JP2002365352A - Magnetic field detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce attenuation quantity of magnetic flux, when the leakage magnetic flux of a bias magnet reaches a body to be detected, in a magnetic field detector comprising an IC chip having a magnetoelectric element integrated to a signal processing circuit part and the bias magnet. SOLUTION: The bias magnet 2 is bonded directly to a bare chip 3 (IC chip). For the bonding, an adhesive containing soft ferrite powder (magnetic powder) and a vitreous material is used, and the bonding is made through magnetic bonding force and mechanical bonding force. The bare chip 3 (IC chip) and the bias magnet 2 are covered with a package formed of a mixture of a soft ferrite powder (magnetic powder) and a synthetic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an IC chip in which a magnetoelectric conversion element responding to a change in a magnetic field (or magnetic flux) and a signal processing circuit for processing a signal from the magnetoelectric conversion element are integrated.
The present invention relates to a magnetic field detection device including a bias magnet that applies a magnetic field to a magnetoelectric conversion element, and in particular, when the magnetic field detection device is used as a sensor that measures the rotation speed of a detected object, the leakage magnetic flux of the bias magnet is detected. The present invention relates to a structure that can reduce the amount of attenuation of magnetic flux when it reaches a body.

[0002]

2. Description of the Related Art As a prior art in which a magneto-electric conversion element responding to a change in a magnetic field (or magnetic flux) and a signal processing circuit for driving the magneto-electric conversion element and processing a signal from the magneto-electric conversion element are integrated, for example, A so-called Hall IC, which is an IC chip in which a Hall element using a Hall effect as a magnetoelectric conversion element and a signal processing circuit are integrated into one integrated circuit,
A so-called MRIC, which is an IC chip in which a magnetoresistance element using a magnetoresistance effect and a signal processing circuit are integrated as a magnetoelectric conversion element, is known.

[0003] Here, the Hall element generates a Hall electromotive voltage due to a Hall effect caused by a change in magnetic flux perpendicular to the element plane. Further, among the magnetoresistive elements, a semiconductor magnetoresistive element changes its magnetic resistance due to a change in a magnetic field perpendicular to the element plane, and a ferromagnetic magnetoresistive element among the magnetoresistive elements crosses the element plane in parallel. The magnetic resistance changes due to the change in the magnetic field. Hereinafter, as representative examples of these, Hall IC
Will be described.

The Hall IC is also called a bare chip, and is bonded to a predetermined position on a lead frame made of a metal plate by a bonding action called die bonding. The bare chip forms a Hall element having a Hall effect on a part of a substrate made of a single crystal of Si called a silicon wafer, and further drives the Hall element on another part of the substrate, and also transmits a signal from the Hall element. Electronic circuits that perform conversion processing into desired signals are integrated.

An electrode is formed on the bare chip, and the electrode is electrically connected to a predetermined position on the lead frame via a wire by a connection called wire bonding.

In order to shield the bare chip and the wire-bonded lead frame from the external environment, the entire bare chip and the wire are covered with a synthetic resin by an injection molding operation of a synthetic resin called a resin molding. Has been

Here, in the case where a bias magnet is arranged near such a Hall IC, and both are covered with a synthetic resin and packaged, and used as a magnetic field detecting device, the operation of the Hall IC and the bias magnet will be described. I do.
Here, it is assumed that, for example, a gear portion of a rotating gear made of a magnetic material is arranged near the magnetic field detection device, and the rotation speed of the gear is measured by a Hall IC.

The above-described Hall element generates a Hall effect with respect to the magnetic flux passing through the Hall element in the vertical direction among the magnetic flux leaked from the bias magnet. The magnetic flux passing through the Hall element in the vertical direction is generated when the gear portion and the gap of the rotating gear pass near the Hall element, the distance between the tip of the gear portion and the Hall element, and the rear end of the gear portion. It changes according to the alternation of the distance between the hole element and the Hall element. That is,
In a state where the gear portion of the rotating gear faces the Hall element, the distance between the gear and the Hall element becomes shorter, and the magnetic flux leaking from the bias magnet is drawn by the gear portion as a magnetic material,
Leakage magnetic flux crossing the Hall element perpendicularly increases relatively. On the other hand, when the gap of the gear faces the Hall element, the distance between the gear and the Hall element becomes longer, and the leakage magnetic flux crossing the Hall element perpendicularly decreases. By rotating the gear made of magnetic material in this way,
An alternating magnetic flux change that crosses the Hall element vertically occurs.

The Hall element converts the alternating magnetic flux change into a Hall electromotive voltage change, performs necessary signal processing, and converts it into a rectangular wave signal corresponding to the presence or absence of gear teeth. The time interval between the rise time of this rectangular wave and the rise time of the next rectangular wave is measured, and the rotational speed of the gear is obtained.

By the way, the alternating magnetic flux variation given to the Hall element caused by the rotation of the gear described above is:
In performing predetermined signal processing, an amount of a certain level higher than background noise is required. In order to secure this alternating magnetic flux change amount, it is necessary to increase the leakage magnetic flux of the bias magnet, shorten the distance between the gear and the Hall element, or shorten the distance between the bias magnet and the Hall element. Become. Further, there is a need for an improvement that allows more of the leakage flux from the bias magnet to propagate in the gear direction.

Here, in order to increase the magnetic flux leakage from the bias magnet itself, it is necessary to increase the size of the bias magnet itself, which leads to an increase in the size of the magnetic field detection device itself. Therefore, for example, if there is a restriction on the mounting space of the device, there is a problem that the device cannot be mounted. Therefore, it is important to reduce the size of the magnet as much as possible.

The distance between the gear and the Hall element is determined by a certain distance in consideration of the deflection of the rotating shaft of the gear, the vibration of the device itself, and the variation due to the manufacturing accuracy of the gear and the manufacturing accuracy of the device. For example, it is necessary to secure a distance of 2 mm. Therefore, there is a restriction in reducing the distance between the gear and the Hall element.

As described above, shortening the distance between the bias magnet and the Hall element is the most practical measure for securing an alternating magnetic flux variation due to the rotation of the gear at a certain level or more.

Further, the magnetic flux leaking from the bias magnet changes according to the material of the process from the tip of the bias magnet to the tip of the package. That is, if the material from the bias magnet to the package is made of a magnetic material, the magnetic flux can be forced to pass through the magnetic material (material), and as a result, the leakage flux from the bias magnet can be reduced. Most can be effectively transmitted to the gear. This leads to obtaining a desired alternating magnetic flux with a smaller amount of leakage magnetic flux from the bias magnet. As described above, if a magnetic material is effectively used as a material for the process from the magnetic flux leakage surface of the bias magnet to the end of the package, the magnetic flux leakage from the bias magnet can be efficiently transmitted to the gear.

By the way, as described above, the rotation of the gear is converted into an alternating magnetic flux change of the leakage magnetic flux from the bias magnet, and the alternating magnetic flux change is detected by a magneto-electric conversion element to thereby rotate the gear. In the example of measuring the speed, since the bias magnet is used in the open magnetic circuit, the amount of change in the alternating magnetic flux due to the rotation of the gear is roughly determined by the distance between the bias magnet and the gear. For example, when the distance between the bias magnet and the gear is 3 mm and the magnetic flux density needs to be changed by 70 Gauss or more from the magnetic sensitivity characteristics of the Hall element, the bias magnet is required to have a surface of 5 K Gauss or more. It has been found that a leakage flux is required. As described above, in order to obtain a change in magnetic flux required for detecting the rotation speed, a bias magnet that leaks 70 times the magnetic flux on its surface is required.

FIG. 5 shows the relationship between the magnitude (flux density) of the leakage magnetic flux from the bias magnet and the distance (mm) from the magnetic flux leakage surface of the bias magnet. The attenuation rate of the leakage magnetic flux increases as it approaches the bias magnet, and attenuates to about 1/50 of the magnetic flux on the bias magnet surface at a distance of only 2 mm.

In practice, the height of a Hall IC packaged in a plastic package is about 1.5 mm, and the thickness of a package in which a bias magnet and a Hall IC are integrally molded as a magnetic field detector is 0.5 mm. It is usual to have Accordingly, the thickness reaches 2 mm only by these thicknesses, and the magnetic flux attenuates to about 1/50 of the magnetic flux on the bias magnet surface only by these thicknesses. In addition, a thickness of an adhesive layer for bonding the Hall IC to the bias magnet, a stress buffer layer for applying no stress to the Hall IC when packaging the plastic, and the like are actually required. Therefore, in the case of the magnetic field detecting device using the magnetic flux from the bias magnet as an open magnetic path, only a very small percentage (less than 1/50) of the leakage magnetic flux generated from the bias magnet is used.

Therefore, the distance between the bias magnet and the Hall element, that is, the distance between the bias magnet and the gear, is made as small as possible, and the magnetic material is effectively used as a material for the process from the tip of the bias magnet to the tip of the package. By using this, it is understood that the amount of attenuation of the magnetic flux when the leakage magnetic flux of the bias magnet reaches the gear (detected object) is reduced, and the leakage magnetic flux from the bias magnet can be efficiently transmitted to the gear. .

As a conventional technique for shortening the distance between the bias magnet and the Hall element, and further, the distance between the bias magnet and the gear, there is, for example, JP-A-11-10909. In this publication, a part called a die attachment pad is provided in a part of a lead frame made of copper, which is a non-magnetic material, and a bias magnet is attached so that a magnetic flux leakage surface of the bias magnet contacts a back surface of the die attachment pad. The bare chip forming the Hall IC is adhered to the surface of the die attachment pad with conductive epoxy or polyimide adhesive on the surface of the die attachment pad, and the electrode terminal of the bare chip and the lead frame are joined by a bonding wire. A magnetic field detecting device in which a bare chip, a bias magnet and a wire are overmolded with a synthetic resin is disclosed. FIG. 6 is a schematic diagram showing the joining relationship of the components when such a magnetic field detection device is used as a gear rotation speed detection sensor. In FIG.
This magnetic field detecting device is mounted on a surface of a die attachment pad (FIG. 6).
In FIG. 6, the thickness of the package layer covering the surface (the lower surface in FIG. 6) of the bare chip is directly required to protect the bare chip. By reducing the thickness to the minimum, the distance between the bias magnet and the Hall element, and thus the distance between the bias magnet and the gear, are reduced.

[0020]

However, in such a magnetic field detecting device, since the die mounting pad, which is a part of the lead frame, is interposed between the bare chip and the bias magnet, the lead frame (die mounting pad). , The distance between the Hall element and the bias magnet is increased. In general, the thickness of a lead frame used for an IC or the like is about 0.3 mm. Therefore, in order to transmit the magnetic flux leaking from the surface of the bias magnet to the Hall element, the leakage corresponding to a distance of about 0.3 mm is required. It can be said that the magnetic flux is attenuated.

Further, since the material of the package used in such a magnetic field detecting device and the material of the adhesive bonding the bare chip to the die attaching pad are made of a non-magnetic synthetic resin, the bias magnet is used. As a result, the magnetic material is not effectively used as a material for the process from the magnetic flux leakage surface to the end of the package, and the magnetic flux leakage from the bias magnet is not efficiently transmitted to the gear for the above-described reason.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an integrated circuit including a magnetoelectric conversion element and a signal processing circuit for driving the magnetoelectric conversion element and processing a signal from the magnetoelectric conversion element. In a magnetic field detection device having a chip and a bias magnet for applying a magnetic field to the magnetoelectric conversion element, the amount of magnetic flux leakage when the leakage magnetic flux of the bias magnet reaches the detection target can be reduced, and the leakage magnetic flux from the bias magnet can be efficiently reduced. An object of the present invention is to provide an object that can be transmitted to an object to be detected.

[0023]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a magneto-electric conversion element responsive to a change in a magnetic field, and a signal processing circuit for driving the magneto-electric conversion element and processing a signal from the magneto-electric conversion element. A magnetic field detecting device comprising: an IC chip integrated with a unit; and a bias magnet for applying a magnetic field to the magnetoelectric conversion element, wherein the bias magnet and the IC chip are directly joined. did. It should be noted that the term “change in magnetic field” includes “change in magnetic flux”, and the term “magnetic field detection device” also includes “magnetic flux detection device” (the same applies hereinafter).

According to the present invention, the bias magnet and the IC chip are directly joined, so that
The distance between the Hall element and the bias magnet can be reduced by the thickness of the lead frame. Therefore, it is possible to reduce the amount of attenuation when leakage magnetic flux from the bias magnet reaches the detection target by an amount corresponding to the distance.

More preferably, the bias magnet and the IC chip are directly joined by magnetic joining force and mechanical joining force. Specifically, the bonding between the bias magnet and the IC chip uses an adhesive containing a magnetic powder and glass as a solute, and the magnetic bonding force is guided by the magnetic powder, and the mechanical bonding is performed. The force should be guided by vitreous. Here, the “mechanical bonding force” refers to a bonding force generated by, for example, a so-called anchor effect or the like. The adhesive layer between the bias magnet and the IC chip is generally 50μ
m, but not only vitreous but also magnetic powder as a solute is used as an adhesive, so that at least in the process until the leakage magnetic flux of the bias magnet reaches the package, the adhesive layer Can forcibly pass the magnetic flux through the magnetic body (magnetic powder), and as a result, more of the leakage flux from the bias magnet can be effectively transmitted to the detection target. In addition, since the adhesive used in the present invention contains a magnetic powder, when the bias magnet and the IC chip are bonded, a “magnetic bonding force” particularly occurs between the bias magnet and the adhesive. It works and can generate a stronger bonding force than an adhesive containing only vitreous as a solute.

More preferably, the magnetic permeability of the adhesive is larger than the magnetic permeability of the bias magnet.
As a result, the adhesive layer acts as a transmission layer for the leakage magnetic flux of the bias magnet, which is equivalent to the fact that the magnetic flux leakage surface of the bias magnet has moved to the bonding surface on the IC chip side. The distance between the leak surface and the object to be detected can be substantially reduced.

According to the present invention, there is further provided an IC chip in which a magneto-electric conversion element responsive to a change in a magnetic field and a signal processing circuit for driving the magneto-electric conversion element and processing a signal from the magneto-electric conversion element are integrated. In the magnetic field detecting device, a package is provided with a bias magnet for applying a magnetic field to the magnetoelectric conversion element, wherein the package is made of a mixture of a magnetic powder and a synthetic resin. As a result, as in the case of using the adhesive containing the magnetic powder as a solute as described above, in the process until the leakage magnetic flux of the bias magnet reaches the outer surface of the package, at least the thickness of the package layer is forcibly applied. Thus, the magnetic flux can be passed through the magnetic material (magnetic powder), and as a result, more of the leakage flux from the bias magnet can be effectively transmitted to the detection target.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the magnetic field detecting device according to the present invention will be described below with reference to the drawings. First, a manufacturing procedure of the magnetic field detection device according to the present invention will be described with reference to FIGS. Here, FIG. 1 is a perspective view showing a state where a bias magnet is assembled to a lead frame in a process of manufacturing the magnetic field detecting device according to the present invention. FIG.
FIG. 4 is a schematic diagram showing a joining relationship of each component in the magnetic field detection device according to the present invention in which assembly is completed (excluding a package). In the present embodiment, a case is shown in which a Hall IC is used as an IC chip and a Hall element is used as a magnetoelectric conversion element.

In FIG. 1, the lead frame 1 has at least a positioning hole 11 for the lead frame 1 itself.
A lead 12 required to operate as a Hall IC;
And a projection 13 for positioning the bias magnet 2. The bias magnet 2 has a cylindrical shape, but when fixed to the lead frame 1, the positioning magnet 13 of the lead frame 1 is used.
A flat portion 21 is provided at a position opposed to. Also,
The lead frame 1 is fixed to a device (not shown) for manufacturing the present magnetic field detecting device by a positioning hole 11.

First, the bias magnet 2 is connected to the lead frame 2.
The step of fixing to is described. With respect to the lead frame 1 fixed to the manufacturing apparatus, the bias magnet 2 is lowered from above the fixed lead frame 1 (on the near side in FIG. 1), and the positioning projection 13 and the bias The lead frame 1 is fixed at a predetermined position via the flat portion 21 of the magnet 2. The positioning of the bias magnet 2 in the height direction is performed by inserting a minute cutout (not shown) provided in the flat portion 21 of the bias magnet 2 into the bias magnet 2 provided in the lead frame 1.
This is performed by fitting to the positioning projections 13 of FIG.
At this stage, the bias magnet 2 has not been magnetized yet.

Next, a process of bonding a known bare chip 3 (IC chip) to the bias magnet 2 fixed to the lead frame 1 will be described. First, a screen (not shown) for applying an adhesive (details will be described later) is lowered on the upper surface of the bias magnet 2. A pattern according to the shape of the adhesive layer 4 (see FIG. 2) is formed on the screen,
The desired adhesive layer 4 is formed when the adhesive is applied. The thickness of the screen is about three times the thickness of the adhesive layer 4. Thereafter, an adhesive is applied, and the bare chip 3 is placed on the adhesive layer 4 by applying a necessary load. Then, heat is locally applied to the adhesive layer 4 to dry and solidify the adhesive layer 4. The above manufacturing process is a known technique.

Here, the structure of the adhesive will be described. When the bare chip 3 is bonded to the lead frame 1 by an action called die bonding, an adhesive obtained by dispersing a glass foil as a solute and a metal foil powder such as silver in a solvent made of a synthetic resin is generally used. Is done. The bonding in the present invention is not a bonding by a conventional mechanical bonding force, but a composite of a mechanical bonding force and a magnetic bonding force, so the configuration of the adhesive is different from the conventional configuration, An adhesive containing a soft ferrite powder (magnetic powder) and vitreous as a solute and a synthetic resin as a solvent is used as the adhesive. Soft ferrite is, for example, Ni-Zn ferrite or Mn-Zn ferrite. A mixture of these materials with copper may be used. These soft ferrites are magnetized with a small magnetic field (about 2 to 5 Oersteds) because their coercive force is much smaller than that of the hard ferrites constituting the permanent magnet.

As a procedure for manufacturing the adhesive, first, soft ferrite powder composed of fine particles having a size of 2 to 3 μm is prepared. Next, the soft ferrite powder and the vitreous powder are mixed with a desired synthetic resin having a viscosity necessary to form a solvent. Here, for example, the soft ferrite powder and the vitreous powder are mixed so that the weight ratio is 2: 1. Thereafter, the solution is stirred at a predetermined rotation speed and rotation time so that the soft ferrite powder is homogeneously dispersed in the solution.

Since the soft ferrite has about twice the density of the synthetic resin forming the solvent, the viscosity of the solvent must be adjusted in advance in order to stably disperse the soft ferrite powder in the solution. Will be needed. The solution needs to have a viscosity equal to or higher than a predetermined value in order to stably print the solution on the surface of the bias magnet 2 by a so-called screen printing method. At this time, if necessary, the viscosity at the time of printing is adjusted by heating.

Next, a magnetic field is applied to a solution obtained by mixing the soft ferrite powder and glassy material thus prepared in a synthetic resin to magnetize the soft ferrite powder. The magnitude of the magnetic field applied here may be a magnetic field sufficient for the soft ferrite powder to be magnetized. For example, a magnetic field having a magnitude of about 5 Oe is applied. The soft ferrite powder is
The periphery thereof is surrounded by a solvent of a synthetic resin, and the spontaneous magnetization of the soft ferrite is small because the magnetizing magnetic field is small, so that the soft ferrite powder is not adsorbed to each other. As described above, the adhesive according to the present invention is manufactured.

Next, the solution prepared as described above, in which the soft ferrite powder is stably dispersed in the solvent, is applied to the upper surface of the bias magnet 2 through a screen. Thereafter, the screen is removed and heat is applied to stabilize the solvent. Since the bias magnet 2 is not magnetized but is a ferromagnetic material, the magnetized soft ferrite powder is attracted to the bias magnet 2 by a magnetic bonding force. In addition, the vitreous material enters the surface irregularities of the surface of the bias magnet 2 and the bare chip 3 and generates mechanical bonding force by a so-called anchor effect. The bias magnet 2 is fully magnetized after the magnetic field detection device is completed. Therefore, then
The magnetized soft ferrite powder is strongly attracted to the bias magnet 2 by the magnetic bonding force described above, and the bonding layer 4 (see FIG. 2) and the bias magnet 2 are firmly bonded.

As described above, the step of joining the bias magnet 2 and the bare chip 3 is completed. FIG. 2 shows the joining relationship of the components of the magnetic field detecting device according to the present invention in a state where the joining process of the bias magnet 2 and the bare chip 3 has been completed.

Next, in this state, the electrode terminals (not shown) of the bare chip 3 and the lead frame (not shown) are joined by bonding wires, and the bare chip 3, the bias magnet 2 and the wires (not shown) are bonded. Is packaged with a packaging material (described later). Hereinafter, a packaging method will be described.

The conventional packaging material is usually composed of epoxy resin, but the packaging material used in the present invention is a mixture of conventional epoxy resin and soft ferrite powder (magnetic powder). It consists of. In order to uniformly disperse the soft ferrite powder in the package layer, a package is manufactured in the following process. First, pellets for injection molding comprising a soft ferrite powder composed of particles of 2 μm to 3 μm and an epoxy resin are prepared. In this case, the weight ratio of the soft ferrite powder is 2 and the weight ratio of the epoxy resin pellets is 1. Then, the soft ferrite powder and the epoxy resin pellets are mixed and stirred.
Next, this is heated to 250 ° C. to be melted, extruded into the air, and continuously cut into pellets having a diameter of about 2 mm. A pellet made of a mixture of the ferrite powder and the epoxy resin is used as an injection molding material for a package. The injection molding of the package is performed by a known method.

The packaging process is completed as described above. Thereafter, portions of the lead frame 1 other than the leads 12 are separated from the package body, and the magnetic field detecting device according to the present invention is completed. The magnetic field detection device according to the present invention,
Since only the joining structure of the bias magnet 2 and the bare chip 3 and the package material are different from those of the conventional device, there is no difference from the conventional device in the appearance after completion. FIG.
Shows an overview of a packaged magnetic field detecting device disclosed in the publication relating to the prior art, but this overview can also be applied to the magnetic field detecting device according to the present invention.

The embodiment of the magnetic field detecting device according to the present invention has been described above. According to this embodiment, the following effects are achieved.

First, since the bias magnet 2 and the bare chip 3 are directly joined, the distance between the Hall element and the bias magnet 2 can be reduced by the thickness of the lead frame 1 as compared with the above-described conventional technology. Therefore, it is possible to reduce the amount of attenuation when leakage magnetic flux from the bias magnet 2 reaches the detection target (for example, a gear) by an amount corresponding to the distance.

The adhesive layer 4 is made of soft ferrite powder and vitreous. The soft ferrite generates a magnetic bonding force, and the soft ferrite has a predetermined magnetic permeability (for example, from 2500 to 1 as an initial magnetic permeability).
0000), the magnetic flux leaking from the bias magnet 2 can be intensively guided to the bare chip 3 in order to easily pass the magnetic flux as compared with the conventional glass having an initial magnetic permeability of 1.

Further, since the adhesive layer 4 is made of a magnetic material having a magnetic permeability higher than that of the bias magnet 2, the adhesive layer 4 functions as a magnetic flux transmission layer, and the magnetic flux leakage surface of the bias magnet 2 is a bare chip. This is equivalent to moving to the bonding surface on the third side. Therefore, although the adhesive layer 4 is a thin layer of about 50 μm, the effect that the distance between the magnetic flux leakage surface of the bias magnet 2 and the object to be detected is substantially reduced by the thickness of the adhesive layer 4 also occurs. As a result, the distance from the magnetic flux leakage surface of the bias magnet 2 to the object to be detected is substantially equal to the thickness of the lead frame 1 and the thickness of the adhesive layer 4 compared to the prior art.
Is reduced by an amount corresponding to the sum of the thicknesses of.

The package layer is also made of soft ferrite powder and epoxy resin. The initial permeability of soft ferrite has a value of 2500 to 10000, but the epoxy resin is 1. Therefore, the package layer also acts as a layer for transmitting the leakage magnetic flux from the bias magnet 2. The thickness of the package layer is generally 0.
Although having a thickness of about 5 mm, this package layer transmits magnetic flux significantly as compared with the conventional package layer. The leakage magnetic flux from the bias magnet 2 is attenuated by propagating by a distance corresponding to the thickness of the bare chip 3, but the leakage magnetic flux transmitted to the package layer thereafter is attenuated by a very small amount in the package layer. From the outer surface of the target object (for example, a gear). In this manner, by forming the package from the soft ferrite powder and the epoxy resin, the attenuation of the leakage magnetic flux can be reduced by an amount corresponding to the package thickness of 0.5 mm.

The effect of reducing the amount of attenuation of the leakage magnetic flux from the bias magnet in the embodiment described above will be described with reference to FIG. FIG. 4 is a cross section (left side) of each component of the magnetic field detecting device described in the above-mentioned prior art publication.
FIG. 4 is a schematic diagram comparing a section (right side) of each component of the magnetic field detection device according to the present embodiment.

In FIG. 4, the outer surface of the package (FIG.
And the thickness of the package layer (not shown, for example, a gear, which is assumed to be disposed near (on the lower side of) the outer surface of the package). 0.5 mm) does not change. The same bare chip (0.4 mm in thickness) of the Hall IC is used.

In the present invention, as compared with the prior art, in the propagation distance at which the leakage magnetic flux is attenuated, the thickness of the lead frame (0.3 mm) and the thickness of the package layer (0.5 m) are used.
m) is shortened. That is, in the prior art,
The propagation distance (in the apparatus) where the leakage magnetic flux is attenuated is 1.2 mm, which is the entire distance from the magnetic flux leakage surface of the bias magnet to the outer surface of the package. On the other hand, in the present invention, the thickness of the package is 0.5 mm and the thickness of the lead frame is 0.3 mm.
mm, the propagation distance (in the apparatus) at which the leakage magnetic flux is attenuated is only 0.4 mm corresponding to the thickness of the bare chip.

The result is applied to the magnetic flux attenuation characteristics shown in FIG. In the prior art, when the magnetic flux density of the magnetic flux leakage surface of the bias magnet is set to 1, the magnetic flux density becomes 0.04 when the distance from the magnetic flux leakage surface of the bias magnet is 1.2 mm. On the other hand, in the present invention, when the distance of the bias magnet from the magnetic flux leakage surface is 0.4 mm, the magnetic flux density becomes 0.1. Accordingly, in the prior art, the leakage magnetic flux attenuated by 96% is used, whereas in the present invention, the leakage magnetic flux attenuated by 90% is used.

In order to facilitate understanding of this effect, a comparison will be made with the magnitude of the leakage magnetic flux on the magnetic flux leakage surface of the bias magnet replaced. Here, it is assumed that a magnetic flux of 160 gauss is required on the outer surface of the package in order to measure the rotational speed of, for example, a gear, which is a detection target. In order to obtain this leakage magnetic flux, the conventional technique requires a magnetic flux of 4K Gauss at the magnetic flux leakage surface of the bias magnet. on the other hand,
In the present invention, in order to obtain a magnetic flux of 160 gauss as a magnetic flux leakage on the outer surface of the package, the leakage magnetic flux on the magnetic flux leakage surface of the bias magnet may be 1.6 K gauss. As described above, in the related art, a magnetic flux of 4K Gauss is required on the magnetic flux leakage surface of the bias magnet,
In the present invention, since the magnetic flux leakage surface is equivalent to a bias magnet of only 1.6K gauss, the size of the bias magnet can be greatly reduced by employing the present invention. For example φ7 ×
Assuming that a 4 mm cylindrical magnet generates 4 K gauss of magnetic flux on the magnetic flux leakage surface, a magnet of the same material and the same diameter has a magnet of only 1.1 mm height and a magnetic flux of 1.6 K gauss is generated on the magnetic flux leakage surface. Will be obtained.

Therefore, when the present invention is adopted, the height of the entire device is 0.3 mm corresponding to the thickness of the lead frame and the amount of reduction of the height of the bias magnet as compared with the prior art. It is possible to reduce the distance by 2.9 mm, and a total of 3.2 mm. Thus, in the present invention,
When manufacturing a magnetic field detection device that integrates a bias magnet and a bare chip and applies a resin mold, the height of the device can be significantly reduced, making it easy to integrate and inspecting the entire device after integration. It's easy. Also, needless to say, the size of the bias magnet can be greatly reduced, so that the manufacturing cost of the bias magnet itself can be reduced.

If the package material is a magnetic material mixed with soft ferrite, the entire package will actively propagate magnetic flux, and the leakage flux from the bias magnet will form a closed magnetic path in the package, and the bias magnet will In the direction of the object to be detected.
In order to prevent this, it is preferable to provide a slight gap in the side direction of the bias magnet to prevent the generation of a magnetic flux loop due to the closed magnetic path.

[0053]

As described above, according to the present invention,
An IC in which a magneto-electric conversion element and a signal processing circuit for driving the magneto-electric conversion element and processing a signal from the magneto-electric conversion element are integrated.
In a magnetic field detection device having a chip and a bias magnet for applying a magnetic field to the magnetoelectric conversion element, the amount of magnetic flux leakage when the leakage magnetic flux of the bias magnet reaches the detection target can be reduced, and the leakage magnetic flux from the bias magnet can be efficiently reduced. What can be transmitted to a detection object well can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state where a bias magnet is assembled to a lead frame in a manufacturing process of a magnetic field detection device according to the present invention.

FIG. 2 is a schematic diagram showing a joining relationship of each component in a magnetic field detection device according to the present invention in which assembly is completed (excluding a package).

FIG. 3 is a three-dimensional view showing an overview of a magnetic field detection device according to the present invention.

FIG. 4 is a schematic diagram comparing a cross section (left side) of each component of the magnetic field detection device described in the official gazette of the related art with a cross section (right side) of each component of the magnetic field detection device in the present embodiment. It is.

FIG. 5 is a graph showing the relationship between the magnitude (flux density) of leakage magnetic flux from a bias magnet and the distance (mm) from the magnetic flux leakage surface of the bias magnet.

FIG. 6 is a schematic diagram showing a joining relation of respective components when a magnetic field detection device according to a conventional technique is used as a rotation speed detection sensor of a gear.

[Explanation of symbols]

 2 bias magnet 3 bare chip (IC chip) 4 adhesive layer (adhesive)

Claims (5)

[Claims] An IC chip in which a magneto-electric conversion element responsive to a change in a magnetic field, a signal processing circuit unit for driving the magneto-electric conversion element and processing a signal from the magneto-electric conversion element are integrated, and the magneto-electric conversion element A magnetic field detecting device comprising: a bias magnet for applying a magnetic field to the magnetic field, wherein the bias magnet and the IC chip are directly joined. 2. The magnetic field detecting device according to claim 1, wherein the bias magnet and the IC chip are directly joined by a magnetic joining force and a mechanical joining force. 3. The bonding method according to claim 2, wherein the bias magnet and the IC chip are bonded by using an adhesive containing a magnetic powder and a vitreous material as a solute, and the magnetic bonding force is controlled by the magnetic powder. The magnetic field detecting device is guided by a body, and the mechanical bonding force is guided by the vitreous material. 4. The magnetic field detecting device according to claim 3, wherein the magnetic permeability of the adhesive is larger than the magnetic permeability of the bias magnet. 5. An IC chip in which a magneto-electric conversion element responsive to a change in a magnetic field, a signal processing circuit for driving said magneto-electric conversion element and processing a signal from said magneto-electric conversion element are integrated, and said magneto-electric conversion element A magnetic field detecting device in which a bias magnet for applying a magnetic field is covered with a package, wherein the package is made of a mixture of magnetic powder and synthetic resin.