A flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips

Abstract

The present invention relates to the technical field of mass transfer of LED chips, and in particular to a flexible constant-force suspension leveling micro-motion platform for mass transfer of Micro LED chips. It comprises a moving platform and a base, a plurality of piezoelectric drive units are provided between the moving platform and the base, the piezoelectric drive units are used to correct the deviation of the moving platform, and a plurality of flexible constant-force support units, at least one flexible support unit and at least one set of limiting devices are also provided between the moving platform and the base; one end of the flexible constant-force support unit is connected to the moving platform, and the other end is connected to the base, for bearing the gravity of the moving platform and the load; one end of the flexible support unit is connected to the moving platform, and the other end is connected to the base, for adjusting the stiffness of the moving platform; one end of the limiting device is connected to the moving platform, and the other end is connected to the base, for limiting the maximum longitudinal displacement of the moving platform. The flexible constant-force support unit is in a constant-force suspension state to bear the large load of the moving platform, and then combined with the correction effect of the piezoelectric drive unit to achieve large-stroke feeding and leveling, so as to meet the position requirements between the chip carrier and the target substrate.

Description

Technical Field

[0001] The present invention relates to the technical field of mass transfer of LED chips, and in particular to a flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips. Background Art

[0002] The mass transfer process for Micro LED chips requires mass transfer of Micro LED chips ranging in size from 10μm to 50μm from a chip carrier to a target substrate, with a transfer accuracy of less than 1μm and a transfer yield greater than 99.9999%. Misalignment between the chip carrier and the target substrate can make it difficult for the chip to precisely align with the target substrate's electrodes after it falls, reducing the transfer yield and directly impacting product performance. Since the distance between the chip carrier and the target substrate during mass transfer is typically 50μm, misalignment can lead to collisions between the two. Therefore, ensuring relative parallelism between the chip carrier and the target substrate is crucial. Micro-motion platforms based on piezoelectrically driven flexible transmission have proven to offer significant advantages in precision chip packaging processes, but their application to leveling and positioning for mass transfer of Micro LED chips still presents challenges: the Micro LED leveling and correction system must support a heavy load of 20-25kg and achieve closed-loop positioning with a long range of millimeters along the z-axis. However, the load capacity of the piezoelectric-driven flexible mechanism is limited, and the load capacity is generally within 10kg. In addition, the driving stroke of the piezoelectric-driven flexible mechanism is limited and cannot reach the millimeter level. If a support spring is used, the load capacity can be improved, but the driving force requirement will be increased at the same time, and the balance position requirement is high. The spring is prone to cause eccentric load and collision, and when the z-direction space is limited, the spring structure design is difficult.

[0003] Therefore, it is necessary to start from other directions and provide a closed-loop positioning platform with a large load-bearing mass and a large stroke of millimeters along the z-axis. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a closed-loop positioning platform with a large bearing mass and capable of achieving a long travel range of millimeters along the z-axis direction.

[0005] To solve the above problems, the present invention adopts a technical solution: a flexible constant-force suspension leveling micro-motion platform for mass transfer of Micro LED chips, comprising a moving platform and a base, a plurality of piezoelectric drive units disposed between the moving platform and the base, a plurality of flexible constant-force support units and at least one flexible support unit disposed between the moving platform and the base;

[0006] One end of the flexible constant force support unit is connected to the moving platform, and the opposite end is connected to the base, which is used to support the gravity of the moving platform and the load;

[0007] One end of the piezoelectric drive unit is connected to the moving platform, and the other end is connected to the base, which is used to drive the moving platform to achieve large-stroke feeding and leveling;

[0008] One end of the flexible support unit is connected to the moving platform, and the opposite end is connected to the base, which is used to lock the flexible constant force support unit in the constant force range and adjust the connection stiffness between the moving platform and the base;

[0009] Preferably, the flexible constant force support unit includes a flexible constant force mechanism and a multi-axis flexible hinge three above the center of the flexible constant force mechanism, the multi-axis flexible hinge three is connected to the dynamic platform, and the flexible constant force mechanism is connected to the base.

[0010] Preferably, the flexible constant force mechanism includes a bracket, the bottom end of the bracket is connected to the base, a polygonal frame is provided near the bottom of the bracket, the lowest vertex of the polygonal frame is connected to the inner side of the bottom end of the bracket, the remaining vertices of the polygonal frame do not contact the bracket, the vertex opposite to the lowest vertex of the polygonal frame is the highest vertex of the polygonal frame, the highest vertex of the polygonal frame is connected to the three bottom ends of the multi-axis flexible hinge, and the three top ends of the multi-axis flexible hinge are connected to the dynamic platform;

[0011] A flexible bistable mechanism is also provided above the polygonal frame. The two ends of the flexible bistable mechanism are respectively connected to the inner sides of the two side edges of the bracket. The top vertex of the polygonal frame is passed through the midpoint of the flexible bistable mechanism and is connected to the three bottom ends of the multi-axis flexible hinge; the flexible bistable mechanism is divided into two symmetrical parts by the top vertex of the polygonal frame, one side is the left half and the other side is the right half.

[0012] Preferably, the polygonal frame is a rhombus, each side of the polygonal frame is a rectangular beam type flexible hinge 1, and each side of the flexible bistable mechanism is a rectangular beam type flexible hinge 3.

[0013] Preferably, the piezoelectric drive unit includes a diamond-shaped displacement amplification mechanism, the piezoelectric ceramic stack is located in the diamond-shaped displacement amplification mechanism and coincides with the horizontal diagonal of the diamond-shaped displacement amplification mechanism, the two vertices of the vertical diagonal of the diamond-shaped displacement amplification mechanism are respectively connected to the multi-axis flexible hinge 1 and the multi-axis flexible hinge 2; the top end of the multi-axis flexible hinge 1 is connected to the moving platform, and the bottom end of the multi-axis flexible hinge 2 is connected to the base; the four sides of the diamond-shaped displacement amplification mechanism are all rectangular beam-type flexible hinges 2;

[0014] The diamond-shaped displacement amplification mechanism can amplify and guide the output displacement of the piezoelectric ceramic stack.

[0015] Preferably, a preload spring is provided in parallel with the piezoelectric ceramic stack, and the preload spring is connected to two vertices of the diamond-shaped displacement amplification mechanism.

[0016] Preferably, the flexible support unit is arranged between the moving platform and the base, and is located at the axis of the moving platform or is symmetrically distributed relative to the axis of the moving platform.

[0017] Preferably, at least one set of limiting devices is provided between the moving platform and the base, one end of the limiting device is connected to the moving platform, and the opposite end is connected to the base, and is symmetrically distributed relative to the axis of the moving platform, for limiting the maximum longitudinal displacement of the moving platform.

[0018] Preferably, the limiting device includes an upper limiting part and a lower limiting part, the upper limiting part is a positive L-shape and the top of the vertical part is connected to the moving platform, the lower limiting part is an inverted L-shape and the bottom of the vertical part is connected to the base, and the horizontal part of the upper limiting part is located directly below the horizontal part of the lower limiting part and the two can offset each other.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. Introducing a flexible constant force support unit to replace the traditional spring to offset the influence of gravity on the dynamic platform and chip carrier, achieving near zero stiffness and near suspension effect, which is conducive to achieving high-precision and high-speed control;

[0021] 2. The flexible constant force mechanism has a constant force range, which can be customized according to the chip carrier to meet the requirements of installation error and large z-direction travel. The piezoelectric drive unit is combined to correct the dynamic platform to achieve the position requirements between the chip carrier and the target substrate.

[0022] 3. The flexible constant force mechanism is simpler and more compact, while the existing large stroke adjustment mechanism, such as the air float structure, is more complicated;

[0023] 4. The flexible constant force mechanism has the ability to maintain suspension when power is off. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention;

[0025] Figure 2 It is a structural schematic diagram of the flexible constant force support unit of the present invention;

[0026] Figure 3 Schematic diagram of the structure of the piezoelectric drive unit of the present invention;

[0027] Figure 4 This is a schematic diagram of the suspension principle of the flexible constant force support unit of the present invention;

[0028] Explanation of the accompanying drawings: 1. Moving platform; 2. Base; 3. Flexible constant force support unit; 31. Flexible constant force mechanism; 32. Bracket; 33. Multi-axis flexible hinge three; 34. Polygonal frame; 35. Rectangular beam type flexible hinge one; 36. Flexible bistable mechanism; 361. Left half; 362. Right half; 4. Piezoelectric drive unit; 41. Multi-axis flexible hinge one; 42. Multi-axis flexible hinge two; 43. Piezoelectric ceramic stack; 44. Rectangular beam type flexible hinge two; 45. Diamond displacement amplification mechanism; 46. Preload spring; 5. Flexible support unit; 6. Limiting device; 61. Limit upper part; 62. Limit lower part. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described to better illustrate the principles of the invention and its practical application, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for specific applications.

[0030] like Figure 1-3 As shown, a flexible constant-force suspension leveling micro-motion platform for mass transfer of Micro LED chips includes a moving platform 1 and a base 2. The moving platform 1 is used to carry a chip carrier or a target substrate. A plurality of piezoelectric drive units 4 are provided between the moving platform 1 and the base 2. The piezoelectric drive units 4 are used to drive the moving platform 1 to achieve large-stroke feeding and leveling. Four flexible constant-force support units 3 are also provided between the moving platform 1 and the base 2. The four flexible constant-force support units 3 are symmetrically and evenly distributed around the central axis of the moving platform 1; a flexible support unit 5 is provided on the central axis of the moving platform 1, and two limit devices 6 are symmetrically provided on both sides of the central axis of the moving platform 1. , the limit device 6 is located on the outside of the flexible constant force support unit 3; one end of the flexible constant force support unit 3 is connected to the moving platform 1, and the opposite end is connected to the base 2, which is used to support the gravity of the moving platform 1 and the load on the moving platform 1; one end of the flexible support unit 5 is connected to the moving platform 1, and the opposite end is connected to the base 2. The flexible support unit 5 is used to lock the flexible constant force support unit 3 in the constant force suspension interval and adjust the connection stiffness between the moving platform 1 and the base 2; one end of the limit device 6 is connected to the moving platform 1, and the opposite end is connected to the base 2. The limit device 6 is used to limit the maximum longitudinal displacement of the moving platform 1.

[0031] The flexible constant force support unit 3 includes a flexible constant force mechanism 31 and a multi-axis flexible hinge 33 above the center of the flexible constant force mechanism 31. The multi-axis flexible hinge 33 is connected to the dynamic platform 1, and the flexible constant force mechanism 31 is connected to the base 2. The flexible constant force mechanism 31 includes a bracket 32, the bottom end of the bracket 32 ​​is connected to the base 2, and a polygonal frame 34 is set near the bottom of the bracket 32. Each side of the polygonal frame 34 is a rectangular beam-type flexible hinge 35. When the polygonal frame 34 is a rhombus, as shown in FIG. Figure 2 As shown, the lowest vertex of the polygonal frame 34 is connected to the inner side of the bottom end of the bracket 32, and the other vertices of the polygonal frame 34 are not in contact with the bracket 32. The vertex opposite to the lowest vertex of the polygonal frame 34 is the highest vertex of the polygonal frame 34. The highest vertex of the polygonal frame 34 is connected to the bottom end of the multi-axis flexible hinge 33, and the top of the multi-axis flexible hinge 33 is connected to the dynamic platform 1; a flexible bistable mechanism 36 is also provided above the polygonal frame 34, and the two ends of the flexible bistable mechanism 36 are respectively connected to the inner sides of the two sides of the bracket 32, and the highest vertex of the polygonal frame 34 is sleeved through the flexible bistable mechanism 36. The midpoint of the stable mechanism 36 is connected to the bottom end of the multi-axis flexible hinge three 33; the flexible bistable mechanism 36 is divided into two symmetrical parts by the top vertex of the polygonal frame 34, one side is the left half 361, and the other side is the right half 362. The angle between the left half 361 and the right half 362 is α, and the degree of α satisfies the interval (0, 180). The angle between the left half 361 and the vertical direction is β, and the degree interval of β is (0, 90). The angle between the right half 362 and the vertical direction also satisfies the degree interval of β; each side of the flexible bistable mechanism 36 is a rectangular beam-type flexible hinge three.

[0032] The piezoelectric drive unit 4 includes a diamond-shaped displacement amplification mechanism 45. The piezoelectric ceramic stack 43 forms the horizontal diagonal of the diamond-shaped displacement amplification mechanism 45. The two vertices of the vertical diagonal of the diamond-shaped displacement amplification mechanism 45 are connected to multi-axis flexible hinge 1 41 and multi-axis flexible hinge 2 42, respectively. The top of multi-axis flexible hinge 1 41 is connected to the dynamic platform 1, and the bottom of multi-axis flexible hinge 2 42 is connected to the base 2. Each of the four sides of the diamond-shaped displacement amplification mechanism 45 is connected to rectangular beam-shaped flexible hinge 2 44, which amplifies and guides the output displacement of the piezoelectric ceramic stack. A preload spring 46 is arranged parallel to the piezoelectric ceramic stack 43 and connected to the two vertices of the horizontal diagonal of the diamond-shaped displacement amplification mechanism 45 to enhance the stability of the piezoelectric ceramic stack 43. The working principle of the piezoelectric drive unit 4 is that after the piezoelectric ceramic stack 43 is energized, the piezoelectric ceramic stack 43 extends to both sides in the horizontal direction. Since the four sides of the diamond displacement amplification mechanism 45 are rectangular beam-type flexible hinges 2 44, the piezoelectric ceramic stack 43 extends to both sides in the horizontal direction, driving the diamond displacement amplification mechanism 45 to deform, causing the horizontal diagonal to become longer, and the vertical diagonal of the diamond displacement amplification mechanism 45 to shorten. The vertical diagonal of the diamond displacement amplification mechanism 45 drives the multi-axis flexible hinge 1 41 to move downward, and then drives a corner of the moving platform 1 to deflect downward. Since multiple piezoelectric drive units 4 are set, if any position of the moving platform 1 does not meet the requirements, the corresponding piezoelectric drive unit 4 can be controlled to perform leveling and deviation correction adjustments.

[0033] The flexible support unit 5 is arranged between the moving platform 1 and the base 2, located at the axis of the moving platform 1 or symmetrically distributed relative to the axis of the moving platform 1. The function of the flexible support unit 5 is, on the one hand, to maintain the flexible constant force support unit 3 in the constant force suspension range, and on the other hand, to adjust the connection stiffness between the moving platform 1 and the base 2.

[0034] The limiter 6 is disposed between the movable platform 1 and the base 2, symmetrically distributed about the axis of the movable platform 1. It is used to limit the maximum longitudinal displacement of the movable platform 1. The limiter 6 comprises an upper limiter portion 61 and a lower limiter portion 62. The upper limiter portion 61 is a positive L-shaped portion, with the top of its vertical portion connected to the movable platform 1. The lower limiter portion 62 is an inverted L-shaped portion, with the bottom of its vertical portion connected to the base 2. The transverse portion of the upper limiter portion 61 is located directly below the transverse portion of the lower limiter portion 62, and the two can offset each other. The initial distance between the transverse portions of the upper limiter portion 61 and the lower limiter portion 62 is the maximum longitudinal displacement of the movable platform 1.

[0035] like Figure 4As shown, straight line L1 is the curve of the relationship between the force and displacement of the rectangular beam-type flexible hinge 35, curve S2 is the curve of the relationship between the force and displacement of the flexible bistable mechanism 36, and curve S1 is the curve of the relationship between the force and displacement of the flexible constant force mechanism 31. The longitudinal force value of S1 is equal to the sum of the longitudinal force value of L1 and the longitudinal force value of S2. The intersection A is the direction conversion point of the force of the flexible bistable mechanism 36. The area between points C and D is the constant force suspension interval of the flexible constant force mechanism 31. At this time, the flexible constant force mechanism 31 is in a quasi-zero stiffness state. The intersection B is the midpoint of the constant force suspension interval, which is an ideal equilibrium state. The displacement difference between points C and D is the large-stroke closed-loop interval we need. The displacement interval between points C and D is the constant force suspension interval. The curve S1 formed by superimposing straight line L1 and curve S2 in the constant force suspension interval is shown as follows. Figure 4 The feature shown in is that when the displacement of the flexible constant force mechanism 31 is between the displacement value of point C and the displacement value of point D, the required force is very small, the moving platform is approximately suspended, and the piezoelectric drive unit 4 only needs a very small force to complete the adjustment of the moving platform 1 when correcting the moving platform 1.

[0036] During installation, first fix the flexible constant force support unit 3 on the base 2, and the flexible constant force support unit 3 is arranged in a central symmetrical manner about the center point, generally a square arrangement is selected, and then the moving platform 1 is connected to the flexible constant force support unit 3 to complete the assembly of these three parts. Under the action of the gravity of the moving platform 1 and the load on the moving platform 1, the flexible constant force support unit 3 is pushed into the constant force interval. At this time, the moving platform is in a balanced state and is in an approximately suspended state. Then, the moving platform 1 and the base 2 are connected through the flexible support unit 5, and the moving platform 1 is locked in the constant force suspension interval of the flexible constant force support unit 3. Then, the piezoelectric drive unit 4 and the limit device 6 are installed in sequence; the flexible constant force support unit 3 is designed to balance the gravity of the moving platform 1 and the load, and is in a balanced state within the constant force interval. The piezoelectric drive unit 4 is used to adjust the slight angle or z-direction displacement for correction, which solves the problem of large load in the existing technology.

Claims

1. A flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips, comprising a moving platform (1) and a base (2), wherein a plurality of piezoelectric drive units (4) are provided between the moving platform (1) and the base (2), and characterized in that: A plurality of flexible constant force support units (3) and at least one flexible support unit (5) are further provided between the moving platform (1) and the base (2); One end of the flexible constant force support unit (3) is connected to the moving platform (1), and the opposite end is connected to the base (2), and is used to support the moving platform (1) and the gravity of the load; One end of the piezoelectric drive unit (4) is connected to the moving platform (1), and the opposite end is connected to the base (2), and is used to drive the moving platform (1) to achieve large-stroke feeding and leveling; One end of the flexible support unit (5) is connected to the moving platform (1), and the opposite end is connected to the base (2), and is used to lock the flexible constant force support unit (3) in the constant force range and adjust the connection stiffness between the moving platform (1) and the base (2); The flexible constant force support unit (3) comprises a flexible constant force mechanism (31) and a multi-axis flexible hinge three (33) above the center of the flexible constant force mechanism (31), the multi-axis flexible hinge three (33) is connected to the moving platform (1), and the flexible constant force mechanism (31) is connected to the base (2); The flexible constant force mechanism (31) includes a bracket (32), the bottom end of the bracket (32) is connected to the base (2), a polygonal frame (34) is provided near the bottom of the bracket (32), the bottom vertex of the polygonal frame (34) is connected to the inner side of the bottom end of the bracket (32), the remaining vertices of the polygonal frame (34) do not contact the bracket (32), the vertex opposite to the bottom vertex of the polygonal frame (34) is the top vertex of the polygonal frame (34), the top vertex of the polygonal frame (34) is connected to the bottom end of the multi-axis flexible hinge three (33), and the top end of the multi-axis flexible hinge three (33) is connected to the moving platform (1); A flexible bistable mechanism (36) is further provided above the polygonal frame (34), and both ends of the flexible bistable mechanism (36) are respectively connected to the inner sides of the two sides of the bracket (32), and the top vertex of the polygonal frame (34) is sleeved through the midpoint of the flexible bistable mechanism (36) and connected to the bottom end of the multi-axis flexible hinge three (33); the flexible bistable mechanism (36) is divided into two symmetrical parts by the top vertex of the polygonal frame (34), one side is a left half (361), and the other side is a right half (362); the angle between the left half (361) and the right half (362) is α, and the degree of α satisfies the interval (0, 180); the angle between the left half (361) and the vertical direction is β, and the degree of β is in the interval (0, 90); The polygonal frame (34) is a rhombus, each side of the polygonal frame (34) is a rectangular beam type flexible hinge (35), and each side of the flexible bistable mechanism (36) is a rectangular beam type flexible hinge (3); At least one set of limiting devices (6) is provided between the moving platform (1) and the base (2). One end of the limiting device (6) is connected to the moving platform (1), and the opposite end is connected to the base (2). The limiting device (6) is symmetrically distributed relative to the axis of the moving platform (1) and is used to limit the maximum longitudinal displacement of the moving platform (1).

2. The flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips according to claim 1, characterized in that: The piezoelectric drive unit (4) includes a rhombus-shaped displacement amplifying mechanism (45), a piezoelectric ceramic stack (43) is located in the rhombus-shaped displacement amplifying mechanism (45) and coincides with the horizontal diagonal of the rhombus-shaped displacement amplifying mechanism (45), and two vertices of the vertical diagonal of the rhombus-shaped displacement amplifying mechanism (45) are respectively connected to a multi-axis flexible hinge 1 (41) and a multi-axis flexible hinge 2 (42); the top end of the multi-axis flexible hinge 1 (41) is connected to the moving platform (1), and the bottom end of the multi-axis flexible hinge 2 (42) is connected to the base (2); the four sides of the rhombus-shaped displacement amplifying mechanism (45) are all rectangular beam-type flexible hinges 2 (44); The diamond-shaped displacement amplifying mechanism (45) realizes the amplification and guidance of the output displacement of the piezoelectric ceramic stack (43).

3. The flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips according to claim 2, characterized in that: A preload spring (46) is arranged in parallel with the piezoelectric ceramic stack (43), and the preload spring (46) is connected to two vertices of the diamond-shaped displacement amplification mechanism (45).

4. The flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips according to claim 1, characterized in that: The flexible support unit (5) is arranged between the moving platform (1) and the base (2), and is located at the axis of the moving platform (1) or is symmetrically distributed relative to the axis of the moving platform (1).

5. The flexible constant-force suspension-type leveling micro-motion platform for mass transfer of Micro LED chips according to claim 1, characterized in that: The limiting device (6) comprises a limiting upper part (61) and a limiting lower part (62), wherein the limiting upper part (61) is in a positive L-shape and the top of the vertical part is connected to the moving platform (1), and the limiting lower part (62) is in an inverted L-shape and the bottom of the vertical part is connected to the base (2), and the transverse part of the limiting upper part (61) is located directly below the transverse part of the limiting lower part (62) and the two can offset each other.

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