CN103198922B - A kind of comb electric capacity Precise Assembling Method based on bi-stable state compliant mechanism - Google Patents

Abstract

Comb-tooth capacitors are commonly used microactuators and microsensors in MEMS devices. Comb-tooth-shaped capacitors usually only have a few microns between the teeth, and the gap between the positive and negative plates needs to be precisely controlled. This design proposes a comb-tooth capacitor precision assembly method based on the bistable compliant mechanism, which can improve the precise control of the gap between the positive and negative plates of the comb-shaped capacitor, so that the MEMS devices with the same structure in batches have a consistent and reliable Estimated capacitance values to improve consistency of performance when electrostatic MEMS devices are manufactured in batches.

Description

A precision assembly method for comb capacitors based on bistable compliant mechanism

technical field

The invention relates to a comb-tooth capacitor precision assembly method based on a bistable compliant mechanism, and belongs to the technical field of microactuators and microsensors in MEMS devices.

Background technique

Comb-tooth capacitors are commonly used microactuators and microsensors in MEMS devices. The gap between the positive and negative plates of the comb-tooth capacitor needs to be precisely controlled, so that MEMS devices with the same structure in batches can have consistent and estimable capacitance values, thereby improving the consistency of performance during batch manufacturing of electrostatic MEMS devices. However, the inter-tooth gap of the comb-shaped capacitor is usually only a few microns, which makes it very difficult to adopt a deep reactive ion etching manufacturing process.

Contents of the invention

Aiming at the problem that the gap between the positive and negative plates of a comb-toothed capacitor requires precise control, the present invention proposes a precision assembly method for a comb-toothed capacitor based on a bistable compliant mechanism, which can improve the gap between the positive and negative plates of a comb-toothed capacitor. Precise control of clearance.

In order to achieve the above object, the present invention adopts the following technical solutions.

The fixed combs and movable combs of the comb-shaped capacitor are manufactured by laying on a plane. After the manufacturing is completed, there is a certain horizontal distance between the fixed plate and the movable plate.

In order to realize the cross-assembly and precise positioning of the fixed comb teeth and movable fixed comb teeth, a bistable compliance mechanism connected to it is designed on the rear side of the movable plate. A bistable compliant mechanism is a compliant parallel mechanism with two static equilibrium configurations. Utilizing the bistable compliant mechanism's two-dimensional balance characteristics and compliant motion capability, an on-chip assembly method for micromechanical electronic systems (MEMS) devices is designed. It can be used in a variety of MEMS devices that require precise positioning and structural gap control. This structure has the advantages of simple design and manufacture, structural rigidity and force-deformation analysis, and is suitable for mass production of MEMS devices.

An electrothermal compliance actuator is also designed on the rear side of the bistable compliance mechanism. Electrothermal compliance brake is a kind of micromechanical actuator that can output relatively large output force. Precise motion control of electrothermal microactuators is difficult due to the uncertainty of heat loss. In this design, only the electrothermal micro-actuator is used to drive and control the balance configuration transformation of the bistable compliance mechanism, and the precise assembly and positioning control of the movable plate is realized through the locking block.

Description of drawings

Figure 1 is a schematic diagram of the comb teeth before assembly.

Explanation of the numbers in Figure 1: 1 fixed comb, 2 movable comb, 3 locking block, 4 elastic beam, 5 bistable compliance mechanism, 6 support block, 7 electrothermal driving electrode, 8 microactuator of electrothermal compliance mechanism .

Fig. 2 is a schematic diagram of the assembled comb.

Figure 3 is a working principle diagram of the locking block.

Fig. 4 is a schematic diagram of a flexible bistable bending beam supported at both ends.

Fig. 5 is a schematic diagram of the working principle of the micro-actuator of the electrothermal compliance mechanism.

detailed description

As shown in Figure 1, a comb-tooth capacitor precision assembly method based on a bistable compliant mechanism is characterized in that the device includes: fixed combs 1, movable combs 2, locking blocks 3, and elastic beams 4 , Bistable compliance mechanism 5, support block 6, electrothermal drive electrode 7, electrothermal compliance mechanism micro-actuator 8.

As shown in accompanying drawings 1 and 2, they are the two static equilibrium configurations of the bistable compliance mechanism 5 before and after assembly. Since the bistable compliance mechanism 5 has certain stability in its two static equilibrium configurations, when the device works in a vibrating environment, the position of the movable plate will not change, and stable locking can be realized.

As shown in Figure 3, the structure of the movable plate position locking block 3 adopts a V-shaped contraction groove structure at the end A, and a thin-walled cantilever beam structure at B. When the active plate bracket exerts a force F on the inclined surface of the A end of the locking block 3, the thin-walled beam B of the locking block 3 will produce bending deformation . When the movable plate support passes through the V-shaped groove, the thin-walled beam B of the locking block 3 deforms and returns to its original position, and the A end face of the locking block is pushed against the rear end face of the movable plate support, so that the movable plate cannot return to the original position, and the electrostatic comb shape is realized. Cross-assembly of pinned electrodes. The inclination angle of the inclined surface of the V-shaped groove at the A end of the locking block 3 needs to be matched according to the bending stiffness of the flexible beam B. When the bending stiffness of the flexible beam B is relatively large, the inclination angle of the A-end is designed to be a small value; when the bending stiffness of the flexible beam B is small, the inclination angle of the A-end is designed to be a large value, thereby providing a guarantee for the locking of the movable plate position More reliable support.

As shown in Figure 4, the design of the bistable compliance mechanism 5 adopts a double-end support flexible flexion beam structure. Under the application of external force F, the steady-state configuration of the compliant mechanism can change from the position shown in Figure 4(a) to the position shown in Figure 4(b). This change in steady-state configuration can be used to adjust and assemble the position of moving parts in MEMS devices.

As shown in Fig. 5, the electrothermal compliance mechanism micro-actuator 8 is used to realize the drive conversion of the steady-state configuration of the bistable compliance mechanism 5. When a voltage is applied to both ends of the electrodes of the micro-actuator 8 of the electrothermal compliance mechanism, a current is generated in the compliance beam. Since the compliance beam has a certain resistance, heat will be generated after passing the current. Resistive heating will result in an increase in the length of the compliant beam. Since the electrothermal compliance mechanism adopts a V-shaped beam symmetrical structure, when the length of the compliance beam increases, under the action of symmetrical forces on both sides, the middle support of the flexible beam will only produce horizontal and lateral displacements . The electrothermal micro-actuator can generate a relatively large output force to push the bistable compliant mechanism 5 to change the configuration, thereby realizing the control of the position of the movable electrode of the electrostatic gear shaping. When the movable electrode bracket passes through the V-shaped groove as shown in FIG. 3 , the position of the locking block 3 is restored to realize the locking of the position of the movable electrode plate.

To make the on-chip assembly mechanism work normally, the horizontal structural stiffness of the electrothermal compliance mechanism needs to be designed as , the bending deformation stiffness of the bistable compliant mechanism 5 is designed as , the structural stiffness of the locking block flexible beam is designed as , and the three structural stiffnesses satisfy the relationship .

Claims (4)

1. a comb electric capacity Precise Assembling Method based on bi-stable state compliant mechanism, this assembly method is to fixed fingers and activity Comb plane fanning assembles, and after having assembled, has certain horizontal cross distance between fixed polar plate and movable polar plate, and it is special Levy and be that the employing of this assembly method includes clamping block, spring beam, bi-stable state compliant mechanism, bracer, electrothermal drive electrode, electric heating Fixed fingers, movable comb are assembled by the assembling device of compliant mechanism micro-actuator；Electric heating compliant mechanism micro-cause during assembling Dynamic device promotes bi-stable state compliant mechanism to move, and bi-stable state compliant mechanism drives movable polar plate and the work being fixed on movable polar plate Dynamic comb moves to fixed fingers, and movable comb tooth pushes fixed fingers teeth groove, clamping block locking movable polar plate the most at last, it is achieved Gu Determine comb and the cross assembly of movable comb and precision positioning.

Comb electric capacity Precise Assembling Method based on bi-stable state compliant mechanism the most according to claim 1, it is characterised in that Bi-stable state compliant mechanism is that both-end supports flexibility girder construction in the wrong, is positioned on rear side of movable polar plate and is connected with movable polar plate；Electric heating Compliant mechanism micro-actuator is positioned on rear side of bi-stable state compliant mechanism, drives and controls the conversion of bi-stable state compliant mechanism equilibrium configuration.

Comb electric capacity Precise Assembling Method based on bi-stable state compliant mechanism the most according to claim 1, it is characterised in that Clamping block is made up of with flexible beam V-arrangement retraction slot structure end, and flexible beam is thin-walled cantilever beam structure, V-arrangement retraction slot inclined-plane Inclination angle matches with the bending stiffness of flexible beam.

Comb electric capacity Precise Assembling Method based on bi-stable state compliant mechanism the most according to claim 1, it is characterised in that The horizontal direction rigidity of structure of electric heating compliant mechanism is K₁, the flexural deformation rigidity of bi-stable state compliant mechanism 5 is K₂, clamping block is soft The rigidity of structure of property beam is K₃, then K is met₁>K₂>2K₃。