JP5699747B2 - Crystal oscillator - Google Patents

Description

  The present invention relates to a crystal resonator and improves the structure of a crystal diaphragm.

  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, as shown in Patent Document 1, a pair of metal lead terminals are implanted in the metal base via an insulating material such as glass, and a pair of metal lead terminals are provided in the inner lead portion of the metal lead terminal. Metal flat plate support members are attached to face each other. 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 JP 2010-177976 A

  As the above-described crystal plate for high stability, it is the mainstream to perform plano convex processing. Although it is necessary to design a quartz crystal plate that has been convex-processed with a reduction in size of the crystal unit, there is a problem that a CI value (series resonance resistance value) increases if the crystal plate is designed to be small. . 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.

  Therefore, a quartz diaphragm as shown in Patent Document 2 has been proposed, but it takes time to process the quartz diaphragm into a multi-stage planoconvex shape having different radii of curvature, which increases costs. Moreover, even if the quartz diaphragm is processed into a multi-stage plano-convex shape with different radii of curvature to improve the characteristics, it is technically difficult to achieve an energy trap of the main vibration completely. May occur.

  The present invention has been made to solve the above-described problems, and provides a highly stable crystal resonator having superior electrical characteristics and capable of suppressing spurious vibration while being inexpensive and compatible with downsizing. Objective.

Therefore, the crystal resonator of the present invention has a thickness-sliding crystal diaphragm formed in a substantially disc shape, and a planar surface polishing process having two or more curvature portions having different curvature radii on one surface of the crystal diaphragm. A plano-convex polishing portion having the largest radius of curvature at the center of the quartz plate , and a plano-convex grinding portion having the smallest radius of curvature at the end of the quartz plate, From the center of the quartz diaphragm toward the end of the quartz diaphragm, the radius of curvature of each plano-convex polished portion is formed sequentially smaller, and the surface roughness of each plano-convex polished portion is sequentially formed rough. The surface roughness of the plano-convex polished portion having the largest radius of curvature at the center of the quartz diaphragm is formed to 5 nm to 500 nm by an average roughness (Ra) measurement method, Characterized in that formed on 5μm~50μm was crystallized smallest Plano Convex polishing part surface roughness average roughness of the curvature radius of the end portion of the diaphragm (Ra) measurement method.

  With the above configuration, a plano-convex polishing portion having two or more curvature portions having different curvature radii is formed on one side of the crystal diaphragm, and the plano-convex polishing having the largest curvature radius is provided at the center of the crystal diaphragm. By having a machined part and a plano-convex polished machined part with the smallest radius of curvature at the end of the quartz diaphragm, the reduction of the energy confinement effect is eliminated while accommodating the miniaturization of the quartz diaphragm. The CI value (series resonance resistance value) characteristic of vibration and the CI value (series resonance resistance value) temperature characteristic can be improved. In addition, with the downsizing of the quartz diaphragm, it is possible to improve the adverse effect caused by the formation of only the plano-convex polished portion having a small curvature and the excessive energy confinement effect by the plano-convex polished portion having a large curvature. In particular, the amount of frequency fluctuation due to the driving level of the quartz diaphragm is reduced, and linear and more stable electrical characteristics can be obtained. As a result, the resonance level of the main vibration can be improved and stabilized.

  In addition, because the polishing area is formed only on one main surface (single side) of the quartz diaphragm as a plano-convex grinding part, the design and position recognition of the thickest part (vertex part) of the completed quartz diaphragm is possible. This makes it easy to optimize the frequency design and excitation electrode forming position, and to obtain a crystal plate with excellent productivity. Note that a crystal resonator that uses an overtone having a small vibration region as a main vibration is more preferable than a crystal resonator that uses a fundamental wave as a main vibration in terms of taking advantage of such advantages.

  Further, from the center of the quartz diaphragm toward the end of the quartz diaphragm, the radius of curvature of each plano-convex polishing portion is formed sequentially small, and the surface roughness of each plano-convex polishing portion is sequentially formed rough. Therefore, the surface roughness of the curvature portion at the end portion of the quartz crystal plate can be formed to be rougher than the curvature portion at the center of the quartz plate. In particular, the plano-convex polishing portion at the end of the crystal diaphragm that has a small radius of curvature and takes a long time for polishing but does not adversely affect the main vibration can be processed only by rough polishing, so that the processing time can be dramatically reduced. In addition, it is possible to suppress spurious existing in the vicinity of the end portion of the crystal diaphragm by the plano-convex polishing processing portion at the end portion of the crystal diaphragm having a rough surface processed by the rough polishing. Moreover, the joining strength can also be raised simultaneously by joining the plano-convex grinding | polishing processing part and holding member of the crystal diaphragm edge part with a rough surface roughness with a conductive joining material.

  In the present invention, a plano-convex polishing part having three or more curvature parts having different curvature radii may be configured. In general, the quartz vibration plate can be sharply polished by rough polishing, and the polishing time can be shortened. However, the residual processing stress on the crystal vibration plate increases, and processing strain may remain as the crystal vibration plate. On the other hand, by having three or more curvature portions having different curvature radii, the plano-convex polished portion having the largest curvature radius at the center of the quartz diaphragm and the smallest curvature radius at the end of the quartz diaphragm. These intermediate plano-convex polishing parts are sequentially formed between the plano-convex polishing parts. For this reason, it is formed rough stepwise, and the influence of the processing distortion of the crystal diaphragm can be reduced. In particular, since processing strain that is likely to occur at the end of the quartz diaphragm is not directly transmitted to the center of the quartz diaphragm, adverse effects on the main vibration can be suppressed, which is a more preferable form for suppressing spurious vibration.

  According to the present invention, it is possible to improve the CI value (series resonance resistance value) while reducing the size of the quartz diaphragm at a low cost, and to reduce the frequency fluctuation amount due to the driving level of the quartz diaphragm. It is possible to provide a highly stable crystal resonator capable of obtaining linear characteristics. Further, parasitic oscillation due to spurious vibrations hardly occurs, and CI value (series resonance resistance value) temperature characteristics and the like can be improved.

1 is an exploded perspective view of a crystal resonator showing an embodiment of the present invention. 1 is a plan view of a crystal diaphragm showing Example 1 of the present invention. Sectional drawing along the AA line of FIG. FIG. 6 is a plan view of a crystal diaphragm showing a second embodiment of the present invention. Sectional drawing along the BB line of FIG.

  Next, embodiments of the present invention will be described with reference to the drawings, taking a crystal resonator as an example. FIG. 1 is an exploded perspective view of a crystal resonator showing an embodiment of the present invention, FIG. 2 is a plan view of a crystal diaphragm showing Example 1 of the present invention, and FIG. 3 is a line AA in FIG. FIG. FIG. 4 is a plan view of a crystal diaphragm showing Embodiment 2 of the present invention, and FIG. 5 is a cross-sectional view taken along the line BB of FIG. 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.). For this reason, when mounting the metal support on the metal lead terminal, it can be mounted horizontally and stably without tilting, and the welding area is also expanded, so that the joint strength is improved and the reliability when welding the metal support to the metal lead terminal is improved. Will improve dramatically.

  The metal supports 13 and 14 are, for example, nickel iron-based low thermal expansion alloys having a thermal expansion coefficient close to zero from about half the thermal expansion coefficient of quartz, or a metal material that approximates the thermal expansion coefficient of quartz. If the material is manufactured by Mitsubishi Materials Corporation, MA-INV36 <Fe-36Ni> (Invar / Amber), MA-S-INVER <Fe-32Ni-5Co> (Super Invar), MA902 <Fe-42Ni-Cr-Ti> (NI-SPAN-C) 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.

  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. Note that the present invention is not limited to the configuration of the above-described embodiment, but the tip of the inner lead of the lead terminal is exemplified by a nail head shape, but the present invention can also be applied to a normal inner lead shape. Further, the bonding configuration is not limited to that using a metal brazing material, and a conductive resin adhesive may be used, or a combination of a metal brazing material and a conductive resin adhesive may be used.

  The crystal diaphragm 2 is made of, for example, an AT-cut or SC-cut substantially disk-shaped thickness-sliding crystal diaphragm, and has a third overtone frequency of 5 MHz. Further, on one main surface (one surface) of the quartz diaphragm, a plano-convex polishing portion having two or more curvature portions having different curvature radii is formed. In the first embodiment, two plano-convex polishings are performed in which a plano-convex polishing part 21 having the largest radius of curvature at the center of the crystal diaphragm 2 and a plano-convex polishing part 22 having the smallest radius of curvature at the end of the crystal diaphragm 2. It has a processing part. Furthermore, the radius of curvature of the plano-convex polishing portion is formed in order from the plano-convex polishing portion 21 at the center of the crystal plate 2 toward the plano-convex polishing portion 22 at the end of the crystal plate 2.

  Specifically, the plano-convex polishing portion 21 is configured with a radius of curvature of 400 mm (R400), and the plano-convex polishing portion 22 is configured with a radius of curvature of 150 mm (R150). Note that orientation flats 24 may be formed on both ends of the crystal diaphragm 2 along a specific axis, if necessary. Further, although not shown in the drawings, a bevel polishing portion (for example, one having a radius of curvature of 45 mm (R45)) may be formed at the ends of both main surfaces of the crystal diaphragm 2 as necessary.

  Further, the surface roughness of each plano-convex polishing portion is gradually increased from the plano-convex polishing portion 21 at the center of the crystal plate 2 toward the plano-convex polishing portion 22 at the end of the crystal plate 2. . In Example 1, the surface roughness of the curvature portion of the plano-convex polishing portion 21 is specifically formed to be about 5 nm to 500 nm by an average roughness (Ra) measurement method, and the surface of the curvature portion of the plano-convex polishing portion 22 is formed. The roughness is formed to about 5 μm to 50 μm by an average roughness (Ra) measurement method.

  On the front and back surfaces of the quartz vibrating plate 2, an excitation electrode and an extraction electrode (not shown), a connection electrode between the metal brazing material, and the like are formed by a method such as vacuum vapor deposition or sputtering. The crystal diaphragm 2 on which the electrodes are formed is electrically and mechanically joined to the metal supports 13 and 14 with a metal brazing material (not shown). 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.

  The crystal diaphragm 2 is formed of a substantially disc-shaped thickness-sliding crystal diaphragm having an AT cut or SC cut, for example, and has a fundamental frequency of 10 MHz. In the first embodiment, the quartz diaphragm 2 having two plano-convex polishing portions has been described as an example. However, in the second embodiment, as shown in FIG. A large plano-convex polishing portion 21, a plano-convex polishing portion 22 having the smallest radius of curvature at the end of the crystal diaphragm 2, and a plano-convex polishing portion 23 having an intermediate radius of curvature therebetween, Convex polishing part. Further, as in the first embodiment, the plano-convex polishing part 21 to the plano-convex polishing part 23 at the center of the crystal diaphragm 2 and the plano-convex polishing part at the end of the crystal diaphragm 2 from the plano-convex polishing part 23 to the plano-convex polishing part 23. 22, the radius of curvature of the plano-convex polishing portion is formed so as to be sequentially smaller.

  Specifically, the plano-convex polishing portion 21 is configured with a radius of curvature of 400 mm (R400), the plano-convex polishing portion 23 is configured with a radius of curvature of 200 mm (R200), and the plano-convex polishing portion 22 is configured with a radius of curvature of 100 mm (R100). ). Note that orientation flats 24 may be formed on both ends of the crystal diaphragm 2 along a specific axis, if necessary. Further, although not shown in the drawings, a bevel polishing portion (for example, one having a radius of curvature of 45 mm (R45)) may be formed at the ends of both main surfaces of the crystal diaphragm 2 as necessary.

  Further, the plano-convex polishing portion 21 at the center of the crystal diaphragm 2 is shifted from the plano-convex polishing portion 23 to the plano-convex polishing portion 23 at the end of the crystal diaphragm 2. The surface roughness of the convex polishing process part is formed so as to be rough. In Example 2, the surface roughness of the curvature part of the quartz diaphragm 2 which is specifically the plano-convex polishing part 21 is formed to about 5 nm to 500 nm by an average roughness (Ra) measurement method, and the plano-convex polishing part The surface roughness of the curvature portion of 23 is formed to about 500 nm to 5 μm by the average roughness (Ra) measurement method, and the surface roughness of the curvature portion of the plano-convex polished portion 22 is 5 μm by the average roughness (Ra) measurement method. It is formed to about ˜50 μm.

  According to the first and second embodiments, the reduction of the energy confinement effect is eliminated and the CI value (series resonance resistance value) characteristics and the CI value (series resonance resistance value) of the main vibration are eliminated while corresponding to the miniaturization of the crystal diaphragm 2. ) Temperature characteristics can be improved. Further, as the quartz diaphragm 2 is reduced in size, it is possible to improve the adverse effect caused by the formation of only the plano-convex polished portion having a small curvature and the excessive energy confinement effect by the plano-convex polished portion having a large curvature. In particular, the amount of frequency fluctuation due to the driving level of the quartz diaphragm is reduced, and linear and more stable electrical characteristics can be obtained. As a result, the resonance level of the main vibration can be improved and stabilized.

  Further, since the polishing region is formed only on one main surface (one side) of the quartz diaphragm as the plano-convex grinding portions 21, 22, and 23, the thickest portion (vertex portion) of the completed quartz diaphragm 2 is formed. The design and position recognition are facilitated, the frequency design and the formation position of the excitation electrode can be easily performed, and the crystal diaphragm 2 having excellent productivity can be obtained. It should be noted that the crystal resonator using the third-order overtone having a small vibration region as the main vibration as in the first embodiment has such a merit as compared with the crystal resonator 2 using the fundamental wave as the main vibration as in the second embodiment. Easy to use.

  In addition, the surface roughness of the plano-convex polishing portion (curvature portion) 22 at the end of the quartz diaphragm can be made rougher than the plano-convex polishing portion (curvature portion) 21 at the center of the crystal diaphragm 2. In particular, since the curvature radius is small and the polishing process takes time, but the plano-convex polishing process portion 22 at the end of the quartz diaphragm that hardly causes adverse effects on the main vibration can be processed only by rough polishing, the processing time can be drastically reduced. In addition, the surface roughness processed by the rough polishing (average roughness (Ra) measurement method: 5 μm to 50 μm) is near the end of the crystal diaphragm 2 by the plano-convex polishing section 22 at the end of the crystal diaphragm. The spurious which exists in can be suppressed. Further, by joining the plano-convex polished portion 22 at the end of the crystal diaphragm having a rough surface and the holding member (metal supports 13, 14) with a conductive bonding material (metal brazing material, etc.), the bonding strength is simultaneously increased. be able to.

  Further, as in the second embodiment, by having three or more curvature portions (plano convex polishing portions 21, 22, and 23) having different curvature radii, the plano convex polishing having the largest curvature radius is provided at the center of the crystal diaphragm 2. These intermediate plano-convex polishing parts 23 are sequentially formed between the processing part 21 and the plano-convex polishing part 22 having the smallest radius of curvature at the end of the crystal diaphragm 2. For this reason, it is formed stepwise and rough, and the influence of the processing distortion of the crystal diaphragm 2 can be reduced. In particular, since processing strain that is likely to occur at the end of the quartz diaphragm 2 is not directly transmitted to the center of the quartz diaphragm 2, adverse effects on the main vibration can be suppressed, which is a more preferable form for suppressing spurious vibration.

  According to the above embodiment, 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 applied from the metal supports 13 and 14 to the crystal diaphragm 2. Disappear. Stress against aging can be further suppressed. By forming Cu plating with high thermal conductivity on the external surface of the metal support, Cu plating (metal film) against the temperature outside the package body (lid and base 1) of the crystal unit due to changes in the external environmental temperature M) transmits the temperature to the crystal diaphragm 2 without delay, 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.

  In addition, since the metal film is formed on the front and back main surfaces of the metal supports 13 and 14, there is no bias in the thermal deformation of the entire metal support, and no extra stress is applied to the crystal diaphragm 2. Is preferable. In particular, by using Cu plating as the metal film, 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.

  The crystal unit of the present invention is not limited to a metallic package having lead terminals as in the above embodiment, but is a ceramic laminate in which a ceramic insulating material such as alumina and a conductive material such as tungsten or molybdenum are appropriately laminated. It may be a surface mount type package body using a substrate.

  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 (1)

A quartz crystal,
There is a thickness-slip quartz crystal plate formed in a substantially disk shape,
On one side of the crystal diaphragm, a plano-convex polishing part having two or more curvature parts with different curvature radii is formed,
A plano-convex polishing portion having the largest radius of curvature at the center of the quartz plate , and a plano-convex polishing portion having the smallest radius of curvature at the end of the quartz plate,
From the center of the quartz diaphragm toward the end of the quartz diaphragm, the radius of curvature of each of the plano-convex polishing parts is sequentially reduced, and the surface roughness of each of the plano-convex polishing parts is successively increased. Do Ri,
The surface roughness of the plano-convex polished portion with the largest radius of curvature at the center of the quartz diaphragm is formed to 5 nm to 500 nm by an average roughness (Ra) measurement method
A crystal resonator in which the surface roughness of a polished portion of the plano-convex having the smallest radius of curvature at the end of the crystal diaphragm is formed to 5 μm to 50 μm by an average roughness (Ra) measurement method .

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