JPH11261365A - Package structure for piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the directivity of substrate mounting while a piezoelectric element piece fixed to one end is stored by connecting a pair of holding electrodes and a pair of outer electrodes by conduction patterns having symmetrical forms. SOLUTION: Conduction patterns 12 and 13 which are led out from holding electrodes H1a and H2a are installed to the vicinity of the center of a long side in a package and they have symmetrical forms. Outer electrodes H1 and H2 are oppositely provided at the center of the long side on the base of the package and GND electrodes are provided at four corners. The conduction pattern 12 is led out to the vicinity of the center of the package from the holding electrode H1a and it passes through the outer side of the package. The pattern is connected to the outer electrode H1 at the base of the package through the lead-out part of the outer side of the package. Then, it is electrically conducted. The conduction pattern 13 is led out to the vicinity of the center of the package from the holding electrode H2a and it passes to the outer face of the package. It is connected to the outer electrode H2 of the base of the package through the lead-out part 14 of the outer side of the package and it is electrically conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package structure of a surface mount type piezoelectric vibrator, and more particularly to an improvement of a package structure in which a difference in oscillation characteristics depending on a mounting direction when mounting an oscillation circuit board is eliminated.

[0002]

2. Description of the Related Art In recent years, as electronic components have been mounted at higher density and surface-mounted electronic components have been widely used, surface-mounted piezoelectric vibrators have been widely used as piezoelectric vibrators.
5A and 5B are structural views showing an example of a conventional surface mount type piezoelectric vibrator, in which FIG. 5A is a top view, FIG. 5B is a front view, FIG. 5C is a bottom view, and FIG. (E) is a longitudinal sectional view, (f)
FIG. 4 is an electrode pattern diagram inside a package. One example shown in the figure is a pair of holding electrodes in which excitation electrodes are formed on both surfaces and a piezoelectric vibrator piece 1 having a pair of leading ends led out at one end is provided at one end inside a ceramic package 2. (H1a and H2a) are fixed with a conductive adhesive 3 and are electrically connected to each other, and a metal seam ring 4 is fixed to the upper part of the package in advance. The inside of the package is made airtight by sealing.

[0003] There are two methods for accommodating the piezoelectric vibrator piece 1 in a package: a method of fixing a pair of lead ends protruding to one end of the piezoelectric vibrator piece 1 and a method of fixing a pair of lead ends protruding to both ends. However, it is general that the former method, which does not hinder the mechanical vibration of the piezoelectric vibrator and has excellent electrical characteristics, is selected and configured as in the above example. On the other hand, as shown in FIG. 5 (c), external electrodes H1 and H2 are provided diagonally on the bottom surface of the package main body, and the holding electrodes H1a and H2a are passed through the package in an airtight manner. Are electrically connected via a lead electrode. Further, on the opposite diagonal of the package bottom surface, two GND electrodes electrically connected to the seam ring 4 and the cover 5 on the package upper portion are provided. Since these electrodes are arranged at point-symmetric positions when viewed from the center, 1
Even if rotated by 80 °, the positional relationship between the external electrode and the GND electrode does not change. Therefore, this electrode arrangement has a feature that it functions as a piezoelectric vibrator regardless of which direction the substrate is mounted, and has been conventionally used as a standard.

In the package configured as described above, the fifth
Only one electrode (H2a) needs to be led to the other end of the package via the conductive pattern 6, as shown in FIG. This structure will be described in detail with reference to FIG. FIG. 6 (a) shows that the holding electrode H1a is connected to the external electrode H
FIG. 2B is a cross-sectional structure diagram showing the derivation to No. 1 and FIG. 2B is a cross-sectional structure diagram showing the derivation from the holding electrode H2a to the external electrode H2. Derivation from H1a is a structure that requires only a short length of conductive pattern that penetrates the package and goes around the side surface because H1 is located on the bottom surface as shown in FIG. . On the other hand, as shown in FIG. 3B, the lead from H2a is led to the other end via the conductive pattern 6 because H2 is not at the bottom surface but at the other end of the package. Therefore, after the package is penetrated, the side surface is turned around and the structure is led out to the bottom surface.

When this structure is considered electrically, since the wiring is short on the H1 side with respect to the piezoelectric vibrator piece Y as in the equivalent circuit shown in FIG. 7, the capacitance Cs1 between the H1 portion and the GND is substantially main parasitic. Although the impedance becomes an impedance, the wiring is significantly longer on the H2 side than on the H1 side, so that the inductance L of the conductive pattern 6 is added to the capacitance Cs2 between the H2 part and GND.
2 and the capacitance Cc2 between the conductive pattern 6 and GND become parasitic impedance. That is, since the impedance viewed from H2 includes L2 and Cc2, the impedance has a different value from the impedance viewed from H1, and it is understood that the impedance is electrically asymmetric.

That is, in a surface-mount type piezoelectric vibrator having a structure fixed at one end of a piezoelectric vibrator piece, while having a structural symmetry that a substrate can be mounted in either direction, it is electrically connected. Can be understood to be asymmetric.

[0007]

However, when the surface mount type piezoelectric vibrator is mounted on a printed circuit board or the like of an oscillation circuit having a frequency adjusting function, for example, the external terminal H1 is connected as shown in FIG. In the case where the capacitor is connected to the base side of the transistor and the case where it is connected to the variable capacitor CV side as shown in FIG. In this case, there is a problem that a difference of about several percent occurs in the frequency variable sensitivity at the time.
This phenomenon has been a particular problem in the field of manufacturing high-precision oscillator circuits used for communication devices such as mobile phones. Specifically, for example, it is not possible to satisfy the required standard of the oscillation circuit (for example, the internal frequency variable width) because the frequency sensitivity has decreased by several percent. This has caused such a problem that the specification of the characteristics cannot be satisfied.

In order to avoid these problems, the manufacturer of the piezoelectric vibrator must perform manufacturing, inspection, and packaging in the same direction, which is disadvantageous in terms of equipment, mass productivity, manufacturing cost, and the like. There was a problem that is. Also, on the user side, the development direction, assembling, and the like must be used after sufficient consideration of the mounting direction. If the mounting direction is fixed, the idea is to place both the internal and external electrodes of the package at one end to ensure electrical symmetry and minimize parasitic impedance. However, in the field of general-purpose products that do not require much precision, mechanical symmetry is emphasized, so that two types of pin arrangements coexist, even with the same crystal unit, making handling difficult. Occurs. The present invention has been made in order to solve the above-described problem, and an object of the present invention is to provide a surface-mount type piezoelectric vibrator that accommodates a piezoelectric element piece fixed at one end and has no direction of board mounting. And

[0009]

According to the present invention, in order to achieve the above object, a surface mount type piezoelectric device is provided in which excitation electrodes are formed on both surfaces and a piezoelectric vibrator piece having a pair of lead-out ends led out at one end is housed. In the vibrator, a structure in which a pair of holding electrodes provided at one end inside the package and a pair of external electrodes provided facing the center of the longitudinal side of the package bottom face are connected by conductive patterns having symmetrical shapes. It is characterized by having.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. 1A and 1B are structural views showing an embodiment of the present invention, wherein FIG. 1A is a top view, FIG.
(C) is a bottom view, (d) is a transverse sectional view, (e) is a longitudinal sectional view, and (f) is an electrode pattern diagram inside the package.
According to the embodiment of the present invention, a pair of holding electrodes (a pair of holding electrodes each having an excitation electrode formed on both surfaces thereof and a piezoelectric vibrator piece 7 having a pair of leading ends led out at one end provided at one end inside a ceramic package 8) are provided. H1a and H2a) are fixed with a conductive adhesive 9 and are electrically connected to each other, and a metal seam ring 10 is fixed to an upper portion of the package 8 in advance.
The upper opening is sealed with a metal cover 11 to make the inside of the package airtight. This configuration is the same as the example described in the section of the prior art.

The feature of the present embodiment is that, as shown in FIG. 1 (f), twelve conductive patterns derived from the holding electrode H1a and thirteen conductive patterns derived from the holding electrode H2a are formed inside the package. They are provided up to the vicinity of the center of the longitudinal side, respectively, and they have a symmetrical shape with each other. Further, as shown in FIG. 3C, the external electrodes are such that external electrodes H1 and H2 are provided opposite to each other at the center of the longitudinal side of the package bottom surface, and further, GND electrodes are provided at the four corners. These electrodes are arranged at point-symmetrical positions when viewed from the center of the package.
Even if it rotates by 0 °, the positional relationship between the external electrode and the GND electrode does not change.

The method of deriving the electrodes will be described with reference to FIG. FIG. 2A is a cross-sectional structure diagram showing the lead-out from the holding electrode H1a to the external electrode H1. The 12 conductive patterns are led out from H1a to near the center of the package, penetrate the package outer surface, and further extend outside the package. It is connected to the external electrode H1 on the bottom surface of the package via the lead-out portion on the side surface, and has a structure for obtaining electrical continuity. FIG. 2B is a cross-sectional structural view showing the lead-out from the holding electrode H2a to the external electrode H2. The conductive pattern 13 is led out from H2a to near the center of the package, and penetrates the package outer surface. It is connected to the external electrode H2 on the bottom surface of the package via the lead-out portion 14 on the outer surface of the package, and has a structure for obtaining electrical continuity. Thus, when viewed from the vertical section, the former and the latter have the same structure.

Considering this structure electrically, as shown in the equivalent circuit in FIG.
The capacitance Cs1 between GND, the inductance L1 of twelve conductive patterns, and the capacitance Cc between twelve conductive patterns and GND
1 is the main parasitic impedance, and on the H2 side, H2
The main parasitic impedance is the capacitance Cs2 between the part and GND, the inductance L2 of the thirteen conductive patterns, and the capacitance Cc2 between the thirteen conductive patterns and GND. In the structure of the present invention, the structures derived from H1 to H1a and H2 to H2a are symmetrical to each other, so that Cs1 and Cs2, L1
And L2, and Cc1 and Cc2 have the same size.
That is, the impedance seen from H1 is the same as the impedance seen from H2, and it can be seen that it is electrically symmetric.

Therefore, the surface mount type piezoelectric vibrator of the present invention has a feature that the positional relationship between the external electrode and the GND electrode does not change even if the electrode on the bottom of the package is rotated by 180 °, and furthermore, it is electrically symmetrical. Therefore, there is no difference in the oscillation frequency and the characteristics such as the oscillation frequency sensitivity depending on the mounting direction when mounted on the oscillation circuit board. Therefore, the piezoelectric vibrator can be manufactured ignoring the directionality, so that the mass productivity can be improved and the price can be reduced, and the user does not need to consider the directionality. Therefore, development efficiency can be expected.

The present invention can be variously modified without being limited to the above-described embodiment. That is, in the present invention, since the structure from the internal holding electrode to the external electrode may be provided symmetrically, the same effect as that of the embodiment can be obtained even if, for example, the conductive patterns are provided on the side walls inside the package. .

Furthermore, the surface mount type piezoelectric vibrator according to the embodiment of the present invention cannot be mounted as it is on a printed board or the like having a conventional electrode pattern because the electrode arrangement is different from that of the prior art. As shown in FIGS. 4A and 4B, the electrodes H1 and H2 are provided diagonally, and a conductive pattern is provided at the bottom of the package and at the bottom of the package, respectively. By conducting, it is possible to obtain the effect of the present invention while maintaining terminal compatibility with the prior art product.

Although the present invention has been described by way of an example of a package structure hermetically sealed with a ceramic package and a metal cover, the present invention is not limited to these materials and hermetic sealing methods. Instead, the present invention can be applied to a package structure of a piezoelectric vibrator in which a package (for example, made of ceramic or the like) and a cap (for example, made of ceramic) are hermetically sealed with a sealing material (for example, low-melting glass or resin).

[0018]

As described above, according to the present invention, the piezoelectric vibrator piece fixed at one end is accommodated, and the piezoelectric vibrator piece is provided opposite to the pair of supporting electrodes inside the package and the center of the longitudinal side of the package bottom surface. By making the pair of external electrodes a surface-mounted piezoelectric vibrator connected by conductive patterns having symmetrical shapes, it is possible to eliminate a difference in characteristics depending on a mounting direction on an oscillation circuit board or the like. Therefore, according to the present invention,
Since the piezoelectric vibrator can be manufactured ignoring the direction, it is effective in improving mass productivity and reducing the price, and the user does not need to consider the direction. Can be expected to improve development efficiency.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing one embodiment of the present invention,
(A) is a top view, (b) is a front view, (c) is a bottom view,
(D) is a transverse sectional view, (e) is a longitudinal sectional view, and (f) is an internal view of the package.

FIG. 2 is a sectional structural view according to an embodiment of the present invention;
(A) is from the holding electrode H1a, (b) is the holding electrode H2a
To the external electrode are shown.

FIG. 3 is an electrical equivalent circuit showing one embodiment of the present invention.

FIG. 4 is an electrode arrangement diagram showing a modification of the present invention.

FIG. 5 is a structural view showing one embodiment of the present invention,
(A) is a top view, (b) is a front view, (c) is a bottom view,
(D) is a transverse sectional view, (e) is a longitudinal sectional view, and (f) is an internal view of the package.

FIG. 6 is a cross-sectional structural view in one embodiment of the prior art.
(A) is from the holding electrode H1a, (b) is the holding electrode H2a
To the external electrode are shown.

FIG. 7 is an electrical equivalent circuit in one embodiment of the prior art.

8A and 8B are diagrams illustrating an example of an oscillation circuit, in which FIG. 8A is a diagram in which a terminal H1 is connected to a package side of a transistor, and FIG.

[Explanation of symbols]

1,7 Piezoelectric vibrator piece, 2,8 package, 3,9
Conductive adhesive, 4,10 seam ring, 5,11 cover, 6,12,13 conductive pattern, 14..outer surface lead-out part of package, H1, H2..external electrode, H1a,
H2a: holding electrode, GND: ground electrode, Y:
Piezoelectric vibrator piece, Cs1, Cs2, capacitance between electrode and GND, Cc1, Cc2, capacitance between conductive pattern and GND,
L1, L2 ... Inductance of conductive pattern

Claims (1)

[Claims] 1. A surface mount type piezoelectric vibrator in which a piezoelectric vibrator piece having an excitation electrode on both surfaces and a pair of lead-out ends extending from the excitation electrode to one end is housed in a package, provided at one end inside the package. A pair of holding electrodes and a pair of external electrodes provided to face the center of the long side of the bottom surface of the package are connected by conductive patterns having symmetrical shapes. Package structure.