A grain rotation angle compensation method for a sorting and transfer system

Abstract

The present invention discloses a method for compensating the rotation angle of grains applied to a chip sorting and transfer system. The method drives the XY cross platform of the wafer stage in the chip sorting and transfer system to transfer the grains to the scanning area under the CCD camera, obtains the center position and the deflection angle θ of all grains on the wafer stage; selects a grain on the wafer stage as the target grain; judges the deflection angle θ of the target grain; if it is not equal to zero, drives the wafer stage to rotate ‑θ so that the target grain is in the return position, and drives the wafer stage to perform position compensation of the rotation ‑θ angle, and then performs subsequent operations. The above method is not only applicable to the correction of the deflection angle of single-arm and double-arm grains, but also is not limited by the size of the correction angle. It can effectively realize the compensation of the grain rotation angle without affecting the grain sorting speed, and greatly improves the grain transfer accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of chip sorting, and in particular to a method for compensating a grain rotation angle of a sorting transfer system. Background Art

[0002] As LEDs, especially Mini-LEDs, are widely used in display screens, automotive displays, mobile phones and wearable devices, the production process requirements for LEDs and Mini-LEDs are becoming increasingly higher. In the process of making display devices with LEDs and Mini-LEDs, testing and sorting are an essential step. In the process of LED and Mini-LED chip sorting and transfer, there are strict process requirements for the spacing and angle of grain arrangement. Usually, the grain spacing error must be controlled within plus or minus 30um, and the angle error must be controlled within plus or minus 3 degrees. Since the grains will go through the process of film expansion before sorting, the blue film cannot be guaranteed to be uniformly stressed during expansion, so some grains will often have angle and spacing offsets. The spacing offset can be achieved through translation correction, which is relatively easy to achieve in motion control; and as for the correction of grain angle deviation, since the sorting equipment has transitioned from a single swing arm mode to a double swing arm mode, the angle correction method in the single swing arm mode cannot be directly applied to the double swing arm mode. How to accurately correct the angle of the grain in both swing arm modes so that the grains can be evenly and neatly arranged on the blue film of the material sheet has become a difficult problem that needs to be solved urgently in the sorting and transfer link.

[0003] The chip sorting system in the prior art includes an image recognition system, a wafer table, a mechanical double swing arm and a bin table. The image recognition system is composed of a CCD camera and an image acquisition card. The wafer table includes an XY cross platform, a pin, a nozzle and a mechanical swing arm. The general steps of chip sorting are: move the wafer table to send the center of the grain to the center of the pin; the pin pierces the blue film and lifts the grain, while the nozzle sucks up the grain and peels it off; the swing arm drives the nozzle to place the peeled grains on the bin table in a certain order. The general method of grain angle correction is: first determine the deflection angle of the grain through machine vision, change the rotation angle of the mechanical swing arm to return the grain to the original position during the process of transferring the grain by the mechanical arm, and at the same time compensate for the change in the rotation angle of the swing arm on the bin table, and finally place the corrected grain on the bin table. The correction method of the above-mentioned prior art has the following disadvantages:

[0004] ① It is only applicable to single swing arms. For double swing arms, the rotation angle of the swing arms cannot be changed. When the double swing arms are used to sort grains, the two swing arms are structurally a whole, and the two are symmetrical and fixed. The angle to which one swing arm rotates is the same as the angle to which the other swing arm rotates. At the same time, the wafer table and the bin table are symmetrical. In order to meet the needs of continuous alternating sorting with two arms, the rotation angle of the swing arms is generally fixed at 180°. Only in this way can the suction nozzle and the ejector pin on the swing arm be aligned each time sorting is performed. In order to correct the angle when placing the grains, when the rotation angle of one of the swing arms is changed, the angle of the other swing arm will inevitably change, resulting in the suction nozzle, ejector pin, and camera center not being in the same vertical direction when the nozzle picks up the grains, and sorting cannot be performed normally.

[0005] ② When the deflection angle of the grain is too large, mechanical interference is likely to occur, that is, the angle correction range is limited. This method of correcting the grain angle relies on the parallel operation of changing the swing arm rotation angle and the arrangement area position compensation. When the positive angle θ of the grain offset is small, the swing arm can correct the grain offset by rotating an angle of 90°-θ. As the positive angle θ of the offset slowly increases, the angle of rotation of the swing arm will become smaller and smaller. Due to the limitations of the structure of the sorting machine itself, in order to sort the grains from the feed area to the arrangement area, the rotation angle of the swing arm must be greater than 45°. Therefore, when the positive angle of the grain offset is not less than 45°, in order to correct the grain, the rotation angle of the swing arm must be less than 45°. At this time, the grain sorting cannot be completed normally, so the correction of the positive angle θ of the grain offset is limited and must be less than 45°. Summary of the invention

[0006] The purpose of the present invention is to provide a method for compensating the grain rotation angle of a sorting and transfer system. The method is not only suitable for the correction of the deflection angle of single-arm and double-arm grains, but is also not limited by the size of the correction angle. It can effectively realize the compensation of the grain rotation angle without affecting the grain sorting speed, thereby greatly improving the grain transfer accuracy.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A method for compensating a grain rotation angle of a sorting and transfer system, the method comprising:

[0009] Step 1, driving the XY cross platform of the wafer stage in the chip sorting and transfer system, transferring the grains on the wafer stage to the scanning area under the CCD camera, and identifying them through machine vision to obtain the center position and deflection angle θ of all the grains on the wafer stage;

[0010] Step 2, selecting a crystal grain on the wafer stage as a target crystal grain;

[0011] Step 3, judging the deflection angle θ of the target crystal grain; if θ is equal to zero, moving the wafer stage to send the center position of the target crystal grain to the center of the ejector pin; if θ is not equal to zero, executing step 4;

[0012] Step 4, driving the wafer stage to rotate -θ so that the target crystal grain is in the return position, and driving the wafer stage to perform position compensation of the rotation angle -θ, and then perform subsequent operations;

[0013] Step 5, driving the ejector pin to pierce the blue film and lift up the target crystal grain, while the suction nozzle sucks up the target crystal grain to peel off the target crystal grain;

[0014] Step 6, using the swing arm to drive the suction nozzle to place the peeled target grains on the bin table in a certain order;

[0015] Step 7, then determine whether there are still grains on the wafer stage; if there are grains, select the next grain on the wafer stage as the target grain, and return to step 3 for operation; if there are no grains, the sorting is completed.

[0016] It can be seen from the technical solution provided by the present invention that the above method is not only suitable for the correction of the deflection angle of single-arm and double-arm grains, but is also not limited by the size of the correction angle. It can effectively realize the compensation of the grain rotation angle without affecting the grain sorting speed, thereby greatly improving the grain transfer accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 A schematic flow chart of a method for compensating a grain rotation angle in a sorting and transfer system provided in an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of rotation angle compensation when the deflection angle is θ according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] like Figure 1 The figure is a schematic flow chart of a method for compensating a grain rotation angle of a sorting and transfer system provided by an embodiment of the present invention, the method comprising:

[0022] Step 1, driving the XY cross platform of the wafer stage in the chip sorting and transfer system, transferring the grains on the wafer stage to the scanning area under the CCD camera, and identifying them through machine vision to obtain the center position and deflection angle θ of all the grains on the wafer stage;

[0023] In this step, the machine vision recognition area is completely determined by the position of the lens, and the center of the machine vision recognition area coincides with the center of the lens of the CCD camera and does not change with the position of the wafer stage; wherein the center position coordinates of the grain are physical offsets relative to the center of the CCD camera lens.

[0024] In addition, before performing the operation of step 1, the allowable grain angle deviation range in the chip sorting and transfer system can also be set; the allowable grain angle deviation range is specifically selected according to different deflection range values ​​according to user needs. In specific implementation, the allowable grain angle deviation range commonly used in industry is -15° to +15° or -9° to +9°.

[0025] Step 2, selecting a crystal grain on the wafer stage as a target crystal grain;

[0026] In this step, the grains whose deflection angle θ on the wafer stage exceeds the allowable grain angle deviation range can be classified into the excluded grain set, and the remaining grains can be classified into the to-be-sorted grain set; and then a grain can be selected from the to-be-sorted grain set as the target grain.

[0027] This is because grains with a large deflection angle θ will be missed during chip scanning, making these grains with a large deflection angle θ without detection parameters. Therefore, when sorting chips, a set of grains to be sorted and a set of excluded grains can be set to automatically exclude grains with a large deflection angle that do not meet the requirements from the grain sorting range, thereby increasing the grain transfer speed.

[0028] Step 3, judging the deflection angle θ of the target crystal grain; if θ is equal to zero, moving the wafer stage to send the center position of the target crystal grain to the center of the ejector pin; if θ is not equal to zero, executing step 4;

[0029] In this step, when the wafer stage is moved to bring the center position of the target die to the center of the ejector pin, the center of the ejector pin is aligned with the center of the lens.

[0030] Step 4, driving the wafer stage to rotate -θ so that the target crystal grain is in the return position, and driving the wafer stage to perform position compensation of the rotation angle -θ, and then perform subsequent operations;

[0031] In this step, the position compensation is specifically the X offset and Y offset of the target die in the wafer stage coordinate system after the angle is corrected. The X offset and Y offset are calculated by the rotation matrix:

[0032] like Figure 2 The figure shows a schematic diagram of rotation angle compensation when the deflection angle is θ according to an embodiment of the present invention. In order to conveniently describe the rotation orientation of the wafer stage, a coordinate system is established at the center of the wafer stage, which rotates with the wafer stage and is named as coordinate system {1}; in order to conveniently describe the posture of the target crystal grain, a coordinate system is established on the deflected target crystal grain and is named as coordinate system {2}; and the world coordinate system is named as coordinate system {0};

[0033] Assume that the coordinate system {1} can be rotated around the Z axis by θ 1 , {2} coordinate system is at x 0 The positive direction is offset by θ 2 ;

[0034] According to the rotation matrix principle, the orientation and position relationship between coordinate systems can be described by a matrix, that is, a homogeneous matrix. Then the homogeneous matrix T from {0} to {1} is 01 and the homogeneous matrix T from {1} to {2} 12 They are:

[0035]

[0036] Where P is the coordinate origin of the deflected target grain, and the coordinate of point P in the {1} coordinate system is ['P x ,'P y ,'P z ] T ; A is the rotation center, and the coordinates of point A in the {1} coordinate system are [ 0 A x , 0 A y , 0 A z ] T ;

[0037] The position of the deflected target grain in the {0} coordinate system can be expressed by T 01 and T 12 The calculation results are:

[0038]

[0039] From the above formula, we can see that to make T 02 The pose in is the unit matrix, just let θ 1 +θ 2 =0, that is, θ 1 =-θ 2 , at this time, the coordinates of the position of the deflected target grain in {0} are:

[0040] ['P x cosθ 2 +'P y sinθ 2 + 0 A x ,-'P x sinθ 2 +'P y cosθ 2 + 0 A y ,'P z + 0 A z ] T ;

[0041] After correcting the angle, the offset distance of the target grain is:

[0042]

[0043] Where Δx and Δy represent the X offset in the horizontal direction and the Y offset in the vertical direction of the grain after angle correction, respectively; the deflection angle θ is equal to θ 2 .

[0044] Step 5, driving the ejector pin to pierce the blue film and lift up the target crystal grain, while the suction nozzle sucks up the target crystal grain to peel off the target crystal grain;

[0045] Step 6, using the swing arm to drive the suction nozzle to place the peeled target grains on the bin table in a certain order;

[0046] Step 7, then determine whether there are still grains on the wafer stage; if there are grains, select the next grain on the wafer stage as the target grain, and return to step 3 for operation; if there are no grains, the sorting is completed.

[0047] In addition, after the sorting in step 7 is completed,

[0048] If the user needs to transfer the excluded die set to the bin stage, the XY cross stage of the wafer stage is driven to move the excluded die set on the wafer stage to the scanning area under the CCD camera, and perform subsequent sorting operations, for example:

[0049] Through machine vision recognition, the center position and deflection angle θ of all the grains on the wafer disk are obtained; one of the remaining grains is selected as the target grain; the wafer stage is driven to rotate -θ, and at the same time, the wafer stage is driven to perform position compensation for the rotation angle -θ; the ejector pin is driven to pierce the blue film and lift the grain, and the suction nozzle sucks the grain to peel off the target grain; the swing arm drives the suction nozzle to place the peeled grains on the bin stage in a certain order; it is determined whether there are grains among the remaining grains: if so, the next grain among the remaining grains is selected as the target grain, and the above compensation operation is returned; otherwise, the sorting is completed.

[0050] In summary, the method described in the embodiment of the present invention realizes the parallel operation between the angle correction and the position compensation of the die on the wafer stage, and can effectively realize the compensation of the rotation angle of the die without affecting the die sorting speed, thereby greatly improving the die transfer accuracy.

[0051] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in the field.

[0052] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for compensating the grain rotation angle of a sorting and transfer system, It is characterized in that The method comprises: Step 1, driving the XY cross platform of the wafer stage in the chip sorting and transfer system, transferring the grains on the wafer stage to the scanning area under the CCD camera, and identifying them through machine vision to obtain the center position and deflection angle θ of all the grains on the wafer stage; Step 2, selecting a crystal grain on the wafer stage as a target crystal grain; Step 3, judging the deflection angle θ of the target crystal grain; if θ is equal to zero, moving the wafer stage to send the center position of the target crystal grain to the center of the ejector pin; if θ is not equal to zero, executing step 4; Step 4, driving the wafer stage to rotate -θ so that the target crystal grain is in the return position, and driving the wafer stage to perform position compensation of the rotation angle -θ, and then perform subsequent operations; In step 4, the position compensation is specifically the X offset and Y offset of the target die in the wafer stage coordinate system after the angle is corrected. The X offset and Y offset are calculated by the rotation matrix: A coordinate system is established at the center of the wafer stage, which rotates with the wafer stage and is named as coordinate system {1}; a coordinate system is established on the deflected target die and is named as coordinate system {2}; and the world coordinate system is named as coordinate system {0}; Assume that the coordinate system {1} can be rotated around the Z axis by θ 1 , {2} coordinate system is at x 0 The positive direction is offset by θ 2 ; According to the rotation matrix principle, the orientation and position relationship between coordinate systems can be described by a matrix, that is, a homogeneous matrix. Then the homogeneous matrix T from {0} to {1} is 01 and the homogeneous matrix T from {1} to {2} 12 They are: Where P is the coordinate origin of the deflected target grain, and the coordinate of point P in the {1} coordinate system is ['P x ,'P y ,'P z ] T ; A is the rotation center, and the coordinates of point A in the {1} coordinate system are [ 0 A x , 0 A y , 0 A z ] T ; The position of the deflected target grain in the {0} coordinate system can be expressed by T 01 and T 12 The calculation results are: From the above formula, we can see that to make T 02 The pose in is the unit matrix, just let θ 1 +θ 2 =0, that is, θ 1 =-θ 2 , at this time, the coordinates of the position of the deflected target grain in {0} are: ['P x cosθ 2 +'P y sinθ 2 + 0 A x ,-'P x sinθ 2 +'P y cosθ 2 + 0 A y ,'P z + 0 A z ] T ; After correcting the angle, the offset distance of the target grain is: Where Δx and Δy represent the X offset in the horizontal direction and the Y offset in the vertical direction of the grain after angle correction, respectively; the deflection angle θ is equal to θ 2 ; Step 5, driving the ejector pin to pierce the blue film and lift up the target crystal grain, while the suction nozzle sucks up the target crystal grain to peel off the target crystal grain; Step 6, using the swing arm to drive the suction nozzle to place the peeled target grains on the bin table in a certain order; Step 7, then determine whether there are still grains on the wafer stage; if there are grains, select the next grain on the wafer stage as the target grain, and return to step 3 for operation; if there are no grains, the sorting is completed.

2. The grain rotation angle compensation method of the sorting and transfer system according to claim 1, It is characterized in that Before performing the operation of step 1, the allowable grain angle deviation range in the chip sorting and transfer system is set; the allowable grain angle deviation range is specifically selected according to different deflection range values ​​according to user needs.

3. The grain rotation angle compensation method of the sorting and transfer system according to claim 1, It is characterized in that In step 1, the center of the machine vision recognition area coincides with the center of the lens of the CCD camera and does not change with the position of the wafer stage; The center position coordinates of the grain are physical offsets relative to the center of the CCD camera lens.

4. The grain rotation angle compensation method of the sorting and transfer system according to claim 2, It is characterized in that In step 2, the grains whose deflection angle θ on the wafer stage exceeds the allowable grain angle deviation range are classified into an excluded grain set, and the remaining grains are classified into a to-be-sorted grain set; and then a grain is selected from the to-be-sorted grain set as a target grain.

5. The grain rotation angle compensation method of the sorting and transfer system according to claim 1, It is characterized in that After the sorting in step 7 is completed, If the user needs to transfer the excluded die set to the bin stage, the XY cross stage of the wafer stage is driven to move the excluded die set on the wafer stage to the scanning area under the CCD camera, and perform subsequent sorting operations.

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