JPS6358000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method of manufacturing a piezoelectric sounding body by integrally joining a piezoelectric vibrator and a metal plate having a larger diameter.

Technical Background of the Invention Bimorph vibrators, which are made by bonding a piezoelectric ceramic vibrator and a metal plate, are widely used as piezoelectric sounding bodies in consumer and industrial electronics equipment.

Conventionally, this type of piezoelectric sounding body has been manufactured by applying silver paste to both sides of a piezoelectric ceramic body 1 having a thin disk (or square plate) shape, as shown in FIG. Electrode 2 is provided by baking method, Ni electroless plating method or sputtering method, and after polarization treatment, it is made with organic adhesive to have a diameter larger than piezoelectric ceramic body 1 and approximately the same as piezoelectric ceramic body 1. It is constructed by joining to a metal plate 3 having the same thickness. By applying an AC signal to the lead wires 4 and 4' drawn out from the electrode 2 and the metal plate 3,
It is a sounding body.

On the other hand, recently there has been a strong demand for smaller size and lower frequency piezoelectric sounding elements. In order to meet this demand, there are several problems that need to be solved.

Problems with the Background Art First, lowering the frequency of a piezoelectric sounding body can be achieved in principle by increasing the diameter, but there is a limit to this due to the trend toward miniaturization of peripheral equipment.

Next, in order to lower the frequency of the piezoelectric sounding body without increasing the diameter, it becomes necessary to reduce the thickness of the piezoelectric vibrator and the metal plate. However, when these thin plates are bonded together using conventional adhesive methods, mechanical pressure is applied to the piezoelectric vibrator to bond them, which tends to cause scratches, etc. In extreme cases, the piezoelectric vibrator may crack, crack, or chip. This results in a decrease in yield. In addition, the adhesive does not penetrate sufficiently to the bonding surface between the metal plate and the piezoelectric vibrator, creating an air layer that deteriorates the acoustic properties of the sounding body.Furthermore, depending on the amount of adhesive, the adhesive may protrude after bonding. , the acoustic characteristics may similarly deteriorate. Furthermore, it is necessary to make the piezoelectric vibrator and the metal plate concentric when bonding, and alignment and the like for this purpose is troublesome.

OBJECTS OF THE INVENTION The present invention provides a method for manufacturing a piezoelectric sounding body, which makes it possible to reduce the size and frequency of the piezoelectric sounding body with high reliability and without deterioration of acoustic characteristics.

Summary of the Invention In the present invention, a metal layer formed by electroforming is used as a metal plate to be integrated with a piezoelectric vibrator. In this case, in order to attach a metal layer with a diameter larger than the diameter of the piezoelectric vibrator by electroforming, an aluminum foil whose surface is substituted with zinc is used as an auxiliary means. The aluminum foil has the same outer diameter as the metal to be obtained, and has a hole in the center that is equal to the hole diameter of the piezoelectric vibrator. Electroforming is performed with the piezoelectric vibrator fitted into the hole in the aluminum foil, and a metal layer of a predetermined thickness is continuously applied from the electrode surface of the piezoelectric vibrator to the surface of the aluminum foil. By etching away the aluminum foil, an integral structure of the piezoelectric vibrator and a metal layer having a larger diameter is obtained.

Effects of the Invention According to the present invention, unlike a method using an adhesive, no mechanical pressure is applied to the piezoelectric vibrator, and no strain components remain, so the piezoelectric vibrator is free from scratches, cracks, etc. There is no risk of this happening. Further, since the adhesion between the piezoelectric vibrator and the metal layer is good, and the thickness of the metal layer can be easily controlled, a piezoelectric sounding body with excellent acoustic characteristics can be manufactured with a high yield.

Embodiments of the Invention An embodiment of the invention will be described with reference to FIGS. 2a to 2d. First, as shown in a, electrodes 6 are provided on both sides of the piezoelectric ceramic body 5 by electroless Ni plating or silver paste baking. The electrode 6 on one side extends entirely or partially to the outer periphery of the piezoelectric ceramic body 5 to form an electrode 6'.

On the other hand, as shown in b, an aluminum foil 7 is prepared which has a through hole 8 having the same diameter as the outer diameter of the piezoelectric ceramic body 5 and has an outer diameter of a metal plate required as a piezoelectric sounding body. The surface of this aluminum foil 7 is subjected to a pretreatment similar to ordinary plating, and then a zinc substitution layer is provided in a zinc substitution bath.

The through hole 8 having the same diameter as the piezoelectric ceramic body 5 can be easily formed using a press mold, for example. Then, a piezoelectric vibrator having electrodes a is fitted onto this aluminum foil 7, and as shown in c, this is fixed to a jig 9 having a recess 10 into which the fitted part is fitted. Align the surface with the surface of the electrode 6 of the piezoelectric vibrator.

After fixing it to the jig like this, the aluminum foil 7
A necessary metal layer 11 is formed by electroforming with the electrodes 6 of the piezoelectric vibrator and the piezoelectric vibrator at the same potential.

By using a Ni sulfamate solution, which is generally used for forming thick films, as the electroforming solution, it is possible to form the metal layer 11 with a thickness of 50 to 180 μm in a short time.

Further, by providing a zinc substitution layer on the aluminum foil 7, electroforming can be easily performed. After applying the metal layer 11 of the required thickness, it is taken out from the electroforming bath, washed with water, and then removed from the jig 9. Even if the aluminum foil 7 is added, its thickness is 10 to 20 μm, so it does not affect the electrical characteristics. However, when considering the moisture resistance characteristics when this diaphragm (integrated structure of piezoelectric vibrator and metal plate) is held in a metal case, there are reliability issues such as corrosion of aluminum due to battery action when the holding case is made of dissimilar metals. problem occurs.
Therefore, a portion of the aluminum foil 7 is removed by etching with about 10% caustic soda to obtain a structure in which the piezoelectric vibrator and the metal layer are integrated as shown in d.

The piezoelectric sounding body produced by the above method is
Since the piezoelectric vibrator and the metal plate are not bonded using adhesive, the adhesion is good, and because the electroforming method is used, there is no air gap. Furthermore, since the sulfamic acid bath itself is an electroforming liquid that does not easily cause stress and strain, the formed metal layer does not contain any strain components, so there is little concern that the piezoelectric vibrator will be scratched, chipped, or cracked.

Furthermore, since zinc-substituted aluminum foil was interposed as an auxiliary means, it is possible to easily form a metal layer larger in diameter than the piezoelectric vibrator element. The thickness of this metal layer can also be kept constant by controlling the temperature, current density, and time of the electroforming solution, and variations in acoustic characteristics can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional piezoelectric ceramic bimorph sounding body, and FIGS. 2a to 2d are diagrams for explaining the manufacturing process of a piezoelectric sounding body according to an embodiment of the present invention. 5... Piezoelectric ceramic body, 6... Electrode, 7... Surface zinc-substituted aluminum foil, 8... Hole, 9... Electroforming jig, 10... Recess, 11... Metal layer.

Claims (1)

[Claims] 1. A method for manufacturing a piezoelectric sounding body by integrally joining a piezoelectric vibrator and a metal plate having a larger diameter, the method comprising: a predetermined method of manufacturing a piezoelectric sounding body by integrally joining a piezoelectric vibrator and a metal plate having a larger diameter; A piezoelectric vibrator is fitted into a hole in a shaped aluminum foil, and a metal layer is formed by electroforming with the electrodes of the piezoelectric vibrator and the aluminum foil at the same potential, and then the aluminum foil is removed by etching. , a method for manufacturing a piezoelectric sounding body characterized by obtaining an integral structure of a piezoelectric vibrator and a metal layer.