Low-g value mems inertial switch

Abstract

The utility model relates to a kind of low g value MEMS inertial switch, comprising: trigger component and encapsulation component, trigger component includes fixed column and multiple mass blocks, multiple mass blocks are distributed along the circumference of fixed column, and cantilever beam is arranged between fixed column and mass block, cantilever beam includes multiple bending strips extending along the same plane and mutually parallel, and first and last are connected between adjacent two bending strips, and bending strip includes continuous and alternate convex section and recess section;Encapsulation component includes substrate, baffle and cover plate, baffle is arranged between substrate and cover plate, and the surface of baffle is provided with mounting port, trigger component is arranged in mounting port, and the surface of substrate is provided with first anchor point, and fixed column is arranged on first anchor point.The utility model can reduce equivalent stiffness using W type cantilever beam, silicon mass block improves inertial force, and realizes low g trigger.Secondly, W type cantilever beam can avoid traditional metal spring assembly error, and space occupation is small, without increasing mass block or expanding chip area.

Description

Technical Field

[0001] This utility model relates to the field of microelectromechanical systems (MEMS) technology, and in particular to a low-g value MEMS inertial switch. Background Technology

[0002] MEMS switches (microelectromechanical system switches) are miniaturized electromechanical switches manufactured based on microelectromechanical system technology. Their core function is to control the minute movements of mechanical structures through electrical signals to realize the conduction and disconnection of circuits. Essentially, they integrate the functions of traditional macroscopic mechanical switches onto chips at the micrometer / nanometer scale.

[0003] In existing technologies, the internal inertial triggering mechanism of MEMS switches mostly uses metal springs and mass blocks. However, in the context of low-range (1g–20g) inertial triggering requirements in aerospace, automotive safety, and IoT equipment, traditional inertial switches suffer from high assembly errors due to the use of metal springs. Furthermore, metal springs exhibit significant creep and temperature drift, resulting in a threshold drift >±1g over long-term use, making them unsuitable for low-range inertial triggering requirements. Additionally, the large space occupied by metal springs contributes to the overall large size of the switch. Utility Model Content

[0004] Therefore, the technical problem to be solved by this utility model is to overcome the low threshold accuracy and poor stability of the existing MEMS switches, which makes it difficult to meet the requirements of low-range inertial triggering.

[0005] To solve the above-mentioned technical problems, this utility model provides a low-g MEMS inertial switch, comprising: A triggering component includes a fixed column and multiple mass blocks, the multiple mass blocks being distributed circumferentially along the fixed column, a cantilever beam being provided between the fixed column and the mass blocks, the cantilever beam including multiple bent strips extending along the same plane and parallel to each other, two adjacent bent strips being connected end to end, and the bent strips including continuously alternating protruding sections and concave sections. The encapsulation assembly includes a substrate, a partition, and a cover plate. The partition plate is disposed between the substrate and the cover plate. An installation port is provided through the surface of the partition plate. The triggering component is disposed in the installation port. A first anchor point is provided on the surface of the substrate. A fixing post is disposed on the first anchor point.

[0006] In one embodiment of the present invention, a first limiting groove is provided on the surface of the substrate that is in contact with the partition, and the height of the first anchor point is consistent with the height of the first limiting groove.

[0007] In one embodiment of this utility model, a plurality of contact electrodes are provided in the first limiting groove, and the positions of the contact electrodes correspond to the positions of the mass block.

[0008] In one embodiment of the present invention, the surface of the substrate is provided with a plurality of pads, and the pads are electrically connected to the electrodes via metal leads.

[0009] In one embodiment of this utility model, a limiting block is further provided between the cantilever beam and the mass block, and multiple limiting blocks are provided along the axial direction of the fixed column.

[0010] In one embodiment of the present invention, a second limiting groove is provided on the surface of the cover plate that is in contact with the partition plate, and a second anchor point is provided in the second limiting groove, and the second anchor point is connected to the limiting block.

[0011] In one embodiment of this utility model, the height of the second anchor point is consistent with the height of the second limiting groove.

[0012] In one embodiment of this utility model, the height of the limiting block is equal to the thickness of the partition.

[0013] In one embodiment of this utility model, the partition, the fixed column, the cantilever beam, and the mass block are integrally formed.

[0014] In one embodiment of this utility model, the height of the mass block is equal to the thickness of the partition.

[0015] The above-mentioned technical solution of this utility model has the following advantages compared with the prior art: This invention discloses a low-g MEMS inertial switch. Utilizing the stable Young's modulus of silicon and the matching thermal expansion coefficients of glass and silicon, it employs a W-shaped cantilever beam formed in a single DRIE (deep reactive ion etching) process. The W-shaped cantilever beam reduces the equivalent stiffness, while the silicon mass increases the inertial force, achieving low-g triggering. The W-shaped cantilever beam avoids assembly errors associated with traditional metal springs, occupies less space, and eliminates the need to increase the mass or chip area. Furthermore, the W-shaped cantilever beam eliminates metal creep and temperature drift, improving long-term stability by an order of magnitude and enhancing triggering accuracy. Attached Figure Description

[0016] To make the content of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings. Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is an exploded view of the overall structure of this utility model; Figure 3 for Figure 1 Internal structural sectional view; Figure 4 for Figure 2 The isometric view of the trigger component; Figure 5 for Figure 2 A top-down view of the trigger component; Figure 6 for Figure 2 Schematic diagram of the middle substrate; Figure 7 for Figure 2 Schematic diagram of the middle cover plate; Explanation of reference numerals in the accompanying drawings: 1. Trigger assembly; 2. Encapsulation assembly; 11. Fixing post; 12. Mass block; 13. Cantilever beam; 14. Limiting block; 21. Substrate; 22. Partition plate; 23. Cover plate; 131. Bending strip; 211. First limiting groove; 212. First anchor point; 213. Contact electrode; 214. Pad; 215. Metal lead; 221. Mounting port; 231. Second limiting groove; 232. Second anchor point. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention.

[0018] Reference Figures 1-5 As shown, this utility model discloses a low-g MEMS inertial switch, comprising: Triggering component 1, the triggering component 1 includes a fixed column 11 and a plurality of mass blocks 12, the plurality of mass blocks 12 are distributed circumferentially along the fixed column 11, a cantilever beam 13 is provided between the fixed column 11 and the mass blocks 12, the cantilever beam 13 includes a plurality of bent strips 131 extending along the same plane and parallel to each other, two adjacent bent strips 131 are connected end to end, the bent strips 131 include continuous alternating protruding sections and concave sections; The encapsulation component 2 includes a substrate 21, a partition 22, and a cover plate 23. The partition 22 is disposed between the substrate 21 and the cover plate 23. An installation port 221 is provided through the surface of the partition 22. The trigger component 1 is disposed in the installation port 221. A first anchor point 212 is provided on the surface of the substrate 21. The fixing post 11 is disposed on the first anchor point 212.

[0019] Reference Figures 3-5As shown, the trigger component 1 in this invention is made of N-type (100) oriented silicon wafers. A fixed post 11 is positioned at the center, and multiple mass blocks 12 are circumferentially arranged outside the fixed post 11. The mass blocks 12 are connected to the fixed post 11 via a cantilever beam 13, forming multiple island-like mass blocks 12 around the fixed post 11. The cantilever beam 13 consists of multiple sets of parallel bent strips 131, with adjacent bent strips 131 connected end-to-end to form the cantilever beam 13 as a whole. Specifically, each bent strip 131 is sinusoidally bent, and the multiple bent strips 131 are arranged in parallel in a W-shape. The W-shaped cantilever beam 13 reduces the equivalent stiffness, while the silicon mass blocks 12 increase the inertial force, thus achieving low-g triggering and significantly reducing the volume of the cantilever beam 13. As a preferred embodiment of this invention, the entire W-shaped cantilever beam 13 utilizes bulk silicon technology to reduce the beam width to tens of micrometers and the length to the millimeter level. All bends and widths of the cantilever beam 13 are simultaneously achieved in a single DRIE (Deep Reactive Ion Etching) process, with a linewidth error of <±1 µm. This achieves a precise match between the extremely low stiffness k and the silicon mass block 12. The W-shaped cantilever beam 13 reduces the equivalent stiffness k to 1 / 10 of that of a traditional straight beam, thereby reducing the closing acceleration to the 1g-20g range and controlling the closing threshold accuracy within ±0.5g, without increasing the mass block 12 or expanding the chip area. Furthermore, the connection points of each bending strip 131 employ rounded transitions, eliminating the stress concentration and plastic deformation common in straight beams. Experimental measurements show a hysteresis error of <0.1g, and long-term repeatability is an order of magnitude better than that of a metal spring.

[0020] Reference Figures 1-3 As shown, the material of the partition 22 in the encapsulation component 2 is also an N-type (100) oriented silicon wafer, while the material of the cover plate 23 and the substrate 21 is a BF33 glass sheet. Specifically, the partition 22 is sleeved on the outside of the entire trigger component 1 to protect the internal trigger component 1; the substrate 21 is set at the bottom of the trigger component 1, and the first anchor point 212 on the substrate 21 serves as a support for the fixing post 11; the cover plate 23 is set on the top of the partition 22 to encapsulate the internal trigger structure. The entire switch is a glass-silicon-glass three-layer structure. The glass itself is insulating and its coefficient of thermal expansion matches that of silicon. The trigger component 1 is sealed inside the encapsulation component 2 through anodic bonding.

[0021] This invention utilizes the stable Young's modulus of silicon and the matching thermal expansion coefficients of glass and silicon. It employs a W-shaped cantilever beam 13 formed in a single DRIE (Deep Reactive Ion Etching) process. The W-shaped cantilever beam 13 reduces the equivalent stiffness, while the silicon mass block 12 increases the inertial force, achieving low-g triggering. The W-shaped cantilever beam 13 avoids assembly errors associated with traditional metal springs, requires less space, and eliminates the need to increase the mass block 12 or expand the chip area. Furthermore, the W-shaped cantilever beam 13 eliminates metal creep and temperature drift, improving long-term stability by an order of magnitude and enhancing triggering accuracy.

[0022] Furthermore, referring to Figure 6 As shown, a first limiting groove 211 is provided on the surface of the substrate 21 that is in contact with the partition 22, and the height of the first anchor point 212 is the same as the height of the first limiting groove 211.

[0023] Specifically, a first limiting groove 211 is etched on the surface of the substrate 21, and the position of the first anchor point 212 is reserved. The first limiting groove 211 serves as the lower stroke space and overpass barrier for the mass block 12, eliminating the need for additional silicon blocks or metal pads, simplifying the process flow and eliminating interlayer alignment errors. In the actual packaging process, the position of the fixing post 11 is aligned with the first anchor point 212, and the fixing post 11 and the first anchor point 212 are bonded together.

[0024] Furthermore, referring to Figure 6 As shown, a plurality of contact electrodes 213 are provided in the first limiting groove 211, and the positions of the contact electrodes 213 correspond to the positions of the mass block 12; a plurality of pads 214 are provided on the surface of the substrate 21, and the pads 214 are electrically connected to the electrodes through metal leads 215.

[0025] Specifically, contact electrodes 213 are sputtered and patterned at the bottom of the first limiting groove 211, vertically aligned with the island-type mass blocks 12 on the middle layer plate. Preferably, four mass blocks 12 are provided in this invention, and four sets of contact electrodes 213 are set at corresponding positions within the first limiting groove 211. Metal leads 215 are connected to the positive and negative electrode pads 214, realizing the integration of four independent electrodes and providing a physical basis for single-chip four-threshold. In actual use, in conjunction with the four island mass blocks 12, different thresholds of 1g–20g are naturally generated by process fluctuations. Users only need to select the pads 214 to achieve single-chip four-threshold, reducing iteration costs.

[0026] Furthermore, referring to Figures 4-5 As shown, a limiting block 14 is also provided between the cantilever beam 13 and the mass block 12, and multiple limiting blocks 14 are arranged along the axial direction of the fixed column 11. (Refer to...) Figure 7 As shown, a second limiting groove 231 is provided on the surface of the cover plate 23 that is in contact with the partition plate 22. A second anchor point 232 is provided in the second limiting groove 231 and is connected to the limiting block 14.

[0027] Specifically, the cover plate 23 is wet-etched to form a second limiting groove 231 and a second anchor point 232, the height of which is the same as the height of the second limiting groove 231. The second limiting groove 231 serves both as the upper travel space of the island-type mass block 12 and as a mechanical baffle for overshoot, eliminating the need for an additional silicon limiting structure. The second anchor point 232 is directly aligned and bonded to the limiting block 14, eliminating alignment errors and thermal mismatches caused by traditional glass-silicon-metal multilayer gaskets. In this invention, the mass block 12 is bidirectionally hard-limited by the first limiting groove 211 and the second limiting groove 231; secondly, multiple limiting blocks 14 are arranged between the cantilever beam 13 and the mass block 12, providing lateral baffles for the mass block 12, which can withstand high g-value mechanical impacts without changing the threshold value. This ability to withstand high g-value mechanical impacts without changing the threshold value further improves the stability and reliability of the entire switch.

[0028] In this utility model, the partition 22, the fixed column 11, the cantilever beam 13 and the mass block 12 are integrally formed, wherein the height of the limiting block 14 is equal to the thickness of the partition 22, and the height of the mass block 12 is equal to the thickness of the partition 22.

[0029] Specifically, the method for preparing the inertial switch in this invention is as follows: First, the cover plate 23 is prepared: a BF33 glass plate with a thickness of 400μm is selected; a groove and a second anchor point 232 are made on the back of the cover plate 23 by photolithography and wet etching process, which are used for the movable space of the mass block 12 and the reverse limit; the back of the cover plate 23 and the front of the partition plate 22 are anodicly bonded for the first time.

[0030] Next, the fabrication of the separator 22 and the trigger component 1: Select an N-type (100) crystal orientation single crystal silicon wafer with a thickness of 400 μm; fabricate the common electrode at the position of the mass block 12 on the back side of the separator 22 (the side that is attached to the substrate 21) by sputtering and photolithography; pre-etch the contours of the mass block 12, the cantilever beam 13 and the limiting block 14 on the front side of the separator 22 (the side that is attached to the cover plate 23) by photolithography and etching; perform the first anodic bonding between the front side of the separator 22 and the cover plate 23; etch through the back side of the separator 22 by photolithography and DRIE (deep reactive ion etching) etching process to completely release the mass block 12, the W-shaped cantilever beam 13 and the limiting block 14; finally, perform the second anodic bonding between the back side of the separator 22 and the front side of the substrate 21.

[0031] Fabrication of substrate 21: Select a BF33 glass sheet with a thickness of 400μm; fabricate a first groove and a first anchor point 212 on the front side of substrate 21 (the side that is attached to the partition 22) by photolithography and wet etching processes; fabricate a contact electrode 213 in the first groove by magnetron sputtering, photolithography and etching processes; perform a second anodic bonding between the front side of substrate 21 and the back side of partition 22 to complete the fabrication of MEMS switch sensor.

[0032] In this invention, both the cover plate 23 and the substrate 21 are made of transparent glass, allowing for real-time inspection of the alignment of each component using an optical microscope before wafer bonding, thus reducing packaging failure rate. Furthermore, the glass itself is insulating and its coefficient of thermal expansion matches that of silicon, forming a wafer-level vacuum / inert gas seal after anodic bonding, suppressing temperature drift and corrosion, and improving long-term reliability.

[0033] In summary, this invention introduces a low-g MEMS inertial switch. Utilizing the stable Young's modulus of silicon and the matching thermal expansion coefficients of glass and silicon, a W-shaped cantilever beam 13 is formed in a single DRIE (deep reactive ion etching) process. The W-shaped cantilever beam 13 reduces the equivalent stiffness, while the silicon mass block 12 increases the inertial force, achieving low-g triggering. The W-shaped cantilever beam 13 avoids assembly errors associated with traditional metal springs, occupies less space, and eliminates the need to increase the mass block 12 or expand the chip area. Furthermore, the W-shaped cantilever beam 13 also eliminates metal creep and temperature drift, improving long-term stability by an order of magnitude and enhancing triggering accuracy.

[0034] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A low-g MEMS inertial switch, characterized in that, include: A triggering component includes a fixed column and multiple mass blocks, the multiple mass blocks being distributed circumferentially along the fixed column, a cantilever beam being provided between the fixed column and the mass blocks, the cantilever beam including multiple bent strips extending along the same plane and parallel to each other, two adjacent bent strips being connected end to end, and the bent strips including continuously alternating protruding sections and concave sections. The encapsulation assembly includes a substrate, a partition, and a cover plate. The partition plate is disposed between the substrate and the cover plate. An installation port is provided through the surface of the partition plate. The triggering component is disposed in the installation port. A first anchor point is provided on the surface of the substrate. A fixing post is disposed on the first anchor point.

2. The low-g MEMS inertial switch according to claim 1, characterized in that: A first limiting groove is formed on the surface of the substrate that is in contact with the partition, and the height of the first anchor point is the same as the height of the first limiting groove.

3. The low-g MEMS inertial switch according to claim 2, characterized in that: The first limiting groove is provided with multiple contact electrodes, and the positions of the contact electrodes correspond to the positions of the mass block.

4. The low-g MEMS inertial switch according to claim 3, characterized in that: The substrate has multiple pads on its surface, and the pads are electrically connected to the electrodes via metal leads.

5. The low-g MEMS inertial switch according to claim 1, characterized in that: A limiting block is also provided between the cantilever beam and the mass block, and multiple limiting blocks are provided along the axial direction of the fixed column.

6. The low-g MEMS inertial switch according to claim 5, characterized in that: A second limiting groove is provided on the surface of the cover plate that is in contact with the partition plate. A second anchor point is provided in the second limiting groove and the second anchor point is connected to the limiting block.

7. The low-g MEMS inertial switch according to claim 6, characterized in that: The height of the second anchor point is the same as the height of the second limiting groove.

8. The low-g MEMS inertial switch according to claim 5, characterized in that: The height of the limiting block is equal to the thickness of the partition.

9. The low-g MEMS inertial switch according to claim 1, characterized in that: The partition, fixed column, cantilever beam and mass block are integrally formed.

10. The low-g MEMS inertial switch according to claim 1, characterized in that: The height of the mass block is equal to the thickness of the partition.

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