Patent Publication Number: US-2017363654-A1

Title: Acceleration detection device and manufacturing method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2015-049860 filed on Mar. 12, 2015 and is a Continuation application of PCT Application No. PCT/JP2015/079456 filed on Oct. 19, 2015. The entire contents of each application are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an acceleration detection device fixed to a package member, and to a method of manufacturing such a device. 
     2. Description of the Related Art 
     Japanese Patent No. 4190208 discloses an example of an acceleration detection device. In this acceleration detection device, a piezoelectric element is supported by being enclosed in a support frame. 
     Also, in an acceleration detection device disclosed in Japanese Patent No. 3183177, a piezoelectric element is supported by being enclosed in a case member. 
     In Japanese Unexamined Patent Application Publication No. 2001-074768, a piezoelectric element is fixed to a base member using an instant adhesive and a conductive adhesive. 
     In Japanese Unexamined Patent Application Publication No. 7-202283, a piezoelectric element is enclosed in an element attachment portion of a case member. Furthermore, the piezoelectric element is fixed using a conductive adhesive and an insulative adhesive. 
     In the acceleration detection devices according to Japanese Patent No. 4190208 and Japanese Patent No. 3183177, the piezoelectric element is supported strongly by being directly enclosed in the support frame or the case member. Accordingly, the acceleration detection device is susceptible to the effects of noise produced by the support frame, the case member, or other bending. 
     In the acceleration detection device according to Japanese Unexamined Patent Application Publication No. 2001-074768, the effects of gravity on the piezoelectric element before the instant adhesive and the conductive adhesive solidify makes it easy for the position and holding angle of the piezoelectric element to shift. Furthermore, the instant adhesive and the conductive adhesive expand or shrink significantly during solidification. This also makes it easy for the position and holding angle of the piezoelectric element to shift. 
     Also, in the acceleration detection device according to Japanese Unexamined Patent Application Publication No. 7-202283, expansion or shrinkage when the conductive adhesive and the insulative adhesive solidify makes it easy for the position and holding angle of the piezoelectric element to shift. Furthermore, the piezoelectric element is enclosed by the element attachment portion, and thus, the acceleration detection device is susceptible to the effects of noise produced by the case member or other bending. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention provide acceleration detection devices in which a position and a holding angle of a piezoelectric element do not easily shift and the devices are not susceptible to the effects of noise, and also provide methods of manufacturing such a device. 
     An acceleration detection device according to a preferred embodiment of the present invention includes a piezoelectric element including a top surface and a bottom surface; a sheet-shaped adhesive provided on the bottom surface of the piezoelectric element; and a first package member to which the piezoelectric element is bonded by the sheet-shaped adhesive. 
     In an acceleration detection device according to a preferred embodiment of the present invention, the piezoelectric element includes a piezoelectric member and first and second electrodes provided on the piezoelectric member; and the piezoelectric member includes a top surface, a bottom surface, a first side surface, and a second side surface opposing the first side surface. In this case, it is easy to make an electrical connection with the exterior. 
     In an acceleration detection device according to a preferred embodiment of the present invention, the first electrode is provided on the first side surface of the piezoelectric member, and the second electrode is provided on the second side surface of the piezoelectric member. In this case, it is easy to make an electrical connection with the exterior. 
     In an acceleration detection device according to a preferred embodiment of the present invention, the first electrode is provided on the bottom surface of the piezoelectric member, and the second electrode is provided on the top surface of the piezoelectric member. In this case, it is easy to make an electrical connection with the exterior. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the piezoelectric element preferably includes a first extended electrode, connected to the first electrode and provided on the first side surface of the piezoelectric member, and a second extended electrode, connected to the second electrode and provided on the second side surface of the piezoelectric member. In this case, it is easy to make an electrical connection with the exterior. 
     In an acceleration detection device according to another preferred embodiment of the present invention, a top surface and a bottom surface of a piezoelectric element extend in a longitudinal direction, and the piezoelectric element is fixed by the sheet-shaped adhesive such that the piezoelectric element includes a free end in at least one location. In this case, it is even more difficult for the position and holding angle of the piezoelectric element to shift, and the piezoelectric element is even less susceptible to the effects of noise. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the piezoelectric element is supported in a cantilever state by the sheet-shaped adhesive. In this case, it is even more difficult for the position and holding angle of the piezoelectric element to shift, and the piezoelectric element is even less susceptible to the effects of noise. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the sheet-shaped adhesive extends into one end portion of the piezoelectric element in the longitudinal direction of the piezoelectric element. In this case, the sensitivity is able to be effectively increased. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the acceleration detection device preferably further includes first and second inner electrodes that are provided within the piezoelectric element and that oppose each other. In this case, the electrostatic capacitance is high. This also makes it possible to effectively increase the sensitivity. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the sheet-shaped adhesive is made of an insulative material. In this case, the first electrode and the second electrode are able to be reliably electrically insulated from each other. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the acceleration detection device further includes a second package member bonded to the first package member, and the piezoelectric element is sealed by the first and second package members. In this case, the strength is able to be increased, and the device is not susceptible to the effects of noise from the exterior. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the first package member has a flat plate shape and the second package member has a cap shape. In this case, the strength is able to be increased, and the device is not susceptible to the effects of noise from the exterior. 
     In an acceleration detection device according to another preferred embodiment of the present invention, the first package member includes a recess, and the piezoelectric element is disposed within the recess and the second package member is provided to cover the recess so as to seal the piezoelectric element. In this case, the strength is able to be increased, and the device is not susceptible to the effects of noise from the exterior. 
     A method of manufacturing an acceleration detection device according to a preferred embodiment of the present invention includes preparing a piezoelectric element; affixing a sheet-shaped adhesive to a bottom surface of the piezoelectric element; and bonding the piezoelectric element to a first package member using the sheet-shaped adhesive. In this case, it is possible to obtain an acceleration detection device in which it is even more difficult for the position and holding angle of the piezoelectric element to shift, and the piezoelectric element is even less susceptible to the effects of noise. 
     According to various preferred embodiments of the present invention, acceleration detection devices in which the position and holding angle of a piezoelectric element do not easily shift and that are not susceptible to the effects of noise, as well as methods of manufacturing such devices, are provided. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a plan view of an acceleration detection device according to a first preferred embodiment of the present invention, illustrating the acceleration detection device without a second package member;  FIG. 1B  is a diagram illustrating the acceleration detection device, without the second package member, from the side of a first side surface of a piezoelectric member, according to the first preferred embodiment of the present invention;  FIG. 1C  is a diagram illustrating the acceleration detection device, without the second package member, from the side of a second side surface of the piezoelectric member, according to the first preferred embodiment of the present invention; and  FIG. 1D  is a cross-sectional view of the acceleration detection device, without the second package member, viewed along a line A-A in  FIG. 1A . 
         FIG. 2A  is a perspective view of the acceleration detection device according to the first preferred embodiment of the present invention, and  FIG. 2B  is an exploded perspective view of the acceleration detection device according to the first preferred embodiment of the present invention. 
         FIG. 3A  to  FIG. 3D  are perspective views illustrating an example of a method of manufacturing the acceleration detection device according to the first preferred embodiment of the present invention. 
         FIG. 4  is a plan view of an acceleration detection device according to a first variation of the first preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member. 
         FIG. 5A  is a plan view of an acceleration detection device according to a second variation of the first preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member; and  FIG. 5B  is a cross-sectional view of the acceleration detection device viewed along a line B-B in  FIG. 5A , illustrating the acceleration detection device without the second package member. 
         FIG. 6A  is a plan view of an acceleration detection device according to a third variation of the first preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member; and  FIG. 6B  is a cross-sectional view of the acceleration detection device viewed along a line C-C in  FIG. 6A , illustrating the acceleration detection device without the second package member. 
         FIG. 7A  is a plan view of an acceleration detection device according to a fourth variation of the first preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member; and  FIG. 7B  is a diagram illustrating the acceleration detection device, without the second package member, from the side of the second side surface of the piezoelectric member, according to the first preferred embodiment of the present invention. 
         FIG. 8  is a plan view of an acceleration detection device according to a fifth variation of the first preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member. 
         FIG. 9A  is a plan view of an acceleration detection device according to a second preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member;  FIG. 9B  is a diagram illustrating the acceleration detection device, without the second package member, from the side of the first side surface of the piezoelectric member, according to the second preferred embodiment of the present invention; and  FIG. 9C  is a diagram illustrating the acceleration detection device, without the second package member, from the side of the second side surface of the piezoelectric member, according to the second preferred embodiment of the present invention. 
         FIG. 10  is a plan view of an acceleration detection device according to a first variation of the second preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member. 
         FIG. 11A  is a plan view of an acceleration detection device according to a third preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member;  FIG. 11B  is a diagram illustrating the acceleration detection device, without the second package member, from the side of the first side surface of the piezoelectric member, according to the third preferred embodiment of the present invention;  FIG. 11C  is a diagram illustrating the acceleration detection device, without the second package member, from the side of the second side surface of the piezoelectric member, according to the third preferred embodiment of the present invention; and  FIG. 11D  is a cross-sectional view of the acceleration detection device, without the second package member, viewed along a line D-D in  FIG. 11A . 
         FIG. 12A  is a plan view of an acceleration detection device according to a sixth variation of the first preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member; and  FIG. 12B  is a cross-sectional view of the acceleration detection device viewed along a line E-E in  FIG. 12A , illustrating the acceleration detection device without the second package member. 
         FIG. 13A  is a plan view of an acceleration detection device according to a first variation of the third preferred embodiment of the present invention;  FIG. 13B  is a plan view of the acceleration detection device according to the eighth variation, without the second package member; and  FIG. 13C  is a diagram illustrating the acceleration detection device from the side of the first side surface of the piezoelectric member according to the eighth variation, without the second package member. 
         FIG. 14  is a schematic plan view of an electrode structure on a bottom surface of a first package member according to the first variation of the third preferred embodiment of the present invention. 
         FIG. 15  is a plan view of an acceleration detection device according to a second variation of the third preferred embodiment of the present invention, illustrating the acceleration detection device without the second package member. 
         FIG. 16  is a side cross-sectional view of an acceleration detection device according to a fourth preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described with reference to specific preferred embodiments of the present invention and to the drawings. 
     Note that the various preferred embodiments disclosed in the present specification are merely examples, and it is to be understood that partial replacements or combinations of configurations among different preferred embodiments are also possible. 
       FIG. 1A  is a plan view of an acceleration detection device according to a first preferred embodiment of the present invention.  FIG. 1B  is a diagram illustrating the acceleration detection device from the side of a first side surface of a piezoelectric member, according to the first preferred embodiment.  FIG. 1C  is a diagram illustrating the acceleration detection device from the side of a second side surface of the piezoelectric member, according to the first preferred embodiment.  FIG. 1D  is a cross-sectional view of the acceleration detection device, viewed along the line A-A in  FIG. 1A . Note that a second package member, which will be described later, is not illustrated in  FIGS. 1A to 1D . 
     As illustrated in  FIG. 1A , an acceleration detection device  1  includes a first package member  3 . The first package member  3  has a flat plate shape. Although not particularly limited, the first package member  3  may preferably be made of glass epoxy resin, for example. The first package member  3  may instead be made of a suitable ceramic material. 
     First and second wires  5   a  and  5   b  are provided on the first package member  3 . Furthermore, a sheet-shaped adhesive  4  is provided on the first package member  3 . As illustrated in FIGS.  1 B and  1 C, a piezoelectric element  2  is bonded to the first package member  3  by the sheet-shaped adhesive  4 . The sheet-shaped adhesive is preferably made of an insulative material, such as epoxy resin, for example. Note that the material of the sheet-shaped adhesive  4  is not particularly limited. 
     As illustrated in  FIGS. 1A and 1D , the piezoelectric element  2  includes a piezoelectric member  2 A and first and second electrodes  6   a  and  6   b . The piezoelectric member  2 A preferably has a rectangular or substantially rectangular parallelepiped shape with a longitudinal direction. The piezoelectric member  2 A includes a bottom surface  2 Aa and a top surface  2 Ab extending in the longitudinal direction. Furthermore, the piezoelectric member  2 A includes a first side surface  2 Ac extending in the longitudinal direction and a second side surface  2 Ad opposing the first side surface  2 Ac. The piezoelectric member  2 A is preferably made of a piezoelectric single-crystal, piezoelectric ceramics, or other suitable piezoelectric materials, for example. In the present preferred embodiment, the piezoelectric member  2 A is preferably a single-layer piezoelectric member. Note that the piezoelectric element  2  may include a plurality of piezoelectric member layers. 
     The first electrode  6   a  is provided on the first side surface  2 Ac of the piezoelectric member  2 A. The second electrode  6   b  is provided on the second side surface  2 Ad of the piezoelectric member  2 A. 
     The piezoelectric element  2  is bonded onto the first package member  3  using the sheet-shaped adhesive  4 , which is provided on the bottom surface  2 Aa of the piezoelectric element  2 . In other words, the piezoelectric element  2  is bonded onto the first package member  3  from the bottom surface  2 Aa side of the piezoelectric member  2 A. 
     As illustrated in  FIGS. 1A and 1B , the piezoelectric element  2  includes a first end portion  2   e  corresponding to one end portion in the longitudinal direction. The piezoelectric element  2  also includes a second end portion  2   f  opposing the first end portion  2   e . The piezoelectric element  2  is supported in a cantilever state on the first end portion  2   e  side by the sheet-shaped adhesive  4 . The second end portion  2   f  corresponds to a free end of the piezoelectric element  2 . The sheet-shaped adhesive  4  extends to the first end portion  2   e . However, the sheet-shaped adhesive  4  need not extend to the first end portion  2   e.    
     As illustrated in  FIGS. 1A and 1D , the first electrode  6   a  is electrically connected to a first wire  5   a  by a conductive adhesive  7   a . The second electrode  6   b  is also electrically connected to a second wire  5   b  by a conductive adhesive  7   b . As a result, the piezoelectric element  2  is electrically connected to the exterior. 
     The conductive adhesives  7   a  and  7   b  are provided in positions overlapping with the sheet-shaped adhesive  4  when viewed in plan view from the top surface  2 Ab side of the piezoelectric element  2 . Note that the positions where the first and second electrodes  6   a  and  6   b  are connected to the first and second wires  5   a  and  5   b  by the conductive adhesives  7   a  and  7   b  are not particularly limited. The conductive adhesives  7   a  and  7   b  are not particularly limited, and a Si-based adhesive containing a conductor may preferably be used, for example. 
     As illustrated in  FIGS. 1A to 1D , the longitudinal direction of the piezoelectric element  2  is taken as an x direction. A direction perpendicular or substantially perpendicular to the longitudinal direction of the piezoelectric element  2  is taken as a y direction. A direction perpendicular or substantially perpendicular to an x-y plane is taken as a z direction. Here, the surface of the first package member  3  to which the piezoelectric element  2  is bonded is parallel or substantially parallel to the x-y plane. The first and second electrodes  6   a  and  6   b  oppose each other with respect to the y direction. In other words, a main axis direction of the acceleration detection device  1  is 0 0  or approximately 0 0  relative to the x-y plane. 
       FIG. 2A  is a perspective view of the acceleration detection device according to the first preferred embodiment of the present invention.  FIG. 2B  is an exploded perspective view of the acceleration detection device according to the first preferred embodiment. 
     As illustrated in  FIG. 2A , the acceleration detection device  1  includes a second package member  8  bonded on top of the first package member  3 . The second package member  8  preferably has a cap shape. As illustrated in  FIGS. 2A and 2B , the piezoelectric element  2  is sealed by the first package member  3  and the second package member  8 . 
     The acceleration detection device  1  does not absolutely require the second package member  8 . However, it is preferable that the piezoelectric element  2  be sealed by the first package member  3  and the second package member  8 . Doing so increases the strength of the acceleration detection device  1  and makes the acceleration detection device  1  less susceptible to the effects of mechanical noise from the exterior. Additionally, making the second package member from a metal and setting a potential thereof to a ground potential makes the acceleration detection device  1  less susceptible to the effects of electromagnetic noise. Note that the material of the second package member  8  is not particularly limited, and may preferably be a ceramic material, for example. 
     One of the unique characteristics of the acceleration detection device  1  according to the present preferred embodiment is that the piezoelectric element  2  is bonded to the first package member  3  using the sheet-shaped adhesive  4 . As a result, in the acceleration detection device  1 , the position and holding angle of the piezoelectric element do not easily shift, and the element is not susceptible to the effects of noise. This will be described hereinafter. 
     Conventionally, in an acceleration detection device in which the piezoelectric element is supported by an adhesive, the piezoelectric element is not fully fixed before the adhesive is solidified. It has thus been easy for the holding angle of the piezoelectric element to shift due to the effects of gravity and other forces. Furthermore, the adhesive expands or shrinks when the adhesive solidifies, and the holding angle and position of the piezoelectric element are likely to shift as a result. 
     Alternatively, in the case where the piezoelectric element is held by being enclosed in a case member or a support member, vibrations and other forces have been transmitted easily from the case member or support member to the piezoelectric element. The devices have therefore been susceptible to the effects of noise produced by the case member or support member bending or other otherwise deforming. 
     As opposed to this, according to the present preferred embodiment, the piezoelectric element  2  is supported by the sheet-shaped adhesive  4 , as illustrated in  FIGS. 1A to 1D . The sheet-shaped adhesive  4  supports the piezoelectric element  2  with its surface. The attitude of the piezoelectric element  2  is thus able to be stabilized. Accordingly, shifting in the holding angle is effectively reduced or prevented. 
     The piezoelectric element  2  is bonded onto the first package member  3  using the sheet-shaped adhesive  4 . Accordingly, the piezoelectric element  2  does not make direct contact with the first package member  3 . Furthermore, the piezoelectric element  2  is supported at one location by the sheet-shaped adhesive  4 . As such, the device is not susceptible to the effects of noise caused by bending or other deformation in the first package member  3 . 
     As described above, the first and second electrodes  6   a  and  6   b  are provided on the first and second side surfaces  2 Ac and  2 Ad of the piezoelectric member  2 A. The first and second electrodes  6   a  and  6   b  are electrically connected to the first and second wires  5   a  and  5   b  by the conductive adhesives  7   a  and  7   b . Here, the conductive adhesives  7   a  and  7   b  are provided to electrically connect the first and second electrodes  6   a  and  6   b  and the first and second wires  5   a  and  5   b , but do not provide a strong physical connection. In other words, the conductive adhesives  7   a  and  7   b  provide almost no support for the piezoelectric element  2 . As such, the effects of noise caused by bending or other deformation in the first package member  3  are effectively reduced or prevented. 
     The piezoelectric element  2  is supported in a cantilever state. The sheet-shaped adhesive  4  extends to the first end portion  2   e  of the piezoelectric element  2 . Accordingly, a distance between the supported portion of the piezoelectric element  2  and the second end portion  2   f  corresponding to the free end is able to be lengthened. This makes it possible to effectively improve the sensitivity of the acceleration detection device  1 . 
     Furthermore, as described above, the holding angle of the piezoelectric element  2  does not shift easily, and thus, the piezoelectric element  2  does not shift easily from the main axis of the acceleration detection device  1 . Accordingly, a drop in the sensitivity is effectively reduced or prevented. 
     The first and second electrodes  6   a  and  6   b  are provided on the first and second side surfaces  2 Ac and  2 Ad of the piezoelectric member  2 A, and are exposed to the exterior. It is therefore easy to make an electrical connection with the exterior. Furthermore, the sheet-shaped adhesive  4  is preferably made of an insulative material, and thus the first electrode  6   a  and the second electrode  6   b  are able to be reliably electrically insulated from each other. 
     An example of a method of manufacturing the acceleration detection device according to the first preferred embodiment will be described hereinafter. 
       FIGS. 3A to 3D  are perspective views illustrating an example of a method of manufacturing the acceleration detection device according to the first preferred embodiment. 
     As illustrated in  FIG. 3A , the piezoelectric element  2  including the piezoelectric member  2 A is prepared. Next, the sheet-shaped adhesive  4  is affixed to the bottom surface of the piezoelectric element  2 . At this time, the sheet-shaped adhesive  4  is preferably affixed in a semi-solidified state, so as to extend to the first end portion  2   e  of the piezoelectric element  2 . However, the sheet-shaped adhesive  4  may be provided in a position that does not extend to the first end portion  2   e . The sheet-shaped adhesive  4  does not flow easily, and thus, the affixing position thereof is able to be easily and reliably adjusted. This makes it possible to easily and reliably adjust the sensitivity. 
     Next, as illustrated in  FIG. 3B , the piezoelectric element  2  is bonded to the first package member  3  using the sheet-shaped adhesive  4 . The piezoelectric element  2  is able to be supported on its surface by the sheet-shaped adhesive  4 , and thus, the attitude of the piezoelectric element  2  is made stable. Accordingly, shifting in the holding angle is effectively reduced or prevented. 
     Furthermore, the sheet-shaped adhesive  4  is in a semi-solidified state during the above-described bonding. As such, the sheet-shaped adhesive  4  does not easily change the shape during solidification. Therefore, the position and holding angle of the piezoelectric element  2  do not shift easily. 
     Here, as described above, the first and second electrodes  6   a  and  6   b  are provided on the first and second side surfaces  2 Ac and  2 Ad of the piezoelectric member  2 A. The first and second wires  5   a  and  5   b  are provided on the first package member  3 . 
     Next, as illustrated in  FIG. 3C , the second electrode  6   b  and the second wire  5   b  are electrically connected using the conductive adhesive  7   b . Although not illustrated, the first electrode  6   a  and the first wire  5   a  are electrically connected using a conductive adhesive. 
     Next, as illustrated in  FIG. 3D , the second package member  8  is bonded into the first package member  3  so as to seal the piezoelectric element. The acceleration detection device  1  is obtained as a result. 
     Incidentally, the type of electrical connections between the first and second electrodes  6   a  and  6   b  and the first and second wires  5   a  and  5   b  is not particularly limited. As in the first preferred embodiment, the position and holding angle of the piezoelectric element  2  will not shift easily even if the stated connection is of a different type. This will be described using the following first to third variations as examples. 
     As indicated by an acceleration detection device  41  according to the first variation illustrated in  FIG. 4 , first and second electrodes  46   a  and  46   b  and first and second wires  45   a  and  45   b  may preferably be electrically connected by bonding wires  47   a  and  47   b . More specifically, the first electrode  46   a  includes a first extended electrode  46   a   1  extended to the top surface  2 Ab of the piezoelectric member  2 A. The second electrode  46   b  also includes a second extended electrode  46   b   1  extended to the top surface  2 Ab of the piezoelectric member  2 A. The first extended electrode  46   a   1  and the first wire  45   a  are electrically connected by the bonding wire  47   a . The second extended electrode  46   b   1  and the second wire  45   b  are electrically connected by the bonding wire  47   b.    
       FIG. 5A  is a plan view of an acceleration detection device according to the second variation of the first preferred embodiment.  FIG. 5B  is a cross-sectional view of the acceleration detection device, viewed along the line B-B in  FIG. 5A . Note that the second package member is not illustrated in the drawings aside from the above-described  FIG. 2  and  FIG. 3 , and  FIG. 13A  and  FIG. 14  described below. 
     As illustrated in  FIG. 5B , the first electrode  46   a  of an acceleration detection device  51  includes the first extended electrode  46   a   1  extended to the bottom surface  2 Aa of the piezoelectric member  2 A. The second electrode  46   b  also includes the second extended electrode  46   b   1  extended to the bottom surface  2 Aa of the piezoelectric member  2 A. As illustrated in  FIGS. 5A and 5B , a first wire  55   a  is routed to a position overlapping with the first extended electrode  46   a   1 , when viewed in plan view from the top surface  2 Ab side of the piezoelectric member  2 A. A second wire  55   b  is also routed to a position overlapping with the second extended electrode  46   b   1 , when viewed in plan view. 
     The first and second extended electrodes  46   a   1  and  46   b   1  and the first and second wires  55   a  and  55   b  are bonded by a sheet-shaped adhesive  54 . The sheet-shaped adhesive  54  according to the second variation preferably has anisotropic conductivity. More specifically, the sheet-shaped adhesive  54  is conductive only in a thickness direction, or in other words, in the z direction. Accordingly, the first extended electrode  46   a   1  and the first wire  55   a  are electrically connected. The second extended electrode  46   b   1  and the second wire  55   b  are electrically connected. 
     On the other hand, the sheet-shaped adhesive  54  is not conductive in a direction parallel to the x-y plane. Accordingly, the first extended electrode  46   a   1  and the first wire  55   a  are not electrically connected to the second extended electrode  46   b   1  and the second wire  55   b.    
     Note that the sheet-shaped adhesive  54  may have a conductor passing therethrough in the thickness direction, for example. The above-described anisotropic conductivity is able to be achieved as a result. 
     According to the second variation, the first package member  3  and the piezoelectric element  2  are bonded at one location using the sheet-shaped adhesive  54 . As such, the device is not susceptible to the effects of noise caused by bending or other deformation of the first package member  3 . 
       FIG. 6A  is a plan view of an acceleration detection device according to the third variation of the first preferred embodiment.  FIG. 6B  is a cross-sectional view of the acceleration detection device, viewed along the line C-C in  FIG. 6A . 
     Similarly to the second variation, an acceleration detection device  61  includes the first and second extended electrodes  46   a   1  and  46   b   1 . As illustrated in  FIGS. 6A and 6B , the first extended electrode  46   a   1  and the first wire  55   a  are electrically connected by a bump  67   a . The second extended electrode  46   b   1  and the second wire  55   b  are electrically connected by a bump  67   b.    
     A sheet-shaped adhesive  64  is provided on a portion of the bottom surface  2 Aa of the piezoelectric member  2 A where the first and second extended electrodes  46   a   1  and  46   b   1  are not provided. 
     Returning to  FIGS. 1B and 1C , the sheet-shaped adhesive preferably extends to the first end portion  2   e  of the piezoelectric element  2 . As described above, however, the sheet-shaped adhesive  4  is not absolutely required to extend to the first end portion  2   e . Adjusting the position of the sheet-shaped adhesive  4  makes it possible to adjust the distance between the portion of the piezoelectric element  2  that is supported and the second end portion  2   f  corresponding to the free end. This makes it possible to adjust the sensitivity of the acceleration detection device  1 . 
     Preferred embodiments of the present invention may be favorably applied in acceleration detection devices aside from those in which the piezoelectric element is supported in a cantilever state. For example, in an acceleration detection device  71  according to a fourth variation, illustrated in  FIGS. 7A and 7B , both ends of the piezoelectric element  2  in the longitudinal direction may preferably be supported. 
     More specifically, the acceleration detection device  71  includes a sheet-shaped adhesive  4  extending to the first end portion  2   e . The acceleration detection device  71  also includes a sheet-shaped adhesive  4  extending to the second end portion  2   f . The piezoelectric element  2  is supported on both sides by the sheet-shaped adhesives  4  provided in two locations. Note that the sheet-shaped adhesive  4  is not absolutely required to extend to the first and second end portions  2   e  and  2   f  of the piezoelectric element  2 . 
     The first electrode  6   a  is connected to a first wire  75   a  by the conductive adhesive  7   a  at a position overlapping with the sheet-shaped adhesive  4 , when viewed in plan view from the top surface  2 Ab side of the piezoelectric element  2 . Likewise, the second electrode  6   b  is connected to a second wire  75   b  by the conductive adhesive  7   b  at a position overlapping with the sheet-shaped adhesive  4 , when viewed in plan view. The first and second electrodes  6   a  and  6   b  and the first and second wires  75   a  and  75   b  are electrically connected as a result. 
     Also in this case, the position and holding angle of the piezoelectric element  2  do not easily shift, and the element is not susceptible to the effects of noise. 
     The piezoelectric element  2  may be supported by the sheet-shaped adhesive  4  near the center in the longitudinal direction, or in other words, the x direction, as in an acceleration detection device  81  according to a fifth variation illustrated in  FIG. 8 . The same or similar effects as in the first preferred embodiment are able to be obtained in this case as well. 
       FIG. 9A  is a plan view of an acceleration detection device according to a second preferred embodiment of the present invention.  FIG. 9B  is a diagram illustrating the acceleration detection device from the side of a first side surface of a piezoelectric member, according to the second preferred embodiment.  FIG. 9C  is a diagram illustrating the acceleration detection device from the side of a second side surface of the piezoelectric member, according to the second preferred embodiment. 
     An acceleration detection device  11  includes a plurality of first and second inner electrodes  19   a  and  19   b  that are provided within a piezoelectric element  12  and oppose each other. The piezoelectric element  12  includes a multilayer body of piezoelectric members. Aside from these points, the acceleration detection device  11  has the same or substantially the same configuration as the acceleration detection device  1  according to the first preferred embodiment. Note that at least one each of the first and second inner electrodes  19   a  and  19   b  may be provided. 
     As illustrated in  FIG. 9A , the plurality of first and second inner electrodes  19   a  and  19   b  also oppose first and second electrodes  16   a  and  16   b . The plurality of first inner electrodes  19   a  and the first electrode  16   a  are extended to a first end portion  12   e  of the piezoelectric element  12 . A first connection electrode  16   c  is provided on the first end portion  12   e . The plurality of first inner electrodes  19   a  and the first electrode  16   a  are electrically connected by the first connection electrode  16   c . The plurality of second inner electrodes  19   b  and the second electrode  16   b  are also extended to a second end portion  12   f . A second connection electrode  16   d  is provided on the second end portion  12   f . The plurality of second inner electrodes  19   b  and the second electrode  16   b  are electrically connected by the second connection electrode  16   d.    
     The acceleration detection device  11  includes the first and second inner electrodes  19   a  and  19   b , and thus, has a high electrostatic capacitance. This makes it possible to effectively increase the sensitivity. 
     Furthermore, similarly to the first preferred embodiment, the piezoelectric element  12  is supported by the sheet-shaped adhesive  4  in the present preferred embodiment. Accordingly, the position and holding angle of the piezoelectric element  12  do not easily shift, and the element is not susceptible to the effects of noise. 
     In the present preferred embodiment, the total number of the first and second inner electrodes  19   a  and  19   b  is preferably an even number. The number of layers in the piezoelectric element  12  is preferably an odd number. However, as indicated by an acceleration detection device  91  according to a first variation of the second preferred embodiment illustrated in  FIG. 10 , the total number of the first and second inner electrodes  19   a  and  19   b  may be odd, and the number of layers in the piezoelectric element  12  may be even. 
     In this case, the manner in which the electrodes are connected is different from the second preferred embodiment. More specifically, a first electrode  96   a  is provided on the first end portion  12   e  of the piezoelectric element  12 . The first inner electrodes  19   a  extend to the first end portion  12   e , and are physically and electrically connected to the first electrode  96   a . Second electrodes  96   b  are provided on the first and second side surfaces  12 Ac and  12 Ad of a piezoelectric member  12 A. A connection electrode  16   d  is provided on the second end portion  12   f  of the piezoelectric element  12 . The second electrodes  96   b  are connected by the connection electrode  16   d . Furthermore, the second inner electrodes  19   b  are also electrically connected to the second electrodes  96   b  by the connection electrode  16   d.    
     A first wire  95   a  is electrically connected to the first electrode  96   a  by the conductive adhesive  7   a . A second wire  95   b  extends towards both the first and second side surfaces  12 Ac and  12 Ad of the piezoelectric member  12 A. The second wire  95   b  is connected to the second electrodes  96   b  on both the first and second side surfaces  12 Ac and  12 Ad by the conductive adhesive  7   b . Note that the conductive adhesive  7   b  may be provided in one location. The second wire  95   b  is electrically connected to the second electrodes  96   b  as a result. 
     Similarly to the second preferred embodiment, the electrostatic capacitance of the acceleration detection device  91  is large in this case as well. This makes it possible to effectively increase the sensitivity. Furthermore, the position and holding angle of the piezoelectric element  12  do not easily shift, and the element is not susceptible to the effects of noise. 
     In the acceleration detection devices  11  and  91  according to the second preferred embodiment and the first variation, the piezoelectric element  12  is preferably a multilayer body. Note that the first and second inner electrodes  19   a  and  19   b  may be embedded in a piezoelectric element including a single-layer piezoelectric member. 
       FIG. 11A  is a plan view of an acceleration detection device according to a third preferred embodiment of the present invention.  FIG. 11B  is a diagram illustrating the acceleration detection device from the side of a first side surface of a piezoelectric member, according to the third preferred embodiment.  FIG. 11C  is a diagram illustrating the acceleration detection device from the side of a second side surface of the piezoelectric member, according to the third preferred embodiment.  FIG. 11D  is a cross-sectional view of the acceleration detection device, viewed along the line D-D in  FIG. 11A . 
     As illustrated in  FIGS. 11B and 11C , in an acceleration detection device  21 , a first electrode  26   a  is provided on the top surface  2 Ab of the piezoelectric member  2 A. A second electrode  26   b  is provided on the bottom surface  2 Aa of the piezoelectric member  2 A. Aside from these points, the acceleration detection device  21  has the same or substantially the same configuration as the acceleration detection device  1  according to the first preferred embodiment. 
     As illustrated in  FIG. 11D , the first electrode  26   a  includes a first extended electrode  26   a   1  extended to the first side surface  2 Ac of the piezoelectric member  2 A. The first extended electrode  26   a   1  is electrically connected to the first wire  5   a  by the conductive adhesive  7   a . The second electrode  26   b  also includes a second extended electrode  26   b   1  extended onto the second side surface  2 Ad of the piezoelectric member  2 A. The second extended electrode  26   b   1  is electrically connected to the second wire  5   b  by the conductive adhesive  7   b.    
     As illustrated in  FIGS. 11A and 11C , a cutout portion  26   a   2  is provided in the first electrode  26   a . A gap is provided between the first electrode  26   a  and the second extended electrode  26   b   1  as a result. Likewise, as illustrated in  FIGS. 11A and 11B , a cutout portion  26   b   2  is provided in the second electrode  26   b  as well. A gap is provided between the second electrode  26   b  and the first extended electrode  26   a   1  as a result. The first electrode  26   a  and the second electrode  26   b  are not electrically connected as a result. 
     Note that in the present preferred embodiment, it is sufficient for the first electrode  26   a  and the second electrode  26   b  to not be electrically connected, and the first and second cutout portions  26   a   2  and  26   b   2  are not absolutely required. For example, the first extended electrode  26   a   1  may be provided so as not to extend to the end portion on the bottom surface  2 Aa side of the first side surface  2 Ac of the piezoelectric member  2 A. The second extended electrode  26   b   1  may also be provided so as not to extend to the end portion on the top surface  2 Ab side of the second side surface  2 Ad of the piezoelectric member  2 A. 
     As illustrated in  FIGS. 11B to 11D , in the present preferred embodiment, the first and second electrodes  26   a  and  26   b  oppose each other with respect to the z direction. In other words, the main axis direction of the acceleration detection device  21  is 90° relative to the x-y plane. 
     The main axis direction of the acceleration detection device according to various preferred embodiments of the present invention is not limited to 0° or 90° relative to the x-y plane. An example of this will be described below as a sixth variation of the first preferred embodiment. 
       FIG. 12A  is a plan view of an acceleration detection device according to the sixth variation.  FIG. 12B  is a cross-sectional view of the acceleration detection device, viewed along the line E-E in  FIG. 12A . 
     As illustrated in  FIGS. 12A and 12B , first and second side surfaces  102 Ac and  102 Ad of a piezoelectric member  102 A in a piezoelectric element  102  are slanted relative to the z direction. Accordingly, the first and second electrodes  6   a  and  6   b  oppose each other with respect to a direction slanted from the y direction and the z direction. In the sixth variation, the main axis direction of an acceleration detection device  101  is a direction, in a y-z plane, that is preferably slanted by about 25° relative to the x-y plane, for example. Note that the main axis direction of the acceleration detection device  101  is not particularly limited. 
       FIG. 13A  is a plan view of an acceleration detection device according to a first variation of the third preferred embodiment.  FIG. 13B  is a plan view of the acceleration detection device according to the first variation, without the second package member.  FIG. 13C  is a diagram illustrating the acceleration detection device, without the second package member, from the side of a first side surface of a piezoelectric member, according to the first variation. Note that the dot-dash line F in  FIG. 13B  indicates a portion where the second package member is bonded. 
     As illustrated in  FIGS. 13A and 13B , an acceleration detection device  111  may preferably include a ground wire  115   c   1  on a top surface of a first package member  113 . The ground wire  115   c   1  is not particularly limited, but is preferably electrically connected to the second package member  8  by a conductive adhesive. 
       FIG. 14  is a schematic plan view of the electrode structure on a bottom surface of the first package member  113 . A ground terminal  115   c   2  is provided on the bottom surface of the first package member  113 . As illustrated in  FIGS. 13A, 13C , and  FIG. 14 , the ground wire  115   c   1  is connected to the ground terminal  115   c   2  on the bottom surface from the top surface of the first package member  113  and via a side surface. When the acceleration detection device  111  is mounted from a bottom surface, the second package member  8  is connected to a ground potential via the ground wire  115   c   1  and the ground terminal  115   c   2 . In this case, the device is even less susceptible to the effects of electromagnetic noise. 
     Although not particularly limited, the second package member  8  may be bonded to the first package member  113  using an insulative adhesive at portions aside from those in contact with the ground wire  115   c   1 . 
     As illustrated in  FIG. 13A , first and second wires  115   a   1  and  115   b   1  connected to first and second connection electrodes  16   c  and  16   d  of a piezoelectric element  112  are provided on the top surface of the first package member  113 . Furthermore, a third wire  115   a   5  is provided on the top surface of the first package member  113 . As illustrated in  FIG. 14 , first, second, and third terminal electrodes  115   a   2 ,  115   b   2 , and  115   a   4 , and a third connection electrode  115   a   3 , are provided on the bottom surface of the first package member  113 . The first terminal electrode  115   a   2  and the third terminal electrode  115   a   4  are connected to the third connection electrode  115   a   3 . The first, second, and third wires  115   a   1 ,  115   b   1 , and  115   a   5  illustrated in  FIG. 13A  are connected to the first, second, and third terminal electrodes  115   a   2 ,  115   b   2 , and  115   a   4  from the top surface of the first package member  113 , via the side surface. The first wire  115   a   1  is electrically connected to the third wire  115   a   5  via the first terminal electrode  115   a   2 , the third connection electrode  115   a   3 , and the third terminal electrode  115   a   4 . 
     As illustrated in  FIG. 13C , the piezoelectric element  112  includes a plurality of first and second inner electrodes  119   a  and  119   b  opposing each other in the thickness direction. In this manner, a layering direction of the plurality of inner electrodes  119   a  and  119   b  may correspond to the thickness direction of the piezoelectric element  112 . 
     As illustrated in  FIGS. 13A to 13C , the first package member  113  may preferably include a plurality of recesses, provided in the side surface sides, so as to be opened toward the side surface side and continuous in the thickness direction. The first, second, and third wires  115   a   1 ,  115   b   1 , and  115   a   5  and the ground wire  115   c   1  are provided along the recesses. 
     A first connection wire  16   c  may preferably be connected to the first wire  115   a   1  by the bonding wire  47   a , as in an acceleration detection device  121  according to a second variation illustrated in  FIG. 15 . Likewise, the second electrode  26   b  may preferably be connected to a second wire  115   b   1  by the bonding wire  47   b.    
       FIG. 16  is a side cross-sectional view of an acceleration detection device according to a fourth preferred embodiment of the present invention. 
     A first package member  33  of an acceleration detection device  31  includes a recess  33   a . A second package member  38  preferably has a flat plate shape. Aside from these points, the acceleration detection device  31  has the same or substantially the same configuration as the acceleration detection device  1  according to the first preferred embodiment. 
     The piezoelectric element  2  is located within the recess  33   a  of the first package member  33 . The second package member  38  is bonded to the first package member  33  so as to cover the recess  33   a . Note that as long as the second package member  38  is able to be bonded so as to cover the recess  33   a , the shape of the second package member  38  is not particularly limited. 
     According to the fourth preferred embodiment, the position and holding angle on of the piezoelectric element  2  do not easily shift, and the element is not susceptible to the effects of noise. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.