Thermostat type piezoelectric oscillator

Abstract

To provide a thermostat type piezoelectric oscillator capable of improving a heat insulation effect of a core part by obtaining high reliability in both a mechanical junction of a core substrate to a package and an electrical junction between the core part and the package.SOLUTION: In an OCXO 1 in which a core part 5 is encapsulated inside of a package 2 for heat insulation in a sealed state, the core part 5 includes at least an IC 51 for oscillation, a crystal oscillator 50 and an IC 52 for heaters. The core part 5 is loaded on a core substrate 4. The core substrate 4 is mechanically joined to the package 2 by a nonconductive adhesive agent 7, and the core part 5 and the package 2 are electrically joined by wire bonding. A space 2d is provided between the core substrate 4 and a bottom face of the package 2, and a spacer member 2f is interposed between the core substrate 4 and the bottom face of the package 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a thermostatic chamber type piezoelectric oscillator.

Background Art

[0002] Piezoelectric oscillators such as crystal oscillators change their oscillation frequencies according to temperature based on their inherent frequency-temperature characteristics. Therefore, in order to keep the temperature around the piezoelectric oscillator constant, a thermostatic chamber type piezoelectric oscillator (Oven-Controlled Xtal (crystal) Oscillator: hereinafter also referred to as "OCXO") in which the piezoelectric oscillator is enclosed in a thermostatic chamber is known (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The applicant of the present application has already filed an application for a thermostatic chamber type piezoelectric oscillator in which a core portion in which an oscillation IC, a piezoelectric oscillator, and a heater IC are laminated is supported inside a heat-insulating package via a core substrate (Japanese Patent Application No. 2020-130421: not published at the time of filing this application). In such a thermostatic chamber type piezoelectric oscillator, the performance of the mechanical bonding of the core substrate to the package and the electrical bonding between the core portion and the package affects the reliability of the device. In addition to this, it is also required to enhance the heat insulation effect of the core portion.

[0005] The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a thermostatic chamber type piezoelectric oscillator capable of obtaining high reliability in both mechanical bonding of a core substrate to a package and electrical bonding of a core portion to the package, and further capable of enhancing the heat insulation effect of the core portion.

Means for Solving the Problems

[0006] The present invention is configured as means for solving the above problems as follows. That is, the present invention is a thermostatic chamber type piezoelectric oscillator in which a core portion is hermetically sealed inside a heat-insulating package, and the core portion has a configuration including at least an oscillation IC, a piezoelectric vibrator, and a heater IC. The core portion is mounted on a flexible substrate, and this flexible substrate is mechanically bonded to the package by a bonding material. The core portion and the package are electrically bonded by wire bonding, and a space is provided between the flexible substrate and the bottom surface of the package.

[0007] According to the above configuration, by separating the mechanical bonding of the flexible substrate to the package by the bonding material and the electrical bonding of the core portion to the package by wire bonding, high reliability can be obtained in each. For example, as the bonding material for connecting the flexible substrate to the package, a flexible material that is less likely to have a reduced mechanical bonding strength even under the influence of external stress can be used. Also, in the wire bonding between the core portion and the package, by using a metal wire with low electrical resistance, common impedance noise is less likely to occur, and the CN characteristics of the thermostatic chamber type piezoelectric oscillator can be improved. In addition to this, by connecting the core portion to the package via the flexible substrate and forming a space below the flexible substrate, the heat insulation effect on the core portion can be enhanced.

[0008] In the above configuration, it is preferable that the bonding region for bonding the flexible substrate to the package does not overlap with the arrangement region of the core portion with respect to the flexible substrate in a plan view. In this case, a spacer member is provided in a region on the core portion side rather than the bonding region, and it is preferable that the spacer member is interposed between the flexible substrate and the bottom surface of the package. Thereby, since the thickness of the bonding material applied to the bonding region is defined by the spacer member, the width of the space between the flexible substrate and the bottom surface of the package can be easily defined. Further, by the spacer member, when the bonding material applied to the bonding region shrinks, the flexible substrate can be warped in a direction in which the width of the space between the flexible substrate and the bottom surface of the package increases, and the heat insulation effect with respect to the core portion can be improved.

[0009] In the above configuration, the flexible substrate is preferably made of a resin material having heat resistance, and examples of such a resin material include polyimide. Further, in the above configuration, it is preferable that the core portion is vacuum-sealed inside the package.

[0010] In the above configuration, it is preferable that the flexible substrate has a configuration in which a slit is provided between a mounting region where the core portion is mounted on the upper surface of the flexible substrate and a bonding region for bonding the flexible substrate to the package. Further, it is preferable that the flexible substrate has a configuration in which an opening is provided in a region directly below the core portion. Furthermore, it is preferable that the piezoelectric vibrator is not directly wire-connected to the package, and only the oscillation IC is directly wire-connected to the piezoelectric vibrator.

Effects of the Invention

[0011] According to the thermostatic chamber type piezoelectric oscillator of the present invention, by separating the mechanical bonding of the flexible substrate to the package by the bonding material and the electrical bonding of the core part and the package by wire bonding, high reliability can be obtained in each case. For example, as the bonding material for connecting the flexible substrate to the package, a flexible material that is less likely to have a decrease in mechanical bonding strength even under the influence of external stress can be used. Also, in the wire bonding between the core part and the package, by using a metal wire with low electrical resistance, common impedance noise is less likely to occur, and the CN characteristics of the thermostatic chamber type piezoelectric oscillator can be improved. In addition, by connecting the core part to the package via the flexible substrate and forming a space below the flexible substrate, the heat insulation effect on the core part can be enhanced.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Best Mode for Carrying Out the Invention

[0013] 〔Embodiment 1〕 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] As shown in FIGS. 1 and 2, the OCXO1 according to this embodiment has a structure in which a core portion 5 is disposed inside a substantially rectangular parallelepiped package (housing) 2 made of ceramic or the like and is hermetically sealed by a lid (cover) 3. The package 2 is formed with a recess 2a having an open upper portion, and the core portion 5 is hermetically sealed inside the recess 2a. The lid 3 is fixed to the upper surface of the peripheral wall portion 2b surrounding the recess 2a by seam welding via a sealing material 8, and the inside of the package 2 is in a sealed state (airtight state). As the sealing material 8, for example, a metal-based sealing material such as an Au-Su alloy or solder is preferably used, but a sealing material such as a low-melting glass may also be used. Further, without being limited to these, it is also possible to adopt a configuration of a sealing member by a method such as seam sealing using a metal ring, direct seam sealing without using a metal ring, or beam sealing (seam sealing is preferable in terms of not reducing the degree of vacuum). The internal space of the package 2 is preferably a vacuum (for example, a degree of vacuum of 10 Pa or less) or an atmosphere with a low thermal conductivity such as low-pressure nitrogen or argon. Note that FIG. 2 shows the OCXO1 with the lid 3 removed, showing the internal structure of the OCXO1.

[0015] On the inner wall surface of the peripheral wall portion 2b of the package 2, a stepped portion 2c is formed along the arrangement of connection terminals (not shown). The core portion 5 is disposed on the bottom surface of the recess 2a between a pair of opposing stepped portions 2c, 2c via a core substrate (flexible substrate) 4 made of a plate-like flexible member. Alternatively, the stepped portion 2c may be formed so as to surround the four sides of the bottom surface of the recess 2a. The core substrate 4 is joined to the bottom surface of the recess 2a by a non-conductive adhesive (bonding material) 7, and a space (gap) 2d is formed in the lower portion of the core substrate 4. Further, external terminals (not shown) formed on each component member of the core portion 5 are connected to connection terminals formed on the stepped surface of the stepped portion 2c by wire bonding via wires 6a, 6b. Spacer members 2f, 2f are provided on the inner side of the non-conductive adhesives 7, 7.

[0016] The non-conductive adhesives 7, 7 are disposed at both longitudinal ends of the core substrate 4 and are linearly arranged along the short side direction of the core substrate 4 (the direction perpendicular to the plane of FIG. 1). Each spacer member 2f is disposed so as to be adjacent to the side of the non-conductive adhesive 7 and is linearly arranged along the short side direction of the core substrate 4. Thus, spacer members 2f, 2f are interposed between the core substrate 4 and the bottom surface of the package 2 on the inner side of the non-conductive adhesives 7, 7. The spacer members 2f, 2f support both longitudinal ends of the core substrate 4.

[0017] The core substrate 4 is made of a resin material having heat resistance and flexibility such as polyimide. The spacer member 2f is made of a paste material such as molybdenum or tungsten. The core substrate 4 is provided so as not to contact the bottom surface of the package 2. The thickness of the core substrate 4 is 5 to 100 μm, and the width (distance) of the space 2d between the core substrate 4 and the bottom surface of the package 2 is preferably 5 to 50 μm.

[0018] Also, the bonding region A1 (the application region of the non-conductive adhesive 7) for bonding the core substrate 4 to the package 2 is arranged so as not to overlap with the arrangement region of the core portion 5 on the upper surface of the core substrate 4 in a plan view. As shown in FIG. 2, in a plan view, the core portion 5 is arranged in the inner region of the pair of spacer members 2f, 2f, and the bonding regions A1, A1 are arranged in the outer region of the pair of spacer members 2f, 2f. Note that the distance from the heater IC 52 on the core substrate 4 to the bonding region A1 is preferably 250 to 1000 μm.

[0019] Next, the core portion 5 will be described with reference to FIG. 3. FIG. 3 shows a state where the core portion 5 is mounted on the core substrate 4. The core portion 5 is a packaging of various electronic components used in the OCXO 1, and has a three-layer structure (laminated structure) in which the oscillation IC 51, the crystal oscillator (piezoelectric oscillator) 50, and the heater IC 52 are laminated in order from the upper side. The areas of the oscillation IC 51, the crystal oscillator 50, and the heater IC 52 in a plan view are gradually decreasing upward. The core portion 5 is configured to stabilize the oscillation frequency of the OCXO 1 by adjusting the temperatures of the crystal oscillator 50, the oscillation IC 51, and the heater IC 52, which have particularly large temperature characteristics. Note that although the various electronic components of the core portion 5 are not sealed with a sealing resin, they may be sealed with a sealing resin depending on the sealing atmosphere.

[0020] The crystal oscillator 100 is constituted by the crystal oscillator 50 and the oscillation IC 51. The oscillation IC 51 is mounted on the crystal oscillator 50 via a plurality of metal bumps. By controlling the piezoelectric oscillation of the crystal oscillator 50 by the oscillation IC 51, the oscillation frequency of the OCXO 1 is controlled. Details of the crystal oscillator 100 will be described later.

[0021] A non-conductive adhesive 53 is interposed between the opposing surfaces of the crystal oscillator 50 and the oscillation IC 51, and the opposing surfaces of the crystal oscillator 50 and the oscillation IC 51 are fixed by the non-conductive adhesive 53. In this case, the upper surface of the crystal oscillator 50 (the first main surface 201 of the first sealing member 20) and the lower surface of the oscillation IC 51 are joined via the non-conductive adhesive 53.

[0022] The oscillation IC 51 has a smaller area in plan view than the crystal oscillator 50, and the entire oscillation IC 51 is located within the range of the crystal oscillator 50 in plan view. The entire lower surface of the oscillation IC 51 is joined to the upper surface of the crystal oscillator 50 (the first main surface 201 of the first sealing member 20).

[0023] The heater IC 52 has a configuration in which, for example, a heating element (heat source), a control circuit for controlling the temperature of the heating element (a circuit for controlling current), and a temperature sensor for detecting the temperature of the heating element are integrated. By controlling the temperature of the core portion 5 with the heater IC 52, the temperature of the core portion 5 is maintained at a substantially constant temperature, and the oscillation frequency of the OCXO 1 is stabilized.

[0024] A non-conductive adhesive 54 is interposed between the opposing surfaces of the crystal oscillator 50 and the heater IC 52, and the opposing surfaces of the crystal oscillator 50 and the heater IC 52 are fixed by the non-conductive adhesive 54. In this case, the lower surface of the crystal oscillator 50 (the second main surface of the second sealing member 30) and the upper surface of the heater IC 52 are joined via the non-conductive adhesive 54.

[0025] The crystal oscillator 50 has a smaller area in plan view than the heater IC 52, and the entire crystal oscillator 50 is located within the range of the heater IC 52 in plan view. The entire lower surface of the crystal oscillator 50 (the second main surface of the second sealing member 30) is joined to the upper surface of the heater IC 52.

[0026] 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 by the non-conductive adhesive 55. As the non-conductive adhesives 53, 54, and 55, for example, polyimide-based adhesives, epoxy-based adhesives, etc. are used.

[0027] In the core portion 5 shown in FIG. 3, external terminals for wire bonding are formed on the upper surfaces of the crystal oscillator 50 and the heater IC 52. The wire bonding of the crystal oscillator 50 and the heater IC 52 is not performed before mounting the core portion 5 on the package 2, but is performed after mounting the core portion 5 on the package 2. That is, as shown in FIG. 1, after mounting the core portion 5 on the package 2, the external terminal formed on the upper surface of the crystal oscillator 50 is connected to the connection terminal formed on the stepped surface of the stepped portion 2c via the wire 6a. Also, the external terminal formed on the upper surface of the heater IC 52 is connected to the connection terminal formed on the stepped surface of the stepped portion 2c via the wire 6b. By performing wire bonding after mounting the core portion 5 on the package 2 in this way, wire bonding can be performed efficiently, and the OCXO 1 with excellent mass productivity can be provided.

[0028] The type of the crystal oscillator 50 used for the core portion 5 is not particularly limited, but a device with a sandwich structure that is easy to thin the device can be preferably used. The device with a sandwich structure is composed of first and second sealing members made of glass or crystal, and a piezoelectric vibrating plate made of, for example, crystal and having vibrating electrodes formed on both main surfaces. The first sealing member and the second sealing member are laminated and joined via the piezoelectric vibrating plate, and it is a three-layer structure device in which the vibrating portion of the piezoelectric vibrating plate arranged inside is hermetically sealed.

[0029] An example of a crystal oscillator 100 in which such a crystal oscillator 50 with a sandwich structure and the oscillation IC 51 are integrally provided will be described with reference to FIGS. 4 and 5. Since the crystal oscillator with a sandwich structure itself is known, a detailed description of the internal structure of the crystal oscillator 50 will be omitted.

[0030] As shown in FIG. 4, the crystal oscillator 100 includes a crystal vibrating plate (piezoelectric vibrating plate) 10, a first sealing member 20, a second sealing member 30, and an oscillation IC 51. In this crystal oscillator 100, the crystal vibrating plate 10 and the first sealing member 20 are joined by an annular sealing joint portion 41, and the crystal vibrating plate 10 and the second sealing member 30 are joined by an annular sealing joint portion 42, thereby forming a package having a substantially rectangular parallelepiped sandwich structure. The sealing joint portions 41 and 42 are formed, for example, with a joint pattern (for example, a joint pattern in which a Ti layer and an Au layer are formed from the lowermost layer side) having an Au layer on the joint surfaces of the crystal vibrating plate 10, the first sealing member 20, and the second sealing member 30, and the joints are made by Au-Au diffusion bonding when the joint surfaces are bonded together. According to this configuration, the gap dimensions between the crystal vibrating plate 10 and the respective sealing members 20 and 30 can be made very small, about 0.15 μm to 1 μm, so that it is possible to achieve a configuration advantageous for thinning and reducing the heat capacity of the core portion 5.

[0031] That is, in the crystal oscillator 100, the first sealing member 20 and the second sealing member 30 are joined to both main surfaces of the crystal vibrating plate 10 on which a vibrating portion (not shown) is formed, thereby forming an internal space (cavity) of the package, and the vibrating portion of the crystal vibrating 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 constitutes an oscillation circuit together with the crystal vibrating plate 10.

[0032] Note that in the core portion 5 shown in FIG. 4, the oscillation IC 51 is mounted on the crystal resonator 50 via a plurality of metal bumps 21 (that is, by flip chip bonding). However, the present invention is not limited to this, and as shown in FIG. 6, the oscillation IC 51 may be die-bonded on the crystal resonator 50 and electrically connected to the crystal resonator 50 by wire bonding. Further, a solid electrode 43 to which a GND potential is applied during the operation of the OCXO1 may be formed on the back surface (the joint surface with the heater IC 52) of the crystal resonator 50.

[0033] In the configuration where the oscillation IC 51 is die-bonded onto the crystal oscillator 50, the contact area between the oscillation IC 51 and the crystal oscillator 50 becomes larger compared to flip-chip bonding, and the influence of the heat generated by the oscillation IC 51 is more likely to be transmitted through the crystal oscillator 50 to the heater IC 52 responsible for temperature control. As a result, the temperature in the core part 5, that is, the temperatures of the oscillation IC 51, the crystal oscillator 50, and the heater IC 52 can be efficiently transmitted to the temperature sensor provided in the heater IC 52, enabling high-precision temperature control. That is, originally, it is preferable that the crystal oscillator 50 is not affected by the oscillation IC 51 which is a heat source other than the heater, but in practice, this is difficult. If that is the case, it becomes easier to control if the temperature change of the crystal oscillator 50 due to the oscillation IC 51 can be efficiently transmitted to the temperature sensor of the heater IC 52.

[0034] Also, when the oscillation IC 51 and the crystal oscillator 50 are electrically connected by wire bonding, in the wire bonding between the core part 5 and the package 2, as shown in FIG. 7, it is preferable that there is no direct wire connection between the crystal oscillator 50 and the package 2, and only the oscillation IC 51 is directly wire-connected to the crystal oscillator 50. In FIG. 7, only the crystal oscillator 50 and the oscillation IC 51 are connected via the wire 6c. In this configuration, it is possible to suppress heat from escaping from the crystal oscillator 50 to the package 2 through the wire. As a result, there are advantages such as higher heat insulation for the crystal oscillator 50 and higher temperature controllability for the crystal oscillator 50.

[0035] As shown in FIG. 5, external terminals 22 are formed on the upper surface of the crystal oscillator 50. Among them, two external terminals 22, 22 have the excitation electrodes of the vibrating portion electrically connected to one end (outer peripheral side end portion) thereof (via wirings and through holes in the crystal oscillator 50), and the oscillation IC 51 is connected to the other end (inner peripheral side end portion). Also, the remaining four external terminals (external terminals provided at the four corners) 22 have one end (outer peripheral side end portion) used for wire bonding with the package 2, and the oscillation IC 51 is connected to the other end (inner peripheral side end portion). The oscillation IC 51 is connected to the external terminal 22 by the FCB method using metal bumps.

[0036] In the present embodiment, in the OCXO1 having the above configuration, the core portion 5 is hermetically sealed inside the heat-insulating package 2. The core portion 5 is mounted on a flexible core substrate 4, and this core substrate 4 is mechanically joined to the package 2 by a non-conductive adhesive 7. The core portion 5 and the package 2 are electrically joined by wire bonding, and a space 2d is provided between the core substrate and the bottom surface of the package 2.

[0037] According to the present embodiment, by separating the mechanical joining of the core substrate 4 to the package 2 by the non-conductive adhesive 7 and the electrical joining of the core portion 5 and the package 2 by wire bonding, high reliability can be obtained in each case. For example, as the non-conductive adhesive 7 for connecting the core substrate 4 to the package 2, a flexible one with a mechanical joining strength that is not easily reduced even under the influence of external stress can be used. Also, in the wire bonding between the core portion 5 and the package 2, by using a metal wire with low electrical resistance, common impedance noise is less likely to occur, and the CN (carrier noise) characteristics of the OCXO1 can be improved.

[0038] Specifically, by using the core part 5 in which the oscillation IC 51, the crystal oscillator 50, and the heater IC 52 are stacked, the heat capacity of the core part 5 can be reduced. When the heat capacity of the core part 5 is reduced, temperature control with low power becomes easier, and moreover, the temperature followability of the core part 5 can be improved, thereby improving the stability of the OCXO 1. Also, when the heat capacity of the OCXO 1 is reduced, it becomes more susceptible to external temperature changes. However, by interposing the core substrate 4 between the core part and the package 2, stress and heat dissipation can be reduced.

[0039] Here, consider the case where the core substrate 4 mediates the electrical connection between the core part 5 and the package 2. In this case, the connection between the core part 5 and the core substrate 4 is made on the upper surface of the core substrate 4, and the connection between the core substrate 4 and the package 2 is made on the lower surface of the core substrate 4. Also, for the connection between the core substrate 4 and the package 2, it is necessary to connect the connection terminal on the lower surface of the core substrate 4 and the connection terminal on the upper surface of the package 2 using a conductive adhesive. That is, between the core substrate 4 and the package 2, it is necessary to simultaneously perform electrical connection and mechanical connection by using a conductive adhesive.

[0040] However, a conductive adhesive with a conductive filler mixed in the underfill is harder than a non-conductive adhesive without a conductive filler, and the mechanical bonding strength may decrease under the influence of external stress. Also, regarding electrical connection, the conductive adhesive has a higher electrical resistance than a metal wire or the like, and common impedance noise is likely to occur, so the CN characteristics of the OCXO 1 deteriorate.

[0041] In contrast, in the OCXO 1 according to this embodiment, the crystal oscillator 50 and the heater IC 52 in the core part 5 are directly connected to connection terminals formed in the package 2 via wires 6a, 6b. Therefore, in the core substrate 4, there is no need for a function to mediate the electrical connection between the core part 5 and the package 2.

[0042] As a result, in the OCXO1 according to the present embodiment, the connection between the core part 5 and the package 2 only needs to be a mechanical bond, and a non-conductive adhesive can be used. As the non-conductive adhesive, a flexible one can be used compared with the conductive adhesive, and the mechanical bond strength is less likely to decrease even under the influence of external stress. Also, regarding the electrical connection between the core part 5 and the package 2, the use of a metal wire with low electrical resistance makes it difficult for common impedance noise to occur, so the CN characteristics of the OCXO1 are improved.

[0043] Moreover, regarding the core substrate 4, since it only needs to have the function of supporting the core part 5 with respect to the package 2, the choice of the material of the core substrate 4 can also be expanded. As the core substrate 4, it is preferable to use a material with excellent heat insulation and heat resistance, and it is also preferable to use a flexible substrate so as to suppress the influence of external stress. From such a viewpoint, in the present embodiment, a flexible substrate made of a resin material such as polyimide is adopted as the core substrate 4.

[0044] In addition, according to the present embodiment, by connecting the core part 5 to the package 2 via the core substrate 4 and forming a space 2d below the core substrate 4, the heat insulation effect on the core part 5 can be enhanced. Also, by providing a pair of stepped portions 2c on the package 2 and providing connection terminals on the stepped portions 2c, the connection terminals approach the opening of the package 2, and wire bonding between the core part 5 and the package 2 becomes easier.

[0045] In the present embodiment, spacer members 2f are interposed between both end portions in the longitudinal direction of the core substrate 4 and the bottom surface of the package 2. The spacer members 2f are provided in a region inside the bonding region A1 for bonding the core substrate 4 to the package 2, that is, in a region closer to the core part 5 than the bonding region A1. Since the thickness of the non-conductive adhesive 7 applied to the bonding region A1 is defined by the spacer members 2f, the width of the space 2d between the bottom surface of the core substrate 4 and the package 2 can be easily defined. The thickness of the spacer members 2f is preferably 5 to 50 μm.

[0046] Here, when the spacer member 2f is not provided, the variation in the thickness of the non-conductive adhesive 7 applied to the bonding region A1 increases according to the application amount of the non-conductive adhesive 7, and the variation in the width of the space 2d between the core substrate 4 and the bottom surface of the package 2 also increases. Further, variations occur in the distance from the heater IC 52 on the core substrate 4 to the non-conductive adhesive 7 applied to the bonding region A1. For this reason, it becomes difficult to stably perform wire bonding of the crystal oscillator 50 and the heater IC 52.

[0047] However, in the present embodiment, by defining the thickness of the non-conductive adhesive 7 applied to the bonding region A1 by the spacer member 2f, it is possible to suppress the variation in the width of the space 2d between the core substrate 4 and the bottom surface of the package 2. Further, it is possible to suppress the variation in the distance from the heater IC 52 on the core substrate 4 to the non-conductive adhesive 7 applied to the bonding region A1. Then, by forming the core substrate 4 of a specific material, setting the width of the space 2d between the core substrate 4 and the bottom surface of the package 2 within a predetermined range, and further setting the distance from the heater IC 52 on the core substrate 4 to the non-conductive adhesive 7 applied to the bonding region A1 within a predetermined range, it is possible to stably perform wire bonding of the crystal oscillator 50 and the heater IC 52. That is, at the time of wire bonding, by bending the core substrate 4, bringing the core substrate 4 into contact with the bottom surface of the recess 2a of the package 2, and making the gap between the core substrate 4 and the bottom surface of the package 2 non-existent, it becomes possible to surely apply ultrasonic waves by wire bonding, and it is possible to stably perform wire bonding of the crystal oscillator 50 and the heater IC 52. Specifically, the core substrate 4 may be made of polyimide, the thickness of the core substrate 4 may be 5 to 100 μm, the width of the space 2d between the core substrate 4 and the bottom surface of the package 2 may be 5 to 50 μm, and the distance from the heater IC 52 on the core substrate 4 to the non-conductive adhesive 7 applied to the bonding region A1 may be 250 to 1000 μm.

[0048] In addition, when the width of the space 2d between the core substrate 4 and the bottom surface of the package 2 is greater than 50 μm, or when the distance from the heater IC 52 on the core substrate 4 to the non-conductive adhesive 7 applied to the bonding region A1 is greater than 1000 μm, the core substrate 4 bends too much during wire bonding, making it difficult to perform wire bonding stably.

[0049] Also, according to the present embodiment, by the spacer members 2f, 2f, when the non-conductive adhesives 7, 7 applied to the bonding region A1 contract, the core substrate 4 can be warped in the direction in which the width of the space 2d between the core substrate 4 and the bottom surface of the package 2 increases, thereby improving the heat insulation effect on the core portion 5.

[0050] The present invention can be implemented in various other forms without departing from its spirit, gist, or main features. Therefore, the above-described embodiments are merely illustrative in all respects and should not be construed in a limiting sense. The scope of the present invention is indicated by the claims and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

[0051] For example, in the above embodiment, the crystal oscillator 100 including the crystal resonator 50 having a sandwich structure is used, but the present invention is not limited thereto, and an oscillator other than the sandwich structure (for example, an SMD (Surface Mount Device) type oscillator) may be used.

[0052] Also, the number of heaters included in the OCXO1 is not particularly limited, and the OCXO1 may have other heaters in addition to the heaters included in the heater IC 52. For example, a configuration in which a heater is further added to the upper part of the core portion 5, a configuration in which a heater is added to the mounting region of circuit components arranged other than the core portion 5 in the package 2, and a configuration in which a film-like heater is embedded in the package 2 main body can be considered.

[0053] 〔Embodiment 2〕 In order to enhance the temperature controllability of the OCXO1, it is important to reduce the heat dissipation from the core part 5 to the package 2. Here, the heat dissipation from the core part 5 to the package 2 mainly occurs through heat conduction via the core substrate 4. That is, by reducing the amount of heat conduction through the core substrate 4, the temperature controllability of the OCXO1 can be improved. In the second embodiment, a configuration example of the core substrate 4 that can reduce the amount of heat conduction from the core part 5 to the package 2 will be described.

[0054] FIG. 8 is a plan view showing an example of the shape of the core substrate 4 according to the second embodiment. In FIG. 8, the region R1 is a region on the upper surface of the core substrate 4 where the heater IC 52, which is a part of the core part 5, is mounted, and the region R2 is a region (adhesive application region) on the back surface of the core substrate 4 that is joined to the package 2.

[0055] In the core substrate 4 according to the second embodiment, a slit 401 is provided between the region R1 and the region R2, and this slit 401 narrows the heat transfer path between the region R1 and the region R2. It is possible to reduce the occurrence of heat dissipation from the core part 5 to the package 2 due to heat conduction through the core substrate 4.

[0056] In order to preferably obtain the heat conduction reduction effect (heat insulation effect) by the slit 401, the slit 401 preferably has a longitudinal direction in a direction (vertical direction in FIG. 8) perpendicular to the arrangement direction of the region R2 on both sides of the core substrate 4 (left - right direction in FIG. 8). Thereby, the slit 401 can block the heat transmitted from the region R1 to the region R2 over a wide range, and the heat insulation effect by the slit 401 is improved.

[0057] Note that the dimension in the short - hand direction (left - right direction in FIG. 8) of the slit 401 does not particularly affect the heat insulation effect of the slit 401, and it is preferably made as small as possible from the viewpoint of avoiding a decrease in the strength of the core substrate 4. When the strength of the core substrate 4 decreases, when wire - bonding the core part 5 to the package 2, ultrasonic waves do not efficiently contribute to the bonding, and it becomes difficult to perform good wire - bonding.

[0058] The slit 401 provided between the region R1 and one region R2 is preferably a slit divided into a plurality in the longitudinal direction rather than formed as one long slit (see Fig. 8(a)). Thus, by dividing the slit 401 into a plurality, it is possible to avoid a decrease in the strength of the core substrate 4 compared to the case of forming one long slit.

[0059] Further, the slit 401 is not limited to being formed linearly, and for example, it may have a shape bent in a direction opposite to the periphery of the region R2 (see Fig. 8(b)). Thus, by bending the slit 401 in a direction opposite to the peripheral shape of the region R2, it is considered that the heat conduction to the region R2 can be effectively blocked, and an effective heat insulation effect by the slit 401 can be obtained.

[0060] Further, the slit 401 is not limited to being arranged closer to the region R2 between the region R1 and the region R2, and it may be arranged closer to the region R1 (see Fig. 8(c)). Thus, by arranging the slit 401 closer to the region R1, the heat conduction from the region R1 (that is, the heat conduction from the heater IC 52 which is a heat source) can be effectively blocked near the heat source of the heat radiating from the region R1, and it is considered that an effective heat insulation effect by the slit 401 can be obtained.

[0061] 〔Embodiment 3〕 In this Embodiment 3, another configuration example of the core substrate 4 capable of reducing the amount of heat conduction from the core portion 5 to the package 2 will be described. Fig. 9 is a plan view showing a shape example of the core substrate 4 according to this Embodiment 3.

[0062] In the core substrate 4 according to this Embodiment 3, an opening 402 is provided directly below the heater IC 52 which is a part of the core portion 5, that is, so as to substantially overlap the region R1. By this opening 402, the contact area between the heater IC 52 and the core substrate 4 is reduced, and the amount of heat transfer from the heater IC 52 to the core substrate 4 can be reduced. As a result, it is possible to reduce the occurrence of heat dissipation from the core portion 5 to the package 2 due to heat conduction through the core substrate 4.

[0063] Note that the opening 402 does not completely contain the region R1 inside the opening, and the opening 402 is shaped such that it does not include at least the four corners of the region R1. As a result, the heater IC 52 can be adhesively fixed to the core substrate 4 at its four corners.

[0064] The opening 402 shown in FIG. 9(a) is formed such that the vertical and horizontal dimensions of the opening 402 are larger than the vertical and horizontal dimensions of the region R1. As a result, the region R1 is shaped such that only its four corners are not included in the opening 402. In this case, the contact area between the heater IC 52 and the core substrate 4 can be minimized, and the heat conduction reduction effect (heat insulation effect) due to the opening 402 can be maximized.

[0065] On the other hand, the opening 402 shown in FIG. 9(b) is formed such that the vertical and horizontal dimensions of the opening 402 are smaller than the vertical and horizontal dimensions of the region R1. As a result, the region R1 is shaped such that not only its four corners but also the entire periphery of its outer edge portion are not included in the opening 402. In this case, when wire-bonding the core portion 5 to the package 2, it is possible to ensure that there is no opening 402 directly under the wire-bonding pad of the core portion 5. As a result, the posture of the core portion 5 can be stabilized during wire-bonding, ultrasonic waves can be efficiently contributed to the bonding, and wire-bonding can be easily performed well.

[0066] 〔Embodiment 4〕 In the above-described Embodiments 1 to 3, the package 2 is a single package, but the present invention is not limited thereto. For example, an H-type package or a two-stage stacked package as shown in FIG. 10 can also be used.

[0067] The OCXO1 in the H-type package shown in FIG. 10 has a package 2 in which, in addition to the recess 2a with an open upper part, a recess 2e with an open lower part is formed. In the recess 2e formed on the other main surface opposite to the main surface (the main surface where the recess 2a is formed) which is the mounting part of the core part 5, circuit components such as a capacitor 9 (circuit components mounted with a circuit component bonding material (for example, solder)) can be arranged as adjustment electronic components used in combination with the heater IC 52. Different from the recess 2a, the recess 2e for arranging the capacitor 9 does not need to be sealed by the lid 3.

[0068] Here, the capacitor 9 can also be arranged inside the package (inside the recess 2a) like the core part 5. However, by arranging the circuit components outside the package as shown in FIG. 10, the heat capacity inside the package can be reduced, and temperature control with low power and improvement of the temperature followability of the core part 5 can be achieved. In addition, the generation of post - gaseous substances due to solder, flux, etc. can be eliminated with respect to the atmosphere inside the hermetically sealed recess 2a. For this reason, the adverse effect of the gas on the core part 5 can be eliminated, which is desirable for further stabilizing the electrical characteristics.

[0069] In the present embodiment, the three capacitors 9 are mounted on the other main surface (in this case, the bottom surface of the recess 2e) opposite to one main surface of the package 2. As shown in FIG. 11, the capacitor 9 is joined by solder to a mounting pad 9a (mounting pad for circuit components) formed on the bottom surface of the recess 2e of the package 2. In FIG. 11, the arrangement area of the capacitor 9 is indicated by a dashed - dotted line. A pair of mounting pads 9a, 9a are arranged opposite to each other along the short - side direction of the package 2, and both ends of each of the three capacitors 9 in the short - side direction of the package 2 are joined to the mounting pads 9a, 9a.

[0070] As shown in Fig. 11, the three mounting pads 9a, 9a are arranged at a predetermined interval in the long side direction of the package 2. Each mounting pad 9a is scattered in an island shape on the bottom surface of the package 2. Also, the package 2 and the three capacitors 9 are each rectangular in plan view, and the three capacitors 9 are symmetrically arranged 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. In this case, it is only necessary that the arrangement positions of the three capacitors 9 are line-symmetric with respect to the center lines L1, L2. A plurality (eight in Fig. 11) of external connection terminals 2g are also formed on the lower surface of the package 2 for electrically connecting the OCXO1 to an external circuit board (not shown) provided outside via solder or the like.

[0071] In the present embodiment, since the three capacitors 9 are symmetrically arranged 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, it is possible to make the heat distribution of the entire package 2 uniform. As a result, heat transfer is less likely to be uneven in the entire package 2, and the temperature control and characteristics of the OCXO1 can be stabilized. Also, since the capacitors 9 are arranged in an orderly manner with respect to their orientation and spacing, there is no waste in the mounting positions of the capacitors 9 with respect to the mounting areas on the other main surfaces of the package 2, and the mountability is improved.

[0072] Also, the number of capacitors 9 mounted on the other main surface of the package 2 is not particularly limited, and the number of capacitors 9 may be other than three. Also, circuit components other than the capacitors 9 may be mounted on the other main surface of the package 2. Also, the sizes (volume, surface area) of all the circuit components do not have to be the same.

[0073] In the example of FIG. 11, the three capacitors 9 were arranged symmetrically with respect to both of the center lines L1 and L2. However, it is sufficient if they are symmetric with respect to at least one of the center lines L1 and L2. For example, the three capacitors 9 may be symmetric only with respect to the center line L1 in the short side direction of the package 2, or the three capacitors 9 may be symmetric only with respect to the center line L2 in the long direction of the package 2. As a result, the symmetry of heat transfer in a specific side direction of the package 2 can be maintained, heat transfer is less likely to be biased, and the temperature control and characteristics of the OCXO1 can be stabilized.

[0074] Also, when the capacitor 9 is arranged outside the package, it is not essential to form the recess 2e as in the package 2 shown in FIG. 10. The other main surface on the side opposite to the main surface where the recess 2a is formed may be flat, and the capacitor 9 may be arranged on this flat surface.

[0075] Also, as the OCXO1 of the two-stage stacked package, although not shown, a package having a recess only on one side can be stacked in the vertical direction, electrically and mechanically joined, and the upper package can be hermetically sealed with a lid. In this case, the upper package may be configured to store the core portion 5 in the recess as shown in FIG. 1, and only the capacitor may be stored in the lower package. Further, as another OCXO1, the capacitor 9 may be arranged on the lid 3 of FIG. 1.

[0076] Also, the above-described core portion 5 has a three-layer structure in which the oscillation IC 51, the crystal oscillator 50, and the heater IC 52 are stacked in this order from above. However, the present invention is not limited to this, and the oscillation IC 51 and the crystal oscillator 50 may be arranged flat (side by side) on the heater IC 52. In this configuration, the crystal oscillator 50 is less likely to be affected by the heat from the oscillation IC 51, and the temperatures of the crystal oscillator 50 and the heater IC 52 are likely to be uniform. Therefore, more accurate temperature control can be performed on the crystal oscillator 50, which is the temperature control target, by the temperature sensor provided in the heater IC 52.

[0077] This application claims priority based on Japanese Patent Application No. 2021-031583 filed in Japan on March 1, 2021. By reference thereto, all of its contents are incorporated into this application.

Description of Reference Numerals

[0078] 1 OCXO (oven-controlled crystal oscillator) 2 Package 2d Space 2f Spacer member 4 Core substrate (flexible substrate) 5 Core part 7 Non-conductive adhesive (bonding material) 50 Crystal oscillator (piezoelectric oscillator) 51 Oscillation IC 52 Heater IC

Claims

1. A thermostatic chamber type piezoelectric oscillator in which a core part is sealed in a heat insulating package in a sealed state, wherein the core part has a configuration including at least an oscillation IC, a piezoelectric vibrator, and a heater IC, the core part is mounted on a flexible substrate, and this flexible substrate is mechanically joined to the package by a joining material, the core part and the package are electrically joined by wire bonding, a space is provided between the flexible substrate and the bottom surface of the package, and a spacer member is interposed between the flexible substrate and the bottom surface of the package. A thermostatic chamber type piezoelectric oscillator characterized by this.

2. A thermostatic chamber type piezoelectric oscillator in which a core part is sealed in a heat insulating package in a sealed state, wherein the core part has a configuration including at least an oscillation IC, a piezoelectric vibrator, and a heater IC, the core part is mounted on a flexible substrate, and this flexible substrate is mechanically joined to the package by a joining material, the core part and the package are electrically joined by wire bonding, a space is provided between the flexible substrate and the bottom surface of the package, the thickness of the flexible substrate is 5 to 100 μm, and the width of the space is 5 to 50 μm. A thermostatic chamber type piezoelectric oscillator characterized by this.

3. The thermostatic chamber type piezoelectric oscillator according to claim 1, a joining region for joining the flexible substrate to the package does not overlap with an arrangement region of the core part with respect to the flexible substrate in a plan view, a spacer member is provided in a region on the core part side rather than the joining region. A thermostatic chamber type piezoelectric oscillator characterized by this.

4. The thermostatic chamber type piezoelectric oscillator according to claim 2, a joining region for joining the flexible substrate to the package does not overlap with an arrangement region of the core part with respect to the flexible substrate in a plan view. A thermostatic chamber type piezoelectric oscillator characterized by this.

5. The thermostatic chamber type piezoelectric oscillator according to claim 1 or 2, wherein the flexible substrate is made of a resin material having heat resistance. A thermostatic chamber type piezoelectric oscillator characterized by this.

6. The thermostatic chamber type piezoelectric oscillator according to claim 1 or 2, wherein the core part is vacuum-sealed inside the package. A thermostatic chamber type piezoelectric oscillator characterized by this.

7. The thermostatic chamber type piezoelectric oscillator according to claim 1 or 2, The flexible substrate is characterized in that a slit is provided between a mounting area on the upper surface of the flexible substrate where the core portion is mounted and a bonding area for bonding the flexible substrate to the package. A thermostatic chamber type piezoelectric oscillator.

8. The thermostatic chamber type piezoelectric oscillator according to claim 1 or 2, The flexible substrate is characterized in that an opening is provided in a region directly below the core portion. A thermostatic chamber type piezoelectric oscillator.

9. The thermostatic chamber type piezoelectric oscillator according to claim 1 or 2, The piezoelectric vibrator is not directly wire-connected to the package, and only the oscillation IC is directly wire-connected to the piezoelectric vibrator. A thermostatic chamber type piezoelectric oscillator.

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