JP2004350247A - Piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact piezoelectric oscillator that is compatible with a broad output frequency the frequency adjustment work of which is simplified. <P>SOLUTION: The piezoelectric oscillator includes: a tabular printed circuit board on the upper side of which electronic components configuring at least an oscillation circuit are mounted and to the bottom side of which external electrodes are provided; and a piezoelectric vibrator whose external planar shape is greater than that of the printed circuit board, and the piezoelectric vibrator is fixed via a plurality of pillar members fixed to the upper side of the printed circuit board at a prescribed interval from the printed circuit board, and a space not overlapped with the printed circuit board is reserved at the bottom side of the piezoelectric vibrator, and parts of the electronic components are mounted on the space. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a piezoelectric oscillator, and more particularly to an improvement in a piezoelectric oscillator having a configuration in which a packaged piezoelectric vibrator is fixed on a package portion on which electronic components constituting an oscillation circuit and a temperature compensation circuit are mounted.
[0002]
[Prior art]
Due to the rapid progress in price reduction and miniaturization accompanying the spread of mobile communication devices such as mobile phones, not only the crystal unit and one-chip IC type crystal oscillator used in these communication devices but also the communication quality are affected. There is an increasing demand for a low-cost, small-size discrete crystal oscillator having a high CN characteristic.
[0003]
Hereinafter, conventional piezoelectric oscillators, particularly one-chip IC type piezoelectric oscillators and discrete type piezoelectric oscillators, will be described.
[0004]
Conventional one-chip IC type piezoelectric oscillators include, for example, those disclosed in Japanese Patent Application Laid-Open No. 2001-127551, and FIG. 4 is a longitudinal sectional view showing the configuration. A semiconductor component (IC chip) 51 constituting an oscillating circuit and a temperature compensation circuit, a printed wiring board (ceramic package) 53 having a recess 52 for accommodating the semiconductor component 51 on an upper surface, and accommodating the semiconductor component 51 And a piezoelectric vibrator (quartz vibrator) 54 mounted on the upper surface of the printed wiring board 53 so as to cover the opening of the recess 52. The semiconductor component 51 is accommodated in the recess 52, A piezoelectric oscillator having a structure in which the concave portion 52 is covered and closed by the piezoelectric vibrator 54, wherein the piezoelectric vibrator 54 has a flat surface of a certain size in order to secure a variable width of the oscillation frequency and to prevent an increase in the CI value. While it is necessary to secure the external shape, the semiconductor component 51 has a much smaller external size, and therefore has a sufficient size to accommodate the semiconductor component 51. In order to realize smaller and smaller and less volume reduction to the cage size, towards the printed circuit board 53 is a piezoelectric oscillator, characterized in that to reduce the external dimensions.
[0005]
2. Description of the Related Art A conventional discrete-type piezoelectric oscillator includes, for example, one disclosed in Japanese Patent Application Laid-Open No. 2002-64333, and FIG. 5 is a longitudinal sectional view showing the configuration. An electronic component 62 such as a capacitor, a resistor, and an integrated circuit that constitutes an oscillation circuit and a temperature compensation circuit is mounted on the upper surface of a flat printed wiring board 61, and a column member 63 fixed to the upper surface of the printed wiring board 61. A piezoelectric vibrator (quartz vibrator) 64 is fixed with a predetermined gap therebetween to form an oscillator. This discrete crystal oscillator is also small enough to mount the electronic component 61 by reducing the size of the electronic component 61, establishing a high-density mounting technology for the electronic component 61, and making the wiring pattern of the printed wiring board 61 finer in pitch. It is possible to achieve a reduction in size and volume by reducing the mounting area, that is, by reducing the planar outer shape of the printed wiring board 61.
[0006]
[Patent Document 1]
JP-A-2001-127551.
[Patent Document 2]
JP-A-2002-64333.
[0007]
[Problems to be solved by the invention]
The frequency adjustment of the conventional one-chip IC type crystal oscillator is completed by inputting temperature compensation data and the like to the memory section of the semiconductor component 51 from a side electrode (not shown) provided on the side of the printed wiring board 53. . However, the frequency adjustment of the conventional discrete crystal oscillator is performed by replacing or adding an adjustment electronic component 67 such as a capacitor and a resistor for correcting the variation of the standard value of each of the electronic components 62 and adjusting to a desired output frequency. However, when the printed wiring board 61 is made smaller than the planar outer shape of the crystal unit 64, it becomes extremely difficult to replace or add an electronic component 67.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a piezoelectric oscillator that is small and that can handle a wide output frequency with a variable width.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a flat printed wiring board having at least an electronic component constituting an oscillation circuit mounted on an upper surface thereof and an external electrode provided on a lower surface; A piezoelectric vibrator having a larger planar outer shape with respect to the wiring board, wherein the piezoelectric vibrator is fixed at a predetermined gap via a plurality of column members fixed to the upper surface of the printed wiring board. A space that does not overlap with the printed wiring board is secured on the bottom surface of the piezoelectric vibrator, and a part of the electronic component is mounted in the space.
[0010]
The invention according to claim 2 is characterized in that, in claim 1, a part of the electronic component is an electronic component for frequency adjustment.
[0011]
According to a third aspect of the present invention, in the second aspect, the electronic component for frequency adjustment is a laser trimmable chip component.
[0012]
According to a third aspect of the present invention, in any one of the first to third aspects, the number of the pillar members is three.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiments of the present invention.
[0014]
FIG. 1 is a longitudinal sectional view of a crystal oscillator serving as a piezoelectric oscillator according to an embodiment of the present invention, and FIG. 2 is a bottom view of a crystal resonator according to the embodiment of the present invention.
A crystal oscillator 1 according to an embodiment of the present invention includes a flat printed wiring board 2 having a plurality of electronic components 3 constituting an oscillation circuit and a temperature compensation circuit mounted on lands 5 on an upper surface and having external electrodes 4 on a bottom surface. And a quartz oscillator 11 fixed at a predetermined gap via a column member 20 fixed to the upper surface of the printed wiring board 2. It has a structure in which the lower part of the pillar member 20 is electrically and mechanically fixed to the pillar member fixing pattern 6 and the upper part is electrically and mechanically fixed to the bottom electrodes 16a and 16b. Since the crystal resonator 11 is slightly larger than the planar outer shape of the printed wiring board 2, a space that does not overlap with the printed wiring board 2 can be secured on the bottom surface of the crystal resonator 11, and a part of the electronic components, particularly frequency adjustment, is provided in the space. Electronic components (capacitors) 21 are mounted.
The column member 20 is a metal ball slightly larger than the tallest electronic component of the electronic component 3 and the capacitor 21, for example, a metal ball having a diameter of about 0.1 to 0.3 mm or a resin ball whose surface is covered with a conductive film.
The printed wiring board 2 includes the lands 5 and the column member fixing pattern 6 (substantially circular shape) formed on the upper surface, and the external electrodes 4 formed on the bottom surface. The column member fixing pattern 6 is provided with predetermined lands 5, the external electrodes 4, and a shield layer (not shown).
The quartz resonator 11 has a substantially rectangular package including a package body 12a having a recess and a metal lid 12b for hermetically sealing the recess, and a substantially rectangular quartz resonator element supported in the recess. And four bottom electrodes 16a and 16b are provided at appropriate locations on the bottom surface of the package body 12a. As shown in FIG. 2, each of the bottom electrodes 16a arranged on one diagonal is a ground electrode electrically connected to the metal lid 12b, and each of the bottom electrodes 16b arranged on the other diagonal is arranged on the quartz vibrating element 15. The connection electrodes are electrically connected to an excitation electrode (not shown) to be provided, and the bottom electrodes 16a and 16b have a circular shape for connection to the column member 20 (sphere). A pad electrode 17 for mounting the capacitor 21 is formed near one of the short sides, and is electrically connected to the bottom electrode 16b via a lead electrode extending from the pad 17.
[0015]
When fixing the pillar member 20 on the printed wiring board 2, reflow connection using cream solder applied on the pillar member fixing pattern 6 by screen printing is possible. That is, in this screen printing, the operation of applying cream solder to the land 5 is also performed at the same time, and the electronic component 3 and the column member 20 are placed on the land 5 and the column member fixing pattern 6 to which cream solder has been applied, respectively. Then, the electronic component 3 and the column member 20 are fixed by simultaneously heating in the reflow furnace and then cooling. After fixing the column member 20 on the printed wiring board 2, the bottom electrode of the crystal unit 11 may be fixed above the column member 20 using a conductive adhesive or the like. The connection between the upper part of the column member 20 and the bottom electrode may be performed simultaneously with the reflow connection of the electronic component 33 and the like.
[0016]
The frequency adjustment of the crystal oscillator 1 is based on the result of measuring the required frequency, and the oscillation frequency of the crystal oscillator at a predetermined temperature is changed from the reference frequency by the amount of displacement from the prepared capacitor 21 having several different capacities. Frequency adjustment, that is, a desired output frequency is obtained by selecting a capacitor having capacitance and mounting it on the pad electrode 17. As the adjusting capacitor 21, a laser trimmable capacitor having a metal electrode for trimming on one main surface may be adopted. The metal electrode is mounted on the pad electrode 17 with the metal electrode facing downward, and the metal electrode is trimmed with a laser beam (the trimming electrode 22 is deleted with the laser beam) until a set value is obtained while measuring a required frequency. A desired capacitance, that is, a desired output frequency is obtained by reducing the overlapping area between the metal electrode and the internal electrode of the laser trimmable capacitor.
[0017]
FIG. 3A is a plan view of a crystal oscillator as a piezoelectric oscillator according to another embodiment of the present invention in which a crystal unit is omitted, and FIG. 3B is a bottom view of a crystal unit according to another embodiment. is there.
In the crystal oscillator 1, the electrical and mechanical connection between the printed wiring board 2 and the crystal oscillator 11 is connected using the four column members 20. However, it is necessary to function as a crystal oscillator. The electrical connection is two systems for connecting the crystal vibrating element 15 (the two excitation electrodes disposed on the crystal vibrating element 15) and the oscillation circuit, and desirably, the ground electrode 16a (the metal cover 12b) for exhibiting a shielding effect. ) And a system for connecting the shield layer. Therefore, as shown in FIG. 3A, a quartz oscillator (not shown) is disposed in parallel with a predetermined gap between the quartz oscillator (not shown) and the upper surface of the printed wiring board 32, and the above-described three-system electrical connection is established. In order to realize this, the column members 20 are fixed to the column member fixing patterns 6 (substantially circular shape) disposed substantially at the center of one short side of the printed wiring board 32 and near the other short side, respectively. 3 (b), a bottom electrode 46b is disposed substantially at the center of one short side, and the pad electrode 17 formed on the other short side, as shown in FIG. 3 (b). The bottom electrodes 46a and 46c are arranged in parallel, and are fixed to the column member 20 by soldering or the like. The bottom electrode 46a is a ground electrode that is electrically connected to the metal cover 12b, and the bottom electrodes 46b and 46c are connection electrodes that are electrically connected to an excitation electrode (not shown) provided on the crystal resonator. The bottom electrodes 46a to 46c have a circular shape for connection to the pillar member 20 (sphere), and the bottom electrodes 46b and 46c are electrically connected to the pad electrode 17 via lead electrodes extending from the pad electrode 17, respectively. ing.
[0018]
In the embodiment described above, the bottom electrodes 16a and 16b are arranged diagonally to each other. For example, the bottom electrode 16b may be arranged in parallel with the pad electrode 17 and the bottom electrode 16a may be arranged on the opposite short side. The positions of the bottom electrodes 46a and 46b may be interchanged.
[0019]
In addition to the above-described crystal oscillator according to the embodiment of the present invention, the crystal oscillator includes a capacitor for removing high-frequency noise superimposed on a power supply voltage supplied to electronic components constituting an oscillation circuit and a temperature compensation circuit. It does not matter. A chip resistor or a laser trimmable resistor may be used in addition to a capacitor and a laser trimmable capacitor for fine frequency adjustment.
[0020]
The printed wiring board according to the present invention is not limited to a material used for an insulating layer such as a ceramic wiring board and a resin substrate such as glass epoxy and silicon.
[0021]
Although the present invention has been described using TCXO, it goes without saying that the present invention can be applied to devices such as SPXO, VC-TCXO, VCXO, OCXO, and SAW oscillators.
[0022]
Although the present invention has been described using a crystal oscillator and a crystal resonator (crystal resonator element) constituting the crystal oscillator, the crystal resonator element is a cut angle such as an AT cut, a BT cut, a CT cut, a DT cut, an SC cut, and a GT cut. Needless to say, it can be applied to Further, a crystal oscillator having a fundamental wave or an overtone may be used. Further, it goes without saying that the present invention can be applied to not only quartz but also piezoelectric materials such as langasite, lithium tetraoxide, lithium tantalate, and lithium niobate.
[0023]
【The invention's effect】
According to the first aspect of the present invention, it is possible to obtain a piezoelectric oscillator that is small and that can handle a wide output frequency with a variable width.
[0024]
According to the second aspect of the present invention, there is an effect that a piezoelectric oscillator with improved workability of replacement or addition of a frequency adjustment electronic component, that is, frequency adjustment work can be obtained.
[0025]
According to the third aspect of the present invention, there is an effect that a simple frequency adjustment operation, that is, a low-cost piezoelectric oscillator can be obtained by using a laser trimmable chip component.
[0026]
According to the fourth aspect of the present invention, the number of members (column members) is reduced and the cost is reduced, and a minimum gap is obtained by arranging the minimum members (column members) so as to be substantially triangular. This has the effect that the vibrator can be arranged horizontally.
[Brief description of the drawings]
FIG. 1 is a configuration longitudinal sectional view of a crystal oscillator according to an embodiment of the present invention.
FIG. 2 is a bottom view of the crystal resonator according to the embodiment of the present invention.
FIG. 3 is a configuration diagram of a crystal oscillator as another embodiment of the present invention.
(A) The top view in the state where a crystal oscillator was omitted.
(B) A bottom view of the crystal unit.
FIG. 4 is a longitudinal sectional configuration diagram of a conventional one-chip IC type crystal oscillator.
FIG. 5 is a longitudinal sectional view of a conventional discrete crystal oscillator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator 2 ... Printed wiring board 3 ... Electronic component 4 ... External electrode 5 ... Land 6 ... Pattern 11 ... Crystal oscillator 12a ... Package body 12b ... Metal lid 15 ... Crystal oscillator 16a, 16b ... Bottom electrode 20 ... Column Member 21 ... Capacitor 32 ... Printed circuit board 46a, 46b, 46c ... Bottom electrode 51 ... Semiconductor component (IC chip) 52 ... Recess 53 ... Printed circuit board (ceramic package)
54: Piezoelectric vibrator (quartz vibrator)
Reference numeral 61: printed wiring board 62: electronic component 63: column member 64: quartz oscillator

Claims (4)

A flat printed wiring board having at least an electronic component constituting an oscillation circuit mounted on an upper surface and having an external electrode on a lower surface,
A piezoelectric vibrator having a large planar outer shape with respect to the printed wiring board;
With
A piezoelectric oscillator in which the piezoelectric vibrator is fixed at a predetermined gap via a plurality of column members fixed to the upper surface of the printed wiring board,
A piezoelectric oscillator, wherein a space not overlapping with the printed wiring board is secured on a bottom surface of the piezoelectric vibrator, and a part of the electronic component is mounted in the space. The piezoelectric oscillator according to claim 1, wherein a part of the electronic component is a frequency adjustment electronic component. The piezoelectric oscillator according to claim 2, wherein the electronic component for frequency adjustment is a laser trimmable chip component. The piezoelectric oscillator according to claim 1, wherein the number of the pillar members is three.

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