Oven-type piezoelectric oscillator

Abstract

To provide an oven-controlled Xtal (crystal) oscillator (OCX) that can ensure the thermal insulation of a package and achieve uniform heat distribution in the package.SOLUTION: In an OCXO 1 in which a core unit 5 is hermetically sealed inside a heat-insulating package 2, the core unit 5 includes at least an oscillation IC 51, a crystal unit 50, and a heater IC 52, and further includes a plurality of capacitors 9 attached to the package 2 via solder 9b. The core unit 5 is mounted on one main surface of the package 2 via a core substrate 4, and the plurality of capacitors 9 are joined by solder 9b to mounting pads 9a provided on the other main surface of the package 2 opposite to the one main surface, and only the joint portions with the capacitors 9, of the mounting pads 9a are exposed on the other main surface of the package 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an oven-controlled piezoelectric oscillator. [Background technology]

[0002] Piezoelectric oscillators such as quartz crystal oscillators change their oscillation frequency depending on the temperature based on their inherent frequency-temperature characteristics. Therefore, oven-controlled piezoelectric oscillators (hereinafter also referred to as "OCXOs") are known in which the piezoelectric oscillator is enclosed in a thermostatic oven to maintain a constant temperature around the piezoelectric oscillator (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-205093 [Patent Document 2] Japanese Patent Application Publication No. 2018-14705 Summary of the Invention [Problem to be solved by the invention]

[0004] The applicant has already filed a patent application for an oven-controlled piezoelectric oscillator in which a core section, consisting of a stacked oscillation IC, piezoelectric resonator, and heater IC, is supported inside a heat-insulating package via a core substrate (Patent Application No. 2020-130421: unpublished at the time of filing). In such oven-controlled piezoelectric oscillators, the heat capacity decreases as the package becomes smaller, making the oscillator more susceptible to external temperature changes. This raises concerns that the package's insulation performance may be reduced and the effects of external stress may increase. There is also concern that the heat distribution throughout the package may become uneven.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an oven-controlled piezoelectric oscillator that can ensure the thermal insulation of the package and achieve uniform heat distribution in the package. [Means for solving the problem]

[0006] The present invention provides a means for solving the above-described problems as follows: That is, the present invention provides an oven-controlled piezoelectric oscillator having a core unit hermetically sealed inside a heat-insulating package, the core unit including at least an oscillation IC, a piezoelectric resonator, and a heater IC, and further including a plurality of circuit components attached to the package with a bonding material, the core unit being mounted on one main surface of the package via a core substrate, the plurality of circuit components being mounted on another main surface of the package opposite to the one main surface, the package and the plurality of circuit components each having a rectangular shape in a plan view, and the plurality of circuit components being arranged symmetrically with respect to at least one of a center line in the short side direction and a center line in the long side direction of the package.

[0007] The above configuration ensures the package's thermal insulation and achieves uniform heat distribution within the package. Specifically, by using a core unit including an oscillation IC, a piezoelectric resonator, and a heater IC, the core unit's thermal capacity can be reduced. Reducing the core unit's thermal capacity facilitates temperature control at low power and improves the core unit's temperature tracking, thereby improving the stability of the oven-controlled piezoelectric oscillator. Furthermore, while a reduced package's thermal capacity makes it more susceptible to external temperature changes, interposing a core substrate between the core unit and the package reduces stress and heat loss. Furthermore, since multiple circuit components are symmetrically positioned with respect to at least one of the center lines of the package's short and long sides, symmetry in heat transfer along a specific side of the package is maintained, resulting in uniform heat distribution. This reduces the likelihood of uneven heat transfer along a specific side of the package, stabilizing the temperature control and characteristics of the oven-controlled piezoelectric oscillator. Furthermore, since the circuit components are arranged in a regular orientation and with regular intervals, there is no waste in the mounting positions of the circuit components relative to the mounting area on the other main surface of the package, improving mountability.

[0008] The present invention also provides an oven-controlled piezoelectric oscillator having a core unit hermetically sealed inside a heat-insulating package, the core unit including at least an oscillation IC, a piezoelectric vibrator, and a heater IC, and further including a plurality of circuit components attached to the package with a bonding material, the core unit being mounted on one main surface of the package via a core substrate, the plurality of circuit components being bonded by the bonding material to circuit component mounting pads provided on another main surface of the package opposite to the one main surface, and only the portions of each circuit component mounting pad that are bonded to the circuit components appear on the other main surface of the package.

[0009] According to the above configuration, similar to the configuration described above, the heat insulation of the package can be ensured and the heat distribution in the package can be made uniform. Furthermore, since only the bonding portions of the circuit component mounting pads that are bonded to the circuit components are exposed on the other main surface of the package, regions in the package where heat distribution unnecessarily spreads can be eliminated, the bonding of the circuit components by the bonding material can be stabilized, and the occurrence of bonding defects can be suppressed.

[0010] In the above configuration, it is preferable that the bonding area for bonding the core substrate to the package is arranged to overlap one of the plurality of circuit components in a planar view, and that the core portion is arranged to overlap one of the plurality of circuit components in a planar view.

[0011] According to the above-described configuration, uneven heat transfer is further prevented throughout the package, and heat distribution can be made more uniform.

[0012] In addition, in the above configuration, it is preferable that the core substrate is mounted on the package at both ends of the package in the longitudinal direction, while each of the plurality of circuit components is mounted on the package at both ends of the package in the short side direction.

[0013] According to the above configuration, the mounting direction of the core substrate and the mounting direction of the plurality of circuit components are perpendicular to each other, so that uneven heat transfer is less likely to occur throughout the package, and heat distribution can be made more uniform.

[0014] In the above-described configuration, the core is preferably vacuum-sealed inside the package. By vacuum-sealing the core, the heat insulating properties of the core can be improved.

[0015] In the above configuration, it is preferable that a space be provided between the core substrate and the bottom surface of the package. With this configuration, the core unit is connected to the package via the core substrate, and a space is formed below the core substrate, thereby improving the heat insulating effect for the core unit. [Effects of the Invention]

[0016] According to the present invention, the core section includes an oscillation IC, a piezoelectric resonator, and a heater IC, thereby reducing the core section's heat capacity. Reducing the core section's heat capacity facilitates temperature control at low power and improves the core section's temperature tracking, thereby improving the stability of the oven-controlled piezoelectric oscillator. Furthermore, reducing the package's heat capacity makes it more susceptible to external temperature changes. However, interposing a core substrate between the core section and the package reduces stress and heat loss. Furthermore, since multiple circuit components are symmetrically positioned with respect to the center lines of the package's short and long sides, heat distribution throughout the package is uniform. This reduces uneven heat transfer throughout the package, stabilizing the temperature control and characteristics of the oven-controlled piezoelectric oscillator. This ensures the package's thermal insulation and uniform heat distribution throughout the package. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an OCXO according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the OCXO of FIG. [Figure 3] FIG. 2 is a bottom view of the OCXO of FIG. 1. [Figure 4] 2 is a cross-sectional view showing a schematic configuration of a core section and a core substrate of the OCXO of FIG. 1. [Figure 5] FIG. 5 is a cross-sectional view of a crystal oscillator included in the core portion of FIG. [Figure 6] 5 is a top view of a crystal oscillator included in the core unit of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] As shown in FIGS. 1 to 3 , the OCXO 1 according to this embodiment has a core 5 disposed inside a substantially rectangular parallelepiped package (housing) 2 made of ceramic or the like, and hermetically sealed by a lid 3. The package 2 has a recess 2a that opens upward, and the core 5 is hermetically sealed inside the recess 2a. The lid 3 is fixed to the upper surface of a peripheral wall 2b surrounding the recess 2a via a sealing material 8, thereby sealing the interior of the package 2 in an airtight state. The sealing material 8 is preferably a metal-based sealing material such as an Au-Su alloy or solder, but a sealing material such as low-melting-point glass may also be used. Furthermore, other sealing methods, such as seam sealing using a metal ring, direct seam sealing without a metal ring, or beam sealing, may also be used (seam sealing is preferable to avoid reducing the degree of vacuum). The internal space of the package 2 is sealed in a vacuum (e.g., a vacuum of 10 Pa or less) to improve thermal insulation. 2 shows the OCXO 1 with the lid 3 removed, and FIG. 3 shows the OCXO 1 without the capacitor 9 mounted thereon, each showing the internal structure of the OCXO 1.

[0020] A stepped portion 2c is formed on the inner wall surface of the peripheral wall portion 2b of the package 2 along the arrangement of connection terminals (not shown). The core portion 5 is disposed on the bottom surface of the recessed portion 2a between a pair of opposing stepped portions 2c, 2c, via a plate-shaped core substrate 4. Alternatively, the stepped portion 2c may be formed so as to surround the bottom surface of the recessed portion 2a on all four sides. The core substrate 4 is bonded to the bottom surface of the recessed portion 2a with a non-conductive adhesive 7, and a space 2d is formed below the core substrate 4. The non-conductive adhesive 7 is provided on both longitudinal ends of the core substrate 4, linearly extending along the short-side direction of the core substrate 4 (the direction perpendicular to the plane of FIG. 1). Both longitudinal ends of the core substrate 4 of the package 2 are bonded to the package 2 by the non-conductive adhesive 7. In addition, external terminals (not shown) formed on each component of the core portion 5 are connected to connection terminals formed on the stepped surface of the stepped portion 2c via wires 6a and 6b by wire bonding.

[0021] In this way, by connecting the core unit 5 to the package 2 via the core substrate 4 and forming a space 2d below the core substrate 4, it is possible to improve the heat insulating effect for the core unit 5. Furthermore, by providing a pair of step portions 2c in the package 2 and providing connection terminals in the step portions 2c, the connection terminals are brought closer to the opening of the package 2, facilitating wire bonding between the core unit 5 and the package 2. Note that it is preferable that the bonding region A1 (the application region of the non-conductive adhesive 7) for bonding the core substrate 4 to the package 2 does not overlap with the arrangement region of the core unit 5 on the upper surface of the core substrate 4 in a plan view.

[0022] The OCXO 1 also includes capacitors 9 (three in Figure 1) as adjustment electronic components used in combination with the heater IC 52. The three capacitors 9 are the same size (volume, surface area). The capacitors 9 are solder components (circuit components) that are mounted to the package 2 with solder 9b. If the capacitors 9, which are solder components, are placed inside the package 2 together with the core part 5, gas may be generated due to remelting of the solder 9b, which is the joining material, and this may reduce the degree of vacuum inside the package 2. If the degree of vacuum inside the package 2 decreases, the thermal insulation of the OCXO 1 will also decrease. 1 to 3, in addition to the recess 2a that is open at the top, the package 2 also has a recess 2e that is open at the bottom, and the capacitor 9 is placed in the recess 2e. Note that, unlike the components mounted on the core part 5 (the oscillation IC 51, the crystal unit 50, and the heater IC 52, which will be described later), the capacitor 9 is a component with low temperature characteristics (is not easily affected by temperature), and therefore the recess 2e does not need to be sealed with a lid or the like.

[0023] In this way, by arranging the capacitor 9, which is a solder component, in a location separate from the sealed space (sealed space formed by the recess 2a) in which the core 5 is disposed, it is possible to prevent the degree of vacuum in the sealed space in which the core 5 is disposed from being reduced by gas generated from the solder 9b. This also allows the thermal insulation of the OCXO 1 to be maintained at a good level. Furthermore, the mounting area (in this example, part or all of the recess 2e, etc.) for the circuit components disposed outside the capacitor 9 (outside the sealed space) can be sealed with a sealing resin. In this case, covering the circuit components with the sealing resin can improve the thermal insulation effect between the circuit components and the external space.

[0024] Furthermore, the heat capacity of the sealed space can be reduced by placing the capacitor 9 outside the sealed space in which the core 5 is placed. Reducing the heat capacity of the sealed space enables temperature control with low power consumption and improves the temperature tracking ability of the core 5.

[0025] In this embodiment, the three capacitors 9 are mounted on the other main surface of the package 2 opposite to the one main surface (in this case, the bottom surface of the recess 2e). The capacitors 9 are bonded to mounting pads 9a (circuit component mounting pads) formed on the bottom surface of the recess 2e of the package 2 with solder 9b. A pair of mounting pads 9a, 9a is arranged opposite each other along the short side of the package 2, and both ends of each of the three capacitors 9 in the short side direction of the package 2 are bonded to the mounting pads 9a, 9a. As described above, the core substrate 4 is mounted on the package 2 at both ends in the longitudinal direction of the package 2, while each of the three capacitors 9 is mounted on the package 2 at both ends in the short side direction of the package 2. In this way, the mounting direction of the core substrate 4 and the mounting direction of the capacitors 9 are orthogonal. Furthermore, bonding regions A1 (application areas of the non-conductive adhesive 7) for bonding the core substrate 4 to the package 2 overlap the capacitors 9 located at both ends in the longitudinal direction of the package 2 in a plan view. The core portion 5 is disposed so as to overlap the capacitor 9 located at the center of the package 2 in the longitudinal direction in a plan view.

[0026] As shown in Fig. 3, three pairs of mounting pads 9a, 9a are arranged at predetermined intervals along the long side of the package 2. The mounting pads 9a are scattered like islands on the bottom surface of the package 2. Only the junction portion of each mounting pad 9a with the capacitor 9 is exposed on the other main surface of the package 2, and wiring electrically connected to the mounting pad 9a is provided inside the package 2 and is not exposed on the other main surface of the package 2. Specifically, as shown in Fig. 1, each mounting pad 9a is connected to wiring in a recess (through hole) 2f formed in the package 2, and this wiring is connected to internal wiring 2g formed between the laminated layers of the package 2.

[0027] The package 2 and the three capacitors 9 are each rectangular in plan view, and as shown in Fig. 3, the three capacitors 9 are arranged symmetrically with respect to a center line L1 in the short-side direction and a center line L2 in the long-side direction of the package 2. In this case, it is sufficient that the arrangement locations of the three capacitors 9 are line-symmetric with respect to the center lines L1 and L2. Note that a plurality of external connection terminals 2h (eight in Fig. 3) are formed on the bottom surface of the package 2, and the OCXO 1 can be electrically connected to an external circuit board (not shown) provided externally via solder or the like.

[0028] Next, the core unit 5 will be described with reference to FIG. 4. FIG. 4 illustrates the core unit 5 mounted on the core substrate 4. The core unit 5 is a package containing various electronic components used in the OCXO 1. It has a three-layer structure (laminated structure) in which an oscillation IC 51, a crystal unit (piezoelectric unit) 50, and a heater IC 52 are stacked in this order from top to bottom. The areas of the oscillation IC 51, the crystal unit 50, and the heater IC 52 in a plan view gradually decrease upward. The core unit 5 is configured to stabilize the oscillation frequency of the OCXO 1 by adjusting the temperatures of the crystal unit 50, the oscillation IC 51, and the heater IC 52, which have particularly strong temperature characteristics. Although the various electronic components in the core unit 5 are not sealed with sealing resin, sealing with sealing resin may be used depending on the sealing atmosphere.

[0029] The crystal oscillator 100 is composed of the crystal unit 50 and the oscillation IC 51. The oscillation IC 51 is mounted on the crystal unit 50 via a number of metal bumps. The oscillation frequency of the OCXO 1 is controlled by controlling the piezoelectric vibration of the crystal unit 50 using the oscillation IC 51. Details of the crystal oscillator 100 will be described later.

[0030] A non-conductive adhesive 53 is interposed between the opposing surfaces of the crystal unit 50 and the oscillation IC 51, and the opposing surfaces of the crystal unit 50 and the oscillation IC 51 are fixed together by the non-conductive adhesive 53. In this case, the top surface of the crystal unit 50 and the bottom surface of the oscillation IC 51 are joined together via the non-conductive adhesive 53.

[0031] The area of ​​the oscillation IC 51 in a plan view is smaller than that of the crystal unit 50, and the entire oscillation IC 51 is located within the range of the crystal unit 50 in a plan view. The entire bottom surface of the oscillation IC 51 is bonded to the top surface of the crystal unit 50.

[0032] The heater IC 52 is configured to integrate, 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, and the oscillation frequency of the OCXO 1 is stabilized.

[0033] A non-conductive adhesive 54 is interposed between the opposing surfaces of the crystal unit 50 and the heater IC 52, and the opposing surfaces of the crystal unit 50 and the heater IC 52 are fixed together by the non-conductive adhesive 54. In this case, the bottom surface of the crystal unit 50 and the top surface of the heater IC 52 are joined together via the non-conductive adhesive 54.

[0034] The crystal unit 50 has a smaller area in plan view than the heater IC 52, and the entire crystal unit 50 is located within the range of the heater IC 52 in plan view. The entire bottom surface of the crystal unit 50 is bonded to the top surface of the heater IC 52.

[0035] A non-conductive adhesive 55 is interposed between the opposing surfaces of the heater IC 52 and the core substrate 4, and the opposing surfaces of the heater IC 52 and the core substrate 4 are fixed together by the non-conductive adhesive 55. Examples of the non-conductive adhesives 53, 54, and 55 that can be used include polyimide adhesives and epoxy adhesives.

[0036] In the core unit 5 shown in FIG. 4, external terminals for wire bonding are formed on the top surfaces of the crystal unit 50 and the heater IC 52. Wire bonding of the crystal unit 50 and the heater IC 52 is not performed before mounting the core unit 5 in the package 2, but is performed after mounting the core unit 5 in the package 2. That is, as shown in FIG. 1, after mounting the core unit 5 in the package 2, the external terminals formed on the top surface of the crystal unit 50 are connected via wires 6a to connection terminals formed on the stepped surface of the stepped portion 2c. Furthermore, the external terminals formed on the top surface of the heater IC 52 are connected via wires 6b to connection terminals formed on the stepped surface of the stepped portion 2c. In this way, by performing wire bonding after mounting the core unit 5 in the package 2, wire bonding can be performed efficiently, making it possible to provide an OCXO 1 that is suitable for mass production.

[0037] In the present invention, the crystal unit 50 and the heater IC 52 are not limited to being electrically connected directly to the package 2 by wire bonding. That is, the crystal unit 50 and the heater IC 52 may be electrically connected to the package 2 via the core substrate 4. In this case, relay wiring may be formed on the core substrate 4, and wire bonding or flip-chip bonding may be used to connect the crystal unit 50 and the heater IC 52 to the core substrate 4. Furthermore, in order to connect the core substrate 4 to the package 2, connection terminals may be formed on the surface of the package 2 facing the core substrate 4, and the connection terminals of the core substrate 4 and the package 2 may be connected to each other using a conductive adhesive (a conductive adhesive may be used instead of the non-conductive adhesive 7 in FIG. 1). In this case, the step 2c in FIG. 1 is not particularly necessary and can be omitted.

[0038] However, as shown in Figure 1, a structure that separates the mechanical connection of the core substrate 4 to the package 2 using a non-conductive adhesive 7 from the electrical connection between the core unit 5 and the package 2 using wire bonding is preferable because it ensures high reliability in both the mechanical and electrical connections. For example, the non-conductive adhesive 7 that connects the core substrate 4 to the package 2 can be made of a flexible material that does not easily lose mechanical bond strength even when affected by external stress. Furthermore, using metal wires with low electrical resistance for wire bonding between the core unit 5 and the package 2 reduces the occurrence of common impedance noise, thereby improving the CN (carrier noise) characteristics of the OCXO 1.

[0039] Although there are no particular limitations on the type of quartz crystal unit 50 used in the core portion 5, a sandwich-structured device can be preferably used, which allows for easier thinning of the device. A sandwich-structured device is a three-layered device that is composed of first and second sealing members made of glass or quartz crystal, and a piezoelectric diaphragm made of, for example, quartz crystal and having a vibrating portion with excitation electrodes formed on both main surfaces, in which the first and second sealing members are stacked and bonded via the piezoelectric diaphragm, and the vibrating portion of the piezoelectric diaphragm disposed inside is hermetically sealed.

[0040] An example of a crystal oscillator 100 in which such a sandwich-structured crystal resonator 50 and an oscillation IC 51 are integrally provided will be described with reference to Figures 5 and 6. Figure 5 is a cross-sectional view of the crystal oscillator 100 (cross-sectional view taken along line AA in Figure 6), and Figure 6 is a top view of the crystal oscillator 100. Note that, because sandwich-structured crystal resonators themselves are well known, a detailed description of the internal structure of the crystal resonator 50 will be omitted.

[0041] 5, the crystal oscillator 100 includes a crystal diaphragm (piezoelectric diaphragm) 10, a first sealing member 20, a second sealing member 30, and an oscillation IC 51. In this crystal oscillator 100, the crystal diaphragm 10 and the first sealing member 20 are joined together by an annular sealing joint 41, and the crystal diaphragm 10 and the second sealing member 30 are joined together by an annular sealing joint 42, thereby forming a package with a substantially rectangular sandwich structure. The sealing joints 41 and 42 can be formed, for example, by forming a bonding pattern with an Au layer on the surface of each of the bonding surfaces of the crystal diaphragm 10, the first sealing member 20, and the second sealing member 30 (e.g., a bonding pattern with a Ti layer and an Au layer formed from the bottom layer), and bonding the bonding surfaces together by Au-Au diffusion bonding. According to this configuration, the gap dimension between the quartz crystal vibration plate 10 and each of the sealing members 20, 30 can be made extremely small, about 0.15 μm to 1 μm, which is advantageous for reducing the thickness and the heat capacity of the core portion 5.

[0042] That is, in the crystal oscillator 100, a first sealing member 20 and a second sealing member 30 are bonded to both main surfaces of the crystal oscillating plate 10, on which the vibrating portion (not shown) is formed, to form an internal space (cavity) of the package, and the vibrating portion of the crystal oscillating plate 10 is hermetically sealed in this internal space. The oscillation IC 51 mounted on the first sealing member 20 is a one-chip integrated circuit element that, together with the crystal oscillating plate 10, forms an oscillation circuit.

[0043] As shown in Fig. 6, connection terminals 21 and external terminals 22 are formed on the top surface of the crystal unit 50. One end (outer peripheral end) of the connection terminal 21 is electrically connected to an excitation electrode of the vibrating unit (via wiring or a through-hole inside the crystal unit 50), and the other end (inner peripheral end) is connected to an oscillation IC 51. One end (outer peripheral end) of the external terminal 22 is used for wire bonding with the package 2, and the other end (inner peripheral end) is connected to the oscillation IC 51. The oscillation IC 51 is connected to the connection terminals 21 and external terminals 22 by the FCB method using metal bumps.

[0044] The OCXO1 according to this embodiment uses a core unit 5 in which an oscillation IC 51, a crystal unit 50, and a heater IC 52 are stacked, thereby reducing the heat capacity of the core unit 5. Reducing the heat capacity of the core unit 5 facilitates temperature control with low power, and also improves the temperature tracking ability of the core unit 5, thereby improving the stability of the OCXO1. Furthermore, reducing the heat capacity of the OCXO1 makes it more susceptible to external temperature changes, but by interposing a core substrate 4 between the core unit 5 and the package 2, stress and heat loss can be reduced.

[0045] Furthermore, in this embodiment, the three capacitors 9 are arranged symmetrically with respect to the center line L1 in the short side direction and the center line L2 in the long side direction of the package 2, which makes it possible to achieve uniform heat distribution throughout the package 2. This makes it difficult for heat transfer to be biased throughout the package 2, thereby stabilizing the temperature control and characteristics of the OCXO 1. Furthermore, since the capacitors 9 are arranged in a regular orientation and with regular intervals, there is no wasted space in the mounting positions of the capacitors 9 relative to the mounting area on the other main surface of the package 2, improving mountability.

[0046] Furthermore, in this embodiment, only the joint portion (the portion where solder 9b is applied) of each mounting pad 9a with the capacitor 9 appears on the other main surface of the package 2. Specifically, the wiring electrically connected to each mounting pad 9a is provided inside the package 2 and does not appear on the other main surface of the package 2. This configuration can eliminate areas in the package 2 where heat distribution unnecessarily spreads, stabilize the joint of the capacitor 9 with the solder 9b, and suppress the occurrence of joint defects (mounting defects).

[0047] The present invention can be embodied in various other forms without departing from its spirit, essence, or main features. Therefore, the above-described embodiments are merely illustrative in all respects and should not be interpreted as limiting. The scope of the present invention is defined by the claims and is not limited to the text of the specification. Furthermore, all modifications and variations within the equivalent range of the claims are within the scope of the present invention.

[0048] For example, in the above embodiment, a crystal oscillator 100 including a sandwich-structured crystal resonator 50 is used, but the present invention is not limited to this, and an oscillator other than a sandwich-structure (for example, an SMD (Surface Mount Device) type oscillator) may also be used.

[0049] Furthermore, the number of capacitors 9 mounted on the other main surface of package 2 is not particularly limited, and the number of capacitors 9 may be other than three. Furthermore, circuit components other than capacitors 9 may be mounted on the other main surface of package 2. Furthermore, the sizes (volume, surface area) of all circuit components do not have to be the same.

[0050] In the above embodiment, the three capacitors 9 are arranged line-symmetrically with respect to both the center lines L1 and L2, but it is sufficient if they are line-symmetric with respect to at least one of the center lines L1 and L2. For example, the three capacitors 9 may be line-symmetrical with respect to only the center line L1 in the short side direction of the package 2, or the three capacitors 9 may be line-symmetrical with respect to only the center line L2 in the long side direction of the package 2. This makes it possible to maintain symmetry in heat transfer in a specific side direction of the package 2, making it less likely that heat transfer will be biased, and stabilizing the temperature control and characteristics of the OCXO 1.

[0051] Furthermore, the number of heaters included in the OCXO 1 is not particularly limited, and the OCXO 1 may have other heaters in addition to the heater included in the heater IC 52. For example, possible configurations include a configuration in which an additional heater is added above the core unit 5, a configuration in which a heater is added in a mounting area for circuit components arranged outside the core unit 5 within the package 2, and a configuration in which a film-like heater is embedded in the main body of the package 2.

[0052] In the above embodiment, package 2 is an H-shaped package in which recesses 2a and 2e are formed on different main surfaces. However, the present invention is not limited to this. For example, a two-tiered package may also be used. In the case of an OCXO 1 with a two-tiered package, packages with a recess on only one side may be stacked vertically and electrically and mechanically joined, with the upper package hermetically sealed with a lid. In this case, as shown in FIG. 1, the upper package may be configured to house core 5 in the recess, and the lower package may house capacitor 9. Even in such a two-tiered package, capacitor 9, which is a solder component, can be located in a separate location from the sealed space in which core 5 is located, achieving the same effects as the OCXO 1 with the H-shaped package shown in FIG. 1. [Explanation of symbols]

[0053] 1 OCXO (oven-controlled piezoelectric oscillator) 2 packages 4-core board 5 Core 7 Non-conductive adhesive 9 Capacitors (circuit components) 9a Mounting pad (mounting pad for circuit components) 9b Solder (joint material) 50 Quartz crystal oscillator (piezoelectric oscillator) 51 Oscillator IC 52 Heater IC L1 Center line of the package in the short side direction L2 Center line of the long side of the package

Claims

1. An oven-controlled piezoelectric oscillator in which a core is sealed in a heat-insulating package, The core part includes at least an oscillation IC, a piezoelectric vibrator, and a heater IC, Further, the package includes a plurality of circuit components attached to the package by a bonding material; the core portion is mounted on one main surface of the package via a core substrate, the plurality of circuit components are bonded by the bonding material to circuit component mounting pads provided on another main surface of the package opposite to the one main surface, each of the circuit component mounting pads has a portion thereof exposed on the other main surface of the package, the portion being connected to the circuit component; 10. An oven-controlled piezoelectric oscillator, comprising: a core substrate and a bottom surface of the package; a space provided between the core substrate and the bottom surface of the package;

2. A thermostatic oven-type piezoelectric oscillator according to claim 1, The oven-controlled piezoelectric oscillator is characterized in that the plurality of circuit components are arranged outside the sealed space of the oven-controlled piezoelectric oscillator.

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