JP4864183B2 - Method for manufacturing acceleration sensor element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an acceleration sensor element used in an acceleration detection device that detects acceleration in a predetermined direction and a method for manufacturing the same.
[0002]
[Prior art]
A metal diaphragm with a weight in the center, a metal base that supports the outer periphery of the diaphragm, and an adhesive layer on the surface opposite to the surface on which the diaphragm weight is provided There is known an acceleration detection device including an acceleration sensor element fixed via the interface. The acceleration sensor element used here has an acceleration detection electrode and one or more electrodes including a ground electrode formed on one surface of a piezoelectric ceramic substrate, and a counter electrode facing the acceleration detection electrode on the other surface. And outputs an acceleration signal corresponding to the deformation of the diaphragm based on the acceleration acting on the weight. In such an acceleration sensor element, the counter electrode is usually electrically connected to the ground electrode. Conventionally, a conductive connecting portion made of silver paint or the like connected to both is formed in the adhesive layer between the counter electrode and the diaphragm, and a conductive portion made of conductive adhesive or the like is connected between the diaphragm and the ground electrode. And the counter electrode and the ground electrode were electrically connected.
[0003]
[Problems to be solved by the invention]
However, when a conductive connection portion made of a silver paint is formed in the adhesive layer, the adhesive of the adhesive layer and the silver paint are mixed and the conductivity of the conductive connection portion is lowered. Moreover, since the thermal expansion coefficient differs between the adhesive layer and the conductive connection portion, the adhesive layer may be distorted due to a temperature change and the detection accuracy of the acceleration sensor element may be reduced.
[0004]
An object of the present invention is to provide an acceleration sensor element and a method for manufacturing the acceleration sensor element that can reliably establish conduction between a counter electrode and a ground electrode.
[0005]
Another object of the present invention is to provide an acceleration sensor element that can prevent the detection accuracy of the acceleration sensor from being lowered due to a temperature change, and a method for manufacturing the same.
[0006]
[Means for Solving the Problems]
In the present invention, an acceleration detection electrode and one or more electrodes including a ground electrode are formed on one surface of a piezoelectric ceramic substrate, and a counter electrode facing the acceleration detection electrode is formed on the other surface. The acceleration sensor element is an object of improvement.
[0007]
In the present invention, the ground electrode and the counter electrode are electrically connected through a through-hole conductive portion that penetrates the piezoelectric ceramic substrate. If the ground electrode and the counter electrode are electrically connected using the through-hole conductive portion as in the present invention, the conductive portion between the ground electrode and the counter electrode can be reduced without mixing non-conductive materials as in the prior art. Can be formed. Therefore, electrical conduction between the counter electrode and the ground electrode can be ensured. Further, unlike the prior art, since it is not necessary to form a conductive connection portion in the adhesive layer, the counter electrode and the diaphragm are joined only by the adhesive layer. Therefore, the adhesive layer is not distorted due to a temperature change, and the detection accuracy of the acceleration sensor element can be prevented from being lowered.
[0008]
The acceleration sensor element of the present invention includes a piezoelectric ceramic substrate forming step for forming a piezoelectric ceramic substrate having a through-hole penetrating in the thickness direction, and acceleration detection on the surface using conductive paint on the front and back surfaces of the piezoelectric ceramic substrate, respectively. Forming an electrode for printing and one or more electrodes and forming a counter electrode on the back surface, a polarization process for applying a polarization treatment between the acceleration detection electrode and the counter electrode, and conducting through holes A through-hole conductive part forming step of filling the paint to form a through-hole conductive part and electrically connecting the ground electrode and the counter electrode via the through-hole conductive part; and a conductive paint on the surface of the piezoelectric ceramic substrate And forming a connection pattern connected to the acceleration detecting electrode by printing, and forming a through-hole conductive part And it can be prepared by the method carried out simultaneously using the same conductive paint connection pattern forming step. By manufacturing the acceleration sensor element in this way, the through-hole conductive portion forming step and the connection pattern forming step can be simultaneously performed using the same conductive paint. One print forming process can be reduced compared with the method of printing and forming an electrode. Further, in the conventional acceleration sensor element in which the conductive connection portion is formed in the adhesive layer, it cannot be visually confirmed whether or not the conductive connection portion is formed after the acceleration sensor element and the diaphragm are joined. . On the other hand, the acceleration sensor element manufactured by this method can visually confirm whether or not a through-hole conductive portion is formed from the surface side of the acceleration sensor element even after the acceleration sensor element and the diaphragm are joined. There are advantages.
[0009]
Further, the through-hole conductive portion may be formed before each electrode is printed. In this case, after each electrode is printed and formed, a polarization process is performed between the acceleration detection electrode and the counter electrode. If the acceleration sensor element is manufactured in this way, the ground electrode and the counter electrode are formed so as to cover both end portions of the through-hole conductive portion located on both sides of the piezoelectric ceramic substrate. Can be smoothed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of a triaxial acceleration sensor incorporating an acceleration sensor element according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. As shown in this figure, this triaxial acceleration sensor is fixed on a surface opposite to the surface of the diaphragm 1, the weight 3, the base 5, and the surface of the diaphragm 1 on which the weight 3 is attached. And an acceleration sensor element 7. In the drawing, the thickness of the main part of the acceleration sensor element 7 is exaggerated for easy understanding. Each of these members is housed in a frame-shaped insulating resin case 9. The insulating resin case 9 has three terminal fittings 25 connected to the resin molded body 21 to the output electrodes OX, OY, OZ and the electrodes OD, OE, OD (see FIG. 3) of the acceleration sensor element 7, respectively. .. Are fixed to each other. A metal lid member 6 is attached to the upper opening of the case 9.
[0011]
The diaphragm 1, the weight 3 and the base 5 are configured as a single unit 10 which is integrally formed of a metal material made of brass. The diaphragm 1 has a disk shape. The 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 periphery of the diaphragm 1. The insulating resin case 9 is integrally insert-molded with the single unit 10 as an insert, and a V-shaped groove 5 a for preventing the single unit 10 from being detached from the insulating resin case 9 is provided at the outer periphery of the base 5. 5 are formed continuously in the circumferential direction.
[0012]
In this example, as the acceleration sensor element 7, an acceleration detection electrode pattern E1 for detecting triaxial acceleration is formed on the surface of the piezoelectric ceramic substrate 7a as shown in the plan view of FIG. 3 and the back view of FIG. A piezoelectric triaxial acceleration sensor element formed with a counter electrode pattern E0 is used.
[0013]
The back surface of the piezoelectric ceramic substrate 7a and the counter electrode pattern E0 are joined to the surface of the diaphragm 1 by an adhesive layer 4 made of a synthetic resin material such as epoxy. The piezoelectric ceramic substrate 7a has a quadrangular outline shape, and the portion corresponding to the electrode is polarized so that spontaneous polarization charges are generated when stress is applied to the inside. The polarization process will be described later. As shown in FIG. 3, the piezoelectric ceramic substrate 7a has a weight opposing region 8A, a base opposing region 8B, and an intermediate region 8C located between the weight opposing region 8A and the base opposing region 8B. Yes. The weight 3 is located in the portion corresponding to the weight opposing region 8A, and the base 5 is located in the portion corresponding to the base opposing region 8B. The intermediate region 8C includes a first stress generation region 8C1 that surrounds the weight opposing region 8A, and a second stress generation region 8C2 that is located between the first stress generation region 8C1 and the base opposing region 8B. ing. The first stress generation region 8C1 is a region in which stress is generated when the acceleration is applied to the weight 3, and the acceleration detection electrodes EX1 to EZ4 of the acceleration detection electrode pattern E1 are formed on the surface side. Is formed. The first stress generation region 8C1 is centered on the center of gravity of the weight 3 when acceleration acts on the weight 3 in a direction parallel to the substrate surface of the piezoelectric ceramic substrate 7a (X-axis direction or Y-axis direction). It deforms into a point-symmetrical state (a state where tensile stress is applied and a state where compressive stress is applied). Further, when acceleration acts on the weight 3 in a direction (Z-axis direction) orthogonal to the substrate surface of the piezoelectric ceramic substrate 7a, each part of the first stress generation region 8C1 is deformed to the same state. The second stress generation region 8C2 is a region where only a small amount of stress is generated compared to the first stress generation region 8C1. In FIG. 3, 8D is a boundary line (neutral line) between the first stress generation region 8C1 and the second stress generation region 8C2.
[0014]
Both the acceleration detection electrode pattern E1 and the counter electrode pattern E0 formed on the front and back surfaces of the piezoelectric ceramic substrate 7a are formed by screen printing. As shown in FIG. 3, the acceleration detection electrode pattern E1 includes an X-axis direction detection electrode pattern 13, a Y-axis direction detection 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 includes four Z-axes of a pair of Y-axis direction acceleration detection electrodes EY1 and EY2 and a Z-axis direction detection electrode pattern 17 of a Y-axis direction detection electrode pattern 15 described later. Together with the direction acceleration detection electrodes EZ1 to EZ4, an annular row surrounding the weight opposing region 8A is formed. The electrodes EX1 and EX2 of the pair of X-axis direction acceleration detection electrodes are axisymmetric with respect to the X-axis direction virtual line XL and straddle the weight opposing region 8A and the first stress generation region 8C1. It has a shape close to a rectangle. The X-axis output electrode OX has a substantially square shape, and is formed so as to be positioned on the outer peripheral edge of the piezoelectric ceramic substrate 7a outside the second stress generation region 8C2.
[0015]
The Y-axis direction acceleration detection electrode pattern 15 has a structure in which a pair of Y-axis direction acceleration detection electrodes EY1, EY2 and a Y-axis output electrode OY are connected in series by connection lines L3 to L5. The electrodes EY1 and EY2 of the pair of Y-axis direction acceleration detection electrodes have the same shape as the X-axis direction acceleration detection electrodes EX1 and EX2, and are symmetrical with respect to the Y-axis direction virtual line YL. Moreover, it has a shape close to a rectangle straddling the weight opposing region 8A and the first stress generation region 8C1. Similar to the X-axis output electrode OX, the Y-axis output electrode OY has a substantially square shape and is positioned on the outer peripheral edge of the piezoelectric ceramic substrate 7a outside the second stress generation region 8C2. It is formed side by side with the output electrode OX.
[0016]
The Z-axis direction acceleration detection electrode pattern 17 has a structure in which Z-axis direction acceleration detection electrodes EZ1 to EZ4 and a Z-axis output electrode OZ are connected in series in this order by connection lines L6 to L9. The four Z-axis direction acceleration detection electrodes EZ1 to EZ4 are arranged between the pair of X-axis direction acceleration detection electrodes EX1 and EX2 and the pair of Y-axis direction acceleration detection electrodes EY1 and EY2, respectively. Is formed. Each electrode of the Z-axis direction acceleration detection electrodes EZ1 to EZ4 has a shape close to a rectangle, and similarly to the X-axis direction acceleration detection electrodes EX1 and EX2, the weight opposing region 8A and the first stress generation region. It is formed across 8C1. Similarly to the X-axis output electrode OX, the Z-axis output electrode OZ has a substantially square shape, and is positioned on the outer peripheral edge of the piezoelectric ceramic substrate 7a outside the second stress generation region 8C2. It is formed side by side with the output electrode OX and the Y-axis output electrode OY.
[0017]
Three electrodes OD, OE, and OD are formed side by side so as to be parallel to the output electrodes OX, OY, and OZ at a portion along the side facing the side of the ceramic substrate 7a where the output electrodes OX, OY, and OZ are arranged. ing. The electrode OE constitutes an earth electrode connected to the earth terminal, and the two electrodes OD and OD constitute a dummy electrode only for connecting a supporting dummy terminal.
[0018]
As shown in FIG. 4, the counter electrode pattern E0 formed on the back surface of the piezoelectric ceramic substrate 7a is opposed to the annular counter electrode E0a facing the acceleration detection electrodes EX1 to EZ4 of the acceleration detection electrode pattern E1. And an extending portion E0b extending from the electrode E0a to the edge of the piezoelectric ceramic substrate 7a. The extending portion E0b has an end facing the ground electrode OE of the acceleration detecting electrode pattern E1, and as shown in FIG. 2, the connecting portion OE1 covering the inner wall of the through hole 29 penetrating the piezoelectric ceramic substrate 7a and The through hole conductive portion 27 is electrically connected to the ground electrode OE. Thus, the ground electrode OE and the counter electrode E0a included in the counter electrode pattern E0 are electrically connected via the through-hole conductive portion 27. The through hole conductive portion 27 is formed by filling a through hole 39 penetrating the through hole 29 and each electrode OE, E0 with resin silver, and both ends are exposed on the surfaces of the ground electrode OE and the extending portion E0b. is doing. The ground electrode OE is also electrically connected to the single unit 10 via a conductive adhesive layer 31 passing through the side of the piezoelectric ceramic substrate 7a. Thereby, both the counter electrode E0a and the single unit 10 are electrically connected to the ground electrode OE.
[0019]
Returning to FIG. 3, acceleration in the Z-axis direction (direction perpendicular to the paper surface of FIG. 3) acts on the weight 3 on each part of the piezoelectric ceramic substrate 7a corresponding to the X-axis direction acceleration detection electrodes EX1 and EX2. Then, when the same kind of stress is generated in each part, the acceleration detection electrode EX1 located on one side of the weight opposing region 8A and the acceleration detection electrode EX2 located on the other side spontaneously have opposite polarities. Polarization processing is performed so that polarization charges appear. Similarly to the portions of the piezoelectric ceramic substrate 7a corresponding to the X-axis direction acceleration detection electrodes EX1 and EX2, the portions of the piezoelectric ceramic substrate 7a corresponding to the Y-axis direction acceleration detection electrodes EY1 and EY2 are also weights 3. When the same kind of stress is generated in each part due to the acceleration in the Z-axis direction, the Y-axis direction acceleration detection electrode EY1 located on one side of the weight opposing region 8A and the Y located on the other side Polarization processing is performed so that spontaneous polarization charges having opposite polarities appear on the axial acceleration detection electrode EY2. Further, each part of the piezoelectric ceramic substrate 7a corresponding to the Z-axis direction acceleration detection electrodes EZ1 to EZ4 is all when the same kind of stress is generated in each part due to the Z-axis direction acceleration acting on the weight 3. Polarization processing is performed so that spontaneous polarization charges having the same polarity appear on the Z-axis direction acceleration detection electrodes EZ1 to EZ4. For this reason, when the diaphragm 1 is deformed based on the acceleration acting on the weight 3, the piezoelectric ceramic substrate 7a is bent, and the spontaneous polarization charge generated between the acceleration detecting electrode pattern E1 and the counter electrode pattern E0 is changed. The acceleration in the direction of three axes (X axis, Y axis, Z axis) applied to the weight 3 is measured as a change in current or voltage.
[0020]
Next, a method for manufacturing the acceleration sensor element of the present embodiment will be described. First, as shown in FIG. 5A, a piezoelectric ceramic substrate 7a having a through hole 29 is prepared. This piezoelectric ceramic substrate 7a was formed by forming a through hole 29 on a ceramic substrate in a green sheet state using punching and then firing the ceramic substrate. Next, as shown in FIG. 5 (B), a conductive paint made of glass-silver is applied to the surface of the piezoelectric ceramic substrate 7a, followed by preliminary drying, and acceleration detection electrodes EX1 to EZ4 and electrodes OX to OZ, OD, OE, OD are printed and formed. At this time, the conductive paint forming the ground electrode OE flows out to the back side of the piezoelectric ceramic substrate 7a through the inner wall of the through hole 29, and the connecting portion OE1 is formed on the inner wall of the through hole 29 and the back surface of the piezoelectric ceramic substrate 7a. It is formed. Next, as shown in FIG. 5C, a conductive paint made of glass-silver is applied to the back surface of the piezoelectric ceramic substrate 7a, and then preliminarily dried to print the counter electrode pattern E0. Next, the acceleration detection electrodes EX1 to EZ4, the electrodes OX to OZ, OD, OE, OD and the counter electrode pattern E0 are fired. Next, a polarization process is performed on a predetermined position of the piezoelectric ceramic substrate 7a by applying a DC voltage between the opposing electrodes of the acceleration detection electrodes EX1 to EZ4 and the counter electrode E0a of the counter electrode pattern E0. Next, the through hole 39 surrounded by the inner wall of the connection portion OE1 is filled with a conductive paint made of a resin-silver paint, and the conductive paint of the same material is applied to the surface of the piezoelectric ceramic substrate 7a and then heated and cured. Then, a connection pattern composed of the connection lines L1 to L9 and a through-hole conductive portion 27 as shown in FIG. If the acceleration sensor element is manufactured by such a method, the step of forming the through-hole conductive portion and the step of forming the connection patterns L1 to L9 can be simultaneously performed using the same conductive paint. Compared with the method of forming the through-hole conductive part before the electrode shown in FIG. 6 is printed, one printing process can be reduced. In addition, the acceleration sensor element manufactured by this method has an advantage that it is possible to visually confirm whether or not a through-hole conductive portion is formed from the surface side of the acceleration sensor element even after the acceleration sensor element and the diaphragm are joined. is there.
[0021]
FIGS. 6A to 6C show a mode in which the acceleration sensor element is manufactured by another method. In this method, the through-hole conductive portion is formed before the electrode is printed and is performed as follows. First, as shown in FIG. 6A, a piezoelectric ceramic substrate 7a having a through hole 29 penetrating in the thickness direction is prepared. Next, the through hole 29 is filled with a conductive paint made of a resin-silver paint, and then cured by heating to form a through hole conductive portion 37 as shown in FIG. Next, as shown in FIG. 6C, a conductive paint made of glass-silver is applied to the front and back surfaces of the piezoelectric ceramic substrate 7a, followed by baking, and an acceleration detecting electrode on the surface of the piezoelectric ceramic substrate 7a. EX1 to EZ4 and electrodes OX to OZ, OD, OE ′, OD are printed and formed, and a counter electrode pattern E0 ′ is printed on the back surface of the piezoelectric ceramic substrate 7a. Thereby, the ground electrode OE ′ and the extended portion E0b ′ of the counter electrode pattern E0 ′ are electrically connected through the through-hole conductive portion 37. Next, a polarization process is performed on a predetermined position of the piezoelectric ceramic substrate 7a by applying a DC voltage between the electrodes facing the acceleration detection electrodes EX1 to EZ4 and the counter electrode E0a ′ of the counter electrode pattern E0 ′. Next, a conductive paint made of a resin-silver paint is applied to the surface of the piezoelectric ceramic substrate 7a and then heat-cured to print and form a connection pattern made of connection lines L1 to L9, thereby completing an acceleration sensor element. When the acceleration sensor element 7 is manufactured in this way, the ground electrode OE ′ and the counter electrode pattern E0 ′ are formed so as to cover both end portions of the through-hole conductive portion 37 located on both surfaces of the piezoelectric ceramic substrate 7a. The surfaces of the ground electrode OE ′ and the counter electrode pattern E0 ′ can be made smooth.
[0022]
【Effect of the invention】
According to the present invention, since the ground electrode and the counter electrode are electrically connected using the through-hole conductive portion, the conductive portion between the ground electrode and the counter electrode is not mixed with a non-conductive material as in the prior art. Can be formed. Therefore, electrical conduction between the counter electrode and the ground electrode can be ensured. Further, unlike the prior art, since it is not necessary to form a conductive connection portion in the adhesive layer, the counter electrode and the diaphragm are joined only by the adhesive layer. Therefore, the adhesive layer is not distorted due to a temperature change, and the detection accuracy of the acceleration sensor element can be prevented from being lowered.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a triaxial acceleration sensor incorporating an acceleration sensor element according to an embodiment of the present invention.
FIG. 2 is a partially enlarged view of FIG.
FIG. 3 is a plan view of the acceleration sensor element according to the embodiment of the present invention.
FIG. 4 is a rear view of the acceleration sensor element according to the embodiment of the present invention.
FIGS. 5A to 5D are diagrams used for explaining a method of manufacturing an acceleration sensor element according to an embodiment of the present invention. FIGS.
FIGS. 6A to 6C are views used for explaining a method of manufacturing an acceleration sensor element according to another embodiment of the present invention. FIGS.
[Explanation of symbols]
7 Acceleration sensor element 27 Through-hole conductive part EX1 to EZ4 Electrode for acceleration detection OE Ground electrode E0 Counter electrode pattern E0a Counter electrode E0b Extending part

Claims (1)

An acceleration sensor element in which an acceleration detection electrode and one or more electrodes including a ground electrode are formed on one surface of a piezoelectric ceramic substrate, and a counter electrode facing the acceleration detection electrode is formed on the other surface. A manufacturing method of
A piezoelectric ceramic substrate forming step of forming a piezoelectric ceramic substrate having a through hole penetrating in the thickness direction;
A through hole conductive part forming step of forming a through hole conductive part by filling the through hole with a conductive paint;
One or more electrodes including the acceleration detecting electrode and the ground electrode are printed on the surface of the piezoelectric ceramic substrate using a conductive paint for forming an electrode made of glass-silver , and the through hole is formed through the inner wall of the through hole. An electrode forming step of forming a connection portion that covers an inner wall of the through hole with the electrode-forming conductive paint that has flowed out to the back side of the piezoelectric ceramic substrate, and printing the counter electrode on the back surface of the piezoelectric ceramic substrate;
A polarization treatment step of performing a polarization treatment between the acceleration detection electrode and the counter electrode;
A through hole is formed by filling the through hole with a conductive paint for forming a through hole conductive portion to form a through hole conductive portion, and electrically connecting the ground electrode and the counter electrode through the through hole conductive portion. Hall conductive part forming step,
A connection pattern forming step of applying a pattern-forming conductive paint on the surface of the piezoelectric ceramic substrate and printing a connection pattern connected to the acceleration detection electrode; and
The through-hole conductive part forming step and the connection pattern forming step are performed simultaneously using the conductive paint for forming the through-hole conductive part and the same conductive paint made of resin-silver paint as the conductive paint for pattern formation. A method of manufacturing an acceleration sensor element, characterized in that:

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