JPH11284482A - Multiple-mode crystal resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a guaranteed attenuation by selecting the film thickness of a extraction electrode larger than that of a common electrode so as to reduce the resistance of the extracting electrode extending from the common electrode. SOLUTION: A multiple-mode crystal resonator has input/output electrodes 2a, 2b and a common electrode 3 made of aluminum on one major side and the other major side. Leader electrodes 10a, 10b, which extend from these electrodes to both end outer circumferential parts in different diagonal directions, are made of aluminum and formed altogether through vapor- deposition. An Ag electrode through vapor-deposition is formed on the leader electrodes 10a, 10b of the common electrode 3 larger than the film thickness of the common electrode 3. One major side of a crystal chip 1 is made to face opposite to a shield electrode formed on the bottom face of a face mount package, and a square part with leader electrodes 4a, 4b, 10a, 10b extended from input/output electrodes 2a, 2b and from the common electrode 3 is fixed by a conductive adhesive and a metallic cover is adhered. A guaranteed attenuation of 73 dB is obtained at a frequency which is detuned from a center frequency 130 MHz just by an image frequency 910 kHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-mode crystal resonator as a monolithic filter (MONOLITHIC CRYSTAL FILTER). About the child.

[0002]

2. Description of the Related Art A multi-mode vibrator utilizes acoustic coupling between two pairs of electrodes formed on a crystal blank.
It is useful for communication devices and the like as a filter element for obtaining predetermined transmission characteristics. In recent years, further downsizing and higher frequencies have been demanded, and with this, there has been a problem that the guaranteed attenuation decreases.

FIG. 7 is a diagram of a multi-mode vibrator for explaining a conventional example. FIG. 7A shows one main surface of a crystal blank, and FIG. 7B shows the other main surface. FIG. The multi-mode vibrator has an input / output electrode 2
(Ab) and the common electrode 3 on the other main surface. The extraction electrodes 4 (ab) extend from the input / output electrodes 2 (ab) to the outer peripheral portions at both ends of the crystal blank 1, and the common electrodes 3 are provided with extraction portions 5. These electrodes are made of aluminum (AL) and are formed collectively by vapor deposition.

[0004] Then, for example, the shield electrode 7 formed on the bottom of the surface mounting container 6 and one main surface are opposed to each other.
The outer peripheral portions at both ends where the extraction electrode 4 (ab) extends are fixed to the extraction electrode portion (not shown) by the conductive adhesive 8 (eighth).
Figure). Further, the common electrode 3 is connected to the shield electrode 7 by providing a gold wire by wire bonding in the lead portion 5. Then, a metal cover (not shown) electrically connected to the shield electrode 7 is joined to the opening surface of the surface mount container 6 by seam welding or the like. In such a device, the electrodes are led out from the lead portion 5 provided near the common electrode 3 by the gold wire 9, so that the conduction resistance can be reduced and the guaranteed attenuation can be increased (see Japanese Patent Application Laid-Open No. H8-222987). No.).

[0005]

[Problems to be Solved by the Invention]
However, in the multi-mode vibrator having the above configuration, the common electrode 3 is derived by wire bonding.
Work is difficult due to the downsizing and high frequency (thinning) of the crystal blank 1 and there is a problem that the crystal blank 1 is damaged.
For example, the outer shape of the crystal blank 1 is 5 mm long and 2.5 mm wide,
If the frequency is 100 MHz in the third overtone, the thickness is about 50 μm.

For this reason, instead of wire bonding,
As shown in FIG. 9, it has been considered that the extraction electrodes extend from the common electrode 3 to the outer peripheral portions at both ends in the diagonal direction, and are fixed by the conductive adhesive 8 to perform the electrical derivation. However, in this case, since the thickness of the extraction electrode 10 (ab) is small (in Angstroms), the conduction resistance is increased, and there is a problem that the guaranteed attenuation is reduced. In particular, when the frequency becomes high (about 40 MHz or more in the case of a fundamental wave), since AL having a small mass is used as an electrode due to the bandwidth and the like, the conductivity becomes large as compared with silver or the like, and this problem is remarkable. Was.

(Object of the Invention) It is an object of the present invention to provide a multi-mode vibrator in which the conduction resistance of an extraction electrode extending from a common electrode is reduced to increase the guaranteed attenuation.

[0008]

According to the present invention, a basic solution is to make the thickness of the extraction electrode larger than that of the common electrode.

[0009]

According to the present invention, since the thickness of the extraction electrode is made larger than that of the common electrode, the conduction resistance of the extraction electrode can be reduced. Hereinafter, an embodiment of the present invention will be described.

[0010]

FIG. 1 is a diagram of a multimode vibrator for explaining an embodiment of the present invention. FIG. 1 (a) is a diagram of one main surface of a crystal blank, and FIG. FIG. The same parts as those in the conventional example are given the same numbers, and the description is simplified. The multi-mode vibrator has the input / output electrode 2 (ab) and the common electrode 3 made of AL on one main surface and the other main surface as described above. In this embodiment, the input / output electrode 2 (a
b) and the extraction electrode 10 (ab) extends from the common electrode 3 to the outer peripheral portions at both ends in different diagonal directions. Each of these electrodes is A
L, and are formed collectively by vapor deposition as described above. Then, as shown in FIG. 2, a silver (Ag) electrode is separately deposited on the extraction electrode 10 (ab) of the common electrode 3 by vapor deposition, and is formed to be larger than the film thickness of the common electrode 3. The crystal blank 1 has one main surface opposed to a shield electrode 7 formed on the bottom surface of the surface mounting container 6 and the input / output electrode 2 (a
b) and the extraction electrodes 4 (ab) and 10 (a) from the common electrode 3.
The extended four corners of b) are fixed with a conductive adhesive 8, and a metal cover (not shown) is joined.

FIG. 3 is a transmission characteristic diagram of the present embodiment in comparison with the conventional example. The center frequency is 130 MHz (3
The curve A in the figure is the present embodiment, and the curve B is the conventional example. As is clear from this curve, in the transmission characteristics (curve a) in the present embodiment, the guaranteed attenuation at a frequency detuned by -910 KHz from the center frequency serving as the image frequency is 73 dB, whereas the conventional example (curve a). In (b), it becomes 57 dB. Thus, in this embodiment,
Since the thickness of the extraction electrode 10 (ab) is increased and the conduction resistance is reduced by attaching Ag having better conductivity than that of AL, it can exceed, for example, 70 dB or more, which is a standard for mobile phones and the like.

FIG. 4 is a simulation result diagram showing the relationship between the conduction resistance and the guaranteed attenuation. This simulation was performed based on the equivalent circuit diagram as a filter of the multimode oscillator shown in FIG.
g is a conduction resistance between the common electrode 3 and the shield electrode 7 (earth electrode). Cp is the input / output electrode 2 (ab)
The capacity between. As is apparent from this figure, if the conduction resistance Rg is 0.01 ohm or less, the guaranteed attenuation reaches a peak value and saturates. Incidentally, the conduction resistance between both ends of the extraction electrode 10 (ab) in this embodiment was 0.01Ω, and that in the conventional example was 0.1Ω.

[0013]

[Other Matters] In the above embodiment, an Ag electrode is attached on the extraction electrode 10 (ab) made of AL extending from the common electrode 3 to increase the film thickness. May be attached. Further, as shown in FIG. 6, a part of the common electrode 3 may be drawn out, and an electrode such as Ag having a larger film thickness than the common electrode 3 may be connected thereto.

Although the extraction electrodes 10 (ab) extend from both ends of the common electrode 3 at diagonal ends, the extraction electrodes 10 (ab) may extend to any one of the outer ends. Further, the lead electrode 10 (ab) may be wound around the other main surface to increase the width to further reduce the conduction resistance. In short, the form of the extraction electrode can be changed as needed, and as shown in the simulation, the relationship between the conduction resistance and the guaranteed attenuation indicates that the extraction electrode 10 ( It is sufficient that the film thickness of ab) is larger than the film thickness of the common electrode 3.

[0015]

According to the present invention, since the thickness of the extraction electrode is made larger than that of the common electrode, it is possible to provide a multi-mode vibrator in which the conduction resistance of the extraction electrode is reduced and the guaranteed attenuation is increased.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams of a multimode vibrator for explaining an embodiment of the present invention. FIG. 1A is a diagram of one main surface of a crystal blank, and FIG. 1B is a diagram of the other main surface. is there.

FIG. 2 is a cross-sectional view of a crystal blank, illustrating a multi-mode vibrator for explaining an embodiment of the present invention.

FIG. 3 is a transmission characteristic diagram illustrating the operation and effect of one embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a conduction resistance and a guaranteed attenuation amount, illustrating an embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram obtained by obtaining the characteristics of FIG. 6 for explaining one embodiment of the present invention.

FIG. 6 is a diagram of a multi-mode vibrator for explaining another embodiment of the present invention, and is a partial cross-sectional view of a crystal blank.

7A and 7B are diagrams of a multimode vibrator for explaining a conventional example, wherein FIG. 7A is a diagram of one main surface of a crystal blank and FIG. 7B is a diagram of the other main surface.

FIG. 8 is a cross-sectional view of a crystal blank, illustrating a multi-mode vibrator for explaining a conventional example.

FIG. 9 is a view of the other main surface of a crystal piece for explaining a conventional example.

[Brief description of reference numerals]

1 crystal blank, 2 (ab) input / output electrode, 3 common electrode,
4, 10 (ab) extraction electrode, 5 extraction part, 6-surface mounting container, 7 shield electrode, 8 conductive adhesive, 9 gold wire, 10 extraction electrode.

Claims (1)

[Claims] An input / output electrode is provided on one main surface of a crystal blank.
In a multi-mode crystal resonator having a common electrode on the other main surface and extending an extraction electrode from the common electrode to the outer peripheral end of the crystal piece, the thickness of the extraction electrode is set to be smaller than the thickness of the common electrode. A multi-mode crystal resonator characterized by being enlarged.