JP2004193965A - Structure of piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an oscillation frequency variable range and a starting characteristic of an oscillator are degraded when a solid ground layer for shielding is arranged between an oscillator connection circuit and an oscillation output circuit for reducing floating capacity. <P>SOLUTION: A ground pattern Pgnd2 is disposed in a part corresponding to one oscillator connection pattern Px1 and the ground pattern is not disposed in a part corresponding to the other oscillator connection pattern Px2 for shielding. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a structure of a piezoelectric oscillator, and more particularly to a structure of a piezoelectric oscillator in which an oscillation circuit is formed on a predetermined substrate layer of a container formed of a laminated ceramic substrate.
[0002]
[Prior art]
In recent years, surface mount piezoelectric oscillators have been widely used as a time reference for mobile terminals of mobile radio communication systems such as mobile phones, digital control devices such as computers, etc. Therefore, the size of the piezoelectric oscillator has been reduced. In response to miniaturization of components, the surface-mounting piezoelectric oscillator is generally the same as a piezoelectric vibrator unit in which a piezoelectric vibrating element is accommodated in a concave space formed by firing a laminated ceramic substrate. In this structure, an oscillation circuit portion accommodating oscillation circuit components is joined and integrated into a recessed space formed by firing a laminated ceramic substrate.
A circuit pattern is formed on a predetermined layer of the ceramic substrate, and an oscillation circuit component is mounted on the ceramic substrate. The patterns of the respective layers are connected by connecting conductors to form a circuit.
[0003]
2A and 2B are diagrams showing the structure of a conventional crystal oscillator for surface mounting, wherein FIG. 2A is a longitudinal sectional view, FIG. 2B is an electrode arrangement diagram on the outer bottom surface of the crystal unit, and FIG. It is an electrode arrangement figure of 12 outer bottom surfaces.
As shown in FIG. 1A, the present crystal oscillator 10 includes a crystal unit 11 and an oscillation circuit 12. The crystal vibrator portion 11 is connected to a circuit pattern electrode (not shown) provided on an inner bottom surface of a concave portion 14 of a first container 13 formed of a laminated ceramic substrate having an upward opening. It has a structure in which it is electrically and mechanically connected and fixed by cantilever support with a conductive adhesive, and is sealed with a metal lid 16.
At four corners of the outer bottom surface of the first container 13, connection electrode patterns 17 connected to two output terminals of the crystal resonator element 15 by via holes (not shown) are provided.
[0004]
The oscillation circuit section 12 has an oscillation circuit IC 20 mounted on a pattern electrode (not shown) provided on an inner bottom surface of a recess 19 of a second container 18 formed of a laminated ceramic substrate opened upward. Connection electrodes 22 corresponding to the connection electrode patterns 17 of the first container 13 are provided at four corners of the upper surface 21. Further, pad electrodes 23 for surface mounting as input / output terminals of the oscillator are provided at four corners on the outer bottom surface of the second container 18.
The connection electrode 22 and the pad electrode 23 are connected to the pattern electrode of the oscillation circuit IC 20 by a circuit pattern (not shown) and an inter-substrate connection conductor, respectively. The crystal unit 11 and the oscillation circuit unit 12 have substantially the same planar shape and a substantially rectangular shape. The crystal unit 11 is stacked above the oscillation circuit unit 12, and the connection electrode pattern 17 and the connection electrode 22 are connected to each other. Are integrated by soldering.
When the present oscillator 10 is used, the surface mounting pad electrode 23 of the present oscillator 10 is soldered to a circuit pattern of a printed wiring board of a device such as a portable terminal.
[0005]
FIG. 2B is an electrode arrangement diagram of a connection electrode pattern 17 provided on the outer bottom surface of the crystal unit 11, and FIG. 2C is provided on the outer bottom surface of the oscillation circuit unit 12. FIG. 4 is an electrode arrangement diagram of a pad electrode 23 shown in FIG. All are pattern diagrams when viewed through from above.
As shown in FIG. 2 (b), the connection electrode patterns 17a, b, c, d are usually located at one diagonal (upper right and lower left in the figure) of the four corners of the lower surface. Two terminals of the crystal vibrating element 15 are connected to 17a (XT1) and 17c (XT2). The electrode patterns 17b, d (GND) located on the other diagonal (upper left and lower right in the figure) are both ground ends.
As shown in FIG. 2C, the surface mounting pad electrodes 23a, 23b, 23c and 23d at the four corners of the lower surface of the oscillation circuit section 12 are signal input pad electrodes at the lower left of FIG. Electrodes of a ground terminal 23b (GND), an oscillator output terminal 23c (OUT), and a DC power supply terminal 23d (Vcc) are arranged counterclockwise with reference to 23a (Vcon). The connection is made by an electrode pattern provided on the ceramic layer and via holes connecting the layers.
The electrode arrangement of the connection electrode patterns 17a, b, c, and d in FIG. 2B and the pad electrodes 23a, b, c, and d provided on the lower surface of the oscillation circuit unit 12 in FIG. Both are customary as electrode arrangements for surface-mounting crystal resonators and crystal oscillators and are ready-made standards.
[0006]
In general, in an oscillator, it is well known that unnecessary electromagnetic coupling between a piezoelectric vibrator and an oscillator output circuit has an adverse effect on, for example, circuit characteristics such as load fluctuation characteristics and C / N characteristics of the oscillator. It is. For this reason, various measures are taken to prevent the coupling between the input / output terminals of the circuit and the coupling with the neighboring circuits.
When the crystal unit 11 and the oscillation circuit 12 having the standardized electrode arrangement shown in FIG. 2 are stacked and joined as an oscillator, the surface mounting pad electrode 23c (oscillation output terminal of the oscillation circuit 12) is connected. OUT) is opposed to one of the connection electrode patterns 17a (XT1) and 17c (XT2), which is one connection end of the crystal unit 11. Therefore, there is a problem that the stray capacitance between the two electrodes becomes large, and when this oscillator is mounted on a device or the like and used, the frequency fluctuation of the oscillator increases.
For example, in Japanese Patent Application Laid-Open No. 2000-341043, in order to solve this problem, the arrangement of the connection electrode patterns 17a, b, c, and d of the crystal unit 11 is ignored, ignoring the custom-made standard. A technique is disclosed in which the compatibility is abandoned and changed so as not to face the oscillation output end 23c of the surface mounting pad electrode.
However, according to this method, since the electrode arrangement is different from the above-mentioned standardized electrode arrangement, there is a problem that the method is not versatile and the cost is increased when manufacturing a crystal unit.
[0007]
As another means for preventing unnecessary coupling between circuits in a piezoelectric oscillator composed of a ceramic laminated substrate, a method of providing a ground shield layer between a substrate layer constituting an oscillation circuit and a substrate layer constituting an output terminal is considered.
FIG. 3 is a diagram showing an example of a wiring pattern of a laminated substrate forming the oscillation circuit section 12 of the conventional ceramic laminated crystal oscillator 10 shown in FIG.
The pattern forming the oscillation circuit section 12 includes a surface a shown in FIG. 3A, a surface b shown in FIG. 3B, a surface c shown in FIG. 3C, and a pattern shown in FIG. It consists of four d-planes as shown.
FIG. 3E is a cross-sectional view of the oscillation circuit section 12, and reference numerals a, b, c, and d correspond to the a-plane to the d-plane, respectively.
In the figure, the hatched patterns are ground patterns, and the patterns between the respective layers are connected to each other at via points (not shown) at the points indicated by black circles.
[0008]
The surface a shown in FIG. 3A is a surface having the connection electrode 22 in the uppermost layer of the oscillation circuit portion 12, and the electrodes 22 a and 22 c are connection electrode patterns 17 a of two terminals of the crystal unit 11. , C. The electrodes 22b and 22d are ground electrodes.
The surface b (FIG. 2B) is a pattern electrode for mounting the oscillation circuit IC 20 (shown by a dotted line in the figure) of the oscillation circuit section 12, and mainly has an electrode for the IC 20 and a connection lead pattern thereof.
The c-plane (FIG. 3c) is located between the b-plane and a d-plane described later, and has an earth pattern Pgnd3 (solid earth) mainly applied to almost the entire surface of the substrate layer.
The d surface (d in the figure) is a pattern of the lowermost surface of the oscillation circuit section 12, and has the surface mounting pad electrodes 23a (Vcon), b (GND), c (OUT), and d (Vcc).
[0009]
As shown in FIG. 3 (b), the pattern on the b-side has a ground pattern Pgnd1 between the transducer connection lead pattern Px1 of the IC 20 connected to the connection electrode 22c on the a-side by a via hole and the oscillation output lead pattern Pout1 of the IC 20. Is provided. Further, as shown in FIG. 3C, the c-plane has an earth pattern Pgnd3 (solid earth) on almost the entire surface, and the oscillation output lead pattern Pout1 on the b-plane and the pad electrode 23c (OUT ) And a second oscillation output lead pattern Pout2 connected to each other by via holes.
Due to the above-described shield effect of the ground patterns Pgnd1 and Pgnd3, the stray capacitance between the connection electrode 22c, which is the oscillator connection end of the oscillation circuit section 12, and the pad electrode 23c (OUT) for surface mounting is, for example, 0.055. It is reduced to a low value of 0.07 pF.
[0010]
[Problems to be solved by the invention]
However, as described above, the method of providing a ground pattern or a solid earth layer between the oscillator output circuit and the oscillator output circuit to shield between the circuits reduces the stray capacitance of the circuit,
(1) The variable frequency range of the oscillator is narrowed (2) The starting characteristic of the oscillator is deteriorated, and there is a problem that the operation of a system using the oscillator is adversely affected.
The present invention has been made to solve the above problems, and in an oscillator including a piezoelectric vibrator unit and an oscillation circuit unit having an electrode arrangement of a ready-made standard, an electrode at a vibrator output terminal and an electrode at an oscillator output terminal are provided. It is an object of the present invention to provide a piezoelectric oscillator having good characteristics such as a variable frequency range of the oscillator while minimizing the stray capacitance between them.
[0011]
[Means for Solving the Problems]
In order to solve the above problem, in the invention of claim 1, an oscillation circuit is provided in a first container having a connection electrode pattern on an outer bottom surface and containing a piezoelectric vibrating element therein and having a top opening. And a connection electrode corresponding to the connection electrode pattern of the first container on the upper surface of the side wall of the concave portion, and the concave opening of the second container having a surface mounting pad electrode on the outer bottom surface. Piezoelectric oscillator integrated and stacked as described above, wherein the second container has a first substrate layer having the connection electrode, and a second substrate having an electrode pattern on an upper surface for mounting the oscillation circuit component. And a third substrate layer having a surface mounting pad electrode on the lower surface thereof, wherein the upper surface of the third substrate layer is provided with a surface mounting pad electrode for oscillator output from the oscillator circuit. Oscillation of parts A ground circuit is provided so as to overlap with the output circuit pattern on the second substrate layer connected to the force end, and a connection circuit connecting from the other connection electrode for connecting the vibrator to the other vibrator connection electrode of the oscillation circuit component A ground pattern is not provided at a position corresponding to the pattern.
According to a second aspect of the present invention, in the structure of the piezoelectric oscillator according to the first aspect, the first to third substrate layers are ceramic substrate layers.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on an embodiment shown in the drawings. FIG. 1 is a circuit pattern diagram showing one embodiment of a substrate layer having a circuit pattern in a ceramic laminated substrate forming an oscillation circuit portion of a crystal oscillator as a piezoelectric oscillator according to the present invention.
The oscillation circuit section according to the present invention is shown in the a-plane shown in FIG. 1A, the b-plane shown in FIG. 2B, the c-plane shown in FIG. It consists of four circuit patterns on the d-plane.
The four surfaces a, b, c, and d have a positional relationship corresponding to a, b, c, and d shown in FIG. 3E in the oscillation circuit unit 12 of the crystal oscillator in FIG. The surface is the uppermost layer having the connection electrodes 22a to 22d of the oscillation circuit section 12, the surface b is the layer having the pattern electrode of the oscillation circuit IC 20, the surface c is the intermediate layer between the surfaces b and c, and the surface d is the surface. Are formed on the lowermost layer having the surface mounting pad electrodes 23a to 23d, respectively.
[0013]
Further, the circuit patterns shown in FIGS. 1A, 1B, and 1D are exactly the same as the circuit patterns shown in FIGS. 3A, 3B, and 3D.
As shown in FIG. 1 (c), the feature of the present invention is that the ground pattern Pgnd3 (solid ground) provided on almost the entire c-plane shown in FIG. The point is that the pattern is Pgnd2.
In FIG. 1, the hatched pattern is an earth pattern, and the patterns between the opposing layers are connected by via holes (not shown) at the same point on the pattern shown in FIG.
The crystal oscillator according to the present invention is configured by integrating the oscillation circuit section having the ceramic substrate layer having the above-described configuration and the crystal resonator section.
Therefore, the configuration of the crystal oscillator according to the present invention is the same as that of FIGS. 2 and 3 except for the circuit pattern on the c-plane, and a detailed description of common parts will be omitted.
[0014]
As shown in FIG. 1C, a ground pattern Pgnd2 mainly formed on the c-plane of the oscillation circuit section 12 has a connection electrode 22c with one of the vibrators shown in FIG. The ground pattern Pgnd2 is provided only at a portion corresponding to the transducer connection pattern Px1 of FIG. The ground pattern Pgnd2 is connected to the ground pattern of FIGS. 1A, 1B, and 1D at a point ● by a via hole (not shown).
Then, a portion corresponding to the vibrator connection pattern Px2 of FIG. 1B connected to the connection electrode 22a at the other end connected to the vibrator and the connection electrode 22a has a pattern configuration in which no ground pattern is provided.
[0015]
As described above, only between the transducer connection electrode 22c and the connection pattern Px1 connected to the electrode 22c and the oscillation output lead patterns Pout1 and Pout2 connected to the surface mounting pad electrode 23c (OUT) at the oscillation output end. The ground pattern Pgnd1 and Pgnd2 are provided, and the ground pattern is provided on the c-plane (FIG. 1C) of the portion corresponding to the other vibrator connection electrode 22a. The value of the stray capacitance between the connection electrode 22c for connection and the surface mounting pad electrode 23c at the oscillator output end is approximately 0.06 pF, which is equivalent to that of the conventional pattern, and the upper limit of the variable range of the oscillation frequency of the crystal oscillator is limited. It was confirmed that the magnification was increased by 10 to several tens of ppm.
[0016]
【The invention's effect】
As described above, according to the piezoelectric oscillator using the oscillation circuit portion constituted by the ceramic substrate layer of the present invention, the shield ground pattern is set to the necessary minimum area between the oscillator connection circuit and the oscillation output circuit. Therefore, even with an oscillator having an electrode arrangement of a vibrator part and an oscillation circuit part of a ready-made standard, the circuit characteristics such as the frequency variable range are excellent without increasing the stray capacitance between the vibrator connection terminal and the oscillator output terminal. A piezoelectric oscillator can be provided.
[Brief description of the drawings]
FIG. 1 is a circuit pattern diagram showing one embodiment of a substrate layer having a circuit pattern of a ceramic laminated substrate forming an oscillation circuit portion of a crystal oscillator as a piezoelectric oscillator according to the present invention, wherein FIG. , A-plane pattern diagram, (b) is a b-plane pattern diagram, (c) is a c-plane pattern diagram, and (d) is a d-plane pattern diagram.
FIGS. 2A and 2B are diagrams showing the structure of a conventional crystal oscillator, in which FIG. 2A is a longitudinal sectional view, FIG. 2B is an electrode arrangement diagram on the outer bottom surface of the crystal unit (a perspective view from above), and FIG. FIG. 4 is an electrode arrangement diagram on the outer bottom surface of the oscillation circuit unit (a perspective view from above).
FIGS. 3A and 3B are diagrams showing an example of a wiring pattern of a laminated substrate forming an oscillation circuit section of the conventional ceramic laminated crystal oscillator shown in FIG. 2A, wherein FIG. ) Is a pattern diagram of the b surface, (c) is a pattern diagram of the c surface, (d) is a pattern diagram of the d surface, and (e) is a pattern diagram of the a, b, c, and d surfaces of the oscillation circuit unit. Sectional drawing which shows a positional relationship.
[Explanation of symbols]
10. Crystal oscillator, 11 Crystal oscillator part, 12 Oscillator circuit part
13. first container, 14 recess, 15 crystal oscillator, 16 metal lid,
17a, b, c, d ··· Connection electrode pattern, 18 ··· Second container,
19 recess, 20 IC, 21 sidewall, 22a, b, c, d connection electrode, 23a, b, c, d pad electrode
a, a substrate layer corresponding to the oscillation circuit part a surface,
b: a substrate layer corresponding to the oscillation circuit portion a surface,
c: a substrate layer corresponding to the oscillation circuit part a surface,
d. a substrate layer corresponding to the oscillation circuit part a surface,
Pgnd1, Pgnd2, Pgnd3 ... ground pattern,
Pout1, Pout2 ... Oscillation output lead pattern Px1, Px2 ... Transducer connection pattern

Claims (2)

A first container having a connection electrode pattern on the outer bottom surface and containing a piezoelectric vibrating element therein is accommodated in a concave portion having an opening at an upper side, and an oscillator circuit component is accommodated in a concave portion having an upper opening, and the first container is provided on an upper surface of the concave portion side wall. A piezoelectric oscillator which is stacked and integrated so as to cover the concave opening of a second container having a connection electrode corresponding to the connection electrode pattern of the container and a surface mounting pad electrode on the outer bottom surface, wherein A first substrate layer having the connection electrodes, a second substrate layer having an electrode pattern on the upper surface for mounting the oscillation circuit component, and a third substrate layer having the surface mounting pad electrodes on the lower surface. A container in which a substrate layer is laminated, and an upper surface of the third substrate layer is provided on a second substrate layer which is connected to the oscillation output end of the oscillation circuit component from the surface output pad electrode for the oscillator output. Output circuit pattern and A ground pattern is provided so as to be duplicated, and a ground pattern is not provided at a position corresponding to a connection circuit pattern connected from the other connection electrode for connecting the vibrator to the other vibrator connection electrode of the oscillation circuit component. Characteristic structure of piezoelectric oscillator. 2. The structure of claim 1, wherein said first to third substrate layers are ceramic substrate layers.

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