Mini LED dispensing process based on a photolithography technology

Abstract

The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The application discloses a module plate Mini LED dispensing process based on a photoetching technology, and belongs to the technical field

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a module plate Mini LED dispensing process based on photoetching technology. BACKGROUND

[0002] With the continuous development of display technology, Mini RGB direct display module plate, as a kind of high resolution and high contrast display product, gradually occupies an important position in the display field. Its core manufacturing process mainly includes two technical routes: one is the traditional POB (Package on Board) technology, and the other is the rapidly developing COB (Chip on Board) technology in recent years.

[0003] In the POB technology, Mini LED lamp beads are pasted to the PCB (Printed Circuit Board) by die bonding equipment, and then black grid plates are filled in the gaps between the lamp beads. The main function of the black grid plate is to improve the ink performance of the PCB, enhance the display contrast, and reduce the light crosstalk phenomenon. However, POB technology has obvious limitations: first, the introduction of black grid plate increases the thickness and weight of the module plate, affecting the lightweight design of the product; second, the black grid plate hinders the heat dissipation performance, which may cause the service life of LED lamp beads to be shortened; finally, the production process of POB technology is relatively complex and the cost is high.

[0004] With the continuous progress of LED chip manufacturing technology, COB technology has gradually become the mainstream development direction of Mini RGB direct display module plate. COB technology directly pastes Mini LED chips to the PCB through die bonding equipment, eliminating the traditional step of packaging lamp beads, thereby realizing a lighter and thinner design with higher integration. In addition, COB technology has significant advantages in heat dissipation performance and optical performance, especially suitable for large pitch or indoor small pitch direct display application scenarios. However, COB technology also faces some technical challenges: first, due to the elimination of the black grid plate, COB products have deficiencies in light mixing effect, which may cause light halo or color unevenness; second, the ink consistency of the PCB module plate is difficult to guarantee, affecting the quality of the display effect; finally, the existing black glue covering method usually adopts the process of gluing first and then packaging, which may cause damage to the Mini LED chips themselves, affecting the reliability and service life of the product.

[0005] In view of the above problems, the prior art attempts to improve the performance of COB products by improving the packaging material and process, such as using black glue to cover to improve the ink consistency and light mixing effect. However, these methods often cannot balance process precision and product reliability, especially in the control of packaging glue thickness and amount, resulting in unstable product quality. Therefore, a new packaging process is needed, which can improve the light mixing effect, ink consistency and bright and dark state taste while ensuring the safety of Mini LED chips, and realize precise control of the process and stability of the quality.

[0006] In summary, the existing Mini RGB direct display module board manufacturing technology, especially the COB technology, has advantages in thinness, heat dissipation and optical performance, but still has significant deficiencies in light mixing effect, ink consistency and process reliability. SUMMARY

[0007] In order to solve the deficiencies in the prior art, the present application provides a module board Mini LED dispensing process based on photolithography technology.

[0008] The technical scheme is as follows:

[0009] A module board Mini LED dispensing process based on photolithography technology is provided,

[0010] The Mini LED chip is fixed on the PCB module board by die bonding process;

[0011] The photoresist is coated on the PCB module board, and the mask plate is used to align the position of the Mini LED chip to perform photoetching with ultraviolet light to leave a groove;

[0012] The transparent glue mixed with diffusion powder is stirred to form lens glue with diffusion effect;

[0013] The lens glue with diffusion effect is injected into the position without photoresist on the Mini LED chip by dispensing method, and the lens glue covering height is more than 30 um but not higher than 60 um;

[0014] The PCB module board is irradiated with ultraviolet light to remove the remaining photoresist, and baking is performed;

[0015] Black glue is injected into the gap between the lens glue of two adjacent Mini LED chips and its adjacent lens glue, and baking is performed.

[0016] Further technical scheme, coating photoresist on the PCB module board, after coating the photoresist, using the mask plate to align the position of the Mini LED chip, and performing photoetching with ultraviolet light with a wavelength of 365 nm to 436 nm.

[0017] Further technical solutions, the transparent glue material is epoxy resin, and the viscosity value ranges from 600 mpa.s to 800 mpa.s.

[0018] Further technical solutions, the diffusion powder added in the transparent glue is organic microsphere powder.

[0019] Further technical solutions, the specific steps for irradiating the PCB module board with ultraviolet light to remove the remaining photoresist are as follows:

[0020] After the injection of the Lens glue is completed, the entire PCB module board is irradiated with ultraviolet light to remove the remaining photoresist; the wavelength of the ultraviolet light irradiation is the same as the wavelength of the ultraviolet light used in the photoetching process, and ranges from 365 nm to 436 nm; through the ultraviolet light irradiation, only the area of the Mini LED chip covered by the Lens glue is reserved on the PCB module board.

[0021] Further technical solutions, the black glue includes a two-component epoxy resin solution, a black agent or a black pigment, the viscosity value ranges from 800 mpa.s to 1000 mpa.s, and the black glue has a coverage height of more than 30 um but not higher than 60 um.

[0022] Further technical solutions, the black glue is injected in the walkway between two adjacent Mini LED chips and is baked, and then the black surface protection film is attached to the uppermost layer of the PCB module board and is hot-pressed.

[0023] Further technical solutions, the bottom adhesive layer of the black surface protection film contains diffusion material, which is used to fill the uneven area between the lens glue and the walkway black glue.

[0024] Further technical solutions, the baking temperature is 125°C, and the time is 60 minutes.

[0025] The technical solutions at least include the following technical effects:

[0026] 1. By first coating photoresist on the PCB module board and using photoetching technology to expose and develop the area near the Mini LED chip, etching is performed, which can position and quantify the subsequent dispensing.

[0027] 2. Through the transparent lens glue and the light scattering powder added in the glue, a more uniform mixed light effect is obtained after multiple total internal reflections in the lamp bead.

[0028] 3. The Mini LED chip is first coated with photoresist, and then the photoresist is etched by irradiating ultraviolet light on part of the Mini LED, so as to achieve the purpose of precise positioning of the coating area.

[0029] 4. Cover the Mini LED surface with a layer of transparent lens glue by dispensing to protect, and then remove the remaining photoresist, to achieve fixed usage and consistent coverage height when coating the Mini LED with transparent lens glue, ensuring that the walkway between the two Mini LED chips is neat and meets the coating requirements.

[0030] 5. Inject black glue into the gap between the lens glue and its adjacent lens glue on the PCB, and divide multiple Mini LEDs by black glue to achieve consistent color of the entire PCB.

[0031] 6. The height of the black glue is set high enough over the Mini LED to improve color consistency, but not higher than the height of the lens glue coating to prevent affecting the packaging.

[0032] 7. Light module uniformity at each viewing angle. BRIEF DESCRIPTION OF DRAWINGS

[0033] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0034] Figure 1 A Mini LED dispensing process flowchart based on photolithography technology is provided for a preferred embodiment of the present application;

[0035] Figure 2 A structure diagram of a PCB module board in the prior art;

[0036] Figure 3 A structure diagram of a PCB module board in the prior art for packaging protection process;

[0037] Figure 4 A structure diagram of a PCB module board for die bonding process is provided for a preferred embodiment of the present application;

[0038] Figure 5 A structure diagram of a PCB module board in Figure 4 after the photoresist is laid flat;

[0039] Figure 6 A structure diagram of a PCB module board in Figure 5 after ultraviolet light exposure;

[0040] Figure 7 A structure diagram of a PCB module board in Figure 6 after injecting lens glue mixed with diffusion powder;

[0041] Figure 8 A structure diagram of a PCB module board in Figure 7PCB module board in the UV irradiation of the remaining photoresist, baking structure diagram;

[0042] Figure 9 For the walkway of the PCB module board in the black glue, the structure diagram after baking; Figure 8

[0043] Figure 10 For the top layer of the PCB module board in the black surface protection film attached and hot-pressed structure diagram. Figure 9 DETAILED DESCRIPTION

[0044] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers are used to designate the same elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not meant to represent all implementations consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0045] Embodiment One:

[0046] Mini LED chips (COB products) are applied to small-pitch direct display module boards as an example for illustration.

[0047] As shown in Figure 1 , the present application provides a module board Mini LED dispensing process based on photolithography technology, comprising:

[0048] Fix the Mini LED chips on the PCB module board through die bonding process;

[0049] Coat photoresist on the PCB module board, and use a mask plate to align the position of the Mini LED chips to perform photoetching through a set wavelength of ultraviolet light to leave a groove;

[0050] Stir the transparent glue mixed with diffusion powder to form lens glue with diffusion effect;

[0051] Inject lens glue with diffusion effect into the position without photoresist on the Mini LED chip by dispensing method, and the lens glue coverage height is more than 30 um but not higher than 60 um;

[0052] Irradiate the PCB module board with ultraviolet light to remove the remaining photoresist, and perform baking;

[0053] Inject black glue into the walkway between two adjacent Mini LED chips, and perform baking;

[0054] Attach black surface protection film to the top layer of the PCB module board, and perform hot pressing.​​

[0055] Figures 2-3 The PCB module board in the prior art and the structural diagram of the PCB module board in the prior art are shown in the following figure.

[0056] Compared with the module packaging structure in the prior art, the present application provides a module board Mini LED dispensing process based on photoetching technology. First, the die bonding process is performed to paste the Mini LED chips on the PCB module board. Then, the photoresist is coated on the PCB module board, and the mask plate is used to perform photoetching on the positions corresponding to the Mini LED chips by using ultraviolet light of a certain wavelength. The transparent glue (lens glue) is selected and diffusion powder is added to the glue to improve the light mixing effect. After the photoetching process is completed, the transparent glue is stirred and then applied on the Mini LED chips. The lens glue structure is formed by using the dispensing process to cover the Mini LED chips. Then, the same wavelength of ultraviolet light is used to irradiate the remaining part of the photoresist on the PCB module board to remove the photoresist. After the photoresist is removed, only the Mini LED chips are covered by the lens glue on the PCB module board. The PCB module board is then baked. After baking, black glue is injected between the lens glue and the gap between the adjacent lens glue of the two adjacent Mini LED chips. After the black glue is evenly spread to the walkway area, the black surface protection film is attached and then hot pressed. The adhesive layer under the black surface protection film has diffusion material to fill the uneven areas of the lens and the walkway black glue in the previous process, achieving the final leveling effect and the consistency of the light output. Compared with the prior art, the photoetching technology is used to pre-dig trenches to position and control the diffusion range of the subsequent glue dropping, control the size of the lamp beads, and reserve space for the subsequent walkway. The dispensing process is used to control the amount of glue dropping to ensure the consistency of the lamp bead size and height. The light diffusion powder is stirred in the lens glue to effectively improve the light transmittance and optimize the light mixing effect. The lens glue is used to cover the Mini LED chips to effectively reduce the impact of subsequent processes on the light-emitting components. The walkway black glue process between the lens glue gaps can effectively separate multiple lamp beads and avoid mutual interference, achieving the consistency of the overall color.

[0057] The specific implementation steps are as follows:

[0058] As shown in Figure 4 , first, the die bonding process is performed according to the spacing requirements between the PCB module boards. The Mini LED chips are precisely pasted onto the PCB module boards to ensure the accuracy of the chip positions and lay a foundation for subsequent processes.

[0059] As shown in Figure 5 , after the die bonding process is completed, the photoetching process is performed on the PCB module board. First, a layer of photoresist is uniformly coated on the surface of the PCB module.

[0060] As shown in Figure 6 After the photoresist is coated, the position of the Mini LED chip is aligned using a mask plate, and photoetching is performed using ultraviolet light with a wavelength of 365-436 nm. First, photoresist is coated on the PCB module board, and the Mini LED chip and the surrounding area are exposed and developed using photoetching technology for etching, positioning, and quantification of subsequent dispensing.

[0061] It should be noted that the photoresist exposed to ultraviolet light is etched, and the photoresist not exposed to ultraviolet light is retained, that is, only the photoresist in the part with the Mini LED chip is removed, and the photoresist in the walkway between the two adjacent Mini LED chips is retained. This process can accurately form a pattern corresponding to the Mini LED chip on the photoresist, providing precise positioning for subsequent glue injection and covering.

[0062] As shown in Figure 7 After the photoetching step is completed, transparent glue (Lens glue) is prepared. The main material of this transparent glue is epoxy resin, with a viscosity value range of 600-800 mpa.s, and diffusion powder is added to the lens glue. Preferably, the diffusion powder is organic microsphere powder. The role of the diffusion powder is to enable the glue to produce a diffusion effect after solidification, thereby improving the light uniformity of the Mini LED chip. Subsequently, the transparent glue is accurately injected onto the Mini LED chip through the dispensing process, forming a Lens glue structure that can cover the Mini LED chip, as shown in the light blue area in Figure 7 .

[0063] A layer of transparent lens glue with a thickness of more than 30 um but not higher than 60 um is covered on the surface of the Mini LED chip through dispensing to protect it, and the remaining photoresist is removed to achieve fixed amount and consistent coverage height when coating the transparent lens glue on the Mini LED chip, ensuring that the walkway between the two Mini LED chips is neat and meets the glue coating requirements.

[0064] As shown in Figure 8As shown, after the injection of the Lens glue is completed, the entire PCB module board is irradiated with ultraviolet light to remove the remaining photoresist; the wavelength of the ultraviolet light irradiation is the same as the wavelength of the ultraviolet light used in the photoetching process, and is preferably in the range of 365 nm to 436 nm; through ultraviolet light irradiation, only the area on the PCB module board where the Mini LED chip is covered by the Lens glue is retained. The PCB board is baked at 125°C for one hour, i.e., 60 minutes, to ensure that the Lens glue is completely cured and reaches a stable state. Black glue is injected on the PCB between the gap between the lens glue and its adjacent lens glue, and the black glue is used to separate multiple Mini LEDs to achieve the color consistency of the entire PCB.

[0065] As shown in Figure 9 After baking is completed, black glue (black glue) injection process is performed in the walkway area between the gap between the lens glue between two adjacent Mini LED chips and its adjacent lens glue, wherein the walkway area is indicated by a Figure 9 middle dark short horizontal line. The black glue includes a two-component epoxy resin solution, a black agent or a black pigment, and has a viscosity value in the range of 800 mpa.s to 1000 mpa.s. The black glue fills the walkway area and prevents light leakage to improve the color consistency of the Mini LED. After the black glue is uniformly diffused to the walkway area, 125°C baking is performed again for one hour to cure the black glue.

[0066] The height of the black glue is set to be more than 30 um but not higher than 60 um, which is high enough to improve the color consistency of the Mini LED while not being higher than the height of the lens glue coating to prevent affecting the packaging.

[0067] As shown in Figure 10 Finally, the attachment of the black surface protection film is performed. The bottom adhesive layer of this protection film contains a diffusion material, preferably oca optical glue, which can fill the uneven areas that may exist between the Lens glue and the walkway black glue in the previous process. Through a hot pressing process, the black surface protection film is firmly attached to the PCB board, thereby achieving the effect of overall flatness.

[0068] It should be noted that during the second layer point black glue process, i.e., the attachment of the black surface protection film to the uppermost layer of the PCB module, a whole piece of thermosetting film pressing process can be used instead of point diffusion transparent glue and intermediate walkway black glue, but the thermal stress generated by this process will affect the reliability of the subsequent mini chip welding.

[0069] Example Two:

[0070] The packaged lamp beads (POB products) are applied to a small-pitch direct display module board as an example for illustration.

[0071] The encapsulated lamp beads are pasted on the PCB product, and the black glue is injected between the encapsulated lamp and the adjacent encapsulated lamp beads, so as to achieve the consistency of the ink color of the PCB.

[0072] The black glue is injected to cover the non-encapsulated lamp bead area on the PCB synchronously, so as to achieve the consistency of the ink color when the module is not lit.

[0073] The height of the black glue is set to be more than 20 um but not higher than 60 um.

[0074] The light-emitting module is lit with uniformity in each viewing angle.

[0075] In summary, the Mini LED dispensing process based on the photoetching technology provided by the application has the following technical advantages compared with the prior art:

[0076] 1. Applicable to any size Mini LED chip and encapsulated lamp bead on the PCB;

[0077] 2. Applicable to any spacing;

[0078] 3. The photoetching technology controls the size of the lens glue coating part to be consistent, so that the amount of lens glue is strongly stable;

[0079] 3. The light mixing effect of the lamp beads in the light mixing lens;

[0080] 4. The whole piece of thermosetting film pressing process can be used to replace the existing COB module;

[0081] 5. The process sequence of coating glue first and then coating glue makes the Mini LED have better robustness.

[0082] It should be understood that the application is not limited to the precise construction which has been described above and illustrated in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the application is limited only by the claims that follow.

Claims

1. A module board Mini LED dispensing process based on photolithography technology, characterized in that: Mini LED chips are fixed onto the PCB module board using a die bonding process; Photoresist is coated on the PCB module board, and a mask is used to align the Mini LED chip with ultraviolet light to create a photolithographic groove. Stir the transparent glue mixed with the diffusion powder to form a lens glue with a diffusion effect; Lens adhesive with a diffusion effect is injected into the photoresist-free area of ​​the Mini LED chip by dispensing. The coverage height of the lens adhesive is more than 30 μm but not more than 60 μm. The PCB module board is irradiated with ultraviolet light to remove the remaining photoresist and then baked. Black glue is injected into the channel between two adjacent Mini LED chips and then baked.

2. The module board Mini LED dispensing process based on photolithography technology according to claim 1, characterized in that, Photoresist is coated on the PCB module board. After the photoresist is coated, a mask is used to align the Mini LED chip and photolithography is performed using ultraviolet light with a wavelength set from 365nm to 436nm.

3. The module board Mini LED dispensing process based on photolithography technology according to claim 1, characterized in that, Transparent adhesive materials include epoxy resins with a viscosity range of 600 mPa·s to 800 mPa·s.

4. The module board Mini LED dispensing process based on photolithography technology according to claim 3, characterized in that, The diffusion powder added to the transparent adhesive is an organic microsphere powder.

5. The module board Mini LED dispensing process based on photolithography technology according to claim 1, characterized in that, The specific steps for removing residual photoresist by irradiating the PCB module board with ultraviolet light are as follows: After the lens adhesive is injected, the entire PCB module is irradiated with ultraviolet light to remove any remaining photoresist. The wavelength of the ultraviolet light irradiation is the same as that of the ultraviolet light used in the photolithography process, ranging from 365nm to 436nm; When irradiated with ultraviolet light, only the area on the PCB module board where the Mini LED chip is covered by Lens adhesive remains.

6. The module board Mini LED dispensing process based on photolithography technology according to claim 1, characterized in that, The black adhesive consists of a two-component epoxy resin solution and a blackening agent, with a viscosity range of 800 mPa·s to 1000 mPa·s and a black adhesive coverage height of more than 30 μm but not more than 60 μm.

7. The module board Mini LED dispensing process based on photolithography technology according to claim 1, characterized in that, After injecting black glue into the channel between two adjacent Mini LED chips and baking it, a black surface protective film is attached to the top layer of the PCB module board and then hot-pressed.

8. The module board Mini LED dispensing process based on photolithography technology according to claim 7, characterized in that, The bottom adhesive layer of the black surface protective film contains a diffusion material to fill uneven areas between the lens adhesive and the black adhesive on the walkway.

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