Thermostatic chamber type piezoelectric oscillator

Abstract

To stabilize frequency characteristics of a piezoelectric vibrator by stabilizing a temperature by suppressing a thermal change of the piezoelectric vibrator.SOLUTION: A core part 5 including a multilayer piezoelectric vibrator 50, a base substrate 4, an IC 51 for oscillation, and an IC 52 for heater is stored in a package 2. Coefficients of thermal conductivity are high in the order of the multilayer piezoelectric vibrator 50, the base substrate 4, and a via part 9. A volume of the IC 52 for heater that is a heating section is made equal to or more than that of the multilayer piezoelectric vibrator 50, and a volume of the base substrate 4 is made larger than that of the IC 52 for heater. The via part 9 having the coefficient of thermal conductivity higher than that of the base substrate 4 is formed at four corners of a rectangular second sealing member 30 being joint positions of the IC 52 for heater and the multilayer piezoelectric vibrator 50 with the second sealing member 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric oscillator in which a core part including a piezoelectric vibrator, an oscillation circuit part for vibrating the piezoelectric vibrator, and a heating part for heating the piezoelectric vibrator are hermetically sealed inside a package. [Background technology]

[0002] Piezoelectric vibrators such as quartz crystal vibrators have inherent frequency-temperature characteristics, and their vibration frequency changes depending on the temperature. Therefore, oven-controlled piezoelectric oscillators (e.g., oven-controlled crystal oscillators: hereinafter also referred to as "OCXOs") are known in which the piezoelectric vibrator is enclosed in a thermostatic oven made of a package in order to maintain a constant temperature around the piezoelectric vibrator.

[0003] Furthermore, in order to improve the thermal insulation performance of some OCXOs, it has been proposed to house a piezoelectric vibrator, an oscillation circuit unit for vibrating the piezoelectric vibrator, and a heating unit for heating the piezoelectric vibrator in a supported state inside a thermal insulation package (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 181546 Summary of the Invention [Problem to be solved by the invention]

[0005] The OCXO described above uses a quartz crystal plate as the piezoelectric vibrator. However, as the piezoelectric vibrator becomes smaller, the volume of the quartz crystal plate decreases, and so does its heat capacity. This makes the quartz crystal plate susceptible to changes in the external thermal environment, making it difficult to stabilize its frequency-temperature characteristics. In particular, even slight changes in the temperature of the heating element in response to changes in the external environment can have a significant effect on the quartz crystal plate, causing its frequency-temperature characteristics to become unstable and deteriorate.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to suppress thermal changes in a piezoelectric vibrator to stabilize the temperature and stabilize the frequency-temperature characteristics of the piezoelectric vibrator. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an oven-controlled piezoelectric oscillator in which a core section including at least a piezoelectric resonator, an oscillation circuit section for vibrating the piezoelectric resonator, and a heating section for heating the piezoelectric resonator are hermetically sealed within a package, wherein the piezoelectric resonator is a stacked piezoelectric resonator having a quartz crystal diaphragm with a vibration section in its center and a heat transfer buffer plate bonded to a main surface of the quartz crystal diaphragm, and the core section is interposed between the heat transfer buffer plate of the stacked piezoelectric resonator and the heating section, and includes a base substrate having one surface bonded to the heating section and the other surface bonded to the heat transfer buffer plate, and through holes provided in the base substrate at bonding positions with the heating section and the heat transfer buffer plate are filled with metal to form via sections connecting the heating section and the heat transfer buffer plate, with the stacked piezoelectric resonator, the base substrate, and the via section having increasing thermal conductivity in that order, the heating section has a volume equal to or greater than the stacked piezoelectric resonator, and the base substrate has a volume greater than the heating section.

[0008] According to this configuration, the thermal conductivity is highest in the stacked piezoelectric vibrator, followed by the base substrate and the via portion, and since the volume of the heating portion is equal to or greater than that of the stacked piezoelectric vibrator and the volume of the base substrate is greater than that of the heating portion, the heat transferred from the heating portion can be stored in the base substrate to increase the heat capacity of the core portion, and the thermal changes that affect the stacked piezoelectric vibrator can be made gentler, making the stacked piezoelectric vibrator less sensitive to thermal changes. At the same time, the stacked piezoelectric vibrator becomes less susceptible to changes in the external thermal environment, and the thermal changes of the stacked piezoelectric vibrator can be suppressed to stabilize the temperature, thereby stabilizing the frequency-temperature characteristics of the stacked piezoelectric vibrator.

[0009] Furthermore, vias with higher thermal conductivity than the base substrate are formed at the joining positions of the heating element and the quartz crystal plate of the multilayer piezoelectric resonator to connect the heating element and the heat transfer buffer plate, thereby creating a strong thermal connection between the heating element and the quartz crystal plate, quickly transferring heat from the heating element to the multilayer piezoelectric resonator and minimizing heat transfer delays. As a result, the temperature difference between the heating element and the multilayer piezoelectric resonator is eliminated. At this time, the heat transfer buffer plate (which has the property of not directly transferring heat) is interposed between the vias and the quartz crystal plate of the multilayer piezoelectric resonator, preventing heat from being transferred directly to the quartz crystal plate, preventing the quartz crystal plate from responding too sensitively to thermal changes in the heating element.

[0010] The heat transfer buffer plate of the laminated piezoelectric vibrator is made of a quartz crystal plate, and has a pair of quartz crystal plates sandwiching both main surfaces of the quartz crystal plate. The quartz crystal plate is airtightly attached to the heat transfer buffer plate. It may be sealed.

[0011] With this configuration, the quartz vibration plate is sandwiched between a pair of quartz plates and hermetically sealed in a vacuum state, thereby improving the insulation properties of the quartz vibration plate, making it less susceptible to changes in the external thermal environment, and further stabilizing the frequency-temperature characteristics of the stacked piezoelectric vibrator.

[0012] Another oven-controlled piezoelectric oscillator according to the present invention is an oven-controlled piezoelectric oscillator in which a core section including at least a piezoelectric vibrator, an oscillation circuit section for vibrating the piezoelectric vibrator, and a heating section for heating the piezoelectric vibrator are hermetically sealed inside a package, wherein the piezoelectric vibrator is a framed quartz crystal vibrating plate having a vibrating section, a frame section formed on the outer periphery of the vibrating section, and a holding section that holds the vibrating section and a part of the frame section in a connected state, the core section is interposed between the framed quartz crystal vibrating plate and the heating section, and includes a base substrate that is bonded to the heating section on one side and to the frame section of the framed quartz crystal vibrating plate on the other side, and through holes provided in the base substrate at the bonding positions with the heating section and the frame section of the framed quartz crystal vibrating plate are filled with metal to form vias that connect the heating section and the frame section. The thermal conductivity of the framed quartz crystal vibration plate is highest in the framed quartz crystal vibration plate, followed by the base substrate and the via portion, and the volume of the heating portion is equal to or greater than that of the framed quartz crystal vibration plate, and the volume of the base substrate is greater than that of the heating portion.

[0013] With this configuration, the thermal conductivity of the framed quartz crystal plate is highest, followed by the base substrate and the vias. The volume of the heating section is equal to or greater than that of the framed quartz crystal plate, and the volume of the base substrate is greater than that of the heating section. This allows the heat transferred from the heating section to be stored in the base substrate, increasing the thermal capacity of the core section. This reduces the thermal changes that occur in the framed quartz crystal plate (a piezoelectric vibrator) and reduces its response to thermal changes. At the same time, the framed quartz crystal plate is less susceptible to changes in the external thermal environment, suppressing thermal changes in the framed quartz crystal plate and stabilizing its temperature, thereby stabilizing the frequency-temperature characteristics of the framed quartz crystal plate.

[0014] Furthermore, vias with higher thermal conductivity than the base substrate are formed at the joints between the heating element and the frame of the framed quartz crystal plate, connecting the heating element and the frame. This creates a strong thermal connection between the heating element and the frame, allowing heat to be transferred quickly from the heating element to the framed quartz crystal plate, minimizing heat transfer delays. As a result, the temperature difference between the heating element and the framed quartz crystal plate is eliminated. In this case, heat is not transferred directly to the vibrating element of the framed quartz crystal plate, preventing the vibrating element from responding too sensitively to thermal changes in the heating element.

[0015] The via portion may be formed at a position that does not overlap with the vibrating portion.

[0016] With this configuration, the via portion does not overlap with the vibrating portion, so heat is not transferred directly to the vibrating portion of the quartz vibration plate, and it is possible to reliably prevent the vibrating portion from responding too sensitively to thermal changes in the heating portion.

[0017] The base substrate has a side wall portion on the periphery and a storage portion in the center, The piezoelectric vibrator may be housed and hermetically sealed in a vacuum state by a lid member.

[0018] According to this configuration, the base substrate has side walls on the outer periphery and a storage section in the center, and the piezoelectric vibrator is housed in the storage section and hermetically sealed in a vacuum state by the lid member, thereby improving the insulation properties of the quartz vibration plate of the piezoelectric vibrator in particular and making it less susceptible to changes in the external thermal environment.

[0019] The base substrate may also be mechanically joined to the package by a holding member having a lower thermal conductivity than each member of the core portion, and the core portion may be electrically connected to the package by wire bonding.

[0020] This configuration improves the thermal insulation from the base substrate to the package, making it less susceptible to changes in the external thermal environment, and also makes it possible to achieve the necessary electrical connection from the core section to the outside.

[0021] The inside of the package may be vacuum sealed.

[0022] According to this configuration, the multiple vacuum sealing structure improves the insulation of the core part, particularly the piezoelectric vibrator, against the external thermal environment, stabilizing the temperature environment of the core part, particularly the piezoelectric vibrator, and stabilizing the frequency-temperature characteristics of the piezoelectric vibrator. [Effects of the Invention]

[0023] According to the present invention, the heat transferred from the heating section can be stored in the base substrate to increase the heat capacity of the core section, and the thermal changes that occur in the piezoelectric vibrator can be slowed down, thereby suppressing the thermal changes in the piezoelectric vibrator, stabilizing the temperature, and stabilizing the frequency-temperature characteristics of the piezoelectric vibrator. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a first embodiment of the present invention. [Figure 2] 2 is a plan view of the oven-controlled piezoelectric oscillator of FIG. 1 without a lid. [Figure 3] FIG. 2 is a plan view of a portion of the oven-controlled piezoelectric oscillator of FIG. [Figure 4] 2 is a cross-sectional view of a laminated piezoelectric vibrator of the oven-controlled piezoelectric oscillator of FIG. 1. [Figure 5] 5 is a schematic plan view of a first main surface side of a quartz crystal vibration plate of the multi-layer piezoelectric vibrator of FIG. 4. [Figure 6] 5 is a schematic bottom view of the second main surface side of the quartz crystal vibration plate of the multi-layer piezoelectric vibrator of FIG. 4. [Figure 7] 5 is a schematic plan view of a first main surface side of a first sealing member of the multi-layer piezoelectric vibrator of FIG. 4. [Figure 8] 5 is a schematic bottom view of the second main surface side of the first sealing member of the multi-layer piezoelectric vibrator of FIG. 4. FIG. [Figure 9] 5 is a schematic plan view of the first main surface side of the second sealing member of the multi-layer piezoelectric vibrator of FIG. 4. [Figure 10]5 is a schematic bottom view of the second main surface side of the second sealing member of the multi-layer piezoelectric vibrator of FIG. 4. FIG. [Figure 11] FIG. 10 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a second embodiment of the present invention. [Figure 12] 12 is a plan view of the oven-controlled piezoelectric oscillator of FIG. 11 without a lid. [Figure 13] 12 is a schematic plan view of the first principal surface side of the framed quartz crystal resonator of FIG. 11. [Figure 14] 12 is a schematic bottom view of the second main surface side of the framed quartz crystal resonator of FIG. 11. FIG. [Figure 15] 15 is a cross-sectional view of the framed crystal resonator taken along line AA in FIGS. 13 and 14. FIG. [Figure 16] 12 is a partial plan view showing the positions of vias in the oven-controlled piezoelectric oscillator of FIG. 11. FIG. [Figure 17] FIG. 10 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a third embodiment of the present invention. [Figure 18] FIG. 10 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a fourth embodiment of the present invention. [Figure 19] FIG. 10 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a fifth embodiment of the present invention. [Figure 20] FIG. 10 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a sixth embodiment of the present invention. [Figure 21] FIG. 13 is a cross-sectional view showing a schematic configuration of an oven-controlled piezoelectric oscillator according to a seventh embodiment of the present invention. [Figure 22] FIG. 10 is a cross-sectional view showing a modified example of the laminated piezoelectric vibrator of the oven-controlled piezoelectric oscillator according to the present invention. [Figure 23] FIG. 10 is a cross-sectional view showing a modified example of the electrical connection configuration of the oven-controlled piezoelectric oscillator according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] First Embodiment An oven-controlled piezoelectric oscillator (OCXO) according to a first embodiment of the present invention will be described in detail with reference to Figures 1 to 10. Each of Figures 1 to 10 is illustrated using the same X-axis, Y-axis, and Z-axis.

[0026] 1, the OCXO 1 has a package 2 with a generally concave cross section, which has a recess 2a that opens upward, and a lid 3 that closes the opening on the top surface of the package 2, and a core 5 including a base substrate 4 is housed within the package 2. The package 2 is made of, for example, ceramic, and the lid 3 is made of, for example, a metal plate with a rectangular cross section.

[0027] The core 5 is hermetically sealed in a vacuum state within the recess 2a of the package 2, and a lid 3 is fixed to the upper surface of the peripheral wall 2b surrounding the recess 2a via a sealing material 3a by seam welding, thereby sealing the interior of the recess 2a. The lid 3 is made of a metal base material plate, such as Kovar, with a required plating of nickel or the like formed on its surface. The sealing material 3a is attached to the upper part of the peripheral wall 2b of the package 2, with a required plating of nickel or the like formed on its surface, such as a metal ring, such as Kovar. The lid 3 and the sealing material 3a are then joined together by seam welding after heating. The interior space of the recess 2a is preferably in a high vacuum state (e.g., a vacuum level of 10 Pa or less) or a low vacuum state, or in an atmosphere with low thermal conductivity, such as low-pressure nitrogen or argon. The hermetic sealing (seam sealing) by seam welding is not limited to the present invention, and direct seam sealing without a metal ring may also be used. Furthermore, instead of seam sealing, other methods such as beam sealing or brazing sealing using a metal sealing material such as an Au-Sn alloy or solder may be used. Furthermore, if a ceramic plate or the like is used for the lid 3, a sealing material such as low-melting glass may be used.

[0028] As shown in Figures 1 and 2, a stepped portion 2d where a plurality of connection terminals (wire pads) 2c are arranged is formed on the inner wall surface of the peripheral wall portion 2b of the recessed portion 2a of the package 2. The core portion 5, which will be described in detail later, is disposed in the recessed portion 2a between a pair of opposing stepped portions 2d, 2d, with a base substrate 4 interposed therebetween. The stepped portion 2d may be formed so as to surround all four sides of the bottom surface of the recessed portion 2a. Wire pads 2c formed on the stepped surface of the stepped portion 2d are connected to wire pads 4a formed on the base substrate 4 of the core portion 5 via wires 6a by wire bonding.

[0029] In addition, via wire 6b, a wire pad (see Figure 2) formed on the oscillation IC 51 of the core part 5 is connected to a wire pad 4a formed on the base substrate 4 by wire bonding, and via wire 6c, a wire pad (see Figure 2) formed on the heater IC 52 of the core part 5 is connected to a wire pad 4a formed on the base substrate 4 by wire bonding.

[0030] The base substrate 4 is made of ceramic, for example, and has a sidewall portion 40 integrally formed so as to surround the outer periphery of the base substrate 4, and has a concave space containing portion 41 in the center surrounded by the base substrate 4 and the sidewall portion 40, and the laminated piezoelectric vibrator 50 is contained in this containing portion 41, and a lid member 42 is disposed so as to close the opening on the lower surface side of the sidewall portion 40 opposite to the side on which the base substrate 4 is disposed, thereby hermetically sealing the containing portion 41. Here, the lid member 42 is made of a metal lid, a metal cap, a ceramic lid, or the like, and is fixed with a sealing material to hermetically seal the containing portion 41 in a vacuum state.

[0031] The cover member 42 includes a spacer member 2e, a non-conductive adhesive 7a, a holding member The spacer member 2e is bonded to the bottom surface of the recess 2a via a non-conductive adhesive 7b. A pair of spacer members 2e, made of ceramic, are integrally formed linearly along the short-side direction of the package 2 (i.e., the vertical direction in FIG. 2) by metallization or the like. The spacer members 2e are made of a paste material (metallization material) such as molybdenum or tungsten. A non-conductive adhesive 7a is applied to the top surface of the spacer member 2e, and a pair of plate- or sheet-shaped holding members 8 are respectively provided on top of the spacer member 2e along the short-side direction of the base substrate 4 (the direction perpendicular to the paper surface of FIG. 1). A non-conductive adhesive 7b is applied to each holding member 8, and the underside of the lid member 42 is bonded to the holding member 8. The holding member 8 is formed of, for example, a flexible polyimide resin to insulate the lid member 42, ultimately achieving thermal insulation of the laminated piezoelectric vibrator 50 in the housing portion 41. The holding member 8 may also be formed of glass epoxy resin or quartz. Examples of the non-conductive adhesives 7a and 7b include polyimide adhesives and epoxy adhesives.

[0032] Furthermore, the bonding area (the area where the non-conductive adhesive 7b is applied) for bonding the base substrate 4 to the package 2 is arranged so as not to overlap, in plan view, with the area where the core portion 5 is arranged on the upper surface of the base substrate 4. The spacer member 2e is made of a paste material (metallization material) such as molybdenum or tungsten. For example, a polyimide adhesive or an epoxy adhesive is used as the non-conductive adhesives 7a and 7b.

[0033] Next, the core section 5 will be described with reference to Figs. 1 to 3. The core section 5 has an oscillation IC 51, a heater IC 52 which is a heating section, a base substrate 4, and a laminated piezoelectric vibrator (corresponding to the "piezoelectric vibrator" in the present invention) 50. A non-conductive adhesive 53 such as a polyimide adhesive or an epoxy adhesive is interposed between the opposing surfaces of the oscillation IC 51 and the heater IC 52. The oscillator IC 51 is bonded to the top surface of the heater IC 52 by a non-conductive adhesive 53. A non-conductive adhesive 54 such as a polyimide adhesive or an epoxy adhesive is interposed between the opposing surfaces of the heater IC 52 and the base substrate 4, and the heater IC 52 is bonded in surface contact with the top surface of the base substrate 4. Note that the non-conductive adhesives 53 and 54 may be replaced by a conductive adhesive containing a metallic conductive filler to further enhance heat transfer.

[0034] Furthermore, a conductive adhesive 55, such as a resin-based adhesive such as a silicone-based adhesive, is interposed on the surface facing the base substrate 4 and the laminated piezoelectric vibrator 50, at positions corresponding to the four corners of the laminated piezoelectric vibrator 50 in a planar view, and the laminated piezoelectric vibrator 50 is bonded to the underside of the base substrate 4.

[0035] The oscillation IC 51 can be, for example, an IC for a voltage-controlled crystal oscillator (VCXO), and the oscillation frequency of the OCXO 1 is controlled by controlling the piezoelectric vibration of the stacked piezoelectric vibrator 50 using the oscillation IC 51.

[0036] The heater IC 52 is configured by integrating, for example, a heating element (heat source), a control circuit (current control circuit) for controlling the temperature of the heating element, and a temperature sensor for detecting the temperature of the heating element. By controlling the temperature of the core unit 5 using the heater IC 52, the temperature of the core unit 5 is maintained at a substantially constant temperature, thereby stabilizing the oscillation frequency of the OCXO 1. Note that the temperature sensor may be provided separately from the heater IC 52.

[0037] The structure of the laminated piezoelectric vibrator 50 will be described in detail later, but as shown in Figure 4, it is composed of a quartz vibration plate 10 made of, for example, quartz and having a vibration part with excitation electrodes formed on both main surfaces, and first and second sealing members 20, 30 made of, for example, glass or quartz (second sealing member 30 corresponds to the "heat transfer buffer plate" in this invention, and a "heat transfer buffer plate" has the property of not easily transferring heat directly), and the first sealing member 20 and the second sealing member 30 are stacked and bonded via the quartz vibration plate 10, and the vibration part of the quartz vibration plate 10 arranged inside is airtightly sealed in a vacuum state, making it a three-layer structure device, and the second sealing member (heat transfer buffer plate) 30 is arranged opposite the base substrate 4.

[0038] 1 and 3, nine through holes are provided in a matrix pattern in plan view at positions where the heater IC 52, which is the heating unit in the present invention, and the second sealing member 30 of the stacked piezoelectric vibrator 50, which is the quartz plate in the present invention, overlap with the base substrate 4 in plan view, and these through holes are filled with metal made of a metallization material to form via portions 9, 9a. As shown in FIG. 3, the via portions 9 arranged on the conductive adhesive 55 at the four corners of the second sealing member 30 of the stacked piezoelectric vibrator 50 are located so as not to overlap with the vibration portion 11 of the quartz plate 10 in plan view, and are formed at the bonding positions of the heater IC 52 and the second sealing member 30 of the stacked piezoelectric vibrator 50. For this reason, as shown in FIGS. 3 and 4, these While the vias 9 at the four corners thermally connect the second sealing member 30 and the heater IC 52, the five vias 9a located at other positions do not connect the heater IC 52 to the second sealing member 30 even if they are positioned so as to overlap the vibration portion of the quartz crystal vibration plate 10 in a plan view, and therefore heat is not transferred from the heater IC 52 to the second sealing member 30 via these five vias 9a. Note that the number of vias 9, 9a is not limited to four or five.

[0039] Here, the relationship between the thermal conductivity of the laminated piezoelectric vibrator 50, the base substrate 4, and the via portions 9, 9a is such that the thermal conductivity increases in the order of the laminated piezoelectric vibrator 50 made of quartz, the base substrate 4 made of ceramic such as alumina, and the via portions 9, 9a made of metal such as molybdenum or tungsten. The volumes of the laminated piezoelectric vibrator 50, the base substrate 4, and the heater IC 52 are set so that the volume of the heater IC 52, which is the heating part, is equal to or larger than that of the laminated piezoelectric vibrator 50, and the volume of the base substrate 4 is larger than that of the heater IC 52. That is, the thermal conductivity of quartz is 5.4 W / m·K (orthogonal to the Z axis) to 9.3 W / m·K (parallel to the Z axis at 70°C), the thermal conductivity of the base substrate 4 is 21 W / m·K (room temperature) for alumina, the thermal conductivity of the via portions 9 and 9a using metallized materials is 147 W / m·K for molybdenum and 198 W / m·K for tungsten, and the thermal conductivity of the holding member 8 is 0.16 W / m·K to 0.18 W / m·K for polyimide. Therefore, the thermal conductivity relationship is via portions 9 and 9a > base substrate 4 > laminated piezoelectric vibrator 50, and the volume relationship is heater IC (heating portion) 52 ≧ laminated piezoelectric vibrator 50, i.e., base substrate 4 > heater IC (heating portion) 52. In this way, heat from the heater IC 52 can be stored in the base substrate 4.

[0040] This allows the heat transferred from the heater IC 52 to be stored in the base substrate 4, increasing the heat capacity of the core portion 5, and easing the thermal changes that affect the laminated piezoelectric vibrator 50, making the laminated piezoelectric vibrator 50 less sensitive to thermal changes. At the same time, the laminated piezoelectric vibrator 50 becomes less susceptible to changes in the external thermal environment, suppressing thermal changes in the laminated piezoelectric vibrator 50 and stabilizing the temperature, thereby stabilizing the frequency-temperature characteristics of the laminated piezoelectric vibrator 50.

[0041] 4, a plurality of wire pads Wp are formed on the upper surface of the base substrate 4, and wire pads Wp' having a larger area than the wire pads Wp on the upper surface are formed on the lower surface of the base substrate 4. Vias V are formed by filling conductive material such as metal made of a metallization material into through holes formed vertically through the base substrate 4 and connecting the upper and lower wire pads Wp and Wp' to each other. Wires 6b and 6c connect the oscillation IC 51 and the heater IC 52 to the wire pads Wp on the upper surface of the base substrate 4, and external terminals of the laminated piezoelectric vibrator 50 are connected to the wire pads Wp' on the lower surface of the base substrate 4, thereby electrically connecting the oscillation IC 51 and the heater IC 52 connected to the wire pads Wp on the upper surface by the wires 6b and 6c to the laminated piezoelectric vibrator 50.

[0042] In this way, the core portion 5 is mechanically joined to the bottom surface of the recess 2a of the package 2 and electrically connected to the package 2 by wire bonding using wires 6a, 6b, 6c, wire pads 2c, 4a, etc., and by mechanically joining the core portion 5 to the package 2 with the holding member 8 and non-conductive adhesives 53, 54 interposed therebetween, the necessary electrical connection from the core portion 5 to the outside is realized while improving insulation against the external thermal environment.

[0043] Next, the configuration of the stacked piezoelectric vibrator 50 will be described with reference to Figures 5 to 11. As described above, the stacked piezoelectric vibrator 50 is composed of the quartz crystal vibrating plate 10, and the first and second sealing members 20 and 30, with the second sealing member 30 disposed opposite the base substrate 4.

[0044] The quartz crystal plate 10 is made of, for example, an AT-cut quartz crystal plate that performs thickness-shear vibration. As shown in FIGS. 5 and 6, the first main surface 101 is The first and second principal surfaces 101, 102 are mirror-finished to form a flat, smooth surface. A pair of first and second excitation electrodes 111, 112 are formed on both principal surfaces 101, 102 of the quartz crystal vibrating plate 10. The quartz crystal vibrating plate 10 has a substantially rectangular vibrating portion 11, an outer frame portion 12 that surrounds the outer periphery of the vibrating portion 11, and a holding portion 13 that connects the vibrating portion 11 and the outer frame portion 12 to hold the vibrating portion 11.

[0045] The first excitation electrode 111 is provided on the first main surface 101 side of the vibrating section 11, and the second excitation electrode 112 is provided on the second main surface 102 side of the vibrating section 11. A first extraction wiring 113 and a second extraction wiring 114 are connected to the first excitation electrode 111 and the second excitation electrode 112 to connect these excitation electrodes to external electrode terminals. The first extraction wiring 113 is drawn out from the first excitation electrode 111 and connected to a connection bonding pattern 14 formed on the outer frame section 12 via a holding section 13. The second extraction wiring 114 is drawn out from the second excitation electrode 112 and connected to a connection bonding pattern 15 formed on the outer frame section 12 via the holding section 13.

[0046] On both main surfaces 101, 102 of the quartz crystal plate 10, there are formed annular vibration-side sealing portions in a plan view for bonding the quartz crystal plate 10 to the first sealing member 20 and the second sealing member 30. A vibration-side first bonding pattern 121 is formed as the vibration-side sealing portion on the first main surface 101, and a vibration-side second bonding pattern 122 is formed as the vibration-side sealing portion on the second main surface 102.

[0047] 5 and 6, five hollow through-holes are formed in the quartz crystal vibrating plate 10, penetrating between the first main surface 101 and the second main surface 102. Four of the first through-holes 161 are provided at the four corners of the outer frame portion 12, and the second through-hole 162 is provided in the outer frame portion 12 on the -Z direction side of the vibrating portion 11. A vibration-side first bonding pattern 121 is formed around the first through-hole 161 on the first main surface 101 side, and a vibration-side second bonding pattern 122 is formed around the second main surface 102 side. A connection bonding pattern 124 is formed around the second through-hole 162 on the first main surface 101 side, and a connection bonding pattern 15 is formed around the second through-hole 162 on the second main surface 102 side.

[0048] A through electrode is formed on the inner circumferential surface of each of the first through-hole 161 and the second through-hole 162 to ensure electrical continuity between the electrodes formed on the first main surface 101 and the second main surface 102.

[0049] 7 and 8, the first sealing member 20 is a rectangular parallelepiped substrate formed from, for example, a single AT-cut quartz crystal plate, and the second main surface 202 of this first sealing member 20 that is bonded to the quartz crystal vibration plate 10 is formed as a flat, smooth surface (mirror-finished). The X-, Y-, and Z-axes of the first sealing member 20 are aligned in the same direction as those of the quartz crystal vibration plate 10.

[0050] As shown in FIG. 7, first and second terminals 21 and 22 for wiring formed on the outer surface of the package and a third terminal 23 for shielding (ground connection) are formed on a first main surface 201 of the first sealing member 20 that does not face the quartz crystal plate 10. is connected to the oscillation IC 51 via wire pads Wp, Wp', a via V, and a wire 6c. The first terminal 21 is electrically connected to the first excitation electrode 111 of the quartz crystal vibrating plate 10. The second terminal 22 is electrically connected to the second excitation electrode 112 of the quartz crystal vibrating plate 10. The first and second terminals 21, 22 are provided at both ends in the Z-axis direction, with the first terminal 21 on the -Z direction side and the second terminal 22 on the +Z direction side.

[0051] The third terminals 23 are provided at the four corners and in the central region of the first main surface 201 of the first sealing member 20, and are generally H-shaped. The third terminals 23 are arranged at a predetermined distance from the first and second terminals 21, 22, and are provided in almost all regions of the first main surface 201 of the first sealing member 20 that are not provided with the first and second terminals 21, 22. The third terminals 23 are electrically connected to and grounded by external terminals 32 formed on the second main surface 302 of the second sealing member 30. Note that the third terminals 23 do not necessarily have to be grounded, and the third terminals 23 do not necessarily have to have an electrical connection function.

[0052] As shown in Figures 7 and 8, the first sealing member 20 has six hollow through holes formed therein that penetrate between the first main surface 201 and the second main surface 202, of which four third through holes 211 are provided at the four corners of the first sealing member 20, and the remaining two fourth and fifth through holes 212 and 213 are provided on the -Z direction side and +Z direction side, respectively, in Figures 7 and 8.

[0053] On the inner circumferential surfaces of the third through-hole 211 and the fourth and fifth through-holes 212, 213, through electrodes are formed along the inner wall surfaces of each through-hole to ensure electrical continuity between the electrodes formed on the first main surface 201 and the second main surface 202.

[0054] A first sealing-side bonding pattern 24 is formed on the second main surface 202 of the first sealing member 20 as a first sealing portion for bonding to the quartz-crystal vibrating plate 10. The first sealing-side bonding pattern 24 is formed in a ring shape in a plan view. The first sealing-side bonding pattern 24 is also formed around each third through-hole 211. A connection bonding pattern 262 is formed around the fourth through-hole 212, and a connection bonding pattern 261 is formed around the fifth through-hole 213. A connection bonding pattern 263 is formed on the -Z direction side of the first sealing member 20 relative to the connection bonding pattern 261, and the connection bonding pattern 261 and the connection bonding pattern 263 are connected by a wiring pattern 27.

[0055] 9 and 10, the second sealing member 30 corresponds to the "heat transfer buffer plate" of the present invention and is formed, for example, from a single AT-cut quartz crystal plate in a rectangular shape. The first main surface 301 of this second sealing member 30 that is bonded to the quartz crystal vibration plate 10 is formed as a flat, smooth surface (mirror-finished). The X-, Y-, and Z-axes of the second sealing member 30 are also aligned in the same direction as those of the quartz crystal vibration plate 10.

[0056] A second sealing-side bonding pattern 31 is formed on the first main surface 301 of the second sealing member 30 as a second sealing portion for bonding to the quartz-crystal vibrating plate 10. The second sealing-side bonding pattern 31 is formed in a ring shape in a plan view. The second sealing-side bonding pattern 31 is also formed around the sixth through-hole 33.

[0057] The external terminals 32 are formed in a ring shape on the second main surface 302 of the second sealing member 30, and are formed on almost the entire surface except for a substantially circular portion in the center. The external terminals 32 are also formed around the sixth through-holes 33.

[0058] 9 and 10 , the second sealing member 30 is formed with one hollow sixth through-hole 33 penetrating between the first main surface 301 and the second main surface 302, and this sixth through-hole 33 is provided at one corner of the second sealing member 30. A through electrode is formed on the inner circumferential surface of the sixth through-hole 33 to ensure electrical continuity between the electrodes formed on the first main surface 301 and the second main surface 302. Note that if the third terminal 23 of the first sealing member 20 is not connected to earth, the second sealing member 30 may be configured without the sixth through-hole 33.

[0059] The stacked piezoelectric vibrator 50, consisting of the quartz crystal vibrating plate 10, first sealing member 20, and second sealing member 30 configured as described above, is then diffusion-bonded, for example, between the quartz crystal vibrating plate 10 and the first sealing member 20 with the first vibrating-side bonding pattern 121 and the first sealing-side bonding pattern 24 overlapping each other, and between the quartz crystal vibrating plate 10 and the second sealing member 30 with the second vibrating-side bonding pattern 122 and the second sealing-side bonding pattern 31 overlapping each other, to produce the sandwich-structured package shown in FIG. 4. This hermetically seals the internal space of the package, i.e., the space housing the vibrating unit 11, in a vacuum state. Note that a quartz crystal vibrating plate other than AT-cut may also be used for the quartz crystal vibrating plate 10.

[0060] The various bonding patterns in the laminated piezoelectric vibrator 50 are preferably formed by stacking multiple layers on a quartz plate, with a Ti (titanium) layer and an Au (gold) layer formed from the bottom layer side by vapor deposition or sputtering.

[0061] 4, the vibrating portion 11 of the quartz crystal vibrating plate 10 in the stacked piezoelectric vibrator 50 is hermetically sealed by seal buses 10a and 10b, which serve as annular sealing electrodes in a plan view. The seal bus 10a, which serves as the first sealing electrode, is formed by diffusion bonding the above-mentioned vibration-side first bonding pattern 121 and the sealing-side first bonding pattern 24, and the outer and inner edge shapes of the seal bus 10a are formed to be approximately rectangular. Similarly, the seal bus 10b, which serves as the second sealing electrode, is formed by diffusion bonding the above-mentioned vibration-side second bonding pattern 122 and the sealing-side second bonding pattern 31, and the outer and inner edge shapes of the seal bus 10b are formed to be approximately rectangular.

[0062] The seal buses 10a and 10b are not electrically connected to the wiring connected to the above-described first and second excitation electrodes 111 and 112. On the other hand, the seal buses 10a and 10b are electrically connected to the third terminal 23 of the first sealing member 20 and the external terminal 32 of the second sealing member 30 via the through electrodes in the first through holes 161, the third through holes 211, and the sixth through holes 33. The external terminal 32 is connected to the heater IC 52 via the conductive adhesive 55, wire pads Wp and Wp', vias V, and wires 6c.

[0063] According to the first embodiment, the core section 5 including the stacked piezoelectric vibrator 50, the base substrate 4, the oscillation IC 51, and the heater IC 52 is housed in the package 2, and the thermal conductivity is highest in the stacked piezoelectric vibrator 50, the base substrate 4, and the via sections 9, 9a in that order. The volume of the heater IC 52, which is the heating section, is made equal to or larger than the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than the heater IC 52. This allows the heat transferred from the heater IC 52 to be stored in the base substrate 4, increasing the heat capacity of the core section 5, and easing thermal changes in the stacked piezoelectric vibrator 50, making the response of the stacked piezoelectric vibrator 50 to thermal changes less sensitive. Furthermore, the stacked piezoelectric vibrator 50 is less susceptible to changes in the external thermal environment, suppressing thermal changes and stabilizing the temperature, thereby stabilizing the frequency-temperature characteristics of the stacked piezoelectric vibrator 50.

[0064] Furthermore, vias 9, which have a higher thermal conductivity than the base substrate 4, are formed at the four corners of the rectangular second sealing member 30, at the bonding positions between the heater IC 52 and the second sealing member 30 of the multilayer piezoelectric resonator 50. This allows for a strong thermal connection between the heater IC 52 and the second sealing member 30 of the multilayer piezoelectric resonator 50, allowing for quick heat transfer from the heater IC 52 to the multilayer piezoelectric resonator 50 and reducing heat transfer delays. As a result, the temperature difference between the heater IC 52 and the multilayer piezoelectric resonator 50, which are the heating unit, is eliminated. The five vias 9a other than the vias 9 located at the four corners of the rectangular second sealing member 30 do not connect the heater IC 52 to the second sealing member 30, even though they are positioned to overlap the vibration portion of the quartz crystal vibrating plate 10 in a plan view. Therefore, heat is not transferred from the heater IC 52 to the second sealing member 30 through these five vias 9a.

[0065] Furthermore, since the second sealing member 30 is interposed between the via portions 9, 9a and the quartz vibration plate 10 of the laminated piezoelectric vibrator 50, heat is not directly transferred to the quartz vibration plate 10, and the quartz vibration plate 10 is prevented from responding too sensitively to thermal changes in the heater IC 52.

[0066] Furthermore, a stacked piezoelectric vibrator 50 is used as the piezoelectric vibrator, and the stacked piezoelectric vibrator 50 has a structure in which the quartz vibration plate 10 is sandwiched between a pair of first and second sealing members 20, 30 and hermetically sealed in a vacuum state, thereby improving the thermal insulation of the quartz vibration plate 10 and making it less susceptible to changes in the external thermal environment, thereby further stabilizing the frequency-temperature characteristics of the stacked piezoelectric vibrator 50.

[0067] Furthermore, in order to hermetically seal the inside of the package 2 in a vacuum state, the multiple (triple) vacuum sealing structure, which includes the vacuum sealing structure of the stacked piezoelectric vibrator 50 and the vacuum sealing structure of the housing portion 41 that houses the stacked piezoelectric vibrator 50, which is made up of the base substrate 4, side wall portion 43, and lid member 42, particularly improves the insulation of the core portion 5, which is centered around the stacked piezoelectric vibrator 50, against the external thermal environment, and stabilizes the temperature environment of the core portion 5, which is centered around the stacked piezoelectric vibrator 50. As a result, the frequency-temperature characteristics of the stacked piezoelectric vibrator 50 can be stabilized.

[0068] Second Embodiment An oven-controlled piezoelectric oscillator (OCXO) according to a second embodiment of the present invention will be described in detail with reference to Figures 11 to 16. In the second embodiment, instead of the stacked piezoelectric vibrator 50 of the first embodiment, a framed quartz crystal vibrating plate is used as the piezoelectric vibrator to form the core section 5, and the following description will mainly focus on the differences from the first embodiment. Note that in Figures 11 to 16, the same reference numerals as in Figures 1 to 10 indicate the same or corresponding parts.

[0069] The second embodiment differs from the first embodiment in that, instead of the stacked piezoelectric vibrator 50, a core portion 5 is formed using a framed quartz crystal vibrating plate 501 as the piezoelectric vibrator, as shown in FIG. 11 . As shown in FIG. 12 , the second main surface 502b of the vibrating portion 502 (described later) of the rectangular framed quartz crystal vibrating plate 501 is arranged facing the base substrate 4, and two diagonal corners of the second main surface 502b of the frame portion 504 of the framed quartz crystal vibrating plate 501 are bonded to the underside of the base substrate 4 with a conductive adhesive 55.

[0070] The framed quartz crystal plate 501 is made of a quartz crystal plate as will be described later, and as in the first embodiment, the thermal conductivity increases in the following order: the framed quartz crystal plate 501 made of quartz crystal, the base substrate 4 made of ceramic such as alumina, and the via portion made of metal such as molybdenum or tungsten. The volume of the heater IC 52 is equal to or larger than that of the framed quartz crystal plate 501, and the volume of the base substrate 4 is set larger than that of the heater IC 52. That is, the thermal conductivity has the relationship of via portions 91, 91a > base substrate 4 > framed quartz crystal plate 501, and the volume has the relationship of heater IC (heating portion) 52 ≧ framed quartz crystal plate 501, and base substrate 4 > heater IC (heating portion) 52.

[0071] As shown in FIGS. 13 and 14 , the framed quartz crystal vibrating plate 501 is, for example, an AT-cut quartz crystal plate having a rectangular shape in plan view. The framed quartz crystal vibrating plate 501 includes a rectangular vibrating portion 502 in plan view, a rectangular frame portion 504 that surrounds the vibrating portion 502 with a through-hole 503 sandwiched between the vibrating portion 502 and a retaining portion 505 that connects the vibrating portion 502 to a portion of the frame portion 504 and holds the vibrating portion 502 to the frame portion 504. The retaining portion 505 is located at the corners of the vibrating portion 502 in the +X and -Z directions and is connected to the frame portion 504 so as to close the through-hole 503. The vibrating portion 502, frame portion 504, and retaining portion 505 are formed, for example, by photolithography and wet etching. Dry etching may be used instead of wet etching. The framed quartz crystal vibrating plate 501 may be made of a material other than an AT-cut.

[0072] Rectangular first excitation electrodes 506 and 507 are formed on first and second main surfaces 502a and 502b, respectively, of the vibrating part 502. A first extraction electrode 508 connected to the first excitation electrode 506 is formed on the first main surface 502a of the vibrating part 502 and the first main surface 502a side of the frame part 504, as shown in Fig. 13 , and this first extraction electrode 508 is formed to extend in the -Z direction from corners on the +X direction side and the -Z direction side of the first excitation electrode 506 so as to overlap with the holding part 505, to bend in the -X direction, and to extend in a direction bent by 90 degrees in the +Z direction, thereby forming a substantially L-shape.

[0073] 14, a second extraction electrode 509 is formed on the second main surface 501b of the vibration part 502. This second extraction electrode 509 is formed to extend from corners on the +X direction side and the −Z direction side of the second excitation electrode 507 so as to overlap with the holding part 505, and a first external connection electrode 510 is formed at the tip of the second extraction electrode 509 so as to be continuous with the second extraction electrode 509.

[0074] 14, a third extraction electrode 511 extending linearly from the +Z direction to the -Z direction is formed on the -X-axis side end of the surface of the frame portion 504 on the second main surface 501b side of the vibrating portion 502. As shown in Fig. 15, which shows a cross section taken along line AA in Figs. 13 and 14, the third extraction electrode 511 and the first extraction electrode 508 are connected by an inner surface electrode 512 formed on the inner circumferential surface of the through portion 503. A second external connection electrode 513 is formed on the +Z direction end of the third extraction electrode 511.

[0075] 12, similar to the via portions 9 of the first embodiment, nine via portions 91, 91a are formed in a matrix on the base substrate 4, and as shown in FIG. 16, viewed from a direction perpendicular to the first main surface 501a, the heater IC 52 and the framed quartz crystal plate 501 are formed at positions where they overlap in a plan view. Of the nine via portions 91, 91a, the via portions 91 at the two corners on the -X and +Z sides and the +X and -Z sides overlap with the positions where the first and second external connection electrodes 510, 513 are formed on the frame portion 504 of the framed quartz crystal plate 501, and the via portions 91 are disposed at the joining positions between the heater IC 52 and the frame portion 504 of the framed quartz crystal plate 501, and are connected to the first and second external connection electrodes 510, 513 via the conductive adhesive 55. Therefore, the vias 91 at these two corners do not overlap the vibrating portion 502, and these vias 91 thermally connect the heater IC 52 to the frame portion 504 of the framed quartz crystal vibrating plate 501. The other seven vias 91a are spaced apart from the framed quartz crystal vibrating plate 501, so the heater IC 52 is not thermally connected to the vibrating portion 502 of the framed quartz crystal vibrating plate 501 through these seven vias 91a.

[0076] In the second embodiment, the oscillation IC 51 and the heater IC 52 are electrically connected to the stacked piezoelectric vibrator 50 by wire pads Wp, Wp' and vias V similar to those in FIG.

[0077] According to the second embodiment, the thermal conductivity is highest in the framed quartz crystal plate 501, followed by the base substrate 4 and the vias 91 and 91a. The heater IC 52 has a volume equal to or larger than the framed quartz crystal plate 501, and the base substrate 4 has a volume greater than the heater IC 52. As in the first embodiment, heat transferred from the heater IC 52 can be stored in the base substrate 4, increasing the thermal capacity of the core 5. This reduces thermal changes in the framed quartz crystal plate 501 and reduces its response to thermal changes. Furthermore, the framed quartz crystal plate 501 is less susceptible to changes in the external thermal environment, suppressing thermal changes and stabilizing its temperature, thereby stabilizing the frequency-temperature characteristics of the framed quartz crystal plate 501.

[0078] Furthermore, vias 91, which have a higher thermal conductivity than the base substrate 4, are formed at the two corners of the frame 504 where the heater IC 52 and the frame 504 of the framed quartz crystal plate 501 are bonded, and the heater IC 52 and the frame 504 are connected via these two vias 91 and the conductive adhesive 55, thereby creating a strong thermal connection between the heater IC 52 and the frame 504, quickly transferring heat from the heater IC 52 to the framed quartz crystal plate 501 and minimizing delays in heat transfer. As a result, the temperature difference between the heater IC 52 and the framed quartz crystal plate 501, which are the heating elements, is eliminated.

[0079] Furthermore, according to the second embodiment, because the framed quartz crystal vibrating plate 501 is used as the piezoelectric vibrator, the first and second sealing members 20 and 30 as in the stacked piezoelectric vibrator 50 of the first embodiment are not necessary, and there is an advantage in that the process of sealing the quartz crystal vibrating plate 10 with the two sealing members 20 and 30 is not necessary, thereby reducing costs through fewer components. Furthermore, it is possible to perform frequency adjustment after a certain amount of annealing for aging improvement has been performed, which makes it easier to tune the frequency of the framed quartz crystal vibrating plate 501, and does not require a high level of difficulty in frequency tuning as in the case of the stacked piezoelectric vibrator 50.

[0080] Third Embodiment An oven-controlled piezoelectric oscillator (OCXO) according to a third embodiment of the present invention will be described with reference to FIG. 17, focusing mainly on the differences from the first embodiment. In FIG. 17, the same reference numerals as those in FIGS. 1 to 10 indicate the same or corresponding parts.

[0081] In the first embodiment, a pair of plate- or sheet-shaped holding members 8 are arranged along the vertical direction in Fig. 2, and each holding member 8 is coated with a non-conductive adhesive 7b to bond the holding member 8 to the underside of the lid member 42. However, in the third embodiment, a single sheet- or plate-shaped holding member 81 is prepared, a non-conductive adhesive 7c is applied to the entire underside of the lid member 42, and the holding member 81 is bonded to the underside of the lid member 42 via the non-conductive adhesive 7c. Spacer members 2e are then arranged and bonded to the undersides of both ends of the holding member 81 via the non-conductive adhesive 7a. This differs from the first embodiment in that: the holding member 81 is preferably formed from, for example, a polyimide substrate or polyimide piece. The holding member 81 has a lower thermal conductivity than the stacked piezoelectric vibrator 50 and thus provides thermal insulation for the lid member 42, thereby ultimately achieving thermal insulation for the stacked piezoelectric vibrator 50 in the housing portion 41.

[0082] In the third embodiment, a via portion 9 is formed at the joining position between the heater IC 52 of the base substrate 4 and the second sealing member 30 of the laminated piezoelectric vibrator 50, and the thermal conductivity increases in the order of the laminated piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a, and the volume of the heater IC 52, which is the heating portion, is made equal to or larger than the laminated piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than the heater IC 52, as in the first embodiment.

[0083] According to the third embodiment, the thermal conductivity increases in the order of the laminated piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a, and the volume of the heater IC 52, which is the heating portion, is equal to or larger than the laminated piezoelectric vibrator 50, and the volume of the base substrate 4 is larger than the heater IC 52, so that the same effect as in the first embodiment can be obtained.

[0084] Furthermore, since a single holding member 81, which has a thermal conductivity lower than that of the stacked piezoelectric vibrator 50 and has insulating properties, is placed on the underside of the cover member 42, the insulating effect of the stacked piezoelectric vibrator 50 in the accommodating section 41 is improved compared to the first embodiment in which a pair of holding members 8 is used.

[0085] <Fourth embodiment> An oven-controlled piezoelectric oscillator (OCXO) according to a fourth embodiment of the present invention will be described with reference to FIG. 18, focusing mainly on the differences from the first embodiment. In FIG. 18, the same reference numerals as those in FIGS. 1 to 10 indicate the same or corresponding parts.

[0086] In the first embodiment, the stacked piezoelectric vibrator 50 is sealed by the base substrate 4, the side wall portion 40, and the lid member 42, but the fourth embodiment differs from the first embodiment in that the stacked piezoelectric vibrator 50 is not sealed without the side wall portion 40 and the lid member 42, as shown in FIG. 18.

[0087] In the fourth embodiment, a via portion 9 is formed at the joining position between the heater IC 52 of the base substrate 4 and the second sealing member 30 of the laminated piezoelectric vibrator 50, and the thermal conductivity increases in the order of the laminated piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a, and the volume of the heater IC 52, which is the heating portion, is made equal to or larger than that of the laminated piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than that of the heater IC 52, as in the first embodiment.

[0088] According to the fourth embodiment, the thermal conductivity increases in the order of the stacked piezoelectric vibrator 50, the base substrate 4, and the via portions 9, 9a, and the volume of the heater IC 52, which is the heating portion, is made equal to or larger than the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than the heater IC 52. Therefore, the same effect as in the first embodiment can be obtained without sealing the stacked piezoelectric vibrator 50 with the side wall portion 40 and the lid member 42 of the base substrate 4 as in the first embodiment.

[0089] Furthermore, since the sidewall portion 40 and the lid member 42 as in the first embodiment are not provided, the members and processes for sealing the multi-layer piezoelectric vibrator 50 are not required, which can reduce costs. This can also contribute to a lower height.

[0090] Fifth Embodiment An oven-controlled piezoelectric oscillator (OCXO) according to a fifth embodiment of the present invention will be described with reference to FIG. 19, focusing mainly on the differences from the first embodiment. In FIG. 19, the same reference numerals as those in FIGS. 1 to 10 indicate the same or corresponding parts.

[0091] In the fifth embodiment, instead of the heater IC 52 constituting the core unit 5 in the first embodiment, as shown in FIG. 19 , a heating unit 56 a consisting of a heater resistor such as a film resistor is bonded to the upper surface of the base substrate 4 with a non-conductive adhesive 57 a similar to the non-conductive adhesive 54, and a control unit 58 a equipped with a heater control circuit and an oscillation IC for controlling this heating unit 56 a is arranged next to the heating unit 56 a, and the control unit 58 a is bonded to the upper surface of the base substrate 4 with a non-conductive adhesive 59 a similar to the non-conductive adhesive 53, so that the core unit 5 a is constituted by the heating unit 56 a and the control unit 58 a together with the stacked piezoelectric vibrator 50 and the base substrate 4, which is different from the first embodiment in that.

[0092] In the fifth embodiment, a via portion 9 is formed at the joining position between the heating portion 56a of the base substrate 4 and the second sealing member 30 of the stacked piezoelectric vibrator 50, and the thermal conductivity increases in the order of the stacked piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a, the volume of the heating portion 56a is made equal to or larger than that of the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than that of the heating portion 56a, as in the first embodiment.

[0093] According to the fifth embodiment, the thermal conductivity increases in the order of the stacked piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a. The volume of the heating portion 56a is equal to or larger than that of the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is larger than that of the heating portion 56a. Therefore, even if the heating portion 56a is formed by a heater resistor such as a film resistor, rather than the heater IC 52 as in the first embodiment, the same effect as in the first embodiment can be obtained.

[0094] Sixth Embodiment An oven-controlled piezoelectric oscillator (OCXO) according to a sixth embodiment of the present invention will be described with reference to FIG. 20, focusing mainly on the differences from the first, second, and third embodiments. In FIG. 20, the same reference numerals as those in FIGS. 1 to 10, 11, and 17 indicate the same or corresponding components.

[0095] In the sixth embodiment, as shown in FIG. 20, a framed quartz crystal vibration plate 501 similar to that of the second embodiment (see FIG. 11) is used as the piezoelectric vibrator, and instead of the heater IC 52 constituting the core portion 5 of the third embodiment, a heating portion 56b consisting of a heater resistor such as a film resistor is bonded to the upper surface of the base substrate 4 with a non-conductive adhesive 57b similar to the non-conductive adhesive 54. A control portion 58b equipped with a heater control circuit and an oscillation IC for controlling this heating portion 56b is arranged next to the heating portion 56a, and the control portion 58b is bonded to the upper surface of the base substrate 4 with a non-conductive adhesive 59b similar to the non-conductive adhesive 53. The core portion 5b is formed by the framed quartz crystal vibration plate 501, the base substrate 4, the heating portion 56b, and the control portion 58b.

[0096] In the sixth embodiment, as in the second embodiment, a via portion 91 is formed at the joining position between the heating portion 56b of the base substrate 4 and the frame portion 504 of the framed quartz crystal vibration plate 501, and the thermal conductivity increases in the order of the framed quartz crystal vibration plate 501, the base substrate 4, and the via portions 91 and 91a, the volume of the heating portion 56b is made equal to or larger than the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than the heating portion 56b, as in the first to third embodiments.

[0097] According to the sixth embodiment, the thermal conductivity increases in the order of the framed quartz crystal vibration plate 501, the base substrate 4, and the via portions 91, 91a. The volume of the heating portion 56b is equal to or larger than that of the framed quartz crystal vibration plate 501, and the volume of the base substrate 4 is larger than that of the heating portion 56b. Therefore, even if the heating portion 56b is formed using a heater resistor such as a film resistor rather than a heater IC 52 as in the first to third embodiments, the same effects as those of the first to third embodiments can be obtained.

[0098] Seventh Embodiment An oven-controlled piezoelectric oscillator (OCXO) according to a seventh embodiment of the present invention will be described with reference to FIG. 21, focusing mainly on the differences from the first and fourth embodiments. Note that in FIG. 21, the same reference numerals as those in FIGS. 1 to 10 and 18 indicate the same or corresponding components.

[0099] In the seventh embodiment, instead of the heater IC 52 constituting the core unit 5 of the fourth embodiment, as shown in FIG. 21 , a heating unit 56c consisting of a heater resistor such as a film resistor is bonded to the upper surface of the base substrate 4 with a non-conductive adhesive 57c similar to the non-conductive adhesive 54, and a control unit 58c equipped with a heater control circuit and an oscillation IC for controlling this heating unit 56c is arranged next to the heating unit 56c, and the control unit 58c is bonded to the upper surface of the base substrate 4 with a non-conductive adhesive 59c similar to the non-conductive adhesive 53, and the core unit 5c is formed by the heating unit 56c and the control unit 58c together with the stacked piezoelectric vibrator 50 and the base substrate 4, which is different from the first and third embodiments in that.

[0100] In the seventh embodiment, a via portion 9 is formed at the joining position between the heating portion 56c of the base substrate 4 and the second sealing member 30 of the stacked piezoelectric vibrator 50, and the thermal conductivity increases in the order of the stacked piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a, the volume of the heating portion 56c is made equal to or larger than the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is made larger than the volume of the heating portion 56c, as in the first and fourth embodiments.

[0101] According to the seventh embodiment, the thermal conductivity increases in the order of the stacked piezoelectric vibrator 50, the base substrate 4, and the via portions 9 and 9a. The volume of the heating portion 56c is set to be equal to or larger than the stacked piezoelectric vibrator 50, and the volume of the base substrate 4 is larger than that of the heating portion 56c. Therefore, even if the heating portion 56c is formed using a heater resistor such as a film resistor instead of the heater IC 52 as in the first and fourth embodiments, the same effects as in the first and fourth embodiments can be obtained.

[0102] The present invention is not limited to the above-described configuration, and various design modifications can be made within the scope of the claims.

[0103] For example, in the above-described first, third, fourth, fifth, and seventh embodiments, a laminated piezoelectric vibrator 50 was described in which a flat quartz vibrating plate 10 was sandwiched between first and second sealing members 20 and 30 to airtightly seal the quartz vibrating plate 10. However, instead of the laminated piezoelectric vibrator 50, as shown in Fig. 22, an inverted mesa type laminated piezoelectric vibrator 50a may be used in which a quartz vibrating plate 10A having a vertically symmetrical inverted mesa shape formed by processing both the upper and lower surfaces of the central portion of the quartz plate into a concave shape is sandwiched between the first and second sealing members 20 and 30. In Fig. 22, 111a and 112a are excitation electrodes formed on both main surfaces of the vibrating portion 11A, respectively.

[0104] Furthermore, in a configuration in which the base substrate 4 does not have a side wall portion 40 and a lid member 42 and the laminated piezoelectric vibrator 50 is not sealed, as in the fourth embodiment (see Figure 18), in order to connect the oscillation IC 51 and the heater IC 52 to the laminated piezoelectric vibrator 50, as shown in Figure 23, side electrodes Wpa may be formed at the ends of each opposing side of the base substrate 4, spanning the upper, side, and lower surfaces of the base substrate 4, and vias Va may be formed by filling a conductive material such as metal in vertical through holes provided in the base substrate 4 at positions connected to the conductive adhesive 55, and the oscillation IC 51, the heater IC 52, and the laminated piezoelectric vibrator 50 may be electrically connected by wires 6b, 6c, and 6d via the side electrodes Wpa.

[0105] Furthermore, the number of holding members is not limited to a pair (two) like holding member 8 or one like holding member 81, but may be three or more.

[0106] Furthermore, in the fourth embodiment (see FIG. 18), when electrical connection is made using a conductive bonding material including conductive adhesive 55 or solder, there is no need to form a large-area wire pad Wp′ as shown in FIG. 4 on the underside of the base substrate 4; it is sufficient to form a wire pad with an area equivalent to that of the wire pad Wp on the upper surface side on the underside of the base substrate 4.

[0107] In addition, in the above-described embodiment, the core portions 5, 5a, 5b, and 5c are electrically connected to the package 2 via the base substrate 4, but the core portions 5, 5a, 5b, and 5c may also be electrically connected to the package 2 without going through the base substrate 4.

[0108] In the above-described embodiment, an AT-cut quartz crystal plate is used as the quartz crystal plate 10, but other quartz crystal plates (e.g., SC-cut quartz crystal plate, quartz crystal Z-plate, etc.) may also be used. Furthermore, while the first sealing member 20 and the second sealing member 30 are formed from an AT-cut quartz crystal plate, other quartz crystal plates (e.g., SC-cut quartz crystal plate, quartz crystal Z-plate, etc.) may also be used. Furthermore, the first sealing member 20 and the second sealing member 30 are not limited to quartz crystal, and may be formed from other materials, such as glass or resin. Furthermore, the laminated piezoelectric vibrator may be configured such that two sealing members (a first sealing member and a second sealing member) are not bonded to both main surfaces of the quartz crystal plate to form an airtight seal, but only the second sealing member located on the base substrate side, which functions as a heat transfer buffer plate, is bonded and laminated.

[0109] The present invention can be widely applied to oven-controlled piezoelectric oscillators in which a core unit including at least a piezoelectric vibrator, an oscillation circuit unit for vibrating the piezoelectric vibrator, and a heating unit for heating the piezoelectric vibrator are sealed inside a package. [Explanation of symbols]

[0110] 1. Oven-controlled piezoelectric oscillator (OCXO) 2. Package 4...Base board 40...Side wall 41... Storage area 42...Cover member 5, 5a, 5b, 5c ... Core part 50, 50a...Layered piezoelectric vibrator 8,81 ... Retaining member 9,91 ...Beer section 10,10A crystal diaphragm 11,11A…Vibrating part 51...Oscillation IC 52 ... Heater IC (heating unit) 56a,56b,56c...Heating section 501...Framed crystal plate 502 ... Vibration part 504 ...frame 505...Holding part

Claims

1. In an oven-controlled piezoelectric oscillator, a core section including at least a piezoelectric vibrator, an oscillation circuit section for vibrating the piezoelectric vibrator, and a heating section for heating the piezoelectric vibrator is sealed in a package, The piezoelectric vibrator is a laminated piezoelectric vibrator having a quartz crystal vibrating plate having a vibrating portion in the center and a heat transfer buffer plate bonded to a main surface of the quartz crystal vibrating plate, the core portion is interposed between the heat transfer buffer plate and the heating portion of the laminated piezoelectric vibrator, and includes a base substrate having one surface joined to the heating portion and the other surface joined to the heat transfer buffer plate, a via portion connecting the heating portion and the heat transfer buffer plate is formed by filling a metal into a through hole provided in the base substrate at a joining position between the heating portion and the heat transfer buffer plate, The thermal conductivity of the laminated piezoelectric vibrator is highest in the base substrate, and lowest in the via portion. The volume of the heating section is equal to or larger than the stacked piezoelectric vibrator, and the volume of the base substrate is larger than the heating section.

1. A thermostatic oven type piezoelectric oscillator characterized by:

2. 2. The oven-controlled piezoelectric oscillator according to claim 1, wherein the heat transfer buffer plate of the stacked piezoelectric vibrator is made of a quartz crystal plate, and includes a pair of quartz crystal plates sandwiching both main surfaces of the quartz crystal plate, and the quartz crystal plate is hermetically sealed in a vacuum state.

3. In an oven-controlled piezoelectric oscillator, a core section including at least a piezoelectric vibrator, an oscillation circuit section for vibrating the piezoelectric vibrator, and a heating section for heating the piezoelectric vibrator is sealed in a package, the piezoelectric vibrator is a framed quartz crystal vibrating plate having a vibrating portion, a frame portion formed on the outer periphery of the vibrating portion, and a holding portion that holds the vibrating portion and a part of the frame portion in a connected state; the core portion is interposed between the framed quartz crystal plate and the heating portion, and includes a base substrate having one surface bonded to the heating portion and the other surface bonded to the frame portion of the framed quartz crystal plate; a via portion connecting the heating portion and the frame portion of the framed quartz crystal vibrating plate to each other by filling a metal into a through hole provided at a joining position between the heating portion of the base substrate and the frame portion of the framed quartz crystal vibrating plate, The thermal conductivity of the framed quartz crystal plate is highest, followed by the base substrate and the via portion. an oven-controlled piezoelectric oscillator, wherein the volume of the heating portion is equal to or greater than the framed quartz crystal plate, and the volume of the base substrate is greater than the volume of the heating portion;

4. 4. The oven-controlled piezoelectric oscillator according to claim 1, wherein the via portion is formed at a position where it does not overlap with the vibrating portion.

5. The oven-controlled piezoelectric oscillator according to any one of claims 1 to 3, or claim 4 dependent on claim 1 or claim 3, wherein the base substrate has a side wall portion on its outer periphery and a housing portion in its center, the housing portion housing the piezoelectric vibrator and vacuum-sealing it in an airtight state with a lid member.

6. The base substrate is mechanically joined to the package by a holding member having a lower thermal conductivity than the components of the core portion, and the core portion is electrically connected to the package by wire bonding. The oven-controlled piezoelectric oscillator described above.

7. The inside of the package is vacuum sealed. The oven-controlled piezoelectric oscillator described above.

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