Novel module board Mini LED dispensing process based on photoetching technology

Abstract

The invention discloses a novel module board Mini LED dispensing process based on a photoetching technology, and belongs to the technical field of display. The method comprises the following steps of: coating photoresist on a PCB (Printed Circuit Board) module board, exposing, developing and etching a position and a nearby area where a Mini LED chip is located by utilizing a photoetching technology, only removing the photoresist of the part provided with the Mini LED chip after the photoresist is flatly paved on the PCB module board, pouring lens glue which is subjected to a stirring diffusion powder lifting light mixing process into the PCB module board, and then removing the photoresist of the other part; then, a black glue dispensing process is carried out on the middle walkway; and finally, a coating protection process is carried out on the outermost layer of the PCB module board. According to the novel module board Mini LED dispensing process based on the photoetching technology, it can be guaranteed that the Mini LED can be protected to the minimum extent in the follow-up operation through the design mode of dispensing and coating firstly, the Mini LED is coated with glue firstly and then dispensed through the photoetching technology, it can be guaranteed that the thickness and the using amount of glue are consistent to a certain extent, and stable quality is guaranteed.

Description

Technical Field

[0001] This application relates to the field of display technology, and particularly to a new type of module board Mini LED dispensing process based on lithography technology. Background Art

[0002] With the continuous development of display technology, the Mini RGB direct display module board, as a high-resolution and high-contrast display product, has gradually occupied 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 COB (Chip on Board) technology that has developed rapidly in recent years.

[0003] In the POB technology, Mini LED lamp beads are pasted onto the PCB (printed circuit board) through a die bonding device, and then a black grid plate is filled in the gaps between the lamp beads. The main function of the black grid plate is to improve the ink color performance of the PCB, enhance the display contrast, and reduce the light crosstalk phenomenon. However, the POB technology has obvious limitations: First, the introduction of the black grid plate increases the thickness and weight of the module board, affecting the thin and light design of the product; Second, the black grid plate has a certain hindrance to the heat dissipation performance, which may lead to a shortened lifespan of the LED lamp beads; Finally, the production process of the POB technology is relatively complex and the cost is high.

[0004] With the continuous progress of LED chip manufacturing technology, the COB technology has gradually become the mainstream development direction of the Mini RGB direct display module board. The COB technology directly pastes the Mini LED chips onto the PCB through a die bonding device, eliminating the steps of traditional lamp bead packaging, thus achieving a thinner, lighter, and higher integration design. In addition, the 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, the COB technology also faces some technical challenges: First, due to the cancellation of the black grid plate, the COB products have deficiencies in the mixing light effect, and it is easy to appear halos or color unevenness; Second, it is difficult to ensure the ink color consistency of the PCB module board, affecting the quality of the display effect; Finally, the existing black glue covering method usually adopts the process of applying glue first and then encapsulating, and this process is easy to damage the Mini LED chips themselves, affecting the reliability and lifespan of the products.

[0005] In view of the above problems, in the prior art, attempts have been made to improve the performance of COB products by improving encapsulation materials and processes. For example, black glue is used to cover to improve the ink color consistency and light mixing effect. However, these methods often cannot balance process precision and product reliability. Especially, there are large fluctuations in the control of the thickness and dosage of the encapsulation glue, resulting in unstable product quality. Therefore, there is an urgent need for a new encapsulation process that can improve the light mixing effect, ink color consistency, and bright and dark state taste while ensuring the safety of Mini LED chips, and at the same time achieve precise process control and quality stability.

[0006] In summary, the existing Mini RGB direct display module board manufacturing technologies, especially the COB technology, although have advantages in terms of thinness, lightness, heat dissipation, and optical performance, still have significant deficiencies in terms of light mixing effect, ink color consistency, and process reliability. Summary of the Invention

[0007] In order to solve the above deficiencies existing in the prior art, the present application provides a new type of module board Mini LED dispensing process method based on lithography technology.

[0008] The technical solution is as follows:

[0009] Provide a new type of module board Mini LED dispensing process based on lithography technology,

[0010] Fix the Mini LED chips on the PCB module board through die bonding process;

[0011] Coat photoresist on the PCB module board, and use a mask plate to align with the position where the Mini LED chips are located and perform photolithography to leave grooves through ultraviolet light;

[0012] Stir the transparent glue mixed with diffusion powder to form a lens glue with a diffusion effect;

[0013] Inject the lens glue with a diffusion effect into the positions without photoresist on the Mini LED chips by dispensing;

[0014] Irradiate the PCB module board with ultraviolet light to remove the remaining photoresist, and perform baking;

[0015] Inject black glue into the walkway between the lens glues of two adjacent Mini LED chips and the gap between the adjacent lens glues, and perform baking.

[0016] A further technical solution is to coat photoresist on the PCB module board. After coating the photoresist, use a mask plate to align with the position where the Mini LED chips are located, and perform photolithography through ultraviolet light with a set wavelength of 365 nm to 436 nm.

[0017] Further technical solution: Inject lens glue with a diffusion effect into the position without photoresist on the Mini LED chip by means of dispensing. The covering height of the lens glue is more than 30um but not higher than 60um.

[0018] Further technical solution: The transparent glue material is epoxy resin, and the viscosity value ranges from 600 mpa.s to 800 mpa.s.

[0019] Further technical solution: The diffusion powder added to the transparent glue is organic microsphere powder.

[0020] Further technical solution: The specific steps for irradiating the PCB module board with ultraviolet light to remove the remaining photoresist are as follows:

[0021] After the injection of the lens glue is completed, irradiate the entire PCB module board 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 photolithography process, and the range is 365nm to 436nm; through the ultraviolet light irradiation, only the area of the Mini LED chip covered by the lens glue is retained on the PCB module board.

[0022] Further technical solution: The black glue includes a two-component epoxy resin solution, a blackening agent or melanin, the viscosity value ranges from 800 mpa.s to 1000 mpa.s, and the covering height of the black glue is more than 30um but not higher than 60um.

[0023] Further technical solution: Inject black glue into the aisle between two adjacent Mini LED chips and bake it. After that, attach a black surface protection film to the top layer of the PCB module board and perform hot pressing.

[0024] Further technical solution: The bottom adhesive layer of the black surface protection film contains a diffusion material, which is used to fill the uneven area between the lens glue and the aisle black glue.

[0025] Further technical solution: The baking temperature is 125°C and the time is 60 minutes.

[0026] This technical solution has at least the following technical effects:

[0027] 1. By first applying photoresist on the PCB module board and using photolithography technology to expose and develop in the area where the Mini LED chip is located or nearby for etching, positioning and quantification are carried out for subsequent dispensing.

[0028] 2. Through the production and adjustment of the transparent lens glue and the light-scattering powder added in the glue, a more uniform light mixing effect is obtained after multiple total internal reflections inside the lamp bead.

[0029] 3. First, apply a layer of photoresist to the Mini LED chip, and then etch the photoresist by irradiating ultraviolet light on part of the Mini LED to achieve the purpose of accurately positioning the coated area.

[0030] 4. Protect the Mini LED surface by covering it with a layer of transparent lens glue through dispensing, and then remove the remaining photoresist to achieve a fixed dosage and consistent covering height when applying the transparent lens glue to the Mini LED, ensuring that the aisle between two Mini LED chips is neat and meets the glue application requirements.

[0031] 5. Inject black colloid into the gap between the lens glue and its adjacent lens glue on the PCB, and divide multiple Mini LEDs through the black colloid to achieve the overall ink color consistency of the PCB.

[0032] 6. Set the height of the black colloid high enough to improve the ink color consistency while not exceeding the height of the lens glue coating to prevent affecting the encapsulation.

[0033] 7. The uniformity of each viewing angle of the lighting module is lit. Description of the Drawings

[0034] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments in line with this application, and are used together with the specification to explain the principles of this application.

[0035] Figure 1 A process flow chart of a novel modular board Mini LED dispensing process based on lithography technology provided for a preferred embodiment of this application;

[0036] Figure 2 A schematic structural diagram of a PCB modular board in the prior art;

[0037] Figure 3 A schematic structural diagram of a PCB modular board in the prior art for the encapsulation protection process;

[0038] Figure 4 A schematic structural diagram of a PCB modular board for the die bonding process provided for a preferred embodiment of this application;

[0039] Figure 5 For Figure 4 The structural diagram of the PCB modular board after spreading photoresist;

[0040] Figure 6 For Figure 5 The structural diagram of the PCB modular board after ultraviolet lithography irradiation;

[0041] Figure 7 For Figure 6Schematic diagram of the structure of the PCB module board after injecting lens glue mixed with diffusion powder;

[0042] Figure 8 For Figure 7 Schematic diagram of the structure of the PCB module board after irradiating with ultraviolet light to remove glue and baking;

[0043] Figure 9 For Figure 8 Schematic diagram of the structure of the PCB module board after injecting black glue into the aisle and baking;

[0044] Figure 10 For Figure 9 Schematic diagram of the structure of the PCB module board after attaching and hot - pressing a black surface protection film to the top layer; Detailed implementation mode

[0045] Here, exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0046] Embodiment 1:

[0047] Taking the application of Mini LED chips (COB products) on a small - pitch direct - view module board as an example for illustration.

[0048] As Figure 1 shown, the embodiment of the present application provides a new module - board Mini LED dispensing process based on lithography technology, including:

[0049] Fixing Mini LED chips on the PCB module board through die - bonding technology;

[0050] Coating photoresist on the PCB module board, and using a mask plate to align with the position where the Mini LED chips are located and performing photolithography to leave grooves through ultraviolet light of a set wavelength;

[0051] Stirring the transparent glue mixed with diffusion powder to form lens glue with a diffusion effect;

[0052] Injecting lens glue with a diffusion effect into the positions without photoresist on the Mini LED chips by means of dispensing;

[0053] Irradiating the PCB module board with ultraviolet light to remove the remaining photoresist and performing baking;

[0054] Inject black glue into the aisle between two adjacent Mini LED chips and bake them;

[0055] A black surface protection film is attached to the top layer of the PCB module board and heat pressed.

[0056] Figures 2 - 3 The figure shows a structural schematic diagram of a PCB module board and a packaging and protection process of a PCB module board in the prior art.

[0057] Compared with the module packaging structure in the prior art, the present application provides a new module board Mini LED dispensing process based on photolithography technology, which first performs a solid crystal process to mount the Mini LED chip on the PCB module board. Photoresist is applied to the PCB module board, and a mask is used to perform photolithography at the position corresponding to the Mini LED chip through ultraviolet light of a set wavelength. Transparent glue (lens glue) is selected and diffused powder is added to the glue to enhance the light mixing effect. After the photolithography step is completed, the stirred transparent glue is applied above the Mini LED chip, and a lens glue structure that just covers the Mini LED is formed by a dispensing process. Then the entire PCB module board is irradiated with ultraviolet light of the same wavelength to remove the photoresist on the rest of the board. After the degumming is completed, only the Mini LED chip on the PCB module board is just covered by the lens glue. The PCB module board is baked. After baking, the black glue injection process is carried out between the two adjacent Mini LED chips, the gap between the lens glue and the adjacent lens glue, and the black glue is evenly diffused to the walkway area before baking. Subsequently, a black surface protective film is applied and then a hot pressing process is carried out. The adhesive layer under the black surface protective film has a diffusion material that can fill the uneven area between the lens and the walkway black glue in the previous process, so as to achieve the final leveling effect and achieve light consistency. Compared with the existing technology, the diffusion range of the subsequent glue drop is positioned and controlled by digging grooves in advance through photolithography technology, and space is reserved for the subsequent walkway while controlling the size of the formed lamp beads. Then, the glue drop amount is controlled by glue dispensing to ensure the consistency of the size and height of the lamp beads. By stirring the light diffusion powder in the lens glue, the transmittance can be effectively improved and the mixing light effect can be optimized. By first covering the mini LED with glue dispensing, the impact of subsequent processes on the light-emitting components can be effectively reduced. The black glue dispensing process for the walkway in the gap of the lens glue can effectively divide multiple lamp beads, avoid mutual interference, and achieve overall ink color consistency.

[0058] The specific implementation steps are as follows:

[0059] like Figure 4 As shown in the figure, first of all, it is necessary to carry out the die bonding process according to the spacing requirements between the PCB module boards. The Mini LED chip is accurately mounted on the PCB module board to ensure that the chip is positioned accurately, laying the foundation for subsequent processes.

[0060] As Figure 5 shown, after the die bonding process is completed, the PCB module board is then subjected to photolithography. First, a layer of photoresist is evenly coated on the surface of the PCB module.

[0061] As Figure 6 shown, after the photoresist is coated, the mask is aligned with the position of the Mini LED chip, and photolithography is performed through ultraviolet light with a set wavelength of 365 nm to 436 nm. Among them, photoresist is first coated on the PCB module board, and photolithography technology is used to expose, develop and etch in the area where the Mini LED chip is located and its vicinity, for positioning and quantification of subsequent dispensing.

[0062] It should be noted that the photoresist irradiated by ultraviolet light is etched, while the photoresist not irradiated by ultraviolet light is retained. That is to say, only the photoresist on the part where the Mini LED chip is installed is removed, and the photoresist on the aisle between 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.

[0063] As Figure 7 shown, after the photolithography process is completed, transparent glue (Lens glue) is prepared. The main material of this transparent glue is epoxy resin, and the viscosity value ranges from 600 mPa.s to 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 make the glue produce a diffusion effect after curing, so as to improve the light-emitting uniformity of the Mini LED chip. Subsequently, the transparent glue is precisely injected above the MiniLED chip through the dispensing process to form a Lens glue structure that exactly covers the Mini LED chip, as Figure 7 shown by the light blue area in

[0064] 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 by dispensing for protection, and then the remaining photoresist is removed, so as to fix the dosage and ensure the consistent covering height when coating the transparent lens glue on the Mini LED chip, ensuring that the aisle between two Mini LED chips is neat and meets the dispensing requirements.

[0065] As 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 that used in the photolithography process, preferably in the range of 365 nm to 436 nm. Through the ultraviolet light irradiation, only the area of the Mini LED chips covered by the Lens glue remains on the PCB module board. The PCB board is baked and heated at 125 °C for one hour, i.e., 60 minutes, to ensure that the Lens glue is completely cured and reaches a stable state. Between the gaps of the lens glue and its adjacent lens glue, a black colloid is injected onto the PCB, and multiple Mini LEDs are segmented by the black colloid to achieve the overall black color consistency of the PCB.

[0066] As Figure 9 shown, after baking, a black glue (black colloid) injection process is carried out in the aisle area between the lens glue and its adjacent lens glue between two adjacent Mini LED chips. Among them, the aisle area is as Figure 9 shown by the dark black short horizontal lines in the figure. The black colloid includes a two-component epoxy resin solution, a blackening agent or melanin, and the viscosity value ranges from 800 mPa·s to 1000 mPa·s. The function of the black glue is to fill the aisle area and prevent light leakage to improve the black color consistency of the Mini LED. After the black glue evenly diffuses into the aisle area, it is baked and heated at 125 °C for another hour to cure the black glue.

[0067] The height of the black colloid is set to be more than 30 μm but not higher than 60 μm, ensuring that it is high enough above the Mini LED to achieve the purpose of improving the black color consistency while not being higher than the height of the lens glue coating to prevent affecting the encapsulation.

[0068] As Figure 10 shown, finally, a black surface protective film is attached. The bottom adhesive layer of this protective film contains a diffusion material, preferably oca optical glue, which can fill the uneven areas that may exist between the Lens glue and the aisle black glue in the previous process. Through a hot pressing process, the black surface protective film is firmly attached to the PCB board, thereby achieving an overall flat effect.

[0069] It should be noted that when applying the second layer of black glue process, that is, when attaching the black surface protective film to the top layer of the PCB module, a whole-piece thermosetting laminating process can be used to replace the dot-diffusion transparent glue and the middle aisle black glue, but the thermal stress generated by this process will have an impact on the reliability of subsequent mini chip soldering.

[0070] Example Two:

[0071] Taking the encapsulation lamp bead (POB product) applied to a small-pitch direct-view module board as an example for illustration.

[0072] The encapsulated LED chips are pasted on the PCB product. By injecting the above-mentioned black colloid between the encapsulated LED and its adjacent encapsulated LED chips, the ink color consistency of the PCB is achieved.

[0073] The injected black colloid simultaneously covers the non-encapsulated LED chip area on the PCB, achieving ink color consistency when the module is not lit.

[0074] The height of the black colloid is set to be more than 20um but not higher than 60um.

[0075] The uniformity of the light emission module at each viewing angle.

[0076] In summary, compared with the prior art, a novel module board Mini LED dispensing process based on lithography technology provided by this application has the following technical advantages:

[0077] 1. Applicability to Mini LED chips and encapsulated LED chips of any size on the PCB;

[0078] 2. Applicability to any pitch;

[0079] 3. The lithography technology controls the size of the lens glue coating part to be consistent, making the control of the amount of lens glue have strong stability;

[0080] 3. The light mixing effect of the LED chip in the light mixing lens;

[0081] 4. It can replace the existing COB module and use the whole-piece thermosetting laminating process;

[0082] 5. The process sequence of applying glue first and then coating glue makes the Mini LED have better robustness.

[0083] It should be understood that this application is not limited to the exact structure already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is only limited by the appended claims.

Claims

1. A novel module board Mini LED dispensing process based on photolithography technology, characterized by: Fix the Mini LED chip on the PCB module board through the die bonding process; Coat photoresist on the PCB module board, and use a mask to align the position of the Mini LED chip and perform photolithography to leave grooves through ultraviolet light; Stir the transparent glue mixed with diffusion powder to form lens glue with diffusion effect; Lens glue with diffusion effect is injected into the position without photoresist on the Mini LED chip by dispensing; Irradiate the PCB module board with ultraviolet light to remove the remaining photoresist, and then bake it; Black glue is injected into the aisle between two adjacent Mini LED chips and then baked.

2. According to the novel module board Mini LED dispensing process based on photolithography technology according to claim 1, it is characterized in that: Photoresist is applied on the PCB module board. After applying the photoresist, the mask is used to align the position of the Mini LED chip, and photolithography is performed using ultraviolet light with a set wavelength of 365nm to 436nm.

3. According to the novel module board Mini LED dispensing process based on photolithography technology according to claim 1, it is characterized in that: Lens glue with diffusion effect is injected into the non-photoresist position on the Mini LED chip by dispensing, and the coverage height of the lens glue is more than 30um but not higher than 60um.

4. According to the novel module board Mini LED dispensing process based on photolithography technology according to claim 1, it is characterized in that: The transparent glue material includes epoxy resin, and the viscosity value ranges from 600mpa.s to 800mpa.s.

5. According to the novel module board Mini LED dispensing process based on photolithography technology according to claim 4, it is characterized in that: The diffusion powder added in the transparent glue is organic microsphere powder.

6. The novel module board Mini LED dispensing process based on photolithography technology according to claim 1 is characterized in that: The specific steps of irradiating the PCB module board with ultraviolet light to remove the remaining photoresist are: After the injection of 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 ultraviolet light used in the photolithography process, ranging from 365nm to 436nm; Through the ultraviolet light irradiation, only the area of ​​the Mini LED chip covered by the Lens glue is retained on the PCB module board.

7. The novel module board Mini LED dispensing process based on photolithography technology according to claim 1 is characterized in that: The black glue includes a two-component epoxy resin solution, a black agent or a melanin, and the viscosity value ranges from 800mpa.s to 1000mpa.s. The black glue coverage height is more than 30um but not higher than 60um.

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

9. The novel module board Mini LED dispensing process based on photolithography technology according to claim 8 is characterized in that: The bottom adhesive layer of the black surface protection film contains diffusion material for filling the uneven area between the lens glue and the walkway black glue.

10. The novel module board Mini LED dispensing process based on photolithography technology according to claim 1 is characterized in that: The baking temperature is 125° C. and the baking time is 60 minutes.

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