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FIELD OF THE INVENTION The present invention relates to a piezoelectric buzzer. [Prior Art and
Problem] As shown in FIG. 1, in the piezoelectric buzzer, the electrodes 2 are formed on both
sides of the piezoelectric vibrator 1, and the lead wires 4 are directly connected to the electrodes
2 or through the metal elastic body 3. It is connected. Silver paste is conventionally used for the
electrodes 2 in this piezoelectric buzzer, and as shown in FIG. 5, the silver paste is applied to both
surfaces of the piezoelectric vibrator 1 by printing to form the electrodes 2, and thereafter,
Drying and baking are performed according to the flow shown in FIG. However, silver paste is
expensive, has a large proportion in cost, and has a problem that silver migration occurs when a
direct current voltage is applied in a wet atmosphere, and appropriate vibration characteristics
can not be obtained. Also, the piezoelectric vibrator 1 is desired to be as thin as possible in terms
of vibration characteristics, but if it is made thinner, there is a risk that silver migration may
occur in the electrode 2 at the time (about 800 ° C.) in the baking, and the piezoelectric vibrator
There is also a problem that it is impossible to reduce the thickness of the film. By the way, the
present inventors, in Japanese Patent Application No. 63-167229, Japanese Patent Application
No. 1-139572, etc., have an electric conductivity equivalent to that of a silver paste, such as
screen printing and intaglio printing are easy. Good adhesion of the coating on the insulating
substrate, ■ ability to form fine line circuits, ■ excellent solderability and strength with solder
on the coating, ■ conductivity of the conductive circuit of the solder coat over a long period of
time The copper paste which consists of the following structures which can be maintained was
proposed. Saturated fatty acid or unsaturated fatty acid or metal salt thereof 0.5 with respect to a
total of 100 parts by weight of 85 to 96% by weight of the metal w4 powder, 815 to 4% by
weight of resol type phenol resin, and both A and B And 8 parts by weight, and 1 to 5 1 parts of a
metal chelate forming material, and the resol-type phenol resin B is a 2-substituted one, a 2.4-2
substituted one, 2.4.6-3 which it has. Let l, m, n, a, b, c be infrared transmittances of a substituted
compound, methylol group, dimethylene ether, and phenyl group by infrared spectroscopy,
between each permeability! (I) l / n-0 to 8 to 1.2 (l) l / n = 0.8 to 1.2 (l) l / n-0 to 8 to 1.2 (d)-1 to
2 If a paste having a relation of 1.5 to 1.5 and a paste of twenty are used as the electrodes 2 of
the piezoelectric buzzer, the polymer can be bonded to the piezoelectric vibrator 1, and therefore
it is not necessary to bake like the silver paste, There is no fear of migration, and the thickness of
the piezoelectric vibrator 1 can be reduced.
However, the capacity (capacitance, resonance characteristics) of the copper paste to the
piezoelectric vibrator 1 is lower than that of the silver paste, and is about 60 when the silver
paste is 100. Therefore, sufficient sound pressure can not be obtained. Then, this invention
makes it a subject to improve the capacity ¦ capacitance with a piezoelectric vibrator in said
copper paste. [Means for Solving the Problems] In order to solve the above-mentioned problems,
in the present invention, first, the required weight parts of graphite are mixed into the abovementioned steel paste, thereby forming an electrode. The weight parts and the particle size of the
graphite may be appropriately determined by experiments and the like, for example, 0.5 to 20
parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of the
conventional copper paste. The particle diameter thereof is, for example, 0.1 to 10 μ, preferably
0.1 to 1 n. Moreover, the copper powder particle of the said copper paste can be 0.5-20 n,
Preferably it is set to 5- or less. The metallic copper powder A may have a dendritic shape, a bulk
density of 1.5 to 3.5 g / ce, and a ratio of the specific surface area to the hydrogen reduction loss
of 11,000 or more. For the copper paste, conventional organic solvents can be used
appropriately to adjust the viscosity. 0 For example, known solvents such as butyl carpitol, butyl
carpitol acetate, butyl cellosolve, methyl isobutyl ketone, toluene, xylene, etc. It is lathe removal.
[Example] With the compounding ratio shown in Table 1, three examples of copper powder
diameter: 5n, graphite particle diameter: 0.7μ, weight ratio to copper powder: 1%, 2.5%, 5% The
copper paste was prepared by kneading with a three-wheeled roll for 20 minutes each. As the
resol type phenol resin, one having an infrared transmittance ratio of n n a − = 1.31 was used.
As shown in FIG. 2, the copper paste of the embodiment adjusted in this way was applied to both
surfaces of the false substrate of the piezoelectric vibrator 1 by screen printing to form the
electrodes 2, and the cavity itself was measured. The results of Example 1 are shown in FIG. From
this result, it can be seen that the capacity increases as the content of graphite increases. When
the capacity of the silver paste is 100, it is about 90 in the example. The conductivity, adhesion,
solderability, solderability and printability were examined in the same manner as in Japanese
Patent Application No. 63-167229, etc., and all were satisfactory.
FIG. 4 shows the degree of change in specific resistance due to the copper paste electrode in
which the mixing ratio of metal copper powder (diameter, 5 Ina) and graphite (diameter, 0.7 μ)
is changed. In this case, metal copper powder in this case Resin: 92: 8 (% by weight). [Effects of
the Invention] The present invention is configured as described above, so that it is possible to
obtain a capacity close to that of silver paste. For this reason, the cost can be reduced without
lowering the sound pressure, and since baking is not required, the productivity is improved and
there is no risk of migration due to the baking. Thinning can be achieved.
Brief description of the drawings
1 is a schematic view of an embodiment of the piezoelectric buzzer according to the present
invention, FIG. 2 is a diagram for explaining the production of the embodiment, FIG. 3 is a graph
showing the relation between the amount of addition of graphite and the capacity, and FIG. FIG. 5
is a diagram showing the relationship between the content and the specific resistance, and FIG.
1 · · · Piezoelectric vibrator, 2 · · · · · · · · · · · · · · · · · · · · · metal elastic body, 4 · · · · · · lead wire.