JPS5829650B2 - Oscillator unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the quality of a watch vibrator unit whose case, which houses a piezoelectric vibrator such as a crystal, is made of ceramic.

It is essential that a watch vibrator unit not only have excellent frequency characteristics, but also be thin, small, and inexpensive.

Recently, in order to satisfy these requirements, a new type of resonator unit has been developed in which a tuning fork-shaped thin plate crystal resonator made by etching technology is housed in a ceramic case.

A vibrator unit using a ceramic case will be briefly described below.

This resonator unit consists of a crystal resonator, a ceramic stem that houses the resonator, and a glass lid.
When assembling a vibrator unit, an appropriate thickness of Au is applied as a solder sealing means to the joint surface of the stem and the peripheral edge of the glass using a method such as vacuum deposition or electroplating.
First, the vibrator is fixed using adhesive to a stand that supports the vibrator provided inside the ceramic stem.

Thereafter, the vibrator and the lead terminal of the stem are appropriately connected by wire bonding using an ultra-fine Au wire.

Hermetic sealing is achieved by inserting a solder washer between the stem and the glass lid to obtain the required degree of vacuum (generally 10-2 Torr).
This is carried out by a method of melting the solder washer by infrared heating or high-frequency induction heating while maintaining the above) while applying an appropriate load in a vacuum chamber.

The transducer unit made in this way is much thinner than the conventional transducer unit using a metal case, and is suitable for mass production, making it possible to reduce the cost of the transducer unit. Therefore, it is expected that this will greatly contribute to the spread of crystal watches.

However, in reality, leakage gradually progresses after sealing, increasing internal pressure and causing an increase in the equivalent impedance of the vibrator.
There are many problems in which the oscillation eventually stops, and the reliability is poor, which is a major obstacle in practical use.

The present invention has been made to eliminate the above-mentioned drawbacks, and is intended to improve the quality of the vibrator unit by significantly improving the leakage after sealing by improving the manufacturing method of the ceramic stem.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of the ceramic stem of the present invention. In the figure, 1 is a sealing frame, 2 is a frame that also serves as a pedestal for fixing a vibrator, 3 is a bottom plate, 4 is a joint surface, and 5 is a lead terminal. It is something that

Further, FIG. 2 shows manufacturing process diagrams of the conventional ceramic stem and the present invention.

The ceramic stem is manufactured by a method that is characteristic of a ceramic case for housing electronic components such as ICs, and the method of manufacturing the ceramic stem, which is a characteristic of the present invention, will be described based on the drawings.

First, the bottom of a semi-fired ceramic sheet is shaped, and the sheets are punched out for a seal frame, a frame that also serves as a pedestal, and a bottom plate.

Next, a metal paste such as W or W-Wo is appropriately printed on the sheets for frames 1 and 2 for bonding and as lead terminals.

Thereafter, the sheets for frame 1 and frame 2 are perforated in the desired shape, and after the perforation, the respective sheets are appropriately laminated and bonded under heat and pressure.

Thereafter, heat of around 15,000 C is applied in a protective atmosphere to completely bond the metal paste and each ceramic sheet by firing.

After firing, the metallized surface 4 and electrode 5 of the stem are plated with Ni to a suitable thickness by a method such as electric N1 plating.

Conventional stems are completed by applying Au plating to an appropriate thickness, but the stem of the present invention is completed by applying diffusion heat treatment by applying heat to around 1000°C in a protective atmosphere after Ni plating. After that, apply Ni plating again.
Finally, it is characterized by applying Au plating to an appropriate thickness.

One way to evaluate the hermetic sealing of a resonator unit is to charge a sample into a heated constant temperature bath and forcefully deteriorate the resonator to investigate the equivalent impedance of the resonator. Using the stem produced by the method and the stem produced by the production method of the present invention, the transducer unit produced by the above-described method for producing a transducer was placed in a constant temperature bath at 80°C for 1000 °C.
This figure shows the relationship between the left time and the shift amount of the equal impedance of the vibrator unit.

Since the shift in the equivalent impedance of the vibrator is closely related to clock accuracy, power consumption, etc., it is desirable that the shift amount be as small as possible.

However, according to the figure, in the case of a vibrator unit using a conventional stem, the value increases significantly as the standing time increases, and 10
After 00 hours, it reaches 100KΩ, and the increase is not saturated, and it can be estimated that if it continues further, the increase will be very large.

In comparison, the rise of the vibrator unit using the stem of the present invention took approximately 700 hours, and a saturation phenomenon was observed.
The amount of increase after 00 hours was 40Ω, demonstrating the remarkable effect of the present invention.

The reason why the equivalent impedance of the vibrator increased less when left at high temperatures in the present invention than in the prior art is thought to be the effect of improved stem manufacturing process.

That is, it is presumed that by adding a diffusion heat treatment step after Ni plating, diffusion between the ceramic and the metallized metal, and between the metallized metal and the Ni plating progressed, resulting in a more dense bonding surface.

Figure 4 shows the hermetically sealed vibrator in the above example at 800C.
This figure shows the relationship between the standing time and the yield when the sample was left in a constant temperature bath for 1000 hours.

In this case, the yield means that a vibrator whose equivalent impedance exceeds 350 Ω due to high temperature storage is considered a defective product.

(If the equivalent impedance of a watch vibrator unit is 350Ω or more, there is a practical problem when considering power consumption, etc.

) As is clear from the figure, the yield of the conventional sample and the present invention are both 100% at 100 hours, but as the standing time increases, the yield of the conventional sample decreases significantly, dropping to 40% at 1000 hours. .

However, the present invention shows a yield of 100% in all cases, indicating that it is extremely superior to conventional samples.

As detailed above, the vibrator unit using the ceramic stem of the present invention has superior long-term reliability compared to the vibrator unit using the conventional stem, and its industrial value is extremely high.

In the experimental example, only the case where a crystal resonator was used as the vibrator to be stored was described, but the same effect can be expected even if a piezoelectric resonator other than crystal is used.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a ceramic stem for a vibrator according to the present invention. Figure 2 is a manufacturing process diagram of the conventional stem and the present invention, and Figure 3 is the standing time and vibration when the vibrator unit of the present invention and the conventional transducer unit, which were hermetically sealed, were left in a thermostat at 80°C. A graph showing the relationship between the shift amount of child equivalent impedance,
FIG. 4 is a graph showing the relationship between the standing time and the hermetic sealing yield when the transducer units of the present invention and the conventional transducer unit, which are airtightly sealed, are left in a constant temperature bath at 80°C.

Claims (1)

[Claims] 1. In a vibrator unit in which the stem that houses a piezoelectric vibrator such as a crystal is made of ceramic and is hermetically sealed by soldering, the stem has an electrode pattern for taking it out to the outside and a joint surface on the periphery as a solder sealing means. metallized with W or W-Mo, etc., and after firing, the metalized surface is plated with Ni to an appropriate thickness, and then the stem is heat-treated at an appropriate heating temperature in a protective atmosphere, and the stem is metalized again. A vibrator unit characterized in that it uses a ceramic stem which is produced through a process of Ni plating the surface and then plating the metallized surface of the stem with Au to an appropriate thickness.