A longitudinally driven threshold sensor using a spring structure as a fixed electrode contact

Abstract

The present invention belongs to the technical field of micro-electromechanical systems, and specifically relates to a longitudinal drive threshold sensor using a spring structure as a fixed electrode. It includes a substrate, a damping reduction structure, a movable electrode support column, a movable electrode suspension spring, a movable mass block, a fixed electrode support column, a fixed electrode and a fixed electrode elastic contact. The damping reduction structure, the movable electrode support column and the fixed electrode support column are fixedly arranged on the substrate. The fixed electrode is suspended and connected to the fixed electrode support column, one end of the fixed electrode elastic contact is connected to the fixed electrode, and the other end is connected through a hollow square. One end of the movable electrode suspension spring is connected to the movable mass block, and the other end is connected to the movable electrode support column, and the movable mass block is suspended between the damping reduction structure and the fixed electrode. The sensor introduces the principle of transmission conduction, and by optimizing the stiffness of the two groups of electrode springs, the collision contact between the electrodes becomes a vibration transmission process between the flexible springs.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical systems (MEMS), and in particular relates to a longitudinal drive threshold sensor using a spring structure as a fixed electrode contact. Background Art

[0002] As a new type of passive device, micro vibration threshold sensor is widely used in various microelectronic systems due to its advantages of small size and light weight. Especially with the development of Internet of Things system, various sensor devices are combined with the Internet into a sensor network system, and these sensors are often placed in remote environments or implanted in systems where battery replacement is difficult due to some special needs, causing power supply difficulties. Compared with accelerometers and gyroscopes, vibration threshold sensors do not need to maintain a stable current under normal conditions, and their parasitic power consumption is zero, making them the best choice for vibration monitoring in Internet of Things systems.

[0003] At present, the movable electrode of the inertial vibration threshold sensor is usually composed of a "spring (cantilever beam)-mass block" sensitive element. A fixed structure is made on the edge of the mass block as a fixed electrode contact. There is a certain distance between the two electrodes. When the external acceleration exceeds the set threshold of the sensor, the movable electrode moves in its sensitive direction and contacts the fixed electrode contact, thereby realizing the conduction function of the threshold sensor. When the threshold sensor is turned on, the contact time between the movable electrode and the fixed electrode is an important parameter affecting the performance of the sensor. The larger the contact time pulse width, the higher the contact stability of the device and the simpler the output signal processing; otherwise, the difficulty of processing the output signal is increased. Therefore, extending the contact time between the movable electrode and the fixed electrode is an important means to improve the performance of the threshold sensor.

[0004] As a kind of inertial shock-sensitive device, if the collision contact between the electrodes is rigid contact, not only the contact time is short, but also the device may be damaged and the service life is reduced. Therefore, changing the contact mode between the electrodes is an effective way to improve the performance of the device. Through the search of existing literature, it is found that Luke J. Currano et al. published a paper entitled "Latching in a MEMS shock sensor: Modeling and experiments" in "Sensors and Actuators", "Sensors and Actuators A", 2010, 159, pp. 41-50), proposing a latching sensor sensitive to two directions on the horizontal plane. Although this latching sensor avoids the problem of short contact time caused by rigid collision between electrodes, it can achieve continuous signal output under sufficiently large overload acceleration. However, since the electrodes form a locking structure after collision contact, an unlocking device has to be added to the device, which makes the device structure complicated and easy to be damaged, and such a structure undoubtedly greatly reduces the device's repeatability. Xu Qiu et al. published a paper titled "Design and Optimization of a Stationary Electrode in a Vertically-Driven MEMS Inertial Switch for Extending Contact Duration" in Sensors (Volume 17, 2017, page 527), reporting an inertial switch that uses a multi-hole cantilever beam as a vertical fixed electrode contact to extend the contact time. However, the fixed electrode in the device has limited elastic expansion and contraction, and the manufacturing process has many constraints. Any defect in the cantilever beam may cause the fixed electrode to fail. Comprehensive analysis of current invention results shows that only retractable springs can achieve large elastic deformation, so that the movable electrode and the fixed electrode can achieve the most effective elastic contact during the collision contact process. At present, there is no effective design solution that can effectively solve the elastic contact between electrodes. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a longitudinal drive threshold sensor using a spring structure as a fixed electrode contact. The sensor uses two sets of spring electrodes as movable electrodes and fixed electrode contacts of the threshold sensor, and optimizes the stiffness of the two sets of electrode springs so that the collision contact between the electrodes becomes a vibration transmission process between the flexible springs.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical means: a longitudinal drive threshold sensor using a spring structure as a fixed electrode contact, including a substrate, a damping reduction structure, a movable electrode support column, a movable electrode suspension spring, a movable mass block, a fixed electrode support column, a fixed electrode cantilever beam and a fixed electrode elastic contact.

[0007] A damping reduction structure, a movable electrode support column and a fixed electrode support column are fixedly provided on the substrate. The fixed electrode cantilever beam is suspended and connected to the fixed electrode support column, one end of the fixed electrode elastic contact is connected to the fixed electrode cantilever beam, and the other end is suspended in the middle of the fixed electrode cantilever beam through a hollow square connection. One end of the movable electrode suspension spring is connected to the movable mass block, and the other end is connected to the movable electrode support column, and the movable mass block is suspended between the damping reduction structure and the fixed electrode cantilever beam.

[0008] The beneficial effects of the present invention are as follows: in view of the problem that the rigid collision between the movable electrode and the fixed electrode of the previous threshold sensor easily causes damage to the device and the contact time is short, a longitudinally driven unidirectional vibration threshold sensor is proposed, which uses a spring structure as a vertical fixed electrode contact to achieve elastic contact and thus prolong the contact time. The sensor introduces the principle of transmission conduction. When the two spring electrodes collide with each other, the inertial impact is transmitted from the movable electrode to the fixed electrode, and the coordinated movement of the two electrodes is achieved at the moment of electrode contact, which not only prolongs the contact time, but also avoids the damage to the electrodes caused by the rigid collision between the electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the overall structure.

[0010] Figure 2 It is a schematic diagram of the damping reduction structure and the support column structure.

[0011] Figure 3 It is a schematic diagram of the movable mass block structure.

[0012] Figure 4 It is a schematic diagram of the fixed electrode cantilever beam structure.

[0013] Explanation of the numbers in the accompanying drawings: 1—substrate; 2—damping reduction structure; 3—movable electrode support column; 4—movable electrode suspension spring; 5—movable mass block; 6—fixed electrode support column; 7—fixed electrode cantilever beam; 8—fixed electrode elastic contact. DETAILED DESCRIPTION

[0014] The technical solution is further described below as an embodiment in conjunction with the accompanying drawings. A longitudinal drive threshold sensor using a spring structure as a fixed electrode contact includes a substrate 1, a damping reduction structure 2, a movable electrode support column 3, a movable electrode suspension spring 4, a movable mass block 5, a fixed electrode support column 6, a fixed electrode cantilever beam 7 and a fixed electrode elastic contact 8.

[0015] The substrate 1 is an insulator, and a damping reduction structure 2, a movable electrode support column 3 and a fixed electrode support column 6 are fixedly provided on the substrate 1.

[0016] The damping reduction structure 2 is a rectangular structure, 100-300 microns long, 10-100 microns wide, 5-50 microns thick, and symmetrically distributed in a quadrilateral. The function of the damping reduction structure 2 is to reduce the squeeze film damping effect.

[0017] The movable mass block 5 is a square structure with a side length of 600-1500 microns and a thickness of 20-300 microns. A flow guide hole is provided in the center of the movable mass block 5, and the diameter of the flow guide hole is 100-300 microns. The four sides of the movable mass block 5 are groove-shaped.

[0018] The fixed electrode cantilever beam 7 is a square frame structure with a side length of 1000-1900 microns and a cantilever beam width of 100-300 microns. The four corner points of the fixed electrode cantilever beam 7 extend outward and are suspended and connected to the fixed electrode support column 6.

[0019] The movable electrode suspension spring 4 is composed of four groups of serpentine springs, with a spring line width of 5-50 microns and a thickness of 5-50 microns. One end of the movable electrode suspension spring 4 is connected to the movable mass block 5, and the other end is connected to the movable electrode support column 3, and the movable mass block 5 is suspended between the damping reduction structure 2 and the fixed electrode cantilever beam 7. The movable electrode suspension spring 4 and the movable mass block 5 are symmetrically distributed. The movable mass block 5 is suspended 5-100 microns above the damping reduction structure 2, and the movable mass block 5 is suspended 5-100 microns below the fixed electrode cantilever beam 7.

[0020] The fixed electrode elastic contact 8 is four U-shaped springs, one end of which is connected to the fixed electrode cantilever beam 7, and the other end is connected to the fixed electrode cantilever beam 7 through a hollow square with an inner circle and an outer square, and is suspended on the fixed electrode cantilever beam 7. The spring line is 10-100 microns wide, 5-50 microns thick, and 200-600 microns long. The hollow square is located in the middle of the fixed electrode cantilever beam 7, and the vertical distance between the center point of the fixed electrode elastic contact 8 and the edge line of the movable mass block 5 is 5-50 microns.

[0021] When the external acceleration exceeding the set threshold acts on the spring structure used as the longitudinal driving fixed electrode contact in the normal direction of the surface of the insulating substrate 1, the movable mass block 5 will contact the fixed electrode elastic contact 8 suspended above the movable mass block 5, thereby realizing conduction to the external circuit in the vertical direction.

Claims

1. A longitudinal drive threshold sensor using a spring structure as a fixed electrode contact, comprising a substrate (1), a damping reduction structure (2), a movable electrode support column (3), a movable electrode suspension spring (4), a movable mass block (5), a fixed electrode support column (6), a fixed electrode cantilever beam (7) and a fixed electrode elastic contact (8), characterized in that: The substrate (1) is an insulator, and a damping reduction structure (2), a movable electrode support column (3) and a fixed electrode support column (6) are fixedly provided on the substrate (1); the damping reduction structure (2) is a rectangular structure and is symmetrically distributed in a quadrilateral; the movable mass block (5) is a square structure, and a flow guide hole penetrating the movable mass block (5) is provided at the center of the movable mass block (5); the fixed electrode cantilever beam (7) is a square frame structure, and the four corner points of the fixed electrode cantilever beam (7) extend outwards and are suspended and connected to the fixed electrode support column (6); the movable electrode suspension spring (4) is a serpentine spring, and the movable electrode suspension spring (5) is a serpentine spring. One end of the electrode suspension spring (4) is connected to the movable mass block (5), and the other end is connected to the movable electrode support column (3), and the movable mass block (5) is suspended between the damping reduction structure (2) and the fixed electrode cantilever beam (7), and the movable electrode suspension spring (4) and the movable mass block (5) are symmetrically distributed; the fixed electrode elastic contact (8) is a U-shaped spring, one end of the fixed electrode elastic contact (8) is connected to the fixed electrode cantilever beam (7), and the other end is connected to the fixed electrode cantilever beam (7) through a hollow square with an inner circle and an outer square, and is suspended on the fixed electrode cantilever beam (7), and the hollow square is located in the middle of the fixed electrode cantilever beam (7); The movable electrode suspension springs (4) are symmetrically distributed around the movable mass block (5); The outwardly extending portions of the four corner points of the fixed electrode cantilever beam (7) are distributed at acute angles to the expansion and contraction direction of the movable electrode suspension spring (4).

2. The longitudinal drive threshold sensor using a spring structure as a fixed electrode contact according to claim 1, characterized in that: The damping reduction structure (2) is 100-300 microns long, 10-100 microns wide, and 5-50 microns thick.

3. The longitudinal drive threshold sensor using a spring structure as a fixed electrode contact according to claim 1, characterized in that: The movable electrode suspension spring (4) is composed of four groups of serpentine springs, with a spring line width of 5-50 microns and a thickness of 5-50 microns.

4. The longitudinal drive threshold sensor using a spring structure as a fixed electrode contact according to claim 1, characterized in that: The movable mass block (5) has a side length of 600-1500 microns and a thickness of 20-300 microns. The diameter of the guide hole on the movable mass block (5) is 100-300 microns. The movable mass block (5) is suspended 5-100 microns above the damping reduction structure (2). The movable mass block (5) is suspended 5-100 microns below the fixed electrode cantilever beam (7). The four sides of the movable mass block (5) are groove-shaped.

5. The longitudinal drive threshold sensor using a spring structure as a fixed electrode contact according to claim 1, characterized in that: The fixed electrode elastic contact (8) is four U-shaped springs, the spring line width is 10-100 microns, the thickness is 5-50 microns, and the length is 200-600 microns. The vertical distance between the center of the fixed electrode elastic contact (8) and the edge of the movable mass block (5) is 5-50 microns.

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