JP2017015606A - Structure for suppressing mutual interference between surface acoustic wave resonators, and acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for suppressing mutual interference between surface acoustic wave resonators capable of sufficiently suppressing mutual interference with other surface acoustic wave resonators due to leak from the surface acoustic wave resonator by a simple method and structure, and avoiding generation of interference due to energy to be converted into bulk waves from surface acoustic waves for an acceleration sensor with the surface acoustic wave resonators arranged at a dead zone part and a plurality of detection parts.SOLUTION: A structure 10 a structure for suppressing mutual interference between surface acoustic wave resonators is a structure on a sensor element 1 which is constituted of a plurality of surface acoustic wave resonators 2, 3, etc. disposed on a piezoelectric substrate 9 for generating surface acoustic waves SAW, and which is an elevation structure provided between two surface acoustic wave resonators 3, 4. The piezoelectric substrate 9 is in a form comprising: a support part 9c at the center; weight parts 9a, 9a; and a beam part 9b connecting both. The support part 9c is provided with a reference surface acoustic wave resonator 3, while the beam part 9b is provided with the surface acoustic wave resonators 2, 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a structure for suppressing mutual interference between surface acoustic wave resonators and an acceleration sensor, and more particularly to mutual interference between surface acoustic wave resonators capable of improving the characteristics of an acceleration sensor having a multi-axis sensitivity detection function. The present invention relates to a suppression structure and the like.

  The acceleration sensor is a sensor that detects acceleration, and various information such as tilt, movement, vibration, and impact can be obtained by performing appropriate signal processing. In automobiles, it is used for systems such as airbags and skid control devices.

  For example, Patent Documents 1 and 2 listed below disclose acceleration sensors that use surface acoustic waves, and change the SAW propagation speed by the tensile / compressive stress generated by the bending of the surface acoustic wave resonator forming portion to oscillate. An acceleration sensor that detects a change in frequency is disclosed.

  However, in the conventional technique, it is necessary to load a weight in order to increase the amount of bending, and complicated manufacturing technology and equipment are necessary for multi-axis detection. In particular, the latter of the above documents has a difficulty in increasing the sensitivity, and also has a difficulty in reducing the size of the element and the circuit.

  Therefore, in order to solve these problems, the inventor of the present application has a surface acoustic wave type having a structure having two weight portions and one support portion, or one weight portion and two support portions, and a beam connecting them. An acceleration sensor having at least two surface acoustic wave resonators on the surface of at least two beams was invented and a patent application was filed (Patent Document 3). According to the invention, multi-axis detection can be performed with a high sensitivity by using a simple element structure and only one element without requiring complicated manufacturing technology and equipment. In addition, the elements and circuits can be reduced in size.

JP 2009-243983 A "surface acoustic wave sensor and surface acoustic wave sensor element" JP 2009-243981 A “Surface Acoustic Wave Sensor” Japanese Patent Application No. 2011-189707 “Surface Acoustic Wave Acceleration Sensor and Sensor Element Base” Japanese Patent Laid-Open No. 9-321574 “Surface Acoustic Wave Device” (Japanese Patent No. 3239064)

  Now, in the surface acoustic wave type acceleration sensor, in order to detect multi-axis acceleration, it is necessary to arrange a plurality of detection units on the sensor element, and the acceleration in each axis direction using the information of the plurality of detection units. 1 axis, 2 axis and 3 axis acceleration are detected. When a plurality of surface acoustic wave resonators are arranged on a sensor element as in the configuration of the above-mentioned already-applied invention (Patent Document 3), there is a possibility that correct information cannot be obtained due to the influence of mutual interference.

  FIG. 8 is a perspective explanatory view showing an example of the sensor element structure of the surface acoustic wave type acceleration sensor of the invention of the already filed application. FIG. 9 is a cross-sectional explanatory view showing a surface acoustic wave propagation state in the sensor shown in FIG. As shown in these figures, according to the inventions already filed, the sensor element 81 is composed of the piezoelectric substrate 89 for generating the surface acoustic wave SAW, and the thickness of the central support portion 89c and the weight portions 89a and 89a and the plate thickness connecting them is shown. Is a simple structure composed of a thin beam portion 89b. The configuration example of the sensor element structure is not limited to that illustrated, but the illustrated example is an acceleration in which the reference surface acoustic wave resonator 83 is provided in the support portion 89c and the surface acoustic wave resonators 82 and 84 are provided in the beam portion 89b. It is a sensor.

  However, when a plurality of surface acoustic wave resonators 82, 83, etc. are arranged on the same piezoelectric substrate 89 as described above, the surface acoustic wave excited from the surface acoustic wave resonator 83, for example, as shown in FIG. The SAW propagates on the surface of the piezoelectric substrate 89 and interacts with other surface acoustic wave resonators 84.

  Therefore, conventionally, in order to suppress mutual interference between the plurality of surface acoustic wave resonators 82, 83, etc., a ground electrode is provided between the surface acoustic wave resonators so as to function as a shield for direct waves between the input and output terminals. ing. Alternatively, there is a case where a surface acoustic wave absorber (sound absorbing material) is applied to both ends in the long side direction (surface wave propagation direction) of the surface acoustic wave resonator to suppress unnecessary reflected waves.

  However, in the method of providing the ground electrode, interference due to energy converted from the surface acoustic wave to the bulk wave occurs. On the other hand, in order to adopt a method of applying a surface acoustic wave absorber (sound absorbing material), appropriate manufacturing technology and equipment are required, and management of the sound absorbing material is also required. There is a need for a technique that can sufficiently suppress mutual interference between surface acoustic wave resonators by a simpler method and configuration, and can avoid interference due to energy converted from surface acoustic waves to bulk waves.

  Therefore, the problem to be solved by the present invention is based on the problems of the prior art, and other acceleration sensors in which surface acoustic wave resonators are arranged in the dead zone portion and the plurality of detection portions are caused by leakage from the surface acoustic wave resonator. Interference with surface acoustic wave resonators can be sufficiently suppressed by a simple method and configuration, and interference due to energy converted from surface acoustic waves to bulk waves can also be avoided. It is to provide a mutual interference suppression structure between surface wave resonators.

  As a result of studying the above problems, the present inventor has realized an acceleration sensor having a highly accurate acceleration detection function by suppressing mutual interference between a plurality of surface acoustic wave resonators by performing Au wire connection and Au bump bonding. Has been found to be possible, and based on this, the present invention has been completed. That is, the invention claimed in the present application, or at least the disclosed invention, as means for solving the above-described problems is as follows.

[1] A structure for suppressing mutual interference between resonators in an acceleration sensor having a plurality of surface acoustic wave resonators, and one or a plurality of raised structures provided between two surface acoustic wave resonators A structure for suppressing mutual interference between surface acoustic wave resonators, characterized in that:
[2] The mutual interference suppression structure between surface acoustic wave resonators according to [1], wherein the raised structure is any one of gold (Au), copper (Cu), and aluminum (Al).

[3] The mutual interference suppression structure between surface acoustic wave resonators according to [1] or [2], wherein the raised structure includes at least a wire-connected bump.
[4] The mutual interference suppression structure between surface acoustic wave resonators according to [1] or [2], wherein the raised structure includes at least a single bump.
[5] An acceleration sensor using the mutual interference suppression structure between surface acoustic wave resonators according to any one of [1] to [4].

  Since the mutual interference suppression structure between the surface acoustic wave resonators and the acceleration sensor of the present invention are configured as described above, according to these, the acceleration in which the surface acoustic wave resonators are arranged in the dead zone portion and the plurality of detection portions. For sensors, mutual interference with other surface acoustic wave resonators due to leakage from surface acoustic wave resonators can be sufficiently suppressed by a simple method and configuration, and converted from surface acoustic waves to bulk waves. Generation of interference due to energy can also be avoided. Thereby, it can be set as the acceleration sensor which has a highly accurate acceleration detection function.

  Further, in the present invention, one or more wire connections such as Au and one or more bumps are bonded between a plurality of surface acoustic wave resonators arranged on the sensor element, which is unnecessary while serving as an external connection. A surface acoustic wave can be attenuated. This leads to obtaining the desired effect with less bonding.

  The technique disclosed in Patent Document 4 is input by making the number of pairs of comb electrodes asymmetric with respect to the center comb electrode in a dual mode filter in which a plurality of SAW filters are cascade-connected on a piezoelectric substrate. This is a SAW filter in which impedance and output impedance can be set independently, and there is a reference to mutual interference. However, the mutual interference here relates to interference due to electrical capacitive coupling between the surface acoustic wave resonator (comb electrode) and the ground electrode (GND), and is due to physical surface acoustic waves (vibration energy). The present invention, which aims to suppress mutual interference, is different from both the problem and the solution.

It is a perspective view which shows one Example of the mutual interference suppression structure between the surface acoustic wave resonators of this invention. It is principal part sectional drawing of FIG. It is side sectional drawing which shows the Example of this invention mutual interference suppression structure using only a bump. It is a perspective view which shows the Example of this invention mutual interference suppression structure using a wire connection. It is principal part sectional drawing of FIG. It is a perspective view which shows the Example of this invention mutual interference suppression structure which uses a wire connection and a single bump together. It is principal part sectional drawing of FIG. It is perspective explanatory drawing which shows the example of the sensor element structure of the surface acoustic wave type | mold acceleration sensor of the already applied invention. FIG. 9 is a cross-sectional view illustrating a surface acoustic wave propagation state in the sensor illustrated in FIG. 8.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing an embodiment of a structure for suppressing mutual interference between surface acoustic wave resonators of the present invention. FIG. 2 is a sectional side view of the main part of FIG. As shown in these figures, a mutual interference suppression structure (hereinafter also simply referred to as “mutual interference suppression structure”) 10 between the surface acoustic wave resonators is provided on a piezoelectric substrate 9 for generating a surface acoustic wave SAW. A structure on the sensor element 1 of the acceleration sensor, which includes the surface acoustic wave resonators 2 and 3, and one or a plurality of the surface acoustic wave resonators 3 and 4 provided between the surface acoustic wave resonators 3 and 4. The main structure is a raised structure.

  In the illustrated example, as in the prior art shown in FIG. 8, the piezoelectric substrate 9 is formed of a central support portion 9c, weight portions 9a and 9a, and a beam portion 9b having a thin plate thickness for connecting both. The acceleration sensor is provided with the reference surface acoustic wave resonator 3 on the support portion 9c and the surface acoustic wave resonators 2 and 4 on the beam portion 9b. Although not limited to such a form, the acceleration sensor / sensor element of the present invention also has a structure including a support portion, a weight portion, and a beam portion having a thin plate thickness for connecting both.

  With this configuration, according to the mutual interference suppressing structure 10, the surface acoustic wave SAW excited from the surface acoustic wave resonator 3 is physically attenuated when passing through the mutual interference suppressing structure 10, and other surface acoustic waves are obtained. Mutual interference with the resonator 4 is eliminated. In this way, mutual interference between resonators can be suppressed.

  The specific material or the like of the raised structure forming the mutual interference suppressing structure 10 is not particularly limited as long as it has a characteristic of physically attenuating the passing surface acoustic wave SAW. For example, gold (Au) is particularly effective, but copper (Cu) and aluminum (Al) can also be suitably used for the mutual interference suppression structure 10.

  FIG. 3 is a side sectional view showing an embodiment of the mutual interference suppressing structure of the present invention using only bumps. As shown in the drawing, as the raised structure constituting the mutual interference suppressing structure 310, a single bump can be used. Further, specific materials and the like are as described above. The surface acoustic wave SAW excited from one surface acoustic wave resonator is physically attenuated when passing through the mutual interference suppressing structure 310, that is, the bump, and does not interfere with another surface acoustic wave resonator. .

  One or more bumps may be used alone to form a mutual interference suppression structure, or one or more bumps may be used in combination with one or more wire connections to form a mutual interference suppression structure.

  FIG. 4 is a perspective view showing an embodiment of the mutual interference suppressing structure of the present invention using wire connection. FIG. 5 is a sectional side view of the main part of FIG. As shown in the figure, bumps of the wire connection 46 can be used as the raised structure forming the mutual interference suppressing structure 410. Further, specific materials and the like are as described above. The surface acoustic wave SAW excited from one surface acoustic wave resonator 43 or the like is physically attenuated when passing through the mutual interference suppressing structure 410, that is, the bump of the wire connection 46, and the other surface acoustic wave resonator 42. And the like will not interfere with each other.

  One or a plurality of wire connections may be used alone to form a mutual interference suppression structure, or one or a plurality of bumps may be used in combination with one or a plurality of bumps to form a mutual interference suppression structure.

  In a surface acoustic wave type acceleration sensor that detects multi-axis acceleration, one or a plurality of wire connections 46 made of Au or the like are bonded between a plurality of surface acoustic wave resonators 42, 43, etc. arranged on a sensor element 41, thereby Unnecessary surface acoustic waves can be attenuated by the bumps forming the mutual interference suppressing structure 410 while serving as a connection.

  FIG. 6 is a perspective view showing an embodiment of the mutual interference suppressing structure of the present invention using both wire connection and a single bump. FIG. 7 is a sectional side view of the main part of FIG. As shown in the figure, as the raised structure constituting the mutual interference suppressing structure 710, both the bump (510) of the wire connection 56 and the single bump (610) can be used together. Here, it can be understood that the bumps of the wire connection 56 and the single bumps constituting the mutual interference suppression structure 710 are also the mutual interference suppression structures 510 and 610, respectively. Further, specific materials and the like are as described above.

  With this configuration, in the present embodiment, the surface acoustic wave SAW excited from one surface acoustic wave resonator 53 or the like has the mutual interference suppression structure 710, that is, the bump (mutual interference suppression structure 510) of the wire connection 56 and the single When each of the bumps (mutual interference suppression structure 610) passes through, it receives a physical damping action and does not interfere with other surface acoustic wave resonators 54 and the like. In this example, since there are two places where physical damping action is performed, it can be said that the damping action is larger than the embodiment described with reference to FIGS.

  The number of wire connections used and the number of individual bumps are not limited. As described above, the mutual interference suppressing structure of the present invention may be any pattern of only wire connection, only bump, and wire connection + bump. Further, the acceleration sensor itself using the mutual interference suppression structure between the surface acoustic wave resonators is also within the scope of the present invention.

  According to the structure for suppressing mutual interference between surface acoustic wave resonators and an acceleration sensor according to the present invention, leakage from the surface acoustic wave resonator is detected with respect to the acceleration sensor in which the surface acoustic wave resonator is disposed in the dead zone and the plurality of detection portions. The mutual interference with other surface acoustic wave resonators can be sufficiently suppressed by a simple method and configuration. Therefore, the present invention is highly industrially applicable in this field and all related fields.

DESCRIPTION OF SYMBOLS 1, 41, 51 ... Sensor element 2, 4, 42, 44, 52, 54 ... Surface acoustic wave resonator 3, 43, 53 ... Reference surface acoustic wave resonator 9, 39, 49, 59 ... Piezoelectric substrate 9a ... Weight , 9b: Beam part, 9c: Support part 10, 310, 410, 510, 610, 710 ... Mutual interference suppression structure between surface acoustic wave resonators 46, 56 ... Wire connection 47, 57 ... Wire part 81 ... Sensor element 82, 84 ... surface acoustic wave resonator 83 ... reference surface acoustic wave resonator 89 ... piezoelectric substrate 89a ... weight portion 89b ... beam portion 89c ... support portion SAW ... surface acoustic wave

Claims (5)

It is a structure for suppressing mutual interference between resonators in an acceleration sensor having a plurality of surface acoustic wave resonators, and is one or a plurality of raised structures provided between two surface acoustic wave resonators A structure for suppressing mutual interference between surface acoustic wave resonators. 2. The structure for suppressing mutual interference between surface acoustic wave resonators according to claim 1, wherein the raised structure is any one of gold (Au), copper (Cu), and aluminum (Al). The mutual interference suppression structure between surface acoustic wave resonators according to claim 1, wherein at least a bump for wire connection is included as the raised structure. The mutual interference suppression structure between surface acoustic wave resonators according to claim 1, wherein at least a single bump is included as the raised structure. The acceleration sensor using the mutual interference suppression structure between the surface acoustic wave resonators in any one of Claims 1 thru | or 4.