Magnetic field detection element

Abstract

To provide a magnetic field detection element capable of reducing the distance between a magnetic wire and a detection coil, thereby mitigating sensitivity attenuation.SOLUTION: A magnetic field detection element 1 includes a substrate 2 having a groove 3, a magnetic wire 5 arranged in the groove 3, and a detection coil 4 surrounding the magnetic wire 5. The detection coil 4 has a lower coil 42 positioned within the groove 3 and an upper coil 41 connected to the lower coil 42. The upper coil 41 is provided with a recess 41a that concaves towards a gap s between the lower coil 42 and the magnetic wire 5.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic field detection element mounted in a magnetic field detection device. [Background technology]

[0002] Conventionally, magnetic field detection elements mounted on magnetic field detection devices have been known. For example, Patent Documents 1 to 3 introduce magnetic field detection elements in which a lower coil is formed in a groove formed in a substrate, a magnetic wire is placed on the lower coil, and an upper coil is formed on the magnetic wire. The lower coil is connected to the upper coil to form a detection coil that wraps around the magnetic wire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7201194 [Patent Document 2] Patent No. 7207676 [Patent Document 3] Patent No. 7329782 Summary of the Invention [Problem to be solved by the invention]

[0004] The magnetic field detector detects the effect of changes in the magnetic field response of the magnetic wire on the detection coil as an induced voltage signal. The change in magnetic field response, i.e., the sensitivity of the magnetic field detector, decays inversely proportional to the cube of the distance between the magnetic wire and the detection coil.

[0005] As shown in Fig. 5(a), according to the techniques of Patent Documents 1 to 3, the detection coil is formed along the groove. Therefore, as shown in Fig. 5(b), as the diameter of the magnetic wire 5 becomes smaller, the distance between the detection coil 4 and the magnetic wire 5 increases, resulting in a problem of greater attenuation of sensitivity. On the other hand, if the groove width or depth is changed depending on the diameter of the magnetic wire, it becomes impossible to use a common substrate, which increases the manufacturing cost.

[0006] Therefore, an object of the present disclosure is to provide a magnetic field detection element that can reduce the distance between the magnetic wire and the detection coil and reduce attenuation of sensitivity. [Means for solving the problem]

[0007] In order to solve the above problem, the magnetic field detection device disclosed herein comprises a substrate having a groove, a magnetic wire placed in the groove, and a detection coil surrounding the magnetic wire, wherein the detection coil includes a lower coil placed in the groove and an upper coil connected to the lower coil, and the upper coil includes a recess that is recessed toward the gap between the lower coil and the magnetic wire. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view of the magnetic field detection element of the present disclosure. [Figure 2] 1A is an enlarged perspective view of a main part A of a magnetic field detection element, and FIG. 1B is an enlarged cross-sectional view taken along line BB. [Figure 3] 10A to 10C are schematic cross-sectional views showing variations of recesses. [Figure 4] 5A to 5C are explanatory diagrams showing a method for manufacturing a magnetic field detection element. [Figure 5] FIG. 1 is a schematic cross-sectional view of a conventional magnetic field detection element. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure embodied in a magnetic field detection element 1 will be described below with reference to the drawings. Magnetic field sensors incorporating the magnetic field detection element 1 include, for example, FG (Fluxgate) sensors, MI (Magneto Impedance) sensors, and GSR sensors (registered trademark). In these magnetic field sensors, the magnetic field detection element 1 is provided separately from an ASIC (Application Specific Integrated Circuit) (not shown). The magnetic field detection element 1 and the ASIC are joined by wire bonding.

[0010] As shown in Figures 1 and 2, the magnetic field detection element 1 includes a substrate 2 having a groove 3, a magnetic wire 5 whose properties change in response to an external magnetic field, and a detection coil 4 that surrounds the magnetic wire 5. The magnetic field detection element 1 also includes a wire electrode 7 that supplies electricity to the magnetic wire 5, wiring 8 that electrically connects the magnetic wire 5 and the wire electrode 7, a coil electrode 6 that supplies electricity to the detection coil 4, wiring 8 that electrically connects the detection coil 4 and the coil electrode 6, and a resin layer 23 that eliminates the step between the groove 3 and the magnetic wire 5. The resin layer 23 is made of a positive resist resin material.

[0011] The substrate 2 has a groove 3 for arranging the magnetic wire 5. The groove 3 is formed in an inverted trapezoidal cross section whose inner width narrows from the groove edge 31 toward the groove bottom 33. The material of the substrate 2 is, for example, <100> Single crystal silicon (Si) such as silicon (Si) can be selected. Single crystal silicon has the property that the etching rate varies depending on the crystal orientation. By utilizing this property and performing anisotropic etching on the grooves 3, it is possible to form grooves 3 with an inverted trapezoidal cross section.

[0012] 2(b), the surface of the substrate 2 is covered with an insulating film 21 made of silicon nitride (Si3N4). In addition, an R-shape is formed on the groove edge 31. Since the R-shape is formed on the groove edge 31, disconnection of the lower coil 42 can be prevented.

[0013] The surfaces of the groove bottom 33 and groove bottom corners (corners between the groove bottom 33 and groove side surfaces 32) 34 are coated with a negative resist resin coating 22. An R-shape is formed in the groove bottom corners 34 coated with the resin coating 22. The R-shape is formed by performing a curing heat treatment at 280°C for one hour after exposure, baking, and development. By forming an R-shape in the groove bottom corners 34, it is possible to prevent disconnection of the lower coil 42.

[0014] The detection coil 4 has a lower coil 42 placed in the groove 3 and an upper coil 41 connected to the lower coil 42. The coil pitch of the detection coil 4 is preferably 10 μm or less. The detection coil 4 also has a connection portion 43 (see FIG. 3) that connects the upper coil 41 and the lower coil 42.

[0015] The lower coil 42 is a metal wire printed on the substrate 2. The line width of the lower coil 42 is about 1.0 to 1.2 μm, and the thickness is about 0.7 μm.

[0016] The magnetic wire 5 has wire terminals on both ends. The magnetic wire 5 has a diameter of about 5 to 15 μm, and is entirely covered with insulating glass having a thickness of about 1.0 μm. By performing reactive ion etching (RIE method) using carbon tetrafluoride (CF4) gas on both ends of the magnetic wire 5, the insulating glass can be removed and the wire terminals can be provided.

[0017] The upper coil 41 is a metal wire printed on the resin layer 23 and the magnetic wire 5. The upper coil 41 has a line width of about 1.0 to 1.2 μm and a thickness of about 0.8 μm.

[0018] The upper coil 41 has a recess 41 a recessed toward the gap s between the lower coil 42 and the magnetic wire 5 .

[0019] As shown in Figure 3(a), the magnetic wire 5 can be placed in the center of the groove 3, with multiple recesses 41a provided, and each recess 41a can have the same depth. Alternatively, as shown in Figure 3(b), the magnetic wire 5 can be placed closer to one side of the groove 3 than the center, with multiple recesses 41a provided, with one recess 41a being deeper than the other recesses 41a. Furthermore, as shown in Figure 3(c), the magnetic wire 5 can be placed on one side of the groove 3, with only one recess 41a.

[0020] The recess 41a can be formed in a V-shape or a U-shape that protrudes toward the gap s between the lower coil 42 and the magnetic wire 5. When formed in a U-shape, breakage of the upper coil 41 can be prevented.

[0021] The recess 41a includes a connection portion 43 that connects the upper coil 41 and the lower coil .

[0022] Next, a method for arranging the detection coil 4 and the magnetic wire 5 in the groove 3 in the magnetic field detection element 1 configured as above will be described with reference to FIG.

[0023] (1) Formation of the lower coil As shown in Figure 4(a), first, the substrate 2 is coated with a metal film of about 100 nm. Next, resist is applied according to the lower coil pattern, and then exposed and developed. After that, the substrate 2 is plated and wet-plated. Finally, the resist is removed to form the lower coil 42.

[0024] (2) Fixing the magnetic wire As shown in FIG. 4(b), first, the magnetic wire 5 is placed in the groove 3 in which the lower coil 42 is formed, while being stretched over a jig. Next, a negative resist resin is applied, and a heat treatment at 90°C is performed to temporarily fix the magnetic wire 5 in the groove 3. Finally, after exposure, baking, and development, a curing heat treatment is performed at 280°C for about one hour to fix the magnetic wire 5 in the groove 3. Because the magnetic wire 5 is heat-treated while maintaining tension, the GSR characteristics of the magnetic wire 5 can be improved.

[0025] (3) Elimination of the step between the groove and the magnetic wire As shown in Fig. 4(c), first, a positive resist resin 24 is applied to the surface of the substrate 2. At this time, as shown in Fig. 4(d), a resin layer 23 is formed in the shape of the recess 41a. Thereafter, the substrate 2 is exposed to light, developed, and subjected to a curing heat treatment at 280°C for 1 hour, thereby forming the resin layer 23 that eliminates the step between the groove 3 and the magnetic wire 5.

[0026] (4) Formation of the upper coil As shown in FIG. 4(e), first, the substrate 2 is coated with a metal film of about 100 nm. Next, resist is applied according to the upper coil pattern, and is exposed and developed. After that, the substrate 2 is plated and wet-plated. Finally, the resist is removed to form the upper coil 41.

[0027] Therefore, according to the magnetic field detection element 1 of this embodiment, the recess 41a is provided in the upper coil 41, so that the upper coil 41 can be brought closer to the surface of the magnetic wire 5, and attenuation of the sensitivity of the magnetic field detection element 1 can be reduced. Furthermore, the connection portion 43 is provided in the recess 41a, so that the current-carrying points of the upper coil 41 and the lower coil 42 can be brought closer to the magnetic wire 5. This reduces the length of the detection coil 4 per turn, and reduces the resistance of the detection coil 4. Therefore, the number of turns of the detection coil 4 can be increased while suppressing the resistance value of the detection coil 4, and the sensitivity of the magnetic field detection element 1 can be improved.

[0028] The present disclosure is not limited to the above-described embodiments, and the shape and configuration of each part can be appropriately changed without departing from the spirit of the present disclosure.

Claims

1. A substrate having a groove, a magnetic wire disposed in the groove, and a detection coil surrounding the magnetic wire, the detection coil includes a lower coil disposed in the groove and an upper coil connected to the lower coil; A magnetic field detection element, wherein the upper coil includes a recess recessed toward a gap between the lower coil and the magnetic wire.

2. the upper coil includes a plurality of the recesses; The magnetic field detection element according to claim 1 , wherein the plurality of recesses are formed to have the same depth.

3. the upper coil includes a plurality of the recesses; The magnetic field detection element according to claim 1 , wherein one of the recesses is formed deeper than the other recesses.

4. The magnetic field detection device according to claim 1 , wherein the magnetic wire is disposed closer to one side than the center of the groove.

5. 5. The magnetic field detection element according to claim 1, wherein the recess includes a connection portion that connects the upper coil and the lower coil.

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