JPH0886848A - Magnetism detector - Google Patents

Abstract

PURPOSE: To reduce the air gap between a magnetoresistance element and a protective case to improve the accuracy in a magnetism detector which utilizes the magnetoresistance element. CONSTITUTION: The magnetism detector is constituted in such a way that, in order to derive a lead from a magnetoresistance element chip 1, an insulating film 2 on which a derivation lead 13 has been formed is used, that the face of the lead 13 is set so as to become the side of the magnetoresistance element chip 1, that the face of an insulating layer 8 is set so as to become the side of a protective case and that a device hole 18 in which the insulating layer 8 has been removed on the face of the magnetoresistance element chip is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detector using a magnetoresistive element which senses magnetism and changes its electric resistance value.

[0002]

2. Description of the Related Art InSb, InSb-NiSb, InA
Semiconductors with high carrier mobility such as s or Ni-C
Ferromagnetic materials such as o, Ni-Fe, and Ni-Fe-Co have the property that the resistance value changes when a magnetic field is applied, and utilize the properties of the magnetoresistive element as described above. Is a magnetic detector.

The structure of a general magnetic detector is configured as shown in the schematic sectional view of FIG. Reference numeral 31 in the drawing denotes a magnetoresistive element chip, and a magnetic sensing portion is provided on the surface thereof (immediately below the arrow 35 in the drawing). Reference numeral 32 denotes an electric signal extraction portion (lead extraction) of the magnetoresistive element chip 31. Reference numeral 33 is a bias magnet which is a permanent magnet, and 34 is a metal protective case which also serves as an electromagnetic shield.

Protective case 3 on the magnetoresistive element chip 31
A magnetic material to be detected (for example, a bill) moves in pressure contact with the surface of 4. Since the protective case 34 may bend due to the pressure contact, an air gap (gap) 35 is provided between the magnetoresistive element chip 31 and the protective case 34, and noise due to stress strain of the magnetoresistive element chip 31 is generated (in the future). ,
This is called piezo noise). The air gap also serves as insulation between the protective case 34 and the electric signal takeout portion 32 of the magnetoresistive element chip 31.

FIGS. 6 and 7 show two examples of detailed sectional views in which the conventional air gap 35 and the electric signal extraction portion of the magnetoresistive element chip 31 are further enlarged.

FIG. 6 shows a structure in which a lead frame 36 is used as a portion for taking out an electric signal from the magnetoresistive element chip 31. Mount the magnetoresistive element chip 31 on the resin holder 3
7 is bonded and fixed to the metal plate 7, soldered to the metallic plate lead frame 36, and connected to the metal external terminal 39 by soldering to take out an electric signal from the magnetoresistive element chip 31. The air gap 35 is secured by providing a protrusion 38 on the holder and abutting the protrusion 38 on the protective case 34. The protrusion 38 is the magnetoresistive element chip 3.
The height is set to be equal to or higher than the fixed area of 1 and the occupied area of the lead frame 36.

FIG. 7 shows a structure in which a wire 41 for wire bonding is used in a portion for taking out an electric signal from the magnetoresistive element chip 31. The magnetoresistive element chip 31 is adhesively fixed to the fixed wiring board 42, and the electric signal taken out from the magnetoresistive element chip 31 is bonded and connected to the fixed wiring board 42 by the wire 41.
The connection to the metal external terminal 39 is made by soldering or the like through the through hole. The air gap 35 is secured by fixing the insulating spacer 43 around the fixed wiring board 42.
Is provided higher than the area of the wire 41 and is fixed by adhesion, and the spacer 43 is applied to the protective case 34.

[0008]

As described above, the air gap 35 prevents piezo noise due to stress on the magnetoresistive element chip 31, and insulates the protective case 34 from the electric signal takeout portion of the magnetoresistive element chip 31. Necessary for countermeasures. On the other hand, in order to cope with the recent demand for a slight displacement of the magnetic material to be detected and an improvement in detection sensitivity, it is necessary to bring the object to be detected and the magnetic detection part as close as possible to form a small gap amount and stably.

In the case of setting the air gap by the holder protrusion of FIG. 6, the size of the air gap depends on the thickness of the holder adhesive fixing layer of the magnetoresistive element chip 31, the thickness of the magnetoresistive element chip 31 itself, the thickness of the lead frame 36, The thickness of the adhesive solder layer between the magnetoresistive element chip 31 and the lead frame 36 is the amount obtained by subtracting the holder projection size. There are variations in the thickness of each constituent material, and variations in thickness also occur due to the method of bonding and soldering, and these accumulated variations become the dimensional accuracy of the air gap dimension, so it is difficult to improve the dimensional accuracy.

Generally, the thickness of the magnetoresistive element chip 31 is about 0.6 mm, and even if it has high accuracy, there is a dimensional tolerance of ± 0.05 mm, and the thickness of the lead frame is 0.15 mm, even if it has high accuracy, ± 0. There is a dimensional tolerance of 0.03 mm.
Further, the resin of the holder requires a tolerance of ± 0.05 mm, and even if strict control is required for adhesion and soldering, a tolerance of ± 0.05 mm will be required. By accumulating these, an air gap size variation of ± 0.23 mm occurs. In addition to the above-mentioned variation, the value of the air gap dimension itself needs to be 0.15 mm for the thickness of the lead frame and 0.38 mm or more.

Similarly in the case of setting the air gap by the spacer as shown in FIG. 7, the size of the air gap depends on the thickness of the adhesive between the magnetoresistive element chip 31 and the fixed wiring substrate, the thickness of the magnetoresistive element chip 31 itself, and the spacer thickness. However, it is difficult to reduce the cumulative thickness variation of each constituent material and construction method. That is, the value is not so different from the previous conventional example calculated in FIG.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a stable and highly sensitive magnetic detector by making the dimension accuracy of an air gap highly accurate and reducing the dimension of the air gap itself. .

[0013]

In order to solve the above-mentioned problems, the magnetic detector of the present invention has an insulating film having a lead formed on the surface, a lead forming surface on the magnetoresistive element chip side, and an insulating surface The structure is such that the insulating film on the surface of the magnetoresistive element chip is removed on the side of the protective case, and the lead out of the insulating film is connected to the surface of the magnetoresistive element chip.

[0014]

According to the above structure, the air gap size is the thickness of the insulating film and the thickness of the lead taken out. Both are much thinner than before.

Therefore, the variation in the component thickness such as the thickness of the magnetoresistive element chip itself, the adhesive thickness, the thickness of the holder or the spacer, and the variation in the processing thickness as in the prior art are extremely reduced, and the construction method is simplified. Since the air gap can be regulated stably and thinly, a stable and highly sensitive magnetic detector can be provided.

[0016]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of a magnetic detector according to an embodiment of the present invention. In the figure, 1 indicates InSb, I on the surface.
Semiconductors with high carrier mobility such as nSb-NiSb and InAs, or Ni-Co, Ni-Fe, Ni-Fe-C
A glass chip having a thickness of 0.6 mm formed with a ferromagnetic magnetic resistance portion 11 such as o and a lead extraction electrode portion made of gold having a thickness of about 1 to 2 μm. This structure is the same as that of the magnetoresistive element chip 31 in the description of the conventional example.

Reference numeral 2 is a film in which the lead-out lead 13 is formed on the surface of the insulating layer 8 such as polyimide. The insulating layer such as polyimide on the magnetoresistive element chip 1 is removed. Reference numeral 18 denotes the removed insulating layer region, which is called a device hole, and this device hole serves as an air gap space. The connection between the electrode of the magnetoresistive element chip 1 and the electrode lead-out lead is formed by a step of superposing the electrode and lead of the chip in the device hole and applying a tip of a heater rod kept at high temperature to heat. . 10 is
It is an out terminal portion of the electrode lead-out lead and is soldered to the metal rod-shaped external terminal 4.

Reference numeral 3 is a holder for fixing the magnetoresistive element chip 1, the film 2, the external terminals 4, etc., and has a hole into which the entire chip is inserted. Reference numeral 13 denotes an adhesive fixing portion with the film 2, which is fixed with an adhesive. Reference numeral 16 denotes an adhesive fixing portion with the magnetoresistive element chip 1, which is fixed with an adhesive resin. Reference numeral 5 is a bias magnet of a ferrite sintered body for applying a bias magnetic field to the magnetoresistive element,
The magnetoresistive element chip 1 is bonded and fixed to a holder on the opposite surface. 6 is a protective case made of stainless steel, which is in close contact with the film surface of the film 2.
Reference numeral 7 denotes a hermetically sealing material in the protective case, which also serves to fix the external terminal 4, the holder 3, and the like.

An enlarged sectional view of the magnetoresistive element chip and the film 2 of this embodiment is shown in FIG. 2 (a), and a plan view thereof is shown in FIG. 2 (b). The portion indicated by the alternate long and short dash line in the figure is the magnetoresistive element chip 1, and the magnetic detection portion thereof is the portion 11. A part of the lead-out lead protrudes like a part 12 in a part of the device hole 18 above the magnetic detection part 11 for connecting to the magnetoresistive element chip 1. The film is composed of an insulating layer of 8:25 μm (or 50 μm) polyimide, an adhesive layer of 9:10 μm, an extraction lead of 10:30 μm copper foil, and a total thickness of 65 μm ± 10 μm (or 90 μm ± 1).
0 μm).

With this structure, the air gap is equal to the total thickness of the film 2. That is, the air gap is 65 μm (0.065 mm), which is much smaller than before and the variation is ± 10 μm (0.01 m).
m), which is very accurate.

When a magnetic detector was actually manufactured with this structure, the mounting thickness when the number of samples N = 100 was 2 for the insulating layer.
5 μm, the air gap is in the range of 58 to 84 μm, the insulating layer is 50 μm, the air gap is 82
The range was ˜108 μm. From the above, it can be said that the air gap amount could actually be formed stably and small. Further, no short circuit with the protective case occurred, and no piezo noise occurred in the pressure contact movement detection characteristic test of the detected object.

The value of the air gap is slightly larger than the total thickness of the film because of the magnetoresistive element chip 1.
It is considered that the influence of the thickness of all the electrodes at the connection point with the part 12 of the extraction lead, the passivation film formed on a part of the surface, and the like are exerted in order to connect with.

In this embodiment, the small flexible substrate is used as the film, but the same effect can be obtained and the productivity is improved even if the TAB film capable of producing a large number is used.

Moreover, since the insulating layer 8 of the film 2 is not present in the vicinity of the joining portion of the take-out lead and the joining portion is completely exposed, there is an advantage that cleaning, inspection, repair, etc. of the joining portion can be easily and reliably performed. is there.

Needless to say, the same effect can be obtained by using the film substrate 2 without the adhesive layer 9.

(Embodiment 2) An enlarged sectional view of a magnetoresistive element chip and a film 2 according to a second embodiment of the present invention is shown in FIG.
3B shows a plan view. This example has almost the same configuration as the first example, but as shown by the one-dot chain line in FIG. 3B, the size of the magnetoresistive element chip 1 is larger than the device hole size of the film 2. It is a thing.

With this structure, the magnetoresistive element chip 1
By pressing from the back side so that the film is pressed against the metal case 6, the air gap becomes 8 in FIG. 3 (b).
The value is exactly the same as the thickness of the film at a. The magnetoresistive element chip is made of glass and is substantially rigid, and the bulge at the joint with the part 12 of the lead mentioned in Example 1 is
This is because the shape is slightly deformed by being pressed, and the size is stabilized in the state where the magnetoresistive element chip hits the portion 8a.
That is, there is a merit that variations due to distortion or the like at the joints can be eliminated.

When a magnetic detector was actually manufactured with this structure, the mounting thickness when the number of samples N = 100 was 2 for the insulating layer.
5 μm, air gap is 63-78 μm, insulating layer is 50 μm, air gap is 87
It was within the range of 102 to 102 μm, and the air gap amount could be formed stably and still smaller than that of the first embodiment. This is because the magnetoresistive element chip 1 directly contacts the film 2. In addition, there was no short circuit with the protective case. Regarding the pressure contact movement detection characteristics of the detection object, some piezo noise was observed, but this did not affect the detectability.

(Embodiment 3) An enlarged sectional view of a magnetoresistive element chip and a film 2 according to a third embodiment of the present invention is shown in FIG.
4B shows a plan view. This example has almost the same structure as the first example, but as shown by the one-dot chain line in FIG. 4B, a part of the magnetoresistive element chip 1 contacts the insulating layer of the film at the position 8b. It has a structure.

With this structure, the magnetoresistive element chip 1
4 is pressed from the back side and assembled so that the film is pressed against the metal case 6, the air gap becomes 8 in FIG. 4 (b).
The value is exactly the same as the thickness of the film at point b. This is almost the same as the mechanism of determining the dimensions in the second embodiment. In the second embodiment, the dimension depends on the variation in the total thickness of the insulating layer 8, the adhesive layer 9, and the lead-out lead 13, but in the present embodiment, it depends on the variation in the thickness of only the insulating layer 8.
The accuracy is further increased. Also, of course, the air gap itself becomes smaller.

[0031]

As described above, according to the structure of the present invention, in the film of the insulating layer having the leads formed on the surface, the lead forming surface is on the magnetoresistive element chip side and the insulating layer is on the protective case side. With a structure in which the insulating layer of the film on the magnetic sensing part on the surface of the resistive element chip is removed, connecting the film take-out lead to the surface of the magnetic resistive element chip forms a small air gap with high precision and with a simple construction method. Therefore, it is possible to provide a magnetic detector capable of detecting a slight displacement of a magnetic signal with high sensitivity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a magnetic detector according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a magnetoresistive element chip and a film according to the first embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a magnetoresistive element chip and a film according to a second embodiment of the present invention.

FIG. 4 is an enlarged sectional view of a magnetoresistive element chip and a film according to a third embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a conventional magnetic detector.

FIG. 6 is an enlarged cross-sectional view of a conventional first air gap forming portion.

FIG. 7 is an enlarged cross-sectional view of a conventional second air gap forming portion.

[Explanation of symbols]

 1 Magnetoresistive Element Chip 2 Film 6 Protective Case 8 Insulating Layer 13 Extraction Lead 18 Device Hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keizaburo Kuramasu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A magnetoresistive element chip having a magnetic sensing film on a surface thereof, a protective case, and an insulating layer film having a lead formed on the surface, and a lead forming surface facing the magnetoresistive element chip. Magnetic detection with the insulating layer on the side of the protective case and the insulating layer of the film on the magnetic detection part on the surface of the magnetoresistive element chip is removed, and the lead for taking out the film is connected to the surface of the magnetoresistive element chip. vessel. 2. The magnetic detector according to claim 1, wherein there is no insulating layer on the connection portion of the lead-out lead of the film on the surface of the magnetoresistive element chip. 3. The magnetic detector according to claim 1, wherein the lead-out lead of the film is in contact with the surface of the magnetoresistive element chip, and the insulating layer is present on the contacted portion. 4. The magnetic detector according to claim 1, wherein an insulating layer of a film is in contact with the surface of the magnetoresistive element.