JPS6193799A - Piezoelectric element - Google Patents

Abstract

PURPOSE:To prevent cracked and shaved electrode by constituting the titled element with a silver electrode formed with silver paste baked on both faces of a piezoelectric element main body and a nickel electrode formed with vapor- deposition of nickel on the silver electrode. CONSTITUTION:The silver electrodes 2a, 2b are formed to both faces of the piezoelectric element main body made of a ceramic plate with silver paste baking respectively and nickel is vapor-deposited on the electrodes 2a, 2b to form the nickel electrodes 3a, 3b. For example, the film thickness of the electrodes 2a, 2b is nearly 7mu and the film thickness of the electrodes 3a, 3b is nearly 0.03-0.mu, for example. Thus, since the electrodes 2a, 2b act like strengthening the lateral bonding force of the main body 1 being the ceramic plate and protecting it mechanically, the element is hardly cracked and the electrodes 3a, 3b being the vapor-deposition layer of nickel increase the hardness of the electrode surface so as to prevent the electrode surface from being shaped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric element used in a sound source vibrator of an alarm clock, and more particularly to the structure of its electrode portion.

[Conventional technology]

A piezoelectric element is used as a pressure-sensitive element because it generates an electromotive force when pressure is applied to it, but it also causes vibration when an alternating current voltage is applied to it, so it is also used as a vibrator.

As shown in FIG. 2, the structure of such a conventional piezoelectric element is generally such that silver (Ag) paste is applied to both sides of a piezoelectric element body 1 made of a ceramic plate made of sintered piezoelectric material such as barium titanate. Coating and baking, silver electrodes 2a, 2b
was forming.

These silver electrodes 2a and 2b have silver paste that penetrates between the sintered particles near the surface of the piezoelectric element body 1, and have a strong bonding force in the plane direction, so they reinforce the fragility of the piezoelectric element body 1 made of a ceramic plate. It also plays a role in making it less likely to break.

[Problem that the invention seeks to solve]

However, such a conventional piezoelectric element has a silver electrode 2
Since the hardness of the electrodes a and 2b is low, there is a problem in that when a contact terminal or the like comes into sliding contact with these electrodes, those parts are scraped.

For example, when using such a piezoelectric element as a 75 Tft direct-sounding alarm sound source vibrator for a waterproof alarm clock for divers, the piezoelectric element 10 is placed on the inner surface of the back cover 11 of the watch, as shown in FIG. It is attached using an adhesive 12, and the 7A lid 11 is screwed onto the body 13 (it is necessary to use a screw-in type in order to improve the reliability of waterproofing).

At this time, since the silver electrode 2a is not in sliding contact with the spring-shaped contact terminal 15 led out from the module 14, the piezoelectric element 1
0 will rotate together with the back cover 11. In addition, the third
In the figure, 16 is glass.

17 and 18 are sealing gaskets.

In this way, when the contact terminal 15 or the like comes into sliding contact with the silver electrode 2a or 2b of the piezoelectric element 10, the baked-on layer of the silver paste on the sliding contact portion will be scratched off, and the electrode will no longer be able to fully fulfill its role. It disappears.

In this case, the high frequency current is not uniformly passed from the module 14 to the piezoelectric element 10 through the contact terminals 15 and the back cover 11 over the entire surface of the piezoelectric element 10, and the alarm sound may not be generated or may be insufficient. There was a problem with becoming.

The object of the present invention is to solve these problems in conventional piezoelectric elements.

I [Means for solving the problems] 1' In order to solve the above problems, the piezoelectric element according to the present invention has a piezoelectric element main body 1 made of a ceramic plate (for example, a disk shape), as shown in FIG. On both sides.

Each silver mold is made by baking silver (Ag) paste.
2a and 2b, and further nickel CN1)
The nickel electrodes 3a and 5b are formed by vapor deposition (including the case of ion blating). Note that 1, for example, the film thickness of the silver type ti2a, 2b is about 7μ, and the nickel electrode 3a, ! The film thickness of 1b is about 0.03 to 0.4 μm.

[For production]

Baking of the silver paste (including adhesives, glass, etc.) is performed because the layers of silver electrodes 2a and 2b strengthen the lateral bonding force of the piezoelectric element body 1, which is a ceramic plate, and mechanically protect it. The nickel electrode 3a is made of a vapor-deposited layer of nickel and is hard to break because of the nickel electrode 3a.

3b increases the hardness of the electrode surface, making it difficult to scrape the electrode surface.

[Example J] If such a piezoelectric element is used as a vibrator for an alarm sound source of a waterproof alarm clock as shown in FIG. 3, a large pressing force ( For example, the layer of adhesive 12 interposed between the piezoelectric element 10 and the back cover 11 is made extremely thin to increase the degree of adhesion between the two, and the conductivity of high-frequency current is improved. And vibration propagation efficiency can be improved.

Furthermore, when screwing the back cover 11 with the piezoelectric element 10 pasted onto the body 13, the contact terminal 15 from the module 14 comes into sliding contact with the nickel electrode 3a of the piezoelectric element 10, but since the nickel electrode is hard, it does not get scratched and is stable. A conductive state can be maintained.

By the way, if the only countermeasure is to prevent scratching of the electrode surface, it is conceivable to use a piezoelectric element in which nickel is directly deposited on both sides of the piezoelectric element body 1 to form nickel electrodes. Although resistant to abrasion and abrasion, the nickel vapor-deposited layer has weak lateral bonding strength and is extremely thin, so it cannot increase the mechanical strength of the piezoelectric element.

Therefore, when applying pressure to the piezoelectric element and bonding it to the back cover, it tends to break, and the pressure must be lowered to 2 to 3 kg, which deteriorates the adhesion between the piezoelectric element and the back cover, making it difficult to obtain a sufficient alarm sound. I won't be able to do it.

Note that the piezoelectric element according to the present invention has a high mechanical strength and is resistant to abrasion and abrasion of the electrode surface.

Of course, it can be effectively used not only as a sound source for a waterproof alarm clock as described above, but also as various types of vibrators, pressure sensors, etc. ′ [Effects of the Invention] As explained above, the piezoelectric element according to the present invention has the following effects:
Baking of silver paste protects the piezoelectric element body made of a ceramic plate with a silver electrode layer and increases its mechanical strength, and increases the hardness of the electrode surface with a nickel vapor deposited layer of the nickel electrode. Even if strong pressure is applied when assembling it into a device such as, or a contact terminal or the like comes into sliding contact with the electrode surface, the electrode will not be cracked or scraped.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view showing the structure of a piezoelectric element according to the present invention. FIG. 2 is an enlarged sectional view showing the configuration of a conventional piezoelectric element. FIG. 3 is a schematic cross-sectional view of a waterproof alarm B+ in which a piezoelectric element is assembled as a vibrator for a back cover direct-sounding alarm sound source. 1... Piezoelectric element body 2a+ 2b... Silver electrodes 5a, 3b... Nickel electrodes 10... Piezoelectric element 11... Back cover 12... Adhesive 13...
・Body 14...Module 15
...Contact terminal 16...Glass Figure 1

Claims (1)

[Claims] 1. It consists of a piezoelectric element body made of a ceramic plate, silver electrodes formed by baking silver paste on both sides of the piezoelectric element body, and nickel electrodes formed by vapor-depositing nickel on each of the silver electrodes. piezoelectric element.