JP2008058049A - Vibrator, and vibration type gyroscope using vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce zero-point drift caused by resonance of an electrical connection structure, in a vibrator equipped with a bonding wire. <P>SOLUTION: In the vibrator 110 in which a support part 114 of a vibrator piece is fixed onto a mounting part in a package 120, and which is formed by connecting the first electrode 112 formed on the support part 114 of the vibrator piece to the second electrode 122 formed in the package by the bonding wire 130, a weight 131 is added to the support part 114 of the vibrator piece. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vibrator and a vibratory gyroscope using the vibrator.

  Recently, it has been studied to install a vibrating gyroscope in an automobile and use it for controlling the direction of the body of the automobile. For example, when a vibration type gyroscope is used as a rotation speed sensor used in a vehicle control method of a vehicle body rotation speed feedback type of an automobile, the direction of the steering wheel itself is detected by the rotation angle of the steering wheel. At the same time, the rotational speed at which the vehicle body is actually rotating is detected by the vibration gyroscope. Then, the direction of the steering wheel is compared with the actual rotational speed of the vehicle body to obtain a difference, and based on this difference, correction is made to the wheel torque and the steering angle, thereby realizing stable vehicle body control.

Such a vibrator needs to be housed in a housing member such as a ceramic package, which is mounted on a circuit board, and further housed in a predetermined housing so that the housing can be attached to the vehicle body.
For example, in a vibrator made of a piezoelectric material for use in a vibratory gyroscope, it is necessary to provide an electrode on the vibrator surface, generate an electrical signal corresponding to the rotational angular velocity, and transmit this to the electrode on the circuit board.

  Further, in in-vehicle applications, the operating temperature range of the vibration gyroscope is extremely wide, and for example, it is required to operate stably in a temperature range of −40 ° C. to + 85 ° C. However, it is estimated that the bonding wire for connecting the vibrator side electrode to the substrate side electrode causes a zero point temperature drift. Such a zero point temperature drift is considered to be caused by the fact that the bonding wire has a resonance frequency in a band close to the vibration frequency of the vibrator.

  Therefore, in order to reduce the zero point temperature drift of the electrical output signal from the vibrator using the bonding wire, the working temperature of the vibratory gyroscope is determined by defining the height from the surface of the vibrator to the curved portion of the bonding wire. In the range, an electrical connection structure of a vibrator in which a peak of zero point temperature drift presumed to be caused by resonance with a bonding wire is reduced is disclosed (for example, refer to Patent Document 1).

JP 2003-315047 (page 3-5, FIG. 1)

However, in the case of the electrical connection structure of the vibrator in the prior art, the zero point temperature drift is reduced to some extent, but due to the variation in the manufacturing quality of the bonding wire, the bonding wire is in a band close to the vibration frequency of the vibrator. There is a risk of having a resonance frequency, and it is difficult to reliably prevent the occurrence of a zero point temperature drift.
Further, in the case of the electrical connection structure of the vibrator according to the prior art, it is difficult to reduce the size because the height is limited from the surface of the vibrator to the curved portion of the bonding wire.

  The object of the present invention is to reduce the zero-point temperature drift of the electrical output signal from the vibrator and reduce the size even when the bonding wire has a resonance frequency in a band close to the vibration frequency of the vibrator. It is an object of the present invention to provide a simple vibrator and a vibratory gyroscope using the vibrator.

  In order to achieve the above-described object, the present invention has a vibrator piece support portion fixed to a mount portion in a package, and a first electrode formed on the vibrator piece support portion and the package. In the vibrator formed by connecting the formed second electrode with a bonding wire, a weight is added to the support portion of the vibrator piece.

  Further, it is desirable that a weight is added in the vicinity of the bonding wire connection portion of the first electrode.

Further, it is desirable that weights are added to both end portions of the support portion.

  Furthermore, the weight is preferably made of a metal material such as gold.

  Furthermore, the weight is a resin material applied to at least a part of the surface of the support portion.

  Furthermore, the vibratory gyroscope of the present invention is characterized by using the vibrator according to any one of claims 1 to 5.

  As described above, according to the present invention, the zero-point temperature drift of the electrical output signal from the vibrator can be reduced even when the bonding wire has a resonance frequency in a band close to the vibration frequency of the vibrator. A vibrator that can be miniaturized and a vibratory gyroscope using the vibrator can be realized.

  The vibrator according to the present embodiment and the vibratory gyroscope using the vibrator include a first electrode formed on the support portion of the vibrator piece by fixing the support portion of the vibrator piece to the mount portion in the package. A structure in which the second electrode formed in the package is connected by a bonding wire, and a zero point temperature drift of the electrical output signal from the vibrator is reduced by adding a weight to the support portion of the resonator element. Is.

  1 and 2 show the vibrator in the first embodiment, FIG. 5 shows the vibrator in the second embodiment, and FIG. 6 shows the vibrator in the third embodiment. In addition, about the same component in each Example, the same number is provided and description is abbreviate | omitted. Hereinafter, specific examples of the vibrator according to the present embodiment will be described with reference to FIGS.

FIG. 1 shows a vibrating gyroscope, FIG. 1 (a) is a plan view schematically showing the main part of the vibrating gyroscope, and FIG. 1 (b) is a view showing the orientation of crystal. 2 is a cross-sectional view taken along the line AA ′ in FIG. 1, FIG. 3 is a characteristic diagram showing the measurement result of the temperature change of the conventional rotational angular velocity, and FIG. 4 is the measurement result of the temperature change of the rotational angular velocity of the present invention. FIG. As shown in FIGS. 1 and 2, the vibrating gyroscope 100 of the present embodiment accommodates the vibrator 110 in the internal space S of the package 120 and is made of a transparent glass material or ceramic in order to make the internal space S into a vacuum atmosphere. A lid 124 made of a material or a metal material is sealed with a brazing material 125. In the vibrator 110, a metal electrode not shown in FIG. 1A is formed on the surface of a vibrator piece cut out in a tuning fork shape whose legs extend in the Y-axis direction. The package 120 is formed of a ceramic material having a substantially rectangular shape. A pedestal 121 is provided on the package 120, and the support portion 114 of the vibrator 110 is joined to the pedestal 121 of the package by an insulating adhesive layer 140.

  The bonding wire 130 extends from the excitation electrode 112 that is the first electrode formed on the surface of the support portion 114 of the vibrator 110 to the package side electrode 122 that is the second electrode. 122 is electrically connected. The package side electrode 122 is connected to the external terminal 123. The external terminal 123 is electrically connected to the semiconductor component via a wiring (not shown). Two excitation electrodes 112 are arranged in the vicinity of both ends of the support portion 114 in the short direction of the vibrator 110.

  A gold weight 131 was added in the vicinity of the connection portion of the bonding wire 130 in the excitation electrode 112 described above. The weight of the added gold weight 131 was about 5 μg and was added to all the excitation electrodes 112. The weight of the gold weight 131 is not particularly limited, and a weight may be added as necessary. As for the material of the weight, other metal materials of gold can be used, but gold is preferable in consideration of the excellent corrosion resistance and the large specific gravity that can reduce the volume of the weight. When a bonding wire having a resonance frequency in a band close to the vibration frequency of the vibrator can be specified, a gold weight may be partially added in the vicinity of the bonding wire.

  In addition, a floating electrode 113 is disposed between two excitation electrodes 112 and 112 disposed on the leg side of the vibrator 110. The floating electrode 113 is disposed to increase the electrode area in the support portion 114. When the area of the excitation electrode 112 is small and a gold weight cannot be added, the floating electrode 113 may be provided in the support portion 114 and the weight may be added to the floating electrode 113.

  The rotational angular velocity value was measured from −40 ° C. to 85 ° C. with respect to this vibrating gyroscope. In the vibrator drive mode, the legs of the vibrator 110 bend and vibrate in the X direction as indicated by the arrow D with the root at the center. In the detection mode, when a rotational motion ω is applied about the Y axis, the legs of the vibrator 110 bend and vibrate in the Z direction as indicated by an arrow S1 with the root at the center. As another detection mode, there is a torsional vibration centered on the support portion as indicated by an arrow S2. The rotational angular velocity is measured by measuring these detected vibrations. In this embodiment, in order to increase the output and improve the SN, both bending vibration and torsional vibration are measured.

  Next, a manufacturing method of the vibrating gyroscope having the structure shown in FIGS. 1 and 2 will be described. A chromium film having a thickness of 100 angstroms and a gold film having a thickness of 1500 angstroms were formed at predetermined positions on a wafer made of a quartz Z plate having a thickness of 0.1 mm by sputtering. Further, a resist was coated on both sides of the wafer.

  This wafer is immersed in an aqueous solution of iodine and potassium iodide, and the excess gold film is removed by etching. Further, the wafer is immersed in an aqueous solution of cerium ammonium nitrate and perchloric acid, and the excess chromium film is etched. Removed. The wafer was immersed in ammonium bifluoride at a temperature of 80 ° C. for 20 hours, and the wafer was etched to form the outer shape of the vibrator 110. Using a metal mask, a gold film having a thickness of 2000 angstroms was formed as an electrode film on a chromium film having a thickness of 100 angstroms. Here, the dimensions of the vibrator 110 shown in FIG. 1 were 5.2 mm in length, 1.6 mm in width, 0.1 mm in thickness, and 1.5 mg in weight.

  The vibrator 110 was mounted in a package as shown in FIG. However, the package 120 is formed of a ceramic substrate, an epoxy resin adhesive is used as the insulating adhesive 140 for the support portion 114 of the vibrator and the mounting portion of the package, the heating temperature of the epoxy resin is 150 ° C., and the heating time is It was 1 hour.

A gold wire was used as the bonding wire. A wire diameter of φ25 μm was used. The bonding wire was bonded to the package side electrode 122 and the vibrator 110 on the package surface by ultrasonic bonding. The Kovar lid 124 was fixed by a brazing material 125 in order to keep the space S in the package in a vacuum state. In this embodiment, a gold weight is added by a stud bump method formed by making a ball with a gold wire and bonding it to the excitation electrode 112 by ultrasonic bonding and cutting the tip portion. A gold weight may be added to the excitation electrode 112 by gold plating.

  FIG. 3 shows a conventional measurement result of the temperature change of the rotational angular velocity, and FIG. 4 shows a measurement result of the temperature change of the rotational angular velocity of the present invention. The horizontal axis of the graphs shown in FIGS. 3 and 4 indicates the temperature, and the vertical axis indicates the value of the rotational angular velocity. The horizontal axis expanded around the temperature at which the peak was observed. As shown in FIG. 3, a zero point temperature drift, which is conventionally attributed to bonding wire resonance, was observed around 60 ° C. As shown in FIG. 4, when a gold weight 131 was added to the excitation electrode 112 formed on the support portion 114, this peak was not observed. The weight of the gold weight is preferably 5 μg and is preferably added to all the excitation electrodes. However, if a bonding wire having a resonance frequency in a band close to the vibration frequency of the vibrator can be specified, the gold weight is placed in the vicinity of the bonding wire. The weight may be partially added.

  Thus, by adding the gold weight 131 in the vicinity of the connection portion of the bonding wire 130 in the excitation electrode 112 of the support portion 114 of the vibrator 110, the bonding wire has a resonance frequency in a band close to the vibration frequency of the vibrator. Even in this case, the zero point temperature drift of the electrical output signal from the vibrator can be reduced.

  The vibration type gyroscope in the second embodiment is different from the first embodiment in that the positions where the gold weight 131 is added are both ends of the support portion 114 of the vibrator 110, and the other is the same as the first embodiment. As shown in FIG. 5, the vibrating gyroscope according to the present embodiment is an example in which the positions to which the gold weight 131 is added are added to both ends of the support portion 114 in the short direction of the vibrator 110. The gold weight 131 is added on the excitation electrode 112 by the stud bump method as in the embodiment. As a result, the moment of inertia of the support portion 114 is increased, energy leakage due to torsional vibration is reduced, and the resonance of the wire can be reduced. When the value of the rotational angular velocity was measured from −40 ° C. to 85 ° C. in the same manner as in Example 1 for the vibrating gyroscope obtained in this example, no zero point temperature drift was observed.

  Thus, the vibration type gyroscope in the present embodiment can reduce the zero point temperature drift by adding weights to both ends of the support portion of the vibrator.

  The vibratory gyroscope in the third embodiment is different from the first embodiment in that a resin material is applied as a weight to the surface of the support portion of the vibrator, and the other is the same as the first embodiment. As shown in FIG. 6, the vibrating gyroscope in this embodiment is obtained by applying a resin material to the entire surface of the support portion 114 of the vibrator 110 to form a weight 141. The resin material was coated with an epoxy resin that is easy to handle and has excellent outgas properties after curing. The heating temperature of the epoxy resin was 150 ° C., and the heating time was 1 hour.

The thickness of the epoxy resin applied as the weight 141 is not particularly limited and can be appropriately set in consideration of the effect as the weight, but the same weight as that of the first embodiment is added to the support portion. In this embodiment, the thickness is set to about 10 μm. Moreover, the epoxy resin as the weight 141 can be applied to the entire surface or a part of the surface of the support portion 114, and the region to be applied can be appropriately set in consideration of the effect as the weight. In this embodiment, the weight 141 is formed on the entire surface of the support portion 114. When the value of the rotational angular velocity was measured from −40 ° C. to 85 ° C. in the same manner as in Example 1 for the vibrating gyroscope obtained in this example, no zero point temperature drift was observed.

  As described above, the vibration type gyroscope according to the present embodiment reduces the zero point temperature drift by forming the weight 141 by applying the resin material to the support portion 114 of the vibrator 110 to form the weight 141. Can do.

It is a top view which shows typically the vibration type gyroscope in Example 1 of this invention. It is sectional drawing which shows typically the A-A 'cross section in FIG. It is a graph which shows the rotational angular velocity of the vibrator | oscillator in a prior art. It is a graph which shows the rotational angular velocity of the vibrator | oscillator in Example 1 of this invention. It is sectional drawing which shows typically the vibration type gyroscope in Example 2 of this invention. It is sectional drawing which shows typically the vibration type gyroscope in Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Vibratory gyroscope 110 Vibrator 112 Excitation electrode 113 Floating electrode 114 Support part 120 Package 121 Package base 122 Package side electrode 123 External terminal 124 Cover 125 Solder material 130 Bonding wire 131, 141 Weight 140 Insulating adhesive layer S Inside space

Claims (6)

  A support portion of the vibrator piece is fixed to a mount portion in the package, and a first electrode formed on the support portion of the vibrator piece and a second electrode formed in the package are bonded to a bonding wire. A vibrator comprising: a vibrator, wherein a weight is added to a support portion of the vibrator element. The vibrator according to claim 1, wherein the weight is added in the vicinity of a connection portion of the bonding wire in the first electrode.   The vibrator according to claim 1, wherein the weight is added to both end portions of the support portion.   The vibrator according to any one of claims 1 to 3, wherein the weight is made of a metal material such as gold.   The vibrator according to claim 1, wherein the weight is a resin material applied to at least a part of a surface of the support portion. A vibratory gyroscope using the vibrator according to any one of claims 1 to 5.

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