JP2009284372A - Constant temperature structure of crystal unit - Google Patents

Abstract

To provide a constant temperature structure of a crystal resonator with improved heat transfer efficiency from a chip resistor for heat generation and secondly to reduce a height dimension, and a constant temperature type oscillator using the same.
A crystal resonator having a crystal piece sealed and sealed and having an external terminal is disposed on a circuit board, and the operating temperature of the crystal resonator is made constant by at least a temperature control element having a chip resistor for heating. The chip resistor 3a is a constant temperature structure of a crystal resonator in which a resistance film is formed on one main surface of the chip base. The chip resistor 3a is an empty space provided on the circuit board 4 on the lower surface side of the crystal resonator. The main surface on which the resistive film is formed is disposed so as to face the lower surface of the crystal resonator, and the crystal resonator covers the space 13 on the circuit board 4. It is assumed that the arrangement is arranged.
[Selection] Figure 1

Description

  The present invention relates to a constant temperature structure of a crystal resonator and a constant temperature crystal oscillator (hereinafter referred to as a constant temperature oscillator) using the crystal resonator, and more particularly to a constant temperature structure that keeps the operating temperature of a crystal resonator constant.

(Background of the Invention)
The thermostatic oscillator generally uses a thermostatic bath, and since the operating temperature of the crystal unit is kept constant, the frequency stability is high (frequency deviation is approximately 0.05 ppm or less). For example, a base station for optical communication, etc. Used for communication equipment. In recent years, downsizing of these communication facilities has been permeated, and as a part of that, surface-mount type crystal resonators (hereinafter referred to as surface-mount resonators) are applied. One of these is the one by the present applicant (Patent Document 1).

(An example of conventional technology, Patent Documents 1 and 2)
FIG. 4 is a diagram for explaining a conventional example. FIG. 4 (a) is a cross-sectional view of a thermostatic oscillator, FIG. 4 (b) is a bottom view of a surface-mounted vibrator, and FIG. 4 (c) is a temperature control circuit. FIG.

  The constant temperature oscillator includes a surface-mounted oscillator 1 and an oscillation element 2 that forms an oscillation circuit, and a temperature control element 3 that keeps the operating temperature of the surface-mounted oscillator 1 constant on a circuit board 4. The container 5 is hermetically sealed. In the surface-mounted vibrator 1, a crystal piece 1A is fixed to a concave container body 6 made of ceramic, and a metal cover 7 is covered and hermetically sealed.

  At the four corners of the outer bottom surface (back surface) of the container body 5, there are crystal terminals 8 a and dummy terminals 8 b as mounting terminals. The crystal terminals 8a (two) are provided at a pair of diagonal portions and are connected to an excitation electrode of a crystal piece (not shown). The dummy terminals 8 (two) are provided in another set of diagonal portions, and are usually connected to the metal cover 7 by via holes (not shown), for example, as ground terminals.

  The temperature control element 3 has an operating temperature of the surface-mounted vibrator 1 constant, and includes at least a chip resistor 3a (for example, two), a temperature-sensitive element 3b that detects the operating temperature of the surface-mounted vibrator 1A, and a power transistor 3c. . The chip resistor 3a has a resistance film 3x on one main surface of a chip base made of ceramic, and has electrodes (not shown) on both ends. The temperature sensitive element 3b is, for example, a thermistor whose resistance value decreases with increasing temperature. The power transistor 3c supplies power controlled by a resistance value based on the temperature of the temperature sensitive element 3b to the chip resistor 3a for heat generation.

  Specifically, for example, as shown in FIG. 6 (a), one input terminal of the operational amplifier 12 has a temperature sensitive voltage due to the temperature sensitive element 3b and the resistor Ra, and the other input terminal has resistors Rb and Rc. Apply the reference voltage. Then, a reference temperature difference voltage with respect to the reference voltage is applied to the base of the power transistor 3c, and power is supplied from the DC voltage DC to the chip resistor 3a. Thereby, the power to the chip resistor 3a is controlled by the resistance value depending on the temperature of the temperature sensitive element 3c, and the operating temperature of the surface mounted vibrator 1 is made constant.

  In this example, the temperature sensitive element 3b is connected to one or both of the dummy terminals 8 (ab) of the surface mount vibrator 1. The dummy terminal 8b is not grounded but a floating electrode. As a result, the temperature sensitive element 3b is thermally coupled to the surface-mounted vibrator 1 through the wiring path, so that the operating temperature of the surface-mounted moving element 1 is detected directly (in real time) to improve the responsiveness to temperature changes. To do.

  The circuit board 4 has a two-stage structure of a first board 4 a and a second board 4 b, and the first board 4 a holds the second board 4 b by metal pins 9. The first substrate 3a is made of glass epoxy, and the oscillation element 2 and the temperature control element 3 are disposed on the lower surface except for the surface mount vibrator 1, the chip resistor 3a, the temperature sensitive element 3b, and the power transistor 3c.

  The second substrate 4b is made of ceramic, and the surface mount vibrator 1 and the tall power transistor 3c are disposed on the upper surface, and the heat generating chip resistor 3a and the temperature sensitive element 3b are disposed on the lower surface. A silicon-based thermal conductive resin 10 is applied between the first substrate 4a and the second substrate 4b to cover the chip resistor 3a and the temperature sensitive element 3b. The metal container 5 includes a metal base 5a and a cover 4b. The hermetic terminal 11b of the metal base 5a holds the first substrate 4a, and the cover 5 is hermetically sealed by resistance welding.

  Usually, before joining the metal cover 4b to the metal base 5a, the frequency-temperature characteristics that form the cubic curve of the surface-mount vibrator 1 are individually measured. When the temperature on the high temperature side, which is the operating temperature of the surface-mounted vibrator 1, is 80 ° C., for example, the operating temperature of the surface-mounted vibrator 1 is adjusted to 80 ° C. by adjusting the resistance Ra of the temperature control circuit. Set. Further, the oscillation frequency f is matched with the nominal frequency by an adjustment capacitor (not shown) of the oscillation circuit. Therefore, the adjustment element 2A that requires replacement of the resistor Ra, the adjustment capacitor, and the like is disposed on the outer periphery of the second substrate 4a, for example.

  In such a case, the second substrate 4b is made of ceramic having good thermal conductivity, and the surface mount vibrator 1 is disposed on the upper surface and the chip resistor 3a for heat generation is disposed on the lower surface. In addition, since only the chip resistor 3a, the temperature sensitive element 3b, and the power transistor 3c are basically disposed on the second substrate 4b, the planar outline of the second substrate 4b is reduced.

Furthermore, since the first substrate 4a is made of glass epoxy that is inferior in thermal conductivity to ceramic, heat radiation from the second substrate 4b thermally coupled through the metal pins 9 is reduced. In particular, heat dissipation from the thermally coupled lead wire 11 is reduced. From these, the heat transfer efficiency from the chip resistor 3a to the surface-mounted vibrator 1 is increased.
JP 2005-341191 A JP 2006-311496 A JP 2007-274456 A JP 2007-274455 A

(Problems of conventional technology)
However, in the constant temperature oscillator configured as described above, although the second substrate 4b is made of ceramic having good thermal conductivity, the surface-mounted vibrator 1 and the heat generating chip resistor 3a are disposed on the opposite surface of the second substrate. . Therefore, the heat generated by the chip resistor 3a is absorbed by the second substrate 4b. And one main surface provided with the resistance film 3x which becomes a direct heat source of the chip resistor 3a is the first substrate 4a side. Therefore, there is a problem that the heat transfer efficiency from the chip resistor 3a (resistive film 3x) to the bottom surface of the crystal unit 1 is lowered.

  Further, in order to reduce the heat radiation from the second substrate 4b, the second substrate 4b is made small to basically include only the chip resistor 3a, the temperature sensitive element 3b, and the power transistor 3c, and other oscillation elements 2 and temperature control. The element 3 is disposed on the first substrate 1 (glass epoxy). Therefore, since the first substrate 4a and the second substrate 4b have a two-stage structure, there is a problem that the height dimension has to be increased.

(Object of invention)
It is an object of the present invention to provide a constant temperature structure of a crystal resonator and a constant temperature type oscillator using the same, firstly increasing the heat transfer efficiency from the chip resistor for heat generation and secondly reducing the height dimension.

(Constant temperature structure of crystal unit)
According to the present invention, as shown in the claims (Claim 1), a crystal unit having a crystal piece sealed and sealed and having an external terminal is disposed on a circuit board, and the operating temperature of the crystal unit is set at least. In a constant temperature structure of a crystal resonator in which a resistance film is formed on one main surface of a chip base, the chip resistance is a lower surface of the crystal resonator. The main surface on which the resistive film is formed is disposed to face the lower surface of the crystal resonator, and the crystal resonator is disposed in the space provided in the circuit board on the side. It is set as the structure covered and arrange | positioned on the said circuit board.

(Constant temperature oscillator)
According to a fifth aspect of the present invention, as the crystal resonator holding structure having the circuit board according to the first aspect, a temperature control element forming a temperature control circuit and an oscillation circuit are formed together with the crystal resonator. The constant temperature oscillator is configured by housing the oscillation element in an oscillator container having a mounting terminal.

  With such a configuration according to the first aspect, since the heat generating chip resistor is disposed in the space of the circuit board, the heat generated by the chip resistor is stored in the space. And since one main surface which has a resistance film used as a heat source of chip resistance faces the lower surface of a crystal oscillator, the amount of direct heat transfer to the lower surface of a crystal oscillator is maximized, and heat transfer efficiency is raised. Therefore, for example, the responsiveness based on the temperature sensitive element is improved and the operating temperature of the crystal resonator is made constant.

(Constant temperature oscillator)
According to the fifth aspect of the present invention, the constant temperature oscillator having the constant temperature structure of the crystal resonator according to the first aspect can provide a constant temperature oscillator having a high frequency stability while keeping the operation temperature of the crystal resonator constant.

(Embodiment section)
According to a second aspect of the present invention, in the first aspect, the circuit board comprises at least first and second boards made of glass epoxy laminated in order from the lower side, and the space is an opening provided in the first board. The recess is As a result, the chip resistor is disposed in a void of the second substrate made of glass epoxy having inferior thermal conductivity, and one main surface provided with a resistance film serving as a heat source for the chip resistor is directly connected to the bottom surface of the crystal resonator. Heat transfer efficiency can be increased because they are facing and thermally coupled.

  In claim 3, the circuit board according to claim 1 is composed of at least first, second, and third substrates laminated in order from the lower side, and the first and third substrates are made of glass epoxy and the second substrate is made of glass epoxy. A prepreg or resin is used, and the third substrate on the lower surface side of the chip resistor and on the upper surface side of the chip resistor has a via hole filled with metal. Thereby, the chip resistance is blocked by the first and third substrates made of glass epoxy having inferior thermal conductivity, and is concentrated and radiated to the bottom surface of the surface mount vibrator through the via hole. Therefore, the heat transfer effect can be enhanced.

  In the fourth aspect of the invention, in the first aspect, the circuit board is composed of at least a first and a second board laminated in order from the lower side, and the first board is made of glass epoxy and the second board is made of a prepreg or a resin. Thereby, since the second substrate is a prepreg, the thickness from the surface-mounted vibrator can be reduced, and the heat from the chip resistor can be radiated intensively to the bottom surface of the surface-mounted vibrator. Therefore, even in this case, the heat transfer effect can be enhanced.

  In the sixth aspect of the present invention, in the fifth aspect, the temperature control element and the oscillation element are disposed on the circuit board. Thereby, since the temperature control element and the oscillation element are disposed as a single circuit board as a laminated board, the height dimension can be reduced.

(First embodiment)
FIG. 1 is a diagram for explaining a first embodiment of the present invention. FIG. 1 (a) is a sectional view of a thermostatic oscillator based on a constant temperature structure of a crystal resonator, and FIG. 1 (b) is a plan view of a circuit board. It is. 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.

(Constant temperature structure of crystal unit)
The constant temperature structure of the crystal unit according to the present embodiment is a laminated board in which the circuit board 4 is made up of first and second substrates 4 (ab) in order from the lower side made of, for example, glass epoxy. It has the following void 13. The opening surface of the recess 13a is located in the bottom surface of the surface mount moving element 1, and the bottom surface of the surface mounting mover 1 covers the opening surface and is disposed on the circuit board 4.

  Then, electrodes on both ends (not shown) of the chip resistor 3a for heat generation are fixed to the inner bottom surface of the space 13 (concave portion 13a). In this case, a resistance film 3x as a heat source formed on one main surface of the chip resistor 3a faces the bottom surface of the surface-mounted moving element 1. For example, two chip resistors 3a are connected in series or in parallel. Then, for example, a heat conductive adhesive (not shown) is filled in the recess 13a.

  Here, the temperature sensitive element 3b is fixed to the inner bottom surface of the void 13 like the chip resistor 3a, and is connected to the dummy terminal 8b connected to the metal cover 7 of the surface mount moving element 1 as described above. Further, the power transistor 3c is fixed not on the recess 13a but on the surface of the circuit board 4. Further, the temperature sensitive elements 3 other than the chip resistor 3a, the temperature sensitive element 3b, and the power transistor 3c are disposed on the front surface or the back surface of the circuit board 4.

  With such a constant temperature structure of the crystal resonator, the chip resistor 3a for heat generation is disposed in the space 13 formed as the recess 13a, and one main surface on which the resistance film is formed faces the bottom surface of the surface mounted moving element 1. To do. Therefore, the heat generated by the chip resistor 3a is stored in the recess and is directly transferred to the bottom surface of the surface-mounted moving element 1. Therefore, the heat transfer efficiency with respect to the bottom surface of the surface-mounted moving element 1 is increased. And since the heat conductive adhesive agent is filled in the recess 13a, the heat transfer effect is further enhanced.

  Moreover, in this example, since the circuit board 4 in which the recessed part 13a is formed is made of glass epoxy having poor thermal conductivity, heat is easily stored in the recessed part 13a. And the heat-transfer effect to the bottom face of the surface mount moving element 1 which consists of ceramics excellent in heat conductivity rather than glass epoxy further increases. The power transistors having different calorific values depending on the temperature change are outside the recess 13a, and the temperature in the recess 13a depends only on the chip resistor 3a. Therefore, temperature control can be facilitated.

(Constant temperature oscillator)
In the constant temperature oscillator, an oscillation element 2 that forms an oscillation circuit together with the surface-mounted moving element 1 is disposed on the front and back surfaces of the circuit board 4 having such a constant temperature structure. And the circuit board 4 is hold | maintained to the lead wire 11 as a mounting terminal of the metal base 5a mentioned above, and it accommodates in the container for oscillators sealed and enclosed with the metal cover 5b. The circuit board 4 is not necessarily hermetically sealed, but may be accommodated in an oscillator container having mounting terminals.

  Therefore, in this case, since the operating temperature of the surface-mounted moving element is kept constant regardless of the change in the ambient temperature, it is possible to obtain a highly stable constant temperature oscillator with a highly accurate oscillation frequency. Further, since the temperature sensitive element 3 and the oscillation element 2 are disposed with a single circuit board 4, the height of the constant temperature oscillator can be reduced.

(Second Embodiment)
FIG. 2 is a cross-sectional view of a constant temperature oscillator (excluding an oscillator container) based on a constant temperature structure of a crystal resonator, illustrating a second embodiment of the present invention. In addition, description of the same part as previous embodiment is simplified or abbreviate | omitted.

  In the second embodiment (see Patent Document 4), the circuit board 4 is a laminated board having first to third boards 4 (abc), the first and third boards 4 (ac) are glass epoxy, and the second board. 4b is a prepreg or resin obtained by impregnating glass, carbon fiber or the like with resin. In this example, a circuit pattern (not shown) is formed on the laminated surface of the first substrate 4a, and a semi-molten prepreg is fixed and cured. The thickness of the second substrate 4b (prepreg) covering the surface-mounted vibrator 1 is set to the minimum of a film.

  Then, a circuit pattern or a via hole is provided in the surface of the prepreg, and the third substrate 4c is joined. The laminated surface of the third substrate 4c has a circuit pattern to be bonded to the prepreg circuit pattern, and extends to the surface of the third substrate 3c by a via hole (not shown). Here, a via hole 14 is formed in the third substrate which is the lower surface of the surface-mounted vibrator 1 of the third substrate 3c. The thickness of the third substrate 4c is made smaller than that of the first and second substrates 4 (ab).

  Then, the surface-mounted moving element 1 is disposed on the surface of the third substrate 4c, and faces (faces) one main surface of the chip resistor 3a on which the resistance film 3x is formed. In this example, the temperature sensitive element 3 and the power transistor are on the surface of the third substrate, and the temperature sensitive element 3 approaches the surface mounted moving element 1 and is connected to the dummy terminal.

  With such a constant temperature structure of the crystal resonator, the chip resistor 3a is embedded in the second substrate 4b as a prepreg, and the distance to the bottom surface of the surface mount resonator 1 is minimized. In this case, the volume of the surface-mounted vibrator becomes a void 13. In this example, a via hole (metal) 14 is provided in the third substrate 4 c below the bottom surface of the surface-mounted vibrator 1. Therefore, heat from the chip resistor 3a (resistive film 3x) embedded in the second substrate is radiated in a concentrated manner to the bottom surface of the surface-mounted vibrator 1 through the via hole 14 having excellent thermal conductivity.

  Therefore, it becomes a constant temperature structure of the crystal unit which is excellent in heat transfer efficiency and maintains a constant temperature as compared with the conventional example. Then, the temperature control element 3 that forms the temperature control circuit and the oscillation element 3 that forms the oscillation circuit together with the surface-mounted moving element are housed in an oscillator container having a mounting terminal (not shown) to form a constant temperature oscillator. By doing so, the oscillation frequency can be made highly accurate and the height can be reduced.

  In this example, only the chip resistor 3a is provided on the laminated surface side of the first substrate 4a. However, for example, another oscillation element 2 or temperature control element 3 is provided to reduce the height dimension. You can also. Furthermore, these elements can also be arranged on the laminated surface side of the third substrate 4c.

(Third embodiment)
3 is a cross-sectional view of a constant temperature oscillator (excluding the oscillator container) based on the constant temperature structure of the crystal resonator, illustrating the third embodiment of the present invention. The description will be simplified or omitted.

  In the third embodiment, the circuit board 4 includes a first board 4a and a second board 4b. The first board 4a is made of glass epoxy and the second board 4b is made of the prepreg described above. Again, the prepreg is semi-molten and is fixed after covering the chip resistor 3a and then cured. Then, as described above, the circuit pattern (not shown) is formed on the laminated surface of the second substrate 4b and the surface of the second substrate 4b, and is electrically connected by the via hole of the second substrate 4b.

  In short, the third substrate 4c in the second embodiment is excluded. However, the via hole 14 is not formed below the bottom surface of the surface mount vibrator 1 here. Of course, a via hole may be provided in the second substrate 4b which is the lower surface of the crystal resonator. In this example as well, a resin may be used instead of the prepreg.

  Even in this case, the thickness of the second substrate 4b covering the surface-mounted vibrator 1 is set to a minimum as much as the film, so that heat from the chip resistor 3a (resistive film 3x) is concentrated on the bottom surface of the surface-mounted vibrator. Therefore, the height dimension can be further reduced as compared with the second embodiment, and the heat transfer effect can be enhanced. In the third embodiment, the oscillation element 2 and the temperature control element 3 can be arranged on the laminated surface side of the first substrate 4c as in the second embodiment to further reduce the size.

(Other matters)
In the above embodiment, the constant temperature structure is intended for the surface mount moving element. However, even in the case of a crystal resonator in which a crystal piece is held on a metal base with a lead wire (not shown) and a metal cover is covered. Applicable. In this case, the lead wire is bent so that the main surface of the crystal resonator (metal cover) faces and is fixed to the circuit board.

  In the first to third embodiments, glass epoxy is applied to at least one of the multilayer substrates. However, even if other materials such as ceramics are used, basically, an empty space that becomes the lower surface of the surface mount vibrator is used. A surface-mounted vibrator can be arranged at the location to enhance the heat transfer effect, and this is not excluded from the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a first embodiment of the present invention, in which FIG. 1A is a cross-sectional view of a constant temperature oscillator based on a constant temperature structure of a crystal resonator, and FIG. 1B is a plan view of a circuit board. FIG. 6 is a cross-sectional view of a constant temperature oscillator (excluding an oscillator container) based on a constant temperature structure of a crystal resonator, illustrating a second embodiment of the present invention. It is sectional drawing of a thermostat type oscillator (however, except the container for oscillators) based on the thermostat structure of the crystal oscillator explaining 3rd Embodiment of this invention. FIG. 1A is a cross-sectional view of a constant temperature oscillator, FIG. 1B is a bottom view of a surface-mounted oscillator, and FIG. 1C is a diagram of a temperature control circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Surface mount vibrator | oscillator, 2 Oscillator element, 3 Temperature control element, 4 Circuit board 4, 5 Metal container, 6 Container body, 7 Metal cover, 8 Mounting terminal, 9 Metal pin, 10 Thermal conductive resin, 11 Airtight terminal , 12 operational amplifiers, 13 voids, 14 through holes (via holes).

Claims (6)

  A crystal unit having a crystal piece sealed and sealed and having an external terminal is disposed on a circuit board, and the operating temperature of the crystal unit is made constant by at least a temperature control element having a chip resistor for heating. In the constant temperature structure of the crystal resonator in which a resistance film is formed on one main surface of the mother body, the chip resistor is disposed in a space provided in the circuit board on the lower surface side of the crystal resonator, and the resistor One principal surface on which a film is formed is disposed to face the lower surface of the crystal resonator, and the crystal resonator is disposed on the circuit board so as to cover the void. Constant temperature structure.   2. The crystal circuit according to claim 1, wherein the circuit board includes at least first and second substrates made of glass epoxy laminated in order from the lower side, and the space is a recess formed by an opening provided in the first substrate. Constant temperature structure.   2. The circuit board according to claim 1, wherein the circuit board includes at least a first, a second, and a third board laminated in order from the lower side, the first and the third boards are made of glass epoxy and the second board is made of a prepreg or a resin, A constant temperature structure of a crystal resonator having a via hole filled with a metal in the third substrate which is the lower surface side of the chip resistor and which is the upper surface side of the chip resistor.   2. The constant temperature structure of a crystal resonator according to claim 1, wherein the circuit board is composed of at least a first substrate and a second substrate laminated in order from the lower side, and the first substrate is made of glass epoxy and the second substrate is made of prepreg or resin.   A crystal resonator holding structure having the circuit board according to claim 1, wherein a temperature control element that forms a temperature control circuit and an oscillation element that forms an oscillation circuit together with the crystal resonator are provided for an oscillator having a mounting terminal Constant temperature crystal oscillator housed in a container.   6. The constant temperature crystal oscillator according to claim 5, wherein the temperature control element and the oscillation element are disposed on the circuit board.

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