High-reflectivity Mini LED PCB preparation technology

Abstract

The invention discloses a preparation process of a high-reflectivity Mini LED PCB. The preparation process comprises the following steps of solder mask pretreatment, solder mask screen printing, pre-baking, exposure, development and post-baking. White solder resist ink is adopted for solder resist printing, and a preparation method of the white solder resist ink comprises the steps that photosensitive resin is divided into a first part of photosensitive resin and a second part of photosensitive resin, the first part of photosensitive resin, a photoinitiator A and a monomer with the functionality of 1-2 are evenly stirred and evenly sprayed to the surface of titanium dioxide, then baking and pre-exposure are conducted, and coated titanium dioxide is obtained; and uniformly mixing the coated titanium dioxide with a second part of photosensitive resin, a photoinitiator B, a monomer with the functionality of 3-6 and an auxiliary agent. According to the invention, the titanium dioxide is coated by the photosensitive resin to prepare the coated titanium dioxide, and the dispersity of the titanium dioxide in the ink can be improved without adding a dispersing agent; and moreover, the influence of the doping of the titanium dioxide pigment on the mechanical anchoring capability of the printing ink is reduced, and the adhesive force of the printing ink and the PCB substrate is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuit boards, and specifically relates to a high-reflectivity Mini LED PCB preparation process. Background Art

[0002] Mini LEDs (miniature light-emitting diodes) are small and feature custom-cut designs. They can also be used with flexible substrates to create highly curved backlights. They employ local dimming for improved color quality. They are suitable for large commercial displays, as well as televisions, automotive panels, and gaming laptops. Therefore, Mini LEDs require high reflectivity.

[0003] The main factor affecting the surface reflectivity of Mini LED printed circuit boards is the white solder mask ink layer. Currently, there are two main problems with white solder mask ink: 1. Titanium dioxide is a commonly used pigment in white solder mask ink. Due to its small particle size, it is easy to agglomerate and has poor compatibility with organic resins, resulting in poor dispersibility. Although conventional dispersants can improve the dispersibility of titanium dioxide, different dispersants have different effects on the dispersion of titanium dioxide, requiring a tedious screening process and controlling the adaptability of the dispersant to the system, resulting in a complicated process. In addition, the dispersant is also likely to affect the surface properties of titanium dioxide, thereby affecting the performance of titanium dioxide.

[0004] 2. Currently, in order to produce high-reflectivity Mini LED PCBs, it is usually necessary to increase the amount of white pigment titanium dioxide added to the solder resist ink. When the titanium dioxide content is high, the mechanical anchoring ability of the resin is easily reduced, resulting in reduced ink adhesion.

[0005] In summary, how to provide a high-reflectivity Mini LED PCB preparation process by improving the dispersibility of titanium dioxide in white solder mask ink and reducing the impact of high titanium dioxide content on ink adhesion is an urgent problem that needs to be solved. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a high-reflectivity Mini LED PCB preparation process. Titanium dioxide is coated with a photosensitive resin to obtain coated titanium dioxide. The coated titanium dioxide has good compatibility with the ink system and can improve the dispersibility of titanium dioxide in the ink without adding a dispersant. The method is simple and has no adverse effects. Moreover, the present invention introduces a cationic photopolymerization reaction on the surface of the coated titanium dioxide and the PCB substrate, thereby reducing the impact of the incorporation of titanium dioxide pigment on the mechanical anchoring ability of the ink, thereby improving the adhesion of the ink to the PCB substrate.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A high-reflectivity Mini LED PCB preparation process includes the following steps: (1) Pre-soldering of the PCB substrate (including cleaning and roughening of the substrate); (2) Use white solder resist ink for solder resist screen printing (screen printing, 32T-51T, 20-30μm printing thickness); (3) Pre-baking: 75-80℃×10-40min; (5) Exposure: 365nm wavelength exposure machine, ink surface 300-800mj / cm 2 ; (6) Development: The developing temperature is 28-33°C and the spray pressure is 0.15-0.18 MPa; (7) Post-baking: 150℃, 60min.

[0008] The raw materials for preparing the white solder resist ink include 30-60 parts of photosensitive resin, 20-50 parts of titanium dioxide (0.01-10 μm), 2-10 parts of photoinitiator, 10-30 parts of double bond-containing monomer and 0-20 parts of auxiliary agent.

[0009] The photoinitiator includes photoinitiator A and photoinitiator B in a mass ratio of 1:(8-12), the photoinitiator A includes a free radical photoinitiator with an absorption wavelength range of 380-420 nm, and the photoinitiator B is a free radical photoinitiator with an absorption wavelength range of 320-370 nm.

[0010] Preferably, the photoinitiator A is TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide), 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) or ITX (isopropylthioxanthone), and the photoinitiator B is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone) or 651 (benzoin methyl ether).

[0011] The double bond-containing monomers include 1-2 functional monomers and 3-6 functional monomers in a mass ratio of 1:(9-14).

[0012] Preferably, the 1-2 functional monomer is one or more of an acrylate monomer, vinyl ester monomer, crotonate monomer, or phosphate monomer containing 1-2 double bonds; Preferably, the 1-2 functional monomer comprises a phosphate monomer containing 1-2 double bonds and an acrylate monomer containing 1-2 double bonds in a mass ratio of 1:(1-3). The acrylate monomer containing 1-2 double bonds is one or more of glycidyl methacrylate (GMA), allyl methacrylate (AMA), 1,6-hexanediol diacrylate (HDDA), and tripropylene glycol diacrylate (TPGDA). The phosphate monomer containing 1-2 double bonds is one or both of trimethyl 4-phosphocrotonate and allyl diethyl phosphate.

[0013] More preferably, the 1-2 functional monomer comprises trimethyl 4-phosphocrotonate and glycidyl methacrylate in a mass ratio of 1:(1-3).

[0014] The 3-6 functional monomer is one or any combination of acrylate monomers, vinyl ester monomers, and crotonate monomers containing 3-6 double bonds.

[0015] Preferably, the 3-6 functional monomer is an acrylate monomer containing 3-6 double bonds, and the acrylate monomer containing 3-6 double bonds is one or any combination of trimethylolpropane triacrylate (TMPTA), 3-ethoxy-trimethylolpropane triacrylate (3EOTMPTA), propoxylated trimethylolpropane triacrylate (POTMPTA), isopentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate (DPHA).

[0016] Preferably, the photosensitive resin is unsaturated polyester, acrylic resin, epoxy resin or epoxy acrylic resin. More preferably, the photosensitive resin is epoxy acrylic resin.

[0017] Preferably, the titanium dioxide is rutile titanium dioxide, and the additives include one or any combination of 0.5-2 parts of a leveling agent, 2-6 parts of an antioxidant, 1-3 parts of a defoaming agent, 1-2 parts of an adhesion promoter, and 1-3 parts of an ultraviolet absorber.

[0018] The preparation method of the white ink comprises the following steps: The photosensitive resin was divided into the first photosensitive resin and the second photosensitive resin in a mass ratio of 1: (10-15). The first photosensitive resin, photoinitiator A and 1-2 functional monomer were mixed evenly and sprayed evenly on the surface of titanium dioxide. Then, it was baked at 70-80℃ for 5-10 minutes and pre-exposed in a 395nm exposure machine with an exposure parameter of 50-200 mj / cm 2 , to obtain coated titanium dioxide, mix the coated titanium dioxide with the second portion of photosensitive resin, photoinitiator B, 3-6 functional (double bond) monomer and additives evenly.

[0019] Preferably, the photoinitiator A further comprises a cationic photoinitiator 1, and the mass ratio of the 380-420 nm free radical photoinitiator to the cationic photoinitiator 1 is 1:(0.5-1).

[0020] Preferably, the solder mask pre-treatment further comprises: spraying the cationic photoinitiator 2 solution evenly onto the surface of the PCB substrate, with the spraying amount of the cationic photoinitiator 2 being 0.8-3 g / m 2 , the concentration of cationic photoinitiator 2 solution is 0.5-20%.

[0021] Preferably, the cationic photoinitiator 1 and the cationic photoinitiator 2 are any one or more of diaryl iodonium salts, triaryl sulfonium salts (triaryl hexafluorophosphate sulfonium salts), and alkyl sulfonium salts.

[0022] The present invention also provides a development process in the high-reflectivity Mini LED PCB preparation process, wherein the developer used includes 0.8-1.8 parts of sodium carbonate and 100-150 parts of water.

[0023] Preferably, the developer further comprises 1-4 parts of an amino compound and 1-6 parts of propylene carbonate.

[0024] Preferably, the amino compound is any one or more of nicotinamide ethyl ester, choline acetate, ethanolamine, ammonia water, and triethylamine.

[0025] More preferably, the amino compound comprises 0.4-1 parts of choline acetate and 0.6-3 parts of nicotinamide ethyl ester.

[0026] Technical effects of the present invention: 1. When preparing white solder resist ink, the present invention coats titanium dioxide with a photosensitive resin and then uses low-energy UV for pre-exposure curing (initial setting), thereby producing coated titanium dioxide, which has good compatibility with the ink system and can improve the dispersibility of titanium dioxide in the ink without adding a dispersant. The method is simple and has no adverse effects.

[0027] 2. The white solder resist ink prepared by the present invention is prone to the phenomenon that the photosensitive resin in the coated titanium dioxide undergoes pre-exposure during the subsequent ink exposure, and the photosensitive resin in the coated titanium dioxide and the photosensitive resin in the main body of the ink are cured asynchronously, which affects the dispersion of the titanium dioxide in the ink and the incomplete curing of the resin, and is also prone to stratification due to the decrease in interfacial bonding strength.

[0028] Therefore, the present invention controls the curing speed of the photosensitive resin in the coated titanium dioxide and the photosensitive resin in the ink body by controlling the composition of the photoinitiator and the monomer, wherein the photoinitiator includes photoinitiator A (absorption wavelength range is 380-420nm) and photoinitiator B (absorption wavelength range is 320-370nm), and the monomer includes 1-2 functional monomers and 3-6 functional monomers. Photoinitiator A and 1-2 functional monomers are used in the coated titanium dioxide, and photoinitiator B and 3-6 functional monomers are used in the ink body. This can comprehensively adjust the resin cross-linking speed and achieve synergistic optimization of highly dispersed titanium dioxide and the ink system.

[0029] 3. The 1-2 functional monomers used in the coated titanium dioxide of the present invention are preferably trimethyl 4-phosphobutenoate and glycidyl methacrylate, which can not only improve the adhesion of the surface coating layer on the surface of the titanium dioxide, making the surface coating layer of the titanium dioxide not easy to fall off, and improving the coating stability of the coated titanium dioxide, but also form a rough coating layer on the surface of the titanium dioxide during pre-curing, promote the bite of the rough coated titanium dioxide and the ink system, improve the regional uniformity of the ink layer, and thus improve the reflectivity uniformity.

[0030] 4. The photoinitiator A in the coated titanium dioxide of the present invention also includes a cationic photoinitiator 1, and the pre-solder mask treatment also includes spraying a cationic photoinitiator 2 on the surface of the PCB substrate, so that cationic photopolymerization reactions occur on both the coated titanium dioxide and the PCB substrate surfaces. During the reaction, positive ion active centers are generated on the surface of the titanium dioxide and the substrate surface. As a result, there is a certain repulsive force between the coated titanium dioxide and the surface of the PCB substrate, which reduces the binding between the coated titanium dioxide and the surface of the PCB substrate, and reduces the effect of the incorporation of titanium dioxide pigment on the mechanical anchoring ability of the ink, thereby improving the adhesion of the ink to the PCB substrate.

[0031] 5. Since the coated titanium dioxide used in the white ink of the present invention is a pre-cured product, no cationic photopolymerization reaction occurs in the non-exposed area and there is no repulsive force, so that part of the coated titanium dioxide is bound to the surface of the PCB substrate, which increases the difficulty of development. In addition, there is also active cationic photoinitiator 2 on the surface of the substrate in the unexposed area. Under visible light irradiation, the pre-cured product (coated titanium dioxide) is likely to undergo cationic photopolymerization reaction in the presence of cationic photoinitiator 2, further increasing the difficulty of development. Ordinary developer (sodium carbonate) is likely to cause unclean development.

[0032] Therefore, the present invention uses a developer with a specific composition, using an amino compound as an auxiliary sodium carbonate, to effectively remove ink from unexposed areas. Furthermore, the developer, which uses a mixed solvent of acrylic carbonate and water, has a good solubility effect on both the ink and the cationic photoinitiator 2, significantly improving the development effect. The amino compound is preferably choline acetate and nicotinamide ethyl ester, which can quickly reduce the activity of the cationic photoinitiator 2 and increase the development speed. DETAILED DESCRIPTION

[0033] The above scheme is further described below in conjunction with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are generally the conditions in routine experiments.

[0034] Unless otherwise specified in the following examples, all raw materials were purchased from commercial sources or prepared by conventional methods in the art.

[0035] Example 1 This embodiment provides a high-reflectivity Mini LED PCB manufacturing process, including the following steps: (1) Perform solder mask pretreatment on the PCB substrate (clean and roughen the substrate).

[0036] (2) Use white solder resist ink for solder resist screen printing (32T screen printing, 30μm printing thickness).

[0037] (3) Pre-baking: 78℃×20min.

[0038] (5) Exposure: 365nm wavelength exposure machine, ink surface 500mj / cm 2 .

[0039] (6) Development: The developer is a sodium carbonate aqueous solution with a mass concentration of 1%, a temperature of 30°C, and a spray pressure of 0.16 MPa.

[0040] (7) Post-baking: 150℃, 60min.

[0041] (8) Others (character printing, surface treatment, molding, etc.).

[0042] The raw materials for the preparation of white solder resist ink include 45 parts of epoxy acrylic resin, 35 parts of rutile titanium dioxide (0.5μm), 6 parts of photoinitiator, 20 parts of double bond-containing monomer, 1 part of leveling agent (acrylate), 4 parts of phenolic antioxidant (1010), and 2 parts of silicone defoaming agent.

[0043] The photoinitiator includes a photoinitiator A and a photoinitiator B with a mass ratio of 1:10, wherein the photoinitiator A is TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and the photoinitiator B is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone).

[0044] The double bond-containing monomer includes a 1-2 functional monomer (containing trimethyl 4-phosphobutenoate and glycidyl methacrylate in a mass ratio of 1:2) and a 3-6 functional monomer (dipentaerythritol hexaacrylate (DPHA)) in a mass ratio of 1:10.

[0045] The preparation method of white solder resist ink comprises the following steps: Epoxy acrylic resin was divided into the first part of epoxy acrylic resin and the second part of epoxy acrylic resin in a mass ratio of 1:12. The first part of epoxy acrylic resin, photoinitiator A and 1-2 functional monomer were mixed evenly and sprayed evenly onto the surface of titanium dioxide. Then, it was baked at 75℃ for 7 minutes and pre-exposed in a 395nm exposure machine with an exposure parameter of 100 mj / cm 2 , and obtain coated titanium dioxide, and mix the coated titanium dioxide with the second portion of epoxy acrylic resin, photoinitiator B, 3-6 functional monomer, leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent evenly.

[0046] Example 2 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 1 in that epoxy acrylic resin is replaced with acrylic resin.

[0047] Example 3 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 1 in that the 1-2 functional monomer is glycidyl methacrylate.

[0048] Example 4 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 1 in that the 1-2 functional monomer is trimethyl 4-phosphobutenoate.

[0049] Example 5 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 1 in that the 1-2 functional monomer contains allyl diethyl phosphate and glycidyl methacrylate in a mass ratio of 1:2.

[0050] Example 6 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 1 in that the 1-2 functional monomer contains trimethyl 4-phosphobutenoate and tripropylene glycol diacrylate in a mass ratio of 1:2.

[0051] Example 7 Based on Example 1, this example provides a high-reflectivity Mini LED PCB preparation process, where photoinitiator A includes TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and cationic photoinitiator 1 (triaryl sulfonium hexafluorophosphate) in a mass ratio of 1:0.7.

[0052] The solder mask pretreatment also includes: spraying a 5% concentration of cationic photoinitiator 2 (triaryl hexafluorophosphate sulfonium salt) solution evenly onto the surface of the PCB substrate, and the spraying amount of cationic photoinitiator 2 is 1 g / m 2 , the solvent in the cationic photoinitiator 2 solution is propylene carbonate.

[0053] Example 8 Based on Example 7, this example changes the developer in the development process.

[0054] This embodiment provides a high-reflectivity Mini LED PCB manufacturing process, including the following steps: (1) Perform solder mask pretreatment on the PCB substrate.

[0055] First, the substrate was cleaned and roughened, and then a 5% concentration of cationic photoinitiator 2 (triaryl sulfonium hexafluorophosphate) solution was evenly sprayed onto the substrate surface. The spraying amount of cationic photoinitiator 2 was 1 g / m 2 , the solvent in the cationic photoinitiator 2 solution is propylene carbonate.

[0056] (2) Use white solder resist ink for solder resist screen printing (32T screen printing, 30μm printing thickness).

[0057] The raw materials for the preparation of white solder resist ink include 45 parts of epoxy acrylic resin, 35 parts of rutile titanium dioxide (0.5μm), 6 parts of photoinitiator, 20 parts of double bond-containing monomer, 1 part of leveling agent (acrylate), 4 parts of phenolic antioxidant (1010), and 2 parts of silicone defoaming agent.

[0058] The photoinitiator includes photoinitiator A and photoinitiator B in a mass ratio of 1:10. Photoinitiator A includes TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and cationic photoinitiator 1 (triarylsulfonium hexafluorophosphate) in a mass ratio of 1:0.7. Photoinitiator B is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone).

[0059] The double bond-containing monomer includes a 1-2 functional monomer (containing trimethyl 4-phosphobutenoate and glycidyl methacrylate in a mass ratio of 1:2) and a 3-6 functional monomer (dipentaerythritol hexaacrylate (DPHA)) in a mass ratio of 1:10.

[0060] The preparation method of white solder resist ink comprises the following steps: Epoxy acrylic resin was divided into the first part of epoxy acrylic resin and the second part of epoxy acrylic resin in a mass ratio of 1:12. The first part of epoxy acrylic resin, photoinitiator A and 1-2 functional monomer were mixed evenly and sprayed evenly onto the surface of titanium dioxide. Then, it was baked at 75℃ for 7 minutes and pre-exposed in a 395nm exposure machine with an exposure parameter of 100 mj / cm 2 , and obtain coated titanium dioxide, and mix the coated titanium dioxide with the second portion of epoxy acrylic resin, photoinitiator B, 3-6 functional monomer, leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent evenly.

[0061] (3) Pre-baking: 78℃×20min.

[0062] (5) Exposure: 365nm wavelength exposure machine, ink surface 500mj / cm 2 .

[0063] (6) Development: The developing temperature is 30°C and the spray pressure is 0.16 MPa.

[0064] The developer solution includes 1.3 parts of sodium carbonate, 2.5 parts of an amino compound, 3 parts of propylene carbonate, and 130 parts of water. The amino compound includes 0.5 parts of choline acetate and 2 parts of nicotinamide ethyl ester.

[0065] (7) Post-baking: 150℃, 60min.

[0066] (8) Others (character printing, surface treatment, molding, etc.).

[0067] Example 9 This embodiment provides a high-reflectivity Mini LED PCB manufacturing process, including the following steps: (1) Perform solder mask pretreatment on the PCB substrate.

[0068] First, the substrate was cleaned and roughened, and then a 0.5% concentration of cationic photoinitiator 2 (triaryl sulfonium hexafluorophosphate) solution was evenly sprayed onto the substrate surface. The spraying amount of cationic photoinitiator 2 was 0.8 g / m 2 , the solvent in the cationic photoinitiator 2 solution is propylene carbonate.

[0069] (2) Use white solder resist ink for solder resist screen printing (32T screen printing, 30μm printing thickness).

[0070] The raw materials for preparing white solder mask ink include 30 parts of epoxy acrylic resin, 20 parts of rutile titanium dioxide (0.5μm), 2 parts of photoinitiator, 10 parts of double bond-containing monomer, 0.5 parts of leveling agent (acrylate), 2 parts of antioxidant (1010), and 1 part of silicone defoaming agent.

[0071] The photoinitiator includes photoinitiator A and photoinitiator B in a mass ratio of 1:8. Photoinitiator A includes 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) and cationic photoinitiator 1 (triaryl sulfonium hexafluorophosphate) in a mass ratio of 1:0.5. Photoinitiator B is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone).

[0072] The double bond-containing monomer includes a 1-2 functional monomer (containing trimethyl 4-phosphobutenoate and glycidyl methacrylate in a mass ratio of 1:1) and a 3-6 functional monomer (trimethylolpropane triacrylate (TMPTA)) in a mass ratio of 1:9.

[0073] The preparation method of white solder resist ink comprises the following steps: The epoxy acrylic resin was divided into the first epoxy acrylic resin and the second epoxy acrylic resin in a mass ratio of 1:10. The first epoxy acrylic resin, photoinitiator A and 1-2 functional monomer were mixed evenly and sprayed evenly onto the surface of titanium dioxide. Then, it was baked at 70℃ for 10 minutes and pre-exposed in a 395nm exposure machine with an exposure parameter of 50 mj / cm 2 , and obtain coated titanium dioxide, and mix the coated titanium dioxide with the second portion of epoxy acrylic resin, photoinitiator B, 3-6 functional monomer, leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent evenly.

[0074] (3) Pre-baking: 75℃×40min.

[0075] (5) Exposure: 365nm wavelength exposure machine, ink surface 400mj / cm 2 .

[0076] (6) Development: The developing temperature is 28°C and the spray pressure is 0.15 MPa.

[0077] The developer solution includes 0.8 parts of sodium carbonate, 1 part of an amino compound, 1 part of propylene carbonate, and 100 parts of water. The amino compound includes 0.4 parts of choline acetate and 0.6 parts of nicotinamide ethyl ester.

[0078] (7) Post-baking: 150℃, 60min.

[0079] (8) Others (character printing, surface treatment, molding, etc.).

[0080] Example 10 This embodiment provides a high-reflectivity Mini LED PCB manufacturing process, including the following steps: (1) Perform solder mask pretreatment on the PCB substrate.

[0081] First, the substrate was cleaned and roughened, and then a 10% concentration of cationic photoinitiator 2 (triaryl sulfonium hexafluorophosphate) solution was evenly sprayed onto the substrate surface. The spraying amount of cationic photoinitiator 2 was 3 g / m 2 , the solvent in the cationic photoinitiator 2 solution is propylene carbonate.

[0082] (2) Use white solder resist ink for solder resist screen printing (32T screen printing, 30μm printing thickness).

[0083] The raw materials for preparing white solder mask ink include 60 parts of epoxy acrylic resin, 50 parts of rutile titanium dioxide (0.5μm), 10 parts of photoinitiator, 30 parts of double bond-containing monomer, 2 parts of leveling agent (acrylate), 6 parts of antioxidant (1010), and 3 parts of silicone defoaming agent.

[0084] The photoinitiator includes photoinitiator A and photoinitiator B in a mass ratio of 1:12. Photoinitiator A includes TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and cationic photoinitiator 1 (triaryl sulfonium hexafluorophosphate) in a mass ratio of 1:1. Photoinitiator B is 651 (benzoin methyl ether).

[0085] The double bond-containing monomer includes a 1-2 functional monomer (containing trimethyl 4-phosphobutenoate and glycidyl methacrylate in a mass ratio of 1:3) and a 3-6 functional monomer (dipentaerythritol hexaacrylate (DPHA)) in a mass ratio of 1:14.

[0086] The preparation method of white solder resist ink comprises the following steps: The epoxy acrylic resin was divided into the first epoxy acrylic resin and the second epoxy acrylic resin in a mass ratio of 1:15. The first epoxy acrylic resin, photoinitiator A and 1-2 functional monomer were mixed evenly and sprayed evenly onto the surface of titanium dioxide. Then, it was baked at 80℃ for 5 minutes and pre-exposed in a 395nm exposure machine with an exposure parameter of 100 mj / cm 2 , and obtain coated titanium dioxide, and mix the coated titanium dioxide with the second portion of epoxy acrylic resin, photoinitiator B, 3-6 functional monomer, leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent evenly.

[0087] (3) Pre-baking: 80℃×10min.

[0088] (5) Exposure: 365nm wavelength exposure machine, ink surface 600mj / cm 2 .

[0089] (6) Development: The developing temperature is 33°C and the spray pressure is 0.18 MPa.

[0090] The developer solution includes 1.8 parts of sodium carbonate, 4 parts of an amino compound, 6 parts of propylene carbonate, and 150 parts of water. The amino compound includes 1 part of choline acetate and 3 parts of nicotinamide ethyl ester.

[0091] (7) Post-baking: 150℃, 60min.

[0092] (8) Others (character printing, surface treatment, molding, etc.).

[0093] Example 11 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 8 in that the amino compound is nicotinamide ethyl ester.

[0094] Example 12 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 8 in that the amino compound is choline acetate.

[0095] Example 13 This embodiment provides a high-reflectivity Mini LED PCB preparation process, which differs from Example 8 in that the amino compound is ethanolamine.

[0096] Comparative Example 1 The difference between this comparative example and Example 1 is that the white solder resist ink is prepared using a common formula and a common method, and the raw materials for preparing the white solder resist ink include 45 parts of epoxy acrylic resin, 35 parts of rutile titanium dioxide (0.5 μm), 6 parts of photoinitiator 1173, 20 parts of double bond-containing monomer (dipentaerythritol hexaacrylate), 1 part of leveling agent (acrylate), 4 parts of phenolic antioxidant (1010), and 2 parts of silicone defoaming agent.

[0097] The preparation method of white solder resist ink comprises the following steps: Mix epoxy acrylic resin, rutile titanium dioxide, photoinitiator 1173 and dipentaerythritol hexaacrylate evenly, then add leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent and mix evenly.

[0098] Comparative Example 2 The difference between this comparative example and Example 1 is that the white solder resist ink is prepared using the formula of Example 1 and a common method. The preparation method of the white solder resist ink includes the following steps: Divide the epoxy acrylic resin into the first part of epoxy acrylic resin and the second part of epoxy acrylic resin in a mass ratio of 1:12, mix the first part of epoxy acrylic resin, photoinitiator A, 1-2 functional monomer and titanium dioxide evenly, then add the second part of epoxy acrylic resin, photoinitiator B, 3-6 functional monomer, leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent and mix evenly.

[0099] Comparative Example 3 The difference between this comparative example and Example 1 is that, in the raw materials for preparing the white solder resist ink, photoinitiator B is used instead of photoinitiator A. In this case, photoinitiator A is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone).

[0100] Comparative Example 4 The difference between this comparative example and Example 1 is that, in the raw materials for preparing the white solder resist ink, photoinitiator A is used instead of photoinitiator B, and in this case, photoinitiator B is TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).

[0101] Comparative Example 5 The difference between this comparative example and Example 1 is that, in the raw materials for preparing the white solder resist ink, a 3-6 functional monomer is used instead of a 1-2 functional monomer, and in this case, the 1-2 functional monomer is dipentaerythritol hexaacrylate (DPHA).

[0102] Comparative Example 6 The difference between this comparative example and Example 1 is that, in the raw materials for preparing the white solder resist ink, a 1-2 functional monomer is used instead of a 3-6 functional monomer. In this case, the 3-6 functional monomer contains trimethyl 4-phosphobutenoate and glycidyl methacrylate in a mass ratio of 1:2.

[0103] Comparative Example 7 The difference between this comparative example and Example 1 is that the coated titanium dioxide does not contain photoinitiator A. In this case, the preparation method of the coated titanium dioxide includes the following steps: The first portion of epoxy acrylic resin and 1-2 functional monomer are mixed evenly, sprayed evenly onto the surface of titanium dioxide, and then baked at 75°C for 7 minutes to obtain coated titanium dioxide.

[0104] Comparative Example 8 The difference between this comparative example and Example 1 is that in the preparation method of the white solder resist ink, the surface resin of the coated titanium dioxide is not pre-exposed. In this case, the preparation method of the white solder resist ink includes the following steps: Divide the epoxy acrylic resin into the first part of epoxy acrylic resin and the second part of epoxy acrylic resin in a mass ratio of 1:12, stir the first part of epoxy acrylic resin, photoinitiator A and 1-2 functional monomer evenly, spray them evenly on the surface of titanium dioxide, and then bake them at 75°C for 7 minutes to obtain coated titanium dioxide, mix the coated titanium dioxide with the second part of epoxy acrylic resin, photoinitiator B, 3-6 functional monomer, leveling agent (acrylate), antioxidant (1010) and silicone defoaming agent evenly.

[0105] Comparative Example 9 The difference between this comparative example and Example 1 is that in the preparation method of the white solder resist ink, the surface resin of the coated titanium dioxide is completely cured, and the exposure parameter is modified to 500 mj / cm 2 .

[0106] Comparative Example 10 The difference between this comparative example and Example 8 is that the coated titanium dioxide does not contain cationic photoinitiator 1 (triaryl sulfonium hexafluorophosphate).

[0107] Comparative Example 11 The difference between this comparative example and Example 8 is that when the PCB substrate is subjected to solder mask pre-treatment, the cationic photoinitiator 2 (triaryl sulfonium hexafluorophosphate) solution is not used to spray the substrate.

[0108] Comparative Example 12 The difference between this comparative example and Example 8 is that when the PCB substrate is subjected to solder mask pretreatment, the spraying amount of cationic photoinitiator 2 (triaryl sulfonium hexafluorophosphate) is 0.4 g / m 2 .

[0109] Comparative Example 13 The difference between this comparative example and Example 8 is that when the PCB substrate is subjected to solder mask pretreatment, the spraying amount of cationic photoinitiator 2 (triaryl sulfonium hexafluorophosphate) is 4 g / m 2 .

[0110] Comparative Example 14 The difference between this comparative example and Example 8 is that the developer does not contain an amino compound.

[0111] Comparative Example 15 The difference between this comparative example and Example 8 is that the developer does not contain propylene carbonate.

[0112] 1. PCB board reflectivity test 1. Average reflectivity test The reflectivity of the PCB boards after baking in Examples 1-10 and Comparative Examples 1-9 was tested. The number of samples was five, and the measured average reflectivity results are shown in Table 1 below.

[0113] Table 1 As shown in Table 1, the reflectivity of the Mini LED PCBs obtained using the processes of Examples 1-10 of the present invention ranges from 88.52% to 93.52%, resulting in high-reflectivity Mini LED PCBs. Specifically, the reflectivity of the Mini LED PCBs obtained using the processes of Examples 1-2 and 7-10 ranges from 92.04% to 93.52%, demonstrating relatively high reflectivity.

[0114] Compared with Examples 3-6, the 1-2 functional monomers in the white solder resist inks of Examples 1 and 2 of the present invention include trimethyl 4-phosphobutenoate and glycidyl methacrylate, and the reflectivity of the PCB board is further improved.

[0115] Compared with Example 1, Comparative Example 1, which used a conventional formula and method to prepare white solder mask ink, and Comparative Example 2, which used the formula and method of Example 1, produced white solder mask ink. The results showed a significant decrease in the reflectivity of the PCB. Comparative Examples 3-7 varied the composition of the photoinitiator and double-bond-containing monomer, and Comparative Examples 8-9 varied the exposure method of the coated titanium dioxide. All of these results resulted in a decrease in the reflectivity of the PCB.

[0116] 2. Reflectivity of different areas of PCB board The reflectivity of the PCB boards baked after Examples 1 and 3-8 was tested. Five different areas (test points) of the same PCB board were randomly selected for reflectivity testing. The results are shown in Table 2 below.

[0117] Table 2 As shown in Table 2, compared with Examples 3-6, the reflectivity deviations of different regions of the PCBs produced in Examples 1, 7, and 8 of the present invention are smaller, indicating better reflectivity uniformity. This indicates that controlling the composition of the 1-2 functional monomers in the white solder mask ink can control the reflectivity uniformity of the PCB.

[0118] 2. Curing degree of different solder mask ink areas on PCB board Fourier transform infrared spectroscopy (FTIR) was used to test the curing degree of the exposed PCB boards of Examples 1 and 8 of the present invention and Comparative Examples 3-9, and to test the double bond conversion rates in different ink areas. The results are shown in Table 3.

[0119] Table 3 As shown in Table 3, compared with Comparative Examples 3-9, the double bond conversion rates of different regions of the PCB board after exposure in Examples 1 and 8 of the present invention showed relatively small deviations, indicating good curing uniformity. This indicates that controlling the composition of the photoinitiator and double bond-containing monomer in the white solder mask ink can control the ink's curing effect.

[0120] 3. Effect test of the coated titanium dioxide of the present invention 1. Dispersibility of white solder resist ink White solder resist inks were prepared according to the methods of Examples 1, 8-10 and Comparative Examples 1-9 of the present invention. The dispersion of the inks was observed after being stored for different periods of time. The results are shown in Table 4.

[0121] Table 4 As shown in Table 4, the white solder resist inks prepared in Examples 1, 8-10 of the present invention have good dispersion stability. Compared with Example 1, Comparative Examples 1-9 changed the raw materials and preparation methods of the white solder resist inks, resulting in poor dispersibility of the inks.

[0122] 2. The bonding strength of the coating layer of coated titanium dioxide Coated titanium dioxide was prepared according to the methods of Examples 1 and 3-8 of the present invention. The coated titanium dioxide was placed in a photosensitive resin (epoxy acrylic resin) and stirred at a certain speed for 30 minutes. The shedding of the coating layer on the surface of the titanium dioxide was observed. The results are shown in Table 5.

[0123] Table 5 The results in Table 5 show that compared with Examples 3-6, the surface coatings of the coated titanium dioxide prepared in Examples 1, 7, and 8 of the present invention showed no significant detachment, indicating strong adhesion between the coating and the titanium dioxide. This suggests that controlling the composition of the 1-2 functional monomers in the white solder mask ink can control the adhesion between the coating and the titanium dioxide.

[0124] 4. Adhesion test of solder mask ink on PCB board The adhesion of the white solder resist inks prepared in Examples 1, 7-10, and Comparative Examples 10-13 was tested using a grid knife. The results are shown in Table 6.

[0125] Among them, level 0: the edge of the cut is completely smooth, and there is no peeling on the edge of the lattice.

[0126] Level 1: There is small peeling at the intersection of the cuts, and the actual damage in the grid area is ≤5%.

[0127] Level 2: The edges and / or intersections of the incision are peeled off, and the area is greater than 5% to 15%.

[0128] Level 3: There is partial peeling or large-scale peeling along the edge of the cut, or part of the grid is peeled off. The peeling area exceeds 15%~35%.

[0129] Level 4: Large pieces of the cut edge peel off / or some squares are partially or completely peeled off, and the area is greater than 35% of the cross-cut area. 65%.

[0130] Level 5: There are pieces of paint peeling off at the edges and intersections of the lines, and the total peeling area is greater than 65%.

[0131] Table 6 It can be seen from Table 6 that, based on Example 1, Examples 7-10 introduced cationic photopolymerization reactions on the surfaces of the coated titanium dioxide and the PCB substrate, thereby improving the adhesion of the white solder resist ink.

[0132] Compared with Example 8, Comparative Examples 10-13 changed the addition of cationic photoinitiator 1 and cationic photoinitiator 2, resulting in reduced adhesion of the ink.

[0133] 5. Development effect Development was carried out according to the processes of Examples 1, 7-13 and Comparative Examples 14-15 of the present invention, and the development conditions were observed. The results are shown in Table 7.

[0134] Table 7 As shown in Table 7, the conventional developer (sodium carbonate aqueous solution) used in Example 7 produced a clear image without burrs or residue, but the development time was relatively long, requiring 75 seconds. The introduction of cationic photopolymerization into the white solder mask ink in Example 7 further increased the development difficulty, resulting in poor development quality and a poor development speed (89 seconds).

[0135] Compared with Example 7, Examples 8-12, after developing with a developer containing an amino compound and propylene carbonate, showed significantly improved development effects, with clear images, no burrs or residues, and a development speed of 45-65 seconds. Among them, Examples 8-10 had a relatively high development speed of 45-48 seconds.

[0136] Compared with Example 8, Comparative Examples 14-15 changed the composition of the developer, resulting in poorer developing effect and developing speed.

[0137] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-reflectivity Mini LED PCB manufacturing process, characterized by: The following steps are involved: Solder mask pre-treatment, solder mask silk screen, pre-bake, exposure, development and post-bake; White solder resist ink is used for solder screen printing, wherein the raw materials for preparing the white solder resist ink include 30-60 parts of photosensitive resin, 20-50 parts of titanium dioxide, 2-10 parts of photoinitiator, 10-30 parts of double bond-containing monomer and 0-20 parts of auxiliary agent; The photoinitiator comprises a photoinitiator A and a photoinitiator B in a mass ratio of 1:(8-12), wherein the photoinitiator A comprises a free radical photoinitiator having an absorption wavelength range of 380-420 nm, and the photoinitiator B is a free radical photoinitiator having an absorption wavelength range of 320-370 nm; The double bond-containing monomers include 1-2 functional monomers and 3-6 functional monomers in a mass ratio of 1:(9-14); The preparation method of the white solder resist ink comprises the following steps: The photosensitive resin was divided into the first photosensitive resin and the second photosensitive resin in a mass ratio of 1: (10-15). The first photosensitive resin, photoinitiator A and 1-2 functional monomer were mixed evenly and sprayed evenly on the surface of titanium dioxide. Then, it was baked at 70-80℃ for 5-10 minutes and pre-exposed in a 395nm exposure machine with an exposure parameter of 50-200 mj / cm 2 , obtain coated titanium dioxide, and evenly mix the coated titanium dioxide with the second portion of photosensitive resin, photoinitiator B, 3-6 functional monomers and additives.

2. The preparation process according to claim 1, wherein: The photoinitiator A is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide or isopropylthioxanthone, and the photoinitiator B is 2-hydroxy-2-methyl-1-phenyl-1-propanone or benzoin methyl ether.

3. The preparation process according to claim 1, wherein: The 1-2 functional monomer is one or more of an acrylate monomer, vinyl ester monomer, crotonate monomer, or phosphate monomer containing 1-2 double bonds; The 3-6 functional monomer is one or any combination of acrylate monomers, vinyl ester monomers, and crotonate monomers containing 3-6 double bonds.

4. The preparation process according to claim 1, wherein: The photosensitive resin is unsaturated polyester, acrylic resin, epoxy resin or epoxy acrylic resin, the titanium dioxide is rutile titanium dioxide, and the additives include one or any combination of 0.5-2 parts of a leveling agent, 2-6 parts of an antioxidant, 1-3 parts of a defoaming agent, 1-2 parts of an adhesion promoter, and 1-3 parts of an ultraviolet absorber.

5. The preparation process according to claim 3, wherein: The 1-2 functional monomer includes trimethyl 4-phosphobutenoate and glycidyl methacrylate in a mass ratio of 1:(1-3).

6. The preparation process according to claim 4, characterized in that: The photosensitive resin is epoxy acrylic resin, and the photoinitiator A further includes cationic photoinitiator 1. The mass ratio of the 380-420 nm free radical photoinitiator to the cationic photoinitiator 1 is 1:(0.5-1).

7. The preparation process according to claim 6, characterized in that: The solder mask pre-treatment includes: spraying a cationic photoinitiator 2 solution evenly onto the surface of the PCB substrate, with the spraying amount of the cationic photoinitiator 2 being 0.8-3 g / m 2 .

8. The preparation process according to claim 6 or 7, characterized in that: The cationic photoinitiator 1 and the cationic photoinitiator 2 are any one or more of diaryl iodonium salts, triaryl sulfonium salts, and alkyl sulfonium salts.

9. A development process in the high-reflectivity Mini LED PCB manufacturing process according to claim 1, characterized in that: The developer used in the development process includes 0.8-1.8 parts of sodium carbonate, 1-4 parts of an amino compound, 1-6 parts of propylene carbonate, and 100-150 parts of water; The amino compound is any one or more of nicotinamide ethyl ester, choline acetate, ethanolamine, ammonia water, and triethylamine.

10. The development process according to claim 9, wherein: The amino compound comprises 0.4-1 parts of choline acetate and 0.6-3 parts of nicotinamide ethyl ester.

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