SURFACE MOUNTED INDUCTOR AND METHOD FOR MANUFACTURING THE SAME

Abstract

A surface mounted inductor is equipped with a coil formed by winding a conductive wire, and a formed body in which the coil is sealed with a sealing material that mainly contains metal magnetic powder and a resin. The coil is embedded so that surfaces of lead-out ends are exposed on surfaces of the formed body. The resin at portions of surfaces of the formed body where external terminals are formed is removed, and the metal magnetic powder and a plating layer forming the external terminals are joined to each other, thereby connecting the external terminals and the lead-out ends of the coil.

Claims

1. A surface mounted inductor comprising: a body including metal magnetic powder and a resin, a coil configured by a wound conductive wire and having lead-out ends, the coil being embedded in the body, and external terminals, wherein, surfaces of the body include a first portion where the resin existing in the surfaces of the body is selectively removed according to a shape of the external terminal, and a second portion where the resin existing in the surfaces of the body remains, in the first portion, the metal magnetic powder exposed on the surfaces of the body and a plating layer configuring the external terminals are joined to each other, and the external terminals and the lead-out ends of the coil are connected to each other.

2. The surface mounted inductor according to claim 1, wherein the external terminals include a conductive joint material layer covering the lead-out ends of the coil exposed on the surfaces of the body, and the plating layer covering the conductive joint material layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is a perspective view of a formed body in an embodiment of a surface mounted inductor of the present disclosure.

[0043] FIG. 2 is a perspective view of a processed formed body in the embodiment of the surface mounted inductor of the present disclosure.

[0044] FIG. 3 is a perspective view showing the embodiment of the surface mounted inductor of the present disclosure.

[0045] FIGS. 4(A), 4(B) and 4(C) are schematic views for explaining an external terminal in the embodiment of the surface mounted inductor of the present disclosure.

[0046] FIG. 5 is a perspective view of a conventional surface mounted inductor.

DETAILED DESCRIPTION

[0047] According to one or more embodiments of the surface mounted inductor of the present disclosure, since the resin at the portions of the surfaces of the formed body where the external terminals are formed is removed, the metal magnetic powder forming the formed body is exposed, and plating is easily grown at the portions compared to their surroundings. At this time, by adjusting the shape of the portions of the surfaces of the formed body where the resin is removed, it is easily possible to change the shape of the external terminals. It is also possible to reduce the thickness of the external terminals to as thin as 20 μm or less, so that the size of the formed body can be increased by the reduction in the thickness, or the overall shape can be reduced. When the size of the formed body is increased by the reduction in the thickness of the external terminals, the thickness of the conductive wire can be increased or the size of the coil can be increased.

[0048] Furthermore, according to one or more embodiments of the method for manufacturing the surface mounted inductor of the present disclosure, since the resin at the portions of the surfaces of the formed body where the external terminals are formed is removed, the metal magnetic powder forming the formed body is exposed, and plating is easily grown at the portions compared to their surroundings. At this time, by adjusting the shape of the portions of the surfaces of the formed body where the resin is removed, it is easily possible to change the shape of the external terminals. It is also possible to reduce the thickness of the external terminals to as thin as 20 μm or less, so that the size of the formed body can be increased by the reduction in the thickness, or the overall shape can be reduced. When the size of the formed body is increased by the reduction in the thickness of the external terminals, the thickness of the conductive wire can be increased or the size of the coil can be increased.

[0049] The best mode for carrying out the present disclosure will hereinafter be described with reference to FIG. 1 through FIG. 4.

[0050] FIG. 1 is a perspective view of a formed body in an embodiment of a surface mounted inductor of the present disclosure.

[0051] In FIG. 1, reference numeral 11 denotes a coil, and reference numeral 12 denotes a formed body.

[0052] In the coil 11, by winding a conductive wire in two tiers in an outside-to-outside manner so that both of its ends are positioned at an outer periphery thereof, a coreless coil including a wound portion 11a and lead out ends 11b led out from the wound portion 11a is obtained. A rectangular wire that is rectangular in cross section is used as the conductive wire. The lead-out ends 11b are led out so as to be opposite to each other across the wound portion.

[0053] A formed body 12 is formed with a sealing material containing a resin and a magnetic material so as to incorporate the coil 11. The sealing materials used include those obtained by using the magnetic material such as iron-based metal magnetic powder and the resin such as an epoxy resin and mixing them. On side surfaces opposed in the length direction of the formed body 12, surfaces of the lead-out ends 11b of the coil 11 are exposed.

[0054] On the side surfaces opposed in the length direction of the formed body 12 and on a bottom surface thereof, external terminals 14 are formed thereby connecting the lead-out ends 11b of the coil 11 and the external terminals 14. Each external terminal 14 is formed in an L-shape by a plating layer using a metal material such as Ni or Sn.

[0055] Such a surface mounted inductor is manufactured in the following manner. First, a conductive wire which is rectangular in cross section and provided with an insulation coating is spirally wound in two tiers in an outside-to-outside manner so that both of its ends are positioned at an outer periphery thereof thus forming a wound portion 11a. Thereafter, both the ends of the conductive wire are led out from the outer periphery of the wound portion thereby forming lead-out ends 11b, thus forming a coreless coil 11. The conductive wires used in the present embodiment include those having an imide-modified polyurethane layer as an insulating film. The insulating film may be a polyamide- or polyester-based insulating film, and those with a high heat-resistant temperature are preferred. In the present embodiment, although those which are rectangular in cross section are used, circular conductive wires or those which are polygonal in cross section may also be used.

[0056] Next, by using a sealing material obtained by using the magnetic material such as iron-based metal magnetic powder and the resin such as an epoxy resin and mixing and granulating them into powder, a formed body 12 in which the coreless coil 11 shown in FIG. 1 is embedded is formed by a compression molding method. At this time, the lead-out ends 11b of the coreless coil 11 are configured so that their surfaces are exposed at positions on side surfaces opposed in the length direction of the formed body 12, where external terminals are formed. Although the formed body is made by the compression molding method in the present embodiment, it may also be formed by a molding method such as a powder compacting method.

[0057] Subsequently, after removing the film on the surfaces of the lead-out ends 11b of the coreless coil 11 by mechanical peeling, as shown in FIG. 2, resin components and the like existing at portions 13 on the side surfaces opposed in the length direction of the formed body 12 and on a bottom surface thereof, where the external terminals are formed, are removed by using laser irradiation, blasting treatment, polishing and the like. Thereby, surfaces of the metal magnetic powder forming the formed body 12 and cut surfaces thereof are exposed.

[0058] Furthermore, the formed body 12 is plated with a conductive material, thereby forming a plating layer joined to the metal magnetic powder on the side surfaces opposed in the length direction of the formed body 12 and on the bottom surface thereof, so that the external terminals 14 are formed as shown in FIG. 3. Examples of the conductive materials used include those containing Ni or Sn, or those containing both. The external terminals 14 are connected to the lead-out ends 11b of the coreless coil 11, which are exposed on the surfaces of the formed body 12.

[0059] In the thus formed surface mounted inductor of the present disclosure, since the formed body is formed with the sealing material containing the resin and the metal magnetic powder, as shown in FIG. 4 (A), its surface is covered with a resin 12a, and metal magnetic powder 12b is mixed therein. Here, resin components and the like existing at a portion of the formed body where an external terminal is formed are removed by using laser irradiation, blasting treatment, polishing and the like. Thereby the metal magnetic powder 12b is exposed on the portion of the surface of the formed body where an external electrode is formed as shown in FIG. 4(B). The formed body is plated with the conductive material in this state, thereby forming a plating layer 14 on the portion of the formed body, where the external terminal is formed, as shown in FIG. 4 (C). This is attributed to the fact that, because the metal magnetic powder 12b has a metallic nature, by plating the formed body, an electric current is intensively applied to the portion of the surface of the formed body where the metal magnetic powder is exposed, thereby growing plating, with the result that the plating layer 14 is formed on the portion of the surface of the formed body where the metal magnetic powder is exposed. Although FIG. 4 (C) shows a case where this plating layer 14 is formed of double layers, it may also be formed of a single layer, or of triple layers or more.

[0060] Therefore, in the surface mounted inductor of the present disclosure, the plating layer joined to the metal magnetic powder is formed at the portions of the surfaces of the formed body where the resin has been removed, so that the external terminals connected to the lead-out ends of the coreless coil are formed on the formed body.

[0061] Although the above has described the embodiments of the surface mounted inductor and method for manufacturing the same of the present disclosure, the present disclosure is not limited to these embodiments. In examples, in the sealing material, the iron-based metal magnetic powder was used as the magnetic material, and the epoxy resin was used as the resin. As the magnetic material, metal magnetic powders having other compositions, metal magnetic powder whose surface is coated with an insulator such as glass, and surface-modified metal magnetic powder may also be used. As the resin, a thermoset resin such as a polyimide resin or a phenol resin, and a thermoplastic resin such as a polyethylene resin or a polyamide resin may also be used. Furthermore, the external terminals may also be formed by plating the formed body with a conductive material other than Ni or Sn, thereby forming a plating layer joined to the metal magnetic powder. Furthermore, the formed body may also be plated after applying a joint material composed of a conductive paste and the like containing a conductor such as Ag or Cu to the positions at which the lead-out ends of the coreless coil are exposed on the portions of the formed body, where the external terminals are formed, so as to cover the lead-out ends of the coreless coil. In this case, the bonding strength between the lead-out ends of the coil and the external terminals can be improved by this joint material.

[0062] Furthermore, although the embodiments have shown an example in which the coil is embedded in the formed body so that the surfaces of the lead-out ends of the coil are exposed on the surfaces of the formed body, they may also be configured so that the coil is embedded in the formed body so that the lead-out ends of the coil are led out from the formed body, that the film of the surfaces of the lead-out ends of the coil is removed, that the resin components and the like existing at the portions where the external terminals of the formed body are formed are removed, that the lead-out ends are processed so as to be positioned at the portions where the external terminals are formed, and that, in this state, the formed body is plated, thereby forming the external terminals. Moreover, in this case, the external terminals may also be formed in the following manner: The joint material composed of the conductive paste containing the conductor such as Ag or Cu or the like is applied so as to cover the lead-out ends of the coil, which are positioned at the portions where the external terminals are formed, and, in the state in which the lead-out ends of the coil are fixed to the formed body, the formed body is plated to form the external terminals.