Graphene dispersion liquid, preparation method and application thereof

Abstract

The application discloses a graphene dispersion liquid and a preparation method and application thereof, and belongs to the technical field of PCBs.The graphene dispersion liquid provided by the application comprises modified graphene and a dispersing agent; the pH of the graphene dispersion liquid is 2-6; the modified graphene is TSiPD modified graphene; and the dispersing agent is a mixed aqueous solution of sodium bromide and sodium hypochlorite.The graphene dispersion liquid provided by the application can be used for hole metallization of PCBs, and can significantly improve the uniformity of the conductivity in the holes and the adhesion strength between the graphene and the hole walls.The application further provides a preparation method and application of the graphene dispersion liquid.

Description

Technical Field

[0001] This invention relates to the field of PCB technology, and in particular to a graphene dispersion, its preparation method, and its application. Background Technology

[0002] With the rapid development of technology, electronic products are not only evolving towards being lighter, thinner, shorter, smaller, and more intelligent. Printed circuit boards (PCBs), as the foundation of the electronic information industry, also face a series of technical bottlenecks and challenges, specifically covering raw materials, production technology, environmental protection, and equipment. Hole metallization refers to the process of plating a layer of conductive metal onto the insulating hole walls of printed conductors in each layer using chemical plating and electroplating methods, enabling reliable interconnection. The core issue in the manufacturing process of double-sided printed circuit boards with metallized holes is the hole metallization process itself. Hole metallization technology, as a crucial link in PCB production and a key process for interlayer interconnection, is particularly important in PCB manufacturing.

[0003] Traditional techniques typically employ either chemical copper plating followed by electroplating, or direct electroplating. Chemical copper plating has unavoidable drawbacks, including difficulty in controlling costs, a lengthy process, potential quality issues (chemical copper is highly susceptible to oxidation), and environmental problems (requiring toxic substances like cyanide). Direct electroplating methods include black-hole plating, which involves adding carbonaceous powders such as graphite to the plating solution to increase conductivity. However, this method results in uneven copper plating within the holes and poor adhesion.

[0004] Graphene is a new material with a single-layer sheet structure composed of carbon atoms. It has advantages such as fast heat transfer, fast electron transport, large specific surface area, and strong mechanical properties, and therefore has broad application prospects in the field of electronic technology.

[0005] To address the numerous issues in PCB hole metallization, some researchers have attempted to use graphene to replace copper in chemical copper plating. However, graphene treatment can easily lead to uneven conductivity within the holes, resulting in uneven copper plating in the subsequent process. Furthermore, the graphene-modified material is prone to peeling off. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a graphene dispersion that can be used for hole metallization in PCB boards, significantly improving the uniformity of conductivity within the holes and the adhesion strength between graphene and the hole walls.

[0007] The present invention also provides a method for preparing the above-mentioned graphene dispersion.

[0008] This invention also provides applications of the above-mentioned graphene dispersion.

[0009] According to an embodiment of a first aspect of the present invention, a graphene dispersion is provided, the graphene dispersion comprising modified graphene and a dispersant;

[0010] The pH of the graphene dispersion is 2 to 6;

[0011] The modified graphene is TSiPD-modified graphene;

[0012] The dispersant is a mixed aqueous solution of sodium bromide and sodium hypochlorite.

[0013] The graphene dispersion according to embodiments of the present invention has at least the following beneficial effects:

[0014] (1) The modifier used in this invention is TSiPD, with the following structural formula:

[0015]

[0016] In graphene dispersions, it can adsorb onto the graphene surface, preventing interlayer recombination of graphene and thus improving the dispersion uniformity of the graphene dispersion; when used for hole metallization in PCBs, it can significantly improve the conductivity uniformity within the holes.

[0017] Furthermore, the dispersant has silanol groups on its surface, which gives it a strong adsorption effect on plastic or inorganic material surfaces. In addition, the silanol groups can undergo cross-linking polymerization during the water evaporation process in the aqueous solution, thereby enhancing the adsorption strength between graphene and PCB pore structure.

[0018] (2) The dispersant provided by the present invention includes sodium bromide and sodium hypochlorite, thereby adjusting the surface tension of the dispersant to be closer to that of graphene, thereby improving the uniformity of graphene dispersion in graphene dispersion.

[0019] (3) The present invention limits the pH of the graphene dispersion to 2 to 6. Within this range, TSiPD can exist stably. However, during its use, as the water in the dispersant evaporates, its overall acidity increases, which can promote the hydrolysis and polymerization of TSiPD, thereby improving its hardness and adsorption strength.

[0020] (4) If TSiPD is used alone for dispersion, the amount of TSiPD required is relatively large, and TSiPD is a non-conductive material, which will reduce the conductivity of the graphene dispersion. This invention uses a special dispersant in combination with TSiPD, which can balance its dispersibility, conductivity and adhesion strength between the polymer product and the substrate.

[0021] (5) The graphene dispersion provided by the present invention does not contain polymer compounds (wetting agents, surfactants, binders), thereby the graphene dispersion has a low viscosity and can pass smoothly through small-diameter holes on the PCB, improving wettability to all holes.

[0022] According to some embodiments of the present invention, the pH of the graphene dispersion is 3 to 5. Specifically, it can be approximately 4.

[0023] According to some embodiments of the present invention, the graphene dispersion contains 0.1% to 5% graphene by mass.

[0024] According to some embodiments of the present invention, the graphene dispersion contains 1 to 2% graphene by mass.

[0025] According to some embodiments of the present invention, the graphene dispersion contains 3-4% by mass of graphene.

[0026] According to some embodiments of the present invention, the mass ratio of TSiPD to graphene is 0.1 to 0.8:1.

[0027] According to some embodiments of the present invention, the mass ratio of TSiPD to graphene is 0.2 to 0.4:1.

[0028] According to some embodiments of the present invention, the mass ratio of TSiPD to graphene is 0.6 to 0.7:1.

[0029] According to some embodiments of the present invention, the molar ratio of sodium bromide to sodium hypochlorite is 1:1 to 1.5.

[0030] According to some embodiments of the present invention, the molar ratio of sodium bromide to sodium hypochlorite is 1:1.1 to 1.3. For example, it can be approximately 1:1.2.

[0031] According to some embodiments of the present invention, the sodium bromide in the dispersant comprises 1-3% by mass.

[0032] According to some embodiments of the present invention, the sodium bromide in the dispersant comprises 1.5% to 2.5% by mass. Specifically, it may be about 2%.

[0033] According to an embodiment of a second aspect of the present invention, a method for preparing the graphene dispersion is provided, the method comprising mixing expanded graphite, TSiPD and a dispersant, and then subjecting the mixture to high-pressure homogenization.

[0034] The preparation method provided by the present invention has at least the following beneficial effects:

[0035] The preparation method provided by this invention uses expanded graphite as the raw material, which is lower in cost compared to directly using graphene. Furthermore, this invention only employs a high-pressure homogenization method, combined with a dispersant and TSiPD, to achieve graphene exfoliation and dispersion preparation. The method is simple, efficient, and easy for large-scale production.

[0036] According to some embodiments of the present invention, the pressure of the high-pressure homogenization is 80-100 MPa.

[0037] According to some embodiments of the present invention, the pressure of the high-pressure homogenizer is 85-95 MPa. For example, it can be approximately 90 MPa.

[0038] According to some embodiments of the present invention, the duration of the high-pressure homogenization is 0.25 to 2 hours.

[0039] According to some embodiments of the present invention, the duration of the high-pressure homogenization is 0.5 to 1 hour.

[0040] Within the aforementioned pressure and time range, the exfoliation effect on expanded graphite can be significantly improved, and the number of graphene layers can be reduced.

[0041] According to some embodiments of the present invention, the temperature of the high-pressure homogenization is ≤40°C. Generally speaking, the adsorption of TSiPD by graphene decreases with increasing temperature. Preparing graphene dispersions within the above temperature range can effectively prevent further recombination of the exfoliated graphene and effectively improve the dispersion uniformity of the graphene dispersion.

[0042] According to some embodiments of the present invention, the temperature of the high-pressure homogenization is ≤30°C.

[0043] According to some embodiments of the present invention, the preparation method further includes adjusting the pH of the dispersant prior to the mixing. This avoids the hydrolytic polymerization of the TSiPD during use.

[0044] The pH-adjusting agent for the dispersant includes hydrobromic acid. The concentration of the hydrobromic acid is 15–20 wt%.

[0045] According to an embodiment of a third aspect of the present invention, a PCB is provided, wherein the raw materials for preparing the PCB include the graphene dispersion and a PCB substrate;

[0046] The PCB substrate has holes.

[0047] Since the PCB adopts all the technical solutions of the graphene dispersion described in the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments. Specifically, when the graphene dispersion fills the holes and dries, the conductivity and conductivity uniformity of the hole walls are significantly improved, providing a good foundation for subsequent uniform copper plating.

[0048] According to some embodiments of the present invention, the PCB substrate includes an insulating layer and copper cladding layers disposed on both sides of the insulating layer.

[0049] According to some embodiments of the present invention, the insulating layer is made of at least one of epoxy resin, phenolic resin, polyester, polyimide ester, polyolefin resin, polyurethane and polycyanate resin.

[0050] According to some embodiments of the present invention, the diameter of the hole is ≤0.15mm.

[0051] According to some embodiments of the present invention, the hole ring is ≤0.25mm.

[0052] In the PCB where the graphene dispersion of the present invention is applied, the pore size is relatively small. Therefore, the graphene dispersion in the graphene dispersion needs to have a higher degree of dispersion, moderate viscosity, and higher wettability in order to form a uniform conductive layer inside the pore.

[0053] According to an embodiment of a fourth aspect of the present invention, a method for manufacturing the PCB is provided, the method comprising filling the pores with the graphene dispersion and drying it.

[0054] Since the manufacturing method adopts all the technical solutions of the PCB in the above embodiments, it has at least all the beneficial effects brought about by the technical solutions in the above embodiments. Specifically, compared with traditional chemical copper plating, the manufacturing method provided by the present invention does not require the use of toxic or harmful chemical reagents, significantly improving environmental protection and operational safety; furthermore, it only includes two steps, filling and drying, which significantly saves production processes and costs compared with chemical copper plating.

[0055] According to some embodiments of the present invention, the manufacturing method further includes pretreating the pores before filling the graphene dispersion.

[0056] According to some embodiments of the present invention, the pretreatment includes at least one of plasma pretreatment and corona treatment.

[0057] This increases the amount of active groups on the inner wall of the pore, thereby increasing the adhesion strength between the graphene and the inner wall.

[0058] According to some embodiments of the present invention, the pretreatment time is 0.5 to 5 minutes.

[0059] According to some embodiments of the present invention, the pretreatment time is 1 to 3 minutes.

[0060] According to some embodiments of the present invention, the filling method includes soaking.

[0061] The soaking process also includes stirring the graphene dispersion with the PCB board. This increases the relative speed between the PCB board and the graphene dispersion, thereby improving the efficiency of the graphene dispersion wetting and penetrating the pores, and ultimately improving the efficiency of pore metallization.

[0062] According to some embodiments of the present invention, the stirring speed is 100 to 200 rpm.

[0063] According to some embodiments of the present invention, the stirring speed is 130 to 160 rpm. For example, it can be approximately 150 rpm.

[0064] According to some embodiments of the present invention, the soaking time is 10 to 120 seconds.

[0065] According to some embodiments of the present invention, the soaking time is 30 to 60 seconds. For example, it can be approximately 40 seconds.

[0066] According to some embodiments of the present invention, the manufacturing method further includes micro-etching and copper plating processes performed sequentially after the drying.

[0067] The purpose of the micro-etching process is to etch away the graphene adsorbed on the surface of the copper-clad layer. The duration of the micro-etching process is 30–120 seconds, specifically 50–60 seconds.

[0068] The purpose of copper plating is to fully fill the holes with copper. The copper plating process takes 15 to 30 minutes, specifically about 20 minutes.

[0069] The copper plating process is electroplating. The electroplating current is 10–20 A / dm². 2 .

[0070] In this invention, there are no strict requirements for the micro-etching treatment system and the copper plating treatment system; any existing industrial methods can be used.

[0071] Unless otherwise specified, the term "about" in this invention actually means that the error is allowed to be within ±2%, for example, about 100 is actually 100 ± 2% × 100.

[0072] Unless otherwise specified, "between" in this invention includes the number itself, for example, "between 2 and 3" includes the endpoint values ​​2 and 3.

[0073] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0074] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0075] Figure 1 These are appearance images of the graphene dispersion obtained in Example 1 before and after standing.

[0076] Figure 2 These are the appearance images of the graphene dispersion obtained in Comparative Example 1 before and after standing. Detailed Implementation

[0077] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0078] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0079] Example 1

[0080] This embodiment prepared a graphene dispersion, the composition of which is shown in Table 1; the preparation steps include:

[0081] Expanded graphite (purchased from Pioneer Nano, product number XFI14, CAS number: 7782-42-5, treated at 900℃ before use), TSiPD, and a dispersant (adjusted to pH 3 with 15wt% hydrobromic acid before use) were mixed and homogenized under high pressure. The expanded graphite was then exfoliated to form graphene. The mass of graphene in Table 1 represents the mass of the expanded graphite.

[0082] The temperature for high-pressure homogenization is ≤30℃. During high-pressure homogenization, the temperature will rise. Water baths and ice baths are used during the process. As long as the temperature is controlled within this range, it is acceptable.

[0083] The high-pressure homogenization was performed at a pressure of 90 MPa for 1 hour.

[0084] After high-pressure homogenization, the pH is further adjusted to the pH requirements in Table 1 using 15 wt% hydrobromic acid.

[0085] Example 2

[0086] This embodiment prepared a graphene dispersion, which differs from Example 1 in that:

[0087] The composition varies to some extent, as shown in Table 1.

[0088] Comparative Example 1

[0089] This comparative example prepared a graphene dispersion, which differs from Example 1 in that:

[0090] The composition varies to some extent, as shown in Table 1.

[0091] Comparative Example 2

[0092] This comparative example prepared a graphene dispersion, which differs from Example 1 in that:

[0093] The composition varies to some extent, as shown in Table 1.

[0094] Table 1. Composition of the graphene dispersions obtained in Examples 1-2 and Comparative Examples 1-2

[0095]

[0096] In Table 1, the amount of graphene used is the mass percentage of the graphene dispersion; the amount of dispersant used is the mass percentage of the dispersant. The CAS number of PTCDA is 128-69-8. TSiPD is synthesized according to the method in the reference High Concentration Self-crosslinkable Graphene Dispersion (Junshuo Cui, Shuxue Zhou).

[0097] Application examples

[0098] This example uses the graphene dispersions provided in Examples 1-2 and Comparative Examples 1-2 to perform hole metallization on PCBs. The specific steps include:

[0099] S1. The PCB substrate is treated with argon plasma for 3 minutes; the PCB substrate used in this example has holes with a diameter of 0.12 mm; the structure consists of phenolic resin (insulating layer) and copper cladding layers on both sides of the phenolic resin.

[0100] S2. Using the PCB board obtained in step S1 as a stirring paddle (the axis of the stirring paddle passes through its geometric symmetry axis), stir the graphene dispersions of Examples 1-2 and Comparative Examples 1-2 at a speed of 150 rpm for 40 s min.

[0101] S3. Dry the PCB board obtained in step S2 in a vacuum oven at 60°C.

[0102] S4. Micro-etching treatment: Use a mixed aqueous solution of 100 g / L sodium persulfate and 50 g / L sulfuric acid as the micro-etching solution for 50 seconds; then rinse with deionized water for 1 minute and dry.

[0103] S5. Copper Plating Treatment: The electroplating solution includes 80 g / L copper sulfate, 100 mL / L sulfuric acid (98 wt%), and 20 mg / L dibenzo30-crown-10 dispersant. The electroplating time is 20 min, and the current density is 15 A / dm³. 2 Then rinse with deionized water for 1 minute and dry.

[0104] Test case

[0105] This example first tested the stability of the graphene dispersions obtained in Examples 1-2 and Comparative Examples 1-2. Specifically, after standing at a constant temperature of 25°C for 30 days, the sedimentation problem was observed. A laser particle size analyzer was also used to measure the change in particle size (D90) before and after standing.

[0106] The results showed that the graphene dispersions in Example 1 and Comparative Example 1 remained uniform in color and showed no obvious sedimentation at the bottom after standing, indicating good dispersion stability. In contrast, Comparative Examples 1 and 2 all exhibited significant sedimentation and stratification, indicating that the graphene in these examples could not be stably dispersed and, predictably, could not form uniform pore metallization. Specific test results are as follows: Figures 1-2 As shown, the results of Example 2 and Example 1 are similar, and the results of Comparative Example 1 and Comparative Example 2 are similar.

[0107] The particle size variation results show that Example 1 increased by 4%, Example 2 increased by 8%, Comparative Example 1 increased by 56%, and Comparative Example 2 increased by 43%. Therefore, the data also show that the dispersion stability of Examples 1-2 is significantly higher than that of Comparative Examples 1-2. This also indicates that the graphene dispersion provided by this invention achieves a significantly higher stable dispersion concentration of graphene than <1% in related technologies.

[0108] The second aspect of this example tested the electroplating effect of the PCBs obtained from the application examples, observing whether a uniform copper plating layer was formed inside the holes. The test results showed that in the PCBs obtained in Examples 1 and 2, the copper plating filled the entire volume of the holes, and was uniform and dense; in comparison, the electroplating effect of the PCBs obtained in Comparative Examples 1 and 2 was poor, with problems such as incomplete filling.

[0109] The above results indicate that changing the graphene modifier disrupts the synergistic effect between TSiPD and the dispersant, reduces the dispersion stability of graphene, and decreases the bonding strength between graphene and the pore walls due to the lack of TSiPD. This ultimately leads to uneven graphene adsorption during pore metallization and graphene detachment during subsequent micro-etching processes.

[0110] If sodium bromide in the dispersant is replaced with sodium chloride, although the physicochemical properties of the two are similar, there are still obvious differences in the dispersion of graphene. Specifically, the difference lies in the degree of change in the surface tension of the dispersant. Therefore, a well-dispersed graphene dispersion cannot be obtained, which leads to uneven pore metallization process.

[0111] In summary, the graphene dispersion provided by this invention significantly improves its dispersion uniformity and conductivity through compositional control. Furthermore, since no surfactants or other substances are added, the viscosity of the graphene dispersion is significantly reduced, thereby improving its pore efficiency. Moreover, due to the numerous advantages of the graphene dispersion, the PCB fabricated by graphene pore metallization exhibits superior performance and requires less preparation time. The embodiments of this invention have been described in detail above with reference to the accompanying drawings. However, this invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of this invention. In addition, the embodiments and features described herein can be combined with each other unless otherwise specified.

Claims

1. A graphene dispersion, characterized in that, The graphene dispersion includes modified graphene and a dispersant; The pH of the graphene dispersion is 3-5; wherein the mass percentage of the graphene is 1-5%. The modified graphene is TSiPD-modified graphene; the mass ratio of TSiPD to graphene is 0.1~0.8:

1. The dispersant is a mixed aqueous solution of sodium bromide and sodium hypochlorite; the mass percentage of sodium bromide in the dispersant is 1-3%.

2. The graphene dispersion according to claim 1, characterized in that, The molar ratio of sodium bromide to sodium hypochlorite is 1:1 to 1.

5.

3. A method for preparing the graphene dispersion as described in any one of claims 1 to 2, characterized in that, The preparation method includes mixing expanded graphite, TSiPD and a dispersant, and then homogenizing under high pressure.

4. The preparation method according to claim 3, characterized in that, The pressure of the high-pressure homogenization is 80~100MPa; and / or the duration of the high-pressure homogenization is 0.25~2h.

5. The preparation method according to claim 3 or 4, characterized in that, The temperature of the high-pressure homogenizer is ≤40℃.

6. A PCB, characterized in that, The raw materials for preparing the PCB include the graphene dispersion as described in any one of claims 1 to 2, and the PCB substrate; The PCB substrate has holes.

7. A method for manufacturing a PCB as described in claim 6, characterized in that, The manufacturing method includes filling the pores with the graphene dispersion and drying it.

8. The manufacturing method according to claim 7, characterized in that, The manufacturing method further includes pretreating the pores before filling the graphene dispersion; the pretreatment includes at least one of plasma pretreatment and corona treatment.

Images