JP2008166994A - Piezoelectric vibrator, piezoelectric oscillator, and manufacturing method of piezoelectric vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of vibrator characteristics accompanying adhesion of siloxane gas to the electrode of a piezoelectric vibrating element by preventing diffusion itself of gas from conductive adhesive which holds the piezoelectric vibrating element in a case. <P>SOLUTION: In the piezoelectric vibrator which holds the piezoelectric vibrating element in the case by the conductive adhesive, liquid inorganic material is coated on a surface of the conductive adhesive, and a hardened over-layer is prepared. Liquid glass can be used for the coating material, and aging by outgas from the conductive adhesive can be prevented. Even when a porous coating layer is used, it is effective if the diameter of the molecules is less than a diameter of the outgas molecules. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibrator, a piezoelectric oscillator, and a method of manufacturing the piezoelectric vibrator, and more particularly, the conductivity when a piezoelectric vibration element is mounted and mounted with a conductive adhesive in an insulating container and the container is sealed with a lid. The present invention relates to a piezoelectric vibrator, a method for manufacturing the same, and a piezoelectric oscillator in which adverse effects due to outgas from an adhesive are improved.

  Generally, a piezoelectric oscillator (crystal oscillator) uses a piezoelectric vibration element in which an excitation electrode is formed on a piezoelectric substrate. The piezoelectric vibration element is mounted and mounted in an insulating container with a conductive adhesive, and the container is sealed with a lid. A structure in which an oscillation circuit is connected to the piezoelectric vibrator is adopted. A structural example of an oscillator using a conventional piezoelectric vibrator is shown in FIG. As shown in the figure, a conventional piezoelectric oscillator 1 includes a ceramic container 4 having recesses 2 and 3 formed in the upper and lower parts and an H-shaped cross section. A mounting terminal 5 is provided on the bottom surface of the ceramic container 4. Is provided. A piezoelectric vibration element 6 is mounted in the upper recess 2, which is formed on an internal pad 8 provided on an element mounting surface 7 formed one step higher than the bottom surface of the recess, on one end side of the piezoelectric vibration element 6. The extended excitation electrode connection terminal is bonded with the conductive adhesive 10 and mounted in a cantilever state. The upper recess is hermetically sealed by the lid 11. In the lower recess 3, an IC component 12 constituting an oscillation circuit is connected to and mounted on a lower pad 13 provided on the ceiling surface. The lower pad 13 is electrically connected to the mounting terminal 5 together with the internal pad 8.

  By the way, the piezoelectric vibrator constituting the piezoelectric oscillator employs a structure in which the vibration element is hermetically sealed with a lid while holding the vibration element in the ceramic container with a conductive adhesive, but hermetically sealed in the ceramic container. It has been confirmed that the resonance frequency of the piezoelectric vibrator is lowered with time. Such a phenomenon causes a problem that even when the frequency characteristics are adjusted at the stage of manufacturing the piezoelectric vibrator, the frequency is lowered when the piezoelectric vibrator is assembled.

The cause of such a frequency drop is not clear, but it is recognized that gas is gradually released from the conductive adhesive over time, and that the siloxane in this gas reacts with the excitation electrode to deteriorate the frequency characteristics. Yes. For example, Patent Document 1 considers that the cause of the frequency decrease phenomenon of the vibrator over time is an oxidation phenomenon that occurs in the surface layer of the metal film constituting the electrode. In Patent Document 2, the gas contained in the conductive adhesive or the low-melting glass for bonding containers reacts with the silver of the excitation electrode.

In order to cope with such characteristic deterioration, the technique described in the former patent document 1 provides a protective layer made of an oxide layer or a carbonized layer on the surface layer of the excitation electrode to suppress a frequency drop phenomenon due to a mass increase due to aging oxidation. Trying to. In the latter technique described in Patent Document 2, a nickel coating layer is provided to cover the surface of the electrode film so that the outgas from the conductive adhesive does not directly react with the gold or silver of the electrode film. ing.
JP 7-154187 A JP-A-6-112758

  However, if a protective film is attached to the electrode surface, there is a problem that the characteristics of the piezoelectric vibrator deteriorate. Since the piezoelectric vibrator needs to be precisely matched to the target resonance frequency, the characteristics are adjusted. However, forming a protective film on the surface of the vibrator to be adjusted is equivalent to attaching foreign matter, and the vibrator characteristics Even if it worsens, it does not improve.

  Further, when forming a protective film on the surface of the electrode film, as described in Patent Document 1, since it is a porous film when performing sputtering film formation, the film is formed thick so that outgas molecules do not penetrate the electrode surface. To do is a big challenge. In addition, as described in Patent Document 2, there is a problem that it is difficult in the process to form a three-layer structure including a base film and a surface film so as to sandwich an electrode film.

  The present invention pays attention to the above-mentioned problems, and prevents the gas itself from being diffused from the conductive adhesive that holds the piezoelectric vibration element in the container, whereby the vibrator accompanying the attachment of the siloxane gas to the electrode of the piezoelectric vibration element. The problem is to prevent characteristic deterioration.

  In order to achieve the above object, a piezoelectric vibrator according to the present invention is a piezoelectric vibrator in which a piezoelectric vibration element is held in a container by a conductive adhesive, and a liquid inorganic material is applied to the surface of the conductive adhesive. And a solidified coating layer is provided. Liquid glass can be used as the liquid inorganic material.

In addition, a groove surrounding the conductive adhesive may be formed on the vibration element mounting surface of the container so as to prevent the liquid inorganic material coating liquid from flowing. Alternatively, it may be used in combination with or independently of the flow of the liquid inorganic material coating liquid by providing a notch groove on the piezoelectric vibration element side located around the conductive adhesive. Also good.

Further, the thickness of the contact electrode with the conductive adhesive in the piezoelectric vibration element is increased to form a step with the surrounding electrode surface, thereby preventing the liquid inorganic material coating liquid from flowing to the piezoelectric vibrator electrode side. You may do it.

Further, the piezoelectric vibrator according to the present invention is a porous vibrator having a pore diameter whose upper limit is an outgas molecule size from the conductive adhesive in the piezoelectric vibrator in which the piezoelectric vibration element is held in the container by the conductive adhesive. The surface of the conductive adhesive is covered with an inorganic coating layer.
The piezoelectric oscillator according to the present invention is characterized by mounting the piezoelectric vibrator oscillation circuit component having the above-described configuration.

Further, in the method for manufacturing a piezoelectric vibrator according to the present invention, the piezoelectric vibration element having a metal electrode film is held in a container with a conductive adhesive, and then liquid glass is coated on the outer surface of the conductive adhesive. A glass coating layer that is dried and solidified is formed.

  With the above configuration, in a piezoelectric vibrator having a piezoelectric vibration element that is held in a hermetically sealed container with a conductive adhesive, the surface of the conductive adhesive is covered with an inorganic coating layer inside the sealed space. Exposure is prevented. This prevents outgas emission from the conductive adhesive and prevents siloxane from adhering to the electrode film surface of the piezoelectric vibration element. Therefore, characteristic deterioration such as frequency reduction due to aging is prevented. Furthermore, the inorganic coating layer can be easily formed by using a liquid inorganic material by means of an application means such as a syringe, and there is no problem in the manufacturing process without performing additional processing on the vibration element itself. When applying a liquid inorganic material, if a treatment such as forming a groove in the container or the vibration element corresponding to the peripheral area of the conductive adhesive or increasing the pad electrode of the vibration element is performed, the electrode surface due to surface tension is applied. It is possible to prevent the creeping phenomenon, and it is possible to effectively prevent deterioration of characteristics due to unnecessary attachment.

  Specific embodiments of a piezoelectric vibrator, a piezoelectric oscillator, and a method for manufacturing the piezoelectric vibrator according to the present invention will be described below in detail with reference to the drawings.

1 is a cross-sectional view of the piezoelectric oscillator according to the embodiment, FIG. 2 is a plan view of the piezoelectric oscillator 20 with a lid removed, and FIG. 3 is an enlarged plan view of an adhesive portion of the piezoelectric vibration element.
As shown in these drawings, the piezoelectric oscillator 20 according to the embodiment is a ceramic container in which recesses 22 and 24 are formed in the upper and lower portions and the cross section is H-shaped in the same manner as the conventional example shown in FIG. 26 and a mounting terminal 28 is provided on the bottom surface of the ceramic container 26. A piezoelectric vibration element 30 is mounted in the upper recess 22, and an element mounting surface 32 formed one step higher than the bottom surface of the recess 22 is formed. A connection terminal 37 extending to one end of the piezoelectric vibration element 30 and electrically connected to the excitation electrode 36 is bonded to the internal pad 34 provided on the element mounting surface 32 by a conductive adhesive 38. The piezoelectric vibration element 30 is mounted in the ceramic container 26 in a cantilever state. The upper recess 22 forming the accommodation space for the piezoelectric vibration element 30 is hermetically sealed with a lid 40. In the lower recess 24, an IC component 42 constituting an oscillation circuit is connected to and mounted on a lower pad 44 provided on the ceiling surface. The lower pad 44 is electrically connected to the mounting terminal 28 formed on the bottom surface of the ceramic container 26 together with the internal pad 34.

  In such a configuration, in the piezoelectric oscillator 20 according to the present embodiment, the piezoelectric vibration element 30 is held in a cantilever state by the conductive adhesive 38 in the upper recess 22 of the ceramic container 26. The surface of the conductive adhesive 38 is provided with a coating layer 46 in which a liquid inorganic material is applied and solidified. More specifically, a liquid glass is applied, and a glass coating layer 46 that is solidified by heating is formed on the surface of the conductive adhesive 38. The liquid glass is solidified by drying, but since it is usually heated, a glass having a low temperature is desirable. This is because glass coating is applied after the piezoelectric vibration element 30 is held by the conductive adhesive 38, so long as it vitrifies at a temperature that does not cause thermal effects on the vibration element and the adhesive. For example, glass that vitrifies at room temperature is desirable, and heatless glass (HEATLESS GLASS GS-600 series manufactured by Nikko Co., Ltd.) can be used. This is packed in a syringe and coated on the surface layer of the conductive adhesive 38 in the same manner as in the case of applying the adhesive. By doing so, as shown in FIGS. 1 to 3, the glass coating is located between the conductive adhesive 38 and the piezoelectric vibration element 30 and covers the entire surface of the conductive adhesive 38. Layer 46 is completed.

  Such a piezoelectric oscillator is manufactured as follows. A ceramic container 26 is prepared, and a conductive adhesive 38 is applied to a predetermined portion of the element mounting surface 32 of the upper recess 22. The piezoelectric vibration element 30 to be mounted is brought close to the connection terminal 37 of the excitation electrode so as to contact the conductive adhesive 38, and the piezoelectric vibration element 30 having the excitation electrode 36 is held in a cantilever state in the ceramic container 26. The Next, after the piezoelectric vibration element 30 is held in the ceramic container 26 by the conductive adhesive 38, liquid glass is coated on the outer surface of the conductive adhesive 38. For this, a syringe similar to the syringe used for the conductive adhesive 38 is used, and liquid glass is put in the syringe, and the surface layer surface of the conductive adhesive is coated after mounting the piezoelectric vibration element 30 described above. . A glass coating layer 46 is formed by drying and solidifying it.

After such a glass coating layer 46 is formed, a metal lid 40 is placed on the upper surface of the ceramic container 26 in a nitrogen gas atmosphere, and the upper recess 22 is hermetically sealed. Thereby, the piezoelectric vibrator portion is completed.

Next, an IC component 42 having an oscillation circuit is mounted on a lower pad 44 provided in advance on the ceiling surface of the lower recess 24 of the ceramic container 26, and the lower pad 44 and the mounting terminal 28 are electrically connected. Thus, the piezoelectric oscillator 20 as a whole is completed.

According to such an embodiment, the surface layer surface of the conductive adhesive 38 is covered with the glass coating layer 46, and the conductive adhesive 38 is not exposed to the upper recess 22. As a result, the outgas released from the surface of the conductive adhesive 38 over time is shielded by the glass coating layer 46 and the excitation electrode 36 of the piezoelectric vibration element 30 held in the sealed upper recess 22 is sealed. Siloxane does not adhere to the surface. As a result, it is possible to obtain a product that does not deteriorate characteristics such as frequency reduction due to aging. In addition, the problem of aging due to outgas can be solved without adding a special process such as forming an incidental film on the piezoelectric vibration element.

  Next, FIGS. 4, 5 and 6 show a piezoelectric oscillator 20A according to the second embodiment. These figures correspond to FIGS. 1 to 3 showing the first embodiment. The piezoelectric oscillator 20A according to the second embodiment is different from the first embodiment only in that the element mounting surface 32 in the ceramic container 26 includes a groove 52 surrounding the conductive adhesive. The groove 52 prevents the liquid glass from flowing when the liquid glass is coated on the surface of the conductive adhesive 38, and scoops up the surfaces that are close to each other, particularly in a narrow space. It is prevented from being attached to. The groove 52 is rectangular in the illustrated example, but any shape can be adopted. Further, the depth of the groove 52 may be adjusted according to the supply amount of the liquid glass to be coated, and is supplied more than the coating amount to the exposed area portion of the conductive adhesive 38, so that this excess amount of liquid glass can be accommodated. It is desirable to set the volume.

  In such a second embodiment, the groove 52 prevents the liquid glass that is about to flow in the four directions of the internal pad as if it were a moat, so that the liquid glass as a coating agent is the excitation electrode 36 of the piezoelectric vibration element 30. Can be prevented from crawling.

  FIG. 7 shows a third embodiment. In this case, the groove 52 is formed on the element mounting surface 32 of the ceramic container 26 as in the case of the second embodiment. At the same time, a notch groove 54 having the same function as the groove 52 is formed on the piezoelectric vibration element 30 side. Is. That is, the connection terminal 37 of the piezoelectric vibration element 30 is connected to the conductive adhesive 38, and the first notch is formed on the side edge of the piezoelectric substrate 56 so as to form a stepped surface around the connection terminal 37. A groove 54A is provided, and a second notch groove 54B is provided so as to separate the pair of connection terminals 37 from each other.

FIG. 8 shows a fourth embodiment. In this case, in particular, a dividing groove 58 that prevents the liquid glass from flowing into the excitation electrode 36 on the back surface (adhesion surface side) of the piezoelectric vibration element 30 (although it is contrary to thinning). , May be convex).

  As shown in FIGS. 7 and 8 above, if a configuration in which the notch groove 54 is provided on the piezoelectric vibration element 30 side or the dividing groove 58 is formed around the conductive adhesive 38 is used, the liquid glass It is possible to prevent this solution from climbing up to the excitation electrode 36 of the vibration element and solidifying at the time of coating.

  9 to 10 show a fifth embodiment. In contrast to the groove structure that prevents the liquid glass from flowing in, the embodiment deals with a so-called wall structure as the thick terminal 60 in which the connection terminal 37 of the piezoelectric vibration element 30 is thickened. ing. When the liquid glass is coated, if the side wall surface of the connection terminal 37 cannot be scooped up by surface tension, the excitation electrode 36 is not reached. Therefore, the connection terminal is formed into a thick terminal 60 having such a height that the liquid glass cannot be crawled up.

  Of course, the above-described groove 52, notch groove 54, dividing groove 58, or thick terminal 60 can be used alone or in combination.

Moreover, although the coating layer 46 uses liquid glass, this can use the non-porous liquid inorganic material from which gas is not diffused with time. Of course, even if it is porous, a porous inorganic material having a diameter smaller than the outgas molecules of the conductive adhesive 38 can be used. This example is shown in FIGS. That is, as shown in FIG. 11, a porous coating layer 62 is formed so as to cover the conductive adhesive 38 on the crystal mounting pad (internal pad) 34 formed on the element mounting surface of the container. The outgas molecules 64 are released from the conductive adhesive 38 over time, reach the surface of the conductive adhesive 38 and reach the inner surface portion of the porous coating layer 62 as shown in FIG. As shown in FIG. 13, when the diameter d of the porous portion 66 is smaller than the molecular size D of the outgas, the outgas molecules 64 stay inside the porous coating layer 62 and are not diffused to the outside. Therefore, aging due to outgas can be prevented by laminating and attaching an inorganic material having no conductivity to the surface of the conductive adhesive 38 by vapor deposition or the like until the diameter of the porous portion 66 becomes smaller than the diameter of the outgas molecules 64.

With this configuration, it is possible to prevent the outgas itself from being diffused from the conductive adhesive 38, and it is possible to prevent a characteristic deterioration phenomenon such as a decrease in frequency due to aging.
The present invention can be used for manufacturing a piezoelectric vibrator, an oscillator using the same, and other products.

It is sectional drawing of the piezoelectric oscillator which concerns on 1st Embodiment. It is a top view in the state where the lid of the piezoelectric oscillator was removed. FIG. 3 is an enlarged plan view of an adhesive portion of a piezoelectric vibration element in the same piezoelectric oscillator. It is sectional drawing of the piezoelectric oscillator which concerns on 2nd Embodiment. It is a top view in the state where the lid of the piezoelectric oscillator concerning a 2nd embodiment was removed. It is an adhesion part enlarged plan view of a piezoelectric vibration element in a piezoelectric oscillator concerning a 2nd embodiment. FIG. 6 is a partially exploded perspective view of a piezoelectric vibrator according to a third embodiment. It is a fragmentary sectional view of the piezoelectric vibrator concerning a 4th embodiment. It is a perspective view of the piezoelectric vibration element which concerns on 5th Embodiment. It is a fragmentary sectional view showing the holding state to the container of the vibration element. It is principal part sectional drawing of 6th Embodiment. It is a principal part expanded sectional view of FIG. It is effect | action explanatory drawing of FIG. It is sectional drawing of the conventional piezoelectric oscillator.

Explanation of symbols

20 ......... Piezoelectric oscillator, 22 ......... Upper recess, 24 ......... Lower recess, 26 ......... Ceramic container, 28 ......... Mounting terminal, 30 ......... Piezoelectric vibration element, 32 ......... Element Mounting surface 34... Internal pad 36... Excitation electrode 37 37 Connection terminal 38 Conductive adhesive 40 Lid 42 IC component 44 Lower pad, 46 ......... Coating layer, 52 ......... Groove, 54 ......... Notch groove, 54A ......... First notch groove, 54B ......... Second notch groove, 56 ......... Piezoelectric substrate, 58 ... ...... Slit groove, 60 ......... Thick terminal, 62 ......... Porous coating layer, 64 ......... Outgas molecules, 66 ......... Porous part

Claims (8)

  A piezoelectric vibrator in which a piezoelectric vibration element is held in a container with a conductive adhesive, wherein the surface of the conductive adhesive is coated with a liquid inorganic material and a coating layer is provided.   The piezoelectric vibrator according to claim 1, wherein the liquid inorganic material is liquid glass.   The piezoelectric vibrator according to claim 1, wherein a groove surrounding the periphery of the conductive adhesive is formed on the vibration element mounting surface of the container.   4. The piezoelectric vibrator according to claim 1, wherein a notch groove is provided on a side of the piezoelectric vibration element located around the conductive adhesive. 5.   5. The piezoelectric vibrator according to claim 1, wherein the electrode in contact with the conductive adhesive in the piezoelectric vibration element is thick to form a step with the surrounding electrode surface.   In a piezoelectric vibrator in which a piezoelectric vibration element is held in a container by a conductive adhesive, the conductive adhesive is formed by a porous inorganic coating layer having a pore size with an outgas molecule size from the conductive adhesive as an upper limit. A piezoelectric vibrator characterized in that the surface of the piezoelectric vibrator is coated.   7. A piezoelectric oscillator comprising an oscillation circuit component mounted on the container according to claim 1 or 6.   A piezoelectric vibration element having a metal electrode coating is held in a container with a conductive adhesive, and then a liquid glass is coated on the outer surface of the conductive adhesive and dried to solidify a glass coating layer. A method for manufacturing a piezoelectric vibrator.

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