JP2013167595A - Method of adjusting three-axis angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate adjustment of a vibration balance in a method of adjusting a three-axis angular velocity sensor comprising three axes perpendicular to each other as detection axes.SOLUTION: A three-axis angular velocity sensor comprises a sensor element 2 and a control circuit element 3 which are accommodated in a package 1. The sensor element 2 comprises four vibration pieces 9a to 9d arranged symmetrically around a center at a base part 8 and, making sets of vibration pieces that induce deflections of detection electrodes in which detection signals output according to detection axes are in phase, trims one of the sets of vibration pieces to adjust a mass balance of the detection axes.

Description

  The present invention relates to a method for adjusting a triaxial angular velocity sensor using three axes orthogonal to each other as detection axes.

  Normally, the angular velocity detection using the Coriolis force is, for example, when a tuning fork type sensor element is used, driven and vibrated in a symmetric direction within a vibration plane including a pair of vibrating pieces constituting the sensor element, and the angular velocity is detected. It is known that detection vibration is generated in a direction orthogonal to the vibration plane by application, and a deflection component due to the detection vibration is converted into an electric signal and output as an angular velocity signal.

  And in order to raise the detection accuracy of the angular velocity sensor using such a sensor element, it is necessary to raise the vibration precision in the drive vibration of a sensor element. That is, the sensor element is driven to vibrate in order to use the Coriolis force. However, since the vibration directions of the driving vibration and the detection vibration are orthogonal to each other, an angular velocity is applied unless the driving vibration is vibrated in the vibration plane. Even in the absence, vibration components other than the in-plane vibration component are output as unnecessary signals.

  For this reason, as a method for improving the vibration accuracy of the drive vibration, a method is used in which one vibration piece is partially trimmed to ensure a mass balance with the other vibration piece and to improve the vibration accuracy.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2002-243451 A

  However, in recent years, the development of a three-axis angular velocity sensor with three axes orthogonal to each other as detection axes has been underway, and a single detection is performed to detect the effect of Coriolis force on the vibration components by combining a large number of vibration pieces. If any of the vibrating bars is trimmed to adjust the mass balance with respect to the shaft, the mass balance of another detection shaft will be affected. Therefore, it is difficult to adjust the vibration accuracy of such a three-axis angular velocity sensor. It was.

  Therefore, the present invention solves such a problem and provides an adjustment method capable of easily adjusting the vibration accuracy in the triaxial angular velocity sensor.

  In order to achieve this object, the present invention provides a three-axis angular velocity sensor in which a sensor element and a control circuit element are housed in one package. The sensor element includes four vibrating pieces arranged symmetrically about the base. Then, a pair of vibrating pieces whose detection signals corresponding to the detection axes have the same phase is trimmed with respect to one set to adjust the mass balance with respect to each detection axis.

  By using this adjustment method, it is possible to easily adjust the vibration accuracy in the triaxial angular velocity sensor.

The exploded perspective view of the 3 axis angular velocity sensor concerning the present invention Top view of sensor elements constituting the triaxial angular velocity sensor Schematic diagram showing the detection principle for the angular velocity around the X axis in the sensor element Schematic showing the detection principle for the angular velocity around the Y axis in the sensor element Schematic showing the detection principle for the angular velocity around the Z-axis in the sensor element The figure which shows the trimming part of the sensor element Schematic diagram showing the trimming method of the sensor element

  Hereinafter, a three-axis angular velocity sensor according to an embodiment of the present invention will be described with reference to the drawings.

  The triaxial angular velocity sensor shown in FIG. 1 detects angular velocity using Coriolis force, and the basic structure thereof is a sensor element 2 for detecting angular velocity inside a package 1 having one end opening made of ceramics. The control circuit element 3 for controlling the sensor element 2 is arranged, and the opening of the package 1 is sealed with the upper lid 4. The sensor element 2 is configured to support the sensor element 2 so as to vibrate on the upper part of the control circuit element 3 by interposing a lower lid 5 on the upper surface of the control circuit element 3.

  Further, as shown in FIG. 2, the sensor element 2 has a pair of sides that are opposed to each other on the outer peripheral portion of the sensor element 2 and is supported between the connection portion 6 for external connection and the ends of the pair of connection portions 6. , A base portion 8 that connects the middle point portion of the support portion 7, and four vibrating pieces 9 a, 9 b, 9 c, and 9 d that extend symmetrically from the central portion of the base portion 8.

  The vibrating piece 9a is led out from the center of the base 8 in the positive direction of the X axis, led out in the negative direction of the Y axis at the first bent portion, and negative in the X axis at the second bent portion. Thus, the third bent portion is led out in the positive direction of the Y-axis to form a broad weight portion 10a.

  The vibrating piece 9b has a symmetrical structure with the vibrating piece 9a with the C axis parallel to the X axis passing through the center of the base 8 as the central axis, and is led out from the center of the base 8 in the positive direction of the X axis. Derived in the positive direction of the Y-axis at the bent portion, derived in the negative direction of the X-axis at the second bent portion, derived in the negative direction of the Y-axis at the third bent portion, and widened A weight portion 10b is formed.

  The vibration piece 9c has a symmetrical structure with the vibration piece 9a with the D axis parallel to the Y axis passing through the center of the base 8 as the central axis. The vibration piece 9c is led out from the center of the base 8 in the negative direction of the X axis. Derived in the negative direction of the Y-axis at the bent portion, derived in the positive direction of the X-axis at the second bent portion, derived in the positive direction of the Y-axis at the third bent portion, and widened A weight portion 10c is formed.

  The vibration piece 9d has a symmetric structure with respect to the vibration piece 9c with the C axis as the central axis, and the vibration piece 9b has a symmetric structure with the D axis as the central axis, and the negative direction of the X axis from the center of the base 8 Derived in the positive direction of the Y axis at the first bent portion, derived in the positive direction of the X axis at the second bent portion, and in the negative direction of the Y axis at the third bent portion. A weight portion 10d which is led out and becomes wide is formed.

  The sensor element 2 includes a drive electrode 11 for driving and vibrating the vibration pieces 9a to 9d, detection electrodes 12a to 12j for detecting bending caused by Coriolis force, an electrode pad 13, and wiring electrodes for appropriately connecting them. (Not shown) is provided. The drive electrode 11 and the detection electrodes 12a to 12j are not particularly shown, but have a laminated structure in which a piezoelectric layer made of PZT is sandwiched between an upper electrode made of Au and a lower electrode made of Pt, and the control circuit element 3 The control voltage is applied to the electrode, so that the electrode expands and contracts to excite the drive vibration, or the electrode is bent by the detection vibration caused by the Coriolis force to excite the detection signal.

  Next, detection of angular velocity by the sensor element 2 will be described. First, by applying a control signal having an opposite phase corresponding to the natural vibration frequency of the vibration pieces 9a to 9d from the control circuit element 3 to the pair of drive electrodes 11 provided in each of the vibration pieces 9a to 9d, Due to the reverse expansion and contraction action generated in the pair of drive electrodes 11, the weight portions 10a to 10d provided at the tips of the vibration pieces 9a to 9d are driven to vibrate in a direction spreading from the center as indicated by arrows.

  In this driving vibration state, when an angular velocity is applied around the X axis, as shown in FIG. 3, Coriolis force acts on the vibration component in the Y axis direction in the driving vibration indicated by the broken arrow. The weight portions 10a and 10c and the weight portions 10b and 10d vibrate in the Z-axis direction, and the base portion 8 bends in an S shape in the cross section along the D-axis in accordance with the detected vibration in the Z-axis direction. In response, detection signals having opposite phases are output from the detection electrodes 12 a and 12 b to the control circuit element 3. The detection signals output from the detection electrode 12a and the detection electrode 12b are in opposite phases because the deflection direction of the detection electrode 12a is linked to the vibration of the weight portions 10a and 10c, and the deflection direction of the detection electrode 12b is the weight. This is because the detection electrode 12a and the detection electrode 12b bend in the reverse direction in conjunction with the vibration of the portions 10b and 10d.

  When an angular velocity is applied around the Y axis, as shown in FIG. 4, Coriolis force acts on the vibration component in the X-axis direction in the drive vibration indicated by the dashed arrow, so that the weight portions 10a and 10b and the weight portion 10c. 10d reversely vibrates in the Z-axis direction, and the support portion 7 bends in an S-shape along the C-axis along with the detected vibration in the Z-axis direction, and the detection electrodes 12c and 12d are detected according to the amount of the deflection. Detection signals having opposite phases are output from the electrodes 12 e and 12 f to the control circuit element 3. The detection signals output from the detection electrodes 12c and 12d and the detection electrodes 12e and 12f are in opposite phases because the bending direction of the detection electrodes 12c and 12d is linked to the vibration of the weight portions 10a and 10b. This is because the detection directions of the detection electrodes 12c and 12d and the detection electrodes 12e and 12f are bent in the opposite directions because the bending directions of 12e and 12f are interlocked with the vibration of the weight portions 10c and 10d.

  When an angular velocity is applied around the Z axis, as shown in FIG. 5, Coriolis force acts on the drive vibration indicated by the dashed arrow, so that the weight portion 10a and the weight portion 10d are orthogonal to the vibration direction of the drive vibration. Reversely vibrate in the direction of rotation, and the weight part 10b and the weight part 10c vibrate in the direction orthogonal to the vibration direction of the drive vibration. Then, along with this detection vibration, the sides of the vibration pieces 9a to 9d provided with the detection electrodes 12g to 12j are bent in an arc shape, and the detection electrodes 12g and 12j and the detection electrodes 12h and 12i are in opposite phases according to the amount of the bending. A detection signal is output to the control circuit element 3. The detection signals of the detection electrodes 12g and 12j and the detection electrodes 12h and 12i are in opposite phases because the bending direction of the detection electrodes 12g and 12j is on the side where the weight portions 10a and 10d are provided, and the detection electrodes 12h and 12i This is because the bending direction is opposite to the side where the weight portions 10b and 10c are provided, and the detection electrodes 12g and 12j and the detection electrodes 2h and 12i are bent in the opposite directions. Each of the detection electrodes 12g to 12j is composed of a pair of electrodes similarly to the drive electrode 11, and the expansion and contraction states of the inner and outer electrodes are reversed with respect to the deflection in the parallel arrangement direction of the electrodes. The difference signal is used as a detection signal.

  Next, a method for manufacturing the triaxial angular velocity sensor will be described. The sensor element 2 is formed by batch molding at a wafer level in the same manner as in the semiconductor manufacturing process. Although not shown, the sensor element 2 is formed by sputtering on a sensor element wafer made of silicon. A predetermined electrode is formed and processed into a predetermined outer shape by dry etching. In the lower lid 5 as well, the lower lid wafer made of silicon is processed into a predetermined shape by dry etching. Then, the lower lid wafer and the sensor element wafer are bonded and fixed, and then divided into pieces by dicing, and integrated with the lower lid 5, and the sensor element 2 is mounted on the upper surface of the control circuit element 3 in the individual state. .

  In dry etching when the sensor element 2 is formed, it is difficult to secure a mass balance that satisfies the vibration accuracy required for the vibration pieces 9a to 9d of the sensor element 2 with the processing accuracy. However, it is important to adjust the mass balance after dry etching and ensure the vibration accuracy required for the vibrating bars 9a to 9d as described above.

  Therefore, a method for adjusting the mass balance will be described below. When detecting the angular velocity around the X axis, the sensor element 2 constituting the three-axis angular velocity sensor, as described with reference to FIG. 3, has the vibrating pieces 9a and 9c and the vibrating pieces 9b whose detection vibration directions coincide with each other. The vibration pieces of one set are trimmed according to the state of unnecessary signals, and the mass balance with the other piece of vibration pieces is adjusted.

  When detecting the angular velocity around the Y axis, as described with reference to FIG. 4, the vibration pieces 9a and 9b and the vibration pieces 9c and 9d having the same detected vibration direction are combined, and either one is selected depending on the state of the unnecessary signal. One set of vibrating pieces is trimmed to adjust the mass balance with the other set of vibrating pieces.

  When the angular velocity around the Z axis is detected, as described in FIG. 5, the detection electrodes 12g to 12j are divided into the vibration pieces 9a and 9d and the vibration pieces 9b and 9c that have the same deflection direction in the detection vibration. Depending on the state of the unnecessary signal, one set of vibrating pieces is trimmed to adjust the mass balance with the other set of vibrating pieces.

  As described above, the four vibrating pieces 9a to 9d are grouped for each vibrating piece that excites the bending of the detection electrode in which the detection signal output in accordance with the detection axis to be adjusted has the same phase. By performing trimming on the piece, it is possible to easily adjust the mass balance.

  Further, it is preferable that the portion to be trimmed differs depending on the detection axis to be adjusted, and it is preferable to trim the maximum displacement portion in the detection vibration corresponding to each detection axis.

  Specifically, when the X axis is the detection axis, the maximum displacement portion is, as shown in FIG. 6, the weight portions 10a, 10c and the weight portions 10b, 10d vibrate in the Z-axis direction. It becomes the area | region 14 enclosed with the broken line spaced apart in the Y-axis direction by the root part of 10d. When the Y axis is the detection axis, the maximum displacement portions are separated in the X-axis direction at the roots of the weight portions 10a to 10d because the weight portions 10a and 10b and the weight portions 10c and 10d vibrate in the Z-axis direction. It becomes the area | region 15 enclosed with the broken line. When the Z-axis is used as the detection axis, the maximum displacement portions are the weight portions 10a and 10d, and the weight portions 10b and 10c each vibrate in the vibration direction of the drive vibration. It becomes the area | region 16 enclosed with the broken line separated by the part.

  As described above, the regions 14 to 16 serving as the adjustment portions for the respective detection axes are different, which means that the change in mass balance due to the trimming in the respective adjustment regions has a small influence on the other detection axes.

  Further, the adjustment of the mass balance by trimming can shorten the time required for the adjustment by standardizing the adjustment amount in one trimming and controlling the adjustment amount of the mass balance by the number of trimmings. This is because the sensor element 2 formed at the wafer level has a similar external shape processing state in the vicinity area in the wafer, so that the adjustment in this approximate area can be made a common specification. This is because man-hours can be reduced. Specifically, in the case of trimming adjustment when the X axis is the detection axis, as shown in FIG. 7, the region 14 is divided into six, the number of trimmings is determined according to the degree of adjustment, and a similar adjustment range. If the same number of trimmings are performed and the same number of trimmings are performed, the labor of trimming while confirming individual mass balances can be saved.

  Further, when trimming is performed after the sensor element 2 is separated from the wafer, the surface of the sensor element 2 provided with the electrode pads 13 is measured with a measuring jig (particularly a figure) in order to check the mass balance of the element. (Not shown), the back surface side where the substrate surface is exposed can be trimmed.

  When trimming is performed in a state closer to a finished product, the surface of the sensor element 2 on which the drive electrode 11 and the detection electrodes 12a to 12j are provided is trimmed with the sensor element 2 mounted on the upper surface of the control circuit element 3. It is preferable to do.

  In general, a laser trimming machine is used for such trimming, but the surface to be trimmed is a surface on which the drive electrode 11 and the detection electrodes 12a to 12j are provided, and these electrodes are Au, Since the trimming wavelength for each layer is different in the laminated structure composed of PZT and Pt, it is necessary to prepare a laser trimming machine according to the trimming wavelength of each layer in order to trim the electrode, which is a very large process. End up.

  Therefore, as described above, an effective region for trimming can be specified in advance, and by setting this portion as a non-electrode forming portion where the substrate surface is exposed, it is only necessary to set the trimming wavelength in trimming adjustment to the substrate material. Can be simplified.

  The present invention has an effect that vibration balance can be easily adjusted in a triaxial angular velocity sensor, and is particularly used for electronic devices that require small and highly accurate characteristics such as digital cameras and car navigation systems. This is useful in an axial angular velocity sensor.

DESCRIPTION OF SYMBOLS 1 Package 2 Sensor element 3 Control circuit element 8 Base 9a-9d Vibrating piece 11 Drive electrode 12a-12j Detection electrode 14-16 Adjustment area

Claims (6)

An adjustment method of a triaxial angular velocity sensor that detects a deflection component due to a Coriolis force generated by an angular velocity applied around the detection axis, with the X axis, the Y axis, and the Z axis orthogonal to each other as detection axes. The sensor includes a sensor element, a control circuit element that controls the sensor element, and a package that accommodates the sensor element. The sensor element includes a base and a first that is arranged in parallel in the Y-axis direction with respect to the base. A second vibrating piece, a third vibrating piece arranged symmetrically with the first vibrating piece in the X-axis direction with respect to the base, and the second vibrating piece and the X-axis direction with respect to the base And a fourth vibration piece symmetrically arranged, and the detected vibration with respect to the angular velocity with the X axis as the detection axis is the Z-axis of the first and third vibration pieces and the second and fourth vibration pieces. An angle that vibrates in the opposite direction in the direction and uses the Y axis as the detection axis The first and second vibrating bars and the third and fourth vibrating bars vibrate in the opposite directions in the Z-axis direction, and the detected vibration with respect to the angular velocity with the Z-axis serving as a detection axis. The first and third vibrating bars and the second and fourth vibrating bars vibrate in opposite directions in a direction orthogonal to the vibration direction of the driving vibration, and adjustment of the detected vibration with respect to the angular velocity using the X axis as the detection axis When the first vibration piece and the third vibration piece, or the second vibration piece and the fourth vibration piece are paired, trimming is performed on the one pair to detect the detected vibration. When adjusting the vibration balance and adjusting the detected vibration with respect to the angular velocity with the Y axis as the detection axis, the first vibrating piece and the second vibrating piece, or the third vibrating piece and the fourth As a pair, the vibration piece In adjusting the vibration balance of the detected vibration by adjusting the detected vibration with respect to the angular velocity with the Z axis as the detection axis, the first vibration piece and the fourth vibration piece or the second vibration piece are adjusted. And adjusting the vibration balance of the detected vibration by trimming the one piece and the third piece, and adjusting the vibration balance of the three-axis angular velocity sensor. The method for adjusting a triaxial angular velocity sensor according to claim 1, wherein the adjustment of the vibration balance is performed by trimming a maximum displacement portion of each vibration piece in the detected vibration. 2. The method of adjusting a triaxial angular velocity sensor according to claim 1, wherein an adjustment amount in one trimming is standardized, and an adjustment amount of vibration balance is controlled by the number of trimmings. 2. The method for adjusting a triaxial angular velocity sensor according to claim 1, wherein a drive electrode and a detection electrode are provided on the surface of each vibration piece, and trimming is performed on the back surface of the vibration piece. The method for adjusting a triaxial angular velocity sensor according to claim 1, wherein a drive electrode and a detection electrode are provided on a surface of each vibrating piece, and trimming is performed on the surface of the vibrating piece. 6. The method for adjusting a triaxial angular velocity sensor according to claim 5, wherein an adjustment region is previously defined for each vibrating piece, and the adjustment region is used as a non-electrode forming portion.

Images