JPH0560783A - Manufacture of piezoelectric acceleration sensor - Google Patents

Abstract

PURPOSE:To improve the impact resistance of a piezoelectric acceleration sensor. CONSTITUTION:When the film-shaped piezoelectric body of a piezoelectric acceleration sensor is manufactured, plasma etching is performed on both surfaces of the film of the piezoelectric body. Thereafter, electrodes are bonded so as to form a unitary body. The bonding strength is greatly enhanced, and the impact resistance is remarkably improved. Especially, the sensors can be continuously fabricated in-line in manufacturing because the plasma etching is performed. The mass production is easy. Since the dry process is used, post treatment such as used in chemical treatment is not required, and the production efficiency is extremely high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a piezoelectric acceleration sensor, and more particularly to a method of manufacturing a sensor having excellent impact resistance.

[0002]

2. Description of the Related Art Regarding a piezoelectric type acceleration sensor, we have already utilized electric charges generated by compressing a polymeric piezoelectric film such as PVDF, have a simple structure, are strong against impact, and have large sensitivity anisotropy. A piezoelectric acceleration sensor having a small pyroelectric output has been proposed, and patent applications have been filed as Japanese Patent Application Nos. 1-113255, 1-251405, and 1-318277.

FIG. 1 illustrates such a piezoelectric acceleration sensor device. The piezoelectric acceleration sensor device 1 includes an acceleration sensor unit 4 including a piezoelectric acceleration sensor 2 and a circuit board 3 on which an impedance conversion circuit for converting the output from the piezoelectric acceleration sensor 2 and an output amplification circuit are mounted. Are accommodated in the package 5. The acceleration sensor unit 4 is configured by mounting the piezoelectric acceleration sensor 2 on one surface side of the circuit board 3 and disposing the circuit 6 on the other surface side.

In this piezoelectric acceleration sensor 2, as shown in FIG. 2, metal thin plates 8 made of copper foil or the like are bonded and integrated as electrodes on both sides of a piezoelectric film 7 made of a polymer film such as PVDF. On both sides of the film-like piezoelectric body 9, the support plates 10 and 10 made of a rigid body such as a glass epoxy plate are bonded and integrated to form a sensing portion 11, and the load body 12 is placed on the sensing portion 11. Is configured. A dielectric adhesive such as an epoxy adhesive is used for adhesion between the layers in the sensing unit 11. Reference numeral 13 in the figure indicates the adhesive layer.

Since the piezoelectric acceleration sensor has such a structure, it can be miniaturized, is easy to manufacture, and has a problem in the prior art because a polymer film is used for the piezoelectric body. Piezoelectric body (previously ceramic piezoelectric body)
It also has a number of advantages such as no damage to the piezoelectric body due to its brittleness during impact.

[0006]

However, although such a piezoelectric acceleration sensor has excellent characteristics, the piezoelectric forming the film-shaped piezoelectric body 9 is particularly affected by a lateral impact. In some cases, peeling occurred between the body film 7 and the metal thin plates 8 and 8 adhered to both surfaces thereof, and the acceleration sensor was destroyed. In practice, the current acceleration sensor has sufficient strength, but it is not always satisfactory when used as an impact sensor. It is considered that such peeling is caused by the fact that the piezoelectric film 7 is mainly made of fluorine, so that the adhesive force between the piezoelectric film and the adhesive does not become large.

The present invention has been made in view of the above circumstances, and an object thereof is to improve impact resistance of a conventional piezoelectric acceleration sensor.

[0008]

This problem is solved by a manufacturing method in which, when a film-shaped piezoelectric body of a piezoelectric acceleration sensor is manufactured, plasma etching is performed on both surfaces of the piezoelectric film to bond and integrate electrodes. To be done.

[0009]

The present invention will be described in detail below. In this method, first, the piezoelectric film is subjected to plasma etching.
A piezoelectric polymer film such as a PVDF film is preferably used as the piezoelectric film. In the sputtering system, the piezoelectric film, which is the sample, is placed in a plasma atmosphere such as argon, and by applying a negative direct current to the sample, argon ions collide with the surface of the sample and the surface of the sample becomes uniform. Is etched. On this occasion,
Since the modification of the sample by plasma etching extends only to the extreme surface of the sample, the entire piezoelectric film is not deteriorated. Further, since the temperature of the sample hardly rises, the piezoelectric film is not deteriorated in piezoelectricity. By performing plasma etching on the surface of the piezoelectric film in this manner, many fine irregularities are formed on the surface of the piezoelectric film. Due to these irregularities, an anchoring effect occurs at the time of bonding and the adhesive force increases. Then, thin metal plates, which are electrodes, are bonded and integrated on both sides of the piezoelectric film that has been subjected to the plasma etching treatment to produce a film-shaped piezoelectric body. still,
Copper foil, aluminum foil, or the like is usually used as the electrode, but conductive plastic or the like can also be used. An adhesive is used to bond the electrodes. The adhesive is not limited, but a dielectric adhesive is preferred. Above all, as the dielectric adhesive, an epoxy adhesive having a high adhesive strength is preferably used. Then, when the dielectric adhesive is solidified, the temporary adhesive body of the piezoelectric film and the metal thin plate is integrated by pressing with a predetermined pressure by a pressing machine.
The press machine used for this bonding is not particularly limited, and a general medium-and low-pressure press device whose press pressure can be adjusted relatively accurately can be used.

Next, a support plate is bonded and integrated on both sides of the film-shaped piezoelectric body obtained by bonding and integrating while applying a predetermined pressure. As the material of the support plate, a material having a large rigidity, particularly a glass epoxy plate material, is preferably used. It should be noted that it is possible to carry out the bonding while applying pressure even at the time of this bonding. Therefore, each material of the piezoelectric film, the two metal thin plates and the two support plates is coated with an adhesive at the interface and overlapped with each other. It is also possible to manufacture a laminated body by mounting the laminated body on and adhering to it while applying pressure.

Next, the obtained laminated body is cut into an appropriate shape by using a cutting machine such as a dicing saw to obtain a chip which becomes a sensing portion of the sensor. In this cutting, the planar shape of the film-shaped piezoelectric body is cut into a point-symmetrical shape with the sensing axis as the center of symmetry on a plane parallel to the measurement surface on which the sensor is mounted. The cut chip is adhesively fixed on the circuit board and the load body is adhesively fixed on the upper side of the chip.

This load body has a plane shape of a plane in contact with the sensing portion which is point-symmetrical with the sensing axis as a center of symmetry, and has a cross section of an infinite number of planes passing through the sensing axis and perpendicular to the measurement surface. Sometimes, all the cross-sections have a line-symmetrical shape with the sensing axis as the axis of symmetry, and the material thereof is not particularly limited, but a metal material such as brass (brass) is preferably used. In this way, a piezoelectric acceleration sensor having excellent impact resistance is manufactured.

[0013]

Example A PVDF piezoelectric film having a thickness of 100 μm was cut into a square shape of 5 mm × 5 mm, and both surfaces thereof were subjected to plasma etching treatment. The sputtering apparatus was an RF type, the discharge power was 200 W, and argon gas was used as the gas. The plasma etching treatment time is shown in Table 1 below.
An epoxy adhesive was applied to the piezoelectric film that had been subjected to the plasma etching treatment, and a 30 μm thick copper foil having the same shape (5 mm × 5 mm square shape) was bonded. After that, a glass epoxy plate having a thickness of 1.5 mm and a size of 5 mm × 5 mm was adhered to both surfaces with an epoxy adhesive. This film-shaped piezoelectric body was bonded onto an aluminum block having a weight of 1 kg, and a brass load body having a weight of 5 g was bonded to the other surface with an epoxy adhesive and subjected to an impact resistance test. In the impact resistance test, the aluminum block to which the film-shaped piezoelectric material was fixed was dropped on a concrete block from a height of 1 m in a direction perpendicular to the detection axis of the acceleration sensor, and evaluated by the number of times until it was destroyed. As a comparative example, a sample prepared by the same method except that plasma etching was not performed was subjected to the same test. The results are shown in Table 1.

[0014]

[Table 1]

As can be seen from Table 1, the impact resistance of the piezoelectric film of the present example, which was subjected to the plasma etching treatment, was significantly improved. Further, it has been found that the decrease in piezoelectricity due to the plasma etching treatment is extremely slight, and that there is no problem in using the acceleration sensor.

[0016]

As described above, according to the present invention, when the film-shaped piezoelectric body of the piezoelectric acceleration sensor is manufactured, the piezoelectric film is subjected to the plasma etching treatment and the electrodes are attached thereto. The strength is greatly increased and the impact resistance is dramatically improved. In particular, since it uses a plasma etching process, it can be continuously manufactured in-line during manufacturing, mass production is easy, and since it is a dry process, post-processing such as chemical treatment (for example, rinse) Is unnecessary and the production efficiency is extremely high. Further, in the plasma etching process, the piezoelectric film is not deteriorated in piezoelectricity.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example of a piezoelectric acceleration sensor device.

FIG. 2 is an enlarged side sectional view of a main part of a piezoelectric acceleration sensor.

[Explanation of symbols]

2 ... Piezoelectric acceleration sensor, 3 ... Circuit board (pedestal), 7 ...
Piezoelectric film, 8 ... Metal thin plate (electrode), 9 ... Membrane piezoelectric material, 10 ... Support plate, 11 ... Sensing part, 12 ... Load body, 13
... Adhesive layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Imai 1-5-1 Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] 1. A pedestal rigidly attached to an object to be measured,
The pedestal has a sensing unit fixed to a measurement surface perpendicular to the sensing axis, and a load body made of a rigid body fixed to the sensing unit and acting as an inertial mass unit. The sensing unit is a piezoelectric film. It is composed of a film-shaped piezoelectric body in which electrodes are bonded and integrated on both surfaces, and two supporting plates made of plate-shaped rigid bodies fixed to both surfaces of the film-shaped piezoelectric body, and the planar shape of the film-shaped piezoelectric body is the above-mentioned. It is point-symmetrical with the sensing axis being the center of symmetry in a plane parallel to the measurement plane, and the load body is point-symmetrical with the planar shape of the surface in contact with the sensing section being the center of symmetry of the sensing axis, and In a method of manufacturing a piezoelectric acceleration sensor, which is line-symmetrical with respect to all cross-sections when it is sectioned in a myriad of planes passing through a sensing axis and perpendicular to the measurement surface, the film-shaped piezoelectric body is manufactured. At the time of plasma etching on both sides of the piezoelectric film. Method for manufacturing a piezoelectric type acceleration sensor, which comprises bonding and integrating the electrode after subjected to a treatment.