Process for fabricating piezoelectric vibrator

The present invention relates to a method for manufacturing a piezoelectric vibrator, and particularly relates to a method for manufacturing a piezoelectric vibrator suitable for small size and thinness.

In recent years, with the remarkable miniaturization of devices such as mobile communication devices, further miniaturization and thinning of electronic components such as piezoelectric vibrators used in these devices have been required. In particular, the piezoelectric vibrator having a shape compatible with surface mounting is remarkably reduced in size and thickness. Piezoelectric oscillators with an external size of 5 mm or less in the length direction and a thickness of 2 mm or less have also been developed, and are becoming smaller and thinner in μm units.

As a conventional method for manufacturing such a piezoelectric vibrator, a concave portion for mounting a piezoelectric diaphragm element, which will be described later, is formed in a container having a shape corresponding to surface mounting, which is formed of an insulating material such as ceramics. There is. On the bottom surface of the recess, two electrode pads for connecting elements are formed on one end side or both end sides in the length direction of the container.

As a method of mounting a piezoelectric diaphragm element on such a container to form a piezoelectric vibrator, first, an epoxy-based conductive adhesive is applied to an electrode pad for connecting an element formed on the bottom surface of the container.

Next, the piezoelectric diaphragm element held by the holder or the like is moved so as to be arranged on the epoxy-based conductive adhesive coated with the external connection electrode film. In addition, in order to more reliably electrically connect the piezoelectric vibrating plate element with the epoxy-based conductive adhesive and the electrode pad for element connection, a conductive adhesive is also applied to the electrode film for external connection of the piezoelectric vibrating plate element. It may be applied.

Next, the holder is lowered toward the bottom surface of the recess in the container, and the epoxy-based conductive adhesive applied on the element connection electrode pad and the epoxy-based conductive adhesive formed on the external connection electrode film or the external connection electrode film. Join with adhesive.

After that, the holder is separated from the piezoelectric diaphragm element, and the epoxy-based conductive adhesive formed between the element connection electrode pad and the piezoelectric diaphragm element is heated and solidified. Finally, the piezoelectric vibrator is formed by covering the concave portion opening of the container with a metal lid and airtightly sealing the concave portion space inside the container in which the piezoelectric diaphragm element is mounted.

As a substance that electrically connects and fixes the external connection electrode film of the piezoelectric vibrating plate element and the electrode pad for element connection, in addition to the above-mentioned epoxy-based conductive adhesive, Au is placed on the electrode pad for element connection. Etc. are formed, and the metal bump is melted by ultrasonically vibrating the metal bump while bringing the electrode film for external connection of the piezoelectric vibrating plate element into contact with the metal bump, and the metal bump and the external connection electrode of the piezoelectric vibrating plate element are formed. A piezoelectric vibrator or the like in which a film is conductively fixed is also disclosed.

The following documents are disclosed regarding the method for manufacturing a piezoelectric vibrator as described above.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 11-163653</text></patcit><patcit num="2"><text>Japanese Patent No. 2583866</text></patcit>

The applicant has not found any prior art documents related to the present invention by the time of filing the present application, other than the prior art documents specified in the above-mentioned prior art document information.

<p> However, as the size of the piezoelectric vibrator is further reduced, the area of the electrode pad for connecting the element formed on the inner bottom surface of the recess of the package becomes very small, so that the viscosity is usually several tens to several hundreds as illustrated in FIG. In the conventional application method with a syringe-type dispenser that applies an epoxy-based conductive adhesive of several tens of Pa · s, the tip of the dispenser from which the epoxy-based conductive adhesive is discharged is placed on the electrode pad for element connection. It is very difficult to do so because the tip of the dispenser is larger than the electrode pad for connecting elements.</p><p> Further, it is difficult to make the tip of the dispenser extremely fine in accordance with the miniaturization of the electrode pad for device connection and the narrowing of the coating space due to the viscosity of the epoxy-based conductive adhesive. It should be noted that such a problem occurs even when a connection structure using metal bumps is adopted, and it is difficult to arrange the tip of the bump forming device at a position on the electrode pad for connecting elements to form a metal bump, and miniaturization progresses. However, there is a possibility that the epoxy-based conductive adhesive by the syringe-type dispenser cannot be applied on the electrode pad for connecting the element formed in the container of the piezoelectric vibrator.</p><p> In particular, in the case of a piezoelectric vibrator using a so-called cantilever type piezoelectric diaphragm element support form in which a signal excited by the piezoelectric diaphragm element is extracted from one end in the length direction of the piezoelectric diaphragm, the length of the inner bottom surface of the package recess is long. Two electrode pads must be formed side by side at one end in the longitudinal direction, and as miniaturization progresses, the distance between the element connection electrode pad and the inner wall surface of the container recess becomes extremely narrow. Therefore, when the epoxy-based conductive adhesive is applied to the element connection electrode pad, there is a high possibility that the epoxy-based conductive adhesive will adhere to a place other than the element connection electrode pad, and problems such as short circuit may occur. There is sex.</p><p> Further, the conductive adhesive used for the piezoelectric vibrator generally does not have very high reliability of conductivity at a low excitation level. Therefore, a piezoelectric vibrator that uses a metal bump as a connection fixing material instead of a conductive adhesive has been developed. However, even in such a piezoelectric vibrator, if the piezoelectric vibrator is miniaturized, the electrode pad When forming the metal bump, the capillary for forming the metal bump on the upper surface may hit the inner wall surface of the recess, and the metal bump may not be formed at a desired location.</p>

<p> The present invention has been made to solve the above-mentioned problems. A recess is provided in a container made of an insulating material, and an electrode pad for connecting an element is formed at an end portion of the bottom surface of the recess in the length direction. In the recess, an excitation electrode film and an externally connected electrode film electrically connected to the excitation electrode film are arranged at the ends in the length direction on both the front and back main surfaces. Then, in the method of manufacturing a piezoelectric vibrator in which the external connection electrode film of the piezoelectric vibrating plate element and the electrode pad for element connection are electrically connected and fixed by a conductive material, the element connection formed on the inner bottom surface of the container recess is formed. A process of ejecting thermocurable conductive ink from outside the container onto the electrode pad for element connection from outside the container and adhering it to the surface of the electrode pad for element connection, and on the adhered thermocurable conductive ink. In the process of arranging the piezoelectric vibrating plate element so that the electrode film for external connection and the thermosetting conductive ink are in contact with each other and electrically connected to each other, and the container in which the piezoelectric vibrating plate element is arranged in the recess is heated. A method for manufacturing a piezoelectric vibrator, which comprises a step of firing a thermosetting conductive ink and fixing a piezoelectric vibrating plate element to an electrode pad for connecting an element.</p>

<p> Due to the piezoelectric vibrator described in the present invention and the method for manufacturing the same, the miniaturization has progressed, and the distance between the element connection electrode pad formed in the recess of the container and the inner wall surface of the recess is extremely narrow, and the epoxy system is placed on the element connection electrode pad. Even in a situation where conductive adhesive or metal bumps cannot be formed, the external connection electrode film of the piezoelectric vibrating plate element and the element connection electrode pad are electrically connected, and the piezoelectric vibrating plate element is formed by the element connection electrode pad. Since it can be reliably fixed to the container in which the characteristics are formed, the opening shape is similar to the plane shape of the desired piezoelectric vibrating plate, and the inner bottom surface and the lid are connected to the piezoelectric vibrating plate. The piezoelectric vibrating plate can be mounted in a small package having recesses with the narrowest spacing that does not adversely affect the vibration characteristics of the piezoelectric vibrating plate.</p><p> Further, since the present invention uses a thermosetting conductive ink having a relatively low viscosity as the conductive material, it can be applied very thinly when applied on the electrode pad for device connection.</p><p> Due to these actions, the present invention has the effect of providing a piezoelectric vibrator that is highly reliable and can be miniaturized and thinned.</p>

Hereinafter, an embodiment of a part of the steps of the piezoelectric vibrator manufacturing method according to the present invention will be described with reference to the drawings. FIG. 1 is a process diagram illustrating a part of the steps of the method for manufacturing a piezoelectric vibrator according to the present invention by using a cut-out view of a container. FIG. 2 is an enlarged view showing the inside of the dotted line circle in the process (c) in the process diagram of FIG. 1 in an enlarged manner. In each figure, a part of the structure is not shown for the sake of clarity. Further, each dimension is also shown with some exaggeration, and in particular, the thickness of the electrode pad for element connection, the electrode film, the thermosetting conductive ink, etc. is shown with a remarkably exaggerated.

That is, in the step (a) of FIG. 1, the container 11 has a shape corresponding to surface mounting formed of an insulating material such as ceramic, and a recess 12 is formed on one of the main surfaces. Two electrode pads 13 for connecting elements are formed on the bottom surface of the recess 12 near the inner wall surface of the recess on one end side in the length direction of the package, and the electrode pads 13 for connecting elements are the other of the container 11. It is electrically connected to each of the external connection electrode pads 14 formed on the main surface of the above surface for fixing and conducting to other substrates and the like.

The shape of the recess 12 formed in the container 11 is substantially similar to the length and width of the piezoelectric diaphragm element mounted inside the recess 12 in the direction of the length and width of the recess 12. The dimensions in the length and width directions of 12 are such that when the piezoelectric diaphragm element is inserted into the recess 12, the entire inner wall surface of the recess 12 does not come into contact with the piezoelectric diaphragm element and the vibration characteristics of the piezoelectric diaphragm element. It is formed with dimensions that can maintain the minimum spacing that does not adversely affect it.

Further, in the container 11, a metallized layer 18 is formed on the top of the side wall of the recess, and the container 11 in which these are formed is placed at a predetermined manufacturing work position after cleaning.

In the next steps (b) and (c), a thermosetting conductive ink is used from the outside of the container 11 on the electrode pad 13 for element connection formed on the inner bottom surface of the concave portion of the container 11 by using a jet dispense type dispenser 19. 15 is discharged and adhered to the surface of the electrode pad 13 for element connection. The thermosetting conductive ink 15 is not a paste like the conventional epoxy-based conductive adhesive, but is a low-viscosity (5 to 50 mPa · s) liquid, so the tip of the dispenser can be made as thin as possible. it can. Further, since the element connection electrode pad 13 can be discharged from the outside of the container 11 to the surface of the element connection electrode pad 13, even if the element connection electrode pad 13 is formed near the inner wall surface of the recess of the container 11, it can be applied regardless of the shape and size of the dispenser. .. The thermosetting conductive ink 15 adheres to the surface of the element connection electrode pad 13 and then spreads thinly on the surface of the element connection electrode pad 13.

Next, in step (d), the piezoelectric diaphragm element 16 is electrically connected to the external connection electrode film 17 and the thermosetting conductive ink 15 on the adhered thermosetting conductive ink 15. Arrange as follows. The piezoelectric vibrating plate element 16 has a multi-layered excitation electrode film made of gold and chromium formed on the front and back main surfaces of the rectangular piezoelectric base plate at positions facing each other on the front and back main surfaces. A lead-out electrode film extends from the excitation electrode film to one end in the length direction of the piezoelectric base plate, and an electrode pad 13 for element connection formed in the recess 12 of the container 11 at the tip thereof. An external connection electrode film 17 that sticks to and conducts with the piezoelectric vibrating plate element 16 is formed.

While holding the piezoelectric diaphragm element 16 with a holder (not shown) such as a collet, the external connection electrode film 17 formed on the piezoelectric diaphragm element 16 is placed in the recess 12 of the container 11 arranged at a predetermined position. The piezoelectric diaphragm element 16 is moved to a position facing the formed thermosetting conductive ink 15 and not in contact with the side wall surface in the recess 12, and the piezoelectric diaphragm element 16 is moved to a desired position. When 16 is placed, the piezoelectric diaphragm element 16 together with the holder is lowered horizontally with the bottom surface of the recess and inserted into the recess 22, and the holder is placed at a position where the external connection electrode film 17 comes into contact with the thermosetting conductive ink 15. Remove.

Next, a container in which the piezoelectric diaphragm element 16 is arranged in the recess 12 is inserted into a heating device such as an oven layer, the entire container 11 is heated, the heat-curable conductive ink 15 is fired, and the piezoelectric diaphragm element 16 is fired. Is fixed to the element connection electrode pad 13.

Then, a metal lid (not shown) covering the opening of the recess 12 is placed on the metallized layer 14 at the top of the side wall of the container 12. At this time, in the present invention, as a means for mounting the piezoelectric diaphragm element 16 in the recess 12, an epoxy-based conductive adhesive or the like is not applied as in the conventional case, so that the height of the recess 12 on which the piezoelectric diaphragm element 16 is mounted is high. By using a container with the lowest possible weight, the thickness of the piezoelectric vibrator can be reduced. After that, the atmosphere in the recess 11 is replaced with nitrogen or evacuated to a vacuum, and then airtightly sealed to form a crystal oscillator.

The piezoelectric material constituting the piezoelectric diaphragm element disclosed in this embodiment is used as a piezoelectric material such as quartz, ceramics, or lithium tantalate. The heat-curable conductive ink used in the above examples contains gold or silver particles (particle size of about several nm) as a conductive material, and has a volume resistivity of about 3 × 10.^-6It is Ω cm. Further, the conductive ink of gold particles has the property of firing at 300-odd ° C, and the conductive ink of silver particles has the property of firing at 200-odd ° C in 20 to 30 minutes. Further, although the manufacturing process has been described with only one container in the above embodiment, the present invention can be used even when a method capable of manufacturing a plurality of piezoelectric vibrators at a time by forming a sheet-shaped container group in which a plurality of containers are connected is used. The disclosed technology can exert its effect.

<figref num="1">FIG. 1 is a process diagram illustrating a part of the steps of the method for manufacturing a piezoelectric vibrator according to the present invention by using a cut-out view of a container.</figref><figref num="2">FIG. 2 is a partial cross-sectional view in which the portion of the dotted line circle C shown in FIG. 1 (c) is enlarged and displayed.</figref><figref num="3">FIG. 3 is a cross-sectional view showing an example of application form of the epoxy-based conductive adhesive in the conventional manufacturing process.</figref>

Code description

11, Container 12, Recess 13, Electrode pad for element connection 15, Thermosetting conductive ink 16, Piezoelectric diaphragm element 17, External connection electrode film 19, Jet dispense method dispenser