JP2001094379A - Ceramic base, piezoelectric device and piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic base for constantly securing a seal path though the deviation of a cover position with respect to a ceramic base occurs and a piezoelectric device, a quartz oscillator in particular, satisfactorily maintaining reliability and oscillation characteristic through the use of this. SOLUTION: (1) In a ceramic base which is obtained by laminating a bottom wall and a frame wall and holds a piezoelectric piece on the bottom wall and where a cover is connected to the upper surface of the frame wall with a sealing material, the outline of the frame wall is made smaller than that of the bottom wall. (2) In a piezoelectric device consisting of the ceramic base obtained by laminating the bottom wall and the frame wall, a piezoelectric piece held on the bottom wall and a cover connected with the upper surface of the frame wall with the sealing material, outline of the frame wall is made smaller than that of the bottom wall. (3) In a piezoelectric device consisting of the ceramic base obtained by laminating the bottom wall and the frame wall, a piezoelectric piece held on the bottom wall and an IC chip housed in a recess part formed at the bottom wall and a cover connected with the upper surface of the frame wall with the sealing material, the outline of the frame wall is made smaller than that of the bottom wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial technical field of a ceramic base and a piezoelectric device having a piezoelectric piece housed therein, especially a piezoelectric oscillator. In particular, the opening of the ceramic base is formed by a sealing material such as resin or glass. The present invention relates to a surface mount type crystal oscillator which is hermetically sealed by joining a cover to a surface.

[0002]

2. Description of the Related Art Piezoelectric devices, for example, crystal oscillators, are widely used as various frequency and time reference sources in various electronic devices including communication devices. As one of such devices, there is a device in which an IC chip and a crystal piece are accommodated in a ceramic base and a cover is joined with a sealing material such as glass or resin.

FIG. 6 is a cross-sectional view of a crystal oscillator for explaining a conventional example. The crystal oscillator includes a ceramic base 1, an IC chip 2, a crystal piece 3, and a cover 4. The ceramic base 1 has first and second bottom walls 5.
It consists of a laminate obtained by firing (ab). First in the lowest layer
The bottom wall 5a is a flat plate, the second bottom wall 5b has a hole,
To form At four corners of the first bottom wall 5a, electrodes (not shown) for surface mounting extend. The IC chip 2 is formed by integrating elements constituting an oscillation circuit, and is fixed to the bottom of the recess by, for example, face-down.

The crystal blank 3 covers the IC chip 2 and both ends of the extraction electrode extending from the excitation electrode (not shown) are fixed to the surface of the second bottom wall 5b. The outer shape of the cover 4 is smaller than that of the ceramic base 1 and is concave. Here, the resin 7 is applied to the opening end surface. And ceramic base 1
The opening end face of the cover 4 is positioned on the upper surface of the (second bottom wall 5b), and the resin is heated and melted and joined. In the drawings, reference numeral 8 denotes a bump, and reference numeral 9 denotes a conductive adhesive.

[0005]

[Problems to be Solved by the Invention]
However, in the crystal oscillator having the above configuration, the following problem has occurred due to a positional deviation of the cover 4 with respect to the ceramic base 1 within an allowable error during sealing. That is, when, for example, left and right positional shifts occur between the ceramic base 1 and the cover 4, the width of the joint surface between the open end surface of the cover 4 and the surface of the ceramic base 1 on the outside (left side), a so-called seal path W Becomes smaller (FIG. 7). Therefore, in this case, there has been a problem that the bonding strength is deteriorated, and particularly in the case of resin encapsulation, moisture easily penetrates, and the moisture resistance is reduced, resulting in a lack of reliability.

Further, on the inner side (right side), there is a possibility that the molten resin 7 adheres to the crystal blank 3 to deteriorate the vibration characteristics (not shown). For this reason, it is necessary to reduce the size of the crystal blank 3, and there is a problem that the degree of freedom in design is impaired. In particular, these have become more serious problems as the size of the device has become smaller. Note that a positional deviation exceeding the allowable error results in poor appearance.

(Object of the Invention) It is an object of the present invention to provide a ceramic base which ensures a constant seal path even when there is a displacement, and a piezoelectric device, particularly a piezoelectric oscillator, which uses the ceramic base to maintain good reliability and vibration characteristics. Aim.

[0008]

The basic solution of the present invention is to form a ceramic base 10 by laminating a frame wall 12 on a bottom wall 5 and making the outer shape of the frame wall 12 smaller than the bottom wall 5. Means.

[0009]

According to the present invention, a frame wall 12 whose outer shape is smaller than the bottom wall 5 is provided on the upper surface of the bottom wall 5, and the cover 11 is joined. Therefore, even if the cover 11 is displaced within the allowable error range, the seal path W is kept constant. Hereinafter, an embodiment of the present invention will be described.

[0010]

FIG. 1 is a sectional view of a crystal oscillator 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. The crystal oscillator is sealed by bonding a cover 11 to a ceramic base 10 with a resin 7 as described above. In this embodiment, the ceramic base 10 has a three-layer structure in which a frame wall 12 is laminated in addition to the bottom wall 5 (ab) described above. Frame wall 12
Are smaller than the outer shape of the bottom wall 5 and are laminated on the inner side with a tolerance. The IC chip 2 covers the bottom surface of the recess, and the crystal blank 3 covers the IC chip. Both ends are fixed to the surface of the frame wall 12. The cover is formed in a flat plate shape, and a resin 7 is applied to an outer peripheral portion. Then, the resin is positioned on the frame wall 12 of the ceramic base 10, and the resin is heated and melted for sealing.

With this configuration, even if the cover 11 is displaced within the allowable error range, the seal path W maintains a constant value as the wall width of the frame wall 12, as shown in FIG. I do. Therefore, the bonding strength and the moisture resistance are maintained well, and the reliability is improved. In addition, since the frame wall 12 is fixed and does not displace, the molten resin 7 is
It does not adhere to Therefore, the vibration characteristics can be favorably maintained without impairing the degree of freedom in design.

[0012]

[Others] In the above embodiment, the second bottom wall 5b is provided with a hole and the recess 6 is provided between the second bottom wall 5a and the first bottom wall 5a to accommodate the IC chip 2, but as shown in FIG. , On the contrary, the first
A hole is formed in the bottom wall 5a to make the second bottom wall 5b a flat plate,
May be provided to accommodate the IC chip 2. In this case, the IC chip 2 is protected by filling with resin 13 (so-called potting).

The recess 6 may accommodate not only the IC chip 2 but also other elements such as a capacitor. Further, although both ends of the crystal blank 3 are fixedly held, an extraction electrode may be extended to one end side to hold only one end. In addition, resin 7
Is applied to the cover 11 side, but may be applied to the ceramic base 10 side. In addition, although the sealing is performed by the resin 7, the same applies to the case where glass and other sealing materials are used. The cover 11 may be an insulator such as a ceramic or a metal. And although it was flat-shaped, what is necessary is just to make the joint surface with the frame wall 12 flat.

Further, as shown in FIG.
A recess 14 is formed on the outer periphery of the
May be positioned to prevent misalignment.
Although described as a crystal oscillator, as shown in FIG. 5, a ceramic resonator 15 in which a ceramic base 15 is formed from the bottom wall 5 and the frame wall 12 and only the crystal blank 3 is fixed on the bottom wall 5 is used. If so, the same applies. Furthermore, a so-called MCF (MONOLITHIC CRYSTAR) using a multiplex mode (not shown)
The present invention is similarly applicable to piezoelectric devices such as L FILTER) and surface acoustic wave elements, and the present invention does not exclude these from the technical scope.

[0015]

【The invention's effect】
According to the present invention, since the frame wall is laminated on the bottom wall and the outer shape of the frame wall is made smaller than the bottom wall to form a ceramic base, the piezoelectric piece is accommodated in the ceramic base and the cover is sealed, so there is a misalignment. Also, it is possible to provide a piezoelectric device, in particular, a piezoelectric oscillator, in which the seal path is kept constant and the reliability and the vibration characteristics are well maintained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a crystal oscillator illustrating one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a crystal oscillator illustrating the operation of the present invention.

FIG. 3 is a sectional view of a crystal oscillator illustrating another embodiment of the present invention.

FIG. 4 is a partial sectional view of a crystal oscillator illustrating another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a crystal unit for explaining another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a crystal oscillator illustrating a conventional example.

FIG. 7 is a partial cross-sectional view of a crystal oscillator explaining a problem of a conventional example.

[Explanation of symbols]

1, 10, 15 ceramic base, 2 IC chips,
3 crystal blank, 4, 11 cover, 5 bottom wall, 6 recess, 7
Resin, 8 bumps, 9 conductive adhesive, 12 frame walls,
13 potting agent, 14 depression.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H03H 9/10 H01L 41/08 C

Claims (3)

[Claims] 1. A ceramic base in which a bottom wall and a frame wall are laminated and a piezoelectric piece is held on the bottom wall, and an upper surface of the frame wall and a cover are joined by a sealing material. A ceramic base characterized in that the outer shape of the frame wall is smaller than that of the ceramic base. 2. A piezoelectric device comprising: a ceramic base formed by laminating a bottom wall and a frame wall; a piezoelectric piece held on the bottom wall; and a cover having an upper surface of the frame wall joined by a sealing material. A piezoelectric device, wherein the outer shape of the frame wall is smaller than the bottom wall. 3. A ceramic base formed by laminating a bottom wall and a frame wall, a piezoelectric piece held on the bottom wall, an IC chip housed in a recess provided in the bottom wall, A piezoelectric oscillator comprising a cover having an upper surface joined by a sealing material, wherein an outer shape of the frame wall is smaller than that of the bottom wall.