Three-proofing adhesive for direct-writing 3D printing and preparation method thereof

Abstract

The invention provides a three-proofing adhesive for direct-writing type 3D printing and a preparation method of the three-proofing adhesive. The viscosity of the three-proofing glue is 250000-60000cP, the thixotropic index is 4-6, the three-proofing glue can be used for direct writing type 3D printing with the height-width ratio larger than or equal to 0.3, the water absorption rate of the three-proofing glue is 0.3-0.7%, and the hundred-lattice adhesive force is 4B-5B. The three-proofing adhesive disclosed by the invention has the characteristics of high viscosity, high thixotropy and high conformality, can be used for printing wires with the aspect ratio being greater than or equal to 0.3, also has good humidity and heat resistance, is suitable for direct-writing 3D printing application in the fields of chip packaging and display, is suitable for 3D printing, and has the advantages of high thixotropy and high conformality. The application scene of the glue in the packaging field can be greatly expanded, and the urgent requirements of the electronic industry are met.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic packaging, and in particular to a three-proof adhesive for direct-write 3D printing and a preparation method thereof. Background Art

[0002] At present, with the rapid update and iteration of various electronic devices, electronic products are gradually turning to miniaturization, integration and multifunctionality. Under this trend, the electronic packaging industry has also ushered in rapid development, and the market has increasingly higher requirements for the safety performance and reliability of packaging products. Electronic equipment often needs to operate in complex environments, and its core component circuit boards are easily affected by environmental factors, which may cause corrosion, softening, deformation and other problems, resulting in frequent failures of equipment during long-term use. Therefore, the quality and reliability of products have become the key indicators of consumer attention, among which the "three-proof" (moisture-proof, salt spray-proof, and anti-static) performance is the most valued by the industry and has been listed as a key technical indicator by many manufacturers. As an important protective material in the field of electronic packaging, the three-proof glue can effectively block the damage of environmental erosion factors to circuit boards and related equipment by forming a dense protective layer. With its special formula, the material exhibits excellent high and low temperature resistance, humidity and heat resistance and other characteristics after curing, and can provide long-lasting and reliable protection for electronic components even under extremely harsh working conditions.

[0003] However, most of the "three-proof glue" currently in use are solvent-based products. Their advantages are low viscosity (less than 150mPa.s), easy glue application, and wide application range, but their disadvantages are that the viscosity is too low and the glue has no thixotropic conformality. It is only suitable for full-surface packaging protection as a protective coating, but cannot be used for regional selective packaging protection, high-thickness chip packaging, and dams. On the other hand, low-viscosity three-proof glue mostly uses a large amount of toxic solvents such as benzene as a reagent to adjust the viscosity. During the curing process, toxic and harmful gases will be generated, which seriously affect the health of operators and easily cause occupational diseases. In addition, benzene solvents have a low flash point, are easy to volatilize, and have the risk of being flammable and explosive. Attention should be paid to safety management during storage and use, which increases management costs and production costs. Summary of the invention

[0004] The main purpose of the present invention is to provide a three-proof glue for direct writing 3D printing and a preparation method thereof, so as to solve the problem that the three-proof glue in the prior art has low viscosity and poor thixotropic conformality, resulting in it being only suitable as a protective coating, but cannot be applied to chip packaging and dam directions requiring high film thickness, and is difficult to adapt to direct writing 3D printing.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a three-proofing glue for direct writing 3D printing is provided, the viscosity of the three-proofing glue is 25000-60000 cP, the thixotropic index is 4-6, and it can be used for direct writing 3D printing with an aspect ratio of ≥0.3, and the water absorption rate of the three-proofing glue is 0.3-0.7%, and the hundred-grid adhesion is 4B-5B.

[0006] Furthermore, the three-proof glue includes, by weight: 60 to 90 parts of biphenyl epoxy resin, 10 to 40 parts of multifunctional epoxy resin, 8 to 15 parts of latent curing agent, 10 to 40 parts of core-shell rubber modified epoxy resin and 15 to 40 parts of modified filler; the modified filler includes hydrophobic silica, silane-modified silica and barium sulfate.

[0007] Furthermore, the three-proof adhesive includes, by weight: 70 to 80 parts of biphenyl epoxy resin, 20 to 30 parts of multifunctional epoxy resin, 10 parts of latent curing agent, 15 to 30 parts of core-shell rubber modified epoxy resin and 26 to 33 parts of modified filler.

[0008] Furthermore, the viscosity of the biphenyl epoxy resin is >4000 cP, and the epoxy value is 0.35-0.88; and / or the viscosity of the multifunctional epoxy resin is >500 cP, and the epoxy value is 0.4-0.9; and / or the multifunctional epoxy resin includes one or more of a glycidylamine epoxy resin, an alicyclic multifunctional epoxy resin, and a multifunctional phenolic epoxy resin.

[0009] Further, the latent curing agent includes one or more of dicyandiamide, adipic acid dihydrazide, sebacic acid dihydrazide, imidazole, imidazole modification and boron trifluoride complex.

[0010] Furthermore, the viscosity of the core-shell rubber modified epoxy resin is 2000-40000 cP; and / or the core-shell rubber modified epoxy resin is formed by blending nano rubber and epoxy resin; wherein the particle size of the nano rubber is 10-1000 nm, and the weight ratio of the nano rubber to the epoxy resin is (20-60):100.

[0011] Furthermore, the modified filler includes hydrophobic silica, silane-modified silica and barium sulfate, and the weight ratio of hydrophobic silica, silane-modified silica and barium sulfate is (8-15):8:(8-15).

[0012] Furthermore, the anti-corrosion adhesive also includes 3 to 8 parts of a curing accelerator and 1 to 3 parts of an auxiliary agent by weight; the curing accelerator includes one or more of modified imidazoles, organic urea accelerators and modified amines; and / or the auxiliary agent is an adhesion enhancing coupling agent.

[0013] According to another aspect of the present invention, a method for preparing the above-mentioned three-proof adhesive for direct writing 3D printing of the present invention is provided, comprising the following steps: step S1, mixing and stirring biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler to obtain a first mixture; step S2, adding a latent curing agent to the first mixture and stirring to obtain a second mixture; step S3, grinding the second mixture to a particle size of ≤10μm to obtain a third mixture; step S4, vacuum degassing and pressure filtering the third mixture in sequence to obtain the three-proof adhesive for direct writing 3D printing.

[0014] Furthermore, the vacuum degree of vacuum degassing is 40-100 mbar; and / or the pressure of pressure filtration is 0.5-1.5 kg / cm 2 , the filter size is 300-400 mesh.

[0015] Furthermore, in step S2, after adding the latent curing agent to the first mixture, a curing accelerator and an auxiliary agent are also added, and then stirring is performed.

[0016] Furthermore, the total weight ratio of the biphenyl epoxy resin and the multifunctional epoxy resin to the weight ratio of the curing accelerator is 100:(3-8); and / or the total weight ratio of the biphenyl epoxy resin and the multifunctional epoxy resin to the weight ratio of the auxiliary agent is 100:(1-3).

[0017] By applying the technical solution of the present invention, the three-proof glue has high viscosity and high thixotropic index, with a viscosity of 25000-60000 cP and a thixotropic index of 4-6. The three-proof glue with the above characteristics has the characteristics of high viscosity, high thixotropy and high conformality. It can print wires with an aspect ratio of ≥ 0.3, and can also take into account good moisture and heat resistance. It is suitable for direct-write 3D printing applications in the field of chip packaging and display. The three-proof glue of the present invention is a three-proof glue suitable for 3D printing, high thixotropy and high conformality, which can greatly expand the application scenarios of such glue in the packaging field and meet the urgent requirements of the electronics industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A water-boiled hundred-grid test diagram according to an embodiment of the present invention is shown;

[0020] Figure 2 A top view of a printed wire according to an embodiment of the present invention is shown;

[0021] Figure 3A three-dimensional diagram of a printed wire according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As described in the background technology of the present invention, the existing technology has low viscosity and poor thixotropic conformality of the three-proof glue, which makes it only suitable as a protective coating, but cannot be used in chip packaging and dam directions that require high film thickness, and it is difficult to adapt to the problem of direct writing 3D printing. In order to solve the above problems, in a typical embodiment of the present invention, a three-proof glue for direct writing 3D printing is provided, the viscosity of the three-proof glue is 25000~60000cP, the thixotropic index is 4~6, and it can be used for direct writing 3D printing with an aspect ratio ≥0.3, and the water absorption of the three-proof glue is 0.3~0.7%, and the hundred-grid adhesion is 4B~5B. Those skilled in the art can understand that viscosity and thixotropic index are indicators of the three-proof glue before curing. The curing conditions of the three-proof glue can be 100~150℃ and 20~60min.

[0024] There are significant differences between direct-write 3D printing and other printing technologies in the requirements for printing materials. Direct-write 3D printing directly extrude materials (such as liquids, slurries or soft solids, etc.) through precisely controlled nozzles, and performs planar or laminated printing on a substrate. It relies on the physical or chemical properties of the material itself to solidify and shape, so the printing material is required to have good viscosity and thixotropic conformality. However, the conventional low-viscosity three-proofing glue in the prior art does not have good conformality and thixotropy, which makes it impossible to be applied to planar or three-dimensional 3D printing with certain structural requirements, and it is also impossible to achieve regional selective packaging protection, such as being unable to be applied to specific packaging and dam fields. The viscosity of the three-proofing glue of the present invention is 25000~60000cP, and the thixotropic index is 4~6. The three-proofing glue with the above characteristics has the characteristics of high viscosity, high thixotropy, and high conformality. It can print wires with an aspect ratio of ≥0.3, and is suitable for direct-write 3D printing applications in the chip packaging and display fields.

[0025] The three-proof glue whose water absorption rate and 100-grid adhesion meet the above range also has excellent moisture and heat resistance, which can effectively protect the substrate from the influence of high temperature and high humidity environment, and has very excellent adhesion on inert substrates such as silicon wafers and difficult-to-bond substrates, which can prevent water vapor from penetrating from the bottom, thereby effectively protecting electronic devices and improving packaging reliability. The three-proof glue of the present invention is a highly thixotropic and highly conformal three-proof glue suitable for direct writing 3D printing, which can greatly expand the application scenarios of such glue in the packaging field and meet the urgent requirements of the electronics industry.

[0026] Specifically, in a preferred embodiment, the three-proof adhesive includes, by weight: 60 to 90 parts of biphenyl epoxy resin, 10 to 40 parts of multifunctional epoxy resin, 8 to 15 parts of latent curing agent, 10 to 40 parts of core-shell rubber modified epoxy resin and 15 to 40 parts of modified filler; the modified filler includes one or more of hydrophobic silica, silane-modified silica and barium sulfate.

[0027] The present invention adopts biphenyl epoxy resin and multifunctional (such as trifunctional / tetrafunctional) epoxy resin as matrix resin, wherein 60 to 90 parts of biphenyl epoxy resin are used as main resin. Biphenyl epoxy resin is a special epoxy resin with biphenyl rigid structure, which can effectively improve the strength, mechanical properties and moisture and heat resistance of the cured product. It also has extremely low water absorption rate, which can make the cured product have excellent waterproof performance, which is beneficial to improve the water resistance of the three-proof adhesive.

[0028] 10 to 40 parts of multifunctional epoxy resin can play a role similar to that of a crosslinking agent, and can react and crosslink with biphenyl epoxy resin and latent curing agent to further improve the overall crosslinking degree, rigidity and strength of the cured product, which is beneficial to the improvement of the overall waterproof performance.

[0029] In addition, the cured product of the epoxy resin system has a high resistivity, which makes the three-proof adhesive also have excellent electrical insulation properties, making it more suitable for electronic packaging scenarios.

[0030] The latent curing agent is used as the main curing agent to carry out a curing reaction with the main resin. The latent curing agent is stable at room temperature and can be activated and quickly participate in curing under specific conditions (such as heating, light, etc.). Therefore, mixing the latent curing agent with the epoxy resin to prepare a one-component epoxy glue can reduce the work flow and reduce costs on the one hand; at the same time, the glue can remain stable when stored at room temperature for a long time, which is convenient for long-term construction of the glue. The viscosity value of the three-proof glue of the present invention changes little when stored at room temperature for a long time, which can effectively ensure the long-term discharge stability in the mass production process based on direct writing 3D printing, as well as the packaging processing accuracy of the product. The amount of the latent curing agent can be appropriately added according to the epoxy equivalent of the epoxy resin. The principle is that the epoxy group of the epoxy resin reacts with the group (such as amino group) in the latent curing agent. When the amount of the latent curing agent is 8 to 15 parts, the amount added is slightly larger than the calculated amount, which can ensure that the epoxy resin is completely cured, so that the three-proof glue has a long-term stable high viscosity performance.

[0031] The core-shell rubber modified epoxy resin mainly acts as a toughening agent to enhance toughness and reinforcement. The resin therein can also participate in the curing reaction, and at the same time cooperate with the epoxy resin system to improve the moisture and heat resistance of the three-proof adhesive; the rubber part can improve the toughness, which can avoid brittle failure caused by excessive rigidity of the resin, but excessive dosage may make the cured product too plastic, affecting the glass transition temperature Tg of the material, resulting in a decrease in heat resistance. Therefore, the amount of core-shell rubber modified epoxy resin is preferably 10 to 40 parts.

[0032] Among the modified fillers, the surfaces of hydrophobic silica, silane-modified silica and barium sulfate can be modified to improve the performance of the adhesive, thereby increasing the overall cross-linking degree and improving the thixotropic conformality. They can also play a role in reinforcement and hardness improvement. The amount used can be adjusted according to the thixotropic conformality requirements. The amount of modified filler added should not be too much. Too much will cause the viscosity of the three-proof adhesive to be too high and make it difficult to apply the glue. Therefore, the amount used is preferably 15 to 40 parts.

[0033] The three-proof glue of the present invention is added with epoxy resin with high cross-linking degree and core-shell rubber modified epoxy resin, so that the three-proof glue has excellent adhesion on the substrate. After the three-proof glue is cured, the adhesion can still be maintained at 5B, and no water vapor penetrates into the glue layer during the red ink boiling test, which is significantly improved compared with the conventional three-proof glue on the market. At the same time, the core-shell rubber modified epoxy resin is used to improve the strength of the cured product, reduce the influence of moisture, heat and water vapor, and combine with specially treated modified fillers to improve the overall thixotropy and conformality of the material, while increasing the hardness and strength of the cured product. The glue has a high degree of cross-linking after curing, which is manifested as the cured glue has excellent waterproof performance, which is suitable for direct writing 3D printing. In addition, the above-mentioned composition of the present invention does not need to use toxic solvents such as benzene as reagents for adjusting viscosity, and no toxic and harmful gases are generated during the curing process. It is more green and environmentally friendly, and the management cost and production cost are lower.

[0034] Based on similar reasons, in order to further improve the viscosity performance, mechanical properties and moisture and heat resistance of the three-proof glue after curing, in a preferred embodiment, the three-proof glue includes, by weight: 70 to 80 parts of biphenyl epoxy resin, 20 to 30 parts of multifunctional epoxy resin, 10 parts of latent curing agent, 15 to 30 parts of core-shell rubber modified epoxy resin and 26 to 33 parts of modified filler.

[0035] In a preferred embodiment, the viscosity of the biphenyl epoxy resin is >4000cP (e.g., 4000-40000cP), and the epoxy value is 0.35-0.88; and / or the viscosity of the multifunctional epoxy resin is >500cP (e.g., 500-50000cP), and the epoxy value is 0.4-0.9; and / or the multifunctional epoxy resin includes one or more of a glycidylamine epoxy resin, an alicyclic multifunctional epoxy resin, and a phenolic epoxy resin. The multifunctional epoxy resin can be connected to multiple epoxy groups, and can more fully react and crosslink with the biphenyl epoxy resin, thereby further improving the overall crosslinking degree, viscosity, and three-proofing performance of the three-proofing glue.

[0036] Conventional amine curing agents such as aliphatic amines and aromatic amines react slowly at room temperature after being mixed with epoxy resin. If prepared into a single-component epoxy glue, the viscosity of the glue material will change uncontrollably during the coating or storage process, and the amount of glue coating cannot be accurately controlled, which is not conducive to high-precision project requirements. In a preferred embodiment, the latent curing agent includes one or more of dicyandiamide, adipic acid dihydrazide, sebacic acid dihydrazide, imidazole, imidazole modification and boron trifluoride complex. The above-mentioned latent curing agent needs to be at a specific high temperature (such as 60 to 150°C) to initiate the reaction, which can improve the viscosity stability of the three-proof glue and is more conducive to the preparation, storage and use of high-viscosity single-component epoxy glue. Using 8 to 15 parts of the above-mentioned latent curing agent can further ensure the controllability of the curing process, so that the curing reaction has a more suitable rate, which is conducive to obtaining a three-proof glue with high viscosity and high conformal properties.

[0037] In a preferred embodiment, the viscosity of the core-shell rubber modified epoxy resin is 2000-40000 cP; and / or the core-shell rubber modified epoxy resin is formed by blending nano rubber and epoxy resin; wherein the particle size of the nano rubber is 10-1000 nm, and the weight ratio of the nano rubber to the epoxy resin is (20-60):100. When the core-shell rubber modified epoxy resin is used as a toughening agent, it will not reduce the glass transition temperature Tg of the cured product on the basis of playing the role of conventional toughening agents in improving toughness, thereby further maintaining good heat resistance. The above-mentioned specially modified toughening agent material can further improve the strength of the cured product, increase the overall cross-linking degree, and reduce the influence of moisture, heat and water vapor.

[0038] In order to further improve the crosslinking degree and weather resistance of the cured product, in a preferred embodiment, the modified filler includes hydrophobic silica, silane-modified silica and barium sulfate, and the weight ratio of hydrophobic silica, silane-modified silica and barium sulfate is (8-15):8:(8-15).

[0039] In a preferred embodiment, the three-proof adhesive also includes 3 to 8 parts of a curing accelerator and 1 to 3 parts of an auxiliary agent by weight; preferably, the curing accelerator includes one or more of modified imidazole, organic urea accelerator and modified amine; and / or the auxiliary agent is an adhesion enhancing coupling agent, and may also include one or more conventional auxiliary agents such as a leveling agent, a dispersant, a defoaming agent and a coupling agent. The above components are conducive to making the three-proof adhesive have better adhesion on the substrate, especially on some surface inert substrates such as silicon wafers and substrates with special inert coatings (such as silicon nitride coatings), which can achieve firm adhesion.

[0040] In another typical embodiment of the present invention, a method for preparing the above-mentioned three-proof glue for direct writing 3D printing of the present invention is also provided, comprising the following steps: step S1, mixing and stirring biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler to obtain a first mixture; step S2, adding a latent curing agent to the first mixture and stirring to obtain a second mixture; step S3, grinding the second mixture to a particle size of ≤10μm to obtain a third mixture; step S4, vacuum degassing and pressure filtering the third mixture in sequence to obtain a three-proof glue for direct writing 3D printing.

[0041] Specifically, the present invention first mixes biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler, and then performs a first stirring. During the first stirring process, the components will not react with each other, so high-speed stirring can be used, such as using a high-speed disperser to disperse and mix uniformly to obtain a first mixed material. After the mixed material is cooled to room temperature, the stirring speed can be appropriately reduced, a latent curing agent is added to the first mixed material, and then a second stirring is performed. In this process, reducing the stirring speed can avoid the reaction between the resin and the curing agent due to excessive temperature during the stirring process to obtain a second mixed material.

[0042] Then grind the second mixture, for example, grind it 2 to 5 times in a high-precision three-roller machine or ball mill. Finer grinding is conducive to using a smaller printing needle for printing, and the needle will not be blocked by the particle size, so micron-level printing can be carried out smoothly. Grind to a particle size of ≤10μm to obtain a third mixture. Controlling the particle size can improve the surface quality and detail accuracy of the subsequent solidified material. Within the above range, it can also ensure that the three-proof adhesive material will not cause needle blocking due to excessive filler size during micron-level needle direct writing 3D printing, and will not affect the microstructure of the solidified material. Finally, the third mixture is vacuum degassed and pressure filtered in turn to reduce the foaming residue in the material and filter out the ash and other substances in the processing process, so as to obtain a three-proof adhesive for direct writing 3D printing, which has high viscosity and thixotropic conformality at room temperature, and exhibits high resistivity, low water absorption, high bonding strength and viscosity stability.

[0043] The three-proof glue of this application achieves high viscosity, high conformality and excellent printing performance in the direct writing 3D printing process by using a specific formula and preparation process. Its unique component selection and ingredient ratio not only improves the mechanical strength and stability of the solidified material, but also significantly reduces the water absorption rate, enhances the bonding strength, and maintains good viscosity stability, making the printing process more precise and controllable. In addition, the high resistivity exhibited by the solidified material gives it a significant advantage in electronic packaging and insulation applications, opening up new possibilities for the application of 3D printing technology in the field of precision electronics. This colloidal composition is not only suitable for direct writing 3D printing, but also can be adapted to other 3D printing technologies such as photocuring printing and fused deposition modeling by adjusting the formula, broadening its application range in the manufacturing industry. Its excellent properties such as high viscosity and high conformality make it an ideal choice for manufacturing high-performance and high-precision products, providing strong technical support for innovations in multiple fields such as aerospace, automobile manufacturing, and electronic packaging.

[0044] In order to further promote the uniform dispersion of resin, core-shell rubber modified epoxy resin and modified filler, reduce local uneven mixing or precipitation formation, and improve the uniformity and performance consistency of the three-proof glue, in a preferred embodiment, the stirring speed of the first mixture is greater than the stirring speed of the second mixture, and the difference between the two is 800-1200rpm. Specifically, the stirring speed of the first mixture is 1800-2200rpm, and the time is 10-30min; and / or the speed of the second mixture is 800-1200rpm, and the time is 5-15min. On the basis of ensuring the uniform dispersion of all components, it is possible to better reduce unnecessary reactions caused by temperature increases due to excessive stirring speeds.

[0045] In a preferred embodiment, the vacuum degree of vacuum degassing is 40-100 mbar; and / or the pressure of pressure filtration is 0.5-1.5 kg / cm 2 , the filter size is 300-400 mesh. Under the above conditions, bubbles in the mixing process can be further effectively removed, voids can be formed during the curing process to affect the accuracy and strength of the printed parts, the density and strength of the cured products can be improved, and impurities and uneven particles can be filtered more efficiently to further improve the uniformity of the composition and ensure the consistency and reliability of the printing effect.

[0046] In order to better improve the adhesion of the conformal adhesive on the substrate, in a preferred embodiment, in step S2, after adding the latent curing agent to the first mixture, a curing accelerator and an auxiliary agent are also added, and then stirring is performed.

[0047] Specifically, in a preferred embodiment, the ratio of the total weight of the biphenyl epoxy resin and the multifunctional epoxy resin to the weight of the curing accelerator is 100:(3-8); and / or the ratio of the total weight of the biphenyl epoxy resin and the multifunctional epoxy resin to the weight of the auxiliary agent is 100:(1-3), which is more conducive to achieving firm adhesion on the surface of an inert substrate.

[0048] Typically but not limiting, the three-proof adhesive includes, by weight: 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or a range consisting of any two of them, biphenyl epoxy resin, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or a range consisting of any two of them, multifunctional epoxy resin, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts or a range consisting of any two of them, latent curing agent, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or a range consisting of any two of them, core-shell rubber modified epoxy resin, 15 parts, 20 parts, 25 parts, 26 parts, 30 parts, 33 parts, 35 parts, 40 parts or a range consisting of any two of them, modified filler.

[0049] Typically but not limiting, the epoxy value of the biphenyl epoxy resin is 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.88 or a range consisting of any two of them; the epoxy value of the multifunctional epoxy resin is 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or a range consisting of any two of them.

[0050] Typically but not limiting, the core-shell rubber modified epoxy resin is formed by blending nano rubber with epoxy resin, and the weight ratio of nano rubber to epoxy resin is 20:100, 30:100, 40:100, 50:100, 60:100 or a range consisting of any two of them.

[0051] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0052] Example 1

[0053] The components of the three-proof glue are shown in Table 1, and the types of components are as follows:

[0054] Biphenyl epoxy resin: viscosity is 4500cP, epoxy value is 0.54;

[0055] Multifunctional epoxy resin: alicyclic multifunctional epoxy resin TDE-85, viscosity 2000cP, epoxy value 0.85;

[0056] Latent curing agent: dicyandiamide DICY;

[0057] Core-shell rubber modified epoxy resin: formed by uniformly blending nano rubber with a particle size of 10 to 1000 nm with epoxy resin, the weight ratio of nano rubber to epoxy resin is 40:100, and the viscosity is 2000 to 40000 cP;

[0058] Modified fillers: hydrophobic silica, silane-modified silica and barium sulfate;

[0059] Curing accelerator: organic urea accelerator UR500;

[0060] Auxiliary agent: silane coupling agent KH560.

[0061] The preparation method is as follows:

[0062] Step S1, mixing biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler in proportion, and dispersing them with a high-speed disperser until they are uniformly mixed (speed of 2000 rpm, time of 20 min), to obtain a first mixed material;

[0063] Step S2, cooling to room temperature (20-30° C.), reducing the stirring speed (rotation speed is 1000 rpm, time is 10 min), adding a latent curing agent, a curing accelerator and an auxiliary agent to the first mixture, and then performing a second stirring to obtain a second mixture;

[0064] Step S3, cooling to room temperature (20-30° C.), grinding the second mixed material three times using a high-precision three-roll mill until the particle size is ≤10 μm, to obtain a third mixed material;

[0065] Step S4: vacuum degassing (50 mbar vacuum treatment), pressure filtration (1 kg / cm 2 Filtered with a 350-mesh filter under pressure) to obtain a three-proof adhesive for direct writing 3D printing.

[0066] Examples 2 to 9

[0067] The difference from Example 1 is that the weight proportions of the three-proof adhesive are different, see Table 1.

[0068] Example 10

[0069] The components of the three-proof adhesive are the same as those in Example 1, and the preparation method is as follows:

[0070] Step S1, mixing biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler in proportion, and dispersing them with a high-speed disperser until they are uniformly mixed (speed of 1800 rpm, time of 30 min), to obtain a first mixture;

[0071] Step S2, cooling to room temperature (20-30° C.), reducing the stirring speed (rotation speed is 800 rpm, time is 15 min), adding a latent curing agent, a curing accelerator and an auxiliary agent to the first mixture, and then performing a second stirring to obtain a second mixture;

[0072] Step S3, cooling to room temperature (20-30° C.), grinding the second mixed material twice using a high-precision three-roll mill to a particle size of ≤10 μm, to obtain a third mixed material;

[0073] Step S4: vacuum degassing (vacuuming at 40 mbar), pressure filtering (0.5 kg / cm 2 Filtered through a 300-mesh filter under pressure) to obtain a three-proof adhesive for direct writing 3D printing.

[0074] Embodiment 11

[0075] The components of the three-proof adhesive are the same as those in Example 1, and the preparation method is as follows:

[0076] Step S1, mixing biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler in proportion, and dispersing them with a high-speed disperser until they are uniformly mixed (speed of 2200 rpm, time of 10 min), to obtain a first mixture;

[0077] Step S2, cooling to room temperature (20-30° C.), reducing the stirring speed (rotation speed is 1200 rpm, time is 5 min), adding a latent curing agent, a curing accelerator and an auxiliary agent to the first mixture, and then performing a second stirring to obtain a second mixture;

[0078] Step S3, cooling to room temperature (20-30° C.), grinding the second mixed material 5 times using a high-precision three-roll mill until the particle size is ≤10 μm, to obtain a third mixed material;

[0079] Step S4: vacuum degassing (100 mbar for vacuum treatment), pressure filtration (1.5 kg / cm 2 Filtered through a 400-mesh filter under pressure) to obtain a three-proof adhesive for direct writing 3D printing.

[0080] Comparative Examples 1 to 5

[0081] The difference from Example 1 is that the weight proportions of the three-proof adhesive are different, see Table 1.

[0082] Comparative Example 6

[0083] The difference from Example 1 is that E51 epoxy resin is used to replace the biphenyl epoxy resin and the multifunctional epoxy resin.

[0084] Comparative Example 7

[0085] Technical solution of Example 1 of Chinese Patent CN 105907043 A:

[0086] (1) Preparation of component A: 100 g of epoxy resin E51, 10 g of toughening agent carboxyl liquid nitrile rubber, 30 g of flame retardant aluminum hydroxide, 100 g of filler fumed silica, 0.001 g of degassing agent SAG47 and 5 g of inorganic pigment titanium dioxide are mixed evenly, and then placed in a desiccator for vacuum degassing; after degassing, component A is obtained;

[0087] (2) Preparation of component B: 7 g of curing agent ethylenediamine, 0.001 g of degassing agent SAG47 and 1 g of curing accelerator DMP-30 were mixed evenly, and then placed in a desiccator for vacuum degassing; after degassing, component B was obtained;

[0088] (3) Printing: First, print a thin layer of component A, and then spray-deposit component B on the surface of component A, and then quickly solidify it; then repeat the process of printing a thin layer of component A, and then spray-deposit component B on the surface of component A, and repeat the process of printing until the model is completely printed;

[0089] (4) Post-curing: After the model is completely printed, it is placed in a 120°C oven for post-curing.

[0090] Comparative Example 8

[0091] Technical solution of Example 1 of Chinese Patent CN 114773788 A:

[0092] 30 parts of nano silicone rubber core-shell structure polymer toughened epoxy resin A-1, 30 parts of epoxy acrylate resin B-1, 20 parts of propylene oxide active diluent monomer C-1, 20 parts of butylene oxide active diluent monomer D-1, 5 parts of photoinitiator E-1, 2 parts of photoinitiator E-3, 1 part of defoamer F-1, 1 part of leveling agent G-1, and 1 part of antioxidant H-1 are mixed and heated to 30-100°C, stirred and mixed evenly, and then the photoinitiator is added after cooling. After stirring until uniform, a white viscous liquid is obtained, and a photosensitive resin composition sample is obtained.

[0093] The performance of the three-proof adhesives prepared in the above examples and comparative examples was tested, and the results are shown in Table 2.

[0094] Test content and test method:

[0095] Water absorption rate: Prepare samples according to standard GB / T1034-2008, test the mass change of the material after soaking at room temperature of 23℃ for one day, and calculate the water absorption rate of the cured product;

[0096] Inert substrate water boiling hundred-grid test: First, apply the glue on the surface of the silicon wafer to form a coating of a specific film thickness. After the coating is cured at 120°C for 30 minutes, the sample is placed in a 100°C water bath and boiled for 30 minutes. Then, the sample is prepared according to the national standard GB_T9286-2021 and subjected to a hundred-grid test.

[0097] Viscosity (viscosity stability): Use a Brookfield viscometer to test the viscosity of the glue at 25°C room temperature every week for 4 weeks, and determine the viscosity stability by the change in viscosity.

[0098] Thixotropic index: When testing viscosity, the viscosity data is tested at two different rotation speeds of 1 rpm and 10 rpm respectively. The thixotropic index is characterized by calculating the ratio of viscosity η(1rpm) / η(10rpm).

[0099] Aspect ratio calculation: Use a dispensing machine to perform direct writing 3D printing on the substrate, and use a high-precision sensor to test the line width and line height to calculate the aspect ratio of the printed wire.

[0100] Printed wire morphology: The printed wire was cured at 120°C for 30 min, and the wire shape was observed using ultra-depth of field.

[0101] The test diagram of boiling water in Example 1 is shown in FIG. Figure 1 It can be seen that the adhesion on the surface of the silicon wafer substrate can reach 5B, and the three-proof adhesive of the present invention has good viscosity and adhesion.

[0102] The top view of the printed wire of Example 1 is shown in Figure 2 , it can be seen that the line width is 120μm, the line height is 70μm, and the aspect ratio is 0.58. The three-proof adhesive of the present invention can be used for direct writing 3D printing with an aspect ratio of ≥0.3.

[0103] The three-dimensional image of the printed wire of Example 1 is shown in Figure 3 It can be seen that the glue line presents a retaining wall morphology perpendicular to the substrate from a 3D perspective. The top of the glue line is uniform and flat, with good height consistency; the straightness is good, and there is no bending of the glue line.

[0104] Table 1

[0105]

[0106]

[0107] Table 2

[0108] Performance Testing Viscosity Thixotropic index Water absorption Adhesion (water boiling test) Example 1 31500 4.5 0.46 5B Example 2 27300 4.1 0.52 5B Example 3 30680 4.2 0.56 5B Example 4 31800 4.3 0.36 5B Example 5 57600 5.8 0.68 5B Example 6 25350 4.0 0.69 4B Example 7 55380 4.0 0.69 4B Example 8 25640 4.0 0.68 4B Example 9 26380 4.1 0.70 4B Example 10 25280 4.0 0.70 4B Embodiment 11 25640 4.0 0.69 4B Comparative Example 1 21800 3.7 3.23 0B Comparative Example 2 41660 4.7 2.36 0B Comparative Example 3 24600 5.7 0.89 3B Comparative Example 4 31000 4.1 2.81 5B Comparative Example 5 31700 1.3 1.19 5B Comparative Example 6 33700 4.0 5.17 4B Comparative Example 7 21800 1.2 10.91 2B Comparative Example 8 20960 1.9 9.65 2B

[0109] It can be seen that the conventional E51 epoxy resin used in Comparative Example 6 has poor moisture and heat resistance of the cured product, and it has a bifunctional structure, and the overall crosslinking degree is lower than that of the multifunctional epoxy resin, resulting in a reduced crosslinking degree and poor mechanical properties and moisture and heat resistance.

[0110] The resin, curing agent, etc. used in Comparative Example 7 are all conventional materials, with a low degree of crosslinking, and the moisture resistance of the printed and cured materials is poor, and they do not have the performance of three anti-adhesives. It uses a room temperature curing agent, which is a two-component system. Components A and B need to be loaded and printed separately, and cannot be prepared into a single-component adhesive, and a dual-nozzle solution is required. The preparation cost and equipment cost are high, and the material reacts after the two-component system is mixed. The viscosity of the material is uncontrollable during use or storage, and the dosage cannot be accurately controlled. Moreover, component B is a thin layer spray lamination, which is easy to spray and contaminate other areas on the one hand, and spray lamination on the other hand cannot control the uniformity of the entire surface, which easily leads to unevenness on component A, affecting the subsequent curing uniformity, and there may be an implosion situation in the subsequent overall heating and curing process. In addition, its toughening agent is a conventional carboxyl liquid nitrile rubber (CTBN), which only has a toughening effect and cannot participate in the cross-linking reaction, and the strength of the cured product will be weak. In comparison, the embodiments of the present invention use a latent curing agent, which will not react with the epoxy resin during use or storage, and can only react after the activation conditions are met. Therefore, it can be prepared into a single-component adhesive and is stable for a long time at room temperature; the core-shell structure of the rubber-epoxy resin toughening agent of the present invention has a higher degree of cross-linking and a greater strength of the triple-proof adhesive.

[0111] Conventional photocurable materials are used in Comparative Example 8, and the crosslinking degree of the cured product is low, and the final product has poor resistance to moisture and heat. The prepared adhesive has high fluidity, but does not have high thixotropic shape retention. It can only be used for 3D model printing by SLA (stereoscopic light curing) layered light curing. The model cannot be directly printed out and then photocured. The overall operation process is time-consuming and complicated. The core-shell structure rubber-epoxy resin toughening agent mainly serves to improve the toughness of the cured product and reduce brittle failure, and does not involve resistance to moisture and heat. In comparison, each embodiment of the present invention uses a biphenyl epoxy resin and a multifunctional epoxy resin to form a highly crosslinked product, and cooperates with the core-shell rubber modified epoxy resin to improve the resistance to moisture and heat, and the water absorption rate is very low. The three-proof adhesive of the present invention has high thixotropic shape retention, and can directly print out a 3D structure by stacking and placing it, and then completely photocuring molding in the final step.

[0112] It can be seen from the above that compared with the comparative example, the three-proof glue of the present invention has the characteristics of high viscosity, high thixotropy and high conformality. It can print wires with an aspect ratio of ≥ 0.3, and can also take into account good moisture and heat resistance. It is suitable for direct-write 3D printing applications in the field of chip packaging and display. It is a three-proof glue with high thixotropy and high conformality suitable for 3D printing, which can greatly expand the application scenarios of such glue in the packaging field and meet the urgent requirements of the electronics industry.

[0113] In addition, it can be seen that when each process parameter is within the preferred range of the present invention, the overall effect is better.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-proof adhesive for direct writing 3D printing, characterized in that: The three-proof glue has a viscosity of 25000-60000 cP and a thixotropic index of 4-6, and can be used for direct writing 3D printing with an aspect ratio of ≥0.

3. The water absorption rate of the three-proof glue is 0.3-0.7%, and the hundred-grid adhesion is 4B-5B.

2. The three-proof adhesive for direct writing 3D printing according to claim 1 is characterized in that: The three-proof adhesive comprises, by weight: 60 to 90 parts of biphenyl epoxy resin, 10 to 40 parts of multifunctional epoxy resin, 8 to 15 parts of latent curing agent, 10 to 40 parts of core-shell rubber modified epoxy resin and 15 to 40 parts of modified filler; The modified filler includes hydrophobic silica, silane-modified silica and barium sulfate.

3. The three-proof adhesive for direct writing 3D printing according to claim 2 is characterized in that: In terms of weight, the three-proof adhesive comprises: 70 to 80 parts of the biphenyl epoxy resin, 20 to 30 parts of the multifunctional epoxy resin, 10 parts of the latent curing agent, 15 to 30 parts of the core-shell rubber modified epoxy resin and 26 to 33 parts of the modified filler.

4. The three-proof adhesive for direct writing 3D printing according to claim 2 or 3, characterized in that: The biphenyl epoxy resin has a viscosity of >4000 cP and an epoxy value of 0.35 to 0.88; and / or The viscosity of the multifunctional epoxy resin is >500 cP, and the epoxy value is 0.4-0.9; and / or The multifunctional epoxy resin includes one or more of a glycidylamine epoxy resin, an alicyclic multifunctional epoxy resin and a multifunctional phenolic epoxy resin.

5. The three-proof adhesive for direct writing 3D printing according to any one of claims 2 to 4, characterized in that: The latent curing agent includes one or more of dicyandiamide, adipic acid dihydrazide, sebacic acid dihydrazide, imidazole, imidazole modification and boron trifluoride complex.

6. The three-proof adhesive for direct writing 3D printing according to any one of claims 2 to 5, characterized in that: The viscosity of the core-shell rubber modified epoxy resin is 2000-40000 cP; and / or The core-shell rubber modified epoxy resin is formed by blending nano rubber and epoxy resin; wherein the particle size of the nano rubber is 10-1000 nm, and the weight ratio of the nano rubber to the epoxy resin is (20-60):

100.

7. The three-proof adhesive for direct writing 3D printing according to any one of claims 2 to 6, characterized in that: The modified filler includes the hydrophobic silica, the silane-modified silica and the barium sulfate, and the weight ratio of the hydrophobic silica, the silane-modified silica and the barium sulfate is (8-15):8:(8-15).

8. The three-proof adhesive for direct writing 3D printing according to any one of claims 2 to 7, characterized in that: The three-proof adhesive further comprises 3 to 8 parts of a curing accelerator and 1 to 3 parts of an auxiliary agent by weight; The curing accelerator includes one or more of modified imidazole, organic urea accelerator and modified amine; and / or the auxiliary agent is an adhesion enhancing coupling agent.

9. The method for preparing the three-proof adhesive for direct writing 3D printing according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step S1, mixing and stirring biphenyl epoxy resin, multifunctional epoxy resin, core-shell rubber modified epoxy resin and modified filler to obtain a first mixture; Step S2, adding a latent curing agent to the first mixture and stirring to obtain a second mixture; Step S3, grinding the second mixed material to a particle size of ≤10 μm to obtain a third mixed material; Step S4, vacuum degassing and pressure filtering are performed on the third mixed material in sequence to obtain the three-proof adhesive for direct writing 3D printing.

10. The preparation method according to claim 9, characterized in that: The vacuum degree of the vacuum degassing is 40-100 mbar; and / or The pressure of the pressure filtration is 0.5-1.5 kg / cm 2 , the filter size is 300-400 mesh.

11. The preparation method according to claim 9 or 10, characterized in that: In the step S2, after adding the latent curing agent to the first mixture, a curing accelerator and an auxiliary agent are also added, and then stirring is performed.

12. The preparation method according to claim 11, characterized in that: The ratio of the total weight of the biphenyl epoxy resin and the multifunctional epoxy resin to the weight of the curing accelerator is 100:(3-8); and / or The ratio of the total weight of the biphenyl epoxy resin and the multifunctional epoxy resin to the weight of the auxiliary agent is 100:(1-3).

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