JP2000040937A - SC-cut crystal unit - Google Patents

Abstract

(57) [Abstract] [Purpose] S that can surely suppress B-mode resonance and thereby reliably excite C-mode resonance
Provide a C-cut crystal unit. [Structure] A strip obtained by rotating a plane orthogonal to the Y axis of a crystal of a crystal by about 33 ° about the X axis, and cutting the plane rotated about 22 ° about the Z axis from this rotated position. In the type SC-cut crystal resonator, the long side of the crystal piece is set to ± 10 ° from the ZZ ′ axis direction, and the end in the direction of the long side is supported.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SC-cut type, which is a strip-shaped small-sized quartz piece having a dimension in the long side direction of about 6 mm, which can suppress sub-vibration and obtain good vibration characteristics. It relates to a crystal unit.

[0002]

2. Description of the Related Art Recently, attention has been paid to SC-cut quartz resonators having excellent performances such as stress sensitivity, thermal shock characteristics, and phase noise performance. As shown in FIG. 3, such an SC-cut quartz resonator rotates a plane orthogonal to the Y-axis of the crystal of the quartz crystal by about 33 ° about the X-axis, and further rotates the Z-axis from the rotated position. An electrode is formed on a crystal blank 1 cut out from a plane rotated by about 22 °.

The frequency and temperature characteristics of an SC-cut quartz resonator have a substantially cubic curve having an inflection point near 80 ° C. On the other hand, as a high-stability crystal oscillator, a thermostat-type crystal oscillator that is operated by heating to a constant temperature of about 80 ° C. is known.

[0004] Such an oscillator comprises a heater for heating,
A temperature control circuit for controlling the amount of heat generated by the heater to maintain a constant temperature of about 80 ° C., for example. On the other hand, SC-cut crystal units
When used as a thermostat type crystal oscillator because it has an inflection point near ℃, it will be used in the temperature range where the rate of change of the oscillation frequency with respect to temperature change is the least, and an extremely stable oscillation frequency can be obtained. it can.

Therefore, for example, the 34th FCS (FREQUENCYCONTROLE SYMPOSIU) held in May 1980
M), 187 to 193
C-cut resonator (FUNDAMENTAL MODE SC-CUT RESONATORS)
Various reports have been made as disclosed.

However, such an SC-cut crystal resonator has a B-mode (illustrated B) at a high frequency side near the C-mode (illustrated C) which is the main vibration as shown in the resonance characteristics shown in FIG. And A mode (A in the figure) secondary vibration. Here, since the value of the crystal impedance (hereinafter referred to as CI) of the resonance in the A mode is larger than that in the C mode, it does not matter.

On the other hand, the CI of the B mode is equal to or smaller than that of the C mode. Therefore, when the oscillator is actually manufactured, if the characteristics of the tuning circuit change due to, for example, aging, the oscillator may easily oscillate in the B mode, which is the secondary vibration. Therefore, when an SC-cut crystal resonator is used, the B-mode vibration is suppressed and the C-mode vibration is suppressed in order to surely excite the C-mode main vibration.
I needed to be larger than that of C mode.

For this purpose, for example, there has been devised such as performing convex processing for processing only one main surface of the crystal blank into a convex lens shape. However, even in this case, there is a problem that the sub-vibration cannot be reliably suppressed. Was.

Further, in such a crystal oscillator, a crystal piece having a diameter of, for example, about 10 mm has been used. However, it is desired to reduce the size and weight of the oven controlled crystal oscillator using such a crystal oscillator. Therefore, it was necessary to reduce the size of the quartz resonator itself. However, when the crystal blank is miniaturized, the above-mentioned problem of the sub-vibration becomes more remarkable, and it is necessary to solve this problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an SC-cut which can surely suppress B-mode resonance and thereby can reliably excite C-mode resonance. It is an object to provide a crystal resonator.

[0011]

According to the present invention, a plane orthogonal to the Y axis of a crystal of quartz is rotated about 33 ° about the X axis,
In a rectangular SC-cut crystal resonator cut out from a plane rotated about 22 ° about the Z axis from the rotated position, the long side of the crystal piece is ± 10 ° from the ZZ ′ axis direction, and the long side is Is supported.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to the plan view of the crystal blank shown in FIG. In the figure, reference numeral 11 denotes a strip-shaped SC-cut crystal blank. For example, as shown in FIG. 2, a plane orthogonal to the Y-axis of the crystal of the artificial quartz is rotated by about 33 ° about the X-axis, and further rotated at this rotated position From the SC plate rotated about 22 ° about the Z-axis from a rectangular shape.

[0013] Here, a very small crystal piece of 1.6 mm x 5.8 mm is cut out by rotating its longitudinal direction at different angles in steps of 10 ° from the direction of the XX 'axis to obtain a large number of samples. Made. In addition, these crystal blanks form electrodes on the front and back plate surfaces, lead the electrodes to longitudinal ends, and connect the lead ends to lead terminals implanted on the base to mechanically hold the lead terminals. And electrical connection.

Then, the magnitude of the resonance waveform of the B mode with respect to the C mode was measured for the quartz pieces cut in various directions in the plane of the SC plate. FIG. 3 is a graph showing this result. When the long side of the strip coincides with the XX ′ axis direction, the rotation angle is set to 0 °. As is apparent from this result, the ratio of the magnitude of the resonance waveform in the C mode to the B mode changes in accordance with the cutting direction of the crystal blank. + 16d for ゜
B, the smallest value is −13 dB at a rotation angle of 90 °.

Therefore, the smallest size of the resonance waveform of the B mode which is unnecessary auxiliary vibration with respect to the C mode which is the main vibration is that the long side of the strip-shaped crystal piece is 90 degrees from the XX 'axis.
゜ This is to make the long side of the crystal piece coincide with the ZZ ′ axis direction. Practically, if the long side of the crystal piece is within the range of ± 10 ° in the ZZ ′ axis direction, the main vibration of the C mode is sufficiently strong against the unnecessary B mode resonance, and the crystal is not degraded by spurious characteristics. A vibrator can be obtained.

The base holding the crystal blank is covered with, for example, a cylinder-type cover, and the opening edge of the cover is hermetically fitted to the base to seal the base. Terminals are derived.

This makes it possible to reduce the level of unnecessary sub-vibration relative to the level of main vibration, and eliminates the need for steps that impede mass productivity such as precise convex machining, thereby increasing productivity. Cost can also be reduced. The shape of the crystal piece described in the above embodiment is extremely small and has good vibration characteristics, so that the shape of the crystal oscillator using the same can be reduced.

[0018]

As described in detail above, according to the present invention,
It is possible to realize a small-sized SC-cut crystal unit having an extremely small shape, and to provide an SC-cut crystal unit having a small level of sub-vibration and excellent vibration characteristics.

[Brief description of the drawings]

FIG. 1 is a plan view of a crystal piece of a crystal unit according to an embodiment of the present invention.

FIG. 2 is a graph showing an in-plane rotation angle of a crystal blank and a level ratio between a main vibration and a sub vibration.

FIG. 3 is a diagram illustrating a cut-out angle of a crystal piece in an SC cut.

FIG. 4 is a diagram illustrating response characteristics of main vibration and sub-vibration of an SC-cut quartz resonator.

[Explanation of symbols]

 11 ・ ・ Quartz piece XX ′ ・ ・ XX ′ axis ZZ ′ ・ ・ ZZ ′ axis

Claims (3)

[Claims] 1. A rectangular shape obtained by rotating a plane orthogonal to the Y-axis of a crystal of a quartz crystal by about 33 ° about the X-axis, and cutting the plane rotated about 22 ° about the Z-axis from the rotated position. 2. The SC-cut crystal resonator according to claim 1, wherein the long side of the crystal piece is set to ± 10 ° in the ZZ′-axis direction, and the end in the long side direction is supported. 2. The apparatus according to claim 1, wherein the dimension of the crystal piece in the long side direction is 6 mm or less.
C-cut crystal oscillator. 3. An SC-cut crystal resonator according to claim 1, wherein the crystal blank is housed in a cylindrical container and an electrode is led out from an end of the container.