An arbitrary layer interconnection high-density circuit board and a manufacturing process thereof

Abstract

The application provides an arbitrary layer interconnection high-density circuit board and a preparation process thereof, and belongs to the technical field of printed circuit boards. The preparation process comprises the following steps: modifying silver powder and preparing a conductive adhesive; surface pretreating nano boron nitride powder and modifying the same with hydrochloric acid dopamine; activating alumina with gamma-glycidyl ether oxygen propyl trimethoxysilane; adding phenyl triethoxysilane to prepare a modifier and then preparing an insulating coating; preparing a substrate and cold pressing the substrate. The application prepares a PCB substrate by compounding two copper foils with the insulating coating, and then uses the conductive adhesive to bond the PCB substrate and cold press the same into an arbitrary layer interconnection high-density circuit board. Compared with the circuit board prepared by using semi-cured sheets and copper foils to be cold pressed layer by layer at high temperature, the arbitrary layer interconnection high-density circuit board has the advantages of being lighter and thinner. In addition, the insulating coating has good insulating performance and the conductive adhesive has good conductivity, so that the prepared arbitrary layer interconnection high-density circuit board can work normally.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed wiring board, in particular to an arbitrary layer interconnection high-density circuit board and a preparation process thereof. BACKGROUND

[0002] The high-density interconnection circuit board is a circuit board with higher circuit distribution density made by using micro-blind hole technology, which can realize higher wiring density and more complex circuit design in smaller size, and the arbitrary layer interconnection is a more complex electrical connection design of the high-density interconnection circuit board.

[0003] At present, the existing arbitrary layer interconnection high-density circuit board includes a substrate and a single-sided board, and the single-sided board is laminated on the substrate through a semi-cured layer. Since the semi-cured layer needs to be heated at high temperature for a certain period of time to form a stable semi-cured layer, the high-density interconnection circuit board needs to be made by layer-by-layer multiple lamination, which consumes a large amount of time. Moreover, the semi-cured layer composed of resin and reinforcing material is usually thick, and if the number of layers of the high-density interconnection circuit board is large, the volume of the high-density interconnection circuit board will be too large, which is not light, thin, small and delicate, and cannot meet the needs of electronic products.

[0004] Therefore, we propose an arbitrary layer interconnection high-density circuit board with shorter lamination time and being more light and thin, and a preparation process thereof, to meet the needs of electronic products. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide an arbitrary layer interconnection high-density circuit board and a preparation process thereof.

[0006] S1: modifying silver powder and preparing conductive adhesive

[0007] The γ-glycidyl ether oxypropyl trimethoxysilane is added to the flaky silver powder and the spherical silver powder to prepare modified silver powder, and then the butyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate and lauryl acrylate are used as raw materials to prepare an intermediate, and then the modified silver powder is added to the intermediate to obtain the conductive adhesive;

[0008] S2: surface pretreatment of nano boron nitride powder and modification by hydrochloric acid dopamine

[0009] The nano boron nitride powder and the sodium hydroxide solution are heated and stirred to perform surface pretreatment on the nano boron nitride powder, and then the modified nano boron nitride is obtained by uniformly mixing the nano boron nitride powder with a mixed solution and adding hydrochloric acid dopamine for modification;

[0010] S3: γ-glycidyl ether oxypropyl trimethoxysilane activation of alumina

[0011] Dissolve γ-glycidoxypropyltrimethoxysilane in ethanol, then add acetic acid until the PH is adjusted to 3-4, then add aluminum oxide, heat to reflux at 60-70℃ and stir for 5-6h, after natural cooling to room temperature, perform suction filtration, ethanol washing and drying to obtain activated alumina;

[0012] S4: Add phenyltriethoxysilane to prepare a modifier, and then prepare an insulating coating

[0013] Mix anhydrous ethanol, anhydrous methanol, hydrochloric acid, deionized water, phenyltriethoxysilane and β-3,4-epoxycyclohexyl ethyl trimethoxysilane to prepare a modifier, and then mix with epoxy resin, diamino diphenyl methane, the modified nano boron nitride and the activated alumina to obtain an insulating coating;

[0014] S5: Prepare a substrate and cold-press the substrate

[0015] Coat the above insulating coating on the upper surface of a copper foil, then adhere another copper foil to form a PCB substrate, laser drill and electroplate copper to fill the holes, then adhere by the above conductive adhesive, and cold-press to obtain an arbitrary layer interconnection high-density circuit board.

[0016] Further, the modified silver powder of step S1 and the preparation of the conductive adhesive specifically include the following steps:

[0017] S1.1: Put flaky silver powder and spherical silver powder into a planetary centrifugal stirrer according to a mass ratio of 3-5:6-8, then add anhydrous ethanol and γ-glycidoxypropyltrimethoxysilane accounting for 3-5% of the total mass of the flaky silver powder and the spherical silver powder according to a solid-liquid ratio of 1g:10-12mL, stir and mix uniformly, then place in an oven and dry at 60-80℃ for 2-3h to obtain a modified silver powder;

[0018] S1.2: Add butyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate and lauryl acrylate into a mixing tank, then add γ-methacryloyloxypropyltrimethoxysilane and ethyl acetate into the mixing tank, and fully stir and mix to obtain a premix;

[0019] S1.3: Introduce nitrogen into the reactor until the air is exhausted, then add 2 / 3 of the above premix into the reactor, heat at 70-80℃ for 30-40min, and stir at a speed of 300-400r / min at the same time;

[0020] S1.4: Adjust the stirring speed to 100-200r / min, add the remaining premix, β-hydroxyethyl acrylate and 70-80% ammonium persulfate into the reactor, and react for 3-5h after keeping warm, then add the remaining ammonium persulfate and continue to react for 1-2h, and then naturally cool to room temperature to obtain an intermediate.

[0021] S1.5: Add trimethyl hexamethylene diisocyanate to the above intermediate, fully stir and mix, then add the above modified silver powder, continue to stir and mix, and at the same time, ultrasonic treatment is carried out, and after vacuum degassing, the conductive adhesive is obtained.

[0022] Further, the surface pretreated boron nitride powder in step S2 is modified with dopamine hydrochloride, specifically including the following steps:

[0023] S2.1: Put the sodium hydroxide solution into a heating box, then add the boron nitride powder into the heating box according to the solid-liquid ratio of 1g:25-35mL, heat at a temperature of 100-120℃ for 12-16h, and at the same time, use a stirrer to stir, to obtain a suspension;

[0024] S2.2: The above suspension is subjected to suction filtration, then the filter residue is washed with deionized water for 3-5 times, and is placed in a vacuum drying box for drying for 20-24h, and after grinding, the surface pretreated boron nitride powder is obtained;

[0025] S2.3: The above surface pretreated boron nitride powder and the mixed solution are added into a mixing box according to the solid-liquid ratio of 1g:80-90mL, and are stirred and dispersed to obtain a suspension;

[0026] S2.4: Dopamine hydrochloride is added into the above suspension according to the solid-liquid ratio of 1g:300-400mL, and is stirred at a rate of 200-300r / min by using a stirrer for 4-6h, and after centrifugal filtration, deionized water washing, drying and grinding, the modified boron nitride nano-powder is obtained.

[0027] Further, the modifier is prepared by adding phenyl triethoxysilane in step S4, and then the insulating coating is prepared, specifically including the following steps:

[0028] S4.1: Anhydrous ethanol, anhydrous methanol, hydrochloric acid and deionized water are added into a reaction box according to the volume ratio of 5-6:3-5:1-2:7-8, and are fully stirred and mixed;

[0029] S4.2: Phenyl triethoxysilane and β-3,4-epoxycyclohexyl ethyl trimethoxysilane are added into the reaction box, and are stirred and reacted for 46-48h to obtain a precursor solution;

[0030] S4.3: Sodium hydroxide solution is added into the reaction box until the pH of the above precursor solution is adjusted to 7-8, then a vacuum distillation device in the reaction box is started, and the precursor solution is subjected to vacuum distillation, and after washing and drying, the modifier is obtained;

[0031] S4.4: Dissolve the epoxy resin, the above-mentioned modifier and diamino diphenyl methane in ethyl ether according to the mass ratio of 5-8:1-2:1, then add the above-mentioned modified nano boron nitride and activated alumina, and after fully mixing, the insulating coating is obtained.

[0032] Further, the preparation substrate and normal temperature pressure bonding substrate of step S5 specifically comprises the following steps:

[0033] S5.1: Uniformly coat the insulating coating prepared in step S4.4 on the upper surface of a copper foil to form an insulating coating layer, then bond another copper foil on the insulating layer, and after the insulating coating layer is dried and cured, the PCB substrate is obtained;

[0034] S5.2: According to the requirement, a plurality of the above-mentioned PCB substrates are subjected to laser drilling treatment, and then the drilled holes are subjected to copper plating and hole filling, and the pretreated substrate is obtained;

[0035] S5.3: Uniformly coat the conductive adhesive prepared in step S1.5 on the upper surface of the above-mentioned pretreated substrate, then bond another pretreated substrate on the conductive adhesive, and so on until the required number of layers is reached, and after normal temperature pressure bonding, the arbitrary layer interconnection high-density circuit board is obtained.

[0036] Further, the conductive adhesive comprises 30-40 parts by mass of butyl acrylate, 20-30 parts by mass of methyl methacrylate, 20-30 parts by mass of 2-ethylhexyl acrylate, 8-10 parts by mass of lauryl acrylate, 2-3 parts by mass of gamma-methacryloxypropyl trimethoxysilane, 40-50 parts by mass of ethyl acetate, 6-8 parts by mass of beta-hydroxyethyl acrylate, 3-5 parts by mass of ammonium persulfate, 1-3 parts by mass of trimethyl hexamethylene diisocyanate and 70-80 parts by mass of modified silver powder.

[0037] Further, the mixed solution is prepared by mixing the amino-methane buffer and ethanol according to the volume ratio of 2-4:1.

[0038] Further, the mass ratio of phenyl triethoxysilane to beta-3,4-epoxycyclohexyl ethyl trimethoxysilane is 6-8:1, and the molar ratio of the total molar amount of phenyl triethoxysilane and beta-3,4-epoxycyclohexyl ethyl trimethoxysilane to deionized water is 1:2-3.

[0039] Further, the mass ratio of the modified nano boron nitride and the activated alumina to the epoxy resin is 1:20-30 and 1:10-20, respectively.

[0040] An arbitrary layer interconnection high-density circuit board is prepared by the preparation process of any one of the above-mentioned arbitrary layer interconnection high-density circuit boards.

[0041] Compared with the prior art, the present application has at least the following beneficial effects:

[0042] 1. The present invention forms a PCB substrate by compounding two copper foils with an insulating coating, and then bonding the PCB substrates with a conductive adhesive and pressing them at room temperature in one step to form a high-density circuit board with arbitrary layer interconnections. Compared with the traditional circuit board obtained by pressing prepreg and copper foil layer by layer at high temperature, the present invention has the advantage of being lighter and thinner. At the same time, due to the good insulation performance of the insulating coating and the good conductivity of the conductive adhesive, the prepared high-density circuit board with arbitrary layer interconnections can operate normally under a lighter, thinner and more compact precursor.

[0043] 2. The present invention prepares a conductive adhesive by modifying flaky silver powder and spherical silver powder by mixing them with γ-glycidyloxypropyltrimethoxysilane in a certain proportion, and then fully mixing them with an intermediate prepared from butyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate, and lauryl acrylate. This can effectively reduce the volume resistivity of the conductive adhesive and improve its conductivity. In addition, the conductive adhesive also has excellent holding force, thereby extending the service life of the circuit board.

[0044] 3. The present invention prepares a modifier using phenyltriethoxysilane and β-3,4-epoxycyclohexylethyltrimethoxysilane as raw materials, and then mixes it with epoxy resin to modify the epoxy resin to improve the adhesion of the epoxy resin. Then, by adding activated alumina, the adhesion and insulation performance of the prepared insulating coating can be further improved, preventing the copper foil from falling off, thereby extending the service life of the circuit board.

[0045] 4. The present invention pre-treats the surface of nano-boron nitride powder by mixing it with sodium hydroxide solution, and then modifies it by mixing it with dopamine hydrochloride. The modified nano-boron nitride is added to epoxy resin, which can improve the insulation performance of the obtained insulating coating, thereby ensuring the normal operation of the obtained high-density circuit board with any layer of interconnection. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable one skilled in the relevant art to make and use the present disclosure.

[0047] Figure 1 This is a flow chart of the process for preparing a high-density circuit board with arbitrary layer interconnections adopted in an embodiment of the present invention.

[0048] Figure 2 This is a summary table of performance test results of Examples 1-3 of the present invention.

[0049] Figure 3 The following is a summary table of the comparison results between Example 1 of the present invention and Comparative Example 1.

[0050] Figure 4 Summary table of comparative results of Example 1 of the present application and Comparative Example 2.

[0051] Figure 5 Summary table of comparative results of Example 1 of the present application and Comparative Examples 3 and 4.

[0052] Figure 6 Summary table of comparative results of Example 1 of the present application and Comparative Example 5. DETAILED DESCRIPTION

[0053] An arbitrary layer interconnection high-density circuit board and a preparation process thereof according to the present application are described in detail below in conjunction with the accompanying drawings and specific examples. It should be noted that the following examples are the best, preferred examples, and other alternative ways can also be used by those skilled in the art to implement some known technologies; and the accompanying drawings are only used to more specifically describe the examples, and are not intended to specifically limit the present application.

[0054] Example 1: A preparation process of an arbitrary layer interconnection high-density circuit board, as shown in FIG. 1, includes the following steps: Figure 1

[0055] S1: Modification of silver powder and preparation of conductive adhesive

[0056] The flaky silver powder and the spherical silver powder are added into a planetary centrifugal stirrer at a mass ratio of 3:6, and then anhydrous ethanol and 3% of γ-glycidoxypropyltrimethoxysilane based on the total mass of the flaky silver powder and the spherical silver powder are added at a solid-liquid ratio of 1 g:10 mL, and then stirred and mixed uniformly, and then placed in an oven for drying at 60°C for 2 h to obtain modified silver powder, which is ready for use. Then 30 parts by mass of butyl acrylate, 20 parts by mass of methyl methacrylate, 20 parts by mass of 2-ethylhexyl acrylate, and 8 parts by mass of lauryl acrylate are added into a mixing tank, and then 2 parts by mass of γ-methacryloyloxypropyltrimethoxysilane and 40 parts by mass of ethyl acetate are added into the mixing tank, and then stirred and mixed thoroughly to obtain a premix. Subsequently, nitrogen is introduced into the reactor until the air is completely removed, and then 2 / 3 of the premix is added into the reactor, and heated at 70°C for 30 min while stirring at a speed of 300 r / min. Then the stirring speed is adjusted to 100 r / min, and the remaining premix, 6 parts by mass of β-hydroxyethyl acrylate, and 2 parts by mass of ammonium persulfate are added into the reactor, and then incubated for 3 h, and then the remaining ammonium persulfate is added, and then incubated for another 1 h, and then naturally cooled to room temperature to obtain an intermediate. Then 1 part by mass of trimethylhexamethylene diisocyanate is added into the intermediate, and then stirred and mixed thoroughly, and then 70 parts by mass of the modified silver powder is added, and then stirred and mixed while being subjected to ultrasonic treatment, and then vacuum degassed to obtain a conductive adhesive. ​

[0057] S2: Surface pretreatment of nano boron nitride powder and modification with hydrochloric acid dopamine

[0058] The sodium hydroxide solution was added to a heating box, and then the nano boron nitride powder was added to the heating box at a solid-liquid ratio of 1 g:25 mL. The mixture was heated at a temperature of 100℃ for 12h while stirring with a stirrer to obtain a suspension. The suspension was then subjected to suction filtration, and the filter residue was washed with deionized water for 3 times and dried in a vacuum drying box for 20h. After grinding, the surface pretreated boron nitride powder was obtained. Then, the surface pretreated boron nitride powder and a mixed solution prepared by mixing amino methane buffer and ethanol at a volume ratio of 2:1 were added to a mixing box at a solid-liquid ratio of 1 g:80 mL, and stirred and dispersed to obtain a suspension. Subsequently, hydrochloric acid dopamine was added to the suspension at a solid-liquid ratio of 1 g:300 mL, and stirred with a stirrer at a speed of 200r / min for 4h. After centrifugal filtration, deionized water washing, drying and grinding, the modified nano boron nitride was obtained.

[0059] S3: Activation of alumina with γ-glycidoxypropyltrimethoxysilane

[0060] The γ-glycidoxypropyltrimethoxysilane was dissolved in ethanol, and then acetic acid was added until the pH was adjusted to 3. Alumina was then added, and the mixture was heated to reflux at 60℃ and stirred for 5h. After natural cooling to room temperature, suction filtration, ethanol washing and drying were performed to obtain the activated alumina.

[0061] S4: Preparation of a modifier by adding phenyltriethoxysilane, and preparation of an insulating coating

[0062] Anhydrous ethanol, anhydrous methanol, hydrochloric acid and deionized water were added to a reaction box at a volume ratio of 5:3:1:7, and fully stirred and mixed. Then, phenyltriethoxysilane and β-3,4-epoxycyclohexylethyltrimethoxysilane were added to the reaction box at a mass ratio of 6:1, and the molar ratio of the total amount of phenyltriethoxysilane and β-3,4-epoxycyclohexylethyltrimethoxysilane to deionized water was 1:2. The mixture was stirred and reacted for 46h to obtain a precursor solution. Then, sodium hydroxide solution was added to the reaction box until the pH of the precursor solution was adjusted to 7. Then, a vacuum distillation device in the reaction box was started, and the precursor solution was subjected to vacuum distillation. After washing and drying, the modifier was obtained. Subsequently, epoxy resin, the modifier and diamino diphenylmethane were dissolved in diethyl ether at a mass ratio of 5:1:1, and then the above modified nano boron nitride and activated alumina were added, wherein the mass ratio of the modified nano boron nitride and activated alumina to the epoxy resin was 1:20 and 1:10, respectively. After fully mixing, the insulating coating was obtained.

[0063] S5: Preparation of a substrate and cold pressing of the substrate

[0064] The above insulating coating is uniformly coated on the upper surface of a copper foil to form an insulating coating layer, and then another copper foil is attached to the insulating layer. After the insulating coating layer is dried and cured, a PCB substrate with an insulating coating layer thickness of about 40 μm is obtained. Then, according to the requirements, a plurality of PCB substrates are subjected to laser drilling treatment, and the drilled holes are subjected to copper plating and hole filling. A pretreated substrate is obtained. Then, the above conductive adhesive is uniformly coated on the upper surface of the pretreated substrate, and then another pretreated substrate is attached to the conductive adhesive. In this way, until the required number of layers is reached, after normal temperature pressing, an arbitrary layer interconnection high-density circuit board is obtained.

[0065] Insulating coating performance test:

[0066] First, the insulating coating is uniformly coated on the upper surface of the copper foil, and after curing, a 15 cm x 10 cm copper foil with an insulating coating layer on the surface is taken. The test voltage is set to 250 V, and the volume resistivity is measured by a high resistance meter. The results are shown in Figure 2 .

[0067] Then, according to GB / T9286-2021, the adhesion test is carried out, and the results are shown in Figure 2 .

[0068] Conductive adhesive performance test:

[0069] First, the conductive adhesive is coated on the upper surface of the copper foil, and after curing, the holding adhesion is tested according to GB / T4851-1998 standard. The results are shown in Figure 2 .

[0070] Then, the conductive adhesive is coated in a 20 mm x 20 mm x 0.5 mm mold, and after curing, the volume resistivity is tested by a four-probe tester.

[0071] Example 2: A preparation process of an arbitrary layer interconnection high-density circuit board, as shown in Figure 1 , includes the following steps:

[0072] S1: Modification of silver powder and preparation of conductive adhesive

[0073] The flaky silver powder and the spherical silver powder are added into a planetary centrifugal stirrer in a mass ratio of 4:7, anhydrous ethanol is added in a solid-liquid ratio of 1 g:11 mL, and 4% of the total mass of the flaky silver powder and the spherical silver powder is added as γ-glycidoxypropyltrimethoxysilane, the mixture is stirred and mixed uniformly, and then is placed in an oven for drying at 70°C for 2.5 h to obtain modified silver powder for standby. Then, 35 parts by mass of butyl acrylate, 25 parts by mass of methyl methacrylate, 25 parts by mass of 2-ethylhexyl acrylate, and 9 parts by mass of lauryl acrylate are added into a mixing tank, 2 parts by mass of γ-methacryloyloxypropyltrimethoxysilane and 45 parts by mass of ethyl acetate are added into the mixing tank, the mixture is stirred and mixed thoroughly to obtain a premix liquid. Subsequently, nitrogen is introduced into a reactor until the air is exhausted, 2 / 3 of the premix liquid is added into the reactor, the reactor is heated at 75°C for 35 min while stirring at a speed of 350 r / min, then the stirring speed is adjusted to 150 r / min, the remaining premix liquid, 7 parts by mass of β-hydroxyethyl acrylate, and 3 parts by mass of ammonium persulfate are added into the reactor, the reaction is carried out for 4 h, the remaining ammonium persulfate is added, and the reaction is continued for 1.5 h, and then the reaction mixture is naturally cooled to room temperature to obtain an intermediate. Then, 2 parts by mass of trimethylhexamethylene diisocyanate is added into the intermediate, the mixture is stirred and mixed thoroughly, 75 parts by mass of the modified silver powder is added, the mixture is continuously stirred and mixed while being subjected to ultrasonic treatment, and then is subjected to vacuum degassing to obtain a conductive adhesive.

[0074] S2: Surface pretreatment of nano boron nitride powder and modification with dopamine hydrochloride

[0075] A sodium hydroxide solution is added into a heating tank, nano boron nitride powder is added into the heating tank in a solid-liquid ratio of 1 g:30 mL, the mixture is heated at a temperature of 110°C for 14 h while being stirred with a stirrer to obtain a suspension, the suspension is subjected to suction filtration, the filter residue is washed with deionized water for 4 times, and then is dried in a vacuum drying oven for 22 h. After grinding, a surface pretreated boron nitride powder is obtained. Then, the surface pretreated boron nitride powder and a mixed solution prepared by mixing an amino methane buffer and ethanol in a volume ratio of 3:1 are added into a mixing tank in a solid-liquid ratio of 1 g:85 mL, the mixture is stirred and dispersed to obtain a suspension. Subsequently, dopamine hydrochloride is added into the suspension in a solid-liquid ratio of 1 g:350 mL, the mixture is stirred with a stirrer at a speed of 250 r / min for 5 h, and then is subjected to centrifugal filtration, washing with deionized water, drying, and grinding to obtain modified nano boron nitride.

[0076] S3: γ-glycidoxypropyltrimethoxysilane activated alumina

[0077] γ-glycidoxypropyltrimethoxysilane is dissolved in ethanol, acetic acid is added until the pH is adjusted to 3.5, and then alumina is added. The mixture is heated and refluxed at 65°C for 5.5 h while being stirred, and then is naturally cooled to room temperature. The mixture is subjected to suction filtration, ethanol washing, and drying to obtain activated alumina.

[0078] S4: adding phenyl triethoxysilane to prepare a modifier, and then preparing an insulating coating

[0079] Anhydrous ethanol, anhydrous methanol, hydrochloric acid and deionized water were added into a reaction box in a volume ratio of 5:4:1:8, and then stirred and mixed, and then phenyl triethoxysilane and β-3,4-epoxycyclohexyl ethyl trimethoxysilane were added into the reaction box in a mass ratio of 7:1, wherein the molar ratio of the total amount of phenyl triethoxysilane and β-3,4-epoxycyclohexyl ethyl trimethoxysilane to the deionized water was 1:2, and then the mixture was stirred and reacted for 47 hours to obtain a precursor solution, and then sodium hydroxide solution was added into the reaction box until the pH of the precursor solution was adjusted to 7.5, and then a vacuum distillation device in the reaction box was started to distill the precursor solution under reduced pressure, and then the modified agent was obtained after washing and drying, and then the epoxy resin, the modified agent and the diamino diphenyl methane were dissolved in diethyl ether in a mass ratio of 6:1:1, and then the modified nano boron nitride and the activated alumina were added, wherein the mass ratio of the modified nano boron nitride and the activated alumina to the epoxy resin was 1:25 and 1:15 respectively, and then the mixture was fully mixed to obtain the insulating coating;

[0080] S5: preparing a substrate and pressure bonding the substrate at room temperature

[0081] The above insulating coating was uniformly coated on the upper surface of a copper foil to form an insulating coating layer, and then another copper foil was bonded to the insulating layer, and after the insulating coating layer was dried and cured, a PCB substrate with an insulating coating layer thickness of about 45 μm was obtained, and then a plurality of PCB substrates were laser drilled according to requirements, and then the drilled holes were filled with copper by electroplating to obtain pretreated substrates, and then the above conductive adhesive was uniformly coated on the upper surface of the pretreated substrates, and then another pretreated substrate was bonded to the conductive adhesive, and so on until the desired number of layers was reached, and then the substrates were pressure bonded at room temperature to obtain an arbitrary layer interconnection high-density circuit board.

[0082] Insulating coating performance test:

[0083] First, the insulating coating was uniformly coated on the upper surface of the copper foil, and after curing, a 15 cm x 10 cm copper foil with an insulating coating layer on the surface was taken, and a test voltage of 250 V was set, and the volume resistivity was measured by a high resistance meter, and the results are shown in Figure 2 .

[0084] Then, the adhesion was tested according to GB / T9286-2021, and the results are shown in Figure 2 .

[0085] Conductive adhesive performance test:

[0086] First, the conductive adhesive is coated on the upper surface of the copper foil, and after it is cured, its holding power is tested according to the GB / T4851-1998 standard, and the results are shown in Table 1. Figure 2

[0087] Then, the conductive adhesive is coated in a 20mm x 20mm x 0.5mm mold, and after it is cured, its volume resistivity is tested using a four-probe tester, and the results are shown in Table 2. Figure 2

[0088] Example 3: A preparation process for an arbitrary layer interconnection high-density circuit board, as shown in Table 3, includes the following steps: Figure 1

[0089] S1: Modify silver powder and prepare conductive adhesive

[0090] The flaky silver powder and spherical silver powder are added to a planetary centrifugal stirrer in a mass ratio of 5:8, and then anhydrous ethanol is added in a solid-liquid ratio of 1g:12mL, and γ-glycidoxypropyltrimethoxysilane is added in an amount of 5% of the total mass of the flaky silver powder and spherical silver powder. Stir and mix uniformly, then place in an oven and dry at 80°C for 3h to obtain modified silver powder for standby. Then, 40 parts by mass of butyl acrylate, 30 parts by mass of methyl methacrylate, 30 parts by mass of 2-ethylhexyl acrylate, and 10 parts by mass of lauryl acrylate are added to a mixing tank, and then 3 parts by mass of γ-methacryloyloxypropyltrimethoxysilane and 50 parts by mass of ethyl acetate are added to the mixing tank. Stir well to obtain a premix. Then, nitrogen is introduced into the reactor until the air is completely removed. Then, 2 / 3 of the premix is added to the reactor, heated at 80°C for 40min, and stirred at a speed of 400r / min. Then, adjust the stirring speed to 200r / min, add the remaining premix, 8 parts by mass of β-hydroxyethyl acrylate, and 4 parts by mass of ammonium persulfate to the reactor, and react for 5h. Then, add the remaining ammonium persulfate and continue to react for 2h. Naturally cool to room temperature to obtain an intermediate. Then, 3 parts by mass of trimethylhexamethylene diisocyanate is added to the intermediate and stirred well. Then, 80 parts by mass of modified silver powder is added and stirred while being ultrasonically treated. After vacuum degassing, the conductive adhesive is obtained.

[0091] S2: Surface pretreatment of nano-boron nitride powder and modification with hydrochloric acid dopamine

[0092] ​​​The sodium hydroxide solution is added into a heating box, and then the nano boron nitride powder is added into the heating box according to a solid-liquid ratio of 1 g: 35 mL, heated at a temperature of 120℃ for 16 h, and stirred with a stirrer at the same time to obtain a suspension, and then the suspension is suction filtered, the filter residue is washed with deionized water for 5 times, and then dried in a vacuum drying box for 24 h, and then ground to obtain the surface pretreated boron nitride powder; then the surface pretreated boron nitride powder and a mixed solution prepared by mixing the aminomethyl methane buffer solution and the ethanol according to a volume ratio of 4:1 are added into a mixing box according to a solid-liquid ratio of 1 g: 90 mL, and then stirred and dispersed to obtain a suspension; then the dopamine hydrochloride is added into the suspension according to a solid-liquid ratio of 1 g: 400 mL, and then stirred with a stirrer at a speed of 300 r / min for 6 h, and then centrifuged, washed with deionized water, dried, and ground to obtain the modified nano boron nitride;

[0093] S3: γ-glycidoxypropyltrimethoxysilane activated alumina

[0094] The γ-glycidoxypropyltrimethoxysilane is dissolved in ethanol, and then acetic acid is added until the pH is adjusted to 4, and then the alumina is added, and then heated and refluxed at 70℃ for 6 h with stirring, and then naturally cooled to room temperature, and then suction filtered, washed with ethanol, and dried to obtain the activated alumina;

[0095] S4: adding phenyltriethoxysilane to prepare a modifier, and then preparing an insulating coating

[0096] The anhydrous ethanol, the anhydrous methanol, the hydrochloric acid, and the deionized water are added into a reaction box according to a volume ratio of 6:5:2:8, and then fully stirred and mixed, and then the phenyltriethoxysilane and the β-3,4-epoxycyclohexylethyltrimethoxysilane are added into the reaction box according to a mass ratio of 8:1, and the molar ratio of the total amount of the phenyltriethoxysilane and the β-3,4-epoxycyclohexylethyltrimethoxysilane to the deionized water is 1:3, and then the reaction is stirred for 48 h to obtain a precursor solution, and then the sodium hydroxide solution is added into the reaction box until the pH of the precursor solution is adjusted to 8, and then the vacuum distillation device in the reaction box is started, and then the precursor solution is vacuum distilled, and then washed and dried to obtain the modifier, and then the epoxy resin, the modifier, and the diamino diphenyl methane are dissolved in diethyl ether according to a mass ratio of 8:2:1, and then the modified nano boron nitride and the activated alumina are added, and the mass ratio of the modified nano boron nitride and the activated alumina to the epoxy resin is 1:30 and 1:20 respectively, and then fully mixed to obtain the insulating coating;

[0097] S5: preparing a substrate and pressure bonding the substrate at room temperature

[0098] The above insulating coating is uniformly coated on the upper surface of a copper foil to form an insulating coating layer, and then another copper foil is attached to the insulating layer. After the insulating coating layer is dried and cured, a PCB substrate with an insulating coating layer thickness of about 50 μm is obtained. Then, according to the requirements, a plurality of PCB substrates are subjected to laser drilling treatment, and the drilled holes are subjected to copper plating and hole filling. A pretreated substrate is obtained. Then, the above conductive adhesive is uniformly coated on the upper surface of the pretreated substrate, and then another pretreated substrate is attached to the conductive adhesive. In this way, the required number of layers is obtained. After normal temperature pressing, an arbitrary layer interconnection high-density circuit board is obtained.

[0099] Insulating coating performance test:

[0100] First, the insulating coating is uniformly coated on the upper surface of the copper foil. After curing, a 15 cm x 10 cm copper foil with an insulating coating layer on the surface is taken, and the test voltage is set to 250 V. The volume resistivity is measured by a high resistance meter, and the results are shown in Figure 2 .

[0101] Then, the adhesion test is carried out according to GB / T9286-2021, and the results are shown in Figure 2 .

[0102] Conductive adhesive performance test:

[0103] First, the conductive adhesive is coated on the upper surface of the copper foil. After curing, the adhesive force is tested according to GB / T4851-1998 standard, and the results are shown in Figure 2 .

[0104] Then, the conductive adhesive is coated in a 20 mm x 20 mm x 0.5 mm mold, and after curing, the volume resistivity is tested by a four-probe tester, and the results are shown in Figure 2 .

[0105] Comparative Example 1: The thickness of the commercially available prepreg is compared with the thickness of the insulating coating layer of Example 1, and the results are shown in Figure 3 .

[0106] From Figure 2 and Figure 3 , it can be seen that by combining two copper foils with an insulating coating to form a PCB substrate, and then using a conductive adhesive to bond the PCB substrate and normal temperature pressing to form an arbitrary layer interconnection high-density circuit board, compared with the traditional circuit board obtained by layer-by-layer high temperature pressing of prepreg and copper foil, it has the advantages of being lighter and thinner. At the same time, due to the good insulating properties of the insulating coating and the good conductivity of the conductive adhesive, the arbitrary layer interconnection high-density circuit board obtained can work normally under the premise of being lighter, thinner and smaller.

[0107] Comparative Example 2: The difference between this comparative example and Example 1 is that only the flaky silver powder in Step S1 is replaced with an equal amount of spherical silver powder, and then the conductive performance of the conductive adhesive is tested according to the performance test method in Example 1, and the results are shown in Table 2. Figure 4

[0108] From Figure 2 and Figure 4 it can be seen that by mixing the flaky silver powder and the spherical silver powder in a certain proportion with γ-glycidoxypropyltrimethoxysilane for modification, and then fully mixing with the intermediate prepared from butyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate and lauryl acrylate, etc. as raw materials, the volume resistivity of the conductive adhesive can be effectively reduced, and the conductivity of the conductive adhesive can be improved. In addition, the conductive adhesive also has excellent holding power, thereby prolonging the service life of the circuit board.

[0109] Comparative Example 3: The difference between this comparative example and Example 1 is that the step of preparing the modifier in Step S4 is removed, i.e. the epoxy resin and diamino diphenylmethane are dissolved in diethyl ether, and then modified nano boron nitride and activated alumina are added to prepare the insulating coating, and then the performance of the insulating coating prepared in Comparative Example 3 is tested according to the performance test method of the insulating coating in Example 1, and the results are shown in Table 3. Figure 5

[0110] From the performance test results, it can be seen that by using phenyltriethoxysilane and β-3,4-epoxycyclohexylethyltrimethoxysilane as raw materials to prepare the modifier, and then mixing with the epoxy resin to modify the epoxy resin, the adhesion of the epoxy resin can be improved.

[0111] Comparative Example 4: The difference between this comparative example and Example 1 is that the activated alumina in Step S4 is removed, and then the adhesion of the insulating coating prepared in Comparative Example 4 is tested according to the adhesion test method of the insulating coating in Example 1, and the results are shown in Table 4. Figure 5

[0112] From the test results, it can be seen that the adhesion and insulation performance of the prepared insulating coating can be further improved by adding activated alumina, preventing the copper foil from falling off, thereby prolonging the service life of the circuit board.

[0113] Comparative Example 5: The difference between this comparative example and Example 1 is that Step S2 is removed, and the modified nano boron nitride in Step S4 is removed, and then the insulation performance of the insulating coating prepared in Comparative Example 5 is tested according to the insulation performance test method of the insulating coating in Example 1, and the results are shown in Table 5. Figure 6

[0114] ​​​​From the performance test results, it can be seen that by mixing the nano boron nitride powder with sodium hydroxide solution for surface pretreatment, then mixing with hydrochloric acid dopamine for modification, adding the modified nano boron nitride into the epoxy resin, the insulation performance of the prepared insulation coating can be improved, so as to ensure the normal work of the prepared any layer interconnection high density circuit board.

[0115] The above examples only illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A process for manufacturing an arbitrary layer interconnection high density wiring board, characterized by, It comprises the following steps: S1: modifying silver powder and preparing conductive adhesive S1.1: add flaky silver powder and spherical silver powder into a planetary centrifugal stirrer at a mass ratio of 3-5:6-8, then add anhydrous ethanol at a solid-liquid ratio of 1g:10-12mL and γ-glycidoxypropyltrimethoxysilane accounting for 3-5% of the total mass of flaky silver powder and spherical silver powder, stir and mix uniformly, then place in an oven and dry at 60-80℃ for 2-3h to obtain modified silver powder; S1.2: add butyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate and lauryl acrylate into a mixing tank, then add γ-methacryloyloxypropyltrimethoxysilane and ethyl acetate into the mixing tank, stir and mix thoroughly to obtain a premix; S1.3: introduce nitrogen into the reactor until all air is expelled, then add 2 / 3 of the above premix into the reactor, heat at 70-80℃ for 30-40min while stirring at a speed of 300-400r / min; S1.4: adjust the stirring speed to 100-200r / min, add the remaining premix, β-hydroxyethyl acrylate and 70-80% ammonium persulfate into the reactor, react for 3-5h, then add the remaining ammonium persulfate and continue to react for 1-2h, then naturally cool to room temperature to obtain an intermediate; S1.5: add trimethylhexamethylene diisocyanate to the above intermediate, stir and mix thoroughly, then add the above modified silver powder, continue to stir and mix while performing ultrasonic treatment, then vacuum degas to obtain a conductive adhesive; S2: surface pretreatment of nano boron nitride powder and modification with dopamine hydrochloride Heat and stir nano boron nitride powder and sodium hydroxide solution to perform surface pretreatment on the nano boron nitride powder, then uniformly mix with a mixed solution prepared by mixing aminomethane buffer and ethanol at a volume ratio of 2-4:1, and add dopamine hydrochloride for modification to obtain modified nano boron nitride; The mixed solution is prepared by mixing aminomethane buffer and ethanol at a volume ratio of 2-4:1; S3: γ-glycidoxypropyltrimethoxysilane activated alumina Dissolve γ-glycidoxypropyltrimethoxysilane in ethanol, then add acetic acid until the PH is adjusted to 3-4, then add alumina, heat and reflux at 60-70℃ for 5-6h while stirring, then naturally cool to room temperature, perform suction filtration, ethanol washing and drying to obtain activated alumina; S4: add phenyltriethoxysilane to prepare a modifier, then prepare an insulating coating Mix anhydrous ethanol, anhydrous methanol, hydrochloric acid, deionized water, phenyltriethoxysilane and β-3,4-epoxycyclohexylethyltrimethoxysilane to prepare a modifier, then mix with epoxy resin, diamino diphenylmethane, the above modified nano boron nitride and the above activated alumina to obtain an insulating coating; S5: prepare a substrate and cold-press the substrate Coat the above insulating coating on the surface of a copper foil, then adhere another copper foil to form a PCB substrate, laser drill and electroplate copper to fill the holes of the PCB substrate, then adhere through the above conductive adhesive and cold-press to obtain an arbitrary layer interconnection high-density circuit board.

2. The process for manufacturing an arbitrary layer interconnection high density printed circuit board according to claim 1, wherein The surface pretreatment of the nano boron nitride powder in step S2 and modification with dopamine hydrochloride are specifically as follows: S2.1: The sodium hydroxide solution is put into a heating box, and then the nano boron nitride powder is added into the heating box at a solid-liquid ratio of 1 g:25-35 mL. The mixture is heated at a temperature of 100-120°C for 12-16 h while stirring with a stirrer to obtain a suspension; S2.2: The suspension is filtered, and the filter residue is washed with deionized water for 3-5 times and dried in a vacuum drying box for 20-24 h. After grinding, the surface pretreatment boron nitride powder is obtained; S2.3: The surface pretreatment boron nitride powder and the mixed solution are added into a mixing box at a solid-liquid ratio of 1 g:80-90 mL, and stirred and dispersed to obtain a suspension; S2.4: The dopamine hydrochloride is added into the suspension at a solid-liquid ratio of 1 g:300-400 mL, and stirred at a speed of 200-300 r / min for 4-6 h with a stirrer. After centrifugal filtration, deionized water washing, drying and grinding, the modified nano boron nitride is obtained.

3. The process for manufacturing an arbitrary layer interconnection high density printed circuit board according to claim 2, wherein The preparation of the modifier by adding phenyl triethoxysilane in step S4 and the preparation of the insulating coating are specifically as follows: S4.1: Anhydrous ethanol, anhydrous methanol, hydrochloric acid and deionized water are added into a reaction box at a volume ratio of 5-6:3-5:1-2:7-8, and fully stirred and mixed; S4.2: Phenyl triethoxysilane and β-3,4-epoxycyclohexyl ethyl trimethoxysilane are added into the reaction box, and stirred for 46-48 h to obtain a precursor solution; S4.3: Sodium hydroxide solution is added into the reaction box until the pH of the precursor solution is adjusted to 7-8, and then a vacuum distillation device in the reaction box is started to perform vacuum distillation on the precursor solution. After washing and drying, the modifier is obtained; S4.4: Epoxy resin, the modifier and diamino diphenyl methane are dissolved in diethyl ether at a mass ratio of 5-8:1-2:1, and then the modified nano boron nitride and activated alumina are added. After fully mixing, the insulating coating is obtained.

4. The process for manufacturing an arbitrary layer interconnection high density printed circuit board according to claim 3, wherein The preparation of the substrate and the cold pressing of the substrate in step S5 are specifically as follows: S5.1: The insulating coating is uniformly coated on the upper surface of a copper foil to form an insulating layer, and then another copper foil is attached to the insulating layer. After the insulating coating is dried and cured, a PCB substrate is obtained; S5.2: A plurality of the PCB substrates are laser drilled according to requirements, and the drilled holes are filled with copper by electroplating to obtain pretreated substrates; S5.3: The conductive adhesive prepared in step S1.5 is uniformly coated on the upper surface of the pretreated substrate, and then another pretreated substrate is attached to the conductive adhesive. This process is repeated until the desired number of layers is reached. After cold pressing, an arbitrary layer interconnection high-density circuit board is obtained.

5. The process for manufacturing an arbitrary layer interconnection high density printed circuit board according to claim 1, wherein The conductive adhesive comprises 30-40 parts by mass of butyl acrylate, 20-30 parts by mass of methyl methacrylate, 20-30 parts by mass of 2-ethylhexyl acrylate, 8-10 parts by mass of lauryl acrylate, 2-3 parts by mass of γ-methacryloxypropyltrimethoxysilane, 40-50 parts by mass of ethyl acetate, 6-8 parts by mass of β-hydroxyethyl acrylate, 3-5 parts by mass of ammonium persulfate, 1-3 parts by mass of trimethylhexamethylene diisocyanate, and 70-80 parts by mass of modified silver powder.

6. The process for manufacturing an arbitrary layer interconnection high density printed circuit board according to claim 3, wherein The mass ratio of phenyltriethoxysilane to β-3,4-epoxycyclohexylethyltrimethoxysilane is 6-8:1, and the molar ratio of the total moles of phenyltriethoxysilane and β-3,4-epoxycyclohexylethyltrimethoxysilane to deionized water is 1:2-3.

7. The process for manufacturing an arbitrary layer interconnection high density printed circuit board according to claim 3, wherein The mass ratio of modified nanometer boron nitride and activated alumina to epoxy resin is 1:20-30 and 1:10-20, respectively.

8. A high-density interconnect board of arbitrary layers, characterized by, It is prepared by the preparation process of any layer interconnection high-density circuit board according to any one of claims 1-7.

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