JP2010177976A - Quartz resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quartz resonator for a highly stable product which corresponds to downsizing without degrading a CI value (series resonant resistance value), and reduces an amount of frequency variation because of a driving level of a quartz resonating plate to obtain a linear characteristic. <P>SOLUTION: In a thickness slipping quartz resonating plate 2 of an AT cut formed in a disk shape, there are provided on one face of the quartz resonating plate 2 planoconvex polishing parts 21 and 22 having 2-stage curvature, and a bevel polishing part 23 formed at an end part of the quartz resonating plate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a quartz resonator that oscillates in a thickness-shear vibration mode, and more particularly to an AT-cut thickness-slip quartz crystal plate.

  Since quartz resonators have excellent resonance characteristics, they are widely used as a reference source for frequency and time. A metal thin film electrode is formed on the surface of the quartz diaphragm, and this metal thin film electrode is protected from the outside air. Is hermetically sealed.

  Among these, the crystal resonator used in the thermostatic chamber type crystal oscillator called OCXO currently uses a metallic package. Specifically, a pair of metal lead terminals are planted on the metal base via an insulating material such as glass, and a pair of metal flat plate support members are opposed to the inner lead portion of the metal lead terminal. Attached. The quartz diaphragm is, for example, an SC cut or AT cut quartz diaphragm, and an excitation electrode and an extraction electrode from each excitation electrode are formed on the front and back surfaces. A quartz diaphragm is mounted on the metal support and is electrically and mechanically connected by a conductive bonding material. The metal base is covered with a metal lid and hermetically sealed.

  In addition, OCXO is one in which the frequency is stabilized by controlling the temperature of the crystal unit in a thermostat without affecting the external temperature change, and the frequency stability is 1 × 10 −7 to 1 Since the highest level of frequency stability that can be obtained with a crystal resonator of about × 10 −10 can be obtained, it is used as a reference frequency for radio base stations and transmission lines.

  In Patent Document 1, various shapes of crystal diaphragms are disclosed.

JP 2007-96701 A

  As the above-described crystal plate for high stability, it is the mainstream to perform plano convex processing. In addition, it is necessary to design a quartz crystal plate that has been convex-processed with the miniaturization of the crystal unit. However, if the crystal plate is designed to be small, there is a problem that the CI value (series resonance resistance value) increases. is there. Therefore, it is common practice to reduce the curvature of the convex processing in accordance with the miniaturization of the quartz diaphragm. However, the vibration energy confinement effect is excessive, and overcurrent occurs when the drive level is low (low drive). However, it has problems such as causing nonlinear fluctuations as vibration characteristics. In particular, such a problem due to the convex processing is that a remarkable tendency appears in a small crystal diaphragm having a diameter of 8 mm or less.

  The present invention has been made in order to solve the above-described problems. The present invention has been made to cope with downsizing without deteriorating the CI value (series resonance resistance value), and the amount of frequency fluctuation due to the driving level of the crystal diaphragm is reduced and linear. An object of the present invention is to provide a highly stable crystal resonator capable of obtaining the above characteristics.

  Accordingly, the crystal resonator according to the present invention is a thickness-sliding crystal diaphragm formed in a disk shape, and on one side of the crystal diaphragm, a plano-convex polishing portion having two stages of curvature, and a crystal diaphragm It has the bevel grinding | polishing process part formed in the edge part of this.

  With the above configuration, a plano-convex polishing portion having a two-stage curvature mainly for processing the vibration region of the quartz diaphragm and a bevel polishing portion mainly for processing the end outside the vibration region of the quartz plate are combined. As a result, it is possible to improve the CI value (series resonance resistance value) characteristic, the CI value (series resonance resistance value) temperature characteristic, and the like, while reducing the energy confinement effect while coping with the miniaturization of the crystal diaphragm. Parasitic oscillation due to spurious vibration of the contour system can be made difficult to occur. In addition, along with the downsizing of the quartz diaphragm, the adverse effect of forming only a planar curvature convex part with a small curvature and increasing the energy confinement effect can be improved by the planar part with a large curvature. The amount of frequency fluctuation due to the driving level of the diaphragm is reduced, and linear and more stable electrical characteristics can be obtained. Since the polishing area is formed only on one main surface of the quartz diaphragm as the plano-convex grinding part, it is easy to design and recognize the position of the thickest part (vertex part) of the finished quartz diaphragm. Design and optimization of the formation position of the excitation electrode can be easily performed, and a quartz plate having excellent productivity can be obtained. Further, by forming a bevel polishing portion having a curvature, the thickness of the quartz diaphragm can be continuously reduced in a curved shape from the convex polishing portion having a two-stage curvature toward the end of the quartz diaphragm. Therefore, the spurious vibration of the contour system can be suppressed more efficiently.

  FIG. 5 shows a comparative verification of the DLD characteristics according to the configuration of the conventional and the present invention. That is, FIG. 5 (a) shows the frequency characteristics depending on the driving level of a conventional quartz diaphragm constituted by a plano-convex polishing section having only one stage of curvature, and the CI value (series resonance resistance) characteristics at that time. FIG. 5B is a frequency characteristic depending on the drive level of the crystal diaphragm of the present invention, which is composed of a plano-convex polishing section having two stages of curvature and a bevel polishing section formed at the end of the quartz diaphragm. And CI value (series resonance resistance value) characteristics at that time. As a common item, an AT-cut quartz diaphragm having a disk shape, a diameter of 7.7 mm, and a frequency of 10 MHz is used, and the frequency fluctuation amount when the drive level is varied from 0.001 μW to 100 μW is shown. . As is clear from these verification results, it can be understood that the frequency fluctuation amount is stable without change up to about 10 μW (can maintain linearity) in the present invention.

  Further, in the above-described configuration, the plano-convex polishing portion includes a processing region having a radius of curvature of 400 mm (R400) and a processing region having a curvature radius of 150 mm (R150), and the bevel polishing portion has a radius of curvature of 45 (R45). A region may be configured. In particular, if the crystal diaphragm has a diameter of 7.7 mm or less, the processing region having a radius of curvature of 400 mm (R400) in the plano-convex polishing portion may be configured with a diameter of 1.21 mm to 1.39 mm. . With this configuration, in addition to the above-described effects, a highly stable crystal resonator having more excellent electrical characteristics can be provided. In particular, the CI value (series resonance resistance value) temperature characteristic can be greatly improved.

  FIGS. 6 to 11 show comparison and verification of the frequency temperature characteristic according to the diameter dimension of such a plano-convex polishing region and the CI value (series resonance resistance value) temperature characteristic at that time. As a common item, a disk shape having notches 24, 24 at both ends in one direction as shown in FIG. 4, an AT-cut quartz diaphragm having a diameter of 7.7 mm and a frequency of 10 MHz is used. Plano convex polishing parts 21 and 22 and a plano bevel polishing part 23 are formed only on one main surface of the quartz crystal vibration plate. The plano-convex polishing portion 21 has a radius of curvature of 400 mm (R400), the plano-convex polishing portion 22 has a radius of curvature of 150 mm (R150), and the bevel polishing portion 22 has a radius of curvature of 45 mm (R45). It is configured.

  FIG. 6 (graph 1) shows characteristic data when the diameter of the plano-convex polishing portion 21 is 1.03 mm, and FIG. 7 (graph 2) shows the diameter of the plano-convex polishing portion 21 as 1. FIG. 8 (Graph 3) shows characteristic data when the diameter of the plano-convex polishing portion 21 is 1.21 mm, and FIG. 9 (Graph). 4) shows characteristic data when the diameter of the plano-convex polishing portion 21 is 1.31 mm. In FIG. 10 (graph 5), the diameter of the plano-convex polishing portion 21 is 1.39 mm. FIG. 11 (Graph 6) shows the characteristic data when the diameter of the plano-convex polishing portion 21 is 1.45 mm. It shows the data.

  As is clear from these verification results, the diameter of the plano-convex polishing portion 21 is 1.21 mm (FIG. 8, approximately 15.7% as the diameter ratio of the quartz diaphragm) and 1.31 mm (FIG. 9, quartz vibration). CI value (series resonance) when compared with the case where the diameter ratio of the plate is about 17%) and 1.39 mm (FIG. 10, about 18% as the diameter ratio of the quartz diaphragm) is configured with other diameter dimensions. Resistance value) It is understood that the temperature characteristics are stable and more desirable for implementation.

  According to the present invention, it is possible to improve the CI value (series resonance resistance value) while dealing with the miniaturization of the crystal diaphragm, and it is also possible to reduce the amount of frequency fluctuation due to the drive level of the crystal diaphragm. It is possible to provide a highly stable crystal resonator capable of obtaining linear characteristics. In addition, parasitic oscillation due to the spurious vibration of the contour system hardly occurs, and the CI value (series resonance resistance value) temperature characteristics and the like can be improved.

The disassembled perspective view which shows embodiment of this invention. FIG. 2 is a plan view of the crystal diaphragm according to the first embodiment as viewed from the direction A in FIG. 1. Sectional drawing along the BB line of FIG. The top view of the crystal diaphragm of Example 2, and sectional drawing along the CC line. The graph which shows the DLD characteristic of the quartz diaphragm in the past and this invention. 3 is a graph 1 showing temperature characteristics of the crystal diaphragm of Example 2. 3 is a graph 2 showing temperature characteristics of the crystal diaphragm of Example 2. 3 is a graph 3 showing temperature characteristics of the crystal diaphragm of Example 2. 4 is a graph 4 showing temperature characteristics of the crystal diaphragm of Example 2. 5 is a graph 5 showing temperature characteristics of the crystal diaphragm of Example 2. 6 is a graph 6 showing temperature characteristics of the crystal diaphragm of Example 2.

  Next, embodiments of the present invention will be described with reference to the drawings, taking a crystal resonator as an example. 1 is an exploded perspective view showing an embodiment of the present invention, FIG. 2 is a plan view of the crystal diaphragm of Example 1 as viewed from the direction A in FIG. 1, and FIG. It is sectional drawing along the -B line. FIG. 4 is a plan view of the quartz crystal diaphragm according to the second embodiment and a cross-sectional view taken along the line C-C. In addition, in each form, about the same part, the same number is attached | subjected, and if there is no need in particular, a part of description is omitted.

  The base 1 as a whole has a low-profile long cylindrical shape, and has a structure in which metal lead terminals 11 and 12 are planted through a base body 10 mainly including a metal shell, and an insulating glass G is used as a base body. The metal lead terminals 11 and 12 are integrally formed integrally with each other by being partially filled.

  The metal lead terminals 11 and 12 have an elongated cylindrical shape, and metal supports 13 and 14 to be described later are attached to the tip portions of the inner leads so as to face each other by welding techniques (laser welding, spot welding, etc.).

  The metal supports 13 and 14 are, for example, nickel iron-based low thermal expansion alloys, which use a metal material whose thermal expansion coefficient is close to zero from about half the thermal expansion coefficient of quartz, specifically manufactured by Mitsubishi Materials Corporation. MA-INV36 <Fe-36Ni> (invar / amber), MA-S-INVER <Fe-32Ni-5Co> (super invar) and the like.

  Although not shown, such metal supports 13 and 14 are heated more than the metal support made of copper plating of 3 to 10 μm with respect to the front and back main surfaces of a metal base material such as invar having a thickness of 0.1 mm, for example. A metal film having high conductivity is formed. In addition, it has a lead connecting portion joined to the metal lead terminal, and a crystal diaphragm holding portion that holds the crystal diaphragm described later with a substantially U-shaped cross section. A metal brazing material reservoir portion of the metal support (not shown) in which the molten metal brazing material is accumulated in the quartz vibrating plate holding portion of the metal support and a part of the connection electrode of the quartz vibrating plate are exposed to the external surface. A window portion such as a cutout portion or a hole portion is formed. These metal brazing material reservoirs and windows are preferably used as marks for a quartz diaphragm holding unit which will be described later.

  As the metal brazing material for joining the metal supports 13 and 14 to the quartz crystal diaphragm 2 described later, for example, a gold alloy brazing material pellet such as AuGe, AuSn, Au or the like is used, and the metal brazing material reservoir portion of the metal support is used. It is good to attach with welding beforehand.

  As shown in FIG. 3, the crystal diaphragm 2 is formed of an AT-cut disk-shaped crystal diaphragm, and has a diameter of 7.7 mm and a frequency of 10 MHz. Only one main surface of the crystal diaphragm is used. Plano convex polishing parts 21 and 22 and a plano bevel polishing part 23 are formed. The plano-convex polishing portion 21 has a radius of curvature of 400 mm (R400), the plano-convex polishing portion 22 has a radius of curvature of 150 mm (R150), and the bevel polishing portion 23 has a curvature only on one main surface. It has a radius of 45 mm (R45). As described above, in Example 1 in which all the polishing portions are configured only on one main surface, if a processing upper plate in which one plano bevel polishing region and two plano convex polishing regions are integrated is prepared, Three polishing regions can be efficiently processed by one processing, and productivity can be improved. In addition, by using an AT-cut quartz diaphragm, it is easy to control the thickness system and the contour system spurious by processing the quartz diaphragm and to suppress the spurious, compared to the SC-cut quartz diaphragm. Quartz diaphragm processing technology has been established, and stable supply of members can be achieved, resulting in a cheaper and more stable quartz diaphragm. There is an advantage that it is easy to use as the time until the frequency stabilizes after being used as an OCXO and starting up.

  Excitation electrodes and extraction electrodes (not shown), connection electrodes for metal brazing material, and the like are formed on the front and back surfaces of the crystal diaphragm 2 by a method such as vacuum deposition or sputtering, and melted at the ends of the crystal diaphragm. A metal brazing material reservoir portion of a crystal diaphragm (not shown) in which the later metal brazing material is accumulated is also formed. Each of the electrodes 23 and 24 is made of an electrode material mainly composed of gold. For example, a gold electrode layer is formed on the upper surface of a base electrode layer of chromium or nickel. The metal brazing material connecting electrode and the metal brazing material reservoir portion are rotational axes obtained by rotating the plate surface by + 30 ° and −30 ° from the center point with respect to the Z ′ axis passing through the center point of the main surface of the crystal diaphragm. Of the four points where the ends of the quartz crystal plate intersect with each other, it is desirable to form them at two points facing each other to serve as marks for the metal support joints.

  Then, the metal brazing material connection electrode and the metal brazing material reservoir portion (mark of the support joint portion) of the crystal diaphragm 2 are positioned with respect to the window portion (mark of the quartz crystal plate holding portion) of the metal support holding portion. While aligning, the crystal diaphragm 2 on which the electrodes are formed is electromechanically joined to the metal supports 13 and 14 by a metal brazing material. In such a state, the base 1 on which the crystal diaphragm is mounted is covered with a lid (not shown) and hermetically sealed in a vacuum atmosphere to complete the final crystal unit.

  In the first embodiment, the disk-shaped crystal diaphragm 2 has been described as an example. However, as shown in FIG. 4, the plate from the center point with respect to the Z ′ axis passing through the center point of the main surface of the crystal diaphragm. Notches 24 and 24 perpendicular to any two of the four points where the rotation axis rotated by + 30 ° and −30 ° and the end of the crystal diaphragm intersect are formed. . The bevel polishing portion 23 is configured with a radius of curvature of 45 mm (R45) on both main surfaces of the crystal diaphragm. Since the crystal diaphragm of the second embodiment can be joined to the pair of metal supports at both end portions of the notches 24, 24, it is mounted at a size between the metal supports compared to the crystal diaphragm of the first embodiment. The restriction of the diameter size of the quartz crystal plate to be reduced is alleviated, and a quartz plate having a larger diameter can be arranged and bonded. Further, in Example 2 in which the convex polishing parts 21 and 22 are formed on only one main surface while the bevel polishing part 23 is formed on both main surfaces, the advantages of the plano convex polishing part and the bibevel polishing part Can have the advantages of. In other words, by constructing a plano-convex polishing part that mainly processes the vibration region of the quartz diaphragm, the design and position recognition of the thickest part (vertex part) of the finished quartz diaphragm is facilitated. Design and optimization of the formation position of the excitation electrode can be easily performed, and a quartz plate having excellent productivity can be obtained. In addition, by configuring the vibe bevel polishing portion that mainly processes the end portion outside the vibration region of the quartz diaphragm, the contour vibration mode can be more efficiently suppressed compared to the plano bevel polishing portion. Variations in the CI value (series resonance resistance value) of each crystal diaphragm can be suppressed, and adverse effects of chipping can be reduced.

  According to the above embodiment, the plano-convex polishing parts 21 and 22 having a two-stage curvature mainly for processing the vibration region of the crystal diaphragm 2 and the processing of the end portion outside the vibration region of the crystal diaphragm 2 are mainly used. In combination with the bevel polishing portion 23, the reduction of the energy confinement effect is eliminated while the size of the quartz diaphragm 2 is reduced, and the CI value (series resonance resistance value) characteristic and the CI value (series resonance resistance value) temperature are eliminated. The characteristics can be improved. Parasitic oscillation due to spurious vibration of the contour system can be made difficult to occur. Further, as the quartz diaphragm 2 is reduced in size, it is possible to improve the adverse effect caused by the fact that the energy confinement effect is excessively increased by forming only the plano-convex polishing unit 22 having a small curvature by the plano-convex polishing unit 21 having a large curvature. In addition, the amount of frequency fluctuation due to the driving level of the crystal diaphragm 2 is reduced, and linear and more stable electrical characteristics can be obtained. Since the polishing region is formed only on one main surface of the crystal diaphragm 2 as the plano-convex polishing parts 21 and 22, the design and position recognition of the thickest part (vertex part) of the completed crystal diaphragm 2 This makes it easy to optimize the frequency design and the excitation electrode formation position, and to obtain a crystal plate with excellent productivity. Further, by forming the bevel polishing portion 23 having a curvature, the thickness of the quartz diaphragm is continuously curved from the convex polishing portions 21 and 22 having two stages of curvature toward the end of the quartz diaphragm 2. Therefore, the spurious vibration of the contour system can be suppressed more efficiently.

  The plano-convex polishing portion includes a polishing portion 21 having a radius of curvature of 400 mm (R400) and a polishing portion 22 having a radius of curvature of 150 mm (R150). The bevel polishing portion 23 has a radius of curvature of 45 mm (R45). The area may be configured. In particular, if the crystal diaphragm 2 has a diameter of 7.7 mm or less, the plano-convex polishing portion 21 is configured to have a diameter of 1.21 mm to 1.39 mm, whereby a CI value (series resonance resistance value) temperature. The characteristics can be greatly improved.

  As described above, the CI value (series resonance resistance value) can be improved while adapting to the miniaturization of the crystal diaphragm 2, and the frequency fluctuation amount due to the drive level of the crystal diaphragm 2 can be reduced. It is possible to provide a highly stable crystal resonator capable of obtaining linear characteristics. In addition, parasitic oscillation due to spurious vibration of the contour system hardly occurs, and the CI value (series resonance resistance value) temperature characteristics and the like can be improved.

  In addition, the metal supports 13 and 14 are made of a nickel iron-based low thermal expansion alloy, and are configured by using “Invar”, “Super Invar”, etc. whose thermal expansion coefficient is close to zero from about half the thermal expansion coefficient of quartz. Therefore, the thermal expansion of the metal supports 13 and 14 hardly occurs due to the change of the external environment temperature, and stress due to the change of the external environment temperature is not applied from the metal supports 13 and 14 to the crystal diaphragm 2. Moreover, the stress with respect to secular change can be further suppressed. “Invar” and “Super Invar” are materials with high low thermal expansion as described above, but heat transmitted to the quartz diaphragm due to poor thermal conductivity and poor thermal followability when external heat is applied. However, the start-up characteristics tend to deteriorate. In the present invention, Cu plating (metal film M) having higher thermal conductivity than Invar and Super Invar is formed on the outer surface of the metal support, so that the crystal oscillator package body (with lid and Base 1) The Cu plating (metal film M) transmits the temperature to the crystal diaphragm 2 without delay with respect to the external temperature, and the temperature difference hardly occurs. As a result, while maintaining low thermal expansion, the thermal conductivity can be increased at the same time, and a desirable holding structure for a crystal unit for high stability can be obtained, and the aging characteristics and thermal followability of the crystal unit can be improved simultaneously and more effectively. It is possible to increase the frequency temperature characteristic more stably. The starting characteristics when a crystal resonator is used as the OCXO can also be improved. That is, it is possible to start up the crystal resonator in a shorter time after the crystal resonator is heated to a predetermined temperature in the thermostat and the frequency is stabilized.

  Further, since the metal film M is formed on the front and back main surfaces of the metal supports 13 and 14, there is no bias in thermal deformation as the whole metal support, and no excessive stress is applied to the crystal diaphragm 2. Preferred above. By using Cu plating as the metal film M, wettability is good when the metal brazing material is melted, and the joining force by the metal brazing material can be improved. Plating can be performed relatively inexpensively and easily using a commonly used plating bath, and a metal film having excellent heat conductivity can be formed. Stable heat transfer while reducing costs by forming Cu plating with a thickness of 3-10μm on a 0.1mm-thick metal base made of nickel iron-based low thermal expansion alloys such as Invar and Super Invar Thus, the low thermal expansion performance of the entire support and the adverse effects of unnecessary thermal stress can be eliminated. When the Cu plating is formed thinner than 3 μm, the heat conductivity is lowered. If the Cu plating is thicker than 10 μm, the risk of cracking of the plating increases due to bending of the metal support, etc., and the thermal expansion performance of the entire support is adversely affected, and unnecessary thermal stress is applied to the crystal diaphragm. The risk of becoming more likely to join increases. In particular, the thermal conductivity can be adjusted appropriately depending on the thickness of the Cu plating, and the hunting (overshoot) of the frequency of the crystal resonator is caused by forming the Cu plating with a thickness of 3 to 10 μm as described above. In addition, the holding member can be created under the condition that the heat transmitted to the quartz diaphragm is not delayed.

  Further, the metal brazing material is made of a gold-based alloy brazing material such as AuGe, AuSn, or Au, and the connection between an excitation electrode (not shown) formed on the front and back main surfaces of the quartz crystal plate 2, an extraction electrode, and the metal brazing material A gold electrode layer is formed on the upper surface of a base electrode layer of chromium or nickel whose main component is gold. For this reason, since the excitation electrode and the metal brazing material become a stable material in which deterioration of electrical characteristics such as oxidation does not easily occur, the aging characteristics can be further enhanced.

  In addition, a mark (metal brazing material connecting electrode or metal brazing material reservoir) on the metal support joint of the crystal diaphragm is provided on a mark (metal brazing metal reservoir / window) on the crystal support plate holding part of the metal support. By joining with the molten metal brazing material in the close state, it is possible to join each other in a state where accurate positioning is performed with respect to at least two points having no stress sensitivity among the end portions of the crystal diaphragm. That is, the stress applied to the quartz diaphragm 2 from the outside such as the metal supports 13 and 14 can be made stable, and the stress against the secular change can be suppressed.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof, and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not limited by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  The present invention can be applied to a piezoelectric vibration device such as a crystal resonator.

1 Base 10 Base body 11, 12 Lead terminal 13, 14 Metal support 2 Crystal diaphragm

Claims (3)

A thickness-slip quartz crystal plate formed in a disk shape,
A quartz vibrator having a plano-convex polishing portion having a two-stage curvature and a bevel polishing portion formed at an end of the quartz plate on one side of the quartz plate. 2. The crystal vibration according to claim 1, wherein the plano-convex polished portion includes a processing region having a curvature radius of 400 mm and a processing region having a curvature radius of 150 mm, and the bevel polishing portion includes a processing region having a curvature radius of 45 mm. Child. The diameter of the quartz diaphragm is 7.7 mm or less, and a processing region having a radius of curvature of 400 mm in the plano-convex polishing portion is configured to have a diameter of 1.21 mm to 1.39 mm. The crystal resonator according to claim 1 or claim 2.

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