Low-dielectric insulation fixing adhesive and preparation method thereof

Abstract

The invention discloses a low-dielectric insulation fixing adhesive and a preparation method thereof, and belongs to the technical field of fixing adhesives. The raw materials comprise, by weight, 25-40 parts of an epoxy resin matrix, 5-10 parts of a modified silane coupling agent, 15-30 parts of a low dielectric filler, 8-15 parts of a curing agent, 3-8 parts of a toughening agent, 2-5 parts of a diluent, and 0.5-2 parts of an antioxidant; the low dielectric filler is a composite filler of hollow glass beads and boron nitride, the mass ratio of the hollow glass beads to the boron nitride is (2-3): 1, and the modified silane coupling agent is a gamma-aminopropyltriethoxysilane grafted maleic anhydride modified product; according to the invention, the dielectric constant and the dielectric loss of the adhesive can be reduced, and the insulating property, the bonding strength and the compatibility with a base material can be improved at the same time.

Description

Technical Field

[0001] This invention relates to the field of adhesive fixing technology, specifically to a low dielectric insulating adhesive and its preparation method. Background Technology

[0002] With the rapid development of technologies such as 5G communication and the Internet of Things, electronic devices are moving towards higher frequencies, smaller sizes, and greater integration, placing stringent requirements on the dielectric and insulating properties of adhesives. Low-dielectric insulating adhesives, as core materials for bonding, encapsulating, and fixing components in electronic devices, directly affect the transmission efficiency and stability of high-frequency signals due to their dielectric constant and dielectric loss. An excessively high dielectric constant can lead to signal transmission delays, while excessive dielectric loss can cause signal attenuation and even trigger overheating and malfunctions in the device.

[0003] Currently, most commonly used electronic insulating adhesives on the market are traditional epoxy resin adhesives. Although they possess good bonding strength and insulation properties, they suffer from poor dielectric properties: the dielectric constant of traditional epoxy resin adhesives is mostly above 3.5, and the dielectric loss tangent is greater than 0.01, resulting in severe signal attenuation in high-frequency signal transmission scenarios, making them unsuitable for the high-frequency requirements of 5G equipment. Furthermore, existing low-dielectric fillers, such as hollow glass microspheres and silica, have poor compatibility with the epoxy resin matrix, easily leading to agglomeration and an imbalance between the mechanical and dielectric properties of the adhesive. Moreover, some low-dielectric adhesives require high-temperature and high-pressure curing, resulting in cumbersome production processes, high energy consumption, and difficulty in meeting the bonding requirements of heat-sensitive electronic components. Finally, the heat generated during the operation of electronic equipment can easily cause the adhesive to soften, reducing bonding strength and even causing loss of insulation properties, affecting the long-term reliability of the equipment.

[0004] In summary, existing electronic insulating adhesives, due to their poor dielectric properties, incompatible fillers, and complex curing processes, can no longer meet the application requirements of high-frequency electronic devices such as 5G communication. There is an urgent need to develop an insulating and fixing adhesive with low dielectric constant, low dielectric loss, high bonding strength, and a simple curing process to address the pain points of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a low-dielectric insulating adhesive and its preparation method to solve the problems mentioned in the background art.

[0006] In view of the above problems, the technical solution proposed by the present invention is as follows:

[0007] A low-dielectric insulating adhesive, by weight, comprises the following raw materials: 25-40 parts epoxy resin matrix, 5-10 parts modified silane coupling agent, 15-30 parts low-dielectric filler, 8-15 parts curing agent, 3-8 parts toughening agent, 2-5 parts diluent, and 0.5-2 parts antioxidant; the low-dielectric filler is a composite filler of hollow glass microspheres and boron nitride, wherein the mass ratio of hollow glass microspheres to boron nitride is (2-3):1; the modified silane coupling agent is a modified product of γ-aminopropyltriethoxysilane grafted with maleic anhydride; the epoxy resin matrix serves as the basic framework of the adhesive, and works in conjunction with the modified silane coupling agent; one end of the γ-aminopropyltriethoxysilane grafted with maleic anhydride structure of the modified silane coupling agent can form a chemical bond with the epoxy resin matrix, and the other end can bond with... The functional groups on the surface of the low-dielectric filler are combined, thereby improving the compatibility between the low-dielectric filler and the epoxy resin matrix and preventing filler agglomeration. The low-dielectric filler is made by compounding hollow glass microspheres and boron nitride at a mass ratio of (2-3):1. The low dielectric properties of the hollow glass microspheres and the insulating and thermally conductive properties of boron nitride complement each other. Combined with the insulating properties of the epoxy resin matrix, this reduces the overall dielectric constant of the adhesive and improves the thermal conductivity and insulation properties of the adhesive, thereby meeting the dielectric and insulation requirements of the adhesive for high-frequency signal transmission in electronic devices. The curing agent, toughening agent, diluent, and antioxidant are combined with the main raw materials from the perspectives of curing reaction, mechanical properties, viscosity adjustment, and anti-aging, respectively, thereby improving the comprehensive performance of the adhesive and ensuring its practicality and durability in the bonding of electronic components.

[0008] In a preferred embodiment of the present invention, the epoxy resin matrix is ​​a compound system of bisphenol A type epoxy resin and alicyclic epoxy resin, wherein the mass ratio of the bisphenol A type epoxy resin to the alicyclic epoxy resin is (1-2):1, the epoxy value of the bisphenol A type epoxy resin is 0.51-0.54 eq / 100g, and the epoxy value of the alicyclic epoxy resin is 0.60-0.65 eq / 100g. The epoxy resin matrix is ​​formed by compounding the bisphenol A type epoxy resin and the alicyclic epoxy resin at a mass ratio of (1-2):1. The high adhesion of phenolic A epoxy resin and the low dielectric properties of alicyclic epoxy resin complement each other, thus balancing the adhesive strength and low dielectric requirements of the adhesive. At the same time, the epoxy values ​​of the two epoxy resins are controlled at 0.51-0.54 eq / 100g and 0.60-0.65 eq / 100g, respectively. This combination of epoxy value ranges can regulate the crosslinking density of the epoxy resin matrix, thereby avoiding the problems of increased brittleness of the adhesive due to excessively high crosslinking density or decreased adhesive performance due to excessively low crosslinking density, ultimately improving the overall performance of the adhesive.

[0009] As a preferred embodiment of the present invention, the hollow glass microspheres have a particle size of 50-100 μm and a dielectric constant of less than or equal to 1.8. The boron nitride is hexagonal with a particle size of 1-5 μm and a dielectric constant of less than or equal to 4.0. The low-dielectric filler is pretreated with a silane coupling agent, the amount of which is 1-3% of the total mass of the low-dielectric filler. The difference in particle size between the two fillers creates a gradation effect, which, combined with their low-dielectric properties, results in a more uniform filler distribution in the epoxy resin matrix, reducing dielectric performance fluctuations caused by filler agglomeration. Simultaneously, the low-dielectric filler is pretreated with a silane coupling agent accounting for 1-3% of its total mass. The silane coupling agent forms a modified layer on the filler surface, which, in conjunction with the modified silane coupling agent and the epoxy resin matrix, further enhances the interfacial bonding force between the filler and the matrix, thereby preventing voids at the filler-matrix interface that could lead to increased dielectric loss, and simultaneously enhancing the mechanical properties of the adhesive.

[0010] As a preferred embodiment of the present invention, the curing agent is a compound system of methylhexahydrophthalic anhydride and imidazole accelerator, wherein the mass ratio of methylhexahydrophthalic anhydride to imidazole accelerator is (10-15):1; the imidazole accelerator is 2-ethyl-4-methylimidazole, and the addition amount is 5-8% of the total mass of the curing agent. The curing agent is a compound of methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazole at a ratio of (10-15):1, and 2-ethyl-4-methylimidazole accounts for 5-8% of the total mass of the curing agent. Methylhexahydrophthalic anhydride, as an anhydride curing agent, reacts with the epoxy groups of the epoxy resin matrix to form a stable cross-linked structure. 2-ethyl-4-methylimidazole, as an accelerator, works in conjunction with it to reduce the temperature and time of the curing reaction, thereby avoiding damage to heat-sensitive electronic components caused by high-temperature curing. At the same time, this compounding ratio can control the rate of the curing reaction, thereby ensuring the uniformity of the cross-linked structure and improving the bonding strength and insulation stability of the adhesive.

[0011] In a preferred embodiment of the present invention, the toughening agent is a carboxyl-terminated nitrile butadiene rubber with a number average molecular weight of 3000-5000 and a carboxyl content of 1.5-2.0 mmol / g; the diluent is an reactive diluent AGE with an epoxy value of 0.70-0.75 eq / 100g; the antioxidant is a compound system of antioxidant 1010 and antioxidant 168, with a mass ratio of antioxidant 1010 to antioxidant 168 of 1:1; the toughening agent is a carboxyl-terminated nitrile butadiene rubber with a number average molecular weight of 3000-5000 and a carboxyl content of 1.5-2.0 mmol / g, whose carboxyl groups can react with the epoxy groups of the epoxy resin matrix and graft onto the epoxy resin crosslinking network. In the process of compounding, it works in conjunction with the epoxy resin matrix to improve the toughness and impact resistance of the adhesive, preventing cracking during use due to excessive brittleness. The diluent used is an active diluent AGE with an epoxy value of 0.70-0.75 eq / 100g. Its epoxy groups can participate in the curing reaction, working in conjunction with the epoxy resin matrix and curing agent to reduce the viscosity of the adhesive, improve filler dispersibility and workability, and avoid the decrease in dielectric properties due to the introduction of inactive components. The antioxidant is a 1:1 mixture of antioxidant 1010 and antioxidant 168. The two antioxidants work synergistically by capturing free radicals and decomposing peroxides, respectively, working in conjunction with the epoxy resin matrix to inhibit the oxidative degradation of the adhesive at high temperatures and during long-term use, thereby extending the service life of the adhesive.

[0012] On the other hand, the present invention provides a method for preparing a low-dielectric insulating fixing adhesive, comprising the following steps:

[0013] S1. Low dielectric filler pretreatment: Hollow glass microspheres and boron nitride are mixed in proportion, pretreatment agent and anhydrous ethanol are added, ultrasonically dispersed for 30-40 min, and dried at 80-90℃ for 2-3 h to obtain modified low dielectric filler.

[0014] Specifically, the low-dielectric filler undergoes ultrasonic dispersion and drying pretreatment, which is then combined with the low-dielectric filler and silane coupling agent to ensure uniform grafting of the modifier onto the filler surface. This process also removes moisture from the filler, preventing moisture from causing bubbles to form after the adhesive has cured, thus affecting the dielectric and mechanical properties.

[0015] S2. Premixing of epoxy resin matrix: Add bisphenol A type epoxy resin and alicyclic epoxy resin to the reactor, heat to 60-70℃, stir at 200-300r / min, mix for 15-20min, add modified silane coupling agent, and continue stirring for 30min to obtain premixed resin.

[0016] Specifically, the epoxy resin matrix is ​​premixed under controlled temperature and speed, and a modified silane coupling agent is added. This, combined with the epoxy resin matrix and the modified silane coupling agent, ensures that the two epoxy resins are mixed evenly and that the coupling agent reacts fully with the epoxy resin, laying the foundation for subsequent filler dispersion.

[0017] S3. Addition of fillers and additives: Add modified low dielectric filler to the premixed resin and disperse it for 40-60 min at 1000-1500 r / min using a high-speed disperser. Then add toughening agent, diluent and antioxidant in sequence and stir at low speed for 20-30 min to obtain adhesive base material.

[0018] Specifically, the filler is first dispersed at high speed and then the additives are added at low speed. This is done in combination with low dielectric fillers, toughening agents, diluents, and antioxidants to ensure that the filler is uniformly dispersed in the matrix, while avoiding agglomeration or decomposition of the additives due to high-speed stirring.

[0019] S4. Curing agent compounding and mixing: Methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazol are mixed in proportion, stirred evenly, and then added to the adhesive base material. Vacuum degassing is carried out for 15-20 minutes to obtain a low dielectric insulating fixing adhesive.

[0020] Specifically, after the curing agent is compounded, it is degassed under vacuum and then combined with the curing agent and adhesive base material to ensure uniform dispersion of the curing agent, remove air bubbles from the adhesive, and improve the density of the adhesive.

[0021] S5. Curing and molding: Apply the adhesive to the surface of the substrate to be bonded, pre-cur at 80℃ for 1 hour, then raise the temperature to 120℃ for 2 hours, and finally raise the temperature to 150℃ for 1 hour to complete the bonding and fixing.

[0022] Specifically, step S5 employs a three-stage medium-low temperature curing process, which works in conjunction with the curing agent and epoxy resin matrix to avoid damage to heat-sensitive electronic components during high-temperature curing, while ensuring the integrity of the cross-linked structure and improving the adhesion and insulation performance of the adhesive.

[0023] In a preferred embodiment of the present invention, the ultrasonic dispersion power in step S1 is 300-500W, and the moisture content of the filler after drying is less than or equal to 0.1%. In step S4, the stirring speed during vacuum degassing is 100-150 r / min. Controlling the ultrasonic dispersion power to 300-500W in step S1, in conjunction with the low-dielectric filler and pretreatment agent, ensures that the pretreatment agent can uniformly coat the filler surface while avoiding excessive power that could cause filler breakage and affect low-dielectric properties. The moisture content of the filler after drying is less than or equal to 0.1%, which, in conjunction with the epoxy resin matrix, prevents moisture from forming bubbles during curing, thus avoiding damage to the adhesive's density and dielectric properties. In step S4, the stirring speed during vacuum degassing is controlled at 100-150 r / min, which, in conjunction with the adhesive base material and curing agent, ensures uniform mixing of the curing agent and base material during degassing, while avoiding excessive stirring speed that could reintroduce bubbles, thereby improving the adhesive's molding quality.

[0024] Compared with the prior art, the beneficial effects of this invention are as follows: This low-dielectric insulating adhesive and its preparation method utilize a compound of bisphenol A type and alicyclic epoxy resin as the epoxy resin matrix, combined with a low-dielectric filler composed of hollow glass microspheres and hexagonal boron nitride. By leveraging the low polarizability of the alicyclic epoxy resin and the hollow low-dielectric structure of the hollow glass microspheres, while simultaneously reducing charge polarization through the layered structure of boron nitride, the dielectric constant and dielectric loss of the adhesive are significantly reduced, solving the problems of high-frequency signal transmission delay and attenuation. Addressing the issues of poor compatibility and easy agglomeration between the filler and the epoxy resin matrix, a modified silane coupling agent is used in conjunction with the pretreated low-dielectric filler. One end of the coupling agent is chemically bonded to the epoxy resin matrix, and the other end is bonded to the functional groups on the filler surface. Simultaneously, the particle size of the filler is controlled. The gradation effect further enhances dispersibility, avoiding the imbalance of mechanical and dielectric properties caused by filler agglomeration. Addressing the issues of complex curing processes requiring high temperatures and pressures and incompatibility with heat-sensitive components, a curing agent composed of methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazolium, combined with a three-stage low-temperature curing process, reduces curing temperature and process complexity, preventing damage to heat-sensitive electronic components from high temperatures. To address the problems of adhesive softening, decreased bond strength, and loss of insulation during equipment operation, a carboxyl-terminated nitrile rubber toughening agent improves adhesive toughness, while antioxidants inhibit oxidative aging. Simultaneously, the thermal conductivity of boron nitride, combined with the insulation properties of epoxy resin, effectively dissipates heat generated during equipment operation, preventing adhesive softening and ensuring the long-term reliability of the equipment. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of the preparation method of the low dielectric insulating adhesive disclosed in an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a technical solution: a low-dielectric insulating fixing adhesive, comprising, by weight, the following raw materials: 25-40 parts epoxy resin matrix, 5-10 parts modified silane coupling agent, 15-30 parts low-dielectric filler, 8-15 parts curing agent, 3-8 parts toughening agent, 2-5 parts diluent, and 0.5-2 parts antioxidant; wherein the low-dielectric filler is a composite filler of hollow glass microspheres and boron nitride, wherein the mass ratio of hollow glass microspheres to boron nitride is (2-3):1, and the modified silane coupling agent is a modified product of γ-aminopropyltriethoxysilane grafted with maleic anhydride.

[0028] Specifically, the epoxy resin matrix is ​​first used as the base material for the adhesive, providing a basic bonding and insulating framework. Then, a modified silane coupling agent is added to the epoxy resin matrix. One end of the grafted and modified silane coupling agent reacts with the epoxy groups of the epoxy resin matrix to form covalent bonds, while the polar groups at the other end form hydrogen bonds or chemical bonds with the hydroxyl groups and other functional groups on the surface of the low-dielectric filler. Next, a low-dielectric filler composed of hollow glass microspheres and boron nitride, compounded in a specific ratio, is dispersed into the coupling agent-modified epoxy resin matrix. The hollow... The hollow structure inside the glass microspheres reduces the dielectric constant, while the layered structure of boron nitride enhances insulation and thermal conductivity. Then, a curing agent is added to initiate the cross-linking and curing reaction of the epoxy resin matrix. The toughening agent forms elastic microdomains in the cured system to improve the toughness of the adhesive. The diluent reduces the viscosity of the epoxy resin matrix to improve filler dispersibility and workability. The antioxidant prevents the oxidative degradation of the epoxy resin matrix during use by capturing free radicals. Finally, an adhesive system with low dielectric, high insulation and good mechanical properties is formed.

[0029] As an embodiment of the present invention, the epoxy resin matrix is ​​further comprising a compound system of bisphenol A type epoxy resin and alicyclic epoxy resin, wherein the mass ratio of bisphenol A type epoxy resin to alicyclic epoxy resin is (1-2):1, the epoxy value of the bisphenol A type epoxy resin is 0.51-0.54 eq / 100g, and the epoxy value of the alicyclic epoxy resin is 0.60-0.65 eq / 100g.

[0030] Specifically, first, select a bisphenol A type epoxy resin with an epoxy value of 0.51-0.54 eq / 100g. Utilize the strong polarity and high adhesion brought by the bisphenol A backbone in its molecular structure to provide basic adhesive ability for the adhesive. Then, combine it with an alicyclic epoxy resin with an epoxy value of 0.60-0.65 eq / 100g. Its alicyclic structure has a low polarization rate, which can effectively reduce the dielectric constant of the epoxy resin matrix. Then, mix the two epoxy resins at a mass ratio of (1-2):1, so that the adhesive advantage of the bisphenol A type epoxy resin and the low dielectric advantage of the alicyclic epoxy resin complement each other. During the mixing process, the epoxy groups of the two epoxy resins are evenly distributed. When reacting with the curing agent later, the resins with different epoxy values ​​will form a gradient cross-linking structure, which not only ensures sufficient cross-linking density to maintain adhesive strength, but also reduces molecular polarization due to the presence of the alicyclic structure, thereby achieving a balance between dielectric properties and adhesive properties.

[0031] As an embodiment of the present invention, the hollow glass microspheres have a particle size of 50-100 μm and a dielectric constant of less than or equal to 1.8. The boron nitride is hexagonal with a particle size of 1-5 μm and a dielectric constant of less than or equal to 4.0. The low-dielectric filler is pretreated with a silane coupling agent, and the amount of the pretreatment agent is 1-3% of the total mass of the low-dielectric filler.

[0032] Specifically, hollow glass microspheres with a particle size of 50-100 μm and a dielectric constant of less than or equal to 1.8 are first selected. The air phase formed by their hollow structure reduces the overall dielectric constant. Then, hexagonal boron nitride with a particle size of 1-5 μm and a dielectric constant of less than or equal to 4.0 is selected. Its layered structure can form an insulating and thermally conductive network in the adhesive. Next, the two fillers are mixed in a certain proportion, and 1-3% of a silane coupling agent is added for pretreatment. The hydrolytic groups of the silane coupling agent undergo a condensation reaction with the hydroxyl groups on the surface of the filler. Organic functional groups are grafted onto the surface of the filler to form an organic modified layer. Then, the pretreated low-dielectric filler is added to the epoxy resin matrix. The organic functional groups on the surface of the filler interact with the modified silane coupling agent and the functional groups of the epoxy resin matrix, so that the filler can be uniformly dispersed in the matrix. The particle size distribution of the two fillers allows the small-diameter boron nitride particles to fill the gaps between the large-diameter hollow glass microspheres, reducing the amount of matrix resin used, further reducing the dielectric constant of the adhesive, and improving the interfacial bonding strength between the filler and the matrix.

[0033] As an embodiment of the present invention, the curing agent is further described as a compound system of methyl hexahydrophthalic anhydride and imidazole accelerator, wherein the mass ratio of methyl hexahydrophthalic anhydride to imidazole accelerator is (10-15):1; the imidazole accelerator is 2-ethyl-4-methylimidazole, and the amount added is 5-8% of the total mass of the curing agent.

[0034] Specifically, methylhexahydrophthalic anhydride is first used as the main curing agent. Its anhydride group can undergo a ring-opening addition reaction with the epoxy groups in the epoxy resin matrix to form an ester cross-linked structure, providing basic curing performance for the adhesive. Then, 2-ethyl-4-methylimidazolium, accounting for 5-8% of the total mass of the curing agent, is added as an accelerator, and the mass ratio of methylhexahydrophthalic anhydride to accelerator is controlled at (10-15):1. The imidazole ring in 2-ethyl-4-methylimidazolium can provide active hydrogen, catalyzing the ring-opening reaction of the epoxy groups and accelerating the curing reaction rate. Then, the compounded curing agent is added to the adhesive base. At a lower temperature, the accelerator first forms a complex with the epoxy groups, and then initiates the reaction between the anhydride group and the epoxy groups, gradually forming a uniform cross-linked network. Compared with a single curing agent, this compounded system can complete curing in the medium and low temperature range of 80-150℃, and the reaction rate is controllable, avoiding uneven cross-linking structure due to excessively fast curing or affecting production efficiency due to excessively slow curing.

[0035] In one embodiment of the present invention, the toughening agent is a carboxyl-terminated nitrile butadiene rubber with a number average molecular weight of 3000-5000 and a carboxyl content of 1.5-2.0 mmol / g; the diluent is an reactive diluent AGE with an epoxy value of 0.70-0.75 eq / 100g; and the antioxidant is a compound system of antioxidant 1010 and antioxidant 168, with a mass ratio of antioxidant 1010 to antioxidant 168 of 1:1.

[0036] Specifically, carboxyl-terminated nitrile butadiene rubber with a number average molecular weight of 3000-5000 and a carboxyl content of 1.5-2.0 mmol / g is first added to the adhesive base as a toughening agent. The carboxyl groups on its molecular chain undergo a ring-opening reaction with the epoxy groups of the epoxy resin matrix. The elastic molecular chains of the carboxyl-terminated nitrile butadiene rubber are branched into the cross-linking network of the epoxy resin. When subjected to external force, the elastic molecular chains can absorb energy and deform. Then, an active diluent AGE with an epoxy value of 0.70-0.75 eq / 100g is added. The epoxy groups in its molecules can react with the epoxy resin matrix and the curing agent. The reaction, along with its low molecular weight structure, reduces the viscosity of the epoxy resin matrix, making the low dielectric filler easier to disperse. Then, antioxidants 1010 and 168, compounded in a 1:1 ratio, are added. During the storage and use of the adhesive, antioxidant 1010, as a hindered phenolic antioxidant, first captures the free radicals generated by the oxidation of the epoxy resin matrix, while antioxidant 168, as a phosphite antioxidant, decomposes the peroxides generated during the oxidation process. The two work together to prevent the oxidation chain reaction, delay the aging of the epoxy resin matrix, and ultimately give the adhesive good toughness, workability, and anti-aging properties.

[0037] On the other hand, please see Figure 1This invention provides a technical solution: a method for preparing a low-dielectric insulating adhesive, comprising the following steps:

[0038] S1. Low dielectric filler pretreatment: Hollow glass microspheres and boron nitride are mixed in proportion, pretreatment agent and anhydrous ethanol are added, ultrasonically dispersed for 30-40 min, and dried at 80-90℃ for 2-3 h to obtain modified low dielectric filler.

[0039] S2. Premixing of epoxy resin matrix: Add bisphenol A type epoxy resin and alicyclic epoxy resin to the reactor, heat to 60-70℃, stir at 200-300r / min, mix for 15-20min, add modified silane coupling agent, and continue stirring for 30min to obtain premixed resin.

[0040] S3. Addition of fillers and additives: Add modified low dielectric filler to the premixed resin and disperse it for 40-60 min at 1000-1500 r / min using a high-speed disperser. Then add toughening agent, diluent and antioxidant in sequence and stir at low speed for 20-30 min to obtain adhesive base material.

[0041] S4. Curing agent compounding and mixing: Methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazol are mixed in proportion, stirred evenly, and then added to the adhesive base material. Vacuum degassing is carried out for 15-20 minutes to obtain a low dielectric insulating fixing adhesive.

[0042] S5. Curing and molding: Apply the adhesive to the surface of the substrate to be bonded, pre-cur at 80℃ for 1 hour, then raise the temperature to 120℃ for 2 hours, and finally raise the temperature to 150℃ for 1 hour to complete the bonding and fixing.

[0043] As an embodiment of the present invention, the ultrasonic dispersion power in step S1 is 300-500W, the moisture content of the filler after drying is less than or equal to 0.1%, and the stirring speed during the vacuum degassing process in step S4 is 100-150r / min.

Claims

1. A low-dielectric insulating adhesive, characterized in that, By weight, the raw materials include: 25-40 parts epoxy resin matrix, 5-10 parts modified silane coupling agent, 15-30 parts low dielectric filler, 8-15 parts curing agent, 3-8 parts toughening agent, 2-5 parts diluent, and 0.5-2 parts antioxidant; the low dielectric filler is a composite filler of hollow glass microspheres and boron nitride, the mass ratio of hollow glass microspheres to boron nitride is (2-3):1, and the modified silane coupling agent is a modified product of γ-aminopropyltriethoxysilane grafted with maleic anhydride.

2. The low-dielectric insulating adhesive according to claim 1, characterized in that, The epoxy resin matrix is ​​a compound system of bisphenol A type epoxy resin and alicyclic epoxy resin, wherein the mass ratio of bisphenol A type epoxy resin to alicyclic epoxy resin is (1-2):1, the epoxy value of the bisphenol A type epoxy resin is 0.51-0.54 eq / 100g, and the epoxy value of the alicyclic epoxy resin is 0.60-0.65 eq / 100g.

3. The low-dielectric insulating adhesive according to claim 1, characterized in that, The hollow glass microspheres have a particle size of 50-100 μm and a dielectric constant of less than or equal to 1.

8. The boron nitride is hexagonal with a particle size of 1-5 μm and a dielectric constant of less than or equal to 4.

0. The low-dielectric filler is pretreated with a silane coupling agent, and the amount of the pretreatment agent is 1-3% of the total mass of the low-dielectric filler.

4. The low-dielectric insulating adhesive according to claim 1, characterized in that, The curing agent is a compound system of methyl hexahydrophthalic anhydride and imidazole accelerator, wherein the mass ratio of methyl hexahydrophthalic anhydride to imidazole accelerator is (10-15):1; the imidazole accelerator is 2-ethyl-4-methylimidazolium, and the amount added is 5-8% of the total mass of the curing agent.

5. The low-dielectric insulating adhesive according to claim 1, characterized in that, The toughening agent is a carboxyl-terminated nitrile butadiene rubber with a number average molecular weight of 3000-5000 and a carboxyl content of 1.5-2.0 mmol / g; the diluent is reactive diluent AGE with an epoxy value of 0.70-0.75 eq / 100g; the antioxidant is a compound system of antioxidant 1010 and antioxidant 168 with a mass ratio of 1:

1.

6. A method for preparing a low-dielectric insulating fixing adhesive, characterized in that, When applied to any one or more of the low-dielectric insulating adhesives described in claims 1-5, the method includes the following steps: S1. Low dielectric filler pretreatment: Hollow glass microspheres and boron nitride are mixed in proportion, pretreatment agent and anhydrous ethanol are added, ultrasonically dispersed for 30-40 min, and dried at 80-90℃ for 2-3 h to obtain modified low dielectric filler. S2. Premixing of epoxy resin matrix: Add bisphenol A type epoxy resin and alicyclic epoxy resin to the reactor, heat to 60-70℃, stir at 200-300r / min, mix for 15-20min, add modified silane coupling agent, and continue stirring for 30min to obtain premixed resin. S3. Addition of fillers and additives: Add modified low dielectric filler to the premixed resin and disperse it for 40-60 min at 1000-1500 r / min using a high-speed disperser. Then add toughening agent, diluent and antioxidant in sequence and stir at low speed for 20-30 min to obtain adhesive base material. S4. Curing agent compounding and mixing: Methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazol are mixed in proportion, stirred evenly, and then added to the adhesive base material. Vacuum degassing is carried out for 15-20 minutes to obtain a low dielectric insulating fixing adhesive. S5. Curing and molding: Apply the adhesive to the surface of the substrate to be bonded, pre-cur at 80℃ for 1 hour, then raise the temperature to 120℃ for 2 hours, and finally raise the temperature to 150℃ for 1 hour to complete the bonding and fixing.

7. The method for preparing a low-dielectric insulating fixing adhesive according to claim 6, characterized in that, In step S1, the ultrasonic dispersion power is 300-500W, and the moisture content of the filler after drying is less than or equal to 0.1%. In step S4, the stirring speed during vacuum degassing is 100-150r / min.

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