A kind of LDI laser curing solder resist ink and preparation method thereof

Abstract

The present invention discloses an LDI laser-cured solder mask ink and a preparation method thereof, and relates to the technical field of PCB ink. An LDI laser-cured solder mask ink comprises a main agent and a thermosetting agent, wherein the main agent comprises 50-63 parts of a photocurable resin, 12-24 parts of an active diluent, 8-12 parts of a photoinitiator, 0.3-0.45 parts of a light stabilizer and other auxiliary agents, specifically, the photocurable resin comprises a mixture of epoxy acrylate resin and polyurethane acrylate, and the photoinitiator comprises a mixture of one or more of photoinitiator 819, photoinitiator 907 and photoinitiator ITX. By utilizing a specific ratio of photocurable resin in combination with a photoinitiator having a high addition amount and ultraviolet long-wave photosensitivity, the obtained solder mask ink not only has the characteristics of high sensitivity, but also has low exposure energy required during curing, and can be fully adapted to LDI laser curing technology.

Description

Technical Field

[0001] The invention relates to the technical field of PCB solder resist ink, and in particular to an LDI laser-cured solder resist ink and a preparation method thereof. Background Art

[0002] PCB solder mask ink, also known as solder resist ink, is mainly used to protect the circuits of printed circuit boards. When the solder mask ink is coated and printed on the surface of the circuit board and formed into a solder mask through light curing, it can effectively prevent problems such as oxidation, tin, and burning during the welding process, ensuring the quality and stability of the solder joints and circuit boards.

[0003] Generally speaking, the smaller the line spacing and line width on the printed circuit board, the higher the precision required for the solder mask on the circuit board. Therefore, for high-precision solder mask printing, the quality, fluidity, curing speed and UV irradiation accuracy requirements of the solder mask ink used will be higher.

[0004] Traditional solder resist coatings on printed circuit boards are formed by photocuring solder resist ink using ordinary UV mercury lamps or LED light sources. However, the UV energy distribution of traditional UV mercury lamps or LED light sources may not be uniform enough, so that the UV irradiation accuracy is not high, and some locations may not be fully cured or over-cured. In order to improve the accuracy of UV irradiation, in recent years, the use of LDI laser curing technology to irradiate solder resist ink has emerged. LDI laser curing technology uses LDI laser exposure machine as UV light source, combines infrared and ultraviolet light, reduces the UV energy required for imaging, and can directly form images on solder resist ink by precisely controlling the switch of the laser without the need to use film or film, thereby reducing the manual alignment error of the film or film and significantly improving the imaging accuracy.

[0005] However, since most of the solder mask inks on the market are formulated based on the curing method of ordinary ultraviolet mercury lamp irradiation, they require higher exposure energy and are poorly compatible with LDI laser curing technology, and cannot fully exert the advantages of LDI laser curing technology. Therefore, it is of great significance to provide a solder mask ink suitable for LDI laser curing technology. Summary of the invention

[0006] In order to improve the compatibility of the solution ink with LDI technology and improve the curing efficiency and coating performance of the solder mask ink under LDI laser irradiation, the present application provides an LDI laser-cured solder mask ink and a preparation method thereof.

[0007] In the first aspect, the present application provides an LDI laser curing solder mask ink adopting the following technical solution:

[0008] An LDI laser curable solder resist ink comprises a main agent and a thermal curing agent, wherein the main agent comprises the following raw materials in parts by weight:

[0009] Photocurable resin: 48-63 parts;

[0010] Active diluent: 12-24 parts;

[0011] Photoinitiator: 8-12 parts;

[0012] Light stabilizer: 0.3-0.45 parts;

[0013] Silicone leveling agent: 4-8 parts;

[0014] Dispersant: 4-6 parts;

[0015] Modified filler: 16-20 parts;

[0016] Color and filler: 1-1.4 parts;

[0017] The photocurable resin comprises epoxy acrylate resin and polyurethane acrylate mixed in a weight ratio of 1: (0.8-1.2), the epoxy acrylate resin is any one of o-cresol epoxy acrylate, or a mixture of o-cresol epoxy acrylate and bisphenol A epoxy acrylate, or a mixture of o-cresol epoxy acrylate and epoxidized oil acrylate, or a mixture of o-cresol epoxy acrylate, bisphenol A epoxy acrylate and epoxidized oil acrylate; the active diluent comprises a mixture of one or more of dipentaerythritol hexaacrylate, isobornyl acrylate and triglycidyl isocyanurate, and the photoinitiator comprises a mixture of one or more of photoinitiator 819, photoinitiator 907 and photoinitiator ITX.

[0018] By adopting the above technical solution, epoxy acrylate resin and polyurethane acrylate are mixed as photocurable resin, and a specific active diluent and photoinitiator are used. The selected photoinitiator also has the characteristics of high addition amount and ultraviolet long-wave photosensitivity. The prepared solder mask ink not only has the characteristics of high sensitivity, but also requires low exposure energy during curing, which is conducive to fully adapting to LDI laser curing technology. It can fully initiate curing under the low exposure energy and ultraviolet long-wave band of LDI laser, and can fully improve the curing efficiency and coating performance of the solder mask ink under LDI laser irradiation. Secondly, since the exposure energy required for the prepared solder mask ink is low, when it is applied to ordinary ultraviolet mercury lamps or LED ultraviolet light sources, it can also reduce the use of light sources, which is conducive to saving energy.

[0019] Optionally, the epoxy acrylate resin is a mixture of the o-cresol epoxy acrylate, the bisphenol A epoxy acrylate and the epoxidized oil acrylate, and the mixing weight ratio of the o-cresol epoxy acrylate, the bisphenol A epoxy acrylate and the epoxidized oil acrylate is 1: (0.35-0.5): (0.05-0.1).

[0020] By adopting the above technical solution, bisphenol A epoxy acrylate can give solder mask ink a higher structural rigidity and improve the surface hardness of solder mask ink after curing, while epoxidized oil acrylate has a low viscosity, which can make solder mask ink easier to wash off, improve the developability of solder mask ink, and improve the flexibility and adhesion of solder mask ink after curing. The mutual synergy of the three epoxy acrylate resins is conducive to improving the comprehensive performance of solder mask ink.

[0021] Optionally, the acid value of the o-cresol formaldehyde epoxy acrylate is 54-56 mgKOH / g.

[0022] By adopting the above technical solution and using o-cresol epoxy acrylate with a high acid value, the o-cresol epoxy acrylate can have more reactive acidic functional groups, which is beneficial to improve the reactivity of the photocurable resin, so that the solder mask ink exhibits higher sensitivity and can be fully irradiated and cured by the LDI laser in a short time, exhibiting higher surface hardness.

[0023] Optionally, the photoinitiator is a mixture of photoinitiator 819, photoinitiator 907 and photoinitiator ITX, and the mixing weight ratio of the photoinitiator 819, photoinitiator 907 and photoinitiator ITX is 1: (0.4-0.5): (0.08-0.1).

[0024] By adopting the above technical solution, it is beneficial to further improve the photosensitivity of the solder mask ink in the long-wave ultraviolet band, so that the solder mask ink can have a higher sensitivity, which is beneficial to make the solder mask ink more suitable for low-exposure energy LDI laser curing technology.

[0025] Optionally, the light stabilizer is a mixture of ultraviolet absorber UV-P and light stabilizer UV-770 in a weight ratio of 1: (0.15-0.2).

[0026] By adopting the above technical scheme, the absorption and decomposition of ultraviolet light by the photoinitiator can be reduced by the ultraviolet absorber UV-P, and the photosensitivity of the solder mask ink can be appropriately suppressed. In addition, a small amount of light stabilizer UV-770 can also capture the free radicals generated during the curing process. By properly controlling the amount of free radicals generated in the system, the explosion of the photocurable resin can be reduced. Therefore, under the premise that the solder mask ink has high sensitivity and the exposure energy required for curing is small, the solder mask ink can be kept stable and fully cured, which is conducive to preventing the solder mask ink from being over-cured.

[0027] Optionally, the active diluent is a mixture of the dipentaerythritol hexaacrylate, the isobornyl acrylate and the triglycidyl isocyanurate, and the mixing weight ratio of the dipentaerythritol hexaacrylate, the isobornyl acrylate and the triglycidyl isocyanurate is 1: (0.4-0.9): (0.1-0.2).

[0028] By adopting the above technical solution, the viscosity of solder mask ink can be reduced, the fluidity and construction performance of solder mask ink can be improved, and the shrinkage of solder mask ink during curing can be reduced to prevent cracking and wrinkling. Secondly, both dipentaerythritol hexaacrylate and isobornyl acrylate contain acrylate groups, which can participate in the photocuring reaction as photoinitiator monomers, thereby effectively improving the photoinitiator efficiency and curing speed of colored solder mask ink, which is conducive to making the solder mask ink suitable for low-exposure energy LDI laser curing technology.

[0029] Optionally, the dispersant is any one of TEGO-610S or TEGO-655; the modified filler is barium sulfate, fumed silica and talcum powder mixed in a weight ratio of 10: (0.5-1): (1-1.2), and is modified by epoxy silane coupling agent, pentaerythritol triacrylate and accelerator; the color filler is an organic pigment.

[0030] By adopting the above technical solution, using any one of the dispersants TEGO-610S or TEGO-655 can effectively reduce the surface energy of inorganic modified fillers or organic pigments and fillers, and prevent the modified fillers and pigments from agglomerating, which is beneficial to further improve the dispersibility and stability of the modified fillers and pigments in the photocurable resin, thereby preventing the solder mask ink from floating or blooming after re-curing.

[0031] Optionally, the preparation method of the modified filler comprises the following steps:

[0032] Add the filler to the reaction solvent, stir and disperse, heat to 60-70°C, add silane coupling agent KH560 dropwise, keep the temperature for reaction for 1-2h after the addition is completed, then heat to 100-115°C again, add the accelerator, and then add pentaerythritol triacrylate dropwise, keep the temperature for reaction for 2-2.5h after the addition is completed, filter, and obtain the modified filler.

[0033] By adopting the above technical scheme, epoxy silane can be firstly connected to the surface of the inorganic filler, and then pentaerythritol triacrylate can be connected to the epoxy silane, so that pentaerythritol triacrylate can be grafted on the surface of the inorganic filler, which is beneficial to improve the surface properties of the inorganic filler and improve the compatibility with the photocurable resin.

[0034] Optionally, the mixing weight ratio of the main agent to the thermal curing agent is 1:(0.45-0.5).

[0035] By adopting the above technical solution, the main agent can be quickly hardened during the thermal baking process, so that the substrate coated with solder mask ink can be transferred to the LDI laser exposure machine in the subsequent process.

[0036] In the second aspect, the present application provides a method for preparing an LDI laser-curable solder mask ink using the following technical solution:

[0037] A method for preparing LDI laser-curable solder mask ink comprises the following steps:

[0038] A1. Fully mix the photocurable resin and the reactive diluent to obtain masterbatch A; take 10% of the masterbatch A and fully mix it with the light stabilizer, the silicone leveling agent, the dispersant, the modified filler and the pigment filler, and perform ball milling to obtain masterbatch B;

[0039] A2. Fully mix the remaining masterbatch A and masterbatch B, heat to 120-135°C and continue stirring for 1-2 hours, and obtain the main agent preparation after cooling. Then, add the photoinitiator to the main agent preparation under light-proof state, and keep stirring at room temperature to obtain the main agent, which needs to be stored under light-proof state;

[0040] A3. Before coating on a printed circuit board, mix the main agent with the thermal curing agent to obtain a solder mask ink suitable for LDI laser curing.

[0041] By adopting the above technical solution, the surface activity of the modified filler and the pigment filler can be improved in advance by the dispersant, and the grinding efficiency of the light stabilizer, the modified filler and the pigment filler can be improved at the same time, so that when heated and mixed, each filler additive can be fully mixed with the light-curing resin, which is beneficial to improve the uniformity of the dispersion performance of each raw material in the solder mask ink. Secondly, in the preparation process of the main agent, mixing and storing in the dark throughout the process, and mixing with the thermal curing agent before coating, can effectively prevent the main agent from undergoing a curing reaction, which is beneficial to maintaining the effectiveness of the solder mask ink and extending the storage time of the solder mask ink.

[0042] In summary, the technical solution of this application has at least one of the following beneficial effects:

[0043] 1. By mixing epoxy acrylic resin and polyurethane acrylate in a specific proportion, combined with a specific active diluent and a photoinitiator, a highly sensitive solder mask ink is prepared in a specific proportion. Even under the LDI laser curing conditions with low exposure energy, it can fully initiate curing in a short time, and has high hardness and good adhesion, and can be suitable for the LDI laser curing method.

[0044] 2. The synergistic cooperation between o-cresol epoxy acrylate, bisphenol A epoxy acrylate and epoxidized oil acrylate is beneficial to improve the comprehensive performance of solder mask ink.

[0045] 3. The use of a mixed compound of photoinitiator 819, photoinitiator 907 and photoinitiator ITX is beneficial to further improve the photosensitivity of the solder mask ink in the long-wave ultraviolet band, so that the solder mask ink can have a higher sensitivity and is more suitable for low-exposure energy LDI laser curing technology. DETAILED DESCRIPTION

[0046] The present application is further described in detail below in combination with preparation examples, embodiments and comparative examples. Preparation Example

[0047] [Preparation Example 1-1]

[0048] A modified filler is prepared by modifying a reinforcing filler with an epoxy silane coupling agent, pentaerythritol triacrylate and an accelerator. In this preparation example, the reinforcing filler includes a mixture of three fillers: barium sulfate, fumed silica and talcum powder, and the weight ratio of the barium sulfate, fumed silica and talcum powder is 10:0.5:1.

[0049] A method for preparing a modified filler comprises the following steps:

[0050] Add 200g of barium sulfate, 10g of fumed silica and 20g of talcum powder into toluene solvent, stir and disperse, heat to 70°C, add 60g of silane coupling agent KH560 dropwise, keep the temperature for reaction for 1h after the addition, then heat to 115°C again, add 1.6g of triethanolamine as a promoter, then add 110g of pentaerythritol triacrylate dropwise, keep the temperature for reaction for 2h after the addition, filter, and obtain a modified filler.

[0051] [Preparation Example 1-2]

[0052] A modified filler, which differs from [Preparation Example 1] in that the amount of each reinforcing filler added and the preparation method of the modified filler are different.

[0053] In this preparation example, the weight ratio of barium sulfate, fumed silica and talc is 10:1:1.2.

[0054] A method for preparing a modified filler comprises the following steps:

[0055] Add 200g of barium sulfate, 20g of fumed silica and 24g of talcum powder into toluene solvent, stir and disperse, heat to 70°C, add 32g of silane coupling agent KH560 dropwise, keep the temperature for reaction for 1h after the addition, then heat to 115°C again, add 2.2g of triethanolamine as a promoter, then add 165g of pentaerythritol triacrylate dropwise, keep the temperature for reaction for 2h after the addition, filter, and obtain a modified filler.

[0056] [Preparation Example 2-1]

[0057] A thermal curing agent is prepared by fully mixing the following raw materials:

[0058] 100 g of pentaerythritol tetrakis(3-mercaptopropionate), 300 g of novolac epoxy acrylate, 50 g of melamine and 100 g of dimethyl succinate.

[0059] [Preparation Example 2-2]

[0060] A thermal curing agent is prepared by fully mixing the following raw materials:

[0061] 100 g of pentaerythritol tetrakis(3-mercaptopropionate), 400 g of novolac epoxy acrylate, 50 g of melamine and 50 g of dimethyl succinate. Example

[0062] [Example 1]

[0063] A LDI laser curing solder resist ink comprises a main agent and a thermal curing agent.

[0064] In this embodiment, the main agent includes the following raw materials:

[0065] 630g photocurable resin, 120g reactive diluent, 120g photoinitiator, 4.5g light stabilizer, 40g silicone wetting agent, 60g dispersant, 200g modified filler and 14g pigment filler.

[0066] The photocurable resin is a mixture of o-cresol epoxy acrylate and polyurethane acrylate in a weight ratio of 1:0.8, that is, the photocurable resin includes 350g of o-cresol epoxy acrylate and 280g of polyurethane acrylate. Specifically, the o-cresol epoxy acrylate is AgiSyn 9721H, and the acid value of the grade is 46; the polyurethane acrylate is U-CURE 9110.

[0067] Among them, the active diluent is dipentaerythritol hexaacrylate, isobornyl acrylate and triglycidyl isocyanurate mixed in a weight ratio of 1:0.4:0.2, that is, the active diluent includes 150g of dipentaerythritol hexaacrylate, 60g of isobornyl acrylate and 30g of triglycidyl isocyanurate.

[0068] Among them, the photoinitiator is specifically selected from the light stabilizer 819; the light stabilizer is specifically selected from a mixture of ultraviolet absorber UV-P and light stabilizer UV770, and the ultraviolet absorber UV-P and the light stabilizer UV770 are mixed in a weight ratio of 1:0.2, that is, the light stabilizer includes 3.75g of ultraviolet absorber UV-P and 0.75g of light stabilizer UV770; the silicone wetting agent is specifically selected from BYK-345; the dispersant is specifically selected from the wetting and dispersing agent of the brand TEGO Dispers 610s; the modified filler is specifically selected from a modified filler prepared in [Preparation Example 1-1]; the pigment filler is specifically selected from phthalocyanine green G.

[0069] In this embodiment, the thermal curing agent is specifically selected from a thermal curing agent prepared in [Preparation Example 2-1].

[0070] A method for preparing LDI laser-curable solder mask ink comprises the following steps:

[0071] A1. Fully mix the photocurable resin and the reactive diluent to obtain masterbatch A; take 10% of the masterbatch A and fully mix it with the light stabilizer, the silicone leveling agent, the dispersant, the modified filler and the pigment filler, and perform ball milling treatment, wherein the ball milling speed is set to 2000r / min, until the grinding fineness reaches ≤8μm, to obtain masterbatch B;

[0072] A2. Fully mix the remaining masterbatch A and masterbatch B, heat to 135°C and continue stirring for 1 hour, and obtain the main agent preparation after cooling. Then, add the photoinitiator to the main agent preparation under light-proof state, and keep stirring at room temperature for 30 minutes to obtain the main agent, which needs to be stored in the dark;

[0073] A3. Before coating on a printed circuit board, mix the main agent and the thermal curing agent in a weight ratio of 1:0.5 to obtain a solder mask ink suitable for LDI laser curing.

[0074] [Example 2]

[0075] A LDI laser curing solder resist ink comprises a main agent and a thermal curing agent.

[0076] In this embodiment, the main agent includes the following raw materials:

[0077] 480g photocurable resin, 240g reactive diluent, 80g photoinitiator, 3g light stabilizer, 80g silicone wetting agent, 40g dispersant, 160g modified filler and 10g pigment filler.

[0078] Among them, the photocurable resin is a mixture of epoxy acrylate resin and polyurethane acrylate in a weight ratio of 1:1, that is, the photocurable resin includes 240g of epoxy acrylate resin and 240g of polyurethane acrylate. Furthermore, the epoxy acrylate resin is a mixture of o-cresol epoxy acrylate, bisphenol A epoxy acrylate and epoxidized oil acrylate in a weight ratio of 1:0.5:0.1, that is, the epoxy acrylate resin is composed of 150g of o-cresol epoxy acrylate, 75g of bisphenol A epoxy acrylate and 15g of epoxidized oil acrylate. Specifically, o-cresol epoxy acrylate uses AgiSyn9720S, and the acid value of this brand is 54; polyurethane acrylate uses U-CURE 9110; epoxidized oil acrylate uses AgiSyn 2020.

[0079] Among them, the active diluent is dipentaerythritol hexaacrylate, isobornyl acrylate and triglycidyl isocyanurate mixed in a weight ratio of 1:0.9:0.1, that is, the active diluent includes 120g of dipentaerythritol hexaacrylate, 108g of isobornyl acrylate and 12g of triglycidyl isocyanurate.

[0080] Among them, the photoinitiator is specifically selected from photoinitiator 819; the light stabilizer is specifically selected from a mixture of ultraviolet absorber UV-P and light stabilizer UV770, and the ultraviolet absorber UV-P and the light stabilizer UV770 are mixed in a weight ratio of 1:0.15, that is, the light stabilizer includes 2.6g ultraviolet absorber UV-P and 0.4g light stabilizer UV770; the silicone wetting agent is specifically selected from BYK-345; the dispersant is specifically selected from TEGO Dispers 655 wetting and dispersing agent; the modified filler is specifically selected from a modified filler prepared in [Preparation Example 1-2]; the pigment filler is specifically selected from phthalocyanine green G.

[0081] In this embodiment, the thermal curing agent is specifically selected from a thermal curing agent prepared in [Preparation Example 2-2].

[0082] A method for preparing LDI laser-curable solder mask ink comprises the following steps:

[0083] A1. Fully mix the photocurable resin and the reactive diluent to obtain masterbatch A; take 10% of the masterbatch A and fully mix it with the light stabilizer, the silicone leveling agent, the dispersant, the modified filler and the pigment filler, and perform ball milling treatment, wherein the ball milling speed is set to 2000r / min, until the grinding fineness reaches ≤8μm, to obtain masterbatch B;

[0084] A2. Fully mix the remaining masterbatch A and masterbatch B, heat to 120°C and continue stirring for 2 hours, and obtain the main agent preparation after cooling. Then, add the photoinitiator to the main agent preparation under light-proof state, and keep stirring at room temperature for 30 minutes to obtain the main agent, which needs to be stored in the dark;

[0085] A3. Before coating on a printed circuit board, mix the main agent and the thermal curing agent in a weight ratio of 1:0.5 to obtain a solder mask ink suitable for LDI laser curing.

[0086] [Example 3]

[0087] A LDI laser-curable solder mask ink, which differs from [Example 1] in that the photocurable resin in the main agent is different.

[0088] In this embodiment, the photocurable resin is a mixture of epoxy acrylate resin and polyurethane acrylate in a weight ratio of 1:0.8, that is, the photocurable resin includes 350g of epoxy acrylate resin and 280g of polyurethane acrylate.

[0089] Furthermore, the epoxy acrylate resin is a mixture of o-cresol epoxy acrylate and bisphenol A epoxy acrylate in a weight ratio of 1:0.4, that is, the epoxy acrylate resin is composed of a mixture of 250g of o-cresol epoxy acrylate and 100g of bisphenol A epoxy acrylate.

[0090] Specifically, the o-cresol epoxy acrylate is AgiSyn 9721H, and the acid value of this brand is 46; the polyurethane acrylate is U-CURE 9110.

[0091] [Example 4]

[0092] A LDI laser-curable solder mask ink, which differs from [Example 3] in that the epoxy acrylate resin of the photocurable resin in the main agent is different.

[0093] In this embodiment, the epoxy acrylate resin is a mixture of o-cresol epoxy acrylate, bisphenol A epoxy acrylate and epoxidized oil acrylate in a weight ratio of 1:0.35:0.05, that is, the epoxy acrylate resin is composed of 250g of o-cresol epoxy acrylate, 87.5g of bisphenol A epoxy acrylate and 12.5g of epoxidized oil acrylate.

[0094] Specifically, the o-cresol epoxy acrylate is AgiSyn 9721H, and the acid value of this brand is 46; the polyurethane acrylate is U-CURE 9110; and the epoxidized oil acrylate is AgiSyn 2020.

[0095] [Example 5]

[0096] A LDI laser-curable solder mask ink, which differs from [Example 4] in that a different o-cresol epoxy acrylate is used.

[0097] In this embodiment, the o-cresol-formaldehyde epoxy acrylate is specifically selected from AgiSyn 9720, and the acid value of this brand is 56.

[0098] [Example 6]

[0099] A LDI laser-curable solder mask ink, which differs from [Example 5] in that the photoinitiator is different.

[0100] In this embodiment, the photoinitiator is replaced with a mixed compound of photoinitiator 907 and photoinitiator ITX in equal amounts, and photoinitiator 907 and photoinitiator ITX are mixed in a weight ratio of 1:0.2, that is, the photoinitiator includes 100g of photoinitiator 907 and 20g of ITX.

[0101] [Example 7]

[0102] A LDI laser-curable solder mask ink, which differs from [Example 5] in that the photoinitiator is different.

[0103] In this embodiment, the photoinitiator is replaced with an equal amount of a mixture of photoinitiator 819, photoinitiator 907 and photoinitiator ITX, and photoinitiator 819, photoinitiator 907 and photoinitiator ITX are mixed in a weight ratio of 1:0.5:0.1, that is, the photoinitiator includes 75g of photoinitiator 819, 37.5g of photoinitiator 907 and 7.5g of ITX. Comparative Example

[0104] [Comparative Example 1]

[0105] A solder mask ink, purchased from Morikawa Synthesized Liquid Photosensitive Solder Mask Ink on the market, the specific model is SC-600, green, suitable for ordinary ultraviolet mercury lamp light source irradiation curing, the specific required exposure energy is 300-600mj / cm 2 .

[0106] [Comparative Example 2]

[0107] A solder resist ink, which differs from [Example 1] in that no light stabilizer is added. Performance test data

[0108] Preparation of the sample to be tested: The solder mask ink prepared in each embodiment and comparative example was respectively coated on the processed PCB substrate (the substrate was pre-treated by grinding, degreasing, micro-etching, pickling, water washing and drying, micro-etching rate: 20-40μin, pickling H2SO4 concentration: 3-5%), and the coating thickness was controlled to be 20-20.5μm. After coating, it was placed in a constant temperature ventilated drying oven at 75℃ and heated and dried for 30 minutes to obtain the sample to be tested.

[0109] 1. Ink sensitivity and development: Place a 21-level light gradient ruler on the sample to be tested, place it under a 405nm wavelength LDI laser light source, and set the exposure energy to 30mj / cm 2 , 8 levels, laser scanning time is 12s, the solder mask ink is solidified on the substrate surface, and then the conventional circuit board development method (developer is 1% sodium carbonate aqueous solution, development temperature is 30℃, and the spray pressure of the developer is 1.5kg / cm2) is used for development for 50s, the sample is cleaned with deionized water, dried with hot air, and the number on the light gradient scale where the ink layer is left is visually observed and recorded, which is the ink sensitivity. At the same time, the ink development is judged according to the state of the copper foil exposed after development, among which the copper foil surface is clean for excellent, the copper layer surface has a slight white fog for good, and the copper layer surface has severe white fog and the development is not clean for poor.

[0110] 2. Surface hardness test: Place the sample under the LDI laser light source with a wavelength of 405nm and set the exposure energy to 30mj / cm 2 , level 8, the laser scanning time is 12s, the solder mask ink is cured on the surface of the substrate, and then the test is carried out according to "GB / T 6739-2006 Determination of film hardness of paint and varnish pencil" and using a QHQ pencil hardness tester, and the corresponding pencil hardness of each embodiment and comparative example is recorded.

[0111] 3. Adhesion test: Place the sample under the LDI laser light source with a wavelength of 405nm and set the exposure energy to 30mj / cm 2, level 8, laser scanning time is 12s, the solder mask ink is cured on the surface of the substrate, and then according to GB / T 9286-2021 Paint and varnish scratch test, use a hundred-grid knife at 1cm 2 The cured ink layer is evenly divided into 100 grids of 1mm 2 The scratch should penetrate the cured ink layer. Stick a 1 / 2 inch wide 3M pressure-sensitive tape to the surface of the ink layer. Quickly tear off the tape and the ink layer at an angle of 120°. Grade the coating according to Table 1 in GB / T 9286-2021 Scratch Test for Paints and Varnishes and record the corresponding coating adhesion level.

[0112] Table 1 Performance test data of solder mask ink

[0113]

[0114] Combining Example 1 with Comparative Example 1 and the data in Table 1, it can be seen that the solder mask ink prepared in Example 1 of the present application is not only highly sensitive compared to the solder mask ink suitable for ultraviolet mercury lamp light source on the market, but also has higher hardness and adhesion after LDI laser irradiation. This may be because the exposure energy required for curing the traditional solder mask ink suitable for ultraviolet mercury lamp light source is high, while the exposure energy of LDI laser is low. When applied to LDI laser curing, due to the low sensitivity, it cannot be fully cured in a short time, and the ink coating exhibits poor hardness and adhesion; while the present application adopts epoxy acrylic resin and polyurethane acrylate mixed in a specific ratio, combined with a specific active diluent and a photoinitiator, and mixed in a specific ratio to prepare a highly sensitive solder mask ink, which can be fully cured in a short time even under the LDI laser curing conditions with low exposure energy, and has high hardness and good adhesion, and is suitable for the curing method of LDI laser curing.

[0115] Combining Example 1 with Comparative Example 2 and the data in Table 1, it can be seen that adding a small amount of light stabilizer can appropriately suppress the photosensitivity of the solder mask ink of Example 1, reduce the sensitivity, and improve the adhesion of the solder mask ink after it is completely cured. This may be because the solder mask ink of Comparative Example 2 may have over-cured due to the high amount of photoinitiator 819 added, and the light stabilizer added by Example 1 contains ultraviolet light absorbers and hindered amine light stabilizers, which can not only reduce the absorption of ultraviolet light by the photoinitiator 819, appropriately suppress the photosensitivity of the solder mask ink, but also capture the free radicals generated during the curing process, appropriately control the amount of free radicals generated in the system, and reduce the occurrence of explosions of the photocurable resin. Therefore, under the premise of a high amount of photoinitiator 819 added, it is beneficial to maintain the stability and full curing of the solder mask ink and prevent the occurrence of over-curing.

[0116] Combining Example 1 with Example 3-4 and the data in Table 1, it can be seen that when bisphenol A epoxy acrylate is added to the photocurable resin, the pencil hardness of the ink coating can be improved compared to the mixture of o-cresol epoxy acrylate and polyurethane acrylate alone; and on this basis, a small amount of epoxidized oil acrylate is added to compound it, the pencil hardness of the ink coating will decrease, but the developability and adhesion of the ink coating are improved, and the overall performance is improved. This may be because bisphenol A epoxy acrylate contains an aromatic ring structure, which can give the ink coating high structural rigidity, and with the high reactivity of bisphenol A epoxy acrylate, it can further improve the curing efficiency of the photocurable resin, so that the photocurable resin can be quickly cured at low exposure energy and in a short time to show a higher hardness. Epoxidized oil acrylate contains a long-chain fatty acid structure with low viscosity, which makes the solder mask ink easier to wash off, which is beneficial to improve the developability of the solder mask ink. Moreover, since epoxidized oil acrylate lacks the rigid structure of multiple benzene rings in bisphenol A epoxy acrylate, the molecular chain segments are highly flexible, and the cross-linking density and structural rigidity after full curing are relatively low, which can provide better flexibility and adhesion for the cured ink coating, but it will also cause the hardness of the ink coating to be reduced.

[0117] Combining Example 4 with Example 5 and the data in Table 1, it can be seen that as the acid value of o-cresol epoxy acrylate increases, the sensitivity and hardness of the solder mask ink can be further improved. This may be because as the acid value increases, o-cresol epoxy acrylate has more reactive acidic functional groups, which is beneficial to improving the reactivity of the photocurable resin during the curing process, making the solder mask ink show higher sensitivity, and can be fully cured under a short time of LDI laser irradiation, showing higher surface hardness.

[0118] Combining Examples 5-7 and the data in Table 1, it can be seen that when the photoinitiator is a mixed compound of photoinitiator 819, photoinitiator 907 and photoinitiator ITX, the solder mask ink has a higher sensitivity, which is conducive to making the solder mask ink more suitable for LDI laser curing technology.

[0119] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A LDI laser curable solder mask ink, characterized in that: It includes a main agent and a thermal curing agent, and the main agent includes the following raw materials in parts by weight: Photocurable resin: 48-63 parts; Active diluent: 12-24 parts; Photoinitiator: 8-12 parts; Light stabilizer: 0.3-0.45 parts; Silicone leveling agent: 4-8 parts; Dispersant: 4-6 parts; Modified filler: 16-20 parts; Color and filler: 1-1.4 parts; The photocurable resin comprises epoxy acrylate resin and polyurethane acrylate mixed in a weight ratio of 1: (0.8-1.2); the epoxy acrylate resin is a mixture of o-cresol epoxy acrylate, bisphenol A epoxy acrylate and epoxidized oil acrylate; the mixing weight ratio of the o-cresol epoxy acrylate, the bisphenol A epoxy acrylate and the epoxidized oil acrylate is 1: (0.35-0.5): (0.05-0.1); the active diluent comprises a mixture of one or more of dipentaerythritol hexaacrylate, isobornyl acrylate and triglycidyl isocyanurate; the The photoinitiator is a mixture of photoinitiator 819, photoinitiator 907 and photoinitiator ITX, and the mixing weight ratio of the photoinitiator 819, photoinitiator 907 and photoinitiator ITX is 1: (0.4-0.5): (0.08-0.1); the dispersant is any one of TEGO-610S or TEGO-655; the modified filler is barium sulfate, fumed silica and talcum powder mixed in a weight ratio of 10: (0.5-1): (1-1.2), and is modified by epoxy silane coupling agent, pentaerythritol triacrylate and accelerator; the color filler is an organic pigment.

2. The LDI laser curable solder mask ink according to claim 1, characterized in that: The acid value of the o-cresol-formaldehyde epoxy acrylate is 54-56 mgKOH / g.

3. The LDI laser curable solder mask ink according to claim 1, characterized in that: The light stabilizer is a mixture of ultraviolet absorber UV-P and light stabilizer UV-770 in a weight ratio of 1: (0.15-0.2).

4. The LDI laser curable solder mask ink according to claim 1, characterized in that: The active diluent is a mixture of the dipentaerythritol hexaacrylate, the isobornyl acrylate and the triglycidyl isocyanurate, and the mixing weight ratio of the dipentaerythritol hexaacrylate, the isobornyl acrylate and the triglycidyl isocyanurate is 1: (0.4-0.9): (0.1-0.2).

5. The LDI laser curable solder mask ink according to claim 1, characterized in that: The preparation method of the modified filler comprises the following steps: Add the filler to the reaction solvent, stir and disperse, heat to 60-70°C, add silane coupling agent KH560 dropwise, keep the temperature for reaction for 1-2h after the addition is completed, then heat to 100-115°C again, add the accelerator, and then add pentaerythritol triacrylate dropwise, keep the temperature for reaction for 2-2.5h after the addition is completed, filter, and obtain the modified filler.

6. The LDI laser curable solder mask ink according to claim 1, characterized in that: The mixing weight ratio of the main agent to the thermal curing agent is 1:(0.45-0.5).

7. A method for preparing the LDI laser curable solder mask ink according to any one of claims 1 to 6, characterized in that: The following steps are involved: A1. Fully mix the photocurable resin and the reactive diluent to obtain masterbatch A; take 10% of the masterbatch A and fully mix it with the light stabilizer, the silicone leveling agent, the dispersant, the modified filler and the pigment filler, and perform ball milling to obtain masterbatch B; A2. Fully mix the remaining masterbatch A and masterbatch B, heat to 120-135°C and continue stirring for 1-2 hours, and obtain the main agent preparation after cooling. Then, add the photoinitiator to the main agent preparation under light-proof state, and keep stirring at room temperature to obtain the main agent, which needs to be stored under light-proof state; A3. Before coating on a printed circuit board, mix the main agent with the thermal curing agent to obtain a solder mask ink suitable for LDI laser curing.

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