JP3096472B2 - SC-cut crystal unit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an SC-cut crystal resonator, and more particularly, to suppression of a sub-vibration mode.

(Technical Background of the Invention and Problems Thereof) In general, a quartz resonator exhibits unique characteristics according to a cutting angle with respect to a crystal axis. AT-cut quartz resonators most commonly used at frequencies of several MHZ to several tens of MHZ exhibit a cubic curve-like temperature characteristic having an inflection point near 25 ° C.

By the way, as a reference oscillator that requires a highly stable frequency in a measuring device, a wireless device, or the like, for example, a thermostatic oscillator is used. In this constant-temperature oscillator, the crystal oscillator is housed in a constant-temperature bath heated to a constant temperature of about 80 ° C., so that a change in frequency due to the temperature characteristics of the crystal oscillator is removed to achieve stabilization.

And as a crystal oscillator suitable for such an oscillator
SC-cut quartz resonators are known. The SC-cut quartz resonator has better thermal shock characteristics than the AT-cut quartz resonator, exhibits a zero temperature coefficient at a relatively high temperature of about 80 ° C., and can obtain a high Q value. Such characteristics are extremely desirable characteristics for a highly stable crystal oscillator which is used by being housed in a constant temperature bath at a constant temperature of about 80 ° C., for example.

Therefore, for example, the 34th FC held in May 1980
187 to 19 of S (FREQ.CONTROL SYMPOSIUM)
Page 3 shows the fundamental mode SC-cut resonator (FUNDAMENTAL MOD
Various reports have been made as disclosed as ESC-CUT RESONATORS).

By the way, such an SC-cut crystal resonator has a B-mode (B in the drawing) and an A-band crystal in a high frequency range near the resonance of the C mode (C in the drawing) which is the main vibration as shown in FIG. A sub-vibration in the mode (illustrated A) occurs.

Here, since the value of the crystal impedance (hereinafter abbreviated as CI) of the vibration in the A mode is larger than that in the C mode, it does not pose a particular problem. On the other hand, the CI of the B mode is equal to or smaller than that of the C mode. For this reason, when an oscillator is actually manufactured, there is a problem in that the oscillator oscillates in the B mode of auxiliary vibration.

Therefore, when using an SC-cut crystal unit,
In order to reliably excite the C mode main vibration, it is necessary to suppress the B mode vibration and make its CI larger than that of the C mode. For this purpose, for example, as shown in the plan view in FIG. 5 and the side view in which the dimension in the thickness direction shown in FIG. 6 is exaggerated, a convex process for processing one main surface 12 of the crystal blank 11 into a convex lens shape. Is performed, and the other main surface 13 remains flat. Also, by leading and holding the electrode 14 to the end of the quartz piece in the ZZ'-axis direction,
It is considered to suppress mode oscillation.

However, there has been a problem that such means cannot reliably suppress the B-mode vibration.

(Object of the Invention) The present invention has been made in view of the above circumstances, and it is possible to reliably suppress the resonance of the B mode as well as the A mode, and thereby to surely excite the resonance of the C mode. It is an object of the present invention to provide an SC-cut crystal unit that can be used.

(Summary of the Invention) The present invention relates to a SC-cut double-rotation quartz resonator cut out by rotating about 22 ° from the optical axis and about 35 ° from the electric axis,
Convex processing is performed on one main surface, the other main surface is flat, and the inner diameters of the bevel processing performed on both main surfaces are different, and in the above-described crystal resonator, the bevel processing on the convex processing side is performed. The inner diameter of the bevel processing on the plane side with respect to the inner diameter is larger than 1.1 times and smaller than 1.4 times.

(Example) Hereinafter, an example of the present invention will be described with reference to a plan view shown in FIG.
This will be described in detail with reference to the side view shown in the drawings.

In the drawing, reference numeral 1 denotes an SC-cut crystal blank. The crystal blank 1 has a crystal of about 35 ° from the optical axis (Z axis), for example, 35 ° 5
6 ', a double-turned crystal blank cut out from a plane rotated about 22 ° from the electric axis (X-axis), for example, 22 ° 56'.

Then, the crystal blank 1 is formed into a round plate having a thickness corresponding to a desired resonance frequency. Here, the side ratio, that is, the dimension ratio (XX '/ t) in the X'-axis direction to the thickness t of the crystal blank is 12.5 to
14.0.

Then, one main surface 2 is subjected to convex processing to form a convex lens-shaped curved surface, and the other main surface 3 remains flat.

Then, a beveling process 4 is performed in which the peripheral portions of the main surfaces 2 and 3 are cut obliquely in a straight line. Here, the inner diameters (D1, D2 in the drawing) of the bevel processing of the two main surfaces 2, 3 are made different from each other.

FIG. 3 is a graph showing the ratio of the inner diameter (D2 / D1) of the bevel processing and the ratio of the CI in the B mode and the C mode (CIb / CIc).

That is, based on this result, the inner diameter D1 of the bevel processing of one of the main surfaces 2 subjected to the convex processing is compared with the other main surface 3 of the bevel processing.
The ratio of CI (CIb / CIc) increases in a quadratic curve as the ratio (D2 / D1) of the inner diameter D2 of the beveling process increases.

If the ratio of the inner diameters (D2 / D1) is 1.1 to 1.4, the CI ratio becomes 1.5 or more, thereby suppressing the B-mode resonance and reliably exciting the C-mode resonance.

If the inner diameter ratio is 1.4 times or more, the absolute value of CI becomes large and oscillation becomes difficult, so the inner diameter ratio of bevel processing is 1.
Desirably less than 4 times.

An excitation electrode 5 is formed facing the plate surface of the crystal blank 1 on which a predetermined amount of beveling has been performed, and is led out to, for example, an end in the ZZ ′ axis direction, and is held by a holding member. To make a proper connection.

With such a configuration, the CI of the C mode, which is the main vibration, can be made smaller than the CI of the B mode, and C
An SC-cut crystal unit that can be excited by the main vibration of the mode can be obtained. In addition, since the essential characteristics of the SC-cut crystal unit are not lost even if the inner diameter difference of the bevel processing is changed in this way, a crystal unit suitable for a highly stable oscillator using a thermostat, etc. Can be obtained.

(Effects of the Invention) As described in detail above, according to the present invention, an SC-cut quartz crystal resonator capable of suppressing the resonance of the A mode and the B mode and of surely exciting the resonance of the C mode which is the main vibration. Can be provided.

[Brief description of the drawings]

1 and 2 are a plan view and a side view, respectively, showing an embodiment of the present invention. FIG. 3 is a graph showing an inner diameter ratio of bevel processing and a ratio of CI in B mode and C mode. FIG. 5 is a graph showing resonance characteristics of an SC-cut crystal unit. FIGS. 5 and 6 are a plan view and a side view showing an example of a conventional SC-cut crystal unit. 1 ... crystal blank 2 ... main surface (convex processing) 3 ... main surface (flat surface) 4 ... bevel processing surface 5 ... electrodes D1, D2 ... bevel inner diameter

Continuation of front page (56) References JP-A-54-21189 (JP, A) JP-A-54-21188 (JP, A) JP-A-57-69921 (JP, A) JP-A-55-75323 (JP, A) JP-A-52-47391 (JP, A) JP-A-53-97982 (JP, U) JP-A-51-84381 (JP, U) JP-B-63-66446 (JP, B2) 63-36748 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00-9/19 H03H 9/54-9/60 H03H 3/00-3/04

Claims (1)

(57) [Claims] 1. An SC-cut double-rotation crystal oscillator cut out by rotating about 22 ° from the optical axis and about 35 ° from the electric axis, one of the main faces is subjected to convex processing, and the other main face is flat. The inner diameter of the bevel processing on the flat side is larger than 1.1 times and smaller than 1.4 times the inner diameter of the bevel processing on the convex side compared to the inner diameter of the bevel processing on the convex side. SC-cut crystal oscillator.