JP2008294585A - Crystal oscillator for surface mounting - Google Patents

Abstract

Provided is a surface-mount oscillator in which productivity is improved by reducing an influence on frequency temperature characteristics due to heat generation of an IC chip.
SOLUTION: A container main body 1 made of ceramic having a recess for accommodating an IC chip 2 and a crystal piece is provided, and a plurality of IC terminals provided on a pair of opposing sides of a circuit function surface of the IC chip 2; In the crystal oscillator for surface mounting, wherein a plurality of circuit terminals 5 which are provided in both side regions along the longitudinal direction of the inner bottom surface of the container body 1 and which are connected to the IC terminals are connected using bumps, At least one of the plurality of circuit terminals 5 is configured to extend along the longitudinal direction of the central region between the both side regions.
[Selection] Figure 1

Description

  The present invention relates to a surface mount crystal oscillator (hereinafter referred to as a surface mount oscillator), and more particularly to a surface mount oscillator with an improved heat dissipation effect from an IC chip.

(Background of the Invention)
Since surface-mounted oscillators are small and lightweight, they are built in as a frequency and time reference source, especially in portable electronic devices. In recent years, with the miniaturization, the influence of heat generated by the IC chip has been regarded as a problem.

(Example of conventional technology)
FIG. 5 is a diagram for explaining a conventional example. FIG. 5A is a cross-sectional view of a surface mount oscillator, FIG. 5B is a plan view excluding a cover, and FIG. 5C is a plan view of a crystal piece. is there.

  The surface mount oscillator contains an IC chip 2 and a crystal piece 3 in a container body 1 and is covered and sealed with a cover 4. The container body 1 is made of a laminated ceramic and has a concave shape with an inner wall step. And the inner bottom surface of the container main body 1 has a plurality of, for example, three circuit terminals 5 in both side regions along the longitudinal direction. The two circuit terminals 5 are the crystal terminals at the center and the four terminals on both sides are the power supply, output, ground and standby terminals.

  The two in the center are extended to the upper surface of the second layer by via holes indicated by black dots, and are connected to the crystal holding terminals 6 through wiring lines. Further, the circuit terminals 5 on both sides are connected to the external terminals 7 on the external bottom surface through the laminated surface of the first layer and the second layer. The IC chip 2 integrates at least an oscillation circuit, and an IC terminal (not shown) on the circuit function surface is fixed to the inner bottom surface of the recess by ultrasonic thermocompression using the bumps 8 (so-called flip chip bonding).

  The crystal piece 3 has excitation electrodes 9 on both main surfaces as AT cuts, and both ends of the extended end portion of the extraction electrode 10 are fixed to the inner wall step portion of the container body 1 by the conductive adhesive 11. The frequency-temperature characteristic of the crystal resonator (crystal piece 3) is a cubic curve having an inflection point in the vicinity of room temperature 25 ° C. by AT cut (FIG. 6). In the cubic curve, the coefficients of the third order, the second order, and the first order change depending on the cutting angle.

  In this example, a cutting angle having a maximum value T1 (for example, −5 ° C.) at a temperature point near 25 ° C. and a minimum value T2 (at 65 ° C.) at a temperature point of 25 ° C. or more. Thereby, for example, compared with a linear cubic curve having only a third-order term, by changing the oscillation frequency around room temperature 25 ° C. to the nominal frequency, the temperature changes from around room temperature 25 ° C. to the low temperature side and the high temperature side. Can also reduce the frequency change.

Normally, the slope characteristic (gradient) from the maximum value T1 to the minimum value T2 is made gentle, and the slope characteristics of the maximum value T1 or less and the minimum value T2 or more are made steep. Thereby, for example, the temperature standard in which the range from −10 ° C. to 70 ° C. is within α (10) ppm is satisfied. The frequency temperature characteristic of the crystal oscillator is basically the same as the frequency temperature characteristic of the crystal resonator. The cover 4 is joined to the opening end surface of the container body 1 by seam welding, glass sealing, or the like.
JP 2007-67967 A

(Problems of conventional technology)
However, in the surface mount oscillator configured as described above, the temperature inside the container body 1 also increases due to the heat generation temperature of the IC chip 2. For this reason, the oscillation frequency of the crystal oscillator in the vicinity of the room temperature of 25 ° C. also changes, causing a deviation from the nominal frequency. For this reason, conventionally, it is necessary to cope with, for example, changing the cutting angle of the crystal piece 3 in view of the deviation from the nominal frequency after the assembly of the oscillator.

  However, as the size of the surface-mount oscillator progresses, for example, as the planar outer shape becomes 5.0 × 3.2 mm, the height becomes 1.2 mm or less, and the inner product becomes smaller, the influence of heat generation of the IC chip 2 becomes larger. In this case, the frequency change at the high temperature side and the low temperature side is larger than the frequency change at room temperature of 25 ° C. That is, as described above, since the slope characteristics on the high temperature side and the low temperature side are steeper than the slope characteristics with respect to the temperature in the vicinity of the normal temperature, the frequency change with respect to the temperature change also increases.

  In particular, the frequency temperature characteristic on the high temperature side, which is about 80 ° C. or higher, has a problem in that the frequency deviation Δf / f in the + direction from the reference frequency (nominal frequency) also increases and is away from the upper limit of the frequency temperature characteristic. Become. On the other hand, since the low temperature side below −20 ° C. approaches the reference frequency, there is no particular problem.

  For these reasons, the frequency deviation not only at room temperature but particularly at the high temperature side must be within the standard. Therefore, simply changing the cutting angle of the crystal piece 3 is not sufficient to reduce the productivity. there were. In addition, since the fixing is performed by flip chip bonding, the heat radiation effect is small as compared with the case where the surface opposite to the circuit function surface is fixed and the electrode is led out by wire bonding.

(Object of invention)
SUMMARY OF THE INVENTION An object of the present invention is to provide a surface mount oscillator in which productivity is improved by reducing influence on frequency temperature characteristics due to heat generation of an IC chip.

  The present invention includes a container body made of ceramic having a recess for accommodating an IC chip and a crystal piece, as set forth in the claims (Claim 1), and a set of circuit function surfaces in the IC chip. A plurality of IC terminals provided on opposite sides of the container body and a plurality of circuit terminals provided on both side regions along the longitudinal direction of the inner bottom surface of the container body and facing the IC terminals are connected using bumps. In the surface mount crystal oscillator, at least one of the plurality of circuit terminals is configured to extend along the longitudinal direction of the central region between the two side regions.

  With such a configuration, one of the circuit terminals extends to the central region of the inner bottom surface of the container body (ceramic), thereby increasing the contact area with the container body. Therefore, the heat dissipation effect to the outside through the container body can be enhanced. Therefore, the influence of heat generation of the IC chip is reduced, and the frequency temperature characteristic is made the original frequency temperature characteristic. In particular, the frequency deviation on the high temperature side is suppressed and the frequency deviation is satisfied within the standard.

(Embodiment section)
According to a second aspect of the present invention, in the first aspect, at least one of the circuit terminals is an outermost side in the arrangement direction of the plurality of circuit terminals arranged on the inner bottom surface of the container body, and along the arrangement direction. It protrudes from the outer periphery of the IC chip. Thereby, a contact area with the inner bottom face of a container main body can be enlarged further, and the thermal radiation effect can be improved.

  In the third aspect, at least one of the circuit terminals is the outermost side in the arrangement direction of the plurality of circuit terminals, and protrudes from the outer periphery of the IC chip along the arrangement direction. A plurality of circuit terminals excluding the outermost circuit terminal are positioned in the H-shaped recess. Thereby, a contact area with the inner bottom face of a container main body can be enlarged further, and the thermal radiation effect can be improved.

  According to the fourth aspect of the present invention, in the first or second aspect, the outermost circuit terminal is connected to an external terminal as a ground terminal provided on the outer bottom surface of the container body. Thereby, the electrical influence by having enlarged the area can be decreased.

  In the fifth aspect of the present invention, in the first aspect, the container body has an inner wall stepped portion, and the crystal piece is fixed to the inner wall stepped portion at both ends of the extended end portion of the extraction electrode. Thereby, the frequency temperature characteristic of the crystal oscillator in which the IC chip and the crystal piece are accommodated in the same space is favorably maintained.

(First embodiment)
FIG. 1 is a diagram for explaining a first embodiment of the present invention, and is a plan view excluding a cover of a surface mount oscillator. 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.

  As described above, the surface mount oscillator is fixed to the circuit terminal 5 provided on the inner bottom surface of the container body 1 having a concave shape by the flip chip bonding including the ultrasonic thermocompression bonding using the bumps 8 to the IC terminal 2, The both ends of the crystal piece 3 from which the extraction electrode 10 extends from the excitation electrode 9 are fixed to the inner wall step. Again, the circuit terminals on the inner bottom surface are formed in both side regions along the longitudinal direction, with the two central terminals serving as crystal terminals and both sides serving as the power supply, output, ground and standby terminals.

  And in this embodiment, the circuit terminal 5A for earth | grounding located in the outermost side of the one end side of the arrangement direction among the circuit terminals 5 extends as H shape. That is, the circuit terminal 5A for grounding protrudes from the outer periphery of the IC chip 2 along the arrangement direction, and extends to the outside of the circuit terminal 5 facing the opposite side.

  And it extends to the center area | region used as the middle of the both-sides area | region in which the circuit terminal 5 is located, and crosses. Furthermore, it extends outside the circuit terminal 5 located on the outermost side on the other end side. In short, the pattern is such that the other circuit terminals 5 are located in the concave portions on both sides of the H shape extending on the inner bottom surface of the container body 1.

  With this configuration, when the grounding IC terminal of the IC chip 2 is connected to the circuit terminal 5A by the bump 8, the heat of the IC chip 2 is transferred to the H-shaped circuit terminal 5A. Then, heat is radiated to the outside through the inner bottom surface where the H-shaped circuit terminal 5 is provided. Thereby, since the heat radiation area is made larger than in the case of the conventional circuit terminal 5, the heat radiation effect can be enhanced. Therefore, the frequency temperature characteristic of the crystal resonator is improved.

  Here, since the circuit terminal 5 for grounding is H-shaped, the electrical influence is reduced, and for example, it functions also as a shield layer.

(Second to fourth embodiments)
2 to 4 are plan views excluding the cover of the surface mount oscillator for explaining the second to fourth embodiments of the present invention. In addition, description of the same part as previous embodiment is abbreviate | omitted.

  In the second embodiment (FIG. 2), the grounding circuit terminal 5A is L-shaped and extends to the central region. Then, the outermost three circuit terminals excluding the grounding circuit terminal 5A protrude from the outer periphery of the IC chip 2 along the arrangement direction. In the third embodiment (FIG. 3), the circuit terminal 5 diagonally opposed to the grounding circuit terminal 5A is formed in an L shape and extends to the central region.

  Even in these cases, the contact area with the inner bottom surface of the circuit terminal 5 including the grounding is increased, so that the heat radiation effect is enhanced. And since the area of each of the four circuit terminals 5 is increased to dissipate heat, the heat distribution is made uniform to facilitate heat dissipation.

  In the fourth embodiment, circuit terminals 5B for two central crystal terminals are extended to the central region. Even in this case, the heat dissipation effect is enhanced. The amount of heat transferred to the crystal piece 3 through the wiring path is distributed to the pattern extending in the center, so that the temperature rise gradient of the crystal piece 3 is made gentle.

(Other matters)
In the above embodiment, the IC chip 2 and the crystal piece 3 are accommodated in the same space. For example, the container body is formed in an H shape having recesses on both main surfaces, the crystal piece 3 is set in one recess, and the other recess is set in the other recess. The same applies even when the IC chip 2 is accommodated. Furthermore, the present invention can be applied even when a concave mounting substrate containing an IC chip is bonded to the bottom surface of the surface mounting vibrator.

  In addition, when the surface mount oscillator is a temperature compensation type, the temperature detection element provided in the IC chip and the operating temperature of the crystal resonator are different, and the temperature compensation voltage from the temperature compensation mechanism should be actually compensated. Deviation from temperature compensation voltage. Therefore, the present invention can be applied even in this case.

It is a top view except the cover of the surface mount oscillator explaining 1st Embodiment of this invention. It is a top view except the cover of the surface mount oscillator explaining 2nd Embodiment of this invention. It is a top view except the cover of the surface mount oscillator explaining 3rd Embodiment of this invention. It is a top view except the cover of the surface mount oscillator explaining 4th Embodiment of this invention. FIG. 4A is a cross-sectional view of a surface mount oscillator, FIG. 2B is a plan view excluding a cover, and FIG. 3C is a plan view of a crystal piece. It is a frequency-temperature characteristic view of a crystal resonator (crystal oscillator) for explaining a problem of a conventional example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Container body, 2 IC chip, 3 Crystal piece, 4 Cover, 5 Circuit terminal, 6 Crystal holding terminal, 7 External terminal, 8 Bump, 9 Excitation electrode, 10 Lead electrode, 11 Conductive adhesive agent.

Claims (5)

  A container body made of ceramic having a recess for accommodating an IC chip and a crystal piece; a plurality of IC terminals provided on a pair of opposing sides of a circuit functional surface of the IC chip; and an inner bottom surface of the container body In a surface-mount crystal oscillator formed by connecting bumps to a plurality of circuit terminals that are provided in both side regions along the longitudinal direction of the IC terminals and face each other, at least one of the plurality of circuit terminals is provided. One surface-mount crystal oscillator characterized by extending along the longitudinal direction of a central region between the two side regions.   2. The circuit terminal according to claim 1, wherein at least one of the circuit terminals is an outermost side in the arrangement direction of the plurality of circuit terminals arranged on the inner bottom surface of the container body, and projects from the outer periphery of the IC chip along the arrangement direction. Crystal oscillator for surface mounting.   2. The at least one circuit terminal according to claim 1, wherein at least one of the circuit terminals is an outermost side in the arrangement direction of the plurality of circuit terminals, protrudes from the outer periphery of the IC chip along the arrangement direction, and is H-shaped on the inner bottom surface of the container body. A plurality of circuit terminals excluding the outermost circuit terminal, wherein the plurality of circuit terminals are located in the H-shaped recess.   3. The surface-mount crystal oscillator according to claim 1, wherein the outermost circuit terminal is connected to an external terminal serving as a ground terminal provided on the outer bottom surface of the container body.   2. The surface-mount crystal oscillator according to claim 1, wherein the container body has an inner wall step portion, and the crystal piece is fixed to the inner wall step portion at both ends of the extended end portion of the extraction electrode.

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