JP4499478B2 - Constant temperature crystal oscillator using crystal resonator for surface mounting - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant temperature crystal oscillator using a surface mount crystal resonator, and more particularly to a constant temperature crystal oscillator having a simple structure.

BACKGROUND OF THE INVENTION A crystal oscillator is known as a frequency control element, and is incorporated in various electronic devices as a reference source for frequency and time. One such example is a high-stability crystal oscillator in which a quartz resonator is housed in a constant temperature bath and made constant temperature. These are used, for example, in base stations of communication networks with a frequency stability of 0.05 ppm or less.

(Example of the prior art) FIG. 4 is a diagram for explaining one conventional example, in which FIG. 4 (a) is a cross-sectional view of a constant temperature crystal oscillator, and FIG. 4 (b) is an insertion of the crystal resonator into a constant temperature bath. FIG.

  The crystal oscillator includes a crystal resonator 2, a thermostat 3, an oscillation element 4, and a temperature control element 5 arranged (mounted) on the first and second circuit boards 1 (ab). The first circuit board 1a is supported by metal pins 7a (airtight terminals) as external terminals that are insulated through the metal base 6. The second circuit board 1b is supported by metal pins 7b implanted in the first circuit board 1a. Both the first and second circuit boards are made of a glass epoxy material.

  The crystal unit 2 is formed by sealing and sealing an AT-cut or SC-cut crystal piece (illustrated), for example, in a metal case 9 from which a pair of lead wires 8 are led out. The thermostat 3 is formed by winding a hot wire 11 around a metal cylinder 10 and accommodates the crystal unit 2. Then, the main surface of the metal cylinder 10 is opposed to one main surface of the second circuit board 1 b and is thermally coupled by the heat conductive resin 12. The pair of lead wires 8 of the crystal unit 2 are bent and connected to the second circuit board 1b.

  The oscillation element 4 constitutes an oscillation circuit together with the crystal resonator 2 and is disposed on the other main surface of the second circuit board 1b. The temperature control element 5 includes at least a thermistor 5a as a temperature sensing element, and constitutes a temperature control circuit that controls the temperature of the thermostatic chamber 3 together with the power transistor. And it arrange | positions on the outer periphery of the 1st circuit board 1a except the thermistor 5a. The temperature control circuit detects the temperature of the thermostat 3 by joining the thermistor 5 a to the thermostat 3, for example. And the electric power supplied to the hot wire 11 is controlled based on detected temperature, and the temperature in the thermostat 3 is kept constant. Reference numeral 13 denotes a metal cover.

In such a case, since the operation temperature of the crystal unit 2 is made constant by the thermostatic chamber 3, the frequency change of the vibration frequency due to the temperature change is prevented. In other words, the change of the oscillation frequency based on the frequency temperature characteristic of the crystal unit 2 is prevented. Further, since the second circuit board 1b on which the oscillation element 4 is mounted is disposed on the thermostat 3, the frequency change due to the temperature characteristics of the circuit element itself is also prevented.
JP-A-1-195706

(Problem of the prior art) However, since the crystal oscillator having the above-described configuration uses the crystal unit 2 in which the crystal piece 2 is accommodated in the metal case 9 from which the lead wire 8 is led out, the size is basically increased. Moreover, since the thermostat 3 around which the hot wire 11 is wound is used, it is expensive and complicated in structure. In addition, there is a case in which the hot wire 11 is directly wound around the metal case 9 of the crystal unit 2. However, even in this case, the work of winding the hot wire 11 is required, and there is a problem that the structure is complicated in any case. .

  In addition, in these cases, the frequency stability is set to 0.05 ppm or less as described above and used for base stations. However, for GMS, for example, the frequency stability is set to be relatively moderate 0.1 to 0.2 ppm or less, so overspec Sometimes it became. From this, for example, application of a temperature compensated crystal oscillator (not shown) for surface mounting can be considered, but in this case, the frequency stability is about 1 ppm, and there is a problem that the standard cannot be satisfied.

(Object of the Invention) An object of the present invention is to provide a constant temperature crystal oscillator which facilitates downsizing and simplifies the structure.

According to the present invention, as described in the claims (Claim 1), the surface mount crystal resonator is mounted on the circuit board held by the first metal pin on the base together with the oscillation element and the temperature control element. A constant temperature crystal oscillator using a surface-mounted crystal resonator, wherein a ceramic substrate is held on the circuit board by a second metal pin, and the crystal resonator is a main part of the ceramic substrate. A heat sensitive element having a strong temperature dependency and at least a chip resistor for heat generation is disposed on the other main surface of the ceramic substrate, and the other main surface of the ceramic substrate is the surface of the circuit substrate. A heat conductive resin is provided between the chip resistor and the circuit board so as to face one main surface and are in close contact with each other.

  With such a configuration, the crystal resonator is used for surface mounting, and the chip resistor for heating is arranged on the ceramic substrate, so that a constant temperature crystal oscillator having a simplified structure is basically obtained by promoting downsizing. . Since the thermal sensitive element is provided, for example, if it is a temperature sensitive element, the heating temperature can be directly detected, and if it is an oscillation element, its temperature dependency can be eliminated.

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(Embodiment section)
According to a second aspect of the present invention, an oscillation element constituting an oscillation circuit is disposed on the other main surface of the circuit board facing the ceramic substrate of the first aspect. Thereby, heat is propagated to the oscillation element to make the temperature uniform. Therefore, the characteristic change due to the temperature characteristic of the oscillation element is prevented.

In the third aspect , the thermal sensitive element according to the first aspect is a temperature sensitive element or a voltage variable capacitance element. Thereby, the heat generation temperature of the chip resistor can be directly detected. In addition, it is possible to obtain a voltage controlled oscillator having a stable oscillation frequency with respect to the control voltage by preventing a change in capacitance due to temperature.

In claim 4, the base of claim 1 is a circuit board for surface mounting in which the first metal pins are erected , or a metal base in which the first metal pins are insulated and penetrated. Thus, the base in claim 1 is clarified, and when the base is a circuit board for surface mounting, a constant temperature crystal oscillator for surface mounting can be obtained, and further miniaturization is promoted.

  FIG. 1 is a view for explaining an embodiment of the present invention. FIG. 1 (a) is a sectional view of a constant temperature crystal oscillator, and FIG. 1 (b) is a plan view of a ceramic substrate. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

  The crystal oscillator includes first and second circuit boards 1 (ab) made of glass epoxy as described above. The first circuit board 1a is formed of a laminated board, and has a circuit pattern (not shown) on the laminated surface and has mounting terminals 16 for surface mounting on the outer surface. A heat conductive ceramic substrate 14 held by metal pins 7b is provided on one main surface of the second circuit board 1b. An oscillation element 4 that constitutes an oscillation circuit is disposed in the central region of the other main surface, and a temperature control element 5 that constitutes a temperature control circuit is disposed on the outer peripheral portion.

  On one main surface of the ceramic substrate 14, the crystal resonator 2 for surface mounting is disposed. The surface-mounted vibrator hermetically encloses a crystal piece in a ceramic container, and has mounting terminals (not shown) on the bottom surface of, for example, a square portion. Two chip resistors 15 (ab) for heat generation are disposed opposite to the crystal resonator 2 in the central region of the other main surface facing the second circuit board 1b.

  Further, a thermistor 5a as a temperature sensitive element among the temperature control elements is disposed between the chip resistors 15 (ab). The crystal resonator 2, the chip resistor 15 (ab), and the thermistor 5a are integrally fixed to each other by reflow such as solder (not shown).

  A thermally conductive resin 12 is interposed (adhered) between the surface of the chip resistor 15 (ab) and the second circuit board 1b, and the ceramic substrate 14 is attached to one main surface of the second circuit board 1b by the metal pins 7b. Provide on the side. And the nail | claw part which is not shown in figure provided in the opening end surface of the metal cover 13 is inserted and joined in the hole (not shown) provided in the outer periphery of the 1st circuit board 1a. Thereby, the second circuit board 1a is accommodated.

  In such a case, power is supplied to the chip resistor 15 (ab) for heat generation through the power transistor of the temperature control circuit. Thereby, Joule heat of the chip resistor 15 (ab) is conducted to the ceramic substrate 14 and heated. Then, the crystal unit 2 fixed to the ceramic substrate 14 is similarly heated through the mounting terminals for surface mounting. Further, the thermistor 5a directly detects the temperature of the ceramic substrate 14 immediately below the crystal unit 2 to control the power supply.

  The heat of the chip resistor 15 (ab) is efficiently applied to the second circuit board 1b by the thermally conductive resin 12 closely adhered between the one main surface of the second circuit board 1b and the chip resistor 15 (ab). Propagated. Here, since the oscillation element 5 is disposed on the other main surface of the second circuit board 1b at a portion facing the chip resistor 15 (ab), temperature dependency is eliminated.

  With such a configuration, since the crystal unit 2 is for surface mounting, the crystal oscillator can be basically made smaller than the conventional crystal unit from which the lead wire is derived. Since the chip resistor 15 (ab) and the ceramic substrate 14 are used as the heating source of the crystal unit 2, the structure is simplified as compared with a conventional heating wire wound. And it makes it cheap without the winding work of a hot wire.

  Here, since the first circuit board 1a is used for surface mounting having the mounting terminals 16, a conventional metal base is not required, and further miniaturization (low profile) is promoted.

(Other matters) In the above embodiment, the crystal oscillator is for surface mounting, but it may be as shown in FIG. That is, the circuit board 1 may be directly held by the airtight metal pin 7a of the metal base 6 as in the conventional example. Here, the second circuit board 1b is unnecessary.

  Further, as shown in FIG. 3, the second circuit board 1b may be hermetically sealed by using the metal base 6 for resistance welding, for example. In this case, since each oscillation element 4 and the temperature control element 5 are hermetically sealed, the external environment is shut off to improve the aging characteristics.

  Further, only the thermistor 5a is disposed on the other main surface of the ceramic substrate 14. However, for example, a highly sensitive element such as a voltage variable capacitance element having high temperature dependence is also disposed so as to further prevent a frequency change due to temperature. May be. Further, although only the heating chip resistor 15 (ab) is disposed on one main surface of the ceramic substrate 14, for example, a power transistor of a temperature control circuit may be disposed for heat supply.

  Further, the crystal resonator 2 is provided on one main surface of the ceramic substrate 14, and the chip resistor 15 (ab) and the thermistor 5a are provided on the other main surface. However, the thermal conductivity of the ceramic substrate 14 is good and the heat distribution is macroscopic. Therefore, even if they are the same main surface, the same effect can be obtained. However, since the heat distribution differs microscopically, it is better to arrange them on both main surfaces as in the embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a cross-sectional view of a constant temperature crystal oscillator, and FIG. 1B is a plan view of a ceramic substrate. It is sectional drawing of the crystal oscillator made into the constant temperature type | mold explaining the other Example of this invention. FIG. 6 is a cross-sectional view of a constant temperature crystal oscillator for explaining still another embodiment of the present invention. FIG. 4A is a cross-sectional view of a constant temperature crystal oscillator, and FIG. 2B is an insertion diagram of a crystal resonator in a constant temperature bath.

  DESCRIPTION OF SYMBOLS 1 Circuit board, 2 Crystal oscillator, 3 Constant temperature bath, 4 Oscillator element, 5 Temperature control element, 6 Metal base, 7 Metal pin, 8 Lead wire, 9 Metal case, 10 Metal cylinder, 11 Heat wire, 12 Thermal conduction Resin, 13 metal cover, 14 ceramic substrate, 15 chip resistor, 16 mounting terminal.

Claims (4)

A constant-temperature crystal oscillator using a surface-mount crystal resonator in which a surface-mount crystal resonator is mounted on a circuit board held by a first metal pin on a base together with an oscillation element and a temperature control element. A ceramic substrate is held on the circuit substrate by a second metal pin, the crystal unit is disposed on one main surface of the ceramic substrate, and at least the heat generating surface on the other main surface of the ceramic substrate. A thermal sensitive element having a strong chip resistance and temperature dependency is disposed, and the other main surface of the ceramic substrate is opposed to one main surface of the circuit board and is between the chip resistor and the circuit board. A constant temperature crystal oscillator characterized in that a thermally conductive resin is provided and adhered.   2. The constant temperature crystal oscillator according to claim 1, wherein an oscillation element constituting an oscillation circuit is disposed on the other main surface of the circuit board facing the ceramic substrate.   2. The constant temperature crystal oscillator according to claim 1, wherein the thermal sensitive element is a temperature sensitive element or a voltage variable capacitance element. 2. The constant temperature crystal oscillator according to claim 1, wherein the base is a circuit board for surface mounting in which the first metal pins are erected or the metal base is a metal base through which the first metal pins are insulated and penetrated .

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