Pressure sensor structure

Abstract

A pressure sensor structure comprises a pressure joint, a circumferential weld, a stainless steel sealing shell, a silicone rubber sealing ring, a sensor module and an external connector joint with a metal terminal. Product failure caused by erosion of fluid to the force-sensitive film body of the sensor is reduced, the pressure resistance and the overall strength of the sensor are improved, and the sensor is more convenient to assemble and better in market adaptability due to the simple design structure; the manufacturing cost of the silicon-based piezoresistive pressure sensor core packaged by the pre-integral plastic package is greatly reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of MEMS sensors, in particular to a pressure sensor structure. Background Art

[0002] Pressure sensors used in air conditioning and heat pump systems are required to have high precision, high reliability, good environmental adaptability, and sealing properties.

[0003] MEMS micromechanical pressure sensor is a pressure sensing device that combines microelectronics technology with micromechanical technology and is manufactured using micromachining technology. It can achieve high-precision, high-reliability and miniaturized pressure measurement.

[0004] Piezoresistive pressure sensors are the earliest and most mature commercial products among MEMS micromechanical pressure sensors. When designing a piezoresistive pressure sensor chip, the piezoresistor is placed on the lower surface of the force-sensitive film and sealed in a vacuum cavity through anodic bonding technology. The pressure sensor chip manufactured by this design method is suitable for extremely harsh environments such as moisture, acid and alkali, and electrostatic particles.

[0005] Most of the existing technical solutions for pressure sensors for air conditioners are proposed based on the considerations of water or water vapor intrusion into the pressure sensor causing product failure, weak anti-electromagnetic interference capability, and weak pressure resistance design. Summary of the Invention

[0006] The utility model proposes a pressure sensor structure, which reduces product failure caused by fluid erosion of the sensor force-sensitive film body, while improving the pressure resistance and overall strength of the sensor. The simple design structure makes the sensor assembly more convenient and has better market adaptability.

[0007] A pressure sensor structure comprises a pressure joint, a girth weld, a stainless steel sealing shell, a silicone rubber sealing ring, a sensor module and an external connector joint with metal terminals.

[0008] Furthermore, the pressure fitting is machined from brass bar stock, with a tapered pipe thread formed on the inner surface. A pin and fluid passage hole are designed deeper into the pressure fitting. A plane perpendicular to the pin forms an angle of 30° to 70° with the inner surface of the tapered pipe thread. This design maximizes the contact area between the tip of the fluid fitting and the inner surface of the pressure fitting, ensuring leak-free passage of fluid.

[0009] Furthermore, the stainless steel sealed housing and the pressure joint are tightly connected via a girth weld, thereby enhancing the pressure sensor's ability to withstand pressure damage.

[0010] Furthermore, the sensor module includes: an integrally plastic-encapsulated pressure core, a substrate with a groove for supporting a rubber sealing ring, resistors and capacitors, and a flexible connector, and the flexible connector achieves good grounding of the sensor.

[0011] Furthermore, the pressure core mounted on the surface of the substrate with the groove for carrying the rubber sealing ring in the sensor module is pre-manufactured through an integral plastic packaging process.

[0012] Furthermore, the pressure core includes a MEMS piezoresistive pressure sensor wafer, a copper lead frame carrying the sensor wafer, a stress isolation structure, and a low-stress plastic-encapsulated resin open-cavity housing.

[0013] Furthermore, a nickel-palladium-gold thin film layer is deposited on the inner pins of the copper lead frame and the semi-etched area on the back of the carrier. The inner pins are electrically connected to the sensor chip pads through gold wire bonding, and the semi-etched area on the back of the carrier is connected to the ground terminal of the sensor module substrate to achieve overall grounding.

[0014] Furthermore, the external connector joint includes: a connector base and a metal terminal. The connector base and the metal terminal are pre-formed as a whole by injection molding and can be perfectly plugged into the female connector.

[0015] Furthermore, the external connector and sensor module are connected via a flexible printed circuit board. The sensor chip mounting surface is connected to the metal terminals via extension posts perpendicular to the substrate. The metal terminals are inserted into corresponding holes in the flexible printed circuit board before connection. This structural design significantly improves electromagnetic interference resistance.

[0016] In the pressure sensor designed using the technical solution of the present invention, the fluid is connected to the tapered pipe thread through a fluid pipe joint. At this time, a pin opens the fluid pipe plug, and the fluid enters the cavity composed of the stainless steel sealing joint through the hole, and invades the silicon nitride film layer on the surface of the MEMS piezoresistive pressure sensor chip, causing deformation. At this time, the conditioning chip integrated in the pressure core receives the deformation of the force-sensitive film and converts it into a digital signal output, thereby realizing fluid pressure measurement and real-time monitoring.

[0017] The pressure sensor proposed in this utility model has many outstanding advantages over the existing pressure sensor technology solutions for air conditioners, which are specifically manifested in:

[0018] Advantage 1: The pressure core is manufactured using an integral plastic encapsulation method. When fluid passes through the pressure connector, it only contacts the silicon nitride layer on the surface of the pressure chip's force-sensitive film, eliminating device failure caused by fluid erosion or contamination of the pressure chip's force-sensitive film. This design makes the pressure core widely applicable to extremely harsh environments such as humidity, acidity, alkali, and static particles.

[0019] Advantage 2: The stainless steel sealed housing connects the large end of the housing to the external connector via heat-compression riveting. The metal terminals of the external connector and the connector base are pre-molded as a single unit. The small end of the housing is connected to the pressure connector via girth welding. This design completely isolates the pressure sensor from external water or moisture intrusion that could cause product failure, while also improving the pressure sensor's resistance to pressure and ensuring overall structural strength.

[0020] Advantage 3: A silicone rubber seal is used at the junction between the upper surface of the sensor module substrate and the stainless steel sealing housing, and at the junction between the lower surface of the sensor module substrate and the external connector base. This seal design at the upper and lower substrate junctions prevents fluid leakage through the pressure connector, ensuring stable pressure measurement.

[0021] Advantage 4: The pressure core adopts silicon-based piezoresistive pressure sensor chip, and its manufacturing cost is reduced by nearly 50% compared with the ceramic capacitor core, which can better meet market demand.

[0022] The technical solution provided by the utility model brings considerable results. The technical effect is manifested in solving the shortcomings of existing air-conditioning pressure sensors, such as water or water vapor intruding into the pressure sensor to cause product failure, weak anti-electromagnetic interference capability, weak pressure resistance design, insufficient overall structural strength and poor anti-electromagnetic interference capability; the commercial effect is manifested in the use of a silicon-based piezoresistive pressure sensor core with pre-integrated plastic packaging, which greatly reduces its manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 , an exploded diagram of the pressure sensor according to an embodiment of the present invention.

[0024] Figure 2 , a front cross-sectional view of the pressure sensor according to an embodiment of the present invention.

[0025] Figure 3 , enlarged left and right views of the sensor module of an embodiment of the present invention.

[0026] Figure 4 , an enlarged view of the packaging sheet of the integral plastic packaging structure for the sensor module of the embodiment of the present utility model. DETAILED DESCRIPTION

[0027] To make the technical solutions and advantages of the present invention more clearly understood, the present invention will be further described below in conjunction with specific embodiments and with reference to the accompanying drawings. Identical features are denoted by the same reference numerals in the accompanying drawings. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the description of the present invention refer to directions in the accompanying drawings.

[0028] In the description of this application, it should be noted that the terms "first", "second" and "third" are only used for the purpose of describing the application and cannot be understood as indicating or implying relative importance.

[0029] The explosion structure of the pressure sensor in the embodiment of the utility model is as follows Figure 1 As shown, from left to right are pressure connector 1, stainless steel sealed housing 3, sensor module upper surface sealing ring 4, sensor module 5, sensor module lower surface sealing ring 6, external connector 7. Pressure connector 1 and stainless steel sealed housing 3 are connected by welding to form Figure 2 Next, assemble the sensor module 5. Figure 4 The overall plastic package structure package sheet 501 is welded on the upper surface of the sensor module substrate 5 by surface mounting. Figure 1 The left side surface) pad, and then the electronic components such as the resistor 504 and the capacitor 503 are attached to the upper surface of the sensor module substrate 5 ( Figure 1 The left side of the flexible circuit board (8) is then connected to the back of the sensor module substrate using adhesive and welding materials. The metal stud 502 contacts the pad on the back of the sensor module substrate, forming a reliable solder joint. Finally, all sensor components are connected.

[0030] After the sensor module is assembled, place the rubber seal ring 4 on the upper surface of the sensor module substrate 5. Figure 3 401 area, and place the sensor module horizontally.

[0031] Furthermore, the pressure joint 1 connected by the girth weld 2 and the stainless steel sealing shell 3 are vertically installed on the Figure 2 The rubber sealing ring 4 is positioned to complete the assembly of the sensor module 5, the rubber sealing ring 4, the pressure joint 1 and the stainless steel sealing housing 3.

[0032] Furthermore, the above-mentioned assembly is placed upside down so that the pressure connector 1 is at the bottom. At this time, the rubber sealing ring 6 is placed horizontally on the lower surface of the sensor module 5 ( Figure 1 On area 601 of the right surface).

[0033] Furthermore, the lower surface of the metal sensor module substrate 5 ( Figure 1 The metal column 502 on the right side surface is connected to the external connector metal terminal 701 using a thin wire using soldering to form an electrical conduction path.

[0034] After the assembly is complete, the external connector 7 is placed vertically into the assembled unit, with the larger end facing downward and aligned with the outer slot of the stainless steel housing. The unit is then placed in a special hot isostatic autoclave for heat-compression riveting. The entire pressure sensor is now assembled, with the girth weld and heat-compression riveting completed. This completely sealed structure eliminates damage to the sensor from water or moisture in the external environment, improving its resistance to pressure and electromagnetic interference.

[0035] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible, such as altering the length and diameter of the small end of the pressure connector 1 , altering the inner and outer diameters of the stainless steel sealing housing 3 , and altering the style of the external connector 7 . Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A pressure sensor structure, characterized in that: include: Pressure joint, girth weld, stainless steel sealing shell, silicone rubber sealing ring, sensor module and external connector joint, The inner surface of the pressure joint forms a tapered pipe thread, and a pin and a fluid passage hole are designed at the bottom; the vertical plane of the pin forms a certain angle with the inner surface of the tapered pipe thread; the stainless steel sealing shell and the pressure joint are tightly connected by a ring weld; the sensor module consists of a pressure core, a substrate with a groove for bearing a rubber sealing ring, a resistor and a capacitor, and a flexible connector; the external connector joint contains a connector base and a metal terminal.

2. The pressure sensor structure according to claim 1, characterized in that: The pressure joint is made from a brass bar; the included angle between the vertical plane of the ejector pin and the inner surface of the tapered pipe thread is 30° to 70°.

3. The pressure sensor structure according to claim 1, characterized in that: The pressure core is mounted on the upper surface of the base plate with the groove for bearing the rubber sealing ring.

4. The pressure sensor structure according to claim 1, characterized in that: The pressure core comprises a MEMS piezoresistive pressure sensor wafer, a copper lead frame carrying the sensor wafer, a stress isolation structure, and a low-stress plastic-encapsulated resin open-cavity housing.

5. The pressure sensor structure according to claim 4, characterized in that: A nickel-palladium-gold thin film layer is deposited on the inner pins of the copper lead frame and the semi-etched area on the back of the carrier. The inner pins are electrically connected to the sensor chip pads through gold wire bonding. The semi-etched area on the back of the carrier is connected to the grounding end of the sensor module substrate to achieve overall grounding.

6. The pressure sensor structure according to claim 1, characterized in that: The connector base and the metal terminal are formed into an integral body by injection molding.

7. The pressure sensor structure according to claim 1, characterized in that: The external connector joint is connected to the sensor module through a flexible circuit board, and the sensor chip mounting surface is connected to the metal terminal through an extension column perpendicular to the substrate. The metal terminal is inserted into the corresponding hole of the flexible circuit board before connection.

Images