JPH0477571A - Coating for forming piezoelectric buzzer and its electrode - Google Patents

Abstract

PURPOSE:To obtain the subject coating, containing metallic silver powder, a specific resol type phenolic resin, a saturated or an unsaturated fatty acid (metallic salt thereof) and carbon black, and excellent in adhesion of films onto insulating substrates, solderability, soldering strength, etc. CONSTITUTION:A coating which is a paste for forming piezoelectric buzzer electrodes is obtained by blending (A) 100pts.wt. mixture composed of (i) 85-96wt.% metallic silver powder and (ii) 15-4wt.% resol type phenolic resin establishing the relations between respective transmittances of (l/n) = 0.8-1.2, (m/n) = 0.8-1.2, (b/a) = 0.8-1.2 and (c/a) = 1.2-15 when the infrared transmittances of a 2-monosubstitution product, a 2,4-disubstitution product, a 2,4,6-trisubstitution product, methylol group, dimethylene ether and phenyl group measured by infrared spectroscopy are (l), (m), (n), (a), (b) and (c) with (B) 0.1-8pts.wt. (un)saturated fatty acid (metallic salt thereof) and (C) carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric buzzer and a conductive paint for forming its electrodes.

[Conventional technology]

As shown in FIG. 1, the piezoelectric buzzer includes an electrode 2 formed on the surface of a piezoelectric vibrator 1, and a lead wire 4 connected to the electrode 2 either directly or via a metal elastic body 3.

Conventionally, silver paste has been used for the electrodes 2 in this piezoelectric buzzer, and as shown in FIG. 8, the silver paste is applied to the surface of the piezoelectric vibrator 1 by printing.
is formed, and thereafter, drying, baking, etc. are performed according to the flow shown in the figure, 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 in terms of vibration characteristics. However, when thinning the film, conventional manufacturing methods such as drying and baking require the baking (approximately 8
If a DC voltage is applied in a humid atmosphere after 00°C, silver migration may occur in the electrodes 2, and there is a problem that the piezoelectric vibrator 1 cannot be made thinner.

A known method for thinning the film is heating and curing a conductive paste coating made of metal silver powder and a thermosetting resin, but in this case, the conductivity decreases and the coating on the insulating substrate is reduced. There was a problem that the adhesion of the coating film was poor.

Moreover, the capacity (Cap) of the piezoelectric vibrator by this method is
acity (resonance characteristics) is lower than that in the drying/baking method, and therefore there is also the problem that sufficient sound pressure cannot be obtained.

So this invention's U! The objective is to solve the above-mentioned problems of conventional silver pastes. ■ Has good conductivity. ■ Can be easily screen printed or intaglio printed. ■ Has good adhesion of the coating film to the insulating substrate. , ■ Thin wire circuits can be formed, ■
To provide a silver paste that has excellent solderability and soldering strength on a coating film, (1) maintains the conductivity of a conductive circuit of a solder coat over a long period of time, and (2) improves electrode capacity.

[Means for Solving the Problems] As a means for solving the above problems, in this invention, 85 to 96% by weight of metal silver powder A, 15 to 4% by weight of resol type phenolic resin B, and a total of 100% of both A and B.
The resol type phenolic resin B is composed of 0.1 to 8 parts by weight of saturated fatty acids or unsaturated fatty acids or metal salts thereof, and the required parts by weight of carbon black per 1 part of M1j, and the resol type phenolic resin B is Let the infrared transmittance of the 2.4-disubstituted product, 2.4.63-substituted product, methylol group, dimethylene ether, and phenyl group by infrared spectroscopy be l, m, H, a, b, and c. When, between each transmittance (
B) l/n = 0.8 to 1.2 (b) l/n = 0.8 to 1.2 (c) l/n = 0.8 to 1.2 (2') --= 1. A piezoelectric buzzer electrode forming paint made of a paste satisfying the relationship of 2 to 1.5 was adopted.

Part by weight of carbon blank mixed in the above silver paste,
The particle size may be appropriately determined through experiments, etc., but for example, the particle size is 0.5 to 20 parts per 100 parts by weight of A and B in total.
part by weight, preferably 1 to 10 parts by weight, and the particle size is, for example, 15 (10-'μ) nm-lnm, preferably 15
n- to 50n-.

Further, the electrode may be formed by using silver powder particles of 0.1 to 20 in the silver paste, preferably 1 to 20.
The following shall apply. Carbon black may be further added to the silver powder particle size within this range.

Then, an electrode made of the paste having the above-mentioned structure was formed on the surface of the piezoelectric vibrator, and a lead wire was connected to the electrode either directly or through an elastic body, thereby constructing a piezoelectric buzzer.

[Function] In the silver paste according to the present invention configured as described above, if the amount of metal silver powder is less than 85% by weight, the solderability will be poor, and if it exceeds 96% by weight, the amount of metal silver powder will be insufficient. Without being bound, the resulting electrode becomes brittle, the desired soldering strength cannot be obtained, the conductivity decreases, and screen printability also deteriorates.

Preferably, the content of the resin is 88% by weight or more, more preferably 90 to 93% by weight.

Regarding the resol type phenolic resin used, its chemical amount, the amount of 2-1 substitution product is λ, the amount of 2.4-2 substitution product is μ, 2
．． 4.6-3 If the amount of substituents is ν, the amount of methylol groups is α, the amount of dimethylene ether is β, and the amount of phenyl groups is T, then -β of the above structure is small. That is, the amount of 2-1 substitution product λ
, 2.4-2 substituent amount μ, means that 2.4.6-3 substituent amount ν is larger.

Also, If the value is small, the solderability of the electrode will be poor. If - is large, the conductivity of the electrode will be poor.

α Therefore, as a resol type phenolic resin that makes the hardness of the obtained electrode appropriate and has both good conductivity and solderability, α α shown in the above structure is used. That is, it means that the amount α of methylol groups is larger than the amount β of dimethylene ether and the amount T of phenyl groups.

Generally, as the amount ν of the 2.4.6-3 substituent increases, the crosslinking density of the resol type phenol resin becomes thicker and the electric property becomes better. However, on the contrary, the electrodes tend to become hard and brittle, resulting in poor physical properties.

n a It is suitable that □ is 1.2 to 1.5.

If the amount of the resol type phenolic resin is less than 4% by weight, the metal silver powder will not be sufficiently bound, and the resulting electrode will become brittle, resulting in decreased conductivity and poor screen printability. On the other hand, if it exceeds 15% by weight, the solderability will not be favorable.

Saturated fatty acids, unsaturated fatty acids, or metal salts thereof include saturated fatty acids such as palmitic acid, stearic acid, and arachidic acid having 16 to 20 carbon atoms, and unsaturated fatty acids such as seamarin having 16 to 18 carbon atoms. acids, oleic acid, lyric acid, etc., and their metal salts include salts with metals such as potassium, copper, aluminum, sodium, and zinc.

The use of these dispersants is preferable in blending the metal silver powder with the resol-type phenolic resin because it promotes fine dispersion of the metal silver powder into the resin and forms an electrode with good conductivity.

The blending amount of saturated fatty acids, unsaturated fatty acids, or metal salts thereof is in the range of 0.1 to 8 parts by weight, preferably 1 to 3 parts by weight, based on 100 parts by weight of the total amount of metal silver powder and resol type phenolic resin. Parts by weight.

If the amount of the dispersant is less than 0.1 part by weight, fine dispersion of the metal silver powder cannot be expected, and if it exceeds 8 parts by weight, the conductivity of the electrode will be reduced and the electrode and piezoelectric vibration This is undesirable because it leads to a decrease in adhesion with the child.

In order to adjust the thickness of the silver paste according to the present invention,
Common organic solvents can be used as appropriate. For example,
Butyl carpitol, butyl carpitol acetate,
These are known solvents such as butyl cellosolve, methyl isobutyl ketone, toluene, and xylene.

〔Example〕

With the blending ratio shown in Table 1, Example 1 had silver powder particle size:
0.8m, l, 04.1, 3μ, 3.0μ, 5.0a
y.

Silver pastes were prepared by kneading seven types of silver pastes of 15μ and 20U for 20 minutes using a tricycle roll. In Example 2, silver powder diameter: 5. On, carbon black particle size: 40 μm, 25
μm, 16 μm, weight ratio to silver powder: 1%, 2.
A silver paste was prepared by selecting an appropriate amount from among 5%, 4%, 5%, 6%, 7.5%, and 9% and kneading each with a triaxial roll for 20 minutes. The resol type phenol resin used had an infrared transmittance ratio of -=1.31.

Table (weight ratio) As shown in FIG. 2, the silver paste of Example 1.2 prepared in this way was printed on a piezoelectric vibrator
The electrode 2 was formed by coating the surface of a pseudo-substrate, and the cavity of the electrode 2 was measured.

The results of Example 1 are shown in Figure 3, and the results of Example 2 are shown in Figure 4.
As shown in the figure.

From this result, it can be seen that the smaller the metal silver powder diameter, the larger the cavity, and the larger the carbon black content (added amount), the larger the capacity.

In addition, when inspecting conductivity, adhesion, solderability, soldering strength, and printability, it was found that silver powder with a diameter of 20.5 or less had sufficient S.
t property cannot be obtained, and the same l.

Although the solderability deteriorated below 0-, the results were satisfactory in other respects.

As described above, as the particle size of metallic silver powder becomes smaller, the capacitance improves, but problems arise in conductivity and solderability. This is thought to be because the smaller the particle size, the easier it is to enter the surface of the pseudo substrate (plate voltage vibrator 1), improving the degree of bonding. For this reason, the electrode 2 is made up of multiple layers by applying multiple pastes, and the piezoelectric vibrator 1 side is made up of small-diameter particles and the lead g.
It can be seen that it is better to use large-diameter grains on the 4th side.

Also, metal silver powder diameter = 5. Ol! m, carbon blank diameter: 37 nm, blending ratio (weight ratio) of metallic silver (Ag) and resol type phenolic resin (Re) 86
: 14.88 : 12.90 : 10.92 :
08.93: 07.94:06 to form a silver paste, thereby forming the electrode 2 in the same manner as in the above case,
The filling amount of carbon black was varied and the relationship between the filling amount and the cavity is shown in FIG.

FIG. 6 shows the filling amount (weight ratio with resin) of metallic silver powder (particle size: 5p), for example, 88 in the figure is silver powder: #I4 fat-88:
12) shows the relationship between the cavity and the filling amount of silver paste electrodes with different values.

Figure 7 shows the degree of change in specific resistance caused by silver paste electrodes with varying blending ratios of metallic silver powder (diameter: 51!m) and carbon black (diameter: 40 nm, 25 nm, 16 nm). Metallic silver powder: resin is 92:8 (
weight%).

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to obtain a capacitance electrode close to that of conventional silver paste while maintaining good performance such as conductivity, screen printability, adhesion, and solderability. . For this reason, there is no reduction in sound pressure, and there is no need for baking, which improves manufacturing efficiency, and there is no risk of the baking being caused by migration of silane in a humid atmosphere, so it is possible to make the piezoelectric vibrator thinner. It is possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an example of a piezoelectric buzzer according to the present invention, Fig. 2 is an explanatory diagram of thinning manufacturing, Fig. 3 is a diagram of the relationship between metal silver powder diameter and capacity, and Fig. 4 is the amount of carbon black added. Figure 5 is a diagram showing the relationship between carbon black content and capacity, Figure 6 is a diagram showing the relationship between metal silver powder loading and capacity, and Figure 7 is a diagram showing the relationship between carbon black content and specific resistance. The related diagram, FIG. 8, is a manufacturing explanatory diagram of a conventional example. 1... Piezoelectric vibrator, 2... Electrode, 3
...Metal elastic body, 4...Lead wire. Patent Applicant Tac Electric Cable Co., Ltd. Agent Aya Kamata Figure 2 Silver powder filling amount (weight @ %) Figure 5 Ag/Re 6J1101214 Carbon black addition ff1 (weight %) Figure 7 +o-113nm -o-25nm 3rd Figure 4 Figure 8

Claims (3)

[Claims] (1) 85 to 96% by weight of metal silver powder A, 15 to 4% by weight of resol type phenolic resin B, and 0.00% of saturated fatty acid or unsaturated fatty acid or a metal salt thereof per 100 parts by weight of both A and B. 1 to 8 parts by weight and the required parts by weight of carbon black, and the resol type phenolic resin B has 2-1 substitution, 2, 4-2 substitution, 2, 4, 6-3 substitution , methylol group, dimethylene ether, and phenyl group as determined by infrared spectroscopy as l, m, n, a, b, and c, and between each transmittance (a) l/n=0. 8-1.2 (b) m/n=0.8
~1.2 (c) b/a=0.8-1.2 (d) c/a=1.2-1.5 A paint for forming a piezoelectric buzzer electrode comprising a paste. (2) A paint for forming a piezoelectric buzzer electrode according to claim (1), wherein the metal silver powder A has a particle size of 0.1 to 20 μm. (3) The above-mentioned claims (1) to (2) are applied to the surface of the piezoelectric vibrator.
A piezoelectric buzzer consisting of an electrode made of any of the pastes and a lead wire connected to the electrode either directly or through an elastic body.