JP2006157554A - Piezo-electric vibration cone and piezo-electric device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezo-electric vibration cone capable of preventing a conductive adhesive from fixing to an excitation electrode and performing stabilized and proper oscillation, and to provide a piezo-electric device using the vibration cone. <P>SOLUTION: As for the piezo-electric vibration cone, excitation electrodes are formed on both principal planes of a rectangular and tabular piezo-electric blank. A drawing electrode is derived from the excitation electrode, and connection conduction is established between the drawing electrode and a vessel connecting electrode formed at least near the corner of a side plane at one short side of the piezo-electric blank. The drawing electrode is formed of the principal plane of a piezoelectric substrate via a side plane of its long side, and it is formed of the periphery of each excitation electrode on the front and the rear principal plane of the piezo-electric blank to the vessel connecting electrode where conduction is required to be established. In addition, conduction is established between each excitation electrode and a corresponding vessel connecting electrode through the drawing electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric diaphragm that is one of electronic elements, and a piezoelectric device that accommodates a piezoelectric diaphragm in a cavity of a container body, and more particularly to a piezoelectric diaphragm and a piezoelectric device suitable for high-frequency oscillation using overtones. Here, the piezoelectric diaphragm is an electronic element obtained by processing and manufacturing a crystal, a piezoelectric ceramic, a single crystal piezoelectric body, or the like.

  A conventional piezoelectric vibration plate and a piezoelectric device using the same will be described by exemplifying a quartz crystal vibration plate using quartz as a piezoelectric material and a crystal resonator which is one of the piezoelectric devices using the same. As such a conventional crystal unit, for example, as shown in the figure, a concave portion 22 is formed on the upper surface of a container body 21 made of alumina ceramic or the like, and a rectangular flat plate is formed on the bottom surface of the concave portion 22. A quartz crystal plate 23 on which an excitation electrode is formed is mounted, and a metal lid 24 is attached and bonded to the container body 21 so as to close the opening of the recess 22 to thereby vibrate the quartz crystal. A structure in which the plate 23 is hermetically sealed in a region surrounded by the inner surface of the recess 22 and the lower surface of the lid 24 is known (for example, see Patent Document 1).

  The container body 21 is formed by laminating ceramic insulating plates such as alumina, and a cavity 22 for accommodating the crystal diaphragm 23 is formed therein. The substrate serving as the bottom surface of the cavity 22 is a substrate on which the crystal diaphragm 23 is mounted. External terminal electrodes connected to the electrode pads are formed on the lower surface of the container body 21.

  Further, a seal ring for connecting the lid body 24 by seam welding is disposed around the opening of the cavity 22 of the container body 21. Then, after the quartz diaphragm 23 is accommodated in the cavity 22, while measuring the oscillation frequency of the quartz diaphragm 23, Au or Ag or the like is attached to the excitation electrode formed of Au or Ag by vapor deposition, or an ion gun After passing through the process of adjusting the oscillation frequency by increasing / decreasing the mass of the excitation electrode by using a technique in which an inert gas such as Ar is applied to the excitation electrode by using a technique such as cutting the metal on the surface of the excitation electrode In order to hermetically seal the diaphragm 23, a lid body 24 is attached on the container body 21.

  More specifically, the crystal diaphragm 23 has excitation electrodes attached to both main surfaces of a rectangular plate-shaped crystal base plate, and each main surface region near one short side of the crystal base plate has A container connection electrode extending from the excitation electrode is attached. Further, the electrodes on the front and back sides of the crystal vibrating plate 23 are formed so as to be symmetrical, and the container connecting electrodes formed so as to face each other between the two main surfaces are excited on one main surface of the crystal base plate. The container connection electrode extending from the electrode for electrode is connected to the container connection electrode formed on the other main surface through the connection electrode formed on a part of the long side and the short side of the quartz base plate. It is formed to do. One short side of the quartz substrate is called a fixed end, and the other short side is called a free end.

  The following prior art documents are publicly known for such a piezoelectric diaphragm and a piezoelectric device using the piezoelectric diaphragm.

JP 2001-274649 A

  In addition, the applicant did not come to discover 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, as the piezoelectric device and the piezoelectric diaphragm mounted on the piezoelectric device are miniaturized, the distance between the excitation electrode formed on the main surface of the piezoelectric diaphragm and the container connection electrode becomes shorter. When the piezoelectric diaphragm and the container are connected by a brazing material such as the brazing material, the brazing material adheres to the excitation electrode, and the oscillation of the piezoelectric diaphragm is obstructed or the vibration characteristics are poor. There was a drawback.

  The present invention solves such drawbacks of the prior art, and a piezoelectric diaphragm capable of preventing the brazing material from adhering to the excitation electrode and capable of stably performing good oscillation and the same are used. An object is to provide a piezoelectric device.

  The present invention has been made as a means for solving the above-described problems, and the gist thereof is that both main surfaces of a rectangular flat plate-shaped piezoelectric element plate are formed with excitation electrodes, and are derived from the excitation electrodes. The extraction electrode connected and connected to the container connecting electrode formed at least near the corner of the side surface of one short side of the piezoelectric element plate is desired to be connected from the outer peripheral part of the excitation electrode on each of the front and back main surfaces of the piezoelectric element plate. From the main surface of the piezoelectric substrate to the container connection electrode through the long side surface, each excitation electrode and the corresponding container connection electrode are electrically connected via this extraction electrode A piezoelectric diaphragm characterized by the following.

  In addition, a concave portion penetrating both main surfaces of the piezoelectric element plate having a depth component is formed on the side surface of one short side of the piezoelectric element plate so as to go to the inside of the piezoelectric element. Also, the above-described piezoelectric connecting plate is characterized in that the container connecting electrode is formed on the side surface around the concave opening portion of the side surface of the piezoelectric element plate on which the concave portion is formed.

  Further, the piezoelectric diaphragm described above is characterized in that the surface of the region where the container connection electrode is formed on the piezoelectric element plate is a form polished with an abrasive of # 800 or less or a form similar thereto. .

  Further, each of the above-mentioned means is provided with a piezoelectric vibration plate and a container body having a rectangular cavity and having a pair of element connection electrode pads on one short side of the bottom surface of the cavity. The plate is accommodated in the cavity of the container body, and each container connection electrode of the piezoelectric vibration plate is connected to the element connection electrode pad of the container body through a conductive joining member, and the piezoelectric vibration The piezoelectric device is characterized in that a cavity in which a plate is accommodated is hermetically sealed with a lid.

  According to the piezoelectric diaphragm of the present invention, the extraction electrode and the container connection electrode derived from each excitation electrode are formed in the vicinity of the region where the container connection electrode is formed on the front and back main surfaces of the piezoelectric element plate. Therefore, in the process of mounting the piezoelectric diaphragm in the cavity of the container body constituting the piezoelectric device, the conductive adhesive before curing applied for fixing and conducting the container body and the piezoelectric diaphragm is temporarily Even if it adheres to the surface of the piezoelectric element plate, the low molecular component does not flow out near the excitation electrode formed on the surface of the piezoelectric vibrator, only by flowing on the side surface on which the electrode of the piezoelectric element plate is formed. .

  As a result, in the frequency adjustment step, the characteristics such as the CI (crystal impedance) value of the piezoelectric diaphragm generated due to the low molecular component of the conductive adhesive adhering to the excitation electrode are deteriorated. Can be prevented. As a result, stable and good high-frequency oscillation using overtone oscillation can be performed.

  Further, according to the piezoelectric diaphragm of the present invention, the concave portion penetrating both main surfaces of the piezoelectric element plate having a depth component is formed so as to go from the side surface of the piezoelectric element plate to the inside of the piezoelectric element. The contact surface area of the surface of the container connection electrode to which the conductive adhesive adheres is expanded by forming the container connection electrode on the peripheral surface of the recess opening on the side surface of the piezoelectric base plate on which the surface and the recess are formed. Therefore, the piezoelectric diaphragm can be more firmly fixed to the container body.

  Furthermore, according to the piezoelectric diaphragm of the present invention, the surface portion of the region where the container connection electrode of the piezoelectric diaphragm is formed is polished with an abrasive of # 800 or less, or a surface similar to a form that is polished. By processing this, by forming fine irregularities on the surface of the piezoelectric diaphragm, the surface area of the container connection electrode formed on the surface can be increased. Therefore, the area where the conductive adhesive contacts the surface of the container connection electrode can be expanded, and the piezoelectric diaphragm can be more firmly fixed to the container body.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
1 to 4 show a configuration example of a piezoelectric device using a piezoelectric diaphragm according to the present invention. Here, FIG. 1 is an external perspective view showing an embodiment of the piezoelectric diaphragm of the present invention, (a) is an external perspective view shown from the upper main surface side, and (b) is shown from the lower main surface side. FIG. FIG. 2 is an external perspective view showing another embodiment of the piezoelectric diaphragm of the present invention, (a) is an external perspective view shown from the upper main surface side, and (b) is an external view shown from the lower main surface side. It is a perspective view. FIG. 3 is an exploded perspective view of a piezoelectric vibrator which is one piezoelectric device on which the piezoelectric diaphragm shown in FIG. 1 is mounted. FIG. 4 is a cross-sectional view of the piezoelectric vibrator shown in FIG. 3, and the piezoelectric device includes a piezoelectric diaphragm, a container body, and a lid body.

  The piezoelectric vibrator 12 mainly includes a container body 1 having a substrate, a piezoelectric vibration plate 2, a conductive adhesive 3, and a lid body 4. The container body 1 is composed of a substantially rectangular single plate substrate and a seal ring placed on the surface thereof. The seal ring is brazed and fixed via a sealing conductor film. The container body 1 is formed with a substantially rectangular cavity 5 having an open top, and the piezoelectric diaphragm 3 is accommodated therein. Further, a pair of substantially rectangular element connection electrode pads 7 are formed on the bottom surface of the cavity 5, that is, on one short side of the top surface of the substrate so as to be aligned in the width direction of the short side of the container body 1. .

  More specifically, the seal ring is made of a metal such as Fe—Ni, Fe—Ni—Co, and is formed by brazing or the like on the conductive film for sealing formed on the surface around the substrate, whereby the cavity is formed. A thickness of 5 is specified.

  Further, on the bottom surface of the container body 1, there are formed external connection electrode terminals 6 that are electrically connected to the element connection electrode pads 7 and are joined to an external printed wiring board (not shown) or the like. . The element connection electrode pad 7 and the external connection electrode terminal 6 are connected by a via-hole conductor that penetrates a part of the container body 1. When the element connection electrode pad 7 and the external connection electrode terminal 6 are not formed at the same position, if a wiring conductor having a predetermined shape is formed on the bottom surface of the cavity 5, the connection can be easily made by the via hole conductor. it can. Further, for example, the substrate may be laminated in two layers, and an internal wiring may be formed between the layers. In this case, one end of the internal wiring is connected to the element connection electrode pad 7 via the via-hole conductor, The other end of the internal wiring is connected to the external connection electrode terminal 6.

  The element connecting electrode pad 7 and the sealing conductor film are made of a metal such as molybdenum or tungsten. These conductors are formed by baking a conductive metal paste on the surface of the substrate and then performing Ni and Au plating on the surface. For example, when a bump is formed by baking a conductive metal paste, a conductor to be an element connection electrode pad 7 is formed by printing with a conductive metal paste, and after drying, a conductive metal paste is used on the surface. It is formed by printing according to the shape of the bump and then firing both.

  For example, in the case where crystal is used as the piezoelectric material, the piezoelectric diaphragm 2 is formed on both main surfaces of a substantially rectangular crystal base plate cut according to a predetermined crystal orientation angle (there is AT cut as a typical cutting orientation). Is formed with a pair of container connection electrodes 9 connected to the excitation electrode 8 and separated in the width direction of the piezoelectric element plate in the vicinity of the corner of the side surface of one of the short sides. Has been.

  The lead electrode 10 for connecting the excitation electrode 8 and the container connection electrode 9 on both main surfaces of the piezoelectric diaphragm 2 is the container connection electrode 9 of the excitation electrode 8 formed on both main surfaces of the quartz base plate. The lead electrode is formed on the side surface of the crystal base plate near the outer peripheral end portion of the excitation electrode 8 that is once extended on the main surface from the outer peripheral end portion facing the short side direction of the formed crystal base plate. 10 is led out, and from there through the side surface of the quartz substrate, the container connection electrode 9 formed on the side surface of one short side of the quartz base plate is electrically connected.

  The electrode formation positions of these container connection electrodes 9 are positions corresponding to the element connection electrode pads 7 when the piezoelectric diaphragm 2 is disposed at a predetermined position. Such an excitation electrode 8 and further a container connection electrode 9 are arranged such that a mask having a predetermined shape is arranged on the upper main surface, side surface and lower main surface of the quartz substrate and Au or the like is used by means of vapor deposition or sputtering. , Ag, Cr, etc., or an alloy mainly composed of these metals is formed in a single layer or a laminated structure by vapor deposition or the like. Solder and a conductive adhesive are used for electrical connection and mechanical joining between the container body 1 and the piezoelectric diaphragm 2. In the above description, the case where quartz is used as the base material constituting the piezoelectric diaphragm 2 has been described. However, in addition to quartz, single crystal piezoelectric materials such as piezoelectric ceramics, lithium tantalate and lithium niobate are processed and formed. A base plate (piezoelectric base plate) obtained in this manner may be used.

  A conductive adhesive 3 is applied on the element connection electrode pad 7 formed on the surface of the substrate exposed in the cavity 5, and is formed on the side surface on one short side of the piezoelectric diaphragm 2. The piezoelectric diaphragm 2 is placed so that the container connecting electrode 9 is in contact with the conductive adhesive 3, and the conductive adhesive 3 is adhered thereto. Thus, each excitation electrode 8 of the piezoelectric diaphragm 2 is electrically connected to the external connection electrode terminal 6 formed on the outer surface of the container body 1 via the element connection electrode pad 7.

  Further, as shown in FIG. 2, a concave portion 11 penetrating both main surfaces of the piezoelectric element plate having a depth component is formed on the side surface of one short side of the piezoelectric element plate so as to go to the inside of the piezoelectric element plate. Further, the surface of the container connecting electrode 9 and the surface of the container connecting electrode 9 are made conductive by forming the container connecting electrode 9 on the surface of the recess 11 and the side surface of the recess opening peripheral portion of the piezoelectric base plate on which the recess is formed. Since the contact area with the adhesive can be expanded, the piezoelectric diaphragm 2 can be firmly fixed to the container body 1.

  Similarly, fine irregularities are formed on the surface of the piezoelectric vibration plate 2 by polishing the surface of the base plate on which the container connecting electrode 9 of the piezoelectric vibration plate 2 is formed with an abrasive of # 800 or less. The container connecting electrode 9 is formed on the surface on which the unevenness is formed. As a result, the surface area to which the conductive adhesive 3 of the container connection electrode 9 adheres can be expanded, so that the piezoelectric diaphragm 2 can be firmly fixed to the container body 1. In addition, although polishing with an abrasive was exemplified as a method for forming irregularities on the surface of the base plate, there is another method for forming similar or similar irregularities on the surface of the base plate by laser processing or blasting.

  The lid 4 is made of a flat metal, such as an Fe—Ni alloy (42 alloy) or an F—Ni—Co alloy (Kovar), and the inside of the cavity 5 that accommodates the piezoelectric diaphragm 2 is in a nitrogen gas or vacuum state. The outer shape is formed so as to cover the opening of the cavity 5 so as to be hermetically sealed. Specifically, the lid 4 is placed on the seal ring of the container body 1 in a predetermined atmosphere or vacuum, and the metal on the surface of the seal ring and a part of the metal of the lid 4 are welded. Thus, a predetermined current is applied to perform seam welding to form an airtight seal.

  Note that an Ag brazing layer or the like may be formed in advance on the joint surface side of the lid 4 in order to securely perform hermetic sealing by seam welding. Further, a Ni plating layer may be formed on the surface side of the lid body 4 so that the brazing material melted by seam welding does not wrap around the surface side of the lid body 4 and the brazing material contributing to the bonding does not decrease. Good.

The piezoelectric vibrator described above is manufactured through the following manufacturing process.
First, a substantially rectangular flat plate-shaped piezoelectric element plate is prepared. Next, the excitation electrode 8 on both main surfaces of the piezoelectric element plate, a pair of container connecting electrodes 9 at desired positions on the side surface of one short side of the piezoelectric element plate, and an extraction electrode for electrically connecting them to each other 10 is formed on the piezoelectric element plate to form the piezoelectric diaphragm 2. Further, a container in which a pair of element connecting electrode pads 7 is formed on the surface of the substrate that becomes the bottom surface of the cavity 5 of the container body 1 and a sealing conductor film and a seal ring are formed on the surface around the opening of the cavity 5 A body 1 and a lid 4 are prepared.

  Next, the conductive adhesive 3 is applied to the element connecting electrode pad 7, and the piezoelectric diaphragm 2 is placed on the conductive adhesive 3 on the element connecting electrode pad 7. Specifically, the piezoelectric diaphragm 2 is placed so that the pair of container connecting electrodes 9 are in contact with the portion supplied with the conductive adhesive 3. At this time, the uncured conductive adhesive 3 applied for fixing and conducting the container body 1 and the piezoelectric diaphragm 2 also adheres to the surface of the piezoelectric element plate. Due to the difference between the characteristics of the surface of the container connection electrode 9, the low molecular component of the conductive adhesive 3 is excited by flowing on the surface of the piezoelectric element plate only by moving the side surface of the piezoelectric element plate on which the container connection electrode is formed. There is no moving contact with the working electrode 8. Thereafter, the conductive adhesive 3 is heated to bond and fix the container body 1 and the piezoelectric diaphragm 2.

  Next, the oscillation frequency of the mounted piezoelectric diaphragm 2 is measured using the external connection electrode terminal 6 and the like, and if necessary, the upper main surface of the piezoelectric diaphragm 2 (the surface on the opening side of the cavity 5). The frequency is adjusted by striking an inert gas such as Ar using an ion gun or the like on the surface of the excitation electrode, and scraping the excitation electrode to reduce the mass of the excitation electrode.

  Thereafter, the lid body 4 is placed on a seal ring that forms the cavity 5 of the container body 1 to which the piezoelectric diaphragm 2 is bonded and fixed in a predetermined atmosphere or vacuum, and both are sealed by seam welding. Thereby, the piezoelectric vibrator is completed. In the above embodiment, the piezoelectric vibrator is exemplified as an example of the piezoelectric device using the piezoelectric diaphragm in the present invention. However, other electronic elements that form the piezoelectric diaphragm and the oscillation circuit are packaged in the same package. The present invention can also be implemented in such a piezoelectric oscillator.

  The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the scope of the present invention. For example, in the embodiment described above, the lid body 4 is joined to the container body 1 via the seal ring, but instead of this, a metallization pattern for joining is formed on the upper surface of the substrate. You may make it weld the cover body 4 directly with respect to a metallization pattern.

  Further, in the above-described embodiment, the seal ring is directly attached to the upper surface of the substrate of the container body 1, but instead of this, a frame made of a ceramic material or the like made of the same material as the substrate is integrated with the upper surface of the substrate. In addition, the seal ring may be attached to the upper surface of the frame body.

  Further, in the embodiment described above, for example, the lid 4 is attached onto the container body 1 using a seal ring, but instead of this, with respect to a bonding conductor such as Au—Sn on the upper surface of the container body. The lid 6 may be attached to the container 2 by directly joining the lid 4, and it goes without saying that this case is also included in the technical scope of the present invention.

1A and 1B show an embodiment of a piezoelectric diaphragm according to the present invention, in which FIG. 1A is shown from one main surface side of the piezoelectric diaphragm, and FIG. 1B is shown from the other main surface side of the piezoelectric diaphragm. It is an external perspective view. 2A and 2B show another embodiment of the piezoelectric diaphragm according to the present invention, in which FIG. 2A is shown from one main surface side of the piezoelectric diaphragm, and FIG. 2B is shown from the other main surface side of the piezoelectric diaphragm. FIG. FIG. 3 is an exploded perspective view of a piezoelectric vibrator using the piezoelectric diaphragm shown in FIG. FIG. 4 is a cross-sectional view when the piezoelectric vibrator shown in FIG. 3 is assembled. It is sectional drawing of the conventional crystal oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Container body 2 ... Piezoelectric diaphragm 3 ... Conductive adhesive 4 ... Lid body 5 ... Cavity 6 ... Electrode terminal for external connection 7 ... Electrode pad for element connection 8 ... excitation electrode 9 ... container connection electrode 10 ... extraction electrode 11 ... concave

Claims (4)

  Both main surfaces of the rectangular plate-shaped piezoelectric element plate are formed with excitation electrodes, and are connected to the container formed from the excitation electrode and formed at least near the corners of the side surface of one short side of the piezoelectric element plate. An extraction electrode connected to the electrode for connection is formed from the outer peripheral portion of each excitation electrode to the container connection electrode desired to be connected via the side from the main surface of the piezoelectric substrate, and A piezoelectric diaphragm characterized in that an excitation electrode and a corresponding container connection electrode are electrically connected to each other through the extraction electrode.   A concave portion penetrating both main surfaces of the piezoelectric element plate having a depth component is formed on the side surface of one short side of the piezoelectric element plate so as to go to the inside of the piezoelectric element plate. 2. The piezoelectric diaphragm according to claim 1, wherein the container connection electrode is formed around the recess opening on the surface and the side surface of the piezoelectric element plate on which the recess is formed.   The surface of the region where the container connection electrode is formed on the piezoelectric element plate is in a form polished with an abrasive of # 800 or less or a form similar to that form. 2. The piezoelectric diaphragm according to 1.   4. A container body comprising the piezoelectric diaphragm according to claim 1, claim 2 or claim 3, a rectangular cavity, and a pair of element connection electrode pads provided on one short side of the bottom surface of the cavity. The piezoelectric diaphragm is accommodated in the cavity of the container body, and each of the container connecting electrodes of the piezoelectric diaphragm is connected to the element of the container body via a conductive bonding member. A piezoelectric device characterized in that the cavity, which is connected to an electrode pad and contains the piezoelectric diaphragm, is hermetically sealed with a lid.

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