Modular high-protection multi-mounting mode digital pressure sensor

Abstract

A kind of modular high protection multi-mounting mode digital pressure sensor, including PCB substrate, annular metal protection ring, digital sensor chip, double sealing structure and flexible protective filling layer;PCB substrate bottom is equipped with standard SMT pad, annular metal protection ring is fixed in the edge of substrate and is enclosed to form chip containing cavity, digital sensor chip is attached to substrate surface;Annular metal protection ring and PCB substrate are connected by glue adhesive layer and low-temperature welding layer double process to form airtight double sealing structure, chip containing cavity is filled with flexible protective filling layer of specific hardness and modulus to completely cover digital sensor chip;Annular metal protection ring provides side wall welding surface and mechanical anchoring channel to support various mechanical reinforcement installation mode.This application can effectively improve the anti-vibration and impact performance, sealing reliability and installation flexibility of sensor in high vibration, strong impact and corrosive medium environment, meet IP68 protection level requirements.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a modular, highly protected, multi-installation digital pressure sensor. Background Technology

[0002] Sensor technology plays a fundamental role in industrial automation, process control, and intelligent equipment. Pressure sensors, as key physical quantity sensing elements, directly impact the reliability and measurement accuracy of system operation. With the increasing demands for environmental adaptability of measurement and control equipment in industrial settings, digital pressure sensors must operate stably for extended periods under complex conditions such as frequent vibration, significant impact loads, coexistence of dust and humidity, and contact with corrosive media. Against this backdrop, modular structural design has gradually become an important technical path to improve product consistency, shorten assembly cycles, and adapt to automated production lines. High IP protection ratings are widely used to ensure the sealing reliability of sensors in immersion, spray, and high-dust environments. Multiple installation methods provide compatibility support for different equipment interfaces and space constraints. Simultaneously, sensor housing materials, sealing structures, and lead interface forms must also consider long-term chemical compatibility with various industrial media. Currently, pressure sensor products addressing these comprehensive needs have achieved large-scale application in industries such as energy, chemical, construction machinery, and rail transportation. Among the existing technical solutions, some adopt a bare chip-level solution, which has digital output capabilities and miniaturization advantages, and is fixed by SMT mounting; another type adopts a modular solution with a metal top cap, which achieves dielectric isolation through the metal top cap and relies on adhesive or soldering processes for connection to support specific installation requirements.

[0003] However, in the face of complex working conditions where high vibration, strong impact, humidity and corrosive media coexist, existing digital pressure sensors cannot simultaneously achieve excellent vibration and impact resistance, high-level sealing reliability and flexible mechanical installation methods, which poses a challenge to the long-term stable operation of the product in harsh industrial environments. Summary of the Invention

[0004] In view of the above situation and to overcome the shortcomings of the prior art, the purpose of this invention is to provide a modular, highly protected, multi-installation digital pressure sensor that can effectively solve the technical problem that existing digital pressure sensors cannot simultaneously achieve excellent vibration and shock resistance, high-level sealing reliability, and flexible and diverse mechanical installation methods.

[0005] The technical solution provided by this invention is as follows: a PCB substrate, an annular metal protective ring, and a digital sensor chip. The PCB substrate is square and has standard SMT pads on its bottom for reflow soldering. The annular metal protective ring, made of stainless steel or Kovar alloy, is fixed to the edge of the PCB substrate, forming a closed chip housing cavity. The digital sensor chip is mounted on the surface of the PCB substrate in an LGA package and electrically interconnected through pads. The annular metal protective ring and the PCB substrate are connected by a dual process of adhesive bonding layer and low-temperature soldering layer, forming a double-sealed structure with airtightness. The chip housing cavity is filled with a flexible protective filler layer that completely covers the digital sensor chip, with a Shore hardness of A50–A70 and an elastic modulus of 1.5–3.0 MPa. The annular metal protective ring serves as a rigid mechanical protective shell to enhance vibration and impact resistance, and also provides a side wall welding surface and / or mechanical anchoring channel. It supports mechanical reinforcement installation methods other than SMT, such as laser welding and thermally conductive adhesive dispensing, so that the sensor as a whole meets the IP68 protection level and can work stably for a long time in environments with hydraulic oil, refrigerant and corrosive media with pH 2–12.

[0006] This application provides a modular, highly protected, multi-mountable digital pressure sensor. This solution uses a PCB substrate as a support platform and fixes an annular metal protective ring to its edge to form a closed chip housing cavity. Combined with the LGA packaged digital sensor chip mounting method, it achieves mechanical isolation and physical protection of the sensitive element. Furthermore, a dual process of adhesive bonding and low-temperature soldering is used to connect the annular metal protective ring and the PCB substrate, constructing an airtight double-sealed structure that effectively blocks the intrusion path of external liquids or corrosive media. Finally, by filling the chip housing cavity with a flexible protective filler layer with specific Shore hardness and elastic modulus to completely encapsulate the digital sensor chip, the mechanical stress generated by external dynamic loads can be absorbed and dissipated, thereby significantly suppressing vibration transmission and improving the device's environmental shock resistance. This structural design not only solves the problem of easy failure of single connection processes under thermal stress or mechanical fatigue, but also expands from simple SMT mounting to various mechanical reinforcement installation methods such as laser welding and thermally conductive adhesive dispensing through the side wall welding surface and mechanical anchoring channel provided by the annular metal protective ring. It effectively solves the problems of weak vibration resistance, poor sealing reliability and single installation method of existing sensors in high vibration, strong impact and corrosive media environments, thereby ensuring the stability, consistency and safety of the product in long-term operation in complex industrial sites.

[0007] This application, through the synergistic combination of modular structural design, dual sealing process, and flexible buffer filling, forms a logically rigorous and functionally complete systematic solution. While ensuring high IP protection level and media compatibility, it significantly improves the environmental adaptability and installation flexibility of the sensor, meets the high reliability requirements of industrial pressure measurement equipment under harsh working conditions, and has practical application value. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the overall structure of this application; Figure 2 This is a partial cross-sectional schematic diagram of the annular metal protective ring with a limiting flange and a potting gap in this application. Figure 3 This is an enlarged structural diagram of the junction between the substrate and the protective ring, which has a dual process connection layer, according to this application. Figure 4 This is a top view of the PCB substrate with mechanical anchoring holes according to this application. Wherein: 101-PCB substrate; 102-standard SMT pad; 103-ring metal protective ring; 104-chip housing cavity; 105-digital sensor chip; 106-adhesive bonding layer; 107-low temperature soldering layer; 108-flexible protective filling layer; 201-ring limiting flange; 202-potting gap; 501-mechanical anchoring hole. Detailed Implementation

[0009] The specific implementation of the present invention will be described in detail below with reference to examples and specific circumstances.

[0010] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Example

[0011] In fields such as industrial automation, process control, and intelligent equipment, pressure sensors serve as crucial physical quantity sensing elements, and their performance directly impacts the reliability and measurement accuracy of system operation. With the increasing demands for environmental adaptability of measurement and control equipment in industrial settings, digital pressure sensors must operate stably for extended periods under complex conditions such as frequent vibration, significant impact loads, coexistence of dust and moisture, and contact with corrosive media. However, while existing bare-chip solutions offer miniaturization advantages, they lack mechanical protection structures, exhibiting weak vibration and shock resistance, and only support a single surface mount technology (SMT) method. Under high vibration or strong impact scenarios, solder joint cracking or failure is likely. Traditional modular solutions with metal caps often rely on single adhesive or welding processes, which are prone to interface delamination or seal aging under the coupled effects of thermal cycling and mechanical vibration, resulting in insufficient protection levels and difficulty meeting the stringent requirements of immersion, high-pressure spraying, and long-term compatibility with various industrial media.

[0012] To address the aforementioned issues, this application provides a modular, highly protected, multi-installation digital pressure sensor. It aims to enhance vibration and shock resistance through a combination of modular structural design and dual sealing technology, while also expanding the flexibility of installation methods to ensure long-term stable operation in harsh industrial environments.

[0013] Based on the above issues, such as Figure 1 As shown, this application provides a modular, highly protected, multi-installation digital pressure sensor, comprising: PCB substrate 101, with standard SMT pads 102 on its bottom for reflow soldering mounting; The annular metal protective ring 103, made of stainless steel or Kovar alloy, is fixed to the edge of the PCB substrate 101 and encloses the chip receiving cavity 104. The digital sensor chip 105 is mounted on the surface of the PCB substrate 101 in an LGA package and is electrically interconnected through pads; the digital sensor chip model is BMP388 (Bosch) or LPS28DFW (STMicroelectronics) (known technology, commercially available product); The annular metal protective ring 103 is connected to the PCB substrate 101 through a dual process of adhesive bonding layer 106 and low-temperature welding layer 107, forming an airtight double sealing structure. The chip housing cavity 104 is filled with a flexible protective filling layer 108, which completely covers the digital sensing chip 105. Its Shore hardness is A50–A70 and its elastic modulus is 1.5–3.0 MPa. The annular metal protective ring 103 serves as a rigid mechanical protective shell to enhance vibration and impact resistance, and also provides a side wall welding surface and / or mechanical anchoring channel. It supports mechanical reinforcement installation methods other than SMT, such as laser welding and thermally conductive adhesive dispensing, so that the sensor as a whole meets the IP68 protection level and can work stably for a long time in environments with hydraulic oil, refrigerant and corrosive media with pH 2–12.

[0014] The PCB substrate 101 can refer to a printed circuit board that serves as the carrier and electrical interconnection platform for the sensor system. Its material can be set according to actual conditions; for example, it can be an FR-4 epoxy glass cloth laminate, a high-frequency ceramic substrate, or a polyimide flexible substrate. This embodiment does not impose any special limitations on this. The bottom of the PCB substrate 101 is provided with standard SMT pads 102. These SMT pads 102 can be metallized pads conforming to IPC standards, used to mount the sensor to the target circuit board via reflow soldering on an automated production line. The PCB substrate 101 plays a fundamental role in supporting internal components and constructing electrical pathways in the entire technical solution. It cooperates with the annular metal protective ring 103 to form the main frame of the sensor, and the bottom SMT pads 102 achieve initial electrical connection and mechanical fixation with external systems.

[0015] The annular metal protective ring 103 can refer to a ring-shaped structural component made of metal material. Its material can be stainless steel (such as 304 stainless steel or 316L stainless steel) or Kovar alloy, or other corrosion-resistant alloys selected according to actual corrosion resistance requirements. This embodiment does not impose any special limitations on this. The annular metal protective ring 103 is fixed to the edge of the PCB substrate 101, forming a closed chip receiving cavity 104, which is used to contain and isolate the influence of the external environment. In this solution, the annular metal protective ring 103 has a dual functional positioning: on the one hand, as a rigid mechanical protective shell, it utilizes the high strength and toughness of the metal material to provide a physical barrier for the internal digital sensing chip 105 when the sensor is subjected to external impact or continuous vibration, suppressing the direct action of external dynamic loads on the chip; on the other hand, its sidewalls can serve as welding surfaces or mechanical anchoring channels, supporting laser welding with external mounting bases or mechanical reinforcement through dispensing, thereby compensating for the shortcomings of single SMT mounting in terms of shear resistance. The connection between the annular metal protective ring 103 and the PCB substrate 101 constitutes the outer sealing boundary of the sensor, which is a key structure for achieving a high level of protection.

[0016] The digital sensing chip 105 can refer to a semiconductor chip integrating a pressure-sensitive element and signal processing circuitry. Its package form can be LGA (Land Grid Array) or other surface-mount packages selected according to actual needs; this embodiment does not impose any special limitations on this. The digital sensing chip 105 is mounted on the surface of the PCB substrate 101 and electrically interconnected with corresponding lines on the PCB substrate 101 through pads on its bottom. Located inside the chip housing cavity 104, the digital sensing chip 105 is the core sensing unit of the sensor, responsible for converting external pressure signals into electrical signals. In this solution, the digital sensing chip 105 is completely encapsulated in a flexible protective filler layer 108. This layout allows the chip to avoid damage caused by hard impacts when subjected to mechanical stress through the buffering effect of the surrounding filler layer, while maintaining the stability of the electrical connection.

[0017] The adhesive bonding layer 106 and the low-temperature welding layer 107 together constitute a double-sealed structure for airtightness between the annular metal protective ring 103 and the PCB substrate 101. The adhesive bonding layer 106 can refer to a polymer adhesive layer coated at the interface between the metal and the substrate, and its material can be high-temperature modified epoxy, polyurethane, or silicone, etc., which is not specifically limited in this embodiment. The low-temperature welding layer 107 can refer to a metal alloy solder layer with a low melting point, and its material can be Sn-Bi eutectic solder, Sn-Ag-Cu low-melting-point solder, etc., which is not specifically limited in this embodiment. The adhesive bonding layer 106 and the low-temperature welding layer 107 can be arranged side-by-side or stacked in space, and they work together: the adhesive bonding layer 106 can fill microscopic gaps and provide good stress buffering, preventing crack propagation caused by mismatch in thermal expansion coefficients; the low-temperature welding layer 107 provides a high-strength metallurgical bond, ensuring the overall rigidity and sealing continuity of the structure. This dual-process connection method enables the sensor to effectively block the intrusion path of external media when facing temperature cycling, mechanical vibration and corrosive media erosion, avoiding the risk of leakage caused by the failure of a single connection process, thereby achieving an IP68 or higher protection level.

[0018] The flexible protective filler layer 108 can refer to a polymeric elastomer material that fills the chip cavity 104 and completely covers the digital sensor chip 105. Its material can be addition-cure silicone rubber, flexible epoxy resin, or polyurethane elastomer, etc., and this embodiment does not impose any special limitations on it. The Shore hardness of the flexible protective filler layer 108 can be any value within the range of A50–A70, for example, A55, A60, or A65; its elastic modulus can be any value within the range of 1.5–3.0 MPa, for example, 1.8 MPa, 2.2 MPa, or 2.8 MPa. Specific parameters can be set according to the balance requirements of buffering performance and signal transmission stability in actual application scenarios, and this embodiment does not impose any special limitations on it. The function of the flexible protective filler layer 108 in the technical solution is to absorb external impact energy and dissipate vibration stress through its elastic deformation capability, preventing rigid impacts from being directly transmitted to the digital sensor chip 105, causing chip breakage or solder joint fatigue fracture. Meanwhile, the filling layer also serves to fix the chip position and isolate moisture and corrosive gases, ensuring that the digital sensor chip 105 can maintain long-term working stability in environments with hydraulic oil, refrigerants and corrosive media with pH 2–12.

[0019] The core innovation of this application lies in the construction of a modular protection system consisting of a PCB substrate 101, an annular metal protective ring 103, and a dual sealing process. By designing the annular metal protective ring 103 as both a mechanical protective shell and an interface carrier for multiple installation methods, the unity of structural protection and installation flexibility is achieved.

[0020] The working process and principle of this application are as follows: When the sensor is under high vibration or strong impact conditions, the annular metal protective ring 103 first acts as the first line of defense to withstand external mechanical loads, limiting the deformation range of the overall structure; subsequently, the flexible protective filling layer 108 located in the chip housing cavity 104 undergoes elastic deformation, absorbing and dissipating the remaining kinetic energy transferred to the interior, protecting the digital sensing chip 105 from damage. In terms of sealing, the adhesive bonding layer 106 and the low-temperature soldering layer 107 work together to block media intrusion at both the micro-interface filling and macro-structural connection levels, ensuring the airtightness of the chip housing cavity 104. During installation, users can either perform automated reflow soldering through the standard SMT pads 102 at the bottom of the PCB substrate 101, or perform laser soldering through the sidewalls of the annular metal protective ring 103, or use its provided channels for thermally conductive adhesive dispensing reinforcement, thus adapting to installation requirements of different strength levels.

[0021] As a preferred embodiment, the solution of this application is specifically implemented as follows: A PCB substrate 101 made of FR-4 material is selected, and solder paste pads conforming to IPC standards are printed on its bottom as standard SMT pads 102. A ring-shaped metal protective ring 103 made of 304 stainless steel is placed at a predetermined position on the edge of the PCB substrate 101. On the mating surface between the ring-shaped metal protective ring 103 and the PCB substrate 101, a layer of high-temperature modified epoxy adhesive covering approximately 85% of the mating surface is first coated to form an adhesive layer 106. Then, Sn42Bi58 eutectic solder is used to perform circumferential soldering at 175°C to form a low-temperature soldering layer 107, completing the construction of the double-sealed structure. A digital sensor chip 105 using an LGA package is mounted in the center of the PCB substrate 101, and electrical interconnection is achieved through reflow soldering. Finally, addition-cure silicone rubber with a Shore hardness of A60 and an elastic modulus of 2.2 MPa is injected into the chip receiving cavity 104 formed by the annular metal protective ring 103. After curing, it forms a flexible protective filling layer 108 that completely covers the digital sensor chip 105. This sensor can be directly mounted to a control board through an SMT production line, or it can be further reinforced by laser welding the sidewalls of the annular metal protective ring 103 on high-vibration equipment, achieving long-term reliable operation in hydraulic systems and corrosive gas environments.

[0022] Through the above technical solution, this application achieves the following beneficial effects: Because the annular metal protective ring 103 and the PCB substrate 101 enclose a closed space and fill it with a flexible protective filling layer 108, the sensor's vibration and impact resistance under high vibration and strong impact conditions is significantly improved, avoiding the risk of damage caused by direct exposure of the bare chip; Because the annular metal protective ring 103 and the PCB substrate 101 are connected by a dual process of adhesive bonding layer 106 and low-temperature welding layer 107, the problem of easy failure under thermal cycling or mechanical fatigue of a single connection process is effectively solved, greatly improving long-term sealing reliability and enabling the sensor to meet the IP68 protection level; Because the annular metal protective ring 103 has both mechanical protection and multiple mounting interface functions, the sensor supports both automated SMT mounting and mechanical reinforcement mounting methods such as laser welding and dispensing, greatly expanding installation flexibility and applicability, enabling it to work stably for a long time in complex industrial environments such as hydraulic oil, refrigerants, and corrosive media with wide pH values. Example

[0023] In one optional embodiment, as shown in Figure 2, which is a partial cross-sectional view of an annular metal protective ring with a limiting flange and a potting gap, this application also provides a modular high-protection digital pressure sensor with multiple mounting methods. The height of the inner wall of the annular metal protective ring 103 is greater than the height of the digital sensing chip 105, and its top extends inward to form an annular limiting flange 201. A potting gap 202 of 0.5–1.0 mm is maintained between the limiting flange 201 and the PCB substrate 101 to constrain the flow range of the protective filling layer 108 and enhance the shear strength.

[0024] The height of the inner wall of the annular metal protective ring 103 being greater than the height of the digital sensor chip 105 can refer to the extension dimension of the annular metal protective ring 103 in the direction perpendicular to the surface of the PCB substrate 101, configured to exceed the maximum outline height of the digital sensor chip 105 after mounting. The specific value of this height difference can be set according to the package thickness of the digital sensor chip 105 and the minimum coverage thickness of the required protective filler layer 108, for example, it can be 0.5mm, 1.0mm, or 1.5mm higher than the chip height, etc., and this embodiment does not impose any special limitation on this. In the system linkage, this height difference provides vertical accommodating space for the subsequently formed protective filler layer 108, ensuring that the liquid filling material can completely cover the top and sidewalls of the digital sensor chip 105 after being injected into the chip accommodating cavity 104, while preventing the filling material from overflowing outside the protective ring due to volume expansion, thereby maintaining the overall flatness of the sensor and the assembly compatibility with other components.

[0025] The annular limiting flange 201 can refer to an annular protrusion structure extending horizontally or obliquely from the top edge of the annular metal protective ring 103 towards the center of the chip receiving cavity 104. The limiting flange 201 can be in the form of a right-angle bend, a rounded transition, or a chamfer, and its radial width can be set according to actual process requirements, for example, any value between 0.2mm and 1.0mm; this embodiment does not impose any special limitation on this. Functionally, the annular limiting flange 201 acts as a physical barrier boundary, jointly defining the restricted potting area with the underlying PCB substrate 101. In its interaction with the protective filler layer 108, when liquid silicone or epoxy resin is injected through dispensing or vacuum potting processes, the limiting flange 201 effectively intercepts the leading edge of the flowing material, preventing it from crossing the edge of the protective ring and contaminating the standard SMT pads 102 or other external electrical interfaces located at the bottom of the PCB substrate 101, thus ensuring the yield of subsequent reflow soldering and mounting processes.

[0026] The potting gap 202 of 0.5–1.0 mm can refer to the vertical clearance between the lower surface of the annular limiting flange 201 and the upper surface of the PCB substrate 101. The specific value of this gap can be flexibly selected within the range of 0.5 mm to 1.0 mm according to actual conditions, for example, it can be 0.6 mm, 0.8 mm, or 0.9 mm. This embodiment does not impose any special limitation on this. The existence of this potting gap 202 not only provides a clear thickness limit for the flow of the protective filler layer 108, ensuring that the thickness of the filler layer after curing is uniform and consistent, avoiding stress concentration due to excessive local thickness or insufficient protection due to insufficient thickness; at the same time, this gap constitutes part of the mechanical interlocking structure. When the sensor is subjected to lateral vibration or impact load, the cured protective filler layer 108 fills the gap, using the shear modulus of the material to resist the relative slippage between the annular metal protective ring 103 and the PCB substrate 101, thereby significantly enhancing the shear strength and mechanical stability of the overall packaging structure.

[0027] Specifically, the working process and principle of this application are as follows: In the sensor packaging and manufacturing stage, the digital sensor chip 105 is first mounted on the surface of the PCB substrate 101, and the annular metal protective ring 103 is fixed to the edge of the PCB substrate 101; then, liquid flexible protective material is injected into the closed space formed by the annular metal protective ring 103, the PCB substrate 101, and the annular limiting flange 201 through dispensing equipment or potting equipment; under the action of capillary action and gravity, the liquid material flows in the chip receiving cavity 104 and covers the digital sensor chip 105. When the liquid level rises to the horizontal position where the annular limiting flange 201 is located, it is physically blocked by the limiting flange 201, and the material stops diffusing upward and outward, and is strictly limited within the volume range defined by the potting gap 202; after the material solidifies to form a protective filling layer 108, the filling layer, on the one hand, tightly adheres to the digital sensor chip 105 to provide buffer protection, and on the other hand, fills the limiting flange 201. The gap between the filling layer 108 and the PCB substrate 101 forms a mechanical anchoring effect similar to a rivet. When the external environment applies a lateral shear force, the filling layer 108 absorbs energy through its own elastic deformation and uses the friction and interlocking force generated by its contact surface with the limiting flange 201 and the PCB substrate 101 to prevent the annular metal protective ring 103 from displacing relative to the PCB substrate 101, thereby maintaining the reliability of the internal circuit connection.

[0028] As a preferred embodiment, the solution of this application is implemented as follows: Taking the scenario of monitoring the hydraulic system of engineering machinery as an example, the sensor needs to withstand high-frequency vibration and pressure pulsation. In this embodiment, the annular metal protective ring 103 is made of 304 stainless steel, and its inner wall height is designed to be 1.2mm higher than the height of the digital sensor chip 105. The top extends horizontally inward to form an annular limiting flange 201 with a width of 0.5mm. A potting gap 202 of 0.8mm is maintained between the limiting flange 201 and the PCB substrate 101. During the encapsulation process, liquid silicone rubber of appropriate viscosity is injected into the chip receiving cavity 104 using a vacuum potting device. Under the constraint of the limiting flange 201, the silicone rubber is precisely filled into the predetermined space without any overflow, ensuring the cleanliness of the SMT pads 102 at the bottom of the PCB substrate 101. After curing, the formed protective filling layer 108 not only completely covers the chip, but also firmly fills the 0.8mm gap. Tests showed that the sensor with this structure operated continuously under random vibration with an acceleration of 20g, with no relative slippage of its internal components, no cracking of the solder joints, and a significantly reduced failure rate, meeting the requirements for long-term stable operation under harsh conditions.

[0029] Through the above technical solution, this application achieves the following: by setting an annular metal protective ring with an inner wall height greater than the chip height and an annular limiting flange extending inward from the top, and maintaining a specific range of potting gap between the limiting flange and the PCB substrate, the flow range of the protective filling layer is effectively constrained, preventing liquid filling material from overflowing and contaminating the electrical interface area, thus ensuring the reliability of the automated mounting process. At the same time, since the filling layer forms a mechanical interlocking structure after curing and filling the potting gap, the shear strength between the metal protective ring and the PCB substrate is enhanced, solving the structural failure problem caused by interface slippage under high vibration environment, and improving the overall structural stability and service life of the sensor under complex dynamic loads. Example

[0030] In one optional embodiment, as shown in Figure 3, which is an enlarged structural diagram of the junction between the substrate and the protective ring with dual process connection layers provided in this application, this application also provides a modular, high-protection, multi-installation digital pressure sensor. The adhesive bonding layer 106 is a high-temperature resistant modified epoxy adhesive with a glass transition temperature (Tg) ≥ 150 ℃, and the coating area accounts for ≥ 80% of the bonding surface between the metal protective ring 103 and the PCB substrate 101. The low-temperature welding layer 107 uses Sn-Bi eutectic solder with a melting point ≤ 139 ℃, and welding is completed at 170–180 ℃. The welding temperature is lower than the Tg of the PCB substrate 101 and the temperature resistance limit of the digital sensing chip 105.

[0031] The adhesive layer 106 can refer to an organic polymer adhesive material disposed at the interface between the annular metal protective ring 103 and the PCB substrate 101. Its function is to provide initial mechanical fixation and fill microscopic gaps to aid sealing. The adhesive layer 106 is tightly bonded to both the annular metal protective ring 103 and the PCB substrate 101, connecting them through chemical bonding or physical adsorption. In this application, the adhesive layer 106 is a high-temperature modified epoxy adhesive with a glass transition temperature (Tg) of any value not lower than 150°C, such as 150°C, 160°C, or higher, to ensure that the adhesive layer does not soften or fail under high-temperature conditions. The coating area can be 80% or more of the bonding surface between the metal protective ring 103 and the PCB substrate 101, such as 85%, 90%, or full coverage; this application does not impose any special limitations on this aspect. A larger coating area increases the effective bonding area and disperses shear stress, thus enabling it to jointly bear external loads and block media penetration paths in conjunction with the low-temperature welding layer 107. According to the disclosed implementation concept, this high-temperature modified epoxy adhesive can be, for example, a two-component modified epoxy resin whose linear coefficient of thermal expansion can match that of the metal protective ring and the PCB substrate to reduce thermal stress concentration.

[0032] The low-temperature soldering layer 107 can refer to a metal alloy connecting layer located inside or working in conjunction with the adhesive bonding layer 106. Its function is to provide a high-strength, airtight seal and the mechanical support foundation required for electrical conduction. This low-temperature soldering layer 107 is sandwiched between the annular metal protective ring 103 and the PCB substrate 101, forming a double-sealed structure with the adhesive bonding layer 106. In this application, the low-temperature soldering layer 107 uses a Sn-Bi eutectic solder, whose melting point can be any value not exceeding 139 °C, such as 138 °C or 139 °C. The soldering process temperature can be in the range of 170–180 °C, such as 170 °C, 175 °C, or 180 °C; this application embodiment does not impose any special limitations on this. The key is that the soldering temperature must be lower than the glass transition temperature (Tg) of the PCB substrate 101 and the temperature limit of the digital sensor chip 105 to prevent high temperatures from causing substrate deformation and delamination or damage to the internal structure of the chip. Through cooperation with the adhesive layer 106, the low-temperature soldering layer 107 forms a continuous and dense intermetallic compound layer with lower heat input, achieving reliable hermetically sealed bonding while avoiding the thermal damage risks associated with traditional high-temperature soldering. According to the disclosed implementation concept, the Sn-Bi eutectic solder can be, for example, a Sn42Bi58 alloy, which exhibits good fatigue resistance after solidification and can adapt to minor deformations caused by temperature cycling.

[0033] Specifically, the working process and principle of this application are as follows: During sensor assembly, a high-temperature modified epoxy adhesive is first applied to the bonding surface between the annular metal protective ring 103 and the PCB substrate 101, controlling the coating area to reach more than 80% of the bonding surface to form an adhesive bonding layer 106. Subsequently, Sn-Bi eutectic solder is placed in a preset welding area, and the solder is melted and wetted by heating to 170–180 ℃. After cooling, a low-temperature welding layer 107 is formed. In this process, the high Tg adhesive bonding layer 106 maintains rigidity in a high-temperature environment to prevent interface slippage, while the large-area coating ensures sufficient bonding strength; the low-melting-point low-temperature welding layer 107 completes metallurgical bonding at a relatively mild temperature, providing excellent airtightness. The two work together, with the adhesive bonding layer 106 mainly serving to buffer thermal stress and mechanical vibration, and the low-temperature welding layer 107 mainly serving to block the intrusion of media and provide structural locking. Thus, under the complex working conditions of thermal cycling and mechanical vibration coupling, the occurrence of interface delamination, cracking or sealing failure is effectively suppressed.

[0034] As a preferred embodiment, the specific implementation of this application is as follows: A two-component high-temperature modified epoxy adhesive (such as EPO-TEK 353ND) with a glass transition temperature (Tg) of 155 ℃ is selected and uniformly coated on the bonding surface between the bottom of the 304 stainless steel annular metal protective ring 103 and the edge of the FR-4 PCB substrate 101, with the coating coverage controlled at 85%; then, Sn42Bi58 eutectic solder paste with a melting point of 139 ℃ is applied to the inner ring of the bonding surface by stencil printing or dispensing; subsequently, the component is placed in a reflow oven with a peak temperature set at 175 ℃ and a holding time of 60 seconds to complete the soldering process. This temperature is far lower than the Tg of the PCB substrate 101 (approximately 180 ℃) and the tolerance limit of the digital sensor chip 105 (approximately 200 ℃). After curing, the components underwent 1000 temperature cycles from -40 ℃ to +125 ℃. The test results showed that there was no cracking or delamination at the interface between the adhesive layer 106 and the low-temperature welding layer 107. The leakage rate detected by helium mass spectrometry met the IP68 protection level requirements, verifying the long-term reliability of the dual-process connection structure in harsh thermal environments.

[0035] Through the above technical solutions, this application achieves significant improvements in the dimensional stability and bonding strength of the adhesive layer under high-temperature environments by using a high-glass transition temperature modified epoxy adhesive as the adhesive bonding layer 106 and combining it with a large-area coating process. Furthermore, by using a low-melting-point Sn-Bi eutectic solder as the low-temperature welding layer 107 and completing the welding at temperatures below the temperature limits of the substrate and chip, thermal damage to the sensitive element and substrate caused by high-temperature thermal shock is effectively avoided. Since the adhesive bonding layer 106 and the low-temperature welding layer 107 constitute a dual-sealing structure, their mechanical properties and sealing functions complement and synergize, thus solving the technical problem of interface delamination or sealing failure easily occurring under thermal cycling conditions in traditional single-connection processes. This achieves the technical effect of improving the long-term sealing reliability of sensors in harsh temperature environments such as automotive and industrial applications. Example

[0036] In another embodiment, the method further includes a protective filler layer 108 made of addition-type silicone rubber with a coefficient of thermal expansion of 250–300 ppm / ℃, which matches the coefficient of thermal expansion of the digital sensor chip 105 and the PCB substrate 101, in order to suppress interfacial stress caused by temperature cycling.

[0037] The protective filling layer 108 can refer to a flexible buffer material that fills the chip cavity and completely covers the digital sensor chip. Its material can be addition-cure silicone rubber. Addition-cure silicone rubber is an organosilicon elastomer cured by platinum-catalyzed addition reaction, possessing excellent high and low temperature resistance, chemical stability, and electrical insulation. In the technical solution of this application, the main function of the protective filling layer 108 is to absorb external mechanical impact energy and isolate vibration transmission, while also serving as a dielectric isolation barrier between the internal sensitive element and the external environment. The protective filling layer 108 forms a close fit with the annular metal protective ring 103 and the digital sensor chip 105 in the aforementioned embodiments: the enclosed space formed by the annular metal protective ring 103 defines the geometric boundaries of the protective filling layer 108, while the protective filling layer 108 fills the surface of the digital sensor chip 105 and the surrounding gaps, fixing the chip to the PCB substrate 101 through physical contact. This combination ensures that external dynamic loads first act on the rigid annular metal protective ring 103, and are subsequently attenuated by the elastic deformation of the protective filling layer 108. Ultimately, the stress transmitted to the digital sensing chip 105 is significantly reduced, thus achieving mechanical protection for the chip. Regarding the specific implementation of the protective filling layer 108, its Shore hardness can be set according to actual conditions, for example, it can be A50 or A70. This application embodiment does not impose any special limitations on this, as long as it can ensure sufficient buffering without hindering the normal operation of the chip. Its elastic modulus can also be adjusted according to actual operating conditions, for example, it can be 1.5 MPa or 3.0 MPa.

[0038] The coefficient of thermal expansion (CTE) refers to the relative rate of change of a material's length or volume under a unit temperature change, and is a key physical parameter for measuring the dimensional stability of a material. In this application, the CTE of the protective filler layer 108 is limited to 250–300 ppm / ℃, aiming to match its value range with that of the digital sensor chip 105 and the PCB substrate 101. The digital sensor chip 105 typically uses silicon-based materials or ceramic packaging, which have relatively low CTEs (e.g., silicon is approximately 2.6 ppm / ℃, but the overall equivalent CTE of LGA packaging is greatly affected by the molding compound, typically between 200–300 ppm / ℃). If the PCB substrate 101 uses FR-4 material, its CTE in the planar direction is approximately 12–17 ppm / ℃. However, when considering the thickness direction or the overall module equivalent effect, the composite expansion behavior of each layer of material needs to be comprehensively considered. The term "matching" here does not require numerical values ​​to be exactly equal. Rather, it refers to the expansion or contraction trend of the protective filler layer 108 being coordinated with that of the adjacent digital sensor chip 105 and PCB substrate 101 under a wide temperature range, avoiding significant dimensional differences caused by temperature variations. This technical feature works synergistically with other properties of the protective filler layer 108: when the ambient temperature changes drastically, if the coefficient of thermal expansion of the protective filler layer 108 is much higher or lower than that of the chip and substrate, huge shear stress or peel stress will be generated at the interface. Long-term accumulation may lead to cracking of the filler layer, debonding from the chip, or zero-point drift caused by chip compression. By controlling the coefficient of thermal expansion within the range of 250–300 ppm / ℃, the protective filler layer 108 can expand and contract synchronously with the digital sensor chip 105 and PCB substrate 101 during temperature cycling, thereby effectively suppressing the generation of interface stress. The specific value of the coefficient of thermal expansion can be adjusted according to the selected silicone rubber formulation and filler ratio. For example, it can be 250 ppm / ℃, 300 ppm / ℃, or any intermediate value within this range. This application does not impose any special limitation on this.

[0039] Specifically, the working process and principle of this application are as follows: When the sensor is in a temperature cycling environment (such as heating from -40℃ to +125℃ and then cooling), all components inside the module will experience thermal expansion and contraction. Since the protective filler layer 108 is made of addition-cure silicone rubber with a thermal expansion coefficient of 250–300 ppm / ℃, its dimensional change rate is on the same order of magnitude or has a reasonable matching gradient with the dimensional change rate of the digital sensor chip 105 (especially its LGA package shell) and the PCB substrate 101. During the heating process, the protective filler layer 108, the digital sensor chip 105, and the PCB substrate 101 expand outward simultaneously. Since the expansion degrees of the three are similar, there will be no drastic relative displacement at the contact interface between them, thus avoiding the concentration of shear force; during the cooling process, the three contract synchronously, which also prevents the generation of tensile stress that would lead to delamination or cracking. This design based on matching thermal expansion coefficients ensures that the protective filling layer 108 can play a mechanical buffering role without becoming a new stress source due to temperature changes, thus ensuring the structural integrity and measurement accuracy stability of the sensor over a wide temperature range.

[0040] As a preferred embodiment, the solution of this application is implemented as follows: A two-component addition-type liquid silicone rubber is selected as the base material of the protective filler layer 108. By adjusting the addition ratio of silica filler, its coefficient of thermal expansion is precisely controlled to 280 ppm / ℃. This value is within the limited range of 250–300 ppm / ℃ and is very close to the equivalent coefficient of thermal expansion of a typical LGA packaged digital sensor chip 105 (approximately 260 ppm / ℃). The comprehensive thermal deformation characteristics of the PCB substrate 101 under a multilayer structure are also taken into account. During the manufacturing process, the liquid silicone rubber is injected into the chip receiving cavity 104 formed by the annular metal protective ring 103, completely immersing and covering the digital sensor chip 105. After heat curing, a solid protective filler layer 108 with a predetermined hardness and elastic modulus is formed. When the sensor is applied to scenarios with severe temperature fluctuations, such as automotive engine compartments or industrial hydraulic systems, it has undergone thousands of temperature cycling tests from -40°C to +125°C. Because the thermal expansion behavior of the protective filler layer 108 is consistent with that of the chip and the substrate, no microcrack propagation or debonding phenomenon was observed at the interface. The zero-point output drift of the sensor remained at an extremely low level, verifying the effectiveness of the thermal expansion coefficient matching design.

[0041] Through the above technical solution, this application achieves the following: because the protective filling layer 108 uses addition-type silicone rubber with a specific thermal expansion coefficient range (250–300 ppm / ℃), and this coefficient matches the digital sensor chip 105 and PCB substrate 101, the dimensional changes between the components tend to be synchronized during temperature cycling, significantly reducing the interfacial shear stress and peel stress caused by thermal mismatch. This solves the technical problem of cracking, debonding, or chip drifting under pressure caused by the large difference in thermal expansion between the filling material and the substrate in traditional sensors. It achieves the technical effect of suppressing interfacial stress accumulation, preventing material failure, and improving the long-term reliability and measurement accuracy consistency of the sensor in a wide temperature range environment. Example

[0042] In one optional embodiment, as shown in Figure 4, which is a top view of the PCB substrate with mechanical anchoring holes provided in this application, this application also provides a modular, high-protection, multi-mounting digital pressure sensor. At least two mechanical anchoring holes 501 penetrating the substrate are symmetrically arranged on the outer periphery of the PCB substrate 101. The hole diameter is 0.4–0.8 mm and the position is located within the projection area of ​​the metal protective ring 103. They are used to inject thermally conductive adhesive to achieve dispensing and bonding, or as a laser welding energy introduction channel.

[0043] The mechanical anchoring hole 501 can refer to a through-hole structure formed in the edge region of the PCB substrate 101 and extending through its thickness direction. Its diameter can be set according to actual conditions, for example, it can be 0.4 mm, 0.6 mm, or 0.8 mm; this embodiment does not impose any special limitation on this. The functional positioning of the mechanical anchoring hole 501 in the overall technical solution is to provide an additional mechanical locking path and process channel besides the bottom SMT pad 102. It forms a cooperative relationship with the annular metal protective ring 103 and the PCB substrate 101: the position of the mechanical anchoring hole 501 is strictly limited to the vertical projection area of ​​the annular metal protective ring 103, so that the externally applied fixing force or energy can directly act on the rigid support structure formed by the metal protective ring 103, rather than only acting on the fragile PCB substrate itself. With this layout, when the sensor is exposed to a high-vibration environment, the mechanical anchoring hole 501 allows the introduction of an external medium (such as thermally conductive adhesive) or an energy beam (such as a laser) to form a stable connection between the sensor body and the external mounting base, thereby suppressing the risk of fatigue fracture that may occur due to relying solely on reflow solder joints.

[0044] Specifically, the mechanical anchoring hole 501 supports two main reinforcement modes. In the first mode, the mechanical anchoring hole 501 acts as a fluid channel, allowing liquid thermally conductive adhesive to be injected from the upper surface or side of the PCB substrate 101. The adhesive flows through the hole into the chip receiving cavity 104 or contacts and fuses with the protective filler layer 108, forming a through-type dispensing adhesive structure. This structure not only achieves a mechanical riveting effect but also utilizes the properties of the thermally conductive adhesive to establish an additional heat dissipation path. In the second mode, the mechanical anchoring hole 501 acts as an optical channel, allowing a fiber laser beam to penetrate the hole and reach a specific area on the bottom edge or sidewall of the annular metal protective ring 103. The laser energy is absorbed here and converted into heat energy, achieving a local fusion welding connection between the sensor and the metal mounting base. Since the hole is located within the projection area of ​​the metal protective ring 103, the heat-affected zone of the laser welding is confined within the rigid metal part, avoiding thermal damage to the internal digital sensing chip 105.

[0045] As a preferred embodiment, the solution of this application is implemented as follows: Four mechanical anchoring holes 501 with a diameter of 0.6 mm are symmetrically distributed on the outer periphery of the PCB substrate 101. These holes are evenly distributed within the coverage area of ​​the annular metal protective ring 103. When installing the equipment in high-vibration scenarios, the operator selects thermally conductive silicone and injects the adhesive precisely into the mechanical anchoring holes 501 using a dispensing device. Under gravity and capillary action, the adhesive flows into the internal cavity of the sensor and combines with the original flexible protective filling layer 108. After curing, an integrated adhesive anchoring point is formed. Alternatively, in cases requiring higher strength fixation, the mechanical anchoring holes 501 are used as alignment marks and energy channels. A fiber laser with a wavelength of 1064 nm is used to perform circumferential welding between the annular metal protective ring 103 and the mounting base through the holes. The laser beam passes through the holes and acts directly on the metal bonding surface to form a deep penetration weld, thereby achieving permanent and secure installation of the sensor.

[0046] Through the above technical solution, this application achieves the technical effect of expanding various mechanical reinforcement methods. Because mechanical anchoring holes 501 are provided on the PCB substrate 101 within the projection area of ​​the metal protective ring 103, a through-type locking structure can be formed by injecting thermally conductive adhesive or precise laser welding can be performed through the holes. This solves the technical problem that solder joints are prone to cracking or falling off under strong vibration loads when relying solely on SMT pads 102 for fixation. Therefore, it significantly improves the installation stability and safety of sensors under high vibration conditions such as engineering machinery and rail transportation. Example

[0047] In an optional implementation, the method further includes: a digital sensing chip 105 integrating a temperature compensation circuit and a digital calibration module, with the output transmitted via an I²C or SPI interface; a decoupling capacitor array is configured on the PCB substrate 101 near the chip power supply pin, and a ground shielding strip and a π-type EMI filter circuit are provided on both sides of the signal trace, with a cutoff frequency of 5–15MHz.

[0048] The digital sensor chip 105 can refer to a semiconductor device that integrates signal conditioning, analog-to-digital conversion, and data processing functions. In this application, the digital sensor chip 105 not only senses the physical quantity of pressure but also monitors changes in ambient temperature in real time through an integrated temperature compensation circuit. It corrects the original signal based on calibration coefficients stored in the built-in digital calibration module to eliminate measurement errors caused by temperature drift. This technical feature, together with other circuit components on the PCB substrate 101, constitutes a complete signal acquisition and processing chain. Its function is to improve the accuracy and stability of the signal from the source, ensuring that the output digital signal can truly reflect the measured pressure value. The specific implementation of the temperature compensation circuit and the digital calibration module can be set according to the actual situation. For example, it can be linear compensation based on a lookup table method or nonlinear compensation based on polynomial fitting. This application embodiment does not impose any special limitations on this.

[0049] The I²C or SPI interface refers to a standard serial communication protocol interface used for data communication between the digital sensor chip 105 and an external host system. The I²C (Inter-Integrated Circuit) interface is typically two-wire, including a serial data line and a clock line; the SPI (Serial Peripheral Interface) interface is typically four-wire, including master-output-slave-in, master-in-slave-output, clock, and chip select signal lines. In this application, high-precision pressure data, after temperature compensation and digital calibration, is transmitted to external devices through this interface, realizing digital interaction between the sensor and the control system. This technical feature, combined with the signal traces and filtering circuits on the PCB substrate 101, ensures the integrity of the data during transmission. The specific type of interface can be selected according to the communication requirements of the actual application scenario. For example, an I²C interface can be selected in scenarios with limited pin resources, while an SPI interface can be selected in scenarios requiring high-speed data transmission. This application embodiment does not impose any special limitations on this.

[0050] A decoupling capacitor array refers to a circuit structure composed of one or more capacitors, typically arranged between the power supply pins and ground of the digital sensor chip 105. In this application, the decoupling capacitor array is positioned adjacent to the chip's power supply pins. Its main function is to filter out high-frequency noise on the power supply line and provide local charge reserves for the chip's instantaneous current demands, thereby stabilizing the supply voltage and preventing chip malfunctions or resets caused by power fluctuations. This technical feature, together with the subsequent π-type EMI filter circuit, forms a multi-stage filtering system to jointly construct a low-noise power supply environment. The specific configuration of the decoupling capacitor array can be set according to actual conditions. For example, it can be a single large-capacity capacitor or an array composed of ceramic capacitors of different capacitance values ​​(such as 0.1μF, 10nF, etc.) connected in parallel to cover a wider frequency range. This application embodiment does not impose any special limitations on this.

[0051] The grounding shielding strip can refer to a continuous grounding copper foil area set on both sides or around the signal traces on the PCB substrate 101. In this application, the grounding shielding strip extends along the sensitive signal traces, isolating the signal lines from external electromagnetic interference through electrostatic shielding, while providing a low-impedance path for signal return and reducing signal crosstalk. This technical feature works in conjunction with the decoupling capacitor array and π-type EMI filter circuit to further purify the signal transmission environment from a spatial layout perspective. The width, spacing, and relative position of the grounding shielding strip to the signal lines can be designed according to PCB routing rules and anti-interference requirements. For example, it can be a grounding structure, or a single-sided or double-sided parallel ground line; this application embodiment does not impose any special limitations on this.

[0052] A π-type EMI filter circuit can refer to a filter network structure resembling the Greek letter π, composed of an inductor (or ferrite bead) and two capacitors. In this application, the circuit is connected in series in the signal transmission path or power input path, utilizing the high-frequency blocking characteristics of the inductor and the AC-passing, DC-blocking characteristics of the capacitor to attenuate electromagnetic interference signals in a specific frequency band. This technical feature, in conjunction with a grounding shield, provides a final line of defense against conducted interference, ensuring the purity of signals entering or leaving the digital sensor chip 105. The inductance, capacitance, and cutoff frequency parameters in the π-type EMI filter circuit can be adjusted according to the spectral characteristics of the actual interference source. For example, the cutoff frequency can be set to 5 MHz, 10 MHz, or 15 MHz, or any value within the range of 5–15 MHz; this application embodiment does not impose any special limitations on this.

[0053] Specifically, the working process and principle of this application are as follows: When the sensor is working, the digital sensing chip 105 first senses the current ambient temperature through its internally integrated temperature compensation circuit, and then, in conjunction with the preset parameters in the digital calibration module, corrects the original analog signal output by the pressure-sensitive element in real time to generate a high-precision digital pressure signal. Subsequently, this digital signal is prepared for transmission to the outside via the I²C or SPI interface. During this process, the decoupling capacitor array on the PCB substrate 101 responds instantly to voltage fluctuations at the chip's power supply pins, absorbs high-frequency noise energy, and maintains the stability of the power supply voltage. At the same time, when the signal is transmitted on the PCB traces, the grounding shielding strips on both sides effectively block the coupling interference of external spatial electromagnetic fields. If there are still residual high-frequency interference signals attempting to intrude or transmit, the π-type EMI filter circuit significantly attenuates the noise signals in these frequency bands according to its set 5–15 MHz cutoff frequency. Through the synergistic effect of the above-mentioned on-chip compensation, power supply decoupling, spatial shielding, and filtering network, the integrity of the sensor's output signal and the reliability of communication are ensured in complex electromagnetic environments.

[0054] As a preferred embodiment, the solution of this application is implemented as follows: In a strong electromagnetic interference environment near an industrial frequency converter, the digital sensor chip 105 uses an LGA packaged chip with factory calibration data, which internally incorporates a temperature-pressure compensation algorithm. During the layout on the PCB substrate 101, a 0.1μF and a 10nF ceramic capacitor are placed within 1mm of the chip's VCC pin as a decoupling capacitor array. For the I²C communication lines (SDA and SCL), a 0.3mm wide grounding shield is laid on both sides of the trace and frequently connected to the ground plane via vias. Before the communication line enters the connector, a 600Ω@100MHz ferrite bead is connected in series, and a 100pF capacitor is connected in parallel with ground before and after the ferrite bead, forming a π-type EMI filter circuit with a cutoff frequency of approximately 8MHz. When the frequency converter generates severe electromagnetic fluctuations, this configuration keeps the sensor communication bit error rate at an extremely low level, and the data output is stable and without jumps.

[0055] Through the above technical solutions, this application achieves the following: because the digital sensor chip 105 integrates a temperature compensation circuit and a digital calibration module, it can eliminate measurement deviations caused by changes in ambient temperature at the source, thus improving measurement accuracy under variable temperature conditions; because a decoupling capacitor array is configured on the PCB substrate 101 near the chip power supply pin, it effectively suppresses power supply noise interference to the chip's operation, ensuring power supply stability; because grounding shielding strips are set on both sides of the signal traces and combined with a π-type EMI filter circuit, a multi-protection mechanism from spatial isolation to circuit filtering is formed, significantly attenuating external electromagnetic interference, enabling the sensor to maintain stable data communication even in strong electromagnetic field environments, thereby achieving the technical effect of improving signal integrity and system control robustness. Example

[0056] In another optional embodiment, the method further includes: the sidewall of the annular metal protective ring 103 is provided with a laser welding marking area, the surface roughness Ra ≤ 0.8 μm, and it maintains an assembly tolerance of 0.1–0.3 mm with the edge of the PCB substrate 101 to ensure uniform fiber laser welding penetration and controllable heat-affected zone.

[0057] The laser welding marking area can refer to an annular strip-shaped area or discrete markers located at a specific height on the outer wall of the annular metal protective ring 103. Its function is to indicate the start, end, or continuous trajectory of the scanning path of the fiber laser welding head. This marking area, in conjunction with the annular metal protective ring 103 and the PCB substrate 101, guides the laser beam precisely onto the preset connection interface through a visual positioning system or mechanical limiting device, thereby achieving rapid calibration and repeatable positioning of the welding position on an automated production line. The shape of the marking area can be a continuous circular line, or an intermittent scale line or QR code mark; this embodiment does not impose any special limitation on this. Its width can be set according to the laser spot diameter and the welding process window, for example, it can be any value between 0.5 mm and 2.0 mm.

[0058] A surface roughness Ra ≤ 0.8 μm can refer to the arithmetic mean deviation of the microscopic profile of the annular metal protective ring 103 in the laser welding marking area and its surrounding welding area not exceeding 0.8 micrometers. This parameter characteristic is linked to the fiber laser welding process. A low-roughness surface can reduce the diffuse reflection loss of laser energy, improve energy absorption efficiency, and allow the laser heat to act more concentrated on the material surface, thereby forming a stable and uniformly deep molten pool. If the surface is too rough, the laser beam may scatter, leading to uneven local heating, fluctuations in weld depth, or even porosity defects. This surface roughness can be achieved through precision turning, grinding, or polishing processes. For example, CNC precision turning followed by vibratory grinding can be used, or laser surface treatment technology can be employed. This application does not specifically limit the specific processing technology.

[0059] The assembly tolerance of 0.1–0.3 mm refers to the radial gap between the lower end of the inner wall of the annular metal protective ring 103 and the outer peripheral edge of the PCB substrate 101, which is controlled within the range of 0.1 mm to 0.3 mm. This gap size is closely related to the laser welding process. An excessively large gap will prevent the laser beam from effectively melting the copper plating layer or pads on the edge of the PCB simultaneously, resulting in poor soldering or sealing failure. An excessively small gap may cause assembly difficulties due to component processing errors, or generate excessive stress that squeezes the PCB substrate during thermal expansion. This tolerance range ensures that during fiber laser welding, the beam can simultaneously cover the two components to be welded with an appropriate defocus amount, forming a uniform metallurgical bond. In actual assembly, this tolerance can be achieved through high-precision mold injection positioning, visual correction of automated placement equipment, or dedicated fixture limiting. For example, a vacuum nozzle with a positioning accuracy of ±0.05 mm can be used for placement. This application embodiment does not impose any special limitations on this.

[0060] Specifically, the working process and principle of this application are as follows: During the modular packaging of the sensor, a surface-treated annular metal protective ring 103 is first fitted around the PCB substrate 101. The relative position of the two is controlled by automated equipment to maintain the gap between the annular metal protective ring 103 and the edge of the PCB substrate 101 between 0.1 and 0.3 mm, and the laser welding marking area on the sidewall is confirmed to be identifiable. Subsequently, a fiber laser emits a high-energy laser beam, which scans and welds along the circumference according to the path indicated by the marking area. Because the surface roughness Ra of the welding area is ≤ 0.8 μm, the laser energy is efficiently absorbed and converted into heat energy, causing the material at the contact point between the sidewall of the metal protective ring 103 and the edge of the PCB substrate 101 to rapidly melt and fuse. As the laser beam moves, the molten pool cools and solidifies to form a continuous and dense weld. During this process, strict assembly tolerances ensured the consistency of the weld depth, avoiding incomplete fusion or burn-through caused by gap fluctuations. At the same time, the limited heat input kept the heat-affected zone within a controllable range, preventing high temperatures from causing thermal damage to the internal digital sensor chip 105 and the adhesive bonding layer 106.

[0061] As a preferred embodiment, the solution of this application is implemented as follows: In an industrial production line, an automatic assembly machine with machine vision feedback is used to install the annular metal protective ring 103 onto the PCB substrate 101. The vision system monitors the edge gap between the two in real time. If the gap exceeds the range of 0.1–0.3 mm, it automatically adjusts or rejects defective products. After assembly, a conveyor belt delivers the semi-finished product to the laser welding station. A high-precision camera identifies the laser welding marking area (such as a frosted ring with a width of 1.0 mm) on the side wall of the annular metal protective ring 103 and calculates the welding start coordinates. The fiber laser welding head focuses on the center of the marking area, setting the laser power to 150W, the scanning speed to 20 mm / s, and the defocusing amount to +1.5 mm. The laser beam scans uniformly around the marking area. Because the surface of this area has undergone precision polishing, the Ra value is 0.6 μm, the laser energy absorption rate is stable, and the resulting weld penetration depth is uniform at approximately 0.4 mm, with the heat-affected zone width controlled within 0.2 mm. After welding, the sensor has a robust overall structure, meets IP68 airtightness requirements, and its internal circuitry is not affected by high-temperature shock.

[0062] Through the above technical solution, this application achieves the solution of uneven penetration and thermal damage caused by inconsistent surface conditions or gap fluctuations in traditional welding by setting a low-roughness laser welding marking area on the side wall of the annular metal protective ring 103 and strictly controlling its assembly tolerance with the PCB substrate 101. This ensures the high quality and high repeatability of fiber laser welding and improves the sealing reliability and production efficiency of the sensor module. Example

[0063] In one possible implementation, the method further includes a protective filler layer 108 that, after 1000 temperature cycles from -40 ℃ to +125 ℃, exhibits no cracking, shrinkage, or debonding from the chip or PCB, and has a sensor zero-point drift ≤ ±0.1 %FS and a full-range nonlinear error ≤ ±0.2 %FS.

[0064] The 1000 temperature cycles from -40℃ to +125℃ refers to an accelerated aging test condition applied to the assembled sensor to simulate its long-term service life under extreme high and low temperature alternating environments. This temperature range covers the lower and upper limits of extreme operating conditions commonly seen in industrial and automotive applications, and the 1000 cycles represent the typical accumulated thermal stress within the product's expected lifespan. In practice, the specific holding time and heating / cooling rates of the temperature cycles can be set according to actual testing standards or application requirements, such as following relevant reliability testing standards like JEDEC or AEC-Q100. This application does not impose any special limitations on this. The function of this technical feature is to verify and define the thermomechanical stability of the protective filling layer 108 and its interface with the digital sensor chip 105 and the PCB substrate 101. By combining this with the aforementioned defined material parameters (such as Shore hardness, elastic modulus, and coefficient of thermal expansion) and the double-sealed structure, it ensures that internal stress can be effectively buffered without causing structural damage under repeated thermal expansion and contraction.

[0065] The absence of cracking, shrinkage, and debonding from the chip or PCB refers to the integrity of the protective filler layer 108 after undergoing the aforementioned rigorous temperature cycling tests, both in its macroscopic morphology and microscopic interface. Specifically, "no cracking" means the filler layer itself did not develop cracks due to internal stress concentration; "no shrinkage" indicates good volume stability of the filler layer, with no significant dimensional reduction leading to voids within the protective cavity or additional pulling forces on the chip; and "no debonding" means the bonding interfaces between the filler layer and the surface of the digital sensor chip 105, the surface of the PCB substrate 101, and the inner wall of the annular metal protective ring 103 remain firm, without delamination or peeling. This technical feature relies on the matching design of the thermal expansion coefficients between the selected addition-curing silicone rubber material and the substrate material, as well as the airtight environment formed by the adhesive layer 106 and the low-temperature soldering layer 107, preventing interface hydrolysis and degradation caused by moisture intrusion. In terms of specific implementation methods, it can be determined by means of metallographic section observation, ultrasonic scanning microscopy (SAM) detection, or dye penetration test. As long as the final result meets the requirement of the absence of the above three negative phenomena, it is acceptable. The specific detection methods can be set according to the actual situation.

[0066] A sensor zero-point drift ≤ ±0.1%FS refers to the sensor's output signal under zero pressure load, after completing temperature cycling tests, where the change relative to the initial calibration value does not exceed ±0.1% of the full scale (FS). Zero-point drift is a key indicator of a sensor's long-term stability; excessive zero-point drift usually indicates irreversible mechanical stress damage to the sensitive element or permanent deformation of the packaging structure. In this application, this technical feature, by limiting the upper limit of drift, indirectly reflects the minimal residual stress exerted by the protective filling layer 108 on the digital sensing chip 105 during temperature cycling, demonstrating that the flexibility and stress release capability of the filling material have achieved the expected results. This numerical range is set based on the requirements of high-precision industrial measurement. In practical applications, this threshold can be appropriately adjusted according to the specific accuracy requirements, but in the high-reliability scenario defined in this embodiment, it should be strictly controlled within the range.

[0067] A full-scale nonlinear error ≤ ±0.2%FS means that after completing temperature cycling testing, the maximum deviation between the sensor's output characteristic curve and the ideal straight line across the entire measurement range must not exceed ±0.2% of the full scale. Nonlinear error reflects the linearity of the sensor's input-output relationship. If the filler layer hardens, shrinks, or partially detaches from the chip after temperature cycling, uneven stress on the chip's pressure-sensitive diaphragm will occur, leading to an increase in nonlinear error. This technical feature, together with zero-point drift, constitutes a dual constraint on the stability of the sensor's metrological performance, indicating that the protective filler layer 108 not only maintains physical structural integrity but also effectively protects the sensing mechanism of the digital sensing chip 105 from packaging stress interference. Achieving this target is the result of the synergistic effect of material formulation optimization, structural design (such as the limiting flange 201), and process control (such as the potting gap 202).

[0068] Specifically, the working process and principle of this application are as follows: When the sensor undergoes repeated temperature changes from -40 ℃ to +125 ℃, due to the differences in the coefficients of thermal expansion of the protective filling layer 108, the digital sensing chip 105, and the PCB substrate 101, each component will experience different degrees of expansion and contraction. If the material selection is inappropriate or the interface bonding is insufficient, this thermal mismatch will generate huge shear stress at the interface, causing the filling layer to crack, shrink, or debond from the chip / PCB, thereby transferring abnormal stress to the chip's pressure-sensitive diaphragm, resulting in zero-point drift and excessive nonlinear error. In this technical solution, by selecting addition-cure silicone rubber with a matching coefficient of thermal expansion as the protective filling layer 108, and utilizing its Shore hardness of A50–A70 and elastic modulus of 1.5–3.0 MPa to provide appropriate flexible buffering, the thermal stress is absorbed and dissipated inside the filling layer, rather than being transferred to the chip. Meanwhile, the double-sealed structure between the annular metal protective ring 103 and the PCB substrate 101 prevents the intrusion of external moisture, avoiding accelerated interface aging due to moisture and heat coupling. Therefore, even after 1000 extreme temperature cycles, the protective filling layer 108 can still maintain structural integrity and strong interface bonding, ensuring that the digital sensing chip 105 is in a low-stress state, thereby keeping the sensor's zero-point drift and nonlinear error at extremely low levels.

[0069] As a preferred embodiment, the specific implementation of this application is as follows: A batch of digital pressure sensor samples prepared according to the aforementioned embodiments 1 to 4 are selected and placed in a programmable high and low temperature test chamber. The temperature cycling program is set as follows: lower limit temperature -40 ℃, held for 30 minutes; upper limit temperature +125 ℃, held for 30 minutes; the heating and cooling rate is set to 10 ℃ / min, the switching time does not exceed 5 minutes, and 1000 cycles are run continuously. After the test, the samples are first subjected to visual inspection and non-destructive testing to confirm that there are no visible cracks on the surface and inside of the protective filler layer 108, no obvious shrinkage or depression in volume, and that there are no signs of delamination or debonding at the interface between the chip and the filler layer, and between the PCB and the filler layer, by ultrasonic scanning. Subsequently, the samples are restored to room temperature (25 ℃) and stabilized for 2 hours, and calibration tests are performed on a standard pressure source. The output values ​​of each sample at the zero-pressure point were recorded, and their deviations from the initial values ​​were calculated. The results showed that the zero-point drift of all samples was within ±0.08 %FS, meeting the requirement of ≤±0.1 %FS. Next, multiple pressure points were selected for testing across the entire range, the output curve was fitted, and the full-range nonlinear error was calculated. The results showed that the maximum error was ±0.15 %FS, meeting the requirement of ≤±0.2 %FS. This embodiment verifies the effectiveness and achievability of the technical parameter limits of this application.

[0070] Through the above technical solution, this application achieves the following: because the protective filling layer 108 uses a material with a thermal expansion coefficient matching that of the chip and substrate and has a specific hardness and modulus, and is combined with an airtight double sealing structure, it can effectively suppress material cracking, shrinkage and interface debonding caused by thermal stress after 1000 temperature cycles from -40 ℃ to +125 ℃. This results in a high stability effect with sensor zero drift ≤ ±0.1 %FS and full-range nonlinear error ≤ ±0.2 %FS, ensuring long-term reliable operation of the product in applications with extremely high requirements for lifespan and accuracy, such as automotive and aerospace, and has practical application value.

Claims

1. A modular, high-protection, multi-installation digital pressure sensor, comprising a PCB substrate (101), an annular metal protective ring (103), and a digital sensing chip (105), characterized in that, The PCB substrate (101) is square, with standard SMT pads (102) at the bottom for reflow soldering. An annular metal protective ring (103), made of stainless steel or Kovar alloy, is fixed to the edge of the PCB substrate (101) to form a closed chip housing cavity (104). The digital sensor chip (105) is mounted on the surface of the PCB substrate (101) in LGA package form and electrically interconnected through pads. The annular metal protective ring (103) and the PCB substrate (101) are connected by a dual process of adhesive bonding layer (106) and low-temperature soldering layer (107) to form a double-sealed structure with airtightness. The chip housing cavity (104) is filled with a flexible protective filler layer (108) that completely covers the digital sensor chip (105). The Shore hardness is A50–A70 and the elastic modulus is 1.5–3.0 MPa. The annular metal protective ring (103) serves as a rigid mechanical protective shell to enhance vibration and impact resistance, and also provides a side wall welding surface and / or mechanical anchoring channel to support mechanical reinforcement installation methods such as laser welding and thermal adhesive dispensing, in addition to SMT, so that the sensor as a whole meets the IP68 protection level and can work stably for a long time in environments with hydraulic oil, refrigerant and pH 2–12 corrosive media.

2. The sensor according to claim 1, characterized in that, The inner wall height of the annular metal protective ring (103) is greater than the height of the digital sensing chip (105), and its top extends inward to form an annular limiting flange (201). A potting gap (202) of 0.5–1.0 mm is maintained between the limiting flange (201) and the PCB substrate (101) to constrain the flow range of the protective filler layer (108) and enhance the shear strength.

3. The sensor according to claim 1, characterized in that, The adhesive bonding layer (106) is a high-temperature modified epoxy adhesive with a glass transition temperature (Tg) ≥ 150 ℃ and a coating area of ​​≥ 80% of the bonding surface between the metal protective ring (103) and the PCB substrate (101). The low-temperature welding layer (107) uses Sn-Bi eutectic solder with a melting point ≤ 139 ℃ and is welded at 170–180 ℃. The welding temperature is lower than the Tg of the PCB substrate (101) and the temperature limit of the digital sensor chip (105).

4. The sensor according to claim 1, characterized in that, The protective filler layer (108) is an addition-type silicone rubber with a coefficient of thermal expansion of 250–300 ppm / ℃, which matches the coefficient of thermal expansion of the digital sensor chip (105) and the PCB substrate (101) to suppress interfacial stress caused by temperature cycling.

5. The sensor according to claim 1, characterized in that, The PCB substrate (101) is symmetrically provided with at least two mechanical anchoring holes (501) that penetrate the substrate. The hole diameter is 0.4–0.8 mm and the hole is located in the projection area of ​​the metal protective ring (103). These holes are used to inject thermally conductive adhesive to achieve dispensing and bonding, or as a channel for introducing laser welding energy.

6. The sensor according to claim 1, characterized in that, The digital sensor chip (105) integrates a temperature compensation circuit and a digital calibration module, and the output is transmitted via an I²C or SPI interface. A decoupling capacitor array is configured on the PCB substrate (101) near the chip power supply pin, and a ground shielding strip and a π-type EMI filter circuit are set on both sides of the signal trace, with a cutoff frequency of 5–15MHz.

7. The sensor according to claim 1, characterized in that, The annular metal protective ring (103) has a laser welding marking area on its sidewall, with a surface roughness Ra ≤ 0.8 μm, and maintains an assembly tolerance of 0.1–0.3 mm with the edge of the PCB substrate (101) to ensure uniform fiber laser welding penetration and controllable heat-affected zone.

8. The sensor according to claim 1, characterized in that, The protective filling layer (108) showed no cracking, shrinkage, or detachment from the chip or PCB after 1000 temperature cycles from -40 ℃ to +125 ℃, and the sensor zero-point drift was ≤ ±0.1 %FS, and the full-range nonlinear error was ≤ ±0.2 %FS.

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