JP2004184098A - Magnetic sensor element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a strip-like parallel-flux gate type magnetic sensor element capable of detecting earth magnetism by constitution of a single unit, and capable of reducing a size and an electric power consumption to be mounted on a mobile equipment, and its manufacturing method. <P>SOLUTION: In a core 1 comprising permalloy foil, a width of its longitudinal-directional central part 1a is narrowed compared with those of both end parts 1b, 1b, and a cross-sectional area of the central part 1a is narrower than that of other portion. The core 1 is bonded to a substrate 2 comprising a nonmagnetic and insulating glassy epoxy material. A coil 3 is wound in areas of the central part 1a of the core 1 and the substrate 2 bonded with the central part 1a. Magnetic fluxes are concentrated in the central part 1a of the narrow cross-sectional area, and detection sensitivity is thereby high even in short one. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a parallel flux gate type magnetic sensor element having a configuration in which a coil is wound around a strip-shaped core and a method of manufacturing the same, and more particularly, to a parallel flux gate type magnetic sensor element capable of detecting geomagnetism in a small configuration. And its manufacturing method.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a mobile device such as a mobile phone or a PDA has started a service of providing position information for recognizing a user's current position or a direction of a destination. Orientation sensors are being installed in portable devices. Generally, a magnetic sensor that detects geomagnetism is used as the direction sensor. Such a magnetic sensor is capable of accurately detecting a magnetic field (300 to 400 mOe (milli-Oersted)) of a magnitude approximately equivalent to the geomagnetism, being capable of discriminating the polarity (discrimination of N pole and S pole), and being mounted on a portable device. It is required to be small in size so that it can be used, and to have low power consumption suitable for driving a battery.
[0003]
The Hall element, which is the most common magnetic sensor, has a detectable magnetic intensity of 1 Oe or more, and therefore cannot be used. Then, utilization of a magneto-impedance effect element having higher sensitivity was studied. This magneto-impedance effect element can be mounted on a portable device in terms of sensitivity, size and power consumption, but the polarity cannot be determined by a single element. Therefore, it is necessary to apply a bias magnetic field or differentially connect the two elements to provide a circuit for achieving electrical balance. Therefore, there is a problem in operation stability such as a shift of a zero point, and it is difficult to put it to practical use.
[0004]
Therefore, it is conceivable to use a parallel fluxgate type magnetic sensor capable of high-sensitivity detection including the direction alone. The parallel fluxgate type magnetic sensor includes a type in which a coil is wound around a ring-shaped soft magnetic material core (for example, see Patent Documents 1 and 2), and a type in which a coil is wound around a strip-shaped soft magnetic material core. (For example, see Non-Patent Document 1). In the former type, the size is as large as about 20 to 40 mm square and the power consumption is several hundred mW or more, so that it is difficult to mount it on a portable device. Also, in the latter type, the core length becomes 10 mm or more and the power consumption cannot be reduced so much in order to detect a magnetic field as small as terrestrial magnetism.
[0005]
The principle of detection of a parallel fluxgate type magnetic sensor using a ring-shaped core or a strip-shaped core is the same for any of the cores, as follows. An alternating current (for example, a triangular wave-shaped current) is supplied to the coil wound around the core to generate an alternating magnetic field (for example, a triangular wave-shaped magnetic field) in parallel with the measurement magnetic field. Then, a pulse is generated at a timing (zero cross point) at which the direction of the magnetic field is reversed, and a time interval between adjacent generated pulses is detected. When there is no measurement magnetic field, the time interval between the generated pulses is constant. On the other hand, when the measurement magnetic field exists, the measurement magnetic field is superimposed on the alternating magnetic field, so that the detected time interval is not constant, that is, the time when the magnetic field is in one direction and the magnetic field is in the other direction. Time is different. Therefore, it is possible to detect the direction and magnitude of the measurement magnetic field from the time interval of the generated pulse. The parallel fluxgate type magnetic sensor includes a one-coil type in which one coil is used for excitation and one for detection, and a two-coil type in which the excitation coil and the detection coil are separated. .
[0006]
[Patent Document 1]
JP-A-7-128373 [Patent Document 2]
West German Patent Application Publication No. 3715789 [Non-Patent Document 1]
Shoji Kawahito, "Development and Application of Micro-Fluxgate-Type High-Sensitivity Magnetic Sensor", Sensing Technology Application Workshop 90th Research Meeting Material, February 8, 1994 [0007]
[Problems to be solved by the invention]
In a parallel fluxgate magnetic sensor using a strip-shaped core made of a thin plate-like soft magnetic material having a thickness of about 0.1 mm, since magnetic saturation is used as described above, in order to detect a magnetic field as small as terrestrial magnetism, However, there is a problem that the size becomes large and the power consumption cannot be reduced so much. Non-Patent Document 1 proposes a configuration using a thin-film core formed by an electrodeposition method and a micro solenoid coil as a strip-shaped core and an exciting coil as a configuration capable of miniaturization. It has been difficult to put it to practical use for the purpose of detecting a weak magnetic field of the order of terrestrial magnetism.
[0008]
The present invention has been made in view of such circumstances, and has a stability of operating characteristics originally possessed by a parallel fluxgate type magnetic sensor capable of detecting the magnitude and direction of a magnetic field of the order of terrestrial magnetism in a single configuration. It is an object of the present invention to provide a magnetic sensor element and a method for manufacturing the same, which can be reduced in size and reduced in power consumption to the extent that they can be mounted on a portable device while utilizing the same.
[0009]
[Means for Solving the Problems]
A magnetic sensor element according to a first aspect of the present invention is a parallel fluxgate type magnetic sensor element having a configuration in which a coil is wound around a strip-shaped core. The coil is wound around the central portion in the longitudinal direction.
[0010]
In the magnetic sensor element according to the first aspect of the invention, the center of the strip-shaped core in the longitudinal direction has a smaller sectional area than other portions, and a coil is wound around this portion. Therefore, by concentrating the magnetic flux at the narrow central portion, the magnetic flux density at that portion is increased, and the amount of deviation on the BH curve is increased. Therefore, high sensitivity can be achieved even if the length is short. Specifically, the cross-sectional area of the central portion is set to 以下 or less, more preferably １ ／ or less, of the cross-sectional area of other portions. However, the smaller the cross-sectional area of the central portion, the larger the amount of deviation on the BH curve, but if the cross-sectional area is too small, the detection pulse based on the time variation of the total magnetic flux will be reduced. Since the level is reduced and the detection ability is reduced, 1/100 or more is necessary. Further, it is preferable that the central portion for reducing the cross-sectional area is about 1/2 to 1/10 of the entire length of the core. Since the coil is wound around only the central constricted portion to concentrate the excitation magnetic field on the central constricted portion, the exciting current required for reversing the magnetization can be reduced, and the power consumption can be reduced. That is, since a large magnetic field is locally formed by a small exciting current, power consumption is reduced as a whole. Since the collected magnetic flux is determined by the surface area of the end portion of the core, even if the cross-sectional area of the central portion is reduced as described above, the amount of the measured magnetic field that can be captured does not change and does not cause any problem. The ends of the core are formed on both sides of the central constricted portion, and usually have a rectangular shape from the viewpoint of workability and the like as in the embodiment described later. The dimensions (width, length) of each end on both sides need not be the same, but the amount of magnetic flux collected at those ends is determined by the dimension of the end with the smaller surface area. It is desirable to have the same dimensions from the viewpoints of magnetic efficiency and workability.
[0011]
A magnetic sensor element according to a second invention is characterized in that, in the first invention, a width of a central portion in a longitudinal direction of the core is narrower than other portions.
[0012]
In the magnetic sensor element of the second invention, the width of the central portion in the longitudinal direction of the core is narrowed to reduce the cross-sectional area. In order to reduce the cross-sectional area, a method of reducing the width and a method of reducing the thickness can be considered. If the thickness is too thin, crystal grains of the core material cannot be grown, so that an appropriate coercive force cannot be obtained, and there is a possibility that magnetic properties may be deteriorated. Also, making the width narrower than the thickness makes the etching process easier. For the above reasons, the width is reduced to reduce the cross-sectional area.
[0013]
A magnetic sensor element according to a third aspect of the present invention is the magnetic sensor element according to the first or second aspect, wherein the core is a magnetically annealed permalloy foil.
[0014]
In the magnetic sensor element of the third invention, a magnetically annealed permalloy foil is used as the core. In a parallel fluxgate type magnetic sensor, detection is easy when the coercive force of the core is about 1/10 or less of the measured magnetic field. Therefore, in order to detect geomagnetism of 300 to 400 mOe, the coercive force of the core is required. Is preferably about 30 mOe. Permalloy foil obtained by plating or sputtering has a coercive force of about 1 Oe, and cannot detect terrestrial magnetism. On the other hand, since the coercive force of the magnetically annealed permalloy foil is about 30 mOe, it is used as a core.
[0015]
A magnetic sensor element according to a fourth aspect is characterized in that, in any one of the first to third aspects, the magnetic sensor element is attached to a nonmagnetic and insulating substrate.
[0016]
In the magnetic sensor element according to the fourth aspect, the core is attached to the non-magnetic and insulating substrate. Therefore, since the core is lined with the substrate, the core is not distorted or deformed even if the core is thin, and deterioration of the magnetic characteristics due to the distortion or deformation of the core is prevented.
[0017]
A method for manufacturing a magnetic sensor element according to a fifth aspect of the present invention is a method for manufacturing a parallel fluxgate type magnetic sensor element having a configuration in which a coil is wound around a strip-shaped core, wherein magnetic annealing is performed on the permalloy foil serving as the core. The permalloy foil after magnetic annealing is bonded to a non-magnetic and insulating substrate, the width of the central part in the longitudinal direction of the permalloy foil is made narrower than other parts, and the coil is provided in the central part in the longitudinal direction. Is wound.
[0018]
In the method for manufacturing a magnetic sensor element according to the fifth aspect of the invention, the magnetically annealed permalloy foil is bonded to a non-magnetic and insulating substrate, and the width of the central portion in the longitudinal direction of the permalloy foil is reduced as compared with other portions. Then, a coil is wound around a central portion in the longitudinal direction of the narrow permalloy foil to manufacture a magnetic sensor element. Therefore, a magnetic sensor element that can accurately detect terrestrial magnetism and that can be mounted on a portable device can be easily manufactured.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments.
1A and 1B show the configuration of a magnetic sensor element according to an embodiment of the present invention. FIG. 1A is a perspective view, FIG. 1B is a top view, and FIG. It is a side view.
[0020]
The magnetic sensor element 10 of the present invention has a core 1 made of magnetically annealed permalloy foil, a substrate 2 on which the core 1 is adhered, and a coil 3 wound around the core 1 and the substrate 2. This example is a one-coil parallel fluxgate magnetic sensor element using one coil 3 (excitation detection coil) that is used both for excitation and detection.
[0021]
The core 1 is made of a strip-shaped foil (length: 3 mm, thickness: 10 μm) of permalloy (80% Ni-5% Mo—Fe). The width of the core 1 is not the same in the longitudinal direction, and the width of the central portion 1a over a length of 1 mm is smaller than the width of both ends 1b, 1b over a length of 1 mm, respectively. The width of the central portion 1a is 0.05 mm, the width of both ends 1b, 1b is 0.3 mm, and the width of the central portion 1a is 1/6 of the width of each end 1b, 1b. The central portion 1a is symmetrically narrow in the width direction. The thickness of the core 1 made of permalloy foil is set to be equal to or smaller than the skin thickness of the excitation frequency, so that the influence of the eddy current is reduced.
[0022]
The substrate 2 is made of a non-magnetic and insulating glass epoxy material, and has a length of 3 mm, a width of 0.3 mm, and a thickness of 0.2 mm. A coil 3 made of a polyurethane conductive wire (wire diameter: 17 μm) is wound around the central portion 1a of the core 1 and the region of the substrate 2 to which the central portion 1a is attached, for 200 turns.
[0023]
The overall size of the magnetic sensor element 10 of the present invention is 3 mm in length, 0.3 mm in width, and 0.21 mm in thickness. This size is considerably small, and is mounted on a portable device in terms of size. It can be said that the conditions are satisfied.
[0024]
Next, a method of manufacturing the magnetic sensor element 10 of the present invention having such a configuration will be described with reference to FIGS.
[0025]
First, a permalloy (80% Ni-5% Mo-Fe) plate is foil-rolled to obtain a permalloy foil 11 having a thickness of 10 μm, and this permalloy foil 11 is subjected to magnetic annealing (1100 ° C., 3 hours, hydrogen atmosphere). (FIG. 2A). The permalloy foil 11 thus subjected to the magnetic annealing treatment is bonded to a glass epoxy substrate 12 having a thickness of 0.2 mm using an epoxy adhesive (FIG. 2B).
[0026]
After the adhesive is cured, a narrowed portion 11a having a length of 3 mm and a width of 0.3 mm and having a length of 1 mm and a width of 0.05 mm is formed at the center in the longitudinal direction by photoetching using a predetermined mask pattern. The pattern 14 of the permalloy foil 11 having the above is prepared (FIG. 2C). Then, an area having a length of 3 mm and a width of 0.3 mm having the pattern 14 is cut out including the underlying glass epoxy substrate 12 (FIG. 3D).
[0027]
A polyurethane conductive wire 13 having a diameter of 17 μm is wound 200 times around a portion (length having a constricted portion 11a) extending 1 mm in length in the longitudinal direction of the cut out portion, thereby manufacturing the magnetic sensor element 10 of the present invention (FIG. 3E). ). The cut permalloy foil 11 having the constricted portion 11a becomes the core 1 having the central portion 1a, the cut glass epoxy substrate 12 becomes the substrate 2, and the polyurethane conductive wire 13 becomes the coil 3.
[0028]
The magnetic sensor element 10 of the present invention was adhered to a detection circuit board, and both ends of the coil 3 were connected to the detection circuit, and the magnetic field detection characteristics were measured. FIG. 4 is a diagram showing a configuration of this detection circuit. The detection circuit includes a triangular wave generating circuit 20, a triangular wave removing circuit 30, a Schmitt trigger circuit 40, and a smoothing circuit 50.
[0029]
The triangular wave generating circuit 20 supplies a triangular wave current to the coil 3 of the magnetic sensor element 10 to excite the magnetic sensor element 10 with a triangular wave magnetic field. The triangular wave removing circuit 30 removes the triangular wave generated by the triangular wave generating circuit 20 from the signal obtained by the coil 3 to obtain a true detection signal. This is because the triangular wave from the triangular wave generation circuit 20 is superimposed on the signal obtained by the coil 3 because the coil 3 is used for both excitation and detection. The Schmitt trigger circuit 40 obtains a DR signal indicating a temporal change in the polarity based on the detected waveform from the triangular wave removing circuit 30. The smoothing circuit 50 smoothes the DR signal and outputs an analog voltage proportional to the magnitude of the measured magnetic field.
[0030]
A magnetic field was detected by applying an exciting current of 250 kHz and a peak value of 3.5 mA to the coil 3 of the magnetic sensor element 10 of the present invention. The thickness (10 μm) of the core 1 is almost the same as the skin thickness (about 11 μm) at the excitation frequency (250 kHz). FIG. 5 shows the magnetic field detection characteristics at this time. As shown in FIG. 5, a linear detection characteristic is obtained in a range from 10 mOe to 3 Oe. Therefore, it can be seen that the sensor has sufficient performance as a sensor for detecting geomagnetism (300 to 400 mOe) with high accuracy. In addition, the current value of 3.5 mA is considerably low, the power consumption is small, and it can be said that the current value satisfies the condition for mounting on a portable device in terms of power. As a result of measuring the excitation frequency in the range of 50 kHz (skin thickness of about 25 μm) to 250 kHz (skin thickness of about 11 μm) with a magnetic sensor element (core thickness: 10 μm) of the same dimensions, the same detection capability as described above was obtained. Was obtained.
[0031]
As described above, the magnetic sensor element 10 of the present invention is as small as about 3 mm and can accurately detect terrestrial magnetism including its polarity even with low power consumption. The conditions are met. Also, the manufacturing process is easy without using a special method.
[0032]
Further, in the magnetic sensor element 10 of the present invention, a permalloy foil whose thickness is about the same as or smaller than the skin thickness of the excitation frequency is used as the core 1. The thickness of the core is a factor that determines the density of the magnetic flux concentrated at the central constriction. Basically, it is desirable that the core be thin, but if it is too thin, the magnetic properties of the core material will be reduced as described above. It is desirable to select an optimum thickness according to the required detection sensitivity. Further, in order to make the magnetic flux concentrated on the constricted portion spread uniformly throughout the constricted portion, it is desirable that the thickness of the core be equal to or less than the skin thickness of the excitation frequency. That is, when the core thickness is greater than the skin thickness of the excitation frequency, the eddy current becomes remarkable and acts in a direction that hinders a change in the magnetic flux density, so that a sharp magnetization reversal does not occur, and the detection performance decreases. . Therefore, by thinning the core into a foil shape, it is possible to prevent the detection pulse from being blunted due to the eddy current. Further, not only the thickness of the core, but also the detection sensitivity varies depending on various factors such as the accuracy of the detection circuit and the number of windings of the coil. It has been confirmed that it is desirable to select in the range of skin thickness / core thickness = 1.2 to 2.5. Since the core is thinned in a foil shape, the magnetic permeability does not decrease even when a high-frequency current is applied, and the magnetic characteristics do not deteriorate. Therefore, even if the excitation frequency is set to a relatively high value, a large detection pulse can be obtained with a small number of turns of the coil, so that the configuration of the peripheral circuit can be simplified, and a small-capacity capacitor can be used for the peripheral circuit. Chips are possible. In addition, since the core is thinned in a foil shape, power consumption can be further reduced.
[0033]
Another embodiment of the present invention will be described. In the embodiment described above, the central portion 1a of the core 1 having a small width is provided at the central position in the width direction. However, the position in the width direction where the central portion 1a is provided may be another position.
[0034]
FIG. 6 is a perspective view of a magnetic sensor element 10 according to another embodiment of the present invention. 6, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the example shown in FIG. 6, a central portion 1a in the longitudinal direction, which is narrower than the other portions of the core 1, is provided not at the center in the width direction but at one end.
[0035]
FIG. 7 is a perspective view of a magnetic sensor element 10 according to still another embodiment of the present invention. 7, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the example shown in FIG. 7, the center of the entire core 1 is missing, and the longitudinal central portions 1 a, 1 a having a smaller width than the other portions of the core 1 are separated from both ends instead of the center in the width direction. Is provided.
[0036]
6 and 7 also have a configuration in which the cross-sectional area of the central portion in the longitudinal direction of the core 1 is smaller than the cross-sectional areas of the other portions, so that the magnetic sensor element 10 having the above-described configuration shown in FIG. Of course, the same effect can be obtained.
[0037]
In the above-described embodiment, an example of a one-coil parallel fluxgate type magnetic sensor element using one excitation detection coil that is used for both excitation and detection has been described. The same effect can also be obtained for a two-coil parallel fluxgate type magnetic sensor element having a coil and a coil separately by winding the exciting coil and the detecting coil in a region where the core width is narrow. Needless to say.
[0038]
【The invention's effect】
As described in detail above, in the magnetic sensor element of the present invention, the longitudinal central portion of the strip-shaped core has a smaller cross-sectional area than other portions, and the coil is wound around this portion. With a small size and low power consumption, geomagnetism including its polarity can be detected with high accuracy, and it can be mounted on portable devices such as mobile phones and PDAs.
[0039]
Further, since the magnetic sensor element of the present invention is configured such that the width of the central portion in the longitudinal direction of the core is reduced to reduce the cross-sectional area, an arbitrary shape can be easily manufactured by photoetching.
[0040]
Further, in the magnetic sensor element of the present invention, since a magnetically annealed permalloy foil is used for the core, a low coercive force (about 30 mOe) of the core required for detecting geomagnetism can be realized.
[0041]
Further, in the magnetic sensor element of the present invention, since the core is attached to the non-magnetic and insulating substrate, the core is not distorted or deformed even if it is thin. Magnetic characteristics can be prevented from deteriorating.
[0042]
Moreover, in the magnetic sensor element of the present invention, the thickness of the core is reduced to about the same as or less than the skin thickness of the excitation frequency, so that deterioration of magnetic characteristics due to eddy current can be prevented, and even if a small detection circuit is used. Since detection can be performed with high accuracy, it is easy to make a chip including a detection circuit, and further reduction in power consumption can be realized.
[0043]
Further, in the method for manufacturing a magnetic sensor element of the present invention, the magnetically annealed permalloy foil is bonded to a non-magnetic and insulating substrate, and the width of the central portion in the longitudinal direction of the permalloy foil is reduced as compared with the other portions. Since the coil is wound around the central portion in the longitudinal direction of the narrow permalloy foil to manufacture the magnetic sensor element, a magnetic sensor element that satisfies all the conditions for mounting on a portable device can be easily manufactured.
[Brief description of the drawings]
FIG. 1 is a perspective view, a top view, and a side view showing a configuration of a magnetic sensor element according to an embodiment of the present invention.
FIG. 2 is a diagram showing steps of a method for manufacturing a magnetic sensor element of the present invention in plan view and side view.
FIG. 3 is a diagram showing steps of a method for manufacturing a magnetic sensor element of the present invention in plan view and side view.
FIG. 4 is a diagram showing a configuration of a detection circuit for connecting the magnetic sensor element of the present invention.
FIG. 5 is a graph showing a magnetic field detection characteristic of the magnetic sensor element of the present invention.
FIG. 6 is a perspective view of a magnetic sensor element according to another embodiment of the present invention.
FIG. 7 is a perspective view of a magnetic sensor element according to still another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Core 1a Central part 1b End part 2 Substrate 3 Coil 10 Magnetic sensor element 11 Permalloy foil 11a Neck part 12 Glass epoxy board 13 Polyurethane conductive wire

Claims (5)

In a parallel fluxgate type magnetic sensor element having a configuration in which a coil is wound around a strip-shaped core, a longitudinal central portion of the core has a smaller cross-sectional area than other portions, and the coil is disposed in the longitudinal central portion. A magnetic sensor element characterized by being wound. The magnetic sensor element according to claim 1, wherein a width of a central portion in a longitudinal direction of the core is narrower than other portions. The magnetic sensor element according to claim 1, wherein the core is obtained by magnetically annealing a permalloy foil. The magnetic sensor element according to any one of claims 1 to 3, wherein the magnetic sensor element is attached to a nonmagnetic and insulating substrate. In a method for manufacturing a parallel fluxgate type magnetic sensor element having a configuration in which a coil is wound around a strip-shaped core, a magnetic annealing is performed on the permalloy foil serving as the core, and the permalloy foil after the magnetic annealing is nonmagnetic and Adhering to an insulating substrate, narrowing the width of the central part in the longitudinal direction of the permalloy foil compared to other parts, and winding the coil around the central part in the longitudinal direction of the magnetic sensor element, Production method.

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