HK1234809B - A flexure, stage comprising a flexure array and fabrication method of such flexure - Google Patents

Description

Flexure, platform including flexure array, and method for manufacturing flexure

Technical Field

The present disclosure relates generally to flexures and, more particularly, to low-stiffness flexures that may be used in actuators and motion stages, such as those used in microelectromechanical systems (MEMS).

Background Art

Flexures are used in systems where motion occurs between one part of the system and another. To generate motion, a force must be present. In some cases, this force comes from an actuator or motor that provides the controlled force that generates the motion. In such systems, a flexure is often used to connect the moving part of the system to the fixed part of the system. The flexure must be designed so that its stiffness is low enough to not impede motion in the desired direction. In particular, to reduce the force required by the actuator or motor, the stiffness of the flexure in the direction of motion must be as low as possible.

In the design of low stiffness flexures, the cross-section of the flexure is typically designed to be as small as possible along the bending direction and the length is made as long as possible. However, there are limitations on the design of the dimensions of conventional flexures. In some systems, these dimensions are limited by manufacturing limitations. For example, a stamped metal flexure cannot be made too thin or too long without affecting handling and manufacturability. In other systems, the desire to make the cross-section of the flexure as small as possible conflicts with other system requirements. For example, if the flexure is designed to be electrically charged, then making the flexure cross-section very small increases resistance, which wastes power and, if sufficient current flows through the flexure, can cause failure.

Summary of the Invention

According to various embodiments, a new flexure is disclosed that includes a first support end connected to a first frame, a second support end connected to a second frame, and a bent portion connecting the first support end to the second support end. In conventional flexure designs, bending is avoided because it is associated with sudden failure of the structure when subjected to high compressive stresses. This failure occurs due to a sharp reduction in stiffness caused by bending. However, the flexure disclosed herein takes advantage of this bending effect by operating in a bent state without failure, thereby allowing the stiffness of the flexure to be several orders of magnitude softer than when operating in a normal state.

In one embodiment of the disclosed technology, a flexure includes a first straight portion, a second straight portion, and a bent portion connecting the first straight portion and the second straight portion. In one implementation of this embodiment, the flexure is composed of a polysilicon layer that provides optimal mechanical properties (e.g., improved flexibility) and a metal layer that provides optimal electrical properties (e.g., improved conductivity). In other implementations of this embodiment, the stiffness of the flexure in a bent state is at least an order of magnitude less than the stiffness of the flexure in an unbent state.

In another embodiment of the disclosed technology, a motion stage includes a flexure array comprising a plurality of flexures connected to a first frame and a second frame, wherein the first frame and the second frame are substantially in a plane, the flexure array is substantially in the plane before being bent by the plurality of flexures, and after being bent by the plurality of flexures, the flexure array is bent substantially out of the plane. In one embodiment, a motion limiter prevents failure of the bent plurality of flexures by limiting motion of the flexure array.

In another embodiment of the disclosed technology, a method includes providing a flexure having a length significantly greater than its width and thickness; moving the flexure until it bends; and maintaining the flexure in the bent state during normal operation. In one embodiment, the method further includes limiting the movement of the flexure using a motion limiter to prevent failure of the flexure in the bent state.

Other features and aspects of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate, by way of example, features according to various embodiments.This summary is not intended to limit the scope of the invention, which is defined solely by the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technology according to one or more various embodiments is described in detail with reference to the following figures. These figures are provided for illustrative purposes only and depict only typical or example embodiments of the disclosed technology. These figures are provided to facilitate understanding of the disclosed technology and should not be construed as limiting its breadth, scope, or applicability. It should be noted that for clarity and simplicity of illustration, these figures are not necessarily drawn to scale.

FIG. 1 is a plan view of an example embodiment of a flexure according to the disclosed technology.

2A is an edge view of the flexure of FIG. 1 as manufactured.

2B is an edge view of the flexure of FIG. 1 in a buckled state.

3 is a force-displacement graph of an example embodiment of a flexure according to the disclosed technology.

4A is a plan view of another example embodiment of a flexure according to the disclosed technology.

4B is a three-dimensional perspective view of the flexure of FIG. 4A as manufactured.

4C is a three-dimensional perspective view of the flexure of FIG. 4A in a bent state.

5 is a force-displacement graph of the flexure of FIG. 4A .

6 is a graph of biasing force versus biasing axial displacement for the flexure of FIG. 4A in a bent state.

7 is a tangential force-tangential displacement graph of the flexure of FIG. 4A in a bent state.

8 is a plan view of one example embodiment of a motion stage utilizing an array of flexures in accordance with the disclosed technology.

9 is a plan view of another example embodiment of a flexure according to the disclosed technology.

10 is a plan view of another example embodiment of a flexure in accordance with the disclosed technology.

11 is a plan view of another example embodiment of a flexure in accordance with the disclosed technology.

12 is a plan view of another example embodiment of a flexure in accordance with the disclosed technology.

13 is a plan view of another example embodiment of a flexure in accordance with the disclosed technology.

14 is a plan view of another example embodiment of a flexure in accordance with the disclosed technology.

15 is a plan view of an example embodiment of a variable width flexure in accordance with the disclosed technology.

16 is a graph of normalized force versus normalized displacement illustrating the performance of different flexure designs according to different embodiments of the disclosed technology.

17A is a top plan view of an example embodiment of an offset layer flexure as fabricated in accordance with the disclosed techniques.

17B is a bottom plan view of the offset layer flexure of FIG. 17A as fabricated.

17C is a three-dimensional perspective view of the offset layer flexure of FIG. 17A in a bent state.

18A is a plan view of an example embodiment of a split root flexure as made in accordance with the disclosed technology.

18B is a plan view of the split root flexure of FIG. 18A as fabricated.

18C is a three-dimensional perspective view of the split root flexure of FIG. 18A in a bent state.

19A is a plan view of an example embodiment of a flexure including layers of varying lengths in accordance with the disclosed technology.

FIG. 19B is a three-dimensional perspective view of the flexure of FIG. 19A .

20 is a plan view of a comb drive for a comb-drive actuator that may use the disclosed flexures according to embodiments of the disclosed technology.

21A illustrates a plan view of a comb-drive actuator that may utilize the disclosed flexures according to embodiments of the disclosed technology.

21B illustrates a plan view of a comb-drive actuator that may utilize the disclosed flexures according to embodiments of the disclosed technology.

22A illustrates a plan view of an actuator that may utilize the disclosed flexure according to an embodiment of the disclosed technology.

22B illustrates a cross-sectional view of an actuator that may utilize the disclosed flexure according to an embodiment of the disclosed technology.

22C illustrates a plan view of an actuator that may utilize the disclosed flexure according to an embodiment of the disclosed technology.

22D illustrates a cross-sectional view of an actuator that may utilize the disclosed flexure according to embodiments of the disclosed technology.

The drawings are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It should be understood that the invention can be practiced with modification and alteration, and the disclosed technology is limited only by the claims and their equivalents.

DETAILED DESCRIPTION

According to various embodiments of the disclosed technology, a new flexure is disclosed that includes a first end connected to a first frame, a second end connected to a second frame, and a buckled section connecting the first end to the second end. The disclosed flexure operates flawlessly in a buckled state, allowing the stiffness of the flexure to be several orders of magnitude lower than when operating in a normal state. The flexure can be used in actuators and motion stages, such as those for microelectromechanical systems (MEMS). In one specific embodiment, the flexure can be implemented in a MEMS actuator that moves an image sensor in a camera package.

In various embodiments described below, the bending portion (i.e., the flexible portion) of the flexure is designed to be flexible, such that the cross-section (i.e., thickness and width) of the flexible portion along its bending direction is small, while its length is relatively long. For example, in these embodiments, the flexible portion can be 10 to 30 microns wide, 1 to 3 microns thick, and 500 to 800 microns long. In one specific embodiment, the flexible portion is 25 microns wide, 1.5 microns thick, and 600 microns long. Furthermore, the flexure can be designed to adapt to geometric constraints and minimize stiffness and stress in the deformed flexure.

In these embodiments, the flexure can be manufactured using MEMS technology by patterning its design using photolithography and etching away a polysilicon layer deposited on an oxide-coated silicon wafer. In other embodiments, the flexure can be manufactured using a variety of processes, such as stamping, etching, laser cutting, machining, three-dimensional printing, water jet cutting, and the like. The flexure can be formed from a variety of materials, such as metal, plastic, and polysilicon. In these implementations, the flexure can include one, two, or three layers of these materials. In one embodiment, the flexure is formed from multiple layers of polysilicon and metal, whereby the polysilicon layer provides improved flexibility and reliability, and the metal layer provides improved conductivity. In other embodiments further described below, the flexure can have a variable width, a split layer, an offset layer, or some combination thereof to achieve desired characteristics, such as conductivity and flexibility. As will be appreciated by those skilled in the art, other combinations of these materials can be used to achieve the desired characteristics of the flexure.

FIG1 is a plan view of an exemplary flexure 100 according to one embodiment. As shown, the flexure 100 includes a first support end 111, a second support end 112, and a flexible portion 113 connecting the support end 111 to the support end 112. As described above, in various embodiments, the flexible portion 113 is designed to be flexible so that the cross-section (i.e., thickness and width) of the portion 113 along its bending direction is small, while its length is relatively long. FIG2A and FIG2B show side views of the flexure 100. FIG2A shows the flexure 100 in a pre-bent state after manufacture. FIG2B shows the flexure 100 in a bent state. In one embodiment shown in FIG2B, after the support end 112 is moved toward the support end 111, the flexure 100 transitions to a bent state, causing the flexible portion 113 to bend upward or downward. Because the thickness of the exemplary flexure 100 is less than its width, the flexure 100 bends upward or downward as shown in FIG2B. In other embodiments where the flexure is thicker than it is wide, the flexible portion can bend diagonally.

FIG3 is a force-displacement diagram of an example embodiment of a flexure according to the disclosed technology. As shown, there is a pre-bending regime or state in which the stiffness of the flexure, calculated as the change in force divided by the change in displacement, is relatively high. Once the flexure bends, the flexure enters a post-bending regime in which the stiffness of the flexure is sharply reduced. By operating in the post-bending regime, the stiffness of the flexure is sharply reduced. Therefore, in various embodiments of the disclosed technology, the flexure is operated in a post-bending regime (e.g., as shown in FIG2B ) that is opposite to the pre-bending or manufacturing regime (e.g., as shown in FIG2A ). To prevent the flexure from malfunctioning, in various embodiments, a motion limiter that limits the motion of the flexure may be included in the system (e.g., an actuator) that includes the flexure.

FIG4A is a plan view of another example flexure 200 according to the disclosed technology. As shown, the flexure 200 includes a first support end 211, a second support end 212, and a flexible portion 213 connecting the first support end 211 to the second support end 212. Similar to the flexure 100, the flexure 200 bends in the radial direction between the support ends 211 and 212 and has low stiffness in the post-bending interval. In addition, the design of the flexure 200 provides low stiffness in the direction tangential to the support ends 211 and 212. In particular, the flexure 200 has a "V"-shaped design, which includes two long and straight portions 242, a curved portion 241 connecting the straight portion 242 to the support ends 211-212, and a curved portion 243 connecting the straight portions 242 together.

In various embodiments, the curvature of the curved portions 242-242, the angle of the "V," and the length of the straight portion 242 are designed to accommodate geometric constraints and minimize stiffness and stress in the deformed flexure. For example, in one embodiment, the angle of the "V" can be 35 degrees, the radii of curvature 241 and 243 can be 50 microns, the length of the straight portion 242 can be 650 microns, and the spacing between the support ends 211 and 212 can be 700 microns.

Figures 4B to 4C show three-dimensional stereograms of the flexure 200. Figure 4B shows the flexure 200 as manufactured. Figure 4C shows the flexure 200 in a bent state. In one embodiment, as shown in Figure 4C, after deflecting the support end 212 toward the support end 211, the flexure 200 transitions to a bent state, causing the flexible portion 213 to bend in three dimensions. Because the thickness of the example flexure 200 is less than its width, and due to the "V" shaped geometric design, the flexure 200 bends in three dimensions. This ensures that the bent flexure has very low stiffness in both the radial and tangential directions (i.e., the x and y directions shown in Figures 4B to 4C) between the support ends 211 and 212.

FIG5 is a bias force-bias displacement diagram of the flexure 200 calculated using finite element analysis. As shown, there is a pre-bend interval in which the movable support end 212 has a low axial displacement. In this pre-bend interval, the stiffness of the flexure 200, calculated as the change in force divided by the change in displacement, is relatively high. This pre-bend interval, between zero axial displacement and approximately 0.05 mm axial displacement, corresponds to the shape shown in FIG4B . After the flexure 200 bends, the stiffness of the flexure decreases sharply. This post-bend interval, exceeding approximately 0.15 mm axial displacement, corresponds to the shape shown in FIG4C . In this embodiment, there is a gradual transition range between the pre-bend and post-bend, between approximately 0.05 mm and 0.15 mm axial displacement. By operating in the post-bend interval, the stiffness of the flexure decreases sharply. As shown in FIG5 , in the post-bend interval, the stiffness of the flexure can be several orders of magnitude smaller than in the pre-bend interval. Thus, in various embodiments of the disclosed technology, the flexure is operated in a post-bend range (eg, as shown in FIG. 3 ) as opposed to a pre-bend or manufacturing range (eg, as shown in FIG. 3 ).

FIG6 is a bias force-bias displacement diagram of flexure 200 in a bent state. As shown, flexure 200 is axially pre-deformed by moving movable support end 212 300 microns toward fixed support end 211. The change in force corresponding to the axial displacement toward the biased position is shown. The force required to produce a 150 micron displacement of the biased position is less than 0.9 micronewtons. In these embodiments, the relationship between bias force and bias displacement can be nonlinear and asymmetric. However, since the flexure is softer than the stiffness of the system in various embodiments, the nonlinearity that flexure 200 may introduce to the system is negligible.

As described above, the flexure 200 is axially pre-deformed to a biased position by moving the movable support end 213 toward the fixed support end 212 (e.g., 300 microns). The tangential force corresponding to the tangential displacement can then be measured and plotted, as shown in FIG7 . As shown, the force required to produce a tangential displacement of 150 microns is less than 2.5 micronewtons. The force is linear within a range of ±0.12 microns and begins to bend outside this range. However, since the flexure is very soft in different embodiments, the nonlinearity that the flexure 200 may bring to the system is negligible. In different embodiments, the diagrams of FIG6 and FIG7 can be used to design the entire flexure system.

FIG8 is a plan view of an example embodiment of a motion stage using an array of flexures according to the disclosed technology. As shown, the motion stage includes a movable platform 311 connected to rigid rods or support ends 312 via a flexure array 313. In this embodiment, for each flexure of the flexure array 313, the first support end is part of the movable platform 311 of the motion stage, the second support end is directly connected to one of the rigid rods 312, and a flexible portion connects the first support end (movable platform 311) to the second support end (rigid rod 312). In various embodiments shown in FIG8 , low stiffness in two-dimensional motion can be achieved by pushing the rigid rods 312 toward each other (e.g., in the y-direction shown) so that the flexure array 313 enters a backbend region throughout its range of motion. In these embodiments, the force applied by the flexure array 313 can be offset on both sides so that there is no net force on the platform 311.

In various embodiments, a motion stage and/or a system including a motion stage may include motion limiters that limit horizontal and vertical movement of the movable platform 311 (and, accordingly, the flexure). For example, in FIG8 , the system includes a motion limiter 381 that limits movement in the vertical y-direction, and a motion limiter 382 that limits movement in the horizontal x-direction. As shown, the motion limiter 381 is incorporated into the rigid rod 312 to prevent excessive movement of the first support end of the flexure 313 relative to the second support end. The motion limiter 382 prevents horizontal displacement of the movable platform 311 relative to the rigid rod or support end 312. Thus, the motion limiters 381-382 can prevent failure of the bent portion of the flexure 313 due to excessive displacement in the x-y plane.

In additional embodiments, the flexure 313 can carry current from the movable platform 311 to the rigid end 312. In these embodiments, the flexure 313 can carry current to the electronic components of the motion stage (e.g., an image sensor). For example, electric pads can contact the electronic components of the movable platform 311 and the circuit board of the rigid end 312. In this example, each flexure support end can contact a corresponding electric pad. In implementations of these embodiments, the flexure 313 can carry current with low resistance and is designed to be as soft as possible to avoid requiring additional force on the motor (not shown) that moves the motion stage.

FIG9 is a plan view of another example embodiment of a flexure 400 according to the disclosed technology. As shown, flexure 400 includes a first support end 411, a second support end 412, and a flexible portion connecting support end 411 to support end 412. Flexure 400 has an "S"-shaped design, with the flexible portion including a long, straight portion 442, a curved portion 441 connecting straight portion 442 to support ends 411-412, and curved portions 443 connecting straight portions 442 to each other. In various embodiments, the curvature of curved portions 441 and 443, the angle between straight portions 442, and the length of straight portions 442 are designed to accommodate geometric constraints and minimize stiffness and stress in the deforming flexure.

FIG10 is a plan view of another example embodiment of a flexure 500 according to the disclosed technology. As shown, flexure 500 includes a first support end 511, a second support end 512, and a flexible portion connecting support end 511 to support end 512. Flexure 500 has a serpentine (meandering) design, with the flexible portion including a long, straight portion 542, a curved portion 541 connecting straight portion 542 to support ends 511-512, and curved portions 543 connecting straight portions 542 to each other. In various embodiments, the curvature of curved portions 541 and 543, the number of turns in the serpentine design, and the length of straight portion 542 are designed to accommodate geometric constraints and minimize stiffness and stress in the deforming flexure.

FIG11 is a plan view of another exemplary embodiment of a flexure 600 according to the disclosed technology. As shown, flexure 600 includes a first support end 611, a second support end 612, and a flexible portion connecting support ends 611 and 612. Flexure 600 has an "S"-shaped design, with the flexible portion comprising a long, straight portion 642, a curved portion 641 connecting straight portion 642 to support ends 611 and 612, and a curved portion 643 connecting the straight portions to each other.

FIG12 is a plan view of another example embodiment of a flexure 700 according to the disclosed technology. As shown, flexure 700 includes a first support end 711, a second support end 712, and a flexible portion connecting support ends 711 and 712. In flexure 700, support ends 711 and 712 are not tangentially aligned. Flexure 700 has a serpentine design, with the flexible portion comprising a long, straight vertical portion 742 and a curved portion 743 connecting portion 742 to each other and to support ends 711 and 712.

FIG13 is a plan view of another example embodiment of a flexure 800 according to the disclosed technology. As shown, flexure 800 includes a first support end 811, a second support end 812, and a long, straight flexible portion 842 connecting support ends 811 and 812. In flexure 800, support ends 811 and 812 are not tangentially aligned.

FIG14 is a plan view of another example embodiment of a flexure 900 according to the disclosed technology. As shown, flexure 900 includes a first support end 911, a second support end 912, and a flexible portion connecting support ends 911 and 912. In flexure 900, support ends 911 and 912 are not tangentially aligned. Flexure 900 has a serpentine design, with the flexible portion including a horizontal, long, straight portion 942, a vertical, long, straight portion 944, a curved portion 941 connecting vertical portion 944 to horizontal portion 942, a curved portion 943 connecting vertical portions 944 to each other, and a curved portion 945 connecting horizontal portions 942 to each other.

In various embodiments, the shape of a flexure can be summarized by counting the number of horizontal and vertical straight sections of the flexure. For example, assume that (n, m) represents a design where n is a vertical or nearly vertical straight stripe and m is a horizontal or nearly horizontal straight stripe. In this implementation, flexure 400 can be represented as (0, 3), flexure 500 can be represented as (0, 5), flexure 600 can be represented as (3, 0), flexure 700 can be represented as (5, 0), flexure 800 can be represented as (1, 1), and flexure 900 can be represented as (2, 6).

FIG15 is a plan view of an example embodiment of a variable width flexure 1000 according to the disclosed technology. As shown, flexure 1000 includes a first support end 1011, a second support end 1012, and a flexible portion 1013 connecting support end 1011 to support end 1012. Flexure 1000 has a "V"-shaped design, and flexible portion 1013 includes a long, straight portion 1042 of variable width, a curved portion 1041 connecting straight portion 1042 to support ends 1011-1012, and curved portions 1043 connecting straight portions 1042 to each other. In flexure 1000, straight portion 1042 has a variable width, which can be adjusted in different embodiments to provide flexibility in the design of the flexure, thereby adjusting the stiffness and other physical properties of the flexure, such as the electrical resistance of the flexure. It should be noted that those skilled in the art will understand that variable width can be implemented in the design of other flexures (such as those shown in Figures 5 to 14) to adjust the above-mentioned physical properties (such as resistance and stiffness).

Figure 16 is a graph of normalized force versus normalized displacement illustrating the performance of different flexure designs according to various embodiments of the disclosed technology. As shown, the flexure can have positive or negative stiffness over different post-bend operating ranges.

Figures 17A-17C illustrate an example embodiment of a flexure 1100 including an offset layer according to the disclosed technology. Figures 17A and 17B are top and bottom plan views of the flexure 1100 after fabrication. Figure 17C is a three-dimensional perspective view of the flexure 1100 in a bent state. As shown, the flexure 1100 includes a metal layer 1110, a third layer 1130, and a polysilicon layer 1120 between the metal layer 1110 and the third layer 1130. In these embodiments, the third layer may include silicon oxide or a similar material. In the flexure 1100, the metal layer 1110 and the polysilicon layer 1120 are offset from the third layer 1130, thereby providing a stress-reducing benefit on the flexure 1100 when the flexure 1100 enters the bent state shown in Figure 17C.

Additionally, flexure 1100 includes a variable-width flexible portion that is narrower near the base of the flexure (i.e., the curved portion directly connected to support ends 1111 and 1112) and wider at the center of the flexible portion. In this embodiment, the narrower width near support ends 1111 and 1112 can reduce the stiffness of flexure 1100 in a bent state. The wider width at the center of the flexible portion can increase the electrical resistance of flexure 1100.

Figures 18A-18C illustrate an example embodiment of a flexure 1200 including a split root according to the disclosed technology. Figures 18A and 18B are top and bottom plan views of flexure 1200. Figure 18C is a three-dimensional perspective view of flexure 1200 in a bent state. As shown, flexure 1200 includes a split root of metal 1210 and polysilicon 1220 at a bent portion 1250A-B directly connected to support ends 1211 and 1212 (i.e., near the root end of the flexure). In these embodiments, third layer 1230 and metal layer 1220 may also be split.

Figures 19A-19B illustrate an example embodiment of a flexure 1300 including layers of varying lengths according to the disclosed technology. Figure 19A is a plan view, and Figure 19B is a three-dimensional perspective view of flexure 1300. As shown, flexure 1300 includes a metal layer 1310 and a silicon oxide layer 1320 partially above metal layer 1310. In flexure 1300, only metal layer 1310 covers the entire length of the flexure, thereby ensuring lower stress and lower stiffness for flexure 1300. In contrast, silicon oxide layer 1320 covers only the ends of the flexure (support portions 1311-1312 and the ends of the flexible portion), thereby ensuring that the flexure bends in the correct direction. In these embodiments, layer 1320 can be silicon oxide or any other material that provides residual stress that causes metal flexure 1300 to bend upward in the desired direction. As will be understood by those skilled in the art, the lengths of the layers of the flexure can be varied to adjust the physical properties of the flexure, such as its stiffness and electrical resistance.

Figures 20 to 22A-22D illustrate an actuator for moving an optoelectronic device that may utilize the flexures described herein according to specific embodiments. Figure 20 illustrates a plan view of a comb drive 10 that may be implemented in a comb drive actuator according to embodiments. Comb drive 10 may be an electrostatic comb drive. Comb drive 10 may include comb arrays 15 and 16 that may be fabricated on silicon using MEMS processes, such as photolithography and etching.

As shown, comb array 16 includes teeth 11 and ridges 12 connecting teeth 11. Similarly, comb array 15 includes teeth 13 and ridges 14 connecting teeth 13. Teeth 11 and 13 may be interdigitated so that spaces 17 between teeth 11 are substantially aligned, and spaces 18 between teeth 13 are substantially aligned.

When a voltage is applied between the comb teeth 11 and the comb teeth 13, the comb array 16 and the comb array 15 attract or repel each other through an electrostatic force that is proportional to the square of the applied voltage. This electrostatic force can cause the comb arrays 15 and 16 to move toward or away from each other, depending on the polarity of the electrostatic force (or voltage). In addition, the speed at which the comb arrays 15 and 16 move relative to each other can depend on the applied electrostatic force. Typically, the design of the comb drive 10 is such that the comb teeth 11 and 13 can be pulled into or pushed out of an overlapping state by the electrostatic force between the comb arrays 15 and 16. When the comb arrays 15 and 16 overlap, the comb teeth 11 remain at least partially within the space 17 of the comb array 15, and the comb teeth 13 remain at least partially within the space 18 of the comb array 16.

The ratio of comb teeth width to depth can be selected to prevent comb teeth 11 from bending into comb teeth 13 when comb teeth 11 and 13 are overlapped. For example, comb teeth 11 and/or 13 can be approximately 6 microns wide by approximately 150 microns long. Typically, comb teeth 11 and/or 13 can be between approximately 1 and 10 microns wide and approximately 20 and 500 microns long. When overlap is achieved by electrostatic forces, the total gap between comb teeth 11 and 13 can be determined by subtracting the distance between two adjacent comb teeth 11 (or 13) from the width of one of the corresponding comb teeth 13 (or 11). In some cases, it may be desirable to keep this total gap relatively small to increase the electrostatic force between comb teeth 11 and 13. Furthermore, it may be desirable to keep the total gap large enough to account for variations in the width of comb teeth 11 and/or 13 resulting from process variations. For example, the total gap can be approximately 5 to 10 microns.

The depth of the teeth 11 and 13 can generally be limited by the specific manufacturing process used, particularly the etching aspect ratio of that process, since it is generally desirable that the width of the teeth 11 and 13 at the top be substantially the same as the width of the teeth 11 and 13 at the bottom (the depth of the teeth 11 and 13 is not shown in FIG. 20 , but they will extend into or out of the page). For example, the depth of the teeth 11 and 13 can be approximately 50 to 250 microns. The spaces 17 and 18 can be etched away completely, or can be removed by other methods known in the art of MEMS microfabrication.

FIG21A shows a plan view of a comb drive actuator according to an example embodiment of the present disclosure. As shown in FIG21A , the comb drive actuator includes comb tooth arrays 15 and 16 (some details of which, such as spines 12 and 14, are shown in FIG20 , but not in FIG21A ), a first frame member 21, and a second frame member 19. Although not shown in detail in FIG21A , the comb teeth 11 and 13 extend from left to right within the comb tooth arrays 15 and 16, and vice versa. The spine 14 of the comb tooth array 15 can be attached to the second frame member 19, while the spine 12 of the comb tooth array 16 can be attached to the first frame member 21. This configuration allows for movement of the comb tooth arrays 15 and 16 due to attraction or repulsion, which in turn causes movement of the first frame member 21 and the second frame member 19 (e.g., from left to right, or vice versa, from right to left, in FIG21A ).

FIG21B illustrates a plan view of a comb-drive actuator 20 according to an example embodiment of the present disclosure. As shown in FIG21B , one embodiment of the comb-drive actuator 20 includes one or more comb drives 10 arranged in a substantially parallel manner. In the specific embodiment of FIG21B , there are nine comb drives 10 shown, but different embodiments of the comb-drive actuator 20 may include comb drives 10 of any number, size, and shape. The comb-drive actuator 20 further includes a first frame 22, a second frame 24, and a motion control device 26. The first frame 22 is shown as having a stepped shape, resulting in the comb drives 10 shown in this specific embodiment of the comb-drive actuator 20 having variable lengths. However, in other embodiments (e.g., where all comb drives 10 are of uniform length), the shape of the first frame 22 may vary to allow attachment to the ends of the comb drives 10. In the illustrated embodiment, the stepped shape of the first frame 22 and the corresponding reduced length of the comb drives 10 allow for a reduced footprint of the actuator 30, as will be shown in FIG22A . As will be understood by those skilled in the art upon reading this disclosure, other variations in the length, shape, arrangement, and structure of comb drive 10 may be used to achieve varying degrees, directions, and/or precision of controlled force, various sized footprints, and other characteristics.

While the details of each comb drive 10 are not shown in FIG21B , in the embodiment shown in FIG21B , the spine 12 is connected to the first frame 22, and the spine 14 is connected to the second frame 24. FIG21A illustrates one method for achieving this effect. In different embodiments, the spines 12 and 14 of the comb arrays 15 and 16 can be attached to the first frame 22 and the second frame 24 in different configurations to achieve different purposes. For example, in one embodiment, for each comb drive 10 in a group of comb drives, the spine 12 is attached to the first frame 22, while the spine 14 is attached to the second frame 24. This configuration creates a parallel cascade arrangement of the comb drives 10, which can increase the electrostatic force ultimately applied to the first and second frames 22, 24. In another example embodiment, the comb drives 10 are arranged back-to-back to achieve bidirectional motion. In this configuration, for the first comb drive 10, the spine 12 is connected to the first frame 22, and the spine 14 is connected to the second frame 24. However, for the second comb drive 10, the spine 12 is connected to the second frame 24 and the spine 14 is connected to the first frame 22. This configuration results in a back-to-back placement of the comb drives 10, which allows for bi-directional motion.

Further, with respect to comb drive actuator 20, in various cases, comb drive spines 12 and 14 and first and second frames 22 and 24 can be designed to be sufficiently wide and deep so as to be rigid and substantially non-bending under a range of applied electrostatic forces. For example, spines 12 and 14 can be approximately 20 to 100 microns wide and approximately 50 to 250 microns deep, and first and second frames 22 and 24 can be greater than approximately 50 microns wide and approximately 50 to 250 microns deep.

As described above, one embodiment of the comb drive actuator 20 also includes a motion control device 26 that constrains the motion of the comb tooth arrays 15 and 16 to be substantially parallel to the length of the comb teeth 11 and 13 (e.g., from left to right in FIG. 21B ). In one example implementation of the present disclosure, the motion control device 26 is a dual parallel flexure motion control device, such as shown in FIG. 21B . The dual parallel flexure motion control device can produce nearly linear motion, but there may be slight runout (called arcing motion). However, the gap on one side of the comb teeth 11 may not be equal to the gap on the other side of the comb teeth 11, which can be advantageously used in the design to correct for effects such as arcing motion of the dual parallel flexure motion control device.

Referring again to the embodiment of the comb drive actuator 20 shown in FIG. 21B , the motion control device 26 is a dual parallel flexure. However, the motion control device 26 may include other structures for controlling the motion of the first frame 22 and the second frame 24. In the illustrated embodiment, each motion control device 26 includes thinner portions 25 and 27 at respective ends of the motion control device 26. The thinner portions 25 and 27 allow for flexure as the first frame 22 translates relative to the second frame 24. In terms of dimensions, the thicker portion of the motion control device 26 may be, for example, approximately 10 to 50 microns wide, while the thinner portions 25 and 27 may be approximately 1 to 10 microns wide. In various embodiments, any number and type of motion control devices 26 may be used as needed to control or limit the motion of the comb arrays 15 and 16. Controlled motion can enhance the overall precision with which the actuator 30 moves or positions the platform 45.

FIG22A shows a plan view of an actuator 30 according to an example embodiment of the present disclosure. FIG22B shows a cross-sectional view of an actuator 30 according to an example embodiment of the present disclosure. As shown in FIG22A , the actuator 30 includes an outer frame 32 connected to an inner frame 34 via one or more spring elements 33. Furthermore, the actuator 30 includes one or more comb drive actuators 20 that apply a controlled force (e.g., an electrostatic force generated by a voltage) between the outer frame 32 and the inner frame 34. Embodiments of the actuator 30 are suitable for moving a platform (e.g., 45) having an electrical connection because the actuator 30 enables precise, controlled, and variable forces to be applied between the inner frame 34 and the outer frame 32 in multiple degrees of freedom (e.g., including linear and rotational), and the actuator 30 can be implemented in a very compact footprint. Furthermore, the actuator 30 can utilize MEMS devices to reduce energy consumption. Thus, actuator 30 may provide several benefits over conventional solutions for optical image stabilization and autofocus applications that are constrained by size, power consumption, cost, and performance parameters, such as in smartphones and other applications described herein.

As described with reference to FIG21B , each comb drive actuator 20 includes one or more comb drives 10. Spring elements 33 can be electrically conductive and flexible in all degrees of freedom of motion. In various embodiments, spring elements 33 transmit electrical signals from electrical contact pads on outer frame 32 to electrical contact pads on inner frame 34. In example implementations, spring elements 33 extend from inner frame 34 in one direction, two directions, three directions, or all four directions.

In one embodiment, actuator 30 is fabricated using MEMS technology, such as photolithography and etching of silicon. In one embodiment, actuator 30 moves +/- 150 microns in a plane, and spring elements 33 are designed to allow this range of motion without contacting each other (e.g., so that independent electrical signals can be sent to different spring elements 33). For example, spring element 33 can be an S-shaped flexure having dimensions ranging from approximately 1 to 5 microns in thickness, approximately 2 to 20 microns in width, and approximately 150 to 1000 microns by approximately 150 to 1000 microns in a plane.

To make the spring elements 33 conduct electricity very well with low resistance, the spring elements 33 may comprise, for example, heavily doped polysilicon, silicon, a metal (e.g., aluminum), combinations thereof, or other conductive materials, alloys, and the like. For example, the spring elements 33 may be made of polysilicon and coated with a metal stack of aluminum, nickel, and gold approximately 2000 angstroms thick. In one embodiment, some of the spring elements 33 are designed differently than the other spring elements 33 to control movement between the outer frame 32 and the inner frame 34. For example, four to eight (or some other number) of the spring elements 33 may have a device thickness between approximately 50 and 250 microns. This thickness may slightly restrict out-of-plane movement of the outer frame 32 relative to the inner frame 34.

In another embodiment, the actuator 30 includes a central anchor 36, and the one or more comb drives 20 apply a controlled force between the inner frame 34 and the central anchor 36. In this embodiment, the first frame 22 is connected to or is a major portion of the central anchor 36. The one or more comb drive actuators 20 can be attached to the central anchor 36 in other ways, and the central anchor 36 can be mechanically fixed relative to the outer frame 32. In one embodiment, the second frame 24 is connected to the inner frame 34 via flexures 35 that are relatively stiff in the direction of motion of the corresponding comb drive actuator and relatively flexible in an orthogonal direction. This allows for controlled movement of the inner frame 34 relative to the outer frame 32, resulting in more precise positioning.

In some implementations of the actuator 30, the outer frame 32 is not continuous around the perimeter of the actuator 30, but is instead divided into two, three, or more pieces. For example, FIG22C and FIG22D illustrate a plan view and a cross-sectional view of the actuator 30 according to an example embodiment of the present disclosure, in which the outer frame 32 is divided into two parts, and the spring element 33 extends only in two directions. Similarly, in different embodiments, the inner frame 34 can be continuous or divided into multiple parts.

22A , there may be a total of four comb drives 10, two comb drives 10 actuating in one direction in the plane of the actuator 30, and two comb drives 10 actuating in orthogonal directions in the plane of the actuator 30. Various other arrangements of comb drive actuators 20 are possible. Such arrangements may include more or fewer comb drives 10 and may actuate in more or fewer degrees of freedom (e.g., in a triangular, pentagonal, hexagonal formation, etc.), as will be understood by those skilled in the art upon reading this disclosure.

In one embodiment, platform 45 is attached to outer frame 32 and to central anchor 36. In this manner, platform 45 can secure outer frame 32 relative to central anchor 36 (and/or vice versa). Inner frame 34 can then move relative to outer frame 32 and central anchor 36, and also relative to platform 45. In one embodiment, platform 45 is a silicon platform. In various embodiments, platform 45 is an optoelectronic device, or an image sensor, such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor.

FIG22B illustrates that the dimensions of the actuator 30 can be substantially the same as the dimensions of the platform 45, and that the platform 45 can be attached to the outer frame 32 and the central anchor 36, thereby mechanically fixing the central anchor 36 relative to the outer frame 32. In one example implementation, the platform 45 is an Omni Vision OV8835 image sensor having a 1/3.2" optical format. In this implementation, the dimensions of the actuator 30 and the platform 45 can be equal to approximately 6.41 mm x 5.94 mm. As shown in FIG22D , in one embodiment of the actuator 30, the platform 45 is smaller than the actuator 30, and the platform 45 is attached to the inner frame 34. In this particular embodiment, the outer frame 32 is fixed relative to the inner frame 34, and the inner frame 34 is moved using a different comb drive actuator 20.

Although different embodiments of the present invention have been described above, it should be understood that they are presented only by way of example and are not intended to be limiting. Similarly, different diagrams may depict example structures or other configurations of the present invention, which are used to help understand the features and functions that may be included in the present invention. The present invention is not limited to the example structures or configurations shown, but may be implemented with a variety of alternative structures and configurations to achieve the desired features. In fact, it will be apparent to those skilled in the art how to implement alternative functions, logical or physical partitioning and configurations to achieve the desired features of the present invention. Moreover, a variety of different component module names other than those described herein may be applied to each part. In addition, with respect to the claimed flowcharts, operational descriptions, and methods, the order of the steps proposed herein should not force different embodiments to be implemented as performing the functions in the same order, unless the context indicates otherwise.

Although the present invention has been described above in terms of various representative embodiments and implementations, it should be understood that the various features, aspects, and functions described in one or more of the various embodiments are not limited in applicability to the specific embodiment through which they are described, but may be applied alone or in various combinations to one or more of other embodiments of the present invention, whether or not such embodiment is described, and whether or not such features are proposed as part of such embodiment. Accordingly, the breadth and scope of the present invention should not be limited by any of the above-described representative embodiments.

The terms and phrases used in this document, and variations thereof, unless expressly stated otherwise, should be interpreted as open ended, not restrictive. As in the examples above: the term "including" should be interpreted as meaning "including, but not limited to," etc.; the term "example" is used to provide representative examples of the items being discussed, not an exhaustive or limiting list thereof; the terms "a" or "an" should be interpreted as meaning "at least one," "one or more," etc.; adjectives such as "conventional," "customary," "normal," "standard," "known," and terms of similar meaning should not be interpreted as limiting the items described to a set period or to items available at a set time, but should be interpreted as encompassing conventional, customary, normal, or standard technology that may be available or known now or at any time in the future. Similarly, where this document refers to technology that would be obvious or known to one of ordinary skill in the art, such technology encompasses those technologies that would be obvious or known to one of ordinary skill in the art now or at any time in the future.

The presence in some instances of expanded words and phrases (e.g., "one or more," "at least," "but not limited to," or other similar phrases) should not be taken to indicate that narrower context is desired or required where such expanded phrases may not exist. The use of the term "module" does not imply that the components or functionality described or claimed as part of the module are all constructed in a common package. In fact, any or all of the various components of the module (whether control logic or other components) may be combined in a single package, or maintained separately, and may be further distributed among multiple combinations or packages, or distributed among multiple locations.

In addition, the various embodiments described herein are described in terms of representative block diagrams, flow charts, and other illustrations. As will be apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives may be implemented without limitation to the examples shown. For example, the block diagrams and their associated descriptions should not be construed as mandating the use of a particular structure or configuration.

Claims (22)

1. A flexible member, comprising: The first support end is connected to the first frame; The second support end is connected to the second frame; and The bending portion connects the first support end to the second support end, wherein the bending portion bends in both the radial and tangential directions; Wherein, the length of the flexure is greater than the width of the flexure, the thickness of the flexure is less than the width of the flexure, and the width of the first support end and the second support end is greater than the bending portion connecting the first support end to the second support end. 2. The flexural member according to claim 1, wherein the flexural member comprises a polycrystalline silicon layer. 3. The flexural member according to claim 1, wherein the flexural member includes a metal layer and is conductive. 4. The flexible member according to claim 1, wherein the bent portion connecting the first support end and the second support end has an uneven width. 5. The flexible member according to claim 1, wherein the flexible member, in its unbent state, comprises: First straight section; The second straight section; and The curved portion connects the first straight portion to the second straight portion. 6. The flexural member according to claim 1, wherein the stiffness of the flexural member in the bent state is at least one order of magnitude smaller than the stiffness of the flexural member in the unbent state. 7. The flexural member according to claim 1, wherein the stiffness of the flexural member in the bending state is a positive pre-bending stiffness. 8. The flexural member according to claim 1, wherein the stiffness of the flexural member in the bending state is a negative pre-bending stiffness. 9. The flexible member according to claim 1, wherein the bent portion bends in the radial direction between the first support end and the second support end, and wherein the bent portion bends in the tangential direction to the first support end and the second support end. 10. The flexural member according to claim 1, wherein the bent portion is serpentine. 11. The flexural member according to claim 1, wherein the first support end and the second support end are not tangentially aligned. 12. The flexure of claim 2, wherein the flexure further comprises a conductive metal layer, and wherein the metal layer and the polysilicon layer are offset. 13. The flexure of claim 2, wherein the flexure further comprises a conductive metal layer, and wherein the metal layer and the polysilicon layer are split at at least a portion of the bent portion. 14. The flexure of claim 3, further comprising a silicon oxide layer, wherein the metal layer covers the entire length of the flexure, and wherein the silicon oxide layer covers the first support end, the second support end, and the ends of the bent portion that are connected only to the first support end and the second support end. 15. A platform including an array of flexures, the array of flexures comprising a plurality of flexures connecting a first frame and a second frame, wherein: The first frame and the second frame are on the same plane; The array of flexures is located on the plane before being bent by the plurality of flexures; Furthermore, the array of flexures bends away from the plane after being bent by the plurality of flexures, wherein the plurality of flexures includes a plurality of first support ends and a plurality of second support ends connected by a plurality of bending portions, wherein the plurality of first support ends and the plurality of second support ends have a width wider than the plurality of bending portions, and one or more of the plurality of bending portions bend in the radial direction and in the tangential direction. 16. The platform of claim 15, wherein the length of each of the plurality of flexures is greater than its width. 17. The platform of claim 15, wherein each of the plurality of flexures is conductive. 18. The platform of claim 15, wherein the flexural array has low stiffness in at least one degree of freedom. 19. The platform of claim 15, wherein each of the plurality of flexures comprises at least two layers of material, and wherein at least one layer of material is metal. 20. The platform of claim 15, further comprising a motion limiter configured to prevent malfunction of the plurality of bent flexures by limiting the movement of the flexure array. 21. A method for manufacturing a flexural component, comprising: Provide flexible components with a length greater than their width and thickness; Move the flexure until it bends; and The flexural member is held in a bent state, wherein the width of the first support end and the second support end connected by the bent portion is wider than the bent portion connecting the first support end to the second support end, wherein the bent portion is bent in both the radial and tangential directions. 22. The method of claim 21, further comprising using a motion limiter to restrict the movement of the flexure to prevent the flexure from malfunctioning in a bent state.