JP2001004655A - Acceleration sensor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor having a small variation in thickness in the plane direction of a junction layer, and high measuring precision. SOLUTION: An anisotropic conductive film which has a plurality of conductive particles so as to be dispersed in a plane direction and is capable of being crimped by heat is disposed on the surface of a diaphragm 1. The underside surface of a piezoelectric ceramic substrate is overlapped on the anisotropic conductive film so that the piezoelectric ceramic substrate and the diaphragm 1 may face through the anisotropic conductive film. Pressure and heat are applied between the piezoelectric ceramic substrate and the diaphragm 1 to form a junction layer 4 connected with the piezoelectric ceramic substrate and the diaphragm 1. The respective conductive particles 4b between a counter electrode pattern E0 and the diaphragm 1 are brought into contact with the counter electrode pattern E0 and diaphragm 1, and an interval between the underside surface of the piezoelectric ceramic substrate and the diaphragm 1 is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration using piezoelectric ceramics and a method for manufacturing the same.

[0002]

2. Description of the Related Art A piezoelectric ceramic substrate having an electrode pattern for acceleration detection formed on one surface and a counter electrode pattern opposite to the electrode pattern for acceleration detection formed on the other surface is subjected to polarization processing to receive acceleration. There is known an acceleration sensor that outputs a signal corresponding to an acceleration component in each direction based on spontaneous polarization charges generated in an acceleration detection electrode in each direction due to stress generated in piezoelectric ceramics. The basic principle and technology of this acceleration sensor are described in International Publication WO9.
3/02342 (PCT / JP92 / 00882). In this type of acceleration sensor, a metal diaphragm is bonded to the back surface of the piezoelectric ceramic substrate and the counter electrode pattern via a bonding layer, and a weight is fixed to the diaphragm so as to protrude toward the back surface of the diaphragm. ing. In a conventional acceleration sensor, a bonding layer for bonding the back surface of the piezoelectric ceramic substrate and the counter electrode pattern to the metal diaphragm is formed using an epoxy resin-based adhesive.

[0003]

In this type of acceleration sensor, when the thickness of the bonding layer becomes non-uniform, the parallelism between the piezoelectric ceramic substrate and the diaphragm decreases, and the center line of the weight fixed to the diaphragm is displaced. Variations occur in the angle (ideally 90 °) between the piezoelectric ceramic substrate and the plate surface, and the greater the variation, the greater the variation in the detection accuracy. Therefore, in order to reduce the variation in the accuracy of acceleration detection with this type of acceleration sensor, it is required to increase the parallelism between the ceramic substrate and the diaphragm as much as possible. However, when the bonding layer is formed using an epoxy resin-based adhesive, the thickness of the bonding layer in the surface direction varies greatly, and there is a limit in increasing the parallelism between the piezoelectric ceramic substrate and the diaphragm. Therefore, in the conventional acceleration sensor, there is a limit in reducing the variation in the measurement accuracy of the acceleration.

[0004] It is an object of the present invention to provide an acceleration sensor in which the variation in the thickness dimension in the plane direction of the bonding layer is reduced to reduce the variation in the measurement accuracy, and a method of manufacturing the same.

[0005]

According to the present invention, an acceleration detecting electrode pattern is formed on a front surface, a counter electrode pattern facing the acceleration detecting electrode pattern is formed on a back surface, and the acceleration detecting electrode pattern is opposed to the acceleration detecting electrode pattern. A piezoelectric ceramic substrate in which the portion between the electrode patterns is polarized, a metal diaphragm in which the back surface of the piezoelectric ceramic substrate is joined to the front surface, and a diaphragm fixed to the diaphragm so as to protrude to the back surface side of the diaphragm. The object of the present invention is to improve an acceleration sensor comprising a weight that is attached and a bonding layer that bonds the back surface of the piezoelectric ceramic substrate to the diaphragm. The weight may be formed integrally with the diaphragm and fixed to the diaphragm.

In the present invention, the bonding layer has a structure in which a large number of conductive particles are dispersed and arranged in the plane direction of the diaphragm inside a layer of an adhesive material having electrical insulation and adhesiveness. Then, each of the conductive particles located between the opposing electrode pattern and the diaphragm is brought into contact with the opposing electrode pattern and the diaphragm to determine the distance between the back surface of the piezoelectric ceramic substrate and the diaphragm. In other words, a large number of conductive particles are dispersed in the direction of the surface of the bonding layer in a state in which a large number of conductive particles are mutually insulated by the bonding material inside the layer of the film-like bonding material having electric insulation and adhesiveness. Deploy. Then, each of the conductive particles functions as spacer means for keeping a predetermined interval between the back surface of the piezoelectric ceramic substrate and the diaphragm.

According to the present invention, since each of the conductive particles functions as a spacer means for keeping a predetermined interval between the back surface of the piezoelectric ceramic substrate and the diaphragm, the particle diameter of the conductive particles is made as uniform as possible ( That is, the variation in the particle size) can be reduced, whereby the variation in the thickness dimension in the surface direction of the bonding layer can be reduced. Therefore, according to the present invention, the parallelism between the piezoelectric ceramic substrate and the diaphragm can be increased,
Variations in the measurement accuracy of the acceleration sensor can be reduced. Further, since the conductive fine particles electrically connect the opposing electrode pattern and the metal diaphragm, it is not necessary to separately provide a connecting means for electrically connecting the two.

The thickness of the bonding layer is determined according to the average diameter of the conductive particles or the variation in the diameter. Therefore, it is preferable to use spherical primary particles having an average diameter or a diameter of 4 to 8 μm as the conductive particles. In particular, when primary particles are used as the conductive particles, the amount of deformation or the rate of deformation of the conductive particles when a force is applied in the thickness direction of the bonding layer is stable (becomes the same). The degree can be increased.

The conductive particles can be formed from nickel or the like. Further, the adhesive material may be formed of a synthetic resin material that exhibits an adhesive property when heated and pressed at a temperature of 180 ° C. or less so as not to break the polarization of the piezoelectric ceramic substrate.

In order to manufacture the acceleration sensor according to the present invention, a plurality of conductive particles are dispersed on the back surface of the piezoelectric ceramic substrate and one of the surfaces of the diaphragm in the surface direction, and are heat-pressable. The other side of the back surface of the piezoelectric ceramic substrate and the surface of the diaphragm is placed on the anisotropic conductive film so that the piezoelectric ceramic substrate and the diaphragm face each other via the anisotropic conductive film. A pressing force and heat are applied between the piezoelectric ceramic substrate and the diaphragm in order to heat-press the one conductive film. In the anisotropic conductive film referred to herein, a large number of conductive particles are arranged and dispersed in a plane direction within a layer of an adhesive material having electrical insulation and adhesiveness, and a large number of conductive particles are interconnected by the adhesive material. It is a film insulated.
Such an anisotropic conductive film has conductivity in the thickness direction, but does not have conductivity in the plane direction. In the manufacturing method of the present invention, when a pressing force and heat are applied between the piezoelectric ceramic substrate and the diaphragm, the adhesive material of the anisotropic conductive film adheres to the piezoelectric ceramic substrate and the diaphragm, and the conductive particles face each other. Ensure contact with the electrode pattern and diaphragm.

It is preferable that the heat applied at the time of thermocompression bonding is set to 180 ° C. or less so as not to break the polarization of the piezoelectric ceramic substrate.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of an acceleration sensor according to an embodiment of the present invention applied to a three-axis acceleration sensor. As shown in the figure, the three-axis acceleration sensor is fixed on the surface of the diaphragm 1, the weight 3, the base 5, and the surface of the diaphragm 1 opposite to the surface on which the weight 3 is mounted. And a sensor element 7. In this figure, the thickness of the main part of the sensor element 7 is exaggerated for easy understanding. These members are accommodated in a frame-shaped insulating resin case 9. The insulating resin case 9 has two terminals formed by fixing three terminal fittings 25 connected to the output electrodes OX, OY, OZ and the electrodes OE0 of the sensor element 7 on the resin molded body 21 respectively. The units 11, 11 are fitted. A metal lid member 6 is attached to the upper opening of the case 9.

The diaphragm 1, the weight 3 and the base 5
As shown in FIG. 1, FIG. 2 (A) and FIG. 2 (B), a single unit 1 integrally formed of a metal material made of brass.
It is configured as 0. FIG. 2A is a bottom view of the single unit 10, and FIG.
FIG. 4 is a cross-sectional view taken along line B. Diaphragm 1 has a thickness of about 0.1
mm and a disk shape with a diameter of 12 mm. Weight 3
Has a cylindrical shape, and is integrated with the diaphragm 1 so that an extension of the center line passes through the center of the diaphragm 1. The base 5 has a cylindrical shape and supports the outer peripheral portion of the diaphragm 1. Further, a V-shaped groove 5a that is continuous in the circumferential direction is formed on the outer peripheral portion of the base 5. In the present embodiment, a cylindrical metal material made of brass is prepared, and a cutting process is performed on the cylindrical metal material so as to cut out the weight 3 to form an annular cavity C, and the outer peripheral portion is formed. The V-shaped groove 5a was formed by cutting, and the single unit 10 was integrally formed.

In this example, as the sensor element 7, a piezoelectric ceramic substrate 7a as shown in plan views of FIGS.
An electrode pattern E1 for acceleration detection for triaxial acceleration detection is formed on the front surface of the piezoelectric element, and an annular counter electrode pattern E0 facing the main part of the electrode pattern E1 for acceleration detection is formed on the back surface. An axis sensor element is used.

The back surface of the piezoelectric ceramic substrate 7a and the counter electrode pattern E0 are connected to the diaphragm 1 by the bonding layer 4.
It is joined to the surface. As shown in the partial enlarged view of FIG. 4, the bonding layer 4 has a structure in which a large number of conductive particles 4b are dispersed in a plane direction inside a film-like adhesive material layer 4a. . The adhesive material layer 4a is made of a synthetic resin material such as epoxy which exhibits adhesiveness when heated and pressed at a temperature of 180 ° C. or lower, and has insulating properties as well as adhesiveness. The conductive particles 4b are formed of nickel spherical primary particles. These conductive particles 4b ...
Are dispersed in the surface direction of the diaphragm 1 while being insulated from each other by the adhesive material of the adhesive material layer 4a. Each of the conductive particles 4b located between the opposing electrode pattern E0 and the diaphragm 1 comes into contact with the opposing electrode pattern E0 and the diaphragm 1 to form a predetermined gap between the back surface of the piezoelectric ceramic substrate 7a and the diaphragm 1. It functions as an opening spacer means. In this example, since the conductive particles 4b have an average diameter or a value within a range of 4 to 8 μm, the spacing between the back surface of the piezoelectric ceramic substrate 7a and the diaphragm 1 (the bonding layer Thickness) is approximately 4 to 8 μm over the entire surface of the bonding layer in the surface direction.

The piezoelectric ceramic substrate 7a and the diaphragm 1 were joined as follows. First, as shown in FIG. 5A, an anisotropic conductive film 12 was arranged on the surface of the diaphragm 1. The anisotropic conductive film 12 is a heat-pressable film in which a large number of conductive particles are dispersed in the plane direction and has conductivity in the thickness direction but does not have conductivity in the plane direction. have. Since the anisotropic conductive film 12 has a release film adhered to one side, the anisotropic conductive film 12 is arranged such that the surface of the diaphragm 1 on which the release film is not affixed is in contact with the surface of the diaphragm 1. In this example, an anisotropic conductive film sold under the trade name CP7652K from Sony Chemical Co., Ltd., or AC-720 from Hitachi Chemical Co., Ltd.
An anisotropic conductive film sold under the trade name No. 5 was used. Next, a pressure of ² to 3 kgf / cm ² is applied between the anisotropic conductive film 12 and the diaphragm 1 and 70 to 9
Heat at 0 ° C. was applied for 2 to 3 seconds to temporarily join the anisotropic conductive film 12 to the diaphragm 1. Next, the anisotropic conductive film 1
After the release film is peeled off from the second electrode 2, the acceleration detecting electrode pattern E1 and the counter electrode are arranged such that the piezoelectric ceramic substrate 7a and the diaphragm 1 face each other with the anisotropic conductive film 12 therebetween as shown in FIG. The back surface of the piezoelectric ceramic substrate 7a on which the pattern E0 was formed was overlaid on the anisotropic conductive film 12. Then, in order to heat-compress the anisotropic conductive film 12, between the piezoelectric ceramic substrate 7a and the diaphragm 1, 30 to 40 in the direction shown by the arrow P.
While applying a pressure of kgf / cm ² and applying heat of 150 to 180 ° C. to the anisotropic conductive film 12 for 20 to 30 seconds, the adhesive material of the anisotropic conductive film 12 is adhered to the piezoelectric ceramic substrate 7 a and the diaphragm 1. Each of the particles is divided into the counter electrode pattern E0 and the diaphragm 1
Contact.

In this embodiment, after the anisotropic conductive film 12 is temporarily joined to the diaphragm 1, the anisotropic conductive film 1
2 and the piezoelectric ceramic substrate 7a are joined, but the anisotropic conductive film 12 and the diaphragm 1 may be joined after the anisotropic conductive film 12 is temporarily joined to the piezoelectric ceramic substrate 7a.

The piezoelectric ceramic substrate 7a has a quadrangular contour, and a portion corresponding to the electrodes is subjected to a polarization treatment so that spontaneous polarization is generated when a stress is applied to the inside. The polarization process will be described later in detail.
As shown in FIG. 3, the piezoelectric ceramic substrate 7a includes a weight facing region 8A, a base facing region 8B, and a weight facing region 8B.
Intermediate area 8C located between A and the base facing area 8B
And The weight 3 is located at a portion corresponding to the weight facing region 8A, and the base 5 is located at a portion corresponding to the base facing region 8B. The intermediate region 8C includes a stress generating region 8C1 surrounding the weight facing region 8A, and a stress non-generating region 8C2 located between the stress generating region 8C1 and the base facing region 8B. The stress generating region 8C1 is a region in which the weight 3 is deformed when an acceleration acts on the weight 3 to generate a stress therein, and the acceleration detecting electrodes EX1 to EZ4 of the acceleration detecting electrode pattern E1 are formed on the surface side. I have. When an acceleration acts on the weight 3 in a direction (X-axis direction or Y-axis direction) parallel to the substrate surface of the piezoelectric ceramic substrate 7a, the stress generating region 8C1 becomes point-symmetric with respect to the center of gravity of the weight 3. Different states (tensile stress applied and compressive stress applied)
Deform to. When acceleration acts on the weight 3 in a direction (Z-axis direction) perpendicular to the substrate surface of the piezoelectric ceramic substrate 7a, each part of the stress generating region 8C1 is deformed to the same state. The stress non-generating region 8C2 is a region where substantially no stress is generated even when an acceleration is applied to the weight 3, or a region where only a very small stress is generated even if a stress is generated. In FIG. 3, reference numeral 8D denotes a boundary (neutral line) between the stress generating region 8C1 and the stress non-generating region 8C2.

The acceleration detecting electrode pattern E1 and the counter electrode pattern E0 formed on the front and back surfaces of the piezoelectric ceramic substrate 7a are both formed by screen printing. When the diaphragm 1 is deformed based on the acceleration acting on the weight 3, the piezoelectric ceramic substrate 7a bends, and the spontaneous polarization charge generated between the detection electrode pattern E1 and the counter electrode pattern E0 changes. The applied acceleration in the directions of the three axes (X axis, Y axis, Z axis) is measured as a change in current or voltage. Note that the X axis here
The Y axis and the Z axis are axes extending in directions orthogonal to each other. X
The axis extends in the direction of the X-axis virtual line XL, and the Y axis is Y
It extends in the direction of the axial virtual line YL, and the Z axis extends in a direction orthogonal to the surface direction of the piezoelectric ceramic substrate 7a.

The electrode pattern E1 for acceleration detection includes an X-axis direction detecting electrode pattern 13 and a Y-axis direction detecting electrode pattern 15.
And a Z-axis direction detection electrode pattern 17. The X-axis direction detection electrode pattern 13 has a structure in which a pair of X-axis direction acceleration detection electrodes EX1 and EX2 and an X-axis output electrode OX are connected in series by connection lines L1 and L2.
The pair of X-axis direction acceleration detection electrodes EX1 and EX2 are a pair of Y-axis direction acceleration detection electrodes EY1 and EY2 of the Y-axis direction detection electrode pattern 15 and the Z-axis direction acceleration of the Z-axis direction detection electrode pattern 17, which will be described later. Detection electrodes EZ1
Together with EZ4, an annular row surrounding the weight facing region 8A is formed. The electrodes EX1 and EX2 of the pair of X-axis direction acceleration detection electrodes are line-symmetric with respect to the X-axis direction virtual line XL and straddle the weight facing region 8A and the first stress generation region 8C1. It has a shape close to a rectangle (straddling the area boundary line 8D).

Electrode pattern 15 for detecting acceleration in the Y-axis direction
Has a structure in which two Y-axis direction acceleration detecting electrodes EY1 and EY2 and a Y-axis output electrode OY are connected in series by connection lines L3 to L5. Each of the acceleration detection electrodes EY1 and EY2 of the pair of Y-axis direction acceleration detection electrodes has the same shape as the X-axis direction acceleration detection electrodes EX1 and EX2, and corresponds to the Y-axis direction virtual line YL. It becomes symmetrical and the weight facing region 8A and the first stress generating region 8C1
(Spans the region boundary line 8D). Y-axis virtual line YL and X-axis virtual line X
Since L is orthogonal to each other, the X-axis direction acceleration detection electrode EX1, the Y-axis direction acceleration detection electrode EY1, the X-axis direction acceleration detection electrode EX2, and the Y-axis direction acceleration detection electrode E
Y2 will be arranged at intervals of 90 degrees. The Y-axis output electrode OY has a substantially square shape similarly to the X-axis output electrode OX, and the second stress generation region 8C
Is formed alongside the X-axis output electrode OX so as to be located at the outer peripheral edge of the piezoelectric ceramic substrate 7a outside the substrate.

Electrode pattern 17 for detecting acceleration in the Z-axis direction
Are Z-axis direction acceleration detecting electrode EZ1, Z-axis direction acceleration detecting electrode EZ2, Z-axis direction acceleration detecting electrode EZ3.
Z-axis direction acceleration detection electrode EZ4, Z-axis output electrode OZ
Have a structure in which they are connected in series in this order by connection lines L6 to L9. The four Z-axis direction acceleration detecting electrodes EZ1 to EZ4 have a shape close to a rectangle.
The Z-axis direction acceleration detection electrodes EZ1 to EZ4 are also formed so as to straddle the weight facing region 8A and the first stress generation region 8C1, similarly to the X-axis direction acceleration detection electrodes EX1 and EX2. Also, the Z-axis direction acceleration detecting electrodes EZ1 to EZ4
Represents an electrode E2 between the X-axis direction acceleration detecting electrode EX2 and the Y-axis direction acceleration detecting electrode EY1;
Y1 and X-axis acceleration detection electrode EX1, X-axis acceleration detection electrode EX1 and Y-axis acceleration detection electrode EY2, Y-axis acceleration detection electrode EY2 and X-axis acceleration detection It is arranged at each central portion between the electrodes EX2. Therefore, the Z-axis direction acceleration detecting electrodes EZ1 to EZ4 are arranged at intervals of 90 degrees. The Z-axis output electrode OZ also has a substantially square shape similarly to the X-axis output electrode OX, and the piezoelectric ceramic substrate 7 outside the second stress generation region 8C.
It is formed alongside the X-axis output electrode OX and the Y-axis output electrode OY so as to be located at the edge of a.

Three earth electrodes OE0... Are formed in parallel with the output electrodes OX, OY, OZ in a portion along the side opposite to the side of the ceramic substrate 7a in which the output electrodes OX, OY, OZ are arranged. Have been. Earth electrode OE0
Is connected to the opposing electrode pattern E0 through a through-hole conductive portion penetrating the piezoelectric ceramic substrate 7a and a connection line (not shown). As described above, the output electrodes included in the sensor element 7 are arranged in two groups of OX, OY, OZ and OE0. In addition,
In this example, all three electrodes located on the outer peripheral edge of the piezoelectric ceramic substrate 7a are earth electrodes OE0.
At least one of the three electrodes is a ground electrode OE0,
The remaining electrodes may be used as dummy electrodes only for connecting terminals.

X-axis direction acceleration detecting electrodes EX1, EX2
Is located on one side of the weight opposing area 8A when the same type of stress is generated in each part of the piezoelectric ceramic substrate 7a by applying acceleration in the Z-axis direction to the weight 3 at each part. The polarization processing is performed so that spontaneous polarization charges of opposite polarities appear on the acceleration detection electrode EX1 and the acceleration detection electrode EX2 located on the other side. In this example,
When a tensile stress is generated in each portion of the piezoelectric ceramic substrate 7a corresponding to the X-axis direction acceleration detecting electrodes EX1 and EX2, a negative spontaneous polarization charge appears on one X-axis direction acceleration detecting electrode EX1 and the other ends. The polarization processing is performed so that a positive spontaneous polarization charge appears on the X-axis direction acceleration detection electrode EX2.

The Y-axis direction acceleration detecting electrodes EY1,
Similarly to the respective portions of the piezoelectric ceramic substrate 7a corresponding to the X-axis direction acceleration detection electrodes EX1 and EX2, the weight 3 has a Z portion on the piezoelectric ceramic substrate 7a corresponding to the EY2.
When the same type of stress is generated in each part by the acceleration in the axial direction, the Y-axis direction acceleration detection electrode EY1 located on one side of the weight facing region 8A and the Y-axis direction located on the other side Polarization processing is performed so that spontaneous polarization charges of opposite polarities appear on the acceleration detection electrode EY2. In this example, when a tensile stress is generated in each portion of the piezoelectric ceramic substrate 7a corresponding to the Y-axis direction acceleration detection electrodes EY1 and EY2, a negative spontaneous polarization charge is applied to one Y-axis direction acceleration detection electrode EY1. The polarization processing is performed so that the positive spontaneous polarization charge appears on the other Y-axis direction acceleration detection electrode EY2.

The Z-axis direction acceleration detecting electrodes EZ1 to EZ1
Each part of the piezoelectric ceramic substrate 7a corresponding to the EZ4 is provided with all the Z-axis direction acceleration detecting electrodes EZ1 to EZ4 when the same type of stress is generated in the respective parts by the acceleration in the Z-axis direction acting on the weight 3. Has been subjected to a polarization treatment so that spontaneous polarization charges of the same polarity appear in FIG. In this example, when a tensile stress is generated in the portion of the piezoelectric ceramic substrate 7a corresponding to the Z-axis direction acceleration detecting electrodes EZ1 to EZ4, Z
Polarization processing is performed so that positive spontaneous polarization charges appear on the axial acceleration detection electrodes EZ1 to EZ4.

In this embodiment, the acceleration detection electrodes EX1 to EX1
EZ4 and the counter electrode pattern E0 were screen-printed using a glass-silver paste, and then baked to 5 μm.
After the formation, the piezoelectric ceramic substrate 7a was polarized by applying a DC voltage between the opposing electrodes. Then, the connection lines L1 to L9 are screen-printed with silver paste, and the electrode patterns E1 for acceleration detection are printed.
Was formed.

In this embodiment, an example in which the present invention is applied to a three-axis acceleration sensor is shown. However, a one-axis acceleration sensor for detecting uniaxial acceleration and a two-axis acceleration sensor for detecting orthogonal two-axis acceleration are also used. Of course, the present invention can be applied.

[0029]

According to the present invention, since each of the conductive particles functions as a spacer means for keeping a predetermined interval between the back surface of the piezoelectric ceramic substrate and the diaphragm, the particle diameter of the conductive particles is made substantially uniform. This makes it possible to make the thickness of the bonding layer substantially uniform, thereby reducing the variation in the thickness in the surface direction of the bonding layer. Therefore, the piezoelectric ceramic substrate and the diaphragm can be arranged substantially in parallel, and the accuracy of acceleration measurement can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an acceleration sensor according to an embodiment of the present invention.

FIG. 2A is a bottom view of a single unit used in the three-axis acceleration sensor according to the embodiment of the present invention, and FIG.
It is a BB sectional view taken on the line of (A).

FIG. 3 is a plan view of a sensor element used in the three-axis acceleration sensor according to the embodiment of the present invention.

FIG. 4 is a partially enlarged view of FIG. 1;

FIG. 5 is a view used to explain a step of joining a piezoelectric ceramic substrate and a diaphragm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diaphragm 3 Weight 4 Bonding layer 4a Adhesive material layer 4b Conductive particle 5 Base 7 Sensor element 7a Piezoelectric ceramic substrate 9 Insulating resin case 10 Single unit E0 Counter electrode pattern E1 Acceleration detection electrode pattern

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naohiro Mohri 3158, Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Inside (72) Inventor Tsutomu Sawai 3158, Shimo-Okubo, Osawano-cho, Kamishikawa-gun, Toyama (72) Inventor Masato Ando 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (6)

[Claims] 1. An acceleration detection electrode pattern is formed on a front surface, and a counter electrode pattern facing the acceleration detection electrode pattern is formed on a back surface, between the acceleration detection electrode pattern and the counter electrode pattern. A piezoelectric ceramics substrate having a polarized portion; a metal diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate; and a weight fixed to the diaphragm so as to protrude toward the back surface side of the diaphragm. An acceleration sensor comprising a weight, and a bonding layer for bonding the back surface of the piezoelectric ceramic substrate and the diaphragm, wherein the bonding layer is formed inside an adhesive material layer having electrical insulation and adhesiveness. Has a structure in which a large number of conductive particles are dispersed and arranged in the plane direction of the bonding layer, and the counter electrode pattern and the An acceleration, wherein each of the conductive particles located between the diaphragm and the diaphragm is in contact with the counter electrode pattern and the diaphragm to determine a distance between the rear surface of the piezoelectric ceramic substrate and the diaphragm. Sensor. 2. An acceleration detection electrode pattern is formed on a front surface, and a counter electrode pattern facing the acceleration detection electrode pattern is formed on a back surface, and between the acceleration detection electrode pattern and the counter electrode pattern. A piezoelectric ceramics substrate having a polarized portion; a metal diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate; and a weight fixed to the diaphragm so as to protrude toward the back surface side of the diaphragm. A weight, and an acceleration sensor including a bonding layer that bonds the back surface of the piezoelectric ceramic substrate and the diaphragm, wherein the bonding layer is formed of a film-like adhesive material having electrical insulation and adhesiveness. Inside the layer, a large number of conductive particles are dispersed in the plane direction of the diaphragm while being insulated from each other by the adhesive material. Each of the conductive particles located between the counter electrode pattern and the diaphragm is in contact with the counter electrode pattern and the diaphragm and the back surface of the piezoelectric ceramic substrate. An acceleration sensor which functions as a spacer means for keeping a predetermined interval between the acceleration sensor and the diaphragm. 3. The conductive particles have an average diameter of 4 to 3.
3. The acceleration sensor according to claim 1, comprising spherical primary particles having a value of 8 μm. 4. The method according to claim 1, wherein the conductive particles are made of nickel, and the adhesive material is made of a synthetic resin material exhibiting the adhesiveness when heated and pressed at a temperature of 180 ° C. or less. Or the acceleration sensor according to 2. 5. An electrode pattern for acceleration detection is formed on a front surface, and a counter electrode pattern facing the electrode pattern for acceleration detection is formed on a back surface, between the electrode pattern for acceleration detection and the counter electrode pattern. The piezoelectric ceramic substrate and the diaphragm of an acceleration sensor comprising a piezoelectric ceramic substrate having a portion subjected to polarization processing and a metal diaphragm having a front surface joined to the back surface of the piezoelectric ceramic substrate. A method for manufacturing an acceleration sensor to be manufactured, comprising: a plurality of conductive particles dispersed on a back surface of the piezoelectric ceramic substrate and a surface of the diaphragm; A step of disposing a conductive film, wherein the piezoelectric ceramic substrate and the diaphragm are interposed through the anisotropic conductive film. Stacking the other surface of the back surface of the piezoelectric ceramic substrate and the other surface of the diaphragm on the anisotropic conductive film so as to face each other; and bonding the piezoelectric ceramic substrate to the anisotropic conductive film by heating and pressing. Applying a pressing force and heat between the diaphragm and the diaphragm. 6. The method according to claim 6, wherein the heat to be applied during the thermocompression bonding is 1 heat.
The method for manufacturing an acceleration sensor according to claim 5, wherein the temperature is 80C or lower.