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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] As shown
in the first time, a piezoelectric buzzer has an electrode 2 formed on the screen of a piezoelectric
vibrator 1 and a lead wA 4 connected to this electrode 2 directly or through a metal elastic body
3 It is. Silver paste is conventionally used as the electrode 2 in the second piezoelectric buzzer,
and as shown in FIG. 8, the silver paste is pressed by printing! The electrode 2 is formed by
coating on the screen of the vibrator 1, and thereafter, drying, baking, and the like are performed
by the flow shown in the same drawing, and a piezoelectric buzzer is manufactured. [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 direct gray
voltage may be generated in the electrode 2 after the baking (about 800 ° C.) and a DC voltage
is applied in a wet atmosphere, 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 thinning, gold l!
There is known a method of heating and curing a coating of a conductive paste consisting of
silver powder and a thermosetting resin, but in this case the conductivity is lowered and the
adhesion of the coating on the insulating substrate is poor. was there. In addition, the capacity
(capacitance, resonance characteristics) of the piezoelectric vibrator according to this method is
lower than in the case of the method using the drying and baking, and thus there is a problem
that 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) easy screen printing and intaglio printing, and (2) adhesion of a coating on
insulating substrate Good in properties, can form fine line circuits, has excellent solderability and
strength on soldered films, can maintain the conductivity of conductive circuits in solder coats
for a long time, improves electrode capacity It is to provide a gold paste that can be [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 It consists of 0.1 to 8 parts by weight of saturated fatty acid or
unsaturated fatty acid or metal salt thereof and part by weight of carbon black, and said resol
type phenol resin B is 2-substituted by 1 part by weight. , M-, n-, a-, b-, c-, infra-red transmittance
by infrared spectroscopy of: body, 2.4-2 substitution, 2.4.6-3 substitution, methylol group,
dimethylene ether, phenyl group When it is assumed that each transmittance is between (i) -0,
am 1.2 (ro)-0, 8 to 1.2 (ha)-0, 8 to 1.2 (ni)-1 Piezoelectric buzzer electricity consisting of pastes
that satisfy the relationship Than it was adopted for forming paint.
The weight part of carbon black mixed in the gold paste and the particle size may be
appropriately determined by experiments etc. For example, 0.5 to 20 parts by weight, preferably
100 parts by weight in total of the A and B. The particle size thereof is, for example, 15 (10- "am)
nm to 1 n-, preferably 15 nm to 50 n-. Moreover, the whole powder particle of the said gold
paste can be set as 0.1-20 # 11, and it can be set as an electrode, Preferably it is set as 1- or less.
A carbon blank may be further added as a gold powder particle size in this range. Then, on the
screen of the piezoelectric vibrator, an electrode made of the paste having the above-described
configuration is formed, 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 metal gold
powder is less than 851% by mass, 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 group is γ, it means that
-n 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.
Electricality is improved. However, conversely, the electrode tends to be hard and brittle, and the
physical properties deteriorate. Also, when β is small, the solderability of the electrode is poor,
and if-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, it becomes α α shown in the above-mentioned constitution. 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 T. In general, when the 2.4.6-3 substitution amount 大 き く
is increased, it is suitable that the crosslink density of the resol-type phenol resin is thick and nna
is 1.2 to 1.5. 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 is also brittle, the
conductivity is lowered and the screen printability is deteriorated.
On the other hand, when it exceeds 15% by weight, 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, conventional organic solvents can be used appropriately to adjust the viscosity. For
example, known solvents such as butyl carpitol, butyl carpitol acetate, butyl cellosolve, methyl
isobutyl ketone, toluene, xylene and the like. [Examples] With the compounding ratio shown in
Table 1, Example 1 has gold powder particle size: 0.8μ, 1.0μ, 1.3n, 3.0μ, 5. The gold paste was
prepared by kneading 7 kinds of oμ, 15fm and 20m with a three-wheeled roll for 20 minutes. In
Example 2, the gold powder diameter = 5.0 μ, and the carbon black particle diameter: 40 nm. At
25 nm and 16 nm, the weight ratio to gold powder: 1%, 2.5%, 4%, 5%, 6%, 7.5%, 9%, and select
one as appropriate. The gold paste was prepared by kneading. As the resol type phenol resin, one
having an infrared transmittance ratio of-= 1.31 was used. Table (Weight ratio) As shown in FIG.
2, the gold paste of Example 1.2 adjusted in this manner is applied to the screen of the substrate
of the piezoelectric vibrator 1 by screen printing to form the electrodes 2 as shown in FIG. And
measured their own cabality. The results of Example 1 are shown in FIG. 3, and the results of
Example 2 are shown in FIG. From the results, it is understood that the smaller the diameter of
the metal powder, the larger the capacity, and the larger the carbon black content (addition
amount), the larger the capacity.
When the conductivity, adhesion, solderability, solderability and printability were examined,
sufficient conductivity could not be obtained with a gold powder diameter of 0.5 n or less, and
with 1 ° On or less. Although the solderability worsened, it was satisfactory in other respects. As
described above, when the particle size of the metal gold powder is reduced, problems of the
conductivity and the solderability occur on the other hand, while the capacity is improved. It is
considered that this is because the smaller the grain size on the surface of the false board (plate
voltage oscillator 1), the more the welding progresses and the bonding degree is improved. For
this reason, a plurality of pastes are applied so that the electrodes 2 are formed in a plurality of
layers, and the piezoelectric vibrator 1 side has small diameter grains, and leads f! It turns out
that it is good to make 4 side the large diameter grain. In addition, metal gold powder diameter:
5. On, in the carbon black diameter: 37 nm, the compounding ratio (weight ratio) of metal gold
(Ag) to resole type phenol resin (Re) 86: 14.8 B: 12.90: 10.92: 08.93: 07 A gold paste of .94: 06
was formed, whereby the electrode 2 was formed in the same manner as described above, the
carbon black loading was changed, and the relationship between the loading and the coverage is
shown in FIG. In FIG. 6, the coverage of metal gold powder (particle size: 5 n) (weight ratio with
resin, for example, weight ratio with resin, for example, 88: gold powder: resin-88: 12) is covered
by the gold paste electrode and its charge Show the relationship with FIG. 7 shows the degree of
change in specific resistance of the gold paste electrode in which the blending ratio of metal gold
powder (diameter 5 um) and carbon blank (diameter, 40 nm, 25 nm, 16 nm) was changed. In this
case, metal gold powder: resin was 92: 8 (% by weight). [Effects of the Invention] Since the
present invention is configured as described above, a capacity electrode close to that of a
conventional silver paste in a state where various performances such as conductivity, screen
printability, adhesion and solderability are well maintained. It can be done. For this reason, the
reduction of the sound pressure is not caused, the productivity is improved because the baking is
not required, and there is no possibility of the migration under the wet atmosphere of the baking,
so that the thinning of the piezoelectric vibrator can be achieved.
Brief description of the drawings
1 is a schematic diagram 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 relation diagram of
metal gold powder diameter and capacity, and FIG. Figure 5 shows the relationship between
carbon blank addition and capacity Figure 6 shows the relationship between metal gold powder
loading and capacity Figure 7 shows the relationship between carbon black content and specific
resistance FIG. 8 is a production explanatory view of a conventional example.
1 · · · Piezoelectric vibrator, 2 · · · · · · · · · · · · · · · · · · · · · metal elastic body, 4 · · · · · · lead wire.
Patent Assignee Tack Electric Wire Co., Ltd. Attorney Attorney Futaba Fig. 2 Filled amount of
gold powder (Weight it 1%) Fig. 5 Carbon black addition amount (% by weight) Fig. 7-o-160 m-o-
25 nm Fig. Figure