JP2001091613A - Multichip module for magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multichip module for a magnetic sensor having little magnetic influence on IC chips. SOLUTION: In this multichip module for a magnetic sensor, magnetic sensor chips 1 for detecting magnetism and IC chips 2 for processing electric signals are arranged and accommodated in the same package 5, and first members 4 formed of material with magnetism collecting properties are accommodated so as not to be overlapped with the IC chips 2, while a second member 6 formed of material with magnetism collecting properties is provided being spread around the package 5. The lines of magnetic flux passing through the package 5 enter the second member 6 and converge on the first members 4 to avoid the IC chips 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-chip module for a magnetic sensor which is packaged by combining an IC chip with a magnetic sensor chip, and more particularly to a multi-chip module for a magnetic sensor having a small magnetic influence on the IC chip. It is.

[0002]

2. Description of the Related Art A multi-chip module for a magnetic sensor is configured such that a magnetic sensor chip for detecting magnetism and a semiconductor IC chip for processing an electric signal output from the magnetic sensor chip are bonded to one lead frame to form a gold wire or The magnetic sensor chip and the IC chip are sealed in the same package by making an electrical connection with aluminum wires or the like and covering the magnetic sensor chip and the IC chip with a resin or ceramics and packaging them. . This multi-chip module for a magnetic sensor can be used, for example, as a rotation sensor that is inserted into a magnetic circuit passing through a gear and captures a magnetic flux fluctuation when the gear rotates to output it as a voltage fluctuation.

[0003]

A multi-chip module for a magnetic sensor is used in a magnetic circuit. Therefore, the IC chip in the package is affected by the magnetic field of the magnetic circuit. The characteristics of the IC chip fluctuate under the influence of a magnetic field, or normal signal processing becomes difficult due to the influence of magnetic noise.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a multi-chip module for a magnetic sensor having a small magnetic influence on an IC chip.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a multi-sensor for a magnetic sensor in which a magnetic sensor chip for detecting magnetism and an IC chip for processing an electric signal are housed side by side in the same package. In the chip module, a first member made of a material having a magnetism collecting property is accommodated in the package so as not to overlap the IC chip, and a second member made of a material having a magnetism collecting property is placed in the package. It is provided by spreading around.

[0006] The first member may overlap the magnetic sensor chip.

[0007] The material may be a ferrite material.

[0008] The magnetic sensor chip may be a Hall element or a magnetoresistive element.

The magnetic sensor chip may face a rotating gear, and a voltage change corresponding to a magnetic flux change detected by the magnetic sensor chip may be output from the IC chip.

[0010]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, in a multi-chip module for a magnetic sensor according to the present invention, two Hall element chips (magnetic sensor chips) 1 and a semiconductor IC chip 2 are alternately arranged on a lead frame 3. A first member 4 made of a magnetic collecting material is superimposed on each of the Hall element chips 1, and the magnetic sensor chip 1, the first member 4 and the IC
The chip 2 is housed in a package 5 and the package 5
A second member 6 made of a magnetic flux collecting material is adhered to the outer periphery of.

As described above, one or more first members 4 made of a magnetic material having a property of collecting magnetism are accommodated in a position other than the IC chip 2 in the package 5. Ferrite and the like can be cited as the magnetic flux collecting material constituting the first member 4. The first member 4 is, for example, a ferrite chip (or a ferrite pin) in which ferrite is formed in a chip shape (or a pin shape). The position where the ferrite chip 4 is arranged may be on the lead frame 3 or on the magnetic sensor chip 1. When the magnetic flux lines of the magnetic circuit passing through the multi-chip module for magnetic sensors are concentrated on the ferrite chip 4, the magnetic flux lines entering the IC chip 2 are reduced.

Around the package 5, a second member 6 made of a magnetism collecting material having a property of collecting magnetism is extended. Ferrite or the like can be given as a magnetic flux collecting material constituting the second member 6. The second member 6 is, for example, a ferrite plate in which ferrite is formed in a plate shape.
Two ferrite plates 6 are attached to the surface of the package 5 so as to be in contact with the upper ends of the respective ferrite chips 4 and widely cover the upper part of the lead frame 3. This allows
Most of the magnetic flux lines coming from above the package 5 enter the ferrite plate 6 and are concentrated on the ferrite chip 4, so that the magnetic flux lines entering the IC chip 2 shielded by the ferrite plate 6 are greatly reduced. Will do.

The specific structure and manufacturing method of the magnetic sensor multi-chip module shown in FIG. 1 will be described.

Two Hall element chips 1 each having a size of 0.6 mm × 0.6 mm × 0.3 mm, which are magnetic sensors, are bonded on a lead frame 3 with silver paste.
An IC chip 2 having a rectangular wave conversion function of a size of 1.2 mm × 1.6 mm × 0.3 mm is similarly bonded with a silver paste. Thereafter, heat treatment is performed in a nitrogen atmosphere to cure the silver paste. Next, as an electrical arrangement, a gold wire having a diameter of 0.03 mm is wired between the electrodes of the chips 1 and 2 and wire-bonded. next,
0.1mm × 0.1mm × on the Hall element chip 1
A 0.3 mm ferrite chip 4 is bonded on the magnetic sensing surface of the Hall element with an epoxy resin, and the epoxy resin is cured by heat treatment. Thereafter, glass epoxy resin is sealed by transfer molding, and 7 mm × 7 mm × 1.5
An mm package 5 is formed. Next, solder coating and lead cutting are performed. A 3 mm × 5 mm × 0.5 mm ferrite plate 6 is attached to the surface of the package 5 thus prepared. In addition, each dimension is length x width (right and left of a figure) x thickness (up and down of a figure).

In the magnetic sensor multi-chip module configured as described above, the magnetic flux lines that would enter the IC chip 2 without the magnetic flux collecting material are avoided by the magnetic flux collecting material to other places. As a result, fluctuations in the offset characteristics and the hysteresis width can be suppressed from about 10% to about 2%.

Next, an experiment for confirming whether the effect of magnetism is reduced by the present invention will be described.

First, a confirmation module was created. FIG.
As shown in FIG. 2, two Hall element chips 1 are provided on a lead frame 3 in the same arrangement as in FIG. 1, and a Hall element chip (magnetic sensor chip) 7 for monitoring is provided at a position where the IC chip 2 is provided in FIG. Provided. By performing wire bonding only to the monitor Hall element chip 7,
The electrodes of the monitor Hall element chip 7 were electrically connected to external leads. Next, a ferrite chip 4 is bonded to the two Hall element chips 1 as in FIG. 1, a package 5 is formed by transfer molding, a lead portion is subjected to solder coating and lead cutting, and a ferrite plate is formed on the surface of the package 5. 6 was pasted together. The confirmation module thus created can originally measure the intensity of the magnetism passing through the position where the IC chip 2 is provided by the monitor Hall element chip 7.

Further, a module for comparison was prepared. FIG.
As shown in FIG. 5, a package 5 is formed by providing only a monitor Hall element chip 7 on a lead frame 3.
A module without the ferrite chip 4 and the ferrite plate 6 was obtained.

The confirmation module was attached to the rotation sensor evaluation device shown in FIG. The rotation sensor evaluation device causes the upper surface of the module 41 to face the rotating gear 42 so that the magnetically sensitive surface of the magnetic sensor chip in the module 41 faces the gear 42, and the permanent magnet 4 on the lower surface of the module 41.
3 is provided. The magnetic flux lines from the permanent magnet 43 pass through the module 41 and reach the gear 42. Gear 42
Are alternately passed near the upper surface of the module 41 so that the magnetic flux lines passing through the module 41 change. In response, the magnetic flux passing through the monitoring Hall element chip in the module 41 changes.
When a constant voltage of, for example, 5 V is applied to the input side of the monitoring Hall element chip and the output side of the monitoring Hall element chip is observed, the output potential fluctuates.

FIG. 5 shows the output potential fluctuation of the monitor Hall element chip when the confirmation module is attached to the rotation sensor evaluation device. FIG. 5 also shows the output potential fluctuation of the monitor Hall element chip when the comparison module is attached to the rotation sensor evaluation device. The output potential of the waveform 51 in the case of the comparison module greatly fluctuates according to the rotation of the gear. On the other hand, in the waveform 52 in the case of the confirmation module, the output potential hardly fluctuates, and it can be seen that the magnetic flux passing through the monitoring Hall element chip does not change even if the magnetic flux passing through the module changes.

From this experimental result, it is found that the multi-chip module for a magnetic sensor of the present invention including the ferrite chip 4 and the ferrite plate 6 reduces the magnetic fluctuation applied to the IC chip by 10 compared to the conventional multi-chip module for a magnetic sensor.
%.

Next, another embodiment of the present invention will be described.

(1) The ferrite chip 6 is not mounted on the outer periphery of the package 5 but is
Even when only the IC chip 2 is provided, the number of magnetic flux lines entering the IC chip 2 can be reduced. However, the effect is considered to be smaller than when the ferrite plate 6 is provided.

(2) A groove for attaching a ferrite plate may be formed on the surface of the package 5 and the ferrite plate 6 may be attached to this groove. Thereby, the attaching position can be made accurate, and the unevenness on the upper surface of the module due to the ferrite plate 6 can be eliminated.

(3) Another ferrite chip 4 or another ferrite plate 6 may be adhered to the lower part of the ferrite chip 4 inside the package 5, that is, the lower surface of the lead frame 3 or the lower surface of the package 5, so as to enter the IC chip 2. The effect of reducing the generated magnetic flux lines can be increased.

(4) The ferrite chip 4 may be inserted into the package 5 in which the ferrite chip 4 is not accommodated by performing additional processing. Thus, the module manufacturing line of the present invention is formed only by adding a post-process to the conventional module manufacturing line. Further, it is possible to remodel a conventional module ready-made product into the module of the present invention.

The present invention can be widely applied to a magnetic sensor multi-chip module packaged by combining an IC chip with a magnetic sensor chip for purposes other than the rotation sensor.

[0029]

The present invention exhibits the following excellent effects.

(1) The magnetic flux lines entering the IC chip are
For example, it can be suppressed to 10%, and the characteristic fluctuation of the rotation sensor due to magnetic fluctuation can be suppressed to, for example, 2%.

(2) When the first member made of the magnetic collecting material is made to overlap the magnetic sensor chip, the magnetic flux lines can be concentrated on the magnetic sensor chip. Thereby, the sensitivity of the rotation sensor can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a multi-chip module for a magnetic sensor according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a confirmation module.

FIG. 3 is a side sectional view of a comparative module.

FIG. 4 is a configuration diagram of a rotation sensor evaluation device.

FIG. 5 is a fluctuation waveform diagram of the output potential of the Hall element chip obtained by the rotation sensor evaluation device.

[Explanation of symbols]

 Reference Signs List 1 Hall element chip (magnetic sensor chip) 2 IC chip 3 Lead frame 4 Ferrite chip (first member) 5 Package 6 Ferrite plate (second member)

Claims (5)

[Claims] 1. A multi-chip module for a magnetic sensor, in which a magnetic sensor chip for detecting magnetism and an IC chip for processing an electric signal are arranged and housed in the same package, a first material made of a material having a property of collecting magnetism. Characterized in that said member is accommodated in said package so as not to overlap with said IC chip, and a second member made of a material having a property of collecting magnetism is spread and provided around said package. Multi-chip module. 2. The multi-chip module for a magnetic sensor according to claim 1, wherein the first member overlaps the magnetic sensor chip. 3. The multi-chip module for a magnetic sensor according to claim 1, wherein the material is a ferrite material. 4. The multi-chip module for a magnetic sensor according to claim 1, wherein said magnetic sensor chip is a Hall element or a magnetoresistive element. 5. The magnetic sensor chip according to claim 1, wherein the magnetic sensor chip faces a rotating gear, and a voltage fluctuation corresponding to a magnetic flux fluctuation detected by the magnetic sensor chip is output from the IC chip. A multichip module for a magnetic sensor as described in the above.