Thermostatic oven type piezoelectric oscillator

Abstract

To provide a thermostatic oven type piezoelectric oscillator that uses a bonding material to improve mounting stability and bonding strength, and reduces the impact of shocks caused by external stress on a core portion.SOLUTION: In an OCXO 1 in which a core portion 5 is hermetically sealed inside a heat-insulating package 2, the core portion is mounted on a holding member 4, a core substrate is mechanically joined to the package 2 at an end of the core substrate by a bonding material 7, the core portion and the package are electrically joined by wires 6a and 6b, and a space 2d is provided between the core substrate and the bottom surface of the package via a spacer member 2f. The upper surface of the spacer member is formed such that a peripheral end 21f is lower than a central portion 22f in a plan view, and the non-conductive adhesive formed between the core substrate and the spacer member bonds the core substrate and the spacer member in a state in which the thickness increases from the central portion of the spacer member in a plan view toward the periphery.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Piezoelectric oscillators such as quartz crystal oscillators change their vibration frequency depending on temperature based on their inherent frequency-temperature characteristics. To keep the temperature around the piezoelectric oscillator constant, oven-controlled piezoelectric oscillators (hereinafter also referred to as "OCXOs") are known in which the piezoelectric oscillator is enclosed in a thermostatic oven (see, for example, Patent Document 1). The OCXO described in Patent Document 1 has a core section in which an oscillation IC, a piezoelectric oscillator, and a heater IC are stacked, and is supported inside a heat-insulating package by a bonding material via a holding member (core substrate), and the necessary wiring is performed using wire bonding. This achieves miniaturization while improving the heat insulation of the core section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 186124 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of the OCXO, a bonding material such as a resin adhesive is used as a base to raise the holding member (core substrate), but the height is not stable with bonding material alone, which can lead to product variation and height differences between the ends. There was also concern that the bonding strength could vary.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an oven-controlled piezoelectric oscillator in which the mounting stability and bonding strength of a bonding material are improved. [Means for solving the problem]

[0006] The present invention provides a means for solving the above problems as follows: That is, the present invention provides an oven-controlled piezoelectric oscillator having a core section sealed in a heat-insulating package, the core section including at least an oscillation IC, a piezoelectric resonator, and a heater IC, the core section being mounted on a holding member, the holding member being mechanically joined by a bonding material together with a spacer member formed on the inner bottom surface of the package, the core section and the package being electrically joined by wires, a space being provided between the holding member and the inner bottom surface of the package via the spacer member, the upper surface of the spacer member being formed so that the peripheral ends are lower than the central portion in a plan view, and the bonding material formed between the holding member and the spacer member bonds the holding member and the spacer member in a state in which the thickness increases from the central portion of the spacer member toward the periphery in a plan view.

[0007] According to the above configuration, the bonding material formed between the retaining member and the spacer member bonds the retaining member and the spacer member in a state in which it becomes thicker from the center of the spacer member toward the periphery when viewed in a plane, thereby increasing the bonding strength between the retaining member and the spacer member due to the anchor effect and making it possible to soften impacts on the retaining member.

[0008] Furthermore, in the oven-controlled piezoelectric oscillator, a space is provided between the holding member and the inner bottom surface of the package via a spacer member formed on the inner bottom surface of the package, so that a stable gap is formed between the inner bottom surface of the package and the core or holding member, and there is no variation in insulation due to variation in the gap to the holding member or tilt. As a result, the insulation effect for the core can be improved, and the electrical characteristics of the oven-controlled piezoelectric oscillator are also stabilized.

[0009] Furthermore, by forming a core unit that brings together the necessary components and joining this core unit to the package via a holding member, it is possible to provide an oven-controlled piezoelectric oscillator that is easily adapted to miniaturization.

[0010] In addition, by separating the mechanical bonding of the core to the package by the holding member and bonding material from the electrical bonding between the core and the package by wire bonding, high reliability can be obtained for each. For example, the holding member on which the core is mounted and the bonding material connecting the holding member on which the core is mounted to the package can be made of a material with high thermal insulation properties, and can also be made of a flexible material whose mechanical bonding strength is not easily reduced even when affected by external stress. In addition, by using a metal wire with low electrical resistance in the wire bonding between the core and the package, common impedance noise is less likely to occur, and the CN characteristics of the oven-controlled piezoelectric oscillator can be improved. Effect of the Invention

[0011] According to the oven-controlled piezoelectric oscillator of the present invention, the mounting stability and bonding strength of the bonding material can be improved. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an OCXO according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the OCXO of FIG. [Diagram 3] FIG. 2 is a bottom view of the OCXO of FIG. 1. [Figure 4] FIG. 2 is a plan view of the package of the OCXO of FIG. 1. [Diagram 5] 2 is a cross-sectional view showing a schematic configuration of a core section and a core substrate of the OCXO shown in FIG. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of a crystal oscillator (a crystal resonator and an oscillation IC) in the core portion of FIG. 5. [Figure 7] FIG. 2 is an enlarged cross-sectional view of the holding portion of FIG. [Figure 8]10(a) to 10(d) are cross-sectional views showing modified examples of OCXO. [Figure 9] FIG. 11 is a cross-sectional view showing a schematic configuration of an OCXO according to another embodiment. [Figure 10] FIG. 10 is an enlarged cross-sectional view of the holding portion of FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 4, the OCXO 1 according to this embodiment has a structure in which a core part 5 is disposed inside a recess 2a of a package (housing) 2 made of ceramic or the like and having a substantially H-shaped cross section, and the core part 5 is hermetically sealed by a lid 3. Fig. 2 shows the OCXO 1 with the lid 3 removed, and illustrates the internal structure of the recess 2a of the package 2.

[0014] In detail, as shown in FIG. 1 and FIG. 2, the OCXO 1 has a package 2 with a cross section of a substantially H-shaped shape, in which a recess 2a that is open at the top and a recess 2e that is open at the bottom are formed. A core part 5 is sealed in an airtight state inside the recess 2a of the package 2. A lid 3 is fixed to the upper surface of a peripheral wall part 2b that surrounds the recess 2a by seam welding via a sealing material 8, and the internal space of the recess 2a is sealed (airtight) in a high or low vacuum atmosphere (for example, a vacuum degree of 10 Pa or less). In particular, by storing the core part 5 described later in the internal space of an insulating package (housing) 2 made of ceramic or the like with low thermal conductivity and airtightly sealing it under a vacuum atmosphere, the thermal conductivity to the outside is suppressed, and a heat-insulating package structure with better heat insulation is obtained. Seam sealing by seam welding is a preferable method for preventing a decrease in the degree of vacuum, and any method of seam sealing using a metal ring or direct seam sealing without using a metal ring may be used.

[0015] It should be noted that the sealing method is not limited to the above embodiment, and it is also possible to adopt a sealing member structure using other methods such as beam sealing, or sealing by heating the atmosphere using a metal-based sealing material such as an Au-Su alloy or a sealing material such as a low-melting glass, etc. Also, the atmosphere is not limited to a vacuum atmosphere, and may be a low-pressure nitrogen or argon atmosphere.

[0016] 1 and 3, in a recess 2e formed on the other main surface opposite to the main surface (the main surface on which the recess 2a is formed) that serves as the mounting portion of the core portion 5 of the package 2, circuit components such as a capacitor 9 are disposed as adjustment electronic components used in combination with the heater IC 52 of the core portion 5. Unlike the recess 2a, the recess 2e does not need to be sealed by the lid 3.

[0017] In this way, by arranging the circuit components outside the space accommodating the core unit 5 of the package 2, it is possible to control the temperature of the core unit 5 with low power and improve the temperature tracking of the core unit 5. In addition, it is possible to prevent subsequent generation of gas due to solder, flux, etc. in the atmosphere inside the hermetically sealed recess 2a. This is desirable in that it prevents the core unit 5 from being adversely affected by gas and further stabilizes the electrical characteristics.

[0018] In this embodiment, three capacitors 9 are mounted on the other main surface of the package 2 opposite to the one main surface (in this case, the bottom surface of the recess 2e). The capacitors 9 are joined by solder to mounting pads 9a formed on the bottom surface of the recess 2e of the package 2. The arrangement area of ​​the capacitors 9 is indicated by a dashed line in FIG. 3. A pair of mounting pads 9a, 9a are arranged facing 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. A plurality of external connection terminals 2g (eight in FIG. 3) are also formed on the bottom surface of the package 2 for electrically connecting the OCXO 1 to an external circuit board (not shown) provided outside via solder or the like.

[0019] The number of capacitors 9 mounted on the other main surface of package 2 is not particularly limited, and the number of capacitors 9 may be other than three. Furthermore, circuit components other than capacitors 9 may be mounted on the other main surface of package 2. Furthermore, the sizes (volume, surface area) of all circuit components do not need to be the same.

[0020] As shown in FIG. 1 and FIG. 2, a step portion 2c is formed on the inner wall surface of the peripheral wall portion 2b of the recess 2a of the package 2 along the arrangement of a plurality of connection terminals (wire pads) 2h. The core portion 5 is disposed on the bottom surface (inner bottom surface) of the recess 2a between a pair of opposing step portions 2c, 2c via a core substrate (flexible substrate) made of a plate-like flexible material having a rectangular shape in a plan view as a holding member 4. Alternatively, the step portion 2c may be formed so as to surround the bottom surface of the recess 2a on all four sides. The wire pads 2h formed on the step surface of the step portion 2c are connected to the wire pads formed on each component of the core portion 5 by wire bonding via wires 6a, 6b.

[0021] Specifically, the wire pad 2h of the step portion 2c is connected via a wire 6a to a wire pad (see FIG. 2) formed on the oscillation IC 51 of the core portion 5. The wire pad 2h of the step portion 2c is connected via a wire 6b to a wire pad (see FIG. 2) formed on the heater IC 52 of the core portion 5. In addition, the wire pad (see FIG. 2) formed on the crystal resonator 50 of the core portion 5 is connected by wire bonding to the wire pad (see FIG. 2) formed on the oscillation IC 51 via a wire 6c. Each of the wires is made of, for example, gold.

[0022] The holding member 4 is bonded to the bottom surface of the recess 2a by a bonding material 7, and a space (gap) 2d is formed in the lower portion of the holding member 4. Specifically, a pair of spacer members 2f are provided at a predetermined interval on the bottom surface of the package 2, and the bonding material 7 is applied onto each spacer member 2f. The bonding material 7 mechanically bonds the holding member 4 to the bottom surface of the package 2 at both ends of the holding member 4. The spacer members 2f and the bonding material 7 are provided linearly along the short side direction of the holding member 4 (the direction perpendicular to the paper surface of FIG. 1).

[0023] Moreover, a bonding region (application region of bonding material 7) for bonding the holding member 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 holding member 4 in a plan view. The holding member 4 is made of a heat-resistant and flexible resin material such as polyimide. The spacer member 2f is made of a metallized material such as molybdenum or tungsten, and is integrally formed on the bottom surface (inner bottom surface) of the recess 2a of the package 2 by a method such as screen printing. For example, a polyimide-based adhesive, an epoxy-based adhesive, or the like is used as the bonding material 7. The holding member 4 may be formed of a glass epoxy substrate, a quartz plate, a metal plate, or the like.

[0024] Next, the core unit 5 will be described with reference to Fig. 5. Fig. 5 illustrates the core unit 5 mounted on the holding member 4. The core unit 5 is a package of various electronic components used in the OCXO 1, and has a three-layer structure (laminated structure) in which an oscillation IC 51, a crystal oscillator (piezoelectric oscillator) 50, and a heater IC 52 are stacked in this order from the top. The areas of the oscillation IC 51, the crystal oscillator 50, and the heater IC 52 in a plan view gradually decrease toward the top.

[0025] The core unit 5 is configured to stabilize the oscillation frequency of the OCXO 1 by adjusting the temperatures of the crystal unit 50, the oscillation IC 51, and the heater IC 52, which have particularly large temperature characteristics. Although the various electronic components of the core unit 5 are not sealed with sealing resin, they may be sealed with sealing resin depending on the sealing atmosphere.

[0026] The crystal oscillator 100 is configured by the crystal resonator 50 and the oscillation IC 51. For example, a VCXO IC can be used as the oscillation IC 51, in which case the crystal oscillator 100 is configured as a VCXO. The oscillation frequency of the OCXO 1 is controlled by controlling the piezoelectric vibration of the crystal resonator 50 with the oscillation IC 51.

[0027] A non-conductive adhesive 53 is interposed between the opposing surfaces of the crystal unit 50 and the oscillation IC 51, and the opposing surfaces of the crystal unit 50 and the oscillation IC 51 are fixed together by the non-conductive adhesive 53. In this case, the top surface of the crystal unit 50 (the first main surface of the first sealing member 20) and the bottom surface of the oscillation IC 51 are joined together via the non-conductive adhesive 53.

[0028] The area of ​​the oscillation IC 51 in a plan view is smaller than that of the crystal unit 50, and the entire oscillation IC 51 is located within the range of the crystal unit 50 in a plan view. The entire bottom surface of the oscillation IC 51 is bonded to the top surface of the crystal unit 50 (the first main surface of the first sealing member 20).

[0029] The heater IC 52 is configured to integrate, for example, a heating element (heat source), a control circuit (current control circuit) for controlling the temperature of the heating element, and a temperature sensor for detecting the temperature of the heating element. By controlling the temperature of the core unit 5 using the heater IC 52, the temperature of the core unit 5 is maintained at a substantially constant temperature, and the oscillation frequency of the OCXO 1 is stabilized. Note that the temperature sensor may be provided as a separate member from the heater IC 52.

[0030] A conductive adhesive 54 is interposed between the opposing surfaces of the crystal unit 50 and the heater IC 52, and the opposing surfaces of the crystal unit 50 and the heater IC 52 are fixed to each other by the conductive adhesive 54. In this case, the lower surface of the crystal unit 50 (the second main surface of the second sealing member 30) and the upper surface of the heater IC 52 are joined via the conductive adhesive 54. For example, an epoxy adhesive or the like is used as the conductive adhesive 54. The use of the conductive adhesive 54 increases the thermal conductivity of the crystal unit 50 and the heater IC 52. Note that the fixing is not limited to the conductive adhesive, and a non-conductive adhesive can also be used.

[0031] The crystal unit 50 has an area smaller than that of the heater IC 52 in a plan view, and the entire crystal unit 50 is located within the range of the heater IC 52 in a plan view. The entire lower surface of the crystal unit 50 (the second main surface of the second sealing member 30) is bonded to the upper surface of the heater IC 52.

[0032] A non-conductive adhesive 55 is interposed between the opposing surfaces of the heater IC 52 and the holding member 4, and the opposing surfaces of the heater IC 52 and the holding member 4 are fixed to each other by the non-conductive adhesive 55. For example, a polyimide adhesive or the like is used as the non-conductive adhesives 53 and 55. Note that the fixing is not limited to the non-conductive adhesive, and a conductive adhesive may also be used.

[0033] 5, wire pads (see FIG. 2) for wire bonding are formed on the upper surfaces of the oscillation IC 51, the crystal unit 50, and the heater IC 52. The wire bonding of the oscillation IC 51, the crystal unit 50, and the heater IC 52 is not performed before the core unit 5 is mounted on the package 2, but is performed after the core unit 5 (holding member 4) is mounted on the package 2.

[0034] That is, as shown in Figs. 1 and 2, after the core unit 5 (holding member 4) is mounted on the package 2, the wire pad formed on the upper surface of the crystal unit 50 is connected to the wire pad formed on the oscillation IC 51 via the wire 6c. The wire pad formed on the oscillation IC 51 is connected to the wire pad 2h formed on the step surface of the step portion 2c via the wire 6a. The wire pad formed on the upper surface of the heater IC 52 is connected to the wire pad 2h formed on the step surface of the step portion 2c via the wire 6b. In this way, by performing wire bonding after mounting the core unit 5 on the package 2, the wire bonding can be performed efficiently, and an OCXO 1 with excellent mass productivity can be provided.

[0035] Although the type of crystal unit 50 used in the core portion 5 is not particularly limited, a sandwich-structured device that is easy to make thin can be preferably used. A sandwich-structured device is a three-layered device that is composed of first and second sealing members made of glass or crystal, and a piezoelectric diaphragm made of, for example, crystal and having a vibration part with excitation electrodes formed on both main surfaces, in which the first and second sealing members are laminated and bonded via the piezoelectric diaphragm, and the vibration part of the piezoelectric diaphragm arranged inside is hermetically sealed.

[0036] An example of a crystal oscillator 100 in which such a sandwich-structured crystal resonator 50 and an oscillation IC (e.g., a VCXO IC) 51 are integrally provided will be described with reference to Fig. 6. Note that since the sandwich-structured crystal resonator itself is well known, a detailed description of the internal structure of the crystal resonator 50 will be omitted.

[0037] As shown in Fig. 6, the crystal oscillator 100 is configured to include a crystal vibration plate (piezoelectric vibration plate) 10, a first sealing member 20, a second sealing member 30, and an oscillation IC 51. In this crystal oscillator 100, the crystal vibration plate 10 and the first sealing member 20 are joined by an annular sealing joint 40, and the crystal vibration plate 10 and the second sealing member 30 are joined by an annular sealing joint 40, thereby forming a package with a substantially rectangular sandwich structure. The sealing joints 40, 40 can be, for example, formed on the respective joining surfaces of the crystal vibration plate 10, the first sealing member 20, and the second sealing member 30 with a bonding pattern (for example, a bonding pattern in which a Ti layer and an Au layer are formed from the bottom layer side) with an Au layer on the surface, and bonding is performed by Au-Au diffusion bonding when the joining surfaces are attached to each other.

[0038] According to this configuration, the gap dimension between the quartz crystal plate 10 and each of the sealing members 20, 30 can be made extremely small, at about 0.15 μm to 1 μm, which is advantageous for making the core portion 5 thinner and reducing its heat capacity.

[0039] In the crystal oscillator 100, a first sealing member 20 and a second sealing member 30 are bonded to both main surfaces of the crystal vibration plate 10 on which the vibration part (not shown) is formed, thereby forming an internal space (cavity) of the package, and the vibration part of the crystal vibration plate 10 is hermetically sealed in this internal space. A plurality of external terminals 22 are formed on the upper surface of the first sealing member 20. Two of the external terminals 22 are electrically connected to the excitation electrodes of the vibration part of the crystal vibration plate 10 at one end (via wiring or through holes in the crystal vibrator 50), and electrically connected to the oscillation IC 51 at the other end by wires 6c. The oscillation IC 51 is die-bonded on the first sealing member 20 and electrically connected to the crystal vibrator 50 by wire bonding. 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 vibration plate 10. The oscillation IC 51 may be mounted on the crystal resonator 50 by FCB (Flip Chip Bonding) using metal bumps such as gold.

[0040] Here, it is preferable that the crystal unit 50 and the package 2 are not directly wire-connected, and only the oscillation IC 51 is directly wire-connected to the crystal unit 50. In this embodiment, the crystal unit 50 and the oscillation IC 51 are only connected via the wire 6c. This configuration can prevent heat from escaping from the crystal unit 50 to the package 2 through the wire. As a result, there are advantages such as improved insulation for the crystal unit 50 and improved temperature controllability for the crystal unit 50.

[0041] In this embodiment, in the OCXO 1 having the above configuration, a feature is the joining structure between the holding member 4 on which the core unit 5 is mounted and the inner bottom surface (bottom surface of the recess 2a) of the package 2. This feature will be described below.

[0042] As shown in Figs. 1 and 7, the spacer member 2f is integrally formed on the bottom surface of the recess 2a of the package 2 (the inner bottom surface of the package), and the upper surface of the spacer member 2f is formed so that the peripheral end 21f is lower than the central portion 22f in a plan view. The holding member 4 is joined to the upper surface of the spacer member 2f with the bonding material 7 applied to the upper surface. At this time, the bonding material 7 formed between the holding member 4 and the spacer member 2f bonds the holding member 4 and the spacer member 2f in a state where the thickness increases from the central portion 22f of the spacer member 2f in a plan view toward the periphery where the peripheral end 21f is located. The bonding material 7 is, for example, a non-conductive adhesive such as a polyimide adhesive or an epoxy adhesive.

[0043] More specifically, the spacer member 2f is formed of the above-mentioned metallized material, and is formed in a substantially rectangular shape when viewed in cross section, with an R-shaped inclined portion 23f formed at the edge of the upper surface of the spacer member 2f. Then, by applying the bonding material 7 to the upper surface of the spacer member 2f configured in this manner and bonding it to the holding member 4, the bonding material 7 formed between the holding member 4 and the spacer member 2f is applied and formed along the R-shaped inclined portion 23f. As a result, the holding member 4 and the spacer member 2f can be bonded in a state in which the bonding material 7 gradually becomes thicker from the center of the spacer member 2f toward the periphery in a plan view.

[0044] By using such a bonding structure between the holding member 4 and the bottom surface of the recess 2a of the package 2 (the inner bottom surface of the package), a sufficient and stable gap space is formed between the holding member 4 and the bottom surface of the recess 2a of the package 2, eliminating variations in insulation due to gap variations and tilt, improving the insulating effect for the core portion 5, and stabilizing the electrical characteristics of the oven-controlled piezoelectric oscillator.

[0045] In addition, since the bonding material 7 bonds the retaining member 4 and the spacer member 2f in a state in which the thickness gradually increases from the central portion 22f of the spacer member 2f in a planar view toward the periphery where the peripheral end portion 21f is located, an anchor effect is generated and the bonding strength between the retaining member 4 and the spacer member 2f can be increased.

[0046] Furthermore, since the bonding material 7 made of a resin such as a polyimide-based adhesive or an epoxy-based adhesive gradually becomes thicker toward the periphery of the spacer member 2f, it is possible to soften the impact caused by the up and down movement or bending of the holding member 4, thereby preventing damage to the core portion 5 mounted on the upper part of the holding member 4 and preventing breakage of the wire portion electrically connecting the core portion 5 to the package 2.

[0047] The upper surface structure of the spacer member disclosed in the above embodiment as the joining structure between the holding member 4 carrying the core portion 5 and the inner bottom surface (bottom surface of the recess 2a) of the package 2 and the state of the joining material 7 formed between the holding member and the spacer member are merely examples. For example, various changes are possible as shown in Figs. 8(a) to (d). Figs. 8(a) to (d) show enlarged cross-sectional views of the spacer member as the holding portion. Note that the same parts as those in the above embodiment are given the same numbers and some of the explanations are omitted.

[0048] The embodiment of Fig. 8(a) differs from the above embodiment in that the cross-sectional shape of the spacer member 2f1 is formed to be substantially elliptical. The material of the spacer member 2f1 is a paste material (metallized material) such as molybdenum and tungsten, as in the above embodiment. By applying a bonding material 7 to the upper surface of the spacer member 2f thus configured and bonding it to the holding member 4, the bonding material 7 is formed between the holding member 4 and the spacer member 2f in a state in which the thickness gradually increases radially from the apex or top side of the spacer member 2f1 toward the periphery.

[0049] In the embodiment of FIG. 8(a), compared to the above-described embodiments, the bonding material 7 can be made gradually thicker in a continuous manner toward the periphery, so that the impact of the up and down movement or bending of the holding member 4 can be further reduced.

[0050] In the embodiment of FIG. 8(b), a spacer member 2f21 having a substantially elliptical cross-sectional shape and a spacer member 2f22 having a smaller planar area than the spacer member 2f21 and having a substantially elliptical cross-sectional shape are provided, and the spacer member 2f22 is laminated on the spacer member 2f21. The material of the spacer member 2f21 and the spacer member 2f22 is a paste material (metallized material) such as molybdenum and tungsten, as in the above embodiment. The bonding material 7 is applied to the upper surfaces of the spacer member 2f21 and the spacer member 2f22 thus configured and bonded to the holding member 4, so that the bonding material 7 is formed between the holding member 4, the spacer member 2f21, and the spacer member 2f22 in a state in which the thickness gradually increases radially from the apex or top side of the spacer member 2f22 toward the periphery including the spacer member 2f21.

[0051] 8(b), in addition to the advantages of the configuration of the embodiment of FIG. 8(a), the contact area of ​​the bonding material 7 applied to the upper surface of the spacer member is increased, which contributes to further improving the bonding strength. Also, the thickness of the spacer member can be increased, which is more advantageous for securing a gap between the holding member 4 and the package 2.

[0052] The embodiment of Figure 8(c) has a spacer member 2f31 having a cross-sectional shape formed into an approximately rectangular shape, a spacer member 2f32 having a smaller planar area than spacer member 2f31 and having a cross-sectional shape formed into an approximately rectangular shape, a spacer member 2f33 having a smaller planar area than spacer member 2f32 and having a cross-sectional shape formed into an approximately rectangular shape, and a spacer member 2f34 having a smaller planar area than spacer member 2f33 and having a cross-sectional shape formed into an approximately rectangular shape, and is formed by stacking spacer member 2f32 on top of spacer member 2f31, stacking spacer member 2f33 on top of spacer member 2f32, and stacking spacer member 2f34 on top of spacer member 2f33.

[0053] The material of the spacer members 2f31 to 2f34 is a paste material (metallized material) such as molybdenum and tungsten, as in the above embodiment. By applying the bonding material 7 to the upper surfaces of the spacer members 2f31 to 2f34 thus configured and bonding them to the holding member 4, the bonding material 7 is formed between the holding member 4 and the four spacer members 2f31 to 2f34 in a state in which the thickness of the bonding material 7 gradually increases radially from the apex or top side of the spacer member 2f34 toward the periphery including the spacer members 2f33, 2f32, and 2f31.

[0054] 8(c) also increases the contact area of ​​the bonding material 7 applied to the upper surface of the spacer member, further contributing to improved bonding strength. In addition, the thickness of the spacer member can be increased, providing a more advantageous configuration for securing a gap between the holding member 4 and the package 2.

[0055] In the embodiment of FIG. 8(d), a spacer member 2f41 is formed in a substantially rectangular cross-sectional shape and has an R-shaped edge on the top surface, and a spacer member 2f42 is formed in a substantially rectangular cross-sectional shape and has an R-shaped edge on the top surface, and is formed by stacking the spacer member 2f42 on the top of the spacer member 2f41. The material of the spacer member 2f41 and the spacer member 2f42 is different from the above embodiment and is made of a paste material such as alumina (alumina coating material), for example. By applying the bonding material 7 to the top surfaces of the spacer member 2f41 and the spacer member 2f42 configured in this manner and bonding them to the holding member 4, the bonding material 7 is formed between the holding member 4, the spacer member 2f41, and the spacer member 2f42 in a state where the thickness gradually increases radially from the apex or top side of the spacer member 2f42 toward the periphery including the spacer member 2f41.

[0056] 8(d) also increases the contact area of ​​the bonding material 7 applied to the top surface of the spacer member, which contributes to improving the bonding strength. Also, the thickness of the spacer member can be increased, which is advantageous for increasing the gap between the holding member 4 and the package 2. In addition, by using a paste material such as alumina (alumina coating material) as the material of the spacer member, further improvement in adhesion can be expected depending on the material of the bonding material 7 compared to metallized materials, which contributes to improving the bonding strength.

[0057] In the above embodiment, a sandwich-structured crystal unit 50 is used, but the present invention is not limited to this, and a crystal unit other than a sandwich-structured crystal unit (for example, an SMD (Surface Mount Device) type crystal unit) may be used.

[0058] In addition, in the above embodiment, a package having a cross-sectional shape of approximately H-shape with recesses formed on the top and bottom is used as OCXO1, but the present invention is not limited to this, and a single-shaped package may be used in which a recess is formed only on the top side, the bottom side opposite the top surface is flat, and the upper recess is hermetically sealed with a lid, or a two-tiered package may be used in which such single-shaped packages are stacked vertically and electrically and mechanically joined, and the recess of the upper package is hermetically sealed with a lid.

[0059] The embodiment shown in Fig. 9 shows an example of a modification of the above embodiment, in which an SMD type crystal unit is used and a single-shaped package is used. Below, an OCXO according to another embodiment will be described with reference to Figs. 9 and 10. Note that the same numbers are used for parts similar to the above embodiment, and some of the explanations will be omitted, with the differences being mainly described.

[0060] 9, the OCXO 1X according to another embodiment has a structure in which a core portion 5X is disposed inside a recess 2Xa of a package (housing) 2X made of ceramic or the like and having a substantially concave cross-sectional shape, and is hermetically sealed by a lid 3. A plurality of external connection terminals 2Xg are also formed on the bottom surface of the package 2X for electrically connecting the OCXO 1X to an external circuit board (not shown) provided outside via solder or the like.

[0061] As shown in Fig. 9, a step portion 2Xc having a plurality of connection terminals (wire pads) (not shown) is formed on the inner wall surface of the peripheral wall portion 2Xb of the recess 2Xa of the package 2X. The core portion 5X is disposed on the bottom surface (inner bottom surface) of the recess 2Xa between a pair of opposing step portions 2Xc, 2Xc via a pair of holding pieces made of a plate-like flexible material having a rectangular shape in a plan view as a holding member 4X. The connection terminals (not shown) formed on the step surface of the step portion 2Xc are connected by wire bonding to wire pads formed on each component of the core portion 5X via wires 6a, 6b.

[0062] The holding member 4X is bonded to the bottom surface of the recess 2Xa by a non-conductive adhesive (bonding material) 7, and a space (gap) 2Xd is formed in the lower part of the core part 5X (crystal oscillator (piezoelectric oscillator) 50X). Specifically, a pair of spacer members 2Xf are provided at a predetermined interval on the bottom surface of the package 2X, and the bonding material 7 is applied on each spacer member 2Xf. The bonding material 7 mechanically bonds the holding member 4X to the bottom surface of the package 2X. Each spacer member 2Xf and the bonding material 7 are provided linearly along the holding member 4X. The holding member 4X is made of a resin material having heat resistance and flexibility, such as polyimide. The spacer member 2Xf is made of a paste material (metallization material) such as molybdenum or tungsten, and is formed integrally with the bottom surface (inner bottom surface) of the recess 2a of the package 2 by a method such as screen printing. For example, a polyimide-based adhesive, an epoxy-based adhesive, or the like is used as the bonding material 7. The holding member 4X may be formed of a glass epoxy substrate, a quartz plate, a metal plate, or the like.

[0063] Next, the core part 5X will be described with reference to Fig. 9. Fig. 9 illustrates the core part 5X mounted on the holding member 4X. The core part 5X is a package of various electronic components used in the OCXO 1X, and has a three-layer structure (laminated structure) in which an oscillation IC 51, a heater IC 52, and a crystal oscillator (piezoelectric oscillator) 50X are laminated in this order from the top. The areas of the oscillation IC 51, the heater IC 52, and the crystal oscillator 50X in a plan view gradually decrease toward the top.

[0064] The crystal oscillator is configured by the crystal unit 50X and the oscillation IC 51. For example, a VCXO IC can be used as the oscillation IC 51, in which case the crystal oscillator is configured as a VCXO. The oscillation IC 51 controls the piezoelectric vibration of the crystal unit 50X, thereby controlling the oscillation frequency of the OCXO 1X.

[0065] The heater IC 52 is configured to integrate, for example, a heating element (heat source), a control circuit (current control circuit) for controlling the temperature of the heating element, and a temperature sensor for detecting the temperature of the heating element. By controlling the temperature of the core unit 5X using the heater IC 52, the temperature of the core unit 5X is maintained at a substantially constant temperature, and the oscillation frequency of the OCXO 1X is stabilized. Note that the temperature sensor may be provided as a separate member from the heater IC 52.

[0066] A non-conductive adhesive 53 is interposed between the opposing surfaces of the oscillation IC 51 and the heater IC 52, and the opposing surfaces of the oscillation IC 51 and the heater IC 52 are fixed to each other by the non-conductive adhesive 53. In this case, the top surface of the heater IC 52 and the bottom surface of the oscillation IC 51 are joined via the non-conductive adhesive 53.

[0067] The area of ​​the oscillation IC 51 in a plan view is smaller than that of the heater IC 52, and the entire oscillation IC 51 is located within the range of the heater IC 52 in a plan view. The entire lower surface of the oscillation IC 51 is joined to the upper surface of the heater IC 52 (the first main surface of the first sealing member 20).

[0068] A conductive adhesive 54 is interposed between the opposing surfaces of the heater IC 52 and the crystal unit 50X, and the opposing surfaces of the heater IC 52 and the crystal unit 50X are fixed together by the conductive adhesive 54. In this case, the bottom surface of the heater IC 52 and the top surface of the crystal unit 50X are joined together via the conductive adhesive 54.

[0069] The area of ​​the heater IC 52 in a plan view is smaller than that of the crystal unit 50X, and the entire heater IC 52 is located within the range of the crystal unit 50X in a plan view. The entire bottom surface of the heater IC 52 is bonded to the top surface of the crystal unit 50X.

[0070] A non-conductive adhesive 55 is interposed between the opposing surfaces of the quartz crystal unit 50X and the pair of holding members 4X, and the opposing surfaces of the quartz crystal unit 50X and the pair of holding members 4X are fixed to each other by the non-conductive adhesive 55. As the non-conductive adhesives 53 and 55, for example, a polyimide adhesive or the like is used, and as the conductive adhesive 54, for example, an epoxy adhesive or the like is used.

[0071] 9, wire pads for wire bonding (not shown) are formed on the upper surfaces of the oscillation IC 51, the crystal unit 50X, and the heater IC 52. The wire bonding of the oscillation IC 51, the crystal unit 50X, and the heater IC 52 is not performed before the core unit 5X is mounted on the package 2X, but is performed after the core unit 5X is mounted on the package 2X.

[0072] That is, as shown in Fig. 9, after the core unit 5X is mounted on the package 2X, the wire pad formed on the upper surface of the crystal unit 50X is connected to the wire pad formed on the oscillation IC 51 via the wire 6c. The wire pad formed on the oscillation IC 51 is connected to the wire pad formed on the step surface of the step portion 2c via the wire 6a. The wire pad formed on the upper surface of the heater IC 52 is connected to the wire pad formed on the step surface of the step portion 2c via the wire 6b. In this way, by performing wire bonding after mounting the core unit 5X on the package 2X, the wire bonding can be performed efficiently, and an OCXO 1X with excellent mass productivity can be provided.

[0073] Unlike the above embodiment, the crystal unit 50X used in the core unit 5X is an SMD type crystal unit. Specifically, a crystal unit (not shown) is bonded and mounted in a storage section of a package (housing) made of ceramic or the like and having a substantially concave cross-sectional shape by a conductive bonding material (not shown), and the package is hermetically sealed by a sealing material (not shown) formed in the opening of the package by a lid (not shown).

[0074] Here, it is preferable that the crystal unit 50X and the package 2X are not directly wire-connected, and only the oscillation IC 51 is directly wire-connected to the crystal unit 50X. In this embodiment, the crystal unit 50X and the oscillation IC 51 are only connected via the wire 6c. This configuration can prevent heat from escaping from the crystal unit 50X to the package 2X through the wire. As a result, there are advantages such as improved insulation for the crystal unit 50X and improved temperature controllability for the crystal unit 50X.

[0075] The OCXO 1X according to the other embodiments also has a feature in the joining structure between the holding member 4X carrying the core portion 5X and the inner bottom surface of the package 2X (the bottom surface of the recess 2Xa). This feature will be described below.

[0076] As shown in Figures 9 and 10, the spacer member 2Xf is integrally formed on the bottom surface of the recess 2Xa of the package 2X (the inner bottom surface of the package), and the upper surface of the spacer member 2Xf is formed so that the peripheral end 21Xf is lower than the central portion 22Xf in a plan view. The holding member 4X is joined to the upper surface of the spacer member 2Xf, which is coated with a bonding material 7 made of a non-conductive adhesive. At this time, the bonding material 7 formed between the holding member 4X and the spacer member 2Xf bonds the holding member 4X to the spacer member 2Xf in a state where the bonding material 7 becomes thicker from the central portion 22Xf of the spacer member 2Xf in a plan view toward the periphery where the peripheral end 21Xf is located.

[0077] More specifically, the spacer member 2Xf is formed of the above-mentioned metallized material, and is formed in a substantially rectangular shape when viewed in cross section, with an R-shaped inclined portion 23Xf formed at the edge of the upper surface of the spacer member 2Xf. Then, by applying the bonding material 7 to the upper surface of the spacer member 2Xf configured in this manner and bonding it to the holding member 4X, the bonding material 7 formed between the holding member 4X and the spacer member 2Xf is applied and formed along the R-shaped inclined portion 23Xf. As a result, the holding member 4X and the spacer member 2Xf can be bonded to each other with the bonding material 7 gradually becoming thicker from the center of the spacer member 2Xf toward the periphery in a plan view.

[0078] By adopting such a bonding structure between the holding member 4X and the bottom surface of the recess 2Xa of the package 2X (the inner bottom surface of the package), a sufficient and stable gap space is formed between the holding member 4X and the bottom surface of the recess 2Xa of the package 2X, eliminating variations in insulation due to gap variations and tilt, improving the insulating effect for the core portion 5X, and stabilizing the electrical characteristics of the oven-controlled piezoelectric oscillator.

[0079] In addition, since the bonding material 7 bonds the retaining member 4X and the spacer member 2Xf in a state in which the thickness gradually increases from the central portion 22Xf of the spacer member 2Xf in a planar view toward the periphery where the peripheral end portion 21Xf is located, an anchor effect is generated and the bonding strength between the retaining member 4X and the spacer member 2Xf can be increased.

[0080] Furthermore, since the bonding material 7 made of a resin such as a polyimide-based adhesive or an epoxy-based adhesive gradually becomes thicker toward the periphery of the spacer member 2Xf, it is possible to soften the impact caused by the up and down movement or bending of the holding member 4X, thereby preventing damage to the core portion 5X mounted on the upper part of the holding member 4X and preventing breakage of the wire portion electrically connecting the core portion 5X to the package 2X.

[0081] In the above embodiment, the core portion 5 (or 5X) has a three-layer structure in which the oscillation IC 51, the quartz crystal oscillator 50 (or 50X), and the heater IC 52 are stacked in this order from the top, but the present invention is not limited to this, and the configuration may be such that the other components are placed flat (side by side) on top of the component with the largest planar area.

[0082] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present invention is not interpreted solely by the above-described embodiments, but is defined by the claims. Also, all modifications within the scope and meaning equivalent to the claims are included. [Explanation of symbols]

[0083] 1,1X OCXO (oven-controlled piezoelectric oscillator) 2,2X Package 2d space 3 Lid 4,4X retaining member 5,5X Core 6a, 6b, 6c Wire 7 Non-conductive adhesives (bonding materials) 8. Encapsulating materials 50,50X Quartz Crystal (Piezoelectric) 51 Oscillation IC 52 Heater IC 53,54,55 Non-conductive adhesive 5 100 Crystal Oscillator

Claims

[Claim 1] An oven-controlled piezoelectric oscillator in which a core portion is hermetically sealed inside a heat-insulating package, The core portion includes at least an oscillation IC, a piezoelectric vibrator, and a heater IC, the core portion is mounted on a holding member, and the holding member is mechanically joined to a spacer member formed on an inner bottom surface of the package by a bonding material; the core and the package are electrically connected by wires; a space is provided between the holding member and the inner bottom surface of the package via the spacer member; The spacer member has an upper surface formed such that a peripheral end portion is lower than a central portion in a plan view, the bonding material formed between the holding member and the spacer member bonds the holding member and the spacer member in a state in which the bonding material becomes thicker from a central portion toward a periphery in a plan view of the spacer member, 1. A thermostatic oven type piezoelectric oscillator comprising:

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