JP2010230513A - Acceleration sensor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor and a method of manufacturing the same coping with reduction in size while suppressing the effect of undulation by a wiring conductor. <P>SOLUTION: The acceleration sensor includes: a sensor element 20 including a fixing part 3, a weight part 1 displaced relative to the fixing part 3 when acceleration is applied thereto, and a beam part 2 having one end connected to the fixing part 3 and the other end connected to the weight part 1, and bent with the displacement of the weight part 1; a first substrate 30 having a flat plate shape on which the sensor element 20 is mounted; a base body 40 on which the first substrate 30 is mounted and in which wiring conductor 41 is arranged therein or on a surface 40S on which the first substrate 30 is mounted; and a first adhesive 10 intervening between the first substrate 30 and the base body 40, for fixing the first substrate 30 to the base body 40. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an acceleration sensor for detecting acceleration and a method for manufacturing the acceleration sensor.

  FIG. 9 is a sectional view of a conventional acceleration sensor. The acceleration sensor shown in the figure has a configuration including a sensor element 100 and a base body 200 on which the sensor element 100 is mounted.

  The sensor element 100 includes a weight part 101, a frame-shaped fixing part 102 surrounding the weight part 101, a beam part 103 connected to the weight part 101 and the fixing part 102, and a piezoresistor formed on the beam part 103. Element (not shown) (see, for example, Patent Document 1).

  When an external force corresponding to the acceleration is applied to the acceleration sensor having such a sensor element 100, the weight part 101 moves, and accordingly, the beam part 103 is deformed, and the piezoresistive element is also deformed. The acceleration is detected based on the change in resistance value due to the deformation of the piezoresistive element.

  Such a sensor element 100 is fixed to the base body 200 by an adhesive 104 interposed between the lower surface of the fixing portion 102 and the main surface of the base body 200.

  A gap g is formed between the lower surface of the weight part 101 and the main surface of the base body 200. By forming the gap g in this portion, the weight portion 101 can be moved freely. The dimension of the gap g is set to a predetermined range in accordance with the acceleration measurement range. As a method of controlling the size of the gap g, a method of mixing a spherical spacer member 105 with the adhesive 104 is known. The size of the gap g can be adjusted by using the spacer member 105 having a predetermined diameter (see, for example, Patent Document 2).

JP 2004-184081 A JP-A-4-274005

  By the way, in the conventional acceleration sensor as shown in FIG. 9, the wiring conductor is normally provided in the inside of the base body 200 or on the main surface. Signals are input / output between the sensor element 100 and the outside via the wiring conductor.

  When the wiring conductor is provided inside the base body 200, the surface of the base body 200 is undulated under the influence of the thickness of the wiring conductor. In this case, in the main surface of the base body 200, the region immediately above the wiring conductor is a portion that is raised from the other portion (hereinafter also referred to as a raised portion). When a wiring conductor is provided on the main surface of the base body 200, the wiring conductor itself becomes a raised portion as it is.

  When such a raised portion exists on the mounting surface of the sensor element 100, various problems occur.

  For example, if the raised portion exists in the region immediately below the weight portion 101, the dimension of the gap g between the lower surface of the weight portion 101 and the bottom portion of the base body 200 becomes smaller than a desired value. Thus, when the dimension of the gap g becomes smaller than a desired value, the range of acceleration that can be measured is changed, leading to a problem that acceleration that should originally be detectable cannot be detected.

  In addition, when the raised portion is below the fixed portion 102, the sensor element 100 is mounted in an inclined state, resulting in a decrease in acceleration detection accuracy.

  Such a problem can be solved by arranging the wiring conductor so as to avoid the area immediately below the sensor element 100, but in that case, the area immediately below the sensor element 100 cannot be used as the wiring area of the wiring conductor. In order to secure the area, the base body 200 must be enlarged, which leads to an increase in the size of the acceleration sensor.

  That is, in the conventional acceleration sensor, it has been difficult to reduce the size of the acceleration sensor while solving the problem caused by the raised portion.

  The present invention has been invented to solve the above-described problems, and an object of the present invention is to provide an acceleration sensor and a method for manufacturing the acceleration sensor that can be reduced in size while suppressing the influence of undulation caused by the wiring conductor. For the purpose.

  The acceleration sensor of the present invention includes a fixed portion, a weight portion that is displaced with respect to the fixed portion when acceleration is applied, one end connected to the fixed portion, and the other end connected to the weight portion. A sensor element having a beam portion that bends in accordance with a displacement; a flat plate-like first substrate on which the sensor element is mounted; and a base on which the first substrate is mounted. A base on which a wiring conductor is disposed on a surface on which the first substrate is mounted, and a first base for interposing the first substrate and the base, and fixing the first substrate to the base And an adhesive.

  The acceleration sensor manufacturing method of the present invention includes a fixed portion, a weight portion that is displaced with respect to the fixed portion when acceleration is applied, one end connected to the fixed portion, and the other end connected to the weight portion. A step of preparing a sensor element having a beam part that bends in accordance with the displacement of the weight part, a flat first board on which the sensor element is mounted, and a base body on which the first board is mounted And a step of preparing a base on which a wiring conductor is disposed on the inside or a surface on which the first substrate is mounted, and applying a viscous member serving as a first adhesive to the main surface of the base Then, the step of mounting the first substrate on the base so that the viscous member is interposed between the first substrate and the base, and the sensor element on the first substrate And a process of mounting.

  According to the present invention, the sensor element is mounted on the flat plate-like first substrate, and the first substrate is mounted on the base body on which the wiring conductor is provided. That is, the sensor element is not directly mounted on the base body on which the wiring conductor is provided, but is mounted on the base body via the flat first substrate. Therefore, on the surface on which the sensor element is mounted, the region immediately below the sensor element is kept flat, and is hardly affected by the raised portions present on the second mounting substrate. In addition, since the wiring conductor can be routed in the region directly below the sensor element on the base body, it is not necessary to separately secure the wiring conductor routing region, and an acceleration sensor corresponding to downsizing can be provided.

1 is a perspective view of an acceleration sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the acceleration sensor shown in FIG. 1 and corresponds to a cross section taken along line A-A ′ of FIG. 1. It is a perspective view of the sensor element mounted in the acceleration sensor shown in FIG. It is sectional drawing of the sensor element mounted in the acceleration sensor shown in FIG. 1, and is equivalent to the cross section when it cut | disconnects by the B-B 'line | wire of FIG. FIG. 4 is a perspective view of a state where a second substrate is attached to the sensor element shown in FIG. 3. It is a perspective view which shows the modification 1 of the acceleration sensor which concerns on embodiment of this invention. It is a perspective view which shows the modification 2 of the acceleration sensor which concerns on embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the acceleration sensor which concerns on embodiment of this invention. It is sectional drawing which shows the conventional acceleration sensor schematically.

  Exemplary embodiments of an acceleration sensor and an acceleration sensor manufacturing method according to the present invention will be described below in detail with reference to the drawings. Note that the drawings used in the following embodiments are schematic, and the dimensional ratios in the drawings do not necessarily match the actual ones.

<Acceleration sensor>
FIG. 1 is a perspective view of an acceleration sensor according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG.

As shown in FIGS. 1 and 2, the acceleration sensor according to the present embodiment is mainly composed of a sensor element 20, a first substrate 30 on which the sensor element 20 is mounted, and a base body 40 on which the first substrate is mounted. It is configured.
First, the sensor element 20 according to the present embodiment will be described. FIG. 3 is a perspective view of the sensor element 20.

  The sensor element 20 is configured as, for example, a three-dimensional acceleration sensor using a piezoresistive effect, and can detect acceleration in the X-axis, Y-axis, and Z-axis directions in the three-dimensional orthogonal coordinate system.

  As shown in FIG. 3, the sensor element 20 includes a weight part 1, a frame-shaped fixing part 3 surrounding the weight part 1, a beam part 2 connected to the weight part 1 and the fixing part 3, and a beam part 2. The resistance element 5 is formed. The weight part 1, the fixing part 3, and the beam part 2 are integrally formed, for example, by processing an SOI (Silicon on Insulator) substrate.

  The weight part 1 in this embodiment is comprised from the main part 1a distribute | arranged to the center of the opening part of the fixing | fixed part 3, and the four attachment parts 1b distribute | arranged to the four corners of the main part 1a. The main portion 1a has a substantially square planar shape, and the length of one side is set to, for example, 0.2 mm to 0.5 mm. Moreover, the thickness of the main part 1a is set to 0.2 mm-0.625 mm, for example. The attachment portion 1b has a substantially square shape in the same manner as the main portion 1a, and the length of one side thereof is set to 0.1 mm to 0.4 mm, for example. Moreover, the thickness of the attachment part 1b is set to 0.2 mm-0.625 mm so that it may have the same thickness as the main part 1a. In addition, the planar shape of the main part 1a and the attachment part 1b is not restricted to a square, Arbitrary shapes, such as a circle and a rectangle, are possible.

  When acceleration is applied to the sensor element 20, a force corresponding to the acceleration acts on the weight part 1, and the beam part 2 is bent as the weight part 1 moves. Although the weight part 1 can be constituted only by the main part 1a, since a larger force acts on the weight part 1 by providing the attachment part 1b, the bending of the beam part 2 with respect to the acceleration increases, Detection sensitivity can be improved.

  A fixing portion 3 is formed so as to surround the weight portion 1. The fixed portion 3 has a substantially square opening in the center, and has a substantially square opening slightly larger than the weight portion 1 at the center. The length of one side of the fixed part 3 in plan view is set to, for example, 0.8 mm to 3.0 mm. The width of each side in the plan view of the fixed part is set to 0.1 mm to 1.8 mm, for example. Moreover, the thickness of the fixing | fixed part 3 is set to 0.2 mm-0.625 mm, for example.

  The beam portion 2 is formed so as to connect the central portion on the upper surface side of each side of the main portion 1 a and the central portion on the upper surface side of each side in the inner periphery of the fixed portion 3. In the sensor element 20 in the present embodiment, two beam portions 2 in total, two in the X-axis direction with the main portion 1a of the weight portion 1 sandwiched therebetween and two in the Y-axis direction with the main portion 1a of the weight portion 1 sandwiched therebetween. Is provided. The beam portion 2 is formed so as to have flexibility. When acceleration is applied to the sensor element 20, the weight portion 1 moves, and the beam portion 2 bends as the weight portion 1 moves. For example, the length of the beam portion 2 is set to 0.1 mm to 0.8 mm, the width is set to 0.01 mm to 0.2 mm, and the thickness is set to 5 μm to 20 μm. Thus, flexibility is expressed by forming the beam portion 2 to be elongated and thin.

  A plurality of resistance elements 5 are formed on the upper surface of the beam portion 2. The resistance element 5 is a detection element for detecting the bending amount of the beam portion 2. More specifically, the resistive element 5 is a piezoresistive element formed by implanting boron into an SOI substrate. In the present embodiment, these resistances are placed at predetermined positions on the beam portion 2 so that the acceleration in the three-axis directions (X-axis direction, Y-axis direction, and Z-axis direction in the three-dimensional orthogonal coordinate system shown in FIG. 3) can be detected. Element 5 is formed. For example, two resistance elements 5 for detecting acceleration in the X-axis direction are provided on the two beam parts 2 extending in the X-axis direction, and two resistance elements 5 are arranged on each beam part 2. . Among these four resistance elements 5, the resistance elements arranged on the fixed part 3 side are connected in series, the resistance elements arranged on the main part 1a side are connected in series, and these are connected in series A bridge circuit is configured by connecting them in parallel.

  The two beam portions 2 extending in the Y-axis direction are provided with four resistance elements 5 for detecting the acceleration in the Y-axis direction. These resistance elements 5 are used for detecting the acceleration in the X-axis direction. The bridge circuit is configured by arranging the resistor elements 5 in the same manner and connecting the resistor elements to each other.

  Further, although not shown in FIG. 3, four resistance elements 5 for detecting acceleration in the Z-axis direction detect acceleration in the X-axis direction on two beam portions 2 extending in the X-axis direction. These four resistance elements 5 are formed to be aligned with each other. The resistance element 5 for acceleration detection in the Z-axis direction differs from the resistance element 5 for acceleration detection in the X-axis direction in the way of connecting the resistance elements, and in this embodiment, extends in the X-axis direction. A bridge is formed by connecting in series the resistance element 5 on the fixed part 3 side provided in one of the two beam parts and the resistance element 5 on the main part 1a side provided in the other beam part 2. The circuit is configured.

  When acceleration is applied to the sensor element 20 in which such a bridge circuit is assembled, the beam portion 2 bends as described above, and the resistance element 5 is deformed along with this bending, so that the output voltage detected by the bridge circuit changes. To do. The direction and magnitude of the applied acceleration can be detected by taking out the change in the output voltage based on the change in the resistance value as an electrical signal and processing it with an external IC. Note that the resistance element 5 for acceleration detection in the Z-axis direction may be provided in the two beam portions 2 extending in the Y-axis direction in the same manner as that provided in the beam portion 2 extending in the X-axis direction.

  An element-side electrode pad 4 that is electrically connected to the resistance element 5 is provided on the upper surface of the fixed portion 3, and the connection between the resistance elements and the electric power from the resistance element 5 are provided via the element-side electrode pad 4. The signal is taken out.

  FIG. 4 is a cross-sectional view of the sensor element 20 taken along line B-B ′ of FIG. As shown in FIG. 4, the sensor element 20 is formed by processing a semiconductor substrate 29. The semiconductor substrate 29 is, for example, an SOI substrate. The semiconductor substrate 29 has a structure in which a semiconductor layer 21, an insulating layer 23, and a support layer 25 are stacked in this order from the upper surface side.

The semiconductor layer 21 and the support layer 25 are made of silicon, for example. The insulating layer 23 is made of, for example, SiO ₂ . The thickness of the semiconductor layer 21 is, for example, 5 μm to 20 μm. The thickness of the insulating layer 23 is, for example, 0.1 μm to 5 μm. The thickness of the support layer 25 is, for example, 200 μm to 650 μm.

  The fixed portion 3 and the weight portion 1 are composed of a semiconductor layer 21, an insulating layer 23, and a support layer 25, and the beam portion 2 is composed of a semiconductor layer 21.

  A second substrate 50 is attached to the upper surface side of the sensor element 20. FIG. 5 shows a perspective view of the sensor element 20 with the second substrate 50 attached thereto. The second substrate 50 is for suppressing breakage of the beam portion 2 when excessive acceleration is applied. A relatively small gap is secured between the weight portion 1 and the second substrate 50 so that the weight portion 1 can be displaced upward (see FIG. 2). Then, when excessive acceleration is applied to the acceleration sensor and the weight portion 1 is displaced upward, the weight portion 1 comes into contact with the second substrate 50 and the displacement is restricted. Thereby, it can suppress that the beam part 2 is damaged.

  The second substrate 50 is disposed to face the sensor element 20. The second substrate 50 is formed in a size that covers the entire weight portion 1. The second substrate 50 has substantially the same shape as the planar shape of the sensor element 3, and a cutout portion 50 a for exposing the element-side electrode pad 4 is provided on the side surface of the second substrate 50. Yes. As the second substrate 50, a glass substrate, a silicon substrate, or the like can be used, but an insulating substrate is preferably used from the viewpoint of preventing a short circuit with the metal thin wire 61.

  The second substrate 50 is fixed to the sensor element 20 via an adhesive at the four corners of the upper surface of the fixing portion 3. The adhesive material includes a plurality of spherical spacer members. The size of the gap between the second substrate 50 and the weight portion 1 can be adjusted by this spacer member. Since the dimension of the spacer member diameter is substantially the same as the gap dimension, the gap size can be controlled by adjusting the spacer member diameter. The diameter of the spacer member is, for example, 4 μm to 30 μm.

  As shown in FIG. 2A, the sensor element 20 is mounted on a flat first substrate 30, and the first substrate 30 is mounted on the base body 40. In other words, the sensor element 20 is mounted on the base body 40 via the first substrate 30.

  A wiring conductor 41 electrically connected to the sensor element 20 and a plating conductor used for plating are provided in the base body 40 and the main surface 40S. Signals are input and output between the sensor element 20 and an external predetermined circuit via the wiring conductor 41. When the wiring conductor 41 is inside the base body 40, a raised portion 42 that rises from the other portion is formed on the main surface 40 </ b> S of the base body 40 depending on the thickness of the wiring conductor 41. On the other hand, the wiring conductor 41 formed on the main surface 40S is also a raised portion 42, which is a raised portion from the other portions. The thickness of the raised portion 42 is, for example, 3 μm to 20 μm.

  When the sensor element 20 is mounted on the main surface 40S on which such a raised portion 42 exists, it is a factor that causes a problem that acceleration that should be originally detected cannot be detected and a decrease in acceleration detection accuracy. That's right.

  On the other hand, according to the acceleration sensor according to the present embodiment, the sensor element 20 is not directly mounted on the base body 40 on which the wiring conductor 41 is provided, and the base body is interposed via the flat first substrate 30. 40, the flatness of the region immediately below the sensor element 20 is maintained on the surface on which the sensor element 20 is mounted, and is hardly affected by the raised portion 42 present in the base body 40. In addition, since the wiring conductor 41 can be routed in a region immediately below the sensor element 20 in the base body 40, there is no need to separately provide a wiring region of the wiring conductor 41, and an acceleration sensor corresponding to downsizing can be provided. Can do.

  The first substrate 30 is a flat plate member, and its outer periphery substantially coincides with the outer periphery of the fixed portion 3 when viewed in plan. In other words, the side surface of the first substrate 30 and the side surface of the sensor element 20 (the outer peripheral surface of the fixed portion 3) are flush with each other. As the first substrate 30, an insulating substrate is preferably used, and a glass substrate, a ceramic substrate, a silicon substrate whose surface is covered with an insulating film, and the like can be exemplified. In this embodiment, a glass substrate is used. The thickness of the first substrate 30 is, for example, about 50 μm when the planar shape of the first substrate 30 is 1 mm × 1 mm.

  The sensor element 20 and the first substrate 30 are bonded via a second adhesive material 9. As the second adhesive 9, a silicone resin, an epoxy resin, or the like can be used. Among these, it is preferable to use a silicone resin which is a resin having a relatively low Young's modulus from the viewpoint of relaxing the residual stress during bonding. The second adhesive material 9 is provided at positions corresponding to the four corners of the lower surface of the fixing portion 3. When the beam part 2 is connected to the center part of the upper surface four sides of the weight part 1a as in the present embodiment, the sensor element 20 and the first substrate 30 are joined at the four corners of the fixed part 3. Since the distance between the joint portion of the sensor element 20 to the first substrate 30 and the beam portion 2 is increased, the residual stress that can be generated due to the joining by the second adhesive material 9 is given to the beam portion 2. The influence can be reduced, and deterioration of the electrical characteristics of the acceleration sensor device can be suppressed.

  The first substrate 30 is for mounting the sensor element 20 and at the same time, for suppressing the beam portion 2 from being damaged when excessive acceleration is applied. A relatively small gap is secured between the weight part 1 and the first substrate 30 so that the weight part 1 can be displaced downward. Then, when excessive acceleration is applied to the acceleration sensor and the weight portion 1 is displaced downward, the weight portion 1 contacts the first substrate 30 and the displacement is restricted. Thereby, it can suppress that the beam part 2 is damaged. A spherical spacer member 11 having a predetermined diameter is kneaded in the second adhesive material 9. That is, the size of the gap between the lower surface of the weight portion 1 and the main surface 30 </ b> S of the first substrate 30 is adjusted by the spacer member 11. The spacer member 11 is a spherical member having a predetermined hardness such as silica, silicon, divinylbenzene, and the diameter thereof is, for example, 4 to 30 μm.

  The first substrate 30 is mounted on the base body 40 via the first adhesive material 10.

  The first adhesive 10 is made of silicone resin, epoxy resin, or the like. The height dimension of the first adhesive material 10 (the dimension from the main surface 40S to the apex of the first adhesive material 10) is the height dimension of the protuberance 42 (the dimension from the main surface 40S to the apex of the protuberance 42). It is formed so as to be larger. As a result, the first substrate 30 is not in contact with the raised portion 42, and the influence of the raised portion 42 hardly appears on the main surface 30 </ b> S of the first substrate 30, and the main surface 30 </ b> S that is the mounting surface of the sensor element 20. The flatness is maintained. It is preferable to use the same material for the first adhesive material 10 and the second adhesive material 9. By using the same material, the first adhesive 10 and the second adhesive 9 can be cured at the same time, and the acceleration sensor productivity can be increased as compared with the case where the first adhesive 10 and the second adhesive 9 are separately cured.

  The first adhesive 10 is bonded only to the central portion of the first substrate 30 when viewed in plan. When the difference between the linear expansion coefficients of the first substrate 30 and the base 40 is large, the first adhesive material 10 is bonded to only one central portion of the first substrate 30 in this manner, thereby increasing the linear expansion coefficient. The deformation of the first substrate 30 due to the difference can be suppressed.

  The base body 40 has a substantially rectangular parallelepiped shape, and a cavity for accommodating the sensor element 20 is formed inside. The base 40 is formed by laminating five insulating layers 40a to 40e made of a ceramic material or the like.

  The insulating layers 40a and 40b are made of a flat member. The insulating layers 40c, 40d, and 40e are frame-shaped members having a hole at the center. The sizes of the holes in the insulating layers 40c and 40d are provided to be slightly larger than the sensor element 20, and the holes in the insulating layer 40e are formed to be larger than the holes provided in the insulating layers 40c and 40d. Has been.

  A plurality of substrate-side electrode pads 44 are formed on the base body 40. These substrate-side electrode pads 44 are provided on the upper surface of the insulating layer 40d exposed from the hole of the insulating layer 40e. The substrate-side electrode pad 4 is electrically connected to the element-side electrode pad 4 provided on the upper surface of the fixed portion of the sensor element 20 by a thin metal wire 61. An external terminal 43 is provided on the lower surface of the base body 40, and the external terminal 43 is connected to the substrate-side electrode pad 4 via a via-hole conductor 45 and a wiring conductor 41 provided inside the substrate. That is, the electrical signal of the sensor element 20 is extracted to the outside through the element side electrode pad 4, the metal thin wire 6, the substrate side electrode pad 44, the external terminal 2, and the like.

  The lid 60 is fixed to the upper surface of the base body 40 so as to close the opening of the cavity of the base body 40, whereby the sensor element 20 is hermetically sealed in the cavity. The lid 60 is made of, for example, a metal plate such as 42 alloy, stainless steel, or kovar, and is bonded to the base 40 by a bonding material 62 such as silver solder, Au—Sn, or epoxy resin.

  When the lid 60 is made of metal, it is preferable that the upper surface of the second substrate 50 is located at a position higher than the apex of the thin metal wire 61. Since the first adhesive material 10 and the second adhesive material 9 expand and contract to some extent, the entire sensor element 20 may be displaced upward when a large acceleration is applied. Since the second substrate 50 is first brought into contact with the lid 60 by placing the upper surface higher than the apex of the fine metal wire 61, the fine metal wire 61 can be prevented from coming into contact with the metal lid 60. That is, since it is possible to suppress the metal thin wire 61 serving as the input / output path for the electric signal from coming into contact with the metal lid, the signal can be input / output normally.

(Modification 1)
FIG. 6 is a cross-sectional view showing Modification 1 of the acceleration sensor according to the above-described embodiment. The cross-sectional view of FIG. 6 corresponds to the cross section taken along the line AA ′ of FIG. The acceleration sensor according to the modification 1 further includes an IC chip 70 that performs arithmetic processing on the electrical signal detected by the resistance element 5. In the acceleration sensor according to the first modification, the IC chip 70 is accommodated in a cavity provided on the lower surface side of the base body 40. The IC chip 70 is electrically connected to the sensor element 20 and the external terminal 2 through a via-hole conductor 45 and a wiring conductor 41 provided on the base body 40. The IC chip 70 includes, for example, an amplifier circuit that amplifies the output signal of the sensor element 20, a temperature compensation circuit that corrects the temperature characteristics of the sensor element 20, and a noise removal circuit that removes noise. By providing such an IC chip 70, acceleration can be detected with high accuracy.

  As shown in FIG. 6, when a cavity is provided on the back side and the IC chip 70 is arranged there, the number of the wiring conductors 41 connected to the IC chip 70 increases, and the number of the raised portions 42 also increases. Therefore, although the possibility that a problem due to the raised portion 42 occurs is increased, the detection range of acceleration is changed by mounting the sensor element 20 via the flat first substrate 30 even in such a case. It is possible to cope with downsizing of the acceleration sensor while suppressing the acceleration.

(Modification 2)
FIG. 7 is a cross-sectional view showing Modification Example 2 of the acceleration sensor according to the above-described embodiment. 7 corresponds to a cross section taken along line AA ′ of FIG. The acceleration sensor according to the modified example 2 further includes a spherical spacer member 11 kneaded in the first adhesive material 10. As the spacer member 11, one having a diameter dimension equal to or larger than the thickness dimension of the wiring conductor 41 is used. By kneading such a spacer member 11 in the first adhesive 10, the height dimension from the main surface 40S of the first substrate 30 (the dimension between the main surface 40S and the lower surface of the first substrate 30). ) Is equal to or greater than the thickness of the raised portion 42, and the raised portion 42 is not subjected to a large load from the sensor element 20 or the first substrate 30. Therefore, the flatness of the main surface of the first substrate 30 is hardly affected by the raised portion 42, and a gap between the lower surface of the weight portion 1 and the main surface 30S of the first substrate 30 is set as desired. Can be kept in size. Thereby, it can suppress that the detection range of acceleration changes from the desired range. The diameter dimension of the spacer member 11 is a value obtained by taking an average value of the spacer member 11 included in the first adhesive 30.

<Method for manufacturing acceleration sensor>
Next, the manufacturing process of the acceleration sensor according to the present embodiment will be described with reference to FIG. 8 is a portion corresponding to a cross section taken along line AA ′ of FIG.

(Process for preparing sensor elements)
First, a sensor element 20 having a fixed portion 3, a weight portion 1, a fixed portion 3 and a beam portion 2 connected to the weight portion 1 is prepared.

  The sensor element 20 is manufactured using, for example, an SOI substrate as shown in FIG. 4. First, a resistive element made of piezoresistor is formed by implanting boron into the silicon layer on the surface of the SOI substrate by an ion implantation method. 5 is formed. Next, the sensor element 20 is manufactured by forming the weight portion 1, the fixing portion 3, and the beam portion 2 by applying a conventionally known semiconductor microfabrication technique such as sputtering or etching.

(Step of preparing first substrate and base)
On the other hand, a flat plate-like first substrate 30 on which the sensor element 20 is mounted and a base body 40 on which the first substrate 30 is mounted, the wiring conductor 41 on the inside or on the surface on which the first substrate 30 is mounted. Is prepared.

  The first substrate 30 is a flat plate member made of a glass substrate, a silicon substrate, a ceramic substrate, or the like. In this embodiment, a glass substrate is used. The first substrate 30 has a rectangular shape when seen in a plan view, and has a size that substantially matches the outer periphery of the fixed portion 3 of the sensor element 20.

  The base 1 is formed by laminating a plurality of insulating layers 40a to 40e. Specifically, first, a slurry obtained by adding and kneading a suitable organic binder, organic solvent, etc. to ceramic powder such as glass-ceramic and alumina is tape-molded to a predetermined thickness by a conventionally known doctor blade method or the like. Thus, a semi-cured ceramic green sheet is formed, and these are cut into a predetermined size to produce a sheet serving as each insulating layer. Next, the produced sheets are laminated in a predetermined order, press-molded, and then fired at a high temperature to produce the substrate 1 (FIG. 8A).

  A wiring conductor 41 and a plating conductor used for plating are formed on the inside of the substrate 1 and the main surface 40S. The wiring conductor 41 is formed in a predetermined pattern on the main surface of each insulating layer before firing a conductive paste obtained by kneading a metal powder such as Ag, Ag-Pd, Ag-Pt, or Cu, an organic binder, or an organic solvent. It is formed by printing and baking. The thickness of the wiring conductor 41 after firing is about 10 μm to 20 μm. When the wiring conductor 41 is provided inside the base body 40, the wiring conductor 41 is affected by the thickness of the wiring conductor 41 and is raised on the main surface 40 </ b> S of the base body 40. Part 42 is formed. When the wiring conductor 41 is provided on the main surface 40S, it becomes the raised portion 42 itself.

  In addition to the wiring conductor 41, the substrate 40 is formed with external terminals 43, substrate-side electrode pads 44, via-hole conductors 45, and the like. These can be formed in the same manner as the wiring conductor 41 using the same material as the wiring conductor 41.

(First board mounting process)
Next, a step of mounting the first substrate 30 on the base body 40 is performed. In this step, as shown in FIG. 8B, first, a viscous member 10 ′ that becomes the first adhesive 10 is applied to the main surface 40 </ b> S of the base body 40. In the present embodiment, the viscous member 10 ′ is applied to the central portion of the main surface 40 </ b> S of the base body 40. The viscous member 10 ′ is adjusted to have a predetermined viscosity. Specifically, when the viscous member 10 ′ is applied, the viscosity is adjusted so as to maintain a predetermined height without being excessively spread, and the viscosity is adjusted to about 7 Pa · s, for example. The viscous member 10 ′ adjusted to have a predetermined viscosity in this way is applied such that its apex is higher by about several μm than the apex of the raised portion 42. Since the thickness of the wiring conductor 41 is generally grasped at the stage where the base body 1 is manufactured, the height of the viscous member 10 ′ is higher than the apex of the raised portion 42 by adjusting the viscosity and the coating amount of the viscous member 10 ′. It can apply | coat so that it may become. The viscous member 10 ′ is made of, for example, a resin material such as an epoxy resin or a silicone resin, and is applied using a dispenser or the like.

  Next, as shown in FIG. 8C, the first substrate 30 is placed such that the viscous member 10 ′ is interposed between the first substrate 30 and the base body 40 (arrow M1 in the figure). Mounting step). The first substrate 30 is placed on the viscous member 10 'using a suction device such as a collet. At this stage, since the viscous member 10 ′ is not cured, if the base 40 is moved, the first substrate 30 placed on the viscous member 10 ′ may be displaced. Therefore, the gap between the side surface of the first substrate 30 and the inner wall surface of the cavity (inner peripheral surfaces of the holes of the insulating layers 40c and 40d) is set to a predetermined range so that the first substrate 30 is not greatly displaced. It is preferable to keep it. Specifically, the gap between the side surface of the first substrate 30 and the inner wall surface of the cavity is preferably in the range of 10 μm to 25 μm. Thereby, even when the base 40 is moved, the first substrate 30 is not greatly displaced.

(Sensor element mounting process)
In the mounting process of the sensor element 20, as shown in FIG. 8C, first, a viscous member 9 ′ that becomes the second adhesive 9 is applied to the main surface 30 </ b> S of the first substrate 30. For example, silicone resin or epoxy resin can be used as the viscous member 9 ′, but it is preferable to use the same material as the viscous member 10 ′. By making the viscous member 10 'serving as the first adhesive 10 and the viscous member 9' serving as the second adhesive 9 the same material, the viscous member 10 'and the viscous member 9' can be cured simultaneously. It is possible to increase the productivity of the acceleration sensor.

  The viscous member 9 ′ is applied to positions corresponding to the four corners of the lower surface of the fixing unit 3 using a dispenser or the like. Further, the viscous member 9 ′ includes a spherical spacer member 11 for providing a gap having a predetermined size between the lower surface of the weight portion 1 and the main surface 30 </ b> S. The spacer member 11 is a spherical member having a predetermined hardness, such as silica, silicon, divinylbenzene, and the diameter thereof is, for example, 4 μm to 30 μm.

  After applying the viscous member 9 ′ to the main surface 30 </ b> S of the first substrate 30, the sensor element 20 is mounted on the main surface 30 </ b> S of the first substrate 30 (a mounting process indicated by an arrow M <b> 2 in the drawing). When the first substrate 30 is placed on the viscous member 10 ′ and the sensor element 20 is placed thereon, the viscous member 10 ′ spreads around by these weights, and its height decreases. Since the viscous member 10 ′ is adjusted to a predetermined viscosity, the apex of the viscous member 10 ′ is higher than the apex of the raised portion 42 even at this stage. In this state, the viscous members 9 ′ and 10 ′ are heated to cure both viscous members, thereby fixing the first substrate 30 to the base body 40 and the sensor element 20 to the first mounting substrate 30.

  Since the viscous members 9 ′ and 10 ′ are not cured immediately after the placement process M2, the first substrate 30 and the sensor element 20 may be misaligned when the base body 40 is moved. As described above, the gap between the side surface of the first substrate 30 and the inner wall surface of the cavity and the gap between the side surface of the sensor element 20 and the inner wall surface of the cavity are set in the range of 10 μm to 25 μm. Thus, the first substrate 30 and the sensor element 20 are not greatly displaced.

(Sealing process)
Next, the second substrate 50 is attached to the upper surface of the sensor element 20. The second substrate 50 may be attached before the sensor element 20 is mounted on the base body 40. Thereafter, the element-side electrode pad 4 provided on the sensor element 20 and the substrate-side electrode pad 44 provided on the base body 40 are connected by a thin metal wire 61 made of gold, copper, aluminum or the like. Finally, the sensor lid 20 is sealed in the cavity of the base body 40 by bonding a metal lid 60 made of 42 alloy or the like to the upper surface of the base body 40 with a bonding material 62. Thereby, the acceleration sensor as a product is completed.

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

  For example, in the above-described embodiment, a piezoresistive acceleration sensor using a piezoresistive element as a detection element has been described. However, the present invention can be applied to a capacitive acceleration sensor using a capacitive element as a detection element. Is also applicable.

  Further, in the above-described embodiment, the first adhesive material 10 is bonded to only one central portion of the first substrate 30. However, the bonding location of the first adhesive material 10 is not limited to this, and there are a plurality of locations. May be adhered to each other, or may be adhered to the entire lower surface of the first substrate 30.

  In the above-described embodiment, the manufacturing method of mounting the sensor element 20 on the first substrate 30 after mounting the first substrate 30 on the base body 40 has been described. However, the mounting of the first substrate 30 and the sensor element 20 is described. The order is not limited to this, and the first substrate 30 may be mounted on the base 40 after the sensor element 20 is mounted on the first substrate 30.

DESCRIPTION OF SYMBOLS 1 ... Weight part 2 ... Beam part 3 ... Fixed part 4 ... Board | substrate side electrode pad 5 ... Resistance element 10 ... 1st adhesive material 20 ... Sensor element 30 ...・ First substrate 40 ... Base

Claims (6)

A fixed portion, a weight portion that is displaced with respect to the fixed portion when acceleration is applied, a beam that has one end connected to the fixed portion and the other end connected to the weight portion, and bends as the weight portion is displaced. A sensor element having a portion;
A flat first substrate on which the sensor element is mounted;
A base on which the first substrate is mounted, and a base on which a wiring conductor is disposed inside or on a surface on which the first substrate is mounted;
An acceleration sensor, comprising: a first adhesive that is interposed between the first substrate and the base body and fixes the first substrate to the base body.   The sensor element is fixed to the first substrate by a second adhesive interposed between a lower surface of the fixing portion and a mounting surface of the first substrate, and the first adhesive and the first The acceleration sensor according to claim 1, wherein the two adhesives are made of the same material.   The acceleration sensor according to claim 1, wherein the first adhesive material includes a spherical spacer member, and a diameter dimension of the spacer member is equal to or greater than a thickness dimension of the wiring conductor. In a state where a predetermined interval is provided between the cavity provided in the base, the electrode pad provided on the upper surface of the fixed portion, the metal thin wire connected to the electrode pad, and the upper surface of the weight portion. A second substrate disposed on the sensor element; and a metal lid for closing the opening of the cavity;
2. The acceleration according to claim 1, wherein the base body, the sensor element, and the second substrate are accommodated in the cavity, and an upper surface of the second substrate is at a position higher than an apex of the thin metal wire. Sensor. The sensor element has a detection element for detecting the amount of bending of the beam portion,
The acceleration sensor according to claim 1, further comprising an IC chip that processes a detection signal from the detection element. A fixed portion, a weight portion that is displaced with respect to the fixed portion when acceleration is applied, a beam that has one end connected to the fixed portion and the other end connected to the weight portion, and bends as the weight portion is displaced. A step of preparing a sensor element having a portion;
A flat first substrate on which the sensor element is mounted and a base on which the first substrate is mounted, and a wiring conductor is disposed inside or on the surface on which the first substrate is mounted. A step of preparing a substrate;
After applying a viscous member serving as a first adhesive to the main surface of the base, the first substrate is moved to the first substrate in such a manner that the viscous member is interposed between the first substrate and the base. Mounting on a substrate;
Mounting the sensor element on the first substrate.

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