JP2014168041A - Magnetic core and inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic core and an inductor which are suitable for various modules including a power source module or the like.SOLUTION: A magnetic core 310X comprises a binder component 314X, and soft magnetic metal powder pieces 312 having flat shapes which are bonded together by the binder component, and has elasticity. The magnetic core includes 60 vol.% or more of the soft magnetic metal powder pieces and 10-25 vol.% of pores 318X. The binder component includes a silicon oxide as a primary component.

Description

  The present invention relates to a module including a circuit board and an inductor. The module is, for example, a power supply module that is mounted on an electronic device and supplies power. Furthermore, this invention relates to the magnetic core and inductor suitable for a module.

  With the miniaturization of circuit boards, heat per volume generated from electronic components such as switching transistors and power supply control ICs (Integrated Circuits) mounted on the circuit boards is increasing. In general, an inductor generates a large amount of heat. For this reason, a module including a circuit board and an inductor needs to have a structure for effectively radiating heat to the outside. A module having such a structure is disclosed in Patent Document 1, for example.

  The module of Patent Document 1 includes an active component layer (circuit board) and a passive component layer. The passive layer includes an LTCC inductor made of LTCC (Low Temperature Co-fired Ceramics). The circuit board is laminated on the LTCC inductor via a heat spreader. Since the module is configured as described above, the heat generated by the LTCC inductor or the circuit board can be dispersed by the heat spreader.

  Patent Document 2 discloses a magnetic core formed by alternately stacking sintered soft magnetic alloy layers and insulating layers.

US Patent Application Publication No. 2007/0230221 JP 2002-289419 A

  However, the module of Patent Document 1 needs to include a heat spreader in order to cool the LTCC inductor and the circuit board. In addition, it is necessary to provide a heat sink in order to dissipate heat generated by the LTCC inductor and the circuit board more effectively. In other words, it is necessary to incorporate a heat radiating member such as a heat spreader or a heat sink into the module. This complicates the module structure and increases the size of the module. Further, since ceramics such as LTCC are brittle materials, they are easily damaged when brought into close contact with other members (for example, members for heat dissipation). Furthermore, as described in Patent Document 1, the thermal conductivity of the LTCC inductor is low. For this reason, even if the module includes a member for heat dissipation, it is difficult to sufficiently dissipate heat.

  Further, not limited to LTCC inductors, in general, although the inductor is the main heat generation source in the module, the thermal conductivity of the conventional inductor is low. For this reason, it is difficult to effectively dissipate the heat generated by the inductor.

  In order to produce an inductor using the magnetic core disclosed in Patent Document 2, it is necessary to provide different through holes in the sintered soft magnetic alloy layer and the insulating layer. Furthermore, it is necessary to laminate the sintered soft magnetic alloy layer and the insulating layer so that the through holes overlap appropriately. That is, it takes a lot of work, and it is not easy to produce an inductor having a shape and size suitable for the module.

  Accordingly, an object of the present invention is to provide a module having a simple structure capable of effectively radiating heat generated by an inductor, and a magnetic core and an inductor suitable for the module.

According to the present invention, as the first module,
A module comprising a circuit board and an inductor,
The circuit board has an opposite surface and an opposite surface located on opposite sides in the vertical direction,
The inductor includes a magnetic core and a coil, the magnetic core is formed using a soft magnetic metal material, and the magnetic cores are opposed surfaces positioned on opposite sides in the vertical direction. And the opposing surface of the magnetic core is disposed so as to oppose the opposing surface of the circuit board in the vertical direction, and the heat dissipation surface of the magnetic core is It is arranged outside the module so that heat can be dissipated, the coil has a coil part and a connection end, the coil part winds at least a part of the magnetic core, and the connection end is A module connected to the facing surface of the circuit board is obtained.

According to the present invention, the second module is a first module,
A module in which the heat dissipation surface of the magnetic core is at least partially exposed to the outside of the module is obtained.

Further, according to the present invention, the third module is the first or second module,
A module in which the heat dissipation surface of the magnetic core is at least partially in contact with a cooling member outside the module is obtained.

According to the present invention, as the fourth module, any one of the first to third modules,
The magnetic core is formed to be elastically deformable, and the magnetic core is formed with a through hole,
The coil portion of the coil penetrates the through hole so as to elastically deform the inner wall of the through hole, and the inductor is held by a pressing force applied to the coil portion by the inner wall of the through hole. Module is obtained.

According to the present invention, the fifth module is any one of the first to fourth modules,
A heat dissipating member;
As the heat dissipation member, a module attached to the heat dissipation surface of the magnetic core is obtained.

Further, according to the present invention, the sixth module is a fifth module,
It further includes a connecting member made of a heat conductor,
The connecting member is a module that connects the heat radiating member and the circuit board via the magnetic core.

According to the present invention, the seventh module is a fifth or sixth module,
A module in which the heat dissipating member is at least partially in contact with a cooling member outside the module is obtained.

According to the present invention, the eighth module is any one of the first to seventh modules,
A module having electronic components mounted on the facing surface of the circuit board is obtained.

According to the present invention, the ninth module is any one of the first to seventh modules,
A module in which electronic components are not mounted on the facing surface of the circuit board is obtained.

According to the present invention, the tenth module is any one of the first to ninth modules,
The module is a power module that supplies power to the outside of the module.

According to the invention, the eleventh module is any one of the first to tenth modules,
The soft magnetic metal material is a soft magnetic metal powder having a flat shape,
A module in which the magnetic core is formed by binding the soft magnetic metal powder with an insulating material is obtained.

According to the present invention, the twelfth module is an eleventh module,
A module in which the soft magnetic metal powder is contained in the magnetic core by 55% by volume or more is obtained.

According to the present invention, the thirteenth module is an eleventh module,
A module in which the soft magnetic metal powder is contained in the magnetic core by 60% by volume or more is obtained.

According to the present invention, the fourteenth module is an eleventh module,
A module containing 70% by volume or more of the soft magnetic metal powder in the magnetic core is obtained.

According to the invention, the fifteenth module is any one of the eleventh to fourteenth modules,
As the magnetic core, a module having an electrical resistivity of 10 KΩ · cm or more is obtained.

Further, according to the present invention, as the first magnetic core,
A magnetic core in which a soft magnetic metal powder having a flat shape is bound by a binder component, and a magnetic core having elasticity,
60% by volume or more of the soft magnetic metal powder and 10% by volume or more and 25% by volume or less of pores,
As the binder component, a magnetic core mainly composed of silicon oxide is obtained.

According to the present invention, the second magnetic core is a first magnetic core,
A magnetic core having a rubber hardness of 92 or more and 96 or less according to ISO7619-type D is obtained.

Further, according to the present invention, the third magnetic core is the first or second magnetic core,
A magnetic core having a Young's modulus of 10 GPa or more and 90 Gpa or less is obtained.

According to the present invention, the fourth magnetic core is a third magnetic core,
A magnetic core having a Young's modulus of 20 GPa or more and 50 GPa or less is obtained.

According to the present invention, the fifth magnetic core is any one of the first to fourth magnetic cores,
A magnetic core having an electrical resistivity of 10 KΩ · cm or more is obtained.

According to the present invention, the sixth magnetic core is any one of the first to fifth magnetic cores,
A magnetic core having a real component of relative permeability at a frequency of 1 MHz is 100 or more.

According to the present invention, the seventh magnetic core is any one of the first to sixth magnetic cores,
The soft magnetic metal powder provides a magnetic core made of an Fe-based alloy.

According to the present invention, the eighth magnetic core is any one of the first to sixth magnetic cores,
The soft magnetic metal powder provides a magnetic core made of an Fe-Si alloy.

According to the present invention, the ninth magnetic core is any one of the first to sixth magnetic cores,
The soft magnetic metal powder provides a magnetic core made of an Fe—Si—Al alloy or an Fe—Si—Cr alloy.

According to the present invention, the tenth magnetic core is any one of the first to ninth magnetic cores,
It has a flat plate shape
A magnetic core having a flat plate thickness of 1 mm or less is obtained.

According to the present invention, as the eleventh magnetic core,
A magnetic core comprising a plurality of tenth magnetic cores as magnetic core components,
A magnetic core in which a plurality of the magnetic core components are stacked with an adhesive is obtained.

According to the invention, the twelfth magnetic core is any one of the first to eleventh magnetic cores,
At least part of the surface is covered with insulating resin,
A magnetic core in which a part of the insulating resin is impregnated in the surface layer of the magnetic core is obtained.

According to the invention, the thirteenth magnetic core is any one of the first to twelfth magnetic cores,
A magnetic core having a saturation magnetic flux density of 0.5 T or more is obtained.

According to the present invention, as the first inductor,
An inductor comprising any one of the first to thirteenth magnetic cores and a coil,
The coil is an inductor having a coil portion and a connection end.

According to the present invention, the second inductor is a first inductor,
A through hole is formed in the magnetic core,
The coil part of the coil has a penetration part,
In the through portion, an inductor penetrating the through hole is obtained.

Further, according to the present invention, the third inductor is a second inductor,
A plurality of the through holes are formed in the magnetic core,
The coil portion of the coil has a plurality of the through portions and a connecting conductor,
The connecting conductor is attached to the magnetic core so as to connect the end of the penetrating portion on the upper surface or the lower surface of the magnetic core,
The thickness of the magnetic core after the connection conductor is attached to the magnetic core is 2.5% or more and 5.0 compared to the thickness of the magnetic core before the connection conductor is attached to the magnetic core. % Or less,
When the coil portion is removed from the magnetic core, an inductor is obtained in which the thickness of the magnetic core recovers to approach the thickness before the connection conductor is attached to the magnetic core.

According to the present invention, the fourth inductor is a second or third inductor,
The through portion of the coil penetrates the through hole so as to elastically deform the inner wall of the through hole, and the coil is held by a pressing force applied to the through portion by the inner wall of the through hole. Is obtained.

Further, according to the present invention, the fifth inductor is any one of the first to fourth inductors,
As the coil, an inductor having no insulation coating is obtained.

  The magnetic core of the inductor of the module according to the present invention is formed using a soft magnetic metal material. For this reason, the thermal conductivity of the magnetic core can be improved by increasing the filling rate of the soft magnetic metal material. By disposing one surface of the magnetic core having high thermal conductivity on the outside of the module so that heat can be dissipated, heat generated from the inductor can be effectively dissipated. Furthermore, since the magnetic core according to the present invention has elasticity, it is easy to process, and a magnetic core and an inductor having a shape and size suitable for the module can be manufactured relatively easily.

1 is a perspective view schematically showing a module according to a first embodiment of the present invention. It is a perspective view which shows the circuit board of the module of FIG. It is a side view which shows the module of FIG. Here, the electronic components mounted on the circuit board are not drawn. It is sectional drawing which shows the module of FIG. 1 along the IV-IV line. Here, the electronic components mounted on the circuit board are not drawn. It is a perspective view which shows the inductor of the module of FIG. Here, the hidden portion of the inductor coil is drawn with a broken line. Further, the material of the magnetic core is schematically shown in an ellipse drawn with a one-dot chain line. It is a perspective view which shows the magnetic core of the inductor of FIG. Here, a hidden portion of the through hole of the magnetic core is drawn with a broken line. It is a perspective view which shows the coil of the inductor of FIG. Here, the boundary line (imaginary line) between the penetration part and connection part of a coil is drawn with the dashed-dotted line. FIG. 8A is a partially enlarged perspective view showing the through hole of the magnetic core and the through part of the coil of FIG. 5 in a state before the through part is inserted into the through hole. FIG. 8B is a side sectional view showing a partially enlarged view of the through hole of the magnetic core and the through part of the coil in FIG. FIG. 9A is a plan sectional view showing a partially enlarged view of the through hole of the magnetic core and the through part of the coil in FIG. FIG. 9B is a cross-sectional plan view illustrating a modified example of the through hole and the through portion of FIG. FIG. 9C is a cross-sectional plan view illustrating another modification of the through hole and the through portion of FIG. It is a perspective view which shows typically the module by the 2nd Embodiment of this invention. Here, the hidden 1st connection part among the coils is drawn with the broken line. Moreover, the hidden part is drawn with the broken line among the holding holes which hold | maintain the connection member of a module. It is sectional drawing which shows the module of FIG. 10 along the XI-XI line. Here, the electronic components mounted on the circuit board are not drawn. It is a perspective view which shows typically the module by the 3rd Embodiment of this invention. Here, the hidden 1st connection part of the coil, a part of penetration part, and a part of connection part are drawn with the broken line. It is sectional drawing which shows the module of FIG. 12 along the XIII-XIII line. It is a side view which shows typically the inductor by the 4th Embodiment of this invention. Here, hidden portions of the inductor coil and the spacer are drawn with broken lines. In addition, the components of the magnetic core are schematically shown in a circle drawn by a one-dot chain line. It is an image which shows a part of cross section of the magnetic core by the 4th Embodiment of this invention. It is a disassembled perspective view which shows typically the components of the inductor of Examples 1-4 of this invention, and Comparative Examples 1-6. It is a perspective view which shows typically the inductors of Examples 1-3 of this invention and Comparative Examples 1-6. FIG. 18A is a perspective view schematically showing a magnetic core according to a fourth embodiment of the present invention and a prepreg that holds the magnetic core. FIG. 18B is a perspective view schematically showing the inductor according to the fourth embodiment of the present invention. It is a graph which shows the inductance with respect to the frequency of the inductor of Example 1 of this invention and Comparative Examples 1-3. It is a graph which shows the inductance with respect to the bias current of the inductor of Example 1 of this invention and Comparative Examples 1-3. It is a graph which shows the inductance with respect to the frequency of the inductor of Example 2 of this invention and Comparative Examples 4-6. It is a graph which shows the inductance with respect to the bias current of the inductor of Example 2 of this invention and Comparative Examples 4-6. It is a graph which shows the inductance with respect to the frequency of the inductor of Example 3, Example 4 of this invention, and Comparative Examples 1-3. It is a graph which shows the inductance with respect to the bias current of the inductor of Example 3, Example 4 of this invention, and Comparative Examples 1-3.

  In the following description, terms indicating positions such as “upper” and “lower” do not indicate absolute positions, but merely indicate relative positions in the drawings.

(First embodiment)
As shown in FIG. 1, the module (power supply module) 10 according to the first embodiment of the present invention includes a circuit board 200 and an inductor 300. The module 10 according to the present embodiment is a power module 10 that is mounted on, for example, an electronic device (not shown) and supplies power to the outside of the module. However, the present invention can be applied to modules other than the power module 10.

  As shown in FIGS. 1 to 4, the circuit board 200 has a facing surface 220 and a facing surface 230 that are located on opposite sides in the vertical direction. Each of the facing surface 220 and the opposite surface 230 according to the present embodiment is a horizontal plane orthogonal to the vertical direction.

  As shown in FIG. 2, electronic components 240 such as a switching transistor, a power supply control IC, and a capacitor are mounted on the facing surface 220 according to the present embodiment. On the other hand, the electronic component 240 is not mounted on the opposite surface 230 according to the present embodiment. More specifically, the opposite surface 230 is a solid surface. However, the circuit board 200 may be formed differently. For example, while the electronic component 240 is mounted on the opposite surface 230, the opposite surface 220 may be a solid surface. In other words, the electronic component 240 may not be mounted on the facing surface 220.

  A signal line (not shown) made of a conductor is formed on the facing surface 220, and the electronic components 240 are thereby connected to each other. In addition, two connection ends 250 are formed on the facing surface 220. Each of the connection ends 250 is connected to a signal line (not shown).

  As shown in FIG. 1 and FIGS. 3 to 5, the inductor 300 includes a magnetic core 310 and a coil 350 made of a metal (that is, a material having high thermal conductivity).

  As shown in FIG. 5, the magnetic core 310 according to the present embodiment is formed using a soft magnetic metal material 312. Specifically, the magnetic core 310 is mainly formed of a soft magnetic metal powder 312 having a flat shape and a binder (insulating material) 314 made of an insulating resin. Such a magnetic core 310 can be formed by binding soft magnetic metal powder 312 with a binder 314. For example, a soft magnetic metal powder 312 is mixed with a solvent, a thickener, and a thermosetting binder component (binder 314) to prepare a slurry, and the applied slurry is heated to volatilize the solvent, thereby volatilizing the solvent. Can be formed.

  The magnetic core 310 according to the present embodiment has a high electrical resistivity because the soft magnetic metal powder 312 is bound by the insulating binder 314. Specifically, the magnetic core 310 has an electrical resistivity of 10 KΩ · cm or more. In other words, the magnetic core 310 has good insulating properties. For this reason, the magnetic core 310 can be brought into direct contact with the conductor. Furthermore, the magnetic core 310 according to the present embodiment has high strength and has some elasticity. In other words, the magnetic core 310 is formed to be elastically deformable.

  Since the magnetic core 310 according to the present embodiment is formed as described above, the saturation magnetic flux density, the relative magnetic permeability and the magnetic permeability of the magnetic core 310 are increased by increasing the filling rate of the soft magnetic metal powder 312 (that is, the metal material). Thermal conductivity can be improved. Specifically, in order to obtain a sufficient thermal conductivity while maintaining magnetic properties, it is preferable that the soft magnetic metal powder 312 is contained in the magnetic core 310 by 55 volume% or more and 85 volume% or less. When the filling rate of the soft magnetic metal powder 312 is within the above range, a high saturation magnetic flux density, a high relative magnetic permeability, and a high thermal conductivity can be achieved. On the other hand, when the filling rate of the soft magnetic metal powder 312 exceeds 85% by volume, the electrical resistivity is remarkably lowered, and a large eddy current loss occurs inside the inductor 300.

  Since the magnetic core 310 according to the present embodiment includes 55% by volume or more of the soft magnetic metal powder 312, as described above, the magnetic core 310 has a high saturation magnetic flux density, a high relative magnetic permeability, and a high thermal conductivity. . In order to further increase the relative permeability of the magnetic core 310, the soft magnetic metal powder 312 is preferably contained in the magnetic core 310 by 60% by volume or more, and the magnetic core 310 contains 70% by volume or more. More preferably.

  The magnetic core 310 according to the present embodiment has a magnetic property equal to or higher than that of, for example, a ferrite magnetic core made of ferrite. More specifically, the magnetic core 310 has the same inductance and electrical resistivity as the ferrite magnetic core, and has a DC superposition characteristic superior to that of the ferrite magnetic core. Furthermore, the magnetic core 310 has a higher thermal conductivity than the ferrite core, which has conventionally been the highest. Furthermore, unlike the ferrite magnetic core, the magnetic core 310 is not easily damaged even under a pressing force, and the magnetic characteristics are not easily deteriorated. As can be understood from the above description, the magnetic core 310 according to the present embodiment is particularly suitable as the inductor 300 of the power supply module 10 through which a large current flows.

  As long as the magnetic core 310 having high thermal conductivity is formed using a soft magnetic metal material, it may be formed by a method different from the present embodiment. For example, a metal thin film made of Zr—Co—Ta or permalloy can be formed on the insulating layer by sputtering. A magnetic core having a thickness of about 1 mm and a high thermal conductivity can be formed by laminating several tens or more of the metal thin films and insulating layers thus formed.

  As shown in FIGS. 1, 5, and 6, the magnetic core 310 has a facing surface 320 and a heat radiating surface 330 that are located on opposite sides in the vertical direction. Each of the facing surface 320 and the heat radiating surface 330 according to the present embodiment is a horizontal plane orthogonal to the vertical direction. A plurality of through holes 340 are formed in the magnetic core 310. Specifically, the magnetic core 310 according to the present embodiment is formed with two rows of through-hole groups each including five through-holes 340. Each of the through holes 340 has a cylindrical shape and penetrates the magnetic core 310 in the vertical direction. An inner wall 342 is formed in the through hole 340 (see FIG. 6).

  As shown in FIGS. 5 and 7, the coil 350 includes a coil part 360 and a connection part 370. Specifically, the coil part 360 includes a plurality of penetration parts (via conductors) 362, a plurality of first connection parts (connection conductors) 364, and a plurality of second connection parts (connection conductors) 366.

  The through portions 362 are inserted into the through holes 340 of the magnetic core 310, respectively. For this reason, according to the present embodiment, two rows of through portion groups each including five through portions 362 are formed. The 1st connection part 364 has connected the upper end of the penetration part 362 of one penetration part group, and the upper end of the penetration part 362 of the other penetration part group. The 2nd connection part 366 has connected the lower end of penetration part 362 of one penetration part group, and the lower end of penetration part 362 of the other penetration part group. That is, the penetrating part 362, the first connecting part 364, and the second connecting part 366 are connected to each other so as to wind a part of the magnetic core 310. In other words, the coil part 360 winds at least a part of the magnetic core 310.

  Referring to FIGS. 2 to 5, of the through portions 362, the two most distant through portions 362 extend long downward from the through hole 340, thereby forming a connection portion 370. . A connection end 372 is formed at the lower end of the connection portion 370. Therefore, the coil 350 has two connection ends 372. The connection end 372 is connected to the connection end 250 of the facing surface 220 of the circuit board 200, whereby the coil 350 is electrically connected to the electronic component 240 via a signal line (not shown) of the circuit board 200. It is connected to the.

  As shown in FIGS. 8A and 8B, the through portion 362 according to the present embodiment has a cylindrical shape similar to that of the through hole 340. However, the diameter Rc of the through portion 362 is slightly larger than the diameter Rh of the through hole 340. Since the magnetic core 310 according to the present embodiment has elasticity, the through portion 362 can be inserted into the through hole 340 even when the diameter Rc is larger than the diameter Rh. Further, when the through portion 362 has a diameter Rc that is almost the same as the diameter Rh, the through portion 362 can be pressed to be crushed after being inserted into the through hole 340 to increase the diameter of the through portion 362.

  The through part 362 inserted into the through hole 340 as described above (that is, the coil part 360) penetrates the through hole 340 so as to elastically deform the inner wall 342 of the through hole 340. The elastically deformed inner wall 342 applies a pressing force (elastic force) to the penetrating portion 362 of the coil portion 360. For this reason, the coil 350 is held on the magnetic core 310 by the pressing force that the inner wall 342 applies to the penetrating part 362 (that is, to the coil part 360).

  As can be understood from the above description, the magnetic core 310 according to the present embodiment allows the insertion of the through portion 362 having a larger diameter than the through hole 340 and can reliably hold the inserted through portion 362. It has moderate elasticity. For this reason, the magnetic core 310 can hold the coil 350 only by the elastic force (pressing force) of the inner wall 342. Further, even when the elastic force of the inner wall 342 is somewhat small, the coil 350 is temporarily held by the through hole 340 and then fixed between the through part 362 and the through hole 340 with an adhesive. 350 can be reliably held. That is, according to the present embodiment, the coil 350 can be held only by the through hole 340.

  As shown in FIG. 9A, each of the through portion 362 and the through hole 340 according to the present embodiment has a circular cross section. For this reason, the through portion 362 inserted into the through hole 340 is firmly held by the entire inner wall 342 of the through hole 340. However, each of the through part 362 and the through hole 340 may have a cross section other than a circle as long as the through part 362 is held at two or more points on the inner wall 342. For example, as shown in FIG. 9B, the through-hole 362 may have a circular cross section, while the through-hole 340 may have a rectangular cross section. Further, as shown in FIG. 9C, the through-hole 362 may have a rectangular cross section, while the through hole 340 may have a circular cross section. However, in order to hold the through portion 362 more reliably, it is preferable to configure the through portion 362 and the through hole 340 as in the present embodiment.

  As shown in FIGS. 1, 3, and 4, the facing surface 320 of the magnetic core 310 of the inductor 300 configured as described above is disposed so as to face the facing surface 220 of the circuit board 200 in the vertical direction. ing. The facing surface 320 and the facing surface 220 are connected by a coil 350 having a high thermal conductivity. Further, the heat radiating surface 330 of the magnetic core 310 is exposed to the outside of the module 10.

  Since the module 10 is configured as described above, the heat generated by the circuit board 200 can be radiated from the facing surface 220 to the facing surface 320 of the magnetic core 310 mainly via the connection portion 370 of the coil 350. it can. Since the magnetic core 310 has a high thermal conductivity, the heat received by the facing surface 320 is effectively transferred to the heat radiating surface 330 together with the heat generated from the inductor 300 and is radiated to the outside of the module 10. As can be understood from the above description, heat radiation to the outside of the module 10 is promoted by at least partially exposing the heat radiation surface 330 of the magnetic core 310 to the outside of the module 10. Can be cooled.

  According to the present embodiment, inductor 300 itself that generates large heat can be used as a member for heat dissipation. Therefore, heat generated from the circuit board 200 and the inductor 300 can be radiated without providing a heat radiating member such as a heat sink between the facing surface 220 of the circuit board 200 and the facing surface 320 of the inductor 300. According to the present embodiment, the module 10 can be effectively cooled while downsizing the module 10.

  According to the present embodiment, the facing surface 320 of the magnetic core 310 and the facing surface 220 of the circuit board 200 are connected only by the connection portion 370 of the coil 350. However, the magnetic core 310 and the circuit board 200 may be connected by another member in addition to the coil 350. For example, the magnetic core 310 and the circuit board 200 may be connected by a metal having a large thermal conductivity such as copper or aluminum. With this configuration, the inductor 300 can be more reliably fixed to the circuit board 200 and the heat radiation path from the circuit board 200 to the inductor 300 can be increased.

  According to the present embodiment, the entire heat radiation surface 330 is exposed to the outside of the module 10. However, the heat radiation surface 330 may be covered with another member as long as heat can be radiated to the outside. For example, a part or the whole of the heat radiation surface 330 may be coated with a thin resin. Furthermore, the outer periphery of the inductor 300 may be covered with resin or metal. Furthermore, the outer periphery of the module 10 can be covered with resin or metal.

  The heat radiating surface 330 may be at least partially in contact with a cooling member (for example, a heat sink) outside the module 10. As described above, the magnetic core 310 is not easily damaged even under a pressing force, and the magnetic properties are not easily deteriorated. For this reason, the heat radiation surface 330 can be brought into close contact with the external cooling member by a strong pressing force. When comprised in this way, the module 10 can be cooled more effectively. As understood from the above description, the circuit board 200 and the inductor are arranged by disposing the heat radiation surface 330 (that is, one surface) of the magnetic core 310 having high thermal conductivity to the outside of the module 10 so that heat can be radiated. Heat generated from 300 can be effectively dissipated.

(Second Embodiment)
As can be understood from FIGS. 1 and 10, a module (power supply module) 10A according to the second embodiment of the present invention is a modification of the module 10 (see FIG. 1) according to the first embodiment. The module 10A includes a circuit board 200 that is the same as the module 10, an inductor 300A that is slightly different from the inductor 300 of the module 10, a heat dissipation member 400 that the module 10 does not include, and a plurality of (four according to the present embodiment) connecting members. 500 and coating 600. Hereinafter, the difference between the module 10A and the module 10 will be mainly described.

  As shown in FIGS. 10 and 11, the inductor 300 </ b> A has a magnetic core 310 </ b> A and a coil 350. The magnetic core 310A has almost the same structure as the magnetic core 310 (see FIG. 6). However, four holding holes 346 are formed in the magnetic core 310A. The holding holes 346 are formed at the four corners of the magnetic core 310A so as to penetrate the magnetic core 310A in the vertical direction.

  The heat radiating member 400 is formed from a material having excellent thermal conductivity such as metal (that is, a heat conductor) so as to have a rectangular frame shape. The heat radiating member 400 is attached to the heat radiating surface 330 of the magnetic core 310A. Since the magnetic core 310A has a high electrical resistivity, the heat dissipating member 400 made of metal can be brought into contact with the heat dissipating surface 330 without performing an insulating process. Further, since the magnetic core 310A is formed of the same material as that of the magnetic core 310 (see FIG. 6), the magnetic core 310A is not easily damaged even under a pressing force, and the magnetic characteristics are not easily deteriorated. For this reason, the heat radiating member 400 can be brought into close contact with the magnetic core 310A by a strong pressing force.

  The heat radiating member 400 is formed with four holding holes 410. The holding holes 410 are formed at positions corresponding to the holding holes 346 of the magnetic core 310A so as to penetrate the heat radiating member 400 in the vertical direction.

  Each of the connecting members 500 is formed from a heat conductor so as to have a cylindrical shape. The connecting member 500 is held in the holding hole 410 of the heat dissipation member 400 and the holding hole 346 of the magnetic core 310A. As described above, the magnetic core 310A has appropriate elasticity. For this reason, by making the diameter of the connecting member 500 slightly larger than the diameter of the holding hole 346, the connecting member 500 can be reliably held by the magnetic core 310A without using an adhesive. The connecting member 500 may be held by being fitted into the holding hole 410 of the heat radiating member 400, or may be formed integrally with the heat radiating member 400.

  Each of the connecting members 500 extends downward from the heat radiating member 400 and is connected to the facing surface 220 of the circuit board 200. In other words, the connecting member 500 connects the heat radiating member 400 and the circuit board 200 via the magnetic core 310A.

  The coating 600 according to the present embodiment is formed from a thin resin. The coating 600 covers a portion of the heat dissipation surface 330 of the magnetic core 310 that is not in contact with the heat dissipation member 400. By covering the heat radiating surface 330 with the coating 600, the first connecting portion 364 of the coil 350 exposed to the heat radiating surface 330 can be protected. Further, by forming the coating 600 so as to have an appropriate thickness, heat radiation from the heat radiation surface 330 is not significantly hindered. As understood from the above description, the heat radiating surface 330 according to the present embodiment is also disposed outside the module 10A so as to be able to radiate heat. However, when it is necessary to radiate heat more effectively, the heat radiating surface 330 may not be covered with the coating 600.

  According to the present embodiment, the heat generated from the circuit board 200 and the inductor 300 </ b> A can be transmitted to the heat radiating member 400 via the connecting member 500 and radiated from the heat radiating member 400. That is, the module 10A according to the present embodiment has a heat dissipation path by the connecting member 500 in addition to the heat dissipation path by the coil 350 (particularly, the connecting portion 370). For this reason, module 10A can be cooled more effectively.

  Similarly to the first embodiment, the outer periphery of the inductor 300A and the outer periphery of the module 10A may be covered with resin or metal. The heat radiation surface 330 may be at least partially in contact with a cooling member outside the module 10A such as a heat sink. Furthermore, the heat radiating member 400 may also be at least partially in contact with a cooling member outside the module 10A. As described above, the magnetic core 310A is not easily damaged even under a pressing force, and the magnetic characteristics are not easily deteriorated. For this reason, the heat radiating member 400 is brought into close contact with the external cooling member by a strong pressing force, and thereby the module 10A can be further effectively cooled.

(Third embodiment)
As understood from FIGS. 10 and 12, the module (power supply module) 10B according to the third embodiment of the present invention is a modification of the module 10A (see FIG. 10) according to the second embodiment. The module 10B includes a circuit board 200B slightly different from the circuit board 200, an inductor 300A similar to the module 10A, a heat radiating member 400, a connecting member 500, and a coating 600. Hereinafter, the difference between the module 10B and the module 10A will be mainly described.

  As can be understood from FIGS. 12 and 13, the circuit board 200B has a box shape. Specifically, the circuit board 200 </ b> B has side wall portions 210 that extend upward from the four sides of the facing surface 220. The circuit board 200B configured as described above can be formed from, for example, a plurality of plate-like circuit boards. The electronic component 240 is not mounted on the facing surface 220 of the circuit board 200B according to the present embodiment. On the other hand, various electronic components 240 are mounted on the opposite surface 230 of the circuit board 200B according to the present embodiment.

  The inductor 300 </ b> A and the heat dissipation member 400 are accommodated in a space surrounded by the facing surface 220 and the side wall portion 210. The second connecting portion 366 of the coil 350 is disposed so as to contact or approach the facing surface 220. For this reason, the length of the connecting portion 370 of the coil 350 according to the present embodiment is short (see FIG. 12).

  As shown in FIGS. 12 and 13, a plurality of (eight according to the present embodiment) terminals 260 are provided on the side wall portion 210. Each of the terminals 260 is connected to the electronic component 240 via a signal line (not shown). The terminal 260 is electrically connected to an external device of the module 10B in order to perform, for example, current input / output, output voltage monitoring, and switching frequency control.

  As shown in FIG. 13, the module 10 </ b> B configured as described above can be connected to the external circuit board 800. The external circuit board 800 according to the present embodiment is provided with a cooling member 810 having a large thermal conductivity. The cooling member 810 can be formed from metal, for example. The cooling member 810 is provided at a position corresponding to the heat radiating member 400 of the module 10B. When the terminal 260 is connected to the external circuit board 800, the heat dissipation member 400 is in close contact with the cooling member 810. For this reason, the heat generated by the module 10 </ b> B can be effectively radiated from the heat radiating member 400 to the cooling member 810. The heat radiating member 400 may be fixed to the cooling member 810 by soldering, for example. In this case, the module 10B can be cooled more effectively.

(Fourth embodiment)
As understood from FIGS. 5 and 14, the inductor 300X and the magnetic core 310X according to the fourth embodiment are modifications of the inductor 300 and the magnetic core 310 according to the first embodiment. That is, the inductor 300X and the magnetic core 310X have the same structure and function as the inductor 300 and the magnetic core 310. Hereinafter, the inductor 300X and the magnetic core 310X will be described in more detail than in the first embodiment.

  As shown in FIG. 14, the inductor 300X according to the present embodiment includes a magnetic core 310X, a coil 350, and a spacer 820X. Similar to the first embodiment, the coil 350 is formed of a metal (for example, copper) having no insulating coating. However, the coil 350 may have an insulating coating. The coil 350 has a coil part 360 and a connection part 370.

  The magnetic core 310X is a magnetic core in which a soft magnetic metal powder 312 having a flat shape is bound by a binder component 314X. The magnetic core 310X according to the present embodiment is a dust core. The magnetic core 310X has a flat plate shape orthogonal to the vertical direction. The thickness of the flat plate shape of the magnetic core 310X is 1 mm or less.

  Similar to the first embodiment, the flat soft magnetic metal powder 312 is produced, for example, by flattening a particulate soft magnetic metal powder (material powder) using a ball mill. The material powder (that is, the soft magnetic metal powder 312) is preferably made of an Fe-based alloy in order to obtain necessary magnetic characteristics. Furthermore, the soft magnetic metal powder 312 is preferably made of an Fe—Si alloy. Furthermore, the soft magnetic metal powder 312 is preferably made of an Fe—Si—Al alloy (Sendust) or an Fe—Si—Cr alloy. When the soft magnetic metal powder 312 contains Si and Al, the ratio of Si in the soft magnetic metal powder 312 is preferably 3 wt% or more and 18 wt% or less, and the ratio of Al is 1 wt% or more. And it is preferable that it is 12 weight% or less. In this case, the magnetocrystalline anisotropy constant and magnetostriction constant of the magnetic core 310X are reduced, and the magnetic properties are improved. Further, when the magnetic core 310X is manufactured, a passive film containing Si and Al is formed on the surface of the soft magnetic metal powder 312 and the electric resistance of the magnetic core 310X is improved.

  The binder component 314X for binding the flat soft magnetic metal powder 312 has silicon oxide as a main component. Such a binder component 314X is obtained from a binder 314 containing Si. For example, as in the first embodiment, a soft magnetic metal powder 312 is mixed with a solvent, a thickener, and a binder 314 to produce a slurry. At this time, for example, a methylphenyl silicone resin may be used as the binder 314. The applied slurry is heated to volatilize the solvent to produce a preform that is the material of the magnetic core 310X. Unlike the ferrite, the preform is not formed from a brittle material and can be pressure-molded. The preformed body is compressed by pressurization to produce a molded body after pressurization. When the pressed compact is heat-treated at a high temperature (for example, 600 ° C.), the magnetic core 310X is obtained.

  When compressing a preform by pressurization, structural distortion arises and there exists a possibility that a relative magnetic permeability may fall by this. According to the present embodiment, the relative permeability is restored to a high value by the above-described heat treatment at a high temperature.

  The organic component of the methylphenyl silicone resin is decomposed by the above-described heat treatment at a high temperature. Further, the solid content of the methylphenyl silicone resin becomes a binder component 314X made of vitreous whose main component is silicon oxide, and binds the soft magnetic metal powder 312. That is, since the soft magnetic metal powder 312 is bound by an inorganic material, the magnetic core 310X thus manufactured can withstand reflow due to a high temperature of about 260 ° C. Further, since the soft magnetic metal powder 312 is bound by an insulator, the magnetic core 310X has excellent frequency characteristics and a high electrical resistivity of 10 kΩ · cm or more. Since the magnetic core 310X according to the present embodiment has a high electrical resistivity, the coil portion 360, which is a conductor, can be brought into direct contact with the magnetic core 310X, similarly to the magnetic core 310 (see FIG. 5).

  The organic component of the binder 314 is lost by the above-described heat treatment at a high temperature. For this reason, the binder 314 loses heat and a hole 318X is formed inside the magnetic core 310X. That is, the magnetic core 310X includes the soft magnetic metal powder 312, the binder component 314X, and the holes 318X.

  In the above-described heat treatment at a high temperature, the temperature varies depending on the part of the molded body, and therefore the thermal expansion varies depending on the part. Further, the size at which the binder 314 contracts and the speed at which the binder 314 is decomposed differ depending on the part. For this reason, when the thickness of the molded body after pressurization is large, a large internal stress may be generated to cause cracks and peeling. Furthermore, in the above-described heat treatment at a high temperature, gas is generated inside the molded body as the binder 314 is decomposed. When the thickness of the molded body after pressurization is large, the gas generated at the back of the molded body is not easily diffused to the outside. For this reason, there is a possibility that the pressure of the gas increases inside the molded body, and cracks and peeling occur. If the thickness of the molded body after pressurization is 1 mm or less, cracks and peeling do not occur even in the above-described heat treatment at high temperature. Therefore, the thickness of the molded body after pressurization is desirably 1 mm or less. The thickness of the molded body after pressing is more preferably 0.7 mm or less.

  In order to improve the magnetic properties, the magnetic core 310X preferably includes 60% by volume or more of the soft magnetic metal powder 312. In this case, the magnetic core 310X has a high saturation magnetic flux density and a high magnetic permeability equivalent to ferrite. Specifically, the magnetic core 310X having a saturation magnetic flux density of 0.5T or more can be obtained. That is, the magnetic core 310X according to the present embodiment is difficult to be magnetically saturated and can be downsized. Further, it is possible to obtain the magnetic core 310X in which the real component of the relative permeability at a frequency of 1 MHz is 50 or more. Furthermore, it is possible to obtain the magnetic core 310X in which the real component of the relative permeability at a frequency of 1 MHz is 100 or more. Specifically, according to the present embodiment, the real component of the relative permeability in the initial permeability range becomes a maximum value (Y) due to magnetic resonance at a predetermined frequency (X MHz) of 1 MHz or higher. The predetermined frequency (X MHz) and the maximum value (Y) satisfy the conditional expression of X × Y ≧ 300. For this reason, an increase in eddy current loss, an increase in core loss, and a decrease in noise absorption performance can be prevented.

  As shown in FIG. 15, the soft magnetic metal powder 312 (flat powder) of the magnetic core 310X is oriented so as to be orthogonal to the thickness direction (vertical direction). In other words, the soft magnetic metal powder 312 is oriented so as to be parallel to a horizontal plane (predetermined plane) orthogonal to the thickness direction. For this reason, the demagnetizing factor in the direction parallel to the predetermined surface is reduced, and the relative permeability can be increased as described above. That is, the easy axis of magnetization of the magnetic core 310X extends in a direction parallel to the predetermined plane. In order to further increase the relative permeability in the direction parallel to the predetermined plane, the average aspect ratio of the soft magnetic metal powder 312 is preferably 10 or more.

  Further, the soft magnetic metal powders 312 are stacked in the thickness direction while being shifted from each other in a direction parallel to the predetermined surface. For this reason, even if a crack occurs, the progress of the crack can be prevented. That is, according to the present embodiment, it is possible to obtain the magnetic core 310X having a thickness of, for example, 1.0 mm or less or 0.5 mm or less and having a high toughness as compared with ferrite that is a ceramic material.

  Referring to FIG. 14, the magnetic core 310 </ b> X preferably includes air holes 318 </ b> X of 10 volume% or more and 25 volume% or less. In other words, the volume ratio (porosity) of the holes 318X included in the magnetic core 310X is preferably 10% by volume or more and 25% by volume or less. A desired porosity can be obtained by adjusting the amount of the binder 314 at the time of producing the slurry and the pressure at which the preform is compressed by pressurization. When the porosity is 10% by volume or more, the magnetic core 310X has elasticity, and it becomes easy to process the magnetic core 310X in various ways. When the porosity is 25% by volume or less, the magnetic core 310X can contain sufficient soft magnetic metal powder 312.

  The volume ratio of the binder component 314X included in the magnetic core 310X is preferably 10% by volume to 30% by volume. When the volume ratio of the binder component 314X is smaller than 10% by volume, the magnetic core 310X does not have sufficient strength. Moreover, when the volume ratio of the binder component 314X is larger than 30 volume%, the volume ratio of the soft magnetic metal powder 312 cannot be 60 volume% or more, and the porosity cannot be 10 volume% or more.

  In summary, the magnetic core 310X according to the present embodiment has a soft magnetic metal powder 312 of 60% by volume or more, a binder component 314X of 10% by volume to 30% by volume, and 10% by volume to 25% by volume. And vacancies 318X. Moreover, the rubber hardness by ISO7619-typeD of the magnetic core 310X is 92 or more and 96 or less. That is, the magnetic core 310X can be elastically deformed.

  Since the magnetic core 310X is an elastic body, the Young's modulus can be measured as follows. First, a flat magnetic core 310X having a width (w) and a thickness (t) is prepared. Next, the two supported portions of the magnetic core 310X are supported from below. At this time, the supported parts are separated by a distance (L) in the longitudinal direction of the magnetic core 310X. Next, the pressed part located between the supported parts is pressed from above with a load (P). The strain (δ) caused by the load (P) is measured. As is well known, the Young's modulus can be calculated from the above-mentioned width (w), thickness (t), distance (L), load (P) and strain (δ). According to the present embodiment, magnetic core 310X having a Young's modulus of 10 GPa or more and 90 GPa or less can be obtained. Moreover, the magnetic core 310X whose Young's modulus is 20 GPa or more and 50 GPa or less can be obtained by mainly adjusting the porosity of the magnetic core 310X.

  As can be understood from FIG. 14, the magnetic core 310 </ b> X configured as described above can be processed in various ways. For example, a plurality of through holes 340 are formed in the magnetic core 310X according to the present embodiment. Similarly to the first embodiment (see FIG. 5), the coil portion 360 of the coil 350 includes a plurality of through portions 362, a first connecting portion 364, and a second connecting portion 366. . The through part 362 of the coil part 360 penetrates the through hole 340 in the vertical direction. Specifically, the through portion 362 penetrates the through hole 340 so as to elastically deform the inner wall 342 of the through hole 340. The coil 350 is held by a pressing force that the inner wall 342 of the through hole 340 applies to the through portion 362. That is, according to the present embodiment, as in the first embodiment, the through portion 362 inserted into the through hole 340 has a pulling strength without using an adhesive.

  Specifically, since the magnetic core 310X includes holes 318X having an appropriate volume%, the portion (press-fit portion) around the inner wall 342 is appropriately compressed and deformed. For this reason, the stress generated in the press-fitting portion extends to the entire magnetic core 310X, and the magnetic core 310X is prevented from being deformed and broken.

  Similar to the first embodiment (see FIG. 5), the first connecting portion 364 is attached to the magnetic core 310X so as to connect the end of the penetrating portion 362 on the upper surface of the magnetic core 310X. Similarly, the 2nd connection part 366 is attached to the magnetic core 310X so that the edge part of the penetration part 362 may be connected in the lower surface of the magnetic core 310X. At this time, the 1st connection part 364 and the 2nd connection part 366 can be firmly fixed to penetration part 362 by various methods, such as resistance welding and ultrasonic welding, and can be attached to magnetic core 310X by this.

When the first connecting portion 364 and the second connecting portion 366 are attached to the magnetic core 310X, the magnetic core 310X is entirely compressed in the vertical direction. Therefore, the thickness (t ₁ ) of the magnetic core 310X after the first connecting portion 364 and the second connecting portion 366 are attached to the magnetic core 310X is the same as that of the first connecting portion 364 and the second connecting portion 366. Compared to the thickness (t ₀ ) of the magnetic core 310X before being attached to the wire, it decreases by 2.5% or more and 5.0% or less. On the other hand, when the coil part 360 is removed from the magnetic core 310X, the thickness (t ₁ ) of the magnetic core 310X is the thickness (t ₀ ) before the first connecting part 364 and the second connecting part 366 are attached to the magnetic core 310X. Recover as you approach. That is, the reduced thickness of the magnetic core 310X (about 2.5% to 5.0% of the thickness (t ₀ )) is almost restored.

  As can be understood from the above description, the magnetic core 310X according to the present embodiment is easily compressed to a predetermined thickness due to the air holes 318X included therein and the elasticity of the soft magnetic metal powder 312. In addition, it has the property of easily recovering from a compressed state. For this reason, the upper surface and the lower surface of the magnetic core 310X are pressed against the first connecting portion 364 and the second connecting portion 366, respectively, by the repulsive force in the thickness direction (vertical direction) of the magnetic core 310X. For this reason, even when there is a gap between the through portion 362 of the coil 350 and the inner wall 342 of the through hole 340, the first connecting portion 364 and the second connecting portion 366 can be held and fixed.

  The magnetic core 310X configured as described above can firmly hold not only the coil unit 360 but also various members. Such processability of the magnetic core 310X is similar to the processability of wood that can be nailed, and the process for processing the magnetic core 310X is remarkably simplified, and the processing reliability is improved.

  For example, as shown in FIG. 14, a holding hole 346X is formed in the magnetic core 310X according to the present embodiment. The spacer 820X includes a main body portion 822X and a held portion 824X. In a horizontal plane perpendicular to the vertical direction, the main body portion 822X is considerably larger than the holding hole 346X, and the held portion 824X is slightly larger than the holding hole 346X. The held portion 824X configured as described above can be press-fitted and fixed into the holding hole 346X in the same manner as the penetration portion 362. Further, when the held portion 824X is press-fitted into the holding hole 346X, the lower surface of the main body portion 822X comes into contact with the upper surface of the magnetic core 310X. Since the main body portion 822X has a large size in the horizontal plane, it is possible to prevent scraps generated when the held portion 824X is press-fitted.

  The inductor 300X and the magnetic core 310X according to the present embodiment can be variously modified as in the first embodiment. For example, the size of the through portion 362 in the horizontal plane may be smaller than the size of the through hole 340 in the horizontal plane. That is, the through portion 362 may be passed through the through hole 340 instead of being press-fitted into the through hole 340. In this case, the through portion 362 may be fixed to the through hole 340 with an adhesive, for example. Moreover, each of the 1st connection part 364 and the 2nd connection part 366 may be joined to the penetration part 362 with a pressure, and may be joined by soldering. Moreover, you may form the recessed part corresponding to each of the 1st connection part 364 and the 2nd connection part 366 in the site | part which contacts each of the 1st connection part 364 and the 2nd connection part 366 among the magnetic cores 310X. . Thereby, each of the 1st connection part 364 and the 2nd connection part 366 is hold | maintained more reliably by the magnetic core 310X.

  Further, all or part of the surface of the magnetic core 310X may be covered with an insulating resin. As the insulating resin, for example, an acrylic resin or a polyolefin resin may be used. By comprising in this way, the insulation of the surface of the magnetic core 310X further improves. Furthermore, even if a crack occurs, the progress of the crack can be prevented more reliably. A part of the insulating resin is impregnated in the surface layer of the magnetic core 310X. For this reason, generation | occurrence | production and progress of a crack can be prevented further reliably.

  Further, the magnetic core may include a plurality of magnetic core components each functioning as a magnetic core. More specifically, a plurality of magnetic core components (for example, the magnetic core 310X) may be laminated via an adhesive, thereby producing one magnetic core. As described above, since the magnetic core 310X according to the present embodiment has a structure in which cracks are unlikely to occur, the occurrence of cracks can be suppressed when the laminated magnetic core components (magnetic core 310X) are pressure-bonded. That is, a laminated magnetic core having a thickness exceeding 1 mm can be obtained while suppressing cracks. At this time, the thickness of each of the laminated magnetic cores 310X may be 1 mm or less. However, the thickness of each of the magnetic cores 310X is preferably 0.5 mm or less.

  Ferrite, which is a ceramic material, has a high relative magnetic permeability of 50 or more or 100 or more in the MHz band. Moreover, ferrite has sufficient rigidity without providing a reinforcing member or the like. For this reason, ferrite is generally used as a magnetic core material. However, since ferrite is a brittle material, it is difficult to form a magnetic core using a simple, highly accurate and reliable joining method such as indentation, driving, press-fitting, and strong press-fitting.

  On the other hand, since the magnetic core according to the present invention is formed from a soft magnetic metal powder having a flat shape, the fracture does not proceed in the thickness direction even when the magnetic core is thin. For this reason, the magnetic core according to the present invention has higher toughness than the magnetic core made of ferrite. Furthermore. When the volume ratio of the voids formed inside the magnetic core is within a predetermined range, the magnetic core has elasticity. For this reason, it can process easily. For example, a hole can be formed in the magnetic core. When another member is press-fitted into the hole formed in the magnetic core, the periphery of the hole in the magnetic core is elastically deformed. For this reason, it can prevent that the stress which arose by press injection reaches the whole magnetic core, and the whole magnetic core deforms and destroys. As can be understood from the above description, by using the magnetic core according to the present invention, the degree of freedom in designing the inductor is greatly increased, and it becomes possible to manufacture a small and highly reliable inductor.

  Furthermore, the present invention can be applied to magnetic parts other than the magnetic core and the inductor.

  Hereinafter, the magnetic core and inductor according to the present invention will be described in more detail with specific examples.

  First, the porosity of the holes included in the magnetic core according to the present invention will be described in detail.

(Preparation of a preform for measuring porosity (1))
Soft magnetic metal powder was used as a material for the preform. More specifically, water atomized powder of Fe—Si—Cr alloy was used. The powder contained 3.5 wt% Si and 2 wt% Cr. Moreover, the powder had an average particle diameter (D50) of 33 μm. The powder was flattened using a ball mill. Specifically, the powder was subjected to a forging process for 8 hours and then subjected to a heat treatment at 800 ° C. for 3 hours in a nitrogen atmosphere, thereby obtaining a flat Fe—Si—Cr powder. Next, a slurry was prepared by mixing a flat powder with a solvent, a thickener, and a thermosetting binder component. Ethanol was used as the solvent. A polyacrylic acid ester was used as the thickener. As the thermosetting binder component, a methylphenyl silicone resin was used. The amount of polyacrylic acid ester added was 3% by weight with respect to the flat-shaped powder, and the amount of solid content of the methylphenyl silicone resin was 4% by weight with respect to the flat-shaped powder. The slurry was applied on a PET (polyethylene terephthalate) film by a die slot method. Then, it dried at 60 degreeC for 1 hour, the solvent was removed, and this produced the preform.

(Production of flat plate for measuring porosity (1))
The preform was cut using a punching die, thereby obtaining a plurality of square sheets 30 mm wide and 30 mm long. A predetermined number of sheets were stacked and placed in a mold. The sheet in the mold was subjected to pressure molding for 1 hour at a molding pressure of 2 MPa at a temperature of 150 ° C. to obtain a molded body after pressure molding. At this time, 11 molded bodies having various thicknesses were produced by changing the number of sheets stacked (predetermined number). For example, a molded body having a thickness of 1 mm was produced from about 30 sheets. The molded body was subjected to heat treatment at 550 ° C. for 2 hours in the air, thereby preparing 11 flat plates. By this heat treatment, the thickener was almost completely pyrolyzed and did not remain in the flat plate. In addition, by this heat treatment, the solid content of the methylphenyl silicone resin became a binder component (a binder component after the heat treatment) made of glassy containing silicon oxide as a main component, and the heat loss was reduced. For example, when heat treatment for 1 hour was performed in the air at 550 ° C. for 1 hour, the solid weight loss of the methylphenyl silicone resin was 20% by weight.

(Measurement of porosity of flat plate (1) and investigation of crack generation rate of flat plate)
The molding density of the produced flat plate was measured by Archimedes method. Specifically, the true density of only the flat-shaped powder was calculated as 7.6 g / cm ^3, and the density after curing of the methylphenyl silicone resin was calculated as 1.3 g / cm ³ . From these numerical values, the volume filling rate of the metal component, the volume filling rate of the binder component after the heat treatment, and the porosity were calculated for the flat plate. In addition, the four sides of the flat plate were visually observed to investigate the occurrence rate of cracks.

  Table 1 shows the results of the above measurement and investigation.

  The cracks that occurred were fine in all cases, and it was possible to prevent the cracks beforehand by coating the side with resin. Further, when the thickness of the flat plate was 1.0 mm or less, almost no cracks were generated, and it was not necessary to prevent the cracks from occurring.

(Preparation of preform for measuring porosity (2))
Soft magnetic metal powder was used as a material for the preform. More specifically, water atomized powder of Fe—Si—Cr alloy was used. The powder contained 3.5 wt% Si and 2 wt% Cr. Moreover, the powder had an average particle diameter (D50) of 33 μm. The powder was flattened using a ball mill. Specifically, the powder was subjected to a forging process for 8 hours and then subjected to a heat treatment at 800 ° C. for 3 hours in a nitrogen atmosphere, thereby obtaining a flat Fe—Si—Cr powder. Next, a slurry was prepared by mixing a flat powder with a solvent, a thickener, and a thermosetting binder component. Ethanol was used as the solvent. A polyacrylic acid ester was used as the thickener. As the thermosetting binder component, a methylphenyl silicone resin was used. At this time, 11 kinds of values between 2% by weight and 20% by weight with respect to the flat powder were used as the solid content of the methylphenyl silicone resin. The slurry was applied on a PET (polyethylene terephthalate) film by a die slot method. Then, it dried at 60 degreeC for 1 hour, the solvent was removed, and 11 types of preforming bodies from which the addition amount of methylphenyl silicone resin differed by this were produced.

(Production of flat plate for measuring porosity (2))
The preform was cut using a punching die, thereby obtaining a plurality of square sheets 30 mm wide and 30 mm long. A predetermined number of sheets having the same amount of methylphenyl silicone resin added were laminated and placed in a mold. The sheet in the mold was subjected to pressure molding for 1 hour at a molding pressure of 2 MPa at a temperature of 150 ° C. to obtain a molded body after pressure molding. At this time, 11 types of molded articles with different addition amounts of methylphenyl silicone resin were produced. Further, 15 molded bodies were produced for each type. The molded body was subjected to heat treatment at 550 ° C. for 1 hour in a nitrogen atmosphere, thereby producing 11 types × 15 flat plates with different amounts of methylphenyl silicone resin added. Each thickness of the flat plate was 0.7 mm. By this heat treatment, the thickener was almost completely pyrolyzed and did not remain in the flat plate. In addition, by this heat treatment, the solid content of the methylphenyl silicone resin became a binder component (a binder component after the heat treatment) made of glassy containing silicon oxide as a main component, and the heat loss was reduced. For example, when heat treatment for 1 hour was performed in the air at 550 ° C. for 1 hour, the solid weight loss of the methylphenyl silicone resin was 20% by weight.

(Measurement of porosity of flat plate (2))
The molding density of the produced flat plate was measured by Archimedes method. Specifically, the true density of only the flat-shaped powder was calculated as 7.6 g / cm ^3, and the density after curing of the methylphenyl silicone resin was calculated as 1.3 g / cm ³ . From these numerical values, the volume filling rate of the metal component, the volume filling rate of the binder component after the heat treatment, and the porosity were calculated for the flat plate.

(Production of laminate and investigation of crack occurrence rate)
11 types × 5 laminates were prepared from 11 types × 15 flat plates. That is, a single laminate was produced from three flat plates having the same amount of methylphenyl silicone resin added. Specifically, first, three flat plates were laminated via an adhesive. As the adhesive, a one-part epoxy resin (Reginas Chemical S-71) was used. Next, the laminated flat plate was mirror-polished and then sandwiched between two stainless steel plates having a thickness of 10 mm. Next, the laminated flat plate was pressurized through a stainless steel plate. Specifically, using a hydraulic press machine, the laminated flat plates were pressed at a pressure of 15 MPa at a temperature of 170 ° C. for 3 hours to adhere the flat plates. By the above-mentioned method, five laminated bodies were produced from each type of 15 flat plates. After the adhesion was completed, the four sides of the laminate were visually observed to investigate the occurrence rate of cracks.

  Table 2 shows the results of the above measurement and investigation.

  As shown in Table 2, when the volume filling rate of the binder component was 7% by volume and the porosity was 33% by volume, the strength of the laminate was insufficient and peeling occurred. Also, cracks occurred when the porosity was less than 10% by volume. When the porosity is less than 10% by volume, the laminated body does not contain enough pores and hardly compresses and deforms. For this reason, the shear stress generated inside the laminate when bonded by pressure cannot be absorbed by the compressive deformation of the laminate. As a result, it is considered that a crack occurred. On the other hand, cracks did not occur when the volume filling rate of the binder component was 9.5% by volume to 37% by volume and the porosity was 10% by volume to 25.5% by volume. In this case, the amount of the binder component is appropriate, the laminate has sufficient strength, and has an appropriate porosity. For this reason, it is considered that the shear stress generated in the laminated body when bonded by pressure is absorbed by the compressive deformation of the laminated body. That is, when the porosity of the laminate is controlled to be 10% by volume or more and 25.5% or less, the pores inside the laminate allow compressive deformation, which causes cracks. Hateful.

  Next, the magnetic cores and inductors of Example 1 and Comparative Examples 1 to 3 will be described.

(Preparation of preform for magnetic core of Example 1)
Soft magnetic metal powder was used as a material for the preform. More specifically, a gas atomized powder of Fe—Si—Al alloy (Sendust) was used. The powder had an average particle size (D50) of 55 μm. The powder was flattened using a ball mill. Specifically, the powder was subjected to a forging process for 8 hours and then subjected to a heat treatment at 700 ° C. for 3 hours in a nitrogen atmosphere to obtain a flat Sendust powder. Next, a slurry was prepared by mixing the sendend powder having a flat shape with a solvent, a thickener, and a thermosetting binder component. Ethanol was used as the solvent. Polyvinyl butyral was used as a thickener. As the thermosetting binder component, a methylphenyl silicone resin was used. The slurry was applied on a PET (polyethylene terephthalate) film by a die slot method. Then, it dried at 60 degreeC for 1 hour, the solvent was removed, and this produced the preform.

(Preparation of flat plate for measuring magnetic core characteristics)
The preform was cut using a punching die, thereby obtaining a plurality of square sheets 30 mm wide and 30 mm long. A predetermined number of sheets were stacked and placed in a mold. The sheet in the mold was subjected to pressure molding at a molding pressure of 200 MPa for 1 hour at a temperature of 150 ° C. The thickness of the molded body after pressure molding was 0.25 mm. The molded body after pressure molding was subjected to heat treatment at 600 ° C. for 1 hour in a nitrogen atmosphere, thereby producing a flat plate.

(Characteristics of flat plate)
The produced flat plate had a density of 4.9 g / cm ³ and a volume resistivity of 10 KΩ · cm or more. From the density of the flat plate, the volume filling rate of the metal material (that is, soft magnetic metal powder) in the flat plate was determined. The volume filling rate of the metal material was about 67%. The flat plate was sandwiched between two glass epoxy substrates (FR-4) having a thickness of 1.5 mm, a length of 50 mm, and a width of 50 mm, and pressed with a pressure of 100 MPa. At this time, the flat plate was not damaged at all. Thus, unlike the conventional ceramic-based magnetic core materials such as Ni—Zn ferrite, the produced flat plate had extremely high strength against an external force perpendicular to the plane of the flat plate.

(Preparation of flat plate for magnetic core of Example 1)
The preform was cut using a punching die to obtain a plurality of rectangular sheets having a width of 15 mm and a length of 11 mm. A predetermined number of sheets were stacked and placed in a mold. The sheet in the mold was subjected to pressure molding at a molding pressure of 200 MPa for 1 hour at a temperature of 150 ° C. The thickness of the molded body (ie, flat plate) after pressure molding was 0.9 mm.

(Preparation of magnetic core of Example 1)
As shown in FIG. 16, the inductor core of Example 1 was manufactured using the molded body after pressure molding. Specifically, four via holes (that is, through holes) having a diameter of 0.8 mm were provided at predetermined positions of the molded body by drill cutting. Next, the molded body was subjected to heat treatment at 600 ° C. for 1 hour in a nitrogen atmosphere, thereby producing a magnetic core. The produced magnetic core had a density of 4.9 g / cm ³ and a volume resistivity of 10 KΩ · cm or more. From the density of the magnetic core, the volume filling rate of the metal material (soft magnetic metal powder) in the magnetic core was determined. The volume filling rate of the metal material was about 67%.

(Production of magnetic cores of Comparative Examples 1 to 3)
Three types of commercially available Ni-Zn ferrite sintered bodies (magnetic core materials 1 to 3) were used as the magnetic cores of the inductors of Comparative Examples 1 to 3, respectively. Specifically, the real components of the relative permeability at 1 MHz of the magnetic core materials 1 to 3 were 200, 260, and 550, respectively. In addition, each of the magnetic core materials 1 to 3 had a volume resistivity of 10 KΩ · cm or more. Cutting and polishing in the thickness direction were performed so that each of the magnetic core materials 1 to 3 had a flat plate shape of 15 mm in width, 11 mm in length, and 0.9 mm in thickness. As shown in FIG. 16, four via holes (that is, through holes) having a diameter of 0.8 mm were provided at predetermined positions of the flat plate-shaped sintered body by ultrasonic processing. As described above, the magnetic cores of Comparative Examples 1 to 3 were produced. Since the magnetic cores of Comparative Examples 1 to 3 were made of Ni—Zn ferrite, they had good high frequency characteristics.

(Production of conductor parts for coil of Example 1 and Comparative Examples 1 to 3)
As shown in FIG. 16, a cylindrical copper wire having a diameter of 0.8 mm and a length of 1.8 mm and having no insulating film was produced. The produced copper wire was used as a via conductor (that is, a through portion of the coil) to be inserted into the via hole. Moreover, the connection conductor of the coil was produced from the copper plate which has width 2mm and thickness 0.3mm, and does not have an insulating film. Specifically, the copper plate was cut so as to have a predetermined length. A hole having a diameter of 0.8 mm was formed by drill cutting at a predetermined position of the cut copper plate.

(Production of inductors of Example 1 and Comparative Examples 1 to 3)
As understood from FIGS. 16 and 17, a via conductor was inserted into the via hole of the magnetic core of Example 1. The connecting conductors were arranged above and below the magnetic core so that the holes of the connecting conductor overlapped with the via conductors. The magnetic core, via conductor and connecting conductor arranged as described above were sandwiched between two stainless steel plates. The via conductor and the connecting conductor were joined by applying a pressure of 15 kgf to the stainless steel plate. The joint portion of the via conductor with the connecting conductor was deformed by pressure. Specifically, the diameter of the joint portion of the via conductor was larger than the initial diameter of 0.8 mm. As shown in FIG. 17, the inductor of Example 1 was produced as described above. Similarly to the inductor of Example 1, inductors of Comparative Examples 1 to 3 were produced.

(Inductor characteristics of Example 1, Comparative Examples 1-3: Inductance)
For each of the inductors of Example 1 and Comparative Examples 1 to 3, the inductance of 1 MHz and the frequency characteristics of the inductance were measured. The 1 MHz inductance was measured using an LCR meter (HP4284A) manufactured by Agilent Technologies. The frequency characteristic of the inductance was measured using an impedance analyzer (4294A) manufactured by Agilent Technologies. As shown in FIG. 19, the inductor of Example 1 of the present invention has an inductance comparable to that of a Ni—Zn ferrite inductor. In addition, the inductor of Example 1 has no inductance reduction due to eddy current loss or the like up to about 4 MHz. Furthermore, even if it compares with any of the inductance of Comparative Examples 1-3 which has a favorable high frequency characteristic, it has a high inductance to high frequency more than equivalent.

(Inductor characteristics of Example 1 and Comparative Examples 1-3: Inductance with respect to bias current)
As shown in FIG. 20, the inductor of Example 1 of the present invention has a significantly superior inductance when the bias current is large, as compared with the inductors of Comparative Examples 1 to 3. For example, when the bias current is 5 A, the inductor of Example 1 has an inductance approximately twice that of the inductors of Comparative Examples 1 to 3. Since the magnetic core of the inductor of Example 1 is made of a metal powder having a saturation magnetic flux density higher than that of the Ni—Zn ferrite, it has a large inductance as described above. As can be understood from the above description, the inductor of the first embodiment is an inductor suitable for energizing a large current, in which the inductance does not easily decrease even when a large current is energized.

(Inductor characteristics of Example 1 and Comparative Examples 1 to 3: thermal conductivity)
Thermal conductivity was measured for each magnetic core of the inductors of Example 1 and Comparative Examples 1 to 3. The thermal conductivity was measured using FTC-1 manufactured by ULVAC-RIKO. The thermal conductivity of the magnetic core of Example 1 was 7.5 W / m · K. On the other hand, the thermal conductivity of the magnetic cores of Comparative Examples 1 to 3 was 3.5 to 4.5 W / m · K. Therefore, the thermal conductivity of the magnetic core of Example 1 was about twice that of the magnetic cores of Comparative Examples 1 to 3.

  As can be understood from the above description, the inductor according to the present invention has a higher strength than the conventionally used Ni-Zn ferrite, and the inductance is unlikely to decrease even when a large current is applied. Furthermore, it has a high thermal conductivity. Therefore, it can be used as an inductor of a module according to the various embodiments described above.

  Next, the magnetic cores and inductors of Example 2 and Comparative Examples 4 to 6 will be described.

(Preparation of preform for magnetic core of Example 2)
Soft magnetic metal powder was used as a material for the preform. More specifically, a gas atomized powder of Fe—Si—Al alloy (Sendust) was used. The powder had an average particle size (D50) of 55 μm. The powder was flattened using a ball mill. Specifically, the powder was subjected to a forging process for 8 hours and then subjected to a heat treatment at 700 ° C. for 3 hours in a nitrogen atmosphere to obtain a flat Sendust powder. Next, a slurry was prepared by mixing the sendend powder having a flat shape with a solvent, a thickener, and a thermosetting binder component. Ethanol was used as the solvent. A polyacrylic acid ester was used as the thickener. A methyl silicone resin was used as the thermosetting binder component. The slurry was applied on a PET (polyethylene terephthalate) film by a die slot method. Then, it dried at 60 degreeC for 1 hour, the solvent was removed, and this produced the preform.

(Preparation of flat plate for magnetic core of Example 2)
The preform was cut using a punching die to obtain a plurality of rectangular sheets having a width of 15 mm and a length of 11 mm. A predetermined number of sheets were stacked and placed in a mold. The sheet in the mold was subjected to pressure molding at a molding pressure of 20 kg / cm ² for 1 hour at a temperature of 150 ° C. The thickness of the molded body (ie, flat plate) after pressure molding was 0.9 mm.

(Preparation of magnetic core of Example 2)
As shown in FIG. 16, the magnetic core of the inductor of Example 2 was manufactured using the molded body after pressure molding. Specifically, four via holes (that is, through holes) having a diameter of 0.8 mm were provided at predetermined positions of the molded body by drill cutting. Next, the molded body was subjected to heat treatment at 600 ° C. for 1 hour in a nitrogen atmosphere, thereby producing a magnetic core. The produced magnetic core had a density of 4.9 g / cm ³ and a volume resistivity of 10 KΩ · cm or more. From the density of the magnetic core, the volume filling rate of the metal material (soft magnetic metal powder) in the magnetic core was determined. The volume filling rate of the metal material was about 67%.

(Production of inductor of Example 2)
As understood from FIGS. 16 and 17, a via conductor was inserted into the via hole of the magnetic core of Example 2. As the via conductor, as in Example 1, a copper wire having no insulating coating was used. The connecting conductors were arranged above and below the magnetic core so that the holes of the connecting conductor overlapped with the via conductors. As a connection conductor, the copper plate which does not have an insulating film similarly to Example 1 was used. The magnetic core, via conductor and connecting conductor arranged as described above were sandwiched between two stainless steel plates. The via conductor and the connecting conductor were joined by applying a pressure of 15 kgf to the stainless steel plate. The joint portion of the via conductor with the connecting conductor was deformed by pressure. Specifically, the diameter of the joint portion of the via conductor was larger than the initial diameter of 0.8 mm. The inductor manufactured as described above was heat-treated at 650 ° C. for 1 hour in a nitrogen atmosphere. As a result of the heat treatment, the joint portion between the via conductor and the connecting conductor was diffusion-bonded, thereby reducing the electrical resistance at the joint portion. As shown in FIG. 17, the inductor of Example 2 was manufactured as described above.

(Production of Inductors of Comparative Examples 4 to 6)
From the inductors of comparative examples 1 to 3, inductors of comparative examples 4 to 6 were respectively produced. Specifically, in the same manner as the inductor of Example 2, the inductors of Comparative Examples 1 to 3 were subjected to heat treatment at 650 ° C. for 1 hour in a nitrogen atmosphere, thereby producing the inductors of Comparative Examples 4 to 6, respectively.

  Table 3 shows the rate of occurrence of breakage when the inductor was manufactured.

(Measurement of characteristics of inductors of Example 2 and Comparative Examples 4 to 6)
For each of the inductors of Example 2 and Comparative Examples 4 to 6, an inductance of 1 MHz and frequency characteristics of the inductance were measured. The 1 MHz inductance was measured using an LCR meter (HP4284A) manufactured by Agilent Technologies. The frequency characteristic of the inductance was measured using an impedance analyzer (4294A) manufactured by Agilent Technologies.

(Inductor characteristics of Example 2 and Comparative Examples 4 to 6: Inductance)
As shown in FIG. 21, the inductor of Example 2 of the present invention has an inductance comparable to that of a Ni—Zn ferrite inductor. In addition, the inductor of Example 2 has no inductance reduction due to eddy current loss or the like up to about 1 MHz. Furthermore, even if it compares with any of the inductance of Comparative Examples 4-6 which has a favorable high frequency characteristic, it has a high inductance to high frequency more than equivalent. Further, from the measurement result of Example 2, the coil part is not short-circuited even when heat treatment is performed at a high temperature in a state where the coil part formed of the via conductor and the connecting conductor and the magnetic core of Example 2 are in close contact with each other. I understand that.

  Table 4 shows the inductance of the inductor when the bias current is 5A.

(Inductor characteristics of Example 2 and Comparative Examples 4 to 6: Inductance with respect to bias current)
As shown in FIG. 22 and Table 4, the inductor of Example 2 of the present invention has a larger bias current than the inductors of Comparative Examples 4 to 6 (inductors using Ni—Zn ferrite cores). It can be seen that the inductance is significantly superior. Specifically, for example, when the bias current is 5 A, the inductance value is approximately twice as large as that of the inductors of Comparative Examples 4 to 6. This is because a metal powder having a higher saturation magnetic flux density than that of Ni—Zn ferrite is used as the magnetic core material. It can be seen that the inductor having the configuration of the second embodiment of the present invention is an inductor suitable for large current application, in which the inductance does not easily decrease even when a large current is applied.

  Next, the magnetic core and inductor of Example 3 and Example 4 will be described.

(Preparation of powder for magnetic core of Example 3 and Example 4)
Soft magnetic metal powder was used as a material for the preform. More specifically, a gas atomized powder of Fe—Si—Al alloy (Sendust) was used. The powder had an average particle size (D50) of 55 μm. The powder was flattened using a ball mill. Specifically, the powder was subjected to a forging process for 8 hours and then subjected to a heat treatment at 700 ° C. for 3 hours in a nitrogen atmosphere to obtain a flat Sendust powder. The average major axis (Da), average maximum thickness (ta) and average aspect ratio (Da / ta) of the prepared powder (flat metal powder) were measured. Specifically, a flat metal powder was impregnated with a resin and cured to prepare a cured body. Next, the cured body was polished. Next, the shape of the flat metal powder located on the polished surface was observed using a scanning electron microscope. Specifically, for 30 flat metal powders, the major axis (D) and the thickness (t) of the thickest part were measured, and the aspect ratio (D / t) was calculated. The obtained aspect ratio (D / t) was averaged to obtain an average aspect ratio (Da / ta). The average long diameter (Da) of the flat metal powder was 60 μm, and the average maximum thickness (ta) was 3 μm. The average aspect ratio (Da / ta) was 20.
(Preparation of preform for magnetic core of Example 3 and Example 4)
Next, a slurry was prepared by mixing the sendend powder having a flat shape with a solvent, a thickener, and a thermosetting binder component. Ethanol was used as the solvent. A polyacrylic acid ester was used as the thickener. A methyl silicone resin was used as the thermosetting binder component. The slurry was applied on a PET (polyethylene terephthalate) film by a die slot method. Then, it dried at 60 degreeC for 1 hour, the solvent was removed, and this produced the preform.

(Preparation of flat plate for magnetic core of Example 3)
The preform was cut using a punching die to obtain a plurality of rectangular sheets having a width of 15 mm and a length of 11 mm. A predetermined number of sheets were stacked and placed in a mold. The sheet in the mold was subjected to pressure molding at a molding pressure of 2 MPa for 1 hour at a temperature of 150 ° C. The thickness of the molded body (ie, flat plate) after pressure molding was 0.9 mm.

(Preparation of magnetic core of Example 3)
As shown in FIG. 16, the magnetic core of the inductor of Example 3 was manufactured using the molded body after pressure molding. Specifically, four via holes (that is, through holes) having a diameter of 0.8 mm were provided at predetermined positions of the molded body by drill cutting. Next, the molded body was subjected to heat treatment at 650 ° C. for 1 hour in a nitrogen atmosphere, thereby producing a magnetic core. The produced magnetic core had a density of 4.9 g / cm ³ and a volume resistivity of 10 KΩ · cm or more. From the density of the magnetic core, the volume filling rate of the metal material (soft magnetic metal powder) in the magnetic core was determined. The volume filling rate of the metal material was about 67%. Further, the volume filling rate of the post-curing component of the methyl-based silicone resin (that is, the binder component composed of a vitreous containing silicon oxide as a main component) was about 18%, and the porosity was about 15%. The thickener was almost completely pyrolyzed by the heat treatment and did not remain in the magnetic core.

(Production of inductor of Example 3)
As shown in FIGS. 16 and 17, the inductor of Example 3 was manufactured in the same manner as the inductors of Example 1 and Example 2.

(Preparation of magnetic core of Example 4)
The preform was cut using a punching die to obtain a plurality of rectangular sheets having a width of 15 mm and a length of 11 mm. A predetermined number of sheets were stacked and placed in a mold. The sheet in the mold was subjected to pressure molding at a molding pressure of 2 MPa for 1 hour at a temperature of 150 ° C. The thickness of the molded body (ie, flat plate) after pressure molding was 0.9 mm. Next, the molded body was subjected to heat treatment at 650 ° C. for 1 hour in a nitrogen atmosphere to produce the magnetic core of Example 4.

(Production of Inductor of Example 4)
As shown in FIG. 18A, a prepreg having a thickness of 0.3 mm was prepared. A rectangular hole having a width of 15 mm and a length of 11 mm was formed in the prepreg. Three prepregs were stacked to produce a prepreg having a thickness of 0.9 mm. The magnetic core of Example 4 was arrange | positioned inside the hole of a prepreg. As shown in FIG. 18B, a resin substrate having a thickness of 0.5 mm was prepared. The resin board is a single-sided copper foil board. Specifically, a copper foil conductor pattern was formed on one surface of the resin substrate. Two resin substrates were arranged above and below the prepreg and the magnetic core, respectively, so that the conductor pattern was positioned on the upper surface and the lower surface, to produce a laminate. Next, the laminate was subjected to pressure molding at a molding pressure of 3 MPa for 1 hour at a temperature of 180 ° C. The inductor of Example 4 was manufactured using the laminated body after pressurization. Specifically, four via holes (that is, through holes) having a diameter of 0.8 mm were provided by drill cutting at a predetermined position (see FIG. 16) of the laminate. A copper via conductor having a diameter of 0.8 mm was inserted into the via hole. The via conductor and the conductor pattern of the resin substrate were joined by soldering, whereby the inductance of Example 4 was produced. As understood from the above description, the magnetic core of the inductance of Example 4 was disposed inside the laminated resin substrate including the prepreg.

(Measurement of Inductor Characteristics of Example 3 and Example 4)
For each of the inductors of Examples 3 and 4, the 1 MHz inductance and the frequency characteristics of the inductance were measured. The 1 MHz inductance was measured using an LCR meter (HP4284A) manufactured by Agilent Technologies. The frequency characteristic of the inductance was measured using an impedance analyzer (4294A) manufactured by Agilent Technologies.

(Inductor characteristics of Example 4 and Comparative Examples 1-3: Inductance)
As shown in FIG. 23, the inductor of Example 4 of the present invention has an inductance comparable to that of a Ni—Zn ferrite inductor. Further, in the inductor of the fourth embodiment, the inductance is not reduced by eddy current loss or the like up to about 1 MHz. Furthermore, even if it compares with any of the inductance of Comparative Examples 1-3 which has a favorable high frequency characteristic, it has a high inductance to high frequency more than equivalent.

(Inductor characteristics of Example 4 and Comparative Examples 1 to 3: Inductance with respect to bias current)
As shown in FIG. 24, the inductor of Example 4 of the present invention is obtained when the bias current is increased as compared with the inductors of Comparative Examples 1 to 3 (inductors using Ni-Zn ferrite cores). It can be seen that the inductance is remarkably excellent. Specifically, for example, when the bias current is 5 A, the value of the inductance is approximately twice that of the inductors of Comparative Examples 1 to 3. This is because a metal powder having a higher saturation magnetic flux density than that of Ni—Zn ferrite is used as the magnetic core material. It can be seen that the inductor having the configuration of Example 4 of the present invention is an inductor suitable for large current application, in which the inductance does not easily decrease even when a large current is applied.

(Characteristics of Inductor of Example 3 and Example 4)
Further, as shown in FIGS. 23 and 24, the inductor of the fourth embodiment is almost the same as the inductor of the third embodiment although the magnetic core is built in the laminated resin substrate unlike the inductor of the third embodiment. Have the same magnetic properties. That is, the magnetic core according to the present invention is not damaged by the pressurization when sandwiched between the substrates, and excellent magnetic properties are maintained even after being sandwiched between the substrates.

  As mentioned above, although the Example of this invention was described, organic binders, such as a thickener and a thermosetting binder component, are not limited to the Example mentioned above. A specific organic binder may be appropriately selected according to the soft magnetic metal powder. Further, the amount of the organic binder added may be appropriately adjusted according to the soft magnetic metal powder. For example, by adjusting the addition amount of the thermosetting binder component in proportion to the surface area of the soft magnetic metal powder, a suitable result similar to the above-described example can be obtained.

  Moreover, in the Example and the comparative example mentioned above, although the conductor which does not have an insulating film was used as a coil part, you may use the conductor which has an insulating film in a predetermined | prescribed site | part, for example. Further, when the via conductor and the connecting conductor are joined together by applying pressure, fusing or current pulse energization may be performed simultaneously to promote joining. Further, the diffusion bonding of the bonded portion by heat treatment may not be performed. On the other hand, if necessary, diffusion bonding may be promoted by interposing metal powder nanoparticles in the joint.

10, 10A, 10B module (power supply module)
200, 200B Circuit board 210 Side wall part 220 Opposite surface 230 Opposite surface 240 Electronic component 250 Connection end 260 Terminal 300, 300A, 300X Inductor 310, 310A, 310X Magnetic core 312 Soft magnetic metal powder (soft magnetic metal material)
314 Binder (insulating material)
314X Binder component 318X Hole 320 Opposing surface 330 Heat radiation surface 340 Through hole 342 Inner wall 346, 346X Holding hole 350 Coil 360 Coil portion 362 Through portion (via conductor)
364 1st connection part (connection conductor)
366 Second connecting part (connecting conductor)
370 Connection portion 372 Connection end 400 Heat radiation member 410 Holding hole 500 Connection member 600 Coating 800 External circuit board 810 Cooling member 820X Spacer 822X Main body portion 824X Holding portion

Claims (18)

A magnetic core in which a soft magnetic metal powder having a flat shape is bound by a binder component, and a magnetic core having elasticity,
60% by volume or more of the soft magnetic metal powder and 10% by volume or more and 25% by volume or less of pores,
The binder component is a magnetic core mainly composed of silicon oxide. The magnetic core according to claim 1,
A magnetic core having a rubber hardness of 92 or more and 96 or less according to ISO 7619-type D. The magnetic core according to claim 1 or 2, wherein
A magnetic core having a Young's modulus of 10 GPa or more and 90 Gpa or less. The magnetic core according to claim 3,
A magnetic core having a Young's modulus of 20 GPa or more and 50 GPa or less. A magnetic core according to any one of claims 1 to 4,
A magnetic core having an electrical resistivity of 10 KΩ · cm or more. A magnetic core according to any one of claims 1 to 5,
A magnetic core whose real component of relative permeability at a frequency of 1 MHz is 100 or more. A magnetic core according to any one of claims 1 to 6,
The soft magnetic metal powder is a magnetic core made of an Fe-based alloy. A magnetic core according to any one of claims 1 to 6,
The soft magnetic metal powder is a magnetic core made of an Fe-Si alloy. A magnetic core according to any one of claims 1 to 6,
The soft magnetic metal powder is a magnetic core made of an Fe-Si-Al alloy or an Fe-Si-Cr alloy. A magnetic core according to any one of claims 1 to 9,
It has a flat plate shape
The magnetic core whose thickness of the flat plate shape is 1 mm or less. A magnetic core comprising a plurality of magnetic cores according to claim 10 as a magnetic core component,
A magnetic core in which a plurality of the magnetic core components are laminated via an adhesive. A magnetic core according to any one of claims 1 to 11,
At least part of the surface is covered with insulating resin,
A magnetic core in which a part of the insulating resin is impregnated in a surface layer of the magnetic core. A magnetic core according to any one of claims 1 to 12,
A magnetic core having a saturation magnetic flux density of 0.5 T or more. An inductor comprising the magnetic core according to any one of claims 1 to 13 and a coil,
The coil is an inductor having a coil portion and a connection end. The inductor according to claim 14, wherein
A through hole is formed in the magnetic core,
The coil part of the coil has a penetration part,
The through portion is an inductor penetrating the through hole. The inductor according to claim 15, wherein
A plurality of the through holes are formed in the magnetic core,
The coil portion of the coil has a plurality of the through portions and a connecting conductor,
The penetrating portion penetrates the through hole,
The connecting conductor is attached to the magnetic core so as to connect the end of the penetrating portion on the upper surface or the lower surface of the magnetic core,
The thickness of the magnetic core after the connection conductor is attached to the magnetic core is 2.5% or more and 5.0 compared to the thickness of the magnetic core before the connection conductor is attached to the magnetic core. % Or less,
When the coil part is removed from the magnetic core, the thickness of the magnetic core recovers to approach the thickness before the connection conductor is attached to the magnetic core. An inductor according to claim 15 or claim 16,
The through portion of the coil penetrates the through hole so as to elastically deform the inner wall of the through hole, and the coil is held by a pressing force applied to the through portion by the inner wall of the through hole. Inductor that is. An inductor according to any one of claims 14 to 17,
The coil is an inductor having no insulation coating.