JP4363990B2 - Surface mount crystal unit - Google Patents

Description

The present invention relates to a surface mount crystal resonator (hereinafter referred to as a surface mount resonator), and more particularly to a surface mount resonator by seam welding.

(Background of the Invention) Surface mounted resonators are particularly small and light, and are therefore built in portable electronic devices. As one of such devices, there is a surface-mounted vibrator in which a container body that encloses a crystal piece and a metal cover are joined by seam welding.

(Example of Prior Art) FIG. 5 is a view for explaining one conventional example. FIG. 5 (a) is a cross-sectional view of a surface-mounted vibrator, and FIG. 5 (b) is a plan view of a crystal piece.

The surface-mounted vibrator is formed by mounting a crystal piece 2 on a container body 1 and joining a metal cover 3. The container body 1 is made of a laminated ceramic having a concave shape, and has a bottom wall 1a and a frame wall 1b. A rotating metal ring 4 is brazed to the upper surface of the frame wall 1b. The metal ring 4 is, for example, Kovar (Kv)
And The outer surface (bottom surface and side surface) of the container body 1 has external terminals for surface mounting (not shown).

The quartz crystal piece 2 is formed in, for example, a rectangular AT cut, has excitation electrodes 5 on both main surfaces, and extends extraction electrodes 6 on both sides of one end portion (FIG. 5 (b)). Then, both ends of the extended end portion of the extraction electrode 6 are fixed to the inner bottom surface of the container body 1 by the conductive adhesive 7.

The metal cover 3 is made of Kovar (Kv) like the metal ring 4 and has a Ni film (not shown) formed by plating, for example, on the surface. Then, the pair of metal rollers 8 are energized while rotating while abutting and pressing the opposing two sides (long side and short side) of the metal cover 3, and seam welding is performed. That is, the Ni film of the metal cover 3 is melted by Joule heat, and the metal cover 3 is joined to the metal ring 4.
JP-A-5-243409

(Problems of the prior art) However, the surface mount vibrator having the above-described configuration has the following problems during seam welding. First, although the opposing surfaces of the metal ring 4 and the metal cover 3 are both flat, they are microscopic uneven surfaces. Accordingly, Joule heat is generated particularly at the contact portion at the convex portion, and local bonding is performed. As a result, the bonding at the recess becomes insufficient,
In particular, when the bonding is insufficient in the direction of circulation, there is a problem that the airtightness deteriorates (airtight failure). The airtight defect deteriorates the vibration characteristics including the frequency fluctuation and becomes a fatal defect for the crystal resonator.

Second, when the Ni film is melted by seam welding, metal scrap (Ni) is generated and scattered (so-called splash), and directly adheres to the crystal piece 2, for example. Alternatively, it adheres to the inside of the container body 1 and adheres to the crystal piece 2 at a later date due to external impact or the like. This deteriorates the vibration characteristics including frequency fluctuations immediately after sealing or after aging.

(Object of the invention) The present invention firstly ensures airtightness. Second, splash is prevented. Accordingly, an object of the present invention is to provide a surface-mount resonator that maintains good vibration characteristics and aging characteristics.

(Points of interest and application) In the present invention, for example, a method of forming a metal container by resistance welding shown in Patent Document 1 is focused, and this is applied to seam welding of a surface-mounted vibrator.

The present invention (Claim 1) includes a concave container body having a metal ring on the upper surface of a frame wall, at least a crystal piece accommodated in the container body, and a metal joined to the metal ring of the container body by seam welding. In the surface mount crystal resonator including the cover, the metal cover has a triangular annular protrusion having an apex on the outermost periphery, and the metal ring has a height smaller than the annular protrusion on the innermost periphery. The water structure has an annular ridge .

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In the present invention (Claim 1), an annular protrusion having a height larger than the annular protrusion of the metal ring is provided on the metal cover and joined. Therefore, the metal ring and the metal cover are joined in contact with each other in a point in which the metal ring and the metal cover are in contact with each other when the metal roller is pressed. This ensures airtightness.

In addition, since the metal ring is provided with an annular protrusion that has an inner periphery relative to the annular protrusion of the metal cover, it is possible to prevent metal scrap generated during seam welding from entering the container body. This prevents metal scraps from adhering to the crystal piece. As a result, the vibration characteristics and the aging characteristics are maintained well.

FIG. 1 is a cross-sectional view of a surface mount vibrator for explaining a first embodiment of the present invention. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

As described above, the surface-mounted vibrator accommodates the crystal piece 2 in the concave container body 1 having the metal ring 4 on the upper surface of the frame wall 1b, and the metal cover 3 is joined by seam welding and hermetically sealed.
Here, a triangular annular protrusion 9 is provided on the outermost periphery of the metal cover 3. The annular protrusion 9 is integrally formed when the metal cover 3 is pressed.

With such a configuration, the annular protrusion 9 of the metal cover 3 comes into contact with the metal ring 4 of the container main body 1 in a rotating direction. Further, even if there is a non-contact portion, the joining in the direction in which the annular protrusion 9 is crushed and circulates when the pair of metal rollers 8 is pressed and energized (during melting) is ensured. Therefore, airtightness is ensured, and vibration characteristics and aging characteristics due to airtight leakage are improved.

Further, since the annular protrusion 9 is provided on the outermost periphery of the metal cover 3, the protrusion formed on the cover is deformed at the time of joining, so that stress at the time of sealing is hardly applied to the entire package. As a result, frequency change and secular change due to stress generated in the package are reduced.

FIG. 2 is a cross-sectional view of a surface mount vibrator for explaining a second embodiment of the present invention. The previous first
Description of the same part as the embodiment is omitted or simplified.

In the second embodiment, an annular protrusion 9 is provided on the outer periphery of the metal cover 3 as in the first embodiment. And here, the annular jetty 10 is provided in the metal ring 4 provided in the upper surface of the frame wall 1b of the container main body 1. FIG.
The annular jetty 10 is located on the inner periphery of the annular protrusion 9 and has a height equal to or less than that of the annular protrusion 9.

If it is such a structure, since the metal scrap produced at the time of seam welding will be interrupted | blocked by the annular jetty 10, the penetration | invasion into the container main body 1 is prevented. Therefore, even after sealing or after aging, the metal scrap does not adhere to the crystal piece 2, so that the vibration characteristics including the frequency fluctuation and the aging characteristics are maintained well.

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  In the above embodiment, seam welding is used, but beam welding may also be used, and in summary, it can be applied to joining means in which metal scraps are generated.

FIG. 3 is a cross-sectional view of a surface-mounted vibrator for explaining the first embodiment of the present invention. It is sectional drawing of the surface mount vibrator explaining the 2nd example of the present invention. FIG. 6 is a cross-sectional view of a surface-mounted vibrator for explaining another embodiment of the present invention. FIG. 6 is a cross-sectional view of a surface-mounted vibrator for explaining another embodiment of the present invention. It is a figure explaining a prior art example, the figure (a) is a sectional view of a surface mount vibrator, and the figure (b) is a top view of a crystal piece.

1 container body, 2 crystal piece, 3 metal cover, 4 metal ring, 5 excitation electrode, 6,
Extraction electrode, 7 conductive adhesive, 8 metal roller, 9 annular projection, 10 annular jetty.

Claims (1)

For surface mounting, comprising: a concave container body having a metal ring on the upper surface of the frame wall; at least a crystal piece housed in the container body; and a metal cover joined to the metal ring of the container body by seam welding. In the quartz resonator, the metal cover has a triangular annular protrusion having an apex on the outermost periphery, and the metal ring has an annular protrusion having a height smaller than the annular protrusion on the innermost periphery. A crystal resonator.

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