Manufacturing Method of Coil Component

Abstract

To prevent a plating film from being formed on an unintended portion.SOLUTION: A method of manufacturing a coil component includes the steps of: forming a compact with a pattern of a precursor of a coil conductor 30 formed therein, the compact including metal magnetic particles; performing heat treatment of the compact to form a magnetic base substance 10 that has a first region 22 having a first region surface 22a on its surface and a second region 24 having a second region surface 24a on its surface, the first region surface 22a and the second region surface 24a being adjacent to each other; processing the second region surface 24a into a surface having surface roughness larger than that of the first region surface 22a; forming an external electrode 60 electrically connected with the coil conductor 30 on the first region surface 22a; and forming a plating film 64 on the first region surface 22a by the electrolytic plating method as a part of the step of forming the external electrode 60.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention , C relates to a method for manufacturing coil parts.

Background Art

[0002] There are cases where a magnetic substrate is formed using metal magnetic particles having excellent magnetic saturation characteristics such as soft magnetic alloys instead of ferrite. An external electrode is formed on the surface of the magnetic substrate. Here, it is known that the resin is removed by irradiating the surface of the magnetic substrate with a laser to expose the metal magnetic particles, the electrical resistance of the surface of the magnetic substrate is lowered, and then an external electrode is formed on the surface of the magnetic substrate using a plating method (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a plating film is formed on the surface of a magnetic substrate formed using metal magnetic particles by an electrolytic plating method, the plating film may be formed so as to extend to an unintended portion.

[0005] The present invention has been made in view of the above problems, and an object thereof is to suppress the formation of a plating film in an unintended portion.

Means for Solving the Problems

[0006] The present invention includes a step of forming a molded body containing metal magnetic particles in which a pattern of a precursor of a coil conductor is formed inside, , having a first region surface and a second region surface adjacent to the first region surface on the surface, a step of heat-treating the molded body and magnetic to form a magnetic substrate, a step of forming a metal film on the first region surface, and after the step of forming the metal film , a step of processing the surface of the second region into a surface having a larger surface roughness than the surface of the first region; after the step of processing the second region surface, a plating film is formed on the metal film using an electrolytic plating method, electrically connecting to the coil conductor and including the metal film and the plating film a step of forming an external electrode on the surface of the first region, and , being A method for manufacturing a coil component comprising the steps of:

[0007] The present invention includes metal magnetic particles , having a first region surface and a second region surface adjacent to the first region surface on the surface a step of forming a molded body, heat-treating the molded body, and magnetic a step of forming a magnetic substrate, a step of winding a conductor around the magnetic substrate to form a coil conductor, a step of forming a metal film on the first region surface, and after the step of forming the metal film, a step of processing the surface of the second region into a surface having a larger surface roughness than the surface of the first region, after the step of processing the second region surface, on the metal film forming a plating film using an electrolytic plating method, electrically connecting to the coil conductor, the metal film and an external electrode including the plating film, formed on the first region surface A method for manufacturing a coil component comprising the steps of:

[0008] In the above configuration, The step of forming the metal film is a step of forming the metal film by a sputtering method or by applying a conductive paste it can be configured as follows.

[0009] In the above configuration, the step of processing the surface of the second region can be configured as a step of acid-treating the surface of the magnetic substrate.

[0010] In the above configuration, the step of processing the surface of the second region can be configured as a step of removing the metal magnetic particles from the surface of the magnetic substrate and providing a depression on the surface of the magnetic substrate.

[0011] In the above configuration, when the metal magnetic particles are contained in the magnetic substrate, they have an oxide film on their surface, and the step of processing the surface of the second region can be configured as a step of exposing the oxide film of the metal magnetic particles in the depression.

[0012] In the above configuration, it may further include a step of incorporating a resin into the magnetic substrate, and the step of processing the surface of the second region may be a step of exposing the resin within the recess.

[0013] In the above configuration, the metal magnetic particles can be configured to be a soft magnetic alloy mainly composed of iron.

Advantages of the Invention

[0015] According to the present invention, it is possible to suppress the formation of the plating film in an unintended portion.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a perspective view of a coil component according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the coil component of FIG. 1. [Figure 3] FIG. 3 is an exploded perspective view of the magnetic substrate of the coil component of FIG. 1. [Figure 4] FIG. 4 is a flowchart showing an example of a method for manufacturing a coil component according to a first embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view near an external electrode of a coil component according to a comparative form. [Figure 6] FIGS. 6(a) and 6(b) are cross-sectional views near an external electrode of a coil component according to a first embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of a method for manufacturing a coil component according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a side view of a coil component according to a third embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart showing an example of a method for manufacturing a coil component according to a third embodiment of the present invention.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with appropriate reference to the drawings. However, the present invention is not limited to the illustrated embodiments. In addition, the same reference numerals are assigned to common components in the plurality of drawings. Note that each drawing is not necessarily drawn to an exact scale for convenience of explanation. Also, each step shown in the present invention may be performed in any order and a single step may be performed multiple times, unless the dependency relationship is clearly indicated. Before, after, and between each step, any steps not described may be included.

[0018] [First Embodiment] FIG. 1 is a perspective view of a coil component 300 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the coil component 300 of FIG. 1. FIG. 3 is an exploded perspective view of a magnetic substrate 10 of the coil component 300 of FIG. 1. FIGS. 1, 2, and 3 show a multilayer inductor used as a passive element in various circuits. The multilayer inductor is an example of a coil component applicable to the present invention. The present invention can be applied to a power inductor used in a DC-DC converter or various other coil components.

[0019] As shown in FIGS. 1, 2, and 3, the coil component 300 in the first embodiment includes a magnetic substrate 10, a coil conductor 30 embedded in the magnetic substrate 10, and a pair of external electrodes 60 electrically connected to the coil conductor 30. The "length" direction, "width" direction, and "height" direction of the coil component 300 are defined as the "L-axis" direction, "W-axis" direction, and "T-axis" direction, respectively. The L-axis, W-axis, and T-axis are perpendicular to each other. The direction of the coil axis A of the coil conductor 30 is not particularly restricted, but for example, it extends along the T-axis direction. The size of the magnetic substrate 10 is not particularly limited, but for example, the length dimension (dimension in the L-axis direction) is 0.2 mm to 6.0 mm, the width dimension (dimension in the W-axis direction) is 0.1 mm to 4.5 mm, and the height dimension (dimension in the T-axis direction) is 0.1 mm to 4.0 mm.

[0020] The magnetic substrate 10 has a generally rectangular parallelepiped shape (substantially rectangular parallelepiped shape). The outer surface of the magnetic substrate 10 is defined by six faces. Note that the substantially rectangular parallelepiped shape includes cases where each vertex is rounded, each side (the boundary portion of each face) is rounded, or each face has a curved surface.

[0021] In the first embodiment, when referring to the vertical direction of the coil component 300, the vertical direction in FIGS. 1, 2, and 3 is used as a reference. That is, the positive direction of the T-axis direction is the upward direction, and the negative direction is the downward direction.

[0022] The magnetic substrate 10 is formed of a plurality of metal magnetic particles. In the first embodiment, the magnetic substrate 10 is formed by a plurality of metal magnetic particles being bonded via an oxide film formed on the surface of the metal magnetic particles. The oxide film formed on the surface of the metal magnetic particles is an oxide of the elements constituting the metal magnetic particles. The metal magnetic particles are formed of a soft magnetic alloy material such as an iron-silicon-chromium-based, iron-silicon-aluminum-based, or iron-silicon-chromium-aluminum-based material, a metal magnetic material such as iron or nickel, an amorphous magnetic metal material, or a nanocrystalline magnetic metal material. In the first embodiment, it is assumed that the metal magnetic particles are formed of a soft magnetic alloy material mainly composed of iron. Being mainly composed of iron means that the ratio of iron to the total amount of the elements constituting the soft magnetic alloy is 50 wt% (weight %) or more, and may be 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0023] For example, the metal magnetic particles may be alloy particles containing iron and silicon, or may be alloy particles containing iron and a metal element M having a greater ionization tendency than iron. Examples of the metal element M include chromium, aluminum, zirconium, titanium, manganese, and the like. As an example, the metal particles may be alloy particles of iron, silicon, and one or more metal elements M (for example, at least one of chromium and aluminum) having a greater ionization tendency than iron. The proportion of iron may be 85 wt% to 97 wt%, the proportion of silicon may be 1.5 wt% to 7 wt%, and the proportion of the metal element M may be 1.5 wt% to 8 wt%. The metal particles may contain unintended impurities such as oxygen and / or carbon. The proportion of the impurities may be 1 wt% or less. Further, the metal particles may contain cobalt, nickel, copper, sulfur, phosphorus, and / or boron, etc. The composition ratio of the metal particles can be calculated, for example, by photographing a cross-section of the magnetic substrate 10 with a scanning electron microscope at a magnification of about 3000 to 20000 times and using the ZAF method by energy-dispersive X-ray analysis (EDS).

[0024] The coil conductor 30 has a winding portion 32. The winding portion 32 has winding patterns C11 to C15 and vias V1 to V4. The winding patterns C11 to C15 extend along a plane (LW plane) orthogonal to the coil axis A and are separated from each other in the direction of the coil axis A (T-axis direction). Among the winding patterns C11 to C15, the adjacent winding patterns in the T-axis direction are electrically connected via the vias V1 to V4. Thereby, the winding portion 32 that winds around the coil axis A is formed.

[0025] One end of the winding portion 32 is electrically connected to one external electrode 60 by a lead-out portion 34a formed by vias V5 and V6. The other end of the winding portion 32 is electrically connected to the other external electrode 60 by a lead-out portion 34b formed by vias V11 to V16.

[0026] The magnetic substrate 10 includes a main body portion 20 composed of magnetic layers 11 to 15 provided with a circumferential portion 32, an upper cover layer 16 provided on the main body portion 20 and composed of one or more layers, and a lower cover layer 17 provided under the main body portion 20 and composed of one or more layers. The circumferential patterns C11 and vias V1, V11 are formed in the magnetic layer 11, the circumferential patterns C12 and vias V2, V12 are formed in the magnetic layer 12, the circumferential patterns C13 and vias V3, V13 are formed in the magnetic layer 13, the circumferential patterns C14 and vias V4, V14 are formed in the magnetic layer 14, and the circumferential patterns C15 and vias V5, V15 are formed in the magnetic layer 15. The vias V6, V16 are formed in the lower cover layer 17.

[0027] The circumferential patterns C11 to C15 and the vias V1 to V6, V11 to V16 are formed of a metal material having excellent conductivity, such as silver, palladium, copper, aluminum, or an alloy thereof.

[0028] A pair of external electrodes 60 are provided on the surface of the magnetic substrate 10. In the first embodiment, the pair of external electrodes 60 are provided separately in the L-axis direction on the lower surface of the magnetic substrate 10. One of the pair of external electrodes 60 is electrically connected to one end of the circumferential portion 32 via a lead-out portion 34a, and the other is electrically connected to the other end of the circumferential portion 32 via a lead-out portion 34b. The external electrode 60 includes a metal film 62 and a plating film 64. The metal film 62 is formed of, for example, silver, palladium, copper, or an alloy thereof. The plating film 64 is, for example, a laminated film of a nickel plating film and a tin plating film.

[0029] The magnetic substrate 10 has a first region 22 having a first region surface 22a on its surface, and a second region 24 having a second region surface 24a adjacent to the first region surface 22a on its surface. The first region surface 22a and the second region surface 24a are provided, for example, on the lower surface of the magnetic substrate 10. The external electrode 60 is provided on the first region surface 22a of the lower surface of the magnetic substrate 10. The first region surface 22a has a smaller surface roughness than the second region surface 24a. That is, the first region surface 22a with a smaller surface roughness of the lower surface of the magnetic substrate 10 is covered with the metal film 62 of the external electrode 60, and the metal film 62 is not provided on the second region surface 24a with a larger surface roughness. Also, as shown in FIG. 2, both the first region surface 22a and the second region surface 24a may be provided on the same surface of the magnetic substrate 10. As long as the first region surface 22a is adjacent to the second region surface 24a, they may be provided on different surfaces of the magnetic substrate 10. Since the second region surface 24a has a larger surface roughness than the first region surface 22a, the arithmetic mean roughness Ra is larger than that of the first region surface 22a. For example, the second region surface 24a may have an arithmetic mean roughness Ra that is 1.1 times or more, 1.3 times or more, or 1.5 times or more larger than that of the first region surface 22a. As an example, the arithmetic mean roughness Ra of the first region surface 22a is 0.3 to 0.6, and the arithmetic mean roughness Ra of the second region surface 24a is 0.35 to 0.7. Note that the surface roughnesses of the first region surface 22a and the second region surface 24a can be obtained by observing the L-T cross section of the magnetic substrate 10. The measurement of the arithmetic mean roughness Ra can be performed with an appropriate standard length according to the size of the surface roughness. The arithmetic mean roughness Ra is defined by JIS B0601.

[0030] [Manufacturing method] FIG. 4 is a flowchart showing an example of a method for manufacturing the coil component 300 according to the first embodiment of the present invention. As shown in FIG. 4, first, a molded body having a pattern of a precursor of the coil conductor 30 inside is formed (step S10). The molded body is formed by the following method. First, an upper laminate that becomes the upper cover layer 16 is formed. The upper laminate is formed by laminating a plurality of magnetic sheets. The magnetic sheet is obtained, for example, by applying a slurry to the surface of a plastic base film, drying it, and cutting the dried slurry into a predetermined size. The slurry is prepared by mixing metal particles made of a soft magnetic alloy mainly composed of iron with an organic binder, a solvent, and the like. As the organic binder, for example, a resin material having excellent insulation properties such as polyvinyl butyral (PVB) resin or epoxy resin is used. As the solvent, for example, toluene is used.

[0031] Next, a lower laminate that becomes the lower cover layer 17 is formed. The lower laminate is formed by laminating composite sheets in which unfired conductor vias are provided in the magnetic sheets described above. The composite sheet is obtained by forming through holes at positions corresponding to the vias V6 and V16 of the magnetic sheet and embedding a conductive paste in the through holes using, for example, screen printing. Note that the conductor vias may be formed by a method other than screen printing.

[0032] Next, an intermediate laminate that becomes the main body 20 is formed. The intermediate laminate is formed by laminating composite sheets provided with unburned conductor patterns that become the circumferential patterns C11 to C15 and unburned conductor vias that become the vias V1 to V5, V11 to V15 on magnetic sheets that become the magnetic layers 11 to 15 (the conductor patterns and conductor vias become the patterns of the precursors of the coil conductors). To form this composite sheet, first, through holes are formed at positions corresponding to the vias V1 to V5, V11 to V15 of the magnetic sheet described above. Next, an unburned conductor pattern is formed on the magnetic sheet by printing a conductive paste on the magnetic sheet using, for example, screen printing. At this time, the conductive paste is filled into the through holes formed in the magnetic sheet. Thereby, an unburned conductor pattern that becomes the circumferential patterns C11 to C15 and unburned conductor vias that become the vias V1 to V5, V11 to V15 are formed on the magnetic sheet. Note that the conductor pattern and the conductor via may be formed by a method other than screen printing.

[0033] Next, the lower laminate, the intermediate laminate, and the upper laminate are laminated in this order from the negative direction side to the positive direction side of the T-axis direction. The main body laminate is formed by thermocompression bonding this laminate using a press or the like. Then, a molded body having the pattern of the precursor of the coil conductor 30 inside is formed by cutting the main body laminate into desired sizes using a cutting machine such as a dicing machine or a laser processing machine.

[0034] Next, the magnetic base 10 is formed by performing a heat treatment for firing on the molded body (step S12). The heat treatment is performed at a predetermined temperature in an atmosphere containing oxygen. By this heat treatment, an oxide film made of the material component of the metal magnetic particles is formed on the surface of the metal magnetic particles contained in the molded body, and the magnetic base 10 is formed by a plurality of metal magnetic particles being bonded to each other through the oxide film. The coil conductor 30 is formed inside the magnetic base 10.

[0035] Next, in order to chamfer (round) the ridge lines and corners on the surface of the magnetic substrate 10, remove foreign matters such as deposits on the surface, and remove the generated burrs, the magnetic substrate 10 is subjected to a polishing process such as barrel polishing (step S14). This polishing process step may be performed, for example, after the step S10 of forming the molded body or after the step 16 of forming the metal film 62, for example.

[0036] Next, a metal film 62 constituting the external electrode 60 is formed on the surface of the magnetic substrate 10 (step S16). The metal film 62 is formed on the first region surface 22a, which is the surface of the first region 22 of the magnetic substrate 10, by, for example, sputtering or applying a conductive paste. Note that the metal film 62 may be formed by applying a conductive paste to the magnetic sheet of the lower laminate that becomes the lowermost layer of the magnetic substrate 10 in step S10 to form a conductor pattern that becomes the metal film 62, or after pressing the laminate to form the main body laminate or after individually separating the main body laminate into chips, applying a conductive paste to form a conductor pattern that becomes the metal film 62.

[0037] Next, the surface of the magnetic substrate 10 is processed (step S18) so that the second region surface 24a, which is the surface of the second region 24 of the magnetic substrate 10, becomes a surface with a larger surface roughness than the first region surface 22a, which is the surface of the first region 22. For example, by subjecting the surface of the magnetic substrate 10 to an acid treatment, the second region surface 24a of the magnetic substrate 10 is processed into a surface with a larger surface roughness than the first region surface 22a. The first region surface 22a is the surface covered with the metal film 62, and the second region surface 24a is the surface adjacent to the first region surface 22a not covered with the metal film 62. As long as this surface processing step is performed before the subsequent step S20 of forming the plating film 64 constituting the external electrode 60, the order of the steps can be set as appropriate. For example, by performing it after the step S16 of forming the metal film 62 constituting the external electrode 60, the first region surface 22a, which is the surface of the first region 22, can be covered with the metal film 62, and only the second region surface 24a, which is the surface of the second region 24, can be selectively processed, which is preferable.

[0038] Here, an explanation will be given regarding that by acid-treating the surface of the magnetic substrate 10, the surface 24a of the second region of the magnetic substrate 10 is processed into a surface with a larger surface roughness than the surface 22a of the first region. Acid treatment using an acid solution such as a phosphoric acid solution, a hydrochloric acid solution, or a sulfuric acid solution can dissolve metals such as metallic iron by appropriately setting conditions (such as concentration, temperature, treatment time, pH, etc.), while not dissolving oxide films such as silicon oxide, chromium oxide, and iron oxide.

[0039] There may be a case where metal magnetic particles are exposed on the surface of the magnetic substrate 10. For example, by performing the polishing treatment in step S14 above, the oxide film formed on the metal magnetic particles near the surface of the magnetic substrate 10 may be damaged, and the metal magnetic particles may be exposed on the surface of the magnetic substrate 10. By performing the step of the polishing treatment before the step of forming the metal film 62, the ridge line portion of the entire magnetic substrate 10 can be made into a certain shape without being affected by the metal film 62. When the metal magnetic particles on the surface of the magnetic substrate 10 are at the ridge line portion of the magnetic substrate 10, the stress due to the polishing treatment is concentrated, so in particular, the oxide film formed on the metal magnetic particles is easily damaged, and the metal magnetic particles are easily exposed on the surface of the magnetic substrate 10. When acid treatment is performed under appropriate conditions in a state where the metal magnetic particles are exposed on the surface of the magnetic substrate 10, only the metal magnetic particles not covered by the oxide film formed on the metal magnetic particles are dissolved, and depressions from which some metal magnetic particles are removed are formed on the surface of the magnetic substrate 10. On the other hand, on the surface of the magnetic substrate 10 covered with the metal film 62, since it is difficult for the acid solution to reach due to the presence of the metal film 62, it is difficult to form depressions from which metal magnetic particles are removed. Also, on the surface of the magnetic substrate 10 covered with the metal film 62, for example, the oxide film formed on the metal magnetic particles is difficult to be damaged by the polishing treatment, so the metal magnetic particles remain covered by the oxide film and are difficult to dissolve in the acid solution, and depressions from which metal magnetic particles are removed are difficult to be formed on the surface of this part of the magnetic substrate 10. From this, the step of forming the metal film 62 may be performed before the step of the polishing treatment. From such a situation, the surface 22a of the first region covered with the metal film 62 on the surface of the magnetic substrate 10 becomes a surface with a small surface roughness, and the surface 24a of the second region not covered with the metal film 62 becomes a surface with a large surface roughness.

[0040] Also, by performing the acid treatment under appropriate conditions, it is possible to prevent the oxide film formed on the surface of the metal magnetic particles from being dissolved. Therefore, in the depressions formed by the dissolution of the metal magnetic particles due to the acid treatment, the oxide films formed on the surfaces of other metal magnetic particles are exposed. For this reason, the acid solution does not erode the inside of the magnetic substrate 10.

[0041] Note that the method of processing the second region surface 24a of the magnetic substrate 10 into a surface with a larger surface roughness than the first region surface 22a is not limited to the case where it is performed by acid treatment. For example, it may be performed by other methods such as sandblasting and polishing only the second region surface 24a. Further, the processing of the surface roughness may be performed in combination with other processes.

[0042] Next, on the metal film 62 provided on the first region surface 22a of the magnetic substrate 10, an electroplated film 64 constituting the external electrode 60 is formed using the electroplating method (step S20). Thereby, an external electrode 60 composed of the metal film 62 and the electroplated film 64 and electrically connected to the coil conductor 30 is formed. The electroplated film 64 is formed, for example, by the barrel plating method.

[0043] [Comparative form] The coil component according to the comparative form is different from the first embodiment in that a second region surface having a larger surface roughness than the first region surface is not formed on the surface of the magnetic substrate. In other respects, it is the same as the first embodiment. Further, the coil component according to the comparative form is formed by the same method as the manufacturing method described in the first embodiment except that the processing for processing the surface of the magnetic substrate into the first region surface and the second region surface is not performed.

[0044] FIG. 5 is a cross-sectional view near the external electrode of the coil component according to the comparative form. FIG. 5 is a diagram schematically showing an SEM image obtained by observing a cross-section of the coil component according to the comparative form with a scanning electron microscope (SEM). In the observed coil component, a magnetic substrate 110 is formed of metal magnetic particles made of a soft magnetic alloy containing 95 wt% of iron, 3.5 wt% of silicon, and 1.5 wt% of chromium. The external electrode 160 is formed of a metal film 162 made of silver and a plating film 164 which is a laminated film of a nickel plating film and a tin plating film formed by an electrolytic plating method on the metal film 162.

[0045] As shown in FIG. 5, in the comparative form, since no processing is performed on the surface of the magnetic substrate 110 to process it into a first region surface and a second region surface, the surface of the magnetic substrate 110 has a small surface roughness both on the surface not covered by the metal film 162 and on the surface covered by the metal film 162. The plating film 164 formed by the electrolytic plating method extends from above the metal film 162 to the surface of the magnetic substrate 110. It is considered that the plating film 164 extends to the surface of the magnetic substrate 110 for the following reasons. As described above, for the magnetic substrate 110, for example, the oxide film formed on the metal magnetic particles near the surface of the magnetic substrate 110 may be damaged by polishing treatment, and the metal magnetic particles may be exposed on the surface of the magnetic substrate 110. When the metal magnetic particles on the surface of the magnetic substrate 110 are at the ridge line portion of the magnetic substrate 110, the stress due to the polishing treatment is concentrated, so that the oxide film formed on the metal magnetic particles is particularly likely to be damaged, and the metal magnetic particles are likely to be exposed on the surface of the magnetic substrate 110. In addition, when the plating film 164 is formed by electrolytic plating such as barrel plating, the oxide film on the surface of the metal magnetic particles is also damaged by the contact of the coil parts with each other, and in particular, the oxide film on the surface of the metal magnetic particles at the ridge line portion is damaged, and the metal magnetic particles are likely to be exposed on the surface of the magnetic substrate 110. Therefore, it is considered that the electrical resistance on the surface of the magnetic substrate 110 becomes low, and the plating film 164 extends from above the metal film 162 to the surface of the magnetic substrate 110. Although an oxide film may be formed by natural oxidation of the surface of the exposed metal magnetic particles, since this oxide film cannot be said to have high insulation, it is considered that plating growth will occur.

[0046] With the miniaturization of electronic devices, the miniaturization of coil parts has also progressed, so the distance between the pair of external electrodes 160 has become narrower. For this reason, if the plating film 164 extends and is formed to an unintended location, the withstand voltage between the pair of external electrodes 160 becomes insufficient, and there is a risk of problems occurring in the coil part.

[0047] [Cross-section Evaluation of the First Embodiment] Figs. 6(a) and 6(b) are cross-sectional views of the vicinity of the external electrode 60 of the coil component 300 according to the first embodiment. Figs. 6(a) and 6(b) are diagrams schematically showing SEM images obtained by observing the cross-section of the coil component 300 with a scanning electron microscope (SEM). The observed coil component 300 has a magnetic substrate 10 formed of metal magnetic particles made of a soft magnetic alloy of iron: 95 wt%, silicon: 3.5 wt%, and chromium: 1.5 wt%. The external electrode 60 is formed of a metal film 62 made of silver and a plating film 64 which is a laminated film of a nickel plating film and a tin plating film formed on the metal film 62 by an electrolytic plating method. The coil component 300 in Figs. 6(a) and 6(b) is subjected to a treatment of immersing the magnetic substrate 10 in a phosphoric acid solution having a concentration of 5 vol% (volume%) to 25 vol% (volume%) and a temperature of 50°C to 70°C for 5 minutes to 30 minutes as the acid treatment described in step S18 of Fig. 4. Conventionally, in order to deposit a phosphate on a portion where the oxide film (insulating film) on the surface of the metal magnetic particles is damaged to form a defect and the metal magnetic particles are exposed to enhance the insulation, a phosphoric acid treatment is known. The phosphoric acid treatment at this time is adjusted to conditions that do not dissolve the metal magnetic particles. For example, a treatment of immersing in a phosphoric acid solution having a concentration of 0.1 vol% (volume%) and a temperature of 50°C for 5 minutes is adopted.

[0048] As shown in Figs. 6(a) and 6(b), since the magnetic substrate 10 is subjected to the phosphoric acid treatment, some of the metal magnetic particles are dissolved on the surface of the second region 24a of the magnetic substrate 10 that is not covered by the metal film 62, and depressions are formed in the magnetic substrate 10. Therefore, on the surface of the magnetic substrate 10, a first region surface 22a that is covered by the metal film 62 and has a small surface roughness and a second region surface 24a that is not covered by the metal film 62 and has a large surface roughness are formed. The plating film 64 formed on the metal film 62 on the first region surface 22a does not extend to the second region surface 24a having a large surface roughness, and the tip of the plating film 64 is located near the boundary between the first region surface 22a and the second region surface 24a.

[0049] It is considered that the plating film 64 did not extend to the surface 24a of the second region for the following reasons. Since the surface 24a of the second region has a large surface roughness and thus is likely to have a high electrical resistance on the surface, it is considered that the plating film 64 did not extend to the surface 24a of the second region. Also, the depressions formed on the surface 24a of the second region are small because they are formed by removing the metal magnetic particles. When the plating film 64 is formed by electrolytic plating, it is difficult for metal to deposit in the depressions, so it is also considered that the plating film 64 did not extend to the surface 24a of the second region. Furthermore, since the oxide film formed on the surface of other metal magnetic particles is exposed in the depressions from which the metal magnetic particles have been removed, the electrical resistance is likely to be high. Also, since the oxide film in the depressions is not easily damaged even when the coil components collide with each other by electrolytic plating such as barrel plating, it is considered that the plating film 64 did not extend to the surface 24a of the second region.

[0050] As described above, according to the present first embodiment, as shown in FIG. 4, a molded body in which a pattern of a precursor of the coil conductor 30 is formed inside is formed to contain metal magnetic particles (step S10). The molded body is heat-treated to form a magnetic substrate 10 having a first region 22 with a first region surface 22a on the surface and a second region 24 with a second region surface 24a on the surface, and the first region surface 22a and the second region surface 24a are adjacent to each other (step S12). The surface 24a of the second region is processed into a surface having a larger surface roughness than the surface 24a of the first region (step S18). As part of the step of forming the external electrode 60 electrically connected to the coil conductor 30, a plating film 64 is formed on the first region surface 22a using electrolytic plating (step S20). The present first embodiment includes steps S10, S12, S18, and S20 as described above. Thereby, the formation of the plating film 64 extending from the first region 22 to the second region 24 is suppressed. Therefore, the formation of the plating film 64 in an unintended portion can be suppressed. Note that the step of processing the surface 24a of the second region into a surface having a larger surface roughness than the surface 22a of the first region is not limited to being performed after the molded body is heat-treated to form the magnetic substrate 10, and may be performed before the molded body is heat-treated.

[0051] Further, in the first embodiment, as shown in FIG. 4, as part of the step of forming the external electrode 60, a step of forming a metal film 62 on the surface 22a of the first region is provided (step S16). Thereby, it is possible to suppress the plating film 64 formed on the metal film 62 from extending outside the metal film 62, and it can be formed in a portion intended for the plating film 64.

[0052] Also, in the first embodiment, by acid-treating the surface of the magnetic substrate 10, the surface 24a of the second region of the magnetic substrate 10 is processed into a surface having a larger surface roughness than the surface 22a of the first region. By acid-treating the surface of the magnetic substrate 10, metal magnetic particles are dissolved in the surface 24a of the second region of the magnetic substrate 10 that is not covered by the metal film 62, forming small depressions. Also, the oxide film formed on the surface of other metal magnetic particles can be exposed within the depressions. Therefore, it is possible to suppress the plating film 64 from being formed by extending to the second region 24.

[0053] Also, in the first embodiment, metal magnetic particles are removed from the surface of the magnetic substrate 10, and depressions are provided on the surface of the magnetic substrate 10 to form the surface 24a of the second region having a large surface roughness. Since the depressions from which the metal magnetic particles have been removed are small, it becomes difficult for metal to be deposited in the depressions when the plating film 64 is formed by electrolytic plating, and it is possible to suppress the plating film 64 from being formed by extending to the second region 24.

[0054] Also, in the first embodiment, the metal magnetic particles have an oxide film on their surfaces when they are contained in the magnetic substrate. And a surface 24a of the second region is formed in which the oxide film formed on the surface of other metal magnetic particles is exposed in the depressions from which the metal magnetic particles have been removed. Thereby, it is possible to suppress the surface electrical resistance of the surface 24a of the second region from decreasing, and it is possible to suppress the plating film 64 from being formed by extending to the second region 24. In the first embodiment, a case where an oxide film is formed on the surface of the metal magnetic particles by heat-treating the molded body for forming the magnetic substrate 10 is shown as an example, but an oxide film may be formed on the surface of the metal magnetic particles at the time when the molded body is formed.

[0055] Also, according to the first embodiment, as shown in FIG. 2, the magnetic substrate 10 containing metal magnetic particles has a first region 22 having a first region surface 22a on the surface, and a second region 24 having a second region surface 24a adjacent to the first region surface 22a on the surface and having a larger surface roughness than the first region surface 22a. The external electrode 60 including the plating film 64 is provided on the first region surface 22a of the magnetic substrate 10. By providing the plating film 64 on the first region surface 22a of the magnetic substrate 10, the plating growth is suppressed as described above, so that the external electrode 60 formed in the intended portion can be obtained.

[0056] In addition, in the first embodiment, as shown in FIG. 4, the process of forming a chamfered ridge line on the first region surface 22a by polishing the surface of the magnetic substrate 10 may be included (step S14). By chamfering and polishing the surface of the magnetic substrate 10, the metal magnetic particles are exposed on the surface of the magnetic substrate 10, the electrical resistance of the surface of the magnetic substrate 10 becomes low, and the plating growth is likely to occur. However, by processing the second region surface 24a into a surface having a larger surface roughness than the first region surface 22a, it is possible to suppress the plating film 64 formed in the first region 22 from extending to the second region 24.

[0057] In the above first embodiment, the case where the external electrode 60 is provided only on the lower surface of the magnetic substrate 10, that is, the case of a one-sided electrode, is shown as an example, but it is not limited to this case. The external electrode 60 may be a two-sided electrode extending from the lower surface of the magnetic substrate 10 to the end surface (WT surface), or may be a five-sided electrode extending from the lower surface of the magnetic substrate 10 to the upper surface via the end surface (WT surface) and the side surface (LT surface).

[0058] [Second Embodiment] The second embodiment of the present invention is different from the first embodiment in that a magnetic substrate is formed with a resin provided around metal magnetic particles. Since the perspective view and cross-sectional view of the second embodiment are the same as FIGS. 1 and 2 of the first embodiment, illustration and description thereof are omitted. FIG. 7 is a flowchart showing an example of a method for manufacturing a coil component according to the second embodiment of the present invention. As shown in FIG. 7, first, the same steps S30 and S32 as steps S10 and S12 in FIG. 4 of the first embodiment are performed to form a magnetic substrate 10. Next, the magnetic substrate 10 is impregnated with a resin and cured (step S34). As the resin, a resin having excellent insulation properties such as polyvinyl butyral (PVB) resin or epoxy resin is used. Thereafter, the same steps S36, S38, S40, and S42 as steps S14, S16, S18, and S20 in FIG. 4 of the first embodiment are performed. When the surface of the magnetic substrate 10 is acid-treated in step S40 to process the second region surface 24a into a surface having a larger surface roughness than the first region surface 22a, the resin formed around the metal magnetic particles is exposed in the depressions from which the metal magnetic particles on the second region surface 24a have been removed. Therefore, the acid solution does not erode the inside of the magnetic substrate 10. For example, the area of the resin exposed on the second region surface 24a is larger than the area of the resin exposed on the first region surface 22a.

[0059] Note that in FIG. 7, as a method for forming the magnetic substrate 10 with a resin provided around the metal magnetic particles, a method is exemplified in which a molded body is heat-treated to create an oxide film on the surface of the metal magnetic particles, and the magnetic substrate 10 in which the metal magnetic particles are bonded to each other via the oxide film formed on the surface is formed, and then the magnetic substrate 10 is impregnated with a resin. However, the magnetic substrate 10 with a resin provided around the metal magnetic particles may be formed by other methods. For example, in the flowchart of FIG. 7, step S34 is not performed. Instead, in steps S30 and S32, a molded body having a pattern of a precursor of the coil conductor 30 inside is formed using a mixture of metal magnetic particles having an oxide film in advance and a resin, and this molded body is heat-treated to cure the resin, thereby forming the magnetic substrate 10 in which the metal magnetic particles are solidified with the resin.

[0060] Also in the second embodiment, a molded body in which a pattern of a precursor of the coil conductor 30 is formed inside is formed to contain metal magnetic particles (step S30). The molded body is heat-treated to form a magnetic base body 10 having a first region 22 with a first region surface 22a on the surface and a second region 24 with a second region surface 24a on the surface, and the first region surface 22a and the second region surface 24a are adjacent to each other (step S32). The second region surface 24a is processed into a surface having a larger surface roughness than the first region surface 22a (step S40). As part of the process of forming the external electrode 60 electrically connected to the coil conductor 30, a plating film 64 is formed on the first region surface 22a using an electrolytic plating method (step S42). The second embodiment includes steps S30, S32, S40, and S42 as described above. Thereby, similarly to the first embodiment, the formation of the plating film 64 extending from the first region 22 to the second region 24 is suppressed. Therefore, it is possible to suppress the formation of the plating film 64 in an unintended portion. Note that the step of processing the second region surface 24a into a surface having a larger surface roughness than the first region surface 22a is not limited to the case of being performed after heat-treating the molded body to form the magnetic base body 10, and may be performed before heat-treating the molded body.

[0061] Further, in the second embodiment, a step of causing the magnetic base body 10 to contain a resin is included (step S34), and a second region surface 24a is formed in which the resin is exposed in the recess from which the metal magnetic particles have been removed. The resin can have a higher electrical resistance than the insulating film formed on the surface of the metal magnetic particles. Therefore, in addition to being able to suppress a decrease in the electrical resistance of the second region surface 24a due to the exposure of the oxide film formed on the surface of the metal magnetic particles, it is possible to further suppress a decrease in the electrical resistance of the second region surface 24a due to the exposure of the resin, and to suppress the formation of the plating film 64 extending to the second region 24. Note that in the second embodiment, the case where the magnetic base body 10 is caused to contain the resin by impregnating the magnetic base body 10 with the resin is shown as an example, but the magnetic base body 10 may be caused to contain the resin by forming a molded body containing the metal magnetic particles and the resin.

[0062] [Third Embodiment] In the above-described first and second embodiments, the case of a stacked coil component has been described as an example. In the third embodiment, an example of a wound coil component will be described. FIG. 8 is a side view of a coil component 400 according to the third embodiment of the present invention. As shown in FIG. 8, the coil component 400 according to the third embodiment has a magnetic substrate 10a including a shaft portion 70 and a pair of flange portions 72 provided at both ends of the shaft portion 70. The coil conductor 30 is formed by winding a wire 74 with an insulating coating around the shaft portion 70. The wire 74 with an insulating coating has a core wire made of, for example, copper, silver, palladium, or a silver-palladium alloy, and the circumferential surface thereof is covered with an insulating coating made of a resin material such as polyimide, polyamideimide, polyurethane, or polyester. The cross-sectional shape of the core wire may be circular or rectangular.

[0063] On one of the pair of flange portions 72, a first region 22 having a first region surface 22a on the surface and a second region 24 having a second region surface 24a adjacent to the first region surface 22a on the surface are provided. The second region surface 24a has a larger surface roughness than the first region surface 22a. The external electrode 60 is provided on the first region surface 22a having a small surface roughness. The external electrode 60 is not provided on the second region surface 24a having a large surface roughness. One of the pair of external electrodes 60 is electrically connected to one end of the coil conductor 30, and the other is electrically connected to the other end of the coil conductor 30.

[0064] In the third embodiment, a first region surface 22a and a second region surface 24a adjacent to the first region surface 22a and having a larger surface roughness than the first region surface 22a may be provided on the surfaces of each of the pair of flange portions 72, and one external electrode 60 may be provided on the first region surface 22a of each of the pair of flange portions 72. The position of the external electrode 60 is not limited to this example and can be arbitrarily set as long as it is on the surface of the magnetic substrate 10.

[0065] [Manufacturing Method] FIG. 9 is a flowchart showing an example of a method for manufacturing the coil component 400 according to the third embodiment of the present invention. As shown in FIG. 9, first, a molded body for forming the magnetic substrate 10a is formed (step S50). For example, a molded body having a shaft portion 70 and a pair of flange portions 72 is formed by filling a magnetic paste containing metal magnetic particles into the cavity of a mold and performing press forming.

[0066] Next, the magnetic substrate 10a is formed by performing heat treatment for firing on the molded body (step S52). The heat treatment is performed at a predetermined temperature in an atmosphere containing oxygen. By this heat treatment, an oxide film made of an oxide of the material component of the metal magnetic particles is formed on the surface of the metal magnetic particles contained in the molded body, and the magnetic substrate 10a is formed by the plurality of metal magnetic particles being bonded to each other through the oxide film.

[0067] Next, in order to chamfer (R-process) the ridge line portion of the magnetic substrate 10a, remove foreign matters such as deposits on the surface, and remove generated burrs, the magnetic substrate 10a is subjected to polishing treatment such as barrel polishing (step S54). This step of polishing treatment may be, for example, after step S50 of forming the molded body or, for example, after step S56 of forming the metal film 62.

[0068] Next, a metal film 62 constituting the external electrode 60 is formed on the surface of the flange portion 72 of the magnetic substrate 10a (step S56). The metal film 62 is formed on the first region surface 22a which is the surface of the first region 22 of the magnetic substrate 10a, for example, by sputtering or applying a conductive paste.

[0069] Next, the surface of the magnetic substrate 10 is processed (step S58) so that the second region surface 24a, which is the surface of the second region 24 of the magnetic substrate 10a, becomes a surface with a larger surface roughness than the first region surface 22a, which is the surface of the first region 22. This step can be performed, for example, by the acid treatment described in the first embodiment. As a result, the second region surface 24a of the surface of the magnetic substrate 10a that is not covered with the metal film 62 becomes a surface with a larger surface roughness than the first region surface 22a covered with the metal film 62. Note that the surface of the magnetic substrate 10a may be processed into the first region surface 22a and the second region surface 24a by a method other than the acid treatment.

[0070] Next, a coil conductor 30 is formed by winding a wire 74 with an insulating coating around the shaft portion 70 of the magnetic substrate 10a (step S60).

[0071] Next, an electroplating film 64 that constitutes the external electrode 60 is formed on the metal film 62 provided on the first region surface 22a of the magnetic substrate 10a using the electroplating method (step S62). As a result, the external electrode 60 composed of the metal film 62 and the electroplating film 64 is formed. Then, one end of the coil conductor 30 is electrically connected to one of the pair of external electrodes 60, and the other end is electrically connected to the other of the external electrodes 60.

[0072] According to the third embodiment, as shown in FIG. 9, a molded body containing metal magnetic particles is formed (step S50). The molded body is heat-treated to form a magnetic substrate 10a having a first region 22 with a first region surface 22a on the surface and a second region with a second region surface 24a on the surface, and the first region surface 22a and the second region surface 24a are adjacent to each other (step S52). The second region surface 24a is processed into a surface having a larger surface roughness than the first region surface 22a (step S58). A coil conductor 30 is wound around the magnetic substrate 10a to form it (step S60). An electrolytic plating film 64 is formed on the first region surface 22a of the magnetic substrate 10 by using an electrolytic plating method, and is electrically connected to the coil conductor 30 to form an external electrode 60 including the plating film 64 (step S62). The third embodiment includes steps S50, S52, S58, S60, and S62 as described above. Thereby, similar to the first embodiment, the formation of the plating film 64 extending from the first region 22 to the second region 24 is suppressed. Therefore, it is possible to suppress the formation of the plating film 64 in an unintended portion. Note that the step of processing the second region surface 24a into a surface having a larger surface roughness than the first region surface 22a is not limited to being performed after the molded body is heat-treated to form the magnetic substrate 10, and may be performed before the molded body is heat-treated.

[0073] In addition, in the wound coil component shown in the third embodiment above, similar to the second embodiment of the stacked coil component, a magnetic substrate 10a provided with resin around the metal magnetic particles may be formed. That is, in the flowchart of FIG. 9, a step of impregnating the magnetic substrate 10a with resin and curing it may be provided. Also, in steps S50 and S52, a molded body may be formed using a mixture of metal magnetic particles having an oxide film in advance and resin, and the molded body may be heat-treated to cure the resin, thereby forming a magnetic substrate 10a in which the metal magnetic particles are solidified with the resin.

[0074] In the third embodiment above, the case where the magnetic substrate 10a is a drum core is shown as an example, but it may be a T-core, or may be other types of cores.

[0075] As described above in detail regarding the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0076] 10, 10a Magnetic substrate 11 - 15 Magnetic layer 16 Upper cover layer 17 Lower cover layer 20 Body part 22 First region 22a Surface of the first region 24 Second region 24a Surface of the second region 30 Coil conductor 32 Circumferential part 34a, 34b Lead - out part 60 External electrode 62 Metal film 64 Plating film 70 Shaft part 72 Flange part 74 Conductive wire 110 Magnetic substrate 160 External electrode 162 Metal film 164 Plating film 300, 400 Coil component

Claims

1. Forming a molded body having a pattern of a precursor of a coil conductor formed therein, having a first region surface and a second region surface adjacent to the first region surface on the surface, and containing metal magnetic particles; Heat-treating the molded body to form a magnetic substrate; Forming a metal film on the first region surface; After the step of forming the metal film, processing the second region surface into a surface having a larger surface roughness than the first region surface; After the step of processing the second region surface, forming a plating film on the metal film using an electrolytic plating method, electrically connecting to the coil conductor, and forming an external electrode including the metal film and the plating film on the first region surface. A method for manufacturing a coil component comprising the steps of:

2. Forming a molded body containing metal magnetic particles and having a first region surface and a second region surface adjacent to the first region surface on the surface; Heat-treating the molded body to form a magnetic substrate; Winding a conductor around the magnetic substrate to form a coil conductor; Forming a metal film on the first region surface; After the step of forming the metal film, processing the second region surface into a surface having a larger surface roughness than the first region surface; After the step of processing the second region surface, forming a plating film on the metal film using an electrolytic plating method, electrically connecting to the coil conductor, and forming an external electrode including the metal film and the plating film on the first region surface. A method for manufacturing a coil component comprising the steps of:

3. The step of forming the metal film is a step of forming the metal film by a sputtering method or by applying a conductive paste. The method for manufacturing a coil component according to claim 1 or 2.

4. The step of processing the second region surface is a step of acid-treating the surface of the magnetic substrate. The method for manufacturing a coil component according to any one of claims 1 to 3.

5. The step of processing the second region surface is a step of removing the metal magnetic particles from the surface of the magnetic substrate and providing a depression on the surface of the magnetic substrate. The method for manufacturing a coil component according to any one of claims 1 to 4.

6. When the metal magnetic particles are contained in the magnetic substrate, they have an oxide film on their surface. The step of processing the second region surface is a step of exposing the oxide film of the metal magnetic particles in the depression. The method for manufacturing a coil component according to claim 5.

7. further comprising a step of incorporating a resin into the magnetic substrate, The step of processing the surface of the second region is a step of exposing the resin in the recess, according to the method for manufacturing a coil component according to claim 5 or 6. **Claim 8** The method for manufacturing a coil component according to any one of claims 1 to 7, wherein the metal magnetic particles are soft magnetic alloys mainly composed of iron.

Images