JP2007333546A - Piezoelectric single crystal vibrator and piezoelectric vibration gyroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric single crystal vibrator, small-sized, having high function and low-cost, and a piezoelectric vibration gyroscope constructed by the piezoelectric single crystal vibrator. <P>SOLUTION: A reference potential electrode 16a on the upper surface is electrically connected to a reference potential electrode 16b on the lower surface through a through hole formed on an additional mass part, and a detecting electrode 20a on the upper surface is electrically connected to a detecting electrode 20c on the lower surface through a through hole 13a, whereby the wired electrodes can be reduced, and the number of nodes to a circuit board can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric single crystal vibrator using a piezoelectric single crystal material and a piezoelectric vibration gyro configured using the piezoelectric single crystal vibrator, and more particularly to a structure and mounting method of a piezoelectric single crystal vibrator.

  Piezoelectric vibrators are used in a wide range of fields such as sensors, oscillators, surface acoustic wave filters, ultrasonic motors, acoustic elements, transformers, and the like. Among piezoelectric materials used for piezoelectric vibrators, in particular, piezoelectric single crystal materials generally have a high mechanical quality factor (hereinafter referred to as Qm), a small characteristic change with respect to a temperature change, a uniform material and high reliability, It is characterized by excellent mass productivity of materials and is often used as a vibrator for electronic parts such as sensors, oscillators, surface acoustic wave filters, and the like.

  As an example of mass production of piezoelectric vibrators using these piezoelectric single crystal materials, the following manufacturing method is used. First, a metal thin film serving as an electrode is formed on a piezoelectric single crystal wafer by sputtering, vacuum deposition, or the like, a resist is patterned by so-called photolithography, and then the metal thin film is etched to form an electrode pattern. After that, the resist is patterned again by photolithography, and the piezoelectric single crystal is etched or sandblasted to be processed into a desired vibrator shape. Finally, the vibrator is cut into individual pieces by a dicing saw. Thus, a large number of piezoelectric single crystal vibrators are obtained from one wafer.

  As the market for portable devices such as mobile phones, portable audios, and digital cameras grows larger, there is a strong demand for downsizing, higher functionality, and lower costs of electronic components used in the market. In the case of electronic parts using a piezoelectric single crystal vibrator, the piezoelectric single crystal vibration is used to fix the piezoelectric single crystal vibrator on the circuit board without hindering the vibration of the piezoelectric single crystal vibrator and to perform a desired function. A mounting means for electrically connecting the child and the circuit board is required. As a method of mounting these piezoelectric single crystal vibrators on a circuit board wired with a signal processing circuit, the wiring bonding method, the GGI method (Gold to Gold Interconnection), or a method using a conductive adhesive is used. The product is sealed.

  Patent Document 1 discloses an example of a piezoelectric device connected by a wire bonding method.

  Patent Document 2 discloses an example of a magnetic sensor in which an electrode and an IC chip are electrically connected by a GGI method.

  Further, Patent Document 3 discloses an example of a surface mount type piezoelectric vibrator in which upper and lower pattern electrodes and inner layer electrodes are electrically connected through a through hole.

JP 2005-094461 A JP 2005-003477 A JP 2005-0665104 A

  When the wire bonding method disclosed in Patent Document 1 is used, the piezoelectric single crystal vibrator is fixed to the circuit board with an adhesive, and the wire is routed between the electrode of the piezoelectric single crystal vibrator and the electrode of the circuit board. In order to make a simple connection, there is a problem that a space for routing the wire is required, and there is a problem that a certain distance is required between the electrode of the piezoelectric single crystal vibrator and the electrode of the circuit board. In addition, since the mounting is a two-step process including adhesive fixing and wiring, there is also a problem that the manufacturing cost increases.

  When the GGI method disclosed in Patent Document 2 is used, fixing and electrical connection can be performed at the same time. However, since gold (Au) is used, the material cost increases, and the connection strength is insufficient only by the GGI method. In general, an underfill material made of silicone or the like for reinforcement is required, which causes a problem that the material cost and the manufacturing cost increase.

  On the other hand, when conductive adhesive is used, fixing and electrical connection can be performed at the same time, so manufacturing costs can be reduced, and silver (Ag), which is cheaper than gold (Au), is generally used, so material costs It is possible to reduce the size of the product by reducing the adhesive application area while ensuring the adhesive strength. Compared to the wire bonding method and the GGI method, the method of using a conductive adhesive is This is an advantageous mounting method in all aspects. Therefore, there is a means that uses a conductive adhesive to form a large number of electrodes on the piezoelectric single crystal vibrator to realize a plurality of or high-performance functions in the piezoelectric single crystal vibrator. However, with the miniaturization of the piezoelectric single crystal vibrator, there are restrictions on the electrodes that can be formed, and there is a problem that wiring on the piezoelectric single crystal vibrator is difficult or impossible.

  In view of this, there is a method of easily forming a circuit by electrically connecting the pattern electrodes on the upper and lower surfaces and the inner layer electrode through the through holes using the through hole method. However, the through-hole method disclosed in Patent Document 3 is not sufficiently compatible with downsizing at the present stage, and there is a problem in forming a complicated circuit pattern.

  The present invention has been made to solve the conventional problems, and provides a piezoelectric single crystal vibrator that is small, highly functional, and low in cost, and a piezoelectric vibration gyro configured using the piezoelectric single crystal vibrator. is there.

  In order to solve the above problems, the present invention has electrodes formed on the main surfaces of the front and back surfaces of a piezoelectric single crystal plate made of a piezoelectric single crystal material, and is electrically connected to a circuit board by a conductive adhesive. A piezoelectric single crystal resonator that is mechanically fixed, wherein a through hole is formed in a part of the piezoelectric single crystal plate, an electrode formed on one main surface, and a remaining main surface The piezoelectric single crystal vibrator is characterized in that the formed electrode is electrically connected through a through hole.

  Further, the piezoelectric vibration gyro is configured by using a piezoelectric single crystal vibrator.

  Therefore, according to the present invention, it is possible to obtain a small-sized, high-function, low-cost piezoelectric single crystal vibrator and a piezoelectric vibration gyro configured using the piezoelectric single crystal vibrator.

  FIG. 1 is an explanatory view of a through hole portion of a piezoelectric single crystal vibrator according to an embodiment of the present invention. FIG. 1A is an enlarged view of a through hole portion (in the vicinity of the additional mass portion 11a), and FIG. 1B is a cross-sectional view along AA ′. Embodiments of the present invention will be described with reference to the drawings. The upper reference potential electrode 16a is electrically connected to the lower reference potential electrode 16b via a through hole 12a formed in the additional mass portion, and the upper detection electrode 20a is connected to the lower detection electrode via the through hole 13a. 20c is electrically connected.

  FIG. 2 is a top view showing the outer shape of the piezoelectric single crystal resonator according to the embodiment of the present invention. FIG. 3 is an electrode arrangement diagram on the upper surface of the piezoelectric single crystal resonator according to the embodiment of the present invention. FIG. 4 is an electrode arrangement diagram of the lower surface of the piezoelectric single crystal resonator according to the embodiment of the present invention. Embodiments of the present invention will be described with reference to the drawings. This piezoelectric single crystal vibrator is a piezoelectric vibration gyro capable of detecting a biaxial angular velocity. For convenience of explanation, as shown in FIGS. 2, 3, and 4, the thickness direction of the piezoelectric single crystal vibrator is taken as the X axis, the vertical direction in the drawing is taken as the Y axis, and the horizontal direction in the drawing is taken as the Z axis.

  From the top view showing the outer shape of FIG. 2, the piezoelectric single crystal vibrator 1 penetrates into a rectangular plate and punches out a part of the rectangular plate, so that the arms 15 a, 15 b, 15 c, 15 d A structure that holds the four additional mass portions 11a, 11b, 11c, and 11d, which are the vibration portions, is formed as an integral body. Through holes 12a and 13a, 12b and 14a, 12c and 13b, and 12d and 14b are formed in the additional mass part, respectively. In addition, the piezoelectric single crystal vibrator 1 is formed with electrodes for functioning as a piezoelectric vibration gyro and electrodes for improving vibration efficiency and detection efficiency on both the front and back surfaces. From the electrode arrangement diagram on the upper surface of FIG. 3, the drive electrodes 17a, 17b, 18a and 18b, the detection electrodes 20a, 20b, 21a and 21b, and the reference potential electrode 16a are formed on the upper surface. From the electrode arrangement diagram on the lower surface of FIG. 4, the drive electrodes 17c, 17d, 19a, 19b, the detection electrodes 20c, 20d, 21c, 21d, and the reference potential electrode 16b are formed on the lower surface.

  As described above, the reference potential electrodes 16a and 16b are electrically connected via the through holes 12a, 12b, 12c, and 12d, and the upper detection electrode 20a is connected to the lower detection electrode 20c via the through hole 13a. Electrically connected. Similarly, in the other additional mass portions, the detection electrode 21a is connected to the detection electrode 21d via the through hole 14a, the detection electrode 20b is connected to the detection electrode 20d via the through hole 13b, and the detection electrode 21b is connected to the detection hole 21b via the through hole 14b. It is electrically connected to the detection electrode 21c.

  An example of the manufacturing process of this piezoelectric single crystal vibrator will be briefly described. As the piezoelectric single crystal material, quartz, lithium niobate, lithium tantalate, langasite, or zinc oxide is used. Through holes are formed on these wafers by etching or sand blasting using a resist patterned by photolithography as a mask. Next, a film of Au is formed by sputtering or vacuum deposition with Cr as a base as an electrode. At this time, since the film is also formed on the inner wall of the through hole, conduction between the upper surface and the lower surface is ensured. Thereafter, using a resist patterned by photolithography as a mask, Au and Cr are removed by etching to form an electrode. Next, penetration processing is performed by etching or sandblasting using a resist patterned by photolithography again as a mask to obtain a piezoelectric single crystal vibrator. The piezoelectric single crystal vibrator 1 thus obtained is mounted on the package with a conductive adhesive fixed and electrically connected.

  On the top surface, an AC voltage is applied between the drive electrodes 17a and 17b and the drive electrodes 18a and 18b, and on the bottom surface, the drive electrodes 17c and 17d and the drive electrodes 19a and 19b are in reverse phase with the drive electrodes. AC voltage is applied to As a result, the additional mass portions 11a and 11c vibrate in the X-axis direction, and 11b and 11d vibrate in the X-axis direction in the opposite phase. When a rotational angular velocity is applied around the Y-axis in this vibration state, vibration in the Z-axis direction is excited by Coriolis force, and this can be electrically detected from the detection electrodes 20a and 20c and the detection electrodes 20b and 20d. it can. When a rotational angular velocity is applied around the Z axis, vibration in the Y axis direction is excited by the Coriolis force, and this is electrically detected from the detection electrodes 21a and 21d and the detection electrodes 21b and 21c. By processing these detection signals and outputting them, a piezoelectric vibration gyro capable of detecting a biaxial angular velocity can be obtained.

  In the case of the present invention, since the detection electrode and the reference potential electrode can be wired through the through-holes while forming electrodes on both main surfaces in order to improve drive efficiency and detection efficiency, the arms 15a, 15b, 15c , 15d can be reduced, and the number of connection points with the circuit board can be reduced. Further, even when the number of electrodes increases, it is possible to simplify the wiring by increasing the number of through holes. Since the through-hole is formed in the additional mass portion, the vibration characteristic itself is not affected by only reducing the volume corresponding to the volume of the through-hole, and the characteristics as a vibrator can be obtained. The through hole may be formed not in the additional mass portion but in a portion where the piezoelectric effect or the inverse piezoelectric effect does not occur, such as an outer edge portion which is not affected by the vibration state.

  Next, specific examples will be given, and the piezoelectric single crystal vibrator and the piezoelectric vibration gyro of the present invention will be described in more detail.

  Lithium niobate is used as the piezoelectric single crystal material, the outer dimensions are 4 mm x 4 mm x thickness 0.25 mm, each additional mass part size is 0.75 mm x 1 mm, and the through hole formed in the additional mass part is 0.1 mm x 0.1 mm A piezoelectric single crystal resonator having the shape shown in FIG.

  When this piezoelectric single crystal vibrator is driven at 1.5 Vpp (peak to peak), the resonance frequency of vibration in the X-axis direction is about 20 kHz, and the sensitivity as a piezoelectric vibration gyro is 200 times the amplification factor of the signal processing circuit. At this time, a rotational angular velocity about the Y axis and a rotational angular velocity about the Z axis were both about 0.3 mV / ° / second, and a single piezoelectric single crystal vibrator could detect the biaxial angular velocity.

Explanatory drawing of the through-hole part of the piezoelectric single crystal vibrator concerning embodiment of this invention. FIG. 1A is an enlarged view of a through hole portion (in the vicinity of the additional mass portion 11a). FIG.1 (b) is AA 'sectional drawing. The top view which showed the external shape of the piezoelectric single crystal vibrator concerning embodiment of this invention. The electrode arrangement | positioning figure of the upper surface of the piezoelectric single crystal vibrator concerning embodiment of this invention. The electrode arrangement | positioning figure of the lower surface of the piezoelectric single crystal vibrator concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric single crystal vibrator 10 Piezoelectric single crystal 11a-11d Additional mass part 12a-12d Through hole 13a, 13b Through hole 14a, 14b Through hole 15a-15d Arm 16a, 16b Reference potential electrode 17a-17d Drive electrode 18a, 18b Drive Electrode 19a, 19b Drive electrode 20a-20d Detection electrode 21a-21d Detection electrode

Claims (2)

  A piezoelectric single crystal in which electrodes are formed on the main surfaces of the front and back surfaces of a piezoelectric single crystal plate made of a piezoelectric single crystal material, and are electrically connected to a circuit board by a conductive adhesive and mechanically fixed. A vibrator, wherein a through hole is formed in a part of the piezoelectric single crystal plate, and the electrode formed on one main surface and the electrode formed on the other main surface pass through. A piezoelectric single crystal vibrator characterized in that it is electrically connected through a hole.   A piezoelectric vibration gyro comprising the piezoelectric single crystal resonator according to claim 1.

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