JPH09116047A - Structure of ceramic package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic package having a structure which makes improvement of adhesion strength possible between a gold electrode on a mount part provided in the inner bottom part of a ceramic package and conductive adhesive. SOLUTION: In this package, a ceramic mount part 2 is provided in the inner bottom part of a container 1 formed of ceramic and a metallic electrode film 5 which ensures conduction with outside and has a gold plating layer in a surface layer is provided in the upper surface of the mount part 2, and the package is constituted to fix a quartz element board and a gold parting layer with conductive adhesive 4 and bring them in a continuity. It is constituted to reinforce adhesion between the metallic electrode film 5 and a quartz element board by bonding an exposed part 8 of ceramic obtained by removing at least a part of the metallic electrode film 5 and the conductive adhesive 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the package structure of a piezoelectric device, and more particularly to a mount portion formed on the bottom surface of a ceramic package for supporting a piezoelectric element plate such as a crystal element plate, and the piezoelectric element. The present invention relates to a structure of a ceramic package having improved electrical connection with a board.

[0002]

2. Description of the Related Art As electronic devices such as various communication devices and office automation devices are becoming lighter, thinner and smaller, miniaturization of piezoelectric devices, which are built-in parts, is required. In place of the conventional lead type in which the lead terminals are led out, various surface mount types in which electrodes are formed by coating on the outside of the package have been developed. In addition, even in the surface mount type piezoelectric device, in order to cope with the thinning of the device, as the internal structure of the piezoelectric device, it is not possible to support the piezoelectric element plate on a special substrate provided in the package as in the past. Instead, it is advantageous to employ a structure (direct mount structure) in which the piezoelectric element plate is directly fixed to the inner bottom of the package with a conductive adhesive such as a silver filler adhesive. For example, in a piezoelectric device using a crystal blank as a crystal oscillator, as shown in FIG.
As shown in FIG. 9, the quartz crystal plate 3 is conductively bonded onto the metal electrode film 5 provided on the mount portion 2 which is two protrusions provided on the inner bottom portion of the container 1 made of ceramic. A ceramic package is generally used in which the upper opening of the container 1 is sealed with a metal or ceramic lid after being fixed by the agent 4. The metal electrode film 5 is generally formed by sequentially stacking a tungsten layer, a nickel plating layer, and a gold plating thin film on the ceramic mount portion 2. The reason why the gold-plated thin film layer is the surface layer is that gold has good conductivity,
Moreover, it is difficult to oxidize. However, since gold has a weak bonding force with tungsten, a nickel plating layer is interposed as an intermediate layer. The metal electrode film 5 is connected to an external electrode 6 provided outside the package via a connection conductor (not shown). That is, the metal electrode film 5 is previously formed on the mount portion 2 at the inner bottom portion of the container 1 made of this ceramic, and as shown in FIG. 2, on the gold thin film forming the surface layer of the metal electrode film 5. After the conductive adhesive 4 is applied to the above, the quartz crystal plate 3 is placed, and the conductive adhesive 4 is cured by heating to fix the quartz crystal plate 3 in the container 1 made of ceramic. After that, the opening of the container is sealed with a lid to obtain a completed piezoelectric device.

[0003]

However, in the piezoelectric device having the above-mentioned conventional structure, since the connection strength between the quartz crystal plate and the gold thin film which is the surface layer of the metal electrode film 5 is not always sufficient, the piezoelectric device is not suitable for the piezoelectric device. On the other hand, when vibration or shock is applied, the gold thin film and the conductive adhesive 4 are separated from each other, and the oscillator frequently fails. The present invention has been made in order to prevent the occurrence of a defect in a piezoelectric device using a conventional package as described above, and it has a conductive property with a gold electrode on a mount portion provided on the inner bottom of the ceramic package. An object of the present invention is to provide a ceramic package having a structure capable of improving the adhesive strength with an adhesive.

[0004]

In order to achieve the above-mentioned object, the invention according to claim 1 provides a ceramic mount portion on the inner bottom of a container made of ceramic, and mounts it on the upper surface of the mount portion to the outside. In a ceramic package configured to provide a metal electrode film for ensuring electrical continuity having a gold plating layer on the surface layer, and fix the quartz crystal plate and the gold plating layer with a conductive adhesive to establish electrical continuity , By adhering the exposed portion of the ceramic obtained by removing at least a part of the metal electrode film and a conductive adhesive, so as to reinforce the adhesive force between the metal electrode film and the quartz crystal plate. It is characterized by being configured. According to a second aspect of the invention, a ceramic mount portion is provided on the inner bottom portion of a container made of ceramic, and a metal electrode film for ensuring electrical continuity with the outside is provided on the upper surface of the mount portion, and a gold plating layer is provided on the surface layer. In a ceramic package configured to have a quartz plate and a gold-plated layer with a conductive adhesive for electrical continuity, a nickel layer and a gold layer are formed on the tungsten layer formed on the mount portion. A ceramic electrode is provided by providing a metal electrode film in which thin films are sequentially laminated, fixing a ceramic layer on a tungsten layer adjacent to the metal electrode film, and removing at least a part of the metal electrode film, and the conductive portion. It is characterized in that it is configured to reinforce the adhesive force between the metal electrode film and the quartz crystal plate by adhering it with a conductive adhesive. The invention of claim 3 is characterized in that the exposed portion is composed of a plurality of exposed portions having a small area.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A detailed description will be given below with reference to the drawings showing an embodiment of the present invention. 1 (a) and 1 (b) are a vertical cross-sectional view and a top view of an embodiment of a ceramic package according to the present invention, in which the inner bottom of a box-shaped container 1 made of ceramic and having an open top is shown. A metal electrode film 5 is formed on the upper surface of the protruding mount portion 2. This metal electrode film 5
Is a nickel layer 5b and a gold thin film 5c after the tungsten layer 5a is formed on the ceramic mount portion.
Are sequentially formed by plating. The tungsten layer is formed by printing tungsten in a state of being dissolved in a solvent on a mount portion of a ceramic container before firing using a predetermined mask, and then firing this in a furnace to remove the solvent. It is solidified by evaporation.
Since the adhesive strength between the gold thin film 5c located on the surface layer of the metal electrode film 5 and the conductive adhesive (for example, silver filler adhesive) is not sufficient, the conductive adhesive is separated from the surface of the metal electrode film. As described above, there are easy defects.

The characteristic structure of this embodiment is that the conductive adhesive 4 is applied to the ceramic of the container 1 by removing a part of the metal electrode film 5 to expose a part of the upper surface of the ceramic mount. The point is that it is directly bonded to the part to enhance the joint strength. That is, in the example of the embodiment of FIG. 1, the center portions of the opposing edges of the two mount portions 2 arranged to face each other are cut out as shown in the figure to form the ceramic exposed portion 8, and the metal electrode film 5 and the ceramic exposed portion 8 are covered. After applying the conductive adhesive 4, the crystal element plate 3 is placed thereon. Note that the excitation electrode 6 of the quartz crystal plate is vapor-deposited not only on the upper and lower surfaces as shown in FIG. 2 but also obliquely so as to be attached from the edge corner portion to the end surface. As a result, the electrical connection between the excitation electrode 6 and the conductive adhesive 4 can be ensured simply by placing the edge of the quartz crystal plate 3 on the metal electrode film 5 and drying it. That is, after placing the edge of the quartz crystal plate on the conductive adhesive, the adhesive is applied from above (2
It is not necessary to apply the second coating) to ensure the conduction.
In the method of forming the metal electrode film 5 as described above, the shape of the electrode itself may be previously formed so as to have such a shape,
A part of the electrode film may be removed by etching after forming the rectangular electrode film.

FIGS. 3 (a) and 3 (b) are explanatory views exemplifying a state in which the crystal blanks are bonded by conductive bonding. The exposed portion 8 may be wider than the crystal blanks. Although it may be narrowed or equivalent, the ratio of the area where the adhesive 4 adheres to the gold thin film 5c and the area where the adhesive 4 adheres to the exposed portion 8 is 30 to 70% in the former case. The latter is 70-30
Set it so that it is within the range of%. If the area where the adhesive adheres to the exposed ceramic surface is 80% and the area where the adhesive adheres to the gold thin film is 20%, the electrical resistance becomes excessive and the device characteristics deteriorate. The shape of the exposed portion 8 does not have to be rectangular as shown in the drawing, but various shapes such as a semicircle, a polygon, a star, a cross, and an irregular shape can be selected. Further, as shown in FIG. 4, the exposed portion 8 may be provided in the central portion of the metal electrode film 5. In this case, the ratio of the adhesive area of the adhesive is set within the above range.

Although the ceramic portion is exposed in the exposed portion 8 in the above embodiment, the tungsten layer 5a may be exposed to bond the tungsten layer and the conductive adhesive. . This point is the same in other embodiments described below. By using the package having the above structure, the adhesive strength between the conductive adhesive 4 and the metal electrode film 5 on the mount portion 2 is significantly improved as compared with the conventional case.

Next, in the above-mentioned embodiment, since the exposed portion 8 is only one place and the area of the exposed portion is large, the application position of the adhesive is shifted and an excessive amount is applied on the exposed portion 8. Sometimes. In such a case, the area of the adhesive occupying the metal electrode film 5 becomes too small, and the electrical resistance increases. 5 (a), 5 (b) and 5 (c) are a longitudinal sectional view, a plan view and a plan view of main parts showing a connection state of another embodiment for solving such a problem, and a package of this embodiment. Is the metal electrode film 5 formed on the two mount portions 2 facing each other.
The configuration is characterized in that a plurality of exposed portions 8 having a narrow width (small area) are arranged at the end edges facing each other. In this embodiment, each exposed portion 8 has a narrow strip shape, but this is merely an example, and various shapes such as a triangular shape and an elliptical shape can be adopted. Alternatively, as shown in FIG. 6, the metal electrode film 5
The exposed portion 8 may be provided inside instead of the edge. Alternatively, the exposed portions having a small area such as a rectangle or a circle may be arranged regularly or in a dotted pattern. The adhesive area ratio of the conductive adhesive 4 in this embodiment is, as described in the above embodiment, the ratio of the area where the adhesive 4 adheres to the gold thin film and the area where the adhesive 4 adheres to the exposed portion 8 is 30 to 30%. In contrast to 70%, the latter is set within the range of 70 to 30%. This can prevent an increase in electric resistance.
According to this form example, even if the application position of the conductive adhesive is slightly deviated from the case of the first form example in which the wide area exposure 7 is provided at one place, the conductive adhesive with the above ratio is obtained. It becomes easier to secure the adhesion state of (3), and it is possible to solve the unexpected condition caused by the weak adhesion of the conductive adhesive 4 and the gold thin film 5. With such a modification, the yield of products can be improved as compared with the above-mentioned embodiment.

7 (a) and 7 (b) show another embodiment of the present invention, in which nickel and gold thin films are formed on the tungsten layer while the ceramic layer 10 is formed next to the thin film. While being formed, the conductive adhesive is applied across both layers to reinforce the reduction in the adhesive force between the quartz crystal plate and the gold thin film. (a) is an example where the height of the ceramic layer 10 matches the height of the adjacent gold thin film, and (b) is an example where the height of the ceramic layer 10 is low. On the contrary to (b), the ceramic layer 10 may be lower than the gold thin film. In addition, in the above-mentioned embodiment, the device using the quartz crystal plate is illustrated, but this is only an example, and any piezoelectric material may be used. Therefore, for example, a piezoelectric ceramic may be used. Further, as the form of the piezoelectric material, a convex blank plate is shown in the drawings, but other than this, a bevel polished blank plate, a flat blank plate, a mesa blank plate, or the like may be used. Exciting electrodes 7 made of gold or the like are formed on both front and back surfaces of the crystal blank 3 by vapor deposition or the like.
Since the bonding area between the crystal blank and the conductive adhesive extends to the exposed portion of the crystal blank other than the gold electrode, peeling occurs between the conductive adhesive 4 and the crystal blank 3. do not do.

[0011]

As described above, according to the present invention, the exposed portion of the ceramic obtained by removing at least a part of the metal electrode film and the conductive adhesive are adhered to each other. It can reinforce the adhesive force between the board,
The piezoelectric element such as a crystal blank is peeled off from the package electrode,
It is possible to prevent the situation of falling out. Further, since a metal electrode film in which a nickel layer and a gold thin film are sequentially laminated is provided on the tungsten layer formed on the mount portion, and the ceramic layer is fixed on the tungsten layer adjacent to the metal electrode film, the crystal element is formed. It is possible to prevent the piezoelectric element such as a plate from being peeled off from the electrode portion of the package. In addition, since the exposed portion has a small area and is composed of a plurality of exposed portions, the adhesive strength between the conductive adhesive and the electrode on the mount portion is improved, and peeling of the piezoelectric element plate due to external force such as impact is prevented. It has a remarkable effect in eliminating it.

[Brief description of the drawings]

1A and 1B are a vertical sectional view and a top view of an example of one embodiment of a ceramic package according to the present invention.

FIG. 2 is a diagram showing a method of forming an excitation electrode.

FIG. 3A and FIG. 3B are plan views of a main part of the first embodiment.

FIG. 4 is a plan view of a main part of a modified example of the first embodiment.

5 (a), (b) and (c) are a longitudinal sectional view, a plan view and a main part plan view of a second embodiment of the present invention.

FIG. 6 is a plan view of an essential part of a modification of the second embodiment of the present invention.

7 (a) and 7 (b) are cross-sectional views showing the configuration of the main part of another embodiment of the present invention.

8A and 8B are a vertical sectional view and a plan view of a conventional package, and FIG. 8C is a sectional view of a main part.

9A and 9B are a vertical cross-sectional view and a plan view of a conventional example in which a quartz crystal plate is mounted.

[Explanation of symbols]

1 container, 2 mount part, 3 piezoelectric element plate, 4 conductive adhesive, 5 metal electrode film, 6 external electrode, 7 excitation electrode, 8 exposed part, 10 ceramic layer.

Claims (3)

[Claims] 1. A ceramic mount portion is provided on an inner bottom portion of a container made of ceramic, and a metal electrode film for ensuring continuity with the outside is provided on an upper surface of the mount portion, and a gold plating layer is provided as a surface layer. In a ceramic package that is provided with a ceramic adhesive plate and a gold-plated layer that are fixed by a conductive adhesive to conduct electricity, the ceramic obtained by removing at least a part of the metal electrode film is exposed. A structure of a ceramic package characterized in that the adhesive force between the metal electrode film and the quartz crystal plate is reinforced by adhering the portion and a conductive adhesive. 2. A ceramic mount portion is provided on an inner bottom portion of a container made of ceramic, and a metal electrode film for ensuring continuity with the outside is provided on an upper surface of the mount portion, and a gold plating layer is provided as a surface layer. In a ceramic package configured so that a quartz plate and a gold plating layer are fixed by a conductive adhesive to conduct electricity, a nickel layer and a gold thin film are formed on the tungsten layer formed on the mount portion. A metal electrode film is sequentially laminated, and a ceramic layer is fixed on the tungsten layer adjacent to the metal electrode film, and at least a part of the metal electrode film is removed to obtain conductive adhesion with the exposed portion of the ceramic. A structure of a ceramic package characterized in that it is configured to reinforce the adhesive force between the metal electrode film and the quartz crystal plate by adhering the agent. 3. The structure of the ceramic package according to claim 1, wherein the exposed portion has a small area and is composed of a plurality of exposed portions.