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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric buzzer and a conductive paint for forming an electrode thereof. [Prior Art] In a
piezoelectric buzzer, as shown in FIG. 1, electrodes 2 are formed on both sides of a piezoelectric
vibrator 1 and lead wires 4 are connected to the electrodes 2 directly or through a metal elastic
body 3. It is a thing. 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. [Problems to be Solved by the Invention] The piezoelectric
vibrator 1 of the piezoelectric buzzer is desired to be as thin as possible from the viewpoint of
vibration characteristics. However, if it is made thinner, in the conventional manufacturing
method such as drying and baking, silver migration may occur in the electrode 2 when a DC
voltage is applied in a wet atmosphere after the baking (about 800 ° C.), and piezoelectric
vibration There is a problem that the thickness of the child 1 can not be reduced. As a method of
achieving the above-mentioned thin film formation, there is known a method of heat curing a
coating of a conductive paste consisting of metallic silver powder and a thermosetting resin, but
in this case, the conductivity is lowered and it is formed on the insulating substrate. There is a
problem that the adhesion of the coating is poor. In addition, the capacity (resonance
characteristic) of the piezoelectric vibrator according to this method is lower than in the case of
the above-described drying / baking method, and there is also a problem that a sufficient sound
pressure can not be obtained. Therefore, the object of the present invention is to solve the
problems of the above-mentioned conventional silver paste, (1) having good conductivity, (2)
screen printing, intaglio printing, being a good item, (2) coating on insulating substrate Good
adhesion, ■ can form fine line circuits, ■ is excellent in solderability and strength on soldered
films, ■ can maintain the conductivity of solder-coated conductive circuits for a long time, ■
electrode capacity To provide a gold paste that can be improved. [Means for Solving the
Problems] As means for solving the above problems, in the present invention, a total of 100 of
85 to 96% by weight of metal gold powder A, 815 to 4% by weight of resol type phenolic resin,
and both A and B 0.1 parts by weight to 8 parts by weight of saturated fatty acid or unsaturated
fatty acid or metal salt thereof and required parts by weight of graphite with respect to parts by
weight, and said resol type phenol resin B is a 2-1 substituted compound which it has , 2.4-2
substituted, 2.4.6-3 substituted, methylol group, dimethylene ether, and infrared transmittance of
phenyl group by infrared spectroscopy j! , M, n, a, b, c, and a paste having a relationship of (i) 0,8 to 1.2 (d) -1,2 to 1.5 between the respective transmittances The coating material for forming
a piezoelectric buzzer electrode is adopted.
The weight part of graphite mixed in the gold paste and the particle size may be determined
appropriately by experiments etc. For example, 0.5 to 20 parts by weight, preferably 100 parts
by weight in total of A and B of the paste. The particle size is, for example, 0.1 to 10 fm,
preferably 0.1 n to 1 μ. Moreover, the whole powder grain of the said gold paste can be made
into 0.1-20 f1 m, Preferably it is set to l, n or less. Then, electrodes made of the paste are formed
on both sides of the piezoelectric vibrator, and a piezoelectric buzzer formed by connecting a
lead wire directly or via an elastic body to this electrode is configured. [Function] In the gold
paste according to the present invention configured as described above, when the compounding
amount of the metal gold powder is less than 85% by weight, the solderability deteriorates, and
conversely, when it exceeds 96% by weight, the metal gold powder is sufficiently It is not bound,
the resulting electrode is also poor, the desired soldering strength can not be obtained, the
conductivity is lowered and the screen printability is also deteriorated. Preferably, it is 88% by
weight or more, more preferably 90 to 93% by weight in the composition with the resin. With
respect to the resol type phenol resin to be used, its stoichiometry, the amount of 2-1
substitution is λ, the amount of 2.4-2 substitution is μ, the amount of 2.4.6-3 substitution is ν,
the amount of methylol group is α When the amount of dimethylene ether is β and the amount
of phenyl groups is γ, it means that □ n 小 さ い of the above constitution is smaller. That is, it
means that ν is larger in the 2.4.6-3 substitution amount than the 2-1 substitution amount λ
and the 2.4-2 substitution amount μ. It becomes a a α α. That is, it means that the amount of
methylol group α is larger than the amount of dimethylene ether β and the amount of phenyl
group γ. In general, when the 2.4.6-3 substitution amount ν is increased, the crosslink density
of the resol-type phenolic resin is thick and the n-n conductivity is improved. However,
conversely, the electrode tends to be hard and brittle, and the physical properties deteriorate.
When the value of 2 is small, the solderability of the electrode is poor, and when-is large, the
conductivity of the electrode is poor. α Therefore, as a resol-type phenolic resin which makes
the hardness of the obtained electrode appropriate and combines good conductivity and
solderability, n n a 1 shown in the above-mentioned constitution is set to 1.2 to 1.5. Is suitable.
When the amount of the resol-type phenolic resin is less than 4% by weight, the metal gold
powder is not sufficiently bound, the obtained electrode becomes too stiff, the conductivity is
lowered and the screen printability is deteriorated.
On the contrary, when it exceeds 15%, solderability is not preferable. With saturated fatty acids
or unsaturated fatty acids or metal salts thereof, in the case of saturated fatty acids, C16-C20
palmitic acid, stearic acid, arachic acid and the like, in unsaturated fatty acids, such as C16-18
carbon seamarins Acids, oleic acid, rylic acid and the like, and in the case of their metal salts,
salts with metals such as potassium, copper, aluminum, sodium, zinc and the like. The use of
these dispersants is preferable because it promotes the fine dispersion of the metal gold powder
in the resin and forms an electrode with good conductivity in the combination of the metal gold
powder and the resol-type phenolic resin. The compounding amount of the saturated fatty acid
or the unsaturated fatty acid or the metal salt thereof is used in the range of 0.1 to 8 parts by
weight, preferably 1 to 3 with respect to 100 parts by weight in total of the metal gold powder
and the resol type phenolic resin. It is a weight part. When the compounding amount of the
dispersant is less than 0.1 parts by weight, the fine dispersibility of the metal gold powder can
not be expected, and conversely, when it exceeds 8 parts by weight, the conductivity of the
electrode is lowered to make the electrode and the piezoelectric vibrator It is not preferable
because it causes a decrease in adhesion with the In the gold paste according to the present
invention, a conventional organic solvent can be appropriately used in order to adjust the
viscosity. 0 For example, butyl carpitol, butyl carpitol acetate, butyl cellosolve, methyl isobutyl
ketone, toluene, xylene, etc. It is a known solvent. [Example] With the compounding ratio shown
in Table 1, in the example, gold powder diameter: 1μ, graphite particle size: 0.7μ weight ratio to
gold powder: 3% of 1%, 2.5%, 5% each for 20 minutes The gold paste was prepared by kneading
with a three-wheeled roll. As the resol type phenol resin, one having an infrared transmittance
ratio of n n a − = 1.31 was used. The gold paste of the embodiment adjusted as shown in FIG. 2
is applied to both surfaces of the suspected substrate of the piezoelectric vibrator 1 by screen
printing to form electrodes 2 as shown in FIG. 2, and the capacity of the electrode itself is
measured. did. 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. The conductivity, adhesion,
solderability, solderability and printability were examined and all were satisfactory. FIG. 4 shows
the degree of change in specific resistance due to the gold paste electrode in which the mixing
ratio of metal gold powder (diameter, 54) and graphite (diameter, 0.7 m) was changed. In this
case, metal gold powder: resin was 92: 8 (% by weight).
C. Effects of the Invention Since the present invention is configured as described above, it has a
capacity close to that of the conventional silver paste in a state where various performances such
as conductivity, screen printability, adhesion and solderability are well maintained. You can get it.
For this reason, since the sound pressure does not decrease and the baking is not required, the
productivity is improved, and the baking does not have the risk of migration in the subsequent
wet atmosphere. It can be planned.
Brief description of the drawings
Fig. 1 is a schematic view of an example of the piezoelectric buzzer according to the present
invention, Fig. 2 is a production explanatory view of the same side, Fig. 3 is a graph showing the
relation between the amount of addition of graphite and the capacity, Fig. FIG. 5 is a diagram
showing the relationship between resistances and FIG.
1 · · · Piezoelectric vibrator, 2 · · · · · · · · · · · · · · · · · · · · · metal elastic body, 4 · · · · · · lead wire.
Patent Assignee Tack Electric Wire Co., Ltd. Attorney Futaba Figure 2 Figure 3 Figure 4