JP2000236228A - Hermetically sealed structure of piezoelectric vibrator - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent scattering of molten metal during resistance welding and to improve the reliability of a piezoelectric vibrator. SOLUTION: A quartz plate 1 having electrodes formed thereon is mounted on supports 27, 28 of a base, and the supports 27, 28 and the extraction electrodes are conductively joined. Thereafter, the base 2 is covered with the cap 3, the projection 21a of the base is brought into contact with the flange 31 of the cap, and current is applied while applying pressure to both to perform resistance welding. The cap is made of stainless steel, and a nickel thin plate is clad-joined to the outside of the cap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetic sealing structure for a piezoelectric vibrator such as a quartz vibrator, and more particularly to a hermetic sealing structure for resistance welding.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. 4 taking a hermetically sealed structure for a crystal unit as an example. As shown in FIG. 4, the conventional hermetic sealing structure for a crystal unit includes a base 8, a crystal plate 7 installed on the base, and a cap 9 for hermetically sealing the crystal plate. In the base 8, at least two lead terminals 83, 84 are penetrated and implanted in a metal shell 80 via insulating materials 85, 86, and a flange 81 is integrally provided on a peripheral edge thereof. A peak-like projection (projection) 81a is provided on the flange. The shell 80 is made of, for example, iron as a base material, and a nickel plating 82 is formed on a surface of the shell 80. The nickel plating 82 suppresses oxidation of the base material and improves the joining property during resistance welding.

[0003] The quartz plate 7 is mounted on the base 8 via supports 87, 88, and the lead terminals 83,
84 is electrically connected. Then, the crystal resonator 7 is hermetically sealed by resistance welding the cap 9 and the base 8. More specifically, a large current is applied in a very short time while the projection 81a of the base and the flange 91 of the cap are pressed against each other, and resistance welding is performed. In addition, the base material of the cap is nickel-white (alloy of nickel, zinc, and copper), and a nickel plating 92 is formed on the surface thereof. The nickel plating 92 also has a function of suppressing the oxidation of the base material and improving the bondability during resistance welding. In some cases, a part of the cap is soldered. The above-described nickel plating effectively functions to improve the solderability at that time.

[0004]

In the resistance welding method, generally, a projection is provided at a joint portion as described above, and the flange of the cap and the projection are pressed against each other with high pressure.
Apply a large current instantaneously. As a result, the current density at the projection part locally increases, and resistance welding by Joule heat is performed.

However, at the time of welding, the so-called splash phenomenon in which the nickel plating formed on the base material is melted and scattered has been a problem. There are various causes of the splash phenomenon, such as a problem of a material or a problem of manufacturing, and one of them is unevenness of a welding surface (contact surface).
Such irregularities will cause uneven contact resistance,
This causes excessive metal melting, that is, a splash phenomenon. Incidentally, formation of a metal film by plating tends to form unevenness on the surface, and electrolytic plating has a particularly strong tendency. Usually, in the above-mentioned mace plating, electrolytic plating is often used from the viewpoint of the efficiency of film formation, and the above-described conventional configuration has a configuration in which surface irregularities are relatively large.

[0006] A part of the molten metal scattered due to the splash phenomenon enters the inside of the piezoelectric vibrator, and causes a short circuit or the like of an electrode formed on the piezoelectric vibrating element. In addition, in the above-described quartz oscillator, the molten metal adheres to the quartz oscillator, thereby inhibiting the oscillation state thereof, and lowering the electrical characteristics of the quartz oscillator such as a decrease in CI value, thereby improving reliability. Could not be maintained.

The present invention has been made to solve the above problems, and has as its object to prevent the molten metal from scattering during resistance welding and improve the reliability of the piezoelectric vibrator.

[0008]

According to the present invention, at least two lead terminals are implanted through a metal shell through an insulating material. And a base provided with a metal flange on the periphery thereof, a piezoelectric vibrating element installed on the base and electrically connected to the lead terminal, and hermetically covering the piezoelectric vibrating element, In a piezoelectric vibrator comprising a flange of the base and a metal cap having a flange to be resistance-welded, the cap is made of a stainless steel material, and a nickel thin plate is clad-joined to at least the outside of the cap. It is characterized by forming a nickel clad layer.

According to the first aspect, by using a stainless steel material for the cap, resistance welding with the base can be performed at a low voltage without using plating.
Further, by forming the nickel thin plate by cladding, the nickel layer can be selectively formed only on the outside of the cap, and the nickel layer allows the cap portion of the piezoelectric vibrator to be favorably soldered.

[0010] Here, verification data on the bondability between the stainless steel cap and the base will be shown. The samples used were the caps of nickel-plated nickel silver shown in the conventional example (conventional product) and stainless steel (SUS304).
The nickel clad layer is formed on the upper surface (non-welded surface) (product 1 of the present invention) and the nickel clad layer is formed on the upper and lower surfaces (including the weld surface) of stainless steel (SUS304) (product 2 of the present invention) Three examples. In each of the examples of the base, the joint surface with the cap is obtained by applying nickel plating to iron. 2.0 pressurizing condition between cap and base
Kg / cm @ 2 and the lowest applied voltage at which good bonding was obtained was examined. After the joining, the joining is confirmed by checking whether the airtightness is secured by a He leak test. The verification results are shown below. The minimum applied voltage of the conventional product is about 220 V. The minimum applied voltage of the product of the present invention is about 200 V. The minimum applied voltage of the product of the present invention is about 140 V. From the above results, the applied voltage of each of the present products can be reduced compared to the conventional product. Particularly, the product 2 of the present invention can drastically reduce the applied voltage. Therefore, the occurrence of the splash phenomenon can be suppressed in combination with not forming the plating.

According to a second aspect of the present invention, in the hermetically sealed structure of the piezoelectric vibrator according to the first aspect, a nickel cladding layer may be formed on both the outside and the inside of the cap.

The nickel clad layer according to the second aspect has better surface flatness and a uniform contact state between the cap and the base as compared with the conventional plating layer. Therefore, the variation of the contact resistance can be reduced, and the contact resistance itself can be reduced. Therefore, the voltage at the time of welding can also be reduced, and the splash phenomenon that has conventionally easily occurred can be more effectively suppressed. Also, the formation of the nickel layer improves the joinability in resistance welding.

According to a third aspect of the present invention, in the hermetically sealed structure of the piezoelectric vibrator according to the first or second aspect, a nickel clad layer is formed at least in a joint portion of the shell with the cap. It may be.

By joining the nickel thin plate to the base shell by cladding, the joining property at the time of welding is further improved.
In addition, since the formation of unevenness on the bonding surface is suppressed, the occurrence of the splash phenomenon is reduced.

[0015]

Next, a first embodiment of the present invention will be described with reference to the drawings, taking a quartz oscillator as an example of a piezoelectric oscillator. FIG. 1 is an internal sectional view showing an embodiment of the present invention.

The quartz vibrating plate 1 is formed of an AT-cut quartz vibrating plate and has a rectangular shape. Although not shown, an excitation electrode and an extraction electrode are provided on the front and back surfaces by means such as a vacuum evaporation method. The base 2 has a long columnar shape as a whole, and a lead terminal 2
The lead terminals 23 and 24 are electrically independent by filling the through holes of the shell 20 with the insulating glasses 25 and 26. A flange 21 is provided circumferentially on a peripheral portion of the shell 20 which forms a part of the base.
A peak-like projection 21a is integrally formed on the upper part.
Supports 27 and 28 made of a metal plate are joined to part of the lead terminals exposed on the upper surface of the base in a state where the plate surfaces face each other. Each of the supports 27 and 28 has a slit (not shown) into which the above-described quartz diaphragm 1 is inserted.

Stainless steel (for example, SUS30
The cap 3 made of 4) is in the shape of a long cylinder opened downward, and the lower flange 31 is
1 is formed. A nickel thin plate is clad bonded to the outside of the cap. The cap is manufactured by three-dimensional processing by drawing using a stainless steel plate on which a nickel clad layer is formed. According to the clad bonding, a metal layer can be selectively formed on a specific surface, and by forming a nickel layer on the outside of the cap, the connectivity when soldering the cap portion of the piezoelectric vibrator (connection of Easiness) can be improved.

The quartz vibrating plate 1 is mounted on the base supports 27 and 28.
Is mounted, and the support members 27 and 28 and the extraction electrodes (not shown) are conductively joined. Thereafter, the base 2 is covered with the cap 3, the projection 21a of the base is brought into contact with the flange 31 of the cap, and current is applied while applying pressure to both to perform resistance welding, thereby completing hermetic sealing. The energizing voltage may be a relatively low value as described above, and the occurrence of the splash phenomenon is reduced.

Next, a second embodiment of the present invention will be described with reference to the drawings, taking a quartz oscillator as an example. FIG. 2 is an internal sectional view showing the second embodiment. The same components as those in the first embodiment will be described using the same reference numerals, and some description thereof will be omitted.

In this embodiment, a nickel thin plate is also clad and bonded to the inside of the cap to form a nickel clad layer. That is, a nickel clad layer is formed outside the cap 3 by clad bonding, and a nickel clad layer is formed inside. The nickel clad layer is superior in flatness as compared with the layer formation by plating. Therefore, pressure is uniformly applied to the flange portion of the cap and the flange portion of the base, and it is possible to suppress the occurrence of extra metal melting, ie, the occurrence of the splash phenomenon, which has conventionally occurred.

Next, a third embodiment of the present invention will be described with reference to the drawings, taking a surface-mounted crystal resonator as an example. FIG. 3 is an internal cross-sectional view showing the third embodiment.

The base 5 has a package structure with an opening at the top, a flange 51 is formed around the opening, and a circumferential projection is formed at the top of the flange.
The shell 50 constituting the metal part of the base is made of, for example, Kovar, and a nickel clad layer 59 is formed on the upper surface thereof. Lead terminals 53 and 54 are electrically independently attached to the bottom of the base via an insulating glass 52. The insulating glass 52 is formed on the entire bottom surface of the base, and the external lead terminals penetrating the insulating glass are bent by about 90 degrees, so that the piezoelectric vibrator can be mounted on the surface. Support 5 on the inner lead terminals
7, 58 are connected by a method such as spot welding, and a quartz vibrating plate on which excitation electrodes are formed is mounted on the upper surface of the support and is electrically connected.

A plate-like cap 6 for hermetically sealing the inside of the base
Has a base material made of stainless steel, and nickel clad layers 61 and 62 formed by cladding nickel thin plates on upper and lower surfaces thereof. The cap 6 is pressed against the projection 51a formed on the flange of the base to perform resistance welding. According to this embodiment, since the nickel cladding layers 61 and 62 of the cap and the nickel cladding layer 59 formed on the base all have good flatness, the occurrence of the splash phenomenon is suppressed, and the nickel melting is excellent. Airtight sealing can be performed.

Although the above embodiment has been described with reference to a quartz resonator as an example, the present invention can be applied to other piezoelectric vibrating devices such as a quartz filter.

[0025]

According to the first aspect, by using a stainless steel material for the cap, resistance welding with the base can be performed without using plating, and the voltage at the time of welding can be reduced. Further, by forming the nickel thin plate by cladding, the nickel layer can be selectively formed only on the outside of the cap, and the nickel layer allows the cap portion of the piezoelectric vibrator to be favorably soldered. Therefore, scattering of the molten metal during resistance welding can be prevented, and the reliability of the piezoelectric vibrator can be improved.

According to the second aspect, the nickel clad layer can reduce unevenness of the surface unevenness and obtain good flatness as compared with a conventional plating layer. Therefore, the uniformity of the contact between the joint portion of the cap and the base can be improved. Also, the formation of the nickel layer improves the joinability in resistance welding. Therefore, the scattering of the molten metal during resistance welding can be prevented, and the reliability of the piezoelectric vibrator can be further improved.

According to the third aspect of the present invention, the nickel thin plate is clad-joined to the shell of the base, so that the joining property at the time of welding is further improved. In addition, since the formation of unevenness on the bonding surface is suppressed, the occurrence of the splash phenomenon is reduced.

[Brief description of the drawings]

FIG. 1 is an internal sectional view showing a first embodiment according to the present invention.

FIG. 2 is an internal cross-sectional view showing a second embodiment according to the present invention.

FIG. 3 is an internal sectional view showing a third embodiment according to the present invention.

FIG. 4 is an internal sectional view showing a conventional example.

[Explanation of symbols]

 1,4 Quartz diaphragm 2,5 Base 3,6 Cap 31,32,59 Nickel clad layer

Claims (3)

[Claims] At least two lead terminals are penetrated and implanted in a metal shell through an insulating material, and a base provided with a metal flange on a peripheral edge thereof is provided on the base. A piezoelectric vibrator, comprising: a piezoelectric vibrating element electrically connected to a lead terminal; and a metal cap having a flange that is airtightly covered with the piezoelectric vibrating element and resistance-welded to the base flange. A hermetic sealing structure for a piezoelectric vibrator, wherein a base material is made of a stainless steel material and a nickel clad layer formed by cladding a nickel thin plate is formed at least outside the cap. 2. The hermetically sealed structure of a piezoelectric vibrator according to claim 1, wherein a nickel cladding layer is formed on both the outside and the inside of said cap. 3. The hermetic sealing structure of a piezoelectric vibrator according to claim 1, wherein a nickel cladding layer is formed at least in a portion of the shell that is joined to the cap.