COIL COMPONENT

A coil component according to one or more embodiments of the invention includes a base body, a coil conductor embedded in the base body, and an external electrode provided on the base body. The base body has on its surface a first region that has a first reflectance, a second region that has a second reflectance lower than the first reflectance, and a third region that is surrounded by the second region and has a third reflectance higher than the second reflectance. The third region has a shape of a sign.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from Japanese Patent Application Serial No. 2020-164461 (filed on Sep. 30, 2020), the contents of which are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a coil component, a circuit board including the coil component, and an electronic device including the circuit board. The present disclosure also relates to a method of manufacturing a coil component.

BACKGROUND

A sign may be provided to a surface of a base body of a coil component to convey information about the coil component. One example of such a sign on a coil component is text indicating the dimensions, model number, and other information about the coil component, and another example is a marker such as a graphic or symbol indicating the orientation or position of the coil component.

Japanese Patent Application Publication No. 2013-093403 (“the '403 Publication”) describes an electronic component in which a print pattern representing characters is formed on a surface of the base body. This print pattern is printed by an inkjet printer. Japanese Patent Application Publication No. 2004-327885 (“the '885 Publication”) describes a multilayer inductor with a marker for directional identification formed on its surface. The marker for directional identification described in “the '885 Publication” is formed of a material that is able to produce a great color and different from the base material (specifically, a material containing between 10 wt % and 30 wt % of borosilicate glass, between 50 wt % and 80 wt % of TiO2, and the remainder of either ZrO2or Al2O3).

Since the sign formed on the surface of the base body is recognized by observing a photograph taken by an optical camera or by directly observing the surface of the base body with the naked eye, it is desirable that the sign on the base body surface is easily recognizable from other parts of the surface of the base body.

SUMMARY

One of the objects of the invention disclosed herein is to provide a novel technical improvement that makes it easier to recognize a sign on the surface of the base body of the coil component.

The other objects of the disclosure will be apparent with reference to the entire description in this specification. The invention disclosed herein may solve any other drawbacks grasped from the following description, instead of or in addition to the above drawback.

A coil component according to one or more aspects of the invention includes a base body, a coil conductor provided in the base body, and an external electrode provided on the base body. The base body has on its surface a first region that has a first reflectance, a second region that has a second reflectance lower than the first reflectance, and a third region that is surrounded by the second region and has a third reflectance higher than the second reflectance. The third region has a shape of a sign.

According to one or more aspects of the invention, the second reflectance at a wavelength of 700 nm may be 10% or less.

According to one or more aspects of the invention, the second reflectance at a wavelength of 700 nm may be 1% or more.

According to one or more aspects of the invention, the sign may include at least one of a character, number or symbol.

According to one or more aspects of the invention, the surface of the base body is defined by a plurality of surfaces, and the second region may occupy a whole one surface of the plurality of surfaces. According to one or more aspects of the invention, the second region may occupy a part of one surface of the plurality of surfaces.

According to one or more aspect of the invention, the base body may be formed of an Ni—Zn based ferrite material.

According to one or more aspects of the invention, the base body may be formed of a magnetic material containing metal magnetic particles.

One or more aspects of the invention relate to a circuit board including the coil component according to any one of the aspects of the invention. Another aspect of the invention relates to an electronic device comprising the above circuit board.

The electronic device includes the circuit board according to the one or more aspects of the invention.

A method of manufacturing a coil component according to one or more aspects of the invention includes: fabricating a blank body from a magnetic material, the blank body including a conductor thereinside and having a surface that has a first reflectance; forming a low reflectance region in a part of the surface of the blank body, the low reflectance region having a second reflectance lower than the first reflectance; and forming a sign region in the low reflectance region, the sign region having a third reflectance higher than the second reflectance and having a shape of a sign.

A method of manufacturing a coil component according to one or more aspects of the invention includes: fabricating a blank body from a magnetic material, the blank body being defined by a surface having a first reflectance; forming a low reflectance region in a part of the surface of the blank body, the low reflectance region having a second reflectance lower than the first reflectance; forming a sign region in the low reflectance region, the sign region having a third reflectance higher than the second reflectance and having a shape of a sign; and winding a wire around the blank body.

According to one or more aspects of the invention, the low reflectance region may be formed by laser processing.

According to one or more aspects of the invention, the low reflectance region may be formed by blasting.

According to one or more aspects of the invention, the sign region may be formed by laser processing.

Advantageous Effects

According to one or more aspects of the invention, the sign on the surface of the base body of the coil component can be easily recognized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the present invention will be hereinafter described with reference to the accompanying drawings. The constituents common to multiple drawings are denoted by the same reference signs throughout the drawings. For convenience of explanation, the drawings are not necessarily drawn to scale.

A coil component1according to one embodiment of the invention will be hereinafter described with reference toFIGS. 1 and 2.FIG. 1is a perspective view of the coil component1according to the embodiment of the invention, andFIG. 2is a plan view of the coil component1shown inFIG. 1.

The coil component1is, for example, an inductor. The inductor is an example of the coil component to which the invention can be applied to. The invention can also be applied to transformers, filters, reactors, and various any other coil components. Advantageous effects of the invention will be more remarkably exhibited if the invention is applied to coil components and any other electronic components to which large current is applied. An inductor used in a DC-DC converter is an example of a coil component to which large current is applied. The invention may be also applied to coupled inductors, choke coils, and any other magnetically coupled coil components, in addition to the inductors used in DC-DC converters. Applications of the coil component1are not limited to those explicitly described herein.

As shown inFIGS. 1 and 2, the coil component1includes a base body10made of a magnetic material, a coil conductor25embedded in the magnetic base body, an external electrode21electrically connected to one end of the coil conductor25, and an external electrode22electrically connected to the other end of the coil conductor25.

The illustrated coil component1is mounted on a mounting substrate102a. The mounting substrate102amay have land portions103provided thereon. In the case where the coil component1includes two external electrodes21and22, the mounting substrate102ais provided with two landing portions103correspondingly. The coil component1may be mounted on the mounting substrate102aby joining the external electrodes21,22to the corresponding land portions103of the mounting substrate102a. A circuit board102according to one embodiment includes the mounting substrate102aand the coil component1mounted on the mounting substrate102a. The circuit board102can be installed in various electronic devices. Electronic devices in which the circuit board102may be installed include smartphones, tablets, game consoles, electrical components of automobiles, servers, and various other electronic devices. The coil component1may be embedded in the mounting substrate102a.

The base body10has a substantially rectangular parallelepiped shape. In this specification, a “length” direction, a “width” direction, and a “thickness” direction of the coil component1correspond to the “L axis” direction, the “W axis” direction, and the “T axis” direction inFIG. 1, respectively, unless otherwise construed from the context. In one embodiment of the invention, the base body10has a length (the dimension in the L axis direction) of 1.0 to 6.0 mm, a width (the dimension in the W axis direction) of 0.5 to 6.0 mm, and a thickness (the dimension in the T axis direction) of 0.5 to 3.0 mm. The length of the magnetic base body may be 0.3 to 1.6 mm, the width may be 0.1 to 0.8 mm, and the thickness may be 0.1 to 0.8 mm.

The base body10has a first principal surface10a, a second principal surface10b, a first end surface10c, a second end surface10d, a first side surface10e, and a second side surface10f. These six surfaces define the outer periphery of the base body10. The first principal surface10aand the second principal surface10bare opposed to each other, the first end surface10cand the second end surface10dare opposed to each other, and the first side surface10eand the second side surface10fare opposed to each other. As shown inFIG. 1, the first principal surface10alies on the top side in the magnetic base body10, and therefore, the first principal surface10amay be herein referred to as “the top surface.” Similarly, the second principal surface10bmay be referred to as “the bottom surface.” The coil component1is disposed such that the second principal surface10bfaces a circuit board102, and therefore, the second principal surface10bmay be herein referred to as a “mounting surface.” The top-bottom direction of the coil component1refers to the top-bottom direction (the direction along the axis T) inFIG. 1.

The external electrode21is provided on the first end surface10cof the base body10. The external electrode22is provided on the second end surface10dof the base body10. As shown, these external electrodes may extend to the bottom surface of the base body10. The shapes and positions of the external electrodes are not limited to the illustrated example. For example, both of the external electrodes21,22may be provided on the bottom surface10bof the base body10. The external electrodes21and22are separated from each other in the length direction.

The base body10is made of a magnetic material. The base body10includes, for example, a sintered body made of a sintered ferrite material. As the ferrite material for the base body10, a Mn—Zn based ferrite, a Ni—Zn based ferrite, or a ferrite material other than the aforementioned can be used. The base body10may be composed of a magnetic material other than ferrite materials. For example, the base body10may include metal magnetic particles formed of a soft magnetic metal material, a soft magnetic alloy material, or any other known magnetic materials. In the base body10, the metal magnetic particles may be bonded to each other by an oxide film formed on the surface of each particle through a heat treatment. The metal magnetic particles may be a particle mixture obtained by mixing two or more types of particles having different average particle sizes. The metal magnetic particles in the base body10may be bonded to each other with a resin binder. As will be described later, in the process of fabricating the base body10, the surface of the base body10is laser processed. When the base body10includes a resin, such as a binder, the resin should be one that does not thermally decompose (not carbonized by laser processing). When the base body10includes a resin, a resin that is not carbonized under the irradiation conditions during the laser processing is selected.

In one or more embodiments of the invention, the surface of the base body10is divided into a high reflectance region10A and a low reflectance region10B surrounded by the high reflectance region10A. Further, the base body10has a sign region10C situated on the inner side of the low reflectance region10B on the surface thereof.

The reflectance of the high reflectance region10A is referred to as a first reflectance. A second reflectance, which is the reflectance of the low reflectance region10B, is lower than the first reflectance, which is the reflectance of the high reflectance region10A. A third reflectance, which is the reflectance of the sign region10C, is higher than the second reflectance of the low reflectance region10B. The third reflectance may be equal to or higher than the first reflectance. The first, second, and third reflectances may be measured for the high reflectance region10A, the low reflectance region10B, and the sign region10C, respectively using a Hitachi High-Tech Corporation (formerly “Hitachi High-Technologies Corporation”) U-4100 spectrophotometer at 25° C. at a wavelength of 700 nmm and at an incident angle of 10 degrees. The reflectance of the base body10may be, for example, a relative value measured by a relative reflection measurement method. To measure the reflectance of the base body10, an integrating sphere is attached to a spectrophotometer, a barium sulfate white plate is used as a reference sample for baseline correction. After the correction, the base body10is placed in a measurement sample placing area of the integrating sphere in place of the reference sample, the surface of the base body10is irradiated with a measurement light from a light source, and light reflected from the surface of the base body10is detected by a detector. This relative reflectance measurement method can be used to determine the relative reflectance of the base body10with reference to the reference sample. The labels “high” reflectance region10A and “low” reflectance region10B focus on the relative reflectance of the high reflectance region10A to that of the low reflectance region10B, and do not necessarily mean that the high reflectance region10A has an absolutely high reflectance. The first reflectance of the high reflectance region10A may be, for example, 12% or more, 15% or more, 20% or more, 30% or more, 40% or more, or 50% or more. The second reflectance of the low reflectance region10B may be, for example, 10% or less, 12% or less, 16% or less, 25% or less, 33% or less, or 42% or less, when the first reflectance of the high reflectance region10A is 12% or more, 15% or more, 20% or more, 30% or more, 40% or more, or 50% or more, respectively. The third reflectance of the sign region10C may be 20% or more, 30% or more, 40% or more, 50% or more, or 60% or more, when the second reflectance of the low reflectance region10B is 10% or less, 12% or less, 16% or less, 25 or less, 33% or less, or 42% or less, respectively. The first reflectance of the high reflectance region10A may be, for example, more than 1.2 times, 1.5 times, or 2 times higher than the second reflectance of the low reflectance region10B. The third reflectance of the sign region10C may be, for example, more than 1.2 times, 1.5 times, or 2 times higher than the second reflectance of the low reflectance region10B.

In one or more embodiments of the invention, the low reflectance region10B occupies a portion of the surface of the base body10. In the illustrated example, the low reflectance region10B is provided in a portion of a top surface10aof the base body10. In the example shown inFIG. 2, the low reflectance region10B is disposed near the upper left corner of the top surface10ain the paper plane, but the arrangement of the low reflectance region10B is not limited to this. The low reflectance region10B may be situated at any position in the top surface10a. The low reflectance region10B may be provided on a surface other than the top surface10aof the base body10. The low reflectance region10B may be provided not only on a single surface of the base body10(the top surface10ain the example ofFIG. 2), but may also be provided across two or more surfaces. For example, the low reflectance region10B may be provided on the base body10such that it spans the top surface10aand the first end surface10c. When the low reflectance region10B spans two or more surfaces, the sign15may also be formed such that it spans two or more surfaces in accordance with the arrangement of the low reflectance region10B. Two or more low reflectance regions10B may be formed on the base body10.

FIG. 4is a top view of the coil component1according to another embodiment of the invention. In the coil component1shown inFIG. 4, the low reflectance region10B occupies the whole top surface10aof the base body10. In this way, the low reflectance region may cover the whole of one or more of the surfaces defining the base body10.

In one or more embodiments of the invention, the low reflectance region10B may be formed by first fabricating a blank body from a magnetic material according to a conventional method and roughening a portion of the surface of the fabricated blank body. In one or more embodiments of the invention, the low reflectance region10B is formed, for example, by applying a blasting process onto at least one of the surfaces of the blank body formed of the magnetic material. The low reflectance region10B may be provided on the surface of the blank body by any surface processing method other than blasting. For example, the low reflectance region10B is formed by laser processing a portion of the surface of the blank body formed of the magnetic material. When forming the low reflectance region10B by blasting, it is necessary to mask the blank body except for the area that will later serve as the low reflectance region10B. Whereas when forming the low reflectance region10B by laser processing, such masking is not necessary. Further when blasting is performed without masking, the whole surface is blasted and polished so that the base body10diminishes in size. Whereas the laser processing can roughen the entire surface without such size reduction.

The high reflectance region10A is an area of the surface of the base body10other than the low reflectance region10B. The high reflectance region10A occupies a part or all of the area of the surface of the base body10other than the low reflectance region10B. As shown inFIG. 4, the high reflectance region10A may be formed on a surface of the base body10that is different from the surface on which the low reflectance region10B is formed.

In the embodiment shown inFIG. 2, the sign region10C is formed in a shape of a symbol, which is a triangle that can indicate the orientation or position of the coil component1in the illustrated embodiment. The sign region10C may be formed in a shape of a symbol other than a triangle.

The sign region10C may be a character(s) or number(s) indicating various information about the coil component1in addition to the orientation and position of the coil component1.FIG. 5is a top view of the coil component1according to yet another embodiment of the invention. In the coil component1shown inFIG. 5, a sign region10C is formed in the low reflectance region10B, instead of the sign region10C ofFIG. 2. The sign region10C includes numbers and an alphabet in addition to a geometric shape. In this embodiment, the portion consisting of a number(s) and alphabet(s) represents specifically “4R7.” In the art of the invention, the label “4R7” is typically considered to represent the electrical characteristics (L-value and Z-value) of the coil component1. In addition to the electrical characteristics of the coil component1, the sign region10C may be a number(s) or character(s) representing a model number, rated current, dimensions, any other specifications, or any other information about the coil component1, or a combination of a number(s), character(s), and symbol(s) (or geometric shape(s)).

In one or more embodiments of the invention, the sign region10C is formed by laser processing the low reflectance region10B of the blank body formed of a magnetic material. In the laser processing, a laser irradiation device irradiates a laser beam onto an area of a figure corresponding to the sign region10C in the low reflectance region10B of the surface of the blank body. By irradiating the laser with predetermined irradiation conditions onto the roughened low reflectance region10B, the base body10melts in the laser-irradiated area in the low reflectance region10B. The laser-irradiated area in the low reflectance region10B is dented and becomes smoother than a non-laser-irradiated area in the low reflectance region10B.

In one or more embodiments, an arithmetic surface roughness Ra of the high reflectance region10A is smaller than an arithmetic surface roughness Ra of the low reflectance region10B, and an arithmetic mean roughness Ra of the sign region10C is smaller than an arithmetic mean roughness Ra of the low reflectance region10B. For example, the arithmetic surface roughness Ra of the high reflectance region10A may be between 0.05 μm and 0.3 μm, or between 0.1 μm and 0.2 μm (both inclusive). For example, the arithmetic surface roughness Ra of the low reflectance region10B may be between 0.2 μm and 0.6 μm, or between 0.3 μm and 0.5 μm (both inclusive). For example, the arithmetic mean roughness Ra of the sign region10C may be between 0.05 μm and 0.25 μm, or between 0.07 μm and 0.15 μm (both inclusive). When the low reflectance region10B is formed by roughening the high reflectance region10A, the arithmetic mean surface roughness Ra of the low reflectance region10B is larger than the arithmetic mean roughness Ra of the high reflectance region10A. When the sign region10C is formed by laser processing (laser printing), the arithmetic mean roughness Ra of the sign region10C becomes smaller than the arithmetic mean roughness Ra of the low reflectance region10B. The arithmetic surface roughness Ra described herein is measured in accordance with the Japanese Industrial Standard JIS B 0601: 2013.

Referring toFIG. 3, reflection of the light after the incidence on the surface of the base body10will be now described. When the incident light enters the surface of the base body10, specular and diffuse reflections occur on the surface of the base body (reflection surface). The incident light entered the surface of the base body10is specularly and diffusely reflected in each of the high reflectance region10A, the low reflectance region10B, and the sign region10C. Reflection angles of reflected light SR1, SR2, and SR3specularly reflected in the high reflectance region10A, the low reflectance region10B, and the sign region10C, respectively on the surface of the base body10are equal to incident angles of incident light IC1, IC2, and IC3entered into the respective regions. Diffusely reflected light DR1, DR2, and DR3in the highly reflectance region10A, the low reflectance region10B, and the sign region10C, respectively on the surface of the base body10travel in various directions in addition to the directions traveled by the specularly reflected light SR1, SR2, and SR3.

InFIG. 3, the intensity of the specularly reflected light SR1, SR2, SR3and the diffusely reflected light DR1, DR2, DR3are represented by the length of the respective arrows. In general, the higher the reflectance of the reflection surface, the higher the light intensity of the specularly reflected light and the lower the light intensity of the diffusely reflected light. Conversely, the lower the reflectance of the reflection surface, the lower the light intensity of the specularly reflected light and the higher the light intensity of the diffusely reflected light. As described above, the second reflectance, which is the reflectance of the low reflectance region10B, is lower than the first reflectance, which is the reflectance of the high reflectance region10A. Therefore, the intensity of the light SR2specularly reflected in the low reflectance region10B is lower than that of the light SR1specularly reflected in the high reflectance region10A. The intensity of the light SR1and SR2are represented by the length of the respective arrows of SR1and SR2inFIG. 3. Similarly, since the second reflectance, which is the reflectance of the low reflectance region10B, is lower than the third reflectance, which is the reflectance of the sign region10C, the intensity of the light SR2specularly reflected in the low reflectance region10B is lower than the intensity of the light SR3specularly reflected in the sign region10C, which is represented by the arrow lengths of SR2and SR3.

Since the second reflectance of the low reflectance region10B is lower than the first reflectance of the high reflectance region10A, the intensity of the light DR2diffusely reflected in the low reflectance region10B is higher than that of the light DR1diffusely reflected in the high reflectance region10A. The intensity of the light DR1and DR2are represented by the length of the respective arrows of DR1and DR2inFIG. 3. Similarly, since the second reflectance of the low reflectance region10B is lower than the third reflectance of the reflectance of the sign region10C, the intensity of the light DR2diffusely reflected in the low reflectance region10B is lower than the intensity of the light DR3diffusely reflected in the sign region10C, which is represented by the arrow lengths of DR2and DR3.

The sign region10C on the surface of the base body10is determined based on an image obtained by photographing the surface of the base body10with an image capturing device (not shown). When an image of the surface of the base body10is taken by the image capturing device, the light reflected by the surface of the base body10is received by an image sensor of the image capturing device. A RAW image is generated by quantizing an electrical signal obtained by converting the received light, and the RAW image is processed by an image processing engine to obtain an image in a predetermined format. Whether the sign region10C in the surface of the base body10can be easily recognized or not is affected by a difference between the intensity of the light reflected by the sign region10C and received by the image sensor and the intensity of the light reflected by the low reflectance region10B provided around the sign region10C and received by the image sensor. More specifically, by increasing the difference between the intensity of the light reflected by the low reflectance region10B around the labeling region10C and then received by the image sensor and the intensity of the light reflected by the sign region10C and then received by the image sensor, it is possible to increase the light-dark difference (contrast) between the sign region10C and the surrounding low reflectance region10B in the image of the surface of the base body10obtained by the image capturing device, and as a result, the sign becomes easier to be recognized.

The light (SR1, SR2, SR3) specularly reflected by the surface of the base body10is received by the image sensor disposed in a reflection direction symmetrical to the incident direction of the incident light with respect to the normal of the reflection surface, but not by the image sensor located off the reflection direction. On the other hand, the light diffusely reflected by the surface of the base body10travels in various directions from the reflection surface, so it is also received by the image sensor(s) located off the traveling direction of the specularly reflected light.

When taking an image of the base body10that has the sign region10C on its surface, it will be cumbersome if the image sensor and the light source need to be arranged such that the image sensor is in the reflection direction symmetrical to the incident direction of the light with respect to the normal of the reflection surface (i.e., in the direction of travel of the specularly reflected light SR1, SR2, SR3). In addition, when the image sensor and the light source are integrated into a single image capturing device, it may not be possible to place the image sensor in the reflection direction symmetrical to the incident direction of the light from the light source. In addition to the light incident from the light source of the image capturing device, the surface of the base body10receives multiple types of incident light, such as light emitted from room lights installed in the observation environment, ambient light, and light emitted from the light source and reflected by other objects. It is not practical to determine the incident direction of each of these incident lights and determine the arrangement of the image sensor in relation to these incident directions. When the image capturing device takes an image of whole electronic components mounted at different positions on the circuit board, it is not possible in principle to determine just one optimal arrangement of the image capturing device for all of the plurality of components. For this reason, when capturing an image of the base body having a sign on its surface, positioning of the image sensor in the travel direction of the incident light after being reflected. Therefore, of the light reflected from the surface of the base body10, most of the light that enters the image sensor is the diffusely reflected light rather than the specularly reflected light. In other words, in the reflected light received by the image sensor, the ratio of the diffuse reflection component is higher than that of the specular reflection component. Therefore, in the image of the surface of the base body10obtained by photographing, the low-reflectance region, where the intensity of diffusely reflected light is higher, is displayed brighter (or whiter, if the image is binarized). Therefore, in the illustrated embodiment, the image of the surface of the base body10shows the low reflectance region10B relatively bright and the high reflectance region10A and the sign region10C relatively dark.

Next, with reference toFIGS. 6A to 6C, a description is given of a method of manufacturing the coil component1according to one or more embodiments of the invention. The method of manufacturing the coil component1according to one or more embodiments of the invention includes a step of fabricating the blank body of a magnetic material that includes a conductor thereinside, a step of forming the low reflectance region on the surface of the blank body, and a step of forming a sign on the low reflectance region.

The coil component1is manufactured by, for example, a compression molding process. The coil component1may be manufactured by any known method in addition to the compression molding process. For example, the coil component1may be manufactured by a sheet lamination method, a printing lamination method, a thin-film process method, and a slurry build method. In the following, it is assumed that the coil component1is manufactured by the compression molding process.

In the manufacturing method of the coil component1, a blank body100that includes the coil conductor25thereinside and whose surface has the first reflectance is first fabricated as shown inFIG. 6A. The blank body100is made of a magnetic material and has the coil conductor25thereinside. In the step of fabricating the blank body100, first, a plurality of metal magnetic particles and a binder resin are kneaded while being heated to produce a mixed resin composition. Subsequently, the coil conductor25prepared in advance is disposed in a molding die, and the molding die containing the coil conductor25is filled with the mixed resin composition. A compression pressure (for example, 500 kN to 5000 kN) is then applied to the mixed resin composition in the molding die to obtain a molded body. A heat treatment is subsequently performed to heat the molded body, and the blank body100with the coil conductor25thereinside is obtained. In the heat treatment process, the temperature of the molded body is raised to a predetermined heating temperature (e.g., 550° C. to 850° C.), and the molded body is heated at this heating temperature for a predetermined processing time (e.g., 30 minutes to 240 minutes). Through this heat treatment, the binder resin is degreased while the temperature raises, and adjacent ones of the plurality of metal magnetic particles are bonded to each other with the oxide film formed on their surfaces. The degreasing of the binder resin may be performed as a separate heat treatment process from the heat treatment described above. For example, by adding a low-melting-point glass to the mixed resin composition and heat-treating the molded body obtained by molding the mixed resin composition including the low-melting-point glass in a low-oxygen or nitrogen atmosphere, adjacent ones of the plurality of metal magnetic particles may be bonded together by the glass that serves as the binder. The blank body100fabricated by the heat treatment is subjected to a polishing treatment such as barrel polishing as necessary.

As shown inFIG. 6B, the low reflectance region10B having the second reflectance lower than the first reflectance is formed on a surface of the blank body. The low reflectance region10B is formed by laser processing a portion of the surface of the blank body100. In the laser processing, a laser is irradiated by a laser irradiation device on the portion of the surface of the blank body100to roughen this portion. The roughened portion of the blank body100becomes the low reflectance region10B, and the unroughened area becomes the high reflectance region10A. As the laser irradiation device, the ML-9100 manufactured by Amada Miyachi Co., Ltd. can be used. The roughening process to roughen a part of the base body may be performed by blasting instead of or in addition to the laser irradiation.

As shown inFIG. 6C, the sign region10C is formed in the low reflectance region10B. As described above, the base body10is obtained. The sign region10C is formed by laser processing a part of the low reflectance region10B in the surface of the blank body100. As the laser irradiation device for forming the sign region10C, a YV04 laser marker MD-X1000 manufactured by Keyence Corporation can be used. By laser-irradiating the low reflectance region10B with predetermined irradiation conditions, the irradiated area of the low reflectance region10B is melted, and the melted material sublimates. As a result, the laser-irradiated area is recessed and smoothed more than the low reflectance region10B. The sign region10C has the third reflectance higher than the second reflectance of the low reflectance region10B.

Next, a conductor paste is applied to both end portions of the base body10, which is produced in the above-described manner, and the conductive paste is baked to form the external electrode21and the external electrode22. The external electrodes21and22may be formed by sequentially performing Ni plating and Sn plating on the surface of the baked Ag paste. The external electrode21and the external electrode22are provided such that they are electrically coupled to corresponding ends of the coil conductor25provided in the base body10. The external electrodes21and22may be provided on the blank body100before the low reflectance region10B and the sign region10C are formed. In this case, the blank body100on which the external electrodes21and22are provided is subjected to the process of forming the low reflectance region10B and the sign region10C and/or the sign region10C.

As described above, the coil component1that has the low reflectance region10B, the sign region10C and/or the sign region10C formed on the surface of the base body10. The manufactured coil component1is mounted on a substrate2using a reflow process. In this process, the substrate2having the coil component1disposed thereon passes at a high speed through a reflow furnace heated to, for example, a peak temperature of 260° C., and then the external electrodes21,22are soldered to the corresponding land portions3of the substrate2. In this way, the coil component1is mounted on the substrate2, and thus the circuit board102is manufactured.

The illustrated coil component1is an example of a coil component to which the invention can be applied. The invention can also be applied to any other types of coils. For example, the present invention can be applied to a wire-wound coil component in which a wire is wound around a compression core formed of a magnetic material. The wire-wound coil component has a compression core and a winding around the compression core. In such a wire-wound coil component, the compression core corresponds to the base body10. The low reflectance region10B and the sign region10C and/or the sign region10C are formed on the surface of this compression core. Next, a description is given of an example of a manufacturing method of the wire-wound coil component1. The compression core is first fabricated. For example, a Ni—Zn ferrite material is mixed with a binder resin, the mixture is compression molded using a molding die to obtain a drum-shaped molded body, and the molded body is sintered at a prescribed sintering temperature to obtain the compression core. The low reflectance region10B is formed on the surface of this compression core in the same manner as described above, and the sign region10C is formed in the low reflectance region10B.

EXAMPLES

Next, examples will now be described. The samples to be evaluated were fabricated in the following manner. To obtain the molded body, a Ni—Zn ferrite material is mixed with a binder resin, and the mixture was molded using a molding die. The molded body was then sintered at 850° C. in the atmosphere to obtain a rectangular column-shaped blank body made of a ferrite material. Two of these blank bodies were fabricated.

For one of the two blank bodies, laser processing was performed on the whole two surfaces among the surfaces that define the outer shape of the blank body. This laser processing was performed using ML-9100 manufactured by Amada Miyachi Co., Ltd. under the following laser irradiation conditions.Power: 15 AIrradiation probe speed: 3000 mm/sFrequency: 100 kHz.

The surface of the blank body that has been laser processed under the above conditions is hereunder referred to as a laser processed surface.

Printing was then performed on the whole of one of the two laser processed surfaces of the blank body using a YV04 laser marker MD-X1000 manufactured by Keyence Corporation under the following printing conditions.Power: 60%Scan speed: 1250 mm/sFrequency: 400 kHz

Specifically, a “▪” mark was printed on the whole surface of one of the laser processed surfaces of the blank body. An area of the surface of the blank body that has been laser processed under the above conditions is hereunder referred to as a printed region. In the above example, the whole one surface of the blank body was the printed region. The printed region may be an area that occupies a part of a surface of the blank body.

The base body obtained in the above described way was designated as Sample A. Sample A was the base body that is formed of the Ni—Zn ferrite material and has the two laser processed surfaces, and one of the two laser processed surfaces had the “▪” mark printed on the entire surface. Sample A corresponds to the base body10in the embodiment of the invention.

The “▪” mark was also printed on the entire surface of the other rectangular column-shaped blank body made of the ferrite material without the above-described laser processing onto the surface using the ML-9100 manufactured by Amada Miyachi Co., Ltd. In other words, this laser printing was performed onto a non-laser processed surface (not the laser processed surface) of the base body. The base body obtained in the above described way was designated as Sample B. Sample B is not an example of the invention, but a comparative example.

A sample of a base body containing metal magnetic particles was prepared as follows. First, the metal magnetic particles formed of Fe—Si—Cr alloy and epoxy resin were kneaded to produce a mixed resin composition. The mixed resin composition was placed in a molding mold and a molding pressure of 1000 kN was applied to the composition to obtain a rectangular column-shaped molded body. Subsequently, the molded body was heated at 200° C. for 60 minutes to obtain the base body including the metal magnetic particles.

Among the surfaces defining the blank body fabricated as described above, laser processing was performed on the entire two surfaces among the surfaces. This laser processing was performed using ML-9100 manufactured by Amada Miyachi Co., Ltd. under the following laser irradiation conditions.Power: 15 AIrradiation probe speed: 3000 mm/sFrequency: 100 kHz

Printing was then performed on the whole of one of the two laser processed surfaces of the blank body using a YV04 laser marker MD-X1000 manufactured by Keyence Corporation under the following printing conditions. Specifically, a “▪” mark was printed on the entire surface of one of the laser processed surfaces of the blank body.Power: 60%Scan speed: 1250 mm/sFrequency: 400 kHz

The base body obtained in the above described way was designated as Sample C. Sample C was the base body that was formed of the Ni—Zn ferrite material and had the two laser processed surfaces, and one of the two laser processed surfaces had the “▪” mark printed on the entire surface. Sample C corresponds to the base body10in the embodiment of the invention.

Using a U-4100 spectrophotometer manufactured by Hitachi High-Tech Corporation, total reflection measurements were performed on each of Sample A, Sample B, and Sample C with Φ60-mm integrating sphere (10° of incident angle: standard integrating sphere for the same device). Reflectances of the laser processed surface(s) (corresponding to “low reflectance region10B”), surfaces other than the laser processed surface(s) (referred to as an “unprocessed surface,” the unprocessed surface corresponds to the “high reflectance region10A”), and the printed region (corresponding to the “sign region10C”) of each sample were measured at 25° C. with a wavelength of 700 nmm. In the measurement of the reflectances, a barium sulfate white plate was used as a reference sample. The measurement results of the reflectance for the sign region10C are shown in the following Table 1. Since Sample B did not have the laser-processed surface, the reflectance of the laser-processed surface of Sample B is denoted as “N/A” in the table.

When the printed region occupies a part of one surface of the sample (for example, when an alphabet(s) and/or number(s) are printed as in the case of the sign region10C described above), the reflectance of the printed region can be estimated as follows. That is, the reflectance of the laser-processed surface (in the case of the example) or the unprocessed surface (in the case of the comparative example) of the blank body before the printed region is formed is measured using the same measurement method as described above with the U-4100 spectrophotometer of Hitachi High-Tech Corporation. The reflectance measured at this time is denoted as R1. Subsequently, the printed region is formed on one of the surfaces of the blank body, and the reflectance of the laser-processed surface (in the case of the example) or the unprocessed surface (in the case of the comparative example) on which the printed region is formed is measured using the same measurement method as above with the U-4100 spectrophotometer of Hitachi High Tech Corporation. The reflectance measured at this time is denoted as R2. An area Sa of the laser processed surface (in the case of the example) or the unprocessed surface (in the case of the comparative example) left after the printed region has been formed and an area Sb of the printed region are respectively determined. The reflectance R2 after the printed region is formed is expressed as a weighted average of the reflectance of the laser processed surface (in the case of the example) or unprocessed surface (in the case of the comparison example) and the reflectance of the printed region, weighted by their respective areas. Therefore, the reflectance R2 is expressed by the following equation where the reflectance of the printed region is Rx.

Since R1, R2, Sa, and Sb have been measured as described above, Rx can be calculated from the above equation. This Rx is used as an estimate of the reflectance of the printed region.

For each of Samples A and B, the arithmetic mean roughness Ra of the unprocessed surface, the laser-processed surface, and the printed region respectively were measured. As a result of the measurement, the arithmetic mean roughness Ra of the unprocessed surface was 0.15 μm, and the arithmetic mean roughness of the printed region was 0.1 μm. The arithmetic mean roughness Ra of the laser processed surface of Sample A was 0.40 μm. For Sample C, the arithmetic mean roughness Ra of the unprocessed surface, the laser processed surface, and the printed region respectively were measured. As a result of the measurement, the arithmetic mean roughness Ra of the unprocessed surface was 0.19 μm, the arithmetic mean roughness Ra of the laser processed surface was 0.36 μm, and the arithmetic mean roughness Ra of the printed region was 0.13 μm.

Next, characters “4R7” were printed on the laser-processed surface of the blank body made in the same way as Sample A, using the YV04 laser marker MD-X1000 manufactured by Keyence Corporation, under the following printing conditions.Power: 60%Scan speed: 1250 mm/sFrequency: 400 kHz

The area where the characters “4RL” was formed is the printed region, and corresponds to the sign region10C in the above embodiment. The base body obtained in this way was designated as Sample D. Sample D corresponds to the base body10in the embodiment of the invention.

Characters “4R7” were printed on one of the surfaces of the blank body made in the same way as Sample B, using the YV04 laser marker MD-X1000 manufactured by Keyence Corporation, under the same printing conditions. The base body obtained in this way was designated as Sample E. Sample E is not an example of the invention, but a comparative example.

Characters “4R7” were printed on the laser-processed surface of the blank body made in the same way as Sample C, using the YV04 laser marker MD-X1000 manufactured by Keyence Corporation, under the same printing conditions. The base body obtained in this way was designated as Sample F. Sample F corresponds to the base body10in the embodiment of the invention.

An optical camera was used to photograph the surfaces on which “4R7” was printed for each of Sample D, Sample E, and Sample F.FIGS. 7A to 7Cshow the photographs taken by the camera. From the photographs ofFIGS. 7A and 7C, it can be seen that the laser-processed surfaces of Sample D and Sample F (corresponding to the low reflectance region10B) were brighter compared to the “4R7” print pattern. On the other hand, it can be seen fromFIG. 7Bthat the laser-unprocessed surface of the base body made of the ferrite material was as bright as the “4R7” print pattern. For Sample D and Sample F, the contrast between the laser-processed surface and the print pattern was high so that it was easier to recognize the printed “4R7” as compared to Sample E. Whereas for Sample E, the contrast between the print pattern and its background (unprocessed surface) was low, and it was not easy to recognize the printed “4R7” as compared with Sample D and Sample F. In this way, by surrounding the area around the printed region on the surface of the base body with the laser-processed surface having a reflectance lower than that of the printed region, the contrast between the printed region and the surrounding laser-processed surface can be enhanced. It was confirmed that this makes it easier to recognize the printed region.

Samples A to C were also observed with the naked eye. Similar to the photographs ofFIGS. 7A to 7C, in Samples A and C, the contrast between the sign region10C and the low reflectance region10B was high even when observed with the naked eye, and it was easy to recognize the characters “4R7” and the circular symbol on the left side of the characters. Whereas when sample B was observed with the naked eye, the contrast between the sign region10C and the low reflectance region10B was low as inFIG. 7B, and the characters “4R7” and the circle on the left side of the characters were not easily recognized.

Advantageous effects of the above embodiments will be now described. According to one or more embodiments of the present invention, the second reflectance of the low reflectance region10B is lower than the third reflectance of the sign region10C. Therefore the contrast between the sign region10C and its surrounding low reflectance region10B is high, and the sign region10C can be easily distinguished from the surrounding region.

When the surface of the base body10of the coil component1is captured by an image capturing device such as an optical camera, the reflected light from the low reflectance region10B received by an image sensor of the image capturing device includes a larger ratio of the diffusive reflection component rather than the specular reflection component compared to the sign region10C. Therefore, it is not necessary to perform alignment of the image capturing device when the coil component1is photographed by the imaging capturing device in order to check the sign region10C. The low reflectance region10B is brightened in a photograph taken regardless of the arrangement of the image sensor of the image capturing device with respect to the light source. Further, when the sign region10C of the coil component1is observed with the naked eye, the low reflectance region10B looks whiter than the sign region10C regardless of the direction in which the coil component1is observed. As described above, the contrast between the low reflectance region10B and the sign region10C can be enhanced to facilitate the recognition of the sign region10C without adjusting the arrangement of the image capturing device or the position of the observer when observing with the naked eye.

According to one or more embodiments of the invention, the second reflectance of the low reflectance region10B is lower than the first reflectance of the high reflectance region10A, so that the contrast between the low reflectance region10B and the high reflectance region10A surrounding the low reflectance region10B is high. Therefore, when observing the surface of the base body10, the low reflectance region10B can be easily found.

The dimensions, materials, and arrangements of the constituent elements described herein are not limited to those explicitly described for the embodiments, and these constituent elements can be modified to have any dimensions, materials, and arrangements within the scope of the present invention. Furthermore, constituent elements not explicitly described herein can also be added to the described embodiments, and it is also possible to omit some of the constituent elements described for the embodiments.