JP2006261745A - Method of manufacturing piezoelectric vibrator and method of measuring frequency temperature characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric vibrator capable of measuring frequency temperature characteristic in a mode of a piezoelectric vibration piece while reducing manufacturing cost, and a method of measuring the frequency temperature characteristic. <P>SOLUTION: The piezoelectric vibrator has been manufactured by a process of cleaning a piezoelectric blank plate; process of vapor-depositing an excitation electrode on the main surface of the blank plate after cleaning; process of measuring the frequency temperature characteristic of a piezoelectric elements formed by vapor-depositing the excitation electrode; process of dividing the piezoelectric elements into singular pieces after measuring the frequency temperature characteristic; process of mounting each of the singulated piezoelectric elements on a package for piezoelectric vibrator via a conductive adhesive; process of drying the conductive adhesive after mounting; and process of minutely adjusting the main vibration frequency of each of the piezoelectric vibrators after drying. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a piezoelectric vibrator having excellent mass productivity and reduced manufacturing cost, and a measuring method for measuring frequency fluctuation characteristics with respect to changes in ambient temperature.

  Conventionally, electronic parts having functions such as frequency generation sources and filters have been made using piezoelectric materials. Among various piezoelectric materials, piezoelectric vibrators (quartz crystal vibrators) that use quartz that has particularly excellent resonance characteristics are widely used. Has been. Crystal resonators are mounted on OA devices such as computers and mobile communication devices represented by mobile phones, and there is an increasing demand for crystal resonators that are inexpensive and have good frequency characteristics.

The manufacturing process of such a crystal unit will be described with reference to the flowchart of FIG. First, a quartz wafer (base plate) cut out from a crystal is polished to a required external dimension and thickness and cleaned (M30). After cleaning, on the main surface of the crystal element plate, an excitation electrode for exciting the crystal element plate using a metal material such as gold (Au) or silver (Ag), and a crystal resonator package are mounted. For this purpose, an extraction electrode is deposited and each metal electrode film is formed (M31). The crystal element plate on which the metal electrode film is formed is divided into individual pieces, and a crystal element (crystal vibration piece) in which the metal electrode film is formed on each crystal piece is formed (M32). The quartz crystal resonator element is housed in a quartz resonator package via a conductive adhesive in a mounting process (M33), and after drying the conductive adhesive in a drying (annealing) process (M34), By further depositing a metal electrode on the metal electrode film or removing the electrode film by a method such as etching, fine frequency adjustment for obtaining a target main vibration frequency is performed (M35). Thereafter, in order to prevent the secular change caused by the chemical change of the electrode material and maintain the stable performance, the inside of the package is sealed in a vacuum state, and the crystal resonator is completed (M36). After the leak test (M37) for investigating whether the crystal resonator is in a completely sealed state, a drive level test (DLD test) for measuring a frequency fluctuation amount when an excessive current is applied to the crystal resonator, Various electrical characteristics such as measurement of equivalent circuit constants of the crystal resonator are inspected (M38). Among the electrical characteristics, the frequency variation characteristic (frequency temperature characteristic) of the oscillation frequency due to a change in ambient temperature increases the frequency stability of a temperature compensated crystal oscillator (TCXO) configured using the crystal resonator. It is particularly important because of its influence on characteristics, and a strict quality inspection is performed.
As described above, a crystal resonator having extremely high frequency stability can be obtained by performing various electrical characteristic evaluations as described above on a completed crystal resonator.

  However, the conventional method for measuring the electrical characteristics, particularly the frequency temperature characteristics, of the finished crystal unit has the following problems. After the crystal resonator is completed through the above-described series of manufacturing steps, when a defect in the frequency temperature characteristic is confirmed in the inspection step, the crystal resonator determined to be defective is discarded as it is. For this reason, since the package, the lid, and other members constituting the crystal resonator are also discarded at the same time, the loss at the time of manufacture becomes very large, making it difficult to reduce the manufacturing cost.

Thus, for example, Japanese Patent Application Laid-Open No. 2004-128592 is disclosed as means for solving the above problems. In the publication, as shown in FIG. 5, the temperature of the crystal base plate 10 is changed in a state where the crystal base plate 10 is sandwiched between the metal electrode plates 16, and the frequency at the time of temperature change is measured. Thus, the frequency temperature characteristic of the quartz base plate 10 is measured.
According to the publication, by forming the metal electrode plate 16 with heating and cooling means such as a Peltier element, the temperature of the crystal base plate 10 is changed in a state where the crystal base plate 10 is sandwiched, and the temperature change Since the frequency at the time is measured by the network analyzer 15, the frequency temperature characteristic can be measured in the state of the crystal base plate, and if the characteristic defect is confirmed, only the base plate has to be discarded. Can be reduced. In addition, since the quality of the frequency temperature characteristic can be confirmed in the state of the crystal base plate, a good crystal base plate can be stably introduced into the subsequent manufacturing process, and the non-defective product rate can be improved.
JP 2004-128592 A

However, the measurement method as disclosed in the above publication has the following problems. As is well known, the factors that determine the frequency-temperature characteristics of a crystal resonator depend on the cutting angle of the crystal element plate and the size of the crystal resonator element. Here, the size of the quartz crystal resonator element shows a phenomenon that apparently changes depending on the degree of energy confinement in the formation portion of the excitation electrode, and the energy confinement described above depends on the shape (dimension) and film thickness of the excitation electrode. decide. Therefore, since the frequency temperature characteristic varies greatly before and after the excitation electrode is formed on the main surface of the quartz base plate, it is difficult to accurately determine the quality by the frequency temperature characteristic measurement method as described above. There was a point.
The present invention provides a method for manufacturing a piezoelectric vibrator and a method for measuring a frequency temperature characteristic, which can reduce the manufacturing cost and can measure the frequency temperature characteristic of a piezoelectric element in a state close to a product.

  In order to achieve the above object, the present invention provides a step of cleaning a piezoelectric element plate, a step of evaporating an excitation electrode on the main surface of the piezoelectric element plate after cleaning, and a piezoelectric element formed by the excitation electrode evaporation. A step of measuring a frequency temperature characteristic of the element; a step of dividing the piezoelectric element into pieces after forming the frequency temperature characteristic; and forming each piece of the piezoelectric element; and A piezoelectric vibrator is manufactured through a step of mounting via a conductive adhesive, a step of drying the conductive adhesive after mounting, and a step of finely adjusting the main vibration frequency of the piezoelectric element after drying. It is characterized by that.

  Further, in the measurement of the frequency temperature characteristics, the present invention applies a probe provided with heating and cooling means composed of a Peltier element or the like to the excitation electrode, and changes the temperature of the piezoelectric element plate with the probe. The main vibration frequency of the piezoelectric element is measured.

  In the method of manufacturing a piezoelectric vibrator according to the present invention, since a step of measuring frequency temperature characteristics after forming an excitation electrode on the main surface of the piezoelectric element plate is added, a characteristic defect is confirmed in the frequency temperature characteristics measurement step. In this case, since only the piezoelectric element plate needs to be discarded, the loss during manufacturing can be reduced. In addition, since the frequency temperature characteristics are measured with the excitation electrode formed on the piezoelectric element plate, it is possible to evaluate the characteristics in a state close to the product, and supply a good piezoelectric element that is stable in the subsequent manufacturing process. Is possible. Furthermore, since the frequency temperature characteristic is measured by applying an inspection probe to the extraction electrode formed on the piezoelectric element plate, it is possible to perform the measurement without damaging the excitation electrode.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
FIG. 1 is a flow chart showing a manufacturing process of a crystal resonator according to the present invention. In addition, about the structural member similar to what was shown in the above-mentioned prior art example, the same code | symbol is attached | subjected and the description is abbreviate | omitted. The flowchart represents a process of batch processing of crystal elements in the state of a crystal base plate, and the crystal resonator of this example will be described by taking an AT cut crystal resonator as an example.

First, an AT-cut quartz base plate cut out from a quartz crystal is polished to a required external dimension and thickness and cleaned (M30).
After the cleaning step, the quartz base plate has an excitation electrode for exciting each piece of crystal, and an extraction electrode drawn from the excitation electrode to the end of the quartz crystal element. Each crystal element is formed by being sandwiched by a metal mask or the like so as to be formed with a predetermined electrode shape and film thickness on top, and forming an electrode film of a metal material such as Au or Al in a vacuum chamber. A vibrating piece) is formed (M30).

After the formation of the quartz crystal vibrating piece, the frequency temperature characteristic of each quartz crystal vibrating piece is measured in the vacuum chamber (M40). Here, a method of measuring the frequency temperature characteristic will be described with reference to FIG. FIG. 2 is a diagram showing the concept of a measurement system for frequency temperature characteristics in the quartz crystal resonator element.
As shown in FIG. 2, the measurement system includes a network analyzer 15 and a probe 13 connected to the network analyzer 15 and provided with a Peltier element 14 that generates a heating and cooling action due to a current change.
Since the quartz crystal resonator element is formed of an AT-cut quartz base plate, the frequency change Δf / f with respect to the ambient temperature change t, that is, the frequency-temperature characteristic draws a cubic curve as shown in FIG. / F = α (t−t ₀ ) + β (t−t ₀ ) ² + γ (t−t ₀ ) ³ However, α, β, and γ are primary, secondary, and third-order temperature coefficients, respectively, and t ₀ is a reference temperature, for example, + 25 ° C. Since the slope of the frequency temperature characteristic curve depends on the primary temperature coefficient α, the overall temperature characteristic curve can be easily predicted if the primary temperature coefficient α can be obtained.

  Therefore, in the measurement of the frequency temperature characteristic according to the present invention, first, the probe 13 is applied to the extraction electrode 12 formed on the crystal piece 10b, and the temperature of the crystal piece 10b is lower than the predetermined temperature t1 ( The current of the Peltier element 14 provided in the probe 13 is controlled so that t1 <+ 25 ° C.), and the frequency f1 at the temperature t1 is measured by the network analyzer 15. Next, the current of the Peltier element 14 is controlled so that the temperature of the crystal piece 10b becomes a predetermined temperature t2 (t2> + 25 ° C.) higher than + 25 ° C., and the frequency f2 at the temperature t2 is controlled by the network analyzer 15. taking measurement. From the results obtained above, after deriving the primary temperature temperature coefficient α from the formula α = (f2−f1) / (t2−t1), the overall frequency temperature characteristic is predicted from the primary temperature temperature coefficient α. Then, pass / fail judgment is performed. The probe or the quartz element plate is structured to move by an XY stage or the like, and the above-described measurement is similarly performed on each quartz crystal vibrating piece provided on the quartz element plate.

The quartz crystal vibrating piece determined to be a non-defective product by the quality determination is then divided into individual pieces by a dicing saw or the like (M32).
The quartz crystal resonator element is accommodated in a quartz resonator package via a conductive adhesive in a mounting process (M33), and after passing through a drying (annealing) process of the conductive adhesive (M34), the excitation is performed. On the electrode film of the electrode, fine metal frequency adjustment for obtaining the target main vibration frequency is performed by depositing a further metal electrode or removing the electrode film by a technique such as etching (M35).

  Thereafter, in order to prevent the secular change caused by the chemical change of the electrode material and maintain the stable performance, the inside of the package is sealed in a vacuum or a state in which nitrogen gas is sealed, thereby completing the crystal resonator (M36). ). After the leak test (M37) for investigating whether the crystal resonator is kept in a completely sealed state, a DLD test for measuring a frequency fluctuation amount when an excessive current is applied to the crystal resonator, By performing inspection (M38) for various electrical characteristics such as measurement of equivalent circuit constants of the vibrator, a crystal vibrator having extremely high frequency stability can be obtained.

As described above, the step of cleaning the crystal base plate, the excitation electrode on the main surface of the crystal base plate after cleaning,
And a step of evaporating the extraction electrode, a step of measuring the frequency temperature characteristics of each quartz vibrating piece formed after the excitation electrode deposition, a step of dividing the quartz base plate into pieces after measuring the frequency temperature characteristics, A step of mounting the crystal vibrating piece after the division into a crystal resonator package via a conductive adhesive, a step of drying the conductive adhesive after the mounting, and a main vibration of the crystal vibrating piece after drying Since the crystal unit was manufactured through the process of fine-tuning the frequency, it is possible to check the quality of the frequency temperature characteristic at an early stage of the manufacturing process. If a defect is found in the frequency temperature characteristic, only the crystal resonator element is discarded. As a result, the loss during manufacturing can be reduced as compared with the case of evaluating the finished product. In addition, since the frequency temperature characteristics are measured with the excitation electrode formed on the quartz base plate, it is possible to evaluate the characteristics in a state close to the product, and supply a good crystal element that is stable in the subsequent manufacturing process. Is possible. In addition, since the frequency can be easily measured with a temperature change applied to each crystal piece with a probe using a Peltier element, evaluation and inspection suitable for mass production can be performed. Cost can be reduced. The frequency temperature characteristic measurement can be performed without damaging the excitation electrode because a probe for inspection is applied to the extraction electrode.
In the above-described embodiments, the crystal resonator has been described as an example. However, the present invention is not limited to this, and it is obvious that the present invention may be applied to piezoelectric materials other than quartz.

It is a flowchart figure which shows the manufacturing process of the crystal oscillator based on this invention. It is a figure which shows the concept of the frequency temperature characteristic measuring method which concerns on this invention. It is a figure which shows the frequency temperature characteristic in an AT cut quartz substrate. It is a flowchart figure which shows the manufacturing process of the conventional crystal oscillator. It is a figure which shows the concept of the frequency temperature characteristic measuring method of the conventional piezoelectric element board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Crystal base plate 10a, 10b, 10c Crystal piece 11 Excitation electrode 12 Extraction electrode 13 Probe 14, 17 Peltier element 15 Network analyzer 16 Metal electrode

Claims (5)

A step of cleaning the piezoelectric element plate, a step of depositing an excitation electrode and an extraction electrode on the main surface of the cleaned piezoelectric element plate, and a frequency temperature characteristic of the piezoelectric element plate after the electrode evaporation step. A step of dividing the piezoelectric element plate into individual pieces after the step of measuring the frequency temperature characteristics and forming the piezoelectric vibrating piece; and mounting the piezoelectric vibrating piece to the piezoelectric vibrator package via a conductive adhesive Piezoelectric vibrator characterized in that a piezoelectric vibrator is manufactured by a step, a step of drying the conductive adhesive after the mounting step, and a step of finely adjusting the frequency of the piezoelectric vibrating piece after the drying step. Child manufacturing method. The frequency temperature characteristic is measured by applying a probe provided with heating and cooling means to the excitation electrode and measuring the frequency while changing the temperature of the piezoelectric element plate by the probe. The manufacturing method of the piezoelectric vibrator as described. The method for manufacturing a piezoelectric vibrator according to claim 1, wherein the heating and cooling means provided in the probe is a Peltier element. A frequency is measured while changing the temperature of the piezoelectric element plate by applying a probe provided with heating and cooling means to an extraction electrode provided on the main surface of the piezoelectric element plate. Measurement method of frequency temperature characteristics of vibrator. 5. The method for measuring frequency temperature characteristics of a piezoelectric vibrator according to claim 4, wherein the heating and cooling means provided in the probe is a Peltier element.

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