JP5057693B2 - Temperature-compensated crystal oscillator for surface mounting - Google Patents

Description

  The present invention relates to a surface-mounted temperature-compensated crystal oscillator (hereinafter referred to as a temperature-compensated oscillator), and more particularly to a surface-mounted oscillator that ensures temperature compensation at startup.

(Background of the Invention)
A temperature-compensated oscillator for surface mounting is small and light and has high frequency stability with respect to temperature changes, and is therefore built in as a frequency source particularly in portable devices such as mobile phones in which the temperature environment changes. One of such devices is a temperature compensated oscillator in which a temperature compensation mechanism and an oscillation circuit are integrated in an IC chip and hermetically sealed together with a crystal piece.

(Example of conventional technology)
FIG. 4 is a diagram for explaining a conventional example. FIG. 4A is a sectional view of a temperature compensated oscillator for surface mounting, FIG. 4B is a schematic circuit block diagram, and FIG. 4C is an IC chip. FIG. 4D is a plan view of the crystal piece.

The temperature compensated oscillator includes an IC chip 2 and a crystal piece 3 in a concave container body 1 having an inner wall step portion 1 a and a metal cover 4. The container body 1 is made of laminated ceramic, and has a mounting terminal 5 on the outer bottom surface 1b and a temperature compensation data writing terminal (not shown) on the outer surface 1c . A circuit terminal (not shown) is provided on the inner bottom surface 1d of the container body 1, and a crystal holding terminal is provided on the inner wall step portion 1a .

  The IC chip 2 has an IC terminal 15 on one main surface as a circuit function surface, and integrates an oscillation circuit 6 and a temperature compensation mechanism 7 excluding a crystal resonator (crystal piece 3). The IC terminal 15 has at least a pair of crystal terminals, a power source, an output, and a ground terminal, and further has a temperature compensation data write terminal and the like. Each IC terminal 15 is formed on both sides including at least a diagonal portion of one main surface which is a circuit function surface of the IC chip 2.

  Then, one main surface of the IC chip 2 faces the inner bottom surface of the container body 1, and each IC terminal 15 is connected to a circuit terminal on the inner bottom surface by ultrasonic thermocompression using, for example, a bump 8 made of gold. Alternatively, at least the surface of the bump 8 is fixed by reflow using solder. Each IC terminal 15 is connected to a corresponding mounting terminal 5, crystal holding terminal and writing terminal of the container body 1.

  In this case, the space between one main surface of the IC chip 2 and the inner bottom surface of the container body 1 is left as it is, and no resin (so-called underfill) that protects the circuit function surface is applied. This is because the IC chip 2 is hermetically sealed together with the crystal piece 3 and is shielded and protected from the outside, so that no underfill is required.

  The oscillation circuit 6 includes, for example, an inverter amplification element made of CMOS (not shown) and a resonance circuit as a feedback circuit. The resonance circuit includes a crystal resonator (crystal piece 3) and a divided capacitor in the IC chip 2. The temperature compensation mechanism 7 has a temperature sensor composed of a resistor or the like that detects the ambient temperature, and generates a compensation voltage Vc in response to the ambient temperature. The compensation voltage Vc is generated by temperature compensation data from the write terminal based on a frequency temperature characteristic measured in advance.

The crystal piece 3 has excitation electrodes 9 on both main surfaces, and extends extraction electrodes 10 on both sides of one end. Both ends of the extended end portion of the extraction electrode 10 are fixed to the crystal holding terminal of the inner wall step portion 1 a by the conductive adhesive 11. Then, it is electrically connected to the crystal terminal of the IC chip 2 to form a dividing capacitor and a resonance circuit. The metal cover 4 is joined to a metal ring 12 provided on the opening end surface 1e of the container body 1 by seam welding or the like.

In such a case, a compensation voltage Vc based on a change in resistance value (ambient temperature) by the temperature sensor of the temperature compensation mechanism 7 is applied to the voltage variable capacitance element 13 inserted in the oscillation circuit 6 (oscillation loop). As a result, the load capacity as viewed from the crystal resonator is variable, and therefore, for example, the frequency temperature characteristic of a cubic curve depending on the crystal resonator (crystal piece 3) is flattened, and the frequency stability with respect to temperature is increased.
Japanese Patent Laying-Open No. 2003-101348 (for example, FIG. 1)

(Problems of conventional technology)
However, the temperature compensated oscillator having the above configuration has a problem that the frequency stability is deteriorated at the time of start-up and the standard is not sufficiently satisfied. That is, when the temperature compensated oscillator is started, the temperature of the IC chip 2 itself becomes higher than the ambient temperature due to heat generated by an active element such as an oscillation amplifier or a buffer amplifier caused by a circuit current generated in the IC chip 2.

  On the other hand, the crystal resonator (crystal piece 3) operates at a vibration frequency in response to the ambient temperature. Therefore, the temperature sensor in the temperature compensation mechanism integrated in the IC chip 2 detects a temperature higher than the operating temperature of the crystal resonator (crystal piece 3), and uses the compensation voltage Vc based on this as the voltage variable capacitance element 13. Apply to. For example, the temperature sensor detects, for example, 30 ° C., which is higher than this, even though the crystal resonator is operating at 25 ° C. which is the nominal frequency fo.

  Then, the temperature compensation mechanism 7 applies a compensation voltage Vc based on the detected temperature of 30 ° C. to the voltage variable capacitance element 13. Therefore, since the oscillation frequency f changes from the nominal frequency fo, the frequency stability is deteriorated at startup. However, if the temperature of the IC chip 2 and the crystal piece 3 approaches and becomes the same with the passage of time from the start-up, the temperature compensation operation functions normally and satisfies the frequency stability within the standard.

  In this case, in particular, in the cellular phone, the temperature compensation oscillator is activated in response to the clock frequency, and the ON / OFF operation is repeated. Therefore, the malfunction of the temperature compensation operation due to the temperature difference between the IC chip 2 and the crystal resonator at the time of startup increases the problem. Note that the power supply voltage is intermittently operated at the clock frequency in order to save power.

(Object of invention)
An object of the present invention is to provide a surface-mounted temperature compensated oscillator that maintains a frequency stability by improving the temperature compensation operation at startup.

(Points of interest)
The present invention pays attention to the temperature distribution of the IC chip, that is, the temperature distribution in which both sides where the IC terminals 15 are located are radiated through the bumps and the circuit terminals, so that the temperature is lower than the central region. In this case, the heat radiation effect from the IC terminals connected to the mounting terminals such as the power source, the ground, and the output is particularly great.

  According to the first aspect of the present invention, a temperature compensation mechanism having an oscillation circuit and a temperature sensor and supplying a compensation voltage to the voltage variable capacitance element of the oscillation circuit is integrated to provide a circuit function. An IC chip having IC terminals on both sides including at least a diagonal portion of one main surface serving as a surface is fixed to the inner bottom surface of the container body made concave by ultrasonic thermocompression using a bump, and the inner wall step of the container body In the surface-compensated temperature-compensated crystal oscillator in which both sides of one end of the crystal piece are fixed to the part, the active element serving as the heat source of the oscillation circuit and the temperature sensor of the temperature compensation mechanism are the diagonal region of the IC chip. It is set as the structure arrange | positioned spaced apart.

  According to another aspect of the present invention, a temperature compensation mechanism that includes an oscillation circuit and a temperature sensor and supplies a compensation voltage to the voltage variable capacitance element of the oscillation circuit is integrated to provide a circuit function. An IC chip having IC terminals on both sides including at least the diagonal portion is fixed to the inner bottom surface of the container body made concave by ultrasonic thermocompression using bumps, and one end of the crystal piece is attached to the inner wall step of the container body. In the surface-compensated crystal oscillator for surface mounting in which both sides are fixed, an IC terminal for heat radiation fixed by ultrasonic thermocompression using the bump is provided in the central region of the IC chip.

  If it is the structure of Claim 1 in this invention, an active element and a temperature sensor are spaced apart and arrange | positioned in the diagonal part area | region in which an IC terminal is located. In this case, as indicated by the point of interest, the IC terminal is located at the diagonal portion of the IC chip, and the temperature decreases. That is, heat generation in one diagonal region where the active element serving as a heat source is disposed is dissipated through the IC terminals, bumps, and circuit terminals in one diagonal portion, thus preventing heat accumulation.

  In addition, the other diagonal region where the temperature sensor is disposed is farthest from the heat source in one diagonal region and radiates heat through the IC terminals, bumps, and circuit terminals. The temperature rise is suppressed by heat dissipation. Therefore, the temperature detected by the temperature sensor decreases the influence of the temperature rise due to the heat generation source and approaches the ambient temperature that is the operating temperature of the crystal unit.

  As a result, the temperature sensor detects the temperature close to the operating temperature (ambient temperature) of the crystal unit and generates a compensation voltage according to the operating temperature even if the temperature rises due to the heat source when the temperature compensated oscillator starts up. It can be supplied to the voltage variable capacitance element of the oscillation circuit. Therefore, the frequency stability at the time of starting the temperature compensation oscillator can be increased.

  With the configuration of the third aspect, since the heat generating IC terminal 15 fixed by ultrasonic thermocompression using a bump is provided in the central region of the IC chip, the heat radiation effect can be enhanced together with the IC terminals on both sides. Accordingly, similarly to the first aspect, the temperature rise due to the heat source is suppressed, and the detected temperature close to the operating temperature (ambient temperature) of the crystal resonator and the compensation voltage corresponding thereto are obtained. Thereby, the frequency stability at the time of starting of a temperature compensation oscillator can be raised.

(Embodiment section)
According to a second aspect of the present invention, in the first aspect, the IC terminal of the diagonal portion is electrically connected to a mounting terminal provided on the outer bottom surface of the container body. As a result, the mounting terminals such as the power source, the ground, and the output terminal are connected to the circuit pattern of the set substrate, thereby enhancing the heat dissipation effect.

  According to the fourth aspect of the present invention, in the third aspect of the present invention, the active element serving as the heat source of the oscillation circuit and the temperature sensor of the temperature compensation mechanism are disposed apart from each other in the diagonal region of the IC chip. Therefore, the effects of claim 1 and claim 3 are synergistic, and the temperature detected by the temperature sensor is closer to the operating temperature of the crystal resonator.

  In the fifth aspect of the present invention, in the first, second, third, or fourth aspect, a thermally conductive adhesive in which thermally conductive particles are mixed in an adhesive matrix is applied to the outer periphery of the side surface of the IC chip. According to this, the heat generated by the heat source body can be further radiated by the heat conductive adhesive. Therefore, the temperature detected by the temperature sensor is closer to the operating temperature of the crystal resonator, and the frequency stability at the time of startup is further increased.

  FIG. 1 is a diagram of a surface-mounted temperature-compensated oscillator for explaining an embodiment of the present invention. FIG. 1 (a) is a sectional view and FIG. 1 (b) is a plan view of an IC chip. 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.

In the temperature compensated oscillator, as described above, the circuit function surface of the IC chip 2 in which the oscillation circuit 6 and the temperature compensation mechanism 7 are integrated is fixed to the inner bottom surface of the container body 1 by ultrasonic thermocompression bonding using the bumps 8 or by reflow. . IC terminals 15 are provided on both sides including a diagonal portion of one main surface which is a circuit function surface of the IC chip. Further, both ends of one end of the crystal piece 3 from which the extraction electrode 10 extends are fixed to the inner wall step portion 1 a of the container body 1 by the conductive adhesive 11. And the metal cover 4 is joined to the opening end surface 1e of the container main body 1 via the metal ring 12, and is sealed and sealed.

  In this embodiment, active elements 16a serving as heat sources such as an oscillation amplifier and a buffer amplifier in an oscillation circuit integrated in an IC chip are arranged in one diagonal region, and one diagonal portion It is brought close to the IC terminal 15a. Further, the temperature sensor 16b of the temperature compensation mechanism is arranged in the other diagonal region and is brought close to the IC terminal 15b in the other diagonal portion. The diagonal IC terminal 15 (ab) is a power source, a ground, and an output terminal electrically connected to the mounting terminal 5.

  Then, an IC terminal 15c for heat dissipation is provided in the central region of one main surface of the IC chip. Here, three IC terminals 15c for heat dissipation are provided in parallel with the IC terminals 15 on both sides. The IC terminal 15c for heat dissipation is fixed to the circuit terminal on the inner bottom surface by ultrasonic thermocompression bonding or reflow using a bump. The IC terminal 15 c for heat dissipation is connected to the ground terminal in the mounting terminal 5.

  With such a configuration, as described in the column of the effect of the invention, the active element 16a and the temperature sensor 16b serving as a heat generation source are disposed adjacent to the IC terminal 15 (ab). Therefore, due to heat dissipation through the IC terminal 15 (ab), the bump 8 and the circuit terminal, the temperature of the diagonal region of the active element 16a and the temperature sensor 16b decreases.

  Moreover, the diagonal part area | region where the active element 16a used as a heat generating source and the temperature sensor 16b are arrange | positioned most is separated. Therefore, the temperature detected by the temperature sensor 16b is less affected by the temperature generated by the active element 16a. Furthermore, since the IC terminal 15c for heat dissipation is provided in the central area of the IC chip to dissipate heat, the temperature of the IC chip is lowered as a whole together with the IC terminals 15 on both sides.

  For these reasons, even when the temperature compensation oscillator starts up, even if there is a temperature rise due to the heat source, particularly the active element 16a, the temperature sensor 16b has a temperature close to the ambient temperature that is the operating temperature of the crystal resonator (crystal piece 3). To detect. The compensation voltage Vc corresponding to the operating temperature can be supplied to the voltage variable capacitance element 13 of the oscillation circuit 6. Therefore, the frequency stability at the time of starting the temperature compensation oscillator can be increased. This is particularly useful for a temperature compensated oscillator that operates intermittently in response to a clock pulse, such as a cellular phone.

(Second Embodiment)
FIG. 2 is a view of a surface mount oscillator for explaining a second embodiment of the present invention. FIG. 2 (a) is a sectional view and FIG. 2 (b) is a plan view excluding a cover and a metal ring. In addition, the same number is given to the same part as previous embodiment, and the description is simplified or abbreviate | omitted.

  In the second embodiment, in addition to the configuration of the first embodiment, the heat conductive adhesive 14 is applied to the entire outer periphery of the side surface of the IC chip 2. In this case, the outer periphery of the side surface of the IC chip 2 is fixed to the inner bottom surface of the container body 1 by the heat conductive adhesive 14. Here, it fills between the outer periphery of the IC chip 2 and the inner wall of the container body 1. The heat conductive adhesive 14 is made of epoxy based adhesive matrix, and a heat conductive material made of an insulating material such as ceramic (not shown) is mixed into the adhesive matrix.

  With such a configuration, even if the IC chip 2 generates heat due to the circuit current when the temperature compensated oscillator is started, the heat is dissipated to the container body 1 made of the laminated ceramic via the heat conductive adhesive 14. In this case, the volume of the container body 1 with respect to the IC chip 2 is remarkably large and the heat capacity is large, so that the temperature rise of the IC chip 2 is suppressed. Here, since the heat conductive adhesive 14 adheres not only to the inner bottom surface of the container body but also to the inner wall, the heat dissipation effect is enhanced.

  Therefore, the temperature detected by the temperature sensor of the temperature compensation mechanism 7 integrated in the IC chip 2 at the time of starting the temperature compensated oscillator can be made closer to the operating temperature of the crystal resonator as compared with the first embodiment. From this, even at the time of startup, the actual operating temperature of the crystal resonator can be detected and normal temperature compensation can be performed, and the frequency stability can be increased.

  Further, since the outer periphery of the side surface of the IC chip 2 is fixed over the entire periphery, the fixing strength can be increased with respect to the inner bottom surface of the container body 1 as compared with the case of using only the bumps 8 by ultrasonic thermocompression bonding. In addition, since the adhesive base is made of epoxy, for example, the fixing strength is further increased as compared with silicon. Furthermore, since ceramic is used as the heat conducting material, sufficient insulation is ensured to enhance heat conductivity.

(Other matters)
In the above embodiment, the IC terminals 15c for heat radiation are individually formed. However, as shown in FIG. 3, even if each IC terminal 15c is continuously formed in a planar shape with a large area, the circuit terminals to be connected are the same. It is good also as a planar shape continuously. In these cases, the heat dissipation effect can be enhanced by the increase in the area.

  In addition, the heat conductive adhesive 14 is filled (applied) between the entire outer periphery of the side surface of the IC chip 2 and the inner wall surface of the container body 1, but even if applied intermittently as necessary, for example, a temperature sensor It may be only the outer periphery of the side surface where it is located, and can be applied basically from the viewpoint of starting characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a first embodiment of the present invention, where FIG. 1A is a cross-sectional view of a temperature compensated oscillator, and FIG. 1B is a plan view of an IC chip. It is a figure of the temperature compensation oscillator explaining 2nd Embodiment of this invention, The figure (a) is sectional drawing, The figure (b) is a top view except a cover and a metal ring. It is a top view of the IC chip explaining the other example of this invention. FIG. 4A is a cross-sectional view of a temperature compensated oscillator for surface mounting, FIG. 2B is a schematic circuit block diagram, FIG. 1C is a plan view of an IC chip, and FIG. FIG. 4D is a plan view of the crystal piece.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Container body, 2 IC chip, 3 Crystal piece, 4 Metal cover, 5 Mounting terminal, 6 Oscillation circuit, 7 Temperature compensation mechanism, 8 Bump, 9 Excitation electrode, 10 Lead electrode, 11 Conductive adhesive, 12 Metal ring, 13 Voltage variable capacitance element, 14 Thermal conductive adhesive, 15 IC terminal, 15c IC terminal for heat radiation, 16a Active element, 16b Temperature sensor.

Claims (3)

A temperature compensation mechanism having an oscillation circuit and a temperature sensor and supplying a compensation voltage to the voltage variable capacitor of the oscillation circuit is integrated, and IC terminals are provided on both sides including at least a diagonal portion of one main surface serving as a circuit function surface. In a temperature-compensated crystal oscillator for surface mounting in which an IC chip having a concave shape is fixed to the inner bottom surface of a container body using a bump, and both ends of one end of a crystal piece are fixed to the inner wall step of the container body.
An IC terminal for heat dissipation is provided in the central area of the IC chip,
The IC terminal of the diagonal part in the IC chip is any one of a power source, a ground, and an output terminal electrically connected to a mounting terminal provided on the outer bottom surface of the container body,
The active element serving as a heat source of the oscillation circuit and the temperature sensor of the temperature compensation mechanism are arranged separately in the diagonal region of the IC chip ,
The inner bottom surface of the container body and the outer periphery of the side surface of the IC chip are fixed by application of a heat conductive adhesive in which heat conductive particles are mixed in an adhesive matrix
A temperature-compensated crystal oscillator for surface mounting, which maintains a frequency stability by improving a temperature compensation operation at the time of startup . In claim 1,
A temperature-compensated crystal oscillator for surface mounting, wherein the thermally conductive adhesive is applied to all of the inner bottom surface of the container body and the outer periphery of the side surface of the IC chip . In claim 1,
A temperature-compensated crystal oscillator for surface mounting, wherein the thermally conductive adhesive is applied only to the position of the temperature sensor on the inner bottom surface of the container body and the outer periphery of the side surface of the IC chip .