JP3290060B2 - Structure of ceramic package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As electronic devices such as various communication devices and OA devices have become lighter and thinner, smaller piezoelectric devices have been required as built-in components. In place of the conventional lead type in which a lead terminal is led out, various types of surface mounting type in which electrodes are formed outside the package have been developed. Also, in the case of surface mount type piezoelectric devices, in order to respond to the thinning of equipment, it is necessary to support the piezoelectric element on a special substrate provided in the package as in the past as an internal structure of the piezoelectric device. Instead, it is more advantageous to adopt a structure in which the piezoelectric element plate is directly fixed to the bottom of the package with a conductive adhesive such as a silver filler adhesive (direct mount structure). For example, in a piezoelectric device using a quartz crystal plate as a quartz oscillator, FIG.
As shown in FIG. 9, a quartz crystal plate 3 is electrically conductively bonded on a metal electrode film 5 provided on a mount portion 2 which is two protrusions provided on an inner bottom portion of a container 1 formed of ceramic. In general, a ceramic package is used in which the upper opening of the container 1 is sealed with a metal or ceramic lid after being fixed with the agent 4. The metal electrode film 5 is generally formed by sequentially laminating a tungsten layer, a nickel plating layer, and a gold plating thin film on the ceramic mount 2. The reason for making the gold-plated thin film layer a surface layer is that gold has good conductivity,
Also, it is hardly oxidized. 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 in the container 1 made of this ceramic, and as shown in FIG. The quartz crystal plate 3 is placed after applying the conductive adhesive 4, and the conductive adhesive 4 is hardened by heating to fix the quartz crystal plate 3 in the container 1 made of ceramic. Thereafter, the opening of the container is sealed with a lid, thereby completing the piezoelectric device.

[0003]

However, in the above-described piezoelectric device having the conventional structure, 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. On the other hand, when vibrations or shocks are applied, the gold thin film and the conductive adhesive 4 are separated from each other, which often causes a problem that the vibrator is not ejected. SUMMARY OF THE INVENTION The present invention has been made in order to prevent the above-described problems of a piezoelectric device using a conventional package from occurring, and is intended to prevent a piezoelectric device from being electrically conductive with a gold electrode on a mount portion provided at an inner bottom portion of a 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]

According to the first aspect of the present invention, a ceramic mount is provided on the inner bottom of a container made of ceramic, and the upper surface of the mount is connected to the outside. In a ceramic package configured to provide a metal electrode film having a gold plating layer on the surface layer for securing conduction, and fixing the quartz crystal plate and the gold plating layer with a conductive adhesive and conducting. By bonding the exposed portion of the ceramic obtained by removing at least a part of the metal electrode film and the conductive adhesive, the adhesive force between the metal electrode film and the quartz crystal plate is reinforced. It is characterized by comprising. According to a second aspect of the present invention, a ceramic mounting portion is provided on an inner bottom portion of a container formed of ceramic, and a metal electrode film for securing conduction to the outside on the upper surface of the mounting portion, wherein a gold plating layer is provided on a surface layer. In a ceramic package configured to fix the quartz crystal plate and the gold plating layer with a conductive adhesive and to conduct, a nickel layer and a gold layer are formed on the tungsten layer formed on the mount portion. A metal electrode film in which thin films are sequentially laminated is provided, a ceramic layer is fixed on a tungsten layer next to the metal electrode film, and an exposed portion of the ceramic obtained by removing at least a part of the metal electrode film is electrically conductive. The adhesive between the metal electrode film and the quartz crystal plate is reinforced by adhering the adhesive. The invention according to claim 3 is characterized in that the exposed portion is formed of a small area and a plurality of exposed portions.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 (a) and 1 (b) are a longitudinal sectional view and a top view of one embodiment of a ceramic package according to the present invention, which is formed on the inner bottom of a box-shaped container 1 made of ceramic and having an open top. A metal electrode film 5 is formed on the upper surface of the projecting mount 2. This metal electrode film 5
For example, after forming a tungsten layer 5a on a ceramic mounting portion, a nickel layer 5b and a gold thin film 5c are formed.
Are sequentially formed by plating. The tungsten layer is formed by printing a 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 the solvent in a furnace to remove the solvent. It is solidified by evaporating.
In addition, 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 peels off from the surface of the metal electrode film. As described above, there are easy disadvantages.

The characteristic configuration of this embodiment is that a part of the metal electrode film 5 is removed to expose a part of the upper surface of the ceramic mounting portion, so that the conductive adhesive 4 is applied to the ceramic of the container 1. The point is that it is bonded directly to the part to enhance the bonding strength. In other words, in the embodiment shown in FIG. 1, the center portions of the opposing edges of the two mount portions 2 opposed to each other are cut out as shown in the drawing to form a ceramic exposed portion 8, and extend over the metal electrode film 5 and the ceramic exposed portion 8. After applying the conductive adhesive 4, the quartz crystal plate 3 is mounted thereon. As shown in FIG. 2, the excitation electrode 6 of the quartz crystal plate is deposited not only on the upper and lower surfaces but also obliquely so as to adhere from the edge to the end face. As a result, the electrical connection between the excitation electrode 6 and the conductive adhesive 4 is ensured only by placing the edge of the 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 perform the second application to ensure the conduction.
In the method of forming such a metal electrode film 5, the shape of the electrode itself may be formed in advance so as to have such a shape,
After the electrode film having a rectangular planar shape is formed, a part thereof may be removed by etching.

FIGS. 3 (a) and 3 (b) are explanatory views exemplifying a state where the quartz plate is bonded by conductive bonding. The width of the exposed portion 8 may be larger than the width of the quartz plate. 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. And the latter is 70-30
Set so that it is within the range of%. If the area where the adhesive is adhered to the exposed ceramic surface is 80% and the area where the adhesive is adhered to the gold thin film is 20%, the electrical resistance becomes excessive and the characteristics of the device deteriorate. The shape of the exposed portion 8 does not need to be rectangular as shown in the figure, and 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, an exposed portion 8 may be provided at the center of the metal electrode film 5. In this case, the ratio of the adhesive area of the adhesive is set to be in the above range.

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

Next, in the above embodiment, since the exposed portion 8 is located at 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 onto 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. FIGS. 5 (a), 5 (b) and 5 (c) are a vertical sectional view, a plan view, and a plan view of a main part showing a connection state of another embodiment for solving such a problem. Is a metal electrode film 5 formed on two opposing mount portions 2
Is characterized in that exposed portions 8 having a plurality of sandwiched widths (small areas) are arranged at opposing edges. In this embodiment, the shape of each exposed portion 8 is a narrow band shape, but this is merely an example, and various shapes such as a triangular shape, an elliptical shape, and the like can be adopted. Alternatively, as shown in FIG.
The exposed portion 8 may be provided inside instead of the end edge. Alternatively, the exposed portions having a small area such as a rectangle and a circle may be arranged in a regular or dotted pattern. The bonding 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 is bonded to the thin gold film and the area where the bonding agent 4 is bonded to the exposed portion 8 is 30 to 30%. In contrast to 70%, the latter is set to fall within the range of 70 to 30%. Thus, an increase in electric resistance can be prevented.
According to this embodiment, even if the application position of the conductive adhesive is slightly shifted as compared with the case of the first embodiment in which one large-area exposure 7 is provided, the conductive adhesive according to the above ratio is used. Can be easily secured, and an unexpected problem caused by a weak adhesive force between the conductive adhesive 4 and the gold thin film 5 can be solved. Such deformation can improve the yield of products as compared with the above embodiment.

FIGS. 7 (a) and 7 (b) show another embodiment of the present invention, in which a nickel and gold thin film is formed on a tungsten layer while a ceramic layer 10 is arranged adjacent to the thin film. While being formed, a conductive adhesive is applied over both layers so as to reinforce the decrease in the adhesive strength 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. Contrary to (b), the ceramic layer 10 may be lower than the gold thin film. In the above embodiment, a device using a 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. In addition, although a convex elementary plate is shown in the drawings as a form of the piezoelectric material, a bevel polished elementary element, a flat elementary element, a mesa elementary element, or the like may be used instead. Excitation electrodes 7 made of gold or the like are formed on both front and back surfaces of the quartz crystal plate 3 by vapor deposition or the like.
Since the bonding area between the quartz crystal plate and the conductive adhesive also extends to a portion where the quartz crystal plate is exposed other than the gold electrode, peeling occurs between the conductive adhesive 4 and the quartz crystal plate 3. do not do.

[0011]

According to the present invention, as described above, the exposed portion of the ceramic obtained by removing at least a part of the metal electrode film is bonded to the conductive adhesive, so that the metal electrode film and the quartz crystal are bonded. It can reinforce the adhesive strength between the board and
Piezoelectric elements such as quartz plates are peeled off from the electrodes of the package,
It is possible to prevent the occurrence of the situation of dropping. In addition, a metal electrode film in which a nickel layer and a gold thin film are sequentially laminated on the tungsten layer formed on the mount portion is provided, and a ceramic layer is fixed on the tungsten layer next to the metal electrode film. It is possible to prevent a situation in which a piezoelectric element such as a plate peels or falls off from the electrode portion of the package. Further, since the exposed portion is made up of a small area and a plurality of exposed portions, the adhesive strength between the conductive adhesive and the electrode on the mount portion is improved, and the peeling of the piezoelectric element plate due to an external force such as an impact is improved. It has a remarkable effect in eliminating it.

[Brief description of the drawings]

1 (a) and 1 (b) are a longitudinal sectional view and a top view 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.

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

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

FIGS. 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 a main part of a modification of the second embodiment of the present invention.

FIGS. 7A and 7B are cross-sectional views showing the configuration of a main part of another embodiment of the present invention.

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

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

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-252682 (JP, A) JP-A-7-25620 (JP, U) JP-A-6-77328 (JP, U) JP-A-6-32828 48227 (JP, U) JP 5-46115 (JP, U) JP-A 3-39923 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/00-9 / 215

Claims (1)

(57) [Claims] A ceramic mounting portion is provided on the inner bottom of a container made of ceramic, and a metal electrode film for securing conduction with the outside on the upper surface of the mounting portion, and has a gold plating layer on a surface layer. In a ceramic package configured so that the quartz crystal plate and the gold plating layer are fixed and electrically connected to each other with a conductive adhesive , a nickel layer is formed on the tungsten layer formed on the mount portion.
With a metal electrode film in which a
A ceramic layer on the tungsten layer next to the metal electrode film.
A structure of a ceramic package, characterized in that the layer is fixed and the ceramic layer and a conductive adhesive are adhered to each other to reinforce the adhesive force between the metal electrode film and the quartz plate.