An ultra-thick dry film photoresist for copper pillar electroplating and a preparation method thereof

Abstract

The application relates to the technical field of photoresist materials, in particular to a super-thick dry film photoresist for copper column electroplating and a preparation method thereof. The super-thick dry film photoresist comprises the following components: modified polyurethane acrylate 38-48 parts, a first active diluent 12-18 parts, a second active diluent 5-10 parts, a plasticizer 5-10 parts, a photoinitiator 3-8 parts, a leveling agent 0.5-1.5 parts, and a defoaming agent 0.1-0.3 parts; the first active diluent is composite modified dipentaerythritol hexaacrylate, and the second active diluent is trimethylolpropane triacrylate; the photoresist can form a super-thick and defect-free film layer, and the adhesion, electroplating solution corrosion resistance and pattern resolution of the film layer are improved, thereby meeting the stringent requirements of the copper column electroplating process.

Description

Technical Field

[0001] This invention relates to the field of photoresist materials technology, specifically to an ultra-thick dry film photoresist for copper pillar electroplating and its preparation method. Background Technology

[0002] As integrated circuits evolve towards higher density, higher performance, and smaller size, advanced packaging technologies, such as wafer-level packaging (WLP) and 2.5D / 3D packaging, have become crucial for sustaining Moore's Law. Among these technologies, copper pillars, as the core structure for electrical interconnection between the chip and the substrate, directly impact the reliability and performance of the package due to their size, height, and uniformity. To accommodate higher current carrying capacity and lower signal transmission loss, the market is placing increasingly stringent requirements on the height (typically exceeding 100μm) and aspect ratio of copper pillars.

[0003] Dry film photoresists are widely used in patterning electroplating processes due to their ease of operation, high pattern precision, and suitability for large-scale production. However, traditional dry film photoresists face a series of severe challenges when applied to the electroplating of ultra-thick (e.g., greater than 100 μm) and high aspect ratio copper pillars:

[0004] First, insufficient adhesion. Under the impact of prolonged exposure to strong acidic (such as sulfuric acid) electroplating solutions and the hydrogen evolution reaction during the electroplating process, the bonding interface between the photoresist and the copper substrate is prone to failure, leading to swelling, lifting, or even complete peeling of the photoresist film at the edges. This can cause copper plating leakage, pattern distortion, and result in short circuits or open circuits in the product.

[0005] Secondly, it is difficult to balance chemical resistance and mechanical strength. To obtain an ultra-thick film, it is necessary to increase the solid content of the colloid or use a high molecular weight resin. However, this often leads to increased internal stress and decreased flexibility in the film after photocuring, making it prone to brittle cracking in subsequent processes. At the same time, if toughening is pursued excessively, the cross-linking density may be insufficient, making it difficult to resist the chemical erosion and liquid flow of the electroplating solution, resulting in rough sidewalls of the pattern and reduced resolution.

[0006] Secondly, the development process window is narrow. For ultra-thick films, the developer in unexposed areas requires a longer time to fully penetrate and dissolve. If the reactive diluent has too high functionality and too strong molecular rigidity, although it can increase the crosslinking density, it will lead to development difficulties and easy residue formation; if the functionality is too low, the development speed will be too fast, which will easily cause overdevelopment and distortion of the pattern linewidth.

[0007] Currently, although some technologies attempt to improve certain properties by adding adhesion promoters or toughening agents, these often come at the expense of other aspects, making it difficult to simultaneously achieve a balance between high adhesion, excellent resistance to electroplating solutions, high resolution, and good developability in ultra-thick dry films. For example, while using conventional polyurethane acrylate resins combined with high-functionality acrylate monomers can ensure a certain level of hardness and toughness, the film is brittle, and its adhesion to the copper surface remains insufficient under harsh conditions.

[0008] Therefore, developing a dry film photoresist that can comprehensively meet the requirements of ultra-high adhesion, excellent chemical resistance, high resolution, and good processability for ultra-thick copper pillar electroplating has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] To address the existing problems, this invention provides an ultra-thick dry film photoresist for copper pillar electroplating and its preparation method. This photoresist can form an ultra-thick and defect-free film layer, and the film layer's adhesion, resistance to electroplating solution corrosion, and pattern resolution are all improved, meeting the stringent requirements of the copper pillar electroplating process.

[0010] The technical solution of the present invention to solve the above problems is as follows:

[0011] An ultra-thick dry film photoresist for copper pillar electroplating comprises, by weight: 38-48 parts of modified polyurethane acrylate, 12-18 parts of a first reactive diluent, 5-10 parts of a second reactive diluent, 5-10 parts of a plasticizer, 3-8 parts of a photoinitiator, 0.5-1.5 parts of a leveling agent, and 0.1-0.3 parts of a defoamer. The first reactive diluent is a composite modified dipentaerythritol hexaacrylate, and the second reactive diluent is trimethylolpropane triacrylate.

[0012] The modified polyurethane acrylate is prepared by:

[0013] Step 1: Polycaprolactone diol and polytetrahydrofuran ether diol are first dehydrated and purified, and then isophorone diisocyanate (IPDI) and catalyst dibutyltin dilaurate are added at 75-85℃ under nitrogen protection. The reaction is carried out at a constant temperature for 2-3 hours to obtain material 1.

[0014] Step 2: Cool material 1 to 60-70℃, dissolve pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid and polymerization inhibitor p-methoxyphenol in N-methylpyrrolidone to obtain a mixture, add the mixture dropwise to material 1, and continue the reaction at 60-70℃ for 3-4 hours after the addition is complete to obtain material 2;

[0015] Step 3: Cool material 2 to 50-60℃, add hydroxyethyl acrylate and 3-aminopropyltriethoxysilane in sequence, react for 3-5 hours, then decolorize and purify with powdered activated carbon, filter to obtain clear resin, add N,N-dimethylethanolamine to the clear resin for neutralization, then disperse the neutralized resin in a water / ethanol mixed solvent under high speed shear, add silane coupling agent KH-560 and polyvinylpyrrolidone, homogenize to obtain emulsion;

[0016] Step 4: Under stirring, add tetraethyl orthosilicate and ammonia water dropwise to the emulsion obtained in Step 3 at a rate of 0.5-1 mL / min, react at 25-35℃ for 24-48 hours, and then purify to obtain the final product.

[0017] Further, in step 1, the mass ratio of polycaprolactone diol, polytetrahydrofuran ether diol, isophorone diisocyanate, and dibutyltin dilaurate is 30-40:10-15:20-25:0.03-0.08.

[0018] Further, in step 2, the mass ratio of material 1, pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, p-methoxyphenol, and N-methylpyrrolidone is 100:15-25:4-7:3-6:0.04-0.08:7-12.

[0019] Further, in step 3, the mass ratio of material 2, hydroxyethyl acrylate, 3-aminopropyltriethoxysilane, powdered activated carbon, deionized water / ethanol mixed solvent, N,N-dimethylethanolamine, silane coupling agent KH-560, and polyvinylpyrrolidone is 100:10-16:2-3:0.15-0.4:220-350:5.5-6.5:1-2:1-2.5, and the mass ratio of deionized water to ethanol in the deionized water / ethanol mixed solvent is 0.8-1.1:1.

[0020] Further, in step 4, the mass ratio of the emulsion obtained in step 3, tetraethyl orthosilicate, and ammonia is 100:2-6:0.1-0.3, and the concentration of the ammonia is 25%-28%.

[0021] Furthermore, the preparation method of the composite modified dipentaerythritol hexaacrylate is as follows:

[0022] Step a: Add dipentaerythritol hexaacrylate and the polymerization inhibitor p-methoxyphenol to the reactor. Purge with a mixture of nitrogen and oxygen for protection. Stir at 50-70 rpm and 90-110°C. First, add 30%-50% of the catalyst triphenylphosphine and stir until homogeneous. Mix the remaining catalyst triphenylphosphine with glycidyl methacrylate and add it to the reaction system at a flow rate of 200-400 mL / min. After the addition is complete, keep the reaction at 90-110°C for 4-6 hours to obtain a viscous product.

[0023] Step b: Cool the viscous product obtained in step a to 50-60℃, and dehydrate ethoxylated trimethylolpropane triacrylate at 55-65℃ and a vacuum degree ≥-0.09MPa for 0.5-1.5 hours. While stirring at 40-60 rpm, add the dehydrated ethoxylated trimethylolpropane triacrylate to the viscous product obtained in step a at a rate of 10 mL / min, and stir at 50-60℃ for 1-2 hours until the system is homogeneous. The viscosity is controlled at 400-600 mPa·s (adjusted by fine-tuning the amount of ethoxylated trimethylolpropane triacrylate).

[0024] Step c: Wash hydroxyethyl methacrylate phosphate three times with 4-6% sodium bicarbonate solution, then dehydrate it for 1-2 hours at 55-65℃ and a vacuum of -0.07 to -0.09 MPa. Add the dehydrated hydroxyethyl methacrylate phosphate to the product obtained in step b at a rate of 2-5 mL / min, add the catalyst triphenylphosphine, and then stir at 105-115℃ and a vacuum of -0.07 to -0.09 MPa for 20-40 minutes. Break the vacuum, add the catalyst triphenylantimony, and react at normal pressure for 3-5 hours. After the reaction is completed, cool down to 70-80℃, add the antioxidant triphenyl phosphite, stir for 20-40 minutes, and filter through a filter to obtain the final product.

[0025] Further, in step a, the volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixture is 96-98:2-4, and the mass ratio of dipentaerythritol hexaacrylate (DPHA), glycidyl methacrylate (GMA), triphenylphosphine (TPP), and p-methoxyphenol (MEHQ) is 60-70:15-25:0.8-1.2:0.3-0.5.

[0026] Further, in step b, the mass ratio of the viscous product obtained in step a to ethoxylated trimethylolpropane triacrylate is 100:25-35.

[0027] Further, in step c, the mass ratio of the product obtained in step b, hydroxyethyl methacrylate phosphate, triphenylphosphine, triphenyl antimony, and triphenyl phosphite is 100:5-10:0.5-1.0:0.08-0.12:0.04-0.06.

[0028] Furthermore, the plasticizer is polyethylene glycol, the photoinitiator is one or two of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and hydroxycyclohexanebenzophenone, the leveling agent is a polyether-modified polydimethylsiloxane leveling agent, and the defoamer is an organosilicon defoamer or a polyether defoamer.

[0029] The preparation method of the above-mentioned ultra-thick dry film photoresist for copper pillar electroplating is as follows: Modified polyurethane acrylate, first reactive diluent, second reactive diluent, plasticizer, photoinitiator, leveling agent and defoamer are stirred at 300-500 rpm for 30-60 minutes at room temperature until uniformly mixed. Propylene glycol methyl ether acetate solvent is added to adjust the viscosity to 2000-5000 mPa·s at room temperature. After grinding, the photoresist solution is obtained. The solution is coated on PET release film, dried and wound to obtain the finished product. The thickness of the obtained dry film is 50-200 μm.

[0030] The present invention has the following beneficial effects:

[0031] The ultra-thick dry film photoresist for copper pillar electroplating provided by this invention achieves synergistic enhancement of the photocurable crosslinking network in terms of strength, toughness, functionality, and reactivity by introducing modified polyurethane acrylate as the main resin and synergistic effects of a composite modified first reactive diluent (dipentaerythritol hexaacrylate) and a second reactive diluent (trimethylolpropane triacrylate). This photoresist can form an ultra-thick and defect-free film layer that effectively resists the erosion of acid and alkaline plating solutions during electroplating without swelling or peeling, providing a reliable patterned mask solution for the fabrication of copper pillar bumps in advanced packaging. In step 1, the modified polyurethane acrylate reacts with isophorone diisocyanate (IPDI) using two soft segments: polycaprolactone diol (PCL) and polytetrahydrofuran ether diol (PTMG). PCL provides excellent flexibility and adhesion, while PTMG imparts good hydrolysis resistance and low-temperature performance to the resin. The ring structure of IPDI facilitates the formation of rigid hard segments. Through microphase separation of soft and hard segments, an inherently strong polyurethane framework is formed, enabling the final photoresist film to possess both the strength to resist mechanical stress and sufficient flexibility to accommodate the thermal expansion and contraction of the substrate, preventing cracking in ultra-thick film applications. Step 2 introduces carboxyl groups through 2,2-dimethylolpropionic acid (DMPA), providing sites for subsequent aqueous dispersion (Step 3); and introduces highly polar sulfonic acid groups through 2-acrylamido-2-methylpropanesulfonic acid (AMPS). These sulfonic acid groups significantly enhance the chemical bonding between the photoresist and the copper surface, greatly strengthening adhesion, which is crucial for resisting the impact of electroplating solutions. Simultaneously, the incorporation of pentaerythritol triacrylate (PETA) introduces multiple acrylate double bonds into the resin that can participate in photocuring, increasing crosslinking density and reactivity. Step 3 involves end-capping with hydroxyethyl acrylate (HEA) to ensure that all chain ends are photocurable acrylate groups; simultaneously, 3-aminopropyltriethoxysilane (KH-550) is introduced, whose amino group reacts with the residual -NCO, while the ethoxy group serves as a precursor for the subsequent sol-gel reaction. In Step 4, nano-silica (Si) is generated in situ in the polymer emulsion through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under alkaline conditions. (Particles). KH-550, as a coupling agent, can bridge organic resins and inorganic phases, enhancing the compatibility of the two phases. In-situ generated nano-Si By forming an organic-inorganic hybrid structure with polymers, the hardness, heat resistance, chemical resistance (especially resistance to electroplating solutions), and dimensional stability of photoresist films can be significantly improved, while inhibiting film shrinkage during drying and exposure processes, thus ensuring pattern accuracy.

[0032] Furthermore, the first reactive diluent (composite modified dipentaerythritol hexaacrylate), whose bulk dipentaerythritol hexaacrylate is a highly functional monomer, can construct a network with high crosslinking density, giving the film extremely high hardness, chemical resistance, and heat resistance. However, its disadvantages are high viscosity and high brittleness. Through composite modification, glycidyl methacrylate is used for ring-opening modification, introducing longer aliphatic chains and additional hydroxyl groups, which moderately increases the flexibility of the molecular chain. Ethoxylated trimethylolpropane triacrylate is added, whose ethoxy segments are excellent flexible spacers, which can effectively reduce the viscosity of the system and toughen it. Finally, phosphorus-containing hydroxyethyl methacrylate phosphate is introduced. The phosphorus element can further enhance the adhesion to the copper substrate (forming coordination bonds) and may improve flame retardancy. The modified dipentaerythritol hexaacrylate combines high functionality, moderate viscosity, good toughness, and enhanced adhesion. The second reactive diluent (trimethylolpropane triacrylate) has high reactivity and moderate crosslinking ability, which can effectively regulate the overall crosslinking rate and network structure of the system. The first and second reactive diluents work synergistically. The first reactive diluent forms the framework, responsible for establishing a robust and durable main network; the second reactive diluent acts as a regulator and "activation enhancer," rapidly participating in the reaction, filling network gaps, and improving curing speed and conversion rate. Furthermore, trimethylolpropane triacrylate has a low viscosity; when mixed with the high-viscosity first reactive diluent and resin, it effectively reduces the overall system viscosity and improves coating leveling. This combination avoids the excessive hardness and brittleness resulting from using only high-functionality monomers, or the insufficient toughness caused by using low-functionality monomers, achieving a balance between high strength and high toughness. The two multifunctional acrylate groups form a single, covalently cross-linked three-dimensional network through a copolymerization reaction under photoinitiation, giving the cured film both excellent mechanical strength and resistance to chemical solvents / electroplating solutions.

[0033] The flexible polyurethane long chains of the modified polyurethane acrylate act as a "flexible skeleton," dispersing and absorbing external stress, while two highly functional reactive diluents act as "crosslinking nodes," constructing a rigid three-dimensional network. Together, they create the excellent mechanical properties of the ultra-thick film. Furthermore, both the modified polyurethane acrylate resin and the reactive diluent molecules are rich in acrylate double bonds, ensuring excellent photocuring efficiency and high crosslinking density, which are the foundation for high resolution and high chemical resistance. The sulfonic acid groups in the flexible modified polyurethane acrylate resin and the phosphate groups in the first reactive diluent work together on the copper surface, providing better adhesion through strong chemical bonding and physical anchoring, ensuring the integrity of the pattern in harsh electroplating environments.

[0034] In summary, the ultra-thick dry film photoresist for copper pillar electroplating of the present invention, through the reinforcement of the modified polyurethane acrylate substrate, the low viscosity-high crosslinking synergy of the composite reactive diluent, and the introduction of nano-hybrid structures, can still maintain good leveling properties under ultra-thick coating. After curing, the adhesion, resistance to electroplating solution corrosion, and pattern resolution of the film layer are all improved, meeting the stringent requirements of the copper pillar electroplating process. Attached Figure Description

[0035] Figure 1 The development time test results are for the samples obtained in Examples 1-3 and Comparative Examples 1-4. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] All of the following ingredients are commercially available.

[0038] Polycaprolactone diol, molecular weight 2000, and polyether-modified polydimethylsiloxane, purity 99%, were purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.; polytetrahydrofuran ether diol, molecular weight 1000, from Jiangsu Haolong Chemical Co., Ltd.; powdered activated carbon, 200 mesh, from Chengdu Blue Whale Technology Co., Ltd.; dipentaerythritol hexaacrylate, DPHA, from Zhongshan Dixin Chemical Co., Ltd.; polyethylene glycol, PEG, molecular weight 20,000, from Jining Tangyi Chemical Co., Ltd.; silicone defoamer, active ingredient content 99%, from Shouguang Bangze Chemical Co., Ltd.; polyether-modified polydimethylsiloxane leveling agent, active ingredient content 99%, from Hubei Dali Chemical Co., Ltd.

[0039] Example 1

[0040] An ultra-thick dry film photoresist for copper pillar electroplating comprises, by weight: 42 parts modified polyurethane acrylate, 15 parts first reactive diluent, 7 parts second reactive diluent, 8 parts plasticizer, 5 parts photoinitiator, 1 part leveling agent, and 0.2 parts defoamer. The first reactive diluent is a composite modified dipentaerythritol hexaacrylate, and the second reactive diluent is trimethylolpropane triacrylate. The plasticizer is polyethylene glycol. The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and hydroxycyclohexane benzophenone (photoinitiator 184) at a mass ratio of 1:1. The leveling agent is a polyether-modified polydimethylsiloxane leveling agent, and the defoamer is an organosilicon defoamer.

[0041] The modified polyurethane acrylate is prepared by:

[0042] Step 1: Polycaprolactone diol and polytetrahydrofuran ether diol are added to a reactor and dehydrated at 115°C and a vacuum of ≥-0.095 MPa for 45 minutes. The temperature is then lowered to 80°C, and isophorone diisocyanate and dibutyltin dilaurate catalyst are added under nitrogen protection. The mixture is reacted at a constant temperature for 2.5 hours to obtain material 1. The mass ratio of polycaprolactone diol, polytetrahydrofuran ether diol, isophorone diisocyanate, and dibutyltin dilaurate is 35:12:22:0.05.

[0043] Step 2: Cool material 1 to 65°C. Dissolve pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, and the polymerization inhibitor p-methoxyphenol in N-methylpyrrolidone (NMP) to form a mixture. Add the mixture dropwise (4 mL / min) to material 1. After the addition is complete, continue the reaction at 65°C for 3.5 hours to obtain material 2. The mass ratio of material 1, pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, polymerization inhibitor p-methoxyphenol, and N-methylpyrrolidone is 100:20:5:5:0.06:10.

[0044] Step 3: Cool material 2 to 55°C, then add hydroxyethyl acrylate (HEA) and 3-aminopropyltriethoxysilane (KH-550) sequentially for end-capping and silanization reactions. React for 4 hours, then add powdered activated carbon. Maintain constant temperature for decolorization and purification for 37 minutes, followed by hot filtration to obtain a clear resin. Neutralize with N,N-dimethylethanolamine, then disperse the neutralized resin in a water / ethanol mixed solvent under high-speed shear. Simultaneously add silane coupling agent KH-560 and polyvinylpyrrolidone. The polyvinylpyrrolidone was homogenized using a three-roll mill to obtain an emulsion. The mass ratio of material 2, hydroxyethyl acrylate, 3-aminopropyltriethoxysilane (KH-550), powdered activated carbon, deionized water / ethanol mixed solvent, N,N-dimethylethanolamine, silane coupling agent KH-560, and polyvinylpyrrolidone was 100:13:2.5:0.2:280:6:1.5:2. In the deionized water / ethanol mixed solvent, the mass ratio of deionized water to ethanol was 1:1.

[0045] Step 4: Under stirring, tetraethyl orthosilicate (tetraethoxysilane) and ammonia are added dropwise to the emulsion obtained in Step 3 at a rate of 0.8 mL / min. The reaction is carried out at 30°C for 36 hours. The composite emulsion is then finely filtered using a PTFE filter element. The filtrate is spray-dried to obtain a coarse powder, which is then purified by rinsing with ultrapure water and centrifugation. The purified powder is then vacuum-dried to obtain the final product. The mass ratio of the emulsion obtained in Step 3, tetraethyl orthosilicate, and ammonia is 100:4:0.2, and the concentration of the ammonia is 25%.

[0046] The preparation method of the composite modified dipentaerythritol hexaacrylate is as follows:

[0047] Step a: Dipentaerythritol hexaacrylate (DPHA) and polymerization inhibitor p-methoxyphenol (MEHQ) are added to the reactor. A mixture of nitrogen and oxygen is introduced for protection, with a gas flow rate controlled at 4 L / min. The stirring speed is 60 rpm, and the temperature is 100°C. First, 40% of the catalyst triphenylphosphine (TPP) is added and stirred evenly. The remaining catalyst triphenylphosphine is mixed with glycidyl methacrylate (GMA) and added to the reaction system at a flow rate of 300 mL / min. After the addition is complete, the reaction is maintained at 100°C for 5 hours to obtain a viscous product. In the nitrogen and oxygen mixture, the volume ratio of nitrogen to oxygen is 97:3, and the mass ratio of DPHA, glycidyl methacrylate, triphenylphosphine, and p-methoxyphenol is 65:20:1:0.4.

[0048] Step b: Cool the viscous product obtained in step a to 55°C, dehydrate ethoxylated trimethylolpropane triacrylate at 60°C and a vacuum degree ≥-0.09MPa for 1 hour, and add the dehydrated ethoxylated trimethylolpropane triacrylate to the viscous product obtained in step a at a rate of 10mL / min while stirring at 50rpm. Stir at 55°C for 1.5 hours until the system is homogeneous. The viscosity of the obtained product is 500mPa·s. The mass ratio of the viscous product obtained in step a to ethoxylated trimethylolpropane triacrylate is 100:25-35.

[0049] Step c: Wash hydroxyethyl methacrylate phosphate three times with 4-6% sodium bicarbonate solution, then dehydrate for 1.5 h at 60 °C and a vacuum of -0.07 to -0.09 MPa. Add the purified hydroxyethyl methacrylate phosphate to the product obtained in step b at a rate of 3 mL / min, then add the catalyst triphenylphosphine, and then heat to 110 °C at a rate of 1.5 °C / min and dehydrate for 30 minutes at a vacuum of -0.08 MPa. Break the vacuum, add the catalyst triphenylantimony, and react at 110 °C under normal pressure for 4 hours. After the reaction is completed, cool the material to 75 °C at a rate of 2 °C / min, add the antioxidant triphenyl phosphite, stir at 75 °C for 30 minutes, and filter through a filter (pore size 10 μm) to obtain the final product. The mass ratio of the product obtained by b, hydroxyethyl methacrylate phosphate, triphenylphosphine, triphenyl antimony, and triphenyl phosphite is 100:7:0.8:0.1:0.05.

[0050] The above-mentioned method for preparing ultra-thick dry film photoresist for copper pillar electroplating includes the following steps:

[0051] Modified polyurethane acrylate, first reactive diluent, second reactive diluent, plasticizer, photoinitiator, leveling agent and defoamer are stirred at 400 rpm for 45 minutes at room temperature until uniformly mixed. Propylene glycol methyl ether acetate solvent is added to adjust the viscosity to 3500 mPa·s (25℃). The mixture is then ground to a fineness of ≤5μm using a three-roll mill to obtain the photoresist solution. The solution is coated onto a PET release film, dried at 70℃ for 6 minutes and then wound up to obtain the finished product.

[0052] Example 2

[0053] An ultra-thick dry film photoresist for copper pillar electroplating comprises, by weight: 38 parts modified polyurethane acrylate, 18 parts first reactive diluent, 5 parts second reactive diluent, 10 parts plasticizer, 8 parts photoinitiator, 0.5 parts leveling agent, and 0.1 parts defoamer. The first reactive diluent is a composite modified dipentaerythritol hexaacrylate, and the second reactive diluent is trimethylolpropane triacrylate. The plasticizer is polyethylene glycol. The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and hydroxycyclohexane benzophenone (photoinitiator 184) at a mass ratio of 1:1. The leveling agent is a polyether-modified polydimethylsiloxane leveling agent, and the defoamer is an organosilicon defoamer.

[0054] The modified polyurethane acrylate is prepared by:

[0055] Step 1: Polycaprolactone diol and polytetrahydrofuran ether diol are added to a reactor and dehydrated at 120°C and a vacuum of ≥-0.095 MPa for 30 minutes. The temperature is then lowered to 85°C, and isophorone diisocyanate and dibutyltin dilaurate catalyst are added under nitrogen protection. The mixture is reacted at a constant temperature for 2 hours to obtain material 1. The mass ratio of polycaprolactone diol, polytetrahydrofuran ether diol, isophorone diisocyanate, and dibutyltin dilaurate is 30:15:20:0.08.

[0056] Step 2: Cool material 1 to 70°C. Dissolve pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, and the polymerization inhibitor p-methoxyphenol in N-methylpyrrolidone (NMP) to form a mixture. Add the mixture dropwise (4 mL / min) to material 1. After the addition is complete, continue the reaction at 70°C for 3 hours to obtain material 2. The mass ratio of material 1, pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, polymerization inhibitor p-methoxyphenol, and N-methylpyrrolidone is 100:25:4:3:0.08:12.

[0057] Step 3: Cool material 2 to 60℃, then add hydroxyethyl acrylate (HEA) and 3-aminopropyltriethoxysilane (KH-550) sequentially for end-capping and silanization reactions. React for 3 hours, then add powdered activated carbon. Maintain constant temperature for decolorization and purification for 45 minutes, followed by hot filtration to obtain a clear resin. Neutralize with N,N-dimethylethanolamine, then disperse the neutralized resin in a water / ethanol mixed solvent under high-speed shear. Simultaneously add silane coupling agent KH-560 and polyvinylpyrrolidone. The polyvinylpyrrolidone was homogenized using a three-roll mill to obtain an emulsion. The emulsion consisted of material 2, hydroxyethyl acrylate, 3-aminopropyltriethoxysilane (KH-550), powdered activated carbon, deionized water / ethanol mixed solvent, N,N-dimethylethanolamine, silane coupling agent KH-560, and polyvinylpyrrolidone in a mass ratio of 100:16:3:0.15:220:6.5:2:1. The deionized water / ethanol mixed solvent had a mass ratio of deionized water to ethanol of 1.1:1.

[0058] Step 4: Under stirring, tetraethyl orthosilicate (tetraethoxysilane) and ammonia are added dropwise to the emulsion obtained in Step 3 at a rate of 0.5 mL / min. The reaction is carried out at 25°C for 48 hours. The composite emulsion is then finely filtered using a PTFE filter element. The filtrate is spray-dried to obtain a coarse powder, which is then purified by rinsing with ultrapure water and centrifugation. The purified powder is then vacuum-dried to obtain the final product. The mass ratio of the emulsion obtained in Step 3, tetraethyl orthosilicate, and ammonia is 100:2:0.1, and the concentration of the ammonia is 28%.

[0059] The preparation method of the composite modified dipentaerythritol hexaacrylate is as follows:

[0060] Step a: Dipentaerythritol hexaacrylate (DPHA) and polymerization inhibitor p-methoxyphenol (MEHQ) are added to the reactor. A mixture of nitrogen and oxygen is introduced for protection, with a gas flow rate controlled at 7 L / min. The stirring speed is 50 rpm, and the temperature is 110°C. First, 50% of the catalyst triphenylphosphine (TPP) is added and stirred evenly. The remaining catalyst triphenylphosphine is mixed with glycidyl methacrylate (GMA) and added to the reaction system at a flow rate of 200 mL / min. After the addition is complete, the reaction is maintained at 110°C for 4 hours to obtain a viscous product. In the nitrogen and oxygen mixture, the volume ratio of nitrogen to oxygen is 96:4, and the mass ratio of DPHA, glycidyl methacrylate, triphenylphosphine, and p-methoxyphenol is 70:15:0.8:0.3.

[0061] Step b: Cool the viscous product obtained in step a to 50°C, dehydrate ethoxylated trimethylolpropane triacrylate at 55°C and a vacuum degree ≥ -0.09 MPa for 1.5 hours, and add the dehydrated ethoxylated trimethylolpropane triacrylate to the viscous product obtained in step a at a rate of 10 mL / min while stirring at 60 rpm. Stir at 50°C for 2 hours until the system is homogeneous. The viscosity of the obtained product is 400 mPa·s. The mass ratio of the viscous product obtained in step a to ethoxylated trimethylolpropane triacrylate is 100:25.

[0062] Step c: Wash hydroxyethyl methacrylate phosphate three times with 4-6% sodium bicarbonate solution, then dehydrate for 2 hours at 55℃ and vacuum degree -0.07 to -0.09 MPa. Add the purified hydroxyethyl methacrylate phosphate to the product obtained in step b at a rate of 5 mL / min, then add the catalyst triphenylphosphine, and then heat to 105℃ at a rate of 1.5℃ / min and vacuum degree -0.08 MPa for 40 minutes to dehydrate. Break the vacuum, add the catalyst triphenylantimony, and react at 105℃ under normal pressure for 5 hours. After the reaction is completed, cool the material to 80℃ at a rate of 3℃ / min, add the antioxidant triphenyl phosphite, stir at 80℃ for 20 minutes, and filter through a filter (pore size 10 μm) to obtain the final product. The mass ratio of the product obtained in step b, hydroxyethyl methacrylate phosphate, triphenylphosphine, triphenyl antimony, and triphenyl phosphite is 100:10:0.5:0.12:0.04.

[0063] The preparation method of the ultra-thick dry film photoresist used for copper pillar electroplating is the same as in Example 1.

[0064] Example 3

[0065] An ultra-thick dry film photoresist for copper pillar electroplating comprises, by weight: 48 parts modified polyurethane acrylate, 12 parts first reactive diluent, 10 parts second reactive diluent, 5 parts plasticizer, 3 parts photoinitiator, 1.5 parts leveling agent, and 0.3 parts defoamer. The first reactive diluent is a composite modified dipentaerythritol hexaacrylate, and the second reactive diluent is trimethylolpropane triacrylate. The plasticizer is polyethylene glycol. The photoinitiator is a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and hydroxycyclohexane benzophenone (photoinitiator 184) at a mass ratio of 1:1. The leveling agent is a polyether-modified polydimethylsiloxane leveling agent, and the defoamer is an organosilicon defoamer.

[0066] The modified polyurethane acrylate is prepared by:

[0067] Step 1: Polycaprolactone diol and polytetrahydrofuran ether diol are added to a reactor and dehydrated at 110°C and a vacuum of ≥-0.095 MPa for 60 minutes. The temperature is then lowered to 75°C, and isophorone diisocyanate and dibutyltin dilaurate catalyst are added under nitrogen protection. The mixture is reacted at a constant temperature for 3 hours to obtain material 1. The mass ratio of polycaprolactone diol, polytetrahydrofuran ether diol, isophorone diisocyanate, and dibutyltin dilaurate is 40:10:25:0.03.

[0068] Step 2: Cool material 1 to 60°C. Dissolve pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, and the polymerization inhibitor p-methoxyphenol in N-methylpyrrolidone (NMP) to form a mixture. Add the mixture dropwise (4 mL / min) to material 1. After the addition is complete, continue the reaction at 60°C for 4 hours to obtain material 2. The mass ratio of material 1, pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, polymerization inhibitor p-methoxyphenol, and N-methylpyrrolidone is 100:15:7:6:0.04:7.

[0069] Step 3: Cool material 2 to 50°C, then add hydroxyethyl acrylate (HEA) and 3-aminopropyltriethoxysilane (KH-550) sequentially for end-capping and silanization reactions. React for 5 hours, then add powdered activated carbon. Maintain constant temperature for decolorization and purification for 30 minutes, followed by hot filtration to obtain a clear resin. Neutralize with N,N-dimethylethanolamine, then disperse the neutralized resin in a water / ethanol mixed solvent under high-speed shearing. Simultaneously add silane coupling agent KH-560 and polyvinylpyrrolidone. The ketone was homogenized using a three-roll mill to obtain an emulsion. The emulsion consisted of material 2, hydroxyethyl acrylate, 3-aminopropyltriethoxysilane (KH-550), powdered activated carbon, a deionized water / ethanol mixed solvent, N,N-dimethylethanolamine, silane coupling agent KH-560, and polyvinylpyrrolidone in a mass ratio of 100:10:2:0.4:350:5.5:1:2.5. The deionized water / ethanol mixed solvent had a mass ratio of deionized water to ethanol of 0.8:1.

[0070] Step 4: Under stirring, tetraethyl orthosilicate (i.e., tetraethoxysilane) and ammonia are added dropwise to the emulsion obtained in Step 3 at a rate of 1 mL / min. The reaction is carried out at 35°C for 24 hours. The composite emulsion is then finely filtered using a PTFE filter element. The filtrate is spray-dried to obtain a coarse powder, which is then purified by rinsing and centrifugation with ultrapure water. The purified powder is then vacuum-dried to obtain the final product. The mass ratio of the emulsion obtained in Step 3, tetraethyl orthosilicate, and ammonia is 100:6:0.3, and the concentration of the ammonia is 28%.

[0071] The preparation method of the composite modified dipentaerythritol hexaacrylate is as follows:

[0072] Step a: Dipentaerythritol hexaacrylate (DPHA) and polymerization inhibitor p-methoxyphenol (MEHQ) are added to the reactor. A mixture of nitrogen and oxygen is introduced for protection, with a gas flow rate controlled at 3 L / min. The stirring speed is 70 rpm, and the temperature is 90°C. First, 30% of the catalyst triphenylphosphine (TPP) is added and stirred evenly. The remaining catalyst triphenylphosphine is mixed with glycidyl methacrylate (GMA) and added to the reaction system at a flow rate of 400 mL / min. After the addition is complete, the reaction is maintained at 90°C for 6 hours to obtain a viscous product. In the nitrogen and oxygen mixture, the volume ratio of nitrogen to oxygen is 98:2, and the mass ratio of DPHA, glycidyl methacrylate, triphenylphosphine, and p-methoxyphenol is 60:25:1.2:0.5.

[0073] Step b: Cool the viscous product obtained in step a to 60°C, dehydrate ethoxylated trimethylolpropane triacrylate at 65°C and a vacuum degree ≥ -0.09 MPa for 0.5 hours, and add the dehydrated ethoxylated trimethylolpropane triacrylate to the viscous product obtained in step a at a rate of 10 mL / min while stirring at 40 rpm. Stir at 60°C for 1 hour until the system is homogeneous, and the viscosity of the obtained product is 600 mPa·s; wherein, the mass ratio of the viscous product obtained in step a to ethoxylated trimethylolpropane triacrylate is 100:35.

[0074] Step c: Wash hydroxyethyl methacrylate phosphate three times with 4-6% sodium bicarbonate solution, then dehydrate for 1 hour at 65°C and a vacuum of -0.07 to -0.09 MPa. Add the purified hydroxyethyl methacrylate phosphate to the product obtained in step b at a rate of 2 mL / min, then add the catalyst triphenylphosphine, and then heat to 115°C at a rate of 1.5°C / min and a vacuum of -0.08 MPa for 20 minutes to dehydrate. Break the vacuum, add the catalyst triphenylantimony, and react at 115°C under normal pressure for 3 hours. After the reaction is completed, cool the material to 70°C at a rate of 1°C / min, add the antioxidant triphenyl phosphite, stir at 70°C for 40 minutes, and filter through a filter (pore size 10 μm) to obtain the final product. The mass ratio of the product obtained by b, hydroxyethyl methacrylate phosphate, triphenylphosphine, triphenyl antimony, and triphenyl phosphite is 100:5:1.0:0.08:0.06.

[0075] The preparation method of the ultra-thick dry film photoresist used for copper pillar electroplating is the same as in Example 1.

[0076] Comparative Example 1

[0077] An ultra-thick dry film photoresist for copper pillar electroplating, wherein the modified polyurethane acrylate is replaced with a difunctional aliphatic polyurethane acrylate, and the rest is the same as in Example 1.

[0078] Comparative Example 2

[0079] An ultra-thick dry film photoresist for copper pillar electroplating, wherein the active diluent is replaced with a single active diluent, specifically bispentaerythritol hexaacrylate, and the rest is the same as in Example 1.

[0080] Comparative Example 3

[0081] An ultra-thick dry film photoresist for copper pillar electroplating, wherein the active diluent is replaced with a single active diluent, specifically a composite modified dipentaerythritol hexaacrylate, and the rest is the same as in Example 1.

[0082] Comparative Example 4

[0083] An ultra-thick dry film photoresist for copper pillar electroplating, wherein the active diluent is replaced with a single active diluent, specifically trimethylolpropane triacrylate, and the rest is the same as in Example 1.

[0084] The copper-clad laminate was cut into 10cm × 10cm pieces. The upper roller temperature of the dry film laminator was set to 105-110℃, the lower roller to room temperature, and the conveyor speed to 1.5-2.5m / min. The dry film was peeled off from the PET release film and then hot-pressed onto the prepared copper substrate using the laminator, ensuring no bubbles or wrinkles. A 365nm i-line light source was used, with an exposure dose of 200mJ. ², all comparative experiments must be conducted at the same exposure energy: for adhesion testing, a blank mask without patterns (full-area exposure) is used; for electroplating solution resistance testing, masks with patterns of different linewidths / spacings (L / S) are used. After exposure, the samples are placed in a developing machine and developed using a 1% sodium carbonate aqueous solution at 28-30°C. The development time is recorded, i.e., the time required from the sample entering the developing area until the unexposed parts are completely dissolved and the pattern clearly appears. After development, the sample is immediately rinsed thoroughly with deionized water to stop the development reaction, and then dried by blowing or baking.

[0085] Thickness test: According to GB / T 13452.2-2008 "Determination of thickness of color film and varnish film", the overall thickness of the dry film coated on PET release film obtained in Examples 1-3 and Comparative Examples 1-4 was tested using a micrometer. Five different positions were randomly selected on the dry film (avoiding the 10mm edge area to prevent edge effect), and the thickness was measured and recorded. The average value of the five measurements was taken as the dry film thickness of the sample, and then the thickness of the dry film photoresist was calculated.

[0086] Adhesion test: Tested according to GB / T9286-2021 "Paints and Varnishes Cross-cut Test", with a cross-cut spacing of 1mm. After peeling off with 3M 610 tape, the grade is rated (0 is the best, 5 is the worst).

[0087] Electroplating solution resistance test: The patterned sample was immersed in an acidic copper plating solution (CuS) at 50°C. ·5 O: 220g / L S Soak in 180g / L solution for 60 minutes. After removing the sample, observe whether the pattern swells or peels off, and perform the cross-cut adhesion test again, recording the change in the adhesion level.

[0088] The development performance test records the time (in seconds) required for the image to become fully clear under the above standard development conditions.

[0089] Table 1. Test Results

[0090]

[0091] From Table 1, Figure 1 As can be seen, regarding adhesion and electroplating resistance, Examples 1-3 performed excellently, with initial adhesion of level 0 (no peeling). After resistant to electroplating solution (50℃ acidic Cu solution, 60 minutes), they maintained level 0 adhesion without swelling or peeling, indicating that the modified polyurethane acrylate matrix and composite diluent synergistically improved the interfacial bonding between the dry film and the copper substrate and the resistance to electroplating corrosion. In contrast, Comparative Examples 1-4 had weaker initial adhesion (levels 1-3), which further deteriorated after electroplating: the adhesion of Comparative Examples 1-2 dropped to level 4-5 (severe peeling / swelling), Comparative Example 4 completely peeled off, and only Comparative Example 3 maintained level 2 (slight swelling at the edges). This proves that traditional difunctional aliphatic resins (Comparative Example 1) or single reactive diluents (Comparative Examples 2-4) cannot resist electroplating corrosion due to insufficient crosslinking density. Development efficiency: The development time for Examples 1-3 was only 42-50 seconds, significantly faster than that for Comparative Examples 1-4, indicating that the unexposed areas of the high cross-linking density system (Examples 1-3) are more easily dissolved; this further highlights the synergistic effect of this invention in multiple dimensions of "high adhesion + fast development + electroplating resistance". In summary, the test results fully demonstrate that this invention, through material system optimization, solves the technical problems of adhesion, electroplating resistance and development efficiency of ultra-thick dry films, and has significant industrial application value.

[0092] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0093] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An ultra-thick dry film photoresist for copper pillar electroplating, characterized in that, The product comprises, by weight parts: 38-48 parts modified polyurethane acrylate, 12-18 parts first reactive diluent, 5-10 parts second reactive diluent, 5-10 parts plasticizer, 3-8 parts photoinitiator, 0.5-1.5 parts leveling agent, and 0.1-0.3 parts defoamer, wherein the first reactive diluent is composite modified dipentaerythritol hexaacrylate, and the second reactive diluent is trimethylolpropane triacrylate; The modified polyurethane acrylate is prepared by: Step 1: Polycaprolactone diol and polytetrahydrofuran ether diol are first dehydrated and purified, and then isophorone diisocyanate and dibutyltin dilaurate catalyst are added at 75-85℃ under nitrogen protection. The reaction is carried out at a constant temperature for 2-3 hours to obtain material 1. Step 2: Cool material 1 to 60-70℃, dissolve pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid and polymerization inhibitor p-methoxyphenol in N-methylpyrrolidone to obtain a mixture, add the mixture dropwise to material 1, and continue the reaction at 60-70℃ for 3-4 hours after the addition is complete to obtain material 2; Step 3: Cool material 2 to 50-60℃, add hydroxyethyl acrylate and 3-aminopropyltriethoxysilane in sequence, react for 3-5 hours, then decolorize and purify with powdered activated carbon, filter to obtain clear resin, add N,N-dimethylethanolamine to the clear resin for neutralization, then disperse the neutralized resin in a water / ethanol mixed solvent under high speed shear, add silane coupling agent KH-560 and polyvinylpyrrolidone, homogenize to obtain emulsion; Step 4: Under stirring, add tetraethyl orthosilicate and ammonia water dropwise to the emulsion obtained in Step 3 at a rate of 0.5-1 mL / min, react at 25-35℃ for 24-48 hours, and then purify to obtain the final product. The preparation method of the composite modified dipentaerythritol hexaacrylate is as follows: Step a: Add dipentaerythritol hexaacrylate and the polymerization inhibitor p-methoxyphenol to the reactor. Purge with a mixture of nitrogen and oxygen for protection. Stir at 50-70 rpm and 90-110°C. First, add 30%-50% of the catalyst triphenylphosphine and stir until homogeneous. Mix the remaining catalyst triphenylphosphine with glycidyl methacrylate and add it to the reaction system at a flow rate of 200-400 mL / min. After the addition is complete, keep the reaction at 90-110°C for 4-6 hours to obtain a viscous product. Step b: Cool the viscous product obtained in step a to 50-60℃, dehydrate ethoxylated trimethylolpropane triacrylate at 55-65℃ and vacuum degree ≥-0.09MPa for 0.5-1.5 hours, add the dehydrated ethoxylated trimethylolpropane triacrylate to the viscous product obtained in step a at a rate of 10mL / min while stirring at 40-60rpm, and stir at 50-60℃ for 1-2 hours until the system is homogeneous, and control the viscosity at 400-600mPa·s; Step c: Wash hydroxyethyl methacrylate phosphate with 4-6% sodium bicarbonate solution, then dehydrate it at 55-65℃ and vacuum degree -0.07 to -0.09MPa for 1-2 hours. Add the dehydrated hydroxyethyl methacrylate phosphate to the product obtained in step b at a rate of 2-5 mL / min. Add the catalyst triphenylphosphine, then stir at 105-115℃ and vacuum degree -0.07 to -0.09MPa for 20-40 minutes. Break the vacuum, add the catalyst triphenylantimony, and react at normal pressure for 3-5 hours. After the reaction is completed, cool down to 70-80℃, add the antioxidant triphenyl phosphite, stir for 20-40 minutes, and filter through a filter to obtain the final product.

2. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step 1, the mass ratio of polycaprolactone diol, polytetrahydrofuran ether diol, isophorone diisocyanate, and dibutyltin dilaurate is 30-40:10-15:20-25:0.03-0.

08.

3. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step 2, the mass ratio of material 1, pentaerythritol triacrylate, 2,2-dimethylolpropionic acid, 2-acrylamide-2-methylpropanesulfonic acid, p-methoxyphenol, and N-methylpyrrolidone is 100:15-25:4-7:3-6:0.04-0.08:7-12.

4. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step 3, the mass ratio of material 2, hydroxyethyl acrylate, 3-aminopropyltriethoxysilane, powdered activated carbon, deionized water / ethanol mixed solvent, N,N-dimethylethanolamine, silane coupling agent KH-560, and polyvinylpyrrolidone is 100:10-16:2-3:0.15-0.4:220-350:5.5-6.5:1-2:1-2.5, and the mass ratio of deionized water to ethanol in the deionized water / ethanol mixed solvent is 0.8-1.1:

1.

5. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step 4, the mass ratio of the emulsion obtained in step 3, tetraethyl orthosilicate, and ammonia is 100:2-6:0.1-0.3, and the concentration of the ammonia is 25%-28%.

6. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step a, the volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixture is 96-98:2-4, and the mass ratio of dipentaerythritol hexaacrylate, glycidyl methacrylate, triphenylphosphine, and p-methoxyphenol is 60-70:15-25:0.8-1.2:0.3-0.

5.

7. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step b, the mass ratio of the viscous product obtained in step a to ethoxylated trimethylolpropane triacrylate is 100:25-35.

8. The ultra-thick dry film photoresist for copper pillar electroplating according to claim 1, characterized in that, In step c, the mass ratio of the product obtained in step b, hydroxyethyl methacrylate phosphate, triphenylphosphine, triphenyl antimony, and triphenyl phosphite is 100:5-10:0.5-1.0:0.08-0.12:0.04-0.

06.

9. The method for preparing ultra-thick dry film photoresist for copper pillar electroplating according to any one of claims 1-8, characterized in that, Specifically, the modified polyurethane acrylate, first reactive diluent, second reactive diluent, plasticizer, photoinitiator, leveling agent, and defoamer are stirred at 300-500 rpm for 30-60 minutes at room temperature until uniformly mixed. Propylene glycol methyl ether acetate solvent is added to adjust the viscosity to 2000-5000 mPa·s at room temperature. After grinding, a photoresist solution is obtained. The solution is coated onto a PET release film, dried, and wound to obtain the finished product.

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