ELECTRONIC COMPONENT AND METHOD FOR MANUFACTURING THE SAME

An electronic component includes a composite body containing resin and magnetic metal particles, a first metal film provided on an outer surface of the composite body, and a second metal film provided on the first metal film. At least one of the magnetic metal particles is exposed at a contact surface of the composite body that is in contact with the first metal film. The first metal film is in contact with an exposed surface of the at least one of the magnetic metal particles exposed from the contact surface. The film thickness of the first metal film on the exposed surface is 2.9 μm or more.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of priority to Japanese Patent Application No. 2020-122354, filed Jul. 16, 2020, the entire content of which is incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure relates to an electronic component and a method for manufacturing the same.

Background Art

A known electronic component is described in Japanese Unexamined Patent Application Publication No. 2017-103423. The electronic component described in Japanese Unexamined Patent Application Publication No. 2017-103423 includes a composite body made of a composite material of resin and a magnetic metal powder and a metal film provided on an outer surface of the composite body.

SUMMARY

It has been found that, in a case where the electronic component is covered with another metal film, a crack may appear in part of the metal film. Furthermore, intensive investigations have revealed that the magnetic metal powder is dissolved in such case.

Accordingly, the present disclosure provides an electronic component in which the dissolution of magnetic metal particles is suppressed.

According to a preferred embodiment of the present disclosure, an electronic component includes a composite body containing resin and magnetic metal particles, a first metal film provided on an outer surface of the composite body, and a second metal film provided on the first metal film. At least one of the magnetic metal particles is exposed at a contact surface of the composite body that is in contact with the first metal film. The first metal film is in contact with an exposed surface of the at least one of the magnetic metal particles exposed from the contact surface. A film thickness of the first metal film on the exposed surface is 2.9 μm or more.

According to the above embodiment, in the contact surface of the composite body, pinholes are unlikely to occur in the first metal film on the exposed magnetic metal particles. As a result, the dissolution of the magnetic metal particles can be suppressed.

The term “film thickness of the first metal film” as used herein refers to the film thickness of the first metal film in a direction perpendicular to a surface which is one of outer surfaces of the composite body and on which the first metal film is provided.

According to another preferred embodiment of the present disclosure, a method for manufacturing an electronic component includes forming an exposed surface of at least one of magnetic metal particles on an outer surface of a composite body containing resin and the magnetic metal particles, forming a first metal film on the exposed surface by electroless plating such that a film thickness of the first metal film is 2.9 μm or more, and forming a second metal film on the first metal film.

According to this embodiment, on the magnetic metal particles exposed at a contact surface of the composite body that is in contact with the first metal film, pinholes are unlikely to occur in the first metal film on the exposed magnetic metal particles. As a result, an electronic component having good performance can be manufactured.

In accordance with an electronic component according to an embodiment of the present disclosure and a method for manufacturing the same according to an embodiment of the present disclosure, an electronic component having good performance can be provided.

Electronic components according to embodiments of the present disclosure are described below in detail with reference to the attached drawings. The drawings include partly schematic views and do not reflect actual sizes in some cases.

First Embodiment

Configuration

FIG. 1Ais a perspective plan view of an electronic component according to a first embodiment.FIG. 1Bis a sectional view taken along the line A-A ofFIG. 1A.FIG. 2is a partly enlarged view ofFIG. 1B.

The electronic component is, for example, an inductor component1. The inductor component1is, for example, a surface-mount electronic component mounted on a circuit board mounted in an electronic device such as a personal computer, a DVD player, a digital camera, a TV, a mobile phone, or a car electronic system. The inductor component1is not limited to such a surface-mount electronic component and may be an embedded electronic component. The inductor component1is, for example, a component with substantially a cuboid shape as a whole. The shape of the inductor component1is not particularly limited and may be substantially a cylindrical shape, a polygonal column shape, a truncated cone shape, or a prismoid shape.

As illustrated inFIGS. 1A and 1B, the inductor component1includes an element body10having insulating properties; a first inductor element2A; a second inductor element2B, the first and second inductor elements2A and2B being provided in the element body10; a first columnar line31; a second columnar line32; a third columnar line33; a fourth columnar line34, the first, second, third, and fourth columnar lines31,32,33, and34being embedded in the element body10so as to have an end surface exposed from a rectangular first principal surface10aof the element body10; a first external terminal41; a second external terminal42; a third external terminal43; a fourth external terminal44, the first, second, third, and fourth external terminals41,42,43, and44being provided on the first principal surface10aof the element body10; and an insulating film50provided on the first principal surface10aof the element body10. InFIGS. 1A and 1B, a direction substantially parallel to the thickness of the inductor component1is a Z-direction, the positive Z-direction is toward an upper side, and the negative Z-direction is toward a lower side. In a plane substantially perpendicular to the Z-direction, a direction substantially parallel to the length of the inductor component1is an X-direction and a direction substantially parallel to the width of the inductor component1is a Y-direction.

The element body10includes an insulating layer61, a first magnetic layer11provided on the lower surface61aof the insulating layer61, and a second magnetic layer12provided on the upper surface61bof the insulating layer61. The first principal surface10aof the element body10corresponds to the upper surface of the second magnetic layer12. The element body10has a three-layer structure made of the insulating layer61, the first magnetic layer11, and the second magnetic layer12. The element body10may have a one-layer structure consisting of a magnetic layer only, a two-layer structure consisting of a magnetic layer and an insulating layer only, or a four or more-layer structure composed of a plurality of magnetic layers and insulating layers.

The insulating layer61has insulating properties and has a principal surface with substantially a rectangular shape. The thickness of the insulating layer61is, for example, about 10 μm to 100 μm. The insulating layer61is preferably, for example, an insulating resin layer made of an epoxy resin or polyimide resin free from a matrix such as a glass cloth from the viewpoint of the reduction of profile. The insulating layer61may be a sintered body layer made of a magnetic material such as Ni—Zn ferrite or Mn—Zn ferrite or a nonmagnetic material such as alumina or glass or may be a resin substrate layer containing a base material such as a glass-epoxy composite. When the insulating layer61is the sintered body layer, the strength and flatness of the insulating layer61can be ensured, thereby enhancing the workability of a laminate on the insulating layer61. When the insulating layer61is the sintered body layer, the insulating layer61is preferably polished from the viewpoint of the reduction of profile and is particularly preferably polished from a lower side having no laminate.

The first magnetic layer11and the second magnetic layer12have high permeability, have a principal surface with substantially a rectangular shape, and contain resin135and magnetic metal particles136dispersed in the resin135. That is, the first magnetic layer11and the second magnetic layer12are composite bodies containing the resin135and the magnetic metal particles136. The resin135is, for example, an organic insulating material made of an epoxy resin, bismaleimide, a liquid crystal polymer, polyimide, or the like. The magnetic metal particles136preferably contain Fe and may contain a magnetic metal material such as Fe alone, an Fe—Si alloy such as Fe—Si—Cr, an Fe—Co alloy, an Fe alloy such as Ni—Fe, or an amorphous alloy thereof. The average size of the magnetic metal particles136is, for example, about 0.1 μm to 5 μm. At the stage of manufacturing the inductor component1, the average size of the magnetic metal particles136can be calculated as a size (D50) corresponding to a cumulative percentage of 50% in a size distribution determined by a laser diffraction/scattering method. The content of the magnetic metal particles136in each of the first magnetic layer11and the second magnetic layer12is preferably about 20% by volume to 70% by volume. When the average size of the magnetic metal particles136is about 5 μm or less, direct-current superposition characteristics are enhanced and the core loss at high frequency can be reduced by fine powder.

The first inductor element2A and the second inductor element2B include a first inductor wiring21and a second inductor wiring22, respectively, provided substantially in parallel to the first principal surface10aof the element body10. This enables the first inductor element2A and the second inductor element2B to be configured substantially in parallel to the first principal surface10a, thereby enabling the reduction in profile of the inductor component1. The first inductor wiring21and the second inductor wiring22are provided on the same plane in the element body10. In particular, the first inductor wiring21and the second inductor wiring22are provided only on the upper side of the insulating layer61, that is, the upper surface61bof the insulating layer61and is covered by the second magnetic layer12.

The first and second inductor wirings21and22are two-dimensionally wound. In particular, the first and second inductor wirings21and22have a semi-elliptical arch shape as viewed from the Z-direction. That is, the first and second inductor wirings21and22are curved lines wound substantially halfway. The first and second inductor wirings21and22each include a straight portion in an intermediate section. In this application, the term “spiral” of an inductor wiring refers to a two-dimensionally wound curved shape including a spiral shape and includes a curved shape with one turn or less like the first and second inductor wirings21and22. The curved shape may include a partly straight portion.

The thickness of the first and second inductor wirings21and22is preferably, for example, about 40 μm to 120 μm. In an example, the first and second inductor wirings21and22have a thickness of about 45 μm, a width of about 40 μm, and an interline space of about 10 μm. The interline space is preferably about 3 μm to 20 μm from the viewpoint of ensuring insulating properties.

The first and second inductor wirings21and22are made of, for example, an electrically conductive material, that is, a low-electrical resistance metal material such as Cu, Ag, or Au. In this embodiment, the inductor component1includes the first and second inductor wirings21and22, which are provided in a single layer only. This enables the reduction in profile of the inductor component1. The first and second inductor wirings21and22may be metal films and may have a structure in which an electrically conductive layer made of Cu, Ag, or the like is provided on a base layer formed by electroless plating using Cu, Ti, or the like.

The first inductor wiring21includes a first end and a second end which are each located at an outer side portion and which are electrically connected to the first columnar line31and the second columnar line32, respectively, and is curved to form an arch from the first columnar line31and the second columnar line32toward the central side of the inductor component1. Furthermore, the first inductor wiring21includes pad sections which are located at both ends thereof and which have a width larger than that of spiral-shaped sections. The pad sections are directly connected to the first and second columnar lines31and32.

Likewise, the second inductor wiring22includes a first end and a second end which are each located at an outer side portion and which are electrically connected to the third columnar line33and the fourth columnar line34, respectively, and is curved to form an arch from the third columnar line33and the fourth columnar line34toward the central side of the inductor component1.

Herein, suppose that, in each of the first and second inductor wirings21and22, a range surrounded by curved lines formed by the first and second inductor wirings21and22and straight lines connecting both ends of the first and second inductor wirings21and22is an inside diameter section. In this supposition, when viewed from the Z-direction, the inside diameter sections of the first and second inductor wirings21and22do not overlap each other and the first and second inductor wirings21and22are separated from each other.

Furthermore, lines extend from connections between the first and second inductor wirings21and22and the first to fourth columnar lines31to34in a direction which is substantially parallel to the X-direction and which is outward the inductor component1. These lines are exposed to the outside of the inductor component1. That is, each of the first and second inductor wirings21and22includes exposed sections200exposed to the outside from side surfaces (surfaces substantially parallel to the Y-Z plane) substantially parallel to a lamination direction of the inductor component1.

These lines are connected to feeder lines used to perform additional electroplating after the formation of the first and second inductor wirings21and22in the course of manufacturing the inductor component1. The feeder lines enables additional electroplating to be readily performed on an inductor substrate before being divided into inductor components1, thereby enabling the interline distance to be reduced. Performing additional electroplating to reduce the distance between the first and second inductor wirings21and22allows the magnetic coupling between the first and second inductor wirings21and22to be increased, allows the width of the first and second inductor wirings21and22to be increased to reduce the electrical resistance, and enables outer dimensions of the inductor component1to be reduced.

The first to fourth columnar lines31to34extend from the first and second inductor wirings21and22in the Z-direction and penetrate an inner portion of the second magnetic layer12. The first columnar line31extends upward from the upper surface of one end of the first inductor wiring21and has an end surface exposed from the first principal surface10aof the element body10. The second columnar line32extends upward from the upper surface of the other end of the first inductor wiring21and has an end surface exposed from the first principal surface10aof the element body10. The third columnar line33extends upward from the upper surface of one end of the second inductor wiring22and has an end surface exposed from the first principal surface10aof the element body10. The fourth columnar line34extends upward from the upper surface of the other end of the second inductor wiring22and has an end surface exposed from the first principal surface10aof the element body10.

Thus, the first columnar line31, the second columnar line32, the third columnar line33, and the fourth columnar line34linearly extend from the first inductor element2A and the second inductor element2B to the end surfaces exposed from the first principal surface10ain a direction substantially perpendicular to the end surfaces. This enables the first external terminal41, the second external terminal42, the third external terminal43, and the fourth external terminal44to be connected to the first inductor element2A and the second inductor element2B at a shorter distance, thereby allowing the inductor component1to have low resistance and high inductance. The first to fourth columnar lines31to34are made of an electrically conductive material and may be made of, for example, substantially the same material as the first and second inductor wirings21and22.

The first to fourth external terminals41to44are provided on the first principal surface10aof the element body10. The first to fourth external terminals41to44are metal films provided on an outer surface of the second magnetic layer12. The first external terminal41is in contact with the end surface of the first columnar line31that is exposed from the first principal surface10aof the element body10and is electrically connected to the first columnar line31. This allows the first external terminal41to be electrically connected to one end of the first inductor wiring21. The second external terminal42is in contact with the end surface of the second columnar line32that is exposed from the first principal surface10aof the element body10and is electrically connected to the second columnar line32. This allows the second external terminal42to be electrically connected to the other end of the first inductor wiring21.

Likewise, the third external terminal43is in contact with an end surface of the third columnar line33, is electrically connected to the third columnar line33, and is electrically connected to one end of the second inductor wiring22. The fourth external terminal44is in contact with an end surface of the fourth columnar line34, is electrically connected to the fourth columnar line34, and is electrically connected to the other end of the second inductor wiring22.

In the inductor component1, the first principal surface10ahas a first end edge101and second end edge102which correspond to sides of a rectangle and which extend linearly. The first end edge101is an end edge of the first principal surface10athat leads to a first side surface10bof the element body10. The second end edge102is an end edge of the first principal surface10athat leads to a second side surface10cof the element body10. The first external terminal41and the third external terminal43are arranged along the first end edge101, which is on the first side surface10bside of the element body10. The second external terminal42and the fourth external terminal44are arranged along the second end edge102, which is on the second side surface10cside of the element body10. When viewed from a direction substantially perpendicular to the first principal surface10aof the element body10, the first side surface10band second side surface10cof the element body10are surfaces along the Y-direction and coincide with the first end edge101and the second end edge102, respectively. A direction in which the first external terminal41and the third external terminal43are arranged is a direction connecting the center of the first external terminal41to the center of the third external terminal43. A direction in which the second external terminal42and the fourth external terminal44are arranged is a direction connecting the center of the second external terminal42to the center of the fourth external terminal44.

The insulating film50is provided on a portion of the first principal surface10aof the element body10that is provided with none of the first to fourth external terminals41to44. The insulating film50may overlap the first to fourth external terminals41to44in the Z-direction such that end portions of the first to fourth external terminals41to44overlie the insulating film50. The insulating film50is made of, for example, a resin material, such as an acrylic resin, an epoxy resin, or polyimide, having high electrical insulation properties. This enables the insulation between the first to fourth external terminals41to44to be enhanced. The insulating film50serves as a mask when a pattern of the first to fourth external terminals41to44is formed. This leads to an increase in manufacturing efficiency. When the magnetic metal particles136are exposed from the resin135, the magnetic metal particles136can be prevented from being exposed to the outside since the insulating film50covers the exposed magnetic metal particles136. The insulating film50may contain filler made of an insulating material such as silica or barium sulfate.

As illustrated inFIG. 2, the first external terminal41includes a first metal film410provided on the outer surface of the second magnetic layer12and a second metal film411provided on the first metal film410. The second, third, and fourth external terminals42,43, and44have substantially the same configuration as the configuration of the first external terminal41. Therefore, the first external terminal41only is described below.

The first external terminal41includes the first metal film410, which is provided on the outer surface of the second magnetic layer12, and the second metal film411, which is provided on the first metal film410.

The first metal film410mainly contains Cu. The first metal film410is preferably made of a metal material or alloy containing Cu. This allows the first metal film410to have high electrical conductivity. In particular, when the magnetic metal particles136contain Fe, the first metal film410can be readily formed by plating. This is because Fe contained in the magnetic metal particles136and Cu contained in a plating solution induce a substitution reaction to form the first metal film410.

The second metal film411directly covers the first metal film410and contains, for example, Ni or the like. The second metal film411has a role in suppressing the electrochemical migration and solder erosion of the first metal film410.

The first external terminal41may further include a third metal film provided on the second metal film411. The third metal film directly covers the second metal film411, forms the outermost layer of the first external terminal41, and may be made of, for example, a metal such as Au or Sn. The third metal film has a role in ensuring the wettability of solder.

The second magnetic layer12has a contact surface12ain contact with the first metal film410. At least one of the magnetic metal particles136is exposed at the contact surface12a. Thus, the first metal film410is provided on the contact surface12aof the second magnetic layer12and is in contact with the exposed surfaces of the magnetic metal particles136exposed at the contact surface12a.

The first metal film410in contact with the exposed surfaces of the magnetic metal particles136, that is, the first metal film410on the exposed surfaces of the magnetic metal particles136has a film thickness t of, for example, about 2.9 μm or more.

Since the first metal film410has such a film thickness t, a pinhole can be inhibited from occurring in the first metal film410on the magnetic metal particles136exposed at the contact surface12aof the second magnetic layer12.

The term “pinhole” as used herein refers to a through-hole formed in the first metal film410. The through-hole is a hole communicating with the exposed surface of one of the magnetic metal particles136.

The phrase “film thickness t of about 2.9 μm or more” indicates that at least one of measurements of the film thicknesses t may be about 2.9 μm or more.

When there is a pinhole in the first metal film410, the magnetic metal particles136exposed may possibly be melted in the formation of the second metal film411. In such a case, the melted magnetic metal particles136may possibly affect the second metal film411. For example, the mixing of the melted magnetic metal particles136with the second metal film411hardens the second metal film411, so that the second metal film411is likely to crack. However, since the first metal film410has such a film thickness t as described above, the occurrence of a pinhole in the first metal film410can be suppressed and the melting of the exposed magnetic metal particles136can be suppressed, thereby enabling the cracking of the second metal film411to be suppressed. Since the melting of the exposed magnetic metal particles136can be suppressed, the reduction in content of the magnetic metal particles136contained in the second magnetic layer12can be suppressed and the reduction in inductance of the electronic component can be suppressed. Thus, since the first metal film410has such a film thickness t as described above, the influence of a pinhole on the performance of the electronic component can be suppressed.

As described above, the present disclosure has been made to solve a newly found problem. In particular, in a known technique, cracks may possibly occur in part of a metal film as described above. The inventors have performed intensive investigations and, as a result, have found that the above cracks are caused by the hardening of the second metal film411and the hardening of the second metal film411is caused by the fact that the melted magnetic metal particles136mix with the second metal film411through pinholes occurring in the first metal film410. In order to solve the above problem, the inventors have reached the configuration of the present disclosure for the purpose of suppressing the occurrence of pinholes in the first metal film410.

The phrase “film thickness t of the first metal film410on the magnetic metal particles136” refers to the thickness of the first metal film410in a direction substantially perpendicular to the outer surface of the second magnetic layer12on which the first metal film410is provided. The film thickness t of the first metal film410on the magnetic metal particles136is a value determined from a FIB-SIM image of a cross section of the inductor component1. The FIB-SIM image is a cross-sectional image observed with a scanning ion microscope (SIM) using a focused ion beam (FIB). An image can be analyzed using image-processing software (for example, A-zo-kun® developed by Asahi Kasei Engineering Corporation).

The cross section is one set to pass through the centerlines of the first and second columnar lines31and32of the inductor component1as illustrated inFIG. 1B. In this case, the film thickness t of the first metal film410on the magnetic metal particles136can be obtained by measuring a predetermined range in a place in which the first metal film410is provided on the second magnetic layer12. The predetermined range is, for example, a central region of the cross section that is located between the first columnar line31and the insulating film50. In particular, the predetermined range is a region which is 40 μm or more apart from an end portion of the first columnar line31that is located on the insulating film50side and which is 70 μm or more apart from an end portion of the insulating film50that is located on the first columnar line31side.

As described above, the lower limit of the film thickness t of the first metal film410on the magnetic metal particles136is 2.9 μm. This is described in detail with reference toFIG. 4. The present disclosure is not restricted to theory below.

FIG. 4is a graph in which the horizontal axis represents the film thickness t of the first metal film410(the film thickness of Cu inFIG. 4) and the vertical axis represents the ratio of the number of carbon atoms to the sum of the number of the carbon atoms and the number of metal atoms (Cu atoms inFIG. 4) forming the first metal film410and which is one determined as described below.

The magnetic metal particles136used were those containing Fe. A measurement sample including the second magnetic layer12and the first metal film410formed thereon was dipped in a chemical solution (a resin-containing solution prepared by adding sulfuric acid serving as an etching accelerator to an acrylic resin (marketed by ZEON Corporation under the trade name Nipol LX814A) serving as a resin component for the purpose of adjusting the pH and further adding NEWREX® (available from NOF Corporation) serving as a surfactant to the acrylic resin) reacting with Fe to form a film containing carbon. After the measurement sample was taken out of the chemical solution, the measurement sample was heat-treated at 210° C. for 0.5 h and was measured for the percentage of carbon atoms present on the first metal film410by energy dispersive X-ray spectroscopy (SEM-EDX).

That is, when a pinhole is present in the first metal film410on the magnetic metal particles136, Fe contained in the magnetic metal particles136exposed at a surface of the second magnetic layer12reacts with the chemical solution through the pinhole, whereby a carbon film is formed on the exposed surfaces of the magnetic metal particles136. Thus, when a large number of pinholes are present, a large amount of Fe is exposed through the pinholes. When a large amount of Fe is present, the ratio of the number of carbon atoms having reacted with Fe to the sum of the number of the carbon atoms and the number of metal atoms forming the first metal film410is high.

As shown inFIG. 4, when the film thickness t of the first metal film410is small, the above ratio is high. However, when the film thickness t of the first metal film410is large, the above ratio is low. This suggests that the increase in the film thickness t of the first metal film410reduces the number of pinholes in the first metal film410on the magnetic metal particles136. Furthermore, as shown inFIG. 4, when the film thickness t of the first metal film410is about 2.9 μm or more, the above ratio is substantially constant. This result suggests that, when the film thickness t of the first metal film410is about 2.9 μm or more, no pinhole is present in the first metal film410on the magnetic metal particles136. Referring toFIG. 4, when the film thickness t of the first metal film410is about 2.9 μm or more, the ratio of the number of the carbon atoms having reacted with Fe to the sum of the number of the carbon atoms and the number of the metal atoms forming the first metal film410exhibits a constant value. This is probably because the chemical solution reacts with Fe in the first metal film410to form a carbon film.

FIG. 4shows results obtained by investigating a case where the magnetic metal particles136contain Fe. Even in a case where another material, for example, another metal material is used, if the film thickness t of the first metal film410is less than about 2.9 μm, then pinholes probably occur.

The first metal film410on the exposed surfaces of the magnetic metal particles136preferably has a film thickness t of about 15 μm or less. Such a film thickness t enables the first metal film410to be prevented from having excessively high resistance.

Two or more of the magnetic metal particles136are preferably exposed at the contact surface12a. In this case, the distance between a first magnetic metal particle136and a second magnetic metal particle136which are two of the magnetic metal particles136exposed at the contact surface12aand which are adjacent to each other is preferably less than or equal to about twice a film thickness of at least one of the film thickness t of the first metal film410on the first magnetic metal particle136and the film thickness t of the first metal film410on the second magnetic metal particle136.

When the distance between the magnetic metal particles136is such a value as described above, pinholes are more unlikely to occur in the first metal film410on the magnetic metal particles136exposed at the contact surface12aof the second magnetic layer12. Furthermore, according to the above mode, most of spaces between the magnetic metal particles136(and surroundings thereof) can be covered with the first metal film410. As a result, the first metal film410can be formed on the second magnetic layer12so as to be smoother. Furthermore, the second metal film411can also be formed on the first metal film410so as to be smooth.

Herein, the distance between the exposed magnetic metal particles136can be determined from a FIB-SIM image of a cross section in substantially the same manner as that used to measure the film thickness t of the first metal film410on the magnetic metal particles136as described above.

The distance between the first magnetic metal particle136and the second magnetic metal particle136, which are exposed from the contact surface12aand adjacent to each other, is more preferably less than or equal to about twice a film thickness that is a smaller one of the film thickness t of the first metal film410on the first magnetic metal particle136and the film thickness t of the first metal film410on the second magnetic metal particle136.

When the distance between the neighboring magnetic metal particles136is within the above range, the first metal film410can be formed so as to be further smoother.

The average film thickness of the first metal film410is preferably 2.9 μm or more and is, for example, 5 μm or more. Such an average film thickness allows pinholes to be more unlikely to occur in the first metal film410on the magnetic metal particles136exposed at the contact surface12aof the second magnetic layer12.

The phrase “average film thickness of the first metal film410” as used herein refers to the average film thickness of the first metal film410on the second magnetic layer12, that is, the average film thickness of the first metal film410on the resin135and the magnetic metal particles136. The average film thickness of the first metal film410can be measured from substantially the same cross section as that used to measure the film thickness t of the first metal film410on the magnetic metal particles136.

The average film thickness of the first metal film410is, for example, the arithmetic average of values determined from a FIB-SIM image of a cross section of the inductor component1and, in particular, may be the average of ten measurements.

In 95% or more of the exposed magnetic metal particles136, the distance between the neighboring magnetic metal particles136is preferably less than or equal to about twice the average film thickness of the first metal film410. In 100% of the exposed magnetic metal particles136, the distance between the neighboring magnetic metal particles136may be less than or equal to about twice the average film thickness of the first metal film410. In this case, the average film thickness of the first metal film410may be about 5 μm or more.

Herein, the distance between the neighboring magnetic metal particles136is a value measured in a region used to measure the average film thickness and, in particular, is the measurements for ten of the magnetic metal particles136used to measure the average film thickness.

Such a configuration as described above enables pinholes to be more unlikely to occur in the first metal film410on the magnetic metal particles136. As a result, variations in resistance are more unlikely to occur in the first metal film410.

Manufacturing Method

Next, a method for manufacturing the inductor component1is described.

As illustrated inFIG. 3A, an upper surface of an element body10is ground by polishing or the like in such a state that a plurality of inductor wirings21and22and a plurality of columnar lines31to34are covered by the element body10, whereby end surfaces of the columnar lines31to34are exposed from the upper surface of the element body10. Thereafter, as illustrated inFIG. 3B, an insulating film50, which is marked by hatching, is formed over the upper surface of the element body10by a coating method such as spin coating or screen printing, a dry method such as dry film resist lamination, or the like. The insulating film50is, for example, a photoresist film.

Thereafter, in a region for forming external terminals, the insulating film50is removed by photolithography, laser, drilling, blasting, or the like, whereby through-holes50aare formed in the insulating film50such that end surfaces of the columnar lines31to34and part of the element body10(second magnetic layer12) are exposed through the through-holes50a. In this operation, as illustrated inFIG. 3B, the end surfaces of the columnar lines31to34may be entirely exposed from the through-holes50aor may be partly exposed from the through-holes50a. Alternatively, some of the end surfaces of the columnar lines31to34may be exposed from one of the through-holes50a.

Thereafter, as illustrated inFIG. 3C, a first metal film410is formed in the through-holes50aby a method described below and a second metal film411is formed on the first metal film410, whereby a mother substrate100is configured. The first metal film410and the second metal film411form external terminals41to44before being cut. Thereafter, as illustrated inFIG. 3D, the mother substrate100, that is, the sealed inductor wirings21and22are diced into pieces for each pair of the inductor wirings21and22along cutting lines C using a dicing blade or the like, whereby a plurality of inductor components1are manufactured. The first metal film410and the second metal film411are cut along the cutting lines C, whereby the external terminals41to44are formed. The external terminals41to44may be prepared in such a manner that the first metal film410and the second metal film411are cut by such a method as described above or in such a manner that after the insulating film50is removed in advance so that the through-holes50ahave substantially the same shape as that of the external terminals41to44, the first metal film410and the second metal film411are formed.

Furthermore, a third metal film may be provided on the second metal film411. In this case, the first metal film410, the second metal film411, and the third metal film form the external terminals41to44before being cut. In the description ofFIG. 3C, the phrase “first metal film410and second metal film411” is replaced with the phrase “first metal film410, second metal film411, and third metal film”.

Method for Forming First Metal Film410

A method for forming the above-mentioned first metal film410is described.

As described above, in such a state that the through-holes50ahave been formed in the insulating film50, end surfaces of the columnar lines31to34and the element body10are exposed from the through-holes50a. The first metal film410, which is in contact with the element body10and is electrically conductive, is formed on the end surface of the columnar lines31to34that are exposed from the through-holes50aand the upper surface of the element body10by electroless plating. The first metal film410is a layer containing, for example, Cu.

In particular, the first metal film410, which contains Cu, is precipitated on the magnetic metal particles136, which contain Fe, by electroless plating. In detail, the magnetic metal particles136exposed at the contact surface12aof the second magnetic layer12that is in contact with the first metal film410function as a catalyst. Metal (for example, Fe) contained in the magnetic metal particles136and metal (for example, Cu) used to form the first metal film410induce a substitution reaction. As a result, the first metal film410is formed on the magnetic metal particles136.

Thereafter, the first metal film410precipitated on the magnetic metal particles136is grown, whereby the first metal film410is formed on the resin135in the second magnetic layer12. Thereafter, a reducing agent contained in a plating solution decomposes to release electrons and the electrons are supplied to Cu ions in the plating solution, so that a reduction reaction proceeds. In this manner, the first metal film410is formed so as to have a film thickness t of about 2.9 μm or more.

In electroless plating, the reducing agent used may preferably be, for example, formaldehyde. The plating solution may contain a complexing agent such as a Rochelle salt or ethylenediaminetetraacetic acid (EDTA). In the method according to the present disclosure, before plating is performed using the plating solution, plating pretreatment may be performed using a plating pretreatment solution. The plating pretreatment solution contains no catalyst (for example, a Sn-Pd catalyst or the like).

In order to form the first metal film410on the columnar lines (Cu)31to34, for example, the first metal film410precipitated on the magnetic metal particles136may be grown so as to extend on the columnar lines31to34. Alternatively, a Pd layer, that is, a catalyst layer is formed on the columnar lines31to34, and the first metal film410may be formed on the catalyst layer by electroless plating.

Method for Forming Second Metal Film411

The second metal film411is not particularly limited and may be formed by, for example, plating. In the present disclosure, the magnetic metal particles136can be protected with the first metal film410as described above. As a result, the magnetic metal particles136can be prevented from being melted when plating is performed for the purpose of forming the second metal film411. For example, the mixing of the melted magnetic metal particles136with the second metal film411may possibly affect the second metal film411. For example, the second metal film411may possibly be likely to crack because of the mixing of the melted magnetic metal particles136with the second metal film411. However, in the present disclosure, the melting of the magnetic metal particles136can be suppressed and therefore the above problem is unlikely to occur. Furthermore, the contamination of the plating solution can be prevented and the sticking of the plating solution can be prevented.

Second Embodiment

FIG. 5is a partly enlarged view illustrating a second magnetic layer12and a first metal film410in an electronic component1A according to a second embodiment. The second embodiment differs in the film thickness of the first metal film410from the first embodiment. This difference is described below. Other components are substantially the same as those in the first embodiment, are given the same reference numerals as those in the first embodiment, and will not be described in detail.

As illustrated inFIG. 5, in the second embodiment, the first metal film410has a surface irregular structure unlike a configuration according to the first embodiment in which the whole of the first metal film410has a smooth structure. InFIG. 5, a second metal film411is omitted.

In particular, the film thickness t of the first metal film410on magnetic metal particles136exposed at a contact surface12ais about 2.9 μm or more and the film thickness t′ of the first metal film410on resin135at the contact surface12ais less than the film thickness t of the first metal film410. Since the film thickness t of the first metal film410on the magnetic metal particles136is about 2.9 μm or more as described above, the occurrence of pinholes can be suppressed even if the film thickness t′ of the first metal film410on the resin135is small.

The film thicknesses t of portions of the first metal film410on the magnetic metal particles136may be different from each other and the film thickness t of at least one of the portions may be about 2.9 μm or more. All the film thicknesses t of the portions of the first metal film410on the magnetic metal particles136are preferably about 2.9 μm or more.

The present disclosure is not limited to the above-mentioned embodiments and can be modified without departing from the scope of the present disclosure.

In the above embodiments, two inductor elements, that is, the first inductor element2A and the second inductor element2B are provided in the element body10. Three or more inductor elements may be provided in the element body10. In this case, the number of external terminals and the number of columnar lines are six or more.

In the above embodiments, the number of turns of the inductor wirings in the inductor elements is less than one. The number of turns of the inductor wirings may be more than one and the inductor wirings may be curved lines. The number of layers containing inductor wirings included in the inductor element is not limited to one and a multilayer structure including two or more layers may be used. The first inductor wiring of the first inductor element and the second inductor wiring of the second inductor element are not limited to a configuration in which the first and second inductor wirings are provided on the same plane substantially parallel to the first principal surface. The first and second inductor wirings may be arranged in a direction substantially perpendicular to the first principal surface.

A “inductor wiring” is to one that causes inductance in an inductor component by generating magnetic flux when a current flows and the structure, shape, and material thereof are not particularly limited. For example, known wirings, such as meander wirings, having various shapes can be used.

In the above embodiments, the first metal film410and the second metal film411are used as external terminals of the inductor component. The first metal film410and the second metal film411are not limited to this use and may be, for example, internal terminals of the inductor component. The first metal film410and the second metal film411are not limited to being used in inductor components and may be used in other electronic components such as capacitor components and resistor components. The first metal film410and the second metal film411may be applied to a circuit board equipped with such electronic components. The first metal film410and the second metal film411may be, for example, wiring patterns for circuit boards.

In the above embodiments, the first metal film410and the second metal film411are used for external terminals. The first metal film410and the second metal film411may be used for inductor wirings. That is, a composite body may be used instead of a substrate in such a manner that inductor wirings are formed as metal films on the composite body by electroless plating. This enables metal films which serve as inductor wirings and which have the above-mentioned effect to be obtained and enables the metal films to be formed as the above-mentioned effect is exhibited.