JP5346866B2 - Magnetic substrate and electronic circuit module - Google Patents

Description

  The present invention relates to a magnetic substrate and an electronic circuit module including the same.

  Conventionally, a magnetic substrate that uses a magnetic material formed in a plate shape as a wiring substrate is, for example, as disclosed in Patent Document 1, a part of a terminal electrode that constitutes an electrical wiring is embedded and fixed inside the magnetic material There is. In this type of magnetic substrate, it is conceivable that the wiring pattern of the terminal electrode is made of copper foil. However, the accuracy of the wiring pattern may be reduced when the magnetic substrate is mass-produced with copper foil. Therefore, a lead frame obtained by processing a conductive plate material is often used.

Japanese Patent Laid-Open No. 2003-188023

  In the conventional magnetic substrate in which the terminal electrode is embedded in the magnetic body, the terminal electrode can be fixed to the magnetic body, but the thickness dimension becomes large, so there is a limit to the thinning of the magnetic substrate. There is a problem that it occurs. In order to reduce the thickness of the magnetic substrate, for example, it may be possible to expose the entire electrical wiring such as terminal electrodes on the main surface of the plate-shaped magnetic body. When it comprises, there exists a problem that a lead tends to peel from the main surface of a magnetic body.

As a conventional method for improving the adhesion of the lead, the lead surface is roughened in advance before molding the magnetic body (see, for example, Japanese Patent Application Laid-Open No. 2002-299538), or dimples (concave) on the lead. (For example, refer to Japanese Patent Application Laid-Open No. 2009-260282) or an anchor hole penetrating in the thickness direction in the lead can be considered.
However, since the plate-like magnetic body is obtained by compression molding of magnetic powder, even if the lead surface is roughened before molding the magnetic body, the state of the lead surface changes depending on the pressure during compression molding of the magnetic powder. As a result, sufficient adhesion between the lead and the magnetic material cannot be obtained.

  On the other hand, when dimples or anchor holes are formed in the lead, the volume of the lead itself is reduced, so that there is a problem that the electrical resistance of the magnetic substrate as electrical wiring increases. In addition, since the thermal resistance of the lead increases as the volume decreases, electronic components that generate heat during operation, such as IC / LSI for power supply circuits and LEDs, are mounted on the main surface of the magnetic substrate. In such a case, the heat of the electronic component cannot be efficiently transferred to the lead frame, resulting in a problem that the heat dissipation of the magnetic substrate is lowered.

  The present invention has been made in view of the above-described circumstances, and it is possible to improve the adhesion between a magnetic body and a lead while preventing an increase in electrical resistance of the lead and a decrease in heat dissipation of the magnetic substrate. An object of the present invention is to provide a magnetic substrate and an electronic circuit module including the same.

In order to solve this problem, a magnetic substrate of the present invention includes a plate-like magnetic body and a lead made of a conductive plate, and an upper surface of the lead facing in the thickness direction of the magnetic body The lead is sealed with the magnetic body so as to be exposed from the upper surface, and a separate protruding member protruding from the lower surface is fixed to the lower surface of the lead covered with the magnetic body. The protruding member is made of a magnetic material forming the magnetic body .
The lead is a constituent element of a lead frame obtained by subjecting a conductive plate material to press processing, etching processing, and the like, and its shape and size in plan view are arbitrary.

Furthermore, the electronic circuit module of the present invention includes the magnetic substrate and an electronic component mounted on the upper surface of the magnetic substrate so as to be in contact with the leads.
Specific examples of electronic components include various semiconductor elements such as IC / LSI for power supply circuits and LEDs.

According to the magnetic substrate and the electronic circuit module, since the protruding member is fixed to the lower surface of the lead, the substantial contact area between the lead and the magnetic body is increased, and the protruding member is embedded in the magnetic body. As a result, an anchor effect can be obtained, so that the adhesion between the magnetic body and the lead can be improved.
Furthermore, since the protruding member is formed separately from the lead, the volume of the lead itself does not decrease as in the conventional case. Therefore, when the lead functions as the electric wiring of the magnetic substrate, the electric resistance of the lead Can be prevented. In addition, since the increase in the thermal resistance of the lead due to the decrease in volume can be prevented, when the electronic component is mounted on the top surface of the magnetic substrate so as to contact the lead, the heat generated in the electronic component is efficiently transferred to the lead. Can communicate well. That is, it is possible to prevent a decrease in heat dissipation of the magnetic substrate.

Further, since the projecting member can improve the adhesion between the magnetic body and the lead, it is not necessary to separately fix the lead to the magnetic body with an adhesive. That is, since an adhesive having a high thermal resistance is not interposed between the magnetic body and the lead, the heat generated in the electronic component can be efficiently released from the lead to the magnetic body side. For example, in a state where the electronic circuit module is mounted on the mounting board so that the lower surface of the magnetic body faces the mounting surface of the mounting board, the heat generated in the electronic component is efficiently transferred to the mounting board via the leads and the magnetic body. I can escape.
Furthermore, with this configuration, it is possible to prevent the magnetic material from damaging its characteristics. For example, when the magnetic substrate functions as an inductor as described above, the magnetic flux generated in the magnetic body by the coil is disturbed by the protruding member arranged inside the magnetic body or leaks to the outside of the magnetic body. Can be prevented.

Further, in the magnetic substrate, an engagement projecting laterally of the projecting member at the distal end portion of the projecting member and positioned at an interval in the thickness direction with respect to the lower surface of the lead. It is preferable that protrusions are formed.
In this configuration, since the magnetic body enters between the lower surface of the lead and the engaging protrusion, the magnetic body and the lead can be reliably engaged in the thickness direction by the engaging protrusion. Therefore, the adhesion between the magnetic body and the lead can be further improved.

Furthermore, the magnetic substrate may be configured as an inductor by embedding a coil inside the magnetic body.
In this configuration, the magnetic substrate itself functions as an inductor, and the magnetic substrate can be configured as a power supply circuit for the electronic component. Therefore, compared to the case where a separate inductor is mounted on the magnetic substrate together with the electronic component, the magnetic substrate Can be miniaturized.

  According to the present invention, by fixing a separate protruding member to the lower surface of the lead covered with the magnetic body in the lead frame, the electrical resistance of the lead constituting the electrical wiring is increased and the heat dissipation of the magnetic substrate is improved. While preventing the deterioration, it is possible to improve the adhesion between the magnetic body and the lead.

It is a schematic plan view which shows the state which looked at the electronic circuit module which concerns on one Embodiment of this invention from the upper surface of the magnetic body board | substrate. It is AA arrow sectional drawing of the electronic circuit module shown in FIG. It is a BB arrow sectional view of the electronic circuit module shown in FIG. It is a schematic sectional drawing which shows a press molding process among the methods of manufacturing the electronic circuit module shown in FIGS. FIG. 5 is a schematic plan view showing a state after the pressure forming step shown in FIG. 4 as viewed from the upper surface side of the magnetic body. It is a schematic sectional drawing which shows the state after implementing a curing process and a cutting process among the methods of manufacturing the electronic circuit module shown in FIGS.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 to 3, the electronic circuit module 1 according to this embodiment includes a magnetic substrate 2 and a semiconductor element (electronic component) 3 mounted on the upper surface 2 a of the magnetic substrate 2. Has been.
The magnetic substrate 2 has a plate-like magnetic body 4 having electrical insulation, a plurality of leads 22 and 23 disposed on the surface of the magnetic body 4, and a coil embedded in the magnetic body 4 The magnetic body 4 and the coil 5 constitute an inductor. In this configuration, the magnetic body 4 is used to obtain a large magnetic flux density from the magnetic field generated by the coil 5, and it is preferable to select a material having a high magnetic permeability. Note that both ends of the coil 5 are electrically connected to separate leads 22 that form electric wiring of the magnetic substrate 2.

Each of the leads 22 and 23 is formed of a conductive material such as a copper material in a sufficiently thin plate shape as compared with the thickness of the magnetic body. The respective leads 22 and 23 are bent on the flat plate portions 24 and 25 disposed on the upper surface 4a side of the magnetic member 4 forming the upper surface 2a of the magnetic substrate 2 and the flat plate portions 24 and 25, whereby the magnetic member 4 The extension plate portions 26 and 27 arranged on the side surface 4c are roughly configured.
The flat plate portions 24 and 25 of the leads 22 and 23 are sealed with the magnetic body 4 on the upper surface 4 a side of the magnetic body 4. More specifically, the upper surface 24a, 25a of the flat plate portions 24, 25 of each lead 22, 23 facing the thickness direction of the lead 22 is flush with the upper surface 4a of the magnetic body 4. The lower surfaces 24 b and 25 b and the side surfaces 24 c and 25 c of the leads 22 and 23 are covered with the magnetic body 4.
On the other hand, tip portions in the extending direction extending from the flat plate portions 24 and 25 side of the extension plate portions 26 and 27 of the leads 22 and 23 are bent and arranged so as to protrude from the side surface 4c of the magnetic body 4, and are thus provided. 3 and the coil 5 function as external terminals for connecting to the outside. In addition, this front-end | tip part is distribute | arranged so that the lower surface 4b of the magnetic body 4 may become the same plane, and, thereby, the magnetic body board | substrate 2 is comprised as a surface mount type board | substrate.

The plurality of leads 22 and 23 are mainly intended to efficiently release the heat generated in the semiconductor elements 3 and the plurality of first leads 22 mainly intended for the electrical wiring of the magnetic substrate 2. The second lead 23 is roughly divided into two types.
Each first lead 22 is formed in an elongated strip shape. In the illustrated example, one first lead 22 is configured by providing a pair of extension plate portions 26 at both ends of the flat plate portion 24, and the remaining (two) first leads 22 include the flat plate portion 24 and the extension plate portion 26. Are provided one by one. Further, the flat plate portion 24 of each first lead 22 in the illustrated example is formed in a straight line shape in plan view, but in plan view so as to form a wiring pattern suitable for electrical connection with the semiconductor element 3 and the coil 5. An arbitrary shape such as a linear shape and a bent shape may be appropriately combined.

On the other hand, the second lead 23 is formed in a plate shape wider than the first lead 22 so that the contact area with the semiconductor element 3 is large, and the flat plate portion 25 is configured as a die pad for mounting the semiconductor element 3. Has been. The second lead 23 may be electrically connected to the semiconductor element 3 similarly to the first lead 22, but may not be electrically connected. In addition, the second lead 23 in the illustrated example is configured by providing a pair of extension plate portions 27 at both ends of the flat plate portion 25. For example, as with some first leads 22, one end of the flat plate portion 25 is provided. Alternatively, only one extension plate portion 27 may be provided.
The semiconductor element 3 is an LSI, IC, or the like that constitutes a power supply circuit together with an inductor, and is mounted on the upper surface 2a of the magnetic substrate 2 so as to contact the plurality of leads 22 and 23 described above.

A separate projecting member 30 projecting from the lower surface 25 b in the thickness direction of the second lead 23 is fixed to the lower surface 25 b of the flat plate portion 25 of the second lead 23.
The projecting member 30 is made of the same magnetic material as that of the magnetic body 4, and an engaging projection 31 projecting to the side of the projecting member 30 is formed at the distal end of the projecting member 30 in the projecting direction. The engaging protrusions 31 are located at a distance from the lower surface 25 b of the flat plate portion 25 of the second lead 23 in the thickness direction of the second lead 23. In addition, although the engagement protrusion 31 may be formed only in a part of the circumferential direction of the protruding member 30, it may be formed in an annular shape over the entire circumferential direction of the protruding member 30, for example. In addition, a plurality of engagement protrusions 31 may be arranged in the circumferential direction of the protruding member 30, for example.

Further, the projecting member 30 is formed with a wide base end portion in the projecting direction so that a contact area with the lower surface 25b of the second lead 23 is widened. The projecting member 30 is disposed at the center of the lower surface 25b of the flat plate portion 25 of the second lead 23, and is further positioned so as to overlap the central axis of the coil 5 in plan view. The fixing of the protruding member 30 and the second lead 23 may be performed by an adhesive or solder, or may be performed by various types of welding such as ultrasonic welding.
In the illustrated example, only one protruding member 30 is fixed to the lower surface 25b of the flat plate portion 25 of the second lead 23. However, for example, a plurality of protruding members 30 may be fixed. Here, only the fixing of the protruding member 30 to the lower surface 25b of the flat plate portion 25 of the second lead 23 has been described, but the same protruding member 30 is also provided on the lower surface 24b of the flat plate portion 24 of each first lead 22. It is fixed.

Next, a method for manufacturing the electronic circuit module 1 having the above configuration will be described.
When manufacturing the electronic circuit module 1, first, as shown in FIG. 5, a lead frame 20 is prepared by subjecting a conductive plate made of a copper material or the like to pressing or etching (preparation step).
The lead frame 20 includes a pair of connecting portions 21 arranged in parallel with a space between each other, and a plurality of leads protruding integrally from each connecting portion 21 so as to extend from one of the pair of connecting portions 21 to the other. 22. In the illustrated example, the pair of connecting portions 21 seem not to be connected to each other, but are actually connected integrally at the ends of the connecting portions 21 in the longitudinal direction (up and down direction on the paper surface).
In this lead frame, the first lead 22 and the second lead 23 of the plurality of leads 22 and 23 are connected to both the pair of connecting portions 21, and the first lead 22 and the second lead 23 are connected to each other. Intermediate portions in the extending direction are flat plate portions 24 and 25. On the other hand, the remaining (two) first leads 22 are connected to only one connecting portion 21, and the leading end portion in the extending direction of these first leads 22 is a flat plate portion 24.

After the preparation step, the protruding member 30 is fixed to the lower surfaces 24b and 25b of the flat plate portions 24 and 25 of the leads 22 and 23 (fixing step), and then, as shown in FIG. A pressure molding process is performed in which the magnetic powder 14 coated with (binder) is compressed into a plate-like magnetic body 4.
In this process, first, the lead frame 20 is placed upside down on the placement surface M1 of the compression mold M. Further, the flat plate portions 24 and 25 of the leads 22 and 23 of the lead frame 20 are accommodated in the cavity C of the compression molding die M, and the remaining portions of the lead frame 20 (extension plate portions 26 and 26 of the leads 22 and 23 are arranged). 27 and the connecting part 21) are fixed outside the cavity C.

Next, the magnetic powder 14 is placed in the cavity C so as to cover the lower surfaces 24b and 25b and the side surfaces 24c and 25c of the flat plate portions 24 and 25 of the leads 22 and 23 with the magnetic powder 14 and to embed the protruding member 30. The lead frame 20 and the magnetic powder 14 are stacked in the thickness direction of the lead frame 20. Further, the coil 5 is embedded in the magnetic powder 14 at the same time as before or after filling the magnetic powder 14. In this state, by compressing the magnetic powder 14 from the thickness direction of the lead frame 20, the magnetic powder 14 is formed into the plate-like magnetic body 4.
In the state where the pressure forming step is completed, as shown in FIG. 5, the flat plate portions 24 and 25 of the leads 22 and 23 are fixed to the upper surface 4 a side of the magnetic body 4, and The extension plate portions 26 and 27 are arranged so as to protrude from the side surface 4 c of the magnetic body 4.

After the pressure forming step, the magnetic body 4 is heated to completely integrate the resin of the magnetic powder 14 (curing step), and then the connecting portion 21 is cut off from the lead frame 20 to thereby form a plurality of leads 22. , 23 are electrically separated (cutting step).
Further, as shown in FIG. 6, the extension plates 26 and 27 of the leads 22 and 23 protruding from the side surface 4 c of the magnetic body 4 are bent so as to lie over the side surface 4 c of the magnetic body 4. The magnetic substrate 2 is manufactured by bending the tip portions of 26 and 27 so as to protrude from the side surface 4c of the magnetic body 4 (lead forming process).
Finally, mounting the semiconductor element 3 on the upper surface 2a of the magnetic substrate 2 completes the manufacture of the electronic circuit module 1 shown in FIGS. The mounting of the semiconductor element 3 is not limited to the completion of the manufacture of the magnetic substrate 2 and can be performed at least after the curing step.

  As described above, according to the electronic circuit module 1 and the magnetic substrate 2 provided for the electronic circuit module 1 according to the present embodiment, the protruding member 30 is fixed to the lower surfaces 24b, 25b of the flat plate portions 24, 25 of the leads 22, 23. As a result, the substantial contact area between the magnetic body 4 and each of the leads 22 and 23 can be increased, and an anchor effect can be obtained by embedding the protruding member 30 in the magnetic body 4. And the leads 22 and 23 can be improved in adhesion.

  Furthermore, since the projecting member 30 is formed separately from the leads 22 and 23, the volume of the leads 22 and 23 itself does not decrease as in the prior art, so the leads 22 and 23 (particularly the first lead 22). When the electric wiring of the magnetic substrate 2 is made, an increase in the electric resistance of the leads 22 and 23 can be prevented. In addition, since the increase in the thermal resistance of the leads 22 and 23 due to the volume decrease can be prevented, the semiconductor element 3 is mounted on the upper surface 2a of the magnetic substrate 2 so as to be in contact with the leads 22 and 23. Heat generated in the semiconductor element 3 can be efficiently transferred to the leads 22 and 23. That is, it is possible to prevent the heat dissipation of the magnetic substrate 2 from being lowered.

  Further, since the adhesion between the magnetic body 4 and the leads 22 and 23 can be improved by the protruding member 30, it is not necessary to fix the leads 22 and 23 to the magnetic body 4 separately by an adhesive. That is, since no adhesive having a high thermal resistance is interposed between the magnetic body 4 and the leads 22 and 23, heat generated in the semiconductor element 3 can be efficiently released from the leads 22 and 23 to the magnetic body 4 side. . For example, in a state in which the electronic circuit module 1 is mounted on the mounting substrate so that the lower surface 4b of the magnetic body 4 faces the mounting surface of the mounting substrate, the heat generated in the semiconductor element 3 is converted to the leads 22 and 23 and the magnetic body 4. Can be efficiently released to the mounting substrate. In the present embodiment, since the contact area between the second lead 23 and the semiconductor element 3 is increased by forming the second lead 23 wide, the heat of the semiconductor element 3 is released particularly efficiently. Can do.

In addition, since the engaging protrusion 31 is formed at the tip of the protruding member 30, the magnetic body 4 enters between the lower surfaces 24 b and 25 b of the leads 22 and 23 and the engaging protrusion 31. Thus, the magnetic body 4 and the leads 22 and 23 can be reliably engaged in the thickness direction. Therefore, the adhesion between the magnetic body 4 and the leads 22 and 23 can be further improved.
Furthermore, since the magnetic substrate 2 is configured as an inductor, the magnetic substrate 2 can be configured as a power supply circuit together with the semiconductor element 3, so that a comparison with a case where a separate inductor is mounted on the magnetic substrate 2 together with the semiconductor element 3. Thus, the magnetic substrate 2 can be reduced in size.
Further, since the protruding member 30 is made of the same magnetic material as that of the magnetic body, it is possible to prevent the magnetic body 4 from damaging its characteristics. That is, in the magnetic substrate 2 of the present embodiment that functions as an inductor, the magnetic flux generated in the magnetic body 4 by the coil 5 is disturbed by the protruding member 30 disposed inside the magnetic body 4, or outside the magnetic body 4. Leakage can be prevented.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the engagement protrusion 31 may not be particularly formed on the protruding member 30. Even in this case, since the substantial contact area between the magnetic body 4 and each of the leads 22 and 23 is increased by the projecting member 30 and the anchor effect is obtained as in the above embodiment, the magnetic body 4 and the leads 22 and 23 are also obtained. It is possible to improve the adhesiveness to 23.

Further, the flat plate portions 24 and 25 of the leads 22 and 23 are covered with the magnetic body 4 so that only the upper surfaces 24a and 25a thereof are exposed, but at least the lower surfaces 24b of the flat plate portions 24 and 25 are exposed. , 25b may be covered with the magnetic body 4. That is, the flat plate portions 24 and 25 of the respective leads 22 and 23 are not limited to be arranged in the same plane as the upper surface 4a of the magnetic body 4, but are arranged so as to protrude from the upper surface 4a of the magnetic body 4, for example. May be.
Further, the tip portions of the extension plates 26 and 27 of the leads 22 and 23 are arranged so as to protrude from the side surface 4c of the magnetic body 4, but at least as long as they are arranged so as to be connected to the outside. For example, it may be arranged on the lower surface 4 b of the magnetic body 4. The leads 22 and 23 may not be disposed on the side surface 4c of the magnetic body 4, and may be disposed only on the upper surface 4a side of the magnetic body 4, for example.

Further, the semiconductor element 3 that constitutes the power supply circuit together with the magnetic substrate 2 that is an inductor is mounted on the upper surface 2a of the magnetic substrate 2, but at least electronic components that constitute various electronic circuits are mounted. For example, another semiconductor element 3 such as an LED element may be mounted.
Furthermore, not only one semiconductor element 3 is mounted on the upper surface 2a of the magnetic substrate 2, but a plurality of semiconductor elements 3 may be mounted, for example.

DESCRIPTION OF SYMBOLS 1 Electronic circuit module 2 Magnetic substrate 2a Upper surface 3 Semiconductor element (electronic component)
4 Magnetic body 4a Upper surface 5 Coil 22 First lead (lead)
23 Second lead (lead)
24, 25 Flat plate portions 24a, 25a Upper surface 24b, 25b Lower surface 24c, 25c Side surface 30 Projection member 31 Engagement projection

Claims (4)

A plate-like magnetic body and a lead made of a conductive plate material are provided, and the lead is sealed to the magnetic body so that an upper surface facing the thickness direction of the lead is exposed from the upper surface of the magnetic body A magnetic substrate comprising:
A separate protruding member protruding from the lower surface is fixed to the lower surface of the lead covered with the magnetic body ,
The magnetic substrate, wherein the protruding member is made of a magnetic material forming the magnetic body.   An engaging protrusion is formed at the tip end of the protruding member in the protruding direction and protrudes laterally of the protruding member and is spaced from the lower surface of the lead in the thickness direction. The magnetic substrate according to claim 1.   3. The magnetic substrate according to claim 1, wherein a coil is embedded in the magnetic body to be configured as an inductor. 4. 4. An electronic circuit module comprising: the magnetic substrate according to claim 1 ; and an electronic component mounted on an upper surface of the magnetic substrate so as to contact the lead. .

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