A Micro LED circuit board and its manufacturing method

Abstract

This invention relates to a Micro LED circuit board and a method for manufacturing the same. The method includes: providing an auxiliary film; using a laser to melt copper paste, causing the molten copper paste to drip dropwise onto a predefined pad area on a first surface of the auxiliary film to solidify and form pads; wherein, after the copper paste drips onto the pad area, a magnetic field perpendicular to the auxiliary film is applied to one side of the auxiliary film, wherein the direction of the magnetic field is opposite to the direction of the copper paste dripping; forming a circuit pattern connected to the pads on the auxiliary film; removing the auxiliary film to obtain a circuit board; and connecting a Micro LED chip to the pads on the circuit board to obtain a Micro LED circuit board. By using the auxiliary film to determine the position of the copper paste forming pads on the auxiliary film, and by using a magnetic field perpendicular to the direction of the auxiliary film to constrain the outward diffusion range of the copper paste dripping onto the auxiliary film, the size of the solidified copper paste can be precisely controlled, resulting in more accurate position and size of the pads, which is beneficial to improving the yield of Micro LED circuit boards.

Description

Technical Field

[0001] This invention relates to the field of Mirco LED circuit board manufacturing technology, and in particular to a Mirco LED circuit board and its manufacturing method. Background Technology

[0002] With the advancement of LCD (Liquid Crystal Display) screen backlight technology, the display effect provided by traditional LED (Light Emitting Diode) backlight can no longer meet consumers' demands for higher display effects. For this reason, Micro-LED (Micro-Light Emitting Diode) technology has emerged.

[0003] Micro-LED display technology refers to a display technology that uses self-emissive, micrometer-sized LEDs as light-emitting pixel units, assembling them onto a driving panel to form a high-density LED array. Due to the small size, high integration, and self-emissive characteristics of Micro-LED chips, it has greater advantages in terms of brightness, resolution, contrast ratio, energy consumption, lifespan, response speed, and thermal stability compared to LCD and OLED (Organic Light-Emitting Diode) displays.

[0004] Micro-LED products involve thinning, miniaturizing, and arraying LED structures to a size of approximately 1-10 μm. These are then transferred in batches onto a substrate and packaged to create miniature diode displays. As Micro-LED electronic products become smaller and more multifunctional, the integration density of the PCB (Printed Circuit Board) within these products needs to be further increased. The circuit patterns on the PCB are becoming increasingly complex, requiring more and more circuits to be fabricated within a given PCB area. This increased density and complexity of the circuitry places higher demands on the precision of the solder pads and lines on the circuit board.

[0005] Therefore, how to accurately form the circuits on the circuit board is an urgent problem to be solved. Summary of the Invention

[0006] Therefore, it is necessary to provide a Micro LED circuit board and its manufacturing method.

[0007] A method for manufacturing a Micro LED circuit board, comprising:

[0008] Provide auxiliary membranes;

[0009] Laser melting of copper paste is used, so that the molten copper paste is dripped drop by drop onto a predefined pad area on the first surface of the auxiliary film and solidified to form a pad. After the copper paste is dripped onto the pad area, a magnetic field perpendicular to the auxiliary film is applied to one side of the auxiliary film, wherein the direction of the magnetic field is opposite to the direction of copper paste dripping.

[0010] A circuit pattern connected to the pads is formed on the auxiliary film;

[0011] Remove the auxiliary film to obtain the circuit board;

[0012] The Micro LED chip is connected to the pads on the circuit board to obtain a Micro LED circuit board.

[0013] In one embodiment, the step of providing the auxiliary membrane includes:

[0014] The auxiliary membrane is provided and placed horizontally;

[0015] The step of applying a magnetic field perpendicular to the auxiliary film to one side of the auxiliary film after the copper paste is dropped onto the pad area includes:

[0016] After a first preset time following the drop of the copper paste onto the pad area, a vertically upward magnetic field is applied below the auxiliary film until the copper paste solidifies in the pad area to form the pad.

[0017] In one embodiment, the first preset time is 20ms to 60ms.

[0018] In one embodiment, in the step of applying a vertically upward magnetic field below the auxiliary membrane, the duration of the applied magnetic field is 100 ms to 300 ms.

[0019] In one embodiment, the step of applying a vertically upward magnetic field below the auxiliary membrane includes:

[0020] After a second preset time following the application of a vertically upward magnetic field below the auxiliary membrane, multi-source ultrasonic waves are emitted onto the auxiliary membrane along a direction perpendicular to the auxiliary membrane to induce multi-source oscillations in the auxiliary membrane. The duration of the ultrasonic waves is between 50 ms and 150 ms.

[0021] In one embodiment, the second preset time is 10ms to 50ms.

[0022] In one embodiment, the step of forming a circuit pattern connected to the pads on the auxiliary film includes:

[0023] Hot melt adhesive is applied to the first side of the auxiliary film, and the hot melt adhesive on the pads is removed.

[0024] An initial copper layer is deposited on the hot melt adhesive;

[0025] Apply a dry film onto the initial copper layer, expose and develop the dry film;

[0026] Horizontal electroplating is performed in the area outside the dry film coverage area to form a circuit pattern;

[0027] Film stripping and flash etching remove the dry film and the initial copper layer covered by the dry film.

[0028] Remove the auxiliary film and apply hot melt adhesive to the pads and the surface of the circuit pattern;

[0029] Laser cleaning removes the hot melt adhesive from the surface of the pads, exposing the pads on the side where the circuit pattern is located.

[0030] In one embodiment, the solder pads formed by the solidification and accumulation of copper paste are laser-polished to form cylindrical solder pads.

[0031] In one embodiment, the step of providing the auxiliary membrane is further included prior to:

[0032] The auxiliary membrane is placed horizontally, and the coordinates on the auxiliary membrane are determined by machine vision positioning.

[0033] The predefined pad area is determined based on the coordinates on the auxiliary film;

[0034] Laser ablation technology is used to ablate burrs in the pad area.

[0035] A Micro LED circuit board is manufactured using the Micro LED circuit board manufacturing method described in any of the above embodiments.

[0036] The aforementioned Micro LED circuit board and its manufacturing method utilize an auxiliary film to determine the position of the copper paste as a pad in the auxiliary film, and use a magnetic field perpendicular to the direction of the auxiliary film to constrain the outward diffusion range of the copper paste dripping onto the auxiliary film. This allows for precise control of the size of the copper paste as it solidifies, resulting in more accurate position and size of the pads, which is beneficial for improving the yield of Micro LED circuit boards. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic flowchart illustrating a method for manufacturing a Micro LED circuit board according to one embodiment. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] It is worth mentioning that in Micro-LED circuit boards, pads are used to connect to Micro-LED chips. Micro-LED chips are typically 1 to 100 μm in size. Due to the extremely small size of Micro-LED chips, the position of the pads needs to be very precise to align the electrodes on the chip. Furthermore, the position of the pads also affects the distance, shape, and position of the circuitry. Errors in the position and size of the pads will affect the connection of the Micro-LED chip's electrodes, and through cumulative amplification, will affect the accuracy of the circuitry, leading to a decrease in the yield of the circuit board. In existing technology, CN116895726A utilizes an auxiliary film to form the pads and employs a laser 3D forming method to form the pads on the auxiliary film, ensuring the accuracy of the pad position, shape, and size. However, because the copper paste is in liquid droplet form on the auxiliary film, it will freely diffuse until it solidifies before curing. Therefore, although the auxiliary film can help position the formed pads, it still cannot very accurately constrain the size and shape of the copper paste on the auxiliary film. Therefore, this application provides a method for manufacturing a Micro LED circuit board that can constrain the diffusion of copper paste on an auxiliary film, thereby making the size and shape of the formed pads more precise.

[0041] like Figure 1 As shown, this is a method for manufacturing a Micro LED circuit board according to an embodiment of the present invention, comprising:

[0042] Step 110: Provide an auxiliary membrane.

[0043] In this embodiment, the auxiliary film is used to assist in pad positioning and circuit pattern formation. This auxiliary film can be a PET (Polyethylene terephthalate) film or a ceramic film, such as an alumina ceramic film or a silicon nitride ceramic film.

[0044] Step 120: Laser melting of copper paste is used to drop the molten copper paste dropwise onto a predefined pad area on the first surface of the auxiliary film. A magnetic field perpendicular to the auxiliary film is applied to one side of the auxiliary film until the copper paste solidifies to form a pad. The direction of the magnetic field is opposite to the direction of the copper paste drop.

[0045] In this embodiment, a laser is used to heat the copper material, causing the copper material located above the auxiliary film to melt and form copper paste. The copper paste drips onto the pad area on the auxiliary film, and the diffusion of the copper paste on the auxiliary film is restricted by a magnetic field.

[0046] Specifically, when copper paste drips onto the auxiliary film, its shape can be roughly considered as a disk. Subsequently, the copper paste flows and diffuses outward under the action of gravity. In the molten state, the copper paste is still a good conductor and moves in the magnetic field. For force analysis, the outward diffusion of the copper paste can be regarded as multiple individual copper conductors moving outward along the diameter of the disk. At this time, according to the right-hand rule, the induced current is along the tangent of the disk. According to the left-hand rule, the Lorentz force on the copper conductor is perpendicular to the tangent and towards the center of the disk. That is, the direction of the Lorentz force is opposite to the direction of motion. Therefore, it can block the movement of the copper conductor, thus effectively constraining the diffusion of copper paste on the auxiliary film.

[0047] In this embodiment, by setting a magnetic field with a reasonable magnetic induction intensity, the force on the copper paste can be effectively and accurately controlled, the diffusion range can be constrained, and thus the size of the solder pad can be precisely controlled.

[0048] Step 130: Form a circuit pattern on the auxiliary film that is connected to the pads.

[0049] Step 140: Remove the auxiliary film to obtain the circuit board.

[0050] Step 150: Connect the Micro LED chip to the pads on the circuit board to obtain a Micro LED circuit board.

[0051] In this embodiment, the position of the copper paste as a pad is determined by the auxiliary film, and the range of outward diffusion of the copper paste dripping onto the auxiliary film is constrained by a magnetic field perpendicular to the direction of the auxiliary film. This allows for precise control of the size of the copper paste as it solidifies, resulting in more accurate position and size of the pads, which is beneficial for improving the yield of MicroLED circuit boards.

[0052] In order to precisely control the diffusion range of copper paste on the auxiliary film, in one embodiment, the step of applying a magnetic field perpendicular to the auxiliary film to one side of the auxiliary film includes: after the copper paste is dropped onto the pad area, applying a magnetic field perpendicular to the auxiliary film to one side of the auxiliary film.

[0053] In this embodiment, after the copper paste is dripped onto the pad area, but before it solidifies, a magnetic field source is activated to form a magnetic field perpendicular to the auxiliary film. It is worth noting that the copper paste drips in droplet form with a diameter smaller than the pad area. In this embodiment, the magnetic field is applied only after the copper paste has dripped onto the pad area. This allows the copper paste to slightly diffuse upon initial dripping onto the auxiliary film, covering the pad area. The subsequent application of the magnetic field restricts this diffusion, ensuring that the pad size accurately covers the pad area to form the pad.

[0054] In one embodiment, the step of providing the auxiliary membrane includes:

[0055] The auxiliary membrane is provided and placed horizontally;

[0056] The step of applying a magnetic field perpendicular to the auxiliary film to one side of the auxiliary film after the copper paste is dropped onto the pad area includes:

[0057] After a first preset time following the drop of the copper paste onto the pad area, a vertically upward magnetic field is applied below the auxiliary film until the copper paste solidifies in the pad area to form the pad.

[0058] In this embodiment, the copper paste is dripped from above the auxiliary film. Placing the auxiliary film horizontally helps the copper paste to drip accurately onto the pad area of ​​the auxiliary film. Furthermore, placing the auxiliary film horizontally can prevent the copper paste from sliding or spreading to one side due to tilting, so that the copper paste can be formed in a circular shape, making the shape of the pad more precise.

[0059] In this embodiment, the magnetic field source is located below the auxiliary membrane, and the magnetic field direction is vertically upward. The magnetic field passes through the auxiliary membrane and acts on the copper paste dripping onto the auxiliary membrane. In this way, a Lorentz magnetic force can be formed on the copper paste in the direction of the center, which can effectively constrain the diffusion movement of the copper paste.

[0060] In addition, in this embodiment, the magnetic field source is not activated the instant the copper paste falls onto the auxiliary film. Instead, the magnetic field is applied a first preset time after the copper paste falls. The purpose is to allow the copper paste an initial diffusion time so that the copper paste can fully cover the pad area.

[0061] In one embodiment, the first preset time is 20ms to 60ms. In this embodiment, the magnetic field source is activated 20ms to 60ms after the copper paste drips onto the pad area of ​​the auxiliary film to apply a magnetic field to the copper paste. The purpose is to allow the copper paste to diffuse from a droplet shape to a disk shape, reserving diffusion time for the copper paste to spread from a droplet form to cover the pad area. It is worth mentioning that if the magnetic field is activated immediately after the copper paste drips onto the pad area, the droplet-shaped copper paste will be constrained and unable to spread sufficiently. On the other hand, if the first preset time is too long, the copper paste will spread excessively, and the copper paste will be close to solidifying or already solidified. Therefore, in this embodiment, activating the magnetic field source 20ms to 60ms after the copper paste drips onto the pad area of ​​the auxiliary film allows the copper paste to spread sufficiently and effectively avoids excessive diffusion. In one embodiment, the first preset time is 50ms. In this embodiment, the magnetic field source is activated 50ms after the copper paste drips onto the pad area of ​​the auxiliary film, which enables the copper paste to spread out fully and effectively avoids excessive diffusion of the copper paste, thereby forming copper paste that fully covers the pad area, resulting in better copper paste curing and molding effect.

[0062] In one embodiment, in the step of applying a vertically upward magnetic field below the auxiliary film, the duration of the applied magnetic field is 100ms to 300ms. In this embodiment, the application time of the magnetic field is 100ms to 300ms, which can effectively constrain excessive diffusion of copper paste and avoid prolonged operation of the magnetic field, thus effectively saving energy.

[0063] In one embodiment, the step of using laser-melted copper paste, causing the molten copper paste to drip dropwise onto a predefined pad area on a first surface of an auxiliary film, and applying a magnetic field perpendicular to the auxiliary film to one side of the auxiliary film until the copper paste solidifies to form pads, includes:

[0064] Laser melting of copper paste is used, causing the molten copper paste to drip drop by drop. During the dripping process, a vertically upward magnetic field is applied below the auxiliary film. When the copper paste drips onto a predefined pad area on the first surface of the auxiliary film, the magnetic field is stopped. 20ms to 60ms after the copper paste drips onto the pad area of ​​the auxiliary film, a vertically upward magnetic field is applied again below the auxiliary film until the copper paste solidifies to form a pad.

[0065] In this embodiment, a magnetic field is applied during the copper paste dripping process to prevent the droplet-shaped copper paste from deviating. It's worth noting that when the copper paste falls vertically, its velocity direction is parallel to the magnetic field direction, and the Lorentz force on the copper paste is zero. However, if the copper paste deviates during its vertical fall, it will cut the magnetic field lines, thus experiencing a Lorentz force. Therefore, the magnetic field effectively constrains the deviation of the copper paste, allowing it to be precisely dripped onto the pad area. After the copper paste contacts the pad area, the magnetic field is stopped, allowing the copper paste to initially diffuse and cover the pad area. After 20ms to 60ms, the magnetic field is applied again to constrain the copper paste and prevent excessive diffusion, thus forming copper paste that fully covers the pad area, resulting in better solidification and molding. Through this process, the position and size of the molded pads are more precise.

[0066] The specific process of applying the magnetic field is as follows:

[0067] When a molten copper droplet (conductive fluid) moves in a magnetic field, the movement of free electrons within it generates a current density J, which in turn induces a Lorentz force. Therefore, we have: F L =J×B, where F L Let J be the Lorentz force, J be the current density, and B be the magnetic flux density.

[0068] When the copper droplet falls vertically, its velocity direction v is parallel to the direction of the magnetic field B. At this time, the vector value of v×B is 0, and the Lorentz force is 0.

[0069] After the copper droplet contacts the auxiliary film, it begins to flow and diffuse laterally. The velocity v changes direction to horizontal and is perpendicular to the direction of the magnetic field B, θ = 90°. At this time, F L The direction is perpendicular to the direction of velocity v and the direction of magnetic field B, forming a radial contraction force to prevent the copper paste from spreading.

[0070] Specifically, when the copper droplet flows laterally, a ring-shaped vortex is formed inside. The vortex current density J interacts with the magnetic field B to generate a centripetal force.

[0071] F 约束 ∝σvB 2 r 2

[0072] Where σ is the conductivity of the copper liquid, v is the flow velocity, and r is the droplet radius.

[0073] For example: For a droplet with a diameter d = 5 μm (r = 2.5 μm), a magnetic field B = 1 T, and a flow velocity v = 0.5 m / s, then the constraint force is:

[0074] F 约束 ≈1.2×10 -6 N

[0075] This constraint is sufficient to counteract surface tension-driven diffusion.

[0076] High-speed imaging observations showed that after the magnetic field was activated, under conditions of B≥1.2T, the diffusion velocity of the copper paste decreased from 1.2 m / s to 0.3 m / s, and the final diameter was reduced to 60% of that without a magnetic field, a reduction of more than 40%. The radial contraction effect generated by the vertically upward magnetic field through the Lorentz force effectively constrained the diffusion range of molten copper droplets on the auxiliary film, thereby enabling the copper paste to accurately form pads in the pad area.

[0077] In one embodiment, in the step of applying a magnetic field perpendicular to the auxiliary film on one side of the auxiliary film, the magnetic induction intensity of the applied magnetic field is greater than or equal to 1.2T and less than or equal to 1.8T. This effectively confines the copper paste within the desired pad area. In one embodiment, the magnetic induction intensity of the applied magnetic field is 1.5T. Compared to the case without a magnetic field, the diffusion diameter of the copper droplet on the auxiliary film is reduced by about 40%. Since no magnetic field is applied when the copper droplet initially contacts the auxiliary film, the copper droplet can diffuse upon initial contact. Therefore, the magnetic induction intensity of the magnetic field applied after the first preset time is 1.5T, which reduces the diffusion diameter on the auxiliary film by about 25% compared to the case without a magnetic field. This allows for precise control of the copper droplet diffusion, preventing it from spreading outside the pad area, thereby making the pad size more accurate.

[0078] It is worth mentioning that, in order to accurately detect the copper paste dripping onto the pad area, in some embodiments, a CCD (charge coupled device) can be used to acquire images of the auxiliary film, and the copper paste dripping onto the pad can be detected by image analysis, thereby detecting the copper paste dripping onto the pad area and accurately determining the moment when the copper paste contacts the pad area. In order to further accurately determine the moment when the copper paste drips onto the pad area, in some embodiments, an infrared detection probe can also be used to detect the copper paste dripping onto the auxiliary film. The infrared detection probe can identify the temperature of the object and can detect moving objects. Therefore, it can detect the movement of the copper paste in real time and accurately determine the moment when the copper paste drips onto the pad area, thereby achieving precise control of the opening and closing of the magnetic field.

[0079] In one embodiment, the step of applying a vertically upward magnetic field below the auxiliary membrane includes:

[0080] After a second preset time following the application of a vertically upward magnetic field below the auxiliary membrane, multi-source ultrasonic waves are emitted onto the auxiliary membrane along a direction perpendicular to the auxiliary membrane to induce multi-source oscillations in the auxiliary membrane. The duration of the ultrasonic waves is between 50 ms and 150 ms.

[0081] In this embodiment, ultrasound is used to induce localized, multi-source high-frequency vibrations in the auxiliary film. The aim is to ensure that the copper paste in the pad area can spread evenly while being confined by a magnetic field. The use of multi-source ultrasound in this embodiment aims to ensure uniform distribution of vibrations, enabling uniform vibrations in each pad area of ​​the auxiliary film.

[0082] Specifically, the copper paste droplets are characterized by a longer vertical length and a shorter horizontal length. When dropped onto the auxiliary film, the copper paste flows and diffuses horizontally, with the top layer also sliding down. Under the constraint of the magnetic field, the diffusion rate at the edges of the copper paste decreases or stops, and the top layer also stops sliding down. It's worth noting that although the downward diffusion is mainly vertical, horizontal diffusion also occurs and is subject to the magnetic field constraint. This can lead to excessively thick and unevenly distributed copper paste on the pad area. In this embodiment, a multi-source superconducting... The ultrasonic waves allow the ultrasound to act evenly on the auxiliary film, causing it to vibrate uniformly at different locations, especially in the pad area. This vibration drives the top of the copper paste downwards, resulting in a uniform thickness. It's important to understand that the copper paste at the edges, due to its thinner thickness and lower gravitational potential energy, is constrained by the magnetic field, preventing further diffusion. Conversely, the copper paste at the top, with its higher gravitational potential energy, overcomes the magnetic field's constraint and slides downwards using ultrasonic vibration. This allows the copper paste to be evenly distributed, spread out sufficiently, and formed into a more regular and precise disc-shaped pad. It's worth noting that while laser polishing can correct the shape of the pad after it's formed, this only removes excess burrs and protrusions, making localized shape adjustments but not altering the overall shape. Therefore, the combination of ultrasonic vibration and magnetic field constraint allows the copper paste to be constrained and evenly distributed, resulting in a more precisely shaped pad.

[0083] In one embodiment, the second preset time is 10ms to 50ms. In this embodiment, 10ms to 50ms after applying the magnetic field to the copper paste, the ultrasonic source is activated to perform ultrasonic vibration on the copper paste, allowing any copper paste that has not yet slid down and diffused at the top to slide off during vibration. It is worth mentioning that, on the one hand, if the ultrasonic source is activated too early, the copper paste at the edges will spread excessively due to its greater thickness, and the spread will be irregular. On the other hand, if the ultrasonic source is activated too late, the copper paste will have already solidified, and the vibration at this time will not be able to spread the copper paste evenly. Therefore, in this embodiment, activating the ultrasonic source 10ms to 50ms after applying the magnetic field to the copper paste to perform ultrasonic vibration on the copper paste can prevent excessive diffusion of the copper paste, allowing any copper paste that has not yet slid down and diffused at the top to slide off during vibration, so that the copper paste in the pad area can be evenly distributed, with uniform thickness in each part, thereby making the shape of the pad formation more accurate.

[0084] In one embodiment, to form a circuit pattern, the step of forming a circuit pattern connected to the pads on the auxiliary film includes:

[0085] Hot melt adhesive is applied to the first side of the auxiliary film, and the hot melt adhesive on the pads is removed.

[0086] An initial copper layer is deposited on the hot melt adhesive;

[0087] Apply a dry film onto the initial copper layer, expose and develop the dry film;

[0088] Horizontal electroplating is performed in the area outside the dry film coverage area to form a circuit pattern;

[0089] Film stripping and flash etching remove the dry film and the initial copper layer covered by the dry film.

[0090] Remove the auxiliary film and apply hot melt adhesive to the pads and the surface of the circuit pattern;

[0091] Laser cleaning removes the hot melt adhesive from the surface of the pads, exposing the pads on the side where the circuit pattern is located.

[0092] In this embodiment, the circuit pattern is a line connecting each pad, used to transmit and control power to the Micro LED. First, hot melt adhesive is applied to the side of the auxiliary film where the pads are located. Then, the hot melt adhesive on the top surface of the pads is removed, exposing the surface of the pads. The process of removing the hot melt adhesive is as follows: first, a ceramic brush is used to grind the hot melt adhesive from the top of the pad to remove excess hot melt adhesive. Then, a laser cleaning method is used to remove the remaining hot melt adhesive on the pads, so that the top surface of the exposed pads is flush with the surface of the hot melt adhesive.

[0093] Subsequently, an initial copper layer is deposited on the surface of the hot melt adhesive, and the initial copper layer connects to the pads. The thickness of the initial copper layer is less than 1 micrometer, and a thin initial copper layer is deposited on the pads and hot melt adhesive using chemical sputtering or other chemical copper deposition methods.

[0094] Subsequently, a dry film is globally applied to the initial copper layer. Then, the dry film outside the circuit pattern area is removed by exposure and development. The pattern outside the dry film-covered area at this point becomes the subsequent circuit pattern. Horizontal electroplating is then performed in the area outside the dry film-covered area to form a 7-8 micrometer circuit pattern. This circuit pattern is then connected to the solder pads.

[0095] Following this, a flash etching process is performed to remove the dry film, which then removes the initial copper layer covered by the dry film, leaving only the circuit pattern on the hot melt adhesive. Next, the auxiliary film is removed, and double-sided immersion gold plating is applied to the pads. Finally, the auxiliary film is removed.

[0096] Subsequently, plasma technology was used to clean the pads. After removing the auxiliary film, to avoid residual auxiliary film on the bottom of the pads, plasma gas etching was used to etch the bottom of the pads, i.e., the end where the pad and the auxiliary film met, ensuring that no residual auxiliary film material remained on the pads. Then, AOI (Automated Optical Inspection) was performed on the circuit pattern and pads. AOI inspection was conducted on the pads and the circuit pattern formed on top of them to check the appearance and condition of the circuit pattern.

[0097] Subsequently, hot melt adhesive is applied again to the pads and circuit pattern surface. In this step, the hot melt adhesive is used as a solder resist layer and an insulating layer. At this time, the hot melt adhesive covers the circuit pattern and the pads on one side of the circuit pattern.

[0098] Subsequently, laser cleaning is performed again to expose the pads on the side closest to the circuit pattern. The ends of the pads on the side furthest from the circuit pattern have been exposed. At this point, laser cleaning refers to cleaning the end of the pad closest to the circuit pattern, so that both ends of the pad are exposed while the other areas are covered with hot melt adhesive.

[0099] Double-sided immersion gold treatment is applied to the pads. Immersion gold is applied simultaneously to both ends of the exposed pads to increase their conductivity and thickness. During the immersion gold process, a very thin oxide layer forms on the metal surface. This oxide layer effectively prevents metal corrosion, thereby improving the corrosion resistance of the pads and circuit patterns.

[0100] In one embodiment, the solder pads formed by the solidification and accumulation of copper paste are laser-polished to form cylindrical solder pads.

[0101] In this embodiment, after the copper paste has solidified, the pads are polished using a laser to make the shape of the pads more precise.

[0102] In one embodiment, the step of providing the auxiliary membrane is preceded by:

[0103] The auxiliary membrane is placed horizontally, and the coordinates on the auxiliary membrane are determined by machine vision positioning.

[0104] The predefined pad area is determined based on the coordinates on the auxiliary film;

[0105] Laser ablation technology is used to ablate burrs in the pad area.

[0106] In this embodiment, machine vision is first used to accurately determine the coordinates on the auxiliary film, and based on this, the position and size of the pad area are precisely determined. Then, based on the determined position and size of the pad area, laser ablation technology is used to ablate a burr surface on the pad area. The range of this burr surface overlaps with the range of the pad area, and the burr surface has multiple burrs. In this embodiment, the burr surface serves two purposes: firstly, it positions and marks the pad area, ensuring accurate alignment of the copper paste with the pad area; secondly, the burr surface increases the friction of the pad area, which helps to prevent excessive diffusion of the copper paste; and thirdly, during ultrasonic oscillation, the burrs on the burr surface vibrate under the ultrasonic waves, ensuring that pad areas at different locations experience similar vibration amplitudes. Furthermore, the vibration of the burrs strengthens the vibration amplitude on the top of the copper paste, allowing it to slide down. This ensures that the copper paste not only fully covers the pad area but is also evenly distributed, resulting in a more precise shape of the formed pad.

[0107] In one embodiment, a Micro LED circuit board is provided, which is manufactured using the Micro LED circuit board manufacturing method described in any of the above embodiments.

[0108] In this embodiment, the position of the copper paste as a pad is determined by the auxiliary film, and the range of outward diffusion of the copper paste dripping onto the auxiliary film is constrained by a magnetic field perpendicular to the direction of the auxiliary film. This allows for precise control of the size of the copper paste as it solidifies, resulting in more accurate position and size of the pads, which is beneficial for improving the yield of MicroLED circuit boards.

[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for manufacturing a Micro LED circuit board, characterized in that, include: Provide auxiliary membranes; Laser melting of copper paste is used, so that the molten copper paste is dripped drop by drop onto a predefined pad area on the first surface of the auxiliary film and solidified to form a pad. After the copper paste is dripped onto the pad area, a magnetic field perpendicular to the auxiliary film is applied to one side of the auxiliary film, wherein the direction of the magnetic field is opposite to the direction of copper paste dripping. A circuit pattern connected to the pads is formed on the auxiliary film; Remove the auxiliary film to obtain the circuit board; Connect the Micro LED chip to the pad on the circuit board to obtain the Micro LED circuit board; The step of providing the auxiliary membrane includes: The auxiliary membrane is provided and placed horizontally; The step of applying a magnetic field perpendicular to the auxiliary film to one side of the auxiliary film after the copper paste is dropped onto the pad area includes: After a first preset time following the drop of the copper paste onto the pad area, a vertically upward magnetic field is applied below the auxiliary film until the copper paste solidifies in the pad area to form the pad.

2. The method for manufacturing a Micro LED circuit board according to claim 1, characterized in that, The first preset time is 20ms to 60ms.

3. The method for manufacturing a Micro LED circuit board according to claim 1, characterized in that, In the step of applying a vertically upward magnetic field below the auxiliary membrane, the duration of the applied magnetic field is 100 ms to 300 ms.

4. The method for manufacturing a Micro LED circuit board according to claim 1, characterized in that, The step of applying a vertically upward magnetic field below the auxiliary membrane includes: After a second preset time following the application of a vertically upward magnetic field below the auxiliary membrane, multi-source ultrasonic waves are emitted onto the auxiliary membrane along a direction perpendicular to the auxiliary membrane to induce multi-source oscillations in the auxiliary membrane. The duration of the ultrasonic waves is between 50 ms and 150 ms.

5. The method for manufacturing a Micro LED circuit board according to claim 4, characterized in that, The second preset time is 10ms to 50ms.

6. The method for manufacturing a Micro LED circuit board according to any one of claims 1-5, characterized in that, The step of forming a circuit pattern connected to the pads on the auxiliary film includes: Hot melt adhesive is applied to the first side of the auxiliary film, and the hot melt adhesive on the pads is removed. An initial copper layer is deposited on the hot melt adhesive; Apply a dry film onto the initial copper layer, expose and develop the dry film; Horizontal electroplating is performed in the area outside the dry film coverage area to form a circuit pattern; Film stripping and flash etching remove the dry film and the initial copper layer covered by the dry film. Remove the auxiliary film and apply hot melt adhesive to the pads and the surface of the circuit pattern; Laser cleaning removes the hot melt adhesive from the surface of the pads, exposing the pads on the side where the circuit pattern is located.

7. The method for manufacturing a Micro LED circuit board according to any one of claims 1-5, characterized in that, The solder pads formed by the solidification and accumulation of copper paste are laser-polished to form cylindrical solder pads.

8. The method for manufacturing a Micro LED circuit board according to any one of claims 1-5, characterized in that, Prior to the step of providing the auxiliary membrane, the following also includes: The auxiliary membrane is placed horizontally, and the coordinates on the auxiliary membrane are determined by machine vision positioning. The predefined pad area is determined based on the coordinates on the auxiliary film; Laser ablation technology is used to ablate burrs in the pad area.

9. A Micro LED circuit board, characterized in that, It is manufactured using the manufacturing method of the Micro LED circuit board as described in any one of claims 1-8.

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