Highly insulating blind via PCB and method of making same

Abstract

The application belongs to the technical field of printed circuit board manufacturing, and particularly relates to a high-insulation blind via PCB board and a preparation method thereof. In the preparation of the substrate, the inner chip layer, the epoxy resin glass cloth substrate and the copper foil are first pressed once to obtain a PCB sub-board, then a hole is drilled and plated with copper to obtain a blind hole, and finally the PCB main board is obtained through secondary pressing, hole sealing and solidification, silk screen printing of marks, detection and packaging, so that the high-insulation blind via PCB board is obtained. The secondary pressing makes the sub-boards fully bonded, the 2-butyl long-chain alkyl group is introduced into the insulating epoxy resin to improve the toughness and impact resistance, and the norbornene rigid group is introduced to make the insulating epoxy resin effectively absorb internal stress; the tetrabutyl titanate and barium acetate are prepared into dry gel through gelation, the insulating ceramic powder is prepared through grinding and calcination, the surface is modified through kH-560 to introduce an epoxy group, the dispersibility of the insulating medium filler in the epoxy resin is improved, and the insulation performance of the high-insulation blind via PCB board is improved through gradient temperature curing.

Description

Technical Field

[0001] This invention belongs to the field of printed circuit board manufacturing technology, specifically relating to a high-insulation blind via PCB board and its preparation method. Background Technology

[0002] Printed circuit boards (PCBs) are a general term for printed circuits or finished printed circuit boards. They are important components in electronic products such as integrated circuits. With the continuous improvement of electronic product functions and the increasing complexity of design requirements, the development of equipment towards miniaturization and high integration has become an industry trend. Therefore, the requirements for PCBs are constantly increasing, especially in terms of increasing wiring density and connecting various components within a limited space.

[0003] Chinese invention patent CN116456632B discloses a method for laminating high-layer PCBs. By setting several blind vias as device holes on the surface of the high-layer PCB, BGA sites are provided for electronic devices mounted on the high-layer PCB surface. The improved lamination process produces device holes with better morphology and reliability. These device holes are fabricated through a stacking process, with multiple laminations forming a first buried via in a second sub-board from a first via in the first sub-board. Finally, after final lamination, blind vias are opened corresponding to the first buried vias to form the device holes on the high-layer PCB surface, improving the quality, stability, and reliability of the final device holes. Furthermore, this invention improves the difference in expansion and contraction between layers during high-layer PCB lamination by changing the lamination process, resulting in a flatter and more reliable high-layer PCB. However, the existing technology lacks the technical problem of further refining the composition of the PCB insulation layer to improve the insulation performance of the PCB. Summary of the Invention

[0004] The purpose of this invention is to provide a high-insulation blind via PCB board and its preparation method, which solves the technical problem in the prior art that the insulation performance of the PCB board is not improved by further refining the composition of the insulating layer.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The high-insulation blind via PCB has multiple blind vias on its surface. The PCB has four mounting holes distributed at the four corners of the PCB. It is made by bonding two sub-boards together with insulating epoxy resin. The sub-board is made by sequentially arranging and bonding an inner chip layer, an epoxy resin glass cloth substrate, and copper foil.

[0007] The method for preparing the high-insulation blind via PCB board includes the following steps:

[0008] S1. After cutting the copper-clad laminate, apply photoresist and expose it to transcribe the pattern. Remove excess photoresist and etch the circuit to the surface of the copper-clad laminate to obtain the inner chip layer. Then, press the inner chip layer, epoxy resin glass cloth substrate and copper foil together in one step to obtain the PCB board.

[0009] S2. Drill holes at designated locations, immerse the holes in electroplating solution to plate copper, and obtain blind holes;

[0010] S3. Multiple PCB boards are laminated together to form the main PCB board, and mounting holes are drilled at the designated locations.

[0011] S4. Apply solder resist ink to the surface of the PCB motherboard to seal the holes, heat and bake to cure, grind the board after curing, screen print markings, inspect and package to obtain a high-insulation blind via PCB board.

[0012] Preferably, in step S1, an etching solution prepared from 150-180 g / L copper chloride, 80-120 g / L hydrochloric acid, 0.1-0.5 g / L polyvinylpyrrolidone, and 10-30 g / L hydrogen peroxide is used for etching. The temperature of the first pressing is 170-190°C, the pressing pressure is 1-1.5 MPa, and the pressing time is 60-90 min.

[0013] Preferably, the blind hole in S2 has a pore size of 30~50μm and is prepared by mixing 200~250g / L copper sulfate, 60~80g / L sulfuric acid, 1~10mg / L sodium polydisulfide dipropane sulfonate, 0.05~0.1g / L polyvinylpyrrolidone and 0.1~0.5g / L polyethylene glycol to obtain the electroplating solution.

[0014] Preferably, the temperature of the secondary pressing in S3 is 170~190℃, the pressing pressure is 1~1.5MPa, and the pressing time is 60~120min.

[0015] Preferably, in step S4, the temperature is raised to 70-80℃ for 30-50 minutes, then raised to 120-130℃ for 1-2 hours to cure, and then raised to 150-160℃ for 1-2 hours to cure.

[0016] The method for preparing the insulating epoxy resin includes the following steps:

[0017] S11. Add 2-butyl-1,3-propanediol and organic solvent to a reaction vessel, add p-toluenesulfonyl chloride dropwise under ice bath conditions, add potassium hydroxide and stir the reaction. After the reaction is completed, wash with deionized water, take the organic phase, add anhydrous sodium sulfate to remove water, filter and remove solvent by rotary evaporation, and recrystallize in methanol to obtain intermediate product 1.

[0018] S12. Sodium hydride was added to anhydrous N,N dimethylformamide under a nitrogen atmosphere and stirred to disperse. 5-norbornene-2-methanol and intermediate product 1 were added dropwise under a nitrogen atmosphere. The reaction was heated and the reaction was quenched with deionized water. The mixture was allowed to stand and separate into layers. The aqueous phase was extracted with ethyl acetate and separated into layers. The organic phase was removed by adding anhydrous sodium sulfate to remove water. After filtration, the solvent was removed by rotary evaporation to obtain intermediate product 2.

[0019] S13. Add m-chloroperoxybenzoic acid and dichloromethane to a reaction vessel. Dissolve intermediate product 2 in dichloromethane and then add it dropwise to the reaction vessel. Add 10wt% sodium bisulfite aqueous solution dropwise under ice bath conditions, stir the reaction, and use starch potassium iodide to detect whether the reaction is complete. Wash with 10wt% sodium bicarbonate aqueous solution and deionized water in sequence. Add anhydrous sodium sulfate to remove water. After filtration, remove the solvent by rotary evaporation to obtain insulating epoxy resin.

[0020] As a preferred embodiment, the synthesis of the insulating epoxy resin is illustrated below:

[0021]

[0022] The mass spectrometry analysis results of the insulating epoxy resin are shown below: m / z: 376.26 (100.0%), 377.26 (24.9%), 378.27 (3.9%).

[0023] Preferably, the organic solvent in S11 is any one of dichloromethane, toluene, and acetonitrile, and the mass ratio of 2-butyl-1,3-propanediol, organic solvent, p-toluenesulfonyl chloride, and potassium hydroxide is 1~2:40~50:0.8~1.3:3.5~4.5, and the reaction is carried out at 0~5℃ for 6~8h.

[0024] Preferably, in S12, the mass ratio of sodium hydride, anhydrous NNN dimethylformamide, 5-norbornene-2-methanol and intermediate product 1 is 0.1~0.2:5~15:1~2:5~8, and the reaction is carried out at 60~80℃ for 12~16 hours.

[0025] Preferably, in step S13, the reaction is carried out at 0-25°C with stirring at 300-500 rpm for 18-24 hours, and the mass ratio of intermediate product 2, m-chloroperoxybenzoic acid, dichloromethane and 10wt% sodium bisulfite aqueous solution is 5-7:6-8:40-50:25-35.

[0026] The method for preparing the epoxy resin glass cloth substrate includes the following steps:

[0027] S21. Add insulating epoxy resin, insulating medium filler and ethyl acetate to a mixing tank and stir at high speed. Then add 2-methylimidazolium and methyltetrahydrophthalic anhydride curing agent and continue stirring to obtain insulating slurry.

[0028] S22. The electronic glass fiber cloth is impregnated in the insulating slurry, flattened and heated in a gradient curing process to obtain an epoxy resin glass cloth substrate.

[0029] Preferably, in step S21, the mass ratio of insulating epoxy resin, insulating medium filler, 2-methylimidazole, methyltetrahydrophthalic anhydride curing agent, and ethyl acetate is 80~100:10~20:0.5~2:5~15:100~120. The mixture is stirred at 1500~2500 rpm for 30~60 min, and after adding 2-methylimidazole and the curing agent, it is stirred at 500~1000 rpm for 20~30 min.

[0030] Preferably, in step S22, the temperature is raised to 120-130°C for 1-2 hours and then further raised to 150-160°C for 1-2 hours.

[0031] The method for preparing the insulating dielectric filler includes the following steps:

[0032] S31. Tetrabutyl titanate and acetylacetone are added to ethanol to prepare solution A. Barium acetate is added to deionized water to prepare solution B. Solution A and solution B are mixed at constant temperature, and then subjected to polycondensation reaction by heating. Deionized water is added dropwise for hydrolysis reaction. After aging and drying, dry gel is obtained.

[0033] S32. After grinding the dry gel into powder, it is heated and calcined to obtain insulating ceramic powder. The insulating ceramic powder, kH-560 and deionized water are added to ethanol, heated and reacted, the solid is collected by filtration, washed with deionized water and dried to obtain insulating dielectric filler.

[0034] Preferably, in S31, the volume ratio of solution A to solution B is 1:1, the ratio of tetrabutyl titanate, acetylacetone and ethanol in solution A is (5~6) g: (1.5~2) g: (10~15) mL, and the ratio of barium acetate and deionized water in solution B is (5~6.5) g: (10~15) mL. The mixture is stirred at 40~50℃, heated to 80~90℃ for polycondensation reaction for 2~4 h, and 10~20% of the volume of deionized water of solution A is added dropwise for hydrolysis for 3~4 h. The mixture is then aged for 24~48 h.

[0035] Preferably, in the S32 process, the temperature is raised to 1000~1300℃ and calcined for 2~4h. The ratio of insulating ceramic powder, kH-560, deionized water and ethanol is (10~15)g:(1~2)g:(2~3)mL:(16~17)mL. The temperature is raised to 40~50℃ and reacted for 4~6h. The mixture is then dried at 80~100℃.

[0036] Preferably, the average particle size of the insulating ceramic powder in S32 is 50~200nm.

[0037] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0038] 1. This invention uses p-toluenesulfonyl chloride to sulfonate 2-butyl-1,3-propanediol and then grafts 5-norbornene-2-methanol onto it. The insulating epoxy resin is then prepared by epoxidation with m-chloroperoxybenzoic acid. The introduction of 2-butyl long-chain alkyl groups into the resin improves the resin's toughness and impact resistance, while the introduced norbornene rigid groups improve the resin's heat resistance. This allows the insulating epoxy resin to effectively absorb internal stress and prevent microcracks caused by thermal expansion during the curing process.

[0039] 2. In this invention, tetrabutyl titanate and barium acetate are gelled to prepare a dry gel, which is then ground and calcined to obtain insulating ceramic powder. The insulating ceramic powder is a titanium-barium ceramic, which has high insulation and low dielectric loss properties. Then, epoxy groups are introduced by modifying the surface with kH-560 to improve the dispersibility of the insulating medium filler in the epoxy resin. After the insulating medium filler fills the resin, it forms an inorganic insulating network, which reduces the internal porosity of the resin, so that the obtained epoxy resin glass cloth substrate has excellent insulation properties.

[0040] 3. In the substrate preparation process of this invention, the inner chip layer, epoxy resin glass cloth substrate, and copper foil are first laminated together to obtain a PCB sub-board. Then, blind vias are formed by drilling and copper plating. Finally, the PCB main board is formed by a second lamination. The vias are sealed and cured, screen-printed with markings, inspected, and packaged to obtain a high-insulation blind via PCB board. The second lamination ensures that the sub-boards are fully bonded by insulating epoxy resin, resulting in dense interlayer bonding without delamination. Gradient temperature curing is used to fully cross-link and cure the epoxy resin system, improving the insulation performance of the high-insulation blind via PCB board. The blind vias enable high-density wiring, meeting the needs of miniaturized PCB boards. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The electronic glass fiber cloth involved in this invention has an average thickness of 0.095 mm and a unit area mass of 102 g / m². 2 The solder resist ink model is PS-800.

[0043] Example 1: A high-insulation blind via PCB board with multiple blind vias on its surface. The PCB board has four mounting holes distributed at the four corners of the PCB board. It is made by bonding and pressing two sub-boards together with insulating epoxy resin. The sub-board is made by sequentially arranging and pressing an inner chip layer, an epoxy resin glass cloth substrate, and copper foil together.

[0044] The method for preparing the high-insulation blind via PCB board includes the following steps:

[0045] S1. After cutting the copper-clad laminate, apply photoresist and expose it to transcribe the pattern. Remove excess photoresist and use an etching solution made of 150g / L copper chloride, 100g / L hydrochloric acid, 0.1g / L polyvinylpyrrolidone and 30g / L hydrogen peroxide to etch the circuit onto the surface of the copper-clad laminate to obtain the inner chip layer. Then, laminate the inner chip layer, epoxy resin glass cloth substrate and copper foil together in one step to obtain the PCB board. The lamination temperature is 170℃, the lamination pressure is 1.5MPa and the lamination time is 60min.

[0046] S2. Drill holes at designated locations and immerse the holes in an electroplating solution prepared by mixing 200g / L copper sulfate, 60g / L sulfuric acid, 7mg / L sodium polydisulfide dipropane sulfonate, 0.08g / L polyvinylpyrrolidone and 0.2g / L polyethylene glycol to plating copper, thus creating blind holes with a diameter of 40μm.

[0047] S3. Multiple PCB boards are laminated twice to obtain the main PCB board. The temperature of the second lamination is 180℃, the lamination pressure is 1.5MPa, and the lamination time is 120min. Mounting holes are drilled at the designated positions.

[0048] S4. Apply solder resist ink to the surface of the PCB motherboard and seal the holes. Bake at 80℃ for 50 minutes, then heat to 130℃ for 2 hours and cure for another 2 hours. After curing, grind the board, screen print markings, inspect and package to obtain a high-insulation blind via PCB board.

[0049] The method for preparing the insulating epoxy resin in this embodiment includes the following steps:

[0050] S11. 1.3 g of 2-butyl-1,3-propanediol and 40 g of dichloromethane were added to a reaction vessel. 0.8 g of p-toluenesulfonyl chloride was added dropwise under ice bath conditions. After adding 3.5 g of potassium hydroxide, the mixture was stirred at 0 °C for 6 h. After the reaction was completed, the mixture was washed with deionized water. The organic phase was taken, anhydrous sodium sulfate was added to remove water, the solvent was removed by rotary evaporation after filtration, and the intermediate product 1 was obtained by recrystallization in methanol.

[0051] S12. 0.1 g of sodium hydride was added to 5 g of anhydrous N,N dimethylformamide under a nitrogen atmosphere and stirred to disperse. 1 g of 5-norbornene-2-methanol and 5 g of intermediate product 1 were added dropwise under a nitrogen atmosphere. The mixture was heated to 60 °C and reacted for 12 h. The reaction was quenched with deionized water and allowed to stand to separate the layers. The aqueous phase was extracted with ethyl acetate and separated into layers. The organic phase was removed by adding anhydrous sodium sulfate to remove water. After filtration, the solvent was removed by rotary evaporation to obtain intermediate product 2.

[0052] S13. Add 6g of m-chloroperoxybenzoic acid and 20g of dichloromethane to a reaction vessel. Dissolve 5g of intermediate product 2 in 20g of dichloromethane and then add it dropwise to the reaction vessel. Add 25g of 10wt% sodium bisulfite aqueous solution dropwise under ice bath conditions. Stir the reaction at 500rpm at 10℃ for 24h. Check the reaction end with starch and potassium iodide. Wash with 10wt% sodium bicarbonate aqueous solution and deionized water in sequence. Add anhydrous sodium sulfate to remove water. After filtration, remove the solvent by rotary evaporation to obtain insulating epoxy resin.

[0053] The method for preparing the epoxy resin glass cloth substrate in this embodiment includes the following steps:

[0054] S21. Add 80g of insulating epoxy resin, 20g of insulating medium filler and 100g of ethyl acetate to a mixing tank and stir at 1500rpm for 30min. Then add 0.5g of 2-methylimidazole and 10g of methyltetrahydrophthalic anhydride curing agent and stir at 1000rpm for 20min to obtain insulating slurry.

[0055] S22. The electronic glass fiber cloth is impregnated in the insulating slurry, flattened and heated to 120°C for 1 hour, and then heated to 160°C for 2 hours to obtain the epoxy resin glass cloth substrate.

[0056] The method for preparing the insulating dielectric filler in this embodiment includes the following steps:

[0057] S31. Add 10g of tetrabutyl titanate and 3g of acetylacetone to 20mL of ethanol to prepare solution A. Add 10g of barium acetate to 20mL of deionized water to prepare solution B. Mix 20mL of solution A and 20mL of solution B at a constant temperature of 40℃, raise the temperature to 80℃ for polycondensation reaction for 4h, add 2mL of deionized water dropwise for hydrolysis for 3h, age for 48h, and dry to obtain dry gel.

[0058] S32. After grinding the dry gel into powder, it is heated to 1150℃ and calcined for 4 hours to obtain insulating ceramic powder with an average particle size of 200nm. 10g of insulating ceramic powder, 2g of KH-560 and 2mL of deionized water are added to 16mL of ethanol, heated to 40℃ and reacted for 6 hours. The solid is collected by filtration, washed with deionized water, and dried at 80℃ to obtain insulating medium filler.

[0059] Example 2: A high-insulation blind via PCB board with multiple blind vias on its surface. The PCB board has four mounting holes distributed at the four corners of the PCB board. It is made by bonding and pressing two sub-boards together with insulating epoxy resin. The sub-board is made by sequentially arranging and pressing an inner chip layer, an epoxy resin glass cloth substrate, and copper foil together.

[0060] The method for preparing the high-insulation blind via PCB board includes the following steps:

[0061] S1. After cutting the copper-clad laminate, apply photoresist and expose it to transcribe the pattern. Remove excess photoresist and use an etching solution made of 160g / L copper chloride, 80g / L hydrochloric acid, 0.5g / L polyvinylpyrrolidone and 15g / L hydrogen peroxide to etch the circuit onto the surface of the copper-clad laminate to obtain the inner chip layer. The inner chip layer, epoxy resin glass cloth substrate and copper foil are laminated together in one step to obtain the PCB board. The lamination temperature is 190℃, the lamination pressure is 1MPa and the lamination time is 60min.

[0062] S2. Drill holes at designated locations and immerse the holes in an electroplating solution prepared by mixing 220 g / L copper sulfate, 80 g / L sulfuric acid, 1 mg / L sodium polydisulfide dipropane sulfonate, 0.05 g / L polyvinylpyrrolidone and 0.5 g / L polyethylene glycol to plating copper, thus creating blind holes with a diameter of 50 μm.

[0063] S3. Multiple PCB boards are laminated twice to obtain the main PCB board. The temperature of the second lamination is 190℃, the lamination pressure is 1MPa, and the lamination time is 60min. Mounting holes are drilled at the designated positions.

[0064] S4. Apply solder resist ink to the surface of the PCB motherboard and seal the holes. Bake at 70℃ for 30 minutes, then heat to 130℃ for 1 hour, and then heat to 150℃ for 2 hours. After curing, grind the board, screen print markings, and inspect and package to obtain a high-insulation blind via PCB board.

[0065] The method for preparing the insulating epoxy resin in this embodiment includes the following steps:

[0066] S11. 1.5 g of 2-butyl-1,3-propanediol and 45 g of toluene were added to a reaction vessel. 1 g of p-toluenesulfonyl chloride was added dropwise under ice bath conditions. 4 g of potassium hydroxide was added and the mixture was stirred at 5 °C for 6 h. After the reaction was completed, the mixture was washed with deionized water. The organic phase was taken, anhydrous sodium sulfate was added to remove water, the solvent was removed by rotary evaporation after filtration, and the intermediate product 1 was obtained by recrystallization in methanol.

[0067] S12. 0.15 g of sodium hydride was added to 10 g of anhydrous N,N dimethylformamide under a nitrogen atmosphere and stirred to disperse. 1.5 g of 5-norbornene-2-methanol and 6 g of intermediate product 1 were added dropwise under a nitrogen atmosphere. The mixture was heated to 80 °C and reacted for 12 h. The reaction was quenched with deionized water and allowed to stand to separate the layers. The aqueous phase was extracted with ethyl acetate and separated into layers. The organic phase was removed by adding anhydrous sodium sulfate to remove water. After filtration, the solvent was removed by rotary evaporation to obtain intermediate product 2.

[0068] S13. Add 7g of m-chloroperoxybenzoic acid and 25g of dichloromethane to a reaction vessel. Dissolve 6g of intermediate product 2 in 25g of dichloromethane and then add it dropwise to the reaction vessel. Add 30g of 10wt% sodium bisulfite aqueous solution dropwise under ice bath conditions. Stir the reaction at 300rpm at 0℃ for 24h. Check whether the reaction is complete with starch and potassium iodide. Wash with 10wt% sodium bicarbonate aqueous solution and deionized water in sequence. Add anhydrous sodium sulfate to remove water. After filtration, remove the solvent by rotary evaporation to obtain insulating epoxy resin.

[0069] The method for preparing the epoxy resin glass cloth substrate in this embodiment includes the following steps:

[0070] S21. Add 100g of insulating epoxy resin, 10g of insulating medium filler and 110g of ethyl acetate to a mixing tank and stir at 2500rpm for 60min. Then add 1g of 2-methylimidazole and 15g of methyltetrahydrophthalic anhydride curing agent and stir at 1000rpm for 30min to obtain insulating slurry.

[0071] S22. The electronic glass fiber cloth is impregnated in the insulating slurry, flattened and heated to 125°C for 2 hours, and then heated to 155°C for 2 hours to obtain the epoxy resin glass cloth substrate.

[0072] The method for preparing the insulating dielectric filler in this embodiment includes the following steps:

[0073] S31. Add 11g of tetrabutyl titanate and 4g of acetylacetone to 30mL of ethanol to prepare solution A. Add 13g of barium acetate to 30mL of deionized water to prepare solution B. Mix 30mL of solution A and 30mL of solution B at a constant temperature of 50℃, heat to 90℃ for polycondensation reaction for 3h, add 3mL of deionized water dropwise for hydrolysis for 4h, age for 36h, and dry to obtain dry gel.

[0074] S32. After grinding the dry gel into powder, it is heated to 1250℃ and calcined for 2 hours to obtain insulating ceramic powder with an average particle size of 150nm. 13g of insulating ceramic powder, 1.5g of KH-560 and 3mL of deionized water are added to 17mL of ethanol, heated to 50℃ and reacted for 4 hours. The solid is collected by filtration, washed with deionized water, and dried at 100℃ to obtain insulating medium filler.

[0075] Example 3: A high-insulation blind via PCB board with multiple blind vias on its surface. The PCB board has four mounting holes distributed at the four corners of the PCB board. It is made by bonding and pressing two sub-boards together with insulating epoxy resin. The sub-board is made by sequentially arranging and pressing an inner chip layer, an epoxy resin glass cloth substrate, and copper foil together.

[0076] The method for preparing the high-insulation blind via PCB board includes the following steps:

[0077] S1. After cutting the copper-clad laminate, apply photoresist and expose it to transcribe the pattern. Remove excess photoresist and use an etching solution made of 180 g / L copper chloride, 120 g / L hydrochloric acid, 0.5 g / L polyvinylpyrrolidone and 30 g / L hydrogen peroxide to etch the circuit onto the surface of the copper-clad laminate to obtain the inner chip layer. The inner chip layer, epoxy resin glass cloth substrate and copper foil are laminated together in one step to obtain the PCB board. The lamination temperature is 180℃, the lamination pressure is 1.3 MPa and the lamination time is 80 min.

[0078] S2. Drill holes at designated locations and immerse the holes in an electroplating solution prepared by mixing 225 g / L copper sulfate, 75 g / L sulfuric acid, 1 mg / L sodium polydisulfide dipropane sulfonate, 0.05 g / L polyvinylpyrrolidone and 0.1 g / L polyethylene glycol to plating copper, thus creating blind holes with a diameter of 35 μm.

[0079] S3. Multiple PCB boards are laminated twice to obtain the main PCB board. The temperature of the second lamination is 180℃, the lamination pressure is 1.3MPa, and the lamination time is 90min. Mounting holes are drilled at the designated positions.

[0080] S4. Apply solder resist ink to the surface of the PCB motherboard and seal the holes. Bake at 80℃ for 50 minutes, then at 130℃ for 1 hour, and then at 160℃ for 1 hour. After curing, grind the board, screen print markings, inspect and package to obtain a high-insulation blind via PCB board.

[0081] The method for preparing the insulating epoxy resin in this embodiment includes the following steps:

[0082] S11. Add 2g of 2-butyl-1,3-propanediol and 50g of acetonitrile to a reaction vessel, add 1.3g of p-toluenesulfonyl chloride dropwise under ice bath conditions, add 4.5g of potassium hydroxide, stir and react at 0℃ for 7h. After the reaction is completed, wash with deionized water, take the organic phase, add anhydrous sodium sulfate to remove water, filter and remove solvent by rotary evaporation, recrystallize in methanol to obtain intermediate product 1.

[0083] S12. 0.2 g of sodium hydride was added to 15 g of anhydrous N,N dimethylformamide under a nitrogen atmosphere and stirred to disperse. 2 g of 5-norbornene-2-methanol and 8 g of intermediate product 1 were added dropwise under a nitrogen atmosphere. The mixture was heated to 80 °C and reacted for 12 h. The reaction was quenched with deionized water and allowed to stand to separate the layers. The aqueous phase was extracted with ethyl acetate and separated into layers. The organic phase was removed by adding anhydrous sodium sulfate to remove water. After filtration, the solvent was removed by rotary evaporation to obtain intermediate product 2.

[0084] S13. Add 8g of m-chloroperoxybenzoic acid and 25g of dichloromethane to a reaction vessel. Dissolve 7g of intermediate product 2 in 25g of dichloromethane and then add it dropwise to the reaction vessel. Add 35g of 10wt% sodium bisulfite aqueous solution dropwise under ice bath conditions. Stir the reaction at 500rpm at 10℃ for 18h. Check the reaction end with starch and potassium iodide. Wash with 10wt% sodium bicarbonate aqueous solution and deionized water in sequence. Add anhydrous sodium sulfate to remove water. After filtration, remove the solvent by rotary evaporation to obtain insulating epoxy resin.

[0085] The method for preparing the epoxy resin glass cloth substrate in this embodiment includes the following steps:

[0086] S21. Add 90g of insulating epoxy resin, 10g of insulating medium filler and 100g of ethyl acetate to a mixing tank and stir at 2000rpm for 50min. Then add 2g of 2-methylimidazole and 10g of methyltetrahydrophthalic anhydride curing agent and stir at 500rpm for 25min to obtain insulating slurry.

[0087] S22. The electronic glass fiber cloth is impregnated in the insulating slurry, flattened and heated to 130°C for 2 hours, and then heated to 150°C for 2 hours to obtain the epoxy resin glass cloth substrate.

[0088] The method for preparing the insulating dielectric filler in this embodiment includes the following steps:

[0089] S31. Add 12g of tetrabutyl titanate and 4g of acetylacetone to 30mL of ethanol to prepare solution A. Add 13g of barium acetate to 30mL of deionized water to prepare solution B. Mix 30mL of solution A and 30mL of solution B at a constant temperature of 50℃, heat to 90℃ for polycondensation reaction for 4h, add 3mL of deionized water dropwise for hydrolysis for 4h, age for 24h, and dry to obtain dry gel.

[0090] S32. After grinding the dry gel into powder, it is heated to 1300℃ and calcined for 4 hours to obtain insulating ceramic powder with an average particle size of 50~200nm. 15g of insulating ceramic powder, 1g of kH-560 and 3mL of deionized water are added to 17mL of ethanol, heated to 40℃ and reacted for 6 hours. The solid is collected by filtration, washed with deionized water and dried at 100℃ to obtain insulating medium filler.

[0091] Comparative Example 1 differs from Example 1 in that the insulating epoxy resin is replaced with an alicyclic epoxy resin of model ERL-4221.

[0092] Comparative Example 2 differs from Example 1 in that the insulating dielectric filler is replaced with alumina with an average particle size of 50 nm.

[0093] Comparative Example 3 differs from Example 1 in that it does not contain insulating medium filler.

[0094] Performance testing

[0095] Insulation performance: According to GB / T 4677-2002 "Test Methods for Printed Circuit Boards", the PCBs prepared in each embodiment and comparative example were subjected to an AC voltage of 1000V for 60s, and the PCBs were tested to see if they were broken down.

[0096] Heat resistance: The PCBs prepared in each embodiment and comparative example were immersed in tin at 288°C for 10 seconds, and the PCBs were tested for delamination and bubbling.

[0097] The test results are shown in Table 1 below:

[0098] Table 1 Test Results

[0099]

[0100] As shown in Table 1 above, the PCBs prepared in Examples 1-3 were not broken down after being held at 1000V AC voltage for 60s, indicating that the PCBs prepared by the present invention have good insulation properties and can work normally under high voltage. The insulating dielectric filler and the insulating epoxy resin matrix are firmly bonded at the interface, avoiding breakdown caused by the formation of conductive paths due to poor interface compatibility. This further demonstrates that the PCBs prepared by the present invention have excellent high insulation performance. The PCBs prepared in Examples 1-3 were not delaminated or blistered after being immersed in tin at 288℃ for 10s, indicating that the insulating epoxy resin and insulating dielectric filler prepared by the present invention can reduce the thermal stress expansion mismatch between the epoxy resin glass cloth substrate and the copper foil. This further demonstrates that the PCBs prepared by the present invention have excellent heat resistance.

[0101] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0102] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high-insulation blind via PCB board, characterized in that, Includes the following steps: S1. After cutting the copper-clad laminate, apply photoresist and expose it to transcribe the pattern. Remove excess photoresist and etch the circuit to the surface of the copper-clad laminate to obtain the inner chip layer. Then, press the inner chip layer, epoxy resin glass cloth substrate and copper foil together in one step to obtain the PCB board. S2. Drill holes at designated locations, immerse the holes in electroplating solution to plate copper, and obtain blind holes; S3. Multiple PCB boards are bonded together with insulating epoxy resin to form a PCB main board, and mounting holes are drilled in the designated positions. S4. Apply solder resist ink to the surface of the PCB motherboard and seal the holes. Heat and bake to cure. After curing, grind the board, screen print markings, inspect and package to obtain a high-insulation blind via PCB board. The method for preparing the insulating epoxy resin includes the following steps: S11. Add 2-butyl-1,3-propanediol and organic solvent to a reaction vessel, add p-toluenesulfonyl chloride dropwise under ice bath conditions, add potassium hydroxide and stir the reaction. After the reaction is completed, wash with deionized water, take the organic phase, add anhydrous sodium sulfate to remove water, filter and remove solvent by rotary evaporation, and recrystallize in methanol to obtain intermediate product 1. S12. Sodium hydride was added to anhydrous N,N dimethylformamide under a nitrogen atmosphere and stirred to disperse. 5-norbornene-2-methanol and intermediate product 1 were added dropwise under a nitrogen atmosphere. The reaction was heated and the reaction was quenched with deionized water. The mixture was allowed to stand and separate into layers. The aqueous phase was extracted with ethyl acetate and separated into layers. The organic phase was removed by adding anhydrous sodium sulfate to remove water. After filtration, the solvent was removed by rotary evaporation to obtain intermediate product 2. S13. Add m-chloroperoxybenzoic acid and dichloromethane to a reaction vessel. Dissolve intermediate product 2 in dichloromethane and then add it dropwise to the reaction vessel. Add 10wt% sodium bisulfite aqueous solution dropwise under ice bath conditions, stir the reaction, and use starch potassium iodide to detect whether the reaction is complete. Wash with 10wt% sodium bicarbonate aqueous solution and deionized water in sequence. Add anhydrous sodium sulfate to remove water. After filtration, remove the solvent by rotary evaporation to obtain insulating epoxy resin.

2. The method for preparing a high-insulation blind via PCB board according to claim 1, characterized in that, The organic solvent in S11 is any one of dichloromethane, toluene, and acetonitrile. The mass ratio of 2-butyl-1,3-propanediol, organic solvent, p-toluenesulfonyl chloride, and potassium hydroxide is 1~2:40~50:0.8~1.3:3.5~4.5, and the reaction is carried out at 0~5℃ for 6~8h.

3. The method for preparing a high-insulation blind via PCB board according to claim 1, characterized in that, In S12, the mass ratio of sodium hydride, anhydrous N,N dimethylformamide, 5-norbornene-2-methanol, and intermediate product 1 is 0.1~0.2:5~15:1~2:5~8, and the reaction is carried out at 60~80℃ for 12~16h. In S13, the reaction is carried out at 0~25℃ with stirring at 300~500rpm for 18~24h, and the mass ratio of intermediate product 2, m-chloroperoxybenzoic acid, dichloromethane, and 10wt% sodium bisulfite aqueous solution is 5~7:6~8:40~50:25~35.

4. The method for preparing a high-insulation blind via PCB board according to claim 1, characterized in that, The method for preparing the epoxy resin glass cloth substrate includes the following steps: S21. Add insulating epoxy resin, insulating medium filler and ethyl acetate to a mixing tank and stir at high speed. Then add 2-methylimidazolium and methyltetrahydrophthalic anhydride curing agent and continue stirring to obtain insulating slurry. S22. The electronic glass fiber cloth is impregnated in the insulating slurry, flattened and heated in a gradient curing process to obtain an epoxy resin glass cloth substrate.

5. The method for preparing a high-insulation blind via PCB board according to claim 4, characterized in that, In step S21, the mass ratio of insulating epoxy resin, insulating medium filler, 2-methylimidazole, methyltetrahydrophthalic anhydride curing agent, and ethyl acetate is 80~100:10~20:0.5~2:5~15:100~120. The mixture is stirred at 1500~2500 rpm for 30~60 min. After adding 2-methylimidazole and the curing agent, the mixture is stirred at 500~1000 rpm for 20~30 min. In step S22, the mixture is heated to 120~130℃ and cured for 1~2 h, then heated to 150~160℃ and cured for another 1~2 h.

6. The method for preparing a high-insulation blind via PCB board according to claim 4, characterized in that, The method for preparing the insulating dielectric filler includes the following steps: S31. Tetrabutyl titanate and acetylacetone are added to ethanol to prepare solution A. Barium acetate is added to deionized water to prepare solution B. Solution A and solution B are mixed at constant temperature, and then subjected to polycondensation reaction by heating. Deionized water is added dropwise for hydrolysis reaction. After aging and drying, dry gel is obtained. S32. After grinding the dry gel into powder, it is heated and calcined to obtain insulating ceramic powder. The insulating ceramic powder, kH-560 and deionized water are added to ethanol, heated and reacted, the solid is collected by filtration, washed with deionized water and dried to obtain insulating dielectric filler.

7. The method for preparing a high-insulation blind via PCB board according to claim 6, characterized in that, In S31, the volume ratio of solution A to solution B is 1:

1. The ratio of tetrabutyl titanate, acetylacetone, and ethanol in solution A is (5~6) g: (1.5~2) g: (10~15) mL. The ratio of barium acetate to deionized water in solution B is (5~6.5) g: (10~15) mL. The solutions are mixed at 40~50℃, heated to 80~90℃ for condensation reaction for 2~4 hours, and then solution A is added dropwise. Hydrolyze with 10-20% by volume of deionized water for 3-4 hours, and age for 24-48 hours; calcine in S32 at 1000-1300℃ for 2-4 hours, with the ratio of insulating ceramic powder, kH-560, deionized water and ethanol being (10-15) g: (1-2) g: (2-3) mL: (16-17) mL, react at 40-50℃ for 4-6 hours, and dry at 80-100℃.

8. The method for preparing a high-insulation blind via PCB board according to claim 1, characterized in that, In step S1, etching is performed using an etching solution prepared from 150-180 g / L copper chloride, 80-120 g / L hydrochloric acid, 0.1-0.5 g / L polyvinylpyrrolidone, and 10-30 g / L hydrogen peroxide. The temperature for one pressing is 170-190°C, the pressing pressure is 1-1.5 MPa, and the pressing time is 60-90 min. In step S2, the diameter of the blind via is 30-50 μm, and it is prepared from 200-250 g / L copper sulfate, 60-80 g / L sulfuric acid, and 1-10 g / L hydrogen peroxide. An electroplating solution is prepared by mixing 0.05-0.1 g / L sodium dithiodipropanesulfonate, 0.1-0.5 g / L polyvinylpyrrolidone, and 0.1-0.5 g / L polyethylene glycol. In step S3, the temperature for the second pressing is 170-190℃, the pressing pressure is 1-1.5 MPa, and the pressing time is 60-120 min. In step S4, the temperature is raised to 70-80℃ for baking for 30-50 min, then raised to 120-130℃ for curing for 1-2 h, and then raised to 150-160℃ for curing for 1-2 h.

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