JPH0113519Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure for taking out electrode terminals from a piezoelectric polymer film having a good and robust bonding structure, or a structure for bonding a piezoelectric polymer film and a conductor.

In recent years, single-layer or multi-layer (bimorph) polymeric piezoelectric films made of vinylidene fluoride-based resins have begun to be widely used as electromechanical transducers in applications such as vibration sensors, microphones, and speakers. For example, regarding vibration sensors,
In the past, electrode films were provided on both sides of a ceramic piezoelectric film such as PZT by vapor deposition, and lead wires were soldered to each electrode film. If the surface is curved, the measurement accuracy will be reduced due to poor followability, and the measurable frequency is 500Hz or less, making it impossible to measure high-frequency vibrations that reach about 10kHz, such as those of turbines. , etc. However, a sensor using a polymer piezoelectric film that does not have these drawbacks is essentially suitable.

However, when using such a polymer piezoelectric film as an electromechanical transducer, a major problem is the structure for taking out the lead wires from the electrodes.
Generally, they become brittle and may not be able to withstand continuous use under vibration conditions. For example, the most basic idea is that, similar to the ceramic vibration sensor described above, soldering the lead wires to the electrode film provided on the polymer piezoelectric film is based on the polymer piezoelectric film itself. is unsuitable because it deteriorates due to heat.

In view of the above circumstances, the main purpose of the present invention is to provide a durable electrode extraction structure from a polymer piezoelectric film.

In order to achieve the above-mentioned purpose, the present inventors
First, a conductive adhesive made by dispersing metal powder, carbon powder, etc. in various resin binders, or a low melting point solder (herein, these are collectively referred to as "good conductive adhesives") is used. , we attempted to bond a lead wire to an electrode film on a polymer piezoelectric film. However, these highly conductive adhesives are relatively brittle and cannot withstand continuous vibrations applied during use as electromechanical transducers such as vibration sensors.

Next, as shown in FIG. 1, the present inventors attached a Cu piece 5a to which lead wires 4a and 4b were separately bonded with solder 3 to electrode films 2a and 2b provided on both sides of the polymer piezoelectric film 1, respectively. and 5b,
First, the Cu piece 5a is fixed with a non-conductive adhesive 6 having excellent adhesive strength such as an epoxy resin adhesive.
5b and the electrode films 2a and 2b was attempted to be ensured by applying a highly conductive adhesive 7 along and surrounding the side walls of the conductive pieces 5a and 5b. However, in this case as well, the connection portion 7 made of a highly conductive adhesive was easily destroyed by repeated vibrations applied to the vibration sensor, etc., and was not suitable for practical use.

However, as a result of further research, the present inventors found that while using two types of adhesives, similar to the example shown in Figure 1, vibration stress is transmitted to the highly conductive adhesive, which has a more forced problem. We discovered that a good joint structure could be obtained by using a type of use that is difficult to use, and arrived at the present invention.

The present invention is based on the above-mentioned findings, and the present invention is based on the above-mentioned knowledge. is bonded around the opening via a non-conductive adhesive, and the electrode film and the conductor are electrically connected at the opening via a highly conductive adhesive. That is.

That is, in the electrode terminal extraction structure of the present invention, a conductor is bonded to the electrode film on the polymer piezoelectric film using a non-conductive adhesive that has poor conductivity but excellent adhesive strength, and By ensuring electrical continuity between the conductor and the electrode film on the polymer piezoelectric film using a mechanically weak and highly conductive adhesive at the opening of the conductor where the vibration stress of the body membrane is difficult to transmit.
Overall, a bonded structure with good electrical conductivity and excellent durability can be obtained.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 2 is a schematic cross-sectional view in the thickness direction corresponding to FIG. 1 of an electrode terminal extraction structure for a vibration sensor according to an embodiment of the present invention, and FIG. 3 is a plan view of the same embodiment. . In this embodiment, electrode films 2a and 2b made of vapor-deposited films of Al, Ni, Cr, etc. are provided on both sides of a polymeric piezoelectric film 1, forming a piezoelectric element 10 that forms the sensor part of a vibration sensor as a whole. are doing. To give an example of the dimensions of the piezoelectric element 10, the length is 15 mm, the width is 3 mm, and the thickness is approximately 0.03 mm.
mm, most of the thickness is occupied by the piezoelectric film 1, and the thickness of each of the electrode films 2a and 2b is about 500 Å. Now, in each of these electrode films 2a and 2b,
Non-conductive adhesives such as epoxy resins, cyanoacrylate resins, urethane resins, silicone resins, phenolic resins, acrylic ester resins, butyral resins, nitrile rubbers, chloroprene rubbers, etc., or a small amount of these For example, an outer diameter of 2
Conductive rings 15a and 15b made of Cu, brass, etc., each having an inner diameter of 1 mm and a thickness of 0.05 mm are joined. Further, lead wires 4a and 4b are connected in advance to this conductor ring with solder 3, respectively. Next, the conductor ring 15 bonded in this way
A highly conductive adhesive 17 is placed in the openings of rings a and 15b to ensure conduction between these conductive rings 15a and 15b and electrode films 2a and 2b.

As the conductive adhesive 17, polyethylene,
100 parts by weight of binder resin such as polypropylene, ABS, silicone resin, etc.
A conductive resin adhesive made by dispersing ~1000 parts by weight of metal powder or carbon powder, or, for example, a weight ratio of Sn/Pb/Bi/In=12/18/49/
21 (melting point 57.8℃), Sn/Bi/In=17/57/26 (melting point
A low melting point solder having a composition such as 78.9°C) and a melting point of 80°C or lower can be used.

In the above, an example has been described in which the conductor to be joined to the electrode film is the conductor rings 15a, 15b joined to the lead wires 4a, 4b. However, the conductor to be joined is a lead wire 25 whose tip 25a is wound into a ring shape and flattened by rolling or the like, as shown in FIG. 4a (top view) and FIG. 4b (front view). There may be a fifth
As shown in Figure a (plan view) and Figure 5 b (front sectional view), it may be a strip-shaped conductor 35 having an opening 35 near the end.

Furthermore, if the electrode 2a or 2b provided on the polymer piezoelectric film 1 is made of a material with relatively good heat resistance, such as Ni or Cr, FIG. 6 corresponds to FIG. structure only), the electrode film 2
By applying solder or low melting point solder 18 to the position inside the opening of ring 15a on a, and then applying low melting point solder or conductive resin adhesive 17, a bonding structure that is even stronger and has good electrical conductivity can be achieved. It can be done.

In the above example, a vibration sensor was described as a preferable application example of the electrode terminal extraction structure of the present invention. A similar electrode terminal extraction structure can also be used for applications such as pyrosensors and the like.

As mentioned above, according to the present invention, when bonding a conductor onto a polymer piezoelectric film, two types of adhesives, a non-conductive adhesive and a highly conductive adhesive, are used to solve the problem of strength. A good electrical connection and mechanical durability are achieved by applying a certain highly conductive adhesive to the opening in the conductor to be bonded to make it less susceptible to vibrational stress applied to the piezoelectric polymer film. An electrode terminal extraction structure is provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view in the thickness direction of an example of an electrode terminal extraction structure that the present inventors tested before the present invention;
2 and 6 are respectively sectional views in the thickness direction of an electrode terminal extraction structure according to an embodiment of the present invention, FIG. 3 is a plan view of the embodiment of FIG. 2, and FIG. 4a
5A and 5A are plan views showing examples of conductors to be joined, respectively, and FIGS. 4B and 5B are a corresponding front view and a front sectional view, respectively. 1... Polymer piezoelectric film, 2a, 2b... Electrode,
3... Solder, 4a, 4b... Lead wire, 15a,
15b...Conductor ring, 16...Poor conductive adhesive, 17...Good conductive adhesive, 18...Solder,
25...Lead wire with ring tip, 35...
A strip-shaped conductor with an opening near the tip.

Claims (1)

[Claims for Utility Model Registration] 1. An electrode film provided on at least one surface of a polymeric piezoelectric film is provided with a conductor having an opening near the end via a non-conductive adhesive around the opening. 1. An electrode terminal extraction structure of a polymer piezoelectric film, characterized in that the electrode film and the conductor are electrically connected at the opening by a highly conductive adhesive. 2. The electrode terminal extraction structure according to claim 1, wherein the conductor having an opening near the end is a joined body of a conductor ring and a lead wire. 3. The electrode terminal extraction structure according to claim 1, wherein the conductor having an opening near the end is a strip-shaped conductor having an opening near the end. 4. The electrode terminal lead-out structure according to claim 1, wherein the conductor having an opening near the end is a lead wire whose end is wound into a ring shape and flattened. 5 In the opening, the electrode film and the conductor are
Any one of claims 1 to 4 of the utility model registration claims, which are electrically connected by a highly conductive adhesive covering the electrode film through solder which is applied in advance on the electrode film exposed from the opening. The electrode terminal extraction structure described in . 6. Utility model registration claim No. 6, in which electrode films are provided on both sides of the polymer piezoelectric film, and a conductor having an opening near the end is bonded to each of these electrode films and electrically connected. The electrode terminal extraction structure according to any one of Items 1 to 5.