JP2014011601A - Crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal oscillator for high stability that has excellent aging characteristics and higher reliability.SOLUTION: There is provided a crystal oscillator comprising a base 1 provided with two metal lead terminals implanted penetrating and having plate-like metal supports 13, 14, and a plate-like crystal oscillation plate 2 mounted on the metal supports and electromechanically joined through conductive resin adhesives 4. The metal supports are each made of a nickel iron-based alloy with low thermal expansivity, and a through hole is formed in a joint part of the metal support; and the conductive resin adhesives are made of polyether sulfone resin and the joint part of the metal support and an end of the crystal oscillation plate are joined while the through hole K of the metal support is filled with the conductive resin adhesive.

Description

  The present invention relates to a crystal resonator and improves the holding structure of the 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 formed in a convex and flat disk shape, and excitation electrodes and extraction electrodes from the excitation electrodes 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.

  Patent Document 1 proposes an improved configuration for a crystal structure holding structure for high stability using a metal brazing material such as AuGe (gold-germanium) that can obtain good aging characteristics used in such OCXO. Yes.

JP 2006-186839 A JP 2009-225427 A

  When joining using a metal brazing material such as AuGe (gold-germanium), each was positioned and fixed while being interposed between a metal support and a quartz crystal vibration plate using a solid metal brazing material pellet or a metal brazing ball. The metal brazing material is melted and joined by heating in the state. However, in the configuration of Patent Document 1, when the crystal support plate holding part of the metal support and the connection electrode of the crystal plate are melt-bonded to each other via the metal brazing material, the metal brazing material is excited by the heating state. In some cases, the metal brazing material diffused toward the metal support and interposed between the crystal support plate holding portion of the metal support and the connection electrode of the crystal vibration plate may be in an insufficient state. For this reason, electromechanical joint failure between the metal support and the quartz diaphragm may occur. In addition, the diffusion of the metal brazing material to the excitation electrode has caused a problem that the electrical characteristics of the crystal unit are deteriorated. In particular, in a crystal unit for high stability, the electrode formed on the crystal diaphragm is made of an electrode material mainly composed of gold, and a gold alloy brazing material such as AuGe (gold-germanium) is used. The adverse effect due to diffusion of the brazing material is large.

  One approach to solving these problems is to use only a heat-resistant conductive resin adhesive, but the coefficient of thermal expansion is higher than that of a typical crystal unit for high stability. It is necessary to use a special material with a low value. The combination of the support material and the conductive adhesive that achieves this purpose cannot secure the adhesive strength, so that the conductive resin adhesive peels off after joining, resulting in a decrease in conduction performance or impact resistance. was there.

  The present invention was made in order to solve the above-mentioned problems, and suppresses the interface peeling of the conductive resin adhesive from the metal support, and the bonding property when bonding the metal support and the crystal diaphragm is good. An object of the present invention is to provide a highly reliable crystal resonator for high stability with good aging characteristics.

  Therefore, the crystal resonator according to the present invention is electrically conductive at a base provided with a pair of metal lead terminals, a pair of plate-like metal supports provided on the metal lead terminals, and a joint between the pair of metal supports. It has a plate-shaped crystal diaphragm bonded via a resin adhesive, and is arranged on the inner side of the pair of metal lead terminals with the plate surfaces of the pair of metal support facing each other The crystal diaphragm is disposed between the plate surfaces of the joint portions of the pair of metal supports in a state where the plate surface of the crystal diaphragm is orthogonal to the plate surfaces of the joint portions of the pair of metal supports. The metal support is made of a nickel-iron based low thermal expansion alloy, a through hole is formed in a joint portion of the metal support, and the conductive resin adhesive is made of polyethersulfone. Made of resin, Serial wherein the state which has entered into the through hole of the metal support formed by joining the ends of the quartz plate and the joint portion of the metal support.

  With the above configuration, the metal support is composed of a nickel iron-based low thermal expansion alloy and the conductive resin adhesive is composed of a polyether sulfone resin. The thermal expansion and the thermal expansion of the conductive resin adhesive rarely cause a difference in thermal expansion with respect to the quartz diaphragm. Therefore, the stress due to the change in environmental temperature is applied to the quartz diaphragm from the metal support and the conductive resin adhesive. Giving is suppressed, and stress against secular change can be further suppressed. In addition, it is a material that has high heat resistance as a conductive resin adhesive and is unlikely to generate gas after heat curing. Can be further suppressed. Furthermore, a through hole is formed in the joint portion of the metal support, and the joint portion of the metal support and the end portion of the crystal diaphragm are joined to the through hole with a part of the conductive resin adhesive entering the inside. Therefore, the anchor effect is generated, and the conductive resin adhesive is prevented from peeling off from the metal support. The bond strength between the metal support and the quartz diaphragm is increased, and the impact resistance can be improved while maintaining the conduction performance against aging. In addition, unnecessary excess conductive resin adhesive other than the bonding of the metal support and the crystal diaphragm is absorbed through the through-hole, and therefore, an unnecessary conductive resin adhesive on the plate surface that is the vibration region of the crystal diaphragm. No wraparound or protrusion will occur, and the characteristics of the quartz diaphragm will not be degraded. The above-mentioned merit is that the crystal diaphragm is disposed between the plate surfaces of the pair of metal support joints, particularly in a state where the plate surface of the crystal support plate is orthogonal to the plate surface of the metal support joint portion. This is effective for holding configurations. With such a holding structure, a part of the crystal diaphragm is not mounted on a part of the upper surface of the metal support, so that the tensile shrinkage stress on the crystal diaphragm is symmetrical from both sides. In addition, although the bending stress is hardly applied to the inside of the quartz diaphragm, the weight of the quartz diaphragm is supported only by the conductive resin adhesive. Therefore, by combining the features of the present invention with a holding structure in which the plate surfaces of the quartz crystal plate are orthogonally arranged, it is possible to obtain a holding structure in which it is desirable to further improve impact resistance performance while achieving high stability. . That is, it is possible to provide a highly stable crystal structure holding structure for high stability with good aging characteristics.

  A copper film may be formed on the outer surface of the metal support. With this configuration, in addition to the above-described effects, the adhesive strength with the polyether sulfone resin is increased, and the conductive resin adhesive is prevented from interfacial peeling from the metal support. In addition, even when nickel-iron based low thermal expansion alloys that tend to have relatively low thermal conductivity are used, a copper film with higher thermal conductivity is formed on the external surface of the metal support. The copper film transmits the temperature to the crystal diaphragm without delay with respect to the temperature outside the package body (lid and base) of the crystal unit due to the temperature change, and the temperature difference hardly occurs. By combining such configurations, the aging characteristics and thermal followability of the crystal resonator can be improved simultaneously and more effectively, and more stable frequency-temperature characteristics can be obtained. 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.

  According to the present invention, the conductive resin adhesive is prevented from interfacial debonding from the metal support, the bonding property when the metal support and the quartz diaphragm are bonded is good, and the aging characteristics are good. A crystal resonator can be provided.

The disassembled perspective view which shows embodiment of this invention. The front view which shows the state which assembled FIG. Sectional drawing along the AA line of FIG. The enlarged view of the junction part of FIG. The disassembled perspective view which shows other embodiment of this invention.

  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 front view of the assembled state of FIG. 1, FIG. 3 is a cross-sectional view taken along line AA of the front view of FIG. FIG. 4 is a partially enlarged view of FIG. 3. FIG. 5 is an exploded perspective view showing another embodiment. 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.

-Embodiment of the present invention-
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. For example, the tip portions 11a and 12a on the inner side of the upper part of the base are formed in a nail head shape having a wide width and a flat upper part. Metal supports 13 and 14 to be described later are attached to the tips of the inner leads so as to oppose each other by a welding method (laser welding, spot welding, etc.), and the plates of the crystal support plate joint portions 132 and 142 of the metal support to be described later. They are arranged with their faces facing each other. 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 expanded, so that the joint strength is improved and the reliability when welding the metal support to the metal lead terminal is increased. Will improve dramatically.

The metal supports 13 and 14 are, for example, plate-shaped members having a substantially L-shaped cross section, and are nickel iron-based low thermal expansion alloys, with a thermal expansion coefficient parallel to the crystal Z ′ axis (0.8 * 10 ⁻⁵ / K). ) Less than low thermal expansion metal material. Specifically, if manufactured by Mitsubishi Materials Corporation, MA-INV36 <Fe-36Ni> (invar / amber, coefficient of thermal expansion (0.5-2 * ^10-6 / K)), MA-S-INVER <Fe --32Ni-5Co> (Super Invar, thermal expansion coefficient ^{(0~1.5 * 10 -6 / K)} ), MA902 <Fe-42Ni-Cr-Ti> (NI-SPAN-C, thermal expansion coefficient (6.8 * 10 ^{- 6} / K)) and the like. Such metal supports 13 and 14 include lead connection portions 131 and 141 that are joined to the inner end portions 11a and 12a of the metal lead terminals, and crystal diaphragm joint portions 132 and 142 that hold the crystal diaphragm 2. have. A plurality of through holes K are formed in the crystal diaphragm joint portions 132 and 142. In this embodiment, for example, about 30 circular ones having a diameter of about 0.15 mm are formed.

  The crystal diaphragm 2 is made of, for example, an SC cut crystal diaphragm, and is configured in a planar disk shape that has been subjected to plano convex polishing. Excitation electrodes 25 and 26, extraction electrodes 27 and 28, and connection electrodes 23 and 24 that are end electrodes of the extraction electrodes 27 and 28 are formed on the front and back main surfaces of the quartz crystal diaphragm 2. These electrodes are made of an electrode material mainly composed of gold. For example, an Au (gold) electrode layer is formed on the upper surface of a base electrode layer of Cr (chromium) or Ni (nickel). In addition, the Z ′ axis passing through the center point O of the main surface of the quartz crystal plate and the end of the quartz crystal plate cross each other, and arc-shaped notches (orientation flats) are respectively formed at the ends of the two opposing points. F1 and F2 are formed. In the vicinity region including the notches F1 and F2, a rough surface region (not shown) having a surface roughness of about 5 μm is formed by, for example, a diamond # 600 grindstone. The connection electrodes 23 and 24 are formed on the upper surface of the rough surface region, and the conductive resin adhesive 4 described later is bonded to the upper portion of the rough surface region, thereby further improving the bonding strength. Contributing to The rough surface area is not limited to a grindstone, and may be configured by other methods such as etching. The rough surface region is not limited to the region formed in the vicinity region including the orientation flat, and may be formed only in the end surface region of the orientation flat.

  The conductive resin adhesive 4 is made of, for example, a polyether sulfone resin containing a metal powder such as silver and has a heat resistance temperature of 460 ° C. or higher according to a thermal decomposition temperature measurement method. For this reason, the optimal conductive resin adhesive 4 having a high heat-resistant temperature, hardly causing a difference in thermal expansion and expansion with respect to the quartz diaphragm 2 and generating less gas after heat curing is obtained.

  The conductive resin adhesive 4 made of polyethersulfone resin is provided on the upper portion of the rough surface region formed in the adjacent region including the notches F1 and F2 of the crystal diaphragm 2 and on the connection electrodes 23 and 24. Is applied, and the quartz diaphragm 2 in which the conductive resin adhesive 4 is bonded to the metal supports 13 and 14 is mounted. At this time, in the state where the plate surface of the crystal diaphragm 2 is orthogonal to the plate surface of the crystal support plate joints 132 and 142 of the metal support, the plate surface of the crystal support plate joints 132 and 142 of the metal support is between A crystal diaphragm 2 is disposed. The base 1 (pre-sealing crystal resonator) before hermetic sealing, in which the conductive resin adhesive 4 and the crystal diaphragm 2 are attached to the crystal support plate joints 132 and 142 of the metal support, is carried into a heating furnace. . For example, a high-vacuum annealing furnace is used as the heating furnace, and the entire pre-sealing crystal resonator (base) is heated in a vacuum atmosphere to cure the conductive resin adhesive 4. As described above, as shown in the cross-sectional views of FIGS. 3 and 4, the metal supports 13 and 14 and the connection electrodes 23 and 24 of the crystal diaphragm are joined together electrically and mechanically through the conductive resin adhesive 4. . Moreover, since a part of the conductive resin adhesive 4 has entered the insides of the plurality of through holes K of the metal support, an anchor effect is generated, and the conductive resin adhesive 4 is prevented from peeling off from the metal support. .

  The crystal unit of the embodiment of the present invention is completed by covering the base crystal unit with a lid (not shown) and sealing hermetically in, for example, a vacuum atmosphere.

  According to the above embodiment, the thermal expansion of the metal supports 13 and 14 and the thermal expansion of the conductive resin adhesive 4 are hardly caused by the change in the external environment temperature, so that the thermal expansion difference with respect to the quartz crystal plate 2 is hardly generated. Since the stress due to the change in the environmental temperature is not applied from 14 to the quartz diaphragm 2, the stress due to the change in the ambient temperature is applied from the metal supports 13 and 14 and the conductive resin adhesive 4 to the quartz diaphragm 2. Is suppressed, and stress against secular change can be further suppressed. In addition, since polyethersulfone is used as the conductive resin adhesive 4, it is a material having high heat resistance and hardly generating gas after heat curing. Is also suppressed, and changes in characteristics with respect to aging can be further suppressed. Further, a through hole K is formed in the crystal support plate bonding portions 132 and 142 of the metal support, and the crystal support plate bonding portion 132 of the metal support is in a state where a part of the conductive resin adhesive 4 enters the inside of the through hole K. , 142 and the upper portion of the rough surface region formed in the adjacent region including the cutout portions F1, F2 of the crystal diaphragm 2 and the upper portion of the connection electrodes 23, 24 are joined, so that an anchor effect is generated and conductive. The adhesive resin adhesive 4 is prevented from peeling off from the metal supports 13 and 14. The adhesive strength between the metal supports 13 and 14 and the quartz diaphragm 4 is increased, and the impact resistance performance can be enhanced while maintaining the conduction performance against aging. In addition, the unnecessary surplus conductive resin adhesive 4 other than the joining of the metal supports 13 and 14 and the crystal diaphragm 4 is absorbed through the through-hole K, so that the plate surface (the vibration region of the crystal diaphragm 4) ( The unnecessary conductive resin adhesive 4 does not wrap around or protrude from the excitation electrodes 25, 26, etc., and the characteristics of the quartz diaphragm 2 are not deteriorated. The above-described merits are, in particular, in the state where the plate surface of the crystal diaphragm 2 is orthogonal to the plate surface of the crystal support plate joints 132 and 142 of the metal support, the crystal support plate joints 132 and 142 of the metal support. This is effective for a holding configuration in which the crystal diaphragm 2 is disposed between the two plate surfaces, that is, a holding configuration in which a part of the crystal plate 2 is not in surface contact with the surfaces of the crystal support plate joint portions 132 and 142 of the metal support. That is, it is possible to provide a highly stable crystal structure holding structure for high stability with good aging characteristics.

-Other embodiments of the present invention-
Next, the configuration of a crystal resonator according to another embodiment of the present invention will be described with reference to FIG. In the embodiment of FIG. 5, only a part of the configuration of the metal supports 13 and 14 is different from the above embodiment, and the basic configuration is the same. Therefore, the same parts are denoted by the same reference numerals, a part of the description is omitted, and only the differences are described. 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. Is used. A metal film M having a higher thermal conductivity than the metal support is formed on the outer surfaces of the metal supports 13 and 14. More specifically, the metal film M having higher thermal conductivity than the metal supports 13 and 14 made of Cu plating (copper film) of 3 to 10 μm is formed on the front and back main surfaces of a metal base material such as Invar having a thickness of 0.1 mm. did.

  With such a configuration, the metal supports 13 and 14 hardly cause thermal expansion due to a change in environmental temperature, or a difference in thermal expansion between the crystal diaphragm 2 and the metal supports 13 and 14 hardly occurs. Stress from changes in the environmental temperature is not applied from the supports 13 and 14 to the quartz diaphragm 2, and stress due to secular change can be further suppressed. That is, the aging characteristic can be further enhanced. In addition, the Cu-plated (copper film) metal film M increases the adhesive strength with the polyethersulfone resin, and the conductive resin adhesive 4 is prevented from being peeled off from the metal supports 13 and 14. Further, even when a nickel iron-based low thermal expansion alloy having a relatively low thermal conductivity is used, a Cu-plated (copper film) metal film M is formed on the outer surfaces of the metal supports 13 and 14. Thus, the metal film M of the Cu plating (copper film) transmits the temperature to the crystal diaphragm 2 without delay with respect to the temperature outside the package body (lid and base) of the crystal unit due to the change of the environmental temperature, and the temperature difference is It rarely happens. As a result, more stable frequency temperature characteristics can be obtained. Further, when a crystal resonator is used as the OCXO, it is possible to start the crystal resonator in a short period of time until the crystal resonator is heated to a predetermined temperature in the thermostat and the frequency is stabilized (improvement of start-up characteristics).

  When forming such a metal film M, it is more preferable to form it on the front and back main surfaces of the metal supports 13 and 14. This is because the metal film M is formed on the front and back main surfaces of the metal supports 13 and 14 so that the thermal deformation of the metal support as a whole is not biased, and no excessive stress is applied to the crystal diaphragm 2. . The effect of forming the metal film M is particularly effective for a highly stable crystal resonator that is hermetically sealed in a vacuum atmosphere. When hermetically sealed in a vacuum atmosphere, the temperature difference with respect to the external environment is not affected by radiant heat from the outside of the package body, and the effect of only heat transfer via the metal lead terminals 11 and 12 and the metal supports 13 and 14 is increased. The benefits of the metal film M that increases thermal conductivity are particularly likely to occur.

  Further, Cu plating is preferable as the metal film M having high thermal conductivity. By using Cu plating, it is possible to select an optimum material desirable for a highly stable crystal resonator capable of obtaining the above-described effects. In other words, it is a metal material with extremely high thermal conductivity that can be stably supplied at a lower price than other noble metals with high thermal conductivity such as Au (gold) and Ag (silver), and Cu plating is also used for general purposes. Therefore, it can be formed relatively inexpensively and easily. Further, since Cu can be processed with the same etching solution as Invar and the like, a support material with high processability can be obtained by combining Cu and Invar or Super Invar. When the metal film M is formed by Cu plating, it is more desirable to form the film thickness to about 3 to 10 μm. By setting the Cu plating film thickness in this way, it is possible to maintain stable heat transfer while suppressing costs, and to maintain the low thermal expansion performance of the entire support and to eliminate the adverse effects of unnecessary thermal stress. When the Cu plating is formed thinner than 3 μm, the heat conductivity is lowered. When the Cu plating is formed thicker than 10 μm, the risk of plating cracking 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 2. The risk of becoming more likely to be added increases.

  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. Other crystal diaphragms such as an AT cut are not limited to the SC cut quartz diaphragm. The metal film M may be formed on one main surface of the front and back surfaces of the metal support or may be partially formed. Further, not only Cu (copper) plating but also a metal film such as Au (gold), Ag (silver), Al (aluminum) may be used.

  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.

DESCRIPTION OF SYMBOLS 1 Base 10 Base main body 11,12 Lead terminal 13,14 Metal support 2 Crystal diaphragm 4 Conductive resin adhesive M Metal film

Claims (2)

A base provided with a pair of metal lead terminals, a pair of plate-like metal supports provided on the metal lead terminals, and a joint between the pair of metal supports are joined via a conductive resin adhesive. It has a plate-shaped crystal diaphragm,
The crystal vibration plate is disposed on the inner side of the pair of metal lead terminals in such a manner that the plate surfaces of the joint portions of the pair of metal supports face each other, and the plate surfaces of the joint portions of the pair of metal supports. A crystal resonator in which the crystal diaphragm is disposed between the plate surfaces of the joint portion of the pair of metal supports, with the plate surfaces orthogonal to each other,
The metal support is made of a nickel iron-based low thermal expansion alloy,
A through hole is formed in the joint portion of the metal support,
The conductive resin adhesive is made of a polyether sulfone resin, and is formed by joining the joint portion of the metal support and the end portion of the crystal diaphragm in a state of entering the inside of the through hole of the metal support. A featured crystal unit. 2. The crystal resonator according to claim 1, wherein a copper film is formed on an outer surface of the metal support.

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