JPH0378307A - Vessel for surface mounted type piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To thin and miniaturize a vessel and to reduce cost by specifying the material constitution of the vessel and forming the metallized films of a terminal electrode and a fixed electrode of a thick film burning conductive material. CONSTITUTION:The material of the vessel contains 45-55weight% of boro-silicate glass powder and the balance alumina powder. Then, the mean grain diameter is set to be less than 2.5mum. A composite material in which the mean grain diameter of boro-silicate glass is smaller than the mean of alumina power is sintered and formed. The metallized films 2 of the terminal electrode 3' and the fixed electrode 3'' are formed by the thick film burning conductive material. The burning temperature of the vessel can be set low and it can be processed in air. Then the vessel can be constituted by the general thick film material as an electrode member conducting the inside and outside the vessel and the vessel. Thus, material cost and working cost become inexpensive, a surface becomes dense vitreousness, the deterioration of a characteristic owing to out- gas is reduced and the vessel can be made small and thin.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an airtight container in which a piezoelectric vibrator such as a crystal is sealed in a vacuum or an inert gas, and particularly relates to an ultra-small piezoelectric vibrator suitable for surface mounting. More specifically, it relates to a container constructed by sintering an alumina-glass composite material as a material for the container and simultaneously firing an electrode.

Piezoelectric resonators, especially quartz crystal resonators, have extremely stable natural frequencies, and their use has recently expanded in the electronics field, especially for crystal watches and small portable electronic devices that are becoming thinner, smaller, and less expensive. The wave of I
There is an increasing demand for an ultra-thin flat plate shape as an element of the time reference signal of a C card.The present invention is designed to cope with the above-mentioned snowy landscape, and is an ultra-compact type for surface mounting. The present invention provides a container for a piezoelectric vibrator made of a sintered alumina-glass composite body as a material suitable for making the vibrator thinner, smaller, and less expensive.

[Conventional technology]

Conventionally, the airtight container for storing small piezoelectric vibrators was developed by the Special Publication Publication in 1982.
As disclosed in Japanese Patent No. 18371, a ceramic container is usually used with a glass lid sealed with solder or low melting point glass.

An alumina ceramic container is generally used as the ceramic container, and its manufacturing method is similar to that of an IC package. That is, W as an internal conductor on an alumina green sheet.

M o -M n metal paste was used for screen printing, a frame punched from an alumina green sheet was placed on top of the screen printing, and the frame was heat-pressed. Containers have been put into practical use which are then plated with Ni, solder or Au to facilitate bonding and soldering.

[Problem to be solved by the invention]

By the way, the manufacturing process in the above manufacturing method is complicated, especially in a hydrogen or reducing gas atmosphere to prevent oxidation of the W and Mo-Mn electrodes, and at a high temperature of about 1500°C to sinter the alumina. A process was necessary. This led to an increase in costs, including safety issues, and had the disadvantage of not being able to meet the demand for large numbers of people.

[Means to solve the problem]

The above-mentioned problems can be solved by the ultra-small piezoelectric vibrator container according to the present invention. That is, it is a flat bottomed container in which a thin plate-shaped piezoelectric vibrator is hermetically sealed, and a terminal electrode for conductive connection is provided at the outer end of the container, and the piezoelectric vibrator is provided on a part of the inner bottom surface of the container. A container is provided with a fixed electrode that fixes the terminal electrode, and the fixed electrode and the terminal electrode are conductively connected, and the material of the container contains 45 to 55% by weight of borosilicate glass powder, the remainder is alumina powder, and the alumina powder is A composite material is formed by sintering in which the average particle size of the powder is 2.5 μm or less and the average particle size of the borosilicate glass powder is smaller than the average particle size of the alumina powder, and the terminal electrode and the fixed The above-mentioned problems are solved by a surface-mounted pressure transducer container characterized in that the metallization of the electrodes is made of a thick-film fired conductive material.

[Effect]

As mentioned above, the feature of the container according to the present invention lies in its material, and in particular, the action of turning it into a liquid phase during the sintering process is important. The borosilicate glass powder acts as a sintering aid, and the borosilicate glass powder interposed between the alumina powders softens almost simultaneously throughout, flows, and surrounds the alumina powder to perform liquid phase sintering. It is possible to manufacture a container made of a homogeneous fired body with little generation.

To explain this in more detail, alumina powder and borosilicate glass powder with smaller particle sizes are generally more useful. In particular, since the melting point of alumina powder is higher than that of borosilicate glass, its particle size hardly changes after firing, so if a coarse particle size is used, the surface roughness after firing will increase. For this reason, it is desirable to use powder with a small particle size if possible.

On the other hand, the most ideal method is to fill the porosity of the alumina powder particles in a close-packed arrangement with borosilicate glass and perform liquid phase sintering. can be minimized and the strength can be increased, and the porosity should be zero. However, in reality, the alumina powder particles are not arranged in a close-packed manner, and the wettability of the alumina powder particles and the borosilicate glass powder particles must be taken into consideration. Therefore, the design amount is also considered based on the coordination of the alumina powder particles, which are considered to have a large porosity. Therefore, assuming that the alumina powder particles are of the same size, and modeling a three-dimensional arrangement of alumina powder particles, the porosity will be 48%.

The amount of borosilicate glass filling this porosity is 1% since its specific gravity is about 3.

Furthermore, considering the influence of the wettability of the alumina powder particles and borosilicate glass powder particles, the minimum required amount of borosilicate glass is about 45% by weight. Therefore, if the borosilicate glass powder does not contain 45% by weight or more, the borosilicate glass powder will not be sufficiently filled around the alumina powder particles, resulting in a dense, airtight alumina-glass composite fired body with low porosity. Hard to get caught.

〔Example〕

An embodiment of the present invention will be described below based on the drawings. 1st
The plan view in Figure 2 and Figure 2 shows the essential base materials for the container of the piezoelectric vibrator of the present invention. By the zero-order doctor blade method, glass powder with an average particle diameter of 1.3 μm was added to 45% by weight of an organic binder, a plasticizer, and an appropriate solvent such as toluene or methyl ethyl ketone as usual, and kneaded in a ball mill to prepare a slurry. A green sheet with a thickness of 160 μm was molded. This green sheet is punched out as shown in FIGS. 1 and 2, and a conductor 3 as shown in FIG. 3 is screen printed with a thick film paste of Ag/Pd on the main surface 1' of the bottom plate 1 shown in FIG.

Thick film paste is applied to surface 1'' at both outer ends along with the pattern on main surface 1'. The printed matter is dried, and then the frame 2 shown in FIG. 2 is placed in a predetermined position on the main surface 1' of FIG. 3. At this time, if the number of frames 2 is stacked and laminated according to the thickness and shape of the piezoelectric vibrator to be accommodated, a container with a bottom of the required depth can be obtained. On the upper surface 2', a metallized film for sealing the glass M6 will be applied later, so the thick film paste described above is printed and dried.Figure 4 is a plan view of the laminated product +a+ The cross section of the A-A' section is shown in the same figure ('b
), after the degreasing process, the temperature increase rate was 1.
Heat rapidly at 5℃/min, and when it reaches 900℃,
Sinter at atmospheric pressure for 0 minutes. Through this sintering, the conductive paste becomes each electrode for conductive connection. That is, surface 1 of the outer end
'', the terminal electrode 3' on the back side connected to it, and the fixed electrode 3'' on a part of the bottom surface inside the container (main surface 1' of the bottom plate 1) are the fusion bond between the main surface 1' and the 2nd main surface of the bottom plate 1. Ag passed between the interfaces/
They are connected by a conductor 3 made of Pd. Next, among the exposed conductor parts, at least the surface of the terminal electrode 3' and the fixed electrode 3' and the sealing surface of the upper surface 2' of the frame are coated with Ni by electrolytic plating to a thickness of about 3 μm. A metal film with a thickness of 2 μm is produced, and the metal film becomes as shown in the cross-sectional view of FIG. 4 (bl).

A container formed in this manner houses a crystal resonator 4 as shown in FIG. This figure 5 shows the fixed electrode 3″
The base of the vibrator 4 is bonded to the top of the vibrator 4 using a 21-electrode adhesive or the like, thereby achieving both electrical connection and mechanical holding. (bl in the same figure is a cross-sectional view taken along the line A-A' in the same figure (81). After fixing the piezoelectric vibrator 4, the glass lid 5 is sealed with a sealing material such as solder in a vacuum or an inert gas atmosphere. This is a completed piezoelectric vibrator unit shown in the state shown in No. 6, which is hermetically sealed by melting.

Pressure is a feature of the present invention! As mentioned above, the vibrator container has the challenge of achieving both mechanical strength and airtightness, and various tests were conducted using sample pieces and containers manufactured under the above-mentioned sintering conditions.

As a result, the results shown in Table 1 were obtained for the sample pieces.

In the same table, when the airtightness was tested using a commonly used He leak test, samples 1 to 4 had a specified value of I
It was recognized that there was no leakage at Xl0-'atm cc/sec or less, and Samples 5 and 6 exceeded this specified value. The reason for this is that, as mentioned above, the amount of alumina was too large, which resulted in insufficient wetting of the borosilicate glass and the formation of pores.

In addition, regarding mechanical strength, as a result of this bending strength test, which evaluated the bending strength by pressurizing the center of a sample supported at two points with an interval of 2 ha, it was found that The strength that should be applied to the piezoelectric vibrator container applied to the conventional alumina container is approximately 2500 kg.
/ CD, 1650kg/ as necessary and sufficient strength.
cIII was set as the low limit.

Next, using the material of sample 4 and using the manufacturing method described above, a length of 6.8N was obtained.
, a tuning fork-shaped crystal resonator was housed in a rectangular container with external dimensions of 3.1 n in width and 0.481 m in height, and the thickness was 0.1 m in vacuum.
A piezoelectric vibrator unit was created by sealing a 2wm glass lid with a solder seal. Immediately after this sealing, the average value of the n=12 series resonant resistors R8 was 25Ω. This value is the same as that of a conventional ceramic container sealed using the same sealing method. In order to perform an accelerated leak test on these 12 samples, they were left in an environment pressurized to 5.5 atmospheres for 24 hours.

The subsequent R value was Ω at X=30.1. This change is largely due to outgas generated at the initial stage of encapsulation. This amount of change is about 10% higher for conventional alumina containers.The reason for this is that although there is almost no difference between the two in terms of airtightness, which corresponds to slow leaks, the initial outgas is reduced by the surface layer of alumina porcelain. The microporous layer contained in the rough surface acts on this, whereas the container of the present invention has a glassy surface layer, and it can be assumed that its density acts effectively on this. Here, the ultra-small container to which the present invention is applied has an internal volume of approximately 0.25 m.
The degree of decrease in the degree of vacuum due to the gas released into this gas is a matter that is particularly strictly controlled.
The container of the present invention was effective. The piezoelectric vibrator unit described above was subjected to high-temperature storage deterioration tests and thermal shock cycle tests under general electronic component test conditions, and there was no difference in comparison to conventional alumina containers with a proven track record, and the results were sufficient for practical use. characteristics were obtained.

〔Effect of the invention〕

As explained above, the container for the surface-mounted piezoelectric vibrator according to the present invention can be sintered at a low temperature and can be processed in the atmosphere.

It can be constructed from a general thick film material as an electrode material for conduction to the outside and other parts, and the material and processing costs are low, and
The present invention provides a compact and thin piezoelectric vibrator container for surface mounting, which has a dense glassy surface and exhibits less characteristic deterioration due to outgas.

[Brief explanation of drawings]

FIGS. 1 and 2 are plan views of punched green sheets to which the present invention is applied. Figure 3 shows Ag/P on the bottom plate of Figure 1.
FIG. 3 is a plan view of d-paste printed by screen printing. Fig. 4 is related to the present invention, and the frame shown in Fig. 2 is laminated on the substrate shown in Fig. 3 (al front view, fb
1 is a sectional view. Fig. 5 shows a case where a crystal resonator is mounted on the container of the present invention and a glass lid is sealed (Al front view, (BL sectional view). 1...Bottom plate 1'...Main surface 2... ...Frame body 2'...Top surface 3...Conductor 3'...Terminal electrode 3'...Fixed electrode 4...Crystal resonator 5...Glass lid 6...・Sealing material 10...Piezoelectric vibrator unit or more

Claims (1)

[Claims] A flat bottomed container in which a thin plate-shaped piezoelectric vibrator is hermetically sealed, and a terminal electrode for conductive connection is provided at the outer end of the container, and the piezoelectric vibrator is fixed to a part of the inner bottom surface of the container. A container is provided with a fixed electrode, and the fixed electrode and the terminal electrode are conductively connected, and the material of the container contains 45 to 55% by weight of borosilicate glass powder, and the remainder is alumina powder. The average particle size is 2.5 μm or less,
A composite material in which the average particle size of the borosilicate glass powder is smaller than the average particle size of the alumina powder is sintered and formed, and the metallization of the terminal electrode and the fixed electrode is made of a thick film fired conductive material. A surface-mounted piezoelectric vibrator container featuring: