JP2008026018A - Piezoelectric single crystal vibrator and piezoelectric vibration gyroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small sized and a low cost piezoelectric single crystal vibrator and a piezoelectric vibration gyroscope constituted by using the piezoelectric single crystal vibrator while maintaining the mounting reliability of the piezoelectric single crystal vibrator. <P>SOLUTION: Four arms 12a, 12b, 12c and 12d are connected at the center of the piezoelectric vibrator 1, an insulation membrane 20 is formed on detection electrodes 15, 16, 17, 18, and a reference electrode 19 so as to mask them and insulate each electrode electrically, thus prevent the generation of short circuit with the other electrode is prevented. The yield is increased while improving the reliability. <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 on which a signal processing circuit is wired, there are a wire bonding method, a GGI method (Gold to Gold Interconnection), or a method using a conductive adhesive. After mounting and wiring, the product is sealed at the end.

  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.

  Patent Document 3 discloses an example of a surface acoustic wave filter in which an electrode and a piezoelectric substrate are bonded using a conductive adhesive.

JP 2005-094461 A JP 2005-003477 A Japanese Patent Laid-Open No. 11-251867

  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.

  In addition, when the conductive adhesive disclosed in Patent Document 3 is used, fixing and electrical connection can be performed at the same time, so that the manufacturing cost can be reduced, and silver (Ag), which is cheaper than gold (Au). Is generally used, the material cost can be reduced, and if the adhesive application area is reduced while ensuring the adhesive strength, the product can be made smaller. Thus, compared to the wire bonding method and the GGI method, the method using the conductive adhesive can be said to be an advantageous mounting method in all aspects.

  In the case of a piezoelectric single crystal vibrator, a vibrator having a complicated shape can be manufactured by etching or sandblasting as described above, so that a vibrator having a higher function can be obtained. However, when an electrode is formed on a piezoelectric single crystal resonator having a small size and a complicated shape, there are restrictions on wiring, and an electrode arrangement with good driving efficiency and an electrode arrangement for detecting the piezoelectric effect are not necessarily provided. There was a problem that I could not. In addition, due to the complicated structure, the number of electrode terminals is increased, which increases the number of assembly steps and increases the manufacturing cost.

  The present invention has been made in order to solve the conventional problems. A small-sized and low-cost piezoelectric single crystal vibrator and the piezoelectric single crystal vibrator are used while ensuring mounting reliability of the piezoelectric single crystal vibrator. An object of the present invention is to provide a configured piezoelectric vibration gyro.

  In order to solve the above problems, the present invention has an electrode formed on at least one main surface of the front surface or the back surface 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 vibrator that is electrically connected to and mechanically fixed, and an insulating film is formed on a portion where a plurality of electrodes including at least two electrodes having the same potential are wired; The piezoelectric single crystal vibrator is characterized in that the at least two electrodes having the same potential are directly connected in an insulated state through an insulating film to form one electrode wiring.

The insulating film is a piezoelectric single crystal vibrator characterized by comprising at least one selected from SiO ₂ , Si ₃ N ₄ , polyimide, and photoresist.

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

  Therefore, according to the present invention, a compact and low-cost piezoelectric single crystal vibrator and a piezoelectric vibration gyro configured using the piezoelectric single crystal vibrator are obtained while ensuring mounting reliability of the piezoelectric single crystal vibrator. be able to.

  FIG. 1 is an enlarged view of the vicinity of a central portion where an insulating film of a piezoelectric single crystal vibrator according to an embodiment of the present invention is formed. FIG. 1A shows a wiring diagram of an electrode before forming an insulating film, FIG. 1B shows a wiring diagram of an insulating film and a newly formed electrode after forming the insulating film, and FIG. 10 shows a conventional insulating film. It is a wiring diagram of the electrode when there is not. Embodiments of the present invention will be described with reference to the drawings. An insulating film 20 is formed in a central portion where the four arm portions 12a, 12b, 12c, and 12d are connected so as to cover the detection electrodes 15, 16, 17, and 18 and the reference potential electrode 19. Drive electrodes 13a, 13b, 14a, and 14b are formed on the insulating film 20, and each electrode is electrically insulated.

The material of the insulating film 20 is preferably any of SiO ₂ , Si ₃ N ₄ , polyimide, and photoresist, but is not limited thereto, and any insulating material can be used. .

  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 a diagram showing an electrode arrangement on the upper surface of the piezoelectric single crystal vibrator and an arrangement of the insulating film according to the embodiment of the present invention. This piezoelectric single crystal vibrator is a piezoelectric vibration gyro capable of detecting a biaxial angular velocity. Hereinafter, for convenience of explanation, as shown in FIGS. 2 and 3, the thickness direction of the piezoelectric single crystal vibrator is defined as the X axis, the vertical direction in the drawing is defined as the Y axis, and the horizontal direction in the drawing is defined as the Z axis.

  The piezoelectric single crystal vibrator 1 holds four additional mass portions 11a, 11b, 11c, and 11d as vibration portions inside by penetrating a rectangular plate and punching out a part of the rectangular plate. The structure is formed as a single body. In addition, the piezoelectric single crystal vibrator 1 is formed with an electrode for functioning as a piezoelectric vibration gyro, and an electrode for improving vibration efficiency and detection efficiency. Drive electrodes 13a, 13b, 14a, 14b, detection electrodes 15, 16, 17, 18, and a reference potential electrode 19 are formed from the electrode arrangement diagram on the upper surface of FIG. Further, an insulating film 20 is formed in a central portion where the four arm portions 12a, 12b, 12c, and 12d shown in FIG. 2 are connected so as to cover the detection electrodes 15, 16, 17, and 18 and the reference potential electrode 19. Has been. Drive electrodes 13a, 13b, 14a, and 14b are formed on the insulating film 20, and each electrode is electrically insulated.

  An example of the manufacturing process of this piezoelectric single crystal vibrator will be described. As the piezoelectric single crystal material, quartz, lithium niobate, lithium tantalate, langasite, or zinc oxide is used. A film is formed on these wafers by sputtering or vacuum deposition with Au as an electrode and Cr as a base. Next, a resist is formed into a desired pattern by photolithography, Au and Cr are removed by etching, and the resist is further removed to form the detection electrodes 15, 16, 17, 18 and the reference potential electrode 19.

  Next, in the formation of the insulating film, it is directly printed or formed by photolithography and etching after film formation by sputtering, vacuum evaporation, or CVD (chemical vapor deposition). Thereafter, Au is formed again by sputtering or vacuum deposition with Cr as a base, a resist pattern is formed by photolithography, Au and Cr are removed by etching, and the resist is further removed to drive electrodes 13a, 13b, 14a, 14b is formed. Next, a resist is formed into a desired pattern by photolithography, through-penetration is performed by etching or sandblasting, and the resist is removed to obtain the piezoelectric single crystal vibrator 1. The piezoelectric single crystal vibrator 1 obtained in this way is mounted on a circuit board (not shown) by fixing and electrically connecting with a conductive adhesive.

  In this state, when an AC voltage is applied between the drive electrodes 13a and 14a, the additional mass parts 11a and 11c vibrate in the X axis direction, and the additional mass parts 11b and 11d vibrate in the X axis direction in the opposite phase. To do. When a rotational angular velocity is applied around the Z axis in this vibration state, the vibration in the Y axis direction is excited by the Coriolis force, so that it can be electrically detected from the detection electrodes 15 and 16. When a rotational angular velocity is applied around the Y axis, vibration in the Z-axis direction is excited, and can be detected electrically from the detection electrodes 17 and 18. By processing these detection signals and outputting them, a piezoelectric vibration gyro capable of detecting a biaxial angular velocity can be obtained.

  As shown in FIG. 3, since the drive electrodes 13a and 13b are connected to one through the insulating film 20, the connection with the external electric circuit can be completed at one place. Similarly, since the drive electrodes 14a and 14b are connected to one through the insulating film 20, the connection with the external electric circuit can be completed at one place. If the insulating film 20 is not provided, since the detection electrodes 15 and 18 and the reference potential electrode 19 having different potentials from the drive electrodes 13a and 13b are wired between the drive electrodes 13a and 13b, as shown in FIG. Each of them must be independently connected to wiring and an external electric circuit, resulting in an increase in assembly cost.

  For the same reason, the drive electrodes 14a and 14b can be connected to the external electric circuit in one place. However, when the insulating film 20 is not provided, the detection electrodes 16 and 17 and the reference potential electrode 19 having different potentials are not connected. As shown in FIG. 10, the drive electrodes 14a and 14b must be independently connected to the wiring and the external electric circuit, resulting in an increase in assembly cost.

  In the case of the present invention, the cost for forming the insulating film 20 is newly generated. However, since the insulating film 20 can be formed in units of wafers, the cost per piezoelectric single crystal vibrator can be kept low. On the other hand, since the assembly for connection can be processed only one piezoelectric single crystal vibrator one by one, the cost increases by the number of connections. In the case of the present invention, since the cost reduction by reducing the number of connections is larger than the cost increase for forming the insulating film, a piezoelectric vibration gyro capable of detecting the biaxial angular velocity can be obtained while reducing the total cost. .

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

  FIG. 4 is a top view showing the outer shape of the piezoelectric single crystal resonator according to the embodiment of the present invention, and FIG. 5 is a completed arrangement of the surface electrode and the insulating film according to the embodiment of the present invention. 6, FIG. 7, and FIG. 8 are diagrams showing a process of sequentially forming electrodes and an insulating film. FIG. 6 is an exploded view of the lower layer electrode and the insulating film, FIG. 6A is a layout diagram of the lower layer electrode, and FIG. 6B is a layout diagram of the insulating film. FIG. 7 is a layout diagram of the lower layer electrode and the insulating film, and FIG. 8 is a layout diagram of the upper layer electrode. FIG. 9 is a layout diagram of electrodes on the back surface according to the embodiment of the present invention. This piezoelectric single crystal vibrator is a piezoelectric vibration gyro capable of detecting a biaxial angular velocity. Hereinafter, for convenience of explanation, as illustrated, the thickness direction of the piezoelectric single crystal vibrator is defined as an X axis, the vertical direction in the drawing is defined as the Y axis, and the horizontal direction in the drawing is defined as the Z axis.

  The manufacturing process of this piezoelectric single crystal vibrator will be briefly described. A piezoelectric single crystal having the shape shown in FIG. 4 is used, in which lithium niobate is used as the piezoelectric single crystal material, the outer dimensions are 2.7 mm × 4.7 mm × thickness 0.25 mm, and each additional mass part size is 0.8 mm × 0.8 mm. Crystal oscillator 2 was produced. The piezoelectric single crystal vibrator 2 holds the four additional mass portions 31a, 31b, 31c, and 31d, which are vibrating portions, by penetrating a rectangular plate and punching a part of the rectangular plate. The structure is formed as a single body.

  On these wafers, Cr was deposited as an electrode and Au was deposited as a base by sputtering. Next, a resist was formed into a desired pattern by photolithography, Au and Cr were removed by etching, and the resist was further removed to form the detection electrode 36 and the detection electrode 37a shown in FIG. Next, an insulating film 38 was formed on the four arm portions 32a, 32b, 32c, and 32d by sputtering, and the insulating film pattern shown in FIG. 6B was formed by photolithography and etching. In this pattern, openings 39a and 39b of an insulating film are provided. As a result, as shown in FIG. 7, the detection electrode 37a is exposed from the openings 39a and 39b of the insulating film, and the exposed portions become connection portions 40a and 40b. The upper electrode pattern including the detection electrodes 35a and 35b and the detection electrodes 37b and 37c shown in FIG. 8 is formed on the insulating film 38 in the same process as the detection electrode 36 and the detection electrode 37a. The electrode and the insulating film were completed. As the insulating film, a polyimide film having a thickness of 4 μm was used.

  At this time, the connection part 40c on the detection electrode 37b and the connection part 40a on the detection electrode 37a are electrically connected, and the connection part 40d on the detection electrode 37c and the connection part 40b on the detection electrode 37a are electrically connected, As a result, the detection electrodes 35a and 35b and the detection electrode 37a have the same potential.

  Next, the drive electrodes 33 and 34 shown in FIG. 9 are formed on the back surface by the same process as the formation of the front surface electrodes. After the electrodes on both sides and the insulating layer were formed in this way, a resist was formed into a desired pattern by photolithography, through-etching was performed by etching or sandblasting, and the resist was removed to obtain the piezoelectric single crystal vibrator 2 .

  Drive electrodes 33 and 34 and detection electrodes 35a, 35b, 36, and 37a are formed as electrodes for functioning as a piezoelectric vibration gyro of the piezoelectric single crystal vibrator 2. An insulating film 38 is formed on the four arm portions 32a, 32b, 32c, and 32d, and the detection electrodes 35a and 35b, the detection electrode 36, and the detection electrode 37a on the arm portions are insulated by the insulating film 38. .

  The piezoelectric single crystal resonator 2 obtained in this way is mounted on the package with a conductive adhesive fixed and electrically connected. In this state, when an AC voltage is applied to the drive electrodes 33 and 34 in FIG. 9, the additional mass portions 31a and 31c vibrate in the X-axis direction, and 31b and 31d vibrate in the X-axis direction in the opposite phase. When a rotational angular velocity is applied around the Z axis in this vibration state, the vibration in the Y axis direction is excited by the Coriolis force, so that charges are generated in the arm portions 32e, 32f, 32g, and 32h, and the detection electrodes 35a, 35b and Since a potential difference is generated between the detection electrodes 37b and 37c, it can be electrically detected. Further, when a rotational angular velocity is applied around the Y axis, vibration in the Z axis direction is excited, so that charges are generated in the arm portions 32b and 32d and a potential difference is generated between the detection electrode 36 and the detection electrode 37a. Can be detected. By processing these detection signals and outputting them, a piezoelectric vibration gyro capable of detecting a biaxial angular velocity can be obtained.

  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, both the rotational angular velocity around the Y axis and the rotational angular velocity around the Z axis were approximately 0.5 mV / ° / second, and the biaxial angular velocity could be detected with one piezoelectric single crystal vibrator.

  In the present invention, the detection electrode 37a and the detection electrode 37b having the same potential are connected to the connection portion 40c (40a) through the insulating film 38, and the detection electrode 37a and the detection electrode 37c having the same potential are connected to the connection portion 40d. (40b) and each is electrically connected to one. As described above, since the insulating film 38 is provided, the detection electrodes 35a, 35b, 36, and 37a can be electrically wired on the arm portions 32a, 32b, 32c, and 32d, and the angular velocity can be detected. Necessary electrodes could be formed. If the insulating film 38 is not provided, the wiring structure as shown in FIG. 5 is impossible. If two-axis angular velocities are to be detected, the left half is used for Y-axis detection and the right half is used for Z-axis detection. It must be formed separately from the electrodes. As a result, the detection efficiency is poor, and the gyro sensitivity is approximately 0.25 mV / ° / second for both the rotational angular velocity about the Y axis and the rotational angular velocity about the Z axis under the same circuit conditions as described above, which is as low as the aforementioned half. End up. In the case of the present invention, wiring is performed on all the arm portions of the Y-axis detection electrode and the Z-axis detection electrode, so that detection is performed at twice the efficiency as compared with the case without the insulating film 38 described above. The sensitivity of the gyro was doubled to a sensitivity of 0.5 mV / ° / second, and a highly sensitive gyro was obtained.

  The number of connections with the external electric circuit is increased by separating the detection electrodes 35a and 35b, but the detection electrode 37a is used for both the Y-axis angular velocity detection and the Z-axis angular velocity detection. Since it is not necessary to provide a reference potential electrode, the total number of connections could be reduced. Although the cost of newly forming the insulating film 38 is generated, the total cost can be reduced because the cost reduction by reducing the number of connections is greater.

The enlarged view of the central part vicinity in which the insulating film of the piezoelectric single crystal vibrator concerning embodiment of this invention is formed. FIG. 1A is a wiring diagram of electrodes before forming an insulating film. FIG. 1B is a wiring diagram of an insulating film and an electrode newly formed after the insulating film is formed. 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, and the figure which showed arrangement | positioning of an insulating film. The top view which showed the external shape of the piezoelectric single crystal vibrator concerning the Example of this invention. The arrangement completion drawing of the surface electrode and insulating film concerning the Example of this invention. The exploded view of a lower layer electrode and an insulating film. FIG. 6A is a layout diagram of lower-layer electrodes, and FIG. 6B is a layout diagram of insulating films. FIG. 6 is a layout diagram of lower electrodes and insulating films. FIG. 6 is a layout diagram of upper layer electrodes. FIG. 3 is a layout diagram of electrodes on the back surface according to the embodiment of the present invention. Wiring diagram of electrodes when there is no conventional insulating film

Explanation of symbols

1, 2 Piezoelectric single crystal vibrators 11a to 11d Additional mass portions 12a to 12d Arm portions 13a, 13b, 14a, 14b Drive electrodes 15, 16, 17, 18 Detection electrodes 19 Reference potential electrodes 20, 38 Insulating films 31a to 31d Mass part 32a-32h Arm part 33, 34 Drive electrode 35a, 35b, 36, 37a-37c Detection electrode 39a, 39b Opening part 40a-40d of insulating film Connection part

Claims (3)

  An electrode is formed on at least one main surface of the front or back surface of a piezoelectric single crystal plate made of a piezoelectric single crystal material, electrically connected to a circuit board by a conductive adhesive, and mechanically fixed. In the piezoelectric single crystal vibrator, an insulating film is formed on a portion where a plurality of electrodes including at least two electrodes having the same potential are wired, and the at least two electrodes are interposed through the insulating film. A piezoelectric single crystal vibrator characterized in that electrodes having the same potential are directly connected in an insulated state to form one electrode wiring. _2. The piezoelectric single crystal resonator according to claim 1, wherein the insulating film is made of at least one selected from SiO ₂ , Si ₃ N ₄ , polyimide, and a photoresist.   A piezoelectric vibration gyro comprising the piezoelectric single crystal resonator according to claim 1 or 2.

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