Electrostatic scanning micromirror

Abstract

The application discloses a kind of electrostatic scanning micromirror, including upper micro-mirror body and lower bonding base, micro-mirror body includes frame and mirror surface, frame back is fixed on bonding base;The mirror surface upper and lower ends are respectively connected with connecting part, and are connected with frame through pivot;The outside of connecting part is processed with moving tooth, and the position of the inside of frame opposite with moving tooth is processed with static tooth.The electrostatic scanning micromirror of the application sets a special connecting part between pivot and mirror surface, by setting comb tooth on the outside of connecting part, can increase comb tooth arrangement area, enhance the driving force of micro-mirror, increase the maximum deflection angle of micro-mirror.Simultaneously, by setting different structure isolation groove on frame, frame is divided into different functional areas, and all comb tooth groups are divided into driving comb tooth group and feedback comb tooth group, while driving mirror surface deflection, can monitor mirror surface deflection angle in real time, improve the accuracy of mirror surface deflection angle control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-electro-mechanical system, and particularly to an electrostatic scanning micromirror based on MEMS processing technology. BACKGROUND

[0002] MEMS refers to micro-electro-mechanical system, which is a revolutionary new technology developed on the basis of microelectronics technology, and is a high-tech electronic mechanical device made of technologies such as photolithography, etching, thin film, silicon microfabrication and precision machining. MEMS devices are widely used in high-tech industries and are a key technology related to scientific and technological development, economic prosperity and national security. Among them, the scanning micromirror is a light reflection type device developed by applying MEMS technology, which drives the mirror surface to deflect under the action of micro driving force through the torsion structure of the mirror surface, realizes the reflection scanning of the light beam in one or two dimensions, has the advantages of low cost, high reliability, miniaturization and easy mass production, and has a huge application market in the fields of optical communication, laser projection, laser radar and three-dimensional imaging. The electrostatic scanning micromirror in the prior art includes a mirror surface and a frame, and the mirror surface and the frame are connected together through two rotating shafts. When working, different voltages are applied between the moving teeth and the static teeth of the micromirror comb tooth group, the electrostatic force between the comb teeth is changed, the relative torsion of the comb teeth is caused, and then the mirror surface is deflected around the rotating shaft as the axis. However, the rotating shaft of the scanning micromirror cannot be too long, otherwise the rigidity of the rotating shaft will be poor and the deflection process will be prone to breakage. Due to the limitation of the length of the rotating shaft, the number of comb teeth on both sides of the rotating shaft is limited. The smaller the number of comb teeth, the smaller the electrostatic force during work, and the smaller the maximum driving force of the whole micromirror, which limits the maximum deflection angle and application range of the micromirror. Moreover, during the chip packaging stage, the micromirror needs to be picked up by a vacuum suction nozzle of a chip mounter and mounted on a PCB, but due to the existence of the hollow back cavity of the micromirror, the conventional suction nozzle cannot construct a vacuum environment, and only a specially made suction nozzle can be used, which increases the difficulty of testing and the cost of the chip. At the same time, due to the existence of the back cavity, the micromirror can only be glued at the bottom edge and fixed on the PCB, which is unstable and may fall off abnormally, and has low reliability. SUMMARY

[0003] In view of the shortcomings in the prior art that the electrostatic scanning micromirror is limited by the length of the rotating shaft, the number of comb teeth is limited, the maximum driving force is limited during work, the deflection angle of the micromirror is affected, and the micromirror is difficult to pick up and fix during the packaging stage, the present application provides a novel electrostatic scanning micromirror, which can greatly increase the number of comb tooth groups, increase the driving force, improve the maximum deflection angle of the micromirror, and reduce the difficulty of picking up and fixing during the packaging stage, thereby improving the yield and reliability without lengthening the rotating shaft and ensuring the strength of the rotating shaft.

[0004] The technical scheme adopted by the present application is as follows:

[0005] An electrostatic scanning micromirror comprises a micromirror body and a bonding base plate, the micromirror body comprises a frame and a mirror surface, the back of the frame is fixed on the bonding base plate; the mirror surface is connected with the frame through a rotating shaft at both ends; the outer side of the connecting part is processed with a moving tooth, and the inner side of the frame is processed with a static tooth opposite to the moving tooth.

[0006] As a further improvement of the above technical solution:

[0007] A metal flat electrode is made on the bonding base plate, and the flat electrode is located on one side of the central axis of the mirror surface; a through hole is processed on the frame, and an external lead wire is connected with the flat electrode through the metal in the through hole.

[0008] A groove is processed on the bonding base plate opposite to the mirror surface.

[0009] The connecting part is composed of an upper U-shaped structure and a lower square structure, the square structure is connected with the mirror surface; one end of the rotating shaft is connected with the inner side of the frame, and the other end is connected with the bottom of the U-shaped structure of the connecting part.

[0010] The frame is divided into a left driving part, a middle deflection part and a right feedback part by a plurality of isolation grooves, and the rotating shaft is connected with the deflection part; the static tooth of the driving part and the moving tooth of the connecting part form a driving comb tooth group, and the static tooth of the feedback part and the moving tooth of the connecting part form a feedback comb tooth group.

[0011] Two semi-enclosed deflection isolation grooves are processed on the frame, the inside of the deflection isolation grooves is the deflection part, and the deflection part is connected with the rotating shaft; a feedback isolation groove is processed outside the deflection isolation groove, the feedback part is between the deflection isolation groove and the feedback isolation groove, and the driving part is outside the feedback isolation groove; the end of the feedback isolation groove divides the comb tooth group on the side of the connecting part into two parts, the static tooth in the feedback part away from the mirror surface and the corresponding moving tooth form a feedback comb tooth group, and the static tooth inside the driving part and the corresponding moving tooth form a driving comb tooth group.

[0012] A first electrode is processed on the surface of the driving part for connecting with an external driving device; a second electrode is processed on the surface of the deflection part; and a third electrode is processed on the surface of the feedback part for connecting with an external testing device.

[0013] The connecting part is processed as a hollow structure; the comb tooth is trapezoidal or triangular; and the mirror surface is square, circular or elliptical.

[0014] The electrode has a large electrode and a small electrode, the small electrode is used for probe detection chip, and the large electrode is used for final packaging lead bonding.

[0015] The beneficial effects of the present application are as follows:

[0016] The electrostatic scanning micromirror of the application sets a special connecting part between the rotating shaft and the mirror surface, and sets comb teeth on the outside of the connecting part, so as to increase the comb teeth arrangement area, enhance the driving force of the micromirror, and increase the maximum deflection angle of the micromirror.

[0017] The application fixes the bonding base plate on the back of the micromirror, and makes the flat plate electrode on the bonding base plate, so as to test the deflection angle of the mirror or provide greater driving force. Meanwhile, the bottom of the bonding base plate is flat and has no hollow, so the chip can be picked up by vacuum through the suction nozzle of the conventional chip mounter, and compared with directly fixing the micromirror with uneven bottom on the PCB, the bonding base plate can be more stably and conveniently glued and fixed on the PCB.

[0018] The comb teeth of the application adopt trapezoidal or triangular structure, the distance between the adjacent two comb teeth is smaller, more comb teeth can be set without increasing the length of the comb teeth area, and compared with the rectangular comb teeth in the prior art, greater driving force can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the first embodiment of the application.

[0020] Figure 2 It is a sectional view of the first embodiment of the application.

[0021] Figure 3 It is a sectional view of the second embodiment of the application.

[0022] Figure 4 It is a structural schematic diagram of the third embodiment of the application.

[0023] Figure 5 It is a structural schematic diagram of the fourth embodiment of the application.

[0024] Figure 6 It is a schematic diagram of the connecting part with different shapes in the application.

[0025] Figure 7 It is a schematic diagram of the comb teeth with different shapes in the application.

[0026] In the figure: 1, frame; 1-1, driving part; 1-2, deflection part; 1-3, feedback part; 2, mirror surface; 3, rotating shaft; 4, connecting part; 5, isolation groove; 6, driving comb tooth group; 7, feedback comb tooth group; 8, first electrode; 9, second electrode; 10, third electrode; 11, deflection isolation groove; 12, feedback isolation groove; 13, bonding base plate; 14, through hole; 15, flat plate electrode. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application will be described below with reference to the accompanying drawings.

[0028] Example One:

[0029] As shown in Figure 1 and Figure 2 , the electrostatic scanning micromirror of the present application includes an upper micromirror body and a bonding base plate 13 below, the micromirror body includes a frame 1 and a mirror surface 2, the back of the frame 1 is fixed on the bonding base plate 13, and the bottom surface of the bonding base plate 13 is flat. Because the bottom of the bonding base plate 13 is flat, compared with directly fixing the micromirror on the PCB, the bonding base plate 13 can be more stable and more convenient to glue and fix on the PCB. The bonding base plate 13 is made of glass, silicon, metal or the like, and the frame 1 and the mirror surface 2 are processed and made of silicon material or metal alloy. The frame 1 is divided into a left driving part 1-1, a middle deflection part 1-2 and a right feedback part 1-3 from left to right, and the three parts are electrically isolated by isolation grooves 5 and do not conduct to each other. The shape of the mirror surface 2 is preferably square, circular or oval. The mirror surface 2 is connected with the connecting part 4 at the upper and lower ends respectively, and the connecting part 4 is connected with the deflection part 1-2 through the rotating shaft 3. When the scanning micromirror of the present application works, the mirror surface 2 and the connecting part 4 at both ends deflect together with the rotating shaft 3 as the axis. The overall structure of the connecting part 4 is a U-shaped structure at the upper part and a square structure at the lower part, and the square structure is connected with the mirror surface 2 and has a width greater than that of the rotating shaft 3. One end of the rotating shaft 3 is connected with the inner side of the deflection part 1-2, and the other end is connected with the bottom of the U-shaped structure of the connecting part 4. The outer side of the connecting part 4 is processed with a driving tooth.

[0030] As shown in Figure 1 , the left driving part 1-1 inside the driving tooth of the connecting part 4 is processed with a static tooth at the position opposite to the driving tooth, and the static tooth and the driving tooth of the connecting part 4 together form a driving comb tooth group 6. The surface of the driving part 1-1 is also processed with a first electrode 8 for connecting with an external driving device, and the surface of the deflection part 1-2 is processed with a second electrode 9, which is preferably a ground electrode. By applying different voltages between the first electrode 8 and the second electrode 9, electrostatic force can be generated between the static tooth and the driving tooth of the driving comb tooth group 6 to drive the mirror surface 2 to deflect. All the electrodes of the present application have a large electrode and a small electrode. The small electrode is used for probe detection chip, and the large electrode is used for final packaging wire bonding, which effectively prevents the small electrode from being damaged after being probed multiple times, and causes abnormality that cannot be wired.

[0031] The inner side of the right feedback part 1-3 is also processed with a static tooth at the position opposite to the driving tooth of the connecting part 4, and the static tooth and the corresponding driving tooth of the connecting part 4 together form a feedback comb tooth group 7. The surface of the feedback part 1-3 is also processed with a third electrode 10 for connecting with an external test device to measure the capacitance of the feedback comb tooth group 7 when the mirror surface 2 deflects, and then obtain the angle of deflection of the mirror surface 2.

[0032] When the electrostatic scanning micromirror of the embodiment works, the driving signal is provided to the driving comb set 6 by applying voltage between the first electrode 8 and the second electrode 9, and the mirror surface 2 and the connecting part 4 jointly deflect around the rotating shaft 3 under the action of the electrostatic force between the moving comb and the static comb. Meanwhile, the moving comb and the static comb of the feedback comb set 7 are at a certain angle and have a certain capacitance value, and the angle of the mirror surface 2 can be calculated by measuring the capacitance of the feedback comb set 7 through the third electrode 10.

[0033] In the embodiment, since the length of the connecting part 4 is greater than the length of the rotating shaft 3, compared with the scanning micromirror of the prior art, the comb arrangement area can be increased by the connecting part 4, more combs can be processed, and the driving force of the whole scanning micromirror can be further improved, and the maximum deflection angle of the mirror surface 2 can be increased. Meanwhile, since the combs of the feedback comb set 7 are also increased, the feedback capacitance signal is larger, the influence of the environmental noise on the feedback capacitance value can be effectively reduced, and the accuracy of the mirror surface deflection angle measurement can be improved.

[0034] Of course, in the present application, the whole frame 1 can also be divided into the driving part 1-1 and the deflection part 1-2 by the isolation groove 5, that is, Figure 1 The two sides of the deflection part 1-2 are the driving part 1-1, so that all the combs form the driving comb set 6, and the driving force of the micromirror is further improved. The measurement of the mirror surface deflection angle can be monitored by an external measurement device.

[0035] As shown in Figure 2 The flat plate electrode 15 made of metal is made on the bonding base plate 13 below the mirror surface 2, and the flat plate electrode 15 is located on one side of the central axis of the mirror surface 2. Meanwhile, the through hole 14 is processed on the frame 1, and the external lead wire is connected to the flat plate electrode 15 through the metal in the through hole. When the micromirror works, the distance between the mirror surface 2 and the flat plate electrode 15 changes due to the vibration of the mirror surface 2, which causes the capacitance between the mirror surface 2 and the flat plate electrode 15 to change. By connecting the external test system through the metal lead wire, the capacitance change between the plates caused by the deflection of the mirror surface 2 can be detected, and the deflection angle of the mirror surface 2 can be calculated. Of course, the driving voltage can also be provided to the flat plate electrode 15, and the driving force can be provided to the mirror surface 2 through the electrostatic force between the mirror surface 2 and the flat plate electrode 15.

[0036] Embodiment two:

[0037] As shown in Figure 3 The middle part of the bonding base plate 13 is processed into a groove, which can provide enough deflection space for the edge of the mirror surface 2 when the mirror surface 2 deflects, prevent the edge of the mirror surface 2 from touching the bottom, and improve the maximum deflection angle of the whole micromirror.

[0038] Embodiment three:

[0039] AsFigure 4 As shown, the connecting part 4 and the rotating shaft 3 in this embodiment are the same as in Embodiment 1. On the frame 1, the deflection part 1-2 is first isolated from other parts by two U-shaped deflection isolation grooves 11. The deflection part 1-2 is connected to the rotating shaft 3 and has a second electrode 9. A feedback isolation groove 12 is machined outside the deflection isolation groove 11. The feedback part 1-3 is located between the feedback isolation groove 12 and the deflection isolation groove 11. A third electrode 10 is machined on the feedback part 1-3. The end of the feedback isolation groove 12 divides the comb teeth group on the side of the connecting part 4 into upper and lower parts. Among them, the stationary teeth on the feedback part 1-3 away from the mirror surface 2 and the corresponding moving teeth form the feedback comb teeth group 7, and the stationary teeth on the inner side of the driving part 1-1 and the corresponding moving teeth form the driving comb teeth group 6.

[0040] The deflection isolation groove 11 and feedback isolation groove 12, with their special structures, allow for a reasonable allocation of the number of drive teeth and feedback teeth. In actual design and manufacturing, the feedback isolation groove 12 can be positioned appropriately based on the required driving force and feedback capacitance value of the micromirror, thereby obtaining a reasonable number of drive teeth and feedback teeth that simultaneously meet the requirements for both driving force and feedback accuracy.

[0041] Example 4:

[0042] like Figure 5 As shown, in this embodiment, the deflection isolation groove 11 is also used to isolate the deflection part 1-2 from other parts, and all the comb teeth at the positions of the upper and lower connecting parts 4 are used to form the drive comb tooth group 6. On the two opposite side frames 1 of the mirror surface 2 where there is no connecting part 4, feedback isolation grooves 12 are processed to isolate the feedback part 1-3 and the drive part 1-1. In the area on the inner side of the feedback part 1-3 opposite to the mirror surface 2, pairs of stationary teeth and moving teeth are processed respectively, which together form the feedback comb tooth group 7.

[0043] When the scanning micromirror in this embodiment is working, the mirror 2 is driven to deflect by the electrostatic force between the comb teeth of the drive comb group 6. When the mirror 2 deflects, the moving teeth and stationary teeth of the feedback comb group 7 also form a certain angle and have a certain capacitance value. By measuring the capacitance of the feedback comb group 7 through the third electrode 10, the angle of rotation of the mirror 2 can be calculated.

[0044] Of course, the feedback comb tooth group 7 can also be processed only on one side of the mirror surface 2. With the structure of this embodiment, the drive comb tooth group 6 with the largest number of comb teeth can be obtained, resulting in greater driving force. At the same time, the feedback comb tooth group 7 is formed at the positions on both sides of the mirror surface 2 to provide real-time feedback on the deflection angle of the mirror surface 2.

[0045] Example 5:

[0046] Figure 6 The diagram shows four different structures of the connecting part 4. Figure 6a is a basic structure, and the connecting part 4 is a solid structure. Figure 6 b to 6d are all hollow structures, and the connecting part 4 is processed with different shapes of through holes. The connecting part 4 is processed as a hollow structure, which can reduce the overall weight of the micro mirror and also improve the heat dissipation effect of the micro mirror.

[0047] Example six:

[0048] Figure 7 Three different structures of the comb teeth are shown. Figure 7 a is a basic structure, and the comb teeth are rectangular. Figure 7 The comb teeth of b are trapezoidal, Figure 7 The comb teeth of c are triangular. In particular, the comb teeth are designed as triangular, and the spacing between two adjacent comb teeth is smaller than that of the rectangular comb teeth. A larger number of triangular comb teeth can be arranged in the same length. The more comb teeth, the greater the driving force. Through the special-shaped comb teeth of the embodiment, especially the triangular comb teeth, more comb teeth can be arranged without increasing the length of the comb tooth area, thereby improving the driving force of the micro mirror.

[0049] The above description is an explanation of the present application, not a limitation of the application. The present application can be modified in any form without departing from the spirit of the present application.

Claims

1. An electrostatically scanned micromirror, characterized by: The micro-mirror body including the upper part and the bonding base plate (13) below, the micro-mirror body including the frame (1) and the mirror surface (2), the back of the frame (1) is fixed on the bonding base plate (13); the mirror surface (2) is connected with the connecting part (4) at both ends respectively, and is connected with the frame (1) through the rotating shaft (3); the outer side of the connecting part (4) is processed with the moving tooth, and the inner side of the frame (1) is processed with the static tooth opposite to the moving tooth; the bonding base plate (13) is processed with the metal flat electrode (15), and the flat electrode (15) is located on one side of the central axis of the mirror surface (2); the frame (1) is processed with the through hole (14), and the external lead wire is connected with the flat electrode (15) through the metal in the through hole; the frame (1) is separated into the driving part (1-1) and the deflection part (1-2) by the isolation groove; the surface of the driving part (1-1) is processed with the first electrode (8) for connecting with the external driving device; the surface of the deflection part (1-2) is processed with the second electrode (9); the electrode has a big one and a small one, the small one is used for probe detection chip, and the big one is used for final packaging lead bonding; the moving tooth and the static tooth are trapezoidal or triangular.

2. The electrostatically scanned mirror of claim 1, wherein: The middle part of the bonding base plate (13) is processed with the groove opposite to the mirror surface (2).

3. The electrostatically scanned mirror of claim 1, wherein: The connecting part (4) is composed of the U-shaped structure on the upper part and the square structure on the lower part, and the square structure is connected with the mirror surface (2); one end of the rotating shaft (3) is connected with the inner side of the frame (1), and the other end is connected with the bottom of the U-shaped structure of the connecting part (4).

4. The electrostatically scanned mirror of claim 1, wherein: The frame (1) is separated into the left driving part (1-1), the middle deflection part (1-2) and the right feedback part (1-3) by the multiple isolation grooves (5), and the rotating shaft (3) is connected with the deflection part (1-2); the static tooth of the driving part (1-1) and the moving tooth of the connecting part (4) form the driving comb tooth group (6), and the static tooth of the feedback part (1-3) and the moving tooth of the connecting part (4) form the feedback comb tooth group (7).

5. The electrostatically scanned mirror of claim 1, wherein: The frame (1) is processed with two half-enclosed deflection isolation grooves (11), the inside is the deflection part (1-2), and the deflection part (1-2) is connected with the rotating shaft (3); the deflection isolation groove (11) is processed with the feedback isolation groove (12) outside, the feedback part (1-3) is between the deflection isolation groove (11) and the feedback isolation groove (12), and the feedback isolation groove (12) is outside the driving part (1-1); the end of the feedback isolation groove (12) divides the comb tooth group of the side edge of the connecting part (4) into two parts, the static tooth far away from the mirror surface (2) on the feedback part (1-3) and the corresponding moving tooth form the feedback comb tooth group (7), and the static tooth inside the driving part (1-1) and the corresponding moving tooth form the driving comb tooth group (6).

6. The electrostatic scanning micromirror according to claim 4 or 5, characterized in that: The surface of the feedback part (1-3) is processed with the third electrode (10) for connecting with the external testing device.

7. The electrostatically scanned mirror of claim 1, wherein: The connecting part (4) is processed as a hollow structure; the mirror surface (2) is square, circular or oval.

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