Oven-type piezoelectric oscillator

Abstract

To provide a thermostatted piezoelectric oscillator capable of efficiently heating a piezoelectric vibrator and suppressing deterioration of phase noise characteristics.SOLUTION: There is provided a thermostatted piezoelectric oscillator in which an insulating substrate 6 on which a crystal oscillator 2, an oscillation IC 3, and a heater IC 4 as a heating element are mounted is housed and sealed in a case 7. The crystal oscillator 2 and the heater IC 4 are mounted on each main surface of the insulating substrate 6, and the crystal oscillator 2 and the heater IC 4 are thermally coupled to each other via a thermal via 54 as a heat conducting part provided so as to penetrate the insulating substrate 6, and the heater IC 4 is electrically connected to neither the crystal oscillator 2 nor the oscillation IC 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] One type of piezoelectric oscillator used in mobile communication devices, etc. is a thermostatic oven-type piezoelectric oscillator in which a piezoelectric vibrator is heated by a heating element such as a heater, and the heating by the heating element is controlled to obtain a stable frequency.The applicant has also proposed a thermostatic oven-type crystal oscillator in Patent Publication No. 2021-158585 (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-158585 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned Patent Document 1 discloses an embodiment in which a heater substrate, which is a heating element, is directly mounted on a quartz crystal oscillator, which is a piezoelectric oscillator.

[0005] By mounting a heating element on the piezoelectric vibrator and directly bonding it in this way, it is possible to efficiently heat the piezoelectric vibrator, thereby reducing power consumption, and also to reduce the planar size and achieve miniaturization.

[0006] However, when the heating element is in operation, noise generated in the temperature control circuit that controls the heat generation of the heating element affects the piezoelectric vibrator directly bonded to the heating element, degrading the phase noise characteristics in the low detuning frequency range.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an oven-controlled piezoelectric oscillator that can efficiently heat a piezoelectric resonator while suppressing deterioration of phase noise characteristics. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention is configured as follows.

[0009] (1) The oven-controlled piezoelectric oscillator of the present invention is an oven-controlled piezoelectric oscillator in which at least a piezoelectric vibrator, an oscillation circuit for oscillating the piezoelectric vibrator, and an insulating substrate carrying a heating element for heating the piezoelectric vibrator are housed and sealed in a case, The piezoelectric vibrator is mounted on one of the two main surfaces of the insulating substrate, and the heating element is mounted on the other of the two main surfaces. The piezoelectric vibrator and the heating element are thermally coupled to each other via a heat conductive portion that penetrates both of the two main surfaces of the insulating substrate in the thickness direction. The heating element is electrically connected to both the piezoelectric vibrator and the oscillation circuit. a first thermal conductor thermally coupled to the thermal conduction portion is formed in at least a part of a piezoelectric vibrator mounting region on the one main surface of the insulating substrate where the piezoelectric vibrator is mounted, and a second thermal conductor thermally coupled to the thermal conduction portion is formed in at least a part of a heat generating element mounting region on the other main surface of the insulating substrate where the heat generating element is mounted, and the thermal capacity of the piezoelectric vibrator is smaller than the total thermal capacity of the heat conducting portion, the first thermal conductor, and the second thermal conductor. .

[0010] According to the present invention, the piezoelectric vibrator and the heating element are mounted on one main surface and the other main surface of the insulating substrate, respectively, so that the influence of noise generated during operation of the heating element on the piezoelectric vibrator can be reduced compared to a configuration in which the piezoelectric vibrator and the heating element are directly bonded. Furthermore, because the heating element is not electrically connected to either the piezoelectric vibrator or the oscillation circuit, the influence of noise can be further reduced, and deterioration of the phase noise characteristics of the oven-controlled piezoelectric oscillator can be prevented.

[0011] Furthermore, the piezoelectric vibrator and the heating element are thermally coupled via a heat-conducting portion that penetrates the insulating substrate in the thickness direction, so that heat from the heating element can be quickly transferred to the piezoelectric vibrator, enabling efficient heating. Furthermore, the heat conducting portion, which is thermally coupled to the piezoelectric vibrator and the heating element, is thermally coupled to a first heat conductor formed in the piezoelectric vibrator mounting area and is also thermally coupled to a second heat conductor formed in the heating element mounting area.Therefore, the heat of the heating element is quickly transmitted to the piezoelectric vibrator via the second heat conductor, the heat conducting portion, and the first heat conductor, thereby enabling the piezoelectric vibrator to be heated more efficiently.

[0012] (2) In a preferred embodiment of the present invention, the heat generating element is a heater IC incorporating a heat generating portion, a temperature sensor, and a temperature control circuit that controls the heat generation of the heat generating portion based on the temperature detected by the temperature sensor, and the heater IC is not electrically connected to the heat conducting portion.

[0013] According to this embodiment, the heater IC, which is a heating element, is not electrically connected to the piezoelectric resonator or the oscillation circuit, nor is it electrically connected to the heat-conducting part that is thermally coupled to the piezoelectric resonator. In other words, since the heater IC is electrically disconnected from any of the piezoelectric resonator, the oscillation circuit, and the heat-conducting part, it is possible to effectively suppress the effect of noise generated during operation of the heater IC on the piezoelectric resonator, and to prevent deterioration of the phase noise characteristics of the oven-controlled piezoelectric oscillator.

[0014] In addition, since the temperature sensor is built into the heater IC that is thermally coupled to the piezoelectric vibrator, it can accurately detect the temperature of the piezoelectric vibrator, and the temperature control circuit can control the temperature of the piezoelectric vibrator to a constant temperature.

[0017] (4) In yet another embodiment of the present invention, the first thermal conductor and the piezoelectric vibrator are not electrically connected.

[0018] According to this embodiment, the first thermal conductor between the heat conducting portion thermally coupled to the heating element and the piezoelectric vibrator is thermally coupled to the piezoelectric vibrator but is not electrically connected, thereby effectively suppressing the impact on the piezoelectric vibrator of noise generated when the heating element is operating.

[0019] (5) In one embodiment of the present invention, at least a portion of the first thermal conductor in the piezoelectric vibrator mounting region overlaps with the piezoelectric vibrator in a plan view.

[0020] According to this embodiment, the first thermal conductor in the piezoelectric vibrator mounting area overlaps with the piezoelectric vibrator, so that heat from the heat generating element can be transferred to the piezoelectric vibrator more quickly.

[0021] (6) In a preferred embodiment of the present invention, a third thermal conductor is formed on the surface of the piezoelectric vibrator opposite to the surface facing the insulating substrate, and the third thermal conductor is extended to the opposing surface and thermally coupled to the first thermal conductor.

[0022] According to this embodiment, the heat from the heating element is transmitted not only to the first thermal conductor in the piezoelectric vibrator mounting area, which is the surface of the piezoelectric vibrator facing the insulating substrate, but also to the third thermal conductor on the surface of the piezoelectric vibrator opposite the facing surface. As a result, the piezoelectric vibrator is heated from both its top and bottom, reducing the temperature gradient within the piezoelectric vibrator and stabilizing the temperature of the piezoelectric vibrator.

[0023] (7) In another embodiment of the present invention, the heat conducting portion is electrically connected to the ground of the oscillation circuit.

[0024] According to this embodiment, the heat conducting portion between the piezoelectric vibrator and the heating element is electrically connected to the ground of the oscillation circuit, so that the influence of noise from the heating element can be suppressed by the shielding function. [Effects of the Invention]

[0025] According to the present invention, the piezoelectric vibrator and the heating element are mounted on one main surface and the other main surface of the insulating substrate, respectively, and the heating element is not electrically connected to either the piezoelectric vibrator or the oscillator circuit. This reduces the effect on the piezoelectric vibrator of noise generated during operation of the heating element, and prevents deterioration of the phase noise characteristics of the oven-controlled piezoelectric oscillator.

[0026] Furthermore, since the piezoelectric vibrator and the heating element are thermally coupled via a heat-conducting portion that penetrates the insulating substrate in the thickness direction, the heat from the heating element can be quickly transferred to the piezoelectric vibrator for efficient heating, thereby achieving low power consumption. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of an oven-controlled crystal oscillator according to one embodiment of the present invention. [Figure 2] FIG. 2 is a bottom view of the crystal unit of FIG. [Figure 3]FIG. 3 is a top view of the insulating substrate of FIG. 1, where FIG. 3(a) shows the state before the crystal unit and adjustment components are mounted, and FIG. 3(b) shows the state after the crystal unit and adjustment components are mounted. [Figure 4] FIG. 4 is a bottom view of the insulating substrate of FIG. 1, where FIG. 4(a) shows the state before the heater IC and the oscillation IC are mounted, and FIG. 4(b) shows the state after the heater IC and the oscillation IC are mounted. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an enlarged portion of the mounting portion of the crystal unit and heater IC in FIG. [Figure 6] FIG. 6 is a block diagram showing a schematic configuration of the oven-controlled crystal oscillator of FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view corresponding to FIG. 5 of another embodiment of the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view corresponding to FIG. 5 of still another embodiment of the present invention. [Figure 9] FIG. 9 is a schematic cross-sectional view corresponding to FIG. 5 of another embodiment of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view showing the configuration of the main part of a conventional oven-controlled crystal oscillator used to evaluate the phase noise characteristics. [Figure 11] FIG. 11 shows the phase noise characteristics when the heater is ON and OFF, where (a) in FIG. 11 shows the conventional example, (b) in FIG. 11 shows the first embodiment, (c) in FIG. 11 shows the second embodiment, and (d) in FIG. 11 shows the third embodiment. [Figure 12] FIG. 12 is a diagram showing the phase noise characteristics of the conventional example and the first to third embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0029] FIG. 1 shows an oven-controlled crystal oscillator (OCXO) according to one embodiment of the present invention. ’ FIG. 1 is a schematic cross-sectional view showing the configuration of a quartz crystal oscillator.

[0030] The oven-controlled crystal oscillator 1 of this embodiment includes an insulating substrate 6 on which at least a crystal resonator 2, an oscillation IC 3, and a heater IC 4 as a heating element are mounted, and the insulating substrate 6 is housed in a case 7 and hermetically sealed.

[0031] A plurality of adjustment parts 5 such as trimmer capacitors for adjusting the characteristics of the oven-controlled crystal oscillator 1 are mounted on the insulating substrate 6, and the oscillation IC 3 and the adjustment parts 5 form an oscillation circuit section that causes the crystal resonator 2 to oscillate.

[0032] The case 7 is configured by joining a metal cover 9 to an insulating base substrate 8, and the outer shape of the case 7 is a substantially rectangular parallelepiped. The joining of the base substrate 8 and the metal cover 9 is performed in an atmosphere of an inert gas such as nitrogen gas or in a vacuum atmosphere, and the internal space of the case 7 is filled with an inert gas such as nitrogen gas or is evacuated.

[0033] The insulating substrate 6 and the base substrate 8 are wiring substrates made of substrate materials such as glass epoxy, ceramic, and glass.

[0034] As described below, wiring patterns are formed on both main surfaces of the insulating substrate 6. The crystal unit 2 and adjustment components 5 are bonded to one main surface, the upper surface, of the insulating substrate 6 with a bonding material such as solder 55, and the heater IC 4 and oscillation IC 3 are bonded to the other main surface, the lower surface, with a bonding material such as a conductive adhesive 56 made of silver paste.

[0035] The insulating substrate 6 is supported on the base substrate 8 by a plurality of metallic pin members 10. Each pin member 10 is made of, for example, Cu, has a cylindrical shape, and electrically connects the wiring pattern of the insulating substrate 6 to the wiring pattern of the base substrate 8. A plurality of mounting terminals 11 of the oven-controlled crystal oscillator 1 are formed on the outer bottom surface of the base substrate 8.

[0036] The crystal unit 2 mounted on the insulating substrate 6 is a surface-mount type and includes a container 16 housing a crystal element (crystal resonator element) 60, which is a piezoelectric element. The container 16, which is rectangular in plan view, houses the crystal element 60 in an insulating container body 16a made of ceramic or the like and has a recess. A metal lid 16b is bonded to the container body 16a to provide an airtight seal. As shown in FIG. 2, first and second external electrodes 17 and 18 connected to the crystal element 60 are formed on the bottom surface of the container body 16a, i.e., on two diagonally opposite corners of the outer bottom surface of the crystal unit 2. FIG. 2 is a perspective view of the crystal unit 2 from above, corresponding to FIG. 3(b) described below.

[0037] The first and second external electrodes 17, 18 are electrically connected to the excitation electrodes on the front and back of the crystal element 60. A resonator-side thermal conductor 19, which will be described later, is formed on the outer bottom surface of the crystal unit 2 in the remaining area excluding the areas where the first and second external electrodes 17, 18 are formed. The resonator-side thermal conductor 19 is made of a metal material, for example, the same metal material as the first and second external electrodes 17, 18. The resonator-side thermal conductor 19 is not electrically connected to the crystal element 60.

[0038] The oscillator-side thermal conductor 19 may be omitted, and a conventional four-terminal crystal oscillator having third and fourth external electrodes at two diagonally opposite corners in addition to the first and second external electrodes 17 and 18 may be used.

[0039] 3A and 3B are diagrams schematically illustrating the top surface of the insulating substrate 6 on which the crystal unit 2 is mounted, with FIG. 3A showing the state before the crystal unit 2 and the adjustment components 5 are mounted, and FIG. 3B showing the state after the crystal unit 2 and the adjustment components 5 are mounted. In FIG. 3, only the main wiring patterns are shown.

[0040] Metal pin members 10 shown in FIG. 1 are inserted into the peripheral portion including the four corners of rectangular insulating substrate 6 and joined with solder 55, and a plurality of connection terminals 20 to 24 are formed which are electrically connected to a plurality of mounting terminals 11 on the bottom surface of oven-controlled crystal oscillator 1, respectively.

[0041] In this embodiment, the oscillator circuit section, which includes the crystal unit 2, oscillation IC 3, and adjustment components 5, has separate conductive paths from the heater IC 4. The oven controlled crystal oscillator 1 includes, as the plurality of connection terminals 20-24, a first power supply connection terminal (VDD1) 20, a first ground connection terminal (GND1) 21, and an output connection terminal (OUT) 22, which are electrically connected to the oscillator circuit section as described below, as well as a second power supply connection terminal (VDD2) 23 and a second ground connection terminal (GND2) 24, which are electrically connected to the heater IC 4 as described below.

[0042] The insulating substrate 6 has a central region serving as a crystal unit mounting region where the rectangular crystal unit 2 in plan view is mounted. In this crystal unit mounting region, first and second crystal unit mounting pads 25 and 26 corresponding to the first and second external electrodes 17 and 18 of the crystal unit 2 shown in Fig. 2 are formed, and when the crystal unit 2 is mounted, the first and second external electrodes 17 and 18 of the crystal unit 2 are electrically connected to the first and second crystal unit mounting pads 25 and 26, respectively.

[0043] In addition, a first thermal conductor 27 corresponding to the oscillator-side thermal conductor 19 of the quartz oscillator 2 shown in Figure 2 is formed in the quartz oscillator mounting area, and the quartz oscillator 2 is mounted, and the oscillator-side thermal conductor 19 is joined to the first thermal conductor 27 with solder 55.

[0044] The first thermal conductor 27 is made of a metal material such as copper, gold, or aluminum.

[0045] This first thermal conductor 27 is formed in a position where it overlaps with the crystal element 60 housed in the container 16 of the crystal oscillator 2 in a planar view, and can efficiently transfer heat from the heater IC4 to the crystal element 60 of the crystal oscillator 2.

[0046] Four thermal vias 54, which will be described later, are formed penetrating the insulating substrate 6 in the area where the first thermal conductor 27 is formed near the center of the crystal unit mounting area.

[0047] 3(b), the first vibrator mounting pad 25 electrically connected to the first external electrode 17 of the quartz crystal vibrator 2 is electrically connected to a first land 32 around the first through hole 31 via wiring patterns 28-29 and an adjustment component 5, and this first land 32 is electrically connected to the first through hole 31. Furthermore, the second vibrator mounting pad 26 electrically connected to the second external electrode 18 of the quartz crystal vibrator 2 is electrically connected to a second land 35 around the second through hole 34 via a wiring pattern 33, and the second land 35 is electrically connected to the second through hole 34.

[0048] 4A and 4B are diagrams showing the underside of the insulating substrate 6 on which the heater IC 4 and the oscillation IC 3 are mounted, with Fig. 4A showing the state before the heater IC 4 and the oscillation IC 3 are mounted, and Fig. 4B showing the state after the heater IC 4 and the oscillation IC 3 are mounted and wire-bonded. Note that Fig. 4 is a perspective view from the top shown in Fig. 3.

[0049] On the peripheral edge including the four corners of the insulating substrate 6, the first and second power supply connection terminals 20, 23, the first and second ground connection terminals 21, 24, and the output connection terminal 22 are formed on the upper surface so as to continue to the lower surface.

[0050] The second power supply connection terminal 23 is connected to a second power supply pad 49 via a wiring pattern 48, and the second ground connection terminal 24 is connected to a second ground pad 51 via a wiring pattern 50. The second power supply pad 49 and the second ground pad 51 are formed near a heater IC mounting area where a heater IC 4, which is rectangular in plan view, is mounted. As shown in FIG. 4(a), a second thermal conductor 52 is formed in this rectangular heater IC mounting area. This second thermal conductor 52 is made of a metal material such as copper or aluminum. Four thermal vias 54 are formed through the formation area of ​​the second thermal conductor 52.

[0051] As shown in FIG. 4(b), the second power supply pad 49 and the second ground pad 51 are electrically connected to the corresponding electrodes of the heater IC 4 by bonding wires 53, respectively.

[0052] In this manner, the second power supply connection terminal 23 and the second ground connection terminal 24 are electrically connected to the heater IC.

[0053] On the other hand, the first power supply connection terminal 20 is connected to a first power supply pad 37 via a wiring pattern 36, and the first ground connection terminal 21 is connected to a first ground pad 40 via a wiring pattern 38 and an oscillation IC mounting pad 39 on which an oscillation IC 3 is mounted. The output connection terminal 22 is connected to an output pad 42 via a wiring pattern 41.

[0054] A third land 43 is formed around the first through hole 31 electrically connected to the first land 32 on the upper surface of the insulating substrate 6, and this third land 43 is electrically connected to the first through hole 31. As described above, the first land 32 on the upper surface of the insulating substrate 6 is electrically connected to the first resonator mounting pad 25 which is electrically connected to the first external electrode 17 of the quartz crystal resonator 2, and therefore the third land 43 is electrically connected to the first resonator mounting pad 25. This third land 43 is connected to the first resonator pad 44, and therefore the first resonator pad 44 is electrically connected to the first external electrode 17 of the quartz crystal resonator 2 mounted on the upper surface of the insulating substrate 6 via the first through hole 31, etc.

[0055] A fourth land 45 is formed around the second through hole 34, which is electrically connected to the second land 35 on the upper surface of the insulating substrate 6, and this fourth land 45 is electrically connected to the second through hole 34. As described above, the second land 35 on the upper surface of the insulating substrate 6 is electrically connected to the second resonator mounting pad 26, which is electrically connected to the second external electrode 18 of the quartz crystal resonator 2, and therefore the fourth land 45 is electrically connected to the second resonator mounting pad 26. This fourth land 45 is connected to the second resonator pad 46, and therefore the second resonator pad 46 is electrically connected to the second external electrode 18 of the quartz crystal resonator 2 mounted on the upper surface of the insulating substrate 6 via the second through hole 34, etc.

[0056] The first power supply pad 37, the first ground pad 40, the output pad 42, the first vibrator pad 44 and the second vibrator pad 46 are formed to surround the rectangular oscillation IC mounting pad 39 which is wider than the area on which the oscillation IC 3 is mounted.

[0057] The first power supply pad 37, the first ground pad 40, the output pad 42, the first vibrator pad 44 and the second vibrator pad 46 are electrically connected to the corresponding electrodes of the oscillation IC 3 by bonding wires 47, respectively, as shown in FIG. 4(b).

[0058] As described above, the heater IC4 is electrically connected to the second power supply connection terminal 23 and the second ground connection terminal 24, while the crystal resonator 2 is electrically connected to the oscillation IC3, which is electrically connected to the first power supply connection terminal 20, the first ground connection terminal 21, and the output connection terminal 22.

[0059] That is, the heater IC4 is electrically separated from the oscillation circuit section including the crystal unit 2 and the oscillation IC3.

[0060] As described above, according to this embodiment, the crystal unit 2 and the heater IC 4 as a heating element are mounted on the top and bottom surfaces of the insulating substrate 6, respectively. Therefore, the crystal unit 2 is less susceptible to the effects of noise generated by the heater IC 4 compared to a configuration in which the crystal unit 2 and the heater IC 4 are directly bonded to each other.

[0061] Furthermore, since the heater IC4 is not electrically connected to the oscillation circuit section including the crystal unit 2 and the oscillation IC 3, the influence of noise generated by the heater IC4 on the crystal unit 2 can be further reduced, which makes it possible to prevent deterioration of the phase noise characteristics of the oven-controlled piezoelectric oscillator 1, as will be described later.

[0062] Furthermore, the oven-controlled crystal oscillator 1 of this embodiment is configured as follows so that the crystal resonator 2 can be efficiently heated by the heater IC 4.

[0063] FIG. 5 is an enlarged cross-sectional view of the portion of FIG. 1 where the crystal resonator 2 and the heater IC 4 are mounted.

[0064] 3(a) and 4(a), the insulating substrate 6 of this embodiment is provided with four thermal vias 54 as heat conduction portions that penetrate the insulating substrate 6 in the thickness direction. Each thermal via 54 is formed in a cylindrical shape by filling a metal into a circular through-hole in a plan view.

[0065] In this way, the thermal via 54 is filled with metal, so it can efficiently transfer heat and can suppress the effects of noise from the heater IC 4 compared to a through hole that is not filled with metal.

[0066] The metal material to be filled into the through-holes is preferably a metal material with high thermal conductivity, such as hardened Ag paste or Cu.

[0067] As shown in Fig. 3(a), four thermal vias 54 are formed so as to penetrate vertically through an area on the upper surface of the insulating substrate 6 where the crystal unit 2 is mounted, and as shown in Fig. 4(a), an area on the lower surface of the insulating substrate 6 where the heater IC 4 is mounted. The four thermal vias 54 are arranged vertically, horizontally, and around the center of the rectangular mounting area.

[0068] The number, size, shape, etc. of the thermal vias 54 are appropriately set depending on the size, heat generation amount, etc. of the crystal unit 2 and the heater IC 4.

[0069] The first thermal conductor 27 connected to one end of each thermal via 54 is formed in the mounting area for the quartz crystal unit 2 on the upper surface of the insulating substrate 6. As shown in Fig. 3(a), this first thermal conductor 27 is formed to extend from the center of the rectangular quartz crystal unit mounting area to the periphery, excluding the two first and second oscillator mounting pads 25, 26. This first thermal conductor 27 is formed to be slightly wider than the oscillator-side thermal conductor 19 on the bottom surface of the quartz crystal unit 2.

[0070] As described above, the crystal unit 2 is joined by solder 55 to the mounting area on the top surface of the insulating substrate 6 where the first thermal conductor is formed.

[0071] The second thermal conductors 52 connected to the other ends of the thermal vias 54 are formed in the heater IC4 mounting area on the underside of the insulating substrate 6. The second thermal conductors 52 are formed in an area including the thermal vias 54 in the rectangular heater IC4 mounting area.

[0072] As described above, the heater IC 4 is bonded by the conductive adhesive 56 to the mounting area on the lower surface of the insulating substrate 6 where the second thermal conductor 52 is formed.

[0073] The first and second thermal conductors 27, 52 on the top and bottom of the insulating substrate 6 are connected to four thermal vias 54 formed to penetrate the insulating substrate 6, so that the first and second thermal conductors 27, 52 are thermally coupled to the thermal vias 54. Furthermore, the crystal unit 2 is joined to the first thermal conductor 27 with solder 55, and the heater IC 4 is joined to the second thermal conductor 52 with a conductive adhesive 56. Therefore, the crystal unit 2 and the heater IC 4 on the top and bottom of the insulating substrate 6 are thermally coupled by the solder 55, the first thermal conductor 27, the thermal vias 54, the second thermal conductor 52, and the conductive adhesive 56.

[0074] Here, being thermally coupled means a state in which heat is conducted by direct or indirect contact.

[0075] In this embodiment, the crystal unit 2 and the heater IC4, which is a heat generating element, are thermally coupled by the four thermal vias 54, which serve as heat conduction portions that penetrate the insulating substrate 6 in the thickness direction. This allows the heat of the heater IC4 to be quickly transferred to the crystal unit 2 for efficient heating, thereby achieving low power consumption.

[0076] Furthermore, each thermal via 54 is thermally coupled to the first thermal conductor 27 formed in the mounting area of ​​the insulating substrate 6 for the crystal unit 2 and the second thermal conductor 52 formed in the mounting area of ​​the insulating substrate 6 for the heater IC4. Therefore, the heat of the heater IC4 is rapidly transferred to each thermal via 54 by the second thermal conductor 52 in the mounting area for the heater IC4, and is also rapidly transferred to the crystal unit 2 by the first thermal conductor 27 in the mounting area for the crystal unit 2 via each thermal via 54, thereby enabling the crystal unit 2 to be heated even more efficiently.

[0077] Furthermore, similar to the heater IC 4, the thermal vias 54 and the first and second thermal conductors 27, 52 are electrically disconnected from the oscillation circuit section including the crystal unit 2 and the oscillation IC 3, and therefore the crystal unit 2 can be prevented from being affected by noise generated in the heater IC 4.

[0078] The heater IC 4 has a heat generating unit including a heater resistor and a power transistor, a temperature control circuit that controls the heat generating unit, a temperature sensor, etc., located on its active surface (bottom surface). The heater IC 4 has its non-active surface, opposite to its active surface, bonded to the bottom surface (bottom surface) of the insulating substrate 6. This means that the active surface is located farther from the crystal unit 2, reducing the impact of noise generated in the temperature control circuit and heat generating unit on the crystal unit 2. Furthermore, because the silicon that makes up the body of the heater IC 4 has high electrical resistance, the silicon can prevent the impact of noise generated in the temperature control circuit and heat generating unit on the active surface from spreading to the non-active surface, which is on the insulating substrate 6 side.

[0079] On the other hand, silicon has good thermal conductivity, so heat from the heat generating portion on the active surface side can be transferred to the non-active surface side, which is the insulating substrate 6 side, via silicon.

[0080] The heater IC4 is electrically connected to the second power supply pad 49 and the second ground pad 51 provided on the insulating substrate 6 only by the bonding wire 53, so that the outflow of heat from the heater IC4 to places other than the thermal via 54, etc. can be suppressed compared to when the heater IC4 is joined to pads formed on the insulating substrate 6 by bumps or solder without using bonding wires.

[0081] FIG. 6 is a schematic block diagram showing the oven-controlled crystal oscillator 1 of this embodiment having the above-described configuration.

[0082] The insulating substrate 6 is mounted with a crystal oscillator 2, an oscillation circuit section 57 including an oscillation IC 3 and adjustment components 5, and the first power supply connection terminal 20, the first ground connection terminal 21 and the output connection terminal 22 of this oscillation circuit section 57 are electrically connected to the corresponding mounting terminals 11 of the base substrate 8 via the pin members 10.

[0083] In addition, a heater IC4 is mounted on the insulating substrate 6 as a heating element, and the second power supply connection terminal 23 and the second ground connection terminal 24 of this heater IC4 are electrically connected to the corresponding mounting terminals 11 of the base substrate 8 via the above-mentioned pin members 10.

[0084] The crystal unit 2 mounted on the upper surface of the insulating substrate 6 and the heater IC 4 mounted on the lower surface of the insulating substrate 6 are thermally coupled by thermal vias 54 or the like as heat conduction parts.

[0085] As described above, according to this embodiment, the crystal unit 2 and the heater IC 4 are mounted on the top and bottom surfaces of the insulating substrate 6, respectively, and the heater IC 4 is electrically disconnected from the oscillation circuit unit including the crystal unit 2 and the oscillation IC 3. This reduces the effect of noise generated by the heater IC 4 on the crystal unit 2, and prevents deterioration of the phase noise characteristics of the oven-controlled piezoelectric oscillator 1.

[0086] Furthermore, the crystal unit 2 and the heater IC 4 are thermally coupled by the thermal vias 54 that penetrate the insulating substrate 6 in the thickness direction, so that the heat of the heater IC 4 can be quickly transferred to the crystal unit 2 for efficient heating, thereby achieving low power consumption.

[0087] FIG. 7 is a cross-sectional view corresponding to FIG. 5 of another embodiment of the present invention.

[0088] In this embodiment, a metal lid 161b constituting the container 161 of the quartz crystal oscillator 21 is connected to the oscillator-side thermal conductor 19 on the bottom surface of the quartz crystal oscillator 21 by a through electrode 161c formed to penetrate the container body 161a.

[0089] This thermally couples the oscillator-side thermal conductor 19 on the underside of the quartz oscillator 21 to the lid 161b that forms the upper surface of the container 161, and the quartz oscillator 21 is heated from above and below by the oscillator-side thermal conductor 19 on the underside, which is thermally coupled to the first thermal conductor 27, and the lid 161b on the upper surface, thereby reducing the temperature gradient in the quartz oscillator 21.

[0090] Furthermore, the temperature of the crystal element 60 inside the container 161 can be more easily uniformed, improving the frequency temperature characteristics.

[0091] FIG. 8 is a cross-sectional view corresponding to FIG. 5 of yet another embodiment of the present invention.

[0092] In this embodiment, instead of multiple small-diameter thermal vias 54, the insulating substrate 6 is provided with columnar thermal vias 54a in which large-diameter columnar metal is embedded, and further, a metal plate 58 is provided on the upper surface of the first thermal conductor 27 on the upper surface of the insulating substrate 6.

[0093] By adding the columnar thermal vias 54a, which are large-diameter metal columns, and the metal plate 58 in this way, the heat capacity of the thermal conductor between the crystal unit 2 and the heater IC 4 can be increased, and frequency fluctuations due to temperature fluctuations can be suppressed, thereby stabilizing the frequency.

[0094] FIG. 9 is a cross-sectional view corresponding to FIG. 5 of another embodiment of the present invention.

[0095] The quartz crystal vibrator 22 of this embodiment is a known quartz crystal vibrator 22 having a three-layer (sandwich) structure including a quartz crystal vibrating plate 22a, which is a piezoelectric vibrating plate having excitation electrodes formed on both main surfaces, a first sealing member 22b that covers and hermetically seals the excitation electrodes on one main surface of the quartz crystal vibrating plate 22a, and a second sealing member 22c that covers and hermetically seals the excitation electrodes on the other main surface of the quartz crystal vibrating plate 22a.

[0096] Unlike the oscillation IC 3 of each of the above embodiments, the oscillation IC 31 of this embodiment is mounted by flip-chip bonding its mounting terminals (consisting of multiple terminals) to multiple mounting pads formed on the first sealing member 22b of the quartz crystal unit 22. These mounting pads are electrically connected to the excitation electrodes of the quartz crystal plate 22a and the external electrodes on the bottom surface of the second sealing member 22c via the wiring pattern on the first sealing member 22b and multiple through-hole electrodes, etc. The heater IC4 is not electrically connected to the excitation electrodes of the quartz crystal plate 22a or the oscillation circuit built into the oscillation IC 31.

[0097] The thermal capacity of the crystal unit 22 with this three-layer structure is smaller than the combined thermal capacity of the thermal vias 54a and the first and second thermal conductors 27, 52, so the heat from the heater IC4 can be transferred more quickly to the crystal unit 22. As a result, the time required to heat the crystal unit 22 is shortened, and power consumption can be reduced.

[0098] Furthermore, this three-layered crystal unit 22 can be made smaller and thinner than a crystal unit in which a crystal element is housed in a box-shaped container body with a recess and a lid is joined to the container body to seal it airtight.

[0099] The present inventors evaluated the phase noise characteristics of the conventional example and Examples 1 to 3 corresponding to the embodiments of the present invention.

[0100] As a conventional example, an oven-controlled crystal oscillator was used, which has a configuration in which a crystal unit 2' and an oscillator circuit board 3' are mounted on an insulating substrate 6', and a heater IC 4' is directly mounted on the crystal unit 2' via an adhesive 56', as shown in FIG. 10.

[0101] The required wiring pattern and resonator mounting pads are formed on the insulating substrate 6'. The crystal resonator 2' is a surface-mount type crystal resonator having four conventional external electrodes (four terminals) on the bottom surface without the resonator-side thermal conductor 19, and the crystal element 60' is housed and hermetically sealed in a container 16' having a box-shaped container body 16a' and a lid 16b'.

[0102] The oscillator circuit board 3' and the crystal unit 2' form an oscillator circuit section.

[0103] The heater IC 4' incorporates a heat generating portion, a temperature sensor, and a temperature control circuit, and is bonded onto the crystal oscillator 2' with an adhesive 56'.

[0104] In this conventional example, on an insulating substrate 6', the ground (GND) of the heater IC 4' is connected to the ground (GND) of the oscillator circuit substrate 3' and to two external electrodes of the crystal resonator 2' that are not connected to the crystal element 60'.

[0105] That is, the heater IC 4' is electrically connected to the oscillator circuit board 3' and the crystal unit 2'.

[0106] Example 1 is the oven-controlled crystal oscillator 1 of the embodiment shown in Figures 1 to 6. Example 2 is similar to Example 1, except that the thickness of the solder 55 between the crystal unit 2 and the insulating substrate 6 is increased from 0.05 mm in Example 1 to 0.5 mm, which is ten times the thickness, and the heat capacity is increased as in the embodiment of Figure 8 above. Example 3 is similar to Example 2, except that the metal lid 161b of the crystal unit 21 is connected to the first thermal conductor 27 via a through electrode 161c formed in the container 161 as in the embodiment of Figure 7 above.

[0107] 11 is a diagram showing phase noise characteristics when the heater is ON and OFF for the conventional example and Examples 1 to 3. In the figure, the horizontal axis is the detuning frequency indicating the difference from the oscillation frequency, and the vertical axis is the phase noise, with the phase noise when the heater is ON indicated by a solid line and the phase noise when the heater is OFF indicated by a dashed line. Figure 11(a) shows the conventional example, Figure 11(b) shows Example 1, Figure 11(c) shows Example 2, and Figure 11(d) shows Example 3, respectively.

[0108] Table 1 below shows the difference in phase noise between when the heater is ON and when the heater is OFF at a detuning frequency of 1 Hz for the conventional example and each of Examples 1 to 3.

[0109] [Table 1]

[0110] As shown in FIG. 11(a) and Table 1, in the conventional example in which the heater IC 4' is mounted directly on the crystal unit 2' and is electrically connected to the oscillator circuit board 3' and the crystal unit 2', the difference in phase noise between when the heater is ON and when the heater is OFF at a detuning frequency of 1 Hz is 26.02 dB.

[0111] In contrast to this, in Example 1, in which the crystal unit 2 and the heater IC 4 are mounted on both sides of the insulating substrate 6, respectively, and are thermally coupled by the thermal vias 54 penetrating the insulating substrate 6 and the first and second thermal conductors 27, 52, and further the heater IC 4 is not electrically connected to the crystal unit 2 and the oscillation circuit unit, as shown in FIG. 11(b) and Table 1, the difference in phase noise between when the heater is ON and when the heater is OFF at a detuning frequency of 1 Hz is 16.93 dB, which is an improvement of 9.09 dB in phase noise compared to the conventional example.

[0112] In addition, in Example 2, in which the thickness of the solder 55 between the crystal resonator 2 and the insulating substrate 6 is increased by 10 times in Example 1 to increase the heat capacity, as shown in FIG. 11(c) and Table 1, the difference in phase noise at a detuning frequency of 1 Hz between when the heater is ON and when the heater is OFF is 12.34 dB, which is an improvement of 4.59 dB compared to Example 1 and an improvement of 13.68 dB compared to the conventional example.

[0113] In Example 2, the thickness of the solder is increased, which increases the heat capacity compared to Example 1. This is thought to have resulted in a relatively slower heat conduction from the heater IC4, averaging the "heat fluctuations" originating from the heater IC4 over time, and improving the phase noise characteristics compared to Example 1.

[0114] In Example 3, in which the metal lid 161b of the quartz crystal oscillator 21 in Example 2 is connected to the oscillator-side thermal conductor 19 via a through electrode 161c formed in the container 161 of the quartz crystal oscillator 21, the difference in phase noise between when the heater is ON and when the heater is OFF at a detuning frequency of 1 Hz is 9.75 dB, which is an improvement of 2.59 dB in phase noise compared to Example 2 and an improvement of 16.27 dB in phase noise compared to the conventional example.

[0115] In Example 3, the metal cover 161b and the vibrator-side thermal conductor 19 are connected via the through electrode 161c, which is thought to further increase the heat capacity and further mitigate the "thermal fluctuations" caused by the heater IC4, thereby improving the phase noise characteristics.

[0116] FIG. 12 shows all of the phase noise characteristics when the heater is ON for the conventional example and each of Examples 1 to 3 in FIGS. 11(a) to 11(d).

[0117] In FIG. 12, a thin solid line L1 indicates the conventional example, a dashed line L2 indicates the first embodiment, a dot-and-dash line L3 indicates the second embodiment, and a thick solid line L4 indicates the third embodiment.

[0118] As shown in FIG. 12, in comparison with the conventional example, Examples 1 to 3 can reduce phase noise at low detuning frequencies, particularly at detuning frequencies below 10 Hz.

[0119] As described above, it can be seen that the phase noise characteristics of each of the first to third embodiments of the present invention are better than those of the conventional example.

[0120] The shapes of the first thermal conductors 27 and the second thermal conductors 52 formed on the upper and lower surfaces of the insulating substrate 6 in the above embodiment are not limited to those described above and may be any shape. Furthermore, at least one of the first thermal conductors 27 and the second thermal conductors 52 may be omitted. This prevents the first thermal conductors 27 and the second thermal conductors 52 from protruding from the crystal unit 2 and the heater IC 4 in a plan view, thereby preventing heat from leaking from the protruding portions. This allows heat to be transferred to the crystal unit 2 while suppressing heat loss from the heater IC 4.

[0121] In the above embodiment, the temperature sensor is built into the heater IC, but it may be provided on the crystal resonator side, for example, on the upper surface side of the insulating substrate, without being built into the heater IC.

[0122] In another embodiment of the present invention, a thermal via as a heat conducting portion may be electrically connected to the ground on the oscillation circuit portion side, and the influence of noise from the heater IC 4 may be suppressed by the shielding function.

[0123] In the above embodiment, the heater IC is used as the heating element, but the heating element is not limited to the heater IC, and may be a heater substrate, a power transistor, or the like.

[0124] The present invention is not limited to oven-controlled crystal oscillators equipped with crystal resonators, but can of course also be applied to oven-controlled piezoelectric oscillators equipped with piezoelectric resonators using lithium niobate, lithium tantalate, or the like.

[0125] As another embodiment of the present invention, an acceleration sensor may be mounted, and the acceleration sensor may detect acceleration caused by vibration of the piezoelectric vibrator, and compensation may be made for fluctuations in frequency due to acceleration. [Explanation of symbols]

[0126] 1. Oven-controlled crystal oscillator 2,21,22 crystal oscillator 3,31 Oscillation IC 4 Heater IC (heating element) 5 Adjustment parts 6. Insulating substrate 7 Cases 8 Base board 9 Metal Cover 27 First thermal conductor 52 Second thermal conductor 54,54a Thermal via

Claims

1. An oven-controlled piezoelectric oscillator in which at least a piezoelectric vibrator, an oscillation circuit for oscillating the piezoelectric vibrator, and an insulating substrate on which a heating element for heating the piezoelectric vibrator is mounted are housed and sealed in a case, the piezoelectric vibrator is mounted on one of the two main surfaces of the insulating substrate, and the heating element is mounted on the other of the two main surfaces, and the piezoelectric vibrator and the heating element are thermally coupled to each other via a heat conductive portion that is provided so as to penetrate both main surfaces of the insulating substrate in a thickness direction; the heating element is not electrically connected to either the piezoelectric vibrator or the oscillation circuit, a first thermal conductor thermally coupled to the thermal conduction portion is formed in at least a portion of a piezoelectric vibrator mounting region on the one main surface of the insulating substrate where the piezoelectric vibrator is mounted, and a second thermal conductor thermally coupled to the thermal conduction portion is formed in at least a portion of a heat generating element mounting region on the other main surface of the insulating substrate where the heat generating element is mounted; the heat capacity of the piezoelectric vibrator is smaller than the total heat capacity of the heat conductive portion, the first heat conductor, and the second heat conductor; 1. A thermostatic oven type piezoelectric oscillator characterized by:

2. the heat generating element is a heater IC incorporating a heat generating portion, a temperature sensor, and a temperature control circuit that controls heat generation from the heat generating portion based on the temperature detected by the temperature sensor; the heater IC is not electrically connected to the heat conductive portion; 2. The oven-controlled piezoelectric oscillator according to claim 1.

3. The first thermal conductor and the piezoelectric vibrator are not electrically connected to each other.

3. The oven-controlled piezoelectric oscillator according to claim 1.

4. At least a portion of the first thermal conductor in the piezoelectric vibrator mounting region overlaps with the piezoelectric vibrator in a plan view.

4. The oven-controlled piezoelectric oscillator according to claim 1.

5. a third thermal conductor is formed on a surface of the piezoelectric vibrator opposite to a surface facing the insulating substrate, the third thermal conductor extending to the facing surface and thermally coupled to the first thermal conductor; 5. The oven-controlled piezoelectric oscillator according to claim 1.

6. the heat conductive portion is electrically connected to the ground of the oscillation circuit; 6. The oven-controlled piezoelectric oscillator according to claim 1.

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