Thermostatic bath piezoelectric oscillator

Abstract

The present invention provides a thermostatic piezoelectric oscillator capable of high-precision control of both the temperature of the heating element and the piezoelectric vibration of the piezoelectric vibrator, while reducing costs. The thermostatic piezoelectric oscillator (1) has a core (5) having a crystal resonator (50), an oscillator IC (51), and a heater IC (52). In the thermostatic piezoelectric oscillator (1), the core (5) is supported in a package (2) by an intermediate member (4) and sealed inside the package (2) in a sealed state.

Description

Technical Field

[0001] This invention relates to a thermostatic bath type piezoelectric oscillator. Background Technology

[0002] Piezoelectric oscillators, such as crystal resonators, have inherent frequency-temperature characteristics, and their vibration frequency changes with temperature. Therefore, in the prior art, there is a type of oven-controlled piezoelectric oscillator (OCXO) in which the piezoelectric oscillator is enclosed in an oven to keep the area around the piezoelectric oscillator at a constant temperature (for example, see Patent Document 1).

[0003] As described above, the OCXO requires high-precision control of both the temperature of the heating element and the piezoelectric vibration of the piezoelectric resonator. In existing technologies, both the temperature of the heating element and the piezoelectric vibration of the piezoelectric resonator are controlled using a separate IC (e.g., OCXO-IC). This necessitates the installation of such an expensive IC, thereby increasing the manufacturing cost of the OCXO.

[0004] [Patent Document 1]: Japanese Patent No. 6376681 Summary of the Invention

[0005] In view of the above, the purpose of this invention is to provide a thermostatic tank piezoelectric oscillator that can both achieve high-precision control of the temperature of the heating element and the piezoelectric vibration of the piezoelectric vibrator and reduce costs.

[0006] As a technical solution to the above-mentioned technical problems, the present invention provides a thermostatic bath type piezoelectric oscillator. This thermostatic bath type piezoelectric oscillator includes a core portion, which comprises a piezoelectric vibrator, an oscillator IC, and a heating element. The core portion is characterized by being supported in a package via a core substrate and sealed within the package in a sealed state. Here, the heating element can be a heater IC and / or a thin-film heater. In other words, the core portion can contain both a heater IC and a thin-film heater, or it can contain only a heater IC or only a thin-film heater. When only a heater IC is provided in the core portion, it is preferable that the heater IC is an integral structure comprising a heating element (heat source), a temperature control circuit (current control circuit) for the heating element, and a temperature sensor for detecting the temperature of the heating element. On the other hand, when only a thin-film heater is provided in the core portion, it is preferable that the temperature regulation IC for the thin-film heater is set independently of the core portion.

[0007] Based on the above structure, by sealing the core within the package, temperature changes in the piezoelectric resonator within the core can be suppressed as much as possible, even if external temperatures change. Therefore, temperature regulation by the OCXO can be performed within a relatively small temperature range, simplifying the components required for temperature regulation and thus reducing costs. Furthermore, by using an IC that primarily controls the temperature of the heating element (e.g., a heater IC) in conjunction with an oscillator IC that primarily controls the piezoelectric vibration of the piezoelectric resonator, both the temperature of the heating element and the piezoelectric vibration of the piezoelectric resonator can be controlled with high precision. This significantly reduces costs compared to using an IC capable of controlling both the temperature of the heating element and the piezoelectric vibration of the piezoelectric resonator (e.g., an OCXO-IC).

[0008] In the above structure, it is preferable that a recess with an upper opening is formed on the package body, and the core portion is supported by the core substrate in a state of suspension inside the package body.

[0009] Based on the above structure, since the core is supported by the core substrate within the package, the OCXO can be made smaller. This reduces the heat capacity of the OCXO, enabling high-precision temperature control.

[0010] In the above structure, preferably, a pair of opposing stepped portions are formed inside the package, the core substrate is configured to be mounted between the pair of stepped portions, and the core portion is accommodated in the space between the pair of stepped portions.

[0011] Based on the above structure, the core substrate can be easily fixed within the package using the stepped portion of the package. Furthermore, since the core is housed within the space between a pair of stepped portions inside the package, the OCXO can be further miniaturized. This reduces the heat capacity of the OCXO, enabling high-precision temperature control.

[0012] In the above structure, preferably, the core substrate is fixed to the step portion by a polyimide-based conductive adhesive.

[0013] Furthermore, the encapsulation body can suffer thermal and temporal damage due to sealing, aging, and deterioration over time. Therefore, when using resin-based adhesives with low heat resistance as conductive adhesives, gases may be generated within the encapsulation body due to decomposition and softening, potentially hindering the OCXO from achieving high-precision temperature control. To address this, the above structure uses polyimide-based adhesives with low thermal conductivity and high heat resistance as conductive adhesives to prevent the aforementioned adverse effects.

[0014] In the above structure, preferably, the piezoelectric vibrator includes a first sealing member, a second sealing member, and a piezoelectric vibrating plate. The first sealing member and the second sealing member are made of glass or quartz crystal. The piezoelectric vibrating plate has a vibrating portion made of quartz crystal and having excitation electrodes formed on two main surfaces. The first sealing member and the second sealing member are stacked and joined together with the piezoelectric vibrating plate in between. The vibrating portion of the piezoelectric vibrating plate disposed inside is hermetically sealed.

[0015] Based on the above structure, the sandwich structure described above, which enables a lower profile, is used as a piezoelectric oscillator, thus allowing for a lower profile and miniaturization of the core. This reduces the heat capacity of the core, enabling high-precision temperature control using an OCXO.

[0016] Invention effects:

[0017] Based on this invention, by sealing the core within a package, temperature variations in the piezoelectric resonator within the core can be suppressed as much as possible, even when external temperatures change. Therefore, temperature regulation of the OCXO only needs to be performed within a small temperature range, thus simplifying the components required for temperature regulation and reducing costs. Furthermore, by using an IC that primarily controls the temperature of the heating element in conjunction with an oscillator IC that primarily controls the piezoelectric vibration of the piezoelectric resonator, high-precision control of both the heating element's temperature and the piezoelectric resonator's piezoelectric vibration can be achieved separately. This significantly reduces costs compared to using an IC capable of controlling both the heating element's temperature and the piezoelectric resonator's piezoelectric vibration (e.g., an OCXO-IC). Attached Figure Description

[0018] Figure 1 This is a cross-sectional view showing the general structure of the OCXO involved in this embodiment.

[0019] Figure 2 It means Figure 1 A cross-sectional view of the core structure of the OCXO.

[0020] Figure 3 It means Figure 2 A top view of the core section.

[0021] Figure 4 It is a schematic representation Figure 2 A schematic diagram of the components of the crystal oscillator in the core part.

[0022] Figure 5 yes Figure 4 A top view of the first main face side of the first sealing member of the crystal oscillator.

[0023] Figure 6 yes Figure 4 A top view of the second main face side of the first sealing member of the crystal oscillator.

[0024] Figure 7 yes Figure 4 A top view of the first main surface of the crystal oscillator of a crystal oscillator.

[0025] Figure 8 yes Figure 4 A top view of the second main surface of the crystal oscillator of a crystal oscillator.

[0026] Figure 9 yes Figure 4 A top view of the first main face side of the second sealing member of the crystal oscillator.

[0027] Figure 10 yes Figure 4 A top view of the second main face side of the second sealing member of the crystal oscillator.

[0028] Figure 11 This is a cross-sectional view showing the general structure of the OCXO involved in the modified example.

[0029] Figure 12 It means Figure 11 A cross-sectional view of the core component and core substrate of the OCXO.

[0030] Figure 13 It means Figure 12 Top view of the core component and core substrate.

[0031] <Explanation of Figure Labels>

[0032] 1. Thermostatic bath type piezoelectric oscillator

[0033] 2 Package

[0034] 4. Interposer (core substrate)

[0035] 5. Core Department

[0036] 50 Crystal resonator (piezoelectric oscillator)

[0037] 51 Oscillator IC

[0038] 52 Heater IC

[0039] 100 Crystal Oscillator Detailed Implementation

[0040] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0041] like Figure 1As shown, the OCXO1 of this embodiment is configured such that a core portion 5 is disposed inside a roughly rectangular package (shell) 2 made of ceramic or the like, and is hermetically sealed by a cover 3. A recess 2a with an opening at the top is formed on the package 2, and the core portion 5 is hermetically sealed inside the recess 2a. A peripheral wall portion 2b surrounds the recess 2a, and the cover 3 is fixed to the top surface of the peripheral wall portion 2b by a sealing material 8, thus sealing the interior of the package 2. Preferably, the sealing material 8 is a metallic sealing material such as an Au-Sn alloy or solder, but a sealing material such as low-melting-point glass can also be used. Preferably, the internal space of the package 2 is a vacuum, or a low-pressure atmosphere with low thermal conductivity such as nitrogen or argon.

[0042] A stepped portion 2c is formed on the inner wall surface of the peripheral wall portion 2b of the package 2. The extending direction of the stepped portion 2c is consistent with the arrangement direction of the connecting terminals (not shown in the figure). The core portion 5 is connected to the connecting terminals formed on the stepped portion 2c through a plate-shaped intermediate member (core substrate) 4. Specifically, the connecting terminals formed on the stepped surface of the stepped portion 2c are connected to the top surface of the intermediate member 4 (where the conductive adhesive 7 is used) through the conductive adhesive 7. Figure 1 The connection terminal is connected on the lower side surface (4a). Furthermore, a connection terminal is formed on the bottom surface of the core portion 5. Figure 1 The external terminals (not shown in the diagram) on the upper surface 5a of the core 5 are connected to the connecting terminals formed on the top surface 4a of the intermediate member 4 by conductive adhesive 6. The external terminals of the bottom surface 5a of the core 5 are formed in the area of ​​the bottom surface 5a of the core 5 where the metal wiring 54a described later is not formed. The conductive adhesive 6 and conductive adhesive 7 are, for example, polyimide adhesives, epoxy adhesives, etc.

[0043] Intermediate member 4 is configured to be positioned between opposing stepped portions 2c within the encapsulation body 2, and core portion 5 is housed within the space between the stepped portions 2c. On the top surface of core portion 5 ( Figure 1 A gap is provided between the lower surface 5b of the core portion 5 and the bottom surface 2d of the recess 2a of the package body 2. Thus, the core portion 5 can... Figure 2 The state shown is flipped upside down and fixed on the intermediate member 4. The core part 5 is supported by the intermediate member 4 in a suspended state inside the package 2.

[0044] Below, refer to Figure 2 , Figure 3 The core part 5 will be explained. Figure 2 The diagram shows the core 5 with its bottom surface 5a positioned on the lower side and its top surface 5b positioned on the upper side (relative to...). Figure 1 (The state of flipping up and down).

[0045] The core section 5 is constructed by encapsulating various electronic components used in the OCXO1, such as the crystal resonator 50, oscillator IC 51, heater IC 52, and surface-mount capacitors (bypass capacitors) 53a-53c, and sealing these components on the crystal substrate 54 with sealing resin 57. In particular, the core section 5 is configured to stabilize the oscillation frequency of the OCXO1 by temperature regulation of the crystal resonator 50, oscillator IC 51, heater IC 52, etc., which have large temperature characteristics. Furthermore, it is preferable to seal the various electronic components of the core section 5 with sealing resin 57, but sealing with sealing resin is not required depending on the sealing atmosphere. For example, in the case of an inert gas sealing atmosphere, sealing with sealing resin is not required, and the various electronic components used in the OCXO1 can be covered by a cover to mitigate the effects of heat convection.

[0046] The crystal oscillator 100 consists of a crystal resonator 50 and an oscillator IC 51. The oscillator IC 51 is mounted on the crystal resonator 50 via multiple metal protrusions 51a. The oscillation frequency of the OCXO1 is controlled by controlling the piezoelectric vibration of the crystal resonator 50 using the oscillator IC 51. The heater IC 52 is an IC that regulates the temperature of the core 5, controlling the current flowing to the thin-film heaters (heater substrates) 56a and 56b used in the core 5. The heater IC 52 is mounted on the crystal substrate 54 via multiple metal protrusions 52a.

[0047] The core 5 has two opposing crystal substrates, 54 and 55. Metal wirings 54a and 55a are formed on the crystal substrates 54 and 55, respectively, and serve as thin-film heaters 56a and 56b. The thin-film heaters 56a and 56b are constructed by depositing metal wirings 54a and 55a, which are resistive films, onto the surfaces of the crystal substrates 54 and 55, which serve as substrates. The regions in the crystal substrates 54 and 55 where the metal wirings 54a and 55a are formed function as thin-film heaters (heater substrates) 56a and 56b for temperature regulation.

[0048] Here, Figure 3 The illustration of the upper crystal substrate 55 and metal wiring 55a is omitted, and the heating areas of the upper and lower thin-film heaters 56a and 56b are shown with dashed lines. Furthermore, Figure 2In this embodiment, a laminated substrate using crystal wafers 54b and 54c is used as the crystal substrate 54. Internal wiring 54d, primarily electrically connected to the heater IC 52, is inserted between crystal wafers 54b and 54c of the crystal substrate 54. The internal wiring 54d is electrically connected to external terminals (not shown) formed on the bottom surface of the crystal substrate 54, and is electrically connected to the outside via the aforementioned intermediate member 4, package 2, etc. However, the present invention is not limited to this; the crystal substrate 54 can also be a single-layer substrate using a single crystal wafer. Furthermore, while the shapes and heating areas of the upper and lower thin-film heaters 56a and 56b may differ somewhat, the upper and lower thin-film heaters 56a and 56b can also be of the same shape to obtain the same heating area.

[0049] The core portion 5 is constructed by arranging a crystal resonator 50, an oscillator IC51, and a heater IC52 with large temperature characteristics between two crystal substrates (crystal substrate 54 and crystal substrate 55). Specifically, the core portion 5 is configured such that the crystal resonator 50, the oscillator IC51, and the heater IC52 are sandwiched between two thin-film heaters (heater substrates) for temperature regulation (i.e., thin-film heaters 56a and 56b). In other words, the crystal resonator 50, the oscillator IC51, and the heater IC52 are arranged between the thin-film heater 56a formed on the lower crystal substrate 54 and the thin-film heater 56b formed on the upper crystal substrate 55. The lower thin-film heater 56a is arranged to cover the area below the crystal resonator 50, the oscillator IC51, and the heater IC52; the upper thin-film heater 56b is arranged to cover the area above the crystal resonator 50, the oscillator IC51, and the heater IC52. Here, "covering" means that when viewed from above, most (or all) of the crystal resonator 50, oscillator IC51, and heater IC52 overlap with the crystal substrate 54 and crystal substrate 55, excluding cases where only a portion (e.g., a few percent to twenty or thirty percent) overlaps with the crystal substrate 54 and crystal substrate 55.

[0050] Furthermore, among the surface mount capacitors 53a to 53c, two surface mount capacitors (surface mount capacitor 53b and surface mount capacitor 53c) are sandwiched between two thin-film heaters (heater substrates) (thin-film heater 56a and thin-film heater 56b). The two smaller surface mount capacitors (surface mount capacitor 53b and surface mount capacitor 53c) are mounted on the lower crystal substrate 54, and the upper crystal substrate 55 is configured to contact the top surfaces of surface mount capacitors 53b and 53c. On the other hand, the largest surface mount capacitor 53a is mounted on the lower crystal substrate 54 but is not covered by the upper crystal substrate 55.

[0051] There is no particular limitation on the type of crystal resonator 50, but a sandwich structure that facilitates device miniaturization is preferred. The sandwich structure device includes a first sealing member, a second sealing member, and a piezoelectric vibrating plate. The first and second sealing members are made of glass or quartz crystal, and the piezoelectric vibrating plate has a vibrating portion, for example, made of quartz crystal, with excitation electrodes formed on two main surfaces. The first and second sealing members are stacked and joined together with the piezoelectric vibrating plate in between, and the vibrating portion of the piezoelectric vibrating plate disposed inside is hermetically sealed.

[0052] Below, refer to Figures 4 to 10 The crystal oscillator 100 having the above-described sandwich structure of crystal resonator 50 will be described.

[0053] like Figure 4 As shown, the crystal oscillator 100 is configured to include a crystal vibrating plate (piezoelectric vibrating plate) 10, a first sealing member 20, a second sealing member 30, and an oscillator IC51. In this crystal oscillator 100, the crystal vibrating plate 10 is joined to the first sealing member 20, and the crystal vibrating plate 10 is joined to the second sealing member 30, thereby forming a sandwich-structure package with an approximately rectangular parallelepiped structure. In other words, in the crystal oscillator 100, the first sealing member 20 and the second sealing member 30 are respectively joined to the two main surfaces of the crystal vibrating plate 10 to form the internal space (cavity) of the package, and the vibrating part 11 (see reference) Figure 7 , Figure 8 It is airtightly sealed within the internal space.

[0054] The crystal oscillator 100 is, for example, a package with a size of 1.0 × 0.8 mm, achieving miniaturization and a low profile. Furthermore, to achieve miniaturization, no parapet is formed in the package; instead, the electrodes are connected via through-holes. The oscillator IC 51, mounted on the first sealing member 20, is a single-chip integrated circuit element that, together with the crystal oscillator 10, constitutes an oscillation circuit. The crystal oscillator 100 is mounted on the crystal substrate 54, for example, using solder or the like.

[0055] like Figure 7 , Figure 8 As shown, the crystal oscillator 10 is a piezoelectric substrate made of quartz crystal, and its two main surfaces (first main surface 101 and second main surface 102) are configured as flat and smooth surfaces (mirror finish). The crystal oscillator 10 uses an AT-cut quartz crystal sheet that undergoes thickness shear vibration. Figure 7 , Figure 8 In the crystal oscillator 10 shown, the two principal surfaces 101 and 102 of the crystal oscillator 10 are the XZ′ plane. In this XZ′ plane, the direction parallel to the short side direction of the crystal oscillator 10 is taken as the X-axis direction, and the direction parallel to the long side direction of the crystal oscillator 10 is taken as the Z′ axis direction.

[0056] A pair of excitation electrodes (first excitation electrode 111 and second excitation electrode 112) are formed on the two main surfaces 101 and 102 of the crystal oscillator 10. The crystal oscillator 10 includes: a vibrating part 11 configured as approximately rectangular, an outer frame part 12 surrounding the outer periphery of the vibrating part 11, and a holding part 13 that holds the vibrating part 11 by connecting the vibrating part 11 and the outer frame part 12. In other words, the crystal oscillator 10 is a structure in which the vibrating part 11, the outer frame part 12, and the holding part 13 are integrated. The holding part 13 extends (protrudes) from only one corner of the vibrating part 11 in the +X direction and the -Z′ direction toward the outer frame part 12 in the -Z′ direction. A through part (slit) 11a is formed between the vibrating part 11 and the outer frame part 12, and the vibrating part 11 and the outer frame part 12 are connected only by the holding part 13.

[0057] A first excitation electrode 111 is disposed on the first main surface 101 side of the vibration part 11, and a second excitation electrode 112 is disposed on the second main surface 102 side of the vibration part 11. Lead wires (first lead wire 113 and second lead wire 114) for connecting these excitation electrodes to external electrode terminals are connected to the first excitation electrode 111 and the second excitation electrode 11. The first lead wire 113 extends from the first excitation electrode 111 and is connected to a connection bonding pattern 14 formed on the outer frame part 12 via a holding part 13. The second lead wire 114 extends from the second excitation electrode 112 and is connected to a connection bonding pattern 15 formed on the outer frame part 12 via a holding part 13.

[0058] On the two main surfaces (first main surface 101 and second main surface 102) of the crystal oscillator 10, vibration-side sealing portions for engaging the crystal oscillator 10 with the first sealing member 20 and the second sealing member 30 are respectively provided. The vibration-side sealing portion of the first main surface 101 has a vibration-side first engagement pattern 121; the vibration-side sealing portion of the second main surface 102 has a vibration-side second engagement pattern 122. The vibration-side first engagement pattern 121 and the vibration-side second engagement pattern 122 are provided on the outer frame portion 12 and are annular when viewed from above.

[0059] In addition, such as Figure 7 , Figure 8 As shown, five through holes are formed on the crystal oscillator 10, penetrating between the first main surface 101 and the second main surface 102. Specifically, four first through holes 161 are respectively provided in the four corner areas (corner areas) of the outer frame portion 12. Second through holes 162 are provided on one side of the outer frame portion 12 located in the Z′ axis direction of the oscillator 11. Figure 7 , Figure 8(The center is the -Z′ direction side). Connecting patterns 123 are formed around the first through hole 161. In addition, connecting patterns 124 are formed on the first main surface 101 side and connecting patterns 15 are formed on the second main surface 102 side around the second through hole 162.

[0060] In the first through hole 161 and the second through hole 162, through electrodes are formed along the inner wall surface of each through hole. These through electrodes are used to enable the conduction of the electrodes formed on the first main surface 101 and the second main surface 102. In addition, the middle portion of each of the first through hole 161 and the second through hole 162 becomes a hollow through portion that passes between the first main surface 101 and the second main surface 102.

[0061] Secondly, such as Figure 5 , Figure 6 As shown, the first sealing member 20 is a cuboid substrate made of an AT-cut quartz crystal sheet. The second main surface 202 of the first sealing member 20 (the surface that engages with the crystal oscillator 10) is made into a flat and smooth surface (mirror finish). Furthermore, although the first sealing member 20 does not have a vibrating section, by using an AT-cut quartz crystal sheet, similar to the crystal oscillator 10, the thermal expansion rates of the crystal oscillator 10 and the first sealing member 20 are the same, thereby suppressing thermal deformation in the crystal oscillator 100. In addition, the orientations of the X-axis, Y-axis, and Z′-axis in the first sealing member 20 are the same as those in the crystal oscillator 10.

[0062] like Figure 5 As shown, six electrode patterns 22 are formed on the first main surface 201 of the first sealing member 20. These six electrode patterns 22 include mounting pads for mounting an oscillator IC 51, which serves as an oscillation circuit element. The oscillator IC 51 uses metal protrusions (e.g., Au protrusions) 51a (see reference). Figure 4 It is bonded to the electrode pattern 22 by flip chip bonding (FCB).

[0063] like Figure 5 , Figure 6 As shown, six through holes are formed on the first sealing member 20. These six through holes are respectively connected to six electrode patterns 22 and pass through the first main surface 201 and the second main surface 202. Specifically, four third through holes 211 are provided in the four corner areas (corner portions) of the first sealing member 20. Fourth through holes 212 and fifth through holes 213 are respectively provided in... Figure 5 , Figure 6 The +Z′ direction and the -Z′ direction.

[0064] In the third through hole 211, the fourth through hole 212, and the fifth through hole 213, through electrodes are formed along the inner wall surface of each through hole. These through electrodes are used to enable conduction between the electrodes formed on the first main surface 201 and the second main surface 202. Furthermore, the middle portion of each of the third through hole 211, the fourth through hole 212, and the fifth through hole 213 forms a hollow through portion that connects the first main surface 201 and the second main surface 202.

[0065] A sealing-side first engagement pattern 24 is formed on the second main surface 202 of the first sealing member 20. This sealing-side first engagement pattern 24 serves as a sealing-side first sealing portion that engages with the crystal oscillator 10. When viewed from above, the sealing-side first engagement pattern 24 is annular.

[0066] Furthermore, on the second main surface 202 of the first sealing member 20, connecting engagement patterns 25 are formed around the third through hole 211. Connecting engagement patterns 261 are formed around the fourth through hole 212, and connecting engagement patterns 262 are formed around the fifth through hole 213. Additionally, a connecting engagement pattern 263 is formed on the opposite side (-Z′ direction side) of the connecting engagement pattern 261 in the long axis direction of the first sealing member 20. The connecting engagement patterns 261 and 263 are connected by wiring patterns 27.

[0067] Secondly, such as Figure 9 , Figure 10 As shown, the second sealing member 30 is a cuboid substrate made of an AT-cut quartz crystal sheet. The first main surface 301 of the second sealing member 30 (the surface that engages with the crystal oscillator 10) is configured as a flat and smooth surface (mirror finish). Furthermore, in the second sealing member 30, it is preferable to also use an AT-cut quartz crystal sheet like the crystal oscillator 10, and the orientation of the X-axis, Y-axis, and Z′-axis is the same as that of the crystal oscillator 10.

[0068] A second sealing-side engagement pattern 31 is formed on the first main surface 301 of the second sealing member 30. The second sealing-side engagement pattern 31 serves as a second sealing portion that engages with the crystal oscillator 10. When viewed from above, the second sealing-side engagement pattern 31 is annular.

[0069] Four external electrode terminals 32 are provided on the second main surface 302 of the second sealing member 30. These four external electrode terminals 32 are electrically connected to the crystal substrate 54, for example, via solder. The external electrode terminals 32 are located at the four corners (corner portions) of the second main surface 302 of the second sealing member 30. The external electrode terminals 32 are electrically connected to external terminals (not shown) formed on the bottom surface of the crystal substrate 54, and are electrically connected to the outside via the aforementioned intermediate member 4, encapsulation body 2, etc.

[0070] like Figure 9 , Figure 10 As shown, four through holes are formed on the second sealing member 30, passing through the first main surface 301 and the second main surface 302. Specifically, four sixth through holes 33 are provided in the four corner areas (corner portions) of the second sealing member 30. A through electrode is formed along the inner wall surface of each sixth through hole 33, which is used to achieve conductivity between the electrodes formed on the first main surface 301 and the second main surface 302. Thus, through the through electrodes formed on the inner wall surface of the sixth through holes 33, conductivity is achieved between the electrodes formed on the first main surface 301 and the external electrode terminals 32 formed on the second main surface 302. Furthermore, the middle portion of each sixth through hole 33 becomes a hollow through portion passing through the first main surface 301 and the second main surface 302. Additionally, connection patterns 34 are formed around the sixth through holes 33 on the first main surface 301 of the second sealing member 30.

[0071] In the crystal oscillator 100 comprising the aforementioned crystal vibrator 10, first sealing member 20, and second sealing member 30, the crystal vibrator 10 and the first sealing member 20 are diffusely bonded with the first bonding pattern 121 on the vibrating side and the first bonding pattern 24 on the sealing side overlapping, and the crystal vibrator 10 and the second sealing member 30 are diffusely bonded with the second bonding pattern 122 on the vibrating side and the second bonding pattern 31 on the sealing side overlapping, thereby forming a... Figure 4 The shown is a sandwich-structured package. Thus, the internal space of the package, i.e., the storage space for the vibrating part 11, is airtight.

[0072] At this time, the aforementioned bonding patterns also diffuse and bond together in a state of overlapping. Then, through the bonding of the bonding patterns, the crystal oscillator 100 realizes the electrical conduction of the first excitation electrode 111, the second excitation electrode 112, the oscillator IC51, and the external electrode terminal 32.

[0073] Specifically, the first excitation electrode 111 is connected to the oscillator IC 51 via the first lead wire 113, the wiring pattern 27, the fourth through hole 212, and the electrode pattern 22 in sequence. The second excitation electrode 112 is connected to the oscillator IC 51 via the second lead wire 114, the second through hole 162, the fifth through hole 213, and the electrode pattern 22 in sequence. In addition, the oscillator IC 51 is connected to the external electrode terminal 32 via the electrode pattern 22, the third through hole 211, the first through hole 161, and the sixth through hole 33 in sequence.

[0074] In the crystal oscillator 100, it is preferable that various bonding patterns are formed by stacking multiple layers on the crystal wafer, and that Ti (titanium) layers and Au (gold) layers are deposited starting from the bottom layer side. Furthermore, it is preferable that other wiring or electrodes formed on the crystal oscillator 100 have the same bonding pattern structure, thereby enabling the simultaneous formation of bonding patterns, wiring, and electrode patterns.

[0075] In the crystal oscillator 100 configured as described above, the sealing portions (sealing paths) (sealing portions 115 and 116) that provide an airtight seal to the vibrating portion 11 of the crystal oscillator 10 are annular in plan view. The sealing path 115 is formed by the diffusion bonding of the first bonding pattern 121 on the vibrating side and the first bonding pattern 24 on the sealing side, and the outer and inner edge shapes of the sealing path 115 are approximately octagonal. Similarly, the sealing path 116 is formed by the diffusion bonding of the second bonding pattern 122 on the vibrating side and the second bonding pattern 31 on the sealing side, and the outer and inner edge shapes of the sealing path 116 are approximately octagonal.

[0076] As described above, in this embodiment, the core 5 is configured to be supported in the package 2 by the intermediate member 4 and sealed inside the package 2 in a sealed state. Then, by controlling the current supplied to the thin-film heaters 56a and 56b by the heater IC 52, the temperature of the space (temperature regulation space) between the upper and lower thin-film heaters (thin-film heaters 56a and 56b) can be regulated.

[0077] Based on this embodiment, the crystal resonator 50, oscillator IC51, and heater IC52 can be precisely (at a constant temperature) regulated within the temperature regulation space sandwiched between the upper and lower thin-film heaters (thin-film heater 56a, thin-film heater 56b). Furthermore, by encapsulating the core 5 within the package 2, temperature variations in the crystal resonator 50 of the core 5 can be suppressed as much as possible, even if external temperatures change. Therefore, temperature regulation based on the OCXO1 can be performed within a relatively small temperature range, simplifying the components required for temperature regulation and thus reducing costs. Furthermore, by using heater IC52, which mainly controls the temperature of thin-film heaters 56a and 56b, and oscillator IC51, which mainly controls the piezoelectric vibration of crystal resonator 50, high-precision control can be achieved for the temperature of thin-film heaters 56a and 56b and the piezoelectric vibration of crystal resonator 50, respectively. Compared with the case of using ICs (such as OCXO-IC) that can control both the temperature of thin-film heaters 56a and 56b and the piezoelectric vibration of crystal resonator 50, the cost can be significantly reduced.

[0078] In this embodiment, a recess 2a with an opening at the top is formed on the package 2, and the core 5 is supported inside the package 2 in a suspended state by the intermediate member 4. Thus, by supporting the core 5 in the package 2 with the intermediate member 4, the OCXO1 can be made shorter. This reduces the heat capacity of the OCXO1, enabling high-precision temperature control.

[0079] More specifically, a pair of opposing stepped portions 2c are formed inside the package 2, the intermediate member 4 is configured to be mounted between the pair of stepped portions 2c, and the core portion 5 is housed within the space between the pair of stepped portions 2c. Thus, the intermediate member 4 can be easily fixed within the package 2 using the stepped portions 2c of the package 2. Furthermore, by housing the core portion 5 within the space between the pair of stepped portions 2c inside the package 2, the OCXO1 can be further reduced in size. This reduces the heat capacity of the OCXO1, enabling high-precision temperature control.

[0080] However, the encapsulation 2 is susceptible to thermal and temporal damage due to sealing, aging, and deterioration over time. Therefore, when using resin-based adhesives with low heat resistance as conductive adhesives 6 and 7, gas may be generated inside the encapsulation 2 due to decomposition and softening, potentially hindering the OCXO1 from achieving precise temperature control. Therefore, in this embodiment, polyimide-based adhesives and epoxy-based adhesives with low thermal conductivity and high heat resistance are used as conductive adhesives 6 and 7 to prevent the aforementioned problems.

[0081] Furthermore, in this embodiment, a sandwich-structure crystal resonator 50, as a piezoelectric oscillator, is used, where the vibrating part 11 is hermetically sealed internally as described above, thus achieving a low profile. Therefore, the core part 5 can be further reduced in size and miniaturized. This reduces the heat capacity of the core part 5, enabling the OCXO1 to achieve high-precision temperature regulation. The thickness of the crystal resonator 50 is, for example, 0.12 mm, which is very thin compared to crystal resonators in the prior art. Therefore, compared to prior art OCXOs, the heat capacity of the core part 5 can be significantly reduced, thereby reducing the heat generated by the heater in the OCXO1 with the aforementioned core part 5, which is beneficial for achieving low energy consumption. Moreover, the temperature tracking performance of the core part 5 can be improved, thereby enhancing the stability of the OCXO1. Furthermore, as described above, in the sandwich-structure crystal resonator 50, the vibrating part 11 is hermetically sealed without the use of adhesive, thereby suppressing the adverse effects of heat convection caused by outgas generated by the adhesive. In other words, when using an adhesive, thermal convection occurs within the hermetically sealed space of the vibrating section 11 due to the circulation of released gas generated by the adhesive, which may hinder the vibrating section 11 from achieving high-precision temperature control. However, in the three-overlapping crystal resonator 50, the aforementioned released gas is not generated, thus enabling the vibrating section 11 to achieve high-precision temperature control.

[0082] Furthermore, in the sandwich-structured crystal resonator 50, the bonding member formed by the bonding of the sealing path 115, sealing path 116, and the bonding pattern is made of a thin-film metal layer. Therefore, the vertical (stacked) thermal conductivity of the crystal resonator 50 is good, and the temperature of the crystal resonator 50 can be rapidly equalized. In the case of sealing paths 115, sealing path 116, etc., the thickness of the thin-film metal layer is less than 1.00 μm (specifically, 0.15 μm to 1.00 μm in the Au-Au bonding of this embodiment), which is very thin compared to the metal paste sealing material (e.g., 5 μm to 20 μm) using Sn in the prior art. As a result, the vertical (stacked) thermal conductivity of the crystal resonator 50 can be improved. In addition, since the crystal oscillator 10 is bonded to the first sealing member 20 in multiple bonding regions, and the crystal oscillator 10 is bonded to the second sealing member 30 in multiple bonding regions, the thermal conductivity of the crystal resonator 50 in the vertical (stacked) direction is even better.

[0083] In this embodiment, a through portion 11a is formed between the vibrating portion 11 and the outer frame portion 12 of the crystal oscillator 10, and the vibrating portion 11 and the outer frame portion 12 are connected only by a holding portion 13. The holding portion 13 extends from a corner of the vibrating portion 11 in the +X and -Z′ directions toward the outer frame portion 12. Since the holding portion 13 is located at a corner of the outer periphery of the vibrating portion 11 where piezoelectric vibration displacement is smaller, compared to the case where the holding portion 13 is located outside the corner (in the middle of the edge), it is possible to prevent piezoelectric vibration from leaking to the outer frame portion 12 via the holding portion 13, thereby enabling the vibrating portion 11 to perform piezoelectric vibration more efficiently. Furthermore, compared to the case where two or more holding portions 13 are provided, it is possible to reduce the stress acting on the vibrating portion 11 and reduce the frequency shift of piezoelectric vibration caused by such stress, thereby improving the stability of piezoelectric vibration.

[0084] This invention can be modified in various ways without departing from its spirit, purpose, or main features. Therefore, the above embodiments are merely examples and should not be construed as limiting interpretations. The scope of this invention is defined by the claims and is not limited by the description. Furthermore, all modifications and alterations falling within the scope of the claims are within the scope of this invention.

[0085] In the above embodiment, a sandwich-structured crystal resonator 50 is used as the piezoelectric oscillator, but the invention is not limited to this and piezoelectric oscillators with other structures can also be used. Furthermore, the oscillator IC51 and heater IC52 are mounted using the FCB method with metal protrusions, but the invention is not limited to this and the oscillator IC51 or heater IC52 can also be mounted by wire bonding.

[0086] In the above embodiment, thin-film heaters 56a and 56b are used as the heater substrate, but the method is not limited to this; heaters with other structures can also be used for temperature regulation of the core 5. The number of heaters is not particularly limited. However, from the viewpoint of achieving a lower profile and smaller size for the core 5, it is preferable to use thin-film heaters 56a and 56b as the heater substrate. Furthermore, since the heater IC52 disposed inside the core 5 generates a large amount of heat, it can also be used as a heat source for temperature regulation of the core 5.

[0087] Furthermore, in the above embodiment, the core 5 is configured to sandwich the crystal resonator 50, oscillator IC 51, heater IC 52, and surface mount capacitors 53b and 53c between two thin-film heaters (thin-film heaters 56a and 56b). However, as long as the various electronic components used in the OCXO1 are packaged, the core 5 with other structures can also be sealed inside the package. Furthermore, since the temperature characteristics of the surface mount capacitors 53a to 53c are smaller than those of the crystal resonator 50, oscillator IC 51, and heater IC 52, it is not necessary to place all of the surface mount capacitors 53a to 53c between the upper and lower thin-film heaters (thin-film heaters 56a and 56b), and their number is not particularly limited.

[0088] The core unit 5 described above employs a structure including a crystal resonator 50, an oscillator IC 51, a heater substrate, a heater IC 52, and multiple capacitors. However, the core unit 5 can also employ a structure including a crystal resonator 50, an oscillator IC 51, and a heater IC 52. For example, as... Figures 11-13 As shown, the core 5 is configured as a three-layer structure (stacked structure) consisting of an oscillator IC51, a crystal resonator 50, and a heater IC52 stacked sequentially from the top. The bottom surface of the heater IC52 is joined to the top surface of the intermediate member 4. Based on this structure, in addition to the heater IC52, the oscillator IC51 also functions as a heating element. Therefore, heating elements exist above and below the crystal resonator 50, thereby enabling balanced heating of the crystal resonator 50 from both above and below.

[0089] Thus, as a component of the core part 5, at least a crystal resonator 50, an oscillator IC 51, and a heater IC 52 are required. When the heater IC 52 is used as a heat source, the heater substrate can be omitted. Specifically, the heater IC 52 is preferably constructed by integrating a heating element (heat source), a control circuit (current control circuit) for temperature control of the heating element, and a temperature sensor for detecting the temperature of the heating element into a single unit. Furthermore, multiple capacitors can be provided as components independent of the core part 5. These multiple capacitors can be housed in the same space as the core part 5 inside the package 2, or they can be housed in different spaces.

[0090] Below, on Figures 11-13 The OCXO1A shown will be used for illustration. In this modified example of the OCXO1A, the core 5 is configured as a three-layer structure (stacked structure) in which the oscillator IC51, the crystal resonator 50, and the heater IC52 are stacked sequentially from the top. Such a core 5 is disposed inside the package 2 and hermetically sealed by the cover 3.

[0091] Specifically, a stepped portion 2c is formed on the inner wall surface of the peripheral wall portion 2b of the package 2. The extending direction of the stepped portion 2c is consistent with the arrangement direction of the connecting terminals (not shown). The core portion 5 is connected to the connecting terminals formed on the stepped portion 2c via a plate-shaped intermediate member (core substrate) 4. The intermediate member 4 is configured to be positioned between a pair of opposing stepped portions 2c in the package 2, and a space 2d is formed between the pair of stepped portions 2c and below the intermediate member 4. Furthermore, the connecting terminals formed on the stepped surface of the stepped portion 2c are connected to the connecting terminals (not shown) formed on the bottom surface 4b of the intermediate member 4 via a conductive adhesive 7. In addition, external terminals (not shown) formed on each component of the core portion 5 are connected to the connecting terminals 4c formed on the top surface 4a of the intermediate member 4 via wires 6a and 6b through wire bonding. For example, a polyimide adhesive or an epoxy adhesive is used as the conductive adhesive 7.

[0092] Figure 12 , Figure 13 The diagram shows the core 5 mounted on the intermediate member 4. Viewed from above, the areas of the oscillator IC51, crystal resonator 50, and heater IC52 in the core 5 gradually decrease upwards. Furthermore, the various electronic components of the core 5 are not sealed with sealing resin, but may be sealed with sealing resin depending on the sealing atmosphere. The crystal oscillator 100 is composed of the crystal resonator 50 and the oscillator IC51, and the structure of the crystal oscillator 100 is the same as in the embodiment described above (see reference). Figures 4 to 10 ).

[0093] A non-conductive adhesive (bottom filler) 53 is sandwiched between the opposing surfaces of the crystal resonator 50 and the oscillator IC 51, and the opposing surfaces of the crystal resonator 50 and the oscillator IC 51 are fixed by the non-conductive adhesive 53. In this case, the top surface of the crystal resonator 50 (the first main surface 201 of the first sealing member 20) and the bottom surface of the oscillator IC 51 are bonded by the non-conductive adhesive 53. For example, a polyimide adhesive, an epoxy adhesive, etc., can be used as the non-conductive adhesive 53. Furthermore, external terminals formed on the top surface of the crystal resonator 50 ( Figure 5 The electrode pattern 22 shown is connected to the connection terminal 4c formed on the top surface 4a of the intermediate member 4 via wire bonding through the wire 6a.

[0094] Viewed from above, the area of ​​oscillator IC51 becomes smaller than that of crystal resonator 50, and the entire oscillator IC51 is located within the area of ​​crystal resonator 50. The entire bottom surface of oscillator IC51 is bonded to the top surface of crystal resonator 50 (first main surface 201 of first sealing member 20).

[0095] The heater IC52 is constructed by integrating a heating element (heat source), a control circuit for temperature control of the heating element (current control circuit), and a temperature sensor for detecting the temperature of the heating element into a single structure. By controlling the temperature of the core 5 using the heater IC52, the temperature of the core 5 can be maintained at a near-constant temperature, thereby stabilizing the oscillation frequency of the OCXO1A.

[0096] A non-conductive adhesive 54 is sandwiched between the opposing surfaces of the crystal resonator 50 and the heater IC 52, fixing the opposing surfaces of the crystal resonator 50 and the heater IC 52 in place. In this case, the bottom surface of the crystal resonator 50 (the second main surface 302 of the second sealing member 30) is bonded to the top surface of the heater IC 52 by the non-conductive adhesive 54. For example, a polyimide adhesive or an epoxy adhesive may be used as the non-conductive adhesive 54. External terminals (not shown) formed on the top surface of the heater IC 52 are connected to connecting terminals 4c formed on the top surface 4a of the intermediate member 4 via wire bonding through wire 6b.

[0097] Viewed from above, the area of ​​the crystal resonator 50 becomes smaller than that of the heater IC52, and the entire crystal resonator 50 is located within the area of ​​the heater IC52. The bottom surface of the crystal resonator 50 (the second main surface 302 of the second sealing member 30) is integrally bonded to the top surface of the heater IC52.

[0098] A conductive adhesive 55 is sandwiched between the opposing surfaces of the heater IC 52 and the intermediate member 4, and the opposing surfaces of the heater IC 52 and the intermediate member 4 are fixed by the conductive adhesive 55. In this case, the bottom surface of the heater IC 52 and the top surface 4a of the intermediate member 4 are bonded by the conductive adhesive 55. Thus, the heater IC 52 is grounded via the conductive adhesive 55 and the intermediate member 4. For example, a polyimide adhesive or an epoxy adhesive can be used as the conductive adhesive 55. Furthermore, if the heater IC 52 is grounded, for example, via a wire, a non-conductive adhesive similar to the non-conductive adhesives 53 and 54 described above can be used instead of the conductive adhesive.

[0099] As described above, a plurality of connection terminals 4c are formed on the top surface 4a of the intermediate member 4. Furthermore, a plurality of ( Figure 13 There are two 4d surface mount capacitors (bypass capacitors). Furthermore, there are no particular restrictions on the size or number of 4d surface mount capacitors.

[0100] The above describes the case where the core part 5 is equipped with heater IC52, thin-film heater 56a, and thin-film heater 56b (refer to...). Figures 1-3), and the case where only heater IC52 is provided in core part 5 (refer to Figures 11-13 The description has been provided, but a structure in which only a thin-film heater is provided in the core part 5 can also be adopted. In other words, the heating element provided in the core part 5 can also be a heater IC and / or a thin-film heater. In the case where only a thin-film heater is provided in the core part 5, it is preferable to provide a temperature regulation IC for the thin-film heater separately from the core part 5.

[0101] Alternatively, the following structure can be adopted: the intermediate member (core substrate) 4 on which the core 5 is mounted is not bonded to the top surface of the stepped portion 2c of the package 2, but is bonded to the inner bottom surface of the recess 2a by adhesive, and is directly wire-bonded from the connection terminals of the heater IC 52 and the crystal resonator 50 to the top surface of the stepped portion 2c. Based on this structure, it is more advantageous to achieve a lower profile than the structure in which the intermediate member 4 supports the core 5 on the top surface of the stepped portion 2c.

[0102] This application claims priority based on Japanese Patent Application No. 2020-060353, filed in Japan on March 30, 2020. It goes without saying that all contents of that application are incorporated herein by reference.

[0103] [Industry Applicability]

[0104] This invention is applicable to a thermostatic tank type piezoelectric oscillator having a core comprising a piezoelectric vibrator, an oscillator IC, and a heater IC.

Claims

1. A thermostatic bath type piezoelectric oscillator, comprising a core, the core having a piezoelectric vibrator, an oscillator IC, and a heating element, characterized in that: The core component is supported within the package by a core substrate and is sealed inside the package in a sealed state. The core portion is a stacked structure in which the oscillator IC, the piezoelectric vibrator and the heating element are stacked sequentially from the top, and the bottom surface of the heating element is bonded to the top surface of the core substrate.

2. The thermostatic bath type piezoelectric oscillator according to claim 1, characterized in that: A recess with an opening at the top is formed on the package body. The core is supported by the core substrate and is suspended inside the package.

3. The thermostatic bath type piezoelectric oscillator according to claim 2, characterized in that: A pair of opposing stepped portions are formed inside the package. The core substrate is configured to be mounted between the pair of stepped portions, and The core portion is housed within the space between the pair of stepped portions.

4. The thermostatic bath type piezoelectric oscillator according to claim 3, characterized in that: The core substrate is fixed to the stepped portion using a polyimide-based conductive adhesive.

5. The thermostatic bath type piezoelectric oscillator according to any one of claims 1 to 4, characterized in that: The piezoelectric vibrator includes a first sealing member, a second sealing member, and a piezoelectric vibrating plate. The first sealing member and the second sealing member are made of glass or quartz crystal. The piezoelectric vibrating plate has a vibrating part made of quartz crystal and excitation electrodes formed on two main surfaces. The first sealing member and the second sealing member are stacked and joined across the piezoelectric vibrating plate. The vibrating part of the piezoelectric vibrating plate disposed inside is hermetically sealed.

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