Preparation method of CTI600V halogen-free high-Tg curing glue solution and copper-clad plate

Abstract

The present application relates to a kind of CTI600V halogen-free high Tg curing glue liquid and the preparation method of copper-clad plate, belong to the field of curing glue for PCB plate, and curing glue liquid component includes phenolic epoxy resin, isocyanate modified epoxy resin, four functional epoxy resin, linear phenolic resin, phosphorus-containing phenolic resin, aromatic amine curing agent, curing accelerator, inorganic filler, nitrogen-containing flame retardant and organic solvent.In raw material, linear phenolic resin is solid resin, and epoxy resin and phosphorus-containing phenolic resin are liquid resin.Copper-clad plate prepared with the curing glue liquid has glass transition temperature >160 DEG C, excellent heat resistance, halogen-free flame retardant, low CTE and high CTI, and also has excellent CAF resistance, especially suitable for new energy vehicle charging equipment and battery system and other PCB application scenarios with strict requirements on reliability and safety.

Description

Technical Field

[0001] This invention belongs to the field of resin curing adhesives for PCB boards, and particularly relates to a halogen-free curing adhesive with a high glass transition temperature. Background Technology

[0002] With the rapid development of high-end electronics industries such as new energy vehicles, charging infrastructure, and smart grids, higher requirements are being placed on the comprehensive performance of printed circuit board (PCB) substrates. Traditional FR-4 copper-clad laminates generally use brominated flame retardants, making it difficult to meet the halogen-free requirements of environmental regulations such as RoHS. Moreover, their tracking index (CTI) is typically only 175V to 250V, far below the 600V safety standard required for high-voltage applications. Furthermore, due to their low glass transition temperature (Tg), traditional materials are prone to deformation or delamination failure under high-temperature service conditions.

[0003] Therefore, developing an environmentally friendly copper-clad laminate that combines halogen-free flame retardancy (UL94 V-0 rating), CTI≥600V, and high Tg (>160℃) has become a key technological direction to meet the urgent needs of demanding application fields such as new energy vehicle charging equipment and battery systems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a CTI600V halogen-free high Tg curing adhesive and a copper-clad laminate, so as to meet the requirements of halogen-free flame retardancy, tracking index (CTI) I ≥ 600V, and glass transition temperature (Tg) > 160℃.

[0005] The technical solution adopted in this invention is: a CTI600V halogen-free high Tg curing adhesive, with the following raw materials and mass ratios: 14-16 parts of phenolic epoxy resin 10-12 parts of isocyanate-modified epoxy resin, 2-4 parts of tetrafunctional epoxy resin 6-8 parts of linear phenolic resin, 16-20 parts of phosphorus-containing phenolic resin, 1-4 parts of aromatic amine curing agent Curing accelerator 0.001-0.1 parts, 25-35 parts of inorganic filler 1-4 parts of nitrogen-containing flame retardant 15-25 parts organic solvent Of the above raw materials, linear phenolic resin is a solid resin, while epoxy resin and phosphorus-containing phenolic resin are liquid resins. All the above parts refer to the pure mass parts of the raw materials, of which phenolic epoxy resin, isocyanate modified epoxy resin, tetrafunctional epoxy resin, linear phenolic resin, phosphorus-containing phenolic resin, aromatic amine curing agent, curing accelerator, inorganic filler, nitrogen-containing flame retardant and organic solvent total 100 parts.

[0006] Furthermore, the epoxy equivalent of the phenolic epoxy resin was 170-190 g / eq, purchased from Sichuan Dongcai Technology Group Co., Ltd., model DFE238B; the epoxy equivalent of the isocyanate modified epoxy resin was 270-310 g / eq, purchased from Tongyu New Materials (Guangdong) Co., Ltd., model TER295K75; and the epoxy equivalent of the tetrafunctional epoxy resin was 195-230 g / eq, purchased from Shandong Shengquan New Materials Co., Ltd., model SQSN-4132A70.

[0007] Furthermore, the linear phenolic resin has a softening point temperature of 104-109℃, free phenol ≤1000ppm, and electrical conductivity ≤4.5μs / cm.

[0008] Furthermore, the phosphorus content of the phosphorus-containing phenolic resin is 8.5%-9.5%, and the solid content is 59%-61%.

[0009] Furthermore, the aromatic amine curing agent is DDS, namely 4,4-diaminodiphenyl sulfone; the curing accelerator is 2MZ, namely 2-methylimidazole.

[0010] Furthermore, the inorganic filler is one or more mixtures of boehmite, aluminum hydroxide, barium sulfate, and their modified forms.

[0011] Furthermore, the nitrogen-containing flame retardant is melamine cyanurate (MCA), with a D50 of 0.5-1.5 μm and a D99 of less than 10 μm.

[0012] 8. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: the organic solvent is one or any mixture of butanone, cyclohexanone, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

[0013] The method for preparing the cured adhesive from the above raw materials is as follows: First, add the organic solvent and liquid resin to the mixing tank, start stirring to fully dissolve the materials, control the temperature inside the tank at 20-40℃, and stir for 60-90 minutes; then, continue to add solid resin, aromatic amine curing agent, curing accelerator, nitrogen-containing flame retardant and inorganic filler to the tank, and continue stirring for 60-90 minutes to mix the materials evenly, and then perform high-efficiency shearing and emulsification for more than 210 minutes to obtain the adhesive for electronic fiberglass cloth. The final adhesive has a solid content of 66-69%, a viscosity of 15-35s in the fourth cup, and a gelation time of 280-320s at 171℃.

[0014] The method for preparing copper-clad laminate using the above-mentioned curing adhesive is as follows: Electronic fiberglass cloth is impregnated in a vertical coating machine, and the adhesive is evenly coated on the surface of the fiberglass cloth. After baking in an oven at 165-225℃, the adhesive content of the prepreg is controlled at 44±2%, and the flowability is 15-25%, to obtain a fiberglass cloth prepreg. 1-8 fiberglass cloth prepregs are stacked, and an electrolytic copper foil is applied to each side. The mixture is hot-pressed at 80-230℃ and 0.8-2.8MPa for more than 160 minutes. Then, it is cold-pressed at 1-1.5MPa for 60-90 minutes to obtain the copper-clad laminate.

[0015] Compared with the prior art, the advantages of the present invention are as follows: This application uses phenolic epoxy resin, tetrafunctional epoxy resin, and isocyanate-modified epoxy resin as the main resins, aromatic amine curing agents and linear phenolic resins to form the curing system, phosphorus-containing phenolic resin and nitrogen-containing environmentally friendly flame retardants, imidazole curing accelerators, modified barium sulfate and boehmite as functional fillers, and ketone and ether organic solvents. The dense network formed through multifunctional synergistic curing ensures that the cured product has extremely high crosslinking density and excellent heat resistance. Through the formation of phosphorus-nitrogen synergy, a highly efficient intumescent flame retardant system is constructed. During combustion, it releases gases to dilute the flame and inflate the char layer, while also helping to form a dense charcoal heat insulation barrier, thus efficiently achieving the goals of halogen-free, low-smoke, and high flame retardancy. The use of modified barium sulfate and boehmite as fillers improves dimensional stability and resistance to tracking inertia (CTI) without affecting flame retardant efficiency.

[0016] The copper-clad laminate prepared using the curing adhesive and method exhibits a high glass transition temperature (Tg > 160℃), excellent heat resistance, halogen-free flame retardancy, low CTE, and high CTI. Compared to a tracking index ≥ 600V, it meets high-voltage safety requirements. Furthermore, the copper-clad laminate possesses excellent resistance to CAF (cathode frost), making it particularly suitable for PCB applications with stringent reliability and safety requirements, such as charging equipment and battery systems for new energy vehicles. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments. The embodiments are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention. Example 1

[0018] A method for preparing a CTI600V halogen-free high Tg copper-clad laminate that combines environmental friendliness and reliability includes the following steps: (1) Preparation of adhesive solution for electronic fiberglass cloth: By weight percentage, the adhesive for electronic fiberglass cloth comprises: 14.63% phenolic epoxy resin (85% solids), 11.08% isocyanate-modified epoxy resin (75% solids), 2.35% tetrafunctional epoxy resin (70% solids), 6.58% linear phenolic resin (100% solids), 17.24% phosphorus-containing phenolic resin (60% solids), 1.25% DDS (curing agent), 0.0063% 2-methylimidazole (curing accelerator), 13.06% modified barium sulfate (inorganic filler), 13.06% boehmite (inorganic filler), 1.31% melamine cyanurate (nitrogen-containing flame retardant), 5.22% methyl ethyl ketone (organic solvent), with the balance being ethylene glycol monomethyl ether (organic solvent), approximately 14.2%.

[0019] a. Add methyl ethyl ketone, ethylene glycol monomethyl ether, phenolic epoxy resin, isocyanate modified epoxy resin, tetrafunctional epoxy resin and phosphorus-containing phenolic resin to a stirred tank, start stirring to dissolve them completely, control the temperature inside the tank at 30℃, and stir for 60 minutes. b. Continue to add linear phenolic resin, DDS and 2-methylimidazole dissolved in an appropriate amount of organic solvent, as well as modified barium sulfate, boehmite and melamine cyanurate to the reactor. Stir continuously for 120 minutes to mix evenly, then turn on high-efficiency shearing and emulsify for 210 minutes to obtain the adhesive solution for electronic fiberglass cloth.

[0020] The final adhesive solution had a solid content of 68%, a viscosity of 22s in the fourth cup, and a gelation time of 306s at 171℃.

[0021] (2) Preparation of semi-cured sheets Electronic fiberglass cloth is impregnated in a vertical gluing machine, and then the electronic fiberglass cloth is uniformly coated with adhesive on the surface of the fiberglass cloth. After baking at 165-225℃ for 90-120s, the adhesive content of the semi-cured sheet is measured to be 44.6% and the flowability is 19.2%, thus producing a fiberglass cloth semi-cured sheet.

[0022] (3) Preparation of copper-clad laminate Eight prepreg sheets are stacked together, and 1 ounce of electrolytic copper foil is applied to each side. The mixture is then hot-pressed at 80-230℃ and 0.8-2.8MPa for 160 minutes, followed by cold pressing at 1.5MPa for 60 minutes to obtain the copper-clad laminate.

[0023] The performance of the obtained copper-clad laminate was tested, and the test results are shown in Table 1. Example 2

[0024] A method for preparing a CTI600V halogen-free high Tg copper-clad laminate that combines environmental friendliness and reliability includes the following steps: (1) Preparation of adhesive solution for electronic fiberglass cloth: By weight percentage, the adhesive for electronic fiberglass cloth comprises: 14.43% phenolic epoxy resin (85% solid content), 10.93% isocyanate-modified epoxy resin (75% solid content), 2.32% tetrafunctional epoxy resin (70% solid content), 6.60% linear phenolic resin (100% solid content), 1.29% DDS (curing agent), 16.70% phosphorus-containing phenolic resin (60% solid content), 0.0062% 2-methylimidazole (curing accelerator), 12.89% modified barium sulfate (inorganic filler), 12.89% aluminum hydroxide (inorganic filler, preferably aluminum hydroxide with high heat resistance), 1.24% melamine cyanurate (nitrogen-containing flame retardant), 5.15% cyclohexanone (organic solvent), and 15.57% propylene glycol monomethyl ether (organic solvent).

[0025] a. Add cyclohexanone, propylene glycol monomethyl ether, phenolic epoxy resin, isocyanate modified epoxy resin, tetrafunctional epoxy resin and phosphorus-containing phenolic resin to a stirred tank, start stirring to dissolve them completely, control the temperature inside the tank at 30℃, and stir for 60 minutes. b. Continue to add linear phenolic resin, DDS and 2-methylimidazole dissolved in an appropriate amount of organic solvent, as well as barium sulfate, high heat-resistant aluminum hydroxide and melamine cyanurate to the reactor. Stir continuously for 120 minutes to make it evenly mixed, then turn on high-efficiency shearing and emulsify for 210 minutes to obtain the adhesive solution for electronic fiberglass cloth.

[0026] The final adhesive solution had a solid content of 67.5%, a viscosity of 20s (Fourth Cup), and a gelation time of 298s / 171℃.

[0027] (2) Preparation of semi-cured sheets Electronic fiberglass cloth is impregnated in a vertical gluing machine, and then the electronic fiberglass cloth is evenly coated with adhesive on the surface of the fiberglass cloth. After baking at 165-225℃ for 90-120s, the adhesive content of the semi-cured sheet is controlled at 44.2% and the flowability is 18.7%, thus obtaining a fiberglass cloth semi-cured sheet.

[0028] (3) Preparation of FR-4 copper clad laminate Eight prepreg sheets are stacked together, and 1 ounce of electrolytic copper foil is applied to both sides. The mixture is then hot-pressed at 80-230℃ and 0.8-2.8MPa for 160 minutes. Finally, it is cold-pressed at 1.5MPa for 60 minutes to obtain the FR-4 copper-clad laminate.

[0029] The performance of the obtained copper-clad laminate was tested, and the test results are shown in Table 1.

[0030] Table 1 Summary of Main Properties of Sheet Metal

[0031] A 1.5mm thick double-sided copper-clad board with 1oz / 1oz copper foil was used. According to the CAF test pattern, the PTH hole wall spacing was designed to be 0.3mm, 0.35mm, 0.4mm, 0.45mm and 0.65mm, and the hole diameter was 0.3mm. The board was processed into test boards at the PCB manufacturer. Four samples were taken for each formula for testing. Before the CAF test, six reflow soldering cycles were performed. The CAF test conditions were: 85℃ / 85%RH, 100VDC, failure was judged by resistance less than 108 ohms, and the test time was 1000hr.

[0032] The results show that both formulations can still pass the 1000-hour CAF test when the minimum hole-to-wall spacing is reduced to 0.3 mm.

[0033] In summary, this copper-clad laminate is a high-performance board material with high Tg, halogen-free flame retardancy, and CTI≥600V. Its various indicators are well-balanced and excellent, especially meeting the stringent requirements of PCBs used in new energy vehicle charging equipment and battery systems for heat resistance, high-voltage safety, and environmental reliability. It has good prospects for industrial application.

Claims

1. A CTI600V halogen-free high Tg curing adhesive, characterized in that: The raw materials and their quality ratios are as follows: 14-16 parts of phenolic epoxy resin 10-12 parts of isocyanate-modified epoxy resin, 2-4 parts of tetrafunctional epoxy resin 6-8 parts of linear phenolic resin, 16-20 parts of phosphorus-containing phenolic resin, 1-4 parts of aromatic amine curing agent Curing accelerator 0.001-0.1 parts, 25-35 parts of inorganic filler 1-4 parts of nitrogen-containing flame retardant 15-25 parts organic solvent Of the above raw materials, linear phenolic resin is a solid resin, while epoxy resin and phosphorus-containing phenolic resin are liquid resins. All the above parts refer to the pure mass parts of the raw materials, of which phenolic epoxy resin, isocyanate modified epoxy resin, tetrafunctional epoxy resin, linear phenolic resin, phosphorus-containing phenolic resin, aromatic amine curing agent, curing accelerator, inorganic filler, nitrogen-containing flame retardant and organic solvent total 100 parts.

2. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The epoxy equivalent of phenolic epoxy resin was 170-190 g / eq, purchased from Sichuan Dongcai Technology Group Co., Ltd., model DFE238B; the epoxy equivalent of isocyanate modified epoxy resin was 270-310 g / eq, purchased from Tongyu New Materials (Guangdong) Co., Ltd., model TER295K75; and the epoxy equivalent of tetrafunctional epoxy resin was 195-230 g / eq, purchased from Shandong Shengquan New Materials Co., Ltd., model SQSN-4132A70.

3. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The softening point temperature of linear phenolic resin is 104-109℃, the free phenol content is ≤1000ppm, and the electrical conductivity is ≤4.5μs / cm.

4. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The phosphorus content of phosphorus-containing phenolic resin is 8.5%-9.5%, and the solid content is 59%-61%.

5. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The aromatic amine curing agent is DDS, namely 4,4-diaminodiphenyl sulfone; the curing accelerator is 2MZ, namely 2-methylimidazole.

6. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The inorganic filler is one or more of boehmite, aluminum hydroxide, barium sulfate and their modified forms.

7. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The nitrogen-containing flame retardant is melamine cyanurate (MCA), with a D50 of 0.5-1.5 μm and a D99 of less than 10 μm.

8. The CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: The organic solvent is one or any mixture of butanone, cyclohexanone, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

9. A method for preparing the CTI600V halogen-free high Tg curing adhesive according to claim 1, characterized in that: First, add the organic solvent and liquid resin to the mixing tank, start stirring to fully dissolve the materials, control the temperature inside the tank at 20-40℃, and stir for 60-90 minutes. Then, continue to add solid resin, aromatic amine curing agent, curing accelerator, nitrogen-containing flame retardant and inorganic filler to the tank, and continue stirring for 60-90 minutes to mix the materials evenly. Then, perform high-efficiency shearing and emulsification for more than 210 minutes to obtain the adhesive for electronic fiberglass cloth. The final adhesive has a solid content of 66-69%, a viscosity of 15-35s in the fourth cup, and a gelation time of 280-320s at 171℃.

10. A method for preparing a copper-clad laminate, characterized in that: Using the adhesive prepared by the method described in claim 9, electronic fiberglass cloth is impregnated in a vertical coating machine, and the adhesive is uniformly coated onto the surface of the fiberglass cloth. After baking in an oven at 165-225℃, the adhesive content of the prepreg is controlled at 44±2%, and the flowability is 15-25%, to obtain a fiberglass cloth prepreg. 1-8 fiberglass cloth prepregs are stacked, and an electrolytic copper foil is applied to each side. The mixture is hot-pressed at 80-230℃ and 0.8-2.8MPa for more than 160 minutes. Then, it is cold-pressed at 1-1.5MPa for 60-90 minutes to obtain a copper-clad laminate.

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