Assembling the integrated soft force sensor

Abstract

A method for manufacturing a force sensor and a force sensor are provided. The force sensor can be used to measure contact force. The force sensor includes a substrate with an electromagnetic sensing element that contactlessly senses a field created by a target. The target is contained within a flexible component that is deformable under force. The flexible component is treated to enhance the reliability and durability of the force sensor.

Description

[Technical Field]

[0001] The present invention relates to the field of force sensors, and more particularly to force sensors with position sensing and their manufacture. [Background technology]

[0002] Force sensors are used in many applications, and each type must meet certain requirements, such as compactness, sensitivity range, and reliability.

[0003] For example, force sensors can be used as feedback to assist in automated manipulation of objects, where it is typically difficult to control the force applied to the object, potentially leading to manipulation errors, misplacement of the manipulated part, or even damage to the part.

[0004] In the field of robotics, force-torque sensors are often integrated into robotic clamps and hands, for example in the mechanical parts that drive the movement of the gripping parts (claws, fingers, etc.). However, this measurement is indirect: it is not easy to measure the deformation of the contact surface with the handled part. To solve this, it is necessary to measure the actual contact force. This can be achieved by using a flexible material, such as an elastomer, whose surface contacts and grips the object, and the deformation of this surface is measured as an indicator of the force applied to the object. The deformation can be measured with a position sensor on the substrate on which the flexible material is placed, which detects the position of a target, such as a magnet, that moves as the flexible material deforms.

[0005] The sensitivity of a force sensor is therefore determined by the resistance of the flexible material to deformation. If the flexible material has very low resistance to deformation, the sensitivity will be high, but the force sensor will be less responsive to large forces. In extreme cases, impact forces or large contact forces may damage the electronics of the position sensor. These requirements must also be compatible with compactness requirements so that the force sensor can be integrated into larger systems.

[0006] A key requirement, primarily for object manipulation, is reliability when the contact area is subjected to shear forces. Flexible materials must not break or separate from the substrate due to these forces. Preferably, the position sensor should also be able to reliably measure these forces.

[0007] It is desirable to provide a force sensor that is sensitive, compact, and reliable even under shear forces, with a long life span. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of embodiments of the present invention to provide a compact and reliable sensor for accurately sensing forces, particularly contact and shear forces, over a wide range of forces. It is a further object of the present invention to provide an assembly including such a sensor, and to provide a method for manufacturing the sensor. [Means for solving the problem]

[0009] In one aspect, the present invention provides a method for manufacturing a force sensor, the method including providing a flexible component having one surface as a mounting surface, the component further including (e.g., embedding) a target component.

[0010] A substrate is then provided that has a receiving surface and includes at least one sensing element that is capable of detecting changes in a magnetic field (electromagnetic field) caused by movement of the target part.

[0011] The method includes attaching a mounting surface of a flexible component to a receiving surface of a substrate by surface activating the mounting surface, and providing an adhesive layer in contact with at least the mounting surface by sandwiching the adhesive layer between both the receiving surface and the mounting surface. Advantages of embodiments of the present invention include improved attachment between the flexible component and the sensing portion of the sensor, resulting in a more reliable force sensor. Advantages include secure attachment of elastomers, such as rubber or silicone, to molding compounds, such as epoxies, for long-term use. Advantages include the ability to measure high shear forces because of the improved attachment provided.

[0012] In some embodiments, the substrate is a semiconductor package and the at least one sensing element is an integrated circuit included in the semiconductor package, forming a chip. Attaching the flexible component to the substrate includes attaching a mounting surface of the flexible component to a receiving surface of the semiconductor package.

[0013] An advantage of embodiments of the present invention is that they have a very small footprint, resulting in a very compact device.

[0014] In some embodiments, applying surface activation comprises applying plasma treatment. An advantage of embodiments of the present invention is that ionic treatments such as plasma treatments can be used to locally treat the surface of the flexible component, thus allowing for very controlled surface activation, which advantageously increases the hydrophilicity of the surface, improving the bond between the material of the flexible component and the material of the adhesive layer and improving adhesion.

[0015] In some embodiments, providing the flexible component comprises forming the flexible component as a single piece by injection molding.

[0016] An advantage of embodiments of the present invention is that the part can be provided as a single unit with no joints, resulting in uniform properties and a low risk of breakage. An additional advantage is that the method is compatible with mass production platforms such as injection molding and microelectronic assembly.

[0017] In some embodiments, providing a flexible component comprises providing a target component and incorporating it within the flexible component.

[0018] An advantage of embodiments of the present invention is that no adhesive is required to attach the target component to the flexible component, thus reducing the chance of adhesive failure.

[0019] In some embodiments, providing a substrate including a sensing element includes providing a sensing element adapted to sense magnetic fields in at least two different directions.

[0020] An advantage of embodiments of the present invention is that a multi-directional force sensor can be provided, which can sense forces in two directions, e.g., two perpendicular directions, e.g., 3D, rather than just one component. Such a sensor can be used, for example, as a grip sensor, allowing objects to be firmly grasped and lifted with less gripping force than would be required to damage or deform the object.

[0021] In some embodiments, the method includes providing a cavity in the flexible component, the cavity being at least partially surrounded by the flexible component and adapted to enhance mobility of the target component.

[0022] An advantage of embodiments of the present invention is that high sensitivity can be obtained, with the added advantage that the stable lifetime of the sensor can be extended.

[0023] In certain embodiments, it may be preferable to provide a vent to fluidly connect the cavity in the flexible part to the exterior of the force sensor.

[0024] An advantage of embodiments of the present invention is that the mobility of the target component is not hindered by pressure differences, resulting in improved mobility and faster response times.

[0025] Providing a cavity may include providing an open cavity, where the mounting surface includes an opening to the mounting surface. The flexible component may have a bell shape. An advantage of embodiments of the present invention is that they can provide a highly sensitive force sensor while protecting the chip by reducing pressure on the surface of the chip.

[0026] In one aspect, the present invention provides a force sensor including a flexible component that holds a target component. The flexible component has a mounting surface distal to the target component. The force sensor also includes a semiconductor package including at least one sensing element for detecting a magnetic field generated by the target component. The package also includes a receiving surface. The flexible component is attached to the semiconductor package at the mounting surface that is received and attached to the receiving surface. The flexible component includes a cavity disposed between the target component and the semiconductor package. An advantage of embodiments of the present invention is that the force sensor is both sensitive and flexible without sacrificing protection for the electronic device.

[0027] In one aspect, the present invention provides a force sensor including a flexible component that holds a target component. The flexible component has a mounting surface distal to the target component. The force sensor further includes a substrate having a receiving surface and a sensing element that detects a magnetic field generated by the target component. The flexible component is attached to the substrate by an adhesive layer that contacts the mounting surface and has a chemical bond with the mounting surface provided by activation of the mounting surface, thereby improving adhesion between the flexible component and the adhesive layer.

[0028] An advantage of embodiments of the present invention is that the force sensor is reliable and sensitive to high contact and shear forces.

[0029] In some embodiments, the flexible part having an activated surface further comprises a cavity disposed between the target part and the semiconductor package of the force sensor.

[0030] An advantage of embodiments of the present invention is that they provide a force sensor that is highly sensitive to high contact and shear forces.

[0031] In embodiments comprising a cavity, the flexible part may further comprise a vent hole that provides a fluid connection between the cavity and the exterior of the force sensor.

[0032] An advantage of embodiments of the present invention is that the mobility of the target part is not hindered by pressure differences, thus improving mobility and reducing response time.

[0033] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

[0034] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 shows a side view of a force sensor according to an embodiment of the present invention and an example of a contact force applied to the force sensor. [Figure 2] FIG. 2 shows an exploded cross-sectional view of a force sensor according to an embodiment of the present invention. [Figure 3]FIG. 3 shows a schematic diagram of steps in a manufacturing method according to an embodiment of the present invention. [Figure 4] FIG. 4 shows a side view of a force sensor according to an embodiment of the present invention. [Figure 5] FIG. 5 shows a perspective view of cavities in two flexible components used in a force sensor according to an embodiment of the present invention. [Figure 6] Figure 6 shows the results of shear tests conducted at shear forces equivalent to up to 1 kg on flexible parts bonded with epoxy with and without surface plasma treatment, and on flexible parts bonded with silicone with and without surface plasma treatment. [Figure 7] Figure 7 shows a cross section of a flexible part containing a cavity, with various locations of vent holes shown in the part. [Figure 8] Figure 8 shows three stages of the force sensor: on the left it is in a rest position, and in the middle and right images increasing compressive forces are applied.

[0036] The drawings are schematic and non-limiting, and the size of some of the elements in the drawings may be exaggerated and not drawn to actual scale for illustrative purposes.

[0037] Any reference signs in the claims should not be construed as limiting the scope.

[0038] In different drawings, the same reference signs refer to the same or similar elements. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims, the dimensions and relative dimensions not corresponding to actual implementations of the invention.

[0040] Furthermore, terms such as first, second, etc. in the specification and claims are used to distinguish between similar elements and not necessarily to describe an order in time, space, ranking, or otherwise. The terms so used are interchangeable under appropriate circumstances, and it is understood that the embodiments of the invention described herein are capable of operation in orders other than those described or illustrated herein.

[0041] Furthermore, terms such as up, down, and the like in the specification and claims are used for descriptive purposes and are not necessarily used to describe relative positions. The terms so used are interchangeable under appropriate circumstances, and it is understood that the embodiments of the invention described herein are capable of operation in orientations other than those described or illustrated herein.

[0042] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed thereafter, nor as excluding other elements or steps. Thus, it is interpreted as specifying the presence of a stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the term "comprising" covers both situations where only the stated features are present, and situations where these features and one or more other features are present. Therefore, the scope of the expression "a device comprising means A and B" should not be interpreted as being limited to a device consisting only of components A and B. This means that, in the context of the present invention, the relevant components of the device are only A and B.

[0043] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, although they may. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

[0044] Similarly, in describing exemplary embodiments of the invention, it should be understood that various features of the invention may be grouped together in a single embodiment, figure, or description to streamline the disclosure and facilitate understanding of one or more of the various aspects of the invention. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description of the Invention are hereby expressly incorporated into this Detailed Description of the Invention, with each claim standing on its own as a separate embodiment of the invention.

[0045] Furthermore, although some embodiments described herein include some features and not others included in other embodiments, combinations of features from different embodiments are intended to form different embodiments within the scope of the present invention and as would be understood by one of ordinary skill in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0046] In the description set forth herein, numerous specific details are set forth. However, it is understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0047] In the present invention, when reference is made to a "target part" or simply "target", it refers to a shaped part of material whose change in position is detected by a sensing element.

[0048] When a "flexible part" is mentioned in embodiments of the present invention, it refers to a shaped part of a material that has flexible properties, for example, it may be compressible and preferably has elastic properties, returning to its original shape when no force is applied. When a force is applied to a flexible part, particularly when compressed, the material matrix that forms the part is displaced. In some embodiments, the term "elastomer" is used, but the present invention is not limited to parts made of elastomeric polymers.

[0049] The category of force sensors includes those that include one or more sensing elements that detect the positional displacement of a target component when a force is applied to the sensor. The present invention relates to force sensors that include one or more non-contact sensing elements that are configured to detect the position and / or displacement of a target component without physically contacting the target component. More specifically, the force sensors of the present invention are configured to detect mechanical forces, particularly contact forces acting on a flexible component incorporating a target.

[0050] The sensing is based on electromagnetic sensing. For example, it may be based on detecting a magnetic or electromagnetic field depending on the position of the target. In some embodiments, the sensing is based on a change in the magnetic (or electromagnetic) field due to the movement of the target. The target may be capable of generating a magnetic field, e.g., a magnet, or a conductor capable of inducing a magnetic field. The sensing element can detect the position or its change based on the properties of the field. The sensing element generates a signal that is processed to obtain a readable output representative of the applied force. The target and sensing element may be appropriately selected and combined to generate or induce an electromagnetic field whose change is caused by the movement of the target and whose detection by the sensing element correlates with the amount of displacement of the target. For example, a magnetic sensing element (e.g., a Hall sensor) may be combined with a magnet as a target. The chip may be configured to generate a signal representative of the force causing the displacement of the target. For example, the chip may include processing means (e.g., an integrated circuit on a semiconductor substrate) configured to apply a nonlinear model to directly derive the force. Alternatively, the position of the target can be calculated to obtain the force causing the displacement of the target.

[0051] Movement of the target upon contact is provided by a resilient or flexible part that supports the target. Upon contact, the flexible part deforms in response to the contact force. The target, which is part of the flexible part, also moves.

[0052] Because the relative positions of the sensing element and the target are important, reliable connections are required between the components forming the sensor, particularly the component containing the sensing element, and the target included in the flexible component.

[0053] The present invention provides an improved force sensor with an improved connection between a flexible component containing a target and a substrate containing a sensing element. This allows the force sensor to exhibit high resilience over a wide range of contact forces, either compressive or shear. In some embodiments, the flexible component is attached directly to a semiconductor package containing the sensing element through improved attachment. In these embodiments, the flexible component is shaped to fit within a small area of ​​the semiconductor package (chip). Integrating the elastomer and target directly onto the package and within the package's outline boundaries offers significant advantages in compactness and integration with devices such as claws and robotic hands. However, the present invention is not limited thereto, and attachment may also be performed on a substrate containing the chip, e.g., including connections to the chip. The substrate may be a printed circuit board (PCB).

[0054] In some embodiments, fabrication of the flexible component includes activation of the attachment surface, which improves adhesion of the flexible component to the chip. The flexible component may also include features that improve force sensitivity by improving the deformation and elastic response of the flexible component to applied forces.

[0055] A force sensor and aspects of its fabrication are illustrated in FIGS. 1 and 2. FIG. 1 shows a side view of a force sensor according to an embodiment of the present invention. The force sensor includes a flexible component 200 and a substrate 12 that includes at least one sensing element. The substrate includes a sensing element capable of detecting a force 500 applied to the flexible component. The sensing element can detect a normal force (a compressive component 501 directed toward the sensing element) and can also detect a shear component 502 of the force perpendicular to the compressive component. The flexible component 200 and the substrate 12 are connected by an adhesive layer 300. The adhesive layer extends to one side of the flexible component 200. This side is referred to as the "adhesive surface." The adhesive layer covers the so-called receiving surface 11 of the substrate 12. Force sensors according to embodiments of the present invention include flexible components with features that enhance reliability over time. As described further below, in some embodiments, the flexible component includes cavities that reduce the displacement of the flexible component perpendicular to the compression direction more than the displacement of the flexible component in the compression direction, thereby reducing strain on the flexible material and improving reliability over time. In some embodiments, the mounting surface of the flexible component 200 is activated. Activation improves chemical bonding with the adhesive layer 300. The substrate includes one or more sensing elements and electronics capable of processing the sensing element signals, aligning the sensing elements with a target (not shown) on the flexible component so that the sensing elements can sense fields from the target. For example, the substrate 12 may be a PCB that includes connections to sensors integrated into the chip for sensing electromagnetic fields and / or changes therein caused by the target and / or its movement. The substrate may be selected to have a high affinity with the material of the adhesive layer. In some embodiments, the substrate includes fiberglass epoxy resin.

[0056] FIG. 2 shows an exploded view of a transverse cross section of a force sensor 10 according to some embodiments. A semiconductor package, or chip for short 100, is at the bottom. For example, it includes an integrated circuit mounted on a semiconductor die 102. The semiconductor die 102 may be protected from the outside by a packaging material 110, such as an overmold material, e.g., epoxy resin. Chip 100 further incorporates a sensing element 103. Signals generated by the sensing element and processed by the circuitry may be transmitted to a reading device via pins 101, as is well known. Pins 101 may be connected to a substrate (not shown).

[0057] As mentioned above, the force sensor 10 further includes a flexible part 200 having a target part 201 disposed thereon. The target part 201 may be a magnet. The sensing element 103 responds to a magnetic field (electromagnetic field) from the target part 201, e.g., a magnetic field generated by the target. Movement of the target can be measured by the sensing element, e.g., movement toward the sensing element due to a compressive force applied to the flexible part. The sensing element 103 may be a magnetic field sensor, such as a Hall sensor.

[0058] In the embodiments of the present invention, when a compressive force is mentioned, it refers to a force applied in the Z direction between the target and the sensing element. When a shear force is mentioned in the embodiments of the present invention, it refers to a force applied perpendicular to the direction of the compressive force (thus, a force in at least the X and / or Y direction perpendicular to the normal to the contact surface, e.g., perpendicular to the Z direction of the compressive force). Hereinafter, a plane containing a direction perpendicular to the compressive force is referred to as the "XY plane." The force applied to the sensor may have a compressive component and a shear component.

[0059] In some embodiments, the sensor can ultimately measure twist, as well as the linear vertical movement of the magnet in space, as well as the rotation of the magnet (e.g., defined by two angles). This can be implemented using a 3D sensor, such as a 3D Hall sensor composed of a combination of a horizontal Hall element (responsive to movement perpendicular to the IC) and a vertical Hall element (responsive to movement parallel to the IC). In some embodiments, implementations can provide a 3D sensor made of a horizontal Hall element and a magnetic concentrator positioned to separately concentrate components of the magnetic field in different directions. In some embodiments, magnetoresistive elements such as AMR, GMR, or TMR can be used.

[0060] In embodiments where a flexible component is attached to chip 100, the footprint of the flexible component must be manufactured to fit the area of ​​chip 100.

[0061] The flexible component 200 includes a cavity 206, which distances the target component 201 from the sensing element. The flexible component includes a mounting surface 202. In this embodiment, the surface is annular in shape when the flexible component has an open cavity at the mounting surface, and only a cross section of this surface is shown in FIG. 2 . The flexible component may have other suitable shapes, such as a square annulus bounded by a square nested within another square (e.g., two concentric squares), or the inner and outer boundaries may have different shapes, such as a circle and a square, or vice versa, depending on the available space, etc. The flexible component 200 is attached to the chip 100 by a layer of adhesive 300 on a suitable receiving surface 111 of the chip 100, e.g., the surface closest to the sensing element 103. The packaging material 110 may be part of the outer surface of the packaging material 110, e.g., the outer surface of the chip case.

[0062] The adhesive layer of the force sensor secures the flexible component and the chip together. This type of force sensor can be attached to the area where force measurement is required. In fields such as robotics, accurate force measurement is useful for controlling applied forces, such as the gripping force of a robot claw. Robots grasp objects supported by computer-assisted visual feedback. To achieve human-like dexterity, tactile sensors must be incorporated into the robot's hand or claw. These sensors must be small and capable of detecting forces within a sensitivity range sufficient for the required application. The present invention provides a force sensor for sensing contact between a robot's hand or claw and an object being handled. The force sensor described above can measure not only compressive forces but also shear forces.

[0063] A common problem with force sensors is their reduced reliability when subjected to high forces. Shear forces, in particular, are a major cause of reliability issues, leading to loose components and flexible components detaching from their receiving areas. In the present invention, the problem is even greater because the receiving area is at least as large as or smaller than the chip footprint. This is because a smaller attachment area means less adhesive, which significantly increases the likelihood of delamination when forces, especially shear forces, increase. Furthermore, the need to make the flexible components smaller to fit the chip reduces the amount of deflection allowed by the amount of elastic material, resulting in a lower measurement sensitivity.

[0064] In one aspect, the present invention relates to a method for manufacturing a force sensor. The method is generally illustrated in the schematic diagram of FIG. 3. The method includes providing a flexible component including a target component (S10), providing a substrate with a sensing element and a receiving substrate (S20), and attaching the flexible component to the receiving surface of the substrate (S30). In some embodiments, the substrate is a semiconductor package or chip that integrates one or more sensing elements and circuitry for processing sensed signals.

[0065] The manufacturing method includes providing a flexible component (S10) to enhance reliability under high forces. In some embodiments, the flexible component is provided (S10) with a shape and size such that the mounting surface 202 conforms to the surface area on the chip (particularly the largest external surface area of ​​the chip).

[0066] In particular, the flexible component is preferably provided as a single component, for example by embedding a target. This may involve providing an elastomer such as silicone or rubber. In particular, the component may be provided by injection molding (S11). This method eliminates joints between the flexible materials, homogenizes them, and reduces "weak" areas that may be prone to tearing. Alternatively, the flexible component may be fabricated by assembling multiple components. In some embodiments, the flexible component may be provided by additive manufacturing, for example 3D printing.

[0067] In some embodiments, the flexible component and the target component are provided separately, and the target component is introduced into the flexible component. For example, the flexible component may have an opening formed therein for introducing the target. In a preferred embodiment, the flexible component is formed (S11) around the target, for example by injection molding, and the injected material is in direct contact with the target component, for example, a magnet is overmolded with the material of the flexible component.

[0068] For calibration, the distance between the target and the sensing element in a rest position (with no applied force) must be carefully controlled. The strength of the coupling between the target and the sensing element, the need for a reasonably compact device, and the level of force that will be applied must be considered, along with adequate protection of the electronics. In some embodiments of the invention, providing a flexible part includes forming a cavity (S12) to distance the target from the mounting surface (and from the sensing element once assembled).

[0069] FIG. 4 shows a side view of force sensor 10. Here, flexible component 200 is a transparent truncated dome with a flat surface for receiving force, revealing target component 201 and cavity 206, which improves deformation of the flexible component. Forming the cavity (S12) allows the flexible component to undergo large deformation in response to small contact forces (allowing for a smaller target size since sensitivity is no longer limited by field strength), while protecting the underlying electronics from impact forces and the like. This improves protection of the electronics without sacrificing sensitivity.

[0070] In embodiments of the method that include forming a cavity (S12), the method may further include forming a vent hole 207 (S13) to fluidly connect the cavity 206 in the flexible part 200 to the outside of the force sensor 10. The vent hole 207 may be formed wide enough to ensure the necessary ventilation in the deformation cavity 206 during force application. This reduces the pressure within the cavity while applying a deformation force to the flexible part. An advantage of embodiments of the present invention is that the mobility of the target is not hindered by pressure differences, thereby improving mobility and reducing response time. Manufacturing a flexible part with a vent hole by injection molding can be achieved by introducing a molded part with the desired shape. In particular, in a preferred embodiment, the molded part that defines the vent hole 207 is used to simultaneously hold the target part 201, for example, during molding. In FIG. 4, the vent hole 207 has a "chimney" shape and fluidly connects the cavity to the outside through the top of the flexible part, in the area opposite the mounting surface. The vent hole may be formed from two elongated parts shaped to hold the target, so the target does not need to be placed on top of the mold part that forms the cavity, for example. This allows the space between the target and the cavity to also be filled with elastomer. Once the flexible part is formed, the elongated parts can be removed from the top and bottom, trimming the shape of the vent and releasing the target within the flexible material.

[0071] In some embodiments, providing a flexible part includes fabricating a structure for retaining the target. This structure may include a beam extending between the interior walls of the cavity. Exemplary retaining structures 203, 213 are shown in the perspective views of different flexible parts 200, 210 shown in FIG. 5 . In the case of injection molding, a portion of the mold may support the target before injecting the molding compound that forms the flexible part. The space between these parts forms the retaining structures 203, 213. Other structures, such as reinforcing protrusions 204, may also be included during fabrication, as shown in the flexible part 210 on the right side of FIG. 5 .

[0072] In some embodiments, an open cavity is formed in the flexible component, with the opening, e.g., an opening in the mounting surface, positioned to face the sensing element. The flexible component may have a hollow shape, e.g., resembling a bell or cowbell. Figures 4 and 5 show such an open cavity 206, 206 in a bell-shaped flexible component 200, 210. Despite the significantly reduced mounting surface 202, the disadvantages are overcome by the advantages of being able to easily form the component, e.g., by injection molding, which is fast, reliable, and provides high-quality components, as discussed above.

[0073] However, the invention is not limited in this respect. The cavity may be formed with an internal wall surrounding the cavity and an external mounting surface, i.e., no opening to the cavity through the mounting surface. In this way, the area of ​​the mounting surface can be increased. Such a cavity without an opening to the mounting surface can be formed by assembling separate parts, or by additive manufacturing as described above, or by other methods.

[0074] The method further includes attaching (S30) the flexible component to a substrate, such as a semiconductor package or chip. In some embodiments, this includes providing an adhesive and using it to attach the flexible component to an outer surface of the package of the chip 100, such as a packaging material 110, e.g., an epoxy casing that protects the sensing element and / or integrated circuit. The flexible component is positioned such that the portion of the flexible component that includes the target is away from the sensing element of the chip. In embodiments of the invention, if the flexible component includes a cavity, the flexible component is attached to the chip such that the cavity remains between the chip and the target.

[0075] The adhesive can be any adhesive suitable for chip packaging. For example, the adhesive can be composed of silicone, epoxy resin, or the like. FIG. 4 shows an adhesive layer 300 sandwiched between a flexible component 200 and a semiconductor package 100 (e.g., a chip). The adhesive layer 300 can be applied, for example, to the mounting surface 202 of the flexible component, and then the flexible component with the adhesive layer is secured to the receiving surface of the semiconductor package. In another embodiment, an adhesive is applied to the receiving surface 111 of the chip 100, and the flexible component is brought into contact with the adhesive. For example, a layer of adhesive can be placed on the receiving surface of the chip 100, and the flexible component can be placed on top of the adhesive. This is preferable if the flexible component has a cavity opening on the mounting surface to minimize the amount of adhesive extending inside the cavity, especially along the cavity walls.

[0076] As described below, the presence of the cavities reduces deformation perpendicular to the compression direction, thereby improving the lifespan of the flexible component and simplifying its attachment to the substrate. In a preferred embodiment, the method includes activating the attachment surface 202 of the flexible component 200 (S31) before contacting it with the adhesive of the adhesive layer 300, prior to attaching the flexible component to the substrate (S30). Activation is achieved by treating the surface to increase its hydrophilicity, thereby improving adhesion. In some embodiments, activation is achieved by exposing the surface to a high-energy ionic charge. In some embodiments, activation is achieved by plasma treatment. Activation refers to making the surface more hydrophilic, for example, by forming carboxyl groups or, in the case of elastomers, breaking surface bonds. It should be noted that the plasma treatment (parameters, energy, etc.) is appropriate for activating the surface, rather than simply cleaning it. The plasma can be generated, for example, outdoors using a plasma torch. Alternatively, the plasma can be generated in a controlled atmosphere, for example in a processing chamber, at a controlled atmosphere, for example atmospheric pressure, or at a lower pressure, for example 0.1-10 mBar.

[0077] Multiple parts can be processed simultaneously. For example, a processing chamber (such as a closed chamber with a controlled atmosphere) can be used to process multiple flexible parts. In some embodiments, a pick-and-place machine can be configured to assemble a device by picking up a flexible part and contacting it with a plasma (e.g., generated by a plasma torch), and then placing the flexible part in the required location.

[0078] The plasma can be generated using ambient air (even in the chamber) as the input gas, or any suitable gas (e.g., Ar, O2, N2). The plasma can be a DC, AC, or RF plasma. The power of the generator can be between 100 W and several kW, e.g., 300 W or 500 W, and the frequency can be between 10 kHz and 200 kHz, e.g., 20 kHz or 100 kHz. The duration of plasma activation can be several tens of seconds (e.g., 50 seconds), but can also be shorter, e.g., a few seconds. Any suitable process conditions can be used, as long as surface activation is achieved.

[0079] The present invention is not limited to plasma treatment, other surface activation methods may also be performed, such as other physical and / or chemical methods that can treat the surface to be more hydrophilic.

[0080] In some embodiments of the present invention, the mounting surface 202 of the flexible component is activated and contacted with an adhesive before hydrophobic recovery occurs, so that the surface 202 remains hydrophilic even when in contact with the adhesive layer 300. For example, contact with the adhesive can occur immediately after surface treatment, or can occur within, for example, an hour, for example, during in-line assembly.

[0081] FIG. 6 is a graph showing the results of shear tests for four deformations using different processes and materials. The shear tests were performed on a flexible part attached to a chip, such as the force sensor 10 shown in FIG. 4. The first graph 401 shows the results for a flexible part attached to a chip using epoxy 3609, with no plasma treatment performed on the flexible part. The shear strength (kg) reached approximately 0.25, resulting in adhesive failure. The third graph 403 shows the results for a flexible part attached to a chip using silicone 7503, with no plasma treatment performed on the flexible part. The shear strength was less than 0.75, resulting in adhesive failure. The second and fourth graphs 402 and 404 show the results for epoxy 3609 and silicone 7503, respectively, with no adhesive failure and shear strengths exceeding 1 kg. In these cases, the adhesive surfaces were plasma treated before contacting the adhesive.

[0082] The manufacturing process can be carried out in a simple manner within the framework of passive alignment. For example, the manufacturing process can be automated using simple tools such as "pick and place" machines, which may or may not have computer vision. The machine can pick up the flexible part and align it in the XY plane. This alignment allows for planar placement with an accuracy of about 100 microns in the XY plane. Passive alignment does not require reading the sensing element at the same time as placing the flexible part in order to optimize its position. Surprisingly, it was found that the present invention provides a sensor in which passive alignment is sufficient, without the need for active alignment.

[0083] The pins 101 of the chip can then be connected to a board, such as a PCB, to power the force sensor and output a signal. The force can be applied directly to the flexible component. Alternatively, the chip can be connected to a substrate or board, and then the flexible component can be glued to it after activating the mounting surface.

[0084] In one aspect, the present invention provides a force sensor with improved sensitivity and reliability. The force sensor includes a flexible component attached to a receiving surface of a substrate, e.g., a chip, where the attachment surface of the flexible component does not extend beyond the chip. The flexible component includes a cavity, making it highly flexible and highly responsive to applied forces. In some embodiments, the sensor may be highly responsive to a wide range of applied force values. The sensor is less susceptible to damage from shear forces.

[0085] 4 shows a cross section of a force sensor according to an embodiment of the present invention. It includes a flexible part 200 attached to a chip 100 by an adhesive layer 300 between one of the faces of the flexible part 200 (the so-called mounting face 202) and the receiving face 111 of the chip 100. The flexible part 200 includes a target part 201. The flexible part may be cylindrical, conical, or dome-shaped. These are merely examples; other designs may be tailored to specific applications.

[0086] A cavity 206 between the chip 100 and the target component 201 provides a regulated spacing between the target component 201 and the sensing element 103. In some embodiments, the cavity 206 is open at the mounting surface 202, such that the cavity is open to the receiving surface 111 of the chip 100. The presence of the cavity opening at the mounting surface 202 reduces the mounting area, but allows for easier manufacturing (e.g., injection molding) and a wider deformation range (both compressive and shear), improving sensitivity compared to compact elastomeric components.

[0087] Force sensors according to embodiments of the present invention exhibit low degradation over time. Surprisingly, the flexible component exhibits very limited deformation in the horizontal direction (perpendicular to the compression direction) due to the presence of the cavities. Since the horizontal extension is smaller than the vertical extension, the material is subjected to less strain and is less likely to be damaged. Repeatability improves over time, thereby increasing the durability of the force sensor.

[0088] In some embodiments, the flexible component includes support beams or general retaining structures 203 that prevent the target component 201 from falling into the cavity 206. The flexible component 200 on the left side of FIG. 5 shows that the retaining structures 203 can extend horizontally from the inner wall of the cavity 206. In some embodiments, a combination of reinforcing structures 204 and retaining structures 213 can be provided, as shown in the flexible component 210 on the right side of FIG. 5. The reinforcing structures can be vertically oriented ribs. For example, on the inner wall of the cavity 216, the structures 204 can include chamfers that extend vertically and horizontally along the wall to improve resistance to compression, if desired.

[0089] The flexible component may further include at least one vent hole 207, 217 (shown in FIG. 4 and also in the right-hand flexible component 210 in FIG. 5 ), which ensures pressure relief from the cavity when force is applied. If air remains in the cavity when force is applied to the flexible component, deformation (by compression or shear) becomes more difficult. The vent hole 207 advantageously improves the sensitivity and response time (detection speed) to 3D forces (compression and shear). It also prevents the flexible component from being damaged or dislodged when very large forces are applied. As shown in FIG. 4 , the vent hole 207 may extend from the inner wall of the cavity to the side or outer wall of the flexible component away from the chip.

[0090] FIG. 7 shows a cross-section of an alternative embodiment of a flexible part 220, in which the vent 208 is closer to the mounting surface, e.g., closer to the mounting surface than the force-bearing surface of the flexible part, e.g., located in the lower half of the flexible part, where half is considered half the height. This figure also shows an alternative example in the same diagram, in which the vent is a groove 209 through the mounting surface between the outer wall of the flexible part and the cavity. In this case, adhesive should not be left in the groove when the mounting surface is contacted with the adhesive layer, so that the vent is not blocked. While both vents 208, 209 are shown in the same figure, the flexible part may have a limited number of vents (e.g., only one) to maintain structural integrity.

[0091] In one aspect, the present invention provides a force sensor including a flexible component attached to a substrate with an adhesive layer. The mounting surface of the flexible component is treated and activated to improve adhesion to the adhesive layer. A force sensor can be formed by the method of the present invention. Thus, the force sensor may include, for example, cavities, vents, etc., and the substrate may be a PCB with a chip containing the sensing element and processing electronics, or the substrate may be the chip's packaging. The mounting surface 202 of the flexible component 200 (see FIG. 4 ) may exhibit increased carbonyl functionality and decreased organic bonds compared to the remainder of the flexible component. The open organic bonds in the flexible component material react with the adhesive material, forming chemical bonds between the flexible material of the mounting surface 202 and the adhesive layer 300, improving adhesion.

[0092] Figure 8 shows the force sensor in use. The force sensor is configured to receive a (compressive) force 500, which is measured at a region of the flexible component 200 distal to the tip 100, e.g., the tip of a dome-shaped flexible component 200. As shown from the left schematic diagram, where no force is applied, to the center and right schematic diagrams, where force 500 is applied, the flexible component deforms, changing the position of the target within it. The sensing element detects this change in position and generates a signal that is processed into a signal representative of the applied force. The force sensor can also be adapted to measure forces in different directions, e.g., shear force or a component of shear force. The figure also shows that, as mentioned above, the cavity limits deformation in the horizontal direction, making it smaller than the vertical direction, resulting in significantly less strain on the material. The horizontal elastomer deformation, dx_elastomer, can be measured and compared to the vertical (compressive) displacement of the magnet, dz_magnet. The ratio of deformation (dx_elastomer) to displacement (dz_magnet) may be between 10% and 50%, such as between 20% and 40%, for example between 25% and 30%.

[0093] The sensing and processing are performed by a sensing element and an integrated circuit connected to it, respectively. Both may be provided within the chip. In some embodiments, the force sensor is compact, and the mounting surface of the flexible component is limited to the surface area of ​​the chip, particularly on the outer surface of the chip mold or casing. The force sensor can be connected to a PCB or substrate of the gripping portion of the robotic hand, allowing for accurate measurement of compressive and shear forces. The shear component of the force may occur, for example, when lifting a grasped object with a robotic hand under the influence of gravity. The durability of the force sensor is improved by improved adhesion, the presence of cavities in the flexible component, or both. In some embodiments, activation of the mounting surface of the flexible component improves the adhesion of the flexible component, reducing or preventing delamination of the flexible component.

Claims

1. A method of manufacturing a force sensor (10), comprising: providing (S10) a flexible component (200) with a mounting surface (202) and further including a target component (201); providing (S20) a substrate (12, 100) comprising a receiving surface (11, 111) for mounting the flexible component (200), the substrate (12, 100) further comprising a sensing element (103) configured to detect a change in a magnetic field from movement of the target component (201); Attaching the mounting surface of the flexible component to the receiving surface (11, 111) by applying a surface activation (S31) to the mounting surface of the flexible component and sandwiching an adhesive layer between both the receiving surface (11, 111) and the mounting surface (202) to provide the adhesive layer in contact with at least the mounting surface (S30); A method comprising:

2. 2. The method of claim 1, wherein providing the substrate includes providing a semiconductor package (100), the sensing element being an integrated circuit included in the semiconductor package (100), thereby forming a chip, and attaching the mounting surface includes attaching the mounting surface of the flexible component to the receiving surface (111) of the semiconductor package (100).

3. The method according to claim 1 or 2, wherein the surface activation (S31) comprises plasma treatment.

4. The method of any one of claims 1 to 3, wherein providing (S10) the flexible component comprises forming (S11) the flexible component as a single component by injection molding.

5. The method of claim 1 , wherein providing the flexible component comprises providing the target component and incorporating the target component within the flexible component.

6. 6. The method of claim 1, wherein providing a substrate including sensing elements comprises providing sensing elements adapted to sense magnetic fields in at least two different directions.

7. 7. The method of claim 1, wherein providing (S10) the flexible part comprises providing (S12) a cavity at least partially surrounded by the flexible part, the cavity adapted to enhance mobility of the target part.

8. 8. The method of claim 7, further comprising providing (S13) a vent (207, 208, 209) fluidly connecting the cavity of the flexible part with the exterior of the force sensor.

9. 9. The method of claim 7 or claim 8, wherein providing the flexible component comprises providing an open cavity, and the mounting surface comprises an opening to the mounting surface.

10. A force sensor comprising a flexible part (200) that holds a target part (201) and a semiconductor package (100), wherein the flexible part (200) has an attachment surface (202) distal to the target part (201), the semiconductor package (100) includes a sensing element (103) that detects a magnetic field generated by the target part and a receiving surface (111), the flexible part (200) is attached to the semiconductor package (100), the attachment surface (202) is accommodated in and attached to the receiving surface (111), and the flexible part (200) includes a cavity (206) located between the target part (201) and the semiconductor package (100).

11. 1. A force sensor comprising: a flexible part (200) holding a target part (201), the flexible part (200) having an attachment surface (202) distal to the target part (201); the force sensor further comprising a substrate (12, 100) including a receiving surface (111) and a sensing element (103) for detecting a magnetic field generated by the target part; the flexible part (200) being attached to the substrate (12, 100) by an adhesive layer (300) in contact with the attachment surface (202) and chemically bonding to the attachment surface (202) upon activation of the attachment surface (202), improving adhesion of the flexible part (200) to the adhesive layer (300).

12. The force sensor of claim 11, further comprising a cavity (206) located between the target component (201) and the semiconductor package (100).

13. 13. The force sensor of claim 10 or claim 12, wherein the flexible part (200) further comprises vents (207, 208, 209) providing a fluid connection between the cavity and the exterior of the force sensor.

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