JP5426839B2 - Manufacturing method of magnetic sensor - Google Patents

Description

The present invention provides a magnetic sensor for detecting a relative magnetic field change caused by the movement of the detection target, a method for manufacturing a magnetic sensor provided with the bias magnet for generating a bias magnetic field to be applied to the magnetoresistive element .

In a magnetic sensor for detecting a relative magnetic field change caused by the movement of a detection object, a magnetoresistive element formed of a thin film of an alloy mainly composed of a ferromagnetic metal such as Ni, Fe, Co or the like is widely used. . This magnetoresistive element has a property that the resistance value changes according to the direction of the strength of the magnetic field. The response of the magnetoresistive element is ΔR / R ₀ (ΔR = change in resistance of the ferromagnetic thin film metal, R ₀ = Measured as the nominal resistance of the ferromagnetic thin film metal).

For example, as shown in FIG. 5A, when a magnetic field H is applied in a direction (X direction) perpendicular to the current flow direction (Y direction) of a magnetoresistive element made of a ferromagnetic thin film metal, The relationship between the strength (H) of the magnetic field and ΔR / R ₀ representing the change in the resistance value of the magnetoresistive element is a bell shape (ΔR / R ₀ is approximately proportional to H ² ) as shown in FIG. Decrease) graph. A magnetic sensor is configured by converting the change in the resistance value of the magnetoresistive element into an output as a voltage change by combining an equivalent circuit with a ferromagnetic thin film metal pattern. As an example of the equivalent circuit, various circuits such as a case where two magnetoresistive elements are used as shown in FIG. 5C and a case where four magnetoresistive elements are used as shown in FIG. A configuration has already been proposed.

  When utilizing as a magnetic sensor in a region where the change in resistance value is not saturated in this manner, the NiFe alloy has an anisotropic magnetic field of about 300 A / m, and the NiCo alloy and NiFeCo alloy have an anisotropic magnetic field of about 1 kA / m, as shown in FIG. However, there is a problem that hysteresis occurs in the vicinity of the zero magnetic field when a magnetic field is applied continuously in positive and negative directions.

  However, as shown in FIG. 7A, by applying a bias magnetic field (about 300 A / m or more for Fe alloy, about 1 kA / m or more for NiCo alloy and NiFeCo alloy) in parallel with the extending direction of the magnetoresistive element. The hysteresis is eliminated as shown by the broken line in FIG. When the magnetic field strength is further increased, as shown in FIG. 7C, the operating range (a range in which the rate of change in resistance value is not saturated) extends to the high magnetic field side.

  When it is necessary to determine whether the magnetic field is positive or negative, as shown in FIG. 8A, by applying a bias magnetic field perpendicular to the extending direction of the magnetoresistive element, the bias as shown by the broken line in FIG. The operating point (point where the resistance change is 0%) is shifted according to the strength of the magnetic field. Therefore, it is possible to determine whether the magnetic field is positive or negative.

  Thus, the magnetic sensor in which the bias magnetic field is applied to the magnetoresistive elements in the X to Y directions can be used for various applications. For example, Patent Document 1 and Patent Document 2 have already been proposed as magnetic sensors to be used by applying a bias magnetic field to such a magnetoresistive element.

  The magnetic detector described in Patent Document 1 is characterized by providing a positioning unit for positioning the magnetoresistive element and the bias magnetic field magnet at the same time. The effect of reducing the installation time is realized.

In addition, in the magnetoresistive sensor described in Patent Document 2, the magnet has a structure in which the lines of magnetic force from the magnet are guided vertically in at least the sensing direction (y direction) in the sensitive area of the sensor. This minimizes the magnetic field in the sensitive direction in the positioning plane between the sensor element and the magnet, which causes an offset in the characteristic curve of the sensor element, and subsequent trimming of the magnetoresistive sensor. It becomes unnecessary.
Japanese Patent Laid-Open No. 11-21409 JP 2005-501265 A

  Although the magnetic detector described in Patent Document 1 and the magnetoresistive sensor described in Patent Document 2 are used for different purposes, a method of applying a permanent magnet as a method of applying a bias magnetic field to the magnetoresistive element is used. Adopted. In this type of application, a magnetic flux density of about 15 mT or more is required as the magnetic field strength applied to the magnetoresistive element. In such a case, the method of bonding a large permanent magnet away from the magnetoresistive element rather than adhering a small and strong permanent magnet to the magnetoresistive element is more uneven in bias magnetic field intensity due to positioning errors due to bonding. Is relaxed to some extent. That is, there is a problem in that it is difficult to position a permanent magnet that generates a bias magnetic field if the permanent magnet is reduced in size and placed close together.

  If the magnetic field applied to the magnetoresistive elements constituting the equivalent circuit (for example, the magnetoresistive elements (R1 to R4) of the equivalent circuit shown in FIG. 5D) is nonuniform, the offset potential of Vout varies. Problems such as variations in output sensitivity and distortion in the output waveform. In order to solve the same problem as this, Patent Document 2 devised the shape of the permanent magnet, and Patent Document 1 attempts to improve the adhesion accuracy.

  However, there is a problem that the accuracy of the method itself is limited as long as the bonding method is adopted, such as the bonding accuracy between the substrate on which the magnetoresistive element is formed and the lead frame, the package molding accuracy, and the permanent magnet bonding accuracy.

The present invention has been made in view of the above-mentioned problems, and can be used to eliminate a positioning error between a magnetoresistive element and a permanent magnet by a simple and inexpensive method, and to manufacture a suitable magnetic sensor that can be miniaturized with high accuracy. It is intended to provide a method .

According to a first aspect of the present invention, there is provided a method for forming a magnetic sensor for detecting a magnetic field change caused by relative movement between a magnetic sensor and a detection object by providing a substrate with a magnetoresistive element and a magnetic body. A step of forming an array of magnetoresistive elements, electrodes, protective films, etc. on one surface of the substrate made of silicon, glass or ceramic, and the other surface of the substrate, each of the magnetoresistive elements Aligned by photolithography at the relevant position and formed concave portions in an array shape by microblasting method, and a mixture of magnetic powder and resin is poured into the concave portions by potting or printing method to become the magnetic material The step of forming a permanent magnet by magnetizing the cured product and the other surface of the substrate on which the permanent magnet is disposed are polished to adjust the thickness of the permanent magnet. It is a manufacturing method of a magnetic sensor, characterized in that comprising the step of.

According to a second aspect of the present invention, there is provided a method of forming a magnetic sensor for detecting a magnetic field change caused by relative movement between a magnetic sensor and a detection object by providing a magnetoresistive element and a magnetic body on a substrate. , silicon, on one surface of the substrate made of glass or ceramic, and forming magnetoresistive element, electrodes, a protective film or the like in an array, a second surface of said substrate, each of said magnetoresistive Aligned by photolithography at the position related to the element, and formed a concave portion in an array shape by a microblast method, and a mixture of magnetic powder and resin is poured into the concave portion by a potting or printing method to become the magnetic body. forming a cured product, comprising the steps of forming a permanent magnet magnetized in the cured product, adjusting the thickness of the permanent magnet by polishing the entire other surface of the substrate to the permanent magnet is arranged It is a manufacturing method of a magnetic sensor, characterized in that comprising the step of.

According to the first aspect of the present invention, the step of forming an array of magnetoresistive elements, electrodes, protective films, etc. on one surface of the substrate made of silicon, glass or ceramic, and the other surface of the substrate Then, alignment is performed by photolithography at a position related to each of the magnetoresistive elements, and concave portions are formed in an array shape by a microblast method, and a mixture of magnetic powder and resin is formed in the concave portions by a potting or printing method. A step of forming a hardened material that is poured into the magnetic material, a step of magnetizing the hardened material to form a permanent magnet, and polishing the other surface of the substrate on which the permanent magnet is disposed to polish the permanent magnet. since so as to form a magnetic sensor and adjusting the thickness of the positional relationship accuracy between the magnetoresistive element is ensured, and the shape of the magnet after magnetized magnetic material on the shape of the recess Shape accuracy is determined What is also ensured. Therefore, the problem that the bias magnetic field is uniformly applied to the magnetoresistive element, the offset potential of Vout fluctuates, the output sensitivity varies and the output waveform is distorted is eliminated, and the miniaturization can be performed with high accuracy. Moreover, the accuracy of the concave shape can be several μm or less by the microblast method. Further, by adjusting the thickness of the permanent magnet by polishing the other surface of the substrate, it was possible to obtain a magnetic field strength with little variation in proportion to the thickness of the magnetic material. This makes it possible to adjust the magnetic field strength applied to the magnetoresistive element in a wide range without changing the mixing ratio of the magnetic powder and the amount of magnetization after curing.

According to the second aspect of the present invention, silicon, on one surface of the substrate made of glass or ceramic, and forming magnetoresistive element, electrodes, a protective film or the like in an array, the other surface of the substrate a is, the aligned photolithography at positions associated with each magnetoresistive element recesses in the micro blasting formed in an array, in the recess, potting or printing a mixture of a magnetic powder and a resin A step of forming a cured product to be the magnetic material by pouring by a construction method, a step of adjusting the thickness of the cured product by polishing the other surface of the substrate on which the cured product is disposed, and a method of attaching the cured product to the cured product. Since the magnetic sensor is formed by the process of forming a permanent magnet by magnetizing , the positional relationship accuracy with the magnetoresistive element is guaranteed, and the shape of the magnet after magnetizing the magnetic material is also the shape of the recess By Shape accuracy is determined is also ensured. Therefore, the problem that the bias magnetic field is uniformly applied to the magnetoresistive element, the offset potential of Vout fluctuates, the output sensitivity varies and the output waveform is distorted is eliminated, and the miniaturization can be performed with high accuracy. Moreover, the accuracy of the concave shape can be several μm or less by the microblast method. Further, by adjusting the thickness of the permanent magnet by polishing the other surface of the substrate, it was possible to obtain a magnetic field strength with little variation in proportion to the thickness of the magnetic material. This makes it possible to adjust the magnetic field strength applied to the magnetoresistive element in a wide range without changing the mixing ratio of the magnetic powder and the amount of magnetization after curing.

In the method of manufacturing a magnetic sensor according to the present invention, a magnetic sensor for detecting a magnetic field change caused by relative movement between the magnetic sensor and a detection target is formed by providing a magnetoresistive element and a magnetic body on a substrate. in the method, a silicon on one surface of the substrate made of glass or ceramic, magnetoresistive element, electrodes, a protective film or the like and forming the array, a second surface of said substrate, each of the magnetic Aligned by photolithography at a position related to the air resistance element, and formed a concave portion in an array shape by a microblast method, and a mixture of magnetic powder and resin is poured into the concave portion by a potting or printing method, and the magnetic body forming a cured product becomes, and the step of forming the permanent magnet magnetized in the cured product, the permanent by polishing the entire other surface of the substrate to the permanent magnet is arranged Characterized in that comprising the step of adjusting the thickness of the stone. Details will be described below.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a structural diagram of a magnetic sensor 10 singulated as an embodiment of the present invention. In the magnetic sensor 10, a magnetoresistive element 11 and an electrode 12 are formed on the surface of a substrate 13. A concave portion 14 is formed on the back surface of the substrate 13, and a magnetic material 15 is formed in the concave portion 14, which is a cured product of magnetic powder and resin, and is magnetized after curing to be a permanent magnet. 15 is a feature of the present invention and a method of manufacturing the magnetic sensor.

  A permanent magnet is formed by magnetizing a magnetic material that is a cured product of magnetic powder and resin, and a bias magnetic field is applied from the permanent magnet to the magnetoresistive element. Since even a small permanent magnet is close to the magnetoresistive element, a relatively large bias magnetic field of about 30 mT can be applied to the magnetoresistive element, and the magnetic sensor can be miniaturized. Also, the permanent magnet is close to the magnetoresistive element, but unlike the conventional technology, the adhesive method is not used, so the positional relationship accuracy with the magnetoresistive element is guaranteed, and the shape of the permanent magnet is also determined by the shape of the recess. Accuracy is also guaranteed. Therefore, the bias magnetic field is uniformly applied to the magnetoresistive element, and the problems that the offset potential of Vout fluctuates, variation in output sensitivity and distortion in the output waveform are solved with high accuracy. A small magnetic sensor can be configured.

An example of a method for manufacturing the magnetic sensor 10 of the present invention will be described with reference to FIG. In the manufacturing method described with reference to FIG. 2, a plurality of magnetic sensors are simultaneously formed on the same substrate and then separated into individual pieces.
First, as shown in FIG. 2A, the magnetoresistive element 11, the electrode 12, the protective film, etc. (not shown) are formed in an array on the surface of the substrate 13 made of silicon, glass or ceramic. The surface of the substrate 13 is processed.

  Next, as shown in FIG. 2B, recesses 14 are formed in an array on the back surface of the substrate 13 by an etching method or a microblast method. The position of the recess 14 is adjusted with each magnetoresistive element formed on the surface of the substrate 13. In the microblasting method, if the silicon carbide or alumina is used with a particle size of # 300 to 1000, the accuracy of the shape of the manufactured recess 14 can be several μm or less as in the etching method. Since the pattern position of the magnetoresistive element on the front surface and the recess (61) on the back surface are aligned by photolithography, positional accuracy of several μm or less is guaranteed.

  In the above-described embodiment, the step of forming the magnetoresistive element on one surface of the substrate is performed first, and the magnetic powder and the resin are placed in the concave portion formed on the other surface of the substrate at a position related to the magnetoresistive element. The process of forming the hardened material that becomes the magnetic material by pouring the mixed material was performed later, but the order was reversed and the other side of the substrate was magnetically formed in the recess formed at the position related to the magnetoresistive element. A process of forming a cured product that becomes a magnetic material by pouring a mixture of powder and resin may be performed first, and a process of forming a magnetoresistive element on one surface of the substrate may be performed later.

  After the formation of the recess 14, as shown in FIG. 2 (c), the magnetic material 15, which is a mixture of magnetic powder and resin, is poured into the recess 14 in a state before being singulated, and thereafter The curing process is performed. As a result, the amount of magnetic material of each magnetic sensor can be made uniform. Finally, by magnetizing the magnetic body 15, the magnetic body 15 becomes a permanent magnet and the magnetic sensor 10 is completed. Magnetization of the magnetic body 15 may be performed in the state of the integrated substrate shown in FIG. 2C, or may be magnetized after separation.

In this way, by casting and hardening the magnetic body 15 by potting or printing and magnetizing it, the variation as a function of the permanent magnet after magnetization is reduced. Moreover, since the magnetic direction of the magnet can be set by magnetization, the polarity direction can be easily determined. Furthermore, as a feature of this structure, since it can be easily magnetized with a coil or a coil with a yoke, saturation magnetization (2 to 5 times the coercive force , which is a magnetic powder characteristic) is possible, and a mixture of magnetic powder and resin Stable magnetic characteristics can be obtained even with certain magnetic materials.

The characteristics of the magnetic sensor 10 configured as described above will be described.
As an example, as shown in FIG. 4A, the characteristics were measured by forming the magnetoresistive element 11 and the electrode 12 on the surface of a glass substrate 13 having a size of 2 mm × 2 mm and a thickness of 0.35 mm. (Described in FIG. 3 of the aforementioned Japanese Patent Application Laid-Open No. 2006-208025 by the present applicant). A magnetoresistive element having a pattern shown in FIG. 3A is formed on the surface of the glass substrate 13. The eight magnetoresistive elements are connected as shown in FIG. 3B to form electrodes 12 (omitted in FIG. 3A). Also, as shown in FIG. 4A, a recess (55) having a depth of 0.25 mm is formed on the back surface of the substrate 13, and a magnetic material that is a mixture of magnetic powder and resin is poured into the recess 14 and cured. The magnetic body 15 is created. Thereafter, the air core coil is magnetized with a saturated magnetic field so as to be in the polarity direction shown in FIG. By this magnetization, the magnetic body 15 becomes a permanent magnet, and a bias magnetic field is applied to each magnetoresistive element as shown in FIG.

  In the structure as described above, when the offset potentials of Vout1 to Vout4 in the connection state shown in FIG. 3B were measured before and after magnetization, fluctuations in potential could be suppressed to about 1 mV / V or less. .

  Next, the magnetic powder is made of ferrite-based magnetic powder and rare earth (SmFeN) -based magnetic powder, the mixing ratio with the epoxy resin is changed, and a magnetic material is manufactured. Magnetization was performed to confirm the intensity of the bias magnetic field applied to the magnetoresistive element.

  With the ferrite-based magnetic powder, it was possible to obtain a magnetic field strength with little variation when the magnetic force of the bias magnetic field applied to each of the magnetoresistive elements shown in FIG. 4C was about 10 mT or less.

When the rare earth (SmFeN) magnetic powder is determined at a blending ratio of 50 to 90 wt%, the magnetic field of the bias magnetic field applied to each magnetoresistive element shown in FIG. 7a is in the range of about 30 mT or less in proportion to the mixing ratio. Thus, it was possible to obtain a magnetic field intensity with a wide range and little variation.
In addition, the rare earth (SmFeN) magnetic powder had an iHc ( coercive force ) of about 700 kA / m in the VSM measurement, and was able to obtain a strong characteristic against a demagnetizing field. By using rare earth (SmFeN) magnetic powder as a preferable state, there is no fluctuation of the offset potential of Vout1 to Vout4, and it is possible to widen the operating range (range of magnetic field change caused by relative motion with the object to be detected). It is.

  Further, the back surface was polished in the state before magnetization of FIG. 4B (the state of FIG. 2C), and the thickness of the substrate and the thickness of the magnetic material were reduced gradually. As a result, it was possible to obtain a magnetic field strength with little variation in the magnetic field of the bias magnetic field after magnetization in proportion to the thickness of the magnetic material. This makes it possible to adjust the magnetic field strength applied to the magnetoresistive element in a wide range by manufacturing without changing the mixing ratio of magnetic powder and the amount of magnetization after curing in the initial process and polishing after manufacturing. Was found to be possible.

  In the above-described embodiment, the magnetoresistive element pattern shown in FIG. 3A has been described. However, this is only an example, and the present invention is not limited to this, and has various pattern layouts. (For example, described in FIG. 9 of Japanese Patent Laid-Open No. 11-21409, FIG. 8 of Japanese Patent Laid-Open No. 59-19810, etc.). That is, by applying the manufacturing method of the present invention to a magnetic sensor that uses a permanent magnet bonding method, the lead frame bonding accuracy, package molding accuracy, and permanent magnet bonding accuracy of the conventional permanent magnet bonding method are described. Therefore, it is possible to provide a suitable magnetic sensor that can eliminate the problem of limitations in the above and can be miniaturized with high accuracy.

  Further, the present invention can be applied to a relatively small operating range (bias magnetic field) such as a current sensor and a geomagnetic sensor as an application, and is not limited thereto.

It is sectional drawing showing the structure of the magnetic sensor 10 by this invention. It is the schematic diagram showing the manufacturing process of the magnetic sensor 10 by this invention. (A) is the schematic diagram showing an example of the magnetoresistive element pattern formed in the board | substrate surface of the magnetic sensor 10 by this invention, (b) is the circuit diagram showing the connection. (A) is sectional drawing showing the state before pouring of the magnetic body 15 of the magnetic sensor 10 by this invention, (b) is sectional drawing showing the state after pouring the magnetic body 15, ( (c) is a schematic diagram showing the direction of the bias magnetic field after magnetization. (A) is the perspective view showing the structure of the general magnetoresistive element, (b) is the graph showing the relationship between the magnetic field applied to a magnetoresistive element, and resistance value change, (c) and (D) is the schematic diagram showing an example of the equivalent circuit using a magnetoresistive element. It is a graph showing the mode of the hysteresis which arises in a magnetoresistive element. (A) is the schematic diagram showing the state at the time of applying a bias magnetic field in parallel with the extending direction of a magnetoresistive, and (b) and (c) are the graphs showing the characteristic in this case. (A) is the schematic diagram showing the state at the time of applying a bias magnetic field perpendicular | vertical to the extending | stretching direction of a magnetoresistive, and (b) is a graph showing the characteristic in this case.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Magnetic sensor, 11 ... Magnetoresistive element, 12 ... Electrode, 13 ... Board | substrate, 14 ... Recessed part, 15 ... Magnetic body.

Claims (2)

In a method of forming a magnetic sensor for detecting a magnetic field change caused by relative movement between a magnetic sensor and a detection object by providing a magnetoresistive element and a magnetic body on a substrate, the magnetic sensor is made of silicon, glass, or ceramic. on one surface of the substrate, magnetoresistive element, electrodes, and the step of the protective film or the like formed in an array, a second surface of said substrate, photolithography said associated with each magnetoresistive element position a step to form a recess in an array with a micro blasting an alignment, to form the in the recess, the cured product which becomes the magnetic body by pouring a mixture of a magnetic powder and a resin potting or printing technique in, this consisting the steps of: constituting a permanent magnet magnetized in the cured product, the step of adjusting the thickness of the permanent magnet by polishing the entire other surface of the substrate to the permanent magnet is arranged Method of producing a magnetic sensor characterized by. In a method of forming a magnetic sensor for detecting a magnetic field change caused by relative movement between a magnetic sensor and a detection object by providing a magnetoresistive element and a magnetic body on a substrate, the magnetic sensor is made of silicon, glass, or ceramic. on one surface of the substrate, magnetoresistive element, electrodes, and the step of the protective film or the like formed in an array, a second surface of said substrate, photolithography said associated with each magnetoresistive element position a step to form a recess in an array with a micro blasting an alignment, to form the in the recess, the cured product which becomes the magnetic body by pouring a mixture of a magnetic powder and a resin potting or printing technique in, a step of the cured product to adjust the thickness of the cured product was polished the entire other surface of the substrate arranged, in that it consists of a step which constitutes a permanent magnet magnetized in the cured product Manufacturing method of a magnetic sensor according to symptoms.

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