JPH0477568A - Coating for forming piezoelectric buzzer and its electrode - Google Patents

Abstract

PURPOSE:To obtain the subject coating, containing metallic gold powder, a specific resol type phenolic resin and a saturated or an unsaturated fatty acid (metallic salt thereof), and excellent in adhesion of films onto insulating substrates, solderability, stability, etc., of electric conductivity for a long period. CONSTITUTION:A coating which is a paste for forming piezoelectric buzzer electrodes is obtained by blending (A) 0.1-8pts.wt. (un)saturated fatty acid (metallic salt thereof) with (B) 100pts.wt. mixture composed of (i) 85-96wt.% metallic gold 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) = 1.2-1.5 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).

Description

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

[Prior art]

As shown in FIG. 1, the piezoelectric buzzer has electrodes 2 formed on both sides of a piezoelectric vibrator 1, and a lead wire 4 connected to the electrodes 2 either directly or via a metal elastic body 3.

Silver paste has conventionally been used for the electrodes 2 in this piezoelectric buzzer, and as shown in FIG. 3, the silver paste is applied to both sides of the piezoelectric vibrator 10 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.

[Problem 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, 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 warm atmosphere after 00'C), there is a risk that silver migration will occur in the electrode 2, and there is a problem that the piezoelectric vibrator 1 cannot be made thinner.

Above a! A known method for forming a film is to heat-cure a film of conductive paste made of metal silver powder and thermosetting resin, but in this case, the conductivity decreases and the coating on the insulating substrate becomes difficult. There were problems such as poor adhesion of the film.

Therefore, the object of this invention is to solve the above-mentioned problems of the conventional silver paste, which are as follows: 1) It has good conductivity, 2) It is suitable for screen printing and intaglio printing, and 2) It is suitable for coating on insulating substrates. We propose a gold paste that has good adhesion, ■ allows the formation of thin wire circuits, ■ has excellent solderability and soldering strength on the coating film, and ■ maintains the conductivity of the conductive circuit in the solder coat over a long period of time. It is in.

[Means to solve the problem]

In order to solve the above problems, the present invention contains 85 to 96% by weight of metal gold powder A and 8% by weight of resol type phenolic resin.
15 to 4% by weight, and 0.1 to 8 parts by weight of saturated fatty acids or unsaturated fatty acids or metal salts thereof based on a total of 100 parts by weight of both A and B, and the resol type phenolic resin B , the 2-1 substitution it has, 2.
4-2-substituted product, 2.4.6-3-substituted product, methylol group,
When the infrared transmittance of dimethylene ether and phenyl group by infrared spectroscopy is defined as l, m, n, a, b, and c, there is a difference between each transmittance! (a) l/n = 0.8-1,2 (b) c/a = 0.8-1.2 (c) l/n = 0.8-1,2 (d) l/n = 1 A piezoelectric buzzer electrode forming paint made of a paste satisfying the following relationship was adopted.

The metal gold powder A has an average particle diameter of 0.1 to 20-2, preferably 1n or less.

Then, electrodes made of the paste having the above-described structure were formed on both sides of the piezoelectric vibrator, and lead wires were connected to the electrodes either directly or through an elastic body, thereby constructing a piezoelectric buzzer.

[Effect]

In the gold paste according to the present invention configured as described above, if the amount of metal gold powder blended is less than 85% by weight, the solderability will be poor, and if it exceeds 96% by weight, the metal gold powder will not be sufficiently bound. The resulting electrode also becomes brittle, the desired soldering strength cannot be obtained, the electrical conductivity decreases, and the screen printability also deteriorates.

Preferably, the content in the blend with 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 substituent cap is ν, the amount of methylol group is α, the amount of dimethylene ether is β, and the amount of phenyl group is γ, the fact that the above structure is large means that -ren, soil is n
This means that ν ν is small. That is, it means that the amount of 2.4.6-3 substitution product ν is larger than the amount of 2-1 substitution product λ and the amount of 2.4-2 substitution product μ.

In addition, if `` and -'' in the above configuration are large, a
a The fact that S is small above α
α, that is, it means that the amount of methylol groups α is larger than the amount of dimethylene ether β and the amount of phenyl groups γ.

In general, as the amount ν of 2.4.6-3 substituents increases, the crosslinking density of the resol type phenolic resin increases. The guidance of
n Electricity improves. However, on the contrary, the electrode tends to become hard and brittle, resulting in poor physical properties.

Furthermore, if 1 is small, the solderability of the electrode will be poor, and 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, 1 m b □ □ shown in the above structure is 0.8 to 1.2, respectively. , n n a □ is 1.2 ~
A value of 1.5 is suitable.

If the amount of the resol type phenolic resin is less than 4% by weight, the metal gold 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 gold powder with the resol type phenolic resin because it promotes fine dispersion of the metal gold 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 gold powder and resol type phenolic resin. Parts by weight.

If the amount of the dispersant is less than 0.1 parts by weight, fine dispersion of the metal gold powder cannot be expected, and if it exceeds 8 parts by weight, the conductivity of the electrode will be reduced and the electrodes and piezoelectric vibrator may be damaged. This is not preferable because it leads to a decrease in adhesion with the material.

In order to adjust the viscosity, the gold paste according to the present invention includes:
Conventional 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〕

Metallic gold powder with a particle size of 1n, a resol type phenolic resin with an infrared transmittance ratio shown in Table 1, and an oleic resin potassium were mixed in the proportions shown in Table 2 (parts by weight), and some butyl calpitol was added as a solvent. The gold paste was prepared by kneading with a tricycle roll for 20 minutes. In particular, Example 3
The metal gold powder average particle size is 1μ, and 2 is the same average particle size: 0.
It was set as 5-.

As shown in the flowchart of FIG. 2, each of these examples is coated on both sides of the pseudo substrate of the piezoelectric vibrator 1 by screen printing to form the electrodes 2. In order to examine the various characteristics of the electrodes 2, first, Each piezoelectric vibrator 1 with electrode 2 was immersed in an organic acid flux bath for 4 seconds, and then immersed in a 250°C molten solder bath (
It was immersed in Pb/5n=40/60) for 5 seconds, pulled up, and simultaneously blown with hot air at 2 to 6.0 atm and 220 to 230''C, and then washed.

At this time, the average thickness of the solder coat soldered to the electrode 2 is 1
It was 0μ.

Table 2 shows the results of examining various characteristics of the electrode 2 obtained through this process.

Here, the electrical conductivity of the electrode is a value obtained by measuring the volume resistivity of the electrode 2 that has been heat-cured.

The adhesion of the electrode is determined by drawing 11 parallel lines perpendicular to each other at intervals of one embryo on the coating film that will become the electrode, in accordance with the base test method of JIS K5400 (1979).
When a cut is made in the shape of a substrate so that 100 squares are formed inside, and the coating film is peeled off with cellophane tape, the number of substrate squares remaining on the insulating substrate is determined. It is.

Solderability was evaluated by observing the soldered state on the electrode 2 using a low magnification stereoscopic microscope and using the following criteria.

○ mark: The surface is smooth and the solder is adhered to the entire surface. △ mark: The electrode is partially exposed. × mark: The solder is only partially attached. Printability refers to the viscosity adjustment. When forming the electrode 2 by screen printing using the gold paste obtained in the above, the ease of printing was observed and evaluated according to the following criteria.

O mark: Good formation of electrode 2 △ mark: Somewhat difficult to form electrode 2 × mark: 1 is difficult to form electrode 2 Next, soldering strength refers to glass/epoxy resin A land with a diameter of 3 φ and a thickness of 25 mm is placed on the substrate (for example, G10).
Form a coating film of ~30°C, 130~180°C x 1
After curing the coating film by heating for 0 to 60 minutes, a lead wire (tin-plated annealed copper wire of 0.1 wφ) is vertically soldered (using 63Sn eutectic solder) onto the land, and The lead wire was pulled vertically at a pulling speed of 50 m/min with the lead wire fixed, and its strength was determined.

As can be seen from the results, each example has an appropriate combination of specific compounded materials, resulting in improved conductivity of the electrode (coating film), adhesion of the electrode, solderability, soldering strength, and printability. It has good properties such as: Further, the obtained cured electrode can be directly soldered using a normal organic acid fluxing agent.

Next, regarding Comparative Examples, in Comparative Examples 1, 2, and 3, the infrared transmittance ratio of the resol-type phenolic resin used was not appropriate, and therefore the electrode 2 with preferable solderability could not be obtained. Comparative Example 4 is not preferable because the amount of metal gold powder is small, so that the solder only partially adheres to the piezoelectric vibrator 1 during soldering.

In Comparative Example 5, there is a large amount of metal gold powder and the metal gold powder is not sufficiently bound, so the conductivity of the electrode is unstable, the obtained electrode 2 is also brittle, and screen printing is somewhat difficult, which is not preferable.

〔Effect of the invention〕

As explained in detail above, the piezoelectric buzzer in which electrodes are formed using the electrode forming paint according to the present invention has improved manufacturability because baking is not required when forming the electrodes, and a moist atmosphere is provided after baking. Since there is no fear of migration underneath, there is an effect that the piezoelectric vibrator can be made thinner.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of a piezoelectric buzzer according to the present invention, FIG. 2 is an explanatory diagram of manufacturing the same embodiment, and FIG. 3 is an explanatory diagram of conventional manufacturing. 1... Piezoelectric vibrator, 2... Electrode, 3
......Metal elastic body, 4...Lead wires Table 1 Below margins Below margins

Claims (3)

[Claims] (1) 85 to 96% by weight of metal gold 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 for a total of 100 parts by weight of both A and B. 1 to 8 parts by weight, and the resol type phenolic resin B has 2-1 parts by weight.
The infrared transmittance of the substituted product, 2, 4-2 substituted product, 2, 4, 6-3 substituted product, methylol group, dimethylene ether, and phenyl group by infrared spectroscopy is determined by l, m, n, a, b, When c, between each transmittance (a) l/n = 0.8 to 1.2 (b) m/n = 0.8 to 1.2 (c) b/a = 0.8 to 1.2 (d) A piezoelectric buzzer electrode forming paint comprising a paste satisfying the following relationship: c/a = 1.2 to 1.5. (2) The metal gold powder A has an average particle diameter of 0.1 to 20μ
The paint for forming a piezoelectric buzzer electrode according to claim 1, characterized in that m. (3) A piezoelectric buzzer comprising electrodes made of the paste according to claim (1) formed on both sides of a piezoelectric vibrator, and lead wires connected to the electrodes directly or via an elastic body.