JPS59880Y2 - Vibrator for piezoelectric buzzer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piezoelectric buzzer vibrator having electrodes formed on both sides of a piezoelectric ceramic substrate.

Conventionally, in this type of piezoelectric buzzer vibrator, electrodes were formed by baking silver paste on both sides of a piezoelectric ceramic substrate at a temperature of 750 to 850°C. Many, and the thickness is 0.1~Q, 3 m
Since the vibrator is as thin as 1.5 m, when it is bonded to a metal diaphragm with an epoxy adhesive under a pressure of about 2 kg/cm2 and heat of about 100°C for about 30 minutes to make it conductive, the vibrator There was a problem in that more than 10% of the total number of defective products were broken, chipped, or cracked.

An object of the present invention is to provide a piezoelectric buzzer vibrator that is free from such inconveniences.

The reason why the piezoelectric porcelain substrate of the conventional vibrator described above has a large degree of warpage is that when the substrate is baked at a high temperature like a silver electrode, variations in the material of the piezoelectric porcelain substrate are amplified and become apparent. This is thought to be due to the synergistic effect of the silver electrode itself shrinking when the silver paste changes into a silver layer at the baking temperature.

Focusing on this point, the present invention uses a paste mainly composed of zinc powder, which has a lower baking temperature (550°C to 650°C) than silver paste, and applies this to both types of piezoelectric ceramic substrate 1. It is characterized in that the electrodes 3 are formed by baking onto the surfaces 2, 2.

Hereinafter, the present invention will be explained with reference to the embodiments shown in the drawings.

Example 1 Pb (Zr-Ti) Q3 powder with 5b205 and N
10. A small amount of N b 20 s powder was added, stirred in a ball mill, and then pre-calcined, the pulverized powder was formed into a sheet, punched into a circular shape, and heated at 1200°C.
After baking for 2 hours, the thickness Q is 15mm and the outer diameter is 25mm.
A φ ceramic substrate was created.

Next, a zinc paste having the composition shown in Table 1 was applied to the 23° 5 mm diameter surface of both sides of the ceramic substrate using a 250 mesh screen, dried at 150°C for 20 minutes, and then dried in the air for 50 minutes.
Baking is performed in a tunnel furnace at temperatures of 0° C., 550° C., 600° C., and 650° C. for 20 minutes, 40 minutes, or 60 minutes to form a zinc electrode 3 with a thickness of approximately 5 μm on the amphiboid surface 2 as shown in the first diagram. A total of 800 porcelain substrates 1 were produced, 100 each.

These ceramic substrates were polarized by applying a DC voltage of 25 kV/cm for 1 hour in silicone oil at 110° C. to produce a piezoelectric buzzer vibrator.

Next, this vibrator was made with an outer diameter of 34°7 mmφ and a thickness of 0.2 mm.
Approximately IQm on a brass plate (diaphragm) with a diameter of 5mm and a warpage of 30p or less
Approximately 2 kg of epoxy resin adhesive is applied by screen printing, and a press plate with heat-resistant hard rubber on the end surface is used to apply approximately 2 kg of epoxy resin adhesive.
The adhesive was bonded by heating at 100° C. for 30 minutes while applying a pressure of g/cm2.

Then, the vibrator bonded to this metal diaphragm is assembled into a resin case together with a separately excited electric circuit drive source (3Vp-p rectangular wave), and the circumference of the metal diaphragm is fixed to the case to generate an electronic buzzer. And so.

Table 2 shows cracks when a vibrator is bonded to a diaphragm when a zinc electrode is formed on a ceramic substrate by changing the baking temperature and baking time, and when a silver electrode is baked at 750°C for 40 minutes. Equal failure rate, failure rate of resonance impedance (
Characteristic defect rate) and sound pressure are shown.

Defects such as cracks were confirmed using a 10x magnifying glass after the bonding process.

As shown in FIG. 2, the resonance impedance of the piezoelectric buzzer is determined from the reading of a voltmeter 7 connected across a resistor 6 inserted in the circuit connecting the piezoelectric buzzer 4 to the sweep oscillator 5, and the resonance impedance is determined at a resonance frequency of 2°. Those whose value exceeded 200Ω near 6kHz were considered defective.

Sound pressure was measured using a precision sound level meter, 10c vertically above the piezoelectric buzzer.
The maximum sound pressure at m was measured.

8 is a frequency counter.

As is clear from Table 2, the defect rate such as cracks of the piezoelectric porcelain substrate of the present invention is 0 to 3%, whereas the formation of the piezoelectric ceramic substrate after applying silver paste and baking at 750°C for 40 minutes was not possible.
The defective rate of 00 pieces of vibrators is 12%, and the characteristic defective rate of the remaining ones after excluding the defective products is 0 to 3%, while that of the one using silver paste is 8%. It has been found that the defective rate of the vibrator of the present invention is significantly lower than that of the vibrator using silver paste, and on the other hand, there is no significant difference in sound pressure.

Example 2 Pb(Mg 1/3, Nb2/3)03-PbZrO3
A sample containing -PbTiO3 with a trace amount of NiO added was prepared in the same manner as in Example 1, and the defective rate such as cracks, the characteristic defective rate, and the sound pressure were measured.

The results were almost the same as in Example 1, as shown in Table 3.

Example 3 A zinc paste having the composition shown in Table 1 was applied to a PZT sintered body prepared in the same manner as in Example 1, and baked in the air at 550°C for 60 minutes and 600°C for 40 minutes, resulting in a film thickness of 2°5. Similar characteristics were measured for 100 samples each having a diameter of 10μ.

As shown in Table 4, the measurement results show that by controlling the zinc electrode film thickness, the rate of defects such as cracks and defective characteristics could be improved, and the output sound pressure could also be improved.

Example 4 Both mold surfaces 2 of the ceramic substrate 1 of the vibrator produced in Example 1
, 2, and a layer of nickel or copper 9 was deposited thereon by electroless plating as shown in Figure 3, to produce 20 vibrators.

When these samples were measured for defects such as cracks, defective characteristics, sound pressure, etc., the results were exactly the same as those of Example 1.

This product had improved solderability compared to that of Example 1.

As described above, according to the present invention, a paste containing zinc powder as a main component is baked as the electrodes formed on both sides of the piezoelectric ceramic substrate that constitutes the piezoelectric buzzer vibrator, which makes it more effective than conventional methods. The occurrence of defects such as cracks, defects in resonance impedance, etc. can be further reduced without reducing the sound pressure, and the economical effect is particularly significant in the case of mass production.

[Brief explanation of the drawing]

1A and 1B are an enlarged plan view and a side view of an example of the piezoelectric buzzer vibrator of the present invention, FIG. 2 is a circuit diagram for measuring the resonant impedance of the piezoelectric buzzer, and FIG. 3 is the vibration FIG. 6 is an enlarged side view of another example of a child; 1...Piezoelectric ceramic substrate, 2...Main surface,
3...Zinc electrode, 4...Piezoelectric buzzer,
9...Nickel or copper.

Claims (1)

[Scope of utility model registration request] A vibrator for a piezoelectric buzzer, in which electrodes 3 are formed on both mold surfaces 2, 2 of a piezoelectric ceramic substrate 1 by baking a paste containing zinc powder as a main component.