Deformation detection sensor

Abstract

The present invention relates to a deformation detection sensor. The deformation detection sensor (10) comprises: a detection electrode (13); a first ground electrode (12); a piezoelectric film (15) sandwiched between the detection electrode (13) and the first ground electrode (12); a substrate (16) on which the detection electrode (13) and the second ground electrode (14) are formed; a wiring (20) connected to the detection electrode (13); and a bonding member (30) bonding the wiring (20) and the detection electrode (13).

Description

Technical Field

[0001] The present invention relates to a deformation detection sensor for detecting deformation of a detection object. Background Art

[0002] Patent Document 1 discloses a pressure sensor using a piezoelectric film. The piezoelectric film is sandwiched between a detection electrode and a ground electrode. The pressure sensor detects a pressure by detecting a potential difference generated between the detection electrode and the ground electrode.

[0003] Patent Document 1: International Publication No. 2015 / 159628

[0004] A pressure sensor like that described in Patent Document 1 requires wiring to output the sensor's signal to the computation circuit. To connect the sensor and wiring, mounting components such as terminal blocks are used. However, the use of mounting components increases the thickness of the sensor, preventing the effective utilization of the thin piezoelectric film's characteristics. Furthermore, a mounting area for mounting the terminal blocks, etc., on the sensor is required. Summary of the Invention

[0005] Therefore, an object of the present invention is to provide a deformation detection sensor that can effectively utilize the characteristics of a thin piezoelectric film without requiring a mounting portion for mounting a terminal member or the like on the sensor.

[0006] The deformation detection sensor of the present invention comprises: a detection electrode; a first ground electrode; a second ground electrode; a piezoelectric film sandwiched between the detection electrode and the first ground electrode; a substrate on which the detection electrode and the second ground electrode are formed; wiring connected to the detection electrode; and a bonding member bonding the wiring to the detection electrode. The bonding member overlaps with the first ground electrode in a plan view and is disposed on a second surface of the substrate opposite to the first surface on which the piezoelectric film is disposed.

[0007] Thus, in the deformation detection sensor of the present invention, the wiring and detection electrodes are joined by a bonding member (e.g., solder, anisotropic conductive resin, etc.). As a result, the deformation detection sensor of the present invention does not use terminal components, effectively utilizing the characteristics of the thinner piezoelectric film. Furthermore, because the bonding occurs on the second surface opposite to the first surface on which the piezoelectric film is disposed, there is no need for a mounting portion on the surface of the piezoelectric film. This increases the area occupied by the piezoelectric film and reduces the overall sensor area.

[0008] According to the present invention, it is possible to provide a deformation detection sensor that can effectively utilize the characteristics of a thin piezoelectric film without requiring a mounting portion such as a terminal member to be mounted on the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 (A) is a top view of the electronic device 1 including the pressure sensor 10. Figure 1 (B) is a side view of the electronic device 1 .

[0010] Figure 2 (A) is a top view of the pressure sensor 10. Figure 2 (A) is a cross-sectional view taken along line AA.

[0011] Figure 3 It is a cross-sectional view of a pressure sensor 10A according to Modification 1.

[0012] Figure 4 (A) is a top view of a pressure sensor 10B according to Modification 2. Figure 4 (B) is a cross-sectional view along line AA.

[0013] Figure 5 It is a cross-sectional view of a pressure sensor 10C according to Modification 3.

[0014] Figure 6 4 is a cross-sectional view of a pressure sensor 10D according to a fourth modification.

[0015] Figure 7 It is a cross-sectional view of a pressure sensor 10E according to Modification 5.

[0016] Figure 8 It is a top view of the pressure sensor 10F.

[0017] Figure 9 (A) is a perspective view of the pressure sensor 10F. Figure 9 (B) is a partially exploded stereogram.

[0018] Figure 10 (A) is Figure 8 The cross-sectional view of line AA is shown. Figure 10 (B) is Figure 8 A cross-sectional view along line BB is shown. DETAILED DESCRIPTION

[0019] Figure 1 (A) is a plan view of the electronic device 1 including the pressure sensor 10 . Figure 1 (B) is a side view of the electronic device 1 .

[0020] The electronic device 1 is, for example, an information processing terminal such as a smartphone. The electronic device 1 includes a housing 2, a front panel 3, and a display device 4. The housing 2 incorporates various circuits of the information processing terminal.

[0021] The display device 4 includes an electrostatic capacitance sensor 5 and a display unit 6. The electrostatic capacitance sensor 5 detects a touch operation on the front panel 3. The display unit 6 is composed of an LCD or an OLED, and displays an image.

[0022] The front panel 3 deforms when pressed by a finger or the like. The pressure sensor 10 is an example of a deformation detection sensor of the present invention. The pressure sensor 10 deforms integrally with the front panel 3. The pressure sensor 10 has a rectangular shape when viewed from the front.

[0023] Figure 2 (A) is a top view of the pressure sensor 10. Figure 2 (A) is a cross-sectional view taken along line AA. The pressure sensor 10 includes a piezoelectric film 15 , a substrate 16 , wiring 20 , and a connecting member 50 .

[0024] The first ground electrode 12 is arranged on the first principal surface of the piezoelectric film 15, and the detection electrode 13 is arranged on the second principal surface. The detection electrode 13 is arranged on the first principal surface of the substrate 16, and the second ground electrode 14 is arranged on the second principal surface.

[0025] The wiring 20 includes a wiring base material 23 , a wiring ground electrode 22 formed on a first main surface of the wiring base material 23 , and a wiring detection electrode 21 formed on a second main surface of the wiring base material 23 .

[0026] The detection electrode 13 of the base material 16 and the wiring detection electrode 21 of the wiring 20 are bonded together by a bonding member 30 .

[0027] The connection member 50 is connected to an object to be detected for deformation, such as the surface panel 3. Thus, the connection member 50 deforms along with the deformation of the surface panel 3. The second ground electrode 14 is attached to the upper surface of the connection member 50 via an adhesive (not shown).

[0028] The substrate 16 is made of an insulating material such as polyimide. Electrodes such as copper foil are formed on both main surfaces of the substrate 16. In this example, the electrode formed on the first main surface of the substrate 16 on the first ground electrode side serves as the detection electrode 13, and the electrode formed on the second main surface on the opposite side serves as the second ground electrode 14.

[0029] The piezoelectric film 15 is attached to the upper surface of the detection electrode 13 via an adhesive (not shown). The first ground electrode 12 is attached to the upper surface of the piezoelectric film 15. The first ground electrode 12 is made of, for example, a conductive adhesive and a metal thin film.

[0030] The area of ​​the first ground electrode 12 is substantially the same as or larger than the area of ​​the piezoelectric film 15 , and covers the piezoelectric film 15 in a plan view.

[0031] In a plan view, the base material 16 extends laterally along the longitudinal direction of the piezoelectric film 15. In this extended portion, a bonding member 30 is disposed on the upper surface of the detection electrode 13. The bonding member 30 electrically and physically connects the detection electrode 13 and the wiring detection electrode 21.

[0032] Wiring substrate 23 is made of an insulating material such as polyimide. Electrodes such as copper foil are formed on both main surfaces of wiring substrate 23. In this example, the electrode formed on the first main surface of wiring substrate 23, which is on the first ground electrode side, serves as wiring ground electrode 22, while the electrode formed on the second main surface on the opposite side serves as wiring detection electrode 21.

[0033] The first ground electrode 12 and the second ground electrode 14 are connected to the wiring ground electrode 22 via a via conductor (not shown) and the like.

[0034] The bonding member 30 is made of, for example, solder, anisotropic conductive resin, etc. The anisotropic conductive resin is thermally compressed to electrically connect and physically bond the detection electrode 13 and the wiring detection electrode 21 .

[0035] In a plan view, the bonding member 30 overlaps with the second ground electrode 14 and the wiring ground electrode 22. Therefore, shielding properties are improved in the bonding member 30. Furthermore, both the second ground electrode 14 and the wiring ground electrode 22 are composed of electrodes formed on the base material 16 and the wiring base material 23, respectively. Therefore, mechanical strength is improved in the bonding member 30.

[0036] In the pressure sensor 10A of the present embodiment, since no terminal member is used for the electrical connection between the substrate 16 and the wiring 20 , the characteristics of the thin piezoelectric film 15 can be effectively utilized.

[0037] Next, Figure 3 : is a cross-sectional view of a pressure sensor 10A according to Modification 1. Figure 2 The common structures of (B) are denoted by the same reference numerals and their description is omitted.

[0038] Pressure sensor 10A of Modification 1 includes a reinforcing member 70 between connecting member 50 and second ground electrode 14. Reinforcing member 70 is formed, for example, from a SUS plate. Reinforcing member 70 is joined to second ground electrode 14 and connecting member 50 using a joining member such as solder. Consequently, in pressure sensor 10A of Modification 1, shielding properties and mechanical strength of joining member 30 are improved.

[0039] Next, Figure 4 (A) is a top view of a pressure sensor 10B according to Modification 2. Figure 4 (B) is the cross-sectional view of line AA. Figure 2 (A) and Figure 2The common structures of (B) are denoted by the same reference numerals and their description is omitted.

[0040] In this example, the electrodes formed on the first and second principal surfaces of substrate 16 are patterned. The electrodes formed on the first principal surface are divided into detection electrode 13A and ground electrode 13B. Detection electrode 13A is positioned opposite piezoelectric film 15. Ground electrode 13B is positioned so as not to oppose piezoelectric film 15 and to substantially overlap substrate 16 and wiring 20 when viewed from above.

[0041] The electrodes formed on the second main surface are divided into detection electrodes 14A and ground electrodes 14B. Figure 4 As shown by the hatching in (A), the detection electrode 14A is formed at a position where the substrate 16 and the wiring 20 overlap when viewed from above, and at a position where it overlaps with a portion of the piezoelectric film 15. Furthermore, the detection electrode 14A is formed on the substrate 16 except at both ends in the short-axis direction. The ground electrode 13B is formed at a position where it overlaps substantially the entire surface of the piezoelectric film 15 when viewed from above, and at a position where it overlaps with the substrate 16 and the wiring 20 when viewed from above. The ground electrode 13B is arranged on both ends in the short-axis direction of the position where the substrate 16 and the wiring 20 overlap when viewed from above.

[0042] Detection electrodes 13A and 14A are electrically connected by via conductors 90 at locations where they overlap with piezoelectric film 15 in a plan view. The locations of via conductors 90 are not limited to this example. In other words, in this example, the detection electrodes are composed of a first electrode (detection electrode 13A) disposed on the first surface of substrate 16 and a second electrode (detection electrode 14A) disposed on the second surface.

[0043] The electrodes formed on the first main surface of the wiring base material 23 are also patterned. The electrodes formed on the first main surface of the wiring base material 23 are divided into wiring detection electrodes 21A and wiring ground electrodes 21B. When viewed from above, the wiring detection electrodes 21A are formed at locations other than the ends in the short-axis direction of the wiring base material 23. When viewed from above, the wiring ground electrodes 21B are formed at both ends in the short-axis direction of the wiring base material 23.

[0044] The wired detection electrode 21A and the detection electrode 14A are connected by a bonding member 30. In addition, the wired ground electrode 21B and the ground electrode 14B are connected by another bonding member (not shown).

[0045] A first ground electrode 12A is adhered to the upper surface of the piezoelectric film 15. The first ground electrode 12A is made of, for example, a conductive adhesive and a metal film. In the pressure sensor 10B of Modification 2, the first ground electrode 12A is adhered not only to the upper surface of the piezoelectric film 15 but also to the entire surface of the substrate 16. The first ground electrode 12A is also adhered to the ground electrode 13B. The ground electrode 13B is connected to the ground electrode 14B via a via conductor (not shown) or the like. In other words, in this example, the first ground electrode is composed of the first ground electrode 12A, which is a conductive member adhered to the piezoelectric film 15, and the ground electrode 13B arranged on the first surface side of the substrate 16.

[0046] In the pressure sensor 10B of Modification 2, wiring 20 is bonded to the second principal surface of the substrate 16, which is opposite the first principal surface on which the piezoelectric film 15 is disposed. This eliminates the need for a mounting portion for connecting wiring 20 on the first principal surface on which the piezoelectric film 15 is disposed. In other words, the pressure sensor 10B of Modification 2 can increase the area occupied by the piezoelectric film 15. In other words, even with the same piezoelectric film 15 area, the overall sensor area can be reduced.

[0047] Figure 5 : is a cross-sectional view of a pressure sensor 10C according to Modification 3. Figure 4 The same components as those in the cross-sectional view of (B) are denoted by the same reference numerals, and description thereof will be omitted.

[0048] In the pressure sensor 10C according to the third modification, the area of ​​the piezoelectric film 15 is larger than that of the pressure sensor 10B according to the second modification. Figure 5 In the example of , the piezoelectric film 15 is also arranged at a position overlapping with the bonding member 30 in a plan view. Thus, the pressure sensor 10C of the modification 3 can further increase the area occupied by the piezoelectric film 15 .

[0049] Figure 6 : is a cross-sectional view of a pressure sensor 10D according to Modification 4. Figure 5 The same structures in the cross-sectional views are marked with the same reference numerals and descriptions thereof are omitted.

[0050] exist Figure 6 In the example of FIG, the wiring 20 is connected to the surface panel 3 of the object to be detected as deformation. Figure 6 In the example, the wiring ground electrode 22 of the wiring 20 is in contact with the surface panel 3, but in reality, the wiring 20 is attached to and fixed to the surface panel 3 via an adhesive or the like. In addition, in this example, the surface panel 3 is the object of deformation detection, but of course, the frame 2 can also be the object of deformation detection.

[0051] The pressure sensor 10D connects the wiring 20 to the object to be detected for deformation. Therefore, when the object is deformed, the deformation caused by the deformation of the object can be transmitted to the piezoelectric film 15 through the connection portion of the wiring 20. As a result, the detection sensitivity of the pressure sensor 10D is improved. Figure 5 When the output of the pressure sensor 10C is 0.15Vpp (Vpp is the peak-to-peak voltage), under the same conditions Figure 6 The output of the pressure sensor 10D is reduced to 0.22 Vpp, an increase of approximately 1.5 times. Furthermore, it is possible to detect strain in an area larger than the area of ​​the piezoelectric film 15. In particular, the sensitivity to pressure detection at the connection portion to the wiring 20 is significantly improved.

[0052] Next, Figure 7 : is a cross-sectional view of a pressure sensor 10E according to Modification 5. Figure 2 In the cross-sectional view of (B), the same structures are denoted by the same reference numerals and description thereof is omitted.

[0053] In a plan view, the base material 16 and the connecting member 50 extend laterally along the long axis direction of the piezoelectric film 15. Figure 7 In the plan view, the second ground electrode 14 also extends laterally along the long axis direction of the piezoelectric film 15 , but it is not essential for the second ground electrode 14 to extend laterally.

[0054] In this extended portion, the substrate 16 and the connecting member 50 are connected to the surface panel 3, which is the object to be detected for deformation. In other words, even in the position where the piezoelectric film 15 is not configured when viewed from above, the substrate 16 is connected to the object to be detected for deformation. Therefore, when the object is deformed, the deformation caused by the deformation of the object can be transmitted to the piezoelectric film 15 via the connecting portion. As a result, the detection sensitivity of the pressure sensor 10E is improved. In addition, it is possible to detect deformation of a portion with an area larger than the area of ​​the piezoelectric film 15. In particular, the detection sensitivity of a press on the portion extended to the side is significantly improved.

[0055] Next, Figure 8 10F is a top view showing the overall structure of the pressure sensor 10F. Figure 9 (A) is a perspective view of the pressure sensor 10F. Figure 9 (B) is a partial exploded stereogram. Figure 10 (A) is Figure 8 A cross-sectional view along line AA is shown. Figure 10 (B) is Figure 8 A cross-sectional view along line BB is shown.

[0056] The pressure sensor 10F of this example includes a sensor portion 80 and a wiring portion 81. The wiring portion 81 includes circuit components 39 such as an amplifier circuit and an output terminal 390. The sensor portion 80 includes an adhesive 200 and a spacer 201. Figure 10 As shown in (A), an adhesive 200 is adhered to the ground electrode 14B. The adhesive 200 is made of, for example, an acrylic adhesive. An insulator 201 is adhered to the adhesive 200. The insulator 201 protects the adhesive surface of the adhesive 200. The insulator 201 has a demolding portion for peeling off the insulator 201. The demolding portion is a portion of the insulator 201 that is not adhered to the adhesive 200. The user of the piezoelectric sensor 100 (for example, the manufacturer of the electronic device) peels off the insulator 201 by gripping the demolding portion with tweezers or the like and pulling it. After peeling off the insulator 201, the adhesive 200 is adhered to the frame of the electronic component or the like. In addition, it is not necessarily necessary to provide the circuit component 39.

[0057] The first ground electrode 12A is attached to the ground electrode 13B. However, in this example, the first ground electrode 12A does not overlap with the bonding member 30 when viewed from above. If both the first ground electrode 12A and the ground electrode 13B overlap with the bonding member 30 and the thickness of the first ground electrode 12A deviates, the bonding strength of the bonding member 30 may deviate. In addition, if both the first ground electrode 12A and the ground electrode 13B overlap with the bonding member 30 and the first ground electrode 12A deforms due to heat, the adhesion between the first ground electrode 12A and the ground electrode 13B may also deviate. In this case, the stress involved in the piezoelectric film 15 may deviate, and the characteristics of the sensor may deviate. However, since the first ground electrode 12A does not overlap with the bonding member 30 when viewed from above, such deviations in bonding strength and adhesion can be prevented.

[0058] On the other hand, when viewed from above, the ground electrode 13B overlaps with the substrate 16 and the bonding member 30. Since the ground electrode 13B overlaps with the substrate 16, the main surface of the substrate 16 is easily maintained in a flat shape. If the ground electrode 13B also has a structure that does not overlap with the bonding member 30 when viewed from above, the main surface of the substrate 16 may become uneven due to the influence of the shape of the wiring detection electrode 21A, and the bonding strength of the bonding member 30 may vary. In this embodiment, since the ground electrode 13B overlaps with the substrate 16, the main surface of the substrate 16 is maintained in a flat shape, and the bonding strength of the bonding member 30 can be prevented from varying.

[0059] In addition, in this example, Figure 10As shown in (B), the length (width) A1 of the bonding member 30 along the X direction is wider than the width A2 of the detection electrode 14A and the width A3 of the wiring detection electrode 21A. As a result, the width end of the bonding member 30 contacts the substrate 16 and the wiring substrate 23 during bonding, thereby improving the bonding strength. Figure 10 In the example (B), the width A3 of the wiring detection electrode 21A is wider than the width A2 of the detection electrode 14A. However, the width A2 of the detection electrode 14A may be wider than the width A3 of the wiring detection electrode 21A. That is, the width of either the width A3 of the wiring detection electrode 21A or the width A2 of the detection electrode 14A is wider than the width of the other. Thus, even if the position is slightly deviated during bonding, the entire main surface of either the wiring detection electrode 21A or the detection electrode 14A overlaps with the main surface of the other. Therefore, the stability of the bonding member 30 when bonding is performed by thermocompression bonding is improved.

[0060] Furthermore, width A4 of ground electrode 13B and width A4 of wired ground electrode 22 are greater than width A2 of detection electrode 14A and width A3 of wired detection electrode 21A. Ground electrodes 13B and wired ground electrode 22 reinforce the joint. The wider width of the ground electrodes relative to the detection electrodes further improves the stability of the joint member 30 during thermocompression bonding, preventing the generation of localized high thermal stress.

[0061] Furthermore, unlike detection electrode 14A and wiring detection electrode 21A, the ground electrode is a solid electrode with no patterning at the junction. This wide solid electrode allows heat and pressure to be evenly transmitted to the junction member 30 along the planar direction. Furthermore, this wide solid electrode reduces the variation in stress transmitted from wiring portion 38 to sensor portion 35, thereby reducing variation in sensor characteristics.

[0062] In addition, the wiring portion 81 has a portion (constricted portion 85) whose width is shortened when viewed from above. The wiring portion 81 has the constricted portion 85, thereby improving flexibility. Thus, for the wiring portion 81, even if stress is generated in the wiring substrate 23 of the wiring portion 81 during use, the stress is relieved by the constricted portion 85, and the stress can be suppressed from being transmitted to the sensor portion 80, thereby preventing malfunction of the sensor. In addition, the two main surfaces of the sensor portion 80 and the wiring portion 81 are each covered with an anti-etching agent (not shown), but the anti-etching agent (not shown) can also be removed around the constricted portion 85. The wiring portion 81 can further improve its flexibility by removing the anti-etching agent around the constricted portion 85.

[0063] The description of the present embodiment is illustrative in all respects and does not limit the present invention. The scope of the present invention is not indicated by the above-described embodiment but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope of the claims.

[0064] Description of Reference Numerals

[0065] 1…electronic device; 2…housing; 3…surface panel; 4…display device; 5…capacitance sensor; 6…display portion; 10, 10A, 10B, 10C…pressure sensor; 12, 12A…first ground electrode; 13, 13A…detection electrode; 13B…ground electrode; 14…second ground electrode; 14A…detection electrode; 14B…ground electrode; 15…piezoelectric film; 16…substrate; 20…wiring; 21, 21A…wiring detection electrode; 22…wiring ground electrode; 21B…wiring ground electrode; 23…wiring substrate; 30…joining member; 50…connecting member; 70…reinforcing member; 90…via conductor.

Claims

1. A deformation detection sensor comprising: a first detection electrode; Second detection electrode a first ground electrode; a second ground electrode; a piezoelectric film sandwiched between the first detection electrode and the first ground electrode; a substrate, formed with the first detection electrode and the second ground electrode; The wiring has a wiring substrate, wherein the wiring substrate is formed with a wiring detection electrode; as well as a bonding member electrically bonding the wiring detection electrode and the second detection electrode; The first detection electrode, the first ground electrode, and the piezoelectric film are arranged on the first surface side of the substrate. The second detection electrode, the second ground electrode, and the bonding member are arranged on the second surface side of the substrate. The first detection electrode is electrically connected to the second detection electrode via a via conductor formed in the substrate. The first ground electrode is connected to a third ground electrode disposed on the first surface side of the base.

2. The deformation detection sensor according to claim 1, wherein: A reinforcing member is provided to reinforce the base material and is connected to the second ground electrode to reinforce the base material.

3. The deformation detection sensor according to claim 1 or 2, wherein: The first ground electrode is composed of a conductive member bonded to the piezoelectric film and a first electrode disposed on the first surface side of the substrate.

4. The deformation detection sensor according to any one of claims 1 to 3, wherein: The wiring is connected to an object to be detected for deformation.

5. The deformation detection sensor according to any one of claims 1 to 4, wherein: The joining member overlaps with the first ground electrode in a plan view.

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