JP3248882B2 - Structure of highly stable piezoelectric oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-stability piezoelectric element which uses a heating element without using a thermostat to maintain a constant temperature of a piezoelectric vibrator, thereby realizing a stable temperature holding and miniaturization. More particularly, the present invention relates to a structure of a high-stable piezoelectric oscillator that eliminates a drawback that heat from a heat-generating component is not easily transmitted to a piezoelectric vibrator and temperature fluctuation is large.

[0002]

2. Description of the Related Art Quartz oscillators are widely used as reference frequency generating sources, filters, and the like in communication devices such as communication devices and wireless communication devices, and electronic information devices such as computers. Frequency stability is required. In particular, with the spread of cellular type mobile phones, the demand for highly stable oscillators used in many base stations has been steadily increasing. As is well known, a crystal oscillator is widely used as a stable frequency source. However, when high stable oscillation as described above is required, a crystal oscillator is placed in a thermostat set at a temperature higher than room temperature. A relatively large thermostat-type crystal oscillator that accommodates the same has been used. However, in response to the recent miniaturization of communication devices, there has been a demand for the development of a highly stable oscillator with a simpler configuration and a smaller size. FIG. 3 is a block diagram showing the configuration of a conventional high-stable oscillator, which includes an amplifying unit OSC including a transistor, a capacitor, and a resistor, a crystal unit Xtal, and the crystal unit X.
and a temperature controller TC for keeping the temperature of tal constant. FIG. 4 is a cross-sectional view showing the structure of the high-stable oscillator. An amplifying unit OSC is provided on a printed circuit board PB.
After the temperature control unit TC and the temperature control unit TC are mounted by reflow or the like, a crystal oscillator packaged so as to be superimposed on the thermistor Th (temperature sensing element), heater H (heating element), and power transistor Tr constituting the temperature control unit. It is equipped with a child Xtal. In order to fix the printed circuit board PB, the thermistor Th, the heater H, the power transistor Tr, and the crystal unit Xtal, the thermal conductivity is about 0.5 (W / W).
mK) of silicone adhesive B is used. An insulating tape is wound around the outer periphery of the crystal unit for electrical insulation. Further, it is general to form a highly stable piezoelectric oscillator by housing the entire components mounted on the printed circuit board PB in a metal case. Since the power transistor Tr generates heat when energized, the power transistor Tr is disposed close to the crystal unit so as to use the generated heat as an auxiliary heat source. However, the above-mentioned conventional high-stable piezoelectric oscillator uses an insulating adhesive for connecting a crystal oscillator to a substrate or the like and has a thermal conductivity of about 0.5 (W / m
Since the silicon-based adhesive B of K) was used, the heat generated from the heater H and the power transistor Tr was not efficiently transmitted to the crystal oscillator, and it was difficult to accurately control the temperature. As a result, the temperature fluctuation of the crystal unit is large, and complicated temperature control is required to secure the desired stability of the frequency. Furthermore, since the silicon adhesive has a weak adhesive strength, if peeling occurs between each part and the crystal unit over time, the degree of adhesion is reduced, and sufficient heating and accurate temperature detection can be performed. There was a risk of disappearing.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric vibrator at a constant temperature by utilizing heat generated from a heating element or a heating component constituting an oscillation circuit without using a thermostat. The low thermal conductivity of conventional silicon-based adhesives used to bond crystal units to printed circuit boards and components in high-stability piezoelectric oscillators that have been downsized by maintaining An object of the present invention is to provide a structure of a high-stable piezoelectric oscillator that solves the conventional disadvantage that heat from a heat-generating component or the like is hardly transmitted to a piezoelectric vibrator due to low power and temperature fluctuation is increased.

[0004]

In order to achieve the above object, the present invention is directed to a piezoelectric vibrator, an amplifier for exciting the piezoelectric vibrator, a heater for heating the piezoelectric vibrator, A temperature-sensitive element for detecting the temperature of the piezoelectric vibrator;
A high-stability piezoelectric oscillator, comprising: a temperature control unit that keeps the temperature of the piezoelectric vibrator constant based on the output of the temperature-sensitive element; and a printed board on which these components are mounted. On top, the temperature sensitive element, a heater and a power transistor constituting a temperature control unit are arranged adjacently, and at least a piezoelectric vibrator is mounted on the heater,
At least the heater and the piezoelectric vibrator are fixed by an insulating adhesive, and an insulating epoxy adhesive containing metal particles as a filler is used as the adhesive. The invention according to claim 2 is a piezoelectric vibrator, an amplifier for exciting the piezoelectric vibrator, a heater for heating the piezoelectric vibrator, a temperature-sensitive element for detecting a temperature of the piezoelectric vibrator, A high-stability piezoelectric oscillator comprising: a temperature control unit that keeps the temperature of the piezoelectric vibrator constant based on the output of the temperature-sensitive element; and a printed board on which these components are mounted. A piezoelectric vibrator is mounted using a conductive adhesive, a flexible substrate is bonded on the piezoelectric vibrator using an insulating adhesive, and the temperature-sensitive element, the heater, and the temperature control unit are further mounted on the flexible substrate. The power transistor to be configured is mounted, and an insulating epoxy adhesive using metal particles as a filler is used as the adhesive. The invention according to claim 3 is characterized in that aluminum particles, aluminum nitride particles, or alumina particles are used as the filler.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a high stability piezoelectric oscillator according to a first embodiment of the present invention.
After mounting each component forming the amplifying section (OSC) 2 and each component forming the temperature control section (TC) 3 by reflow or the like, a thermistor Th (temperature sensing element) 4 forming the temperature control section, a heater A crystal resonator Xtal 7 packaged with a metal cap is mounted so as to overlap the H (heating element) 5 and the power transistor Tr 6, and is bonded and fixed with an epoxy-based insulating adhesive 8. The crystal unit Xtal 7 includes, for example, a metal cap 7a in which a crystal unit is hermetically sealed, and a lead terminal 7b extending from the metal cap 7a.
Is inserted into the through hole 1a provided in the
Is fixed to the land on the substrate. The epoxy adhesive 8 for fixing the crystal unit Xtal 7 to the printed circuit board 1, the thermistor Th4, the heater H5, and the power transistor Tr6 has a thermal conductivity in which metal particles such as aluminum are dispersed as a filler. About 1.8 (W / m
It is an insulating adhesive of the order of K). As the filler, metal particles such as aluminum nitride and alumina can be used in addition to aluminum, but other metal materials can also be used as the filler. Since the epoxy-based insulating adhesive 8 has a thermal conductivity about three times higher than that of the silicon-based adhesive and also has a remarkably superior adhesive strength, heat generated from the heater 5 and the power transistor 6 is reduced by the epoxy-based insulating adhesive. The light is efficiently transmitted to the metal cap of the crystal unit 7 through the fin 8. That is, heat is efficiently conducted to the crystal unit via the adhesive 8 interposed between the heater 5 and the power transistor 6 and the crystal unit. In addition, the heat generating component 5 is attached to the adhesive 8 located at a portion other than between the heater 5 and the power transistor 6 and the crystal unit 7.
The heat radiated from 6 is also efficiently transmitted to the crystal unit,
Stable heating can be performed.

Further, since the epoxy adhesive 8 has a strong adhesive force, the components 4, 5, 6 and the crystal unit 7 do not peel off with time, and are stable by the heat generating components 5, 6. As a result, the crystal resonator 7 can be heated, and the temperature can be accurately measured by the thermistor 4.
As a result, even under severe conditions such as temperature changes,
Excellent and stable temperature-frequency characteristics can be exhibited. Next, FIG. 2 is a cross-sectional view showing a main configuration of a high stability piezoelectric oscillator according to another embodiment of the present invention. This high-stability piezoelectric oscillator has a circuit part on a pad on a printed circuit board 1 in which an amplifying unit 2 (OSC) including a transistor, a capacitor, a resistor, and the like, and a thermistor Th4, a heater H5, and a power transistor Tr6 are removed from a temperature control unit. Temperature control circuit T comprising
c3 is connected by soldering by a mounting method such as reflow, and for the crystal unit Xtal 7, a lead terminal 7b extending from the cap 7a is inserted into the through hole 1a of the substrate and fixed. On the other hand, a heat-related element including a thermistor Th4, a heater H5, and a power transistor Tr6 is mounted close to the flexible printed board 15, and one end of the flexible printed board 15 is electrically connected to pads on the printed board using solder or the like. Mechanical connection. An insulating epoxy-based adhesive having good thermal conductivity and strong adhesive strength so that the upper half of the outer periphery of the cap 7a of the crystal unit Xtal 7 and the heat-related element mounting portion of the flexible printed circuit board 15 are in close contact with each other. Adhesively fix with agent 8. The printed circuit board 1 and the lower portion of the cap 7a are also bonded and fixed with the same adhesive 8. The adhesive 8 is an insulating adhesive having a thermal conductivity of about 1.8 (W / mK) in which metal particles such as aluminum are dispersed as a filler. As the filler, metal particles such as aluminum nitride and alumina can be used in addition to aluminum, but other metal materials can also be used as the filler.

The epoxy-based insulating adhesive 8 has a thermal conductivity about three times as high as that of a silicon-based adhesive, and has an extremely excellent adhesive strength, so that the heat generated from the heater 5 and the power transistor 6 can be flexibly printed. The light is efficiently transmitted to the metal cap 7 a of the crystal unit 7 via the substrate 15 and the epoxy-based insulating adhesive 8. That is, the heater 5
And an adhesive 8 interposed between the flexible printed circuit board 15 on which the power transistor 6 is mounted and the crystal unit 7
The heat is efficiently conducted to the crystal unit 7 via the. Further, the heat radiated from the heat-generating components 5 and 6 via the flexible printed circuit board to the adhesive 8 located at a portion other than between the heater 5 and the power transistor 6 and the crystal unit 7 can be efficiently applied to the crystal unit. Conducted and stable heating can be performed. Further, since the epoxy adhesive 8 has a strong adhesive force, the flexible printed circuit board 15 on which the components 4, 5, and 6 are mounted and the quartz oscillator 7 do not peel off with time, and the heating components 5 , 6 can stably heat the crystal resonator 7 and the thermistor 4 can accurately measure the temperature of the crystal resonator. As a result, even under severe conditions such as temperature changes, it is possible to exhibit excellent and stable temperature-frequency characteristics, so that it is possible to omit the metal case for housing the entire components mounted on the printed circuit board. A further miniaturization can be realized. The heater for heating the crystal unit 7 may be at least a heater. If the size of the crystal unit is small, the crystal unit, the heater and the thermistor are connected by the epoxy insulating adhesive. In addition, when the amount of metal particles mixed into the adhesive increases, the thermal conductivity increases, which is preferable. On the other hand, the insulating property cannot be maintained. It can be used in the present invention.

[0008]

The present invention is configured as described above.
In addition to sensing the temperature of the crystal unit more accurately and reducing the heat capacity load seen from the heat-generating components, the response time of the temperature control unit is shortened, and the temperature characteristics are stabilized and improved. It is possible to improve the frequency stability. That is, according to the present invention, miniaturization is realized by maintaining the piezoelectric vibrator at a constant temperature by using heat generated from a heat generating element and a heat generating component constituting an oscillation circuit without using a thermostat. In a stable piezoelectric oscillator, an insulating epoxy-based adhesive filled with a metal filler is used as an adhesive for bonding a quartz oscillator to a printed circuit board and each component, so that the heat of a conventional silicon-based adhesive is It is possible to solve the conventional disadvantage that heat from a heat-generating component or the like is hardly transmitted to the piezoelectric vibrator due to poor conductivity and low adhesive strength, and temperature fluctuation is increased. Also,
Since the adhesive strength of the epoxy-based adhesive is maintained over time, the close contact between the temperature-sensitive element and the crystal unit can be maintained over time, so that accurate temperature measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a high-stable piezoelectric oscillator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a high stability piezoelectric oscillator according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional high stability piezoelectric oscillator.

FIG. 4 is a cross-sectional view showing the structure of a conventional high stability piezoelectric oscillator.

[Explanation of symbols]

Reference Signs List 1 printed circuit board, 2 amplifying section (OSC), 3 temperature control section (TC), 4 thermistor Th (temperature sensing element), 5
Heater H (heating element), 6 power transistor Tr,
7 crystal oscillator Xtal, 7a metal cap, 7b lead terminal, 8 epoxy-based insulating adhesive, 10 solder, etc.
15 Flexible printed circuit board.

Claims (3)

(57) [Claims] 1. A piezoelectric vibrator, an amplifier for exciting the piezoelectric vibrator, a heater for heating the piezoelectric vibrator, a temperature sensitive element for detecting a temperature of the piezoelectric vibrator, and a thermosensitive element A temperature control unit that keeps the temperature of the piezoelectric vibrator constant based on the output of the element, and a printed circuit board on which these components are mounted, and a high-stable piezoelectric oscillator including: The temperature-sensitive element, a heater and a power transistor constituting a temperature control unit are arranged adjacently, and at least a piezoelectric vibrator is mounted on the heater, and at least the heater and the piezoelectric vibrator are fixed with an insulating adhesive, A structure of a highly stable piezoelectric oscillator, wherein an insulating epoxy-based adhesive containing metal particles as a filler is used as the adhesive. 2. A piezoelectric vibrator, an amplifier for exciting the piezoelectric vibrator, a heater for heating the piezoelectric vibrator, a temperature-sensitive element for detecting a temperature of the piezoelectric vibrator, A high-stable piezoelectric oscillator, comprising: a temperature control unit that keeps the temperature of the piezoelectric vibrator constant based on the output of the element; and a printed circuit board on which these components are mounted. A piezoelectric vibrator is mounted using an agent, and a flexible substrate is bonded on the piezoelectric vibrator using an insulating adhesive, and the temperature-sensitive element, the heater, and the temperature control unit are further formed on the flexible substrate. A structure of a highly stable piezoelectric oscillator, wherein a power transistor is mounted, and an insulating epoxy-based adhesive using metal particles as a filler is used as the adhesive. 3. As the filler, aluminum particles,
3. The structure of a highly stable piezoelectric oscillator according to claim 1, wherein aluminum nitride particles or alumina particles are used.