JP2022122459A - crystal oscillator - Google Patents

Abstract

To provide a thermostat-type crystal oscillator having a double-container structure, in which heating means (heater) is provided outside a first container, and which has a structure suitable for temperature control.SOLUTION: A crystal oscillator 10 includes a metal first container 13 containing a crystal vibrator 11 sealed in a container, an oscillator circuit 15 for a crystal vibrator, heating means 17 for the crystal vibrator, a temperature control circuit 19 for the heating means, and a metal second containers 21 containing the first container. The heating means is provided in contact with the bottom surface of the outer surface of the first container, the inside of the first container is a helium atmosphere, and the inside of the second container is a reduced-pressure atmosphere.SELECTED DRAWING: Figure 1

Description

The present invention relates to an oven-controlled crystal oscillator (OCXO: Oven Controlled Xtal Oscillation) having a double container structure using two metal containers.

In thermostatic chamber type crystal oscillators, which require high precision, high airtightness is required for the container containing the crystal oscillator, the oscillation circuit, and the temperature control means. Therefore, a metal container is used as the container.
Further, in order to achieve even higher precision, a constant temperature bath type crystal oscillator (hereinafter sometimes abbreviated as a crystal oscillator) having a double container structure using two metal containers is disclosed in, for example, Patent Document 1. This crystal oscillator includes a metal first container containing a crystal oscillator and a heater, and a metal second container containing the first container.

In this crystal oscillator, a two-turn crystal oscillator such as an SC-cut or M-SC-cut crystal oscillator is used as the crystal oscillator (paragraphs 44 and 60 of Patent Document 1). Also, a plurality of power transistors are used as heaters. Further, the inside of the first container is an inert gas such as nitrogen, or atmospheric pressure or vacuum (same, paragraph 54), and the inside of the second container is an atmosphere lower than atmospheric pressure (same as , paragraph 52).
According to this conventional crystal oscillator, since it has the double structure as described above, it is said that temperature control by the heater can be stably performed (paragraph 52 of the same).

JP 2016-225738 A

However, in a constant temperature oven type crystal oscillator having a double-container structure, when the heater is mounted in the first container as disclosed in Patent Document 1, If there is some problem with a part, there is a high possibility that all of these parts will be wasted.

Furthermore, in the case of the structure disclosed in Patent Document 1, the crystal oscillator and the heater are arranged on the first substrate provided in the first container, and the heater is arranged at a position away from the crystal oscillator. (Fig. 4 of Patent Document 1). Therefore, the heat of the heater is transmitted to the crystal oscillator through the first substrate and through the atmosphere inside the first container. That is, the heat of the heater is transmitted to the crystal oscillator by heat conduction in the first substrate made of an epoxy substrate or the like. Furthermore, when the inside of the first container is filled with nitrogen, the heat of the heater is transmitted to the crystal oscillator under the control of the thermal conductivity of nitrogen (approximately 0.026 W/mK), and the inside of the first container becomes In the case of an air atmosphere, the heat of the heater is transmitted to the crystal oscillator under the control of the thermal conductivity of the air (approximately 0.027 W/mK). It is transmitted to the crystal oscillator by extremely poor thermal conductivity. That is, in the case of the crystal oscillator of Patent Document 1, the first container has a structure that relatively suppresses heat conduction and ensures thermal stability.

Considering the above-mentioned situation in conventional crystal oscillators, it is proposed in this application that there is another preferable structure for temperature control in a constant temperature oven type crystal oscillator having a double container structure. The inventor concerned thought.
This application has been made in view of the above points, and an object of the present invention is to provide a thermostatic chamber type crystal oscillator having a double-container structure in which a heating means (heater) is provided outside the first container. It is an object of the present invention to provide a crystal oscillator of a novel structure having a structure which is provided and which is considered preferable for temperature control.

In order to achieve this object, according to the crystal oscillator of the present invention, there is provided a crystal oscillator sealed in a container, a metal first container containing the crystal oscillator, and an oscillator for the crystal oscillator. A crystal oscillator comprising a circuit, heating means for heating the crystal oscillator, a temperature control circuit for the heating means, and two metal containers containing the first container,
The heating means is provided in contact with an appropriate portion of the outer surface of the first container,
The inside of the first container is a helium atmosphere,
The inside of the second container is characterized by having a reduced pressure atmosphere.

In carrying out the present invention, the second container includes a base having a hermetic structure made of metal and glass, a mounting substrate mounting the first container on a first surface, the first container and Metal leads for floating the mounting board in the second container, the metal leads for connecting the inside and the outside of the crystal oscillator, and a concave portion containing the first container and the mounting board. and a metal lid member joined to the base.
Further, in carrying out the present invention, when the second container has the mounting substrate, the first surface and the second surface opposite to the first surface are provided on the mounting substrate. It is further preferred to have a window connecting the faces.

In carrying out the present invention, the first container includes a base having a hermetic structure made of metal and glass, a metal lead provided on the base for connecting the inside and the outside of the first container, and the crystal. a metal lid member having a recess for accommodating a vibrator and joined to the base;
It is preferable that the heating means is provided in a region of the outer bottom surface of the base facing the crystal oscillator with the base interposed therebetween.
The first container preferably has a mounting board for mounting the crystal oscillator therein, and the crystal oscillator can be mounted on the surface of the mounting board on the base side. preferable. By arranging the crystal oscillator in this way, when the heating means is provided on the outer bottom surface of the base of the first container, the heating means and the crystal oscillator face each other only through the base, so that the heat conduction is enhanced. Because it is easy.

In carrying out the present invention, the reduced pressure atmosphere in the second container is, for example, preferably 10 Pa or less, more preferably 1 Pa or less, and more preferably 0.5 Pa or less.

In the thermostatted crystal oscillator having the double-container structure of the present invention, the atmosphere in the first container is helium. Since the thermal conductivity of helium is approximately 0.144 W/mK, nitrogen (approximately 0.026 W/mK), which is the atmosphere of the first container of Patent Document 1, or air (thermal conductivity of air: approximately 0.027 W/mK) or reduced pressure (vacuum thermal conductivity is substantially 0), about five times higher. Therefore, even if the heating means is provided in contact with the outer surface of the first container, the heat of the heating means is easily transmitted to the inside of the first container. A predetermined temperature controlled by a heating means and a temperature control circuit can be obtained. Moreover, in the case of thermostatic oven type crystal oscillators having a double-container structure, in most cases, the oscillation circuit is mounted in the first container. Therefore, if the heating means is provided in contact with the outer surface of the first container, the oscillation circuit also receives heat from the outer wall of the same container and the same atmosphere as the crystal resonator. The temperature characteristics of the oscillator circuit can be minimized because the temperature is stable as well.
On the other hand, since the atmosphere in the second container enclosing the first container is a reduced-pressure atmosphere, the second container blocks the influence of the lower atmosphere on the first container.
From these, it is possible to provide a crystal oscillator having a novel structure in which a heating means (heater) is provided outside the first container and which has a structure that is considered preferable for temperature control.

FIGS. 1A to 1C are diagrams for explaining, in particular, the structure inside the second container of the constant temperature oven type crystal oscillator 10 having the double container structure of the embodiment. FIGS. 2A to 2C are diagrams for explaining, in particular, the structure inside the first container of the constant temperature oven type crystal oscillator 10 having the double container structure of the embodiment.

Embodiments of the crystal oscillator of the present invention will be described below with reference to the drawings. It should be noted that each drawing used for explanation is only schematically shown to the extent that the present invention can be understood. In addition, in each drawing used for explanation, the same component may be denoted by the same number, and the explanation thereof may be omitted. Also, the shapes, materials, etc. described in the following description are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited only to the following embodiments.

1A is a top view of the crystal oscillator 10 of the embodiment, FIG. 1B is a side view of the crystal oscillator 10 of the embodiment, and FIG. 1C is a bottom view of the crystal oscillator 10 of the embodiment. be.
2A is a top view for explaining the first container 13 of the crystal oscillator 10 of the embodiment and its internal structure, FIG. 2B is a side view of the same, and FIG. 2C is a bottom view of the same. is.
1(A), (B), FIGS. 2(A), and 2(B) show the top view and the side view in a see-through state.
The crystal oscillator of the embodiment comprises a crystal resonator 11, a first container 13, an oscillation circuit 15, a heating means 17, a temperature control circuit 19, a second container 21, a mounting substrate 23, and a window portion 25. . A feature of the present invention is that the heating means 17 is provided in contact with the outer surface of the first container 13, the inside of the first container 13 is made into a helium atmosphere, and the inside of the second container 21 is filled with a helium atmosphere. The reason is that the atmosphere is a reduced pressure. A specific configuration example of each component will be described below.

The crystal oscillator 11 is sealed in a container. Specifically, the crystal vibrator 11 can be configured by sealing a crystal vibrating piece in a metal container, or by sealing a crystal vibrating piece in a ceramic container. is sealed in a metal container, so-called lead type. Since the lead type has higher hermetic reliability, it is suitable for a crystal oscillator (OCXO) that requires high accuracy. As the crystal vibrating piece, a well-known two-rotation crystal vibrating piece is used.

The first container 13 comprises a base 13a, metal leads 13b and a metal lid member 13c. The base 13a has a hermetic structure made of metal and glass. The metal lead 13b is provided on the base 13a and connects the inside and the outside of the first container 13. As shown in FIG. The metal lid member 13c has a recess 13ca for accommodating the crystal oscillator 11, and has an edge joined to the base 13a. Specifically, it is preferable to use the following.
The base 13a should have a square planar shape and be made of, for example, iron or nickel silver, and the part into which the metal lead 13b is inserted should be a glass part suitable for hermetic use. is preferred. It is preferable to use Kovar leads for the metal leads 13b. The lid member 13c has a rectangular planar shape, and is preferably made of stainless steel, nickel silver, or brass. The base 13a and the lid member 13c are joined by a suitable sealing method according to the constituent materials of the base and the lid member, such as a resistance welding sealing method or a solder sealing method, to realize an airtight structure.

The oscillation circuit 15 is not particularly limited as long as it has a configuration that can stably oscillate the crystal resonator 11, and any suitable circuit may be used. Although the oscillation circuit 15 is provided inside the first container 13 in this embodiment, it may be provided outside the first container 13 depending on the design.
The heating means 17 can consist of any suitable material. For example, it can be configured by a power transistor. By using the heat generated when the power transistor is operated, the desired heating can be achieved, and the heat generation temperature can be varied by controlling the energized current during operation. This heating means 17 is provided in contact with the outer surface of the first container 13. In this embodiment, the outer bottom surface of the first container 13, that is, the outer bottom surface of the base 13a, the first container 13 It is provided in a region facing the crystal oscillator 11 provided inside. With this configuration, the crystal oscillator 11 and the heating means 17 face each other, so that the heat of the heating means 17 is easily transmitted to the crystal oscillator 11 .
The temperature control circuit 19 includes a temperature sensor, and any suitable circuit may be used as long as it can appropriately control the temperature of the crystal oscillator 11 .

Moreover, in the case of this embodiment, as shown in FIG. 2B in particular, a mounting board 23 having a rectangular planar shape is provided in the first container 13 . The mounting substrate 23 is provided in a floating state within the first container 13 by means of the metal leads 13b. This mounting board 23 can be configured by any suitable printed wiring board. A crystal resonator 11 is provided on the surface of the mounting substrate 23 on the side of the base 13a, and an oscillation circuit 15 and a temperature control circuit 19 are provided on the opposite surface. Although the description is omitted, the mounting board and the electronic parts such as the crystal oscillator and the parts for the oscillation circuit are connected by soldering or the like.

On the other hand, the second container 21 comprises a base 21a, a mounting substrate 21b, metal leads 21c and a metal lid member 21d. The base 21a has a hermetic structure made of metal and glass. The mounting substrate 21b has a rectangular planar shape, and the first container 13 is mounted on the first surface 21ba thereof. The metal lead 21c is for floating the first container 13 and the mounting board 23 in the first container 13 in the second container 21, and connects the inside and the outside of the crystal oscillator. It is for The metal lid member 21d has a recess 21da that encloses the first container 13 and the mounting substrate 21b, and has an edge joined to the base 21a. Specifically, it is preferable to use the following.

The base 21a has a quadrangular planar shape and is made of, for example, iron or nickel silver, and the portion into which the metal lead 21c is inserted is a glass portion suitable for hermetic use. It is preferable to use
Any suitable printed wiring board is preferably used for the mounting board 21b. A first container 13 is mounted on the first surface of the mounting substrate 21b.
In this embodiment, the mounting substrate 21b has a window portion 25 connecting the first surface 21ba and the second surface 21bb in the area around the area where the first container 13 is mounted. The window part 25 promotes heat transfer between the front and back surfaces of the mounting substrate 21b, so that the temperature controllability of the crystal oscillator 10 can be enhanced. In this embodiment, the windows 25 having a substantially dogleg shape in plan view are provided at four locations around the area of the mounting substrate 21b where the first container 13 is mounted. The shape and opening area can be arbitrarily suitable depending on the design.
It is preferable to use Kovar leads for the metal leads 21c. The lid member 21d has a rectangular planar shape, and is preferably made of stainless steel, nickel silver, or brass.
The base 21a and the lid member 21d are joined by a suitable sealing method according to the constituent materials of the base and the lid member, for example, a resistance welding sealing method, a solder sealing method, or the like. An airtight structure that seals the means 17 is realized.

In the crystal oscillator 10 of this embodiment, the heating means 17 is provided on the outer side surface of the first container, the inside of the first container 13 is a helium atmosphere, and the inside of the second container 21 is a reduced pressure atmosphere. It is preferable that the helium concentration in the first container 13 is as high as possible. Moreover, it is preferable that the reduced-pressure atmosphere in the second container 21 has a high degree of vacuum.

In the crystal oscillator of this embodiment, the thermal conductivity of helium in the first container 13 is approximately 0.144 W/mK. /mK), or about five times higher than the atmosphere (thermal conductivity of air: about 0.027 W/mK) or reduced pressure (thermal conductivity of vacuum is substantially 0). Therefore, even if the heating means 17 is provided on the outer bottom surface of the first container 13, the heat of the heating means 17 is easily transmitted to the inside of the first container 13, so that the crystal oscillator in the first container 13 is heated. 11 is also controlled by the heating means 17 and the temperature control circuit 19, so it can be kept at a predetermined temperature. Further, since the atmosphere in the second container 21 enclosing the first container 13 is a reduced pressure atmosphere, the second container 21 can block the influence of the lower atmosphere on the first container 13 .
From these, it is possible to provide a crystal oscillator having a novel structure in which the heating means (heater) 17 is provided outside the first container 13 and has a structure considered preferable for temperature control. Moreover, since the heating means 17 can be assembled separately from the first container 13 and its internal parts, even if the first container 13 and its internal parts have a problem, the possibility of wasting the heating means can be prevented. .

10: Crystal Oscillator of Embodiment 11: Crystal Oscillator 13: First Container 13a: Base 13b: Metal Lead 13c: Metal Cover Member 15: Oscillation Circuit 17: Heating Means 19: Temperature Control Circuit 21: Second Container 21a: Base 21b: Mounting substrate 21ba: First surface 21bb: Second surface 21c: Metal lead 21d: Metal lid member 23: Mounting substrate 25: Window

Claims (6)

A crystal oscillator sealed in a container, a metal first container containing the crystal oscillator, an oscillation circuit for the crystal oscillator, a heating means for heating the crystal oscillator, and the heating means and a metal second container encasing the first container,
The heating means is provided in contact with an appropriate portion of the outer surface of the first container,
The inside of the first container is a helium atmosphere,
A crystal oscillator, wherein the inside of the second container is a reduced pressure atmosphere. The second container includes a base having a hermetic structure made of metal and glass, a mounting substrate mounting the first container on a first surface, and the second container and the mounting substrate. a metal lead for floating in the container of the crystal oscillator, the lead having a metal lead for connecting the inside and the outside of the crystal oscillator, and a recess for enclosing the first container and the mounting substrate on the base 2. The crystal oscillator of claim 1, further comprising a joined metal lid member. 3. The crystal oscillator according to claim 2, wherein the mounting substrate has a window portion connecting the first surface and a second surface opposite to the first surface. The first container includes a base having a hermetic structure made of metal and glass, a metal lead provided on the base for connecting the inside and the outside of the first container, and a recess for accommodating the crystal oscillator. and a metal lid member joined to the base,
4. The crystal oscillator according to claim 1, wherein said heating means is provided in contact with the outer bottom surface of said first container. The first container is characterized in that it has a mounting board for mounting the crystal oscillator therein, and the crystal oscillator is mounted on the surface of the mounting board on the base side. A crystal oscillator according to any one of claims 1 to 4. 6. The crystal oscillator according to any one of claims 1 to 5, wherein the oscillator circuit is provided within the first container.

Images