JP2010107288A - Acceleration sensor and acceleration sensor mounting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor which can be directly mounted on a conductive member, such as, a metallic member and has high acceleration detection sensitivity. <P>SOLUTION: The acceleration sensor includes external electrodes 41a, 41b, in a case 1 housing a vibrating element 12 therewithin and has a mounting surface, spaced apart from the mounting surface. The acceleration sensor mounting structure allows the mounting surface of the acceleration sensor to be glued to the conductive member, of which the acceleration is to be detected and allows external electrodes to be electrically connected to an external signal processing circuit through wiring. Since the acceleration sensor includes the external electrodes 41a, 41b, in the case 1 which has the mounting surface, spaced apart from the mounting surface, even when it is directly mounted on a metallic conductive member of which the acceleration is to be detected, the external electrodes 41a, 41b are not short-circuited through a metallic housing or interior parts, allowing it to be mounted directly on the metallic conductive member, thereby attaining an acceleration sensor which can be mounted directly on a conductive member, such as, a metallic member and has high acceleration detection sensitivity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acceleration sensor, and more particularly to an acceleration sensor that can be directly mounted on a conductive plate such as metal.

  Conventionally, an acceleration sensor has been used for applications such as detection of acceleration due to impact or fall applied to an electronic device such as a hard disk drive from the outside, and a vibration element having main surface electrodes formed on both main surfaces of a strip-shaped piezoelectric substrate. There is known an acceleration sensor of a type in which both main surfaces of end portions are sandwiched between support members (see, for example, Patent Document 1).

  In such an acceleration sensor, the piezoelectric element is distorted by bending of the vibration element due to the applied acceleration, and a potential difference is generated between the main surface electrodes formed on both main surfaces of the piezoelectric substrate due to charges generated by the piezoelectric effect. Therefore, the acceleration is detected by taking this as an output voltage.

Further, in the conventional acceleration sensor described in Patent Document 1, an external electrode is formed on the entire end face of a rectangular parallelepiped case constituting the acceleration sensor, and this external electrode is used as one main circuit board. The acceleration sensor is joined on the circuit board by soldering on the surface. And the circuit board which joined this acceleration sensor is mounted in members, such as a housing | casing which comprises the electronic device which is going to detect an acceleration. That is, the acceleration sensor is mounted via a circuit board on a member such as a casing constituting an electronic device for which acceleration is to be detected.
JP 2004-170228 A

  However, in the conventional acceleration sensor as described above, a circuit board is interposed between the acceleration sensor and a conductor member such as a casing constituting the electronic device for which the acceleration is to be detected. Since the acceleration applied to the member is not easily transmitted directly to the acceleration sensor, it is difficult to increase the acceleration detection sensitivity.

  In addition, the casing and internal parts constituting an electronic device such as a hard disk drive on which such a conventional acceleration sensor is mounted are metal conductor members, and if the acceleration sensor is directly mounted on these conductor members, the exterior of the acceleration sensor Since the electrodes are short-circuited by the conductor member, the acceleration sensor cannot be directly mounted on the metal conductor member.

  In response to the demands for smaller, lower, and lighter electronic devices, it may be possible to join the acceleration sensor to a thin circuit board. When acceleration is applied to the member, the circuit board having a small thickness is bent, and it becomes difficult to transmit the acceleration to the acceleration sensor, so that there is a problem that accurate acceleration cannot be detected.

  The present invention has been devised in view of the above-described problems in the prior art, and an object thereof is to provide an acceleration sensor that can be directly mounted on a metal conductor member and has high acceleration detection sensitivity. is there.

  The acceleration sensor according to the present invention is characterized in that a case having a mounting surface in which a vibration element is housed has an external electrode spaced from the mounting surface.

  Further, the mounting structure of the acceleration sensor of the present invention is such that the mounting surface of the acceleration sensor of the present invention having the above configuration is bonded to a metal member to detect acceleration with an adhesive, and the external electrode is external signal processing. It is characterized in that it is electrically connected to the circuit by wiring.

  Since the acceleration sensor of the present invention has an external electrode in a case having a mounting surface in which a vibration element is housed and spaced from the mounting surface, the housing constituting the electronic device such as a hard disk drive or the like Even if directly joined to a metal conductor member such as an arm that drives a magnetic head, the external electrodes of the acceleration sensor are not short-circuited by the conductor member, so the metal conductor constituting the electronic device It can be directly mounted on the member, and the acceleration detection sensitivity can be increased.

  Further, according to the mounting structure of the acceleration sensor of the present invention, the mounting surface of the acceleration sensor of the present invention having the above configuration is joined to the conductor member for detecting the acceleration with an adhesive, so that the acceleration is detected. The external electrodes of the acceleration sensor are not short-circuited even when directly joined to the metal conductor member to be worked. Since the acceleration sensor is directly joined to the metal conductor member, the acceleration applied to the conductor member for detecting the acceleration is directly transmitted to the acceleration sensor, so that the acceleration can be detected more accurately. Therefore, the acceleration detection sensitivity can be increased as compared with the conventional structure in which the acceleration sensor is mounted with the circuit board interposed between the acceleration sensor and the conductor member to detect acceleration. And, by connecting the external electrode of the acceleration sensor joined to the conductor member in this way and the external signal processing circuit by wiring, the electrical signal corresponding to the acceleration acting on the conductor member is wired. Can be output to an external signal processing circuit.

  Hereinafter, an acceleration sensor according to the present invention will be described in detail with reference to the accompanying drawings, taking as an example an acceleration sensor having a one-end support structure in which one end of a vibration element is held by a support member.

  FIG. 1 is an external perspective view schematically showing an example of an embodiment of an acceleration sensor of the present invention. 2A is a front view schematically showing a state in which the external electrodes 41a and 41b of the acceleration sensor 10 shown in FIG. 1 are removed, and FIG. 2B is a cross-sectional view taken along line AA in FIG. FIG. 2C is a cross-sectional view taken along line BB in FIG. FIG. 3 is a side view showing a state in which the side surface protection member 33 of the acceleration sensor 10 shown in FIG. 1 is removed. FIG. 4 is a side view showing a state in which the acceleration sensor 10 shown in FIG. 1 is mounted on a conductor member constituting an electronic device (not shown). FIG. 5 is an external perspective view schematically showing the vibration element 12 used in the acceleration sensor 10 shown in FIG. 6 is an exploded perspective view of the vibration element 12 shown in FIG.

  In the acceleration sensor 10 of this example shown in FIGS. 1 to 6, the vibration element 12 in which the principal surface electrodes 15a and 15b are arranged on the piezoelectric substrate 11 has a pair of supporting members on both principal surfaces at one end in the longitudinal direction. The acceleration sensor 10 having a one-end support structure is formed by being sandwiched and supported by 21 and a pair of main surface protection members 31 constituting the case 1 via the same.

  As shown in FIG. 1 and FIGS. 2A to 2C, the acceleration sensor 10 of this example includes a pair of support members 21 disposed on both main surfaces at one end in the longitudinal direction of the vibration element 12. The end faces of the one end and the other end in the longitudinal direction are on the same plane as the end faces of the one end and the other end in the longitudinal direction of the vibration element 12, respectively, and both main surfaces of the vibration element 12 are interposed via a pair of support members 21. It has a pair of rectangular main surface protection members 31 that are spaced apart from each other. In addition, the acceleration sensor 10 of the present example includes a pair of end surface spacer members 22 disposed on the end surfaces of the other end in the longitudinal direction of the pair of main surface protection members 31, and the vibration element 12 and the pair of paired main surface protection members 31 via the end surface spacer members 22. The main surface protection member 31 has an end surface protection member 32 disposed at a distance from the other end surface in the longitudinal direction. Further, the acceleration sensor 10 of the present example includes both side surfaces at one end in the longitudinal direction of the vibration element 12, and both sides of the pair of main surface protection members 31, the end surface protection members 32, the pair of support members 21, and the pair of end surface spacer members 22. A pair of side spacer members 23 disposed on each of the surfaces, and the vibration element 12, a pair of main surface protection members 31, an end surface protection member 32, a pair of support members 21, and a pair of end surfaces via the pair of side spacer members 23 A pair of side surface protection members 33 arranged with a space from each of both side surfaces of the spacer member 22 are provided. Note that the vibration element 12, the pair of support members 21, the pair of main surface protection members 31, the pair of end surface spacer members 22, and the both end surfaces of the end surface protection member 32 are located on the same plane.

  The main surface protection member 31, the end surface protection member 32, the side surface protection member 33, the side surface spacer member 23, and the end surface spacer member 22 constitute a case 1 in which the vibration element 12 is accommodated. It is a mounting surface mounted facing the conductor member for which acceleration is to be detected.

  As shown in FIGS. 5 and 6, the vibration element 12 used in the acceleration sensor 10 of this example is formed by laminating a pair of strip-shaped piezoelectric substrates 11 in the thickness direction, and the principal surface electrodes 15a and 15b are formed on both principal surfaces, respectively. Are arranged. Furthermore, in the vibration element 12 used in the acceleration sensor 10 of the present example, the principal surface electrodes 15a and 15b are respectively disposed on the principal surfaces of the pair of piezoelectric substrates 11 facing each other, and an insulating adhesive is interposed therebetween. 19 are stacked in the thickness direction. In each piezoelectric substrate 11, main surface electrodes 15 a and 15 b formed on both main surfaces thereof are arranged so that parts thereof face each other with the piezoelectric substrate 11 interposed therebetween.

  Further, the main surface electrodes 15a and 15b are drawn to the opposite sides in the width direction at one end face in the longitudinal direction of the vibration element 12, and the main surface electrodes 15a are shown in FIGS. 2 (b) and 2 (c). The main surface electrode 15b is connected to the external electrode 41b via the connection conductor 42 shown in FIG.

  In the acceleration sensor 10 of this example having such a structure, when acceleration having a component in a direction perpendicular to the main surface of the vibration element 12 is applied, a portion sandwiched and supported by the pair of support members 21 is used as a fulcrum. The vibration element 12 bends in the thickness direction, and the piezoelectric substrate 11 is distorted, and charges generated by the piezoelectric effect can be taken out by the main surface electrodes 15a and 15b. In this way, an electrical signal corresponding to the applied acceleration can be output to the outside through the external electrodes 41a and 41b connected to the main surface electrodes 15a and 15b, respectively, and thus functions as the acceleration sensor 10.

  When the acceleration sensor 10 is mounted on a circuit board or the like, if the main surface of the vibration element 12 is parallel to the mounting surface, acceleration having a component in a direction perpendicular to the mounting surface can be detected. When the main surface of the vibration element 12 is perpendicular to the mounting surface, it is possible to detect acceleration having a component in a direction parallel to the mounting surface and perpendicular to the main surface of the vibration element 12. Become. Further, when the vibration element 12 is fixed so as to be inclined with respect to the horizontal direction, it is possible to detect acceleration due to an impact from the lateral direction as well as the vertical direction. In this case, the angle formed by the surface perpendicular to the main surface serving as the mounting surface of the case 1 and the main surface of the vibration element 12 (the angle on the acute angle side) is 20 to 50 ° depending on the application. Set to a range.

  According to the acceleration sensor 10 of the present example, one end in the longitudinal direction of the vibration element 12 is sandwiched between the pair of support members 21 disposed on both main surfaces and the pair of main surface protection members 31 via the support members 21. Since the supported one-end support structure is used, the deflection of the vibration element 12 due to the acceleration is larger than that of the acceleration sensor having the both-end support structure, so that the acceleration sensor 10 having high acceleration detection sensitivity can be obtained.

  In the acceleration sensor 10 of this example, the case 1 that houses the vibration element 12 includes the main surface protection member 31, the end surface protection member 32, the side surface protection member 33, the side surface spacer member 23, and the end surface spacer member 22 as described above. The oscillating element 12 has a space for vibrating, and is configured in a rectangular parallelepiped shape.

  As the pair of end face spacer members 22 and the pair of side face spacer members 23 constituting the case 1 of the acceleration sensor 10 of this example, various insulating materials such as ceramics and synthetic resins can be used. By using this adhesive, the manufacturing process can be greatly simplified. In particular, by using a prepreg obtained by impregnating carbon fiber or glass fiber with a resin or an adhesive that can be in a semi-cured state (B stage) before the main curing, a desired size is provided around the vibration element 12. It becomes easy to form the vibration space. For example, when a thermosetting epoxy adhesive is used, after applying the adhesive on one adhesive surface of the members to be joined using a printing method, the temperature is approximately 50 ° C. to 70 ° C. for 1 hour. Hold for about 2 hours to make the adhesive semi-cured, paste the other of the members to be joined together and adjust the spacing between members as necessary, then at a temperature of about 100 ° C to 200 ° C for 1 hour It may be held for about 2 hours to fully cure the adhesive.

  Further, the pair of main surface protection members 31, the end surface protection members 32, and the pair of side surface protection members 33 constituting the case 1 depend on the thickness of the pair of support members 21, the pair of end surface spacer members 22, and the pair of side surface spacer members 23. The vibration space to be determined is secured around the vibration element 12, and the vibration element 12 is protected. Further, since the pair of main surface protection members 31 also have a function of supporting both main surfaces of the vibration element 12 via the pair of support members 21, the pair of side surface protection members 33 and end surface protection members 32 are also included. It is desirable to increase the thickness. Thus, the acceleration sensor 10 can be made as small as possible while the vibration element 12 is reliably supported. Therefore, the thickness of the pair of main surface protection members 31 is set to about 0.6 mm to 0.8 mm, for example, and the thickness of the pair of side surface protection members 33 and end surface protection members 32 is set to about 0.15 mm to 0.2 mm, for example.

  As such main surface protection member 31, end surface protection member 32, and side surface protection member 33, insulating materials such as various ceramics and synthetic resins can be used, but insulation, moisture resistance, heat resistance, adhesiveness, etc. It is desirable to use an epoxy-based resin that excels in resistance. For example, “EPOX” (registered trademark) manufactured by Mitsui Chemicals, Inc. can be suitably used.

  The piezoelectric substrate 11 constituting the vibration element 12 of the acceleration sensor 10 of this example is made of, for example, a piezoelectric ceramic material such as lead zirconate titanate or lead titanate, and the shape thereof is 1.5 to 3.0 mm in length and 0.4 in width. It has a strip shape of ˜1.0 mm and a thickness of 0.05 to 0.2 mm, and is polarized in the thickness direction.

  Such a piezoelectric substrate 11 is dried by adding a binder to the raw material powder and pressing the raw material powder, or after mixing the raw material powder with water and a dispersing agent using a ball mill to remove the binder, solvent, plasticizer, etc. In addition, it is formed into a sheet by a method such as molding by the doctor blade method, and is laminated and pressed as necessary, and this laminate is fired at a peak temperature of, for example, 1100 ° C. to 1400 ° C. for several hours to form a substrate. Later, it can be fabricated by applying a polarization treatment by applying a voltage of 3 kV / mm to 15 kV / mm at a temperature of 60 ° C. to 150 ° C. in the thickness direction.

  The main surface electrodes 15a and 15b deposited on both main surfaces of the piezoelectric substrate 11 are made of a highly conductive metal such as gold, silver, copper, chromium, nickel, tin, lead, and aluminum as materials. The thickness is, for example, about 0.1 μm to 3 μm, and parts thereof are formed to face each other with the piezoelectric substrate 11 interposed therebetween. For such main surface electrodes 15a and 15b, a metal material is deposited on both main surfaces of the piezoelectric substrate 11 by a conventionally known vacuum deposition, sputtering method or the like, or a predetermined conductor paste containing the above metal material is conventionally used. It can be formed by applying to a predetermined pattern by a known printing method or the like and baking at a high temperature.

  As the insulating adhesive 19 for bonding the piezoelectric substrate 11, an insulating material such as glass cloth base epoxy resin, inorganic glass, epoxy resin or the like can be used. For example, in bonding with a glass cloth base epoxy resin, two piezoelectric substrates 11 are stacked one above the other with a prepreg material impregnated with an epoxy resin between glass fibers, and heated while pressing them. The epoxy resin is compressed to a predetermined thickness and cured. In addition, in bonding with inorganic glass, glass paste is printed and applied between a pair of piezoelectric substrates 11 having main surface electrodes 15a and 15b formed on both main surfaces, and then these are superimposed and a load is applied thereto. Melt and integrate using a firing furnace. In addition, it heats at 300-700 degreeC in a baking furnace. If firing is performed in a vacuum furnace, bubbles can be prevented from being mixed into the glass. At this time, when the bonding is performed at a high temperature of 300 ° C. or higher, the polarization of the piezoelectric substrate 11 is depolarized, and therefore it is necessary to perform the polarization process again after the bonding.

  The support member 21 is an elastic body. For example, when the elastic modulus is smaller than the elastic modulus of the main surface protection member 31, it becomes easy to bend even in the region where the vibration element 12 is sandwiched between the pair of support members 21, and the pair of piezoelectric substrates. Since the area where distortion occurs in each of 11 increases, the detection sensitivity of acceleration can be increased.

  In this case, the elastic modulus of the support member 21 is desirably about 10 MPa to 10 GPa, and particularly desirably about 1 GPa to 10 GPa. Therefore, for example, an epoxy resin having an elastic modulus of about 6 GPa is preferably used as the material of the support member 21. Further, the thickness is 20-100 μm, the width direction extends over the entire vibration element 12, and the length direction extends from one end of the vibration element 12 to a range of 0.5-1.0 mm. Is used.

  In forming such a support member 21, first, a sheet in which two piezoelectric mother substrates to be the piezoelectric substrate 11 are joined is prepared, and a resin paste is printed by screen printing at predetermined positions on both main surfaces of the sheet. This is cured. At this time, if necessary, screen printing may be repeated a plurality of times, or the surface of the cured resin paste may be polished in order to obtain thickness accuracy. Then, while confirming the position of the cured resin paste, the vibration element having the support member 21 attached thereto is cut by using a dicing saw or the like so that the support member 21 and the vibration element 12 having a predetermined length are obtained. You can get 12.

  The shape of the vibration element 12 obtained in this way is, for example, a rectangular parallelepiped shape having a length of 3 mm, a width of 0.5 mm, and a thickness of 0.3 mm. The length of the support region sandwiched between the support members 21 is The length of the free region that is 1 mm and is not sandwiched between the support members 21 is 2 mm. In the following description, one end of the vibration element 12 (end on the side sandwiched by the support member 21) is referred to as a fixed end, and the other end is referred to as a free end.

  In the acceleration sensor 10 of this example, as the external electrodes 41a and 41b, for example, a conductive adhesive containing a conductive filler in resin can be used. As the conductive filler contained in the conductive adhesive, those having good conductivity such as silver and copper are desirable. In addition, as the adhesive resin in the conductive adhesive, in order to prevent the polarization of the piezoelectric substrate 11 from being lost, it is desirable to cure at less than 300 ° C. For example, an epoxy resin or the like can be preferably used.

  The external electrodes 41a and 41b are used to transmit a potential difference generated in the vibration element 12 to an external signal processing circuit via wiring. The acceleration sensor 10 is mounted on, for example, a metal arm that holds a magnetic head of a hard disk, a metal housing that constitutes a hard disk drive, or the like.

  The external electrodes 41a and 41b may be formed on the end face of the rectangular parallelepiped case 1 having a mounting surface with a spacing of 0.2 mm or more from the mounting surface. For example, in the case of an acceleration sensor with dimensions of 2.1 mm in width, 2.1 mm in depth, and 1.5 mm in thickness, a distance of 0.2 to 0.4 mm from the mounting surface and 1.8 mm to 2.4 mm in the width direction of the end surface, in the thickness direction A size of 0.7 mm to 1.0 mm is formed. By forming the external electrodes 41a and 41b at a distance from the mounting surface in this manner, it is possible to effectively prevent the external electrodes 41a and 41b from being short-circuited due to the adhesion of conductors or the occurrence of migration.

  Therefore, in the acceleration sensor 10 of this example, the vibrating element 12 is housed inside, and the external electrodes 41a and 41b are formed on the end face of the rectangular parallelepiped case 1 having the mounting surface at a distance from the mounting surface. Even if it is directly joined to a metal conductor member 51 that is to detect acceleration, such as a metal arm that holds a magnetic head of a hard disk or a housing that constitutes an electronic device such as a hard disk drive, the external electrode 41a 41b are not short-circuited by the conductor member 51, the acceleration sensor 10 can be directly mounted on the conductor member as shown in FIG.

  As described above, in the acceleration sensor 10 of this example, the external electrodes 41a and 41b are formed on the end surface of the rectangular parallelepiped case 1 having the mounting surface at a distance from the mounting surface. Even if directly joined to the metallic conductor member 51, the external electrodes 41a and 41b are not short-circuited by the metallic casing or internal parts.

  Therefore, since the acceleration sensor 10 can be directly mounted on the conductor member 51, the acceleration applied to the conductor member 51 to detect the acceleration is directly transmitted to the acceleration sensor 10, so that the acceleration can be detected more accurately. This is effective in increasing the detection sensitivity of the acceleration sensor. By mounting the acceleration sensor 10 in this way, an electrical signal corresponding to the applied acceleration can be output from the external electrodes 41a and 41b to the external signal processing circuit via the connection conductor. Here, as the wiring for electrically connecting the external electrodes 41a and 41b and the external signal processing circuit, a conductive wire, a metal lead plate, or the like can be used.

  Next, FIG. 7 is an external perspective view showing another example of the embodiment of the acceleration sensor 10 of the present invention. 7, parts similar to those in FIG. 1 are denoted by the same reference numerals.

  In the acceleration sensor 10 of the example shown in FIG. 7, the external electrode 41a is spaced from each of a pair of surfaces facing each other on the end surface of a rectangular parallelepiped case 1 having a mounting surface in which the vibration element 12 is housed. 41b is formed, it is only necessary to join and mount one of a pair of opposing surfaces to a metal member to detect acceleration, so that each of the pair of opposing surfaces can be mounted. The acceleration sensor 10 can be mounted more easily.

  Next, FIG. 8 is an external perspective view showing still another example of the embodiment of the acceleration sensor 10 of the present invention. In FIG. 8, the same parts as those in FIG.

  The acceleration sensor 10 in the example shown in FIG. 8 has an end face on one end side of a rectangular parallelepiped case 1 having a mounting surface in which the vibration element 12 is housed, spaced from each of a pair of faces facing each other. Since the external electrodes 41a and 41b are formed, the external electrodes 41a and 41b can be formed simultaneously when the acceleration sensor 10 is manufactured. Further, since the acceleration sensor 10 can be configured without using the connection conductor 42 that connects the external electrode 41b and the main surface electrode 15b, the structure of the acceleration sensor 10 becomes simpler, which is advantageous in shortening the process. is there.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, the above-described vibration element 12 is an acceleration sensor having a one-end support structure in which one end portion of the vibration element 12 is sandwiched by the support member 21, but the acceleration detection sensitivity may be further reduced. If present, the vibration element 12 may be an acceleration sensor having a both-ends support structure in which both ends are sandwiched between the support members 21.

  In addition, although the acceleration sensor 10 described above has a mounting surface that is perpendicular to the vibration direction of the vibration element 12, it may be an acceleration sensor in which a surface parallel to the vibration direction of the vibration element 12 is the mounting surface.

  Next, a specific example of the acceleration sensor of the present invention will be described by taking the acceleration sensor 10 of the embodiment shown in FIGS. 1 to 3, 5 and 6 as an example.

  First, a binder was added to a raw material powder of lead zirconate titanate, press-molded, and fired at a peak temperature of 1200 ° C. to obtain a block of a piezoelectric body.

  Next, this piezoelectric block is sliced using a wire saw, and both sides are lapped using a lapping machine, whereby a piezoelectric mother substrate having a plurality of element regions that are divided into piezoelectric substrates 11 is obtained. Produced. Here, the thickness of the piezoelectric mother substrate was 100 μm.

  Next, metal thin films to be patterned to become main surface electrodes 15a and 15b were formed on both main surfaces of the piezoelectric mother substrate using a sputtering apparatus. Each metal thin film has a two-layer structure of chromium and silver, and after forming a chromium thin film with a thickness of 0.3 μm, a silver thin film is formed thereon with a thickness of 0.3 μm.

  Next, a piezoelectric mother substrate having a metal thin film formed on both main surfaces is put into a polarization chamber, and a voltage of 300 V is applied for 10 seconds between the metal thin films on both main surfaces to polarize the piezoelectric mother substrate in the thickness direction. did.

  Next, after forming a resist pattern on the surface of the metal thin film using a screen printing method, the metal thin film is patterned by immersion in an etching solution, and then the resist is removed by immersion in toluene. Main surface electrodes 15a and 15b were formed on both main surfaces of each element region of the substrate.

  Next, the two piezoelectric mother substrates on which the principal surface electrodes 15a and 15b are formed in the element regions on both principal surfaces are put into a vacuum oven, and a glass cloth base epoxy resin prepreg is interposed therebetween. Bonding was carried out by holding at 180 ° C. for 2 hours while applying a load. The prepreg was bonded so that the thickness of the prepreg was about 0.1 mm and the polarization directions of the two piezoelectric mother substrates were opposite to each other.

  Next, the piezoelectric mother substrate was cut along a boundary of each element region using a dicing saw and divided into individual pieces, and a plurality of vibration elements 12 as shown in FIGS. 5 and 6 were obtained simultaneously. The shape of the vibration element 12 was a rectangular flat plate having a length of 3 mm, a width of 0.5 mm, and a thickness of 0.3 mm.

  Next, an epoxy resin serving as a support member 21 is applied to both main surfaces within a range of 1 mm from one end in the longitudinal direction of the vibration element 12 and kept at a temperature of 60 ° C. for about 1 hour to be semi-cured. I made it. The thickness of each of the pair of support members 21 was set to 100 μm, and an epoxy resin having a cured support member with an elastic modulus of 6 GPa was used as its material.

  Next, a pair of main surface protective members 31 having the same length and width as the vibration element 12 and a rectangular flat plate shape with a thickness of 0.6 mm are arranged so that the end surfaces at both ends in the longitudinal direction are at both ends in the longitudinal direction of the vibration element 12. It is located on the same plane as the end face, and is pasted with a pair of semi-cured support members 21 so as to face both main surfaces of the vibration element 12 with a gap, and is held at a temperature of 150 ° C. for 1 hour. The support member 21 was fixed by being fully cured.

  Next, an epoxy resin to be a pair of end surface spacer members 22 was applied to the other end portion in the longitudinal direction of the pair of main surface protection members 31, and kept at a temperature of 60 ° C. for about 1 hour to be in a semi-cured state. The thickness of the pair of end face spacer members 22 was set to 50 μm.

  Next, the other end in the longitudinal direction of the pair of main surface protection members 31 and the end surface of the other end in the longitudinal direction of the vibration element 12 are opposed to each other via a pair of semi-cured end surface spacer members 22 with a space therebetween. The end face protection member 32 was affixed, held at a temperature of 150 ° C. for 1 hour, and fixed by curing the pair of end face spacer members 22. The shape of the end face protection member 32 was a rectangular flat plate having a length of 1.7 mm, a width of 0.5 mm, and a thickness of 0.2 mm. Further, both side surfaces of the vibration element 12, the pair of support members 21, the pair of main surface protection members 31, the pair of end surface spacer members 22 and the end surface protection member 32 are positioned on the same surface.

  Next, a pair of side surfaces of one end in the longitudinal direction of the vibration element 12 and a pair of main surface protection member 31, end surface protection member 32, a pair of support members 21, and a pair of end surface spacer members 22 The epoxy resin used as the side spacer member 23 was applied, and kept at a temperature of 60 ° C. for about 1 hour to be in a semi-cured state. The thickness of the pair of side spacer members 23 was set to 50 μm.

  Next, the vibration element 12, the pair of main surface protection members 31, the end surface protection member 32, the pair of support members 21, and the pair of end surface spacer members 22 are spaced apart from each other through a pair of semi-cured side spacer members 23. A pair of side surface protection members 33 were attached so as to face each other and held at a temperature of 150 ° C. for 1 hour to fix the pair of side surface spacer members 23 by main curing. The pair of side surface protection members 33 each have a rectangular flat plate shape having a length of 3.25 mm, a width of 1.7 mm, and a thickness of 0.2 mm.

  Next, a conductive resin serving as the external electrode 41a is applied to one end face in the longitudinal direction of the acceleration sensor 10 so as to be connected to the main surface electrode 15a drawn to the end face, and the other in the longitudinal direction of the acceleration sensor 10 is applied. On the end face of the end, a conductive resin to be the external electrode 41b is applied so as to be connected to the main surface electrode 15b via the connection conductor 42, and is kept at 150 ° C. for 1 hour to be cured, thereby making a pair of external The electrodes 41a and 41b were formed to complete the acceleration sensor 10. As the conductive resin, an epoxy resin conductive adhesive containing silver particles as a conductive filler was used. The external electrodes 41a and 41b were formed on the end surfaces of the acceleration sensor 10 with an interval of 0.2 mm from both main surfaces.

  Since the acceleration sensor of the present invention thus obtained has external electrodes spaced from the mounting surface in a case having a mounting surface, a metal arm that holds the magnetic head of the hard disk, Even if it is directly joined to a metal conductor member that is to detect acceleration, such as a housing constituting an electronic device such as a hard disk drive, the external electrodes are not short-circuited by the metal conductor member. It can be directly mounted on the conductor member. Further, since it can be directly mounted on a metal conductor member, the acceleration applied to the metal conductor member for detecting the acceleration is directly transmitted to the acceleration sensor, so that the acceleration detection sensitivity can be improved.

  Therefore, the acceleration sensor of the present invention thus obtained can be directly mounted on a metal conductor member to detect acceleration, and is an excellent acceleration sensor with high acceleration detection sensitivity.

It is an appearance perspective view showing typically an example of an embodiment of an acceleration sensor of the present invention. (A) is a front view schematically showing a state in which the external electrodes 41a and 41b of the acceleration sensor shown in FIG. 1 are removed, (b) is a cross-sectional view taken along the line AA in FIG. It is the BB sectional view taken on the line of FIG. It is a side view which shows the state which removed the side surface protection member 33 of the acceleration sensor shown in FIG. It is a side view which shows the state which mounted the acceleration sensor shown in FIG. It is an external appearance perspective view which shows typically the vibration element used for the acceleration sensor shown in FIG. FIG. 6 is an exploded perspective view of the vibration element shown in FIG. 5. It is an external appearance perspective view which shows the other example of embodiment of the acceleration sensor of this invention. It is an external appearance perspective view which shows the other example of embodiment of the acceleration sensor of this invention.

Explanation of symbols

1. Case
10. ・ Acceleration sensor
11 ... Piezoelectric substrate
12 ... Vibration element
13 .... Elastic body
15a, 15b ... Main surface electrode
21 ... Support members
22 ・ ・ ・ ・ End spacer
23 .. Side spacer member
31 ... Main surface protection member
32 ... End face protection member
33 ... Side protection member
41a, 41b ... External electrodes
42 ・ ・ ・ ・ Connection conductor
51 ・ ・ ・ ・ Conductive member
52 ・ ・ ・ ・ Adhesive

Claims (2)

  An acceleration sensor comprising: a case having a mounting surface in which a vibration element is housed; and an external electrode spaced from the mounting surface.   The mounting surface of the acceleration sensor according to claim 1 is bonded to a conductor member to detect acceleration by an adhesive, and the external electrode is electrically connected to an external signal processing circuit by wiring. The mounting structure of the characteristic acceleration sensor.

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