JP2022155186A - inductor - Google Patents

Abstract

To improve fastening strength of an external electrode.SOLUTION: An inductor 1 has an element assembly 2 in which a coil conductor 20 is embedded in a core 30 containing metal magnetic powder and a resin, and external electrodes 4 formed on the surface of the element assembly 2, wherein the element assembly 2 has, based on the total mass of the metal magnetic powder and the resin, a ratio of the metal magnetic powder of 96.7 wt.% or more and 97.4 wt.% or less and a ratio of the resin of 2.6 wt.% or more and 3.3 wt.% or less, and a surface where the external electrodes contact on the surface of the element assembly 2 has a metal area ratio that is a ratio of the area of the metal occupied in the total area of the metal magnetic powder and the resin of 65% or more and 75% or less.SELECTED DRAWING: Figure 5

Description

The present invention relates to inductors.

Patent Literature 1 discloses a conductive paste for forming terminal electrodes of multilayer ceramic electronic components. Moreover, Patent Document 1 discloses that the conductive paste contains conductive powder and a resin component, the conductive powder is silver powder, and the average particle size is 0.1 μm or more and 10 μm or less.

Japanese Patent Laid-Open No. 2020-088353

When the conductive paste disclosed in Patent Document 1 is applied to the base body of an inductor, which is a type of electronic component, and used to form an external electrode of the inductor, the average particle size of the conductive powder is relatively small. Since it is large, the contact area between the conductive particles becomes small, the current path becomes small, and the resistance value of the external electrode becomes relatively large.

Therefore, by mixing conductive powder with a smaller average particle size into the conductive paste, the problem of the resistance value of the external electrodes can be improved. However, when a conductive powder with a smaller average particle size is mixed, the dispersibility of the conductive powder in the resin deteriorates. Therefore, it is necessary to improve the dispersibility of the conductive powder by using, for example, an acrylic resin as a resin component. There is
However, when an acrylic resin or the like is used as the resin component, the adhesion strength of the conductive paste to the element body is weakened, causing a problem that the external electrodes are easily peeled off.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inductor having an element body capable of improving the bonding strength of external electrodes.

One aspect of the present invention is an inductor comprising: a body in which a coil conductor is embedded in a core containing metal magnetic powder and resin; and external electrodes formed on the surface of the body, wherein the body comprises , based on the total weight of the metal magnetic powder and the resin, the ratio of the metal magnetic powder is 96.7 wt% or more and 97.4 wt% or less, and the ratio of the resin is 2.6 wt% or more and 3.3 wt% or less. and the surface of the element contacting the external electrode has a metal area ratio of 65% or more and 75% or less, which is the ratio of the area of the metal magnetic powder to the total area of the metal magnetic powder and the resin. It is characterized by

According to the present invention, the fixing strength of the external electrodes can be improved.

1 is a perspective view of an inductor according to a first embodiment of the present invention, viewed from the upper surface side; FIG. It is the perspective view which looked at the inductor from the mounting surface side. 2 is a see-through perspective view showing the internal configuration of an inductor; FIG. 1 is a schematic diagram of a manufacturing process of an inductor; FIG. It is a schematic diagram which shows the structure of LT cross section of an inductor. FIG. 4 is a diagram showing the relationship between surface roughness and fixing strength of external electrodes; It is a figure which shows the relationship between a metal area ratio and surface roughness. FIG. 4 is a diagram showing a micrograph of a cross section of an external electrode portion of an inductor, together with a micrograph of the surface of an electrode formation portion; FIG. 5 is a schematic diagram showing the configuration of the LT cross section of the inductor according to the second embodiment of the present invention; FIG. 3 is a diagram showing a correspondence relationship between a cross-sectional configuration of a portion including an extending portion of an external electrode and a plan view configuration of an inductor viewed from a mounting surface; FIG. 11 is a schematic diagram showing the configuration of the LT cross section of the inductor according to the third embodiment of the present invention;

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 1 is a perspective view of the inductor 1 according to the present embodiment viewed from the upper surface 12 side, and FIG. 2 is a perspective view of the inductor 1 viewed from the mounting surface 10 side.
The inductor 1 of this embodiment is configured as a surface-mounted electronic component, and includes a substantially rectangular parallelepiped element body 2 and a pair of external electrodes 4 provided on the surface of the element body 2. 2 is configured as a mounting surface 10 (FIG. 2) to be mounted on the surface of a circuit board (not shown).

Hereinafter, in the element body 2 , the surface facing the mounting surface 10 is defined as the upper surface 12 , and among the four surfaces other than the upper surface 12 and the mounting surface 10 , the surfaces at both ends in the longitudinal direction of the element body 2 are referred to as end surfaces 14 . is called a side surface 16.
As shown in FIG. 1, the distance from the mounting surface 10 to the upper surface 12 is defined as the thickness T of the element body 2, the distance between the pair of side surfaces 16 is defined as the width W of the element body 2, and the pair of end surfaces 14 is defined as the length L of the prime field 2. The direction of thickness T is defined as thickness direction DT, the direction of width W is defined as width direction DW, and the direction of length is defined as length direction DL.

FIG. 3 is a see-through perspective view showing the internal configuration of the inductor 1. As shown in FIG.
The element body 2 includes a coil conductor 20 and a substantially rectangular parallelepiped core 30 in which the coil conductor 20 is embedded.

The core 30 is a molded body obtained by compression-molding a mixed powder of metal magnetic powder (soft magnetic powder) and resin into a substantially rectangular parallelepiped shape by applying pressure and heat while enclosing the coil conductor 20 .

In addition, the metal magnetic powder of the present embodiment includes particles having two types of particle sizes: large first magnetic particles having a relatively large average particle size and second small magnetic particles having a relatively small average particle size. contains. As a result, during compression molding, the second magnetic particles, which are small particles, enter between the first magnetic particles, which are large particles, together with the resin, thereby increasing the filling rate of the core 30 and increasing the magnetic permeability. . In this embodiment, the average particle diameters of the metal particles of the first magnetic particles and the second magnetic particles are 24.4 μm and 4.0 μm, respectively. The average particle size of the first magnetic particles is preferably 24 μm or more and 39 μm or less, and the average particle size of the second magnetic particles is preferably 3 μm or more and 5 μm or less. In addition, the metal magnetic powder may contain particles having an average particle size between the first magnetic particles and the second magnetic particles, thereby including particles having three or more particle sizes.

In the present embodiment, both the first magnetic particles and the second magnetic particles are particles having a metal particle and an insulating film with a thickness of several nanometers or more and several tens of nanometers or less covering the surface of the metal particle. Fe—Si system amorphous alloy powder is used for the insulating film, and zinc phosphate is used for the insulating film. By covering the metal particles with the insulating film, the insulation resistance and the withstand voltage are increased.
The amount of the second magnetic particles is 25% by weight based on the total weight of the magnetic particles contained in the mixed powder.

In the first magnetic particles, the metal particles include Cr-less Fe--C--Si alloy powder, Fe--Ni--Al alloy powder, Fe--Cr--Al alloy powder, Fe--Si--Al alloy powder, Fe-- Ni alloy powder and Fe--Ni--Mo alloy powder may be used.

In addition, in the first magnetic particles and the second magnetic particles, the insulating film may contain other phosphates (magnesium phosphate, calcium phosphate, manganese phosphate, cadmium phosphate, etc.) or resin materials (silicone-based resin, epoxy resin, etc.). resin, phenolic resin, polyamide-based resin, polyimide-based resin, polyphenylene sulfide-based resin, etc.) may be used.

In the mixed powder of the present embodiment, an epoxy resin containing a bisphenol A type epoxy resin as a main component is used as the resin material.
The epoxy resin may be a phenol novolac type epoxy resin.
Also, the resin material may be other than the epoxy resin, and may be two or more types instead of one type. For example, thermosetting resins such as phenol resins, polyester resins, polyimide resins, and polyolefin resins can be used as the resin material in addition to epoxy resins.

The coil conductor 20 includes, as shown in FIG. The winding portion 22 is formed by spirally winding a conductor wire so that both ends of the conductor wire are located on the outer circumference and connected to each other on the inner circumference. Inside the element body 2 , the coil conductor 20 is embedded in the core 30 with the central axis of the winding portion 22 along the thickness direction DT of the element body 2 . It is pulled out to each of the pair of end faces 14 and electrically connected to the external electrode 4 .

The external electrode 4 is a so-called five-sided electrode provided over the entire surface of the end surface 14 and a part of each of the mounting surface 10 adjacent to the end surface 14, the upper surface 12, and the pair of side surfaces 16. is electrically connected to the wiring of the circuit board by appropriate mounting means.

The inductor 1 having such a configuration is used in a power supply circuit having a charge pump type DCDC converter and an LC filter for stepping up the voltage with a capacitor and a switch. , smartphones, car electronics, medical and industrial machines. However, the use of the inductor 1 is not limited to this, and can also be used, for example, in a tuning circuit, a filter circuit, a rectifying/smoothing circuit, and the like.

In addition, in the inductor 1 , an element protective layer may be formed over the entire surface of the element 2 excluding the range of the external electrodes 4 . Thermosetting resins such as epoxy resins, polyimide resins and phenol resins, or thermoplastic resins such as polyethylene resins and polyamide resins can be used for the material of the body protective layer. These resins may further contain a filler containing silicon oxide, titanium oxide, or the like.

FIG. 4 is a schematic diagram of the manufacturing process of the inductor 1. FIG.
As shown in the figure, the manufacturing process of the inductor 1 includes a coil conductor molding process, a tablet molding process, a thermoforming/hardening process, a barrel polishing process, and an external electrode forming process.

The coil conductor molding process is a process of molding the coil conductor 20 from the conducting wire. In this process, the coil conductor 20 is formed into a shape having the above-described winding portion 22 and a pair of lead portions 24 by winding the conductive wire in a winding method called "alpha winding". The alpha winding refers to a state in which the conducting wire functioning as a conductor is spirally wound in two stages so that the lead-out portions 24 at the winding start and the winding end are positioned on the outer periphery. The number of turns of the coil conductor 20 is not particularly limited.

The tablet molding process is a process of molding a preform called a tablet.
The preform is formed by pressurizing the mixed powder, which is the material of the base body 2, into a solid shape that is easy to handle. Two types of tablets are formed: a first tablet (for example, E-shaped) and a second tablet having an appropriate shape (for example, I-shaped or plate-shaped) that covers the groove of the first tablet.

In the thermoforming and curing step, the first tablet, the coil conductor, and the second tablet are set in a molding die, and while applying heat, pressure is applied in the overlapping direction of the first tablet and the second tablet to cure them. to integrate the first tablet, the coil conductor, and the second tablet. As a result, the element body 2 in which the coil conductor 20 is enclosed in the core 30 is molded.

The barrel polishing step is a step of barrel polishing the molded body, and the corners of the element body 2 are rounded by this step.

The external electrode forming process is a process of forming the external electrodes 4 on the element body 2, and includes a laser irradiation process and an electrode layer forming process.

FIG. 5 is a schematic diagram showing the configuration of the LT cross section of the inductor 1. As shown in FIG. Note that the LT cross section is a cross section along the LT plane including the length direction DL and the thickness direction DT of the core 30 .
The laser irradiation step is a step of modifying the surface of the electrode forming region 70 on which the external electrode 4 is to be formed by irradiating the electrode forming region 70 on which the external electrode 4 is to be formed on the surface of the element body 2 with a laser beam.
After laser irradiation, a cleaning process (for example, an etching process) may be performed to clean the surface of the electrode formation region 70 .

The metal layer forming step is a step of forming the external electrodes 4 by laminating various metal layers on the electrode forming region 70 whose surface has been modified by laser irradiation.
Specifically, in this step, first, a base electrode 74 is formed by applying a conductive resin paste to the entire surface of the electrode forming region 70 , and a nickel (Ni) layer 76 is formed on the surface of the base electrode 74 . , and a tin (Sn) layer 78 are laminated in this order by plating to form the external electrodes 4 .

The conductive resin paste, which is the material of the base electrode 74, is a mixed material obtained by mixing conductive powder and resin. .88. The content of the conductive powder is preferably 0.87 or more and 0.89 or less.

Further, in the present embodiment, the conductive powder is silver powder, and includes first conductive particles and second conductive particles having different average particle sizes.
In the present embodiment, the average particle size of the first conductive particles is 5 μm, the average particle size of the first conductive particles is preferably 1 μm or more and 30 μm or less, the average particle size of the second conductive particles is 80 nm, The average particle size of the second conductive particles is preferably 0.5 nm or more and 200 nm or less.

In the present embodiment, the ratio of the average particle sizes of the first conductive particles and the second conductive particles (= average particle size of the second conductive particles / average particle size of the first conductive particles) is 0.2 or more and 0.11 or less. , the compounding ratio (weight ratio) of the first conductive particles and the second conductive particles is 6:4. The compounding ratio (weight ratio) of the first conductive particles and the second conductive particles is preferably 3.5 or more for the second conductive particles.
In addition, the content ratio of the first conductive particles and the resin (= first conductive particles / resin) is 0.528, preferably 0.522 or more and 0.534 or less, and the content ratio of the second conductive particles and the resin (second conductive particles/resin) is 0.352, preferably 0.348 or more and 0.356 or less.

Moreover, in this embodiment, the resin is an acrylic thermosetting resin.

According to the base electrode 74, the conductive powder contains the first conductive particles and the second conductive particles having different average particle sizes, and the average particle size of the second conductive particles is larger than the average particle size of the first conductive particles. Since they are small, the second conductive particles enter the gaps between the first conductive particles. As a result, the contact between the conductive particles in the conductive powder is not only the contact between the first conductive particles and the second conductive particles, but also the contact between the first conductive particles and the second conductive particles. Area increases. Such an increase in contact area increases the number of current paths in the conductive powder, thereby reducing the resistance value of the external electrode 4 including the underlying electrode 74 .

Here, in the element body 2, the fixing strength of the external electrodes 4 formed in the electrode forming regions 70 is improved by surface modification using laser irradiation to the electrode forming regions 70 in the external electrode forming process. ing.

More specifically, in the element body 2 of the present embodiment, the ratio of the metal magnetic powder to the total weight of the metal magnetic powder and the resin (=weight of the metal magnetic powder/(weight of the metal magnetic powder+weight of the resin)) is 97 wt %, and the ratio of resin (=weight of resin/(weight of metal magnetic powder+weight of resin)) is molded from mixed powder of 3.0 wt %. Furthermore, in the element body 2 after laser irradiation, the electrode formation region 70, which is the surface in contact with the external electrode 4, has a metal area ratio of 70%, whereas the portions other than the electrode formation region 70 are made of metal. The area ratio is 38%.
In this case, the electrode forming region 70 has a surface roughness Sa of 10 μm, while the surface of the element body 2 other than the electrode forming region 70 has a surface roughness Sa of 1.8 μm. , and the electrode forming region 70 is roughly five times or more rougher than the other portions.
The metal area ratio is the ratio of the area of the metal magnetic powder to the total area of the metal magnetic powder and the resin (=area of the metal magnetic powder/(total area of the resin and the metal magnetic powder)).

Table 1 shows the experimental results of examining the relationship between the surface roughness Sa and the bonding strength (unit: kg/mm ² ) of the external electrode 4, and FIG. 6 is a graph of the experimental results of Table 1.
Note that the experimental results in Table 1 show that the surface roughness Sa is changed by changing the irradiation intensity (energy) of the laser beam irradiated to the electrode forming region 70, and the external electrodes 4 formed on the electrode forming region 70 are fixed. This is the result obtained by measuring the strength. Bonding strength was measured using a bond tester.

Considering that the threshold Ath of the adhesion strength that does not cause the problem of peeling is practically 0.4 (kg/mm ² ), as shown in Table 1 and FIG. If it is 8 (μm) or more, it can be seen that a fixing strength equal to or greater than the threshold value Ath is obtained.
As described above, in the inductor 1 of the present embodiment, the surface roughness Sa of the electrode formation region 70 is 10 μm, so it can be seen that sufficient bonding strength is obtained.

Table 2 shows the experimental results of examining the relationship between the metal area ratio and the surface roughness Sa, and FIG. 7 is a graph of the experimental results of Table 2.
In Table 2, area energy (unit: mJ/mm ² ) is laser energy per unit area.
The experimental results in Table 2 are the average values of the metal area ratios measured for the three element bodies 2, and the metal area ratio for each element body 2 is measured as follows.
First, a photographing point is set within the surface of the electrode forming region 70 for each of the end surface 14 , the upper surface 12 and the mounting surface 10 of the element body 2 . The imaging point is an intersection obtained by connecting the four corners of the electrode forming region 70 diagonally on each surface of the imaging target. Then, each photographing point is photographed at a magnification of 500 using the backscattered electron mode of the scanning electron microscope, and the photographed image of each photographing point is binarized. Next, the metal magnetic powder is specified in each photographed image after binarization, and the ratio of the area occupied by the metal magnetic powder in each photographed image is obtained as the metal area ratio. Then, the average value of the metal area ratio of each photographed image is taken as the metal area ratio of the element body 2 .
In addition, regarding the metal area ratio of the surface other than the electrode forming region 70 in the element body 2, the four corners of each of the top surface 12 and the mounting surface 10 of the element body 2 are diagonally connected to each other. Using the intersecting point as a photographing point, the metal area ratio of the electrode forming region 70 is measured in the same manner as described above.

As shown in Table 2 and FIG. 7, the surface roughness Sa increases as the metal area ratio increases. As shown in FIG. 6, the adhesion strength equal to or higher than the threshold value Ath can be obtained if the surface roughness Sa is 4.8 (μm) (Bth in FIG. 6) or higher. can be obtained if the metal area ratio is about 65% or more (Cth in FIG. 7), as shown in FIG.

FIG. 8 is a diagram showing a micrograph of the cross section of the external electrode 4 portion of the inductor 1 together with a micrograph of the surface of the electrode forming region 70 .
As shown in the figure, a large number of magnetic particles 80 (the first magnetic particles and the second magnetic particles) are present in the electrode forming region 70 (surface) of the element body 2, and the electrode forming region 70 is irradiated with a laser, the resin on the surface is removed, and the adjacent magnetic particles 80 are fused together. The fusion of the magnetic particles 80 in the electrode forming region 70 becomes more pronounced as the laser irradiation intensity increases, thereby increasing the metal area ratio.

However, through the measurements of FIGS. 7 and 8, it was found that if the laser irradiation intensity becomes too strong, grain shedding occurs in the electrode forming region 70, and unevenness occurs on the surface of the external electrode 4 formed there. ing. Specifically, when the metal area ratio is 75% (Cmax in FIG. 7) or less, no unevenness of the external electrode 4 due to shedding is observed, but when the metal area ratio is 78% or more, unevenness of the external electrode 4 is observed. rice field.
Therefore, it can be said that the metal area ratio is preferably 75% or less in order to prevent unevenness on the surface of the external electrode 4 .

From the above, when the metal area ratio of the electrode forming region 70 is 65% or more and 75% or less, the fixing strength of the external electrodes 4 becomes sufficient, and the occurrence of unevenness on the surface of the external electrodes 4 is suppressed. I know it can be done.

The inventors found that the ratio of the metal magnetic powder (=the weight of the metal magnetic powder/(the weight of the metal magnetic powder + the weight of the resin)) to the total weight of the metal magnetic powder and the resin was 96.5%. If it is 7 wt % or more and 97.4 wt % or less and the ratio of the resin (= resin weight/(metal magnetic powder weight + resin weight)) is 2.6 or more and 3.3 wt % or less, the metal area ratio and It has been confirmed by experiments that the above-described relationship between the fixing strength and the generation of unevenness on the surface of the external electrode 4 can be obtained.

According to this embodiment, the following effects are obtained.

The inductor 1 of this embodiment includes an element body 2 in which a coil conductor 20 is embedded in a core 30 containing metal magnetic powder and resin, an external electrode 4 formed in an electrode forming region 70 on the surface of the element body 2, is an inductor 1 having The base body 2 has a metal magnetic powder ratio of 96.7 wt % or more and 97.4 wt % or less and a resin ratio of 2.6 or more and 3.3 wt % based on the total weight of the metal magnetic powder and resin. In the electrode forming region 70 of the element body 2, the metal area ratio, which is the ratio of the area of the metal to the total area of the metal and resin generated from the metal magnetic powder, is 65% or more and 75% or less.
As a result, the fixing strength of the external electrodes 4 becomes sufficient, and the occurrence of unevenness on the surfaces of the external electrodes 4 is suppressed.

In the present embodiment, the external electrode 4 is a base electrode formed in the electrode formation region 70 of the base body 2 by a conductive resin paste containing first conductive particles and second conductive particles having different average particle diameters and a resin. 74 , and plating layers (a nickel layer 76 and a tin layer 78 ) formed on the surface of the base electrode 74 .
Since the base electrode 74 contains the first conductive particles and the second conductive particles having different average particle diameters, the flow path and area of the current in the base electrode 74 are increased, and the external electrode 4 including the base electrode 74 is increased. Resistance value can be reduced.

[Second embodiment]
FIG. 9 is a schematic diagram showing the configuration of the LT cross section of the inductor 1 according to the second embodiment of the present invention. FIG. 10 is a diagram showing the correspondence relationship between the cross-sectional configuration of the portion including the extension portion 90 of the external electrode 4 and the plan view configuration of the inductor 1 viewed from the mounting surface 10. As shown in FIG.

The inventors have found that when the metal area ratio of the electrode forming region 70 of the element body 2 is 65% or more and 75% or less, not only the fixing strength of the conductive resin paste but also the fixing strength of the nickel layer 76 Through experiments similar to the experiments according to FIGS. 6 and 7 of the first embodiment, it was found that the surface roughness of the external electrodes 4 can be suppressed to the same level as that of the resin paste.
More specifically, when the metal area ratio of the electrode formation region 70 is 65% or more, the conductivity of the electrode formation region 70 is increased, which facilitates the growth of the plating in the electrode formation region 70. Since the contact area between the nickel layer 76 and the nickel layer 76 can also be increased, the bonding strength is improved. On the other hand, if the metal area ratio of the electrode formation region 70 exceeds 75%, the intensity of the laser irradiation becomes too strong and the metal magnetic powder sheds, making it difficult for the plating to grow, and unevenness occurs on the surface of the external electrode 4 . or

In this manner, the fixing strength of the nickel layer 76 is also increased according to the metal area ratio of the electrode forming region 70 .
Therefore, it has a base electrode 74 made of a conductive resin paste, a nickel layer 86 (plated layer) on the base electrode 74, and a tin layer 78 on the nickel layer 76, and has a metal area ratio of 65% or more. In the external electrode 4 in which the base electrode 74 is formed in 75% or less of the electrode forming area 70, the fixing strength of the external electrode 4 can be increased as compared with the first embodiment by performing the following. That is, as shown in FIGS. 9 and 10, by providing an extending portion 90 in direct contact with the surface of the electrode formation region 70 on the nickel layer 76 (plating layer) of the external electrode 4, the base electrode 74 and the electrode are formed. In addition to being fixed to the formation region 70 , the extending portion 90 also increases the fixing strength of the external electrodes 4 , making it more difficult for the external electrodes 4 to come off. Further, as shown in FIG. 9, both of the pair of external electrodes 4 are provided with extending portions 90 on the mounting surface 10 and the upper surface 12, respectively, and further, as shown in FIG. By extending between the pair of side surfaces 16 of the one, the fixing strength is increased compared to the case where the extension 90 is not provided.
In the external electrode 4 of the present embodiment, the metal area ratio of the surface of the electrode forming region 70 in contact with the extension 90 is higher than the metal area ratio of the surface of the element body 2 other than the electrode forming region 70, and Even if it is less than 65%, the bonding strength can be made higher than that of the first embodiment by the bonding strength of the base electrode 74 and the bonding strength of the extension portion 90 . In addition, by setting the metal area ratio of the surface of the electrode forming region 70 in contact with the extending portion 90 to 65% or more and 75% or less, the electrical conductivity of the electrode forming region 70 is lower than when the metal area ratio is less than 65%. With the increase in , the plating grows easily in the electrode formation region 70, and the contact area between the metal magnetic powder and the nickel layer 76 can be increased, so that the fixing strength of the extension 90 can be increased.

[Third embodiment]
FIG. 11 is a schematic diagram showing the configuration of the LT cross section of the inductor 1 according to the third embodiment of the present invention.
As described in the second embodiment, when the metal area ratio of the electrode formation region 70 of the element body 2 is 65% or more and 75% or less, the adhesion strength of the nickel layer 76 to the electrode formation region 70 is improved, and , the occurrence of unevenness on the surface of the external electrode 4 is suppressed.
Therefore, as shown in FIG. 11, an external electrode 4 in which a nickel layer 76 and a tin layer 78, which are plating layers, are directly formed on the electrode forming region 70 without forming the underlying electrode 74 on the electrode forming region 70 of the element body 2. can also be configured. In this case, the plating layer is directly connected to the lead-out portion 24 of the coil conductor 20 in the external electrode 4 .
The plating layers may be formed in the order of the copper (Cu) layer, the nickel layer 76, and the tin layer 78, and the external electrodes 4 with sufficient fixing strength can be obtained even with the plating layers.

Each embodiment described above is an example of one aspect of the present invention, and can be arbitrarily modified and applied without departing from the scope of the present invention.

In each of the above-described embodiments, the shape of the external electrode 4 is not limited to a five-sided electrode, and may be, for example, an L-shaped electrode or a bottom electrode.

Unless otherwise specified, the horizontal and vertical directions, various numerical values, shapes, and materials in the above-described embodiments are ranges that exhibit the same effects as those directions, numerical values, shapes, and materials (so-called equal ranges). including.

REFERENCE SIGNS LIST 1 inductor 2 element body 4 external electrode 20 coil conductor 30 core 70 electrode forming region (surface with which the external electrode contacts)
74 base electrode 76 nickel layer (plating layer)
78 tin layer 90 extension

Claims (4)

An inductor comprising: an element body in which a coil conductor is embedded in a core containing metal magnetic powder and resin; and an external electrode formed on the surface of the element body,
The element is
Based on the total weight of the metal magnetic powder and the resin, the ratio of the metal magnetic powder is 96.7 wt% or more and 97.4 wt% or less, and the ratio of the resin is 2.6 wt% or more and 3.3 wt% or less. can be,
The surface of the element contacting the external electrode has a metal area ratio of 65% or more and 75% or less, which is the ratio of the area of the metal magnetic powder to the total area of the metal magnetic powder and the resin.
An inductor characterized by: The external electrodes are
a base electrode formed on the surface of the element by a conductive resin containing first conductive particles and second conductive particles having different average particle diameters, and a resin;
a plating layer formed on the surface of the base electrode;
2. The inductor of claim 1, comprising: The plating layer is
3. The inductor according to claim 2, further comprising an extending portion extending from the base electrode to the surface of the element body. The external electrodes are
2. The inductor according to claim 1, further comprising a plating layer formed on the surface of the element body.

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