Crystal oscillator and crystal device

Abstract

To provide a compact quartz oscillator and quartz device that can easily operate stably even at higher temperatures than conventional devices. [Solution] The quartz oscillator (10) comprises a vibrating part and a capacitor (15) electrically connected to the vibrating part. The vibrating part has a quartz crystal (11) and two excitation electrodes (12) positioned on either side of the quartz crystal (11). The capacitor (15) has a dielectric material with a Curie point of 80°C to 140°C and electrodes located on the dielectric material.

Description

Technical Field

[0001] The present disclosure relates to a crystal oscillator and a crystal device.

Background Art

[0002] The resonance frequency of a crystal oscillator changes due to the temperature dependence of the crystal. Conventionally, crystals with a small change in resonance frequency near room temperature, such as AT cut, have been widely used. Patent Document 1 discloses a technique related to a crystal device having a temperature compensation circuit, and by the operation of the temperature compensation circuit, a resonance frequency more stable with respect to temperature change can be obtained even on the higher temperature side than before. The temperature compensation circuit is not limited to an analog circuit and may have an IC or the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a crystal device with an added IC circuit, the size and cost increase accordingly. On the other hand, in a conventional crystal device, the stable range of the crystal oscillator on the higher temperature side is narrow and the stability is insufficient. Therefore, a crystal oscillator and a crystal device that are small and can operate stably at a temperature higher than before are provided.

Means for Solving the Problems

[0005] One aspect of the present disclosure is as follows. [1] A vibrating part having a crystal piece and two exciting electrodes positioned sandwiching the crystal piece, A capacitor having a dielectric with a Curie point of 80°C or higher and 140°C or lower and an electrode positioned on the dielectric, and being electrically connected to the vibrating part, A quartz crystal oscillator equipped with the following features. [2] The dielectric is a quartz crystal oscillator as in [1], wherein the maximum second relative permittivity at 80°C to 140°C is 2 to 50 times the minimum first relative permittivity at 60°C to 75°C. [3] A quartz crystal oscillator according to [1] or [2], wherein the deviation of the resonant frequency from a reference frequency, which is the resonant frequency at the temperature at which the smallest first relative permittivity is obtained between 60°C and 75°C, is within ±10 ppm in the range of -40°C to 140°C. [4] The dielectric comprises BaTiO3, and is a quartz oscillator according to any of [1] to [3]. A quartz oscillator from any of [5][1] to [4], A package housing the aforementioned quartz crystal oscillator, A crystal device equipped with a crystal. [6] A quartz oscillator comprising a quartz crystal, A package housing the aforementioned quartz crystal oscillator, Equipped with, The package has a dielectric having a Curie point of 80°C or more and 140°C or less, and electrodes located on the dielectric, and a capacitor electrically connected to the quartz crystal. Crystal device. [Effects of the Invention]

[0006] According to this disclosure, a compact quartz oscillator that can be easily obtained and operates stably even at higher temperatures than conventional ones can be obtained. [Brief explanation of the drawing]

[0007] [Figure 1] This is an overall perspective view showing a quartz device having a quartz oscillator element in one embodiment. [Figure 2] This is a magnified view of the area around the capacitor of a quartz crystal oscillator. [Figure 3] This is a diagram illustrating the circuit of a quartz crystal oscillator. [Figure 4] This figure shows the trend of the rate of shift in the resonant frequency with respect to temperature. [Figure 5]This is an exploded perspective view showing a quartz device in one embodiment. [Figure 6] This is a diagram showing the bottom side of the base. [Figure 7] This is a diagram showing one embodiment of the structure of a capacitor. [Modes for carrying out the invention]

[0008] The embodiments will be described below with reference to the drawings. Figure 1 is an overall perspective view showing a quartz device 1 having a quartz oscillator element 10 according to one embodiment. Note that the interior is shown with the cover 30 removed.

[0009] The crystal device 1 comprises a crystal oscillator 10 and a package 20. The crystal device 1 may include a cover 30, or the cover 30 may be a separate component from the crystal device 1.

[0010] Package 20 comprises a housing 21, a connection pad 22, and an external connection pad 23. The housing 21 has a recess 201 on one side, in this case on the +Z side. The housing 21 may be made of an insulating material such as ceramic material or glass material, or a semiconductor material, or a combination thereof.

[0011] Two connection pads 22 are located side by side on the bottom surface of the recess 201. The two connection pads 22 may also be arranged in the Y direction near the +X side end of the recess 201. The external connection pads 23 are located on the -Z side surface of the housing 21, opposite to the aforementioned side surface. The connection pads 22 are electrically connected to the external connection pads 23 by wiring extending inside and on the surface of the housing 21. The external connection pads 23 may be located at the four or three corners on the -Z side surface of the housing 21. The connection pads 22 and external connection pads 23 may be conductive thin films, or multiple thin films may be laminated together. For example, the connection pads 22 and external connection pads 23 may be made of molybdenum, copper, silver, tungsten, etc., and their surfaces may be covered with a nickel plating or gold plating layer.

[0012] The crystal oscillator 10 is housed in the recess 201. The crystal oscillator 10 includes a crystal piece 11, excitation electrodes 12, lead-out wires 13, and connection electrodes 14, and may further include a capacitor 15.

[0013] The crystal piece 11 is, for example, a thin plate of AT-cut crystal. The thickness of the crystal piece 11 in the +Z direction is determined according to the resonance frequency. The resonance frequency may be 50 MHz or higher. For example, when the resonance frequency is 76.8 MHz, the thickness is about 22 μm. Also, the thickness of the crystal piece 11 may be different between the vibration part 101 near the center where vibration occurs and at least a part of the peripheral part that is fixed and supported. The crystal piece 11 may have a mesa shape in which the thickness of the vibration part 101 is larger than the thickness of the peripheral part, or an inverse mesa shape in which the thickness of the vibration part 101 is smaller than the thickness of the peripheral part. The size of the crystal piece 11 viewed from the +Z direction in plan view is smaller than the size of the recess 201 in plan view. The crystal piece 11 may be rectangular in plan view. Here, the X-axis is defined along the longitudinal direction of the crystal piece 11 in plan view.

[0014] The thin plate-shaped crystal piece 11 has excitation electrodes 12, lead-out wires 13, and connection electrodes 14. The excitation electrodes 12 are respectively located on both the ±Z sides of the vibration part 101. The connection electrodes 14 are respectively located on both the ±Z sides of the support part. The lead-out wires 13 connect the excitation electrodes 12 and the connection electrodes 14 on each surface of the crystal piece 11. The shape of the excitation electrodes 12 is not particularly limited, and may be, for example, circular or elliptical. The excitation electrodes 12 on both sides may be located overlapping in plan view, and may have the same shape and be in the same position in plan view. The support part where the connection electrodes 14 are located may be located at the +X side end of the crystal piece 11.

[0015] At least one of the connection electrodes 14, for example, the connection electrode 14 located on the +Z side, is connected to the capacitor 15. The electrical signal path including the excitation electrode 12, the lead wire 13, the connection electrode 14, and the capacitor 15 located on the +Z side wraps around to the -Z side and is connected and fixed to the connection pad 22 via the conductive joining member 40. The conductive joining member 40 may be a conductive adhesive. The conductive joining member 40 solidifies after joining to support the crystal piece 11. The crystal piece 11 is supported by the conductive joining member 40 near the +X side end and is in a cantilever state separated from the housing 21 on the -X side.

[0016] Figure 2 is an enlarged view near the capacitor 15. The capacitor 15 has a structure in which a dielectric 153 is sandwiched between two electrodes 151 and 152. The electrodes 151 and 152 may be comb-shaped electrodes in which a plurality of teeth face each other and extend alternately in a predetermined direction, for example, the Y direction. The dielectric 153 filling the space between the teeth may be, for example, BaTiO3. Note that the number, interval, length, and ratio of the teeth in FIG. 2 do not reflect the actual values. When there are a plurality of capacitors 15, the plurality of capacitors may be arranged in parallel. The electrode 151 may be connected to the connection electrode 141 on the +Z side surface, and the electrode 152 may be connected to the connection electrode 142 extending across the +Z side surface and the -Z side surface. As described above, the connection electrode 141 may be connected to the lead wire 13, and the connection electrode 142 may be joined to the conductive joining member 40.

[0017] The lid 30 is joined to the upper end of the side wall surrounding the recess 201 of the package 20, thereby sealing the inside of the recess 201. The lid 30 may be a conductor, for example, a metal containing iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy thereof, such as Kovar. The lid 30 may be a flat plate, or it may have rounded corners or its edges may be thinner than its center. The lid 30 may be joined to the package 20 by a conductive joining member, for example, a brazing material. Alternatively, the lid 30 may be joined to the package 20 by solder. Alternatively, the conductive joining member may be a conductive adhesive containing silver particles in a resin, i.e., silver paste. The joining member may also be molten glass material or the like. The inside of the recess 201 to be sealed may be a near-vacuum or under reduced pressure. Alternatively, the inside of the recess 201 may be filled with an inert gas or nitrogen, or it may be ordinary air.

[0018] Next, the temperature characteristics of the quartz oscillator 10 will be explained. As described above, the resonant frequency of the AT-cut quartz piece 11 changes with temperature according to a cubic function. The cubic function has a point of symmetry at approximately 25°C, and the difference between the maximum value on the low-temperature side and the minimum value on the high-temperature side tends to increase as the cut angle deviates from the AT cut. By cutting the quartz crystal within an appropriate range, the deviation rate Δf / f0, which is the ratio of the amount of deviation Δf of the resonant frequency to the reference frequency f0, falls within an acceptable range in the normal operating temperature range of -30°C to 85°C. The acceptable range is, for example, in the range of ±10 to 30 ppm, and can be changed depending on the application.

[0019] However, at temperatures higher or lower than this temperature range, the resonant frequency changes rapidly according to the cube of the temperature, making it impossible to obtain an appropriate resonant frequency. In one embodiment, as shown in Figure 3, the temperature characteristics of the quartz oscillator 10 are adjusted by electrically connecting a capacitor 15 in series with the vibrating part 101 having an excitation electrode 12 and a quartz crystal piece 11. The dielectric 153 used in the capacitor 15 has a Curie point near the upper limit of the above temperature range, and the capacitance of the capacitor 15 changes significantly as the relative permittivity increases near the Curie point. That is, such a dielectric 153 may be a ferroelectric material such as BaTiO3, which loses its ferromagnetism at temperatures above the Curie point. As the capacitance of the capacitor 15 increases, the increase in the resonant frequency of the vibrating part 101 in the high-temperature range is reduced.

[0020] Figure 4 shows the trend of the resonant frequency shift rate Δf / f0 with respect to temperature. The thin solid line L1 shows the temperature dependence of the resonant frequency in a conventional AT-cut quartz oscillator. As shown above, a cubic function trend is observed, with a maximum value slightly below 0°C and a minimum value slightly above 60°C, using 25°C as the reference.

[0021] To reduce the absolute value of the deviation rate Δf / f0 at high temperatures, the cubic function can be rotated with respect to 25°C, as shown by the dashed line L2. However, this results in a decrease in accuracy outside the high-temperature range, as the deviation rate Δf / f0 near the maximum and minimum values ​​becomes larger than that shown by the thin solid line L1.

[0022] The thick solid line L3 shows the trend of the slip rate Δf / f0 when the capacitors 15 are connected in series. Up to the minimum value of the thin solid line L1, approximately 70°C, a similar trend to that of the thin solid line L1 is obtained, but the thick solid line L3 does not show a significant increase in the slip rate Δf / f0 even above 70°C. The Curie point of BaTiO3, which is the dielectric 153 of the capacitor 15 in one embodiment, is approximately 125°C. Therefore, as the capacitance of the capacitor 15 increases with increasing temperature up to approximately 125°C, the increase in the slip rate Δf / f0 is also reduced up to that temperature. When the temperature rises further than the Curie point of the dielectric 153, the relative permittivity decreases according to the Curie-Weiss law, the resonant frequency of the vibrating part 101 increases, and the slip rate Δf / f0 increases significantly.

[0023] The dielectric 153 needs to have an appropriate increase in relative permittivity near the Curie point. For example, the dielectric 153 may be at least twice as large as the first relative permittivity, which is the minimum value of the relative permittivity, with the second relative permittivity being the maximum relative permittivity between 80°C and 140°C as the reference relative permittivity. The first relative permittivity may be determined, for example, by the minimum value of the relative permittivity in the range of 60°C to 75°C, which includes the above minimum value. On the other hand, if the relative permittivity becomes too large, the slip rate Δf / f0 will become excessively negative. Therefore, the second relative permittivity may be limited to 50 times or less the first relative permittivity. Also, if the Curie point is too high above 85°C, the increase in capacitance of the capacitor 15 will be insufficient even above 85°C, and the increase in the slip rate Δf / f0 will not be appropriately reduced. Therefore, the Curie point of the dielectric 153 may be, for example, around 80°C to 140°C.

[0024] The quartz oscillator 10, which has a capacitor 15 containing the dielectric 153, maintains a stable resonant frequency even in the normal temperature range of -30°C to 85°C, and especially in the range of -40°C and above, as shown by the thick solid line L3 above. On the other hand, even when the temperature exceeds 85°C, the quartz oscillator 10 maintains a deviation rate Δf / f0 within an acceptable range, particularly within ±10 ppm, up to 125°C. The capacitance of the capacitor 15 may be appropriately determined so that the maximum absolute value of the deviation rate Δf / f0 is within an acceptable range in the desired temperature range, and the deviation rate Δf / f0 is small on average.

[0025] Figure 5 is an exploded perspective view showing a crystal device 1a in one embodiment. The crystal device 1a comprises a crystal oscillator 10a, a base 20a, a wall 50a, and a cover 30a. The base 20a, wall 50a, and cover 30a are stacked sequentially in the Z direction.

[0026] The base body 20a has a recess 201a on its upper surface. The recess 201a may be narrower in the X direction and wider in the Y direction than the planar size of the crystal oscillator 10a. The base body 20a may have wirings 241, 242 and through via conductors 251, 252. The wirings 241, 242 are located on the upper surface of the base body 20a. The wirings 241, 242 are connected to each of the two connecting electrodes 141 in the crystal oscillator 10a. One end of the through via conductor 251 is connected to the wiring 241. One end of the through via conductor 252 is connected to the wiring 242. The wirings 241, 242 and the through via conductors 251, 252 are conductors and may be, for example, molybdenum, copper, silver, tungsten, etc. Furthermore, their surfaces may be covered with a layer of nickel plating or gold plating.

[0027] The wall 50a may have the same shape and size as the base 20a in a plan view. The wall 50a has a through hole 501. A quartz crystal oscillator 10a is housed in the through hole 501. The thickness of the wall 50a is greater than or equal to the thickness of the quartz crystal oscillator 10a. In a plan view, the through hole 501 is larger than the quartz crystal oscillator 10a and does not come into contact with the quartz crystal oscillator 10a. The base 20a and the wall 50a may be made of insulating materials such as ceramic materials or glass materials, or semiconductor materials, or a combination thereof. The base 20a and the wall 50a may have an integrated structure.

[0028] The lid 30a is joined to the upper surface of the wall 50a along at least the peripheral edge, sealing the through hole 501 and the recess 201a. The lid 30a may have a recess on its lower side in the area that overlaps with the through hole 501 in a plan view. The interior of the recess communicates with the interior of the through hole 501 and the recess 201a. The lid 30a may be a conductor, for example, a metal containing iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy thereof, such as Kovar. A conductive joining member, such as brazing material, may be used to join the lid 30a to the wall 50a. Alternatively, the lid 30 may be joined to the package 20 by solder. Alternatively, the conductive joining member may be a conductive adhesive containing silver particles in a resin, i.e., silver paste. The joining member may also be molten glass material or the like.

[0029] The crystal oscillator 10a may have the same configuration as the crystal oscillator 10, except that it does not have a capacitor 15.

[0030] Figure 6 shows the bottom side of the base 20a. As shown in Figure 6(a), external connection pads 23 are located at the four corners of the bottom surface of the base body 20a, which is located on the -Z side. The external connection pads 23 are conductors and may be made of, for example, molybdenum, copper, silver, tungsten, etc. The external connection pads 23 may be formed by screen printing. Of these, a through via conductor 251 is connected to external connection pad 231, and a through via conductor 252 is connected to external connection pad 232. External connection pad 233 is connected to the ground surface. External connection pad 232 is connected to a signal line to which an AC voltage is applied. External connection pad 234 may be in a floating state and not connected to any other conductor.

[0031] A capacitor 26 may be located between the external connection pads 231 and 233. That is, as shown in Figure 6(b), the capacitor 26 is located in series with the vibrating part 101a. The capacitor 26 has the same characteristics and functions as the capacitor 15 described above. That is, the dielectric of the capacitor 26 has a Curie point around 80°C to 140°C, and the relative permittivity takes a maximum value near this Curie point. The maximum value of the relative permittivity may be more than twice and less than 50 times the relative permittivity at the frequency where the resonant frequency of the vibrating part 101a takes a minimum value.

[0032] Figure 7 shows one embodiment of the structure of the capacitor 26. For example, the capacitor 26 may have comb-shaped electrodes 261 and 262 and a dielectric 263. Comb-shaped electrode 261 is connected to an external connection pad 231, and comb-shaped electrode 262 is connected to an external connection pad 233. Comb-shaped electrode 261 has multiple comb-shaped electrodes extending parallel to the -Y direction, and comb-shaped electrode 262 has multiple comb-shaped electrodes extending parallel to the +Y direction. The comb-shaped electrodes of comb-shaped electrode 261 and comb-shaped electrode 262 are arranged alternately, one by one, in the X direction. The gaps between the comb-shaped electrodes may be filled with dielectric 263. This increases the opposing area between the comb-shaped electrodes 261 and 262, and increases the relative permittivity of the capacitor 26 relative to its size. Note that the number, length, thickness, and spacing of the comb teeth in this figure do not reflect the actual number or ratio. The capacitance of capacitor 26 may be appropriately determined such that the maximum absolute value of the deviation rate Δf / f0 is within the acceptable range within the desired temperature range, and the deviation rate Δf / f0 is small on average.

[0033] As described above, the quartz oscillator 10 comprises a vibrating section 101 having a quartz crystal 11 and two excitation electrodes 12 positioned on either side of the quartz crystal 11, and a capacitor 15. The capacitor 15 has a dielectric 153 with a Curie point of 80°C to 140°C, and electrodes 151 and 152 positioned above the dielectric 153, and is electrically connected to the vibrating section 101. By connecting the capacitor 15 to the vibrating section 101, the relative permittivity of the capacitor 15 increases at temperatures higher than room temperature, between 80°C and 140°C, thereby reducing the increase in the resonant frequency of the quartz oscillator 10. Therefore, this quartz oscillator 10 is small, easy to use, and operates stably even at higher temperatures than conventional oscillators. In other words, a quartz oscillator 10 that can easily and inexpensively operate stably in environments with high heat generation or large temperature fluctuations, such as outdoors, inside automobiles, or in factories, can be obtained without using ICs or the like.

[0034] Furthermore, the dielectric material may have a maximum second relative permittivity between 80°C and 140°C that is 2 to 50 times the minimum first relative permittivity between 60°C and 75°C. By having the second relative permittivity within an appropriate range, both the increase and decrease in the resonant frequency at high temperatures can be reduced to a suitable range, thereby reducing the range of fluctuation in the resonant frequency.

[0035] Furthermore, the quartz oscillator 10 may have a deviation rate of ±10 ppm from the resonant frequency at the temperature where it takes the minimum first relative permittivity between 60°C and 75°C, within the range of -40°C to 140°C. Due to its high frequency accuracy, the quartz oscillator 10 can be used in a wide range of fields, including commercial applications.

[0036] Furthermore, the dielectric 153 may contain BaTiO3. Since BaTiO3 has a suitable Curie point for the quartz oscillator 10, it becomes possible to easily and stably use the conventional quartz oscillator 10 even in a higher temperature range.

[0037] The crystal device 1 of this embodiment may include the crystal oscillator 10 described above and a package 20 housing the crystal oscillator 10. With this crystal device 1, a more stable frequency signal can be easily obtained over a wide temperature range.

[0038] Alternatively, the crystal device 1a of this embodiment may include a crystal oscillator 10a comprising a crystal quartz piece 11, and a base body 20a and a wall body 50a as a package for housing the crystal oscillator 10a. The base body 20a may have a capacitor 26. The capacitor 26 may have a dielectric 263 having a Curie point of 80°C to 140°C, and comb-shaped electrodes 261 and 262 positioned above the dielectric 263. Thus, the capacitor 26 electrically connected to the vibrating portion 101a may be located in the base body 20a. By positioning the capacitor 26 outside the crystal quartz piece 11, adverse effects on the vibration of the crystal quartz piece 11 are reduced. Furthermore, the base body 20a provides more space for the capacitor 26 compared to the portion of the crystal oscillator 10a outside the vibrating portion 101a, making it easier to mount the capacitor 26 without changing the size.

[0039] The above embodiments are illustrative examples, and various modifications are possible. For example, although the above explanation used a one-handed crystal oscillator 10 as an example, the crystal oscillator may have other structures.

[0040] Furthermore, while the above states that frequency accuracy can be maintained up to 140°C, any upper limit other than 140°C is acceptable as long as the upper limit of the range in which accuracy can be maintained can be raised above 85°C. Also, depending on the application, the permissible range of frequency to be maintained may be more lenient than the above, such as ±20ppm to ±30ppm.

[0041] Furthermore, the structure of capacitors 15 and 26 may be arbitrary. Capacitors 15 and 26 may have a three-dimensional structure on the crystal oscillator 10 or on the base 20a. The electrodes on the dielectric 263 do not have to be comb-shaped. Two electrodes may be positioned on opposite sides of the dielectric 263, sandwiching the dielectric 263.

[0042] Furthermore, although BaTiO3 was used as an example of a dielectric material in the above explanation, it is not limited to this. Other suitable ferroelectric materials with Curie points may also be used.

[0043] Furthermore, the package 20, the base 20a, and the wall 50a may accommodate components other than the quartz crystal oscillator. The recesses and through holes that accommodate these components may be common to the quartz crystal oscillator and other components, or they may be different.

[0044] Furthermore, the specific details such as structure, configuration, materials, and size shown in the above embodiments may be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention as described in the claims and its equivalents. [Explanation of Symbols]

[0045] 1, 1a Crystal device 10, 10a Quartz crystal oscillator 101, 101a Vibration part 11 crystal piece 12 Excitation electrode 13 Leader wires 14, 141, 142 connecting electrodes 15 Capacitors 151,152 electrodes 153 Dielectrics 20 packages 20a bottom body 201, 201a Recess 21 cabinets 22 connection pads 23, 231~234 External connection pads 241, 242 Wiring 251, 252 Through via conductors 26 Capacitors 261, 262 comb-shaped electrode 263 Dielectrics 30, 30a lid body 40 Conductive bonding member 50a Wall 501 Through hole

Claims

1. A vibrating section having a quartz crystal and two excitation electrodes positioned on either side of the quartz crystal, A capacitor having a dielectric with a Curie point of 80°C or more and 140°C or less, and an electrode located on the dielectric, and electrically connected to the vibrating part, A quartz crystal oscillator equipped with the following features.

2. The quartz oscillator according to claim 1, wherein the dielectric has a maximum second relative permittivity at 80°C to 140°C that is 2 to 50 times greater than the minimum first relative permittivity at 60°C to 75°C.

3. The quartz oscillator according to claim 1, wherein the deviation of the resonant frequency from a reference frequency, which is the resonant frequency at the temperature at which the minimum first relative permittivity is obtained between 60°C and 75°C, is within ±10 ppm in the range of -40°C to 140°C.

4. The dielectric material is BaTiO ３ The quartz oscillator according to claim 1, which includes the following:

5. A quartz oscillator according to any one of claims 1 to 4, A package housing the aforementioned quartz crystal oscillator, A crystal device equipped with a crystal.

6. A quartz oscillator comprising a quartz crystal and two excitation electrodes positioned on either side of the quartz crystal, A package housing the aforementioned quartz crystal oscillator, Equipped with, The package has a dielectric having a Curie point of 80°C or more and 140°C or less, and electrodes located on the dielectric, and a capacitor electrically connected to the quartz crystal. Crystal device.

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