JP4710852B2 - Piezoelectric vibration device - Google Patents

Description

  The present invention relates to a piezoelectric vibration device such as a crystal resonator. The present invention relates to a holding structure for a piezoelectric vibration device having an airtight terminal structure in which metal lead terminals are integrally formed with an insulating material interposed in a metal base.

  Examples of the piezoelectric vibration device include a crystal resonator, a crystal filter, a crystal oscillator, and the like. For example, a crystal resonator is widely used as a reference source for frequency and time because it has excellent resonance characteristics. In these piezoelectric vibration devices, a metal thin film electrode is formed on the surface of a crystal vibration plate (piezoelectric vibration plate), and the metal thin film electrode is hermetically sealed by a package body in order to protect the metal thin film electrode from the outside air.

  Conventionally, in a piezoelectric vibration device having an airtight terminal structure, a pair of metal lead terminals are implanted in the metal base via an insulating material such as glass, and a pair of metal flat plates are provided on the inner side of the metal lead terminal. The support members are attached to face each other. The piezoelectric diaphragm is, for example, an AT-cut quartz diaphragm that undergoes thickness shear vibration, and an excitation electrode and an extraction electrode from each excitation electrode are formed on the front and back surfaces. A piezoelectric diaphragm is mounted on the support, and is electrically and mechanically connected by a conductive bonding material. The metal base is covered with a metal lid, and these are air-bonded to each other by a technique such as resistance welding. The structure is hermetically sealed. However, in the piezoelectric vibration device, by configuring the support member, the overall height of the piezoelectric vibration device is increased, and it is not possible to cope with the reduction in height required on the electronic device side. In addition, there is a problem that the cost is increased as a whole.

Therefore, as shown in Patent Document 1, a piezoelectric vibration device has been proposed in which a support member is omitted, a part of a metal lead terminal is processed, and a piezoelectric diaphragm is directly held on the metal lead terminal.
JP 2001-160730 A

  However, as shown in Patent Document 1, in the piezoelectric vibration device in which a support member is omitted and a part of the metal lead terminal is processed and the piezoelectric diaphragm is directly held by the metal lead terminal, the support member is interposed. Compared to the holding structure, the impact resistance performance is inferior, and it is indispensable to use a silicone-based soft conductive resin adhesive. However, in the configuration using the silicone-based conductive resin adhesive, the oxidation formed on the top surface of the corrosion prevention film such as nickel formed on the outer surface of the metal lead terminal and the metal base. There was a problem that the layer was adversely affected. That is, the conductive resistance of the bonding interface between the metal lead terminal and the silicone-based conductive resin adhesive increases due to the influence of the oxide layer, and the conductive performance of the piezoelectric vibration device may be lowered. As a result, electrical performance deterioration such as a series resonance resistance value (CI value) of the piezoelectric vibration device may occur.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a low-cost piezoelectric vibration device having improved impact resistance and improved conduction performance.

In order to solve the above problems, a piezoelectric vibration device according to the present invention includes, as shown in claim 1, a metal base in which at least two metal lead terminals are implanted through an insulating material, and the metal lead. A piezoelectric diaphragm on which an excitation electrode mounted on a terminal and electrically connected via a silicone-based conductive resin adhesive is formed, and a metal lid formed by hermetically covering the piezoelectric diaphragm A piezoelectric vibration device comprising: a corrosion prevention film on the outer surface of the metal lead terminal and the metal base; and an oxidation layer of the corrosion prevention film formed on the top surface of the corrosion prevention film. the inner side of the lead terminals are formed mounting surface for mounting the piezoelectric vibrating plate, the junction region of at least the conductive resin adhesive of the mounting surface, the excitation of the metal lead terminal and the piezoelectric vibrating plate against oxidation layer Are formed conductive bonding material for improving the conductivity of the electrode, both ends electromechanical said piezoelectric diaphragm by using the conductive resin adhesive at the top of the conductive bonding material of the mounting surface It is characterized in that it is directly joined to.

With the above configuration, the outer surface of the metal lead terminal and the metal base has a corrosion prevention film and an oxide layer of the corrosion prevention film formed on the top surface of the corrosion prevention film, and on the inner side of the metal lead terminal. Has a mounting surface on which the piezoelectric diaphragm is mounted, and at least a conductive resin adhesive bonding region on the mounting surface improves the conductivity between the metal lead terminal for the oxide layer and the excitation electrode of the piezoelectric diaphragm. A conductive bonding material is formed, and both ends of the piezoelectric diaphragm are directly electromechanically bonded using the upper silicone conductive resin adhesive of the conductive bonding material on the mounting surface. More reliable conduction with the electrode of the piezoelectric diaphragm on the inner side of the lead terminal can be ensured. As a result, it is possible to provide an inexpensive piezoelectric vibration device with excellent electrical connectivity by improving the conduction performance and improving the series resonance resistance value of the piezoelectric vibration device while improving the impact resistance performance.

  That is, even if the buffering action is limited by omitting the support, the piezoelectric diaphragm is attached to the mounting surface via the silicone-based conductive resin adhesive, so that the impact resistance can be improved. In order to cope with the problem of deterioration in the conduction performance of the silicone-based conductive resin adhesive with respect to the oxide layer, at least the silicone-based conductive resin adhesive bonding region of the mounting surface has a conductivity that improves the conductivity with respect to the oxide layer. Since the conductive bonding material is formed, the conductive bonding material can be easily and reliably formed on the mounting surface, and the silicone-based conductive resin adhesive that is not directly bonded to the oxide layer is the most suitable for the corrosion prevention film. There is no adverse effect of the oxide layer formed on the upper portion, and the conduction performance between the mounting surface of the metal lead terminal and the electrode of the piezoelectric diaphragm is improved. As a result, it is possible to improve the electrical characteristics such as the series resonance resistance value (CI value) of the piezoelectric vibration device.

Further, in addition to the above-described configuration, the mounting surface on the inner side of the metal lead terminal forms a mounting portion in which a wide nail head portion, a wide brim portion, or a wide and flat tip portion is bent inward. It is preferable. With this configuration, in addition to the above-described effects, the mounting is stable when the piezoelectric diaphragm is joined to the mounting surface on the inner side of the lead terminal, and the bonding strength between the piezoelectric diaphragm and the mounting surface is reinforced and stabilized. Further, it is possible to suppress twisting at the short side portion of the piezoelectric diaphragm during impact resistance. As a result, the problem that the piezoelectric diaphragm is cracked and the conductive resin adhesive is peeled off from the mounting surface of the lead terminal is eliminated.

  Further, in addition to the above-described configuration, both ends of the piezoelectric diaphragm are electromechanically directly connected to the nail head portion by using an epoxy-based conductive resin adhesive as a conductive bonding material for improving the conductivity with respect to the oxide layer. It is characterized by being joined.

  By comprising in this way, in addition to the above-mentioned effect, the conductive performance of the joining interface is improved by an epoxy-based conductive resin adhesive that is not adversely affected by the oxide layer, and a more flexible silicone-based The buffering action can be improved by the conductive resin adhesive. At the bonding interface between the epoxy-based conductive resin adhesive and the silicone-based conductive resin adhesive, mutual conduction performance can be improved by the metal filler components contained in each other. It is more preferable to use a modified epoxy-based conductive resin adhesive softer than 4B as the epoxy-based conductive resin adhesive, which can further improve impact resistance and conduction performance.

  As described above, it is possible to provide an inexpensive piezoelectric vibration device with excellent electrical connectivity by improving the conduction performance while improving the impact resistance and eliminating the increase in the series resonance resistance value of the piezoelectric vibration device.

  Next, embodiments of the present invention will be described with reference to the drawings, taking a crystal resonator as an example. FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a plan view before covering the cover of FIG. 1, and FIG. 3 is a plan view before mounting the piezoelectric diaphragm of FIG. is there.

  The piezoelectric diaphragm 2 is made of an AT-cut quartz diaphragm, and is processed into a rectangular shape having a short side and a long side. Excitation electrodes 21 and 22 and extraction electrodes 21a and 22a are provided on the front and back surfaces by means such as vacuum deposition. In addition, the extraction electrode is made to wrap around the opposite main surface in order to ensure electrical connection described later. A main electrode layer mainly composed of silver or gold is formed in a laminated structure of at least one layer on a base electrode layer of chromium or nickel as the electrode material.

  The base 1 as a whole has a low-profile long cylindrical shape, and has a structure in which metal lead terminals 11 and 12 are planted through a base body 10 mainly including a metal shell, and an insulating glass G is used as a base body. These metal lead terminals 11 and 12 are electrically independent by being filled in a part. A circumferential flange 10a is integrally provided at the lower peripheral portion of the base body. In addition, although not shown in figure, the circumferential protrusion part (projection) is integrally formed in the flange 10a.

  The lead terminals 11 and 12 have an elongated cylindrical shape made of Kovar or the like, and at the front end portion on the inner side of the upper portion of the base, there are nail head portions 11a and 12a having a wide mounting surface and a substantially circular shape in plan view and a flat upper portion. Is formed. These nail head portions 11a and 12a are formed by press working using metal ductility or the like. Exemplifying specific dimensions of the lead terminal portion, the lead terminals 11 and 12 have a wire diameter of about 0.32 to 0.45 mm, whereas the nail head portions 11a and 12a have a width dimension d of 0.7 to 0.7 mm. It is formed to about 0.9 mm.

  Although not shown, the metal portions exposed on the surfaces of the base 1 and the lead terminals 11 and 12 are provided with an inexpensive and practical nickel plating film for preventing corrosion. In particular, in this embodiment, an electrolytic nickel plating film by an electrolytic plating method is formed to about 4 μ to 6 μm, and an electroless nickel plating film by an electroless plating method is formed to about 2 μ to 5 μm on the upper surface. The electrolytic nickel plating film has a higher melting point than the electroless nickel plating, and can be formed before the insulating glass G is fired to obtain a corrosion prevention function before and after the firing. The electroless nickel plating film is formed with a more uniform film quality than the electrolytic nickel plating film, so it not only improves the wettability of solder etc., but also the top surface such as phosphorus or boron caused by reducing agent Eutectoid to form an amorphous structure, and a hard anticorrosion film having better corrosion resistance can be obtained. In other words, the electroless nickel plating film is an inexpensive but extremely practical and reliable film as a corrosion prevention film on the top surface of the metal lead terminal and metal base. There is also a problem that the conduction resistance of the bonding interface with the agent tends to be high. In the present invention, these problems can be improved by combining with a conductive bonding material for improving the conductivity described later.

  The metal lid 3 has a long cylindrical shape with an open bottom surface, and has a flange 31 corresponding to the flange 10a of the base at the opening, and is hermetically sealed by resistance welding to the base 1. Done.

  A conductive bonding material D for improving conductivity with respect to the oxide layer is applied and formed in a bonding region of a silicone-based conductive resin adhesive S described later on the upper surfaces of the nail head portions 11a and 12a. The formation region of the conductive bonding material D is not limited to the upper surfaces of the nail head portions 11a and 12a, and may be formed by coating the entire nail head portions 11a and 12a.

  Further, a silicone-based conductive resin adhesive S having a pencil hardness of about 6B is formed on the upper surfaces of the nail head portions 11a and 12a on the inner side of the metal lead terminals and on the upper surface of the region where the conductive bonding material D is applied and formed. Is applied. The conductive resin adhesive S is mounted in a state where the central portion of the short side of the piezoelectric diaphragm 2 is close to the vicinity of the center of gravity of the nail head portion to which the conductive resin adhesive S is applied, and the conductive resin adhesive S is cured. As a result, both ends of the long side of the piezoelectric diaphragm 2 and the nail head portions 11a and 12a are directly bonded and attached electromechanically.

  For example, a modified epoxy-based conductive resin adhesive (pencil hardness of about 4B) is used as the conductive bonding material D, and the modified epoxy-based conductive resin adhesive is applied to the upper surface of the nail head portion. And is cured to form a solid material of the conductive bonding material D. After that, the silicone-based conductive resin adhesive S is applied to the upper portion, and after mounting the piezoelectric diaphragm 2, it is directly bonded electromechanically by being cured.

  After mounting the piezoelectric diaphragm 2, after performing necessary processing such as annealing, the base 1 is covered with the lid 3, although not shown, the welding electrode bodies are brought into contact with both flanges, and pressure is applied to both. Energization is performed while applying resistance welding, and the hermetic sealing is completed.

  In the embodiment of the present invention, the metal lead terminals 11 and 12 are embedded through the insulating glass G, mounted on the metal lead terminal in the same direction as the plane of the metal base, and A rectangular piezoelectric diaphragm 2 on which an excitation electrode to be electrically connected via a silicone-based conductive resin adhesive S is formed, and a metal lid 3 formed by airtightly covering the piezoelectric diaphragm. A piezoelectric vibration device comprising: an electroless nickel plating film (corrosion prevention film) and an uppermost oxide layer of the electroless nickel plating film formed on the outer surface of the metal lead terminal and the metal base. In addition, wide nail head portions 11a and 12a for mounting the piezoelectric diaphragm are formed on the inner side of the metal lead terminal, and at least the silicone-based conductivity of the nail head portion is formed. In the bonding region of the fat adhesive S, a conductive bonding material D made of a modified epoxy-based conductive resin adhesive that improves the conductivity with respect to the oxide layer is formed, and the conductive bonding material of the nail head portion At the upper part, both ends of the long side of the piezoelectric diaphragm 2 are directly electromechanically joined using the silicone-based conductive resin adhesive S.

  Even if the buffering action is limited by omitting the support, the piezoelectric diaphragm is attached to the nail head part via the soft silicone-based conductive resin adhesive S, thereby improving impact resistance. Can be made. Then, in order to cope with the problem of deterioration of the conduction performance of the silicone-based conductive resin adhesive S with respect to the oxide layer, the upper surfaces of the nail head portions 11a and 12a are modified epoxy-based conductivity that improves the conductivity with respect to the oxide layer. Since the solid material of the conductive bonding material D made of a resin adhesive is formed, the silicone-based conductive resin adhesive S that is not directly bonded to the oxide layer is not adversely affected by the oxide layer. In addition, the metal filler component contained in each other bites into each other at the bonding interface between the modified epoxy conductive resin adhesive and the silicone conductive resin adhesive, resulting in an anchor effect and mechanical bonding. Not only the strength is improved, but also an electrical conduction path is secured, and the conduction performance can be improved. As a result, the conduction performance between the nail head portions 11a and 12a of the metal lead terminal and the extraction electrodes 21a and 22a of the piezoelectric diaphragm 2 is improved, and the electromechanical connectivity is enhanced. In this embodiment, since a modified epoxy type conductive resin adhesive softer than 4B is used, further impact resistance and conduction performance can be improved. As described above, the electrical characteristics such as the series resonance resistance value (CI value) of the piezoelectric vibrating device can be improved.

-Other embodiments-
In the present embodiment, the nail head portions 11a and 12a are formed on the inner side of the metal lead terminal. However, as shown in FIG. And connecting portions 13 and 14 that are gradually thinned and gradually widened, and mounting portions 15 and 16 that are wider and flatter than the lead terminals formed at the tips of the connecting portions. The present invention can also be applied to a configuration of a metal lead terminal (a mounting portion in which a wide and flat tip portion is bent inward). In this embodiment, the modified epoxy type conductive resin adhesive S softer than the pencil hardness 4B is applied to the upper surface of the plate-like mounting portions 15 and 16 from the inside thereof and cured to form a conductive bonding material. A solid substance of D is formed. The silicone-based conductive resin adhesive S is applied to the upper portion of the solid material and the upper surfaces of some of the mounting portions 15 and 16, and after mounting the piezoelectric diaphragm 2, the material is cured and electromechanically. Directly joined. In such a configuration, the mounting portions 15 and 16 are disposed in the inner portions where the inner metal lead terminals 11a and 12a are implanted, and therefore can be applied to a smaller crystal diaphragm. In addition, the connection portion can reduce the transmission of stress and enhance the buffer function. Further, since the silicone-based conductive resin adhesive S is directly bonded to the mounting portions 15 and 16 while ensuring conduction by a part of the conductive bonding material D, the mechanical bonding strength can be improved.

  Further, as shown in FIG. 5, the present invention can also be applied to a configuration of a metal lead terminal in which wide flange portions 17 and 18 are formed on the inner side of the metal lead terminal as a mounting surface. In this embodiment, the modified epoxy type conductive resin adhesive S softer than the pencil hardness 4B is applied to the upper surface of the wide brim portions 17 and 18 and hardened to cure the conductive bonding material D. A solid is formed. The silicone-based conductive resin adhesive S is applied to the upper portion of the solid material and the upper surfaces of some of the collar portions 17 and 18, and after mounting the piezoelectric diaphragm 2, it is cured electromechanically. Directly joined. In such a configuration, since the projections 19 and 19 are formed outside the flange portions 17 and 18, the projections 19 and 19 function as positioning when the piezoelectric diaphragm is mounted, so that the mounting accuracy is improved. Further, since the silicone-based conductive resin adhesive S is directly bonded to the mounting portions 15 and 16 while ensuring conduction by a part of the conductive bonding material D, the mechanical bonding strength can be improved.

  In the present embodiment, a solid material of a modified epoxy-based conductive resin adhesive softer than 4B is used as the conductive bonding material D that is not adversely affected by the oxide layer. A solid material made of a superior epoxy-based conductive resin adhesive, a polyimide-based conductive resin adhesive, a urethane-based conductive resin adhesive, or a brazing material such as silver solder or gold tin solder. Also good. In addition, the conductive resin adhesive S (conductive bonding material D) having a curing temperature close to that of the silicone-based conductive resin adhesive S is not limited to a solid material, but a paste-like material. It is possible to apply in advance and cure at the same time.

  Further, at least on the surface of the inner side mounting surface (the nail head portions 11a and 12a, the mounting portions 15 and 16, the wide brim portions 17 and 18 and the like) of the metal lead terminal, the silver plating layer is formed on the upper portion of the nickel plating layer. Flash plating, gold plating, or a multilayer plating layer combining these may be formed, reducing the adverse effect of the oxide layer formed on the top of the corrosion prevention film such as electroless nickel plating, and the conductive resin adhesive The conduction performance of the bonding interface can be improved.

  Note that the configurations exemplified in the above embodiment can be combined with each other. As an example of the piezoelectric vibration device of the present invention, a crystal resonator is illustrated, but a crystal filter, a crystal oscillator, or the like may be used.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof, and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not limited by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

Sectional drawing which shows embodiment of this invention. The top view before putting the cover of FIG. The top view before mounting the piezoelectric diaphragm of FIG. Sectional drawing which shows other embodiment of this invention. Sectional drawing which shows other embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 Base 10 Base main body 11,12 Lead terminal 2 Piezoelectric diaphragm 3 Lid

Claims (1)

A metal base in which at least two metal lead terminals are implanted through an insulating material, and an excitation mounted on the metal lead terminal and electrically connected via a silicone-based conductive resin adhesive A piezoelectric vibration device comprising a piezoelectric diaphragm having electrodes formed thereon and a metal lid formed by airtightly covering the piezoelectric diaphragm,
On the outer surface of the metal lead terminal and the metal base, a corrosion prevention film and an oxide layer of the corrosion prevention film are formed on the top surface of the corrosion prevention film,
A mounting surface on which the piezoelectric diaphragm is mounted is formed on the inner side of the metal lead terminal, and at least the conductive resin adhesive bonding region of the mounting surface has a metal lead terminal and a piezoelectric diaphragm on the oxide layer . A conductive bonding material that improves the conductivity with the excitation electrode is formed,
A piezoelectric vibration device, wherein both ends of the piezoelectric vibration plate are directly electromechanically bonded using the conductive resin adhesive at an upper portion of the conductive bonding material on the mounting surface .

Images