JP2013120919A - Coil enclosed dust core and device having the same, manufacturing method of coil enclosed dust core, and manufacturing method of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coil enclosed dust core capable of joining between a terminal and a coil appropriately at a joint while reducing the manufacturing cost, and to provide a manufacturing method therefor.SOLUTION: The coil enclosed dust core has a dust core 3, a coil 2, and a terminal 4 for external connection being connected electrically with the coil. The coil 2 is formed by winding a copper wire, for example. The terminal 4 has a Cu base material, and an Ni or Ni alloy layer formed on the surface of the Cu base material. At a position of the surface electrode 42 of the terminal 4, an Au layer is further formed on the surface of the Ni or Ni alloy layer. At the joint 44 of the terminal and coil, surface of the Ni layer is exposed as the joint surface with the coil and joined to the coil.

Description

  The present invention relates to a terminal structure of a coil-embedded dust core used for inductors, transformers, and other electronic components.

  A coil-enclosed dust core applied to electronic components or the like has a structure in which a coil is enclosed inside a dust core. A terminal portion is provided as a separate member from the coil, and the coil and the terminal portion are joined. The terminal part is exposed to the outside from the dust core for external connection.

  For this reason, it must be the structure which joins between a coil and a terminal part appropriately. For example, resistance welding is performed between the terminal portion and the coil in the coil-encapsulated core. For this reason, a terminal part must be the structure which can be resistance-welded with a coil. In addition, as shown in Patent Document 1, when an Fe-based metallic glass alloy is used as the powder core material, heat treatment is required, so the terminal portion needs to have excellent heat resistance.

  For example, conventionally, an Ag plating layer is formed on the surface of the terminal portion. The surface of the Ag plating layer is a mounting surface that is electrically connected to the mounting substrate.

  By the way, in said structure, since the terminal part surface was an Ag plating layer, there existed a problem which raise | generates a migration easily. For this reason, there is a risk of short-circuiting between the electrode components mounted on the mounting substrate.

  Therefore, the migration problem described above can be solved by using an Au plating layer on the surface of the terminal portion as shown in, for example, Patent Documents 2 to 4 below instead of the Ag plating layer. However, in Patent Documents 2 to 4, the formation range of the Au plating layer is unknown, and nothing is described about the configuration of the joint portion between the coil and the terminal portion.

  Therefore, when the Au plating layer shown in Patent Documents 2 to 4 is used, if the Au plating layer having a high material cost is formed over a wide range, there is a problem that the manufacturing cost is increased accordingly. In addition, in the configuration in which the terminal part is provided as a separate member from the coil, the joining structure between the coil and the terminal part is optimized and can be joined easily, and the joint between the terminal part of the dust core and the mounting substrate is made possible. It was important to stabilize.

JP 2006-339525 A JP 2004-55572 A JP-A-2005-39187 Japanese Patent Laid-Open No. 11-3817

  The present invention is for solving the above-described conventional problems, and in particular, a coil-filled dust core capable of suppressing the manufacturing cost to a low level and appropriately joining the terminal portion and the coil at the joint portion, and a method for producing the same. Another object of the present invention is to provide a device having a coil-embedded dust core capable of appropriately and stably soldering a coil-embedded dust core and a mounting substrate, and a method for manufacturing the same.

The coil-embedded dust core in the present invention is
Having a dust core, a coil covered with the dust core, and a terminal portion for external connection electrically connected to the coil;
The coil has a configuration formed by winding a wire having a surface layer containing at least Cu as a main component,
The terminal portion has a Cu base and a Ni or Ni alloy layer formed on the surface of the Cu base,
At the position of the surface electrode part exposed to the outside from the dust core of the terminal part, an Au layer is formed on the surface of the Ni or Ni alloy layer,
In the joint portion between the terminal portion and the coil, the Ni or Ni alloy layer is exposed on the surface of the terminal portion to be a joint surface with the coil and is joined to the coil. It is.

Moreover, the manufacturing method of the coil inclusion powder core in this invention is
A dust core, a coil that is covered with the dust core and that is formed by winding a wire having a surface layer mainly composed of Cu, and a terminal portion for external connection that is electrically connected to the coil. Have
Forming a Ni or Ni alloy layer on the surface of the Cu base material constituting the terminal portion;
A step of forming an Au layer at the position of the surface electrode portion exposed to the outside from the dust core when the Ni or Ni alloy layer is formed and the dust core is formed;
In the joint part between the terminal part and the coil, the Ni or Ni alloy layer exposed on the surface of the terminal part is used as a joint surface with the coil, and the step of joining between the terminal part and the coil;
Molding the dust core, embedding the coil with the terminal portion connected in the dust core, and molding the dust core so that the surface electrode portion of the terminal portion is exposed to the outside The process of
It is characterized by having.

  In the present invention, the terminal portion has a laminated structure of a Cu base material and a Ni or Ni alloy layer, and the surface electrode portion has a laminated structure in which an Au layer is formed on the surface of the Ni or Ni alloy layer. Thus, the manufacturing cost can be reduced by limiting the formation range without forming the Au layer at the joint portion with the coil. In the present invention, the Ni or Ni alloy layer plays a role as a base of the Au layer and a bonding surface at the bonding portion. And in the junction part of a terminal part and a coil, it is set as the laminated structure of Cu base material / Ni or Ni alloy layer / wire (coil). As described above, the joint portion has a laminated structure in which Ni of different materials are sandwiched between Cu materials of the same kind of material, so that the joint strength between the terminal portion and the coil can be stabilized.

  Moreover, in this invention, it is preferable that the joining surface of the said coil in the said junction part is fuse | melted and solidified. Thereby, joining strength can be raised. In the present invention, the Ni or Ni alloy layer in the joint is preferably melted and solidified.

  Moreover, in this invention, it is preferable that the said terminal part and the said coil are resistance-welded in the said junction part. If Cu is the same material, it cannot be properly joined by resistance welding, but resistance welding can be performed properly by interposing different kinds of Ni or Ni alloy between Cu, and stable joint strength (welding strength) Can be obtained.

  Moreover, in this invention, it is preferable that the said powder core has an Fe group metal glass alloy. Thereby, soft magnetic characteristics can be improved. Moreover, although heat processing is required by using Fe-based metallic glass, the terminal structure of the present invention has excellent heat resistance.

  A device having a coil-embedded dust core and a method for manufacturing the same according to the present invention include the coil-embedded dust core described above and a mounting substrate, and is formed on the surface electrode portion of the terminal portion. The Au layer and the electrodes of the mounting board are solder-bonded to each other.

  ADVANTAGE OF THE INVENTION According to this invention, between the terminal part of a coil enclosure dust core and the electrode of a mounting board | substrate can be soldered appropriately and stably.

  According to the coil-embedded dust core and the manufacturing method thereof of the present invention, the manufacturing cost can be reduced and the terminal portion and the coil can be appropriately joined.

  In addition, according to the device having the coil-enclosed dust core and the manufacturing method thereof of the present invention, the terminal portion of the coil-enclosed dust core and the electrode of the mounting substrate can be soldered appropriately and stably.

FIG. 1 is a perspective view partially showing an embodiment of a coil-embedded dust core to which the present invention is applied, FIG. 2 is a partial front view showing a state where the coil-embedded dust core shown in FIG. 1 is mounted on a mounting substrate. 3 is a partially enlarged longitudinal sectional view of a portion surrounded by A in FIG. 4A is a partially enlarged longitudinal sectional view of a portion surrounded by B in FIG. 1, and FIG. 4B is a modification of FIG. 4A. 5 (a), 5 (b), and 5 (c) are process diagrams showing the method for manufacturing the coil-embedded dust core of the present embodiment (each figure shows a partial plan view during the manufacturing process). 6 (a), 6 (b), and 6 (c) are continuations of FIG. 5 and are process diagrams showing a method for manufacturing the coil-embedded dust core of the present embodiment (each figure is a partial plan view during the manufacturing process). Show). 7 (a) and 7 (b) are partial enlarged longitudinal sectional views showing a welding process between the coil and the terminal portion in the process of FIG. 6 (b).

  FIG. 1 is a perspective view showing a partially transparent embodiment of a coil-embedded dust core to which the present invention is applied, and FIG. 2 shows a state where the coil-embedded dust core shown in FIG. 1 is mounted on a mounting substrate. FIG. 3 is a partial front view of the portion surrounded by A in FIG. 2. The coil-enclosed dust core shown in FIG. 1 has the mounting surface facing upward, and the coil-enclosed dust core shown in FIGS. 2 and 3 is a state in which the coil-enclosed dust core shown in FIG. (Mounting surface is facing down).

  A coil-embedded dust core 1 shown in FIG. 1 includes a dust core 3, an air-core coil 2 covered with the dust core 3, and a terminal portion 4 electrically connected to the air-core coil 2. Is done.

  The air core coil 2 is formed by spirally winding a copper wire (wire material) coated with an insulating film. The wire may be a round wire or a flat wire. Further, a structure in which a surface layer mainly composed of Cu is formed around the core material instead of the copper wire may be employed. In any case, a wire whose surface is made of Cu or a Cu alloy is used.

  The air-core coil 2 includes a winding part 2a and lead-out end parts 2b and 2b drawn from the winding part 2a. The number of turns of the air-core coil 2 is appropriately set according to the required inductance.

  The powder core 3 is obtained by solidifying and molding the powder of an Fe-based metallic glass alloy (Fe-based amorphous alloy) in this embodiment with a binder.

Fe-based metallic glass alloy in the present embodiment (Fe-based amorphous alloy) is, for example, the composition formula is represented by _{Fe 100-abcxyzt Ni a Sn b} Cr c P x C y B z Si t, 0at% ≦ a ≦ 10 at%, 0 at% ≦ b ≦ 3 at%, 0 at% ≦ c ≦ 6 at%, 6.8 at% ≦ x ≦ 10.8 at%, 2.2 at% ≦ y ≦ 9.8 at%, 0 at% ≦ z ≦ It is 4.2 at%, 0 at% ≦ t ≦ 3.9 at%.

  As described above, the Fe-based metallic glass alloy of the present embodiment includes Fe as a main component and addition of Ni, Sn, Cr, P, C, B, and Si (however, Ni, Sn, Cr, B, and Si are added). Is a soft magnetic alloy obtained by adding

  The Fe-based metallic glass alloy has excellent soft magnetic properties, and by using the Fe-based metallic glass alloy, it can be made into a coil-enclosed dust core having high DC inductance and high inductance. Further, the glass transition temperature (Tg) of the Fe-based metallic glass alloy can be set to about 740 K (Kelvin) or less.

Fe-based metallic glass alloy of the present embodiment, the composition formula is represented by _{Fe 100-cxyzt Cr c P x} C y B z Si t, 1at% ≦ c ≦ 2at%, 8.8at% ≦ x ≦ 10. It is more preferable that 8 at%, 5.8 at% ≦ y ≦ 8.8 at%, 1 at% ≦ z ≦ 2 at%, and 0 at% <t ≦ 1 at%.

Thereby, the glass transition temperature (Tg) can be made 720K or less, the conversion vitrification temperature (Tg / Tm) can be made 0.57 or more, the saturation magnetization Is can be made 1.25 or more, and the saturation mass magnetization σs can be 175 ×. 10 ⁻⁶ Wbm / kg or more.

The Fe-based metallic glass alloy of the present embodiment, the composition formula is represented by _{Fe 100-acxyzt Ni a Cr c} P x C y B z Si t, 4at% ≦ a ≦ 6at%, 1at% ≦ c ≦ 2at %, 8.8 at% ≦ x ≦ 10.8 at%, 5.8 at% ≦ y ≦ 8.8 at%, 1 at% ≦ z ≦ 2 at%, and 0 at% <t ≦ 1 at% are more preferable.

Thereby, the glass transition temperature (Tg) can be made 705 K or less, the conversion vitrification temperature (Tg / Tm) can be made 0.56 or more, the saturation magnetization Is can be made 1.25 or more, and the saturation mass magnetization σs can be set to 170 ×. 10 ⁻⁶ Wbm / kg or more.

The Fe-based metallic glass alloy of the present embodiment, the composition formula is represented by _{Fe 100-acxyz Ni a Cr c} P x C y B z, 4at% ≦ a ≦ 6at%, 1at% ≦ c ≦ 2at%, It is more preferable that 8.8 at% ≦ x ≦ 10.8 at%, 5.8 at% ≦ y ≦ 8.8 at%, and 1 at% ≦ z ≦ 2 at%.

Thereby, the glass transition temperature (Tg) can be made 705 K or less, the conversion vitrification temperature (Tg / Tm) can be made 0.56 or more, the saturation magnetization Is can be made 1.25 or more, and the saturation mass magnetization σs can be set to 170 ×. 10 ⁻⁶ Wbm / kg or more.

  In the present embodiment, the Fe-based metallic glass alloy having the above composition formula can be manufactured, for example, in a powder form by an atomizing method or in a strip shape (ribbon shape) by a liquid quenching method.

  The Fe-based metallic glass alloy powder has a substantially spherical shape or an ellipsoidal shape. A large number of the Fe-based metal glass alloy powders exist in the core, and the Fe-based metal glass alloy powders are insulated from each other by a binder (binder resin).

Examples of the binder include epoxy resins, silicone resins, silicone rubbers, phenol resins, urea resins, melamine resins, PVA (polyvinyl alcohol), acrylic resins, and other liquid or powder resins, rubbers, water glass ( Na ₂ O—SiO ₂ ), oxide glass powder (Na ₂ O—B ₂ O ₃ —SiO ₂ , PbO—B ₂ O ₃ —SiO ₂ , PbO—BaO—SiO ₂ , Na ₂ O—B ₂ O ₃ —ZnO, CaO—BaO—SiO ₂ , Al ₂ O ₃ —B ₂ O ₃ —SiO ₂ , B ₂ O ₃ —SiO ₂ ), glassy substances (SiO ₂ , Al ₂ O ₃ , ZrO produced by the sol-gel method) ₂ and TiO ₂ as main components).

  Further, zinc stearate, aluminum stearate or the like may be added as a lubricant. The mixing ratio of the binder is 5% by mass or less, and the addition amount of the lubricant is about 0.1% by mass to 1% by mass.

  In addition, the compacting core 3 of this embodiment is not limited to the structure which has the above-mentioned Fe group metal glass alloy.

  As shown in FIG. 1, a housing recess 30 for housing a part of the terminal portion 4 is formed on the mounting surface 3 a for the mounting substrate. The storage recess 30 is formed to be exposed on the side surfaces 3b and 3c of the dust core 3 facing each other on both sides of the mounting surface 3a. As shown in FIG. 1, the terminal portion 4 is bent, and a part of the terminal portion 4 is stored in the storage recess 30.

  The terminal portion 4 is formed by bending a thin plate-like hoop material as shown in a manufacturing method described later. The terminal portion 4 is embedded in the dust core 3 and electrically connected to the extended ends 2b, 2b of the air-core coil 2, and a surface electrode exposed on the outer surface of the dust core 3. Part 42. The surface electrode portion 42 is formed by bending from the side surfaces 3b, 3c of the powder core 3 to the mounting surface 3a, and includes a first bent portion 42a and a second bent portion 42b.

  As shown in FIG. 2, the coil-embedded dust core 1 of this embodiment shown in FIG. 1 is mounted on a mounting substrate 10.

  An electrode 11 is provided on the surface of the mounting substrate 10. The electrode 11 is connected to the wiring portion that is integral with or separate from the electrode 11.

  As shown in FIG. 2, the coil-embedded dust core 1 has a mounting surface 3 a directed toward the mounting substrate 10, and the surface electrode portion 42 of the terminal portion 4 exposed to the outside of the coil-embedded dust core 1 and the mounting substrate 10. The electrodes 11 are joined by the solder layer 12.

  As shown in FIG. 2, a fillet-like solder layer 12 can be formed between the surface electrode portion 42 of the terminal portion 4 and the electrode 11 of the mounting substrate 10.

  As shown in FIG. 3, the surface electrode portion 42 of the terminal portion 4 of this embodiment includes a Cu base 15, a Ni or Ni alloy layer 16 formed on the surface of the Cu base 15, and a Ni or Ni alloy layer. 16 is formed in a laminated structure with an Au layer 17 formed on the surface of 16. As shown in FIG. 3, the Au layer 17 is located on the outermost surface of the surface electrode portion 42. Therefore, the surface of the Au layer 17 is a solder joint surface between the electrodes 11 of the mounting substrate 10.

  The thickness of the Cu base material 15 is about 200 μm. The material of the Cu base 15 is not particularly limited, but oxygen-free copper is preferably applied in order to avoid a reduction in coil efficiency due to copper loss.

  The thickness of the Ni or Ni alloy layer 16 is preferably about 1 to 5 μm. The Ni or Ni alloy layer 16 is for appropriately depositing when Au is plated, and for suppressing the diffusion from the Cu base material 15 as much as possible. An alloy or a Ni-Ag alloy is preferable.

The Au layer 17 is formed on the surface of the Ni or Ni alloy layer 16 with a thickness smaller than that of the Ni or Ni alloy layer 16. For example, the thickness of the Au layer 17 is about 0.02 μm to 0.07 μm.
Both the Ni or Ni alloy layer 16 and the Au layer 17 can be formed by plating.

  FIG. 4A shows a portion B shown in FIG. 1 cut from the height direction along the X1-X2 direction shown in FIG. 1 in a state where the coil-embedded dust core 1 of FIG. It is a partial longitudinal cross-sectional view.

  As shown in FIG. 4A, the connection end portion 40 of the terminal portion 4 with the coil 2 is constituted by a laminated structure of the Cu base material 15 and the Ni or Ni alloy layer 16, and the Ni or Ni alloy layer 16 is joined. The surface. And the connection end part 40 of the terminal part 4 and the extension end part 2b of the coil 2 are joined. That is, the joint portion 44 has a laminated structure of Cu base material 15 / Ni or Ni alloy layer 16 / copper wire 43. In this embodiment, the terminal part 4 and the coil 2 can be joined by resistance welding (spot welding).

  FIG. 4B shows a configuration in which Ni or Ni alloy layers 16 and 18 are formed on both surfaces of the Cu base material 15 in the thickness direction. Thereby, corrosion of Cu base material 15 of terminal part 4 exposed to the exterior of dust core 3 can be prevented. However, it is better not to form the Ni or Ni alloy base material 18 on the back surface 15b side of the Cu base material 15 at the position of the joint portion 44, as will be described in the manufacturing method described later.

  As described above, in this embodiment, the Au layer 17 is limited to the surface electrode portion 42. The Au layer 17 is necessary to ensure solder wettability and does not require a very thick film thickness. Since Au is rich in ductility, the Au layer 17 can be formed very thin. In the present embodiment, the Au layer 17 is preferably formed thinner than the Ni or Ni alloy layer 16. Thus, the use of Au can be reduced, and the manufacturing cost can be reduced.

  Further, in the present embodiment, the Ni or Ni alloy layer 16 is formed on the surface of the Cu base 15 of the terminal portion 4, and this Ni or Ni alloy layer 16 is used as the base of the Au layer 17 in the surface electrode portion 42. The joint portion 44 between the portion 4 and the coil 2 is exposed on the surface of the terminal portion 4 to serve as a joint surface with the coil 2. Thereby, in the joining part 44, it becomes a laminated structure with Cu base material 15 / Ni or Ni alloy layer 16 / copper wire 42 (coil 2). In the present embodiment, the Ni or Ni alloy layer 16 can be formed on the entire surface of the Cu base material 15, and the Ni or Ni alloy layer 16 at the joint 44 and the Ni or Ni alloy layer 16 at the surface electrode portion 42 are formed. Can be formed continuously. There may be a region where the Ni or Ni alloy layer 16 is not formed between the Ni or Ni alloy layer 16 at the joint portion 44 and the Ni or Ni alloy layer 16 at the surface electrode portion 42, but the Cu substrate 15 If the Ni or Ni alloy layer 16 is formed over the entire surface, the manufacturing can be facilitated and the manufacturing cost can be reduced.

  As described above, in the present embodiment, the Ni or Ni alloy layer 16 is used as a bonding surface with the air-core coil 2, and a laminated structure in which a different material Ni or Ni alloy is sandwiched between Cu materials of the same kind at the bonding portion 44. As a result, the bonding strength between the terminal portion 4 and the coil 2 can be stabilized.

  In this embodiment, it is preferable that the joining surface of the coil 2 (extension end part 2) in the joining part 44 is melted and solidified. That is, when the vicinity of the surface of the copper wire 43 in contact with the Ni or Ni alloy layer 16 shown in FIGS. 4A and 4B is melted and solidified, the bonding strength between the coil 2 and the terminal portion 4 can be increased. . At this time, it is preferable that the Ni or Ni alloy layer 16 in the joint 44 is in a melted and solidified state in order to increase the joint strength.

  In particular, in this embodiment, it is preferable that resistance welding be performed between the air-core coil 2 and the terminal portion 4. In resistance welding, as shown in FIGS. 4A and 4B, a current is passed while the Cu base material 15 and the copper wire 43 of the air-core coil 2 are pressure-bonded via the Ni or Ni alloy layer 16, and the resistance is reduced. The base materials are joined by heat (Joule heat). If there is no Ni or Ni alloy layer 16 and resistance welding between the Cu base material 15 and the copper wire 43, resistance welding between the same kind of materials results, and therefore the Cu base material 15 and the copper wire 43 cannot be joined appropriately. On the other hand, in this embodiment, it is possible to join Cu appropriately by resistance welding by using the Ni or Ni alloy layer 16 having a higher electric resistance than Cu as the welding surface.

  As described above, in the present embodiment, the coil 2 and the terminal portion 4 can be appropriately joined while suppressing the manufacturing cost. Further, no migration occurs when an Ag layer is used as the surface layer of the terminal portion 4.

  In the present embodiment, the dust core 3 can be formed using an Fe-based metallic glass alloy. Thereby, a soft magnetic characteristic can be improved and it can be set as the coil enclosure dust core which has the outstanding DC superposition characteristic with a high inductance.

  By using an Fe-based metallic glass alloy, heat treatment necessary for amorphization is performed. In the present embodiment, the glass transition temperature (Tg) of the Fe-based metallic glass alloy can be lowered, and therefore the optimum heat treatment temperature for the dust core 3 can be lowered. Here, the “optimum heat treatment temperature” is a heat treatment temperature that can effectively relieve stress strain and reduce core loss to a minimum with respect to the Fe-based metallic glass alloy.

  In the terminal portion 4 of this embodiment, the Ni or Ni alloy layer 16 is formed on the surface of the Cu base material 15, and in the surface electrode portion 42, the Au layer 17 is formed on the surface of the Ni or Ni alloy layer 16. It has a laminated structure. Thereby, even if it heat-processes, it can suppress that a quality change arises and can improve heat resistance.

  FIG. 5 is a process diagram showing a method for manufacturing the coil-embedded dust core 1 of the present embodiment. Each step is shown in a partial plan view.

  5A, a thin plate-like hoop material 20 (corresponding to the Cu base material 15) in which a plurality of punched terminal portions 4 are continuous is formed.

  Next, in the step of FIG. 5B, the Ni or Ni alloy layer 16 is formed by plating over the entire surface 20 a of the hoop material 20. In FIG. 5B, the Ni or Ni alloy layer 16 is indicated by oblique lines. At this time, the Ni or Ni alloy layer 16 is formed with a film thickness of about 1 μm to 5 μm. The Ni or Ni alloy layer 16 is formed for resistance welding with the air-core coil 2 at the connection end portion 40 and as a base layer for the Au layer 17 at the surface electrode portion 42. 5B, the Ni or Ni alloy layer 16 can be formed by plating not only on the front surface 20a of the hoop material 20 but also on the back surface.

  Next, in the step of FIG. 5C, an Au layer 17 is partially formed on the surface of the Ni or Ni alloy layer 16 by plating. In FIG. 5C, the formation region of the Au layer 17 is indicated by oblique lines from different two directions. In this embodiment, the Au layer 17 is formed at the position of the surface electrode portion 42. The Au layer 17 is formed with a very thin film thickness of about 0.02 μm to 0.07 μm. The Au layer 17 is formed in the surface electrode portion 42 to ensure solder wettability. Therefore, the Au layer 17 can be formed very thin only at the position of the surface electrode portion 42.

  Subsequently, in the step of FIG. 6A, a predetermined portion of the hoop material 20 is cut. Thereby, the connection end part 40 with the air-core coil 2 can be formed in the terminal part 4. The Ni or Ni alloy layer 16 is exposed on the surface of the connection end 40. In FIG. 6A, only one terminal portion 4 is shown enlarged.

  Next, in the process of FIG. 6B, resistance welding is performed on the extended end 2 b of the air-core coil 2 and the connection end 40 of the terminal portion 4. In the connection end portion 40, the exposed Ni or Ni alloy layer 16 is a bonding surface (welding surface) with the air-core coil 2.

  FIG. 7 is a partially enlarged longitudinal sectional view of the extended end 2b of the air-core coil 2 and the connecting end 40 of the terminal portion 4 during the welding process.

  7A, between the Ni or Ni alloy layer 16 at the connection end portion 40 of the terminal portion 4 and the extended end portion 2b of the air core coil 2, the terminal portion 4 and the air core coil 2 are connected. Pressure welding is performed by resistance welding electrodes 25 and 26 arranged on both sides. As shown in FIG. 7A, the Ni or Ni alloy layer 16 is interposed between the Cu base 15 and the copper wire 43. In the state shown in FIG. 7A, a voltage is applied between the resistance welding electrodes 25 and 26 to pass a current. At this time, Ni or Ni alloy having high resistance preferentially generates Joule heat, and Ni or Ni alloy, Cu or Ni or Ni alloy and Cu are melted to appropriately connect between the same kind of Cu base material 15 and the copper wire 43. Can be joined. The surface of the copper wire 43 constituting the coil 2 located at the bonding interface, the Ni or Ni alloy layer 16, or the surface of the Ni or Ni alloy layer 16 and the copper wire 43 is melted and solidified, thereby bonding at the bonding interface. Strength (welding strength) can be stably increased.

  In FIG. 7A, Ni or Ni alloy layers 16 and 18 are formed on both surfaces of the Cu base material 15, and the Ni or Ni alloy layer 18 also generates Joule heat during resistance welding. For this reason, the material of the resistance welding electrode 26 is devised or the welding conditions are optimized so that the connection between the resistance welding electrode 26 and the connection end 40 of the terminal portion 4 does not stick.

  Alternatively, as shown in FIG. 7B, resistance welding is performed by forming the Ni or Ni alloy layer 16 only on the front surface side of the Cu base material 15 and not providing the Ni or Ni alloy layer 18 on the back surface 15b. It is possible to prevent the electrode 26 and the connection end portion 40 of the terminal portion 4 from sticking to each other. Further, the Ni or Ni alloy layer 18 may be formed except for the region where the resistance welding electrode 26 abuts on the back surface 15 b of the Cu base material 15.

  Next, in FIG.6 (c), the powder core 3 is press-molded, the air-core coil 2 is embed | buried in the powder core 3, and also the unnecessary part of Cu base material is cut | disconnected.

When the dust core 3 is configured to include a powder of Fe-based metallic glass alloy (Fe-based amorphous alloy) and a binder, it is necessary for the powder core 3 to be amorphous. Apply heat treatment.
Then, the surface electrode portion 42 shown in FIG. 6C is bent as shown in FIG.

  In the present embodiment, the amount of Au used can be reduced as much as possible, the manufacturing cost can be reduced, and the extended end portion 2b of the air-core coil 2 and the surface electrode portion 42 of the terminal portion 4 are appropriately joined (welded). be able to.

  Thereafter, as shown in FIGS. 2 and 3, the surface electrode portion 42 and the electrode 11 of the mounting substrate 10 are solder-bonded by a reflow process. The heating temperature at the time of Pb-free solder bonding is about 245 to 260 ° C.

In the present embodiment, the above composition formula, by using a _{Fe 100-abcxyzt Ni a Sn b} Cr c P x C y B Fe based metallic glass alloy represented by _z Si _t (Fe-based amorphous alloy) The heat treatment temperature for the dust core 3 can be set to about 350 ° C to 400 ° C.

  The surface electrode portion 42 of the terminal portion 4 of the present embodiment has a laminated structure in which the Au layer 17 is formed on the surface of the Cu base material 15 via the Ni or Ni alloy layer 16. Thereby, even if heat treatment at about 350 ° C. to 400 ° C. is performed, the Au layer 17 is not altered and excellent heat resistance can be obtained.

  Therefore, as shown in FIGS. 2 and 3, when the coil-embedded dust core 1 is solder-bonded to the mounting substrate 10, the surface electrode portion 42 with the Au layer 17 exposed on the outermost surface has good solder wettability. The fillet-like solder layer 12 can be appropriately formed between the terminal portion 2 and the electrode 11 of the mounting substrate 10, and appropriate and stable solder bonding can be performed.

  A coil having an inductance of 1.5 μH (copper wire (flat wire): 0, 21 mm × 0.87 mm and a terminal portion were resistance-welded.

  The terminal part was formed of a Cu base / Ni layer (1 μm, 2 μm, 3 μm). The numerical value in the parenthesis indicates the film thickness.

  Then, resistance welding was performed between the terminal portion and the coil using the Ni layer as the welding surface. The voltage at that time was 1.10 V to 1.6 V / 3 ms, and the air pressure was 0.4 MPa.

  In the experiment, as an example, ten terminals each having a Ni layer thickness of 1 μm and a coil were resistance-welded, and the DC resistance Rdc was measured. The DC resistance Rdc was measured using a probe having a clip type connection terminal. The same applies to Table 2 below. An experiment was conducted as a comparative example in which an Ag layer having a thickness of 5 μm was formed on the surface of the Ni layer (1 μm), and the Ag layer was used as a welding surface. The experimental results are shown in Table 1 below.

As shown in Table 1, the DC resistances Rdc of the example and the comparative example were almost the same.
Next, the direct current resistance Rdc and tensile strength of a plurality of examples in which the thickness of the Ni layer was set to 2 μm and 3 μm, and the resistance was welded between the terminal portion and the coil using the Ni layer as a welding surface were measured. Tensile strength was measured with a universal testing machine. The experimental results are shown in Table 2 below.

  As shown in Table 2, it was found that the direct current resistance Rdc could be 8.2 mΩ or more and 10.0 mΩ or less, and the tensile strength could be 5 N or more.

  It seems that the heat generation amount is increased and copper is also melted by increasing the thickness of the Ni layer. The direct current resistance Rdc tended to increase slightly as the Ni layer was thickened, but the welding strength was stable. This is considered due to the fact that copper (coil side) melted and solidified.

DESCRIPTION OF SYMBOLS 1 Coil enclosed powder core 2 Air core coil 2b Lead end 3 Powder core 4 Terminal part 10 Mounting substrate 11 Electrode 12 Solder layer 15 Cu substrate 16 Ni or Ni alloy layer 17 Au layer 20 Hoop material 25, 26 Resistance welding electrode 40 connection end 42 surface electrode 43 copper wire 44 joint

Claims (12)

Having a dust core, a coil covered with the dust core, and a terminal portion for external connection electrically connected to the coil;
The coil has a configuration formed by winding a wire having a surface layer containing at least Cu as a main component,
The terminal portion has a Cu base and a Ni or Ni alloy layer formed on the surface of the Cu base,
At the position of the surface electrode part exposed to the outside from the dust core of the terminal part, an Au layer is formed on the surface of the Ni or Ni alloy layer,
In the joint portion between the terminal portion and the coil, the Ni or Ni alloy layer is exposed on the surface of the terminal portion to be a joint surface with the coil and is joined to the coil. Encapsulated powder core.   The coil-embedded dust core according to claim 1, wherein a bonding surface of the coil in the bonding portion is melted and solidified.   The coil-embedded dust core according to claim 1 or 2, wherein the Ni or Ni alloy layer in the joint is melted and solidified.   The coil-embedded dust core according to any one of claims 1 to 3, wherein the terminal portion and the coil are resistance-welded at the joint portion.   The coil-embedded dust core according to any one of claims 1 to 4, wherein the dust core is configured to include an Fe-based metallic glass alloy.   A coil-embedded dust core according to any one of claims 1 to 5 and a mounting substrate, wherein the Au layer formed on the surface electrode portion of the terminal portion and an electrode of the mounting substrate A device having a coil-embedded dust core, characterized in that is solder-bonded. A dust core, a coil that is covered with the dust core and that is formed by winding a wire having a surface layer mainly composed of Cu, and a terminal portion for external connection that is electrically connected to the coil. Have
Forming a Ni or Ni alloy layer on the surface of the Cu base material constituting the terminal portion;
A step of forming an Au layer at the position of the surface electrode portion exposed to the outside from the dust core when the Ni or Ni alloy layer is formed and the dust core is formed;
In the joint part between the terminal part and the coil, the Ni or Ni alloy layer exposed on the surface of the terminal part is used as a joint surface with the coil, and the step of joining between the terminal part and the coil;
Molding the dust core, embedding the coil with the terminal portion connected in the dust core, and molding the dust core so that the surface electrode portion of the terminal portion is exposed to the outside The process of
A method for producing a coil-embedded dust core, comprising:   The method for producing a coil-embedded dust core according to claim 7, wherein a joining surface of the coil in the joining portion is melted and solidified.   The method for producing a coil-embedded dust core according to claim 7 or 8, wherein the Ni or Ni alloy layer in the joint is melted and solidified.   10. The method for manufacturing a coil-embedded dust core according to claim 7, wherein resistance welding is performed between the terminal portion and the coil at the joint portion.   The method for producing a coil-embedded dust core according to any one of claims 7 to 10, wherein the dust core is formed by including an Fe-based metallic glass alloy and has a heat treatment step on the dust core. .   It has between the coil enclosure dust core described in any one of Claims 7 thru / or 11, and a mounting board, and between the Au layer formed in the surface electrode part of the terminal part, and the electrode of the mounting board A method for manufacturing a device having a coil-embedded dust core, wherein the device is soldered.

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