Ink jet method of Micro OLED

Abstract

The invention provides an ink-jet method of a Micro OLED, and relates to the technical field of ink-jet printing of Micro OLEDs, the ink-jet method comprises an ink-jet unit and a laser following unit, the ink-jet unit comprises an ink-jet head, an ink-jet platform and an ink-jet control system, the laser following unit comprises a first non-contact sensor fixedly connected with the ink jet head, a second non-contact sensor fixed on the ink jet platform and a laser following control system, and the ink jet platform comprises an operation area and a correction area. Laser follows dynamic calibration and drawn patterns and is transmitted to the ink jet control system to control the ink jet head to jet ink, and the problems that in the prior art, the height of the ink jet head and the wafer target ink jet area is difficult to control, the glue amount precision is insufficient, and glue overflows or is not fully filled are effectively solved.

Description

Technical Field

[0001] This application relates to the technical field of inkjet printing for Micro OLED, and particularly to an inkjet method for Micro OLED. Background Art

[0002] In recent years, Micro OLED (Micro Organic Light Emitting Diode) display technology has been widely used in fields such as AR / VR (Augmented Reality / Virtual Reality), smart glasses, and micro displays due to its advantages of high resolution, high contrast, fast response, and low power consumption. The wafer plays a core role in the manufacturing process of Micro OLED. Among them, inkjet printing technology is used to accurately ink-fill glue inside the chips on the wafer, ensuring that the glue is evenly distributed without bubbles, filling the voids of the microcavities, preventing water and oxygen penetration, and extending the lifespan, thus solving problems such as insufficient accuracy of the glue volume in traditional dispensing, which is likely to cause glue overflow or incomplete filling.

[0003] In the prior art, during inkjet printing, the surface roughness and warpage of the wafer itself directly affect the glue volume accuracy. If the wafer is uneven, the inkjet droplets may deviate from the target position. If the surface of the wafer is high or low, there will be a difference in the inkjet height between the inkjet head and the wafer, resulting in uneven or overflowing glue and affecting pixel defects. Summary of the Invention

[0004] The present invention proposes an inkjet method for Micro OLED to solve the technical problems of difficult height control between the inkjet head and the target inkjet area of the wafer and low glue volume accuracy in the prior art, and to draw a pattern, clearly divide the area, ensure that the glue only accurately covers the inkjet area, and avoid waste or misprinting.

[0005] To solve the above problems, the technical solution adopted by the present invention is: The present invention provides an inkjet method for Micro OLED for inkjetting on a wafer, including an inkjet unit. The inkjet unit includes an inkjet head, an inkjet platform, and an inkjet control system, and is characterized in that: The inkjet method includes the following steps: S1. Draw a pattern: Draw a pattern in the same proportion according to the wafer size to distinguish the inkjet area from the blank area; S2. Data transmission: Transmit the pattern to the inkjet control system; S3. Calibration: Calibrate the height between the inkjet head and the inkjet surface; S4. Inkjet parameter calculation: Calculate the pixel size and longitudinal DPI based on the pattern data; S5. Dynamic inkjet: The laser following control system dynamically calibrates the height between the surface of the inkjet head and the inkjet area of the wafer, and the inkjet head performs inkjetting according to the calculated DPI; It also includes the step of calibrating the height of the inkjet head.

[0006] Furthermore, in step S1, drawing the pattern includes the following steps: a. Draw a square boundary according to the set rules; b. Draw die areas of the same size according to the positions of each die on the wafer, and set corresponding multiple coordinates for each die area; c. Draw a spacing between the die areas; d. Set the die area as the inkjet area; set the area within the square boundary and outside the die area as the blank area.

[0007] Furthermore, the coordinates of each die area are the coordinates at its vertices, and the horizontal distance between adjacent coordinates is the length d1 of the die, and the vertical distance is the width d2 of the die.

[0008] Preferably, there are four marking points preset on the wafer; the marking points intersect along the horizontal and vertical extension lines to enclose a square boundary.

[0009] Preferably, the horizontal DPI of the inkjet head is fixed. Calculate the number of inkjet dots in a single row in the length direction of the die area, and then calculate the inkjet weight in a single row; divide the total weight preset for the die area by the inkjet weight in a single row to obtain the vertical DPI of the inkjet head.

[0010] In addition, the present invention also includes a laser following unit. The laser following unit includes a first non-contact sensor fixedly connected to the inkjet head, a second non-contact sensor fixed on the inkjet platform, and a laser following control system. The inkjet platform includes an operation area and a calibration area.

[0011] Preferably, based on the above laser tracking unit, the steps of calibrating the height of the inkjet head include: Measuring the height H1 of the first non-contact sensor from the calibration area; Measuring the relative height H2 between the ink outlet of the inkjet head and the second non-contact sensor; Calculating the height difference H3 = H1 - H2 between the first non-contact sensor and the ink outlet of the inkjet head; Measuring the height H4 from the first non-contact sensor to the surface of the inkjet area, and calculating the relative height H5 = H4 - H3 between the ink outlet of the inkjet head and the surface of the inkjet area at this time; the distance that the inkjet head needs to move is H5.

[0012] Furthermore, it is set that there is a working height H6 between the inkjet head and the surface of the inkjet area, and the height that the inkjet head needs to move is H5 - H6.

[0013] Preferably, the second non-contact sensor is embedded in the calibration area, and the second non-contact sensor, the inkjet platform, and the calibration area are on the same horizontal plane.

[0014] The present invention provides an inkjet method for Micro OLED, which controls an inkjet head to perform inkjet by laser following dynamic calibration and transmitting a drawn pattern to an inkjet control system, effectively solving the problems in the prior art such as difficult height control of the inkjet head and the wafer target inkjet area, insufficient glue amount accuracy, glue overflow, or incomplete filling. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions proposed by the present invention, the following will be described in detail with reference to embodiments and drawings. It should be understood that the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can make changes to these drawings under the concept of the present invention.

[0016] Figure 1 It is a three-dimensional assembly diagram of an embodiment of the inkjet unit and the laser following unit provided by the present invention; Figure 2 It is a diagram of an embodiment of the drawn pattern provided by the present invention.

[0017] 11. Inkjet head; 12. Inkjet platform; 121. Working area; 122. Calibration area; 21. First non-contact sensor; 22. Second non-contact sensor; 31. Pattern; 311. Marking point; 312. Bare chip area; 313. Square boundary. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Please refer to Figure 1 , in this embodiment, the present invention provides an inkjet method for Micro OLED for inkjet on a wafer, including an inkjet unit and a laser following unit. The inkjet unit includes an inkjet head 11, an inkjet platform 12, and an inkjet control system. The laser following unit includes a first non-contact sensor 21 fixedly connected to the inkjet head 11, a second non-contact sensor 22 fixed on the inkjet platform 12, and a laser following control system. The inkjet platform 12 includes a working area 121 and a calibration area 122, and the wafer is carried on the working area 121; The inkjet method includes the following steps: S1. Drawing pattern 31: Draw a pattern 31 in the same proportion according to the wafer size to distinguish the inkjet area and the blank area; S2. Data transmission: Transmit the pattern 31 to the inkjet control system; S3. Calibration: In the calibration area 122, measure the height between the signal emission surface of the first non-contact sensor 21 and the inkjet surface of the inkjet head 11; S4. Inkjet parameter calculation: Calculate the pixel size and the longitudinal DPI (Dots Per Inch) based on the data of pattern 31; the longitudinal DPI is the number of dots per inch in the longitudinal length direction.

[0019] S5. Dynamic inkjet: A laser following control system dynamically calibrates the height between the surface of the inkjet head 11 and the wafer inkjet area, and the inkjet head 11 performs inkjet according to the calculated DPI.

[0020] Please also refer to Figure 2 , in this embodiment, the drawing of pattern 31 in step S1 specifically includes the following steps: a. Measure the wafer diameter and draw a circle of the same size; b. Draw a square boundary 313 around the circle; c. Draw a plurality of bare chip areas 312 of the same size within the circle, and define the boundaries and areas of the boundaries of each bare chip area 312 in the XY plane through coordinates; for example, the boundary of one of the bare chip areas 312 is: the boundary line parallel to the Y-axis and passing through the points (X1, 0) and (X2, 0), and the boundary line parallel to the X-axis and passing through the points (0, Y1) and (0, Y2), and the enclosed area.

[0021] d. Draw a spacing between the bare chip areas 312; here, the spacing is the gap between the bare chips, which is used to separate the bare chips from each other.

[0022] e. The bare chip areas 312 form an inkjet area, and within the square boundary 313, the area outside the bare chip areas 312 is the blank area.

[0023] Since the actual pattern of the wafer is circular, when inkjet printing, the circular pattern 31 cannot be directly transmitted to the inkjet control system. Therefore, in this embodiment, there are four marking points 311 preset on the wafer. Specifically, the marking points 311 will be set within the wafer according to the actual specifications and processes of the wafer, and avoid the positions of the bare chips; of course, some of the marking points 311 can also be symmetrically distributed on two mutually perpendicular diameters of the circle defined by the wafer diameter, and close to or at the endpoints of the wafer diameter, for example Figure 2 the shown layout structure; each marking point 311 is usually in the shape of a "plus" sign, and the extension lines of the marking point 311 along the horizontal and vertical directions intersect to enclose a square boundary 313. Therefore, the actually transmitted pattern 31 is the graphic area enclosed by the square boundary 313.

[0024] In this embodiment, in step S4, the calculation of the inkjet parameters is specifically as follows: The sizes of the wafer and the bare chip can be measured first through an optical microscope. Measure the distance from the center of any one of the marking points 311 to the bare chip. That is to say, the size parameters required for drawing the pattern 31 are provided in this way. The selected marking point 311 is defaulted as the origin to establish an XY coordinate system, and the coordinates of the marking point 311 are (0, 0). The boundary point X1(2, 2), the boundary point X2(30, 2), and the boundary point Y1(2, 26) are measured. Then the length d1 of a single bare chip area 312 = the algebraic difference of the X-axis coordinates of the boundary point X1 and the boundary point X2 = 28 mm, and the width d2 of a single bare chip area 312 = the algebraic difference of the Y-axis coordinates of the boundary point X1 - the boundary point Y1 = 24 mm. That is to say, the length d1 of a single bare chip area 312 is 28 mm, and the width d2 of a single bare chip area 312 is 24 mm; d1 and d2 are the physical sizes of a single bare chip and need to be converted into pixel sizes. The pixel size = d1 / 25.4 × horizontal DPI (the horizontal DPI is the number of dots per inch in the horizontal direction). The horizontal DPI is fixed by the number of holes of the inkjet head 11 (such as 360 DPI) and does not need to be adjusted. Then the horizontal single-row pixel size of the length d1 of a single bare chip area 312 is 28 / 25.4 × 360 = 399 px. That is to say, the number of pixel points of a single bare chip area 312 in the horizontal (length direction) is 399 px, ensuring that the ink drop landing point of each pixel is consistent with the design and avoiding display defects.

[0025] In this embodiment, further, in order to make the weight of a single bare chip reach the target weight and thus meet the glue amount accuracy, the DPI in the longitudinal (width direction) can be adjusted to make the number of inkjet times in the longitudinal direction more. The specific steps are as follows: a. Calculate the total weight of the horizontal single-row ink drops: For example, if the ink density is 1.02 g / mL, the single-drop volume is 6 pL, and the single-row pixels (number of ink drops) are 399 px, the weight w = ρ × v × the number of single-row ink drops (number of horizontal pixels), That is: w = 1.02 g / mL × 6 × 10 -9 mL × 399 px = 2.4 μg; b. Calculate the number of rows required for the longitudinal ink drops: For example, if the total target weight of the bare chip area is 3.2 mg, the number of required rows = the total target weight / the single-row weight, That is: the number of required rows = 3.2 mg × 10³ μg / 2.4 μg ≈ 1333 rows c. Calculate the DPI of the longitudinal ink drops: For example, if the measured width of the longitudinal single bare chip area 312 is 24 mm, that is, the printed ink drop width is 24 mm, Vertical DPI = Pixel × 25.4 / Width d2 of a single bare chip area 312; That is: Vertical DPI = 1333px × 25.4 / 24mm ≈ 1411.

[0026] After calculating the vertical DPI according to the total target weight, in pattern 31, for the bare chip areas 312 corresponding to the horizontal and vertical DPI, there is a gap between adjacent bare chip areas 312. In pattern 31, the inkjet area and the blank area have different colors. For example, the inkjet area is black and the blank area is white, and each DPI of the inkjet area and the blank area is classified. The DPI of the inkjet area is 1, and the DPI of the blank area is 2, which is convenient for the inkjet control system to identify.

[0027] In this embodiment, due to the different thicknesses of the wafers themselves and the inconsistent flatness of the wafer surfaces, in order to achieve high-precision inkjet printing, during inkjetting, laser real-time following and dynamic height compensation are required to adapt to the unevenness of the wafer surface and improve the inkjet uniformity.

[0028] Each time a wafer is replaced, calibration is first performed, including the following steps: a. The first non-contact sensor 21 and the inkjet head 11 move above the calibration area 122 and emit signals to measure the first height from the first non-contact sensor 21 to the plane of the calibration area 122. The laser following control system records the first height as H1; b. The inkjet head 11 moves above the second non-contact sensor 22. The second non-contact sensor 22 emits signals to measure the second height from the second non-contact sensor 22 to the surface of the inkjet head 11. The laser following control system records the second height as H2; c. Subtract the second height H2 from the first height H1 to calculate the third height between the first non-contact sensor 21 and the surface of the inkjet head 11. The laser following control system records the third height as H3; d. The first non-contact sensor 21 moves to the inkjet area of the wafer, emits signals, measures the height H4 from the first non-contact sensor 21 to the surface of the inkjet area, calculates H4 - H3, and calculates the height from the inkjet head 11 to the inkjet area, that is, H5.

[0029] The second non-contact sensor 22 is embedded in the calibration area 122, and the second non-contact sensor 22 is on the same horizontal plane as the inkjet platform 12. After the inkjet control system calculates H5, it commands the inkjet head 11 to move to the working area 121 to perform inkjetting on the inkjet area of the wafer. When inkjetting the same wafer, there is a target height, namely H6, between the inkjet head 11 and the surface of the inkjet area. The inkjet head 11 does not directly contact the inkjet area, and non-contact ranging is used to avoid contamination or damage caused by mechanical contact. Since the positions of different inkjet areas are different, H4 will change. Therefore, in order to maintain the target height of H5 for each inkjetting, the first non-contact sensor 21 follows in real time and dynamically adjusts the height of the inkjet head 11 to ensure a stable inkjet distance.

[0030] For example, H6 is 0.5 mm. During calibration, H1 is 4 mm, H2 is 1 mm, and H3 is calculated to be 3 mm. When performing inkjetting, H3 remains unchanged. The first non-contact sensor 21 emits a signal to the target inkjet area A1 and measures that when H4 is 5 mm, the wafer in area A1 is relatively thin. H5 = H4 - H3 - H6 = 5 mm - 3 mm - 0.5 mm = 1.5 mm. The distance that the inkjet head 11 needs to move downward is 1.5 mm. The inkjet head 11 and the first non-contact sensor 21 are fixedly connected, so they always move synchronously, and the first non-contact sensor 21 is next to the inkjet head 11, making the height error measured by the first non-contact sensor 21 the smallest.

[0031] For example, H6 is 0.5 mm. During calibration, H1 is 4 mm, H2 is 1 mm, and H3 is calculated to be 3 mm. When performing inkjetting, H3 remains unchanged. The first non-contact sensor 21 emits a signal to the target inkjet area A2 and measures that when H4 is 3 mm, the wafer in area A2 is relatively thick. H5 = H4 - H3 - H6 = 3 mm - 3 mm - 0.5 mm = -0.5 mm. The inkjet head 11 needs to move upward by 0.5 mm.

[0032] In the above embodiments, the descriptions of the various embodiments have their own emphases. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0033] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0034] As described above, this is a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An inkjet method for Micro OLED for inkjetting on a wafer, including an inkjet unit, the inkjet unit includes an inkjet head (11), an inkjet platform (12) and an inkjet control system, and is characterized in that: The inkjet method includes the following steps: S1. Draw a pattern (31): Draw the pattern (31) in the same proportion according to the wafer size, and distinguish the inkjet area and the blank area; S2. Data transmission: Transmit the pattern (31) to the inkjet control system; S3. Calibration: Calibrate the height between the inkjet head (11) and the inkjet surface; S4. Inkjet parameter calculation: Calculate the pixel size and longitudinal DPI based on the pattern (31) data; S5. Dynamic inkjet: The laser following control system dynamically calibrates the height between the surface of the inkjet head (11) and the inkjet area of the wafer, and the inkjet head (11) performs inkjet according to the calculated DPI; It also includes the step of calibrating the height of the inkjet head (11).

2. The inkjet method of the Micro OLED according to claim 1, wherein, In step S1, when drawing the pattern (31), it includes the following steps: a. Draw a square boundary (313) according to the set rules; b. Draw bare chip areas (312) of the same size according to the positions of each bare chip on the wafer, and set corresponding multiple coordinates for each bare chip area (312); c. Draw a spacing between the bare chip areas (312); d. Set the bare chip area (312) as the inkjet area; set the area within the square boundary (313) and outside the bare chip area (312) as the blank area.

3. The inkjet method of the Micro OLED according to claim 2, wherein, The coordinates of each bare chip area (312) are the coordinates at its vertices, and the horizontal distance between adjacent coordinates is the length d1 of the bare chip, and the vertical distance is the width d2 of the bare chip.

4. The inkjet method of the Micro OLED according to claim 3, characterized in that, There are preset marking points (311) on the wafer, and there are four of the marking points (311); the marking points (311) intersect along the extension lines in the horizontal and vertical directions to enclose the square boundary (313).

5. The inkjet method of the Micro OLED according to claim 4, characterized in that, The horizontal DPI of the inkjet head (11) is fixed. Calculate the number of inkjet points in a single row in the length direction of the bare chip area (312), and then calculate the inkjet weight in a single row; divide the preset total weight of the bare chip area (312) by the inkjet weight in a single row to obtain the longitudinal DPI of the inkjet head (11).

6. The inkjet method of the Micro OLED according to claim 1, wherein It also includes a laser following unit, the laser following unit includes a first non-contact sensor (21) fixedly connected to the inkjet head (11) and a second non-contact sensor (22) fixed on the inkjet platform (12), and the inkjet platform (12) includes an operation area (121) and a calibration area (122).

7. The inkjet method of the Micro OLED according to claim 6, wherein The steps for calibrating the height of the inkjet head (11) include: Measuring the height H1 of the first non-contact sensor (21) and the calibration area (122); Measuring the relative height H2 between the ink outlet of the inkjet head (11) and the second non-contact sensor (22); Calculating the height difference H3 = H1 - H2 between the first non-contact sensor (21) and the ink outlet of the inkjet head (11); Measure the height H4 from the first non-contact sensor (21) to the surface of the inkjet area, and calculate the relative height H5 = H4 - H3 between the ink outlet of the inkjet head (11) and the surface of the inkjet area at this time; the distance that the inkjet head (11) needs to move is H5.

8. The inkjet method of the Micro OLED according to claim 7, characterized in that, Set a working height H6 between the inkjet head (11) and the surface of the inkjet area, and the height that the inkjet head (11) needs to move is H5 - H6.

9. The inkjet method of the Micro OLED according to claim 8, characterized in that, The second non-contact sensor (22) is embedded in the calibration area (122), and the second non-contact sensor (22) is on the same horizontal plane as the inkjet platform (12) and the calibration area (122).

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