JPH0156564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the frequency of a so-called coupled vibrator in which several vibration modes are coupled. The purpose of the present invention is to provide a coupled resonator with excellent frequency-temperature characteristics (hereinafter referred to as temperature characteristics).There are many consumer devices that require resonators with excellent temperature characteristics. Cut quartz crystals have been used. However, recently, various consumer devices have become smaller, and AT-cut crystal resonators have also been required to be smaller.
The current situation is that miniaturization is difficult due to the large number of vibrations. In particular, when an AT-cut crystal resonator is used as a wristwatch resonator, it must be considerably miniaturized, and when compared with a tuning fork-type bent crystal resonator, it is not completely satisfactory in terms of size. Therefore, recently, a method of forming resonators using photolithography, which applies IC technology, has been applied to the manufacture of resonators, and as a result, it has become possible to provide extremely small resonators. For example, there are
It has been applied to GT cut crystal resonators and bending-torsion crystal resonators that combine bending mode vibration and torsional mode vibration (hereinafter referred to as FT crystal resonators), making it possible to make extremely compact devices. However, these GT
Cut and FT Cut crystal resonators utilize two vibration modes, namely the combination of main vibration and sub vibration, to obtain good temperature characteristics. Therefore, the temperature characteristics are almost determined by the difference between the resonance frequencies of the main vibration and the sub-vibration. Theoretically, it is known how much difference in resonant frequency should be set to provide excellent temperature characteristics, but in reality, it is difficult to maintain a constant difference due to manufacturing variations, and it is the cause of variations in temperature characteristics. Ta. Therefore, the present invention proposes a method for adjusting the resonance frequency and temperature characteristics to reduce variations in the temperature characteristics when adjusting the resonance frequency of the main vibration to the reference frequency f ₀ . The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of the shape and electrodes of a coupled resonator according to the present invention, and is an example of a GT cut crystal resonator in which a vibrating section and two support sections disposed on both sides of the vibrating section are integrally formed. A shows a plan view and B shows a side view. Electrodes 2 and 3 are arranged on the front and back surfaces of the crystal 1,
The vibrator can be easily excited by applying an alternating voltage to both electrodes. Also, the resonance frequencies of the two modes are determined by the width W and the length L, and the resonance frequency of the main vibration due to the width W is f _W and the length L
Let f _L be the resonant frequency of the secondary vibration due to

f _W ∝1/W (1) f _L ∝1/L Furthermore, the temperature characteristics are almost determined by the difference f _W −f _L between both resonance frequencies. FIG. 2 shows a plan view A and a side view B of an embodiment of the GT cut crystal resonator mounted on the support base 4. A crystal resonator 5 is arranged on the support base 4, and the ends 8 and 9 of the resonator are fixed by adhesive or soldering. Excitation electrodes 6 and 7 are arranged on the front and back surfaces of the crystal. Figure 3 shows an example of the temperature characteristics of a GT cut crystal resonator formed by photolithography, and the temperature characteristics vary depending on the strength of the bond. When the coupling between the main vibration and the sub-vibration is weak, that is, δ=f _W −f _L
When δ is large, the line becomes a line a, and when the bond is strong, that is, when δ is small, the line becomes a line b. At this time, the absolute value of the first-order temperature coefficient α is approximately 2.5×
10 ^-6 /℃, which is large and does not provide satisfactory temperature characteristics. However, when δ is the optimum value, the line becomes like a straight line c, showing good temperature characteristics. Coupled oscillators that are generally manufactured exhibit such variable tweeter temperature characteristics. That is, as shown by straight line a, the first-order temperature coefficient α is approximately -
Those with negative values such as 2.5×10 ^-6 /℃,
On the other hand, as shown in straight line b, α is approximately +2.5×10 ^-6 /℃
It shows a wide variety of temperature characteristics, including those with a positive value of , and those where α is almost zero as shown by the straight line c. Also, α of the oscillator after formation is −2.5×
It is within the range of 10 ^-6 /°C to +2.5 ^{×10 -6} /°C. Here, the fact that α is positive, negative, or almost zero is defined as follows.

(1) The fact that the first-order temperature coefficient α is almost zero means that α
is within ±1.0×10 ^-7 /℃.

(2) The first-order temperature coefficient α is positive, which means that α>
It refers to something that is at 1.0×10 ^-7 /℃.

(3) The first-order temperature coefficient α is negative, which means that α is α<-
It refers to something that is at 1.0×10 ^-7 /℃.

Figure 4 shows an example in which weights 10 and 11 are attached to a GT-cut crystal resonator by vapor deposition, at the ends of the resonator in the width W direction and at approximately the center position in the length direction.
Weights 10, 11 are attached symmetrically.
FIG. 5 shows the change in the primary temperature coefficient α with respect to the amount of weights added when the weights 10 and 11 of FIG. 4 are attached by vapor deposition. That is, as the amount of attached weight increases, the primary temperature coefficient α moves to the negative side. FIG. 6 shows an example in which weights 12, 13, 14, and 15 are attached to the four corners of a GT cut crystal resonator by vapor deposition. Figure 7 shows the weights 12, 13 in Figure 6,
The relationship between the first-order temperature coefficient α and the amount of deposited weights when depositing weights 14 and 15 by vapor deposition is shown. As the amount of weight attached increases, the primary temperature coefficient α moves to the positive side. As can be seen from these facts, when the weight is attached as shown in Fig. 4, the primary temperature coefficient α becomes negative by attaching the weight, and when the weight is attached as shown in Fig. 6, the primary temperature coefficient α becomes negative. , by attaching a weight, the primary temperature coefficient α moves to the positive side. That is,
Weights 10 and 11 in Figure 4 and weights 12 and 1 in Figure 6
When the weight is attached between 3, 14, and 15, it can be predicted that the primary temperature coefficient α will not change at all.
Figure 8 shows another example of weight attachment in a GT cut crystal resonator, with weight 10 in Figure 4 and weights 12 and 1 in Figure 6.
Weights 16 and 19 are attached so that they are between 5,
FIG. 3 is a plan view in which weights 17 and 18 are attached between weight 11 and weights 13 and 14; Figure 9 shows the primary temperature coefficient α for the amount of weights attached when the weights 16, 17, 18, and 19 in Figure 8 are attached by vapor deposition.
It can be seen that the primary temperature coefficient α does not change at all due to the attachment of the weight. Figure 10 shows weights 10 and 11 in Figure 4, and weights 12 and 1 in Figure 6.
3, 14, 15, weights 16, 17, 1 in Figure 8
8 and 19 are deposited by vapor deposition, and the change in the resonance frequency of the main vibration with respect to the amount of attached weight is shown, and the straight lines d, e, and f correspond to the cases of Fig. 4, Fig. 8, and Fig. 6, respectively. ing. It can be seen that in any case, the resonance frequency of the main vibration becomes lower depending on the amount of weight attached. Next, the frequency adjustment and temperature characteristic adjustment methods will be specifically explained.

The GT cut crystal resonator shown in Figure 1 is formed by photography and then designed to have the following characteristics.

(1) The resonant frequency of the main vibration is the reference frequency to be matched.
f has a value higher than ₀ . (Usually 1000ppm~
(2000ppm higher) Such a resonator can be easily obtained by selecting the shape and etching time. Next, this vibrator is placed at a certain arbitrary temperature, this temperature is read with a thermometer such as a thermistor, and this temperature is set as _t1 . At this time, the resonance frequency f ₁ of the main vibration is measured. Furthermore, the vibrator is placed at any other temperature, and the temperature _t2 at this time is read in the same manner as above.
At this time, the resonance frequency f ₂ of the main vibration is measured. The primary temperature coefficient α is determined from the following equation using the temperatures t ₁ and t ₂ and the resonance frequencies f ₁ and f ₂ .

α=f ₂ −f ₁ /t ₂ −t ₁ (Hz/℃) ...(2) Also, if we rewrite it using the reference frequency f ₀ to be adjusted, it becomes as follows.

α=f ₂ −f ₁ /f ₀ 1/t ₂ −t ₁ (1/° C.) (3) FIG. 11 shows this situation, and the straight line g is an example when α is positive. The temperature t ₀ is the temperature at which the resonance frequency of the main resonance and the reference frequency f ₀ are matched. temperature
At t ₀ , the main resonance frequency f is higher than the reference frequency f ₀ . Therefore, the resonance frequency f of the main vibration
There are the three methods described above to adjust the frequency f ₀ to the reference frequency f 0 by attaching a weight. However, in this case, since α is positive, α can be further reduced by adopting a method in which α moves to the negative side. That is, this is a method in which weights 10 and 11 shown in FIG. 4 are attached. Straight lines h and i in FIG. 11 show changes in temperature characteristics when the resonant frequency f is adjusted to the reference frequency f ₀ . As it approaches the standard frequency f ₀ , α approaches zero (straight line h), and when adjusted to the standard frequency f ₀ , α becomes almost zero (straight line i). 1st
FIG. 2 shows an example of the temperature characteristics of the present invention obtained in this manner. Straight line j is the temperature characteristic after the vibrator is formed, α≒1.5×10 ^-6 /℃, and straight line k is the temperature characteristic when the main resonance frequency f is adjusted to the reference frequency f ₀ , α≒3×10 ^{- 7} /°C, which is considerably small, indicating good temperature characteristics. In exactly the same way
When α is negative, the main resonance frequency f is the reference frequency.
If a method is adopted in which α moves to the positive side when adjusting to f ₀ , α can be brought even closer to zero. That is, this is a method in which weights 12, 13, 14, and 15 shown in FIG. 6 are attached. Also, when α is almost zero, there is no need to change α, so the resonance frequency f
A method in which α does not change when adjusting to the standard frequency f ₀ , that is, weights 16, 17, 18, 1 in Fig. 8
It is sufficient to use the method of attaching 9. The present invention has been described in detail above, and the gist of the configuration and means related to frequency adjustment can be summarized as follows.

The main vibration and sub-vibration are combined, and the main vibration is
This is a coupled vibrator consisting of a roughly rectangular vibrating part with the secondary vibration in the long side direction, and the resonant frequency of the main vibration of this vibrator is 1000 to 1000 higher than the standard frequency f ₀ to be matched.
In a device whose external shape is formed by etching to a value 2000 ppm higher, the primary temperature coefficient α of this processed resonator is (1) α is almost zero, which means -1.0×10 ^-7 /℃≦α≦ 1.0×10 ^-7 /℃ (2) Positive α is defined as α＞1.0×10 ⁻⁷ /℃ (3) Negative α is defined as α＜−1.0×10 ⁻⁷ /℃. a step of placing the vibrator at a certain arbitrary first temperature t ₁ and measuring the first resonant frequency f ₁ at that time; then placing the vibrator at a certain arbitrary second temperature f ₂ ; Second resonant frequency f ₂ at that time
_{In the step of} measuring
If is negative, the four corners 12 to 1 of the vibrating part of the vibrator
A step of lowering the resonance frequency of the main vibration to match the reference frequency f ₀ by attaching a weight to at least one place of 5;
If the obtained first-order temperature coefficient α is positive, the end 1 of the vibrating part of the vibrator is approximately central in the long side direction.
0 and 11 to lower the resonant frequency of the main vibration and match it to the reference frequency f _0. If the obtained primary temperature coefficient α is almost zero, the vibrating part of the vibrator Said four corners 12~
15, and an end portion 10, 1 approximately at the center in the long side direction.
This is characterized by attaching a weight to at least one place between 16 and 19 between 1 and 1 to lower the resonance frequency of the main vibration and match it to the reference frequency _f0 . Optimal temperature characteristics,
In addition, design a vibrator to obtain the optimum resonance frequency of the main vibration, measure the resonance frequencies f ₁ and f ₂ of the main vibration at arbitrary temperatures t ₁ and t ₂ , and calculate the primary temperature coefficient α from these values.
Furthermore, through vapor deposition, it is possible to provide a GT-cut crystal resonator with excellent temperature characteristics in which the primary temperature coefficient α is almost zero and the resonance frequency of the main vibration is tuned to f ₀ . Ta. This has made it possible, for example, to realize high-precision wristwatches. or,
This method measures the temperature characteristics of each individual vibrator and then adjusts the primary temperature coefficient, which significantly reduces the defective rate due to temperature characteristics. Therefore, it has become possible to reduce costs. Although the present invention has been explained using a GT-cut crystal resonator, it goes without saying that the concept of the present invention can be applied to other coupled resonators, such as an FT-cut crystal resonator.

[Brief explanation of drawings]

FIG. 1 shows an example of the shape and electrodes of a coupled resonator according to the present invention, and is an example of a GT cut crystal resonator. A
B shows a plan view, and B shows a side view. FIG. 2 shows an embodiment of the GT-cut crystal resonator mounted on a support, and shows a plan view A and a side view B. FIG. 3 is a graph showing an example of the temperature characteristics of a GT cut crystal resonator formed by photolithography.
FIG. 4 is a plan view showing an embodiment in which a weight is attached to a GT cut crystal resonator by vapor deposition. FIG. 5 is a graph showing the change in the primary temperature coefficient α with respect to the amount of weight added when the weight shown in FIG. 4 is attached by vapor deposition. FIG. 6 is a plan view showing an embodiment in which weights are attached to the four corners of a GT cut crystal resonator by vapor deposition. FIG. 7 is a graph showing the relationship between the first-order temperature coefficient α and the amount of weight deposited when the weight shown in FIG. 6 is deposited by vapor deposition. FIG. 8 is a plan view showing another embodiment of the weight attachment of the GT cut crystal resonator. FIG. 9 is a graph showing the relationship between the amount of attached weight and the primary temperature coefficient α when the weight of FIG. 8 is attached by vapor deposition. Figure 10 shows weights 10, 11 in Figure 4 and weights 12, 13, 1 in Figure 6.
4, 15, weights 16, 17, 18, 19 in Figure 8
It is a graph showing the change in the resonance frequency of the main vibration with respect to the amount of weight attached when each is attached by vapor deposition,
Straight lines d, e, and f are shown in Figures 4, 8, and 6, respectively.
This corresponds to the case shown in the figure. The straight line g in FIG. 11 is a graph showing the relationship between the main resonance frequency and the temperature of an oscillator with a positive primary temperature coefficient α, and the straight line h
and i indicate the change in temperature characteristics when the resonant frequency is adjusted to the reference frequency f ₀ . FIG. 12 is a graph showing an example of temperature characteristics obtained by the present invention. 10-19... Weight.

Claims (1)

[Claims] 1. A coupled vibrator consisting of a substantially rectangular vibrating part in which the main vibration and the sub-vibration are coupled, with the main vibration in the direction of the short side and the sub-vibration in the direction of the long side. The resonant frequency is 1000 from the reference frequency f ₀ to be matched.
In a device whose outer shape is formed by etching to a value ~2000ppm higher, the primary temperature coefficient α of this processed resonator is: (1) When α is almost zero, -1×10 ^-7 /℃≦ α≦1×10 ^-7 /℃ (2) Positive α is defined as α＞1.0×10 ^-7 /℃ (3) Negative α is defined as α＜−1.0×10 ^-7 /℃ . The process of placing this vibrator at an arbitrary first temperature t ₁ and measuring the first resonant frequency f 1 at that time, then placing the vibrator at an arbitrary second temperature t ₂ and measuring the first resonant frequency f ₁ at that time. The process of measuring the second resonance frequency f ₂ at the time, from the relationship among these t ₁ , f ₁ , t ₂ , f ₂ ,
The primary temperature coefficient α is determined, and if the primary temperature coefficient α is negative, a weight is attached to at least one of the four corners 12 to 15 of the vibrating part of the vibrator to lower the resonant frequency of the main vibration and the reference frequency f ₀ If the obtained first-order temperature coefficient α is positive, the ends 10, 1 of the vibrating part of the vibrator are approximately central in the long side direction.
A step of lowering the resonance frequency of the main vibration to match the reference frequency _f0 by attaching a weight to at least one place of 1;
If the obtained primary temperature coefficient α is almost zero, the four corners 12 to 15 of the vibrating part of the vibrator
and the end portions 10 and 11 approximately in the center in the long side direction, a weight is attached to at least one of the locations 16 to 19 to lower the resonance frequency of the main vibration and match it to the reference frequency f ₀ . How to adjust the frequency of a coupled resonator.