WO2011046090A1

WO2011046090A1 - Magnet device

Info

Publication number: WO2011046090A1
Application number: PCT/JP2010/067786
Authority: WO
Inventors: 眞子　隆志; 敬仁渡邊
Original assignee: 日本電気株式会社
Priority date: 2009-10-13
Filing date: 2010-10-08
Publication date: 2011-04-21
Also published as: JPWO2011046090A1

Abstract

Disclosed is a magnet device provided with a substrate, at least one magnet element mounted on a first principal surface of the substrate, and a soft-magnetic magnetic shield disposed on the first-principal-surface side of the substrate. The magnetic shield is provided with a main section and at least one protruding section. The main section is provided with a bottom surface, located on the first-principal-surface side, and a top surface, located on the side opposite the bottom surface. At least one protruding section is provided on the top surface of the main section. At least one protruding section is provided in a cover region that includes at least the region where the magnetic shield and a magnet element overlap, as seen from above the first principal surface. At least one protruding section is angled with respect to the top surface of the main section, in a direction other than the normal direction.

Description

Magnetic device

The present invention relates to a magnetic device. In particular, the present invention relates to a magnetic device provided with a magnetic shield.

A magnetic element using a magnetic substance is known. For example, a magnetoresistive element (MagnetoResistance
Element) is a magnetic element whose resistance value changes according to the magnetization state of the magnetic substance. A typical magnetoresistive element has a structure in which a non-magnetic layer is sandwiched between two magnetic layers. One magnetic layer is a magnetization fixed layer whose magnetization direction is fixed, and the other is a magnetization free layer whose magnetization direction can be reversed. The resistance value of the magnetoresistive element configured in this way is higher when the magnetization fixed layer and the magnetization free layer are antiparallel than when the magnetization directions are parallel to each other. By using such a magnetoresistive element, a magnetic random access memory (MRAM) and various logic circuits can be configured.

In a magnetic device using a magnetic element, it is important to prevent the magnetization state (magnetization direction, etc.) of the magnetic material from fluctuating due to external disturbances for its normal operation. For this purpose, a “magnetic shield” is generally used.

Patent Document 1 (Japanese Patent Laid-Open No. 2003-309196) discloses a magnetic shield package of a magnetic nonvolatile memory element. FIG. 1 shows a cross-sectional structure of the magnetic shield package. The magnetic shield package 110 includes an MRAM element 111, a wire 112, a lead frame 113, and a magnetic shield 114. The MRAM element 111 is connected to the lead frame 113 by a wire 112. Further, the entire periphery of the MRAM element 111 is surrounded by a hollow magnetic shield 114. The magnetic shield 114 is made of an insulating soft magnetic material and has a rectangular cross-sectional shape as shown in FIG.

FIG. 3 of Patent Document 2 (Japanese Patent Laid-Open No. 2003-124538) shows a mode in which an information storage device is mounted on a BGA substrate and a radiator (heat sink) is mounted on the information storage device. Yes. The radiator is formed to extend in the vertical direction from the surface of the information storage device, and has a function of releasing the heat of the information storage device. This radiator is made of a high permeability material.

JP 2003-309196 A JP 2003-124538 A

However, the structure of Patent Document 1 shown in FIG. 1 has the following problems. That is, in the case of the structure shown in FIG. 1, the magnetic shield 114 is horizontal (parallel to the device surface) above the MRAM element 111. When an external magnetic field He perpendicular to the horizontal magnetic shield 114 is applied, theoretically, the external magnetic field He penetrates the magnetic shield 114 and reaches the vicinity of the MRAM element 111 inside the magnetic shield 114. End up. That is, the desired shielding effect cannot be obtained sufficiently.

On the other hand, in the case of the structure shown in FIG. 3 of Patent Document 2, since the high magnetic permeability material extends in the vertical direction from the surface of the information storage device, it extends in the vertical direction when a vertical external magnetic field He is applied. The member collects the external magnetic field He into the information storage device.

An object of the present invention is to provide a technique capable of further improving the shielding effect in a magnetic device including a magnetic shield.

In one aspect of the present invention, a magnetic device is provided. The magnetic device includes a substrate, at least one magnetic element mounted on the first main surface of the substrate, and a magnetic shield of a soft magnetic material disposed on the first main surface side of the substrate. The magnetic shield includes a main body portion and at least one protrusion. A main-body part is provided with the lower surface located in the 1st main surface side, and the upper surface located in the opposite side to the lower surface. At least one protrusion is provided on the upper surface of the main body. The at least one protrusion is provided in a cover region including a region where at least the magnetic shield and the magnetic element overlap when the first main surface is viewed from above. The at least one protrusion is inclined in a direction other than the normal direction with respect to the upper surface of the main body.

According to the present invention, the shielding effect is further improved in the magnetic device including the magnetic shield.

The above and other objects, advantages, and features will become apparent from the embodiments of the present invention described in conjunction with the following drawings.

FIG. 1 is a cross-sectional view showing a typical magnetic shield package according to the related art. FIG. 2 is a cross-sectional view showing the structure of the magnetic device according to the embodiment of the present invention. FIG. 3 shows an example of a planar arrangement pattern of the protrusions of the magnetic shield according to the present embodiment. FIG. 4 shows another example of the planar arrangement pattern of the protrusions of the magnetic shield according to the present embodiment. FIG. 5 is a cross-sectional view showing the structure of the magnetic device according to the present embodiment. FIG. 6 is a schematic diagram for explaining the effect of the magnetic shield according to the present embodiment. FIG. 7 is a cross-sectional view showing a first modification of the magnetic device according to the present embodiment. FIG. 8 is a conceptual diagram for explaining the magnetic field convergence point. FIG. 9 shows still another example of the planar arrangement pattern of the protrusions of the magnetic shield according to the present embodiment. FIG. 10 is a cross-sectional view showing a second modification of the magnetic device according to the present embodiment. FIG. 11 is a cross-sectional view showing a third modification of the magnetic device according to the present embodiment. FIG. 12 is a cross-sectional view showing a fourth modification of the magnetic device according to the present embodiment. FIG. 13 is a cross-sectional view showing a fifth modification of the magnetic device according to the present embodiment. FIG. 14 is a sectional view showing a sixth modification of the magnetic device according to the present embodiment. FIG. 15A is a cross-sectional view showing a seventh modification of the magnetic device according to the present embodiment. FIG. 15B is a perspective view showing an example of a package of the magnetic device according to the present exemplary embodiment. FIG. 16 is a conceptual diagram showing an example of a method for manufacturing a magnetic shield according to the present embodiment. FIG. 17 is a conceptual diagram showing another example of the method for manufacturing a magnetic shield according to the present embodiment. FIG. 18 is a conceptual diagram showing still another example of the magnetic shield manufacturing method according to the present embodiment.

A magnetic device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1. Basic Structure FIG. 2 is a cross-sectional view showing the structure of the magnetic device 1 according to the embodiment of the present invention. As shown in FIG. 2, the magnetic device 1 includes a substrate 10, a magnetic element 20, and a magnetic shield 30. In the following description, the direction perpendicular to the surface of the substrate 10 is the Z direction, and the plane directions perpendicular to the Z direction are the X direction and the Y direction.

The substrate 10 is a member on which the magnetic element 20 is mounted. Examples of the substrate 10 include a wiring substrate, a lead frame, and a semiconductor substrate. As shown in FIG. 2, the substrate 10 has a first main surface (front surface) 11 on which the magnetic element 20 is mounted, and a second main surface (back surface) 12 opposite to the first main surface 11. ing.

The magnetic element 20 is an element using a magnetic material. Examples of the magnetic element 20 include a magnetoresistive element, an MRAM chip, and a logic circuit using the magnetoresistive element. In the present embodiment, at least one magnetic element 20 is mounted on the first main surface 11 of the substrate 10.

The magnetic shield 30 is made of a soft magnetic material. This soft magnetic material has a sufficiently high relative magnetic permeability (preferably 1000 or more). Examples of the soft magnetic material include iron, nickel, silicon steel, permalloy, ferrite, amorphous magnetic alloy, and nanocrystal magnetic alloy. If there is a concern about a short circuit between the magnetic shield 30 and an internal structure such as a bonding wire, an insulating magnetic material (eg, ferrite) may be used as the material of the magnetic shield 30. Alternatively, the surface of the magnetic shield 30 made of a conductive magnetic material may be coated with an insulator.

As shown in FIG. 2, the magnetic shield 30 is at least disposed on the first main surface 11 side of the substrate 10. Further, the magnetic shield 30 includes a main body portion 31 and at least one protruding portion 32. The lower surface LS of the main body 31 is located on the first main surface 11 side of the substrate 10. On the other hand, the upper surface US of the main body 31 is a surface on the opposite side of the lower surface LS and is located on the opposite side to the first main surface 11 of the substrate 10.

The protrusion 32 is provided on the upper surface US of the main body 31. The region where the protrusion 32 is provided is hereinafter referred to as “cover region RC”. That is, the protrusion 32 is formed on the upper surface US of the main body 31 in the cover region RC. In the present embodiment, the cover region RC includes at least a region where the magnetic shield 30 and the magnetic element 20 overlap. In other words, the protruding portion 32 of the magnetic shield 30 is arranged so as to cover the magnetic element 20. In the example shown in FIG. 2, the cover region RC includes almost the entire area of the magnetic shield 30, and a plurality of protrusions 32 are formed on the upper surface US of the main body 31 in the cover region RC.

Furthermore, as shown in FIG. 2, each protrusion 32 is formed “oblique” with respect to the upper surface US of the main body 31. In other words, the protruding portion 32 is inclined with respect to the upper surface US of the main body portion 31 in a direction other than the normal direction. In other words, the protrusion 32 forms an angle greater than 0 degrees and less than 90 degrees with respect to the upper surface US of the main body 31. In the example shown in FIG. 2, the plurality of protrusions 32 are inclined in the same direction with respect to the upper surface US of the main body 31.

FIG. 3 shows an example of a planar arrangement pattern of the protrusion 32 of the magnetic shield 30 and a cross-sectional structure taken along the line A-A ′. In the example of FIG. 3, plate-like (fin-like) protrusions 32 are arranged in a line along the X direction.

FIG. 4 shows another example of a planar arrangement pattern of the protrusion 32 of the magnetic shield 30 and a cross-sectional structure along the line A-A ′. In the example of FIG. 4, the column structure shown in FIG. 3 is arranged over a plurality of stages. In addition, the column structure is shifted in the X direction between adjacent steps. That is, the plurality of protruding portions 32 are arranged in a staggered manner.

Explanation will be made with reference to FIG. 2 again. The space MC between the magnetic shield 30 and the magnetic element 20 is preferably “magnetically hollow”. This space MC is hereinafter referred to as “magnetic cavity space MC”. “Magnetically hollow” means that the magnetic permeability is extremely low (relative magnetic permeability˜1) compared to the magnetic shield 30 having high magnetic permeability (relative magnetic permeability> 1000). For example, as shown in FIG. 2, the magnetic cavity space MC is physically hollow. Alternatively, as shown in FIG. 5, the magnetic cavity space MC may be filled with a nonmagnetic insulator 40. The nonmagnetic insulator 40 is, for example, a molding resin.

2. Action and Effect With reference to FIG. 6, the effect of the structure according to the present embodiment will be described. Here, an external magnetic field He in the Z direction perpendicular to the device surface (the surface of the substrate 10) is considered.

As described above, the high-permeability magnetic shield 30 has the protrusion 32 on the upper surface US of the main body 31. Further, the protruding portion 32 is inclined with respect to the upper surface US of the main body portion 31. Accordingly, as shown in FIG. 6, the magnetic flux of the external magnetic field He is smoothly guided into the main body 31 through the protrusion 32. The protruding portion 32 can also be referred to as a “magnetic flux guide portion” that efficiently guides the magnetic flux to the magnetic shield 30. The magnetic flux of the external magnetic field He is bent in the direction away from the Z direction by the magnetic flux guide portion 32 and is efficiently guided inside the magnetic shield 30. In particular, the cover region RC in which the protrusion 32 is provided covers the magnetic element 20. Therefore, the magnetic flux of the external magnetic field He is bent in the direction away from the magnetic element 20 above the magnetic element 20 and is prevented from penetrating the magnetic shield 30. Therefore, the shielding effect is improved.

When the magnetic cavity space MC is provided between the magnetic shield 30 and the magnetic element 20, from the viewpoint of the magnetic shield effect, the cover region RC in which the protrusion 32 is provided covers the entire magnetic cavity space MC described above. It is preferable (refer FIG. 2). In the cover region RC, it is preferable that the upper surface US of the main body 31 is not visible at all (see FIGS. 3 and 4). That is, when viewed from above, it is preferable that the upper surface US of the main body 31 in the cover region RC is covered with the plurality of protrusions 32. Thereby, the magnetic flux is effectively guided over the entire cover region RC. However, even if the upper surface US of the main body 31 is somewhat visible from above, the same effect is still obtained.

Since the magnetic permeability of the magnetic cavity space MC between the magnetic shield 30 and the magnetic element 20 is extremely lower than the magnetic permeability of the magnetic shield 30, the magnetic flux once guided inside the magnetic shield 30 having a high magnetic permeability is Leaking into the magnetic cavity space MC is effectively prevented. Therefore, the magnetic shield effect can be further improved.

As described above, according to the present embodiment, the magnetic flux of the external magnetic field He reaching the vicinity of the magnetic element 20 is significantly reduced. That is, the shielding effect by the magnetic shield is improved. The shielding effect is not limited to the external magnetic field in the Z direction. The shielding effect with respect to all directions is similarly realized by the magnetic shield 30 having the protrusion 32.

3. Modified example 3-1. First Modification In the above-described example, the inclination direction of the protrusion 32 is uniform. However, the inclination direction of the protrusion 32 may not be uniform as long as it forms an angle greater than 0 degrees and less than 90 degrees with respect to the upper surface US of the main body section 31.

FIG. 7 is a cross-sectional view showing a first modification of the magnetic device 1. In the present modification, the cover region RC in which the protrusion 32 is formed includes a first cover region RC1 and a second cover region RC2 that is different from the first cover region RC1. The first cover region RC1 and the second cover region RC2 do not overlap each other. In FIG. 7, for the convenience of explanation, the boundary is a boundary line BND. The first cover region RC1 is provided with at least one first protrusion 32-1. The second cover region RC2 is provided with at least one second protrusion 32-2.

The inclination direction of the main body 31 with respect to the upper surface US is opposite between the first protrusion 32-1 and the second protrusion 32-2. More specifically, as shown in FIG. 7, the first protrusion 32-1 is inclined so as to guide the magnetic flux to the left (−X direction), and the second protrusion 32-2 It is inclined to guide to the right (+ X direction). In other words, each of the first projecting portion 32-1 and the second projecting portion 32-2 is inclined so as to approach the upper surface US of the main body 31 as the distance from the boundary line BND increases. As a result of such a structure, as shown in FIG. 7, the magnetic flux of the external magnetic field is “branched” left and right in the magnetic shield 30. This is preferable from the viewpoint of saturation magnetization of the magnetic shield 30. In order to equalize the divided flow rate, the boundary line BND is preferably located near the center of the cover region RC.

Fig. 8 shows an inappropriate example. In the example of FIG. 8, the inclination directions of the first protrusion 32-1 and the second protrusion 32-2 are reversed as compared with the case of FIG. In this case, the left first protrusion 32-1 guides the magnetic flux to the right, and the right second protrusion 32-2 guides the magnetic flux to the left. Therefore, as shown in FIG. 8, a magnetic field convergence point CON is generated. The magnetic flux collected at the magnetic field convergence point CON has to come out from the main body 31 to the magnetic cavity space MC, which is not preferable. In other words, it is only necessary that the plurality of protrusions 32 be arranged so that the magnetic field convergence point CON does not occur.

In addition, the planar arrangement pattern of the protrusion part 32 in this modification is also arbitrary. For example, the structure according to this modification can be realized with the same planar arrangement pattern as that shown in FIG. 3 or FIG. Or as FIG. 9 shows, the structure which concerns on this modification may be implement | achieved also by several concentric truncated cones.

3-2. Second Modification FIG. 10 is a cross-sectional view showing a second modification of the magnetic device 1. The protrusion 32 of the magnetic shield 30 does not have to be linear, and may be curved as shown in FIG.

3-3. Third Modification FIG. 11 is a cross-sectional view showing a third modification of the magnetic device 1. The shape of the main body 31 of the magnetic shield 30 is arbitrary. For example, as shown in FIG. 11, the main body 31 of the magnetic shield 30 may be curved so as to be convex when viewed from the substrate 10. Further, the protrusion 32 may be provided on the top of the curved main body 31.

3-4. Fourth Modified Example FIG. 12 is a cross-sectional view showing a fourth modified example of the magnetic device 1. If the package structure permits, magnetic shields 30 may be provided on both sides of the substrate 10 as shown in FIG. More specifically, the first magnetic shield 30A is arranged on the first main surface 11 side, and the second magnetic shield 30B is arranged on the second main surface 12 side. Each of the magnetic shields 30 A and 30 B is the same as the magnetic shield 30.

The first magnetic shield 30A includes a main body 31A and at least one protrusion 32A. The lower surface LS of the main body 31 A is located on the first main surface 11 side of the substrate 10. On the other hand, the upper surface US of the main body 31 A is located on the side opposite to the first main surface 11 of the substrate 10. The protrusion 32A is provided on the upper surface US of the main body 31A in the cover area RCA. Each protrusion 32A is formed "obliquely" with respect to the upper surface US of the main body 31A.

The second magnetic shield 30B includes a main body 31B and at least one protrusion 32B. The lower surface LS of the main body portion 31 B is located on the second main surface 12 side of the substrate 10. On the other hand, the upper surface US of the main body portion 31B is located on the opposite side of the second main surface 12 of the substrate 10. The protruding portion 32B is provided on the upper surface US of the main body portion 31B in the cover region RCB. Each protrusion 32B is formed "obliquely" with respect to the upper surface US of the main body 31B.

れば According to this modification, the magnetic shielding effect is further improved. From the viewpoint of the flow of magnetic flux, as shown in FIG. 12, the first magnetic shield 30A and the second magnetic shield 30B are preferably symmetrical with the substrate 10 in between. In particular, it is preferable that the arrangement pattern of the

protrusions

32A and 32B is symmetrical with respect to the substrate 10.

3-5. Fifth Modification Although the outer peripheral surface of the magnetic shield 30 may be exposed, it is desirable that the outer side of the magnetic shield 30 is also resin-sealed in view of corrosion prevention and workability. FIG. 13 is a cross-sectional view illustrating a fifth modification of the magnetic device 1. In FIG. 13, the outer peripheral surface of the magnetic shield 30 (surface opposite to the magnetic cavity space MC side) is covered with an external mold resin 50. Thereby, corrosion of the magnetic shield 30 is prevented, and workability is also improved.

Furthermore, magnetic powder may be mixed in the external mold resin 50 outside the magnetic shield 30. That is, the outer peripheral surface of the magnetic shield 30 (surface opposite to the magnetic cavity space MC side) may be covered with the external mold resin 50 mixed with magnetic powder. Thereby, the shielding effect as a whole further increases. Further, the magnetic flux emitted from the end of the magnetic shield 30 can be collected not on the magnetic cavity space MC but on the external mold resin 50 side due to the difference in magnetic permeability. The penetration of the magnetic flux into the magnetic cavity space MC is further suppressed, which is preferable.

3-6. Sixth Modification FIG. 14 is a cross-sectional view showing a sixth modification of the magnetic device 1. In this modification, the magnetic shield 30 is a metal magnetic shield formed of a conductive magnetic material. The metal magnetic shield 30 is grounded. For example, the ground pad 61 is provided on the substrate 10, and the metal magnetic shield 30 is electrically connected to the ground pad 61 via the solder 62. The grounded metal magnetic shield 30 also serves as an electromagnetic wave shield, which is preferable.

3-7. Seventh Modification FIG. 15A is a cross-sectional view showing a seventh modification of the magnetic device 1. In this modification, a plurality of magnetic elements 20 are mounted on the substrate 10, and the magnetic shield 30 is provided in common so as to cover all of the plurality of magnetic elements 20. For example, two MRAM chips 20-1 and 20-2 are mounted on the wiring board 10, and the magnetic shield 30 is provided in common so as to cover both of the MRAM chips 20-1 and 20-2.

FIG. 15A shows a mode in which two MRAM chips 20-1 and 20-2 are arranged in the X-axis direction, but a mode in which a plurality of MRAM chips are arranged in the Y-axis direction, 2 in the X-axis direction and the Y-axis direction. Of course, a dimensional arrangement is also possible.

FIG. 15B shows an example of a multi-chip module package. For example, a plurality of MRAM chips 20 A are mounted on the substrate 10. Further, the MRAM chip 20A and another semiconductor chip 20B may be mixedly mounted in one package. In either case, the magnetic shield 30 is provided so as to cover all the chips.

As long as there is no contradiction, combinations of the above-described modifications are possible.

The present invention includes BGA (Ball Grid Array) package, FCBGA (Flip Chip Ball Grid Array) package, QFP (Quad
It can be applied to various packages (magnetic shield package) such as Flat Package) and multichip module packages.

4). Manufacturing Method Various methods for manufacturing the protrusion 32 according to the present embodiment are conceivable.

For example, as shown in FIG. 16, first, a groove is formed in the magnetic plate that becomes the main body 31. Next, a magnetic material plate serving as the protrusion 32 is driven into the groove. Subsequently, the magnetic platelet is bent in a desired direction.

Alternatively, as shown in FIG. 17, an oblique cut is formed by a blade in the magnetic body plate that becomes the main body 31. Subsequently, a magnetic platelet serving as the protrusion 32 is driven into the oblique cut.

Alternatively, as shown in FIG. 18, after cutting into the magnetic plate with the press teeth, the press teeth are lifted to form the protrusions 32 at once.

The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiment, and can be appropriately changed by those skilled in the art without departing from the gist.

This application claims priority based on Japanese Patent Application No. 2009-236266 filed on Oct. 13, 2009, the entire disclosure of which is incorporated herein.

Claims

A substrate,
At least one magnetic element mounted on the first main surface of the substrate;
A magnetic shield of soft magnetic material disposed on the first main surface side of the substrate,
The magnetic shield is
A main body comprising: a lower surface located on the first main surface side; and an upper surface located on the opposite side of the lower surface;
And at least one protrusion provided on the upper surface of the main body,
The at least one protrusion is provided in a cover region including a region where at least the magnetic shield and the magnetic element overlap when the first main surface is viewed from above,
The at least one protrusion is inclined in a direction other than a normal direction with respect to the upper surface of the main body.
The magnetic device according to claim 1,
The number of the protrusions is plural.
The magnetic device according to claim 2,
When viewed from the upper surface side of the main body, the upper surface of the cover region is covered with the plurality of protrusions.
The magnetic device according to claim 2 or 3,
The plurality of protrusions are inclined in the same direction with respect to the upper surface.
The magnetic device according to claim 2 or 3,
The cover area includes a first cover area and a second cover area different from the first cover area;
The plurality of protrusions are
At least one first protrusion provided in the first cover region;
And at least one second protrusion provided in the second cover region,
Each of the first protrusion and the second protrusion is inclined so as to approach the upper surface as the distance from the boundary between the first cover area and the second cover area increases.
It is a magnetic body device according to any one of claims 1 to 5,
A space between the magnetic shield and the magnetic element is a magnetic cavity.
The magnetic device according to claim 6,
A nonmagnetic insulator is filled between the magnetic shield and the magnetic element, or a space between the magnetic shield and the magnetic element is a cavity.
A magnetic device according to any one of claims 1 to 7,
The number of the magnetic elements is plural,
The cover region covers all of the plurality of magnetic elements.
A magnetic device according to any one of claims 1 to 8,
In addition, it has another magnetic shield of soft magnetic material,
The other magnetic shield is disposed on the second main surface side opposite to the first main surface of the substrate,
The other magnetic shield is
Another main body comprising a lower surface located on the second main surface side and an upper surface located on the opposite side of the lower surface;
And at least one other protrusion provided on the upper surface of the other body part,
The at least one other protrusion is provided in another cover region including a region where at least the other magnetic shield and the magnetic element overlap when the second main surface is viewed from below.
The at least one other projecting portion is inclined with respect to the upper surface of the other main body portion in a direction other than a normal direction.