Electronic component

In a coil component, a main body portion is made of a metal magnetic powder-containing resin, and thus a resin component appears on end surfaces of the main body portion. In addition, since external terminal electrodes are made of a conductive resin, a resin component also appears on the surfaces of the external terminal electrodes. Accordingly, insulating coating layers are integrally covered with high adhesion with the end surfaces of the main body portion and the external terminal electrodes by the insulating coating layers coming into contact with the end surfaces of the main body portion so as to straddle the external terminal electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-207239, filed on 15 Nov. 2019, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an electronic component.

BACKGROUND

An electronic component according to the related art is disclosed in, for example, Japanese Unexamined Patent Publication No. 2014-36149. The electronic component includes a terminal electrode including a baking layer baked on an end surface of a ceramic element body and an insulating coating layer provided so as to cover the terminal electrode. With such an electronic component, it is possible to suppress a solder fillet at a time of surface mounting being formed on the element body end surface side.

SUMMARY

The inventors have repeated research on an insulating coating layer that suppresses solder fillet formation and have newly found a technique with which the adhesion of the insulating coating layer to an element body can be enhanced.

An object of the present disclosure is to provide an electronic component in which the adhesion between an element body and an insulating coating layer is improved.

An electronic component according to one aspect of the present disclosure includes an element body, wiring is provided in the element body, a terminal electrode provided on a surface of the element body and electrically connected to the wiring, and an insulating coating layer covering the terminal electrode. The element body is made of a metal magnetic powder-containing resin and has a mounting surface facing a mounting substrate and a rectangular end surface extending in a direction intersecting with the mounting surface. The terminal electrode is made of a conductive resin and continuously covers the mounting surface and the end surface of the element body. The terminal electrode is separated from all three sides other than a side corresponding to the mounting surface and a U-shaped exposed region where the end surface is exposed from the terminal electrode is formed on the end surface. The insulating coating layer is made of a resin material and integrally covers the terminal electrode and the exposed region on the end surface.

In the electronic component described above, the element body is made of a metal magnetic powder-containing resin, and thus a resin component appears on the end surface of the element body. In addition, since the terminal electrode is made of a conductive resin, a resin component also appears on the surface of the terminal electrode. Accordingly, the insulating coating layer is integrally covered with high adhesion with the end surface of the element body and the terminal electrode by the insulating coating layer made of a resin material coming into contact with the end surface of the element body so as to straddle the terminal electrode.

In the electronic component according to another aspect, a surface roughness of the end surface of the element body is larger than a surface roughness of the terminal electrode. In this case, high adhesion can be realized between the insulating coating layer and the end surface of the element body and peeling from the terminal electrode covered so as to be straddled is suppressed.

In the electronic component according to another aspect, a thickness of the insulating coating layer at an intermediate position of a height position of the element body with respect to the mounting surface is smaller than thicknesses at upper- and lower-side positions with respect to the intermediate position.

Provided according to the present disclosure is an electronic component in which the adhesion between an element body and an insulating coating layer is improved.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function and redundant description is omitted.

The structure of a coil component, which is a type of electronic component, will be described as an electronic component according to the embodiment with reference toFIGS.1to4. For convenience of explanation, XYZ coordinates are set as illustrated in the drawings. In other words, the thickness direction of the coil component is set as the Z direction, the facing direction of external terminal electrodes is set as the X direction, and the direction that is orthogonal to the Z direction and the X direction is set as the Y direction.

A coil component10is a flat coil element and includes a main body portion12(element body) having a rectangular parallelepiped shape, a pair of external terminal electrodes14A and14B provided on the surface of the main body portion12, and a pair of insulating coating layers16A and16B covering the external terminal electrodes14A and14B. The main body portion12has a pair of rectangular end surfaces12aand12bfacing each other in the X direction, a pair of rectangular main surfaces12cand12dfacing each other in the Z direction, and a pair of rectangular side surfaces12eand12ffacing each other in the Y direction. As an example, the coil component10is designed to have a long-side dimension of 2.5 mm, a short-side dimension of 2.0 mm, and a height dimension of 0.8 to 1.0 mm.

The main body portion12is configured to include an insulating substrate20, a coil C provided on the insulating substrate20, and a magnetic body26. More specifically, the coil C (wiring) is provided in the main body portion12including the magnetic body26.

The insulating substrate20is a plate-shaped member made of a non-magnetic insulating material and has a substantially elliptical ring shape when viewed from the thickness direction of the insulating substrate20. An elliptical through hole20cis provided at the middle part of the insulating substrate20. A substrate in which a glass cloth is impregnated with an epoxy-based resin and that has a plate thickness of 10 μm to 60 μm can be used as the insulating substrate20. It should be noted that BT resin, polyimide, aramid, and so on can also be used in addition to the epoxy-based resin. Ceramic or glass can also be used as the material of the insulating substrate20. A mass-produced printed board material may be the material of the insulating substrate20, in particular, a resin material used for a BT, FR4, or FR5 printed board.

The coil C has a first coil portion22A where a first conductor pattern23A for a flat air-core coil provided on one surface20a(upper surface inFIG.2) of the insulating substrate20is insulated and coated, a second coil portion22B where a second conductor pattern23B for a flat air-core coil provided on the other surface20b(lower surface inFIG.2) of the insulating substrate20is insulated and coated, and a through hole conductor25connecting the first conductor pattern23A and the second conductor pattern23B.

The first conductor pattern23A (first planar coil pattern) is a planar spiral pattern serving as a flat air-core coil and is plating-formed of a conductor material such as Cu. The first conductor pattern23A is formed so as to be wound around the through hole20cof the insulating substrate20. More specifically, as illustrated inFIG.2, the first conductor pattern23A is wound clockwise, by three turns, and toward the outside when viewed from the upward direction (Z direction). The height of the first conductor pattern23A (length in the thickness direction of the insulating substrate20) is the same over the entire length.

An outside end portion23aof the first conductor pattern23A is exposed on the end surface12aof the main body portion12and is connected to the external terminal electrode14A covering the end surface12a. An inside end portion23bof the first conductor pattern23A is connected to the through hole conductor25.

As in the case of the first conductor pattern23A, the second conductor pattern23B (second planar coil pattern) is a planar spiral pattern serving as a flat air-core coil and is plating-formed of a conductor material such as Cu. The second conductor pattern23B is also formed so as to be wound around the through hole20cof the insulating substrate20. More specifically, the second conductor pattern23B is wound counterclockwise, by three turns, and toward the outside when viewed from the upward direction (Z direction). In other words, the second conductor pattern23B is wound in the direction that is opposite to the winding direction of the first conductor pattern23A when viewed from the upward direction. The height of the second conductor pattern23B is the same over the entire length and can be designed to be the same as the height of the first conductor pattern23A.

An outside end portion23cof the second conductor pattern23B is exposed on the end surface12bof the main body portion12and is connected to the external terminal electrode14B covering the end surface12b. An inside end portion23dof the second conductor pattern23B is aligned with the inside end portion23bof the first conductor pattern23A in the thickness direction of the insulating substrate20and is connected to the through hole conductor25.

The through hole conductor25is provided through the edge region of the through hole20cof the insulating substrate20and connects the end portion23bof the first conductor pattern23A and the end portion23dof the second conductor pattern23B. The through hole conductor25may include a hole provided in the insulating substrate20and a conductive material (for example, a metal material such as Cu) with which the hole is filled. The through hole conductor25has a substantially cylindrical or substantially prismatic outer shape extending in the thickness direction of the insulating substrate20.

In addition, as illustrated inFIGS.3and4, the first coil portion22A and the second coil portion22B have resin walls24A and24B, respectively. The resin wall24A of the first coil portion22A is positioned between the lines and on the inner circumference and the outer circumference of the first conductor pattern23A. Likewise, the resin wall24B of the second coil portion22B is positioned between the lines and on the inner circumference and the outer circumference of the second conductor pattern23B. In the present embodiment, the resin walls24A and24B that are positioned on the inner and outer circumferences of the conductor patterns23A and23B are designed to be thicker than the resin walls24A and24B that are positioned between the lines of the conductor patterns23A and23B.

The resin walls24A and24B are made of an insulating resin material. The resin walls24A and24B can be provided on the insulating substrate20before the first conductor pattern23A and the second conductor pattern23B are formed. In this case, the first conductor pattern23A and the second conductor pattern23B are plated and grown between the walls that are defined in the resin walls24A and24B. The resin walls24A and24B can be provided on the insulating substrate20after the first conductor pattern23A and the second conductor pattern23B are formed. In this case, the resin walls24A and24B are provided on the first conductor pattern23A and the second conductor pattern23B by filling, coating, or the like.

Each of the first coil portion22A and the second coil portion22B has an insulating layer27, which integrally covers the first conductor pattern23A and the second conductor pattern23B and the resin walls24A and24B from the upper surface side. The insulating layer27may be made of an insulating resin or an insulating magnetic material. The insulating layer27is interposed between the magnetic body26and the conductor pattern23A of the first coil portion22A and the conductor pattern23B of the second coil portion22B and enhances the insulation between the conductor patterns23A and23B and the metal magnetic powder contained in the magnetic body26.

The magnetic body26integrally covers the insulating substrate20and the coil C. More specifically, the magnetic body26covers the insulating substrate20and the coil C from the upward-downward directions and covers the outer circumference of the insulating substrate20and the coil C. In addition, the inner portion of the through hole20cof the insulating substrate20and the inside region of the coil C are filled with the magnetic body26. The magnetic body26constitutes all the surfaces of the main body portion12, that is, the end surfaces12aand12b, the main surfaces12cand12d, and the side surfaces12eand12f.

The magnetic body26is made of a resin containing metal magnetic powder. The metal magnetic powder-containing resin is binder powder in which the metal magnetic powder is bound by a binder resin. The metal magnetic powder of the metal magnetic powder-containing resin constituting the magnetic body26is configured to include magnetic powder containing at least Fe (for example, iron-nickel alloy (permalloy alloy), carbonyl iron, amorphous, non-crystalline, or crystalline FeSiCr-based alloy, and sendust). The binder resin is, for example, a thermosetting epoxy resin. In the present embodiment, the content of the metal magnetic powder in the binder powder is 80 to 92 vol % by volume and 95 to 99 wt % by mass. From the viewpoint of magnetic properties, the content of the metal magnetic powder in the binder powder may be 85 to 92 vol % by volume and 97 to 99 wt % by mass. The magnetic powder of the metal magnetic powder-containing resin constituting the magnetic body26may be powder having one type of average particle diameter or may be mixed powder having a plurality of types of average particle diameters.

In a case where the metal magnetic powder of the metal magnetic powder-containing resin constituting the magnetic body26is mixed powder, the types and Fe composition ratios of the magnetic powders having different average particle diameters may be the same or different. As an example, in the case of mixed powder having three types of average particle diameters, the particle diameter of the magnetic powder having the maximum average particle diameter (large-diameter powder) can be 15 to 30 μm, the particle diameter of the magnetic powder having the minimum average particle diameter (small-diameter powder) can be 0.3 to 1.5 μm, and the magnetic powder having an average particle diameter between the large-diameter powder and the small-diameter powder (intermediate powder) can be 3 to 10 μm. With respect to 100 parts by weight of the mixed powder, the large-diameter powder may be contained in the range of 60 to 80 parts by weight, the medium-diameter powder may be contained in the range of 10 to 20 parts by weight, and the small-diameter powder may be contained in the range of 10 to 20 parts by weight.

The average particle diameter of the magnetic powder is defined by the particle diameter at an integrated value of 50% in the particle size distribution (d50, so-called median diameter) and is obtained as follows. A scanning electron microscope (SEM) photograph of a cross section of the magnetic body26is taken. Image processing is performed on the SEM photograph by software, the boundary of the magnetic powder is determined, and the area of the magnetic powder is calculated. The particle diameter is calculated by the calculated area of the magnetic powder being converted into a circle-equivalent diameter. For example, the particle diameter of 100 or more magnetic powders is calculated and the particle size distribution of these magnetic powders is obtained. The average particle diameter d50is the particle diameter at an integrated value of 50% in the obtained particle size distribution. The particle shape of the magnetic powder is not particularly limited.

As illustrated inFIGS.3,5, and6, the external terminal electrodes14A and14B have a first part14aprovided on the end surfaces12aand12band a second part14bprovided on the main surface12d, which is a mounting surface facing a mounting substrate50, and continuously cover the end surfaces12aand12band the main surface12d. The external terminal electrodes14A and14B have an L shape in a cross section (X-Z cross section) orthogonal to the end surfaces12aand12band the main surface12d.

The external terminal electrodes14A and14B are electrically connected to the coil C provided in the main body portion12(specifically, the outside end portions23aand23cof the conductor patterns23A and23B) at the first part14a. The second part14bis a part that is solder-connected to a terminal52of the mounting substrate50, and a plating layer18is formed on the surface of the second part14b. The plating layer18may include a single layer or may include a plurality of layers. As illustrated inFIG.6, in the present embodiment, the plating layer18includes two layers in which a Ni plating layer18aand a Sn plating layer18bare arranged from the side that is close to the external terminal electrode. It should be noted that the plating layer18is not formed at the first part14aand the first part14aand the insulating coating layer16A are in direct contact with each other.

The external terminal electrode14A has a substantially rectangular shape on the end surface12aas illustrated inFIG.5. The external terminal electrode14A wraps around the main surface12don the side corresponding to the main surface12don the rectangular end surface12aand is separated from all three sides other than the side corresponding to the main surface12d(that is, the side corresponding to the main surface12cand the sides corresponding to the side surfaces12eand12f). Accordingly, a U-shaped exposed region S where the end surface12ais exposed from the external terminal electrode14A is formed on the end surface12a. The other external terminal electrode14B also covers the end surface12bin the same manner as the external terminal electrode14A.

The external terminal electrodes14A and14B are electrodes (so-called resin electrodes) made of a conductive resin in which conductor powder is dispersed in the resin. Metal powder such as Ag powder can be used as the conductor powder constituting the external terminal electrodes14A and14B. An epoxy-based resin can be used as the resin constituting the external terminal electrodes14A and14B.

The external terminal electrodes14A and14B have a surface roughness (arithmetic mean roughness Ra) of, for example, 3 μm. The surface roughness of the end surfaces12aand12bof the main body portion12is, for example, 10 μm and is designed to be larger than the surface roughness of the external terminal electrodes14A and14B.

The insulating coating layers16A and16B cover the end surfaces12aand12bas illustrated inFIGS.1,3, and6. Specifically, the end surfaces12aand12band the external terminal electrodes14A and14B at the parts provided on the end surfaces12aand12bare integrally covered. The U-shaped exposed region S is formed on the end surfaces12aand12bas described above, and the insulating coating layers16A and16B are in contact with the end surfaces12aand12bso as to straddle the external terminal electrodes14A and14B.

As illustrated inFIG.6, the thicknesses of the insulating coating layers16A and16B are not uniform. Specifically, a thickness d at the intermediate position of the height (Z-direction height) of the main body portion12with respect to the main surface12dis designed to be smaller than a thickness d1at the upper-side position and a thickness d2at the lower-side position with respect to the intermediate position. It should be noted that the insulating coating layers16A and16B may have a uniform thickness in another aspect.

The insulating coating layers16A and16B are made of a resin material. Specifically, the insulating coating layers16A and16B are made of a thermosetting resin and can be made of epoxy resin, phenol resin, melamine resin, or the like.

In the coil component10described above, the main body portion12is made of a metal magnetic powder-containing resin, and thus a resin component (for example, epoxy-based resin) appears on the end surfaces12aand12bof the main body portion12. In addition, since the external terminal electrodes14A and14B are made of a conductive resin, a resin component (for example, epoxy-based resin) also appears on the surfaces of the external terminal electrodes14A and14B. Accordingly, the insulating coating layers16A and16B are integrally covered with high adhesion with the end surfaces12aand12bof the main body portion12and the external terminal electrodes14A and14B by, for example, the insulating coating layers16A and16B made of an epoxy-based resin coming into contact with the end surfaces12aand12bof the main body portion12so as to straddle the external terminal electrodes14A and14B. Accordingly, with the coil component10, an improvement in the adhesion between the main body portion12and the insulating coating layers16A and16B is realized.

In addition, in the coil component10, the surface roughness of the end surfaces12aand12bof the main body portion12is larger than the surface roughness of the external terminal electrodes14A and14B, and thus high adhesion is realized between the insulating coating layers16A and16B and the end surfaces12aand12bof the main body portion12and peeling from the external terminal electrodes14A and14B covered so as to be straddled by the insulating coating layers16A and16B is suppressed.

Further, in the coil component10, no plating layer is interposed between the insulating coating layers16A and16B and the external terminal electrodes14A and14B and the insulating coating layers16A and16B are in direct contact with the external terminal electrodes14A and14B. Accordingly, solder is unlikely to crawl up between the external terminal electrodes14A and14B and the insulating coating layers16A and16B.

It should be noted that the present disclosure is not limited to the above-described embodiment and may take various aspects. For example, the coil C may include both the first coil portion and the second coil portion or may include only the first coil portion. In addition, the end surface of the element body does not necessarily have to be orthogonal to the mounting surface and may extend in a direction intersecting with the mounting surface. Further, the electronic component is not limited to the coil component in which the coil is provided in the main body portion and may be, for example, a capacitor or a resistor.