Waterproof button device, input device including button device, and electronic apparatus

Abstract

Embodiments of the present disclosure relate to a waterproof button device, an input device including the button device, and an electronic device. A button device includes a MEMS sensor having a MEMS strain detection structure and a deformable substrate configured to undergo deformation under an external force. The MEMS strain detection structure includes a moving element carried by the deformable substrate via at least a first anchor and a second anchor fixed relative to the deformable substrate and configured to displace on the moving part and generate a deformation force in the presence of the external force; and a stator element capacitively coupled to the moving element. The deformation of the moving element results in a change in capacitance between the moving element and the stator element. Further, the MEMS sensor is configured to generate a detection signal related to the change in capacitance.

Description

Technical Field

[0001] The present disclosure relates to a waterproof MEMS (micro-electromechanical system) button device, an input device including the MEMS button device, and an electronic device. Specifically, reference is made hereinafter to a button that can be operated by a user to generate an electrical signal used by the electronic device for its operation. Background Art

[0002] As is well known, input devices (such as keys, buttons or switches) for portable electronic devices (such as smartphones and smart watches) are generally physical touch elements that enable a user to provide a signal to the portable electronic device. For example, when in standby mode, pressure applied to a button of a smartphone enables the user to reactivate its screen.

[0003] Known input devices include strain sensors that utilize different physical principles to detect commands issued by the user. For example, known strain sensors are piezoresistive sensors that detect user commands through changes in resistance caused by an external force applied to the input device itself (e.g., pressure on a button).

[0004] Currently, it is increasingly desirable that input devices be impermeable to fluids (typically water) to prevent portable electronic devices from malfunctioning due to infiltration of fluids, or to enable the device to be used underwater, for example, when engaging in water sports.

[0005] To this end, existing waterproof input devices are provided with a sealing element (eg, an O-ring) integrated during assembly of the portable electronic device, which prevents water from entering the portable electronic device.

[0006] An example of an input device including an O-ring is described in US Patent No. US2015 / 0092345 A1.

[0007] Another example of a known input device is described in U.S. Patent No. US2016 / 0225551 A1, which discloses a portable electronic device that includes a physical button as an input device. Here, the button includes a cap that can be moved within the housing of the portable electronic device, a flexible element coupled to the cap, and a stress sensor coupled to the flexible element. In use, an external force (e.g., due to pressure applied by a user's finger on the cap) deflects the flexible element, thereby generating a corresponding stress in the stress sensor, which generates an electrical signal and supplies it to a processing element. Summary of the Invention

[0008] One or more embodiments of the present disclosure overcome one or more of the shortcomings of the prior art.

[0009] According to the present disclosure, a button device, an input device, and an electronic apparatus are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a better understanding of the present disclosure, embodiments thereof will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

[0011] Figure 1 A cross section showing a simplified structure of the present input device installed in a portable electronic device;

[0012] Figure 2 Shown Figure 1 A more detailed cross-section of an input device including a MEMS sensor;

[0013] Figure 3 Schematic diagram showing the static condition Figure 2 Top view of the structure of the MEMS sensor;

[0014] Figure 4 schematically illustrates a cross-sectional view of a portion of an input device in a force-applied position;

[0015] Figure 5 is with Figure 3 A similar top view illustrating the Figure 4 The structure of MEMS sensors under stress conditions;

[0016] Figure 6 is a method for processing a Figure 2 A simplified block diagram of a circuit for providing a signal to an input device;

[0017] Figure 7 According to another embodiment, the Figure 2 Schematic top view of the structure of the MEMS sensor;

[0018] Figure 8 is a simplified block diagram of an input device and a signal processing circuit according to another embodiment of the present invention;

[0019] Figure 9 It can be with Figure 6 A top view of the structure of a reference oscillator circuit used together with an input device;

[0020] Figure 10 It can be with Figure 6 A top view of a structure of a different oscillator circuit used together with an input device; and

[0021] Figure 11 Another embodiment of a portable electronic device and the present input apparatus is shown. DETAILED DESCRIPTION

[0022] The present inventors have recognized that in portable devices it is desirable for the input device to exhibit a predefined travel and waterproofness that lasts over time, as well as being of a small size.

[0023] However, the trend toward miniaturization of portable electronic devices is often incompatible with the waterproof components of existing input devices. For example, the size of existing O-rings is not negligible, which can interfere with miniaturization requirements. To achieve both waterproofing and small size, conventional current input devices for portable electronic devices are relatively complex to manufacture and assemble.

[0024] Additionally, existing sealing elements are subject to wear and aging due to, for example, repeated stress from input devices, thereby reducing the waterproof capability of the sealing element.

[0025] Furthermore, known input devices typically have high power consumption levels, which can significantly reduce the battery life of portable electronic devices.

[0026] The present disclosure relates to a MEMS (micro-electromechanical system) button device, an input device including the MEMS button device, and an electronic device. Specifically, reference is made hereinafter to a button that can be operated by a user to generate an electrical signal used by the electronic device for its operation.

[0027] Figure 1 A portion of a portable electronic device 1 is shown comprising an enclosure 2. The enclosure 2 is formed by a base in a housing of the portable electronic device 1, for example made of aluminum, and houses an input device 3 (which is located in the housing). Figure 1 denoted by a box with a dashed outline).

[0028] In some embodiments, in the region of the enclosure 2 , the portable electronic device 1 has a wall 5 with a first surface 5A and a second surface 5B opposite each other and with a cavity 4 configured to accommodate a MEMS device 6 .

[0029] The wall 5 comprises a deformable portion 7 extending over the cavity 4 and forming a membrane 9 having a membrane surface 9A facing the cavity 4. The wall 5 has a small thickness and is therefore highly flexible and highly sensitive to the external force F acting on the deformable portion 7.

[0030] Cavity 4 (e.g., having a parallelepiped or cylindrical shape) has a first base surface formed by membrane surface 9A, a second base surface (also referred to as base surface 5C) extending parallel to first surface 5A and second surface 5B, and side surface 5D. A first plate 15 extends substantially parallel to first surface 5A and second surface 5B within cavity 4. First plate 15 is fixed to side surface 5D and divides cavity 4 into a first cavity portion 4A adjacent to membrane surface 9A and a second cavity portion 4B adjacent to base surface 5C.

[0031] The MEMS device 6 is accommodated in the first cavity portion 4A and is bonded to the film surface 9A of the film 9 by an adhesive layer 11 (eg, glue or a die attach film DAF).

[0032] A first plate 15 forms part of a connection structure 13 of flexible material (e.g., a material commonly used for printed circuit boards, such as Kapton, polyimide, or PVC), which is arranged in cavity 4 and physically and electrically coupled to MEMS device 6. Furthermore, connection structure 13 includes a second plate 17, which is housed in first cavity portion 4A and affixed to MEMS device 6 on a side thereof that is not coupled to membrane surface 9A, and a connector 19, which physically and electrically connects first plate 15 and second plate 17. First plate 15, also made of, for example, a material commonly used for printed circuit boards but more rigid (e.g., FR4 glass-reinforced epoxy laminate), can house a plurality of electronic components (not shown) that are electrically coupled to MEMS device 6 via conductive paths through plates 15, 17 and conductive paths (not shown) in connector 19.

[0033] Figure 2 The input device 3 is shown in more detail.

[0034] In some embodiments, MEMS device 6 includes: a support substrate 20; a MEMS sensor 30, such as a capacitive strain sensor; and processing circuitry 32, such as an ASIC (Application Specific Integrated Circuit).

[0035] The support substrate 20 has a top surface 20A and a bottom surface 20B opposite to each other (wherein “top” and “bottom” refer to Figure 2 The MEMS sensor 30 and processing circuit 32 are fabricated as separate devices, each integrated in a respective semiconductor material die, and secured to the top surface 20A of the support substrate 20 by first and second insulating layers 21 and 23, respectively.

[0036] In some embodiments, the support substrate 20 is a multilayer printed circuit board, for example, of the LGA (land grid array) type, which includes layers or interconnection through holes (not shown) made of a conductive material (for example, copper Cu or aluminum Al), and the support substrate 20 is embedded in an insulating layer (not shown) made of a dielectric material (for example, silicon oxide SiO2).

[0037] The support substrate 20 carries first connection pads 25 made of an electrically conductive material (for example copper or aluminum), which extend on the bottom surface 20B and electrically couple the support substrate 20 to the second board 17 .

[0038] The MEMS sensor 30 includes an active portion 33 coupled to the first insulating layer 21 , and a cap 35 bonded to the active portion 33 via a glue layer 34 .

[0039] Active portion 33 includes body 36 , MEMS structure 42 , and wall region 45 .

[0040] The body 36 is formed by an epitaxial substrate 37 made of a semiconductor material, for example silicon, on which a first insulating layer 38, for example made of silicon oxide (SiO2), extends, which first insulating layer 38 accommodates a connection region 40, for example made of polysilicon, which is electrically coupled to a conductive path (not shown) of the connection structure 13.

[0041] MEMS structure 42 is coupled to conductive region 40 in a manner described below and is configured to receive a bias voltage from conductive region 40 .

[0042] The wall region 45 surrounds the MEMS structure 42 and is fixed to the conductive region 40 via a second insulating layer 44 , for example made of silicon oxide, and to the first insulating layer 38 .

[0043] The cap 35 is made of, for example, a semiconductor material such as silicon, and together with the wall region 45 defines a MEMS cavity 48 accommodating the MEMS structure 42 .

[0044] A first pad 52 of conductive material extends over a portion of body 36 that is in electrical contact with conductive region 40. First pad 52 is wired to a second pad 54 of conductive material that extends over processing circuitry 32 to electrically couple MEMS structure 42 to processing circuitry 32.

[0045] A third pad 56 made of conductive material extends over the processing circuit 32 and is electrically wired to a second connection pad 60 that extends over the top surface 25A of the substrate 25 and is in turn electrically coupled to the first contact pad 25 in a manner not shown.

[0046] A sealing mass 61 , for example made of resin, surrounds and embeds the MEMS sensor 30 and the processing circuit 32 to protect the MEMS sensor 30 and the processing circuit 32 from the external environment except for the top surface of the cap 35 , which is in contact with the adhesive layer 11 and is therefore operatively and dynamically coupled to the membrane 9 .

[0047] Figure 3 An embodiment of a MEMS structure 42 is shown.

[0048] The MEMS structure 42 includes a suspension structure 62 formed by a beam 65, a first arm 63, and a second arm 64, and is anchored to the epitaxial substrate 37 ( Figure 2 ).

[0049] In particular, here the beam 65 extends parallel to the second axis X of the Cartesian coordinate system XYZ and has a centroid axis O which is parallel to the first axis Z of the Cartesian coordinate system XYZ.

[0050] The first arm 63 and the second arm 64 extend in a direction parallel to the third axis Y of the Cartesian coordinate system XYZ and transverse to the beam 65, and are rigid at their first ends by means of first anchors 67 and second anchors 69, respectively, and at their second ends relative to the beam 65 at two points disposed at a distance from the centroid axis O of the beam 65. In some embodiments, the arms 63, 65 are equal to one another, i.e., they have the same size (in some embodiments, the same length L along the third axis Y) and the same weight, and extend a distance d from the centroid axis O. br The suspension structure 62 is identical and is anchored in a symmetrical manner to the respective anchors 67, 69. Therefore, the suspension structure 62 has a rotational symmetry of 180° with respect to the center of mass axis O, which also constitutes the axis of rotation of the suspension structure 62.

[0051] Anchors 67 , 69 are fixed to corresponding portions of the conductive region 40 for biasing the suspended structure 62 .

[0052] The beam 65 includes a first half beam 65A and a second half beam 65B, and in a stationary condition ( Figure 3 ) below, the beam 65 extends along a stationary axis A perpendicular to the center of mass axis O.

[0053] The MEMS structure 42 further includes a first electrode 70A, a second electrode 70B, a third electrode 72A, and a fourth electrode 72B made of a conductive material (e.g., silicon). The first electrode 70A, the second electrode 70B, the third electrode 72A, and the fourth electrode 72B are capacitively coupled to the first half beam 65A and the second half beam 65B, respectively. The MEMS structure 42 is supported by the epitaxial substrate 37 and coupled to the corresponding conductive region 40.

[0054] Specifically, first and second electrodes 70A and 70B are arranged on opposite sides of first half beam 65A, while third and fourth electrodes 72A and 72B are arranged on opposite sides of second half beam 65B.

[0055] The center of mass of the portion of the beam 65 facing the first electrode 70A and the second electrode 70B in a stationary condition (first center of mass M1) is denoted as M1, the center of mass of the portion of the beam 65 facing the third electrode 72A and the fourth electrode 72B (second center of mass M2) is denoted as M2, the centers of the surfaces of the electrodes 70A, 70B, 72A, 72B facing the beam 65 are denoted as ME1-ME4, the distance between the center of mass M1 and the center of the surface ME1 of the first electrode 70A and the distance between the center of mass M2 and the center of the surface ME4 of the fourth electrode 72B are denoted as d1, and the center of mass M2 and the center of the surface ME4 of the fourth electrode 72B in a stationary condition ( Figure 3 ) The distance between the partial centroid M1 and the surface center ME2 of the second electrode 70B and the distance between the partial centroid M2 and the surface center ME3 of the third electrode 72A are expressed as d2, where d1=d2=d.

[0056] In practice, the electrodes 70A, 70B, 72A, and 72B, together with the beam 65, form plates of a first capacitor 73-1, a second capacitor 73-2, a third capacitor 73-3, and a fourth capacitor 73-4, respectively, having capacitances C1, C2, C3, and C4, wherein the first capacitor 73-1 and the fourth capacitor 73-4 are connected in parallel and have a first equivalent capacitance CE1, while the second capacitor 73-2 and the third capacitor 73-3 are connected in parallel and have a second equivalent capacitance CE2.

[0057] In use, the electrodes 70A, 70B, 72A and 72B and the beam 65 are biased with respective bias voltages by the conductive region 40. For example, the electrodes 70A, 70B, 72A and 72B are biased at a first DC voltage V1 having a value between 0.7V and 1V.

[0058] Additionally, the beam 65 is biased at a second voltage V2 having a DC component V between 0.7V and 1V, for example. DC and a square wave AC component V switching between 0.7V and 1V, for example AC .

[0059] As a result of electrodes 70A, 70B, 72A, 72B and beam 65 being biased, beam 65 experiences a total electrostatic force F el , the total electrostatic force is composed of the first electrostatic force F el1 (force acting between the beam 65 and the first and fourth electrodes 70A and 72B) and the second electrostatic force F el2 The sum of the forces acting between the beam 65 and the second and third electrodes 70B, 72A is given by: As indicated above, under static conditions, the first distance d1 and the second distance d2 are identical to each other; therefore, the capacitances C1, C2, C3, C4 are identical to each other, the equivalent capacitances CE1, CE2 are also identical, and the electrostatic force F is given by: el1、F el2 Also the same as each other.

[0060] When an external force F acts on the deformable portion 7 of the portable electronic device 1 ( Figure 4 ), the membrane 9, together with the rest of the MEMS device 6 (and in some embodiments, the proof-mass 61, the cap 35, and the active portion 33 of the MEMS sensor 30), and together with the second plate 17, which operates essentially as a single body, deflects towards the inside of the cavity 4. The deformation of the MEMS device 6 results in the generation of a tensile force F on the anchors 67, 69. t , the anchors 67, 69 therefore tend to be displaced together with the arms 63, 64 relative to the mass axis O. Since the arms 63, 64 are eccentrically fixed to the beam 65, a torque of force is generated which causes a deformation and a rotation of the beam 65 itself, here in the counterclockwise direction around the mass axis (axis of rotation) O.

[0061] refer to Figure 5 , the rotation of the beam 65 about the centroid axis O determines the change in position of the beam 65 relative to the electrodes 70A, 70B, 72A, 72B. Figure 5 In the counterclockwise rotation shown, the beam 65 moves toward the first electrode 70A and the fourth electrode 72B, and away from the second electrode 70B and the third electrode 72A.

[0062] In some embodiments, the first mass center M1 and the second mass center M2 are positioned relative to the stationary position ( Figure 3 ) is expressed as ΔY, the distance between the first centroid M1 and the surface center ME1 of the first electrode 70A (as well as the distance between the second centroid M2 and the surface center ME4 of the fourth electrode 72B) becomes d1-ΔY; similarly, the distance between the first centroid M1 and the surface center ME2 of the second electrode 70B (as well as the distance between the second centroid M2 and the surface center ME3 of the third electrode 72A) becomes d2+ΔY.

[0063] It should be noted that during this step, the fixed electrodes 70A, 70B, 72A, and 72B also displace slightly, but the magnitude of this displacement is reduced by the amplification factor of the mechanical lever (beam 65 - arms 63 and 64) and is therefore negligible. Furthermore, the magnitude of this displacement (the additional change in distance) is the same for all electrodes (70A, 70B, 72A, and 72B); assuming a capacitive differential reading, as discussed below, this change does not affect the useful output signal. Possible second-order effects, such as sensitivity variations (nonlinear factors) depending on the load, are also multiplied by the mechanical amplification factor.

[0064] Therefore, the equivalent capacitance CE1, CE2 and the electrostatic force F el1、F el2 In some embodiments, the first equivalent capacitance CE1 and the first electrostatic force F el1 Increase, and the second equivalent capacitance CE2 and the second electrostatic force F el2 Decrease.

[0065] Therefore, the MEMS sensor 30 generates a first capacitance signal s C1 and the second capacitance signal s C2 , which respectively indicate the changes of the first equivalent capacitance CE1 and the second equivalent capacitance CE2, and then the first capacitance signal s C1 and the second capacitance signal s C2 is transmitted to the processing circuit 32.

[0066] The MEMS sensor 30 and processing circuit 32 are Figure 6 In the block diagram of FIG, they are schematically represented as a MEMS block 30 and an ASIC block 32, respectively.

[0067] In detail, the ASIC block 32 includes an input stage 84, which in some embodiments is a capacitance-to-voltage converter, configured to receive the first capacitance signal s C1 and the second capacitance signal s C2 and generate the output signal s V (e.g., voltage signal), the output signal s V Proportional to the capacitance change ΔC, which is equal to the difference between the equivalent capacitances CE1 and CE2.

[0068] To this end, the tension F t The resulting displacement of the anchors 67 and 69 is represented by ΔL.

[0069] ΔL=ε Y L (1),

[0070] where ε Y is the tensile deformation coefficient, L is as previously described and Figure 3 On the other hand, the relationship between the displacement ΔL and the external force F acting on the deformable portion 7 of the portable electronic device 1 is complex and can be determined, for example, on the basis of FEA (“Finite Element Analysis”) type simulations.

[0071] Therefore, as described below, the capacitance change can be determined. The first mass center M1 and the second mass center M2 are relative to the rest position ( Figure 3 ) is related to ΔL by the following equation:

[0072]

[0073] where D is the distance between the mass center axis O and the first mass center M1 (and the distance between the mass center axis O and the second mass center M2), ΔL has the meaning indicated with respect to equation (3), and as previously described and as in Figure 3 As shown in br is the distance between the arms 63, 64 and the center of mass axis O.

[0074] Therefore, the capacitance change ΔC, which is called the difference between the equivalent capacitances CE1 and CE2, is defined as follows:

[0075]

[0076] where ε is the dielectric constant, A is the area of ​​the electrodes 70 , 72 , d and ΔY have the meanings indicated above. Furthermore, it was confirmed that the capacitance change ΔC is linearly proportional to the external force F applied to the deformable portion 7 of the portable electronic device 1 .

[0077] ASIC block 82 also includes an analog-to-digital conversion stage (ADC) 86 that is configured to receive the output signal s from input stage 84. V and a temperature sensor 88, which is coupled to the analog-to-digital conversion stage 86, and supplies a temperature signal s to the analog-to-digital conversion stage 86 relative to the thermal conditions in which the input device 3 operates T . At the output signal s V and temperature signal s T On the basis of the temperature-compensated digital signal s, the conversion stage 86 generates the temperature-compensated digital signal s in a manner known per se. D .

[0078] ASIC block 32 also includes a filtering stage 90, such as a low-pass digital filter (LPF), which is configured to receive and filter the digital signal s generated by conversion stage 86. D , to generate data for transmission to other devices associated with the apparatus 1 (e.g., to the first board 15 ( Figure 1 ) of the electronic components carried by the filtered signal s f .

[0079] The MEMS block 30 and the ASIC block 32 are also coupled to additional electronic components (in Figure 6 ), such as a voltage and current generating unit 92, an FTP (few-time programmable) memory 94, an oscillator element 96, a timing generator 98 and an interrupt generator 100.

[0080] Figure 7 Another embodiment of the MEMS structure of the input device is shown. In detail, Figure 7 A MEMS structure 142 is shown having Figures 3 to 5 The MEMS structure 42 shown has a similar general structure to that of Figures 3 to 5 Similar parts to those shown and described are in Figure 7 1 and 2 are designated by the same reference numerals and are briefly described.

[0081] In detail, MEMS structure 142 includes beam 65 and arms 63, 64 fixed to anchors 67, 69. Furthermore, MEMS structure 142 includes first and second frame structures 154, 155, which, for example, have quadrilateral (e.g., rectangular) shapes and are rigid relative to beam 65 (in some embodiments, first and second half beams 65A, 65B, respectively). In some embodiments, frame structures 154, 155 include lateral sides 156, which are perpendicular to beam 65 in some embodiments, and longitudinal sides 157, which are parallel to beam 65. The frame structures 154, 155 surround the respective ends of the first half beam 65A and the second half beam 65B and define a first opening 160A, a second opening 160B, a third opening 162A and a fourth opening 162B, which have a quadrilateral (e.g., rectangular) shape and surround the first electrode 70A, the second electrode 70B, the third electrode 72A and the fourth electrode 72B.

[0082] Figure 7 The MEMS structure 142 further includes four electrodes 170A, 170B, 172A, and 172B, hereinafter referred to as the fifth electrode 170A, the sixth electrode 170B, the seventh electrode 172A, and the eighth electrode 172B. The additional electrodes each extend in the corresponding openings 160A, 160B, 162A, and 162B along and parallel to the first electrode 70A, the second electrode 70B, the third electrode 72A, and the fourth electrode 72B, respectively, facing the longitudinal sides 157 of the frame structures 154 and 155.

[0083] The longitudinal sides 157 facing the fifth electrode 170A and the eighth electrode 172B, respectively, are, for example, arranged at a second distance d2 from the electrodes; similarly, the longitudinal sides 157 facing the sixth electrode 170B and the seventh electrode 172A, respectively, are, for example, arranged at a first distance d1 from the electrodes.

[0084] In use, the further electrodes 170, 172 are biased at a first DC bias voltage V1. Furthermore, the beam 65 and the frame structures 154, 155 are biased at a second voltage V2.

[0085] As a result of the additional electrodes 170A, 170B, 172A, 172B and the frame structures 154, 155 being biased, the MEMS structure 142 experiences an additional total electrostatic force F el ', which in turn adds to the first total electrostatic force F el .

[0086] The additional electrodes 170A, 170B, 172A, 172B together with the longitudinal sides 157 of the frame structures 154, 155 form plates of additional capacitors arranged parallel to the capacitors 73-1, 73-2, 73-3 and 73-4. Therefore, the respective capacitances add up and the capacitance of the MEMS structure 142 here is higher than Figure 3 The capacitance of the MEMS structure 42 .

[0087] The MEMS structure 142 is similar to that already mentioned. Figures 3 to 5 The method described above operates in a similar manner.

[0088] Figures 8 to 10 A resonant capacitance type MEMS device 206 is shown, where a change in capacitance is determined based on a change in resonant frequency.

[0089] refer to Figure 8 , the MEMS device 206 includes a MEMS block 230 and an ASIC block 232 connected to the MEMS block 230 .

[0090] The MEMS module 230 includes a reference oscillator circuit 290 that generates a reference drive signal s ref and a measurement oscillator circuit 292, which generates a measurement drive signal s MEMS , the signal indicates the corresponding resonant frequency f r1 、f r2 The oscillating circuits 290, 292 are each formed by a self-sustaining resonant tank (positive feedback) comprising an oscillating element 294, 296 and a driver stage 316, 318 (comprising a respective current-to-voltage conversion stage with a gain of Gm), the driver stage 316, 318 being connected to the respective oscillating element 294, 296.

[0091] In detail, each oscillatory element 294, 296 includes a respective moving mass 300, 302 that is capacitively coupled to a respective drive electrode 304, 306 and a respective sense electrode 308, 310, as shown in FIG. Figure 9 and Figure 10 As shown in detail in and discussed further below.

[0092] The driver stages 316, 318, provided in a manner known per se (eg by means of simple inverters forming Pierce oscillators), receive the respective output signals s from the sensing electrodes 308, 310. out1 、s out2 , the corresponding output signal s out1 、s out2Related to: changes in the capacitance of the capacitors formed between the sensing electrodes 308, 310 and the respective moving masses 300, 302; changes due to the resonant oscillations of the moving masses 300, 302 themselves; and other possible disturbances including deformation of the MEMS device 206 due to the external force F (as discussed in detail below).

[0093] Therefore, the driver stages 316, 318 generate the drive signal s ref 、s MEMS (In some embodiments, at equilibrium, the frequencies are equal to the resonant frequencies f of the respective oscillating circuits 290 and 292. r1 、f r2 AC voltage), and then supply them to the corresponding driving electrodes 304, 306 to make the corresponding moving masses 300, 302 (biased to DC voltage V DC1 , V DC2 ) vibrates at its natural resonant frequency.

[0094] Figure 9 and Figure 10 Shown respectively Figure 8 The MEMS block 230 includes a reference oscillating element 294 and a measuring oscillating element 296 .

[0095] In some embodiments, Figure 9 In FIG. 2 , the reference oscillating element 294 is, for example, a scissor jack type circuit and has a structure similar to that described in European Patent No. EP 3407492.

[0096] Here, the mobile mass 300 of the reference oscillating element 294 (hereinafter also referred to as the reference mobile mass 300 ) has a first resonant frequency f r1 The first oscillating element 294 is a first oscillating element 294, and the first oscillating element 294 is a second ... Figure 2 One of the conductive regions 40 of the MEMS sensor 42 .

[0097] The structure of the reference mobile mass 300 defines a first reference window 380 and a second reference window 382, ​​which have a quadrilateral (e.g., rectangular) shape, which is respectively defined by the following items: the first reference flexible arm 350 and the second reference flexible arm 352, the corresponding parts of the first reference connecting arm 354 and the second reference connecting arm 356, and the reference anchoring arm 360.

[0098] The driving electrodes 304 of the reference oscillating element 294 include a first reference driving electrode 400 and a second reference driving electrode 402 , which face and are parallel to the first reference flexible arm 350 and the second reference flexible arm 352 , respectively.

[0099] Here, reference sensing electrode 306 includes first reference measurement electrode 404 and second reference measurement electrode 406, which face and are parallel to first reference flexible arm 350 and second reference flexible arm 352, respectively, and first reference measurement electrode 404 and second reference measurement electrode 406 are arranged in first reference window 380 and second reference window 382, ​​respectively.

[0100] At rest and without bias, the reference flexible arms 350, 352 are positioned at the same reference distance d3 from the reference measurement electrodes 404, 406 and are connected in parallel therewith to form a total reference capacitance C R of the two capacitors.

[0101] In use, an AC bias voltage is applied between the driven reference electrodes 400, 402 and the reference moving mass 300, causing the reference flexible arms 350, 352 to resonate at a first resonant frequency f r1 The reference flexible arms 350, 352 are deformed in opposite phases and directions along the third axis Y. The subsequent approach / recession of the reference flexible arms 350, 352 relative to the reference measuring electrodes 404, 406 results in a total reference capacitance C R changes and generates a corresponding first output signal s out1 .

[0102] Reference Figure 10 The measuring oscillating element 296 is a double-ended tuning fork type circuit with a double anchor that is sensitive to external forces.

[0103] exist Figure 10 In the embodiment, the mobile mass 302 of the measuring oscillating element 296 (hereinafter also referred to as the mobile measuring mass 302) has a second resonance frequency equal to f r2the resonant frequency and comprises: a first measurement flexible arm 410 and a second measurement flexible arm 412 extending parallel to the second axis X; a first measurement connecting arm 414 and a second measurement connecting arm 416 extending parallel to the third axis Y and connecting the first and second measurement flexible arms 410, 412 together at their ends; and a first measurement anchoring arm 420 and a second measurement anchoring arm 422 extending parallel to the second axis X between the first and second measurement connecting arms 414, 416 and the first and second measurement anchoring arms 430, 432, respectively. The measurement anchoring pieces 430, 432 are fixed to Figure 2 one of the electrically conductive regions 40.

[0104] The moving measurement mass 302 defines a measurement window 440 having, for example, a quadrilateral (e.g., rectangular) shape and encloses the measurement sensing electrode 310.

[0105] In this embodiment, Figure 8 The drive electrode 308 comprises a first measurement drive electrode 445 and a second measurement drive electrode 447 arranged parallel to the first and second measurement flexible arms 410, 412, respectively, at an outer portion of the moving measurement mass 302.

[0106] At rest and without bias, the first and second measurement flexible arms 410, 412 are arranged at the same distance from the measurement sensing electrode 310, which distance is hereinafter referred to as measurement distance d4. The first and second measurement flexible arms 410, 412 together with the measurement sensing electrode 310 form two parallel capacitors having a total measurement capacitance C M .

[0107] In use, an alternating bias voltage is applied to the measurement drive electrodes 445, 447 relative to the moving measurement mass 302, resulting in a flexible deformation of the measurement flexible arms 410, 412 along the third axis Y at the second resonant frequency f r2 at opposite phases and opposite directions. The subsequent approach / indentation of the measurement flexible arms 410, 412 relative to the measurement sensing electrode 310 results in a change of the total measurement capacitance C M and generates a second output signal s out2 .

[0108] Still further, the MEMS device 206 is operative to detect an external force F acting on the deformable portion 7 of the portable electronic device 1 and, thus, on the moving measurement mass 302. Figure 1 The membrane 9 of the enclosure 2 is used as the second resonance frequency f of the oscillating element 296 for measurement. r2 changes.

[0109] In some embodiments, as described for MEMS sensor 42, membrane 9 ( Figure 4 ) induces tensile stress in the MEMS device 206, which acts on both the reference oscillating element 294 and the measuring oscillating element 296 in different ways.

[0110] In fact, since the reference mobile mass 300 is fixed to a single reference anchor 370, the reference oscillating element 294 is insensitive to the deformations of the membrane 9 and therefore moves rigidly with the membrane 9 when the membrane 9 undergoes a deformation due to an external force F. Therefore, the reference mobile mass 300 is not affected by the tensile force F generated by the deformation of the membrane 9. t and deformed, and the first resonant frequency f of the flexible arms 350 and 352 is r1 Basically unchanged.

[0111] Instead, the Rally F t Causes the mobile measurement mass 302 of the measurement oscillating element 296 to undergo a deformation; in some embodiments, as described above with reference to Figure 4 As described, the tension F t Acting in opposite directions on the measurement anchors 430, 432, the measurement anchors 430, 432 are displaced relative to their positions in the absence of external forces. In some embodiments, the measurement anchors 430, 432 are translated in opposite directions along the second axis X so as to move away from the center of mass axis O″ of the measurement oscillatory element 296. In effect, the mobile measurement mass 302 is “stretched” in a direction parallel to the second axis X due to the axial load exerted on the beams 410 and 412 generated by the external force F.

[0112] Since the mobile measurement mass 302 undergoes deformation, the distance between the measurement flexible arms 410, 412 and the sensing electrode 310 changes relative to the actuation movement, resulting in an increase in the stiffness of the measurement flexible arms 410, 412. Therefore, the second resonant frequency f r2 The measurement driver stage 312 thus modifies its measurement driver signal s MEMS , so that the mobile measurement mass 302 is kept at the second resonance frequency f r2 in an oscillating state.

[0113] The driving signal s is thus obtained ref 、s MEMSis supplied to the ASIC block 232 ( Figure 8 ), for these driving signals s ref 、s MEMS Processed to generate a digital signal D,ris , the digital signal s D,ris Indicative effect Figure 1 The external force F on the deformable part 7 of the device 1 is substantially the same as the external force F on the deformable part 7 of the device 1. Basically, the ASIC block 232 measures the driving signal s generated by the measuring oscillating circuit 292. MEMS The cycles of the reference drive signal s are counted and compared with the reference drive signal s generated by the reference oscillation circuit 290. ref The detection is performed when measuring the driving signal s MEMS The number of cycles relative to the reference drive signal s ref The change in the number of cycles makes it possible to detect whether an external force F is applied to the deformable portion 7.

[0114] Figure 11 Various embodiments of portable electronic devices are shown. In some embodiments, Figure 11 Shows the overall structure and Figure 1 The structure of the portable electronic device 1 is similar to that of the portable electronic device 500 .

[0115] In some embodiments, the portable electronic device 500 includes a body 502, for example made of aluminum, having a first body surface 502A and a second body surface 502B; and a recess 504, which extends in the body 502 starting from the first body surface 502A and accommodates an input device (key element) 503.

[0116] The input device 503 includes a housing 505 that is disposed in the recess 504 and has a flexible portion 507 that is in contact with the housing. Figure 1 The flexible portion 7 of is similar and has a membrane 509. In some embodiments, the input device 503 is fixed in the recess 504 by a bonding layer 510 (eg, a layer of glue).

[0117] For the rest, you can refer to Figures 1 to 10 The input device 503 is manufactured in the manner described. In some embodiments, in this case, the electrical signals can be exchanged in a wireless mode with electronic circuits and devices arranged outside the input device 503.

[0118] MEMS sensors and corresponding input devices have various advantages.

[0119] In some embodiments, the MEMS sensor has low power consumption due to the low bias voltage used to operate the MEMS device.

[0120] Furthermore, at the end of the manufacturing process, it is completely housed in the housing (in Figure 1 Shell 2, Figure 11 thus, the MEMS sensor is fully resistant to water or other liquids and therefore does not require a sealing element (e.g., an O-ring) designed to isolate it from the external environment.

[0121] MEMS sensors generally have a small size; for example, they can be manufactured to have an overall thickness of less than 500 μm, and thus can also be used in small-sized electronic devices such as smart watches or smart phones.

[0122] In addition, the detection principle of the MEMS device 6, 206 allows good linearity in response to the deformation of the membrane 9, 509, as well as greater precision in determining the external force F acting thereon; in some embodiments, the applicant has verified that the change in capacitance of the MEMS device 6, 206 is proportional to the deformation of the membrane 9.

[0123] Furthermore, the inspection principle of the MEMS device 6, 206 allows for a good production yield.

[0124] In addition, reference Figures 8 to 10 In this embodiment, MEMS sensor 230 operates at a low resonant frequency, thereby reducing power consumption. However, this does not imply any loss in measurement accuracy or sensitivity. Furthermore, the use of first oscillator circuit 294, which operates as a reference oscillator circuit, eliminates the dependency of changes in the Young's modulus of silicon on temperature changes, thereby enabling more reliable measurements.

[0125] Furthermore, the MEMS device 6 , 206 can be manufactured using techniques or steps commonly used in manufacturing MEMS devices, and thus at a comparable cost.

[0126] Finally, it is apparent that modifications and variations may be made to the MEMS device, the MEMS input device, and the corresponding electronic apparatus described and illustrated herein without departing from the scope of the present disclosure.

[0127] For example, the MEMS sensor may be mounted in the reverse manner, ie with the substrate 20 or the MEMS sensor 30 fixed directly to the sensitive part 7 , with appropriate arrangements for connection to the plates 15 , 17 .

[0128] Moreover, in Figure 10 In an embodiment, the positions of the drive electrodes 445, 447 and the measuring electrode 310 can be swapped, so that the drive electrode is arranged inside the measuring window 440 and the two measuring electrodes 310 are arranged outside the measuring window 440, each electrode facing one of the flexible arms 410, 412.

[0129] The various embodiments described above can be combined to provide other embodiments. If it is necessary to adopt the concepts of various patents, applications, and publications to provide other embodiments, various aspects of the embodiments can be modified. These and other changes can be made to the embodiments based on the above detailed description. In general, in the following claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the description and claims, but should be interpreted to include all possible embodiments and the full range of equivalents to which the claims are entitled. Therefore, the claims are not limited by the disclosure.

Claims

1. An electronic device comprising: A micro-electromechanical system (MEMS) button and a deformable portion, the button including a MEMS sensor, the MEMS sensor including a MEMS strain sensing structure, the deformable portion being configured to undergo deformation in response to an external force, the MEMS strain sensing structure comprising: moving elements; a first anchor and a second anchor, both of which are rigid relative to the deformable portion and are configured to displace and generate a deforming force (F) on the moving element in response to the external force; t );as well as A first electrode and a second electrode are capacitively coupled to the moving element, the first anchor is located between the first electrode and the second electrode on a first side of the moving element, a displacement of the moving element causes a change in capacitance between the moving element and the first electrode and the second electrode, and the MEMS sensor is configured to generate a detection signal based on the capacitance change.

2. The electronic device according to claim 1, wherein the moving element comprises: a beam configured to rotate about a rotation axis in response to the deformation force, the beam having a first beam half and a second beam half; a first arm extending between the first half beam and the first anchor, the first arm coupling the first half beam to the first anchor; a second arm extending between the second half beam and the second anchor, the second arm coupling the second half beam to the second anchor, the first arm and the second arm being eccentric to each other and generating a torque on the beam when subjected to the deforming force; 3 . The electronic device according to claim 2 , wherein the first electrode and the second electrode respectively face and are capacitively coupled to the first half beam and the second half beam, respectively.

4. The electronic device according to claim 3, wherein the MEMS strain sensing structure further comprises a third electrode and a fourth electrode, wherein the moving element comprises: a first frame structure that is rigid relative to the first half-beam and surrounds the first electrode and the second electrode; as well as a second frame structure, which is rigid relative to the second half beam and surrounds the third electrode and the fourth electrode, The first frame structure and the second frame structure are arranged in parallel, the first half beam and the second half beam are opposite to each other, and the first anchor and the second anchor are located between the first frame structure and the second frame structure.

5. The electronic device according to claim 4, wherein the first frame structure and the second frame structure comprise: respective longitudinal sides arranged parallel to and symmetrically relative to the beam; as well as a respective transverse side extending in a direction transverse to said longitudinal side, The first frame structure and the second frame structure define a first opening, a second opening, a third opening and a fourth opening, and the first opening, the second opening, the third opening and the fourth opening are configured to surround the first electrode, the second electrode, the third electrode and the fourth electrode respectively.

6. The electronic device according to claim 5, comprising: A fifth electrode and a sixth electrode are arranged in the first opening and the second opening, and are adjacent to and parallel to the first electrode and the second electrode in the transverse direction, respectively. The fifth electrode and the sixth electrode directly face and are capacitively coupled to the longitudinal side respectively.

7. The electronic device according to claim 1, comprising: A processing circuit is configured to receive and process the detection signal from the MEMS sensor to generate an output signal.

8. The electronic device according to claim 1, comprising: a cap fixed to an active portion of the MEMS sensor and covering the MEMS strain sensing structure; And wherein the active portion includes an electrical connection area and a conductive path electrically coupled to the MEMS strain sensing structure.

9. The electronic device according to claim 8, further comprising: a supporting substrate fixed to the active portion; as well as An electronic processing circuit is supported by the support substrate and electrically coupled to the MEMS strain sensing structure via the electrical connection area and the conductive path.

10. An input device comprising: Micro-electromechanical system MEMS button device; a housing having a cavity and a deformable portion, the cavity including the MEMS button device, the deformable portion overlapping the cavity and directly contacting the MEMS button device; as well as a connecting structure, in the cavity, the connecting structure comprising a connector, a first plate coupled to the housing, and a second plate coupled to the first plate via the connector, the MEMS button device being positioned on the second plate; The MEMS button device comprises: A MEMS sensor including a MEMS strain detection structure; a first anchor; a second anchor; a deformable base configured to undergo deformation in response to an external force; a moving element coupled to the deformable base via the first anchor and the second anchor, the moving element configured to move in response to the deformation of the deformable base; and A first electrode and a second electrode are capacitively coupled to the moving element, the first anchor is located between the first electrode and the second electrode on a first side of the moving element, and movement of the moving element causes a change in capacitance between the moving element and the first electrode and the second electrode. 11 . The input device of claim 10 , wherein the first plate is coupled to a sidewall of the cavity, and the first plate is spaced apart from a bottom surface of the cavity, the bottom surface of the cavity facing the deformable portion.

12. An electronic device comprising: cavity; a micro-electromechanical system (MEMS) button having a MEMS sensor in the cavity; a deformable membrane overlapping the cavity; as well as a MEMS strain detection sensor in said MEMS sensor of said cavity; The MEMS strain detection sensor comprises: a first anchor; Transformable base; a moving element coupled to the deformable base via the first anchor; and A first electrode and a second electrode are capacitively coupled to the moving element, the first anchor is located between the first electrode and the second electrode on a first side of the moving element, and movement of the moving element causes a change in capacitance between the moving element and the first electrode and the second electrode. 13 . The electronic device of claim 12 , wherein the MEMS strain sensing sensor comprises a second anchor, and the moving element is configured to rotate in response to the deformation of the deformable mount.

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