JPS5855688B2 - Manufacturing method of transducer unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a vibrator unit in which a case for housing a piezoelectric vibrator such as crystal is made of ceramic, glass, or the like.

In particular, the vibrator unit for a watch must not only have excellent frequency accuracy, but it is also important to achieve low cost and miniaturization, especially thinness.

Based on this idea, a resonator unit has been developed in which a thin plate tuning fork crystal resonator manufactured by etching technology is housed in a ceramic case.

A conventional vibrator unit using a semi-rack case will be described below.

As described above, this resonator unit is composed of a tuning fork-shaped thin plate crystal resonator, a ceramic base for housing the resonator, and a glass lid. An Au film of an appropriate thickness is fixed for solder sealing.

To assemble, first, the vibrator is fixed to a support provided in a ceramic base using an adhesive or the like, and after fixing, curing is performed.

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

Hermetic sealing, which is the final process of assembly, is completed by sandwiching a solder washer between the base and the glass lid, and melting the solder washer with infrared heating or high-frequency heating while applying an appropriate load in a vacuum chamber.

The vibrator unit made in this way is very thin in shape compared to the conventional vibrator unit using a metal case, and is suitable for mass production, and its low cost has made it possible to greatly popularize quartz watches. It is expected that this will make a contribution.

However, since the hermetic sealing conditions are extremely severe, the sealing yield is poor, which is a major obstacle to lowering the cost.

In addition, there were many slow leaks even after sealing, which caused problems in terms of quality.

The present invention has been made to eliminate the above drawbacks,
After conducting various experiments and studies, it was discovered that by reducing the thickness of the Au film on the glass lid, the hermetic sealing conditions could be widened and the reliability of the hermetic sealing could be improved.

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

FIG. 1 is a perspective view showing each part constituting the resonator unit of the present invention. In the figure, 3 is a tuning fork type thin plate crystal resonator manufactured by photo-etching technology, and 4 is a ceramic base that houses the resonator. This shows a stand, and a suitably thick Au layer is applied to the peripheral joint surface 4a for solder sealing.

Reference numeral 1 denotes a glass lid, which is a feature of the present invention, and an Au thin film 1a is attached to the peripheral joint surface for solder sealing, similar to the base.

The Au film 1a is attached after first depositing a suitable thickness of Cr, which is compatible with glass, by a method such as sputtering or vacuum deposition.

Conventionally, the thickness of the Au thin film is usually 2 to 3 μm, but in the embodiment of the present invention, the thickness of the Au thin film is 300λ, 500 μm, and 100 μm.
A. 5000 people.

Glass lids with thicknesses of 1μ, 2μ, 3μ and 4μ were prepared.

Further, in the figure, reference numeral 2 denotes a solder washer for hermetically sealing the ceramic base 4 housing the vibrator 3 and the glass lid 1.

The transducer unit is hermetically sealed by sandwiching a solder washer 2 between the ceramic base 4 housing the transducer and the glass lid 1, and applying an appropriate load in a vacuum or rare gas using high-frequency heating or infrared heating. The solder washer 2 is melted and completed by the method described in (a).

An embodiment of the present invention will be described below with reference to FIG.

FIG. 2 shows the relationship between the Au film thickness of the glass lid and the time required for hermetically sealing when the thickness of the Au film on the glass lid is changed and the hermetically sealed seal is performed by the method described above at an appropriate output.

As is clear from the figure, the conventional hermetic sealing time when the Au film thickness is 2μ or more is about 60 seconds at most, but in the case of the present invention with a thickness of 0.5μ, it reaches 116 seconds, and the effect of the present invention is Remarkable.

As a means of evaluating the quality of hermetic sealing, in addition to the above-mentioned investigation of the possible time for hermetic sealing, we also conducted forced deterioration by leaving a resonator that had been hermetically sealed in a high temperature environment, and measured the equivalent impedance of the resonator. There is a way to investigate.

FIG. 3 shows the above example in which the Au film thickness on the bonding surface is 1000 mm.
The resonator unit of the present invention, which was hermetically sealed using a plastic glass lid, and the conventional resonator unit, which was hermetically sealed using a glass lid with an Au film thickness of 3 μm on the bonding surface, were placed in a constant temperature bath at 80°C. This figure shows the relationship between the standing time and the amount of increase in the equivalent impedance of the vibrator when the vibrator was left standing for 1000 hours.

Since the change in the equivalent impedance of the vibrator is closely related to the accuracy of the watch, power consumption, etc., it is preferable that the amount of change is as small as possible.

According to the figure, with the conventional product, the increase in temperature is remarkable as the standing time increases, which poses a quality problem.

However, in the present invention, the increase after standing for 1000 hours is about 15 (KΩ) at most, which is considerably lower than the conventional product's 53Ω, and the effect of the present invention is remarkable.

Next, in the claims, the thickness of the Au film on the glass lid is set to 5.
The reason for setting the value to 00A to 1μ will be explained.

First of all, the lower limit was set at 500 people because if it was less than this, the time during which hermetic sealing could be performed would be extremely short and the hermetic sealing yield would be poor, and the reliability after sealing would be poor and the effect of the invention would be lost. .

Further, the upper limit is set to 1 μm because, if this value is exceeded, the time during which hermetic sealing can be performed is rapidly shortened, as is the case with the lower limit, the hermetic sealing yield is reduced, and the reliability is also poor.

As detailed above, the Au film thickness on the bonding surface is 0.05 μ to 1
．． According to the method of manufacturing a vibrator unit of the present invention using a lid with a diameter of 0μ, it is possible to widen the time period during which hermetic sealing can be performed and improve the hermetic sealing yield, which is an object of the present invention. It is possible to reduce the cost.

Furthermore, it has many advantages such as improved reliability after sealing, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing each part constituting an example of a vibrator unit using the present invention, 1...Glass lid, 2...Solder washer, 3...・Tuning fork type thin plate crystal resonator, 4...
... Ceramic stem, 1a... Gold thin film. Fig. 2 is a characteristic diagram showing the relationship between the Au film thickness of the glass lid and the time during which it can be hermetically sealed, and Fig. 3 shows the resonators of the present invention and the conventional method that were hermetically sealed at 80°C. FIG. 3 is a characteristic diagram showing the amount of increase in the equivalent impedance of the vibrator when the vibrator is left in a constant temperature bath for 100 hours.

Claims (1)

[Claims] 1. In a method for manufacturing a vibrator unit in which a vibrator is attached to a base, a lid is tightly attached to the base via a solder layer and a gold layer, and hermetically sealed by heating, the thickness of the gold layer is 5.
00λ to 1μ.