JP2009021726A - Surface-mount crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-mount crystal oscillator enhanced in productivity by reducing an influence on a frequency-temperature characteristic by heat generation of an IC chip. <P>SOLUTION: This surface-mount crystal oscillator is structured such that IC terminals of an IC chip 2 are fixed to the inner bottom surface of a vessel body 1 having an inner wall step part and formed into a recessed shape; the inner wall step part of the vessel body 1 is formed on the total circumference of the inner periphery, and has second crystal terminals 6 electrically connected to first crystal terminals of the IC chip 2 on both sides of one end; an insulation board 12 is arranged on the inner wall step part to isolate a space part with the IC chip 2 fixed therein; an extended outer peripheral part of an extraction electrode of a crystal piece 3 is fixed to a third crystal terminal 14 on the upper surface of the insulation board 12; and the extraction electrode of the crystal piece 3 is electrically connected to the first crystal terminal. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 that suppresses the influence of heat 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)
FIGS. 3A and 3B are diagrams for explaining a conventional example. FIG. 3A is a cross-sectional view of a surface-mount oscillator, and FIG. 3B is a plan view of a crystal piece.

  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 having a bottom wall 1a, an intermediate frame 1b, and an upper wall 1c, and has a concave shape with inner wall steps on both ends. The inner bottom surface of the container body 1 has, for example, a first crystal terminal, a circuit terminal 5 serving as a power source, an output, an earth, and a standby terminal.

  Of the circuit terminals 5, the first crystal terminal is connected to the second crystal terminal 6 on the inner wall step through the wiring path, and the circuit terminals 5 other than this are connected to the external terminal 7 on the outer bottom surface of the container body 1. The IC chip 2 integrates at least an oscillation circuit, and an IC end (not shown) of 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 quartz crystal piece 3 has excitation electrodes 9 on both main surfaces as AT cuts, and both ends of one end portion of the extraction electrode 10 are fixed to the inner wall step portion on one end side of the container body 1 by the conductive adhesive 11. The other end portion of the crystal piece 3 is positioned above the inner wall step portion on the other end side to reduce the amplitude fluctuation width at the time of impact or the like.

  The frequency-temperature characteristic of the crystal resonator (crystal piece 3) is AT-cut, so that a cubic curve having an inflection point in the vicinity of room temperature 25 ° C. is obtained (curve a in FIG. 4). 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, it has a maximum value T1 (for example, −5 ° C.) at a temperature point below about 25 ° C. and a minimum value T2 (at 65 ° C.) at a temperature point of 25 ° C. or more. These temperature characteristics vary depending on the cutting angle.

  In this case, for example, compared with a linear cubic curve having only a third-order term, the temperature changes from near 25 ° C. to low temperature and high temperature by setting the oscillation frequency around 25 ° C. to the nominal frequency. 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 below the maximum value T1 and the minimum value T2 are made steep.

Thereby, for example, the temperature standard where 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 Japanese Patent Laid-Open No. 2003-69366 Japanese Patent Application No. 2006-151801

(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, the smaller the surface-mount oscillator, the greater the influence of heat generated by the IC chip 2, 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. . 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 (curve b in FIG. 4).

  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 specification 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.

(First solving means)
According to the present invention, as shown in the claims (Claim 1), an IC chip is fixed to the inner bottom surface of the concave container body, and a crystal piece is electrically connected to the inner wall step portion of the container body. In the surface-mount crystal oscillator having the first crystal terminal, the inner wall step is formed around the inner periphery of the container body, and an insulating substrate is disposed on the inner wall step to fix the IC chip. A structure in which the space portion formed is cut off, an outer peripheral portion of the extraction electrode of the crystal piece is fixed on the insulating substrate, and the extraction electrode of the crystal piece is electrically connected to the first crystal terminal; To do.

(Second solution)
In the crystal oscillator for surface mounting, the IC chip is fixed to the inner bottom surface of the concave container body, and the first wall terminal is electrically connected to the crystal piece on the inner wall step of the container body. Is a two-stage upper and lower stages, the lower stage is formed around the inner circumference of the container body, an insulating substrate is disposed in the lower stage to block the space where the IC chip is fixed, and the crystal piece The extended outer peripheral portion of the lead electrode is fixed to the upper first crystal terminal.

  With such a configuration of the first and second solving means, the IC chip and the crystal piece are separated from each other by the insulating substrate, and in particular, the gap between the IC chip and the crystal piece is blocked. Therefore, direct heat due to heat generated by the IC chip can be blocked and convection heat can be blocked. Moreover, since it is an insulating substrate, its heat conductivity is inferior to that of a metal plate, so that an increase in temperature due to heat from the insulating substrate can also be suppressed.

(First embodiment)
FIG. 1 is a sectional view of a surface mount oscillator for explaining a first embodiment of the present invention. 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 has the IC terminal of the IC chip 2 fixed to the inner bottom surface of the container body 1 having an inner wall stepped portion and having a concave shape by ultrasonic thermocompression bonding using the bumps 8. The IC terminal of the IC chip 2 is connected to the circuit terminal on the inner bottom surface. A crystal piece 3 is disposed above the IC chip 2.

  In this embodiment, the inner wall step portion of the container body 1 is provided on the entire inner circumference, and has the second crystal terminal 6 that is electrically connected to the first crystal terminal of the IC chip on both sides of the one end portion as described above. . Then, for example, the outer periphery of the lower surface of the insulating substrate 12 made of ceramic is fixed to the inner wall step portion by the insulating adhesive 13 to block the space portion to which the IC chip 2 is fixed.

  The insulating substrate 12 has third crystal terminals 14 on both sides of one end of the upper surface, and is electrically connected to, for example, the fourth crystal terminal 15 on the lower surface via the outer surface. First, for example, both ends of one end of the crystal piece are fixed to the third crystal terminal 14 on the upper surface in advance by the conductive adhesive 11. Next, a conductive adhesive (not shown) is applied to the second crystal terminal 6 on the inner wall step portion of the container body 1, and an insulating adhesive 13 is applied to the entire surface including the outside thereof, followed by heat curing.

  Alternatively, after the insulating substrate 12 is fixed on the inner wall step in the same manner, both sides of one end of the crystal piece are fixed to the third crystal terminal with a conductive adhesive. Finally, the cover 4 is placed on the opening end surface of the container body 1 to hermetically enclose the IC chip 2 and the crystal piece 3.

(Second Embodiment)
FIG. 2 is a cross-sectional view of a surface mount oscillator for explaining an embodiment of the present invention. In addition, description of the same part as 1st Embodiment is abbreviate | omitted or simplified.

  In 2nd Embodiment, the step part of the container main body 1 is made into two steps of an up-and-down stage. The lower stage goes around the entire inner circumference. In the lower stage, the outer periphery of the lower surface of the insulating substrate 12 is fixed by the insulating adhesive 13 to block the space where the IC chip 2 is fixed. The crystal piece 3 is fixed to the upper second crystal terminal 6 by the conductive adhesive 11 at both ends of the extended end portion of the extraction electrode.

  In each of these embodiments, the IC chip 2 and the crystal piece 3 are accommodated in an independent space by the insulating substrate 12, and the IC chip 2 and the crystal piece 3 are blocked by the insulating substrate 12 in particular. Therefore, as described in the column of the effect of the invention, direct heat due to heat generation of the IC chip 2 can be blocked and convection heat can be blocked. Further, since the insulating substrate 12 is inferior in heat conductivity as compared with the metal plate, the temperature rise due to heat from the insulating substrate 12 can be suppressed.

It is sectional drawing of the surface mount oscillator explaining 1st Embodiment of this invention. It is sectional drawing of the surface mount oscillator explaining 2nd Embodiment of this invention. It is a figure explaining a prior art example, the figure (a) is a sectional view of a surface mount oscillator, and the figure (b) is a top view of a crystal piece. It is a frequency-temperature characteristic view of a crystal resonator (crystal oscillator) illustrating a problem of a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container wooden body, 2 IC chip, 3 Crystal piece, 4 Cover, 5 Circuit terminal, 6 2nd crystal terminal, 7 External terminal, 8 Bump, 9 Excitation electrode, 10 Lead electrode, 11 Conductive adhesive agent, 12 Insulating substrate , 13 Insulating adhesive, 14 3rd crystal terminal, 15 4th crystal terminal

Claims (2)

  In the crystal oscillator for surface mounting, the IC chip is fixed to the inner bottom surface of the concave container body, and the first wall terminal is electrically connected to the crystal piece on the inner wall step of the container body. Is formed by circling the inner periphery of the container body, and an insulating substrate is disposed on the inner wall step portion to block the space portion to which the IC chip is fixed, and the outer periphery of the crystal piece lead electrode is extended. A crystal oscillator for surface mounting, wherein a portion is fixed on the insulating substrate and the extraction electrode of the crystal piece and the first crystal terminal are electrically connected.   In the crystal oscillator for surface mounting, the IC chip is fixed to the inner bottom surface of the concave container body, and the first wall terminal is electrically connected to the crystal piece on the inner wall step of the container body. Is a two-stage upper and lower stages, the lower stage is formed around the inner circumference of the container body, an insulating substrate is disposed in the lower stage to block the space where the IC chip is fixed, and the crystal piece A surface-mount crystal oscillator characterized in that an extended outer peripheral portion of the lead electrode is fixed to the upper first crystal terminal.

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