A method for inkjet printing of Micro OLED

Abstract

The present invention provides an inkjet method for Micro OLED, which relates to the field of inkjet printing technology for Micro OLED. The method includes an inkjet unit and a laser following unit. The inkjet unit includes an inkjet head, an inkjet platform, and an inkjet control system. The laser following unit includes a first non-contact sensor fixedly connected to the inkjet head and a second non-contact sensor fixed on the inkjet platform, as well as a laser following control system. The inkjet platform includes an operating area and a calibration area. The laser follows dynamic calibration and draws patterns that are transmitted to the inkjet control system to control the inkjet head for inkjet, effectively solving the problems in the prior art such as difficulty in controlling the height of the inkjet head and the target inkjet area of ​​the wafer, insufficient glue quantity accuracy, and glue overflow or incomplete filling.

Description

Technical Field

[0001] The present application relates to the field of inkjet printing technology for Micro OLED, and in particular 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 AR / VR (augmented reality / virtual reality), smart glasses, microdisplays, and other fields due to its advantages such as high resolution, high contrast, fast response, and low power consumption. The wafer plays a central role in the Micro OLED manufacturing process. Inkjet printing technology precisely dispenses glue into the interior of the chip on the wafer, ensuring even distribution of glue without bubbles. This fills the gaps in the microcavity, prevents water and oxygen penetration, and extends the lifespan. This solves the problems of traditional glue dispensing, which often leads to glue overflow or incomplete filling due to insufficient glue quantity accuracy.

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

[0004] The present invention proposes an inkjet method for Micro OLEDs to solve the technical problems of difficult height control between the inkjet head and the target inkjet area of ​​the wafer, and accurate glue droplet quantity, which exist in the prior art. The method also draws a pattern and clearly divides the area to ensure that the glue only accurately covers the inkjet area, avoiding waste or misprinting.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is:

[0006] The present invention provides an inkjet method for Micro OLED, which is used for inkjet printing on wafers, including an inkjet unit. The inkjet unit includes an inkjet head, an inkjet platform, and an inkjet control system, and is characterized in that:

[0007] The inkjet method includes the following steps:

[0008] S1. Pattern drawing: Draw a pattern in the same proportion according to the wafer size, and distinguish the inkjet area from the blank area;

[0009] S2, data transmission: transmit the pattern to the inkjet control system;

[0010] S3, calibration: calibrate the height between the inkjet head and the inkjet surface;

[0011] S4, inkjet parameter calculation: calculate pixel size and vertical DPI based on pattern data;

[0012] S5, dynamic inkjet: The laser follower control system dynamically calibrates the height between the surface of the inkjet head and the inkjet area of ​​the wafer, and the inkjet head executes inkjet according to the calculated DPI;

[0013] The method also includes a step of calibrating the height of the inkjet head.

[0014] Furthermore, in step S1, drawing the pattern includes the following steps:

[0015] a. Draw the square boundary according to the set rules;

[0016] b. Draw bare chip areas of equal size based on the position of each bare chip on the wafer, and set multiple corresponding coordinates for each bare chip area;

[0017] c. Draw the spacing between the bare chip areas;

[0018] d. Set the bare chip area as the inkjet area; set the area within the square boundary but outside the bare chip area as the blank area.

[0019] Furthermore, the coordinates of each bare chip region are the coordinates of its vertices, 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.

[0020] Preferably, the wafer is preset with four marking points; the marking points intersect along the long lines in the horizontal and vertical directions to enclose a square boundary.

[0021] Preferably, the transverse DPI of the inkjet head is fixed, and the number of inkjet dots in a single line in the length direction of the bare chip area is calculated, and then the inkjet weight of the single line is calculated; the longitudinal DPI of the inkjet head is obtained by dividing the preset total weight of the bare chip area by the inkjet weight of a single line.

[0022] In addition, the present invention also includes a laser following unit, which includes a first non-contact sensor fixedly connected to the inkjet head and a second non-contact sensor fixed on the inkjet platform, as well as a laser following control system. The inkjet platform includes a working area and a correction area.

[0023] Preferably, based on the above-mentioned laser tracking unit, the step of calibrating the inkjet head height includes:

[0024] Measurement of the height H1 of the first non-contact sensor and the calibration area;

[0025] Measurement of the relative height H2 between the ink outlet of the inkjet head and the second non-contact sensor;

[0026] Calculate the height difference between the first non-contact sensor and the ink outlet of the inkjet head: H3 = H1 - H2;

[0027] The height H4 from the first non-contact sensor to the surface of the inkjet area is measured, and the relative height H5 = H4 - H3 between the ink outlet of the inkjet head and the surface of the inkjet area is calculated; the distance the inkjet head needs to move is H5.

[0028] Furthermore, a working height H6 is set between the inkjet head and the surface of the inkjet area, and the height to which the inkjet head needs to move is H5-H6.

[0029] 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.

[0030] The present invention provides an inkjet method for Micro OLEDs, which controls the inkjet head to spray ink by dynamically calibrating and drawing patterns followed by lasers and transmitting them to the inkjet control system. This effectively solves the problems in the prior art such as the difficulty in controlling the height between the inkjet head and the target inkjet area of ​​the wafer, insufficient glue quantity accuracy, and glue overflow or incomplete filling. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions proposed in the present invention, they are described in detail below in conjunction with the embodiments and drawings. It should be understood that the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, these drawings can be changed under the concept of the present invention.

[0032] Figure 1 An assembly perspective view of an embodiment of an inkjet unit and a laser follower unit provided by the present invention;

[0033] Figure 2 A diagram illustrating an embodiment of a drawn pattern provided by the present invention.

[0034] 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

[0035] Please also refer to Figure 1 In this embodiment, the present invention provides an inkjet method for Micro OLED, which is used for inkjet printing on a wafer, and includes an inkjet unit and a laser follower unit. The inkjet unit includes an inkjet head 11, an inkjet platform 12, and an inkjet control system. The laser follower 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 follower control system. The inkjet platform 12 includes an operating area 121 and a calibration area 122. The operating area 121 carries a wafer.

[0036] The inkjet method includes the following steps:

[0037] S1. Drawing pattern 31: Drawing a pattern 31 in the same proportion according to the wafer size, distinguishing between the inkjet area and the blank area;

[0038] S2, data transmission: transmitting the pattern 31 to the inkjet control system;

[0039] S3, calibration: in the calibration area 122, the height between the signal emitting surface of the first non-contact sensor 21 and the inkjet surface of the inkjet head 11 is measured;

[0040] S4. Inkjet parameter calculation: Calculate pixel size and vertical DPI (Dots Per Inch) based on the data in Pattern 31. Vertical DPI is the number of dots per inch in the vertical direction.

[0041] S5. Dynamic inkjet: The laser follower 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.

[0042] Please also refer to Figure 2 In this embodiment, the drawing of the pattern 31 in step S1 specifically includes the following steps:

[0043] a. Measure the wafer diameter and draw a circle of the same size;

[0044] b. Draw a square boundary around the circle 313;

[0045] c. Draw multiple bare chip areas 312 of equal size within the circle, and define the boundaries and regions of each bare chip area 312 using coordinates in the XY plane. For example, the boundaries of one bare chip area 312 are defined as follows: a boundary line parallel to the Y axis and passing through points (X1, 0) and (X2, 0); and a boundary line parallel to the X axis and passing through points (0, Y1) and (0, Y2).

[0046] d. Draw the spacing between the bare chip areas 312; the spacing here is the gap between the bare chips, which is used to separate the bare chips.

[0047] e. The bare chip area 312 forms an inkjet area, and the area outside the bare chip area 312 within the square boundary 313 is a blank area.

[0048] Since the actual pattern of the wafer is circular, it is impossible to directly transmit the circular pattern 31 to the inkjet control system during inkjet printing. Therefore, in this embodiment, there are four marking points 311 preset on the wafer. The specific marking points 311 are set inside the wafer according to the actual wafer specifications and processes, and avoid the position of the bare chip; of course, some 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 located at the end point of the wafer diameter, for example Figure 2 The layout structure shown; each marking point 311 is usually in the shape of a "cross", and the marking points 311 intersect along the long lines along the horizontal and vertical directions to enclose a square boundary 313. Therefore, the actual transmitted pattern 31 is the graphic area enclosed by the square boundary 313.

[0049] In this embodiment, in step S4, the inkjet parameter calculation is specifically as follows: the size of the wafer and the size of the bare chip can be first measured through an optical microscope, and the distance from the center of any marking point 311 to the bare chip is measured, that is, the size parameters required for drawing the pattern 31 are provided. The selected mark point 311 is used as the origin to establish the XY coordinate system by default. The coordinates of the mark point 311 are (0, 0). The boundary points X1 (2, 2), X2 (30, 2), and Y1 (2, 26) are measured. Then, the length d1 of the single bare chip area 312 = the algebraic difference between the X-axis coordinates of the boundary points X1 and X2 = 28 mm, and the width d2 of the single bare chip area 312 = the algebraic difference between the Y-axis coordinates of the boundary points X1 and Y1 = 24 mm. In other words, the length d1 of the single bare chip area 312 is 28 mm, and the width d2 of the single bare chip area 312 is 24 mm. d1 and d2 are the physical dimensions of a single bare chip and need to be converted to pixel dimensions. The pixel dimension is calculated as d1 / 25.4 × horizontal DPI (horizontal DPI is the number of dots per inch in the horizontal direction). The horizontal DPI is fixed by the number of holes in the inkjet head 11 (e.g., 360). DPI), no adjustment is required. Then the horizontal single-row pixel size of the length d1 of a single bare chip area 312 is 28 / 25.4×360=399px. In other words, the number of pixels in the horizontal (length direction) of a single bare chip area 312 is 399px, ensuring that the ink droplet landing point of each pixel is consistent with the design to avoid display defects.

[0050] In this embodiment, in order to achieve the target weight of a single bare chip and thus meet the glue quantity accuracy, the required DPI in the longitudinal direction (width direction) can be adjusted to increase the number of inkjet prints in the longitudinal direction. The specific steps include:

[0051] a. Calculate the total weight of a single horizontal line of ink drops:

[0052] For example, if the ink density is 1.02 g / mL, the volume of a single drop is 6 pL, and the number of pixels (ink drops) in a single row is 399 px, the weight w = ρ × v × the number of ink drops in a single row (the number of horizontal pixels).

[0053] That is: w = 1.02 g / mL × 6 × 10 -9 mL×399px=2.4μg;

[0054] b. Calculate the number of vertical ink drop lines required:

[0055] If the total target weight of the bare chip area is 3.2 mg, the required number of rows = total target weight / single row weight,

[0056] That is: the number of lines required = 3.2mg × 10³μg / 2.4μg ≈ 1333 lines

[0057] c. Calculate the DPI of the vertical ink droplets:

[0058] If the measured width of the single bare chip area 312 is 24 mm, that is, the width of the printed ink droplet is 24 mm,

[0059] Vertical DPI = pixels × 25.4 / width d2 of a single die area 312;

[0060] That is: vertical DPI=1333px×25.4 / 24mm≈1411.

[0061] After the longitudinal DPI is calculated based on the total target weight, in the pattern 31, the bare chip areas 312 corresponding to the transverse and longitudinal DPIs are spaced apart from each other. In the pattern 31, the inkjet area and the blank area have different colors, such as the inkjet area is black and the blank area is white, and each DPI of the inkjet area and the blank area is classified, with the DPI of the inkjet area being 1 and the DPI of the blank area being 2, for easy identification by the inkjet control system.

[0062] In this embodiment, due to the different thicknesses of the wafers themselves, the flatness of the wafer surface is inconsistent. In order to achieve high-precision inkjet printing, real-time laser tracking and dynamic height compensation are required during inkjet printing to adapt to the uneven wafer surface and improve inkjet uniformity.

[0063] Each time a wafer is changed, a calibration is first performed, which includes the following steps:

[0064] a. The first non-contact sensor 21 and the inkjet head 11 are moved to above the calibration area 122, transmitting a signal to measure a first height from the first non-contact sensor 21 to the plane of the calibration area 122, and the laser follower control system includes the first height as H1;

[0065] b. The inkjet head 11 moves to above the second non-contact sensor 22, the second non-contact sensor 22 emits a signal, and a second height from the second non-contact sensor 22 to the surface of the inkjet head 11 is measured. The laser follower control system includes the second height as H2;

[0066] c. The third height between the first non-contact sensor 21 and the surface of the inkjet head 11 is calculated by subtracting the second height H2 from the first height H1. The laser follower control system includes the third height as H3;

[0067] d. The first non-contact sensor 21 moves to the inkjet area of ​​the wafer, emits a signal, 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 H5 from the inkjet head 11 to the inkjet area.

[0068] 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 spray ink on the inkjet area of ​​the wafer. When inkjetting the same wafer, the inkjet head 11 is set at a target height of H6 with the surface of the inkjet area. The inkjet head 11 does not directly contact the inkjet area, and adopts non-contact distance measurement to avoid contamination or damage caused by mechanical contact. The positions of different inkjet areas are different, so H4 will change. Therefore, in order to maintain the target height of H5 every time inkjet is sprayed, 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.

[0069] For example, if H6 is 0.5mm, and during calibration, H1 is 4mm, H2 is 1mm, and H3 is calculated to be 3mm. During inkjet operation, H3 remains unchanged. The first non-contact sensor 21 transmits a signal to the target inkjet area A1. When H4 is measured to be 5mm, the wafer in area A1 is relatively thin. H5 = H4 - H3 - H6 = 5mm - 3mm - 0.5mm = 1.5mm, and the inkjet head 11 must move downward a distance of 1.5mm. The inkjet head 11 and the first non-contact sensor 21 are fixedly connected, so they always move synchronously. The first non-contact sensor 21 is in close proximity to the inkjet head 11, minimizing the height error measured by the first non-contact sensor 21.

[0070] For example, if H6 is 0.5mm, and during calibration, H1 is 4mm, H2 is 1mm, and H3 is calculated to be 3mm. During inkjet operation, H3 remains unchanged. The first non-contact sensor 21 transmits a signal to the target inkjet area A2. If H4 is measured to be 3mm, the wafer in area A2 is relatively thick. Therefore, H5 = H4 - H3 - H6 = 3mm - 3mm - 0.5mm = -0.5mm. Therefore, the inkjet head 11 needs to move upward 0.5mm.

[0071] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0072] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying 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 understood as limiting the present invention.

[0073] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and such modifications or substitutions should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for inkjetting a micro OLED, for inkjetting a wafer, comprising an inkjet unit, wherein the inkjet unit comprises an inkjet head (11), an inkjet platform (12) and an inkjet control system, characterized in that: The inkjet method includes the following steps: S1, drawing a pattern (31): drawing the pattern (31) in the same proportion according to the wafer size, and distinguishing the inkjet area from the blank area; S2, data transmission: transmitting the pattern (31) to the inkjet control system; S3, calibration: calibrating the height between the inkjet head (11) and the inkjet surface; S4, inkjet parameter calculation: calculating pixel size and longitudinal DPI based on the pattern (31) data; S5, dynamic inkjet: the laser follower 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; The method also includes a step of calibrating the height of the inkjet head (11).

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

3. The inkjet method for Micro OLED according to claim 2, wherein: The coordinates of each bare chip area (312) are the coordinates of its vertex, 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 for Micro OLED according to claim 3, wherein: Marking points (311) are preset on the wafer, and there are four marking points (311); the marking points (311) intersect along long lines in the horizontal and vertical directions to enclose the square boundary (313).

5. The inkjet method for Micro OLED according to claim 4, wherein: The transverse DPI of the inkjet head (11) is fixed, and the number of inkjet dots in a single line in the length direction of the bare chip area (312) is calculated, and then the inkjet weight of the single line is calculated; the longitudinal DPI of the inkjet head (11) is obtained by dividing the preset total weight of the bare chip area (312) by the inkjet weight of the single line.

6. The inkjet method for Micro OLED according to claim 1, wherein: The device further comprises a laser following unit, wherein the laser following unit comprises 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), wherein the inkjet platform (12) comprises a working area (121) and a correction area (122).

7. The inkjet method for Micro OLED according to claim 6, wherein: The step of calibrating the height of the inkjet head (11) comprises: measuring a height H1 between the first non-contact sensor (21) and the calibration area (122); measuring a relative height H2 between the ink outlet of the inkjet head (11) and the second non-contact sensor (22); Calculating a height difference H3=H1-H2 between the first non-contact sensor (21) and the ink outlet of the inkjet head (11); The height H4 from the first non-contact sensor (21) to the surface of the inkjet area is measured, and the relative height H5 = H4 - H3 between the ink outlet of the inkjet head (11) and the surface of the inkjet area is calculated; the distance the inkjet head (11) needs to move is H5.

8. The inkjet method for Micro OLED according to claim 7, wherein: It is assumed that there is a working height H6 between the inkjet head (11) and the surface of the inkjet area, and the height to which the inkjet head (11) needs to move is H5-H6.

9. The inkjet method for Micro OLED according to claim 8, wherein: The second non-contact sensor (22) is embedded in the calibration area (122), and the second non-contact sensor (22), the inkjet platform (12), and the calibration area (122) are located at the same horizontal plane.

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