JPH07106893A - Frequency adjustment method for piezoelectric resonator - Google Patents

Abstract

PURPOSE:To reduce the proportion defective by applying a DC voltage to an external connection terminal of a complete product depending on a deviation from a predetermined resonance frequency so as to implement secondary polarization processing to the product. CONSTITUTION:Full face electrodes are formed to both sides of a mother board 1 made of a piezoelectric ceramic by vapor-deposition or the like. A DC voltage is applied between both the electrodes to apply primary polarization processing in the broadwise direction of the mother board 1. The full face electrodes are processed by etching or the like to form vibration electrodes 3a corresponding to discrete components. The vibration electrodes 3a are separated and cut off to generate discrete components. Lead terminals are fitted to the vibration electrodes 3a by soldering or the like. An outer package resin layer is coated by the dip coating or the like. The resonance frequency of each discrete component is measured and when the frequency is, e.g. lower than the prescribed resonance frequency, a predetermined DC voltage is applied to lead terminals to apply secondary polarization processing in an increasing direction of the resonance frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of adjusting the frequency of a piezoelectric resonator, and more particularly to a method of adjusting the polarization degree of a piezoelectric resonator in a thickness extensional vibration mode.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric resonator utilizing a thickness extensional vibration mode is manufactured by the following steps. First, an electrode is formed on almost the entire surface of the mother substrate, and a predetermined electric field is applied to the electrode to perform polarization processing. After that, the electrodes are etched to form individual electrodes, and
The frequency is measured for each individual electrode. Then, the frequency adjustment ink is applied to the electrodes according to the frequency to adjust the frequency on the mother substrate. After that, the mother substrate is separated and cut into individual elements, terminals are attached to this, and then an exterior such as dip coating is applied to complete the product. After that, the frequencies of the individual finished products are measured, and those within the predetermined frequency range are selected as non-defective products.

[0003]

In the case of the above manufacturing method, the frequency measurement and the frequency adjustment are performed at the stage of the mother board. However, the frequency measurement is one point or a few points in the mother board for work. Limited to points. However, since the thickness of the mother board is different between the central part and the peripheral part of the mother board, there is a drawback that the variation of the frequency becomes large at the stage of the finished product and the defective rate increases. Also, since the frequency correlation between the mother board and the finished product is not constant,
Even if it is a good product at the stage of the mother board, it is not always good at the stage of the finished product. Since the finished product with the defective frequency is discarded, there is much waste. Therefore, it is an object of the present invention to provide a method for adjusting the frequency of a piezoelectric resonator, which can reduce the frequency variation in a finished product and can significantly reduce the defective rate.

[0004]

In order to achieve the above object, the present invention provides a step of measuring a frequency of each element having an outer package and a step of selecting each element by comparing the frequency with a predetermined range. And a step of applying a secondary voltage to the external connection terminals of the elements selected as outside the predetermined range so that the frequency thereof falls within the predetermined range.

[0005]

Function: The frequency is measured and the selection is performed in the finished product to which the terminals are connected and the exterior is formed. Secondary polarization processing is performed by applying a DC voltage to the external connection terminal for the finished product that has been determined to be defective by sorting. For example, if the frequency of the finished product is lower than the prescribed range, the DC voltage in the + direction should be applied to adjust the frequency higher, and if it is higher than the prescribed range, the DC voltage in the-direction should be applied. Adjust the frequency lower by. As a result, the frequencies of all finished products can be controlled within a predetermined range, and defective products can be eliminated.

According to the method of the present invention, even if the frequency on the mother substrate becomes higher than the target frequency, it can be corrected at the stage of the finished product, so that it is necessary to perform the primary polarization treatment of the mother substrate so as to be lower than the target frequency beforehand. Therefore, it is easy to perform the primary polarization treatment. Further, it is possible to omit the conventional frequency adjustment by applying the frequency adjustment ink to the mother substrate.

[0007]

EXAMPLE FIG. 1 shows a method of manufacturing a piezoelectric resonator according to the present invention.
Follow the instructions below. First, a mother substrate 1 (FIG. 2) made of a rectangular piezoelectric ceramic substrate that is not subjected to polarization treatment is used.
The whole surface electrodes 2 and 2 are formed on the front and back surfaces of (see) by a method such as vapor deposition (step S ₁ ). Then, by applying a DC voltage between the full-surface electrode 2, 2, performs an order polarization in the thickness direction P on the mother substrate 1 (step S _2).

A resist mask corresponding to the individual electrode pattern is printed on the front and back surfaces of the mother substrate 1 which has been polarized, and is etched (step S ₃ ). As a result, FIG.
As described above, a plurality of individual electrodes 3 having the vibrating electrodes 3a are formed. As a method of forming the individual electrode 3, in addition to the method of forming the individual electrode 3 by utilizing a part of the entire surface electrode 2 as described above, after removing the entire surface electrode 2 by etching or the like, a new method is performed. The individual electrode 3 may be formed.

After forming the individual electrodes 3, the center frequency F ₀ between any one of the individual electrodes 3 on the mother substrate 1 is measured and selected (step S ₄ ). The individual electrode 3 is preset so that its frequency F ₀ is lower than the target frequency range. After the selection, as shown in FIG. 4, the frequency adjusting ink 4 is applied to the vibrating electrode 3a according to the difference with the target frequency range.
It is applied on the surface and frequency is adjusted (step S ₅ ). After the frequency adjustment, the mother substrate 1 is separated and cut for each individual electrode 3 as shown by the broken line in FIG. 4 (step S ₆ ), and the element A as shown in FIG. 5 is obtained.

In FIG. 5, an element A is formed by forming a pair of electrodes 3, 3 on the front and back surfaces of a piezoelectric ceramic substrate 1a, and circular vibrating electrodes 3a, 3a of both electrodes 3, 3 sandwich the piezoelectric ceramic substrate 1a. And are facing each other. Also, the electrodes 3, 3
The terminal electrodes 3b and 3b are formed at symmetrically opposite end portions of the front and back surfaces of the piezoelectric ceramic substrate 1a, and the vibrating electrode 3a and the terminal electrode 3b are electrically connected via a thin lead electrode 3c. When a voltage is applied between the electrodes 3 and 3, the piezoelectric ceramic substrate 1a is polarized in the direction of arrow P.
Piezoelectric ceramic substrate 1a sandwiched between vibrating electrodes 3a, 3a
An energy trap type thickness longitudinal vibration is excited in the area of.

[0011] terminal electrodes 3b of the element A, the lead terminals 5,5 with respect 3b soldered (step S _7), exterior resin layer by dip coating around the still elements A 6
To form a (step S _8), to obtain a finished product B as shown in FIG. 6.
When the exterior resin layer 6 is formed, a cavity 7 serving as a vibration space is formed on the vibration electrode 3a by a known method. After that, frequency selection / control of the finished product B shown in FIG. 7 is performed (step S ₉ ).

In FIG. 7, the frequency F ₀ of the finished product B is measured (step S ₁₀ ). This measurement is performed by bringing the measuring terminals of the measuring device into contact with the lead terminals 5 and 5 of the finished product B. Next, it is selected whether or not the measured frequency F ₀ is within the range of the target frequencies F _{1 to} F ₂ (step S ₁₁ ). F ₁ ≦ F ₀ ≦
If it is F ₂ , the secondary polarization described later as a non-defective product is not performed. If F ₁ > F ₀ , the frequency F ₀ is too low, so
A constant DC voltage in the + direction is applied between the lead terminals 5 and 5 to perform secondary polarization in the direction of increasing the frequency (step S ₁₂ ). On the other hand, if F ₀ > F ₂ , the frequency is too high, so a constant DC voltage in the − direction is applied between the lead terminals 5 and 5, and secondary polarization is performed in the direction of decreasing the frequency (step S
₁₃ ). After performing the secondary polarization as described above, the frequency F is again measured.
Measurement of ₀ (step S ₁₀ ) and selection (step S ₁₁ ) are performed, and secondary polarization is repeatedly performed until the target frequency falls within the range of F _{1 to} F ₂ . In this way, at the stage of the initial finished product B, as shown in FIG.
The frequency distribution shown in FIG. 8A is shown in FIG.
The frequency distribution can be adjusted as described above, and it is possible to generate almost no defective products.

In the above embodiment, a constant DC voltage in the + direction or in the − direction is repeatedly applied during the secondary polarization, but instead of this, the frequency F ₀ and the target value (F ₁
Alternatively, a DC voltage corresponding to the difference from F ₂ ) may be applied. In this case, one secondary polarization is sufficient. Further, in the above embodiment, the frequency adjustment ink 4 is applied at the stage of the mother substrate to adjust the frequency, but this step may be omitted. The present invention is not limited to the piezoelectric resonator with lead terminals as in the embodiments, but can be applied to a chip-type piezoelectric resonator having a resonator element housed in a case. In this case, the external connection terminal may be an external electrode or a metal cap formed on the outer surface of the case.

[0014]

As is apparent from the above description, according to the present invention, a secondary polarization treatment is applied to a completed product which is determined to be defective by frequency selection by applying a DC voltage to the external connection terminal. Since this is done, the frequency of all finished products is within the specified range without being affected by the difference in thickness between the central portion and the peripheral portion of the mother substrate or the frequency variation due to the correlation between the frequencies of the mother substrate and finished products. It can be controlled within. for that reason,
It is possible to eliminate defective products.

[Brief description of drawings]

FIG. 1 is a flow chart of an overall method for manufacturing a piezoelectric resonator according to the present invention.

FIG. 2 is a perspective view showing a state where a full-scale electrode is formed on a mother substrate.

FIG. 3 is a perspective view showing a state where individual electrodes are formed on a mother substrate.

FIG. 4 is a perspective view showing a state where the frequency adjusting ink is applied to the mother substrate.

FIG. 5 is a perspective view of a state in which individual elements are cut.

FIG. 6 is a sectional view of the finished product.

FIG. 7 is a flowchart showing a method of selecting a finished product and adjusting a frequency.

FIG. 8 is a frequency distribution diagram of a finished product before and after frequency adjustment.

[Explanation of symbols]

 1 Mother board 2 Full surface electrode 3 Individual electrode 3a Vibration electrode 4 Frequency adjustment ink 5 Lead terminal 6 Exterior resin

Claims (1)

[Claims] 1. A step of performing primary polarization treatment on a mother substrate, a step of forming a plurality of individual electrodes on the mother substrate, a step of separately cutting the mother substrate for each individual electrode, and In a method for manufacturing a piezoelectric resonator, including a step of connecting a connecting terminal and forming an outer package, a step of measuring the frequency of each element in which the outer package is formed, A step of selecting by comparison, and a step of performing a secondary polarization treatment so that the frequency thereof falls within the predetermined range by applying a DC voltage to the external connection terminals of the elements selected as outside the predetermined range. A method for adjusting the frequency of a piezoelectric resonator, comprising: