JP2004179734A - Surface mount crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface mount crystal oscillator for firstly promoting downsizing, particularly decreasing the height, and secondly improving the oscillation characteristics to facilitate the design. <P>SOLUTION: The surface mount crystal oscillator formed by integrating an IC for configuring an oscillation circuit, a crystal chip, and a planar mounting substrate into a substrate with a recess is configured such that a silicon substrate mounted with the oscillation circuit configuring the IC is adopted for the mounting substrate 1, the cover is made of glass containing ions having mobility, and the silicon substrate and the cover are bonded by anode bonding. For example, pyrex (R) glass is used for the cover. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface-mounted crystal oscillator (hereinafter referred to as a surface-mounted oscillator) in an industrial technical field, and particularly relates to a surface-mounted oscillator that promotes miniaturization.
[0002]
[Prior art]
BACKGROUND OF THE INVENTION Due to their small size and light weight, surface mount oscillators are widely used as frequency and time reference sources, especially in portable electronic devices. In recent years, smaller and smaller surface-mount oscillators have been demanded from the trend toward further miniaturization.
[0003]
(Example of Prior Art) FIGS. 4A and 4B are diagrams of a surface mount oscillator for explaining a conventional example, wherein FIG. 4A is a sectional view and FIG. 4B is a plan view of a crystal blank.
[0004]
The surface mount oscillator includes a mounting substrate 1, an IC chip 2, a crystal blank 3, and a cover 4. The mounting substrate 1 is made of a concave multilayer ceramic having a step on the inner wall, and is formed by laminating a bottom wall 5 and first and second frame walls 6 (ab). Then, an IC connection terminal (not shown) is provided on the bottom surface of the concave portion, a crystal terminal is provided on the step portion, and an external terminal 7 for surface mounting is provided on the outer surface. The external terminal 7 is connected to the IC connection terminal via the lamination surface.
[0005]
The IC chip 2 integrates an oscillation circuit and has an IC terminal (not shown) including at least a power supply, an output, and a ground terminal on one main surface. Then, one main surface of the IC chip 2 is fixed to the IC connection terminal on the bottom surface of the concave portion by ultrasonic thermocompression bonding or thermocompression bonding using the bump 8, and is electrically and mechanically connected.
[0006]
The crystal blank 3 has excitation electrodes 9 on both main surfaces, for example, extending extraction electrodes 10 on both sides of one end. Then, both ends of the extending one end of the extraction electrode 10 are fixed on the crystal connection terminal of the recessed step by the conductive adhesive 10 and electrically and mechanically connected.
[0007]
[Problems to be solved by the invention]
(Problems of the prior art) However, in the surface-mounted oscillator having the above configuration, since the components are the mounting board 1, the IC chip 2, the crystal blank 3, and the cover 4, it is difficult to further reduce the size further. And In the above example, since the IC chip 2 and the crystal blank 3 are arranged in the thickness direction, there is a problem that the height dimension is particularly increased.
[0008]
In addition, since the mounting substrate 1 is made of a laminated ceramic, the thickness of the first frame wall 6a needs to be a certain value or more, for example, a width equal to or more than a certain value in the manufacturing process of laminating and firing the green sheets. Therefore, the area of the inner bottom surface in the container is impaired.
[0009]
On the other hand, the larger the plate surface area of the crystal blank 3, the better the vibration characteristics, and, for example, the capacity ratio C0 / C1 is reduced to increase the degree of freedom in design, thereby facilitating the design. C0 is an equivalent parallel capacitance (capacity between electrodes), and C1 is an equivalent series capacitance. For this reason, a container having a small planar outer dimension and a large inner bottom surface area of the mounting board 1 is required.
[0010]
Further, in the prior art (quartz oscillator), there is one in which the mounting substrate 1 is formed in a flat plate shape, and the concave cover 4 made of ceramic is sealed with glass or resin (not shown). In such a case, since it is integrally formed, the frame width of the cover 4 can be reduced and the inner bottom surface area can be increased. However, in the case of glass sealing, the strength of glass as a bonding material is small, and there is a problem in impact resistance. In the case of resin sealing, there is a problem that external air such as moisture enters and the vibration characteristics are reduced. .
[0011]
(Objects of the Invention) It is an object of the present invention to firstly reduce the height by promoting miniaturization, and secondly to provide a surface-mounted oscillator which facilitates the design by improving the vibration characteristics. And
[0012]
[Non-Patent Document 1] Dictionary of Advanced Materials, issued February 25, 1997, 4th press, pp. 629-630.
[Non-Patent Document 2] Toyota Central R & D Review, Vol. 28, No4 (1993.12) P53-54
[0013]
[Means for Solving the Problems]
(Points of interest and application) The present invention focuses on the anodic bonding technology between the silicon substrate and the glass containing mobile ions described in Non-Patent Documents 1 and 2, and uses the silicon substrate as a flat mounting substrate to form a concave glass. In addition to being applied to the surface mount oscillator container as a cover, the oscillation circuit was integrated (integrated) on a silicon substrate.
[0014]
According to claim 1 of the present invention, a flat mounting substrate is a silicon substrate in which an oscillation circuit is formed into an IC, a concave cover is made of glass having movable ions, and the silicon substrate and the cover are anodically bonded. I do.
[0015]
As a result, the silicon substrate also serves as a conventional mounting substrate and an IC chip, so that the number of components can be reduced and the size can be reduced, particularly the height can be significantly reduced. Further, since the cover is made of glass having a concave shape, the frame width can be reduced. Therefore, it is possible to reduce the planar outer shape and increase the inner bottom surface area. Thereby, the vibration characteristics of the crystal piece are improved. And, without using a sealing material such as glass or resin, the impact resistance is improved and the invasion of outside air is prevented.
[0016]
According to claim 2, the silicon substrate has a crystal terminal electrically connected to the crystal blank on an inner surface, and has an IC terminal including at least a power supply, an output and a ground terminal of the oscillation circuit on an outer surface, An external terminal used for surface mounting of the mounting board and the IC terminal are electrically connected to each other through a sealed electrode through hole. Thereby, the airtightness of the mounting substrate is maintained by the sealed electrode through-hole.
[0017]
In the third aspect, the electrode through-hole is provided on a joint surface between the silicon substrate and the cover. Thereby, the electrode through-hole is shielded by the upper surface of the frame wall of the cover, so that airtightness is ensured.
[0018]
In claim 4, the electrode through-hole is sealed by a metal body provided on the IC terminal. Thereby, the electrode through-hole is shielded by the metal body, so that airtightness is ensured.
[0019]
According to claim 5, the silicon substrate has a crystal terminal electrically connected to the crystal blank 3 on an inner surface, and an IC terminal including at least a power supply, an output and a ground terminal of the oscillation circuit on an outer surface, The IC terminal extends a bonding surface between the silicon substrate and the cover by a conductive path made of Al (aluminum) and is electrically connected to the external terminal. This ensures airtightness.
[0020]
In claim 6, mobile ions contained in the glass of the cover are Na ⁺ or Li ⁺ . This ensures anodic bonding.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram of a surface mount oscillator illustrating 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.
[0022]
The surface mount oscillator is formed by enclosing a crystal blank 3 in a container including a flat mounting board 1 and a concave cover 4. The mounting substrate 1 is a silicon substrate, and the cover 4 is a glass containing mobile ions such as Na ⁺ and Li ⁺ . The silicon substrate has an oscillation circuit integrated therein, and the crystal terminals 11 are exposed on both sides of one end of the inner surface, and the IC terminals 12 such as power supply, output and ground terminals are exposed in the central region. Both ends of the extending end of the extraction electrode of the crystal blank 3 are fixed to the crystal terminal 11 by, for example, bumps 8.
[0023]
Each of the IC terminals 12 extends to the four corners by the conductive path 13. The oscillation circuit is integrated in the central region of the silicon substrate, and the outer peripheral region is a non-circuit region. Further, external terminals 7 for surface mounting are provided at the four corners of the outer surface. Then, the external terminals 7 and the IC terminals 12 are electrically connected by the electrode through holes 14 provided at the four corners. The electrode through hole 14 is provided with a through hole and an electrode is formed by vapor deposition or the like.
[0024]
Here, the glass as the cover 4 is Pyrex (registered trademark) glass containing mobile ions Na ⁺ . Then, the upper surface of the frame wall of the cover 4 is joined by anodic bonding to the outer periphery of the silicon substrate (mounting substrate 1) as a non-circuit area. In this case, the upper surface of the frame wall of the cover 4 is joined so as to cover the electrode through hole 14.
[0025]
In the anodic bonding, the upper surface of the frame wall of the glass (cover 4) is brought into contact with the outer peripheral surface of the silicon substrate (mounting substrate 1), and a negative voltage of about 500 V is applied to the glass side while heating (300 to 400 ° C.). As a result, mobile ions Na ⁺ contained in Pyrex (registered trademark) glass move, and a Na ⁺ ion-depleted layer is formed at the interface with the silicon substrate, thereby generating a large electrostatic attraction. And the interface of both leads to a chemical bond. The contact surface between the mounting board 1 and the cover 4 is mirror-polished.
[0026]
With such a configuration, a silicon substrate on which an oscillation circuit is integrated is applied to the mounting substrate 1, so that the conventional IC chip 2 becomes unnecessary. Therefore, the number of parts can be reduced, and miniaturization is promoted. In particular, in this example, the height dimension can be reduced in each step.
[0027]
In addition, since the cover 4 is made of glass and has a concave shape, the frame width can be reduced, the planar outer shape can be reduced, and the inner bottom surface area can be increased. Accordingly, the outer shape of the crystal blank 3 can be made large, and the vibration characteristics can be improved, thereby increasing the degree of freedom in design. Then, since the mounting substrate 1 is formed by anodic bonding, a glass or resin sealing material is unnecessary as in the related art, and the impact resistance is improved to prevent invasion of outside air.
[0028]
[Other matters]
In the above embodiment, the electrode through-holes 14 are provided on the joint surface between the mounting board 1 and the cover 4, but may be as follows. That is, as shown in FIG. 2, an electrode through-hole 14 may be provided in a non-circuit area inside the cover 4 and shielded by the metal thin plate 15 so as to be electrically connected to the external terminal 7.
[0029]
Further, as shown in FIG. 3, the conductive path 13 from the IC terminal 12 may be made of Al (aluminum) so as to cross the bonding surface with the cover 4 and be connected to the external terminal 7 by the end face electrode 16. In this case, the airtightness is maintained because the conductive path 13 is made of Al as shown in the non-patent document (p630).
[0030]
Further, although the cover 43 is made of Pyrex (registered trademark) glass, it may be made of, for example, devitron glass disclosed in Patent Document 2 (p54), and basically contains mobile ions such as Na ⁺ and Li ⁺ ions. Just fine.
[0031]
The purpose of the present invention is to form a container for a surface-mounted oscillator by anodic bonding of a flat silicon substrate having an integrated oscillator circuit and a concave glass containing movable ions, and a method of fixing a crystal piece and deriving an electrode. Can be arbitrarily formed as required in addition to the above embodiments, and these are not excluded from the technical scope.
[0032]
【The invention's effect】
According to the present invention, basically, the flat mounting substrate 1 is a silicon substrate in which an oscillation circuit is formed into an IC, the concave cover 4 is a glass having movable ions, and the silicon substrate and the cover 4 are anodically bonded. With such a configuration, it is possible to provide a surface-mounted oscillator that promotes miniaturization and particularly reduces the height dimension, and secondly improves vibration characteristics and facilitates design.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams of a surface-mounted oscillator illustrating an embodiment of the present invention. FIG. 1A is a sectional view, and FIG. 1B is a plan view excluding a cover 4.
FIGS. 2A and 2B are diagrams of a surface mount oscillator for explaining another embodiment of the present invention, wherein FIG. 2A is a sectional view and FIG. 2B is a plan view excluding a cover 4;
FIGS. 3A and 3B are diagrams of a surface mount oscillator for explaining still another embodiment of the present invention, wherein FIG. 3A is a sectional view and FIG. 3B is a plan view excluding a cover 4.
4A and 4B are diagrams illustrating a conventional example. FIG. 4A is a cross-sectional view of a surface mount oscillator, and FIG. 4B is a plan view of a crystal blank 3.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 mounting board, 2 IC chip, 3 crystal piece, 4 cover, 5 bottom wall, 6 frame wall, 7 external terminal, 8 bump, 9 excitation electrode, 10 extraction electrode, 11 crystal terminal, 12 IC terminal, 13 conductive path, 14 electrode through hole, 15 metal sheet, 16 end face electrode.

Claims (6)

In a crystal oscillator for surface mounting, in which an IC and a crystal piece constituting an oscillation circuit are integrated in a container consisting of a flat mounting board and a concave cover, the oscillation circuit of the mounting board is made into an IC. A quartz oscillator, wherein the silicon substrate is made of glass having movable ions, and the silicon substrate and the cover are anodically bonded. The silicon substrate has a crystal terminal electrically connected to the crystal blank on an inner surface thereof, and has an IC terminal including at least a power supply, an output and a ground terminal of the oscillation circuit on an outer surface thereof. 2. The crystal oscillator according to claim 1, wherein the external terminal for mounting and the IC terminal are electrically connected by a sealed electrode through hole. 3. The crystal oscillator according to claim 2, wherein said electrode through-hole is provided on a joint surface between said silicon substrate and said cover. 3. The crystal oscillator according to claim 2, wherein said electrode through-hole is sealed with a metal body provided on said IC terminal. The silicon substrate has a crystal terminal electrically connected to the crystal piece on an inner surface, and has an IC terminal including at least a power supply, an output, and a ground terminal of the oscillation circuit on an outer surface, and the IC terminal is Al ( 2. The crystal oscillator according to claim 1, wherein a bonding surface between the silicon substrate and the cover extends through a conductive path made of aluminum and is electrically connected to the external terminal. 2. The crystal unit according to claim 1, wherein said movable ions are Na ⁺ or Li ⁺ .

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