Micro-LED solder resist process based on optical resin film and display device

Abstract

The invention provides a Micro-LED solder resist process based on an optical resin film and a display device, and relates to the technical field of semiconductor manufacturing, and the Micro-LED solder resist process comprises the following steps: carrying out super roughening treatment on a copper surface of a Micro-LED substrate; in a vacuum environment, an optical resin film is attached to the copper surface subjected to super roughening treatment, and a solder mask layer is formed; performing vacuum leveling treatment on the solder mask layer; carrying out curing treatment after exposure; and removing the part, covering the PAD region, of the solder mask layer in a grinding manner to form a solder mask window. The optical resin film is adopted to replace traditional liquid solder resist ink, and the technologies of vacuum fitting, vacuum leveling, curing after exposure, grinding and the like are combined, so that the manufacturing yield, reliability and other performance of the Micro-LED display device can be remarkably improved. As the optical resin film is a solid film, the defects of foreign matters, bubbles, uneven thickness and the like which are easily generated in the printing process of traditional liquid ink are avoided, so that the uniformity and the consistency of the solder mask layer are improved, and the risk of Micro-LED chip failure caused by the defects of the solder mask layer is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a Micro-LED solder mask process and a display device based on an optical resin film. Background Art

[0002] As an emerging display technology, Micro LED has the advantages of self-luminescence, high brightness, high contrast, low power consumption, and long life, and is considered a strong competitor for the next generation of display technology. However, Micro LED has smaller chip size, smaller pitch, and higher density, which puts higher requirements on the manufacturing process. As a key link in the manufacturing process of Micro LED display screens, the solder mask layer protects the circuit, prevents short circuits, and provides insulation, and its manufacturing process challenges are more prominent.

[0003] The traditional Micro LED solder mask process usually follows the PCB or similar process, using liquid solder mask ink and screen printing / inkjet printing, and then forming a solder mask layer through steps such as exposure, development, and curing. However, this traditional process is prone to the following problems when applied to Micro LEDs:

[0004] The accuracy of traditional silk screen / inkjet printing is difficult to meet the delicate requirements, and it is easy to cause defects such as solder mask bridging, open circuit, uneven thickness, etc., which seriously affect the display performance and yield of Micro LED.

[0005] Micro LED chips are tiny in size and have a very low tolerance for foreign matter and defects. Liquid ink is more likely to be mixed with impurities or produce bubbles during the printing process, forming foreign matter, causing the Micro LED chip to fail or display poorly.

[0006] The PAD size and pitch of Micro LED are smaller. The traditional exposure and development processes make it difficult to achieve precise PAD window opening, which can easily lead to ink covering the PAD or PAD copper exposure, seriously affecting the electrical connection reliability and yield of Micro LED.

[0007] Therefore, it is necessary to improve the existing solder mask process related technology to overcome the defects of the existing technology. Summary of the invention

[0008] In order to overcome the problems existing in the related art, one of the purposes of the present invention is to provide a Micro-LED solder mask process based on optical resin film. The solder mask process adopts optical resin film instead of liquid ink, and combines vacuum lamination, vacuum leveling, post-exposure curing and solder mask grinding and other processes to effectively solve the problems of poor precision, easy generation of foreign matter, PAD / copper exposure on ink and so on in the traditional Micro-LED solder mask process, and achieves high precision and high consistency of the solder mask layer, thereby improving product quality, yield and production efficiency, and reducing quality risks.

[0009] A Micro-LED solder mask process based on an optical resin film comprises the following steps:

[0010] Ultra-roughening of the copper surface of the Micro-LED substrate;

[0011] In a vacuum environment, an optical resin film is bonded to a copper surface that has been subjected to an ultra-roughening treatment to form a solder resist layer;

[0012] Performing a post-exposure curing process on the solder resist layer;

[0013] The portion of the solder resist layer covering the PAD area is removed by grinding to form a solder resist window.

[0014] Furthermore, after laminating the optical resin film on the ultra-roughened copper surface, the method further includes performing vacuum leveling on the solder resist layer.

[0015] Adding a vacuum leveling step can further enhance the fit and flatness between the optical resin film and the substrate, eliminate wrinkles and bubbles that may exist on the surface of the optical resin film, thereby improving the quality of the solder mask and further improving the luminous efficiency and uniformity of the Micro-LED chip.

[0016] Furthermore, the step of laminating the optical resin film on the ultra-roughened copper surface under a vacuum environment specifically includes:

[0017] At a vacuum degree of 1 hPa to 10 hPa, 1 kgf / cm 2 Up to 25kgf / cm 2 The optical resin film is bonded to the ultra-roughened copper surface under the conditions of pressure of 1000 ℃ and temperature of 70° C. to 180° C., and the bonding time is 30 s to 360 s.

[0018] The above-mentioned specific parameter range of vacuum bonding can ensure that the optical resin film and the substrate are bonded under the optimal vacuum, pressure and temperature conditions, thereby achieving the best bonding strength and uniformity, and improving the stability and repeatability of the process.

[0019] Furthermore, the vacuum leveling treatment of the solder resist layer specifically includes:

[0020] A release film is used, and a tension of 10N to 50N is applied to the release film at a temperature of 60° C. to 180° C., so that the release film acts on the optical resin film, and the processing time is 10s to 75s.

[0021] Using a release film and performing vacuum leveling treatment under specific temperature and tension conditions can more effectively eliminate wrinkles and stress on the optical resin film, improve its flatness, and avoid damage to the optical resin film caused by direct force, thereby further improving the quality of the solder mask layer.

[0022] Furthermore, the post-exposure curing process specifically includes:

[0023] The temperature is maintained at 80°C to 150°C for 10 min to 70 min, and then maintained at 160°C to 250°C for 10 min to 70 min.

[0024] The above-mentioned post-exposure curing treatment temperature and time parameters can ensure that the optical resin film is fully cured, improve its heat resistance and mechanical strength, and enhance its bonding force with the substrate, thereby improving the reliability and stability of the solder mask layer.

[0025] Further, the step of removing the portion of the solder resist layer covering the PAD area by grinding specifically includes:

[0026] Use a 400-5000 mesh ceramic abrasive brush for grinding.

[0027] By using the ceramic grinding brush with the above mesh size for grinding, the size and position of the PAD window can be precisely controlled to avoid damage to the Micro-LED chip and improve the uniformity and consistency of PAD copper exposure, thereby improving the electrical connection reliability and yield of the Micro-LED display device.

[0028] Furthermore, the optical resin film has a thickness of 10 μm to 100 μm.

[0029] The optical resin film in the above-mentioned thickness range can balance the insulation performance and light transmittance of the solder mask layer, and control the height of the solder mask layer to adapt to Micro-LED chips of different sizes and spacings, thereby optimizing the performance of Micro-LED display devices.

[0030] Furthermore, the optical resin film has a three-layer structure, including a black layer in the middle and release films respectively located on both sides of the black layer.

[0031] Furthermore, the substrate of the release film is selected from polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP).

[0032] The above-mentioned release film substrate material can ensure that the release film has good heat resistance, peelability and chemical stability, avoid contamination or damage to the optical resin film during the vacuum leveling process, and thus ensure the quality of the solder mask layer.

[0033] A second object of the present invention is to provide a Micro-LED display device, wherein the solder resist layer of the Micro-LED display device is prepared by the Micro-LED solder resist process as described above.

[0034] Since the Micro-LED display device prepared by the Micro-LED solder resist process provided by the present invention has a solder resist layer with higher precision, uniformity and reliability, the brightness, contrast, color uniformity and service life of the Micro-LED display device can be significantly improved.

[0035] The beneficial effects of the present invention are:

[0036] The present invention provides a Micro-LED solder mask process based on an optical resin film. The Micro-LED solder mask process based on an optical resin film can significantly improve the manufacturing yield and reliability of Micro-LED display devices by replacing traditional liquid solder mask ink with an optical resin film, and combining vacuum bonding, post-exposure curing and grinding processes. Since the optical resin film is a solid film, it avoids defects such as foreign matter, bubbles and uneven thickness that are easily generated by traditional liquid inks during the printing process, thereby improving the uniformity and consistency of the solder mask layer and reducing the risk of failure of the Micro-LED chip due to defects in the solder mask layer. The vacuum bonding process can ensure that the optical resin film is closely bonded to the substrate, further improve the uniformity and adhesion of the solder mask layer, reduce problems such as delamination and falling off, and enhance the reliability of the device. Post-exposure curing can enhance the heat resistance and mechanical strength of the optical resin film, so that it can better withstand subsequent processing and use environments. Finally, the optical resin film covering the PAD area is removed by grinding, and the window size and position of the PAD can be accurately controlled, thereby improving the electrical connection reliability and yield of the Micro-LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the process of the Micro-LED solder mask process based on optical resin film provided in this application. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0039] Example 1

[0040] like Figure 1 As shown, this embodiment provides a Micro-LED solder mask process based on an optical resin film.

[0041] The optical resin film-based Micro-LED solder mask process includes the following steps:

[0042] 1. Ultra-roughening treatment: Immerse a Micro-LED substrate in a micro-etching solution, such as sodium persulfate solution, for chemical roughening treatment. The treatment time is 2 to 5 minutes at a temperature of 40°C to 60°C. The purpose of this step is to increase the roughness of the copper surface of the substrate and enhance the bonding strength between the subsequent optical resin film and the substrate.

[0043] 2. Vacuum lamination: Place the ultra-roughened Micro-LED substrate into the vacuum lamination equipment and cover the substrate with a 25μm thick optical resin film. The optical resin film has a three-layer structure, including a black layer in the middle and PET release films on both sides of the black layer. The main component of the black layer is epoxy resin, and the thickness of the PET release film is 5μm to 50μm. Set the vacuum degree to 5.5hPa and the pressure to 5.5kgf / cm 2 , the temperature is 125℃, and the bonding time is 195 seconds. The vacuum environment can eliminate bubbles, ensure that the optical resin film is closely attached to the substrate, and form a uniform and defect-free solder mask layer.

[0044] 3. Vacuum leveling: Cover the optical resin film with a layer of PET release film, and apply a tension of 30N to the release film at a temperature of 120°C for 42.5 seconds. This step can further enhance the fit and flatness of the optical resin film and the substrate, and eliminate possible wrinkles and bubbles on the surface of the optical resin film.

[0045] 4. Post-exposure curing: Place the bonded substrate in an oven for post-exposure curing. First keep it at 115°C for 40 minutes, then keep it at 205°C for 40 minutes. Post-exposure curing can enhance the heat resistance and mechanical strength of the optical resin film, and enhance its bonding with the substrate, thereby improving the reliability and stability of the solder mask.

[0046] 5. Solder mask grinding: Use a 2700-mesh ceramic brush to grind the solder mask layer to remove the optical resin film covering the PAD area to form a solder mask window. This step can accurately control the size and position of the PAD window to avoid damage to the Micro-LED chip and improve the uniformity and consistency of PAD copper exposure.

[0047] The Micro-LED display device prepared by the solder resist process in this embodiment is tested:

[0048] The solderability test was conducted under the test condition of 265℃±3℃ / 3s, and the results showed no abnormalities such as discoloration, board explosion, wrinkling, cracked corners, white spots, blistering, oil shedding, etc.

[0049] Thermal stress test was carried out under the test conditions of 288℃±5℃ / 10s / 3 times, and the results showed no abnormalities such as discoloration, board explosion, wrinkling, cracked corners, white spots, blistering, oil shedding, resin shrinkage, pad floating, etc.

[0050] The reflow test was conducted under the test condition of HDI cracking program / 10 times, and the results showed no abnormalities such as discoloration, cracking, wrinkling, cracked corners, white spots, blistering, oil shedding, resin shrinkage, and pad floating.

[0051] The hardness test was conducted under the test conditions of 1H-8H pencil scratch, and the results showed that there were no scratches in the pencil test with a hardness of less than 6H;

[0052] Acid resistance test was carried out under the test condition of 10Vol.% H2SO4 / 30min, and the results showed that there was no defect such as solder mask falling off or ink roughness, stickiness, wrinkling, blistering, discoloration, delamination, white spots, etc.

[0053] The alkali resistance test was carried out under the test condition of 10 Vol.% NaOH / 30min, and the results showed that there was no defect such as solder mask falling off or ink roughness, stickiness, wrinkling, blistering, discoloration, delamination, white spots, etc.

[0054] Solvent resistance test was conducted under the test condition of AR grade isopropyl alcohol / 2min. The results showed that there was no defect such as solder mask falling off or ink roughness, stickiness, wrinkling, blistering, discoloration, delamination, white spots, etc.

[0055] The gold resistance test was carried out under the test conditions of Au:min0.05μm and Ni:min3μm. The results showed that there was no defect such as solder mask falling off or ink roughness, stickiness, wrinkling, blistering, discoloration, delamination, white spots, etc.

[0056] This embodiment uses an optical resin film of PET material, and through a vacuum lamination process, the optical resin film is closely attached to the Micro-LED substrate, and the formed solder mask is uniform and dense, without bubbles or wrinkles. The vacuum leveling step further improves the flatness of the solder mask. The post-exposure curing process makes the performance of the optical resin film more stable. The grinding process of the ceramic brush accurately removes the optical resin film in the PAD area to form a clear solder mask window without damaging the PAD. The Micro-LED display device finally prepared has passed a number of reliability tests, including solderability test, thermal stress test, reflow test, hardness test, acid resistance test, alkali resistance test, solvent resistance test and gold resistance test, and no abnormalities have occurred, proving that the solder mask prepared by this process has excellent heat resistance, chemical resistance and mechanical strength, and can effectively protect the Micro-LED chips and circuits, and improve the reliability and service life of the device.

[0057] Example 2

[0058] like Figure 1 As shown, this embodiment provides a Micro-LED solder mask process based on an optical resin film, and the Micro-LED solder mask process based on an optical resin film includes the following steps:

[0059] 1. Ultra-roughening treatment: Immerse a Micro-LED substrate in a micro-etching solution for chemical roughening treatment. The treatment time is 2 to 5 minutes at a temperature of 40°C to 60°C.

[0060] 2. Vacuum lamination: Place the ultra-roughened Micro-LED substrate into the vacuum lamination equipment and cover the substrate with a 10μm thick optical resin film. Set the vacuum degree to 1hPa and the pressure to 1kgf / cm 2 , the temperature is 70℃ and the bonding time is 30 seconds.

[0061] 3. Vacuum leveling: Cover the optical resin film with a layer of PE release film, and apply a tension of 10N to the release film at a temperature of 60°C for 10 seconds.

[0062] 4. Post-exposure curing: Place the bonded substrates in an oven for post-exposure curing, first at 80°C for 10 minutes, then at 160°C for 10 minutes.

[0063] 5. Solder mask grinding: Use a 5000 mesh ceramic brush to grind the solder mask layer to remove the optical resin film covering the PAD area to form a solder mask window.

[0064] This embodiment uses a thinner optical resin film and performs vacuum lamination at a lower vacuum degree, lower pressure, lower temperature and shorter lamination time, which is beneficial to improving production efficiency and reducing costs. The vacuum leveling and post-exposure curing process further optimizes the performance of the solder mask. The grinding process of the 5000 mesh ceramic brush is suitable for thinner optical resin films and can achieve fine PAD window openings. The solder mask prepared by this process can meet the requirements of Micro-LED devices for thin, high-precision solder mask layers and has good reliability.

[0065] Example 3

[0066] like Figure 1 As shown, this embodiment provides a Micro-LED solder mask process based on an optical resin film, and the Micro-LED solder mask process based on an optical resin film includes the following steps:

[0067] 1. Ultra-roughening treatment: Immerse a Micro-LED substrate in a micro-etching solution for chemical roughening treatment. The treatment time is 2 to 5 minutes at a temperature of 40°C to 60°C.

[0068] 2. Vacuum lamination: Place the ultra-roughened Micro-LED substrate into the vacuum lamination equipment and cover the substrate with a 100μm thick optical resin film. Set the vacuum degree to 10hPa and the pressure to 25kgf / cm 2 , the temperature is 180℃ and the bonding time is 360 seconds.

[0069] 3. Vacuum leveling: Cover the optical resin film with a layer of PP release film, and apply a tension of 50N to the release film at a temperature of 180°C for 75 seconds.

[0070] 4. Post-exposure curing: Place the bonded substrates in an oven for post-exposure curing, first at 150°C for 70 minutes, then at 250°C for 70 minutes.

[0071] 5. Solder mask grinding: Use a 400-mesh ceramic brush to grind the solder mask layer to remove the optical resin film covering the PAD area to form a solder mask window.

[0072] This embodiment uses a thicker optical resin film and performs vacuum lamination under higher vacuum, higher pressure, higher temperature and longer lamination time. The vacuum leveling and post-exposure curing processes have also been adjusted accordingly. The grinding process of a 400-mesh ceramic brush can effectively remove the thicker optical resin film and form a clear solder mask window. The solder mask prepared by this process has excellent high temperature resistance and mechanical strength, and is suitable for Micro-LED devices that have higher requirements for solder mask thickness and heat resistance.

[0073] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the application. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a restriction. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in the subsequent accompanying drawings.

[0074] In addition, it should be noted that the use of terms such as "first" and "second" to limit is only for the convenience of distinction. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A Micro-LED solder mask process based on an optical resin film, characterized in that: The following steps are involved: Ultra-roughening of the copper surface of the Micro-LED substrate; In a vacuum environment, an optical resin film is bonded to a copper surface that has been subjected to an ultra-roughening treatment to form a solder resist layer; Performing a post-exposure curing process on the solder resist layer; The portion of the solder resist layer covering the PAD area is removed by grinding to form a solder resist window.

2. The Micro-LED solder mask process based on optical resin film according to claim 1, characterized in that: After the optical resin film is attached to the ultra-roughened copper surface, the method further includes performing vacuum leveling on the solder resist layer.

3. The Micro-LED solder mask process based on optical resin film according to claim 2, characterized in that: The step of laminating the optical resin film on the ultra-roughened copper surface under a vacuum environment specifically includes: At a vacuum degree of 1 hPa to 10 hPa, 1 kgf / cm 2 Up to 25kgf / cm 2 The optical resin film is bonded to the ultra-roughened copper surface under the conditions of pressure of 1000 ℃ and temperature of 70° C. to 180° C., and the bonding time is 30 s to 360 s.

4. The Micro-LED solder mask process based on optical resin film according to claim 2, characterized in that: The vacuum leveling treatment of the solder mask layer specifically includes: A release film is used, and a tension of 10N to 50N is applied to the release film at a temperature of 60° C. to 180° C., so that the release film acts on the optical resin film, and the processing time is 10s to 75s.

5. The Micro-LED solder mask process based on optical resin film according to claim 1, characterized in that: The post-exposure curing process specifically includes: The temperature is maintained at 80°C to 150°C for 10 min to 70 min, and then maintained at 160°C to 250°C for 10 min to 70 min.

6. The Micro-LED solder mask process based on optical resin film according to claim 1, characterized in that: The step of removing the portion of the solder resist layer covering the PAD area by grinding specifically includes: Use a 400-5000 mesh ceramic abrasive brush for grinding.

7. The Micro-LED solder mask process based on optical resin film according to claim 1, characterized in that: The optical resin film has a thickness of 10 μm to 100 μm.

8. The Micro-LED solder mask process based on optical resin film according to claim 1, characterized in that: The optical resin film has a three-layer structure, including a black layer in the middle and release films respectively located on both sides of the black layer.

9. The Micro-LED solder mask process based on optical resin film according to claim 4, characterized in that: The substrate of the release film is selected from polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP).

10. A Micro-LED display device, characterized in that: The solder resist layer of the Micro-LED display device is prepared by the Micro-LED solder resist process according to any one of claims 1 to 9.

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