JP3201817B2 - Multi-mode crystal oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an MCF (Monolithic Cry).
The present invention relates to a multi-mode type crystal resonator (hereinafter referred to as a multi-mode resonator) as a stal filter, and particularly relates to a multi-mode resonator which increases a guaranteed attenuation.

[0002]

BACKGROUND OF THE INVENTION A multi-mode vibrator is used in communication equipment and the like to obtain a predetermined filter characteristic (transmission characteristic) by utilizing acoustic coupling between, for example, two pairs of electrodes formed on a crystal blank. . One of such devices is to reduce the leakage signal due to the electrical coupling between the input and output electrodes, thereby increasing the guaranteed attenuation (see: Japanese Patent Application No. 60-118993, Japanese Patent Application No. 63-27 / 1988).
3981, Japanese Patent Application No. 1-83007).

[0003]

2. Description of the Related Art FIGS. 6 to 8 are views for explaining a conventional example of such a multimode vibrator. FIG. 6 (a) is a sectional view, and FIG. FIG.
The figure is a bottom view of the container body. The multi-mode vibrator is formed by enclosing a crystal blank 1 in a sealed container 2. The crystal blank 1 is composed of, for example, an AT-cut thickness shear resonator. On one main surface 1a, divided input / output electrodes 3, 4 are formed, and on the other main surface 1b, a common electrode 5 is formed. Input / output electrode 3,
The extraction electrodes 6, 7, and 8 extend from the common electrode 4 and the common electrode 5, respectively. The closed container 2 includes a concave container body 9 and a metal lid 10 formed by seam welding. Bottom surface 9a of container body 9
, A shield electrode 11 is provided at the center thereof, and input / output connection electrodes 12 and 13 are provided on both sides. Shield electrode 1
1 is connected to the common electrode extraction electrode 8 by wire bonding or the like (not shown), and the input / output connection electrodes 12 and 13 are connected to the input / output extraction electrodes 6 and 7 by the conductive adhesive 14 or the like. Then, due to the thickness of the conductive adhesive 14, a gap (electrode gap G) is formed between the one main surface of the crystal blank 1 and the bottom surface of the container body 9 with the shield electrode 11 and the input / output electrodes 3 and 4 facing each other. ). The shield electrode 11 and the input / output connection electrodes 12 and 13 are exposed on the outer surface of the container body 9 and serve as surface mounting terminals. In such a case, since the leak signal directly propagating due to the electrical coupling between the input and output electrodes 3 and 4 is shielded by the shield electrode 11, a decrease in the guaranteed attenuation is prevented. In particular, the electrode gap G is much smaller than the thickness of the conductive adhesive 14. Therefore, it is possible to enhance the shielding effect and expect a large increase in the guaranteed attenuation. Note that guarantee attenuation in the as shown in FIG. 9 refers to the attenuation A (dB) at the points down 910KHz from the center frequency f _0.

[0004]

Problems with the prior art However, in the above-mentioned structure, when the thickness of the conductive adhesive 14 is reduced to reduce the electrode gap G, there is a problem that the guaranteed attenuation is reduced contrary to the expectation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to further clarify the relationship between the electrode gap and the guaranteed attenuation and to provide a multi-mode vibrator that increases the guaranteed attenuation.

[0006]

According to the present invention, an electrode gap is found to have an optimum value (singular point), and the electrode gap is set to a peak value of a guaranteed attenuation amount and its vicinity. Furthermore,
Specifically, the solution is to set the electrode gap from 15 μm to 40 μm. Hereinafter, one embodiment of the present invention,
This will be described with an experimental example that clarifies these.

[0007]

FIG. 1 (abc) shows the electrode gap (horizontal axis, μ
FIG. 7 is a diagram for explaining a relationship between m) and a guaranteed attenuation (vertical axis, dB). FIG. 1 (a) shows the center frequency f ₀ of the multi-mode vibrator at about 22 MHz, FIG.
FIG. 3C shows a case where the frequency is set to 90 MHz. In these experimental examples, the bottom wall 9 of the container body 9 in the prior art example was used.
The crystal blank 1 was fixed on the holding plate corresponding to a, and the electrode gap G corresponding to the thickness of the conductive adhesive 14 was measured with a microscope (photograph). From these experimental results, in any case, as the electrode gap G becomes smaller, the guaranteed attenuation increases, but reaches a peak value near 25 μm of 15 to 40 μm, and rapidly decreases when the value is less than 25 μm. Especially 22MH
z In the case of "FIG. 1 (a)", the peak value is 80 dB or more, and hereinafter, about 8 MHz in the case of 45 MHz "FIG. 1 (b)".
It is understood that the frequency is 70 dB in the case of 0 dB, 90 MHz “FIG. 1 (c)”. Note that the electrode gap G for obtaining the peak value becomes slightly smaller as the center frequency becomes higher. The inventor of the present invention has considered the phenomenon with respect to this experimental result, and it is presumed that the phenomenon is caused as follows. That is, as shown in FIG. 3, the electrode gap G has a peak value, for example, 2
When approaching at a distance of 5 μm or more, the input / output electrodes 3, 4
Leakage signal P ₁ due to electrical coupling (stray capacitance C ₁ ) between
It flows (sucks) into the shield electrode 11 and flows out to the reference potential. Therefore, the input / output electrodes 3 and 4 are shielded, and the guaranteed attenuation increases. Next, when approaching within 25 μm,
Stray capacitances C ₂ and C ₃ are generated between the input / output electrodes 3 and 4 and the shield electrode 11. Then, the leakage signal P ₂ leaks from the input electrode 3 to the output electrode 4 via the stray capacitances C ₂ and C ₃ (FIG. 4). Therefore, it was presumed that the guaranteed attenuation rapidly decreased. In FIG. 3, the stray capacitance C ₂ ,
Although C ₃ is considered to occur, its value is small and the leakage signal P ₂ is very small. It is estimated that the leakage signal P ₁ between the input / output electrodes 3 and 4 is further shielded. Further, although a particular problem leakage signal P ₁ between the input and output electrodes 3 and 4, when said Similar remarks leakage signal generated between the output electrode 3, 4 and the common electrode 5 (not shown) Conceivable. Therefore, as described above, by setting the electrode gap G to the peak value of the guaranteed attenuation and the vicinity thereof, for example, by setting it between 15 and 40 μm, it is possible to obtain a multi-mode vibrator having a good guaranteed attenuation. be able to.

[0008]

[Others] In the above embodiment (experimental example), both ends of the crystal blank 1 are attached to the holding plate (bottom wall of the container body) 9a by the conductive adhesive 1.
4, and the thickness corresponding to the gap is defined as the electrode gap G between the shield electrode 11 and the input / output electrodes 3 and 4.
In this case, it is difficult to make the gap G constant (uniform), so that the gap G may be as shown in FIG. 5, for example. That is, the thicknesses of the shield electrode 11 provided on the bottom wall of the container body 9 and the output connection electrode 4 are made different by about 20 μm when metallized. Then, one end of the crystal blank 1 is fixed with a conductive adhesive 14 of about 5 μ to obtain an electrode gap G. In this case, since the metallization can be made uniform, it is easier to control the electrode gap G to be constant than when only the conductive adhesive 14 is used. In addition, since only one end is fixed and the other end is a free end, impact resistance can be improved. In this figure, the input / output electrodes and the extraction electrodes of the crystal blank 1 are omitted. In addition, the electrode is led out from the other end by wire bonding. As described above, the present invention can be variously modified. Basically, the holding structure of the crystal blank 1 and the like may be arbitrarily designed. In short, the electrode gap between the shield electrode 11 and the input / output electrodes 3 and 4 is essential. A structure in which G is brought close to the peak value of the guaranteed attenuation is included in the technical scope of the present invention. Note that, of course, the shield electrode 11 may be a metal plate or the like.

[0009]

According to the present invention, the optimum value (singular point) is set for the electrode gap.
Since the electrode gap is set at or near the peak value of the guaranteed attenuation, it is possible to provide a multi-mode vibrator that increases the guaranteed attenuation, and its practical merit is very large.

[Brief description of the drawings]

FIGS. 1A and 1B are characteristic diagrams of a guaranteed attenuation amount with respect to an electrode gap G for explaining the operation and effect of the present invention. FIG. 1A shows a center frequency of 22 MHz, FIG. 9
This is the case of 0 MHz.

FIG. 2 is a structural sectional view of a multimode vibrator for one embodiment (experimental example) of the present invention.

FIG. 3 is a schematic diagram for explaining the operation and effect of the present invention, and is a diagram when an electrode gap G approaches by a distance of 25 μm or more.

FIG. 4 is a schematic diagram illustrating the operation and effect of the present invention, and is a diagram when an electrode gap G approaches within 25 μm.

FIG. 5 is a sectional view of a multimode vibrator for explaining another embodiment of the present invention.

FIG. 6 is a sectional view of a multimode vibrator for explaining a conventional example.

FIG. 7 (a) is a view of one main surface of a crystal blank for explaining a conventional example, and FIG. 7 (b) is a view of the other main surface.

FIG. 8 is a diagram of a bottom surface of a container body for explaining a conventional example.

FIG. 9 is a band characteristic diagram showing a guaranteed attenuation of a multi-mode vibrator.

[Explanation of symbols]

1 crystal blank, 2 sealed container, 3 input electrode, 4 output electrode, 5 common electrode, 6, 7, 8 extraction electrode, 9 container body, 9a container bottom, 10 metal cover, 11 shield electrode, 12 input connection electrode, 13 output connection electrode, 14 conductive adhesive.

Continuation of the front page (56) References JP-A-52-141157 (JP, A) JP-A-63-65707 (JP, A) JP-A-2-2611211 (JP, A) JP-A-2-119406 (JP) , A) JP-A-2-98207 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00-9/215 H03H 9/54-9/60

Claims (1)

(57) [Claims] [Claim 1 wherein said input to form a common electrode on the other principal surface to form a first main surface to the input and output electrodes of the crystal piece
Extending the extraction electrode from the electrode to the outer peripheral portion of the crystal piece, the
The outer periphery of the crystal piece with the extraction electrode extended to the bottom of the container body
It is fixed to the provided connection electrode with a conductive adhesive.
In the multi-mode crystal resonator having one main surface of the crystal piece opposed to and close to a shield electrode provided on the bottom surface of the container body to increase the guaranteed attenuation , Thick
Only make the conductive adhesive larger than the shield electrode
The total thickness of the material and the gap between one of the main surfaces of the crystal blank and the shielding electrode is such that the peak value of the guaranteed attenuation exists.
A multi-mode crystal resonator characterized in that the thickness is within 40 μm from 40 μm .