A cavity type MEMS tactile sensor based on PDMS coating and a preparation method thereof

Abstract

This invention discloses a cavity-type MEMS tactile sensor based on PDMS coating, comprising a force transmission structure and a sensor chip. The sensor chip consists of a top device silicon and a bottom substrate silicon. The force transmission structure is made of PDMS material. The device silicon and the substrate silicon are bonded together by fusion bonding. The device silicon includes trenches formed in the device silicon along at least a portion of its peripheral edge, cavities formed in the device silicon along cavities parallel to its peripheral edge, five electrical contacts, four varistor elements, and a Wheatstone full-bridge circuit. By setting a cavity structure with a U-shaped pattern, this invention forms multiple bonding regions on the device silicon, which are distributed not only in the central region of the sensor but also extend to the peripheral edge, effectively increasing the bonding area between the device silicon and the substrate silicon, and significantly improving the structural strength and overall robustness of the MEMS tactile sensor.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a cavity-type MEMS tactile sensor based on PDMS coating and its fabrication method. Background Technology

[0002] In the field of microelectromechanical systems (MEMS) sensing, the design and fabrication of tactile sensors are key technological aspects. Piezoresistive MEMS tactile sensors have become one of the most widely researched and applied tactile sensing solutions due to their advantages such as high sensitivity, ease of integration, and low cost. However, with the increasing demands on sensor performance in fields such as precision robotics and intelligent prosthetics, the limitations of traditional designs are becoming increasingly apparent.

[0003] Conventional MEMS tactile sensor chips typically employ a rigid diaphragm structure with piezoresistors arranged along the edges. External forces act directly on the center of the diaphragm, causing stress concentration in a specific area. This structure not only makes it difficult to further reduce the overall size of the sensor chip, but also makes the brittle silicon-based microstructure highly susceptible to irreversible damage or fracture when subjected to excessive loads, posing a significant risk of overload failure. Furthermore, the exposed sensitive structure lacks effective isolation and protection mechanisms against external environmental interference, resulting in poor measurement signal stability and reduced reliability. Summary of the Invention

[0004] The purpose of this invention is to provide a cavity-type MEMS tactile sensor based on PDMS coating to solve the problems mentioned in the background art.

[0005] In a first aspect, the present invention provides a cavity-type MEMS tactile sensor based on PDMS encapsulation, comprising: The device includes a force transmission structure 3 and a sensor chip. The sensor chip consists of a top device silicon 1 and a bottom substrate silicon 2. The force transmission structure 3 is made of PDMS material. The device silicon 1 and the substrate silicon 2 are bonded together by fusion bonding. The device silicon 1 includes a trench 7 formed in the device silicon 1 along at least a portion of its peripheral edge, a cavity 5 formed in the device silicon 1 along a connection parallel to its peripheral edge, five electrical contacts 4, four varistors 6, and a Wheatstone full-bridge circuit 8. The electrical contacts 4 are partially covered by the force transmission structure 3.

[0006] In one possible implementation of the first aspect, the thickness of the substrate silicon 2 is less than the thickness of the device silicon 1, the trench 7 and the cavity 5 are etched from the structure of the device silicon 1, and the etching depths of the trench 7 and the cavity 5 are equal.

[0007] In one possible implementation of the first aspect, the etching of the device silicon 1 to form trenches 7 and cavities 5 is performed during the same or different steps of the manufacturing process, wherein the cavities 5 form a zigzag pattern in the device silicon 1.

[0008] In one possible implementation of the first aspect, the varistor element 6 is distributed directly above the cavity 5, and the electrical contact 4 is located directly above the varistor element 6.

[0009] In one possible implementation of the first aspect, the electrical contact 4 is connected to the Wheatstone full-bridge circuit 8. The electrical contact 4 may be a solder ball, bump, or other conductive contact, providing a means of applying voltage to and recording voltage from the MEMS tactile sensor.

[0010] In one possible implementation of the first aspect, the Wheatstone full-bridge circuit 8 is formed by patterning a deposited metal layer for detecting resistance changes of a varistor, and the lower surface of the substrate silicon 2 is used to receive applied forces.

[0011] Compared with the prior art, the present invention provides a cavity-type MEMS tactile sensor based on PDMS coating, which has the following advantages: I. By setting a cavity structure with a zigzag pattern, the present invention forms multiple bonding regions on the silicon device, which are not only distributed in the central region of the sensor but also extend to the peripheral edge, effectively increasing the bonding area between the silicon device and the substrate silicon, and significantly improving the structural strength and overall robustness of the MEMS tactile sensor. Second, the sensor chip is covered with PDMS material as the force transmission structure, which can effectively disperse the externally applied stress and avoid damage to the sensitive element caused by local stress concentration. Furthermore, the four piezoresistive elements are connected through the Wheatstone full-bridge circuit, which realizes high sensitivity detection of small deformations and ensures the accuracy and reliability of the force measurement results.

[0012] Secondly, the present invention provides a method for fabricating a cavity-type MEMS tactile sensor based on PDMS coating, comprising: The key parameters of the core structure of the cavity-type MEMS tactile sensor are measured, and the basic property information of PDMS material and cavity molding auxiliary materials is collected. Based on the key parameters of the core structure, the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated. The elastic modulus of the PDMS material is measured, and the molding performance of the auxiliary material is tested to obtain the molding data of the auxiliary material. The encapsulation fit of the cavity MEMS tactile sensor is calculated by combining the molding data of the auxiliary material and the elastic modulus of the material. By combining the encapsulation fit and the deformation threshold of the sensitive unit, the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor are determined. Based on the key parameters of the core structure, the processing execution specifications of the cavity molding mold are set. Combining the molding process requirements and the processing execution specifications, the PDMS material is prepared to obtain the finished product.

[0013] In one possible implementation of the second aspect, calculating the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor based on the key parameters of the core structure includes: Based on the key parameters of the core structure, the structural characteristics of the sensitive unit corresponding to the cavity-type MEMS tactile sensor are calculated. Search for the material properties of the sensing unit corresponding to a cavity-type MEMS tactile sensor; Based on the structural features of the sensitive unit and the material properties of the sensitive unit, the deformation capability of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated. Obtain the working scenario of the sensitive unit corresponding to the cavity MEMS tactile sensor, and calculate the external load of the sensitive unit corresponding to the cavity MEMS tactile sensor based on the working scenario of the sensitive unit. By combining the deformation capability of the sensitive unit and the external load applied to the sensitive unit, the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated.

[0014] In one possible implementation of the second aspect, calculating the encapsulation fit of the cavity-type MEMS tactile sensor by combining the auxiliary material molding data and the material elastic modulus includes: Extract the molding shrinkage rate of the auxiliary material from the molding data of the auxiliary material; Obtain the Poisson's ratio corresponding to the PDMS material; The encapsulation fit of the cavity-type MEMS tactile sensor is calculated by combining the material's elastic modulus, molding shrinkage rate, and Poisson's ratio.

[0015] In one possible implementation of the second aspect, determining the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor by combining the encapsulation fit and the sensitive unit deformation threshold includes: Based on the encapsulation fit, determine the basic curing conditions corresponding to the PDMS material; Obtain the deformation allowable threshold corresponding to the deformation threshold of the sensitive unit; Based on the aforementioned basic curing conditions and the aforementioned allowable deformation threshold, the molding pressure control value of the PDMS material is calculated; Based on the molding pressure control value, the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor are determined.

[0016] As can be seen, this invention calculates the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor based on the key parameters of the core structure, thereby obtaining the precise deformation limit of the cavity-type MEMS tactile sensor. This provides an accurate basis for the subsequent positioning of the sensitive unit in the environment where the cavity-type MEMS tactile sensor is located. This invention calculates the encapsulation fit of the cavity-type MEMS tactile sensor by combining the auxiliary material molding data and the material elastic modulus, thereby obtaining the precise encapsulation fit degree of the cavity-type MEMS tactile sensor. This provides a basis for the subsequent fixing of the sensitive unit in the environment where the cavity-type MEMS tactile sensor is located. This invention determines the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor by combining the encapsulation fit degree and the deformation threshold of the sensitive unit, thereby obtaining the specific operating conditions of the PDMS material molding process to improve the bonding quality between the PDMS material and the sensitive unit. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a structural diagram of a cavity-type MEMS tactile sensor based on PDMS coating according to the present invention; Figure 2 This is a cross-sectional view of a cavity-type MEMS tactile sensor based on PDMS coating according to the present invention; Figure 3 This is a cross-sectional view of a cavity-type MEMS tactile sensor based on PDMS coating according to the present invention; Figure 4 A flowchart illustrating a method for fabricating a cavity-type MEMS tactile sensor based on PDMS coating, as proposed in one embodiment of the invention; In the diagram: 1. Silicon device; 2. Silicon substrate; 3. Force transmission structure; 4. Electrical contact; 5. Cavity; 6. Varistor element; 7. Trench; 8. Wheatstone full-bridge circuit. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 and Figure 2 As shown, the present invention proposes a cavity-type MEMS tactile sensor based on PDMS coating, which includes a force transmission structure 3 and a sensor chip. The sensor chip is composed of a top device silicon 1 and a bottom substrate silicon 2. The force transmission structure 3 is made of PDMS material, and the thickness of the substrate silicon 2 is less than the thickness of the device silicon 1.

[0020] like Figure 3 As shown, the device silicon and the substrate silicon are bonded together by fusion bonding. The device silicon includes trenches formed in the device silicon along at least a portion of the peripheral edge of the device silicon, cavities formed in the device silicon along the periphery of the device silicon, five electrical contacts, four varistor elements, and a Wheatstone full-bridge circuit, and the electrical contacts are partially covered by a force transmission structure.

[0021] Trenches and cavities are etched from the silicon structure of the device, and the etch depths of the trenches and cavities are equal. The etching of the device silicon to form trenches and cavities is performed during the same or different steps of the manufacturing process.

[0022] Trenches can be arranged between MEMS tactile sensors on a silicon wafer and provide tolerance during dicing. By controlling the width of the trenches, the width of the sensor bonding area can be precisely controlled to provide a predetermined level of force measurement sensitivity.

[0023] Since the bonding area of ​​the device silicon is the area excluding the cavity, setting the cavity as a square pattern enables the arrangement of multiple bonding areas. Compared with traditional sensors that only arrange them in the center of the adjacent MEMS tactile sensor, this invention also arranges them on the peripheral edge of the adjacent MEMS tactile sensor, increasing the bonding area between the device silicon and the substrate silicon and improving the strength and robustness of the MEMS tactile sensor.

[0024] The lower surface of the silicon substrate receives the applied force. Varistor elements are positioned directly above the cavity; their resistance changes in the opposite direction as they are stretched and compressed. A Wheatstone full-bridge circuit connects four varistor elements to detect these resistance changes. Upon application of force, the Wheatstone full-bridge circuit becomes unbalanced and outputs a differential voltage proportional to the force applied to the lower surface of the silicon substrate. This differential voltage can be measured via electrical contacts connected to external circuitry. These contacts, located directly above the varistor elements, can be solder balls, bumps, or other conductive contacts, providing a means to apply and record voltages from the MEMS haptic sensor.

[0025] The present invention discloses the working principle and usage process of a cavity-type MEMS tactile sensor based on PDMS coating: In use, the sensor is electrically connected to an external measurement circuit through electrical contacts 4. When an external force is applied to the lower surface of the substrate silicon 2, the force is uniformly transmitted to the sensor chip through the PDMS force transmission structure 3. Under the action of the force, the four piezoresistive elements 6 distributed above the cavity 5 deform. Two of the resistors increase their resistance due to stretching, while the other two decrease their resistance due to compression. This opposite change in resistance is converted into a differential voltage signal output through the Wheatstone full-bridge circuit 8. This voltage signal is proportional to the force applied to the lower surface of the substrate silicon 2. By measuring this differential voltage value, the magnitude of the applied force can be accurately calculated. Since the device silicon 1 adopts a U-shaped cavity design, the bonding area with the substrate silicon 2 is increased, which improves the structural stability and measurement accuracy of the sensor during the force process. At the same time, the trench design ensures the isolation effect between adjacent sensor units and avoids signal crosstalk. Throughout the measurement process, the PDMS force transmission structure not only plays a role in force transmission but also effectively protects the sensor chip from the influence of the external environment.

[0026] See Figure 4 The image shows a method for fabricating a cavity-type MEMS tactile sensor based on PDMS coating according to an embodiment of the present invention, comprising: S1. Measure the key parameters of the core structure of the cavity-type MEMS tactile sensor, and collect the basic property information of PDMS material and cavity molding auxiliary materials. Based on the key parameters of the core structure, calculate the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor.

[0027] This invention calculates the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor based on the key parameters of the core structure, thus obtaining the precise deformation limit of the cavity-type MEMS tactile sensor. This provides an accurate basis for subsequent positioning of the sensitive unit in the environment where the cavity-type MEMS tactile sensor is located. The cavity-type MEMS tactile sensor is a tactile detection device with a cavity structure in a microelectromechanical system. The key parameters of the core structure are data related to the physical dimensions of the cavity-type MEMS tactile sensor, such as the cavity diameter, film thickness, and sensitive unit length. The PDMS material and cavity molding auxiliary materials are also included. The basic attribute information consists of the performance data of the polydimethylsiloxane material and molding auxiliary materials that constitute the cavity-type MEMS tactile sensor, which are used to analyze material properties. The deformation threshold of the sensitive unit is the critical value at which the sensitive unit corresponding to the cavity-type MEMS tactile sensor deforms under force, including the material elastic limit and the safe deformation range during use. Furthermore, the measurement of the key parameters of the core structure of the cavity-type MEMS tactile sensor can be achieved by tools such as optical microscopes and scanning electron microscopes. The acquisition of basic attribute information of PDMS material and cavity molding auxiliary materials can be achieved by material testing methods such as tensile testing and hardness measurement.

[0028] As an embodiment of the present invention, the step of calculating the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor based on the key parameters of the core structure includes: Based on the key parameters of the core structure, the structural characteristics of the sensitive unit corresponding to the cavity-type MEMS tactile sensor are calculated. Search for the material properties of the sensing unit corresponding to a cavity-type MEMS tactile sensor; Based on the structural features of the sensitive unit and the material properties of the sensitive unit, the deformation capability of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated. Obtain the working scenario of the sensitive unit corresponding to the cavity MEMS tactile sensor, and calculate the external load of the sensitive unit corresponding to the cavity MEMS tactile sensor based on the working scenario of the sensitive unit. By combining the deformation capability of the sensitive unit and the external load applied to the sensitive unit, the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated.

[0029] The sensitive unit structural features are the quantification of the geometric dimensions of the sensitive part corresponding to the cavity MEMS tactile sensor; the sensitive unit material properties are the mechanical properties per unit volume of the constituent material corresponding to the cavity MEMS tactile sensor; the sensitive unit deformation capability is the inherent characteristic of the sensitive unit corresponding to the cavity MEMS tactile sensor to resist deformation under force; the sensitive unit working scenario is the environment, contact with objects, and applied force during the use of the cavity MEMS tactile sensor; and the external load of the sensitive unit is the external load that the cavity MEMS tactile sensor may bear during use.

[0030] Optionally, based on the key parameters of the core structure, the structural characteristics of the sensing unit corresponding to the cavity-type MEMS tactile sensor are calculated using the corresponding geometric dimension calculation formula. For example, the material properties of the sensing unit corresponding to the cavity-type MEMS tactile sensor can be queried from the Internet through human-computer interaction. Combining the structural characteristics and material properties of the sensing unit, the deformation capability of the sensing unit corresponding to the cavity-type MEMS tactile sensor is calculated according to the principles of material mechanics and deformation calculation specifications. The working field of the sensing unit corresponding to the cavity-type MEMS tactile sensor can be obtained through on-site testing, usage condition analysis, and communication with designers. Based on the working scenario of the sensitive unit, the external load on the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated according to the magnitude of the contact force, pressure distribution, and possible environmental factors. Combining the deformation capability of the sensitive unit and the external load on the sensitive unit, the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated. The calculation steps are as follows: First, the deformation capability of the sensitive unit is multiplied by a preset safety factor (usually 0.6-0.8) to obtain the allowable deformation limit; then, this limit is compared and analyzed with the estimated deformation caused by the external load on the sensitive unit; finally, the smaller value of the two is taken as the deformation threshold of the sensitive unit.

[0031] S2. Measure the elastic modulus of the PDMS material, perform molding performance testing on the auxiliary material to obtain auxiliary material molding data, and calculate the encapsulation fit of the cavity-type MEMS tactile sensor by combining the auxiliary material molding data and the material elastic modulus.

[0032] This invention calculates the encapsulation fit of the cavity-type MEMS tactile sensor by combining the molding data of the auxiliary materials and the elastic modulus of the material. This allows for the precise encapsulation fit of the cavity-type MEMS tactile sensor, thus providing a basis for the subsequent fixing of the installation position of the sensitive unit in the environment where the cavity-type MEMS tactile sensor is located.

[0033] Wherein, the elastic modulus of the material is the ratio of stress to strain within the elastic range of the PDMS material, reflecting the stiffness characteristics of the material; the auxiliary material molding data are molding performance index data such as flowability and curing shrinkage rate obtained by molding performance testing of the auxiliary material used for cavity molding; the encapsulation fit is the tightness of the connection between the encapsulation part of the cavity MEMS tactile sensor and the sensitive unit. Furthermore, the elastic modulus of the PDMS material can be measured by material testing methods such as tensile testing machine and dynamic mechanical analyzer, and the molding performance testing of the auxiliary material can be achieved by molding testing tools such as rheometer and shrinkage rate measuring instrument.

[0034] As an embodiment of the present invention, the step of calculating the encapsulation fit of the cavity-type MEMS tactile sensor by combining the auxiliary material molding data and the material elastic modulus includes: Extract the molding shrinkage rate of the auxiliary material from the molding data of the auxiliary material; Obtain the Poisson's ratio corresponding to the PDMS material; The encapsulation fit of the cavity-type MEMS tactile sensor is calculated by combining the material's elastic modulus, molding shrinkage rate, and Poisson's ratio.

[0035] Wherein, the molding shrinkage rate is the proportion of volume reduction of the auxiliary material during the molding process; the material Poisson's ratio is the ratio of the transverse strain to the axial strain of the PDMS material under stress.

[0036] Optionally, the molding shrinkage rate corresponding to the auxiliary material can be extracted from the auxiliary material molding data using data parsing technology, such as using regular expressions to match key values ​​in the test report, or reading the corresponding fields in the structured data file using a JSON / XML parser; the material Poisson's ratio corresponding to the PDMS material can be queried from the material database through human-computer interaction.

[0037] Furthermore, as another optional embodiment of the present invention, the encapsulation fit of the cavity-type MEMS tactile sensor is calculated using the following formula, combining the material's elastic modulus, molding shrinkage rate, and material's Poisson's ratio: ; Where A represents the encapsulation fit of the cavity-type MEMS tactile sensor, B represents the elastic modulus of the material, F represents the Poisson's ratio of the material, and S represents the molding shrinkage rate.

[0038] This invention provides a direct understanding of the deformation resistance of PDMS materials by measuring their elastic modulus. A higher elastic modulus indicates a stronger resistance to deformation and a higher stability of the packaging structure. The elastic modulus represents the stress required per unit strain within the elastic range for the PDMS material.

[0039] As an optional embodiment of the present invention, measuring the elastic modulus of the PDMS material includes: Prepare standard samples corresponding to the PDMS material; The standard specimen was subjected to tensile loading, and the stress-strain curve corresponding to the standard specimen was recorded. The slope of the elastic stage corresponding to the standard specimen is determined from the stress-strain curve and used as the elastic modulus of the PDMS material.

[0040] Wherein, the standard specimen is a test sample made of the PDMS material according to standard dimensions; the stress-strain curve is a graphical representation of the stress-strain relationship of the standard specimen during the tensile process; and the slope of the elastic stage is the slope value of the linear part of the stress-strain curve.

[0041] Furthermore, standard specimens corresponding to the PDMS material can be prepared through mold casting and curing processes; the standard specimens can be subjected to tensile loading using a universal testing machine, with tensile force applied at a constant rate, while stress and strain values ​​are recorded using sensors; the slope of the elastic stage corresponding to the standard specimen can be determined from the stress-strain curve using linear regression analysis.

[0042] This invention obtains molding data of the auxiliary material by performing molding performance testing on the auxiliary material, thereby obtaining the flow and solidification characteristics of the auxiliary material for cavity molding during the processing. This provides a basis for adjusting the packaging process of the cavity-type MEMS tactile sensor. The molding data of the auxiliary material is a comprehensive overview of the molding performance of the auxiliary material for cavity molding. Furthermore, by performing molding performance testing on the auxiliary material to obtain molding data, the flowability of the auxiliary material is analyzed to clarify its coverage and uniformity during cavity filling. Then, the dimensional changes of the auxiliary material after molding are understood based on the curing shrinkage rate. By comprehensively considering both, a comprehensive performance characteristic of the auxiliary material during the cavity molding process can be constructed, including the flow behavior at different temperatures and possible shrinkage trends.

[0043] S3. Combining the encapsulation fit and the deformation threshold of the sensitive unit, determine the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor. Based on the key parameters of the core structure, set the processing execution specifications of the cavity molding mold. Combining the molding process requirements and the processing execution specifications, perform the preparation process of the PDMS material to obtain the finished product.

[0044] This invention determines the molding process requirements of the PDMS material on a cavity-type MEMS tactile sensor by combining the encapsulation fit and the deformation threshold of the sensitive unit. This leads to the specific operating conditions of the PDMS material molding process, thereby improving the bonding quality between the PDMS material and the sensitive unit. The molding process requirements refer to the temperature, pressure, and time conditions that the PDMS material needs to meet during the molding process. Furthermore, it first requires a comprehensive analysis of the numerical range of the encapsulation fit to clarify the interface conditions required for the bonding between the PDMS material and the substrate, while accurately grasping the limiting range of the sensitive unit deformation threshold. Based on this, and according to material characteristics and process experience, suitable molding process requirements are determined during the manufacturing process of the cavity-type MEMS tactile sensor to ensure both good encapsulation of the PDMS material and avoidance of excessive deformation of the sensitive unit, thus guaranteeing stable and reliable device performance.

[0045] As an embodiment of the present invention, determining the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor by combining the encapsulation fit and the deformation threshold of the sensitive unit includes: Based on the encapsulation fit, determine the basic curing conditions corresponding to the PDMS material; Obtain the deformation allowable threshold corresponding to the deformation threshold of the sensitive unit; Based on the aforementioned basic curing conditions and the aforementioned allowable deformation threshold, the molding pressure control value of the PDMS material is calculated; Based on the molding pressure control value, the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor are determined.

[0046] Wherein, the basic curing conditions are the combination of temperature and time required for the PDMS material to achieve basic curing; the allowable deformation threshold is the allowable deformation range corresponding to the deformation threshold of the sensitive unit; and the process adjustment coefficient is an adjustment value determined based on material characteristics and process experience.

[0047] Optionally, based on the encapsulation fit, the basic curing conditions corresponding to the PDMS material can be determined by consulting a process comparison table; the allowable deformation threshold corresponding to the deformation threshold of the sensitive unit can be obtained by a quantitative analysis method; and the molding pressure control value of the PDMS material can be calculated by combining the basic curing conditions and the allowable deformation threshold, based on the material molding principle and process calculation specifications.

[0048] Furthermore, as another optional embodiment of the present invention, the molding pressure control value of the PDMS material is calculated using the following formula, combining the basic curing conditions and the deformation allowable threshold: ; Where P represents the molding pressure control value of PDMS material, K represents the process adjustment coefficient, T represents the encapsulation fit, and δ represents the allowable deformation threshold.

[0049] The process adjustment coefficient is a scaling factor determined based on the material properties of PDMS and actual molding experience. It is used to balance the encapsulation fit and deformation limitation when calculating the molding pressure, ensuring that the pressure setting meets the bonding requirements while avoiding excessive deformation. Furthermore, it is achieved by analyzing historical process data or conducting experimental calibration. Specifically, based on successful cases of similar molding in the past, the coefficient value is adjusted through regression analysis or trial and error until the molding result achieves both the ideal encapsulation effect and the deformation control level.

[0050] This invention sets the processing specifications of the cavity molding die based on the key parameters of the core structure, ensuring that the molding die can accurately reproduce the design shape of the cavity structure. This provides a dimensionally accurate molding carrier for PDMS material preparation, thereby ensuring that the final cavity-type MEMS tactile sensor is consistent with the design expectations in terms of structural dimensions. The processing specifications are the specific technical requirements that the molding die must meet during the manufacturing process. These specifications directly determine the dimensional accuracy and surface quality of the cavity structure that the die can form, and are the basis for ensuring that the PDMS material can accurately replicate the target cavity shape.

[0051] As another embodiment of the present invention, the step of setting the processing execution specifications of the forming mold for the cavity based on the key parameters of the core structure includes: The cavity diameter and cavity depth are extracted from the key parameters of the core structure. Based on the cavity diameter, determine the cavity diameter specification corresponding to the molding die; Based on the cavity depth and the preset demolding safety factor, calculate the cavity depth specification corresponding to the molding die; Based on the cavity diameter and cavity depth specifications, the processing execution specifications for the forming mold of the cavity are set.

[0052] Wherein, the cavity diameter specification is the machining standard for the diameter of the cavity portion corresponding to the molding die; the cavity depth specification is the machining standard for the depth of the cavity portion corresponding to the molding die; and the demolding safety factor is a margin factor set to ensure the smooth demolding of the PDMS material.

[0053] Optionally, the cavity diameter and cavity depth can be extracted from the key parameters of the core structure using data filtering techniques. For example, parameter extraction functions in CAD software or Python scripts can be used to parse 3D model data files and directly read the marked cavity geometric dimensions. Based on the cavity diameter, the cavity diameter specification corresponding to the molding die can be determined through an equivalent mapping method. For example, the cavity diameter design value can be directly mapped to the machining diameter of the mold cavity, while considering the material shrinkage characteristics and reserving appropriate machining allowance. Combining the cavity depth and the preset demolding safety factor, the cavity depth specification corresponding to the molding die can be calculated through geometric relationships. For example, the cavity depth can be multiplied by the demolding safety factor (usually 1.05-1.10) to ensure that the molded PDMS component can be successfully demolded and maintain structural integrity.

[0054] This invention, by combining the molding process requirements and the processing specifications, performs the preparation of the PDMS material, thereby improving the controllability of the preparation process, enabling precise molding of the PDMS material, and effectively meeting design requirements. Based on the prepared product, subsequent assembly of the cavity-type MEMS tactile sensor is carried out, ensuring that the sensitive unit maintains normal function in the packaging structure and reducing the risk of performance deviations caused by material shrinkage or molding stress. The processing specifications are the manufacturing standards corresponding to the molding mold, such as cavity depth, sidewall angle, and surface finish standards. Furthermore, based on the key parameters of the core structure, the processing specifications of the cavity molding mold are set, according to the core structure... Key parameters determine the shape, size, and positional accuracy of the cavity in the MEMS tactile sensor. Then, based on this information, the required cavity depth, sidewall angle, surface accuracy, and other processing specifications for the molding die are precisely calculated to ensure that the molding die can accurately replicate the cavity structure. This allows the PDMS material to form a cavity shape that conforms to the design during the molding process, ensuring the accuracy and consistency of the entire preparation process. The PDMS material is then mixed and prepared in accordance with the molding process requirements. According to the processing specifications, the mold processing equipment is controlled, and the mold processing is completed through precision cutting and polishing until the mold size meets the design requirements. This process stops once the mold size meets the design requirements, thereby realizing the preparation and processing of the PDMS material.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cavity MEMS tactile sensor based on PDMS coating, comprising a force transmission structure (3) and a sensor chip, characterized in that: The sensor chip consists of a top device silicon (1) and a bottom substrate silicon (2), and the force transmission structure (3) is made of PDMS material. The device silicon (1) and the substrate silicon (2) are bonded together by fusion bonding. The device silicon (1) includes a trench (7) formed in the device silicon (1) along at least a portion of the peripheral edge of the device silicon (1), a cavity (5) formed in the device silicon (1) along the peripheral edge of the device silicon (1), five electrical contacts (4), four varistors (6), and a Wheatstone full-bridge circuit (8). The electrical contacts (4) are partially covered by the force transmission structure (3).

2. The cavity-type MEMS tactile sensor based on PDMS encapsulation as described in claim 1, characterized in that, The thickness of the substrate silicon (2) is less than the thickness of the device silicon (1), the trench (7) and the cavity (5) are etched from the structure of the device silicon (1), and the etching depth of the trench (7) and the cavity (5) is equal.

3. The cavity-type MEMS tactile sensor based on PDMS encapsulation as described in claim 2, characterized in that, The etching of the device silicon (1) to form trenches (7) and cavities (5) is performed during the same or different steps of the manufacturing process, wherein the cavities (5) form a zigzag pattern in the device silicon (1).

4. The cavity-type MEMS tactile sensor based on PDMS encapsulation as described in claim 1, characterized in that, The varistor element (6) is located directly above the cavity (5), and the electrical contact (4) is located directly above the varistor element (6).

5. A cavity-type MEMS tactile sensor based on PDMS encapsulation as described in claim 1, characterized in that, The electrical contact (4) is connected to the Wheatstone full-bridge circuit (8). The electrical contact (4) may be a solder ball, a bump, or other conductive contact, providing a means to apply voltage to the MEMS tactile sensor and record voltage from the MEMS tactile sensor.

6. The cavity-type MEMS tactile sensor based on PDMS encapsulation as described in claim 1, characterized in that, The Wheatstone full-bridge circuit (8) is formed by patterning a deposited metal layer and is used to detect the resistance change of a varistor. The lower surface of the substrate silicon (2) is used to receive the applied force.

7. A method for fabricating a cavity-type MEMS tactile sensor based on PDMS coating according to any one of claims 1 to 6, characterized in that, The method includes: The key parameters of the core structure of the cavity-type MEMS tactile sensor are measured, and the basic property information of PDMS material and cavity molding auxiliary materials is collected. Based on the key parameters of the core structure, the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated. The elastic modulus of the PDMS material is measured, and the molding performance of the auxiliary material is tested to obtain the molding data of the auxiliary material. The encapsulation fit of the cavity MEMS tactile sensor is calculated by combining the molding data of the auxiliary material and the elastic modulus of the material. By combining the encapsulation fit and the deformation threshold of the sensitive unit, the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor are determined. Based on the key parameters of the core structure, the processing execution specifications of the cavity molding mold are set. Combining the molding process requirements and the processing execution specifications, the PDMS material is prepared to obtain the finished product.

8. The method according to claim 7, characterized in that, The calculation of the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor based on the key parameters of the core structure includes: Based on the key parameters of the core structure, the structural characteristics of the sensitive unit corresponding to the cavity-type MEMS tactile sensor are calculated. Search for the material properties of the sensing unit corresponding to a cavity-type MEMS tactile sensor; Based on the structural features of the sensitive unit and the material properties of the sensitive unit, the deformation capability of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated. Obtain the working scenario of the sensitive unit corresponding to the cavity MEMS tactile sensor, and calculate the external load of the sensitive unit corresponding to the cavity MEMS tactile sensor based on the working scenario of the sensitive unit. By combining the deformation capability of the sensitive unit and the external load applied to the sensitive unit, the deformation threshold of the sensitive unit corresponding to the cavity-type MEMS tactile sensor is calculated.

9. The method according to claim 7, characterized in that, The calculation of the encapsulation fit of the cavity-type MEMS tactile sensor, combining the auxiliary material molding data and the material elastic modulus, includes: Extract the molding shrinkage rate of the auxiliary material from the molding data of the auxiliary material; Obtain the Poisson's ratio corresponding to the PDMS material; The encapsulation fit of the cavity-type MEMS tactile sensor is calculated by combining the material's elastic modulus, molding shrinkage rate, and Poisson's ratio.

10. The method according to claim 7, characterized in that, The process requirements for molding the PDMS material on the cavity-type MEMS tactile sensor are determined by combining the encapsulation fit and the deformation threshold of the sensitive unit, including: Based on the encapsulation fit, determine the basic curing conditions corresponding to the PDMS material; Obtain the deformation allowable threshold corresponding to the deformation threshold of the sensitive unit; Based on the aforementioned basic curing conditions and the aforementioned allowable deformation threshold, the molding pressure control value of the PDMS material is calculated; Based on the molding pressure control value, the molding process requirements of the PDMS material on the cavity-type MEMS tactile sensor are determined.

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