magnetic sensor

Abstract

To reduce irregular magnetic domain walls that occur to a magnetic substance layer.SOLUTION: A magnetic sensor 1 comprises: a sensor chip 20 that has a magnetic substance layers M1-M3, magneto-sensitive elements R1, R2 that are arranged on a magnetic path formed by a magnetic gap composed of the magnetic substance layers M1, M2 and magneto-sensitive elements R3, R4 that are arranged on a magnetic path formed by a magnetic gap composed of the magnetic substance layers M1, M3; and an external magnetic substance 30 that overlaps the magnetic substance layer M1 as seen from a direction Z. The magnetic substance layer M1 has a slit SL that extends in a direction Y and overlaps the external magnetic substance in a plan view. The width in a direction X of the slit SL is larger than the width in the direction X of magnetic gaps G1-G4. Provision of such a slit SL helps suppress the occurrence of irregular magnetic domain walls.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a magnetic sensor, and more particularly to a magnetic sensor including a sensor chip having a magnetic layer that serves as a magnetic path for a magnetic field to be detected, and an external magnetic body that collects the magnetic field to be detected in the sensor chip. [Background technology]

[0002] Patent Document 1 discloses a magnetic sensor that enhances detection sensitivity by using an external magnetic body to collect magnetic flux on a sensor chip. The magnetic flux collected by the external magnetic body is divided into left and right by a magnetic layer provided on the sensor chip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 216651 Summary of the Invention [Problem to be solved by the invention]

[0004] However, near the center of the magnetic layer in the left-right direction, the direction of the magnetic flux collected by the external magnetic body is not fixed, which can cause irregular domain walls.

[0005] Therefore, the present invention aims to reduce irregular domain walls that occur in a magnetic layer in a magnetic sensor that includes a sensor chip having a magnetic layer that serves as a magnetic path for the magnetic field to be detected, and an external magnetic body that collects the magnetic field to be detected in the sensor chip. [Means for solving the problem]

[0006] The magnetic sensor according to the present invention comprises a sensor chip having a first magnetic layer, a second magnetic layer located on one side in a first direction as viewed from the first magnetic layer and adjacent to the first magnetic layer via a first magnetic gap, a third magnetic layer located on the other side in the first direction as viewed from the first magnetic layer and adjacent to the first magnetic layer via a second magnetic gap, a first magnetic sensing element located on a magnetic path formed by the first magnetic gap, and a second magnetic sensing element located on a magnetic path formed by the second magnetic gap, and an external magnetic body overlapping the first magnetic layer in a planar view, wherein the first magnetic layer has a slit extending in a second direction perpendicular to the first direction and overlapping the external magnetic body in a planar view, and the width of the slit in the first direction is greater than the widths of the first and second magnetic gaps in the first direction.

[0007] According to the present invention, the first magnetic layer has a slit with a sufficient width at the position where it overlaps with the external magnetic body, which makes it possible to suppress the generation of irregular domain walls.

[0008] In the present invention, the center of the external magnetic body in the first direction may overlap the slit in plan view, which makes it possible to more effectively suppress the occurrence of irregular domain walls.

[0009] In the present invention, the first magnetic layer has a first region located on one side of the slit in the first direction and a second region located on the other side of the slit in the first direction, and a part of the first region and a part of the second region may be connected without being separated by the slit, which makes it possible to reduce magnetic resistance while suppressing the generation of irregular domain walls.

[0010] In the present invention, the width of the slit in the first direction may vary depending on the position in the second direction, which makes it possible to more effectively suppress the occurrence of irregular domain walls. [Effects of the Invention]

[0011] Thus, according to the present invention, in a magnetic sensor having a sensor chip with a magnetic layer that serves as a magnetic path for the magnetic field to be detected and an external magnetic body that collects the magnetic field to be detected in the sensor chip, it is possible to reduce irregular domain walls that occur in the magnetic layer. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic perspective view showing the appearance of a magnetic sensor 1 according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic exploded perspective view of the magnetic sensor 1. As shown in FIG. [Figure 3] FIG. 3 is a schematic perspective view for explaining the structure of the sensor chip 20. As shown in FIG. [Figure 4] FIG. 4 is a schematic perspective view showing the sensor chip 20 with the magnetic layers M1 to M3 removed. [Figure 5] FIG. 5 is a schematic cross-sectional view for explaining the positional relationship between the slit SL and the external magnetic body 30. As shown in FIG. [Figure 6] FIG. 6 is a schematic plan view showing the shape of the magnetic layer M1 according to the first modified example. [Figure 7] FIG. 7 is a schematic plan view showing the shape of the magnetic layer M1 according to the second modification. [Figure 8] FIG. 8 is a schematic plan view showing the shape of the magnetic layer M1 according to the third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0014] Fig. 1 is a schematic perspective view showing the appearance of a magnetic sensor 1 according to one embodiment of the present invention, and Fig. 2 is a schematic exploded perspective view of the magnetic sensor 1.

[0015] As shown in FIGS. 1 and 2, the magnetic sensor 1 according to this embodiment includes a substrate 10, a sensor chip 20 mounted on a surface 11 that constitutes the XZ plane of the substrate 10, and external magnetic bodies 30 and 40. The sensor chip 20 has an element formation surface 21 and a back surface 22 that constitute the XY plane, side surfaces 23 and 24 that constitute the YZ plane, and a top surface 25 and a mounting surface 26 that constitute the XZ plane. The sensor chip 20 is mounted on the substrate 10 so that the mounting surface 26 faces the surface 11 of the substrate 10. A magnetic sensing element and magnetic layers M1 to M3, which will be described later, are formed on the element formation surface 21 of the sensor chip 20. As described above, in this embodiment, the surface 11 of the substrate 10 and the element formation surface 21 of the sensor chip 20 are perpendicular to each other. However, in the present invention, it is not essential that the two surfaces be perfectly perpendicular to each other; they may have a predetermined inclination relative to the perpendicular.

[0016] The external magnetic bodies 30 and 40 function to collect magnetic flux toward the sensor chip 20 and are made of a highly permeable material such as ferrite. The external magnetic body 30 is a rod-shaped body with its longitudinal direction in the Z direction. It is positioned approximately at the center of the element-forming surface 21 in the X direction so that an end face 31 at one end in the Z direction covers a portion of the magnetic layer M1. The external magnetic body 40 is located on the opposite side of the sensor chip 20 from the external magnetic body 30. The external magnetic body 40 has a longitudinal direction in the Z direction and includes a rod-shaped portion 41 that covers the back surface 22 of the sensor chip 20, and overhanging portions 42 and 43 that protrude from the rod-shaped portion 41 toward the element-forming surface 21 to cover the side faces 23 and 24 of the sensor chip 20, respectively, and are bent to cover a portion of the magnetic layers M2 and M3. This configuration selectively collects magnetic fields in the Z direction, and the collected magnetic fields are applied to the sensor chip 20.

[0017] Fig. 3 is a schematic perspective view for explaining the structure of the sensor chip 20. Fig. 4 is a schematic perspective view showing the sensor chip 20 with the magnetic layers M1 to M3 removed.

[0018] As shown in FIGS. 3 and 4, magnetic sensing elements R1 to R4 and magnetic layers M1 to M3 are provided on the element forming surface 21 of the sensor chip 20. The magnetic layer M1 is located at the center of the element forming surface 21 in the X direction, the magnetic layer M2 is provided adjacent to the magnetic layer M1 on the -X direction side, and the magnetic layer M3 is provided adjacent to the magnetic layer M1 on the +X direction side. A slit SL extending in the Y direction and with the X direction as its width direction is provided in the center of the magnetic layer M1 in the X direction. The slit SL is a region where the magnetic layer M1 is not present, and divides the magnetic layer M1 into a first region M11 located on the -X direction side from the slit SL and a second region M12 located on the +X direction side from the slit SL. The magnetic layer M1 is provided with one slit SL. Furthermore, the magnetic layer M1 does not have any slits extending in the X direction and with the Y direction as its width direction.

[0019] The magnetic layers M1 and M2 form magnetic gaps G1 and G2 extending in the Y direction and with their widths in the X direction. The magnetic layers M1 and M3 form magnetic gaps G3 and G4 extending in the Y direction and with their widths in the X direction. The magnetic sensing elements R1 to R4 are disposed near the magnetic gaps G1 to G4, i.e., on the magnetic path formed by the magnetic gaps G1 to G4. This allows the magnetic field passing through the magnetic gaps G1 to G4 to be applied to the magnetic sensing elements R1 to R4. The magnetic sensing elements R1 to R4 are bridge-connected between terminal electrodes 51 and 52, and differential signals corresponding to the magnetic field appear at terminal electrodes 53 and 54. The terminal electrodes 55 and 56 are connected to a compensation coil (not shown) provided on the element forming surface 21 of the sensor chip 20. The compensation coil is used to perform so-called closed-loop control by canceling out the magnetic field applied to the magnetic sensing elements R1 to R4.

[0020] FIG. 5 is a schematic cross-sectional view for explaining the positional relationship between the slit SL and the external magnetic body 30. As shown in FIG.

[0021] As shown in Figure 5, the external magnetic body 30 is disposed on the magnetic layer M1 so that its center L in the X direction overlaps with the slit SL when viewed from the Z direction. As a result, part of the magnetic flux collected by the external magnetic body 30 flows to the first region M11 of the magnetic layer M1, and another part flows to the second region M12 of the magnetic layer M1. The magnetic flux that flows to the first region M11 of the magnetic layer M1 flows to the magnetic layer M2 through the magnetic gap G1, and the magnetic field passing through the magnetic gap G1 is applied to the magnetic sensing element R1. Meanwhile, the magnetic flux that flows to the second region M12 of the magnetic layer M1 flows to the magnetic layer M3 through the magnetic gap G3, and the magnetic field passing through the magnetic gap G3 is applied to the magnetic sensing element R3.

[0022] As described above, in this embodiment, the slits SL are provided in the magnetic layer M1 that distributes the magnetic flux in the Z direction collected by the external magnetic body 30 into the -X and +X directions, so that the magnetic flux always flows in the -X direction in the first region M11 of the magnetic layer M1 and the magnetic flux always flows in the +X direction in the second region M12 of the magnetic layer M1. In other words, irregular domain walls caused by indeterminate magnetic flux directions are not generated, and measurement noise caused by such domain walls is reduced.

[0023] Here, it is preferable that the width W of the slit SL in the X direction be sufficiently large in consideration of assembly accuracy, and that it be at least wider than the width of the magnetic gaps G1 to G4 in the X direction. This makes it possible to prevent irregular domain walls from occurring even if the relative positions of the sensor chip 20 and the external magnetic body 30 in the X direction are shifted due to assembly errors. However, if the width W of the slit SL in the X direction is too wide, magnetic resistance increases, so it is preferable that the width W of the slit SL in the X direction be half or less of the width of the external magnetic body 30 in the X direction.

[0024] As described above, in the magnetic sensor 1 according to this embodiment, the magnetic layer M1 is provided with slits SL extending in the Y direction, which makes it possible to suppress the generation of irregular magnetic domain walls. Furthermore, the magnetic layer M1 does not have slits extending in the X direction with the Y direction as its width direction, which prevents the magnetic path from being interrupted between the magnetic gaps G1 and G2 or between the magnetic gaps G3 and G4. Therefore, no difference occurs between the magnetic flux densities applied to the magnetic sensing elements R1 and R2, and similarly, no difference occurs between the magnetic flux densities applied to the magnetic sensing elements R3 and R4.

[0025] Here, the slit SL provided in the magnetic layer M1 does not need to completely separate the first region M11 and the second region M12. As shown in the first modified example in Fig. 6, a part of the first region M11 and a part of the second region M12 may be connected without being separated by the slit SL. When such a connecting portion is provided, it is preferable to provide it at the end in the Y direction. This makes it possible to reduce the magnetic resistance of the magnetic layer M1 while suppressing the generation of irregular domain walls.

[0026] Furthermore, as in the second modified example shown in FIG. 7 and the third modified example shown in FIG. 8, the width of the slit SL in the X direction may vary depending on the position in the Y direction. In the second modified example shown in FIG. 7, the width of the slit SL is greatest at the center position in the Y direction and narrows toward the ends in the Y direction. This allows the slit SL to be widened in the central region where domain walls are most likely to occur, thereby minimizing the increase in magnetic resistance and preventing the occurrence of domain walls. In the second modified example shown in FIG. 8, the width of the slit SL is greatest at the center position of the magnetic sensing elements R1 to R4 in the Y direction and narrows as the distance from the center position of the magnetic sensing elements R1 to R4 in the Y direction increases. This allows the width of the slit SL to be widened in the region where the influence of the magnetic domain walls is strong, thereby minimizing the increase in magnetic resistance and reducing measurement noise caused by the magnetic domain walls.

[0027] The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the present invention, and it goes without saying that these modifications are also included within the scope of the present invention. [Explanation of symbols]

[0028] 1 Magnetic sensor 10 Substrate 11 Surface of the board 20 sensor chips 21 Element formation surface 22 Back side 23,24 Side 25 Top 26 Mounting surface 30,40 External magnetic material 31 End face 41 Rod-shaped part 42,43 Overhang G1~G4 magnetic gap M1~M3 Magnetic layer M11 First Region M12 Second Region R1~R4 magnetic sensing element SL Slit

Claims

1. a sensor chip having a first magnetic layer, a second magnetic layer located on one side in a first direction as viewed from the first magnetic layer and adjacent to the first magnetic layer via a first magnetic gap, a third magnetic layer located on the other side in the first direction as viewed from the first magnetic layer and adjacent to the first magnetic layer via a second magnetic gap, a first magnetic sensing element located on a magnetic path formed by the first magnetic gap, and a second magnetic sensing element located on a magnetic path formed by the second magnetic gap; an external magnetic body overlapping the first magnetic body layer in a plan view seen from a third direction orthogonal to the first direction, the first magnetic layer extends in a second direction perpendicular to the first and third directions, and is divided into a first region and a second region by a slit that overlaps with the external magnetic body in a plan view seen from the third direction; A magnetic sensor, wherein the width of the slit in the first direction is greater than the widths of the first and second magnetic gaps in the first direction.

2. 2. The magnetic sensor according to claim 1, wherein a center of the external magnetic body in the first direction overlaps with the slit in a plan view seen from the third direction.

3. 3. The magnetic sensor according to claim 1, wherein the width of the slit in the first direction varies depending on the position in the second direction.

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