JP7824094B2 - magnetic sensor - Google Patents

Description

The present invention relates to a magnetic sensor, and in particular to a magnetic sensor that includes a sensor chip having a magnetic layer that forms 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.

Patent Document 1 discloses a magnetic sensor that improves detection sensitivity by using an external magnetic body to collect magnetic flux on the sensor chip. The magnetic flux collected by the external magnetic body is split to the left and right by a magnetic layer provided on the sensor chip.

International Publication No. 2018/216651

However, near the center of the magnetic layer in the left-right direction, the direction of the magnetic flux collected by the external magnetic material is not fixed, which can result in irregular domain walls.

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.

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 of the first magnetic layer in a first direction and adjacent to the first magnetic layer via a first magnetic gap, a third magnetic layer located on the other side of the first magnetic layer in the first direction and adjacent to the first magnetic layer via a second magnetic gap, a first magnetic sensing element located on the magnetic path formed by the first magnetic gap, and a second magnetic sensing element located on the 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.

According to the present invention, a slit of sufficient width is provided in the first magnetic layer at the position where it overlaps with the external magnetic material, making it possible to suppress the occurrence of irregular domain walls.

In the present invention, the center of the external magnetic body in the first direction may overlap the slit in a planar view. This makes it possible to more effectively suppress the occurrence of irregular domain walls.

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 portion of the first region and a portion of the second region may be connected without being separated by the slit. This makes it possible to reduce magnetic resistance while suppressing the occurrence of irregular domain walls.

In the present invention, the width of the slit in the first direction may vary depending on its position in the second direction. This makes it possible to more effectively suppress the occurrence of irregular domain walls.

In this way, according to the present invention, 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 at the sensor chip, it is possible to reduce irregular domain walls that occur in the magnetic layer.

FIG. 1 is a schematic perspective view showing the appearance of a magnetic sensor 1 according to an embodiment of the present invention. FIG. 2 is a schematic exploded perspective view of the magnetic sensor 1. As shown in FIG. FIG. 3 is a schematic perspective view for explaining the structure of the sensor chip 20. As shown in FIG. FIG. 4 is a schematic perspective view showing the sensor chip 20 with the magnetic layers M1 to M3 removed. 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. FIG. 6 is a schematic plan view showing the shape of the magnetic layer M1 according to the first modification. FIG. 7 is a schematic plan view showing the shape of the magnetic layer M1 according to the second modification. FIG. 8 is a schematic plan view showing the shape of the magnetic layer M1 according to the third modification.

A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

Figure 1 is a simplified perspective view showing the exterior of a magnetic sensor 1 according to one embodiment of the present invention. Figure 2 is a simplified exploded perspective view of the magnetic sensor 1.

As shown in Figures 1 and 2, the magnetic sensor 1 according to this embodiment includes a substrate 10, a sensor chip 20 mounted on the surface 11 of the substrate 10, which constitutes the XZ plane, 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, described below, are formed on the element formation surface 21 of the sensor chip 20. As such, in this embodiment, the surface 11 of the substrate 10 and the element formation surface 21 of the sensor chip 20 are perpendicular. However, it is not essential for the two to be perfectly perpendicular in the present invention; they may have a predetermined inclination relative to the perpendicular.

The external magnetic bodies 30 and 40 serve to collect magnetic flux toward the sensor chip 20 and are both made of a highly magnetically 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 in the center of the element forming surface 21 in the X direction so that its end face 31, located 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 its 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 surfaces 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.

Figure 3 is a schematic perspective view illustrating the structure of the sensor chip 20. Figure 4 is a schematic perspective view showing the sensor chip 20 with magnetic layers M1 to M3 removed.

As shown in Figures 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. Magnetic layer M1 is located at the center of the element forming surface 21 in the X direction, magnetic layer M2 is provided adjacent to the magnetic layer M1 on the -X direction side, and 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 magnetic layer M1 in the X direction. The slit SL is a region where the magnetic layer M1 is not present, and this 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. There is only one slit SL provided in the magnetic layer M1. Furthermore, the magnetic layer M1 does not have any slits extending in the X direction and with the Y direction as its width direction.

Magnetic layers M1 and M2 form magnetic gaps G1 and G2 extending in the Y direction and with their widths in the X direction. Magnetic layers M1 and M3 form magnetic gaps G3 and G4 extending in the Y direction and with their widths in the X direction. Magnetic sensing elements R1 to R4 are positioned near magnetic gaps G1 to G4, i.e., on the magnetic path formed by magnetic gaps G1 to G4. As a result, the magnetic field passing through magnetic gaps G1 to G4 is applied to magnetic sensing elements R1 to R4. 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. Terminal electrodes 55 and 56 are connected to a compensation coil (not shown) located on element formation surface 21 of sensor chip 20. The compensation coil is used to perform so-called closed-loop control by canceling out the magnetic field applied to magnetic sensing elements R1 to R4.

Figure 5 is a schematic cross-sectional view illustrating the positional relationship between the slit SL and the external magnetic body 30.

As shown in FIG. 5, the external magnetic body 30 is positioned 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, thereby applying the magnetic field passing through the magnetic gap G1 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, thereby applying the magnetic field passing through the magnetic gap G3 to the magnetic sensing element R3.

In this manner, in this embodiment, slits SL are provided in the magnetic layer M1, which distributes the magnetic flux in the Z direction collected by the external magnetic body 30 into the -X and +X directions. As a result, magnetic flux always flows in the -X direction in the first region M11 of the magnetic layer M1, and 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 do not occur, and measurement noise caused by such domain walls is reduced.

Here, it is preferable that the width W of the slit SL in the X direction be sufficiently large, taking into account assembly accuracy, and that it be at least wider than the width of the magnetic gaps G1 to G4 in the X direction. This prevents irregular magnetic domain walls from occurring even if an assembly error causes a misalignment in the relative positions of the sensor chip 20 and the external magnetic body 30 in the X direction. However, if the width W of the slit SL in the X direction is too wide, magnetic resistance will increase, so it is preferable that the width W of the slit SL in the X direction be less than half the width of the external magnetic body 30 in the X direction.

As described above, in the magnetic sensor 1 according to this embodiment, the magnetic layer M1 has slits SL extending in the Y direction, which makes it possible to suppress the occurrence 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, so there is no disruption of the magnetic path between the magnetic gaps G1 and G2, or between the magnetic gaps G3 and G4. Therefore, there is no difference in the magnetic flux density applied to the magnetic sensing elements R1 and R2, and similarly, there is no difference in the magnetic flux density applied to the magnetic sensing elements R3 and R4.

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 in the first modified example shown in Figure 6, a portion of the first region M11 and a portion of the second region M12 may be connected without being separated by the slit SL. When providing such a connecting portion, 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.

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, 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 in the Y direction of the magnetic sensing elements R1 to R4 and narrows as it moves away from the center position in the Y direction of the magnetic sensing elements R1 to R4. This allows the width of the slit SL to be widened in regions where the influence of domain walls is strong, minimizing the increase in magnetic resistance and reducing measurement noise caused by domain walls.

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 without departing from the spirit of the present invention, and it goes without saying that these modifications are also included within the scope of the present invention.

1 Magnetic sensor 10 Substrate 11 Surface of substrate 20 Sensor chip 21 Element forming surface 22 Back surface 23, 24 Side surface 25 Top surface 26 Mounting surface 30, 40 External magnetic body 31 End surface 41 Rod-shaped portion 42, 43 Overhanging portion G1 to G4 Magnetic gap M1 to M3 Magnetic body layer M11 First region M12 Second region R1 to R4 Magnetic sensing element SL Slit

Claims (3)

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. 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. 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.