JPH0711029U - Fundamental wave suppression crystal unit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a fundamental wave suppression type crystal unit that suppresses the fundamental wave without lowering the CI value of the third order overtone to obtain more stable third order overtone oscillation. is there. [Structure] In a crystal plate 1 having an excitation electrode 2 and a lead electrode 21 (rear surface not shown) formed and having a diameter of 5.5 mm or less, a bevel size of 0.1 mm from the end of the crystal plate.
Slope polishing of ˜0.5 mm was performed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of a crystal plate of a crystal oscillator of a fundamental wave suppression type that oscillates in a third overtone mode.

[0002]

[Prior art]

 In recent years, as the frequency of crystal units has increased, the overtone mode has been used, and many overtone crystal units have suppressed the fundamental wave in order to obtain a more stable third-order overtone oscillation. It's coming. Such a fundamental wave suppression type crystal oscillator is effective for a circuit in which the oscillation circuit used is the circuit for the fundamental wave or the circuit for the overtone, in which the oscillation of the fundamental wave is easier. Therefore, conventionally, as disclosed in Japanese Patent Laid-Open No. 3-172012, there is a configuration in which the ratio of the crystal plate diameter to the excitation electrode diameter is limited to a certain range and the chamfering is not performed to cause overtone oscillation. .

[0003]

[Problems to be solved by the device]

 However, as shown in Fig. 1 (a graph showing the relationship between the crystal plate diameter and the CI value in a crystal plate without bevel), the fundamental wave can be suppressed remarkably without beveling (beveling), but If the quartz plate diameter becomes smaller to some extent due to higher frequencies and smaller sizes, it will also affect the displacement distribution region of the third-order overtone on the quartz plate (the higher the mode is, the closer the displacement distribution region will be near the center of the quartz plate). Not a little, it was the cause of lowering the CI value of the third overtone. In addition, since a fundamental wave oscillation circuit that is generally configured using a fundamental wave suppression type crystal unit often has a small negative resistance, the CI value standard of the crystal unit used for this is usually It is often required to be smaller than the CI value standard (30Ω to 40Ω) of the third-order overtone crystal unit. When this fundamental wave suppression type crystal unit (without chamfer) is used in the oscillation circuit for the fundamental wave, the fundamental wave can be suppressed, but at the same time, the CI value of the third-order overtone decreases, and the oscillation of the desired order (third-order) occurs. There was a problem that a margin could not be obtained.

An object of the present invention is to provide a fundamental wave suppression type crystal oscillator that can suppress the fundamental wave without lowering the CI value of the third order overtone and obtain more stable third order overtone oscillation. is there.

[0005]

[Means for Solving the Problems]

 Therefore, the fundamental wave suppression type crystal oscillator of the present invention has excitation electrodes formed on at least the front and back surfaces, and in a crystal plate having a diameter of 5.5 mm or less, a slope of 0.1 mm to 0.5 mm from the end of the crystal plate. Polished.

[0006]

[Action]

 As can be seen from the graph (Fig. 1) showing the relationship between the crystal plate diameter and the CI value in the crystal plate without bevel polishing, as the crystal plate diameter becomes smaller from around 5.5 mmφ, the CI value of the third overtone becomes larger. Is high due to the influence near the edge of the quartz plate. On the contrary, when the crystal plate diameter is large (about 6 mmφ or more), the vibration displacement of the third-order overtone occurs only near the center and is almost unaffected by the vicinity of the edge of the crystal plate, so not only the third-order overtone CI value, It can be seen that the CI value of the fundamental wave with a larger vibration displacement is also good. Therefore, by subjecting a quartz plate with a diameter of 5.5 mm or less to bevel polishing, a thickness-slip vibration occurs at the center of the quartz plate where the thickness is uniform, and this vibration reduces the thickness of the quartz as it approaches the peripheral edge of the quartz plate. It is dampened in order to vibrate and hardly vibrates at the peripheral edges. Therefore, the vibration energy of the third-order overtone can be confined without being affected by the vicinity of the edge of the crystal plate, and the third-order overtone C I value can be improved, while suppressing the fundamental wave having a larger vibration displacement.

[0007] Figure 2 is a 30.420MH _Z in tertiary overtone oscillation, 0 mm in crystal oscillator diameter 5.5 mm, the bevel dimensions (length slopes polishing portion from the crystal plate end) It is the graph which represented the average of the CI value of the fundamental wave and the third order overtone when it changed to -0.6 mm by an approximate value. Figure 3 is a tertiary overtone oscillation in 30.420MH _Z, in the crystal oscillator of 5.0mm in diameter, bevel Le dimensions (length slopes polishing portion from the crystal plate end) 0Mm～0 6 is a graph showing an average of CI values of a fundamental wave and a third-order overtone when converted to 0.6 mm by an approximate value. Figure 4 is a 30.420MH _Z in tertiary overtone oscillation, the crystal oscillator of 4.0mm in diameter, bevel dimensions (length slopes polishing portion from the crystal plate end) 0Mm～0.6Mm It is the graph which represented the average of the CI value of the fundamental wave and the third order overtone when it was changed to. FIG. 5 is a graph showing the CI ratios of the fundamental wave and the third-order overtone based on the average approximate values of the CI values of FIGS. 2, 3, and 4.

As shown in the graphs above, the fundamental wave in the bevel size range of 0.1 mm to 0.5 mm can be applied to crystal resonators having diameters of 4.0 mm, 5.0 mm, and 5.5 mm. And a third-order overtone with a CI ratio of 3 times or more secured (generally, if the CI ratio of the fundamental wave and the third-order overtone (C1 ₁ / CI ₃ ) is 3 times or more, a fundamental wave suppression type oscillator It can be used.) And the bevel dimension of 0 mm (without bevel), the CI value of the third overtone is better in both cases.

[0009]

【Example】

 Next, an embodiment of the present invention will be described. FIG. 6 is a sectional view of a crystal plate showing an embodiment of the present invention. FIG. 7 is a plan view showing an embodiment of the present invention. The AT-cut crystal plate 1 that vibrates in the thickness shear vibration has a diameter of 5 mmφ, and is bevel-polished with a bevel size of 0.2 mm by means such as barrel processing. In this example, the container containing the abrasive and the crystal blank was barrel-processed for about 2 hours, whereby the beveling of about 0.2 mm could be performed. Excitation electrodes 2 are formed on the front and back surfaces of the crystal plate 1 (the back surface is not shown), and lead electrodes 21 are formed from the excitation electrode 2 to one end of the crystal plate 1. These electrodes are formed by the method of vacuum evaporation. The crystal plate 1 is electromechanically bonded to a support structure (not shown) and hermetically sealed by an exterior structure (not shown) to have a function as a final crystal unit. When this crystal unit is used as a third-order overtone resonator, the third-order overtone mode of the crystal unit is selectively taken out on the oscillation circuit side in advance.

[0010]

[Effect of device]

 By subjecting the crystal plate to slant polishing, a thickness-slip vibration occurs in the uniform thickness part of the crystal plate, and this vibration is attenuated because the crystal thickness decreases as it approaches the peripheral edge of the crystal plate. Almost no vibration at the peripheral edge. Therefore, in a quartz plate with a diameter of 5.5 mm or less, it is possible to confine the third-order overtone vibration energy and improve the CI value of the third-order overtone while suppressing the fundamental wave having a wider vibration distribution region. Further, as in the present invention, there is a crystal plate having a diameter of 5.5 mm or less, and the CI value of the third overtone is lowered by polishing the slope of 0.1 mm to 0.5 mm from the end of the crystal plate. In addition, since the CI ratio between the fundamental wave and the third-order overton can be secured more than three times, it can be used as a fundamental wave suppression type oscillator. That is, even if the fundamental wave suppression type crystal oscillator according to the present invention is used in an oscillation circuit for a fundamental wave having a small negative resistance, the fundamental wave can be suppressed and the CI of the crystal oscillator used in the oscillation circuit can be suppressed. It is possible to meet the value standard and obtain the vibration margin at the desired order (third order). For this reason, it is possible to provide a highly reliable fundamental wave suppression type crystal oscillator that can obtain more stable third-order overtone oscillation.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a crystal plate diameter and a CI value in a bevel-free crystal plate.

FIG. 2 shows a fundamental wave and a third-order overtone when the bevel dimension (the length of the portion polished from the edge of the crystal plate) of the crystal unit having a diameter of 5.5 mm is changed from 0 mm to 0.6 mm. 5 is a graph showing an average of CI values of the above with approximate values.

FIG. 3 is a fundamental wave and a third-order overtone when the bevel dimension (the length of the portion polished from the edge of the crystal plate) of the crystal unit having a diameter of 5.0 mm is changed from 0 mm to 0.6 mm. 5 is a graph showing an average of CI values of the above with approximate values.

FIG. 4 shows a fundamental wave and a third-order overtone when the bevel size (the length of the portion polished from the edge of the crystal plate) of the crystal unit having a diameter of 4.0 mm is changed from 0 mm to 0.6 mm. 5 is a graph showing an average of CI values of the above with approximate values.

5 is a graph showing CI ratios of a fundamental wave and a third-order overtone based on average approximation values of CI values in FIGS. 2, 3, and 4. FIG.

FIG. 6 is a sectional view of a quartz plate showing an embodiment of the present invention.

FIG. 7 is a plan view of a crystal plate showing an embodiment of the present invention.

[Explanation of symbols]

 1 ... Crystal plate 2 ... Excitation electrode 21 ... Lead electrode

Claims (1)

[Scope of utility model registration request] 1. An excitation electrode is formed on at least the front and back surfaces, and a quartz plate having a diameter of 5.5 mm or less is polished by a slope of 0.1 mm to 0.5 mm from the end of the quartz plate. A fundamental wave suppression type crystal unit.