JP2006101244A - Piezoelectric vibrator, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small piezoelectric vibrator which is sealed airtightly by mounting a piezoelectric raw plate directly on a conductive pad through a bump, and to provide its manufacturing method. <P>SOLUTION: In the manufacturing method of a piezoelectric vibrator, a piezoelectric raw plate is supported by a bump on a conductive pad mounted on an insulating board inside a container and is sealed airtightly. The manufacturing method includes a step of forming film of base electrode material at the main electrode of the piezoelectric raw plate, a step of forming film of a barrier layer on the surface of the main electrode, a step of forming film of main electrode material, a step of mounting the piezoelectric raw plate on the piezoelectric vibrator container by welding the bump and a connection electrode of the piezoelectric raw plate through the bump, and a step of adjusting frequency of the piezoelectric vibrator. In this case, Ag or Ti is used as a material of the barrier layer between the base electrode material and the main electrode material at the main electrode of the piezoelectric raw plate. In the piezoelectric vibrator, the connecting electrode of the piezoelectric raw plate and the piezoelectric vibrator container are directly jointed by welding through the bump. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

          The present invention relates to a small piezoelectric vibrator in which a piezoelectric element plate is directly mounted on a conductive pad via a bump and hermetically sealed, and a manufacturing method thereof.

          In recent years, the type of piezoelectric vibrator has a support structure that supports both ends of the piezoelectric element plate inside the piezoelectric vibrator with two metal pieces called metal supports. In order to be able to cope with mechanical drop impact, the support structure is constructed and hermetically sealed in a cantilevered support state where one piezoelectric element end in the plate longitudinal direction is held. It has been changed to one that holds both ends in the longitudinal direction and is hermetically sealed, and in fact, these two types are roughly divided. Also, the holding structure inside the piezoelectric vibrator of the piezoelectric element plate tends to become a support structure in which the piezoelectric element plate is directly mounted on the substrate inside the piezoelectric vibrator as the outer size of the container is reduced. In the direct mounting of the piezoelectric element plate on the above-mentioned substrate, a joining conductive member such as a conductive adhesive, solder, or a flip chip method similar to a semiconductor integrated component is being introduced.

          On the other hand, in recent trends, centering on transmission systems in the communications field, etc., along with their higher functionality, higher accuracy, smaller size, and lighter weight, the mounted components have also become very rapidly downsized from the market. At present, there are demands for height reduction and further weight reduction and price reduction, and mounting of components such as piezoelectric vibrators on the substrate has been changed from the conventional lead shape described above to DIP (Dual In-line). Package), ZIP (Zig-zag In-line Package), QFP (Quad Flat Package), etc. It is rapidly expanding into a surface-mounted shape with a main electrode.

          An example of a method for mounting the piezoelectric element plate on the substrate inside the piezoelectric vibrator is the length direction of the container at the bottom of the recess formed in a container formed of an insulating material such as ceramics and corresponding to surface mounting. Two conductive pads are formed at one end, and metal bumps (hereinafter referred to as “bumps”) made of gold or the like are formed at arbitrary positions on these conductive pads, and the main surface front and back surfaces of the piezoelectric element plate are formed thereon. While holding the piezoelectric element plate on which the excitation electrode and the external connection electrode are formed and holding it with a holder such as a collet, the holder is attached to the length of the container while applying a load to the bottom surface of the recess of the piezoelectric vibrator container. There is a method in which ultrasonic vibration is performed in the side direction and the external connection electrodes of the piezoelectric base plate and the bumps are melt-bonded by frictional heat. The piezoelectric vibrator can be formed by separating the holder from the previous piezoelectric element plate and covering the concave portion in the container with a metal lid so as to cover the concave opening of the piezoelectric vibrator container. I can do it.

          Conventionally, in order to obtain long-term stability of the characteristics of the piezoelectric vibrator, a heat treatment is applied to the piezoelectric element plate mounted inside the piezoelectric vibrator. In general, this heat treatment diffuses the electrode base material such as chromium (Cr) or nickel (Ni) used as the base electrode material of the piezoelectric base plate into the main electrode material on the upper layer of the electrode base material such as gold (Au). Known.

JP 2000-151345 A JP 2003-224442 A JP 2002-344278 A

          In addition, the applicant did not find any prior art documents related to the present invention by the time of filing of the present application other than the prior art documents specified by the above prior art document information.

          However, when the electrode base material is diffused into the main electrode material on the upper layer of the electrode base material made of gold (Au) or the like by the above heat treatment, as shown in the figure, the surface of the main electrode material on the upper layer of the electrode base material is chromium. A deposited layer is formed by depositing an electrode base material such as (Cr) or nickel (Ni), and as a result, deposited on the melt-bonded interface between the bump made of gold (Au) and the main electrode surface of the piezoelectric element plate. There is a problem that the stability of the long-term characteristics of the piezoelectric vibrator may be impaired due to the formation of the deposited layer of the electrode base material such as chromium (Cr) or nickel (Ni), which has a high electrical resistivity. .

          At the same time, gold (Au) is formed by forming a deposited layer of electrode base material such as chromium (Cr) or nickel (Ni) having a high electrical resistivity deposited at the melt-bonding interface with the main electrode surface of the piezoelectric element plate. There is a problem that a stable fusion bonding strength between the bump made of the above and the main electrode of the piezoelectric element plate may not be obtained.

          The present invention has been made under the above technical background. Therefore, the object of the present invention is to place a piezoelectric element plate directly on a conductive pad via a bump. A compact piezoelectric vibrator that is hermetically sealed, and a method for manufacturing the same.

          To achieve the above object, the present invention provides a piezoelectric vibrator having a structure in which a piezoelectric element plate is hermetically sealed by being supported via a bump on a conductive pad on an insulating substrate inside a piezoelectric vibrator container. In the manufacturing method, a step of forming a base electrode material on the main electrode of the previous piezoelectric element plate, a step of forming a barrier layer on the surface of the main electrode, a step of forming a main electrode material, and a piezoelectric vibrator It consists of a step of melt-bonding the bump and the piezoelectric element plate via the bump to the container and mounting the previous piezoelectric element plate on the piezoelectric vibrator container and a step of adjusting the frequency of the piezoelectric vibrator. Features.

          Further, in the piezoelectric vibrator having a configuration in which the piezoelectric element plate is hermetically sealed by being supported on the conductive pads on the insulating substrate inside the piezoelectric vibrator container through the bumps, the main electrode of the previous piezoelectric element plate is Ag or Ti is used as the material for the barrier layer between the base electrode material and the main electrode material, and the electrode for connecting the piezoelectric element plate and the piezoelectric vibrator container are directly melt-bonded via the bumps. It is characterized by.

          Further, the thickness of the barrier layer of the main electrode is at least 10 nm or more, and is not less than the thickness of the base electrode material of the main electrode.

          Further, the above-described main electrode and the above-mentioned bump to be melt-bonded are made of the same material.

          According to the method for manufacturing a piezoelectric vibrator of the present invention, a barrier layer is provided between the base electrode material and the main electrode material in order to prevent the base electrode material from being deposited on the surface of the main electrode. Precipitation of the electrode material can be prevented, and a remarkably stable melt bonding strength between the main electrode and the bump of the piezoelectric element plate can be obtained.

          Further, according to the method for manufacturing a piezoelectric vibrator of the present invention, since the base electrode material is not deposited on the surface of the main electrode of the piezoelectric base plate by the barrier layer, the heat is applied not only to the joint portion by the bump but also to the entire main electrode surface. Since the film quality hardly changes, the long-term stability of the piezoelectric vibrator can be obtained.

          Moreover, the heat treatment process of the piezoelectric element plate mounted inside the piezoelectric vibrator for obtaining the long-term stability of the piezoelectric vibrator, which has been conventionally performed, is no longer necessary, and the production of the piezoelectric vibrator Cost can be reduced.

          In addition, according to the piezoelectric vibrator of the present invention, since the main electrode and the bump are made of the same material, the melt bonding portion does not have an interface layer, and the melt bonding is very characteristically stable over a long period of time. The melt bonding strength can be obtained. Note that this effect is achieved even when a main electrode material containing up to about 30 wt% of Ag, which is a material having a lower electrical resistivity than Au, is used for the bump material. An almost equivalent effect can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In addition, the same code | symbol in each figure shall show the same object.

          FIG. 1 is a flowchart showing a method for manufacturing a piezoelectric vibrator of the present invention. That is, in the method for manufacturing a piezoelectric vibrator of the present invention, the piezoelectric base plate 1 is hermetically sealed by being supported via the bumps 5 on the conductive pads 4 on the insulating substrate 3 inside the piezoelectric vibrator container 2. In the piezoelectric vibrator manufacturing method, first, a base electrode material 8 is formed on the main electrode 7 of the piezoelectric base plate 1 (S101), and then the surface 9 of the previous main electrode, that is, the surface of the base electrode material 8 is barriered. The layer 10 is formed (S102), and then the main electrode material 11 is formed on the surface of the previous barrier layer 10 (S103), and the bump 5 and the piezoelectric element are further connected to the piezoelectric vibrator container 2 via the bump 5. The piezoelectric element plate 1 is mounted by fusion welding at the connection electrode 12 of the plate 1 (S104), and finally the frequency of the piezoelectric vibrator 6 is adjusted (S105).

          FIG. 2 shows a three-layered main electrode 7 in which a base electrode is provided on the surface of a piezoelectric element plate 1 made of quartz of the present invention, a barrier layer 10 is further provided thereon, and a main electrode 7 is further provided thereon. It is the schematic diagram seen from the general side direction which showed a mode that the film-formed piezoelectric element | base_plate 1 and the bump 5 on the electroconductive pad 4 were melt-bonded. Here, for connecting a piezoelectric vibrator 6 in which chromium (Cr) is formed on the piezoelectric element plate 1 as a base electrode material 8, silver (Ag) is used as a barrier layer, and gold (Au) used as a main electrode material 11 is formed. The electrode 12 and the conductive pad 4 on the insulating substrate 3 are mounted via bumps 5. Here, in the case where the material of the bump 5 and the main electrode material of the piezoelectric element plate 1 are the same, the melt-bonding strength is highest, but the material of the bump 5 and the main electrode material of the piezoelectric element plate 1 are different. Needless to say, this case is also included in the technical scope of the present invention.

          FIG. 3 shows a main electrode 7 having a three-layer structure in which a base electrode is provided on the surface of a piezoelectric element plate 1 made of quartz according to the present invention, a barrier layer 10 is further provided thereon, and a main electrode 7 is further provided thereon. It is the schematic diagram which looked at the piezoelectric material board 1 which carried out the film | membrane from the schematic diagonally upward direction. Here, chromium (Cr) is formed as the base electrode material 8, silver (Ag) is used as the barrier layer 10, and gold (Au) used as the main electrode material 11 is formed on the piezoelectric element plate 1. Here, the barrier layer 10 may not be silver (Ag), and it is needless to say that the technical scope of the present invention includes the case where the base electrode material 8 is a material that does not precipitate on the main electrode surface by heat treatment.

          FIG. 4 shows that when a base electrode is attached to the surface of a conventional piezoelectric element plate 1 made of quartz, and a main electrode is further formed thereon, a heat treatment is applied to the piezoelectric element plate 1 so that the base electrode material 8 is formed on the main electrode. It is the schematic diagram seen from the general side surface direction which shows a mode that it diffuses and the deposited layer of the base electrode material 8 is formed in the main electrode surface. Here, two examples of chromium (Cr) and nickel (Ni) are shown as the base electrode material 8. The method of obtaining long-term stability of the characteristics by applying heat treatment to the piezoelectric element plate 1 has been performed after that, but the bump element 5 is used to connect the piezoelectric element sheet 1 through it. In the case of mounting, the formation of the deposited layer 13 on the surface of the main electrode of the base electrode material 8 by the heat treatment of the piezoelectric element plate 1 has a long-term characteristic of the piezoelectric vibrator 6 because the deposited layer 13 has a large resistivity. There is a risk that the stability of the piezoelectric element plate 1 may be impaired, and there is a possibility that a stable fusion bonding strength with the main electrode of the piezoelectric element plate 1 may not be obtained.

          FIG. 5 is a schematic view seen from the side of the outline showing a state in which the conventional piezoelectric element plate 1 after heat treatment and the bump 5 on the conductive pad 4 are melt-bonded. Since the bump 5 and the piezoelectric element plate 1 are melt-bonded in such a manner as to sandwich the deposited layer 13 of the base electrode material 8 deposited on the main electrode, the stability of the long-term characteristics of the piezoelectric vibrator 6 is consequently impaired. In addition, there is a problem that a stable fusion bonding strength between the main electrode of the piezoelectric base plate 1 and the bump 5 may not be obtained. A piezoelectric vibrator 6 having a single-layer main electrode structure without a base electrode is also conceivable. In the case of the piezoelectric element plate 1 made of quartz, it is preferable as the main electrode material and is easily peeled off from the crystal element plate. The use of a main electrode film made of a main electrode material having a peel strength that does not occur as a single layer has the advantage that high mechanical strength and long-term reliability of the main electrode film can be obtained. However, gold (Au) and silver (Ag), which are currently used mainly as the main electrode material, are nickel (Ni) because their single-layer film does not provide sufficient adhesion to quartz. And an underlayer of the main electrode such as chromium (Cr) is required. In view of such a current situation, the piezoelectric vibrator of the present invention and the manufacturing method thereof have been considered.

3 is a flowchart showing a method for manufacturing a piezoelectric vibrator of the present invention. According to the method for manufacturing a piezoelectric vibrator of the present invention, a piezoelectric element plate having a three-layered main electrode on which a bump is melt bonded and a bump and the piezoelectric element plate are melt bonded to each other via a bump on a conductive pad. It is the schematic diagram seen from the general side surface direction which showed the mode. 1 is a schematic diagram showing a piezoelectric element plate provided with a main electrode having a three-layer structure according to the present invention as viewed obliquely from above. When a base electrode is attached to the surface of a conventional piezoelectric element plate made of quartz, and then a main electrode is attached thereon, and then the piezoelectric element plate is heated, the base electrode material diffuses into the main electrode, and the main electrode It is the schematic diagram seen from the general side surface direction which shows a mode that the deposit layer of base electrode material is formed in the surface. Here, two examples in which chromium (Cr) and nickel (Ni) are used as the base electrode material are shown. It is the schematic diagram seen from the general side direction which showed a mode that the piezoelectric element board after the conventional heat processing and the bump on an electroconductive pad were melt-bonded.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric base plate 2 Piezoelectric vibrator container 3 Insulating substrate 4 Conductive pad 5 Bump 6 Piezoelectric vibrator 7 Main electrode 8 Base electrode material 9 Main electrode surface 10 Barrier layer 11 Main electrode material 12 Connection electrode 13 Precipitation layer 14 Base electrode

Claims (4)

In the method of manufacturing a piezoelectric vibrator having a structure in which the piezoelectric element plate is hermetically sealed by being supported via a bump on a conductive pad on an insulating substrate inside the piezoelectric vibrator container,
Forming a base electrode material on the main electrode of the piezoelectric base plate;
Forming a barrier layer on the surface of the main electrode;
Forming a main electrode material on the surface of the main electrode;
A step of melting and bonding the bump and the piezoelectric element plate via a bump to the piezoelectric vibrator container, and mounting the piezoelectric element plate;
Adjusting the frequency of the piezoelectric vibrator, and a method of manufacturing the piezoelectric vibrator. In the piezoelectric vibrator having a configuration in which the piezoelectric element plate is hermetically sealed by being supported via a bump on a conductive pad on an insulating substrate inside the piezoelectric vibrator container,
Ag or Ti is used for the main electrode of the piezoelectric element plate as a material of a barrier layer between the base electrode material and the main electrode material, and the connection electrode of the piezoelectric element plate and the piezoelectric vibrator container are connected to the bumps. A piezoelectric vibrator characterized in that the piezoelectric vibrator is directly melt-bonded through a metal.           3. The piezoelectric vibrator according to claim 2, wherein the thickness of the barrier layer of the main electrode is at least 10 nm or more and equal to or more than the thickness of the base electrode material of the main electrode.           The piezoelectric vibrator according to claim 2, wherein the main electrode and the bump to be melt-bonded are made of the same material.

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