JP2002076459A - Flexible piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the physical strength of connections of leads and flexible electrodes and reduce the electric resistance. SOLUTION: Flexible electrodes 2a, 2b are formed on both sides of a composite piezoelectric sheet 1 and rigid sheets 4a, 4b are laminated on connections of leads 3a, 3b and the flexible electrodes 2a, 2b. Thus it is possible to raise the physical strength of the connections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible piezoelectric element.

[0002]

2. Description of the Related Art Heretofore, this type of composite piezoelectric element has been as follows.

Japanese Patent Application Laid-Open No. 53-66753 discloses a flexible piezo film (having a thickness of 0.00) comprising a fine powder of a piezoelectric ceramic of lead zirconate titanate and a polyvinylidene fluoride resin.
(1 mm to 1.0 mm) has been proposed. It is disclosed that aluminum vacuum-deposited thin-film electrodes are formed on both surfaces of the flexible film, and lead wires are connected to these electrodes.

In Japanese Patent Application Laid-Open No. 9-294730, as shown in FIG. 3, flexible electrodes 2a and 2b are attached to both sides of a piezoelectric polymer sheet 1, and lead wires 3a and 3b is disclosed.

[0005]

However, even in each of the above-mentioned conventional examples, the specific connection structure when connecting the lead wires 3a, 3b to the flexible electrodes 2a, 2b, the physical strength of the connection portion is high, and No connection configuration with low electrical resistance is disclosed.

As a general connection configuration, a configuration in which both the lead wire and the flexible electrode are fixed with a conductive adhesive is considered. In this case, the flexible electrode 2 of the lead wires 3a and 3b is used.
There is a problem that the physical strength of the connection part is low because the bonding area to the parts a and b is small.

[0007]

According to the present invention, in order to solve the above-mentioned problems, lead wires are respectively connected to flexible electrodes formed on both surfaces of a composite piezoelectric sheet, and the flexible electrodes and the lead wires are connected. The present invention provides a flexible piezoelectric element in which a rigid sheet is laminated on the connection part of (1).

According to the above invention, the rigid sheet is covered with the connecting portion between the flexible electrode and the lead wire, so that the connecting portion is physically protected from external force applied to the connecting portion and the lead wire.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flexible piezoelectric element according to a first aspect of the present invention comprises connecting lead wires to flexible electrodes formed on both surfaces of a composite piezoelectric sheet, respectively. Since the rigid sheet is laminated at the wire connection,
The connection is physically protected from external force applied to the connection and the lead wire. Therefore, the connection strength of the lead wire can be increased.

In the flexible piezoelectric element according to the second aspect of the present invention, the lead wire according to the first aspect is formed by welding a metal foil to one end of a metal wire. By connecting the metal foil to the flexible electrode, the connection area is increased, so that the connection strength can be increased and the resistance of the connection portion can be reduced.

In a flexible piezoelectric element according to a third aspect of the present invention, the lead wire according to the first aspect is formed by soldering a metal foil to one end of a metal wire. The connection area can be increased by connecting the metal foil to the flexible electrode, so that the connection strength can be increased and the resistance of the connection portion can be reduced.

In a flexible piezoelectric element according to a fourth aspect of the present invention, the metal foil according to the second or third aspect has a conductive adhesive layer formed on a surface to which no lead wire is connected. The conductive adhesive layer acts as a physical adhesive layer to the flexible electrode and also has an action to secure conductivity between the metal foil and the flexible electrode. It can be easily connected to flexible electrodes.

In the flexible piezoelectric element according to the fifth aspect of the present invention, the rigid sheet according to the first to fourth aspects is a conductive sheet. When the rigid sheet is laminated on the connection between the lead wire and the flexible electrode, the rigid sheet is electrically connected to the lead wire. As a result, since the rigid sheet acts to increase the connection area, the electric resistance of the connection portion can be reduced.

In the flexible piezoelectric element according to the sixth aspect of the present invention, the rigid sheet according to the fifth aspect is a metal sheet. Since the specific resistance of the metal is small, the electric resistance of the connection portion can be minimized in practical use.

In a flexible piezoelectric element according to a seventh aspect of the present invention, the metal sheet according to the sixth aspect has a conductive adhesive formed on one surface. The conductive adhesive is
Since the metal sheet and the flexible electrode portion including the lead wire are electrically connected, the overall electric resistance can be reduced. In addition, the conductive adhesive can physically fix both.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a flexible piezoelectric element according to Embodiment 1 of the present invention. This flexible piezoelectric element
Flexible electrodes 2 formed on both surfaces of composite piezoelectric sheet 1
a and 2b are connected to lead wires 3a and 3b, respectively, and rigid portions 4a and 4b are laminated on these connection portions.

The composite piezoelectric sheet 1 is made of a composite material obtained by adding a ceramic piezoelectric powder such as lead zirconate titanate to a polymer base material such as an epoxy resin, urethane resin, chloroprene resin, or chlorinated polyethylene resin by a roll method. It is formed by processing into a sheet shape by, for example, the above. Flexible electrode 2
As a and 2, a deposited film, a sputtered film, a fired film of aluminum or silver, or a composite conductor described later is used. As the rigid sheets 4a and 4b, a metal sheet having a thickness of several hundred μm or more made of copper, aluminum, nickel, or the like, a polymer sheet made of polyethylene, polyethylene terephthalate, or the like is used.

As shown in FIG. 1, the rigid sheets 4a, 4a
b is laminated on the connection between the flexible electrodes 2a, 2b and the leads 3a, 3b, so that the rigid sheets 4a, 4b physically contact the flexible electrodes 2a, 2b and the leads 3a, 3b. I do. At this time, the rigid sheets 4a and 4b are fixed to the same connection portion with an adhesive or the like, so that the individual lead wires 3a and 3b are fixed.
The connection area can be increased as compared with the case where b is connected to the flexible electrodes 2a and 2b alone. Therefore, when an external force is applied to the connection portion or the lead wires 3a, 3b, the external force acts on the entire rigid sheets 4a, 4b, and the connection between the lead wires 3a, 3b and the flexible electrodes 2a, 2b. Strength can be increased. In addition, the rigid sheets 4a, 4a
Since b is not easily deformed, and therefore, the connecting portion is also hardly deformed, the shape stability of the connecting portion is also excellent.

It is desirable to use conductive sheets as the rigid sheets 4a and 4b. Since the conductive rigid sheets 4a and 4b are laminated including the lead wires 3a and 3b, the conductive rigid sheets 4a and 4b other than those directly above the lead wires 3a and 3b are placed on the flexible electrodes 2a and 2b. Are laminated. Therefore, the electrical path connecting the leads 3a, 3b and the flexible electrodes 2a, 2b is
Are connected to the flexible electrodes 2a and 2b, and also to the flexible electrodes 2a and 2b via the conductive rigid sheets 4a and 4b. 3b and the electrical resistance of the flexible electrodes 2a and 2b can be reduced.

At this time, it is desirable to use a conductive adhesive as the adhesive. When an insulating adhesive is used, the electrical connection of the rigid sheets 4a and 4b through physical contact between the lead wires 3a and 3b and the flexible electrodes 2a and 2b tends to be unstable, This is because the electrical connection can be stabilized by using the conductive adhesive, and the electrical resistance therebetween can be further reduced.

As the conductive flexible sheets 4a and 4b,
It is preferable to use a metal sheet such as stainless steel.
Since the specific resistance of the metal is small, the flexible sheets 4a and 4b made of metal and the leads 3a and 3b and the flexible electrodes 2a and 2a
The electric resistance during b can be minimized practically. For the flexible electrodes 2a and 2b, a deposited film of aluminum, silver, etc.
When a metal-based film such as a sputtered film or a fired film is used,
It is clear that it is particularly effective.

(Embodiment 2) In FIG. 1, the details have been described using the flat lead wires 3a and 3b.
It is clear that b may be a flat plate, a line, or a plurality of thin wire bundles. These leads 3
When a and 3b are connected to the flexible electrodes 2a and 2b, they cannot be directly welded or soldered, so that it is difficult to make a connection having both sufficiently large strength and small electric resistance at the connecting portion. In such a case, as shown in FIG.
It is preferable to use a collective lead wire 3 to which a metal foil 5 is welded or soldered to one end. The same can be said for the lead wire 3b. As the metal foil 5, a copper or nickel foil having a thickness of several tens μm or more is used.

The lead wire 3a and the metal foil 5 are connected via the welded portion 6 and the soldered portion 6, so that they are physically connected firmly and electrically with a small electrical resistance at the connection portion. You. In addition, a surface that is not connected by welding or soldering (hereinafter, simply referred to as a “bonding surface of the metal foil 5”) and the flexible electrode 2
a is fixed with a conductive adhesive. The bonding surface of the metal foil 5
The area can be made larger than the bonding portion between the lead wire 3a and the flexible electrode 2a. Therefore, the bonding surface of the metal foil 5 and the flexible electrode 2a are connected physically firmly and electrically with a small connection resistance. In this way, the collective lead wire 3 and the flexible electrode 2a are physically strong,
It is electrically connected with a small connection resistance. In addition,
It is desirable to form a conductive adhesive layer on the adhesive surface of the metal foil 5 in advance. This is because the bonding operation becomes easy.

Although one of the flexible electrodes 2a and 2b is shielded from the external environment in order to prevent noise from entering from the external environment, the present invention is applicable to such a configuration. Is effective.

Although the above has been described in detail using the composite piezoelectric material, it is obvious that a polymer piezoelectric material such as PVDF may be used.

[0027]

According to the present invention, as described above,
According to the invention described in Item 7, the lead wire and the flexible electrode can be physically and strongly connected.

[Brief description of the drawings]

FIG. 1 is a sketch of a flexible piezoelectric element according to a first embodiment of the present invention.

FIG. 2 is a sketch of a lead wire according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a lead wire connection configuration of a conventional flexible piezoelectric element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Composite piezoelectric sheet 2a, 2b Flexible electrode 3 Collective lead wire 3a, 3b Lead wire 4a, 4b Flexible sheet 5 Metal foil 6 Welded or soldered part

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masahiko Ito 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A composite piezoelectric sheet comprising: a composite piezoelectric sheet; flexible electrodes formed on both surfaces of the composite piezoelectric sheet; and lead wires respectively connected to the flexible electrodes. A flexible piezoelectric element in which a rigid sheet is laminated at the connection part of a lead wire. 2. The flexible piezoelectric element according to claim 1, wherein the lead wire has a metal foil welded to one end of the metal wire. 3. The flexible piezoelectric element according to claim 1, wherein the lead wire has a metal foil soldered to one end of the metal wire. 4. The flexible piezoelectric element according to claim 2, wherein the metal foil has a conductive adhesive layer formed on a surface to which no lead wire is connected. 5. The flexible piezoelectric element according to claim 1, wherein the rigid sheet is a conductive sheet. 6. The flexible piezoelectric element according to claim 5, wherein the rigid sheet is a metal sheet. 7. The flexible piezoelectric element according to claim 6, wherein a conductive adhesive is formed on one surface of the metal sheet.