JP2005318334A - Piezoelectric vibrator and manufacturing method thereof - Google Patents

Abstract

【Task】
An object of the present invention is to provide a small piezoelectric vibrator in which a piezoelectric element plate is directly placed on a conductive pad via a bump and hermetically sealed, and a manufacturing method thereof.
[Solution]
In order to achieve the above object, the present invention provides a method for manufacturing a piezoelectric vibrator in which a piezoelectric element plate is supported on a conductive pad on an insulating substrate inside a container via a bump and hermetically sealed. A step of evaporating the material, a step of heat-treating the piezoelectric element plate, a step of selectively removing the base electrode material diffused to the piezoelectric element plate electrode and deposited on the electrode surface of the piezoelectric element plate by dry etching, It is characterized by comprising a step of mounting a piezoelectric element plate at a location where the base electrode material has been removed via a bump to a piezoelectric element container, and a step of adjusting the frequency of the piezoelectric element. The object is achieved by the feature that the electrode material and the bump are directly melt-bonded at the place where the deposited base electrode material deposited layer is selectively removed by dry etching.
[Selection] Figure 1

Description

              The present invention relates to a small piezoelectric vibrator in which a piezoelectric element plate is directly placed 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 is actually divided roughly into these two. In addition, the holding structure inside the piezoelectric vibrator of the piezoelectric element plate also tends to be a support structure in which the piezoelectric element plate is directly mounted on the substrate inside the piezoelectric oscillator as the outer size of the container is reduced. In the direct mounting of the piezoelectric element plate on the above-described substrate, an adhesive member such as a conductive adhesive, solder, or a lip 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. The current situation is that there are demands for height reduction, weight reduction and price reduction, and mounting of components such as piezoelectric vibrators on the substrate from the conventional lead shape described above is also a DIP (Dual In-line Package) ), ZIP (Zig-zag In-line Package), QFP (Quad Flat Package), etc., which have terminal shapes of semiconductor component packages, and further, metalized processing was applied to the board side surface of the mounted components It is rapidly expanding into surface-mounted shapes with electrodes.

              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 excitation is performed on the main surface front and back surfaces of the piezoelectric element plate thereon. Place the piezoelectric element plate on which the electrode and external connection electrode are formed and hold it with a holder such as a collet. There is a method in which 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.

In order to obtain stability of the long-term characteristics of the piezoelectric vibrator, a heat treatment is applied to the piezoelectric element plate mounted inside the piezoelectric vibrator, and this heat treatment is used as a material for the base electrode of the piezoelectric element plate. In general, an electrode base material such as chromium (Cr) or nickel (Ni) is diffused into an electrode material on an upper layer of an electrode base material such as gold (Au).
JP 2000-151345 A JP 2003-224442 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, by diffusing the electrode base material into the electrode material on the upper layer of the electrode base material such as gold (Au) by the above heat treatment, chromium (Cr) is formed on the surface of the electrode material on the upper layer of the electrode base material as shown in FIG. ) And nickel (Ni) and other electrode base materials are deposited, and as a result, the electrical resistivity deposited on the melt-bonded interface between the bump made of gold (Au) and the 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 (Cr) or nickel (Ni).

              At the same time, gold (Au), etc. can be 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 fusion-bonding interface with the electrode surface of the piezoelectric element plate. There is a problem that a stable fusion bonding strength between the bump made of the electrode and the electrode of the piezoelectric element plate may not be obtained.

              The present invention has been made under the technical background as described above. Therefore, the object of the present invention is to place the piezoelectric element plate directly on the conductive pad via the bumps and to seal the air. It is an object of the present invention to provide a small piezoelectric vibrator that stops, 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, the step of vapor-depositing the electrode material on the piezoelectric base plate, the step of heat-treating the piezoelectric base plate, and the base electrode material diffused to the electrode of the piezoelectric base plate and deposited on the electrode surface of the piezoelectric base plate are selected. Characterized by a step of removing by dry etching, a step of mounting a piezoelectric element plate at a location where the base electrode material is removed via a bump, and a step of adjusting the frequency of the piezoelectric vibrator. And

              Further, in the piezoelectric vibrator having a structure in which the piezoelectric element plate is supported on the conductive pad on the insulating substrate inside the piezoelectric vibrator container via the bump and hermetically sealed, the piezoelectric element plate is deposited on the surface of the electrode of the piezoelectric element plate. The electrode material and the bump are directly melt-bonded at a portion where the deposited layer of the base electrode material is selectively removed by dry etching.

              Further, the bumps to be melt-bonded with the electrodes are made of the same material.

              Further, the dry etching of the base electrode material is performed by ion beam etching, laser beam etching, or plasma etching.

              According to the method of manufacturing a piezoelectric vibrator of the present invention, the base electrode material deposited on the electrode surface of the piezoelectric element plate is selectively removed by dry etching, so that the electrodes and bumps of the piezoelectric element plate are remarkably stabilized. Melt bonding strength can be obtained.

              Further, according to the method for manufacturing a piezoelectric vibrator of the present invention, the base electrode material deposited on the electrode surface of the piezoelectric element plate is selectively dry-etched only at the melt-bonded portion between the electrode and the bump of the piezoelectric element plate. In order to remove and retain the deposited layer of the base electrode formed on the electrode surface except for the melt-bonded portion, long-term stability of the characteristics of the piezoelectric vibrator can be obtained.

              In addition, according to the piezoelectric vibrator of the present invention, since the electrodes and the bumps are made of the same material, the melt bonding portion does not have an interface layer, and the melt bonding that is most characteristically stable over a long period of time, and the melt bonding Strength 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 according to the present invention, first, an electrode material is vapor-deposited on the piezoelectric element plate 1 (S101), then a step of heat-treating the piezoelectric element plate 1 (S102), and the piezoelectric element plate 1 Only the deposited layer 11 of the ground electrode material at the melt-bonded portion with the bump 5 for melt-bonding the ground electrode material diffused to the electrode 8 and deposited on the electrode surface of the piezoelectric element plate 1 is selectively removed by dry etching. Step (S103), and subsequently, the step of mounting the piezoelectric element plate 1 by melt bonding the bump 5 and the piezoelectric element plate 1 to the piezoelectric vibrator container via the bump 5 at the location where the previous base electrode material has been removed. (S104) and finally a step of adjusting the frequency of the piezoelectric vibrator (S105).

              FIG. 2 shows a piezoelectric element plate 1 after a heat treatment in which a deposited layer 11 of a base electrode material is selectively removed at a portion where a bump is melt-bonded by dry etching, and a conductive pad. It is the schematic diagram seen from the general side direction which showed a mode that the bump 5 on 4 was melt-bonded. In FIG. 2, only the portion of the deposited layer 11 of the base electrode material melt-bonded to the bump 5 within the dotted circle is removed by dry etching by irradiation with an ion beam or a laser beam, and then the previous base electrode material on the bump 5 is removed. The deposited layer 11 is removed and a portion where the electrode material of the piezoelectric element plate 1 is exposed is applied and melt bonded, and the piezoelectric element plate 1 is mounted via the bumps 5. Here, in the case where the material of the bump and the electrode material of the piezoelectric element 1 are the same, the fusion bonding strength is highest, but the material of the bump 5 and the electrode material of the piezoelectric element 1 may be different. It goes without saying that this case is also included in the technical scope of the present invention.

              In FIG. 3, when the base electrode 12 is attached to the surface of the piezoelectric element plate 1 made of quartz, and further the electrode 8 is attached thereon, and then the piezoelectric element plate 1 is heated, the base electrode material diffuses into the electrode 8. It is the schematic diagram seen from the general side direction which shows a mode that the deposit layer 11 of a base electrode material is formed in the electrode surface. Here, two examples of chromium (Cr) and nickel (Ni) are shown as base electrode materials. The method of obtaining long-term stability of the characteristics by applying heat treatment to the piezoelectric element plate 1 has been performed after the double use. In the case of mounting, the formation of the deposited layer 11 on the electrode surface of the base electrode material by the heat treatment of the piezoelectric element plate 1 has a long-term stability of the piezoelectric vibrator because the deposited layer 11 has a large resistivity. There is a risk that the strength may be impaired, and there is a possibility that a stable melt-bonding strength with the electrode 8 of the piezoelectric element plate 1 may not be obtained.

              FIG. 4 is a schematic view of the present invention as viewed obliquely from above, showing one mode of performing dry etching of the selectively deposited layer 11 at the melt-bonded portion of the piezoelectric element plate 1 with the bump 5. Only the portion of the deposited layer 11 of the base electrode material that is melt bonded to the bump 5 can be selectively removed without affecting the characteristics of the material such as the crystal of the piezoelectric element plate 1 by dry etching.

              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 11 of the base electrode material deposited on the electrode 8, the long-term stability of the piezoelectric vibrator may be impaired. In addition, there is a problem that a stable melt-bonding strength between the electrode 8 and the bump 5 of the piezoelectric base plate 1 may not be obtained. A piezoelectric vibrator having a single-layer electrode structure without the base electrode 12 is also conceivable. In the case of the piezoelectric element plate 1 made of quartz, it is preferable as an electrode material and can be easily peeled off from the crystal element. The use of an electrode film made of an electrode material having no peeling strength as a single layer has an advantage that high mechanical strength and long-term reliability of the electrode film can be obtained. However, with gold (Au) and silver (Ag), which are currently used mainly as electrode materials, nickel (Ni) and silver (Ni) A chromium (Cr) underlayer 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 after heat treatment in which a deposited layer of a base electrode material in a portion where a bump is melt-bonded by dry etching is selectively removed, and a bump on a conductive pad are formed. It is the schematic diagram seen from the general side surface direction which showed a mode that it melt-joins. When a base electrode is attached to the surface of a piezoelectric element plate made of quartz and an electrode is further applied thereon, and then the heat treatment is applied to the piezoelectric element plate, the base electrode material diffuses into the electrode, and the base electrode material is applied to the electrode surface. It is the schematic diagram seen from the general | schematic side surface direction which shows a mode that this precipitation layer is formed. Two examples are shown in which chromium (Cr) and nickel (Ni) are used as the base electrode material. It is the schematic diagram seen from diagonally upward which shows one mode of performing dry etching by the beam irradiation of the selective deposition layer of the fusion | melting junction part with the bump of a piezoelectric element board of this invention. 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 a conductive pad were melt-bonded.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric base plate 3 Insulating substrate 4 Conductive pad 5 Bump 8 Electrode 11 Deposition layer 12 Base electrode

Claims (4)

In the method for manufacturing a piezoelectric vibrator having a structure in which the piezoelectric element plate is supported and sealed airtightly on a conductive pad on an insulating substrate inside the piezoelectric vibrator container.
Depositing an electrode material on the piezoelectric base plate;
Heat-treating the piezoelectric element plate;
A step of selectively removing, by dry etching, the base electrode material diffused to the electrode of the piezoelectric element plate and deposited on the electrode surface of the piezoelectric element plate;
Mounting the piezoelectric element plate on the piezoelectric vibrator container through the bumps at a location where the base electrode material is removed;
And a step of adjusting the frequency of the piezoelectric vibrator. In 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,
A piezoelectric vibrator characterized in that the electrode material and the bump are directly melt-bonded at a place where the deposited layer of the base electrode material deposited on the surface of the electrode of the piezoelectric base plate is selectively removed by dry etching. .               The piezoelectric vibrator according to claim 2, wherein the bumps to be melt-bonded to the electrodes are made of the same material.               2. The method of manufacturing a piezoelectric vibrator according to claim 1, wherein dry etching of the base electrode material is performed by ion beam etching, laser beam etching, or plasma etching.

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