vibrating device

Abstract

Vibration device. A vibration device that outputs a high-precision oscillation frequency is provided. The vibration device (1) includes a vibration element (60), a first package (31) that houses the vibration element (60), and a second package (10) that houses and fixes the first package (31). The first package (31) includes a base substrate (32) that has a first surface (32a) on which the vibration element (60) is disposed and a second surface (32b) that is in a front-rear relationship with the first surface (32a) and that contains a single crystal silicon, an integrated circuit (40) that is disposed on the first surface (32a) or the second surface (32b) and that contains a temperature sensor circuit (46) and a heater circuit (47), and a cover (33) that is joined to the base substrate (32) in a manner that houses the vibration element (60) together with the base substrate (32).

Description

Technical Field

[0001] This invention relates to vibration devices. Background Technology

[0002] As an example of a vibrating device, oscillators that stabilize the resonant frequency by heating the vibrating element to stabilize its temperature are known. For example, Patent Document 1 discloses a quartz oscillator (OCXO) with a thermostatic bath, which houses the vibrating element, the heating element, and the circuit elements that serve as the oscillation section in a package made of ceramic or the like, and outputs a stable resonant frequency.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-28360

[0004] However, the vibration device described in Patent Document 1 has the following problem: one end of the vibration element is connected to the heating element. Therefore, the heat from the heating element is difficult to be evenly transferred to the entire vibration element, resulting in a temperature difference within the vibration element and thus degrading the accuracy of the oscillation frequency. Summary of the Invention

[0005] The vibration device includes: a vibration element; a first package housing the vibration element; and a second package housing and securing the first package, the first package comprising: a base substrate having a first side on which the vibration element is disposed and a second side opposite to the first side, comprising monocrystalline silicon; an integrated circuit disposed on the first side or the second side, comprising a temperature sensor circuit and a heater circuit; and a cover coupled to the base substrate in such a manner as to house the vibration element together with the base substrate. Attached Figure Description

[0006] Figure 1 This is a top view showing the outline structure of the vibration device according to the first embodiment.

[0007] Figure 2 yes Figure 1 Sectional view along line AA in the diagram.

[0008] Figure 3 This is a cross-sectional view showing the general structure of the oscillator.

[0009] Figure 4 This is a functional block diagram of an integrated circuit.

[0010] Figure 5 This is a cross-sectional view showing the general structure of the vibration device according to the second embodiment.

[0011] Figure 6 This is a cross-sectional view showing the outline structure of the vibration device according to the third embodiment.

[0012] Label Explanation

[0013] 1. 1a, 1b Vibrating device; 10 Second package; 11 First substrate; 11a Bonding surface; 12 Second substrate; 14 Connecting terminal; 15 External terminal; 16 Cover; 17 Bonding component; 18 Internal space; 30 Oscillator; 31 First package; 32 Base substrate; 32a First surface; 32b Second surface; 33 Cover; 34 Bonding component; 35 Passivation film; 36 Wiring; 37 Insulating film; 40 Integrated circuit; 41 Oscillating circuit; 42 Frequency multiplier circuit; 43 Output circuit; 44 Temperature compensation circuit; 45 Temperature control circuit; 46 Temperature sensor circuit; 47 Heater circuit; 49 Internal connecting terminal; 50 External connecting terminal; 51 Through hole; 52 Through electrode; 55 Outer surface; 56 Recess; 57 Internal space; 60 Vibrating element; 61 Quartz substrate; 62 Excitation electrode; 63 Connecting terminal; 72, 73 Conductive components; 80 Thermal insulation components. Detailed Implementation

[0014] 1. First Implementation Method

[0015] First, refer to Figure 1 as well as Figure 2 The vibration device 1 of the first embodiment will be described.

[0016] In addition, Figure 1 In the diagram, to facilitate explanation of the internal structure of the vibrating device 1, the state with the cover 16 removed is shown. Additionally, for ease of explanation, besides... Figure 4 In the subsequent figures, the X-axis, Y-axis, and Z-axis are shown as three mutually orthogonal axes. The direction along the X-axis is called the "X-direction," the direction along the Y-axis is called the "Y-direction," and the direction along the Z-axis is called the "Z-direction." The side of each axis opposite to the arrow is called the "positive side," and the side opposite the arrow is called the "negative side." The positive side of the Z-direction is also called "up," and the negative side of the Z-direction is called "down."

[0017] like Figure 1 and Figure 2 As shown, the vibration device 1 includes: an oscillator 30 having a first package 31 for housing a vibration element 60; a second package 10 for housing and fixing the first package 31; and a cover 16 forming an internal space 18 between the first package 31 and the second package 10. Therefore, the vibration device 1 of this embodiment is equivalent to a quartz oscillator (OCXO) with a double-package structure and a thermostatic bath.

[0018] The first package 31 consists of a base substrate 32 and a cover 33, with a vibrating element 60 housed between the base substrate 32 and the cover 33.

[0019] The base substrate 32 has a first surface 32a on which the vibration element 60 is disposed, and a second surface 32b opposite to the first surface 32a. An integrated circuit 40, including a temperature sensor circuit 46 and a heater circuit 47, is disposed on the first surface 32a of the base substrate 32, and the vibration element 60 is fixed to it via conductive components 73 such as metal bumps. Therefore, the vibration element 60 is closer to the temperature sensor circuit 46 or the heater circuit 47, thus enabling more accurate detection of the temperature of the vibration element 60 and more stably maintaining the vibration element 60 at a constant temperature. Furthermore, an external connection terminal 50 for bonding the first package 31 and the second package 10 is formed on the second surface 32b of the base substrate 32.

[0020] The first package 31 is made of a semiconductor containing monocrystalline silicon, such as silicon.

[0021] The second package 10 is formed by stacking a flat first substrate 11 and a frame-shaped second substrate 12. In addition, the second package 10 has an upwardly open internal space 18.

[0022] The first package 31 is housed in the internal space 18. The first package 31 is fixed to the mating surface 11a, which is the upper surface of the first substrate 11, via conductive members 72 such as metal bumps. In addition, when the first package 31 is fixed to the second package 10, the connection terminal 14 formed on the mating surface 11a of the second package 10 that is mated with the first package 31 is mechanically and electrically connected to the external connection terminal 50 formed on the second surface 32b of the base substrate 32 constituting the first package 31 via the conductive members 72.

[0023] An external terminal 15 is formed on the lower surface of the second package 10. The external terminal 15 is electrically connected to a connection terminal 14 formed on the first substrate 11 via a through electrode or wiring (not shown).

[0024] The second package 10 is made of various ceramics such as oxide ceramics, nitride ceramics, and carbide ceramics, which have a lower thermal conductivity than the first package 31. Therefore, the thermal conductivity of the first package 31 is higher than that of the second package 10, so the heat from the heater circuit 47 is easily transferred to the entire first package 31. In addition, by covering the first package 31 with the second package 10, which has a lower thermal conductivity, external temperature fluctuations can be effectively suppressed.

[0025] The cover 16 is flat and is joined to the upper surface of the second package 10 via a joining member 17. This creates a hermetically sealed internal space 18 between the second package 10 and the cover 16, within which the first package 31 is housed. Furthermore, the internal space 18 is in a depressurized state, preferably closer to a vacuum. This reduces convective heat transfer from the first package 31 to the second package 10, further maintaining the internal space 18 at a constant temperature.

[0026] Next, refer to Figure 3 Explain the structure of oscillator 30.

[0027] The quartz oscillator 30 in this embodiment is used, for example, as a temperature-compensated quartz oscillator (TCXO) or a single-package quartz oscillator (OCXO) with a thermostatic bath. Figure 3 As shown, such an oscillator 30 has: a first package 31 consisting of a base substrate 32 and a cover 33; and a vibrating element 60 housed in the internal space 57 of the first package 31.

[0028] The first package 31 has a base substrate 32 and a cover 33 that is engaged with the base substrate 32, and a vibrating element 60 is housed in an internal space 57 formed between the base substrate 32 and the cover 33.

[0029] The base substrate 32 is a semiconductor substrate containing single-crystal silicon, and in this embodiment, it is a silicon substrate. The base substrate 32 is not particularly limited, and semiconductor substrates other than silicon, such as germanium, gallium arsenide, gallium phosphide, gallium nitride, silicon carbide, etc., can be used, or substrates other than semiconductor substrates such as ceramic substrates can be used.

[0030] The base substrate 32 is plate-shaped and has a first surface 32a on which the vibration element 60 is disposed and a second surface 32b opposite to the first surface 32a. An insulating film 37 is formed on the surface of the base substrate 32. Furthermore, an integrated circuit 40 electrically connected to the vibration element 60, and wiring 36 electrically connecting functional components such as a temperature sensor circuit 46 and a heater circuit 47 formed on the integrated circuit 40 are formed on the first surface 32a of the base substrate 32. However, the integrated circuit 40 and wiring 36 may also be formed on the second surface 32b instead of the first surface 32a of the base substrate 32.

[0031] A passivation film 35 is formed on the integrated circuit 40, and then an internal connection terminal 49 is formed on the passivation film 35. The internal connection terminal 49 is electrically connected to the wiring 36 for connecting the vibration element 60. Furthermore, an external connection terminal 50 for outputting frequency signals, etc., from the integrated circuit 40 to the outside is formed on an insulating film 37 formed on the second surface 32b of the base substrate 32. Moreover, the base substrate 32 has a through hole 51 penetrating the base substrate 32 in the Z direction, which is the thickness direction. A through electrode 52 is formed by filling the through hole 51 with a conductive material. Therefore, the wiring 36 formed on the first surface 32a of the base substrate 32 can be electrically connected to the external connection terminal 50 formed on the second surface 32b of the base substrate 32 using the through electrode 52.

[0032] The vibration element 60 housed in the internal space 57 includes: a quartz substrate 61; an excitation electrode 62 that causes the quartz substrate 61 to vibrate; a connection terminal 63 that outputs vibration signals to the outside and fixes the vibration element 60 on the first package 31; and a lead electrode (not shown) that electrically connects the excitation electrode 62 and the connection terminal 63.

[0033] The vibrating element 60 is disposed and fixed on the first surface 32a of the first package 31 via conductive components 72 such as metal bumps. Furthermore, when the vibrating element 60 is fixed to the first package 31, the internal connection terminal 49 formed on the base substrate 32 of the first package 31 and the connection terminal 63 formed on the quartz substrate 61 of the vibrating element 60 are mechanically and electrically connected via the conductive components 72. The quartz substrate 61 may be an AT-cut quartz substrate, an SC-cut quartz substrate, a BT-cut quartz substrate, etc.

[0034] Both the cover 33 and the base substrate 32 are silicon substrates. Therefore, the base substrate 32 and the cover 33 have the same coefficient of linear expansion, suppressing the generation of thermal stress caused by thermal expansion, resulting in an oscillator 30 with excellent vibration characteristics. Furthermore, the oscillator 30 can be formed using semiconductor processes, thus enabling high-precision manufacturing and miniaturization of the oscillator 30. However, the cover 33 is not particularly limited, and semiconductor substrates other than silicon, such as germanium, gallium arsenide, gallium phosphide, gallium nitride, and silicon carbide, can also be used. Additionally, substrates other than semiconductor substrates, such as metal substrates like Kovar alloys or glass substrates, can also be used.

[0035] The cover 33 has an opening on the side opposite to the outer surface 55, which is the upper surface of the cover 33, and has a bottomed recess 56 inside for receiving the vibrating element 60. The cover 33 is joined to the first surface 32a of the base substrate 32 via a joining member 34 on its lower surface. Thus, the cover 33 and the base substrate 32 together form an internal space 57 for receiving the vibrating element 60. The joining method of the base substrate 32 and the cover 33 may also be without the joining member 34, but by using a diffusion bonding method or the diffusion bonding of the metals contained in the base substrate 32 or the cover 33.

[0036] Furthermore, the internal space 57 is airtight, in a depressurized state, preferably closer to a vacuum. This reduces viscous resistance and improves the oscillation characteristics of the vibrating element 60. However, the environment of the internal space 57 is not particularly limited; for example, it can be an environment sealed with inert gases such as nitrogen or argon, or it can be in a state other than depressurization, such as atmospheric pressure or pressurization.

[0037] Next, refer to Figure 4 Explain the structure of integrated circuit 40.

[0038] like Figure 4 As shown, the integrated circuit 40 of this embodiment includes an oscillation circuit 41, a frequency multiplier circuit 42, an output circuit 43, a temperature compensation circuit 44, a temperature control circuit 45, a temperature sensor circuit 46, and a heater circuit 47.

[0039] The oscillation circuit 41 is electrically connected to the vibrating element 60, amplifies the output signal of the vibrating element 60, and feeds the amplified signal back to the vibrating element 60, thereby causing the vibrating element 60 to oscillate. The frequency multiplier circuit 42 multiplies the frequency signal output from the oscillation circuit 41. The output circuit 43 outputs the multiplied frequency signal to the outside through the external connection terminal 50.

[0040] The temperature compensation circuit 44 performs temperature compensation based on the temperature information output from the temperature sensor circuit 46, so that the frequency variation of the oscillation signal of the oscillation circuit 41 is less than the frequency-temperature characteristics of the vibrating element 60 itself. This allows for superior temperature characteristics. The temperature compensation circuit 44 can adjust the oscillation frequency of the oscillation circuit 41, for example, by adjusting the capacitance of the variable capacitor circuit connected to the oscillation circuit 41, or by adjusting the frequency of the output signal of the oscillation circuit 41 through a PLL (Phase Locked Loop) circuit or a direct digital synthesizer circuit.

[0041] The temperature control circuit 45 is designed to control the amount of current flowing through the heater circuit 47 based on temperature information output from the temperature sensor circuit 46, thereby maintaining the vibrating element 60 at a constant temperature. For example, the temperature control circuit 45 controls the heater circuit 47 to allow a desired current to flow when the current temperature, as determined by the output signal of the temperature sensor circuit 46, is lower than a set reference temperature, and prevents current from flowing through the heater circuit 47 when the current temperature is higher than the reference temperature.

[0042] Alternatively, for example, the temperature control circuit 45 can also control the flow of current through the heater circuit 47 by increasing or decreasing the current based on the difference between the current temperature and the reference temperature. Here, the temperature sensor circuit 46 serves as both the temperature sensor for the temperature compensation circuit 44 and the temperature sensor for the temperature control circuit 45. Therefore, the number of components can be reduced, and the oscillator 30 can be miniaturized. However, it is not limited to this; the temperature sensor for the temperature compensation circuit 44 and the temperature sensor for the temperature control circuit 45 can also be provided separately.

[0043] The temperature sensor circuit 46 is a temperature-detecting element and can be formed by incorporating a Si diode or a PNP transistor within the integrated circuit 40. Alternatively, by forming platinum, temperature can be detected based on the characteristic that the resistance changes with temperature. Furthermore, the temperature sensor circuit 46 is positioned overlapping the vibrating element 60 when viewed from above in the Z-direction.

[0044] The heater circuit 47 is a heating element formed by incorporating a resistor made of ITO (indium tin oxide) within the integrated circuit 40. It heats up when energized, and the heat output can be adjusted by regulating the current flowing through the resistor. Furthermore, the heater circuit 47 is positioned overlapping the vibrating element 60 when viewed from above in the Z direction.

[0045] As described above, in this embodiment, the vibration device 1 houses the vibration element 60 within a first package 31 with high thermal conductivity, in which a heater circuit 47 is formed. Therefore, through thermal radiation from the entire first package 31 heated by the heater circuit 47, heat from the heater circuit 47 is transferred to the vibration element 60, thus suppressing temperature unevenness within the vibration element 60. Furthermore, a temperature sensor circuit 46 is formed within the first package 31, thereby suppressing the temperature difference between the vibration element 60 and the temperature sensor circuit 46, enabling high-precision temperature control and improving the accuracy of the oscillation frequency output from the vibration device 1.

[0046] Furthermore, conductive components such as metal bumps are used in the electrical connection between the first package 31 and the second package 10, thus enabling miniaturization of the vibrating device 1 compared to the case of using wire bonding.

[0047] 2. Second Implementation Method

[0048] Next, refer to Figure 5 The vibration device 1a of the second embodiment will be described.

[0049] The vibration device 1a of this embodiment differs from the vibration device 1 of the first embodiment in that the position of the first package 31, which is bonded to the first substrate 13 of the second package 10a, is different, and the electrical connection between the external connection terminal 50 and the connection terminal 14a is a conductive lead 72a. Otherwise, it is the same as the vibration device 1 of the first embodiment. In addition, the description will focus on the differences from the first embodiment described above, and the same reference numerals will be used for the same items and their descriptions will be omitted.

[0050] like Figure 5 As shown, in the vibration device 1a, the outer surface 55 of the cover 33 of the first package 31 and the mating surface 11a of the first substrate 13 of the second package 10a are mechanically connected via a mating member 74. That is, compared with the vibration device 1 of the first embodiment, the first package 31 is fixed to the mating surface 11a in an up-down inverted manner. In addition, the external connection terminal 50 formed on the second surface 32b of the first package 31 and the connection terminal 14a formed on the mating surface 11a of the first substrate 13 are electrically connected via a conductive lead 72a.

[0051] By adopting this structure, the base substrate 32 on which the heater circuit 47 is formed can be moved away from the junction of the first package 31 and the second package 10a. Therefore, the first package 31 can be heated effectively. In addition, the influence of external temperature fluctuations on the temperature sensor circuit 46 can be suppressed, and the same effect as the vibration device 1 of the first embodiment can be obtained.

[0052] 3. Third Implementation Method

[0053] Next, refer to Figure 6 The vibration device 1b of the third embodiment will be described.

[0054] Compared to the vibration device 1 of the first embodiment, the vibration device 1b of this embodiment differs in the position of the first package 31, which is joined to the first substrate 13b of the second package 10b; the electrical connection between the external connection terminal 50 and the connection terminal 14b is a conductive lead 72b; and a heat insulation member 80 is provided between the first package 31 and the first substrate 13b of the second package 10b. Otherwise, it is the same as the vibration device 1 of the first embodiment. Furthermore, the description will focus on the differences from the first embodiment described above, and identical items will be marked with the same reference numerals and their descriptions will be omitted.

[0055] like Figure 6As shown, in the vibration device 1b, a heat insulation member 80 is provided between the outer surface 55 of the cover 33 of the first package 31 and the mating surface 11a of the first substrate 13b of the second package 10b. The heat insulation member 80 is fixed to the first substrate 13b via a mating member 75, and the first package 31 is fixed to the heat insulation member 80 via a mating member 76. In addition, the external connection terminal 50 formed on the second surface 32b of the first package 31 and the connection terminal 14b formed on the mating surface 11a of the first substrate 13b are electrically connected by a conductive lead 72b.

[0056] The thermal insulation component 80 is made of a material with a lower thermal conductivity than the second package 10b. There are no particular limitations on such a thermal insulation component 80; for example, various resin materials can be preferably used, particularly porous resin materials such as porous polyimide. Besides resin materials, various glass materials, inorganic porous materials such as silica aerogel, etc., can also be used. Furthermore, the thermal conductivity of the thermal insulation component 80 is not particularly limited, but is preferably 1.0 W / m·K or less. Thus, it becomes a thermal insulation component 80 with sufficiently low thermal conductivity.

[0057] In addition, the insulation component 80 may also contain a gap material with sufficiently low thermal conductivity, such as silicone. This allows for control of the thickness of the insulation component 80, resulting in a more reliable insulation effect.

[0058] By adopting this structure, the heat transfer from the heater circuit 47 formed on the integrated circuit 40 in the first package 31 to the second package 10b can be effectively suppressed, and the same effect as the vibration device 1 in the first embodiment can be obtained.

Claims

1. A vibration device, comprising: a vibration element; a first package that houses the vibration element; and a second package that houses and fixes the first package, the first package including: a base substrate having a first surface on which the vibration element is disposed and a second surface that is in an opposite relationship to the first surface, the base substrate including a single crystal silicon; an integrated circuit provided on the first surface or the second surface, the integrated circuit including a temperature sensor circuit and a heater circuit; a wiring provided on the first surface of the base substrate; an internal connection terminal provided on the integrated circuit and electrically connected to the wiring; an external connection terminal provided on the second surface of the base substrate; a through electrode formed by filling a conductive material in a through hole that penetrates from the first surface to the second surface of the base substrate; and a cap that is joined to the base substrate in a manner that houses the vibration element together with the base substrate, the vibration element being disposed on the integrated circuit and joined to the internal connection terminal, the wiring being electrically connected to the external connection terminal via the through electrode.

2. The vibration device according to claim 1, wherein a thermal conductivity of the first package is higher than a thermal conductivity of the second package.

3. The vibration device according to claim 1, wherein the second package has a connection terminal on a joining surface that is joined to the first package, the external connection terminal being mechanically and electrically joined to the connection terminal via a conductive member.

4. The vibration device according to claim 1, wherein the second package has a connection terminal on a joining surface that is joined to the first package, the external connection terminal being electrically connected to the connection terminal via a conductive lead, an outer surface of the cap being mechanically connected to the joining surface of the second package via a joining member.

5. The vibration device according to claim 1, wherein the first package is fixed to the second package with a heat insulating member interposed therebetween. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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