A MEMS pressure sensor oil-filling core suitable for high-pressure small-molecule medium

Abstract

This invention belongs to the field of pressure sensors, specifically relating to an oil-filled core for a MEMS pressure sensor suitable for high-pressure, small-molecule media. It comprises a pressure ring, a corrugated diaphragm, a core base, sealing steel balls, and components such as silicone oil, a ceramic seat, a pressure chip, and leads located within a sealed cavity formed by the corrugated diaphragm and the core base. This invention addresses the shortcomings of traditional oil-filled cores for MEMS pressure sensors by improving the design in multiple structural and manufacturing aspects, solving problems such as small-molecule media infiltration, lead breakage failure, and high-pressure connection sealing. It is particularly suitable for accurate pressure measurement of high-pressure, small-molecule media.

Description

Technical Field

[0001] This invention belongs to the field of pressure sensors, specifically relating to an oil-filled core for a MEMS pressure sensor suitable for high-pressure small molecule media. Background Technology

[0002] MEMS (Micro-Electro-Mechanical System) pressure sensors are widely used in aerospace, petrochemical, industrial control, and instrumentation fields. They convert external pressure signals into electrical signals, enabling accurate measurement of external pressure. A typical MEMS pressure sensor consists of three parts: a housing, a pressure core, and signal processing circuitry. The pressure core is the core sensing unit of the MEMS pressure sensor.

[0003] Oil-filled isolation packaging is a common packaging method for MEMS pressure sensors. With this packaging, the MEMS pressure chip does not directly contact the external measurement medium and is insensitive to the physicochemical properties of the measurement medium. Therefore, it is often used for pressure measurement in harsh environments. Currently, there is a wide variety of pressure core products on the market, with many styles, basically meeting the needs of the domestic market. However, most pressure cores have a measurement range of 0 MPa to 40 MPa, and there is relatively little research in China on high-pressure cores above 40 MPa. In aerospace and other fields, it is necessary to measure the pressure of small molecule gases such as hydrogen (H2) and helium (He) under high-pressure environments. Because these gases can easily permeate the corrugated diaphragm and mix with silicone oil, the silicone oil expands, generating excess stress that reduces the accuracy of the pressure core's output signal, affecting the application of MEMS pressure sensors in such environments.

[0004] Pressure sensors used in aerospace applications need to withstand harsh environments such as high-frequency vibration and high-speed impact. Because conventional pressure cores only fix the leads at both ends using a bonding process, the bonded leads are arched and immersed in silicone oil, inherently subject to stress. Under high-frequency vibration and high-speed impact conditions, there is a risk of breakage and bonding failure. Summary of the Invention

[0005] To address the problems of existing technologies, this invention proposes an oil-filled core for a MEMS pressure sensor suitable for high-pressure small molecule media, comprising: a pressure ring (1), a corrugated diaphragm (2), a core base (3), a sealing steel ball (4), and silicone oil (5), a ceramic seat (6), a pressure chip (7), and a lead wire (8) located in the sealed cavity formed by the corrugated diaphragm (2) and the core base (3);

[0006] The core base (3) has a cavity at the top. The pressure ring (1) presses the corrugated diaphragm (2) against the upper end of the cavity at the top of the core base (3). The pressure ring (1), the corrugated diaphragm (2), and the core base (3) are sealed by laser welding, so that the corrugated diaphragm (2) and the core base (3) form a sealed cavity.

[0007] The core base (3) has multiple through holes and an oil injection hole at the bottom of the cavity to the bottom surface of the core base (3); the multiple through holes have pins sintered with glass; the oil injection hole is a countersunk hole structure, and after silicone oil (5) is injected, it is pre-pressed in the countersunk hole structure by sealing steel balls (4) and then laser welded to seal it.

[0008] The ceramic seat (6) is a ring structure and is fixed to the bottom of the cavity of the core base (3) by structural adhesive. The ceramic seat (6) has a boss (63), multiple through holes and an oil injection hole on its front side. The multiple through holes and the oil injection hole on the front side of the ceramic seat (6) correspond in size and position to the multiple through holes and the oil injection hole on the core base (3). The boss (63) has multiple cup-shaped glue injection holes (61) adjacent to the multiple through holes on the front side of the ceramic seat (6). The bottom of the multiple cup-shaped glue injection holes (61) has multiple glue flow holes (62).

[0009] The core base (3) has a circular or rectangular recessed platform at the center of the cavity bottom. The pressure chip (7) is placed in the annular structure of the ceramic base (6) and fixed in the recessed platform at the center of the cavity bottom of the core base (3) by chip adhesive. The lead wire (8) passes through the cup-shaped injection hole (61) on the boss (63) and connects the electrode on the pressure chip (7) and the pin in the through hole of the core base (3). The lead wire (8) is fixed by injecting structural adhesive into the cup-shaped injection hole (61).

[0010] The beneficial effects of this invention are:

[0011] The MEMS pressure sensor oil-filled core of this invention is formed by threading the pressure core to the pressure sensor body. A copper washer is used to pre-press the pressure ring end face to form a primary seal. After the primary seal is completed, the flange end face of the pressure core is laser-welded to the pressure sensor body to form a secondary seal. Compared with traditional pressure cores, the threaded connection effectively ensures the connection strength and the reliability of the structure during high-pressure measurement. The double sealing effectively ensures the sealing effect and avoids small molecule media from entering the pressure sensor, which could lead to media leakage or even damage to the pressure sensor.

[0012] The corrugated diaphragm of the MEMS pressure sensor oil-filled core of the present invention adopts a double-sided gold plating process, which effectively avoids the expansion of the silicone oil caused by the infiltration of small molecule media into the internal silicone oil, and ensures the accuracy of the pressure core output signal.

[0013] After the MEMS pressure sensor oil-filled core wire bonding of the present invention is completed, the wire is fixed to the upper surface of the ceramic base by structural adhesive. By reducing the wire suspension length, the impact inertia under high-frequency vibration and high-speed impact environment is reduced, effectively reducing the risk of wire failure. At the same time, by connecting the structural adhesive fixing the wire to the structural adhesive fixing the ceramic base through the through hole on the ceramic base, the connection strength is guaranteed, avoiding the problem of the structural adhesive fixing the wire falling off due to insufficient adhesive application. Attached Figure Description

[0014] Figure 1 This is an overall appearance diagram of the oil-filled core of a MEMS pressure sensor suitable for high-pressure small molecule media according to the present invention;

[0015] Figure 2 This is a cross-sectional view of the structure of an oil-filled core for a MEMS pressure sensor suitable for high-pressure small molecule media according to the present invention.

[0016] Figure 3 This is a structural diagram of the core base of an oil-filled MEMS pressure sensor suitable for high-pressure small molecule media, according to the present invention.

[0017] Figure 4 This is a partially enlarged view of an oil-filled core of a MEMS pressure sensor suitable for high-pressure small molecule media according to the present invention;

[0018] Figure 5 This is a structural diagram of a ceramic base for an oil-filled core of a MEMS pressure sensor suitable for high-pressure small molecule media, according to the present invention.

[0019] In the diagram: 1. Pressure ring, 2. Corrugated diaphragm, 3. Core base, 4. Sealing steel ball, 5. Silicone oil, 6. Ceramic base, 7. Pressure chip, 8. Lead wire, 61. Cup-shaped injection hole, 62. Adhesive flow hole, 63. Boss, 64. Bottom recess, 91. Structural adhesive, 92. Chip adhesive. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] An oil-filled core for MEMS pressure sensors suitable for high-pressure small-molecule media, such as... Figure 1 As shown in Figure 2, it includes: a pressure ring 1, a corrugated diaphragm 2, a core base 3, a sealing steel ball 4, and silicone oil 5, a ceramic seat 6, a pressure chip 7, and a lead wire 8 located in the sealing cavity formed by the corrugated diaphragm 2 and the core base 3.

[0022] The core base 3 has a cavity at its top. The pressure ring 1 presses the corrugated diaphragm 2 against the upper end of the cavity at the top of the core base 3. The pressure ring 1, the corrugated diaphragm 2, and the core base 3 are sealed by laser welding, so that the corrugated diaphragm 2 and the core base 3 form a sealed cavity.

[0023] Multiple through holes and an oil injection hole are provided from the bottom of the cavity of the core base 3 to the bottom surface of the core base 3; pins are sintered with glass in the multiple through holes; the oil injection hole is a countersunk hole structure, and after the silicone oil 5 is injected, it is pre-pressed in the countersunk structure by sealing steel balls 4 and then laser welded to seal it.

[0024] The ceramic base 6 is a ring structure and is fixed to the bottom of the cavity of the core base 3 by structural adhesive 91. The front of the ceramic base 6 is provided with a boss 63, multiple through holes and an oil injection hole. The multiple through holes and the oil injection hole on the front of the ceramic base 6 correspond in size and position to the multiple through holes and the oil injection hole on the core base 3. The boss 63 is provided with multiple cup-shaped glue injection holes 61, which are adjacent to the multiple through holes on the front of the ceramic base 6. The bottom of the multiple cup-shaped glue injection holes 61 is provided with multiple glue flow holes 62.

[0025] The core base 3 has a circular or rectangular recessed platform at the center of its cavity bottom, which facilitates chip positioning during bonding and prevents adhesive overflow. The pressure chip 7 is placed inside the annular structure of the ceramic base 6 and fixed in the recessed platform at the center of the cavity bottom of the core base 3 by chip adhesive 92. The lead wire 8 crosses the cup-shaped injection hole 61 on the protrusion 63 and connects the electrode on the pressure chip 7 to the pin in the through hole of the core base 3. The lead wire 8 is fixed by injecting structural adhesive 91 into the cup-shaped injection hole 61.

[0026] In this embodiment of the invention, the core base 3 and the corrugated diaphragm 2 are made of the same material to ensure welding reliability and compatibility with most measurement media.

[0027] In this embodiment of the invention, both sides of the corrugated diaphragm 2 are gold-plated, with a gold plating thickness of 2 μm on each side. During measurement, this prevents small molecule media from penetrating into the oil-filled core of the MEMS pressure sensor, which could lead to a decrease in the accuracy of the pressure core.

[0028] In this embodiment of the invention, silicone oil is injected into the oil-filled core of the MEMS pressure sensor through the oil injection hole, and the sealing steel ball 7 is pre-pressurized and then laser-welded for sealing.

[0029] In embodiments of the present invention, such as Figure 3 As shown, the core base 3 has connecting threads and a flange. The flange end face has a rectangular or other type of countersunk hole, which serves as the force application point when the thread is pre-tightened. The oil-filled core of the MEMS pressure sensor is threadedly connected to the MEMS pressure sensor body structure. After the pressure ring 1 is pre-pressed with a copper washer for primary sealing, the flange face of the oil-filled core of the MEMS pressure sensor is laser-welded to the MEMS pressure sensor body structure for secondary sealing, forming a stable connection structure.

[0030] In this embodiment of the invention, the area of ​​the recessed platform at the center of the bottom of the cavity of the core base 3 is slightly larger than the bonding area of ​​the pressure chip 7, and the depth of the recessed platform is 0.1 to 0.2 mm; this facilitates the positioning of the pressure chip 7 and prevents the chip adhesive from overflowing.

[0031] In embodiments of the present invention, such as Figure 4 and Figure 5 As shown, the ceramic base 6 reduces the amount of silicone oil 5 required, thus minimizing the impact of silicone oil 5 expansion on the output signal. Furthermore, as a structural component, the lead wire 8 is not only fixed to its upper surface by structural adhesive 91, but also protects the pressure chip 7 and the lead wire 8. A bottom recess 64 is provided on the reverse side of the ceramic base 6. The structural adhesive injected into the cup-shaped injection hole 61 on the front side flows into the bottom recess 64 through the adhesive flow hole 62, forming an "I"-shaped bonding structure with the structural adhesive fixing the ceramic base 6. This "I"-shaped bonding structure provides a strong bond, is not easily detached, and is suitable for various harsh environments.

[0032] In this embodiment of the invention, the lead wire 8 is preferably gold wire, and the pin 33 is made of Kovar alloy.

[0033] When using:

[0034] First, the pressure core is threaded to the pressure sensor body. A copper washer is used for the first sealing at the pressure ring end face. The flange face of the pressure core is laser-welded to the pressure sensor body for the second sealing. The pressure core pin 33 is connected to the signal processing circuit and energized.

[0035] The external high-pressure small-molecule measuring medium comes into contact with the pressure measuring sensitive unit—the pressure core—through the medium channel of the pressure sensor. Because the pressure core is sealed to the pressure sensor body, the measuring medium cannot enter the pressure sensor. Simultaneously, because the corrugated diaphragm 2 uses a double-sided gold-plating process, when the measuring medium comes into contact with the corrugated diaphragm 2, it cannot penetrate into the silicone oil 5. The medium pressure is entirely transmitted to the pressure chip 7 through the corrugated diaphragm 2 and the silicone oil 5. The sensitive diaphragm on the pressure chip 7 deforms under pressure, causing a change in the bridge resistance and disrupting the bridge balance. The circuit consisting of chip 7, lead 8, and pin 33 outputs a voltage, converting the pressure signal into an electrical signal, thereby achieving accurate measurement of the medium pressure.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An oil-filled core for a MEMS pressure sensor suitable for high-pressure small-molecule media, characterized in that, include: Pressure ring (1), corrugated diaphragm (2), core base (3), sealing steel ball (4), and silicone oil (5), ceramic seat (6), pressure chip (7) and lead wire (8) located in the sealed cavity formed by the corrugated diaphragm (2) and the core base (3); The core base (3) has a cavity at the top. The pressure ring (1) presses the corrugated diaphragm (2) against the upper end of the cavity at the top of the core base (3). The pressure ring (1), the corrugated diaphragm (2), and the core base (3) are sealed by laser welding, so that the corrugated diaphragm (2) and the core base (3) form a sealed cavity. The core base (3) has multiple through holes and an oil injection hole at the bottom of the cavity to the bottom surface of the core base (3); the multiple through holes have pins sintered with glass; the oil injection hole is a countersunk hole structure, and after silicone oil (5) is injected, it is pre-pressed in the countersunk hole structure by sealing steel balls (4) and then laser welded to seal it. The ceramic seat (6) is a ring structure and is fixed to the bottom of the cavity of the core base (3) by structural adhesive. The ceramic seat (6) has a boss (63), multiple through holes and an oil injection hole on its front side. The multiple through holes and the oil injection hole on the front side of the ceramic seat (6) correspond in size and position to the multiple through holes and the oil injection hole on the core base (3). The boss (63) has multiple cup-shaped glue injection holes (61) adjacent to the multiple through holes on the front side of the ceramic seat (6). The bottom of the multiple cup-shaped glue injection holes (61) has multiple glue flow holes (62). The core base (3) has a circular or rectangular recessed platform at the center of the cavity bottom. The pressure chip (7) is placed in the annular structure of the ceramic base (6) and fixed in the recessed platform at the center of the cavity bottom of the core base (3) by chip adhesive. The lead wire (8) passes through the cup-shaped injection hole (61) on the boss (63) and connects the electrode on the pressure chip (7) and the pin in the through hole of the core base (3). The lead wire (8) is fixed by injecting structural adhesive into the cup-shaped injection hole (61).

2. The oil-filled core of a MEMS pressure sensor suitable for high-pressure small-molecule media according to claim 1, characterized in that, The corrugated diaphragm (2) is gold-plated on both sides, with a gold plating thickness of 2 μm on each side.

3. The oil-filled core of a MEMS pressure sensor suitable for high-pressure small-molecule media according to claim 1, characterized in that, The core base (3) has connecting threads and flange features.

4. The oil-filled core of a MEMS pressure sensor suitable for high-pressure small-molecule media according to claim 1, characterized in that, The area of ​​the recessed platform at the center of the bottom of the cavity of the core base (3) is slightly larger than the bonding area of ​​the pressure chip (7), and the depth of the recessed platform is 0.1 to 0.2 mm.

5. The oil-filled core of a MEMS pressure sensor suitable for high-pressure small-molecule media according to claim 1, characterized in that, The ceramic base (6) has a bottom recess (64) on the reverse side. The structural adhesive injected into the cup-shaped injection hole (61) on the front side flows into the bottom recess (64) through the adhesive flow hole (62) and forms an "I"-shaped bonding structure with the structural adhesive of the fixed ceramic base (6).

6. The oil-filled core of a MEMS pressure sensor suitable for high-pressure small-molecule media according to claim 1, characterized in that, The oil-filled core of the MEMS pressure sensor is threadedly connected to the main body of the MEMS pressure sensor. After the pressure ring (1) is pre-pressed with a copper washer for a first seal, the flange of the oil-filled core of the MEMS pressure sensor is laser-welded to the main body of the MEMS pressure sensor for a second seal, forming a stable sealed connection structure.

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