JP2003008388A - Surface mounted crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface mounted crystal oscillator preventing frequency change after being mounted to a set substrate. SOLUTION: In the surface mounted crystal oscillator obtained by housing a crystal piece in a base with the surface mounted crystal oscillator formed on its outer surface, covering it and seal-enclosing the crystal piece, a shielding electrode to be grounded to the ground potential is provided at the base.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal resonator for surface mounting (referred to as a surface mounting resonator) as an industrial technical field, and particularly to a crystal resonator for mounting on a set substrate. The present invention relates to a surface mount resonator that prevents a frequency change. (Background of the Invention) Surface mount resonators are small
Because of its light weight, it is widely used as a frequency and time reference source (oscillator) especially in portable equipment.
In recent years, there has been a demand for a surface-mounted vibrator that has a strict vibration frequency accuracy particularly in a communication device (for example, a mobile phone) and has a small frequency change. (Example of Prior Art) FIG. 3 is a sectional view of a surface mount vibrator for explaining a conventional example. The surface mount resonator accommodates a crystal blank 2 in a base 1, covers the metal cover 3, and hermetically seals it. The base 1 is made of a concave multilayer ceramic having a bottom wall 1a and a side wall 1b. And
One end of the inner bottom surface has a pair of terminal electrodes 4 (ab), and the other end has an insulating pillow 5. Further, on the outer surfaces of the side and bottom surfaces, mounting electrodes 6 (ab) for surface mounting are provided at, for example, a pair of diagonal portions, and a pair of terminal electrodes 4 (ab) are provided by conductive paths 7 through the laminated surface of the laminated ceramic. ) And electrically connected. The crystal blank 2 has excitation electrodes 8 (ab) on both main surfaces, and has extraction electrodes 9 (ab) extending on both sides of one end. Then, both ends of one end are fixed to the pair of terminal electrodes 4 (ab) with the conductive adhesive 10 and electrically and mechanically connected. The other end of the crystal blank 2 comes into contact with or comes close to the pillow 5 to reduce the vertical swing width to prevent breakage. [0005] The metal cover 3 is joined to the opening wall of the base 1 by seam welding to hermetically enclose the crystal blank 2. However, on the opening wall surface of the base 1 (the upper surface of the side wall 1b), the metal ring 11 is joined by a brazing material (not shown). Then, the metal cover 3 is mounted on the mounting electrode 6 (c) grounded to the ground potential provided on the other diagonal part of the other set of the base 1.
d) is electrically connected through a through hole 12 provided in the side wall 1b. These are surface-mounted, for example, on a set board 13 constituting a mobile phone. Symbol 15
Is a connection electrode of the set substrate 13. In such a case, since the sealing is performed by seam welding, the degree of sealing is ensured as compared with, for example, resin sealing or glass sealing. For example, in the case of resin sealing, moisture or the like invades, and in the case of glass, it is easily broken, and these points are excellent. In addition, since the metal cover 3 is connected to the mounting electrode 6 (cd) at the ground potential, even if the electric field on which the metal cover 3 is placed changes, the excitation electrode on the upper surface side of the crystal blank 2 (the upper surface excitation electrode). ) Make the volume between 8 (ab) constant. (Problems to be Solved by the Invention)
However, the surface mount resonator having the above configuration has a problem in that the frequency changes during use after being mounted on the set board 13 and assembling a mobile phone or the like. That is, portable devices, including recent mobile phones, are becoming increasingly smaller (thinner). In a mobile phone or the like, characters and the like are input and used with a front keyboard. In this case, the set substrate 13 is warped due to the small thickness due to the pressing force at the time of inputting characters and the like. Therefore, the state changes between when the surface mount resonator is mounted on the set substrate 13 and when the surface mount vibrator is pressed. In this case, the excitation electrodes (the lower surface excitation electrode To change the gap with 8 (ab). Then, generally, a wiring path 14 of a circuit pattern is formed on the front surface, the lamination surface, or the back surface of the set substrate 13 serving as the lower surface of the surface mount resonator. For these reasons, when the keyboard is pressed, the capacitance between the lower surface excitation electrode 8 (ab) and the wiring path 14 is different from that at the time of mounting (when there is no pressing force) due to the change in the gap. It will be. Therefore, there is a problem that the oscillation frequency changes due to a change in capacitance caused by the gap. These problems become more serious as the frequency deviation becomes more severe and as miniaturization (thinning) progresses. (Object of the Invention) It is an object of the present invention to provide a surface mount resonator in which a frequency change after mounting on a set board is prevented. The basic solution of the present invention is to provide a shield electrode grounded to a ground potential on a base for accommodating a crystal blank. In the present invention, since the shield electrode is provided on the base, even if the gap between the lower surface excitation electrode of the crystal blank and the set substrate changes, the capacitance between them is kept constant. Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a sectional view of a surface-mount vibrator for explaining an embodiment of the present invention. The same parts as those in the prior art are denoted by the same reference numerals, and description thereof will be simplified or omitted. As described above, the surface mount resonator has a pair of terminal electrodes 4 (ab) on one end side of the inner bottom surface and an insulating pillow 5 on the other end side, and is connected to the terminal electrodes 4 (ab). Mounting electrode 6 (ab)
For example, the extraction electrode 9 of the crystal blank 2 is placed in a base 1 made of a concave multilayer ceramic having mounting electrodes 6 (cd) connected to the metal cover 3 at one set of diagonal portions and formed at the other set of diagonal portions.
Both ends of the extended one end of (ab) are electrically and mechanically connected to and accommodated in the terminal electrode 4 (ab) by the conductive adhesive 10. In this embodiment, a shield electrode 16 is formed on almost the entire inner bottom surface of the base 1. However, it is electrically independent from the pair of terminal electrodes 4 (ab). Then, for example, it is configured to be electrically connected to the ground electrode through the through hole provided in the side wall 1b of the base 1 described above. With such a configuration, the set substrate 13 on which the surface mount resonator is mounted is warped, and the gap between the lower surface excitation electrode 8 (ab) of the crystal blank 2 and the wiring path of the set substrate 13 changes. Even though the capacitance is shielded by the shield electrode, the capacitance does not change and maintains a constant value. Note that the capacity is the lower excitation electrode 8
The constant value depends on the gap between (ab) and the shield electrode (earth potential). Further, in this example, since the opening surface of the base 1 is sealed by the metal cover 3 connected to the ground electrode, even if the set substrate 13 is laminated and the upper set substrate 13 warps, for example, the upper surface excitation electrode 8 is formed. (Ab)
The capacitance between them does not change. In the above embodiment, the shield electrode is the base 1
Formed on the inner bottom surface of the base 1, for example, the bottom wall 1 of the base 1.
a may be formed on the laminated surface as two layers. When the wiring path of the set substrate 13 is a ground line, it may be formed on the back surface of the base 1 or may be coated with an insulating layer. Further, although the structure is sealed by the metal cover 3,
For example, even if the insulating cover is sealed with resin or glass, no capacitance is generated between the set substrate 13 and the lower surface excitation electrode 8 (ab). Is effective. However, it is preferable to use the metal cover 3 because the electric field from the upper and lower surfaces is shielded and the capacitance does not change. Although the base 1 has a concave shape, the cover may have a concave shape, for example, a flat plate. In this case, the crystal blank 2 is accommodated with the mounting electrodes 6 (ab) mounted on the surface of the set substrate 13. The base is the base one. Also,
Here, the ground potential is not necessarily a zero potential but may be a DC potential. In short, the AC component may be cut off. According to the present invention, since the shield electrode grounded to the ground potential is provided on the base accommodating the quartz piece, a surface mounted resonator which prevents a frequency change after mounting on the set substrate is provided. it can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a surface-mount vibrator for explaining an embodiment of the present invention. FIG. 2 is a plan view of a base explaining one embodiment of the present invention. FIG. 3 is a cross-sectional view of a surface-mount vibrator for explaining a conventional example. FIG. 4 is a plan view of a base for explaining a conventional example. FIG. 5 is a back view of a surface mount resonator for explaining a conventional example. FIG. 6 is a plan view of a crystal blank for explaining a conventional example. [Brief description of reference numerals] 1 base, 2 crystal pieces, 3 metal covers, 4 terminal electrodes, 5 pillows, 6 mounting electrodes, 7
Conductive path, 8 excitation electrode, 9 extraction electrode, 10 conductive adhesive, 11 metal ring, 12 through hole, 13 set substrate, 14 wiring path, 15 connection electrode, 16 shield electrode.

Claims (1)

Claims 1. A surface-mounting quartz crystal in which a quartz-crystal piece is housed and covered with a base having a surface-mounting electrode formed on an outer surface thereof, and the quartz-crystal piece is hermetically sealed. In the vibrator,
A quartz resonator, wherein a shield electrode grounded to a ground potential is provided on the base.