Preparation process of circuit board with ultralow dielectric constant

Abstract

The invention discloses a preparation process of a circuit board with an ultralow dielectric constant, and relates to the technical field of circuit boards, and the preparation process comprises the following steps: S1, manufacturing an inner-layer high-frequency signal circuit: forming the high-frequency signal circuit on a substrate through dry film pasting, exposure, development and etching processes; s2, manufacturing an anti-welding baffle bridge: forming the anti-welding baffle bridge around the high-frequency signal circuit through screen printing, exposure and development processes; s3, processing a vacuum cavity area of the prepreg: removing the prepreg on the upper layer of the high-frequency circuit in a mechanical board milling manner to form a prepreg pit slot; s4, laminating and forming: laminating all layers together in a brownification, board arrangement and board pressing mode to form an outer-layer semi-finished circuit board comprising a vacuum cavity; and S5, processing a non-plated through hole: mechanically drilling at a non-signal line position of the vacuum cavity area to form the non-plated through hole, and obtaining the circuit board with the ultralow dielectric constant.

Description

Technical Field

[0001] The invention relates to the technical field of circuit boards, and in particular to a preparation process of an ultra-low dielectric constant circuit board. Background Art

[0002] As modern electronic devices develop rapidly towards high speed and high frequency, the performance requirements for circuit board materials are becoming increasingly stringent. Among them, the dielectric constant, as a core parameter affecting signal transmission rate and loss, has become a key factor restricting circuit performance in high-frequency application scenarios. Traditional circuit board materials often have high dielectric constants, resulting in significant signal delays and increased energy loss, making it difficult to meet high-precision and high-efficiency transmission requirements.

[0003] In the prior art, the main strategies for reducing the dielectric constant include introducing low dielectric additives or designing porous structures to reduce material density. However, these methods are often accompanied by significant performance compromises: for example, low dielectric additives may weaken the mechanical strength of the material, while porous structures can easily lead to insufficient interlayer bonding, increasing the risk of delamination of the circuit board. In addition, a single material system is usually difficult to balance the needs of rigid support and flexible buffering, resulting in a decrease in overall reliability. At the same time, the choice of solder mask material has a significant impact on circuit performance. The polar groups in traditional solder mask materials are prone to produce additional dielectric losses in high-frequency environments, further exacerbating signal degradation.

[0004] Therefore, the current technical field urgently needs an innovative preparation process that can effectively reduce the dielectric constant of the circuit board without sacrificing mechanical strength and thermal stability. The ideal solution needs to solve the performance contradiction pain points in the existing technology through material synergy optimization and structural design innovation, so as to provide more reliable hardware support for high-frequency electronic devices. Summary of the invention

[0005] The purpose of the present invention is to provide a process for preparing an ultra-low dielectric constant circuit board to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A process for preparing an ultra-low dielectric constant circuit board comprises the following steps: S1: making an inner layer high-frequency signal circuit: forming a high-frequency signal circuit 1 on an inner layer substrate by dry film lamination, exposure, development, and etching processes; S2: Making solder mask bridges: forming solder mask bridges 2 around high-frequency signal line 1 by screen printing, exposure, and development processes; S3: Processing the prepreg vacuum cavity area: Cover the prepreg on the same layer of the solder mask bridge 2, remove the prepreg on the upper layer of the high-frequency circuit by mechanical gong plate, and form prepreg pits 3 on both sides of the solder mask bridge 2; S4: Pressing and forming: Pressing the inner substrate and the outer substrate together by browning, arranging and pressing to form an outer semi-finished circuit board including the vacuum cavity 4; S5: Processing non-plated through holes: Mechanically drilling non-plated through holes 5 at non-signal line positions in the vacuum cavity 4 area to obtain an ultra-low dielectric constant circuit board.

[0007] Furthermore, in step S1, the line width tolerance of the high-frequency signal line 1 is ±10 μm.

[0008] Furthermore, in step S2, the median thickness of the solder mask bridge 2 is equal to the thickness of the upper prepreg of the high-frequency signal line 1, the width of the solder mask bridge 2 is 0.1-0.4 mm, and the solder mask bridge 2 is prepared from solder resist ink.

[0009] Furthermore, in step S3, the distance between the prepreg groove 3 and the high-frequency signal line 1 is 0.5-3 mm, the single-side width of the prepreg groove 3 exceeds the width of the solder mask bridge 2 by 0.1 mm, and the thickness of the prepreg is 1.5-2.5 mil.

[0010] Furthermore, in step S4, the platen parameters are temperature of 180-200° C., pressure of 300-400 psi, and time of 90-120 min.

[0011] Furthermore, in step S5, the diameter of the non-plated through hole 5 is 0.25-1 mm, and the number of the non-plated through holes 5 provided in each vacuum chamber 4 is ≥2.

[0012] Furthermore, the preparation method of the solder resist ink comprises the following steps: Step 1: Add 1,5-naphthalenediol and ethyl 4-bromobutyrate to acetone, stir evenly, add potassium carbonate, heat to 70-75°C and reflux for reaction for 3-4 days, extract the reaction product with ether and hydrochloric acid, wash with deionized water, dry with anhydrous sodium sulfate, filter, collect the organic layer, evaporate and dry to obtain compound 1; add compound 1 to tetrahydrofuran, add 0.5 mol / L sodium hydroxide aqueous solution, react at room temperature for 12-13 hours, add 1 mol / L hydrochloric acid aqueous solution, react for 3-4 days, filter, and dry to obtain compound 2; add compound 2, glycidol, and 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride to tetrahydrofuran, add 4-dimethylaminopyridine, react at room temperature for 24-25 hours, rotary evaporate, wash, centrifuge, and dry to obtain a naphthyl epoxy monomer; Furthermore, in the preparation process of the compound 1, the molar ratio of 1,5-naphthalenediol: ethyl 4-bromobutyrate: potassium carbonate is 9.3:23.1:54; in the preparation process of the naphthyl epoxy monomer, the molar ratio of compound 2: glycidol: 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride: 4-dimethylaminopyridine is 10:30:30:3.

[0013] Step 2: Add the naphthyl epoxy monomer to ethyl 2-2-ethoxyethoxyacetate, heat to 85-86°C, stir evenly, cool to room temperature, add cholic acid and 4-dimethylaminopyridine, heat to 115-120°C for reaction for 12-13h, cool to room temperature, add 1,2,3,6-tetrahydrophthalic anhydride and hydroquinone, heat to 95-98°C for reaction for 7-8h, add glycidyl methacrylate, heat to 110-115°C for reaction for 3-4h, and obtain a naphthyl photocurable resin; Furthermore, in the preparation process of the naphthyl photocurable resin, the mass ratio of naphthyl epoxy monomer: cholic acid: 4-dimethylaminopyridine: 1,2,3,6-tetrahydrophthalic anhydride: hydroquinone: glycidyl methacrylate is 3:5.7:0.052:8.4:0.052:4.2.

[0014] Step 3: adding isophorone diisocyanate to a reaction vessel, adding p-hydroxyanisole, dibutyl tin dilaurate, and hydroxyethyl acrylate, heating to 30-32°C for reaction, and when the isocyanate group content in the reaction system reaches the theoretical value, a double-bond terminated polyurethane precursor is obtained; further heating to 50-52°C, adding isophorone diisocyanate, p-hydroxyanisole, and dibutyl tin dilaurate, stirring evenly, adding polyethylene glycol 100 and 2,2-dihydroxymethylacrylate, keeping warm for reaction, and when the isocyanate group content in the reaction system reaches the theoretical value, a double-bond terminated oligomeric polyurethane is obtained; adding a light-curable epoxy resin containing a dihydroxy group carboxylic acid to a reaction vessel, adding p-hydroxybenzyl ether, dibutyl tin dilaurate, and a double-bond terminated oligomeric polyurethane, heating to 50-52°C, when the isocyanate group content in the reaction system is 0%, adding the product to a methanol aqueous solution for purification, and vacuum drying to obtain a polyurethane-modified light-curable epoxy resin; Furthermore, in the preparation process of the double-bond terminated polyurethane precursor, the mass ratio of isophorone diisocyanate: p-hydroxyanisole: dibutyl tin laurate: hydroxyethyl acrylate is 117:0.17:0.52:59; in the preparation process of the double-bond terminated oligomeric polyurethane, the mass ratio of isophorone diisocyanate: p-hydroxyanisole: dibutyl tin laurate: polyethylene glycol 100, 2,2-dihydroxymethyl methacrylate is 229:0.4:1.2:100:69 ; In the preparation process of polyurethane modified light-curing epoxy resin, the mass ratio of light-curing epoxy resin containing dihydroxy carboxylic acid: hydroxybenzyl ether: dibutyl tin dilaurate: double-bond terminated oligomeric polyurethane is 500:0.99:2.97:50; the light-curing epoxy resin containing dihydroxy carboxylic acid is first prepared by a ring-opening reaction of epoxy resin with acrylic acid and 2,2-dihydroxymethylacrylic acid, and then an esterification reaction with 1,2,3,6-tetrahydrophthalic anhydride.

[0015] Step 4: Add naphthyl photocurable resin and polyurethane modified photocurable epoxy resin to diethylene glycol ethyl ether acetate, add epoxy functionalized silica, thermosetting agent, barium sulfate, ball mill for 30-45 minutes, add phthalocyanine green, active diluent, composite photoinitiator, stir at room temperature for 3-4 hours to obtain solder mask ink.

[0016] Furthermore, in the preparation process of the solder resist ink, the components, by mass, include 2-4 parts of naphthyl photocurable resin, 1-3 parts of polyurethane modified photocurable epoxy resin, 5-7 parts of diethylene glycol ethyl ether acetate, 0.25-0.3 parts of epoxy functionalized silica, 0.25-3 parts of thermosetting agent, 0.75-1 parts of barium sulfate, 0.1-0.15 parts of phthalocyanine green, 0.15-0.2 parts of active diluent, and 0.15-0.2 parts of composite photoinitiator.

[0017] Furthermore, the thermal curing agent is thermosetting epoxy resin NC3000; Furthermore, the active diluent is pentaerythritol triacrylate; Furthermore, the composite photoinitiator is a mixture of 907 and ITX in a mass ratio of 3:2; Furthermore, in the preparation process of the double-bond terminated polyurethane precursor, the theoretical -NCO content is 11.73%, and in the preparation process of the double-bond terminated oligomeric polyurethane, the theoretical -NCO content is 2.36%; Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention achieves ultra-low dielectric constant, high thermal stability and high reliability through the rigid structure of naphthalene-based resin, flexible modification of polyurethane, low dielectric design of vacuum cavity and optimized process parameters, providing an ideal solution for high-frequency circuit boards.

[0018] 2. The rigid naphthalene ring structure of the naphthalene-based photocurable resin in the solder mask ink of the present invention forms an ordered molecular arrangement through π-π stacking, thereby reducing the free vibration of the polar groups hydroxyl and carboxyl. The polyurethane-modified photocurable epoxy resin introduces a flexible chain segment polyethylene glycol to reduce the polar density of the molecular chain. The synergistic vacuum cavity structure reduces the volume share of the dielectric material and uses the air dielectric constant ≈1 to replace the traditional semi-cured sheet, thereby significantly reducing the overall dielectric constant and giving the circuit board an ultra-low dielectric constant performance.

[0019] 3. The present invention utilizes the rigid structure of the naphthalene-based photocurable resin to inhibit the movement of molecular chains at high temperatures and cooperates with the polyurethane-modified photocurable epoxy resin to form a stable three-dimensional cross-linked structure through chemical grafting, thereby greatly improving the thermal stability of the solder resist ink.

[0020] 4. The present invention utilizes the flexibility of the polyurethane chain segment to enhance the interfacial bonding force between the resin and the substrate through hydrogen bonding and physical entanglement, and forms a "rigid and flexible" composite structure through the synergistic effect of the naphthyl resin and the polyurethane, balancing the tensile strength and toughness, and giving the solder mask ink excellent adhesion and mechanical properties; combined with the non-plated through-hole design, the interlayer bonding strength is improved through the mechanical locking effect, reducing the risk of delamination. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a preparation process of an ultra-low dielectric constant circuit board of the present invention; 1: High-frequency signal line; 2: Solder mask bridge; 3: Prepreg pit; 4: Vacuum cavity; 5: Non-plated through hole. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the following examples, the raw materials are all commercially available.

[0024] The preparation method of a naphthyl epoxy monomer comprises the following steps: adding 9.3 mmol 1,5-naphthalene diol and 23.1 mmol 4-bromobutyric acid ethyl ester to acetone, stirring evenly, adding 1.54 mmol potassium carbonate, heating to 70°C for reflux reaction for 3 days, extracting the reaction product with ether and hydrochloric acid, washing with deionized water, drying with anhydrous sodium sulfate, filtering, collecting the organic layer, evaporating and drying to obtain compound 1; adding 10 mmol compound 1 to tetrahydrofuran, adding 0.5 mol / L sodium hydroxide aqueous solution, reacting at room temperature for 12-13 hours, adding 1 mol / L hydrochloric acid aqueous solution, reacting for 3-4 days, filtering, drying, and obtaining compound 2; adding 10 mmol compound 2, 30 mmol glycidol, and 30 mmol 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride to tetrahydrofuran, adding 3 mmol 4-dimethylaminopyridine, reacting at room temperature for 24-25 hours, rotary evaporation, washing, centrifugation, and drying to obtain a naphthyl epoxy monomer; The preparation method of a naphthyl photocurable resin comprises the following steps: adding 3 g of a naphthyl epoxy monomer to ethyl 2-2-ethoxyethoxyacetate, heating to 85° C., stirring evenly, cooling to room temperature, adding 5.7 g of cholic acid and 0.052 g of 4-dimethylaminopyridine, heating to 115° C. for reaction for 12 h, cooling to room temperature, adding 8.4 g of 1,2,3,6-tetrahydrophthalic anhydride and 0.052 g of hydroquinone, heating to 95° C. for reaction for 7 h, adding 4.2 g of glycidyl methacrylate, heating to 110° C. for reaction for 3 h, and obtaining a naphthyl photocurable resin; The preparation method of polyurethane modified light-curing epoxy resin comprises the following steps: adding 117g of isophorone diisocyanate into a reaction container, adding 0.17g of p-hydroxyanisole, 0.52g of dibutyl tin dilaurate, and 59g of hydroxyethyl acrylate, heating to 30°C for reaction, and obtaining a double-bond terminated polyurethane precursor when the isocyanate group content in the reaction system reaches a theoretical value; further heating to 50°C, adding 229g of isophorone diisocyanate, 0.4g of p-hydroxyanisole, and 1.2g of dibutyl tin dilaurate, stirring evenly, and adding 100g of polyethylene. 100 g of diol and 69 g of 2,2-dihydroxymethylacrylate were reacted at a heat preservation condition. When the isocyanate group content in the reaction system reached the theoretical value, a double-bond terminated oligomeric polyurethane was obtained. 500 g of a photocurable epoxy resin containing a dihydroxy carboxylic acid was added to a reaction vessel. 0.99 g of p-hydroxybenzyl ether, 2.97 g of dibutyl tin dilaurate and 50 g of a double-bond terminated oligomeric polyurethane were added. The reaction was heated to 50° C. When the isocyanate group content in the reaction system was 0%, the product was added to a methanol aqueous solution for purification and vacuum dried to obtain a polyurethane-modified photocurable epoxy resin.

[0025] The preparation method of the photocurable epoxy resin containing dihydroxy carboxylic acid comprises the following steps: Under nitrogen protection, 50.0g of diethylene glycol ethyl ether acetate was added to a 1L three-necked flask equipped with a stirrer, the temperature was raised to 90°C, 88.8g of epoxy resin NPCN-704 was added, and the temperature was kept constant for one hour to fully dissolve it, the temperature was lowered to 60°C, 19.1g of acrylic acid and 38.2g of 2,2-dihydroxymethylacrylic acid dissolved in 40g of diethylene glycol ethyl ether acetate were added, the temperature was raised to 70°C, and 1.5g of 4-dimethylaminopyridine dissolved in 2g of diethylene glycol ethyl ether acetate was added, the reaction was stirred at a constant temperature of 95°C for 1 hour, and then the temperature was raised to 105°C and the reaction was stirred at a constant temperature for 12 hours. Then the reaction system was cooled to 80°C, 94.0 g of 1,2,3,6-tetrahydrophthalic anhydride and 0.5 g of hydroquinone dissolved in 30 g of diethylene glycol ethyl ether acetate were added, and the temperature was raised to 90°C and stirred for reaction for 3 hours to obtain a photocurable epoxy resin containing a dihydroxy group carboxylic acid.

[0026] Embodiment 1: A process for preparing an ultra-low dielectric constant circuit board, comprising the following steps: A method for preparing a solder resist ink, comprising the following steps: adding 2 parts of a naphthyl photocurable resin and 3 parts of a polyurethane-modified photocurable epoxy resin to 5 parts of diethylene glycol ethyl ether acetate, adding 0.25 parts of epoxy-functionalized silica, 0.25 parts of a thermosetting agent, and 0.75 parts of barium sulfate, ball milling for 30 minutes, adding 0.1 parts of phthalocyanine green, 0.15 parts of an active diluent, and 0.15 parts of a composite photoinitiator, and stirring at room temperature for 3 hours to obtain a solder resist ink; S1: Making an inner layer high frequency signal line: forming a high frequency signal line 1 on the inner layer substrate by dry film lamination, exposure, development, and etching processes; S2: Making solder mask bridge: forming solder mask bridge 2 around high-frequency signal line 1 by screen printing, exposure and development of solder mask ink; the width of solder mask bridge is 0.2 mm; S3: Processing the prepreg vacuum cavity area: Cover the prepreg on the same layer of the solder mask bridge 2, remove the prepreg on the high-frequency circuit by mechanical gong, and form prepreg pits 3 on both sides of the solder mask bridge 2; the distance between the prepreg pit 3 and the high-frequency signal circuit 1 is 2mm, and the thickness of the prepreg is 2mil; S4: Pressing and forming: Pressing the inner substrate and the outer substrate together by browning, arranging and pressing to form an outer semi-finished circuit board including the vacuum cavity 4; the pressing temperature is 180°C, the pressure is 300psi, and the time is 90min; S5: Processing non-plated through holes: Mechanically drilling non-plated through holes 5 at non-signal line positions in the vacuum chamber 4 area to obtain an ultra-low dielectric constant circuit board, wherein the diameter of the non-plated through holes 5 is 0.5 mm, and the number of the non-plated through holes 5 is 2.

[0027] Embodiment 2: A process for preparing an ultra-low dielectric constant circuit board, comprising the following steps: A method for preparing a solder resist ink, comprising the following steps: adding 3 parts of a naphthyl photocurable resin and 2 parts of a polyurethane-modified photocurable epoxy resin to 5 parts of diethylene glycol ethyl ether acetate, adding 0.25 parts of epoxy-functionalized silica, 0.25 parts of a thermosetting agent, and 0.75 parts of barium sulfate, ball milling for 30 minutes, adding 0.1 parts of phthalocyanine green, 0.15 parts of an active diluent, and 0.15 parts of a composite photoinitiator, and stirring at room temperature for 3 hours to obtain a solder resist ink; The remaining steps are the same as those in Example 1.

[0028] Embodiment 3: A process for preparing an ultra-low dielectric constant circuit board, comprising the following steps: A method for preparing a solder resist ink, comprising the following steps: adding 4 parts of a naphthyl photocurable resin and 1 part of a polyurethane-modified photocurable epoxy resin to 5 parts of diethylene glycol ethyl ether acetate, adding 0.25 parts of epoxy-functionalized silica, 0.25 parts of a thermosetting agent, and 0.75 parts of barium sulfate, ball milling for 30 minutes, adding 0.1 parts of phthalocyanine green, 0.15 parts of an active diluent, and 0.15 parts of a composite photoinitiator, stirring at room temperature for 3 hours to obtain a solder resist ink; The remaining steps are the same as those in Example 1.

[0029] Embodiment 4: A process for preparing an ultra-low dielectric constant circuit board, comprising the following steps: A method for preparing a solder resist ink, comprising the following steps: adding 4 parts of a naphthyl photocurable resin and 3 parts of a polyurethane-modified photocurable epoxy resin to 7 parts of diethylene glycol ethyl ether acetate, adding 0.25 parts of epoxy-functionalized silica, 0.25 parts of a thermosetting agent, and 0.75 parts of barium sulfate, ball milling for 30 minutes, adding 0.1 parts of phthalocyanine green, 0.15 parts of an active diluent, and 0.15 parts of a composite photoinitiator, stirring at room temperature for 3 hours to obtain a solder resist ink; The remaining steps are the same as those in Example 1.

[0030] Comparative Example 1: A process for preparing an ultra-low dielectric constant circuit board, comprising the following steps: A method for preparing a solder resist ink, comprising the following steps: adding 5 parts of a naphthyl photocurable resin to 5 parts of diethylene glycol ethyl ether acetate, adding 0.25 parts of epoxy functionalized silica, 0.25 parts of a thermosetting agent, and 0.75 parts of barium sulfate, ball milling for 30 minutes, adding 0.1 parts of phthalocyanine green, 0.15 parts of an active diluent, and 0.15 parts of a composite photoinitiator, stirring at room temperature for 3 hours to obtain a solder resist ink; The remaining steps are the same as those in Example 1.

[0031] Comparative Example 2: A process for preparing an ultra-low dielectric constant circuit board, comprising the following steps: A method for preparing a solder resist ink, comprising the following steps: adding 5 parts of polyurethane-modified photocurable epoxy resin to 5 parts of diethylene glycol ethyl ether acetate, adding 0.25 parts of epoxy-functionalized silica, 0.25 parts of a thermosetting agent, and 0.75 parts of barium sulfate, ball milling for 30 minutes, adding 0.1 parts of phthalocyanine green, 0.15 parts of an active diluent, and 0.15 parts of a composite photoinitiator, stirring at room temperature for 3 hours to obtain a solder resist ink; The remaining steps are the same as those in Example 1.

[0032] Experiment: Dielectric constant test: According to GB / T1409-2006, the dielectric properties of the circuit boards prepared in the embodiments and comparative examples were tested at room temperature at a frequency of 10 GHz using an impedance analyzer.

[0033] The experimental results are shown in Table 1 below.

[0034] Table 1 Ultra-low dielectric constant circuit board performance test data table

[0035] Conclusion: The circuit board prepared by the present invention has the performance advantage of ultra-low dielectric constant, which is achieved by comprehensively realizing the ultra-low dielectric constant thanks to the rigid structure of the naphthalene-based resin, the flexible modification of the polyurethane, the design of the vacuum cavity and the optimization of the process parameters.

[0036] In Comparative Example 1 and Comparative Example 2, only single components of naphthalene-based photocurable resin and polyurethane-modified photocurable epoxy resin were added, respectively, and the synergistic effect between the two components could not be exerted, resulting in a slight decrease in the dielectric constant.

[0037] The solder resist ink prepared in the examples and comparative examples was coated on the surface of the release paper, dried at 75° C. for 30 min, irradiated with UV light for 60 s, and finally thermally cured at 150° C. for 45 min to obtain a test dry film, and the mechanical properties and thermal stability performance tests were performed.

[0038] The mechanical properties and thermal stability glass transition temperature of the dry film were tested, where the mechanical properties ranged from 2N to 18N at a rate of 2N / min, and the thermal stability heating rate was 5°C / min, with a test range up to 270°C.

[0039] The experimental results are shown in Table 2 below.

[0040] Table 2 Solder resist ink dry film performance test data

[0041] Conclusion: The solder resist ink prepared by the present invention has excellent mechanical properties and thermal stability.

[0042] In Comparative Example 1 and Comparative Example 2, only single components of naphthalene-based photocurable resin and polyurethane-modified photocurable epoxy resin were added, respectively, and the synergistic effect between the two components could not be exerted, resulting in reduced mechanical properties and thermal stability.

[0043] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A process for preparing an ultra-low dielectric constant circuit board, characterized in that: The following steps are involved: S1: Making an inner layer high frequency signal circuit: forming a high frequency signal circuit on the inner layer substrate by dry film lamination, exposure, development, and etching processes (1); S2: Making solder mask bridges: forming solder mask bridges (2) around the high-frequency signal line (1) through screen printing, exposure, and development processes; S3: Processing the prepreg vacuum cavity area: Covering the prepreg on the same layer as the solder mask bridge (2), removing the prepreg on the upper layer of the high-frequency circuit by mechanical gong, and forming prepreg grooves (3) on both sides of the solder mask bridge (2); S4: Pressing and forming: Pressing the inner substrate and the outer substrate together by browning, arranging and pressing to form an outer semi-finished circuit board including a vacuum cavity (4); S5: Processing non-plated through holes: Mechanically drilling non-plated through holes (5) at non-signal line positions in the vacuum cavity (4) area to obtain an ultra-low dielectric constant circuit board.

2. The process for preparing an ultra-low dielectric constant circuit board according to claim 1, characterized in that: In step S1, the line width tolerance of the high-frequency signal line (1) is ±10 μm.

3. The process for preparing an ultra-low dielectric constant circuit board according to claim 1, characterized in that: In step S2, the median thickness of the solder mask bridge (2) is equal to the thickness of the upper prepreg of the high-frequency signal line (1), the width of the solder mask bridge (2) is 0.1-0.4 mm, and the solder mask bridge (2) is prepared from solder mask ink.

4. The process for preparing an ultra-low dielectric constant circuit board according to claim 1, characterized in that: In step S3, the distance between the prepreg pit (3) and the high-frequency signal line (1) is 0.5-3 mm, the single-side width of the prepreg pit (3) exceeds the width of the solder mask bridge (2) by 0.1 mm, and the thickness of the prepreg is 1.5-2.5 mil.

5. The process for preparing an ultra-low dielectric constant circuit board according to claim 1, characterized in that: In step S4, the platen parameters are temperature of 180-200° C., pressure of 300-400 psi, and time of 90-120 min.

6. The process for preparing an ultra-low dielectric constant circuit board according to claim 1, characterized in that: In step S5, the diameter of the non-plated through hole (5) is 0.25-1 mm, and the number of the non-plated through holes (5) provided in each vacuum chamber (4) is ≥ 2.

7. The process for preparing an ultra-low dielectric constant circuit board according to claim 3, characterized in that: The preparation method of the solder resist ink comprises the following steps: Adding naphthyl photocurable resin and polyurethane modified photocurable epoxy resin to diethylene glycol ethyl ether acetate, adding epoxy functionalized silica, thermosetting agent, and barium sulfate, ball milling for 30-45 minutes, adding phthalocyanine green, active diluent, and composite photoinitiator, stirring at room temperature for 3-4 hours, and obtaining solder resist ink; In the preparation process of solder resist ink, the components are calculated by mass, including 2-4 parts of naphthyl photocurable resin, 1-3 parts of polyurethane modified photocurable epoxy resin, 5-7 parts of diethylene glycol ethyl ether acetate, 0.25-0.3 parts of epoxy functionalized silica, 0.25-3 parts of thermosetting agent, 0.75-1 parts of barium sulfate, 0.1-0.15 parts of phthalocyanine green, 0.15-0.2 parts of active diluent, and 0.15-0.2 parts of composite photoinitiator.

8. The process for preparing an ultra-low dielectric constant circuit board according to claim 7, characterized in that: The preparation method of the naphthalene-based photocurable resin comprises the following steps: Add naphthyl epoxy monomer to ethyl 2-(2-ethoxyethoxy)acetate, heat to 85-86°C, stir evenly, cool to room temperature, add cholic acid and 4-dimethylaminopyridine, heat to 115-120°C for reaction for 12-13h, cool to room temperature, add 1,2,3,6-tetrahydrophthalic anhydride and hydroquinone, heat to 95-98°C for reaction for 7-8h, add glycidyl methacrylate, heat to 110-115°C for reaction for 3-4h to obtain naphthyl photocurable resin; In the preparation process of the naphthyl photocurable resin, the mass ratio of naphthyl epoxy monomer: cholic acid: 4-dimethylaminopyridine: 1,2,3,6-tetrahydrophthalic anhydride: hydroquinone: glycidyl methacrylate is 3:5.7:0.052:8.4:0.052:4.

2.

9. The process for preparing an ultra-low dielectric constant circuit board according to claim 8, characterized in that: The preparation method of the naphthyl epoxy monomer comprises the following steps: 1,5-naphthalenediol and ethyl 4-bromobutyrate are added to acetone, stirred evenly, potassium carbonate is added, and the mixture is heated to 70-75°C and refluxed for reaction for 3-4 days. The reaction product is extracted with ether and hydrochloric acid, washed with deionized water, dried over anhydrous sodium sulfate, filtered, the organic layer is collected, and evaporated to dryness to obtain compound 1; compound 1 is added to tetrahydrofuran, 0.5 mol / L sodium hydroxide aqueous solution is added, the mixture is reacted at room temperature for 12-13 hours, 1 mol / L hydrochloric acid aqueous solution is added, the mixture is reacted for 3-4 days, filtered, and dried to obtain compound 2; compound 2, glycidol, and 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride are added to tetrahydrofuran, 4-dimethylaminopyridine is added, the mixture is reacted at room temperature for 24-25 hours, rotary evaporated, washed, centrifuged, and dried to obtain a naphthyl epoxy monomer; During the preparation of compound 1, the molar ratio of 1,5-naphthalenediol: ethyl 4-bromobutyrate: potassium carbonate was 9.3:23.1:54; during the preparation of the naphthyl epoxy monomer, the molar ratio of compound 2: glycidol: 1-ethyl-3-(dimethylaminopropyl)carbodiimide hydrochloride: 4-dimethylaminopyridine was 10:30:30:

3.

10. The process for preparing an ultra-low dielectric constant circuit board according to claim 7, characterized in that: The preparation method of polyurethane modified light-curing epoxy resin comprises the following steps: Add isophorone diisocyanate to a reaction container, add p-hydroxyanisole, dibutyl tin dilaurate, and hydroxyethyl acrylate, and heat to 30-32° C. for reaction. When the isocyanate group content in the reaction system reaches the theoretical value, a double-bond terminated polyurethane precursor is obtained; further heat to 50-52° C., add isophorone diisocyanate, p-hydroxyanisole, and dibutyl tin dilaurate, stir evenly, add polyethylene glycol 100 and 2,2-dihydroxymethylacrylate, and keep warm for reaction. When the isocyanate group content in the reaction system reaches the theoretical value, a double-bond terminated oligomeric polyurethane is obtained; add a light-curable epoxy resin containing a dihydroxy group carboxylic acid to a reaction container, add p-hydroxybenzyl ether, dibutyl tin dilaurate, and a double-bond terminated oligomeric polyurethane, and heat to 50-52° C. When the isocyanate group content in the reaction system is 0%, add the product to a methanol aqueous solution for purification, and vacuum dry to obtain a polyurethane-modified light-curable epoxy resin; In the preparation process of the double-bond terminated polyurethane precursor, the mass ratio of isophorone diisocyanate: p-hydroxyanisole: dibutyl tin laurate: hydroxyethyl acrylate is 117:0.17:0.52:59; in the preparation process of the double-bond terminated oligomeric polyurethane, the mass ratio of isophorone diisocyanate: p-hydroxyanisole: dibutyl tin laurate: polyethylene glycol 100 and 2,2-dihydroxymethyl acrylate is 229:0.4:1.2:100:69; In the preparation process of the modified light-curing epoxy resin, the mass ratio of the light-curing epoxy resin containing dihydroxy carboxylic acid: hydroxybenzyl ether: dibutyl tin dilaurate: double-bond terminated oligomeric polyurethane is 500:0.99:2.97:50; the light-curing epoxy resin containing dihydroxy carboxylic acid is prepared by firstly performing a ring-opening reaction on epoxy resin, acrylic acid and 2,2-dihydroxymethylacrylic acid, and then performing an esterification reaction on epoxy resin and 1,2,3,6-tetrahydrophthalic anhydride.

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