore, the strength of the minimum layer area Z1 is weakest, and the unfired magnetic layer 111 tears in the minimum layer area Z1 (interface C) at the time of degreasing in the firing process. In this way, the fracture can be selectively generated in the weak portion in the unfired magnetic layer 111.

Then, the portion of the lower unfired magnetic layer 111 adhering to the unfired coil wire 121 is fired to form the magnetic film 71. Accordingly, the magnetic film 71 is formed from at least a part of the surface layer region Z0 of the lower unfired magnetic layer 111, and therefore the magnetic film 71 can be easily formed. In short, in the firing step, when the unfired coil wire 121 shrinks, the unfired magnetic layer 111 is broken, and the magnetic film 71 can be formed while forming the void 51.

On the other hand, since the binder amount is the largest in the 2 nd main surface 111b of the upper unfired magnetic layer 111, the strength is the strongest in the 2 nd main surface 111b, and no tear is generated in the portion of the upper unfired magnetic layer 111 on the 2 nd main surface 111b side during degreasing in the firing process. Therefore, the upper magnetic layer 11 can be brought into contact with the coil wiring 21.

In the case of using an unfired magnetic layer in which the amount of the binder simply increases from the 1 st main surface toward the 2 nd main surface, if the amount of the binder contained in the 1 st main surface is the smallest, the unfired magnetic layer is not broken in the firing step, the magnetic film is not formed, and only the void portion is formed.

Then, as shown in fig. 1, the external electrodes 31 and 32 are provided on the main body 10, and the coil component 1 is manufactured. Therefore, the stress is relaxed, and the position of the coil 20 is stabilized. Further, the coil component 1 can be easily manufactured, and when corrosive gas enters the void portion for some reason, the coil component 1 can prevent corrosion of the coil wiring due to the corrosive gas and suppress an increase in the specific resistance of the coil 20.

Next, an example of a method for manufacturing the coil component 1 will be described.

As the unfired magnetic layer, a magnetic sheet was used. The thickness of the magnetic sheet was 35 μm. The magnetic material of the magnetic sheet is a Ni-Cu-Zn ferrite material. The binder of the magnetic sheet is PVB (polyvinyl butyral). The proportion of the binder may be 8 wt% or more and 16 wt% or less. For the magnetic sheet, the amount of the adhesive becomes larger from the upper surface toward the lower surface except for the upper surface.

As the unfired coil wiring, a coil conductor paste was used. The conductor powder of the coil conductor paste is Ag. The binder of the coil conductor paste may be ethyl cellulose, and the proportion of the binder may be 1.0 wt% or more and 5.0 wt% or less.

Then, a laminated block is formed using the magnetic sheet and the coil conductor paste, and is singulated and then fired. During firing, when the coil conductor paste shrinks, a crack (tear) occurs in a portion of the magnetic sheet where the amount of the binder is small, a magnetic film is formed, and a void portion is formed.

Fig. 8 is a schematic diagram based on an image showing the state of the magnetic layer 11, the magnetic film 71, and the coil wiring 21 after firing. In fig. 8, the coil wiring 21 is polished until the cross section can be confirmed, and the thickness is measured by FE-SEM: JSM-7900F (japan electronics), and in low vacuum mode: 20Pa, WD is 10mm, detector: images were acquired by observation under the conditions of LVBEDC and LVSED, and outline lines of the images were drawn. As shown in fig. 8, a gap 51 is provided between the 2 nd surface 21b of the coil wire 21 and the lower magnetic layer 11, and the 1 st surface 21a of the coil wire 21 is in contact with the upper magnetic layer 11. The magnetic film 71 is present on the 2 nd surface 21b of the coil wiring 21.

The present disclosure is not limited to the above-described embodiments, and design changes can be made without departing from the scope of the present disclosure. For example, the increase or decrease in the number of coil wirings can be changed. The shape of the external electrode may be an L-shape or the like.

In the above-described embodiment, the "one side in one direction" is made to be the positive direction of the T direction, and the "the other side in one direction" is made to be the negative direction of the T direction, but the "one side in one direction" may be made to be the negative direction of the T direction, and the "the other side in one direction" may be made to be the positive direction of the T direction. At this time, the lower surface (1 st surface) of the coil wiring is in contact with the magnetic layer on the lower side of the coil wiring, a gap portion is formed between the upper surface (2 nd surface) of the coil wiring and the magnetic layer on the upper side of the coil wiring, and the magnetic film is present on the upper surface of the coil wiring.

In the above embodiment, the upper and lower magnetic layers sandwich only the coil wiring, but an intermediate magnetic layer may be provided in the same layer as the coil wiring in addition to the upper and lower magnetic layers, and the upper and lower magnetic layers sandwich the coil wiring and the intermediate magnetic layer. Accordingly, since the magnetic layer is provided in the middle, the thickness of the coil wiring can be maintained, and the dc resistance value of the coil wiring can be reduced.

In the above embodiment, the air gap is formed between the coil wiring and the lower magnetic layer, but the air gap may be also formed locally between the coil wiring and the upper magnetic layer. The coil wiring is formed of 1 conductor layer, but may be formed by contacting a plurality of conductor layers.