CN114988401A

CN114988401A - Method for directly blackening PCB modified graphene oxide

Info

Publication number: CN114988401A
Application number: CN202210530239.4A
Authority: CN
Inventors: 刘政; 潘志文; 陈伟长; 宋涛
Original assignee: Nantong Circuit Electronic Co ltd
Current assignee: Nantong Circuit Electronic Co ltd
Priority date: 2022-05-16
Filing date: 2022-05-16
Publication date: 2022-09-02
Anticipated expiration: 2042-05-16
Also published as: CN114988401B

Abstract

The invention provides a method for directly blackening a porous circuit board by graphene oxide, which is characterized by comprising the following steps of: (1) cleaning a circuit board, removing glue, putting the circuit board into GO-solution for a period of time, taking out, cleaning and drying; (2) putting the circuit board obtained in the step (1) into a GO + solution for a period of time, taking out, cleaning and drying; (3) putting the circuit board obtained in the step (2) into a reducing agent for reaction, taking out, cleaning and drying; (4) and (4) carrying out electroplating treatment on the surface of the circuit board obtained in the step (3) to obtain the graphene oxide direct black hole circuit board. With the increase of the number of graphene oxide adsorption layers, the conductivity of the graphene oxide is better, so that the time and current power of the subsequent electroplating process are reduced, and the cost is saved.

Description

Method for directly blackening PCB modified graphene oxide

Technical Field

The invention belongs to the technical field of printed boards, and particularly relates to a method for directly blackening a PCB (printed circuit board) modified graphene oxide.

Background

Pcb (printed circuit board), i.e. printed wiring board, printed circuit board for short, is one of the important parts in the electronics industry. Almost every kind of electronic equipment, as small as electronic watches, calculators, as large as computers, communication electronics, military weaponry systems, has electronic components such as integrated circuits, and printed boards are used to electrically interconnect the various components. With the continuous development of electronic technology, the demand of multilayer high-density interconnected circuit boards is gradually increased, and the core problem is how to realize the electrical interconnection between each layer of boards, i.e. the hole metallization process.

The current hole metallization process mainly includes three kinds. The first is the most used chemical copper deposition method at present, which is mainly to deposit a layer of copper on a non-conductive substrate by a series of chemical treatment methods, and then thicken by a subsequent electroplating method to achieve the purpose of electrical interconnection; the second is that conductive materials such as graphite or carbon black are adsorbed on a non-conductive base material, and then a thicker copper layer is formed in the hole through electroplating; the third is to use conductive polymer material, such as thiophene, pyrrole, etc. as conductive material to be adsorbed on the non-conductive substrate, and thicken the copper layer by electroplating.

Specifically, the method comprises the following steps:

(1) the chemical copper deposition method is mature, but the pollution is serious, and the chemical copper deposition method contains substances harmful to human bodies, such as formaldehyde and the like; most of carbon black and graphite are large-particle-size particles, so that the dispersibility is poor, the carbon black and the graphite are easy to settle in an aqueous solution, the adsorption capacity is poor, the conductivity is poor, and a compact conductive layer is difficult to form on a substrate; the conductivity of the conductive polymer material is poorer than that of carbon black and the like, high-temperature cracking is easy to occur in the using process, the production control difficulty is high, and the development of the conductive polymer material is limited.

For the above reasons, it is currently desired to replace the conventional electroless copper deposition process with a carbon-based material having relatively good conductivity, such as graphene, as the conductive material adsorbed on the non-conductive substrate. Graphene is a two-dimensional crystal formed by combining benzene six-membered rings without any unstable bonds, has high chemical stability, is in an inert state on the surface, has weak interaction with other solvents, and has strong van der waals force between graphene sheets, and is easy to aggregate, so that graphene is difficult to dissolve in water and common organic solvents, and further research and application of graphene are greatly difficult. Therefore, before graphene is used, graphene generally needs to be subjected to oxidation treatment, and the obtained graphene oxide sheet layer contains rich oxygen-containing groups, and the functional groups have strong polarity, so that the graphene oxide has good solubility in water, and the subsequent production is facilitated.

(2) The oxygen-containing groups on the surface of the graphene oxide, such as hydroxyl, carboxyl, epoxy and the like, are electronegative in aqueous solution, so that the adsorption process is similar to that of a chemical copper deposition method, the pore wall is positively charged after pore preparation, and a conductive layer is formed in the pore through electrostatic adsorption with the negatively charged graphene oxide, but the graphene oxide breaks the conjugated structure of the graphene due to the introduction of the oxide groups, so that the conductivity of the graphene is remarkably reduced, and therefore the graphene oxide is not conductive, and needs to be reduced after pore preparation adsorption, so that the conductive graphene is obtained. Graphene oxide is a sheet structure, a compact thin film is easily formed on a hole wall, but the thickness of the graphene oxide is only a few nm, so that in order to avoid defects such as film breakage and the like in the subsequent process flow from affecting the conductivity in the hole, the whole-hole adsorption process is generally required to be carried out for many times to ensure that the inside of the hole is completely covered by graphene oxide, the conductivity is enhanced, and the process flow and the cost are increased by repeating the whole-hole adsorption process.

(3) The positive charge of the graphene oxide is mainly realized by grafting amino on the graphene oxide, so that the graphene oxide is positively charged in a solution. The most ideal method at present is to directly condense carboxyl and amino on graphene oxide, the only byproduct is water, but due to the acidity of carboxyl and the alkalinity of amino, only ammonium salt can be generated after the carboxyl and the amino are mixed, and therefore the method is not suitable. The following are common methods for grafting carboxyl and amino groups: acyl chloride method; ② mixed anhydride method; ③ active ester method. Among them, acyl chloride (such as CN201410361609.1) has a fast reaction rate, but easily causes racemization of alpha position of carboxylic acid, and the acylation reagent generates hydrogen sulfide, easily causes the destruction of acid-sensitive group in the substrate; in the mixed anhydride method, carboxylic acid is easy to react with amine to cause the problem of nonselectivity of reaction areas, and the mixed anhydride can generate disproportionation reaction to generate symmetrical anhydride; the active ester method is mainly to graft amino onto graphene oxide by reacting carboxylic acid under the action of alcohol or acid to dehydrate to generate an ester intermediate and then using the ester intermediate and amine to generate amide, but the reaction needs to be carried out in toxic and harmful dichloromethane. There is also currently a method for preparing an amide bond from a carbodiimide compound (R-N ═ C ═ N-R), in which a carbodiimide is converted into an O-acylisourea intermediate (formula 1) and then reacted with an amine to obtain the target amide bond (formula 2), but the intermediate is also subject to 1, 3-rearrangement to produce an N-acylurea (formula 3), which is irreversible, and the degree of amination of the product is reduced since the N-acylurea is not reacted with the amine.

Disclosure of Invention

Aiming at the problems, the invention provides a PCB black hole method for directly adsorbing graphene oxide without using a whole hole agent.

Based on the solution of the above problems, the present invention provides a method for directly blackening a porous circuit board with graphene oxide, which includes a preparation method of modified negative charge graphene oxide and a preparation method of modified positive charge graphene oxide.

The full English name and Chinese definition of the abbreviations presented in this invention are listed.

PCB Printed Circuit Board

GO: graphene oxide

GO +: positive charge graphene oxide

GO-: negatively charged graphene oxide.

The invention provides a preparation method of negative charge graphene oxide, which is characterized by comprising the following steps: (1) adding concentrated sulfuric acid into a reaction container, then adding graphite powder, persulfate and phosphorus oxide, diluting after the reaction is finished, and filtering, washing and drying the solution to obtain a graphite solution; (2) adding concentrated sulfuric acid into the graphite solution obtained in the step (1), then adding potassium permanganate, after the reaction is finished, adding water for dilution, and then adding hydrogen peroxide for reaction to obtain an intermediate solution; (3) and (3) taking out the supernatant obtained in the step (2), washing with an acid solution, filtering and drying the precipitate, dispersing in water, dialyzing the dispersion, centrifuging and drying to obtain negative charge graphene oxide GO-.

According to the preparation method of the negatively charged graphene oxide, in the step (1), the reaction is carried out at 0-100 ℃, preferably at 30-100 ℃, more preferably at 50-100 ℃, and even more preferably at 50-80 ℃.

According to the preparation method of the negative charge graphene oxide, the reaction time in the step (1) is 0.1-24 hours, preferably 1-20 hours, more preferably 1-10 hours, and further preferably 3-5 hours.

According to the preparation method of the negatively charged graphene oxide, the water in the step (1) is preferably deionized water.

According to the preparation method of the negative charge graphene oxide, the persulfate in the step (1) is one or more of potassium persulfate, sodium persulfate, ammonium persulfate and calcium persulfate.

According to the preparation method of the negative charge graphene oxide, the phosphorus oxide in the step (1) is phosphorus pentoxide or phosphorus trioxide; preferably phosphorus pentoxide.

According to the preparation method of the negative charge graphene oxide, the mass ratio of the graphite powder to the persulfate to the phosphorus oxide in the step (1) is 1: 0.1-1, and preferably 1: 0.1-0.5.

According to the preparation method of the negative charge graphene oxide, the filtration in the step (1) is performed by adopting a filter membrane; the filter membrane is preferably a glass fibre filter membrane.

According to the preparation method of the negative charge graphene oxide, potassium permanganate is added under an ice bath condition in the step (2), and the reaction temperature is kept below 10 ℃.

According to the preparation method of the negative charge graphene oxide, after the potassium permanganate is added in the step (2), the reaction is heated and continues to react. Preferably, the temperature in the temperature-raising reaction is 20 to 100 ℃, more preferably 20 to 80 ℃, further preferably 30 to 50 ℃, and most preferably 35 ℃. The reaction time is 0.1-24 h, preferably 1-20 h, more preferably 1-10 h, and further preferably 1-3 h.

According to the preparation method of the negative charge graphene oxide, the water used for diluting in the step (2) is preferably deionized water.

According to the preparation method of the negative charge graphene oxide, the continuous reaction in the step (2) further comprises the steps of adding water into the system for continuous reaction, placing the system in an ice bath when adding water, and raising the temperature after the water is added. Preferably the water is deionized water. Preferably, the temperature is 20-100 ℃, more preferably 20-80 ℃, further preferably 30-50 ℃, and most preferably 35 ℃. The reaction time is 0.1-24 h, preferably 0.5-20 h, more preferably 0.5-10 h, and further preferably 0.5-3 h.

According to the preparation method of the negative charge graphene oxide, in the step (3), the acid is hydrochloric acid, sulfuric acid, nitric acid or acetic acid; the water is preferably deionized water.

According to the preparation method of the negative charge graphene oxide, the mass ratio of the graphite powder, the potassium permanganate and the hydrogen peroxide is 1: 1-20, preferably 1: 1-20: 1-10, more preferably 1: 2-20: 1-10, and further preferably 1: 3-20: 1-8.

The second aspect of the present invention includes a method for preparing a modified positively-charged graphene oxide, which is characterized by comprising the following steps: (1) dispersing the negatively charged graphene oxide GO-of any preceding claim in water, sonicating; (2) adding a dehydrating agent and an inhibitor respectively, then adding amine, and fully reacting to obtain a suspension; (3) and dialyzing and drying to obtain the modified positive charge graphene oxide GO +.

According to the preparation method of the modified positive charge graphene oxide, the dehydrating agent is selected from one or more of DCC (N, N '-dicyclohexylcarbodiimide), DIC (N, N' -diisopropylcarbodiimide), EDC (1-ethyl- (3-dimethylaminopropyl) carbodiimide) or 1, 3-di-p-tolylcarbodiimide.

According to the preparation method of the modified positive charge graphene oxide, the mass ratio of the dehydrating agent to GO-is 1-100: 1, preferably 1-50: 1, more preferably 5-50: 1, and further preferably 5-20: 1.

According to the preparation method of the modified positive charge graphene oxide, the inhibitor is selected from one or more of 4-dimethylamino pyridine, N-hydroxysuccinimide, 1-hydroxybenzotriazole, 1-hydroxy-7-azabenzotriazole or 2-cyano-2- (hydroxyimine) ethyl acetate.

According to the preparation method of the modified positive charge graphene oxide, the mass ratio of the inhibitor to GO-is 0-1000: 1, preferably 1-1000: 1, more preferably 2-1000: 1, and further preferably 10-100: 1.

According to the preparation method of the modified positive charge graphene oxide, the amine is preferably diamine, one amino group and carboxyl group form an amido bond in the reaction process, and one amino group is in positive charge, such as ethylenediamine, butanediamine, hexanediamine, octanediamine and the like, and besides, the diamine satisfying the above requirements falls into the protection scope of the invention. Preferably, the diamines are used in excess during use.

The third aspect of the present invention includes a method for directly blackening a porous circuit board with graphene oxide, which is characterized by comprising the following steps: (1) cleaning a circuit board, removing glue, putting the circuit board into GO-solution for a period of time, taking out, cleaning and drying; (2) putting the circuit board obtained in the step (1) into a GO + solution for a period of time, taking out, cleaning and drying; (3) putting the circuit board obtained in the step (2) into a reducing agent for reaction, taking out, cleaning and drying; (4) and (4) electroplating the surface of the circuit board obtained in the step (3) to obtain the graphene oxide direct black hole circuit board.

According to the method for directly blackening the porous circuit board by using the graphene oxide, the GO-is preferably prepared by adopting the method in the first aspect of the invention.

According to the method for directly blackening the porous circuit board by using the graphene oxide, the GO + is preferably prepared by using the method of the second aspect of the invention.

According to the method for directly blackening the porous circuit board by using the graphene oxide, the period of time is shorter, such as 1-10 min, preferably 1-5 min, and more preferably 1-3 min.

According to the method for directly blackening the porous circuit board by using the graphene oxide, the reaction time of the reduction reaction is 1-10 min, preferably 1-5 min, and more preferably 1-3 min.

The main contributions of the present invention with respect to the prior art are the following:

(1) the conductive material selected by the invention is graphene oxide, has better conductivity compared with other carbon-based materials, is of a sheet structure, and is easy to form a film after being dried. And can achieve better dispersibility without adding other dispersants.

(2) The general whole-pore adsorption process needs to perform whole-pore and multiple adsorption for multiple times to achieve higher adsorption degree, the conventional repeated positive whole-pore-negative adsorption-positive whole-pore-negative adsorption and the like are not needed to form a multilayer structure, the charge property of the graphene oxide is changed, and the graphene oxide is spontaneously assembled layer by layer through electrostatic adsorption, so that the step of the whole-pore agent is reduced.

(3) In the modification process of the graphene oxide, a toxic solvent is not used, and a positively charged amino group is grafted on the graphene oxide based on an active ester method, so that the positively charged graphene oxide is obtained, few byproducts are generated, the amination degree of the graphene oxide is high, and the electrostatic adsorption capacity of the positively charged graphene oxide is enhanced.

(4) The positively charged graphene oxide is directly adsorbed on the hole wall, and then the negatively charged graphene oxide is adsorbed again, so that a multi-layer graphene oxide structure formed by layer-by-layer self-assembly under the action of electrostatic adsorption is formed without repeating the process of no over-adsorption of the whole hole, and a conductive film with good compactness is formed after reduction.

Drawings

FIG. 1: graphene oxide modification process in example 1.

FIG. 2: example 1 SEM images of graphene oxide before and after modification, wherein (a) is GO —, (b) is GO +.

FIG. 3: example 1 XPS plot of modified graphene oxide (GO +).

FIG. 4: backlight diagram after self-assembly electroplating of graphene oxide layer in PCB hole in example 1.

FIG. 5: SEM after self-assembly electroplating of graphene oxide layers within pores of PCB in example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure are clearly and completely described. It is to be understood that the described embodiments are only a few embodiments of the present disclosure, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the disclosure without any inventive step, are within the scope of protection of the disclosure.

Example 1:

adding 3mL of concentrated sulfuric acid into a round-bottom flask, adding 1g of graphite powder, 0.5g of potassium persulfate and 0.5g of phosphorus pentoxide into the flask respectively, reacting at 80 ℃ for 5 hours, and diluting with 1L of deionized water. Filtering the graphite solution by using a glass fiber filter membrane with the aperture of 1.5 microns, then washing the graphite solution by using deionized water again, and drying the graphite solution at room temperature.

② adding the pretreated graphite into 26mL of concentrated sulfuric acid, and stirring in a flask until the graphite is uniformly dispersed. Under the ice-bath condition, 3g of potassium permanganate is slowly added into the flask, and the reaction temperature is ensured to be below 10 ℃. After all additions, the flask was heated to 35 ℃ and reacted for 1 h. Then the flask was placed in an ice bath, 46mL of deionized water was added to the mixture, after stirring at 35 ℃ for 0.5h, heating was stopped, after dilution with 140mL of deionized water, 2.5mL of 30% hydrogen peroxide was added to obtain a bubbling bright yellow intermediate solution.

Taking out supernatant of the mixed solution, thoroughly washing the residual precipitate with 10% hydrochloric acid solution, and filtering. The resulting solid was dried and dispersed in deionized water and the dispersion was dialyzed against a dialysis membrane to remove residual metal or chemical residues. And (4) centrifuging and washing the dispersion liquid for multiple times, and drying to obtain graphene oxide GO-.

And fourthly, dispersing 50mg of graphene oxide powder in 100mL of deionized water, and performing ultrasonic dispersion for 30 min.

Selecting 1-ethyl- (3-dimethylaminopropyl) carbodiimide as a dehydrating agent, adding 0.5g of the 1-ethyl- (3-dimethylaminopropyl) carbodiimide into the GO solution, stirring vigorously, immediately adding 1.5g of 1-hydroxybenzotriazole, reacting for a period of time, adding 10mL of ethylenediamine, and stirring at room temperature for reacting overnight.

Sixthly, dispersing and dialyzing the synthesized suspension in 1L of deionized water to remove residual actual and by-products, and drying to obtain GO +.

GO-washing and removing glue of circuit board, putting into 0.5 mg/mLGO-solution for processing for 3min, taking out, washing and drying.

(viii) GO +: and (3) putting the circuit board in the step (I) into 0.5mg/mLGO + solution for treatment for 3min, taking out, cleaning and drying.

Ninthly, reduction: and (4) putting the circuit board obtained in the step two into a reducing agent for reaction for 3min, taking out, cleaning and drying.

Electroplating on the red: and (4) electroplating the surface of the circuit board obtained in the step (III) to obtain the graphene oxide direct black hole circuit board.

Example 2:

② adding the pretreated graphite into 26mL of concentrated sulfuric acid, and stirring in a flask until the graphite is uniformly dispersed. Under the ice-bath condition, 2g of potassium permanganate is slowly added into the flask, and the reaction temperature is ensured to be below 10 ℃. After all additions, the flask was heated to 35 ℃ and reacted for 1 h. Then the flask was placed in an ice bath, 46mL of deionized water was added to the mixture, after stirring at 35 ℃ for 0.5h, heating was stopped, after dilution with 140mL of deionized water, 2.5mL of 30% hydrogen peroxide was added to obtain a bubbling bright yellow intermediate solution.

(viii) GO +: and (4) putting the circuit board obtained in the step (i) into a 0.5mg/mLGO + solution for treatment for 3min, taking out, cleaning and drying.

Example 3:

② adding the pretreated graphite into 26mL of concentrated sulfuric acid, and stirring in a flask until the graphite is uniformly dispersed. Under the ice-bath condition, 1g of potassium permanganate is slowly added into the flask, and the reaction temperature is ensured to be below 10 ℃. After all the addition was complete, the flask was heated to 35 ℃ and reacted for 1 h. Then the flask was placed in an ice bath, 46mL of deionized water was added to the mixture, after stirring at 35 ℃ for 0.5h, heating was stopped, and after diluting with 140mL of deionized water, 5mL of 30% hydrogen peroxide was added to obtain a bubbling bright yellow intermediate solution.

Example 4:

And GO-washing and removing glue of the circuit board, putting the circuit board into 1 mg/mLGO-solution for processing for 2min, taking out, washing and drying.

(viii) GO +: and (3) putting the circuit board obtained in the step (i) into a 1mg/mLGO + solution for treatment for 2min, taking out, cleaning and drying.

Example 5:

Adding the pretreated graphite into 26mL of concentrated sulfuric acid, and stirring in a flask until the graphite is uniformly dispersed. Under the ice-bath condition, 3g of potassium permanganate is slowly added into the flask, and the reaction temperature is ensured to be below 10 ℃. After all additions, the flask was heated to 35 ℃ and reacted for 1 h. Then the flask was placed in an ice bath, 46mL of deionized water was added to the mixture, after stirring was continued for 0.5h at 35 ℃, heating was stopped, and after dilution with 140mL of deionized water, 2.5mL of 30% hydrogen peroxide was added to obtain an effervescent bright yellow intermediate solution.

Sixthly, dispersing and dialyzing the synthesized suspension in 1L of deionized water to remove residual practical and by-products, and drying to obtain GO +.

And GO-washing and removing glue of the circuit board, putting the circuit board into 2 mg/mLGO-solution for processing for 1min, taking out, washing and drying.

(viii) GO +: and (3) putting the circuit board in the step (I) into a 2mg/mLGO + solution for treatment for 1min, taking out, cleaning and drying.

Ninthly, reduction: and (4) putting the circuit board obtained in the step (II) into a reducing agent for reacting for 3min, taking out, cleaning and drying.

Comparative example 1

Selecting 1-ethyl- (3-dimethylaminopropyl) carbodiimide as a dehydrating agent, adding 0.5g of the dehydrating agent into the GO solution, adding 10mL of ethylenediamine after vigorously stirring and reacting for a period of time, and stirring and reacting at room temperature overnight.

Electroplating in red: and (4) electroplating the surface of the circuit board obtained in the step (III) to obtain the graphene oxide direct black hole circuit board.

Comparative examples 1 to 6

The inhibitor added in the fifth step is respectively 0, 0.1, 0.5, 0.8, 1.0 and 2g, and the rest are the same as the above

The oxidation and amination degree of the graphene oxide is characterized by XPS, the higher the oxidation degree of the graphene oxide is, the higher the carboxyl content is, the better the water solubility is, the more favorable the subsequent amination step is, the higher the amination degree is, the more positive charges are, and the easier the graphene oxide electrostatic adsorption layer with negative charges is to be self-assembled.

The results show that:

the use amount of potassium permanganate is increased, the oxidation degree of graphene oxide is increased, oxygen-containing groups such as carboxyl and the like are increased, subsequent carboxyl and amino are esterified to form an amido bond, the amino is grafted to the surface of the graphene oxide, and the amination degree is higher; the dosage of the inhibitor is gradually increased, and the amination degree of the final product is also higher, so that the inhibitor reacts with an intermediate generated in the reaction process to generate an amido bond, and the generation of byproducts is reduced; the higher the amination degree is, the more positive charges are carried on the graphene oxide, the easier the graphene oxide and the negatively charged graphene oxide form electrostatic adsorption, the better the conductivity is, and the better the final electroplating result is.

Specifically, the following description is provided:

patent CN110923771B proposes that the adsorption of graphene oxide to copper ions can be enhanced by grafting a silane coupling agent on the surface of graphene oxide, so as to improve the electroplating performance, and the modification method and graft used in the method are different from those of the present invention, and the grafting purpose is also different. After the graphene oxide is grafted with the silane coupling agent, the surface amino groups also adsorb active metal ions and finally still present negative charges, and at the moment, the graphene oxide can be adsorbed on the hole wall after the whole hole is formed.

Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.

Claims

1. A preparation method of negative charge graphene oxide is characterized by comprising the following steps: (1) adding concentrated sulfuric acid into a reaction container, then adding graphite powder, persulfate and phosphorus oxide, diluting after the reaction is finished, and filtering, washing and drying the solution to obtain a graphite solution; (2) adding concentrated sulfuric acid into the graphite solution obtained in the step (1), then adding potassium permanganate, adding water for dilution after the reaction is finished, and then adding hydrogen peroxide for reaction to obtain an intermediate solution; (3) and (3) taking out the supernatant obtained in the step (2), washing with an acid solution, filtering and drying the precipitate, dispersing in water, and dialyzing, centrifuging and drying the dispersion to obtain negative charge graphene oxide GO-.

2. The preparation method of graphene oxide with negative charge according to claim 1, wherein the step (1) is carried out at 0-100 ℃; the water is preferably deionized water; the persulfate is one or more of potassium persulfate, sodium persulfate, ammonium persulfate and calcium persulfate; the phosphorus oxide is phosphorus pentoxide or phosphorus trioxide; the filtration is performed by adopting a filter membrane, and the filter membrane is preferably a glass fiber filter membrane.

3. The method according to any one of the preceding claims, wherein in step (2), potassium permanganate is added under ice bath conditions to keep the reaction temperature below 10 ℃; after the potassium permanganate is added, the reaction is heated and continues to react; the water is preferably deionized water.

4. The method according to claim 3, wherein the further reaction comprises adding water to the system, placing the system in an ice bath while adding water, and raising the temperature after the water is added.

5. The method according to any one of the preceding claims, wherein in the step (3), the acid is hydrochloric acid, sulfuric acid, nitric acid or acetic acid; the water is preferably deionized water.

6. The preparation method of negative charge graphene oxide according to any one of the preceding claims, wherein the mass ratio of the raw materials of graphite powder, potassium permanganate and hydrogen peroxide is 1: 1-20.

7. A preparation method of modified positive charge graphene oxide is characterized by comprising the following steps: (1) dispersing the negatively charged graphene oxide GO-of any preceding claim in water, sonicating; (2) respectively adding a dehydrating agent and an inhibitor, then adding amine, and fully reacting to obtain a suspension; (3) and dialyzing and drying to obtain the modified positive charge graphene oxide GO +.

8. The method of claim 7, wherein the dehydrating agent is one or more selected from DCC (N, N '-dicyclohexylcarbodiimide), DIC (N, N' -diisopropylcarbodiimide), EDC (1-ethyl- (3-dimethylaminopropyl) carbodiimide), and 1, 3-di-p-tolylcarbodiimide.

9. The method for preparing modified graphene oxide with positive charge according to any one of claims 7 to 8, wherein the inhibitor is selected from one or more of 4-dimethylamino pyridine, N-hydroxysuccinimide, 1-hydroxybenzotriazole, 1-hydroxy-7-azabenzotriazole or ethyl 2-cyano-2- (hydroxyimine) acetate.

10. A method for directly blackening a porous circuit board by graphene oxide is characterized by comprising the following steps: (1) cleaning a circuit board, removing glue, putting the circuit board into GO-solution for a period of time, taking out, cleaning and drying; (2) putting the circuit board obtained in the step (1) into a GO + solution for a period of time, taking out, cleaning and drying; (3) putting the circuit board obtained in the step (2) into a reducing agent for reaction, taking out, cleaning and drying; (4) electroplating the surface of the circuit board obtained in the step (3) to obtain a graphene oxide direct black hole circuit board; said GO-is prepared by the method of any one of claims 1 to 6, and said GO + is prepared by the method of any one of claims 7 to 9.