High-stability weather-resistant chip packaging adhesive used in extreme environment of air and space and preparation method of high-stability weather-resistant chip packaging adhesive

Abstract

The invention belongs to the technical field of chemical materials, and particularly relates to a high-stability weather-resistant chip packaging adhesive used in an air and space extreme environment and a preparation method of the high-stability weather-resistant chip packaging adhesive. The invention relates to a flame-retardant coating which comprises the following components: bisphenol A type epoxy resin, alicyclic epoxy resin, organic silicon modified epoxy resin, hydroxyl-terminated polyether polyol, core-shell rubber, micron boron nitride, aluminum oxide, nano silicon carbide, graphene (GNP), dicyandiamide (DICY), 2-ethyl-4-methylimidazole (EMI-24), a hindered amine light stabilizer, nano dicerium trioxide and benzyl glycidyl ether. By adopting an organic silicon modified epoxy resin and multi-particle-size grading filler composite system and a stepped curing process, the problems of easy brittle fracture, insufficient heat conductivity, poor radiation resistance, interface layering caused by non-uniform filler dispersion and the like of a traditional epoxy resin-based packaging adhesive in a wide temperature range are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical materials, and specifically relates to a highly stable weather-resistant chip encapsulation adhesive for aerospace extreme environments and a preparation method thereof. Background Art

[0002] With the evolution of aerospace electronic devices towards high performance and miniaturization, the power density of integrated circuit chips continues to climb, and the thermal management challenges in extreme environments (such as high vibration, wide temperature range, and strong radiation) are becoming increasingly severe. As the core material for chip heat dissipation and mechanical protection, the thermal performance of the encapsulation adhesive directly determines the reliability and lifespan of the device. The inherent thermal conductivity of traditional epoxy-based encapsulation adhesives is generally low, making it difficult to meet the heat dissipation requirements of aerospace chips with a local power density exceeding 100 W / cm 2 . Although the thermal conductivity can be improved by adding highly thermally conductive fillers such as alumina and boron nitride, a high filling ratio will cause a sharp increase in viscosity, affecting the filling uniformity of micro-gaps, forming pores or unfilled areas, and exacerbating the thermal resistance. In addition, the thermal expansion coefficients of conventional encapsulation adhesives are significantly different from those of silicon chips and ceramic substrates, and interface delamination or solder joint cracking is likely to occur due to stress concentration during thermal cycling.

[0003] Aerospace devices need to work long-term under a wide temperature range of -65 to 150 °C and strong radiation conditions. However, the glass transition temperature (Tg) of traditional encapsulation adhesives is mostly below 120 °C, and softening occurs at high temperatures, resulting in a decrease in structural strength. Ultraviolet and radiation environments can also cause the breakage of organic resin chains, resulting in the aging, discoloration, and even failure of the colloid. To balance the thermal conductivity and thermal expansion coefficient, existing technologies mostly use multi-sized spherical alumina (such as 5 μm, 10 μm, 20 μm gradation) and fibrous aluminum nitride composite fillers. However, the fibrous fillers are prone to form a network structure, increasing the viscosity, and relying on long-chain silane coupling to improve the dispersibility. Even so, when the filling amount exceeds 80%, problems such as deteriorated fluidity still occur, and defect-free filling of sub-50 μm gaps cannot be achieved. Chinese Patent CN117511476A, a liquid epoxy adhesive and its preparation method and application. The thermal expansion coefficient of traditional epoxy adhesives is usually in the range of 25 - 30 ppm / K, which shows a significant mismatch with silicon chips and ceramic substrates, resulting in interface delamination or solder joint cracking due to stress concentration during thermal cycling.

[0004] In summary, there is an urgent need for a material system for aerospace encapsulation adhesives that combines high thermal conductivity, low thermal expansion coefficient, wide temperature range stability, and excellent processability. Based on the above technical defects, the present invention aims to provide a highly reliable chip encapsulation adhesive solution suitable for aerospace extreme environments through innovative material formulations and curing processes. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the present invention provides a highly stable weather-resistant chip encapsulation adhesive for aerospace extreme environments and a preparation method thereof. By adopting an organosilicon-modified epoxy resin, a multi-particle-size graded filler composite system and a stepwise curing process, the problems of easy brittle cracking, insufficient thermal conductivity, poor anti-radiation performance and interface delamination caused by uneven filler dispersion of traditional epoxy resin-based encapsulation adhesives in a wide temperature range are solved. The high stability of the encapsulation adhesive in the wide temperature range of -65 to 250 °C is achieved, and the comprehensive performance of the impact resistance strength, thermal conductivity coefficient and strength after radiation resistance is improved, meeting the heat dissipation, mechanical protection and long-term reliability requirements of aerospace chips in extreme environments.

[0006] To solve the above technical problems, a technical solution provided by the present invention is: a highly reliable chip encapsulation adhesive suitable for aerospace extreme environments, comprising components in the following weight percentage ranges: bisphenol A type epoxy resin 25% - 35%, alicyclic epoxy resin 10% - 15%, organosilicon-modified epoxy resin 8% - 12%, hydroxyl-terminated polyether polyol 15% - 25%, core-shell rubber 5% - 8%, micron boron nitride 15% - 20%, aluminum oxide 25% - 30%, nano silicon carbide 5% - 8%, graphene (GNP) 0.5% - 1%, dicyandiamide (DICY) 4% - 6%, 2-ethyl-4-methylimidazole (EMI-24) 3% - 5%, hindered amine light stabilizer 0.5% - 1%, nano cerium oxide 2% - 3%, benzyl glycidyl ether 5% - 8%.

[0007] Further, the bisphenol A type epoxy resin is bisphenol A diglycidyl ether (E-51), and the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl epoxy resin.

[0008] Further, the aluminum oxide consists of three particle sizes of 20μm:10μm:5μm = 5:3:2.

[0009] Further, the particle size of the nano silicon carbide is 50 - 100nm, and the micron boron nitride is spherical with a particle size of 10 - 20μm.

[0010] In the aerospace field, the chip encapsulation adhesive needs to face extreme environmental challenges such as a wide temperature range of -65 to 150 °C, strong radiation, and high vibration. However, traditional epoxy resins have many defects and are difficult to meet the usage requirements. Firstly, its crosslinking density is high, and it shows great brittleness after curing, with an elongation at break of less than 5%, and it is easy to break under thermal cycling stress and mechanical shock; secondly, the glass transition temperature (Tg) is mostly lower than 120 °C, it is easy to soften at high temperatures and brittle at low temperatures; thirdly, in an ultraviolet and radiation environment, the chain segments of epoxy resins are prone to breakage, leading to yellowing and performance degradation; fourthly, the interfacial compatibility with inorganic fillers such as boron nitride and alumina is poor, and due to the mismatch of the coefficient of thermal expansion (CTE), delamination problems are extremely likely to occur. Based on this, the present invention proposes to modify epoxy resins with silicone to solve the above problems.

[0011] The preparation method of silicone-modified epoxy resin is as follows:

[0012] (1) Synthesis of silicone oligomer: By mass percentage, add 50% - 60% dimethyldiethoxysilane, 25% - 35% diphenyldiethoxysilane, 3% - 5% hydrochloric acid with a concentration of 5 wt%, and 5% - 10% xylene into a three-necked flask. Under the protection of nitrogen atmosphere, mechanically stir at a speed of 100 - 200 rpm. After fully mixing the raw materials, heat up to 80 - 90 °C and keep reacting at this temperature for 4 - 6 h to promote the hydrolysis and polycondensation reaction of the raw materials to form a polysiloxane oligomer. After the reaction is completed, further purify by vacuum distillation, remove the by-product ethanol at -0.095 MPa and 80 °C, and obtain the polysiloxane oligomer;

[0013] (2) Pre-activation of epoxy resin: Add 1% - 3% of maleic anhydride and 0.1% - 0.3% of triethylamine by mass to bisphenol A epoxy resin (E-51), and stir and react at 80 - 100 °C for 1 - 2 h to pre-activate the carboxylation of A-type epoxy resin (E-51);

[0014] (3) Epoxy resin graft modification reaction: By mass percentage, take 10% - 15% of the organosilicon oligomer prepared in step (1) and 40% - 50% of the bisphenol A epoxy resin (E-51) pre-activated in step (2) and mix them. Then add 0.5% - 1% of tetrabutyl titanate and 40% - 45% of xylene. Under nitrogen protection, disperse the mixture at a high speed of 400 - 500 rpm for 10 - 15 min. Then raise the temperature in stages for reaction. First, raise the temperature to 80 - 85 °C for 1 - 1.5 h of pre-reaction, and then raise the temperature to 120 - 125 °C and react for 3 - 5 h. Add 3% - 5% of nano-silica based on the mass of bisphenol A epoxy resin (E-51) 30 min before the end of the reaction, and perform ultrasonic treatment at 40 kHz and 300 W for 20 - 30 min. Cool the system to 60 °C for standby;

[0015] (4) Post-treatment: Transfer the reaction solution of step (3) to a rotary evaporator, and carry out vacuum desolvation at -0.098 MPa and 80 - 90 °C to remove the xylene solvent until the volatile content is less than 0.5%. After desolvation, perform hot pressing and molding pretreatment on the product at 120 °C for 2 - 4 h, and then filter with a 0.2 μm filter to remove unreacted gel particles and impurities, and finally obtain a modified epoxy resin intermediate;

[0016] (5) Performance strengthening treatment: Place the filtered modified epoxy resin intermediate and 0.3% - 0.5% of polyetheramine (D-230) in a high-pressure reactor, introduce carbon dioxide gas until the pressure reaches 5 - 8 MPa, first maintain at 3 MPa for 1 h, then gradually increase the pressure to 5 - 8 MPa and maintain for 1 - 2 h. After treatment, introduce 0.1 MPa of oxygen and react at 60 °C for 2 h, and then release the pressure and cool down to finally obtain a transparent and uniform modified epoxy resin.

[0017] Further, in step (2), the bisphenol A epoxy resin is bisphenol A diglycidyl ether.

[0018] Further, in step (3), the nano-silica is surface-treated with a silane coupling agent KH-560.

[0019] During the process of modifying epoxy resin with silicone, the active centers of bisphenol A epoxy resin (E-51) are limited. Depending only on the epoxy groups contained in itself, the reaction degree and binding force with silicone oligomers are relatively weak. Maleic anhydride is used to carboxylate bisphenol A epoxy resin. Its carbon-carbon double bond undergoes an addition reaction with the active hydrogen on the epoxy resin molecular chain, introducing carboxyl groups into the epoxy resin molecular structure, greatly increasing the reactive sites of the epoxy resin molecules, providing more binding opportunities for the subsequent reaction with silicone oligomers, and significantly enhancing the chemical bonding between the two. At the same time, when not pre-activated, the epoxy resin and silicone oligomers only interact with each other by weak van der Waals forces. The carboxyl groups introduced by pre-activation can form stronger hydrogen bonds with polar groups (such as silanol groups) in the silicone oligomers, and even undergo esterification reactions to further form chemical bonds, promoting the two molecules to be closely intertwined in the microstructure and improving compatibility. In addition, the introduction of carboxyl groups changes the electron cloud distribution and spatial structure of the epoxy resin molecular chain, increasing the flexibility of the molecular chain. When forming a copolymer with silicone oligomers, it is more conducive to the mutual diffusion and entanglement of the molecular chains, making the formed copolymer network more uniform and dense, thus comprehensively improving the mechanical properties, heat resistance, etc. of the modified epoxy resin. Therefore, the pre-activation step of epoxy resin is a key link to ensure excellent properties of silicone-modified epoxy resin and is indispensable. Therefore, the carboxyl groups introduced in the pre-activation step of epoxy resin play an important role. In the grafting reaction, the carboxyl groups react with the silanol groups of the silicone oligomers to form stable Si-O-C chemical bonds, significantly enhancing the compatibility between the two phases. Secondly, in the supercritical CO2 treatment, after the carboxyl groups are protonated, they react with polyetheramine to optimize the crosslinking network structure, and the glass transition temperature is increased, systematically solving the problems of poor compatibility, uneven filler dispersion and imperfect crosslinking in traditional modification processes, and providing core technical support for aerospace extreme environment encapsulation materials.

[0020] Silicone-modified epoxy resins are the result of a synergistic effect of molecular structural reconstruction and chemical bonding. The flexible Si-O-Si segments introduced by silicone act as "buffer springs" at the molecular level. Their bond angle (approximately 144°) and bond length (Si-O bond length 0.164 nm) give these segments a high degree of freedom, allowing them to undergo conformational changes and segmental slip when subjected to stress. When the material is subjected to external impact or thermal cycling stress, the Si-O-Si segments absorb energy through flexible deformation, effectively dispersing stress concentration and preventing the rigid epoxy resin network from fracturing due to stress overload. In terms of heat resistance and wide temperature stability, the bond energy of the Si-O bond in silicone molecules (452 kJ / mol) is much higher than that of the C-C bond (346 kJ / mol) and the C-O bond (358 kJ / mol) in epoxy resin. At high temperatures, the thermal decomposition temperature of the Si-O-Si segments exceeds 300°C, effectively inhibiting thermal degradation of the molecular chains. At low temperatures, the flexible segments maintain interchain mobility, preventing excessive stacking and brittle cracking caused by reduced thermal motion. The improved environmental aging resistance is due to the unique electronic structure and molecular arrangement of silicone. The low polarity of the Si-O bond (electronegativity difference 0.7) and the helical molecular conformation give it a surface energy of only 20-24 mN / m, significantly lower than that of epoxy resin (35-40 mN / m), which reduces the adsorption efficiency of ultraviolet rays. At the same time, the 3d empty orbitals of the silicon atoms in the Si-O bond can absorb free radicals generated by radiation, reducing the probability of main chain breakage. 6 Gy radiation dose, the Si-O-Si chain segments significantly improve the material strength through the free radical capture mechanism.

[0021] This modification process addresses multiple dimensions, including molecular structure design and interface performance control, effectively resolving the issues of poor interfacial compatibility with inorganic fillers such as boron nitride and alumina, and reducing thermal expansion coefficient mismatch. First, an organosilicon oligomer is introduced, whose flexible -Si-O-Si- backbone forms a stress buffer, alleviating stress concentration under thermal cycling and mechanical impact. Simultaneously, the silanol groups form hydrogen bonds or chemical bonds with the surface hydroxyl groups of the inorganic filler, enhancing interfacial adhesion. Second, carboxyl groups are introduced into the epoxy resin after pre-activation with maleic anhydride, enhancing compatibility with the inorganic filler through polar interactions. These groups are then grafted onto the organosilicon oligomer to form an interpenetrating network, preventing phase separation and promoting uniform dispersion of the filler. Furthermore, nanosilica acts as a "bridge" connecting the resin and filler, dissipating microstresses. Post-treatment with high-pressure CO2 and oxygen regulates the crosslinking density and optimizes surface polarity. Finally, the organosilicon's inherent thermal expansion coefficient is adjusted to a level between that of the epoxy resin and the inorganic filler. The modification process adjusts the overall thermal expansion coefficient, narrowing the gap with the filler and resulting in a smoother thermal expansion gradient for the composite material. Under the synergistic effect of multiple mechanisms, the modified epoxy resin and inorganic filler form a composite system with strong bonding, low stress, and reduced thermal expansion coefficient matching, effectively suppressing the delamination problem.

[0022] To solve the above technical problems, another technical solution provided by the present invention is: a highly stable weather-resistant chip encapsulation adhesive for aerospace extreme environments and a preparation method, and the specific steps are as follows:

[0023] S1: Heat-treat micron boron nitride in a nitrogen atmosphere at 200 - 300 °C to remove surface hydroxyl groups, calcine aluminum oxide at 400 - 500 °C for 30 min, and ultrasonically disperse and modify nano silicon carbide with KH-560 silane coupling agent;

[0024] S2: Weigh the raw materials according to the formula. Add bisphenol A epoxy resin, alicyclic epoxy resin, silicone-modified epoxy resin, hydroxyl-terminated polyether polyol, core-shell rubber, and benzyl glycidyl ether into the mixing container in sequence, stir at a speed of 400 - 500 rpm in a high-speed disperser for 30 - 40 min to fully blend the resin system. Then transfer the mixture to a vacuum degassing device and treat it at a vacuum degree of -0.095 MPa for 30 min to remove the air bubbles introduced during stirring and avoid forming pore defects after curing, obtaining a uniform and stable basic adhesive;

[0025] S3: Put the basic adhesive into a mixer, add micron boron nitride and aluminum oxide in batches. First, stir at a low speed for 15 - 20 min and then increase the speed to 800 - 1000 rpm and stir for 50 - 70 min. Then add nano silicon carbide and graphene, turn on the high-shear disperser with a linear velocity ≥ 20 m / s and assist with ultrasonic treatment at 40 kHz and 300 W, disperse at a vacuum degree of -0.098 MPa for 90 - 120 min, and then further roll and disperse through a three-roll mill to ensure that the filler particle size D90 ≤ 15 μm, forming a delicate and uniform adhesive-filler composite system;

[0026] S4: Mix dicyandiamide and 2-ethyl-4-methylimidazole, add 5% epoxy resin as the coating material, make microcapsules by high-speed dispersion, process them with a jet mill to an average particle size of 10 - 15 μm, then slowly add the microcapsules to the adhesive-filler mixture in the mixer, add a hindered amine light stabilizer and nano cerium oxide in sequence, stir at 800 - 1000 rpm under a vacuum condition of -0.098 MPa for 40 - 60 min, and then perform online homogenization through a static mixer;

[0027] S5: Use a twin-screw degassing machine to perform final degassing on the composite adhesive. Under a vacuum degree of -0.099 MPa and a temperature ≤ 50 °C, achieve efficient degassing through a screw structure with a length-diameter ratio ≥ 40:1, and then filter through 10 μm and 5 μm filters in sequence to remove impurity particles. The adhesive is filled into a container under nitrogen protection, and a stepwise temperature increase process is adopted in the curing stage to finally obtain a chip encapsulation adhesive with stable performance.

[0028] Furthermore, in step S3, the roller spacing of the three-roll mill is 50 μm→20 μm→10 μm in sequence.

[0029] Furthermore, in step S5, the curing stage adopts a step-by-step temperature rise process: first, the initial forming is achieved by curing at 80°C for 2 to 3 hours, then the temperature is raised to 100 to 120°C (with a pressure of 0.5 MPa) for curing for 3 to 4 hours, and then the curing is performed at 140 to 150°C (with a continuous pressure of 0.5 MPa) for 4 to 5 hours, and then the cooling rate is controlled to be ≤5°C / min.

[0030] The high-stability weather-resistant chip encapsulation adhesive and preparation method for extreme aerospace environments provided by the present invention solve the problems of traditional epoxy resin-based encapsulation adhesives such as easy brittle cracking, insufficient thermal conductivity, and poor radiation resistance under a wide temperature range through component design and process optimization. The components form multiple effects through chemical cross-linking and physical synergy: bisphenol A epoxy resin provides a rigid skeleton and epoxy groups, and is blended with alicyclic epoxy resin and silicone-modified epoxy resin to construct a composite cross-linked matrix to improve overall strength; silicone-modified epoxy resin absorbs stress and reduces the thermal expansion coefficient through flexible Si-O-Si chain segments, and pre-activates carboxyl groups to enhance interfacial bonding with fillers and core-shell rubbers, while the 3d empty orbitals of silicon atoms improve radiation resistance. The carboxyl group forms an "epoxy resin-carboxyl-silica" bridging structure with the nano-silica treated with KH-560 through hydrogen bonding or esterification, which promotes the uniform dispersion of the nano-filler and significantly improves the thermal conductivity; the hydroxyl group of the hydroxyl-terminated polyether polyol reacts with the epoxy group of the epoxy resin to open the ring, embed into the cross-linked network and introduce flexible polyether segments, reduce the cross-linking density and increase the elongation at break, and at the same time, the hydroxyl group forms hydrogen bonds with the surface hydroxyl groups of micron boron nitride and aluminum oxide, enhancing the filler interface wettability and improving the dispersion. Its low glass transition temperature (-60°C) is combined with the high temperature stability of the silicone-modified epoxy resin (Tg>160°C), broadening the applicable temperature range of the material to -65~150°C. The elastic core (butadiene) of the core-shell rubber induces silver streaks and shear bands when subjected to stress, absorbing impact energy and enhancing impact strength. The rigid shell (methyl methacrylate) enhances interfacial shear strength through esterification of the carboxyl groups with the carboxyl groups of a silicone-modified epoxy resin and chemical bonding with the hydroxyl groups of a hydroxyl-terminated polyether polyol and the epoxy groups of benzyl glycidyl ether. The low viscosity (3-5 mPa·s) of benzyl glycidyl ether improves the dispersion efficiency of the system. Its benzyl benzene rings adsorb hindered amine light stabilizers and nano-cerium trioxide through π-π stacking, forming a molecular-scale anti-aging composite structure that significantly enhances free radical capture efficiency. The epoxy groups preferentially react with dicyandiamide, regulating the uniform growth of the crosslinked network. Combined with a step-by-step temperature ramp (80°C → 120°C → 150°C), the Tg is uniformly increased to 165-172°C, and the thermal expansion coefficient is stabilized at 10-12 ppm / °C.

[0031] In the process design, micron-sized boron nitride is subjected to high-temperature heat treatment to remove surface hydroxyl groups to reduce agglomeration. Aluminum oxide is calcined to improve crystallinity and enhance the continuity of the heat conduction path. Nano-sized silicon carbide is modified with KH-560 silane coupling agent and forms a chemical bond (Si-O-C bond) with epoxy resin to solve the dispersion problem. In terms of interface bonding and internal stress regulation, the silane coupling agent optimizes the microscopic interface structure through its "dual-function" effect. Its alkoxy end (-OR) undergoes a condensation reaction with the surface hydroxyl groups of the filler to form a covalent bond of Si-O-M (M represents the filler). The organic functional groups at the other end (such as amino groups and epoxy groups) react chemically and physically entangle with the epoxy resin to construct a nano-scale transition layer at the filler-resin interface. This chemical bonding and molecular entanglement effect improve the interfacial shear strength. At the same time, through the homogenization of stress transfer, the internal stress generated due to the mismatch of thermal expansion coefficients is reduced, enhancing the structural stability of the material. In addition, in this invention, through the combined process of "low-speed infiltration - high-speed shearing - ultrasonic cavitation - grinding extrusion", the filler particle size is refined to D90≤15μm. Boron nitride and aluminum oxide form a "thermal conduction skeleton", and nano-sized silicon carbide and graphene are filled in the gaps of the skeleton to construct a continuous thermal conduction network. The curing system adopts the microencapsulation technology, with epoxy resin coating dicyandiamide and imidazole curing agents. At room temperature, the microcapsule wall material (epoxy resin) isolates the contact between the curing agent and the main resin, inhibiting premature cross-linking. When the temperature rises above 80°C, the wall material softens and breaks to release the curing agent, triggering the cross-linking of epoxy resin. Through the "temperature-triggered release" mechanism, the cross-linking synchrony is ensured, avoiding local over-cross-linking or under-cross-linking. The stepwise heating process matches the active windows of different curing agents. In the low-temperature stage, the imidazole curing agent is triggered to form a preliminary network. In the medium-temperature stage, dicyandiamide is activated to increase the cross-linking density. After high-temperature post-curing, a three-dimensional network structure is formed. At the same time, a pressure of 0.5 MPa is applied to inhibit the generation of micropores, and the cooling rate is controlled ≤5°C / min to reduce the internal stress caused by thermal expansion mismatch, finally obtaining a high-performance encapsulation adhesive with a dense microstructure and a glass transition temperature of 160°C or above, meeting the heat dissipation, mechanical protection, and long-term reliability requirements of aerospace chips in extreme environments.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. By introducing flexible Si-O-Si chain segments and high-temperature resistant structures through organosilicon modification of epoxy resin, the glass transition temperature (Tg) of the encapsulation adhesive is increased to above 160°C, solving the problems of high-temperature softening and low-temperature embrittlement of traditional materials. At the same time, the high bond energy and low surface energy characteristics of the Si-O bond endow the material with excellent anti-radiation performance and ultraviolet aging resistance, effectively inhibiting chain segment breakage and yellowing, and meeting the long-term reliability requirements of aerospace equipment in strong radiation and high-vibration environments;

[0034] 2. The molecular network formed by silicone modification enables the elongation at break of the encapsulant to exceed 10%, significantly improving the brittleness of traditional epoxy resins. By modifying the interface between the filler and the resin with a silane coupling agent to construct Si-O-M covalent bonds (M is the filler), the interfacial shear strength is increased to 25 MPa, reducing the mismatch degree of the coefficient of thermal expansion (CTE) with the chip and effectively reducing the stress concentration and delamination risk during thermal cycling. In addition, a continuous thermal conduction network is constructed by a multi-particle-size graded aluminum oxide, boron nitride, nano-silicon carbide, and graphene composite system, increasing the thermal conductivity to 3 - 5 W / m·K and solving the heat dissipation problem of chips with a power density exceeding 100 W / cm 2 for chips;

[0035] 3. Adopting the "three-stage dispersion + microcapsule curing technology" realizes the low-viscosity characteristic of the rubber compound with a viscosity of 40 - 50 Pa·s (25°C), which can meet the defect-free filling of micro-gaps less than 50 μm. The step curing process (80°C → 120°C → 150°C) and pressure control (0.5 MPa) ensure a uniform and dense cross-linked network, avoiding internal stress defects.

[0036] 4. The present invention realizes the coordinated improvement of thermal conductivity, mechanical properties, weather resistance, and processability in a single material system, overcoming problems such as a sharp increase in viscosity and uneven dispersion caused by high filling amounts in traditional technologies, providing key material support for the miniaturization and high power density development of aerospace electronic equipment, and having significant technological innovation and engineering application value. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited thereby. The experimental methods in the following embodiments are all conventional methods unless otherwise specified.

[0038] Embodiment 1

[0039] A highly reliable chip encapsulant suitable for aerospace extreme environments, comprising components within the following weight percentage ranges: bisphenol A epoxy resin 25%, alicyclic epoxy resin 10%, silicone-modified epoxy resin 8%, hydroxyl-terminated polyether polyol 15%, core-shell rubber 5%, micron boron nitride 15%, aluminum oxide 25%, nano-silicon carbide 5%, graphene (GNP) 0.5%, dicyandiamide (DICY) 4%, 2-ethyl-4-methylimidazole (EMI-24) 3%, hindered amine light stabilizer 0.5%, nano-cerium oxide 2%, benzyl glycidyl ether 5%. The bisphenol A epoxy resin is bisphenol A diglycidyl ether (E-51), the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl epoxy resin, the fluorine-containing epoxy resin is tetrafluorobisphenol A epoxy resin, the aluminum oxide is composed of three particle sizes of 20 μm:10 μm:5 μm = 5:3:2, the particle size of the nano-silicon carbide is 50 nm, and the micron boron nitride is spherical with a particle size of 10 μm.

[0040] Preparation method of silicone-modified epoxy resin, the specific steps are as follows:

[0041] (1) Synthesis of silicone oligomer: By mass percentage, add 50% dimethyldiethoxysilane, 25% diphenyldiethoxysilane, 3% hydrochloric acid with a concentration of 5 wt%, and 5% xylene into a three-necked flask. Under the protection of nitrogen atmosphere, mechanically stir at a speed of 100 rpm. After fully mixing the raw materials, heat up to 80 °C and maintain the reaction at this temperature for 4 h to promote the hydrolysis and polycondensation reaction of the raw materials to form a polysiloxane oligomer. After the reaction is completed, further purify by vacuum distillation, remove the by-product ethanol at -0.095 MPa and 80 °C to obtain the polysiloxane oligomer;

[0042] (2) Epoxy resin pre-activation: Add 1% maleic anhydride and 0.1% triethylamine by mass of bisphenol A epoxy resin (E-51), and stir and react at 80 °C for 1 h to carry out carboxylation pre-activation on bisphenol A epoxy resin (E-51);

[0043] (3) Epoxy resin grafting modification reaction: By mass percentage, take 10% of the silicone oligomer prepared in step (1) and 40% of the bisphenol A epoxy resin (E-51) pre-activated in step (2) for mixing, then add 0.5% tetrabutyl titanate and 40% xylene. Under the protection of nitrogen, disperse the mixture at a high speed of 400 rpm for 10 min, and then carry out a staged temperature rise reaction. First, heat up to 80 °C for 1 h of pre-reaction, then heat up to 120 °C and react for 3 h. Add 3% nano-silica by mass of bisphenol A epoxy resin (E-51) 30 min before the end of the reaction. The nano-silica is surface-treated with silane coupling agent KH-560 and ultrasonically treated at 40 kHz and 300 W for 20 min. Cool the system to 60 °C for standby;

[0044] (4) Post-treatment: Transfer the reaction solution in step (3) to a rotary evaporator, carry out vacuum desolvation at -0.098 MPa and 80 - 90 °C to remove the xylene solvent until the volatile content is lower than 0.5%. After desolvation, carry out a 2-h hot pressing and molding pretreatment on the product at 120 °C, and then filter with a 0.2-μm filter screen to remove unreacted gel particles and impurities to finally obtain the modified epoxy resin intermediate;

[0045] (5) Performance enhancement treatment: Place the filtered modified epoxy resin intermediate and 0.3% polyetheramine (D-230) in a high-pressure reactor, introduce carbon dioxide gas until the pressure reaches 5 MPa, maintain at 3 MPa for 1 h first, then gradually increase the pressure to 5 MPa and maintain for 1 h. After treatment, introduce 0.1 MPa of oxygen and react at 60 °C for 2 h, and then release the pressure and cool down to finally obtain a transparent and uniform modified epoxy resin.

[0046] A high-stability weather-resistant chip encapsulation adhesive for aerospace extreme environments and its preparation method are as follows:

[0047] S1: Heat-treat micron boron nitride in a nitrogen atmosphere at 200 °C to remove surface hydroxyl groups, calcine aluminum oxide at 400 °C for 30 min, and ultrasonically disperse and modify nano silicon carbide with KH-560 silane coupling agent.

[0048] S2: Weigh the raw materials according to the formula. Add bisphenol A epoxy resin, alicyclic epoxy resin, organosilicon-modified epoxy resin, hydroxyl-terminated polyether polyol, core-shell rubber, and benzyl glycidyl ether to the mixing container in sequence, stir at 400 rpm in a high-speed disperser for 30 min to fully blend the resin system. Then transfer the mixture to a vacuum degassing device and treat it at a vacuum degree of -0.095 MPa for 30 min to remove the air bubbles introduced during stirring and avoid forming pore defects after curing, obtaining a uniform and stable basic adhesive.

[0049] S3: Put the basic adhesive into a blender, add micron boron nitride and aluminum oxide in batches, stir at low speed for 15 min first and then increase the speed to 800 rpm and stir for 50 min. Then add nano silicon carbide and graphene, turn on a high-shear disperser with a linear velocity ≥20 m / s and assist with ultrasonic treatment at 40 kHz and 300 W, disperse at a vacuum degree of -0.098 MPa for 90 min, and then further roll and disperse through a three-roll mill with roll spacings of 50 μm → 20 μm → 10 μm in sequence to ensure that the filler particle size D90 ≤ 15 μm, forming a delicate and uniform adhesive-filler composite system.

[0050] S4: Mix dicyandiamide and 2-ethyl-4-methylimidazole, add 5% epoxy resin as a coating material, make microcapsules by high-speed dispersion, process them with a jet mill to an average particle size of 10 μm, then slowly add the microcapsules to the adhesive-filler mixture in the blender, add a hindered amine light stabilizer and nano cerium trioxide in sequence, stir at 800 rpm under a vacuum condition of -0.098 MPa for 40 min, and then perform on-line homogenization through a static mixer.

[0051] S5: Use a twin-screw degassing machine to perform final degassing on the composite rubber compound. Under a vacuum of -0.099 MPa and a temperature of ≤50°C, achieve efficient degassing through a screw structure with a length-to-diameter ratio of ≥40:1. Then, filter out impurity particles through 10-μm and 5-μm filter elements in sequence. The rubber compound is filled into a container under nitrogen protection. The curing stage adopts a stepped heating process: first cure at 80°C for 2 h for preliminary shaping, then raise the temperature to 100°C (apply a pressure of 0.5 MPa) and cure for 3 h, and then post-cure at 140°C (maintain a pressure of 0.5 MPa) for 4 h. Subsequently, control the cooling rate at ≤5°C / min to finally obtain a chip encapsulation adhesive with stable performance.

[0052] Example 2

[0053] A highly reliable chip encapsulation adhesive suitable for aerospace extreme environments, comprising components within the following weight percentage ranges: bisphenol A epoxy resin 35%, alicyclic epoxy resin 15%, silicone-modified epoxy resin 12%, hydroxyl-terminated polyether polyol 25%, core-shell rubber 8%, micron-sized boron nitride 20%, aluminum oxide 30%, nano-sized silicon carbide 8%, graphene (GNP) 1%, dicyandiamide (DICY) 6%, 2-ethyl-4-methylimidazole (EMI-24) 5%, hindered amine light stabilizer 1%, nano-sized cerium oxide 3%, benzyl glycidyl ether 8%. The bisphenol A epoxy resin is bisphenol A diglycidyl ether (E-51), the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl epoxy resin, the fluorine-containing epoxy resin is tetrafluorobisphenol A epoxy resin, the aluminum oxide consists of three particle size grades of 20 μm:10 μm:5 μm = 5:3:2, the particle size of the nano-sized silicon carbide is 100 nm, and the micron-sized boron nitride is spherical with a particle size of 20 μm.

[0054] Preparation method of the silicone-modified epoxy resin, the specific steps are as follows:

[0055] (1) Synthesis of silicone oligomer: By mass percentage, add 60% dimethyldiethoxysilane, 35% diphenyldiethoxysilane, 5% hydrochloric acid with a concentration of 5 wt%, and 10% xylene into a three-necked flask. Under a nitrogen protection atmosphere, perform mechanical stirring at a speed of 200 rpm. After fully mixing the raw materials, raise the temperature to 90°C and maintain the reaction at this temperature for 6 h to promote the hydrolysis and polycondensation reaction of the raw materials to form a polysiloxane oligomer. After the reaction is completed, further purify by vacuum distillation, remove the by-product ethanol at -0.095 MPa and 80°C to obtain the polysiloxane oligomer;

[0056] (2) Epoxy resin pre-activation: Add 3% of maleic anhydride and 0.3% of triethylamine by its mass to bisphenol A epoxy resin (E-51), and stir and react at 100°C for 2 h to perform carboxylation pre-activation on bisphenol A epoxy resin (E-51);

[0057] (3) Epoxy resin graft modification reaction: By mass percentage, take 15% of the organosilicon oligomer prepared in step (1) and 50% of the bisphenol A epoxy resin (E-51) pre-activated in step (2) and mix them. Then add 1% of tetrabutyl titanate and 45% of xylene. Under nitrogen protection, disperse the mixture at a high speed of 500 rpm for 15 min. Then raise the temperature in stages for reaction. First, raise the temperature to 85 °C for a pre-reaction of 1.5 h, and then raise the temperature to 125 °C and react for 5 h. Add 5% of nano-silica based on the mass of bisphenol A epoxy resin (E-51) 30 min before the end of the reaction. The nano-silica is surface-treated with silane coupling agent KH-560 and ultrasonic-treated at 40 kHz and 300 W for 30 min. Cool the system to 60 °C for standby;

[0058] (4) Post-treatment: Transfer the reaction solution in step (3) to a rotary evaporator and carry out vacuum desolvation at -0.098 MPa and 90 °C to remove the xylene solvent until the volatile content is less than 0.5%. After desolvation, pre-treat the product by hot pressing at 120 °C for 4 h, and then filter it through a 0.2 μm filter to remove unreacted gel particles and impurities, and finally obtain a modified epoxy resin intermediate;

[0059] (5) Performance enhancement treatment: Place the filtered modified epoxy resin intermediate and 0.5% of polyetheramine (D-230) in a high-pressure reactor, introduce carbon dioxide gas until the pressure reaches 8 MPa, first maintain at 3 MPa for 1 h, then gradually increase the pressure to 8 MPa and maintain for 2 h. After treatment, introduce 0.1 MPa of oxygen and react at 60 °C for 2 h, and then release the pressure and cool down to finally obtain a transparent and homogeneous modified epoxy resin.

[0060] A high-stability weather-resistant chip encapsulation adhesive for aerospace extreme environments and its preparation method, the specific steps are as follows:

[0061] S1: Heat-treat micron boron nitride in a nitrogen atmosphere at 300 °C to remove surface hydroxyl groups, calcine aluminum oxide at 500 °C for 30 min, and ultrasonically disperse and modify nano-silicon carbide with KH-560 silane coupling agent;

[0062] S2: Weigh the raw materials according to the formula. Add bisphenol A epoxy resin, alicyclic epoxy resin, organosilicon-modified epoxy resin, hydroxyl-terminated polyether polyol, core-shell rubber, and benzyl glycidyl ether to the mixing container in sequence, stir at a speed of 500 rpm in a high-speed disperser for 40 min to fully blend the resin system. Then transfer the mixture to a vacuum degassing device and treat it at a vacuum degree of -0.095 MPa for 30 min to remove the air bubbles introduced during stirring and avoid the formation of pore defects after curing, and obtain a uniform and stable basic rubber material;

[0063] S3: Feed the base rubber compound into a blender, add micron boron nitride and aluminum oxide in batches, stir at a low speed for 20 min first and then increase the speed to 1000 rpm and stir for 70 min. Then add nano silicon carbide and graphene, turn on the high-shear disperser with a linear velocity ≥20 m / s and assist with ultrasonic treatment at 40 kHz and 300 W, disperse for 120 min under a vacuum degree of -0.098 MPa, and then further roll and disperse through a three-roll mill with the roll spacing being 50 μm → 20 μm → 10 μm in sequence to ensure that the filler particle size D90 ≤ 15 μm, thus forming a delicate and uniform rubber compound-filler composite system;

[0064] S4: Mix dicyandiamide and 2-ethyl-4-methylimidazole and then add 5% epoxy resin as the coating material, make microcapsules by high-speed dispersion, process them to an average particle size of 15 μm through an air-flow pulverizer, then slowly add the microcapsules to the rubber compound-filler mixture in the blender, add a hindered amine light stabilizer and nano cerium trioxide in sequence, stir at 1000 rpm for 60 min under a vacuum condition of -0.098 MPa, and then perform online homogenization through a static mixer;

[0065] S5: Use a twin-screw degassing machine to perform final degassing on the composite rubber compound. Under a vacuum degree of -0.099 MPa and a temperature ≤50 °C, achieve efficient degassing through a screw structure with a length-diameter ratio ≥40:1, and then filter out impurity particles through 10-μm and 5-μm filters in sequence. The rubber compound is filled into a container under nitrogen protection. The curing stage adopts a stepwise temperature-rising process: first cure at 80 °C for 3 h for preliminary shaping, then raise the temperature to 120 °C (apply a pressure of 0.5 MPa) and cure for 4 h, then post-cure at 150 °C (maintain a pressure of 0.5 MPa) for 5 h, and then control the cooling rate ≤5 °C / min to finally obtain a chip encapsulation adhesive with stable performance.

[0066] Example 3

[0067] A high-reliability chip encapsulation adhesive suitable for the extreme aerospace environment, comprising components in the following weight percentage ranges: bisphenol A epoxy resin 30%, alicyclic epoxy resin 12.5%, silicone-modified epoxy resin 10%, hydroxyl-terminated polyether polyol 20%, core-shell rubber 6.5%, micron boron nitride 17.5%, aluminum oxide 28.5%, nano silicon carbide 6.5%, graphene (GNP) 0.75%, dicyandiamide (DICY) 5%, 2-ethyl-4-methylimidazole (EMI-24) 4%, hindered amine light stabilizer 0.75%, nano cerium oxide 2.5%, benzyl glycidyl ether 6.5%. The bisphenol A epoxy resin is bisphenol A diglycidyl ether (E-51), the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl epoxy resin, the fluorine-containing epoxy resin is tetrafluorobisphenol A epoxy resin, the aluminum oxide consists of three particle size grades of 20μm:10μm:5μm = 5:3:2, the particle size of the nano silicon carbide is 75nm, and the micron boron nitride is spherical with a particle size of 15μm.

[0068] Preparation method of the silicone-modified epoxy resin, the specific steps are as follows:

[0069] (1) Synthesis of silicone oligomer: By mass percentage, add 55% dimethyldiethoxysilane, 30% diphenyldiethoxysilane, 4% hydrochloric acid with a concentration of 5wt%, and 7.5% xylene into a three-necked flask. Under the protection of nitrogen atmosphere, carry out mechanical stirring at a speed of 150rpm. After fully mixing the raw materials, heat up to 85°C and keep the reaction at this temperature for 5h to promote the hydrolysis and polycondensation reaction of the raw materials to form a polysiloxane oligomer. After the reaction is completed, further purify by vacuum distillation, remove the by-product ethanol at -0.095MPa and 80°C to obtain the polysiloxane oligomer;

[0070] (2) Epoxy resin pre-activation: Add 2% maleic anhydride and 0.2% triethylamine by its mass to bisphenol A epoxy resin (E-51), and stir and react at 90°C for 1.5h to carry out carboxylation pre-activation on bisphenol A epoxy resin (E-51);

[0071] (3) Epoxy resin graft modification reaction: By mass percentage, take 12.5% of the organosilicon oligomer prepared in step (1) and 45% of the bisphenol A epoxy resin (E-51) pre-activated in step (2) for mixing. Subsequently, add 0.75% of tetrabutyl titanate and 42.5% of xylene. Under nitrogen protection, disperse the mixture at a high speed of 450 rpm for 12.5 min. Then, raise the temperature in stages for reaction. First, raise the temperature to 82.5 °C for 1.25 h of pre-reaction. Subsequently, raise the temperature to 122.5 °C and react for 4 h. 4% of nano-silica by the mass of bisphenol A epoxy resin (E-51) is added 30 min before the end of the reaction. The nano-silica is surface-treated with silane coupling agent KH-560 and ultrasonic-treated at 40 kHz and 300 W for 25 min. The system is cooled to 60 °C for standby;

[0072] (4) Post-treatment: Transfer the reaction solution of step (3) to a rotary evaporator and carry out vacuum desolvation at -0.098 MPa and 80 - 90 °C to remove the xylene solvent until the volatile content is less than 0.5%. After desolvation, pre-treat the product by hot pressing at 120 °C for 3 h, and then filter it through a 0.2 μm filter to remove unreacted gel particles and impurities, finally obtaining a modified epoxy resin intermediate;

[0073] (5) Performance enhancement treatment: Place the filtered modified epoxy resin intermediate and 0.4% of polyetheramine (D-230) in a high-pressure reactor, introduce carbon dioxide gas until the pressure reaches 6.5 MPa, first maintain at 3 MPa for 1 h, then gradually increase the pressure to 6.5 MPa and maintain for 1.5 h. After treatment, introduce 0.1 MPa of oxygen and react at 60 °C for 2 h, and then release the pressure and cool down to finally obtain a transparent and homogeneous modified epoxy resin.

[0074] A high-stability weather-resistant chip encapsulation adhesive for aerospace extreme environments and its preparation method are as follows:

[0075] S1: Heat-treat micron boron nitride in a nitrogen atmosphere at 250 °C to remove surface hydroxyl groups, calcine aluminum oxide at 450 °C for 30 min, and ultrasonically disperse and modify nano-silicon carbide with KH-560 silane coupling agent;

[0076] S2: Weigh the raw materials according to the formula. Add bisphenol A epoxy resin, alicyclic epoxy resin, organosilicon-modified epoxy resin, hydroxyl-terminated polyether polyol, core-shell rubber, and benzyl glycidyl ether to the mixing container in sequence, stir at a speed of 450 rpm in a high-speed disperser for 35 min to fully blend the resin system. Subsequently, transfer the mixture to a vacuum degassing device and treat it under a vacuum degree of -0.095 MPa for 30 min to remove air bubbles introduced during stirring and avoid forming pore defects after curing, obtaining a uniform and stable basic adhesive;

[0077] S3: Feed the base rubber compound into a blender, add micron boron nitride and aluminum oxide in batches, first stir at a low speed for 17.5 min and then increase the speed to 900 rpm and stir for 60 min. Then add nano silicon carbide and graphene, turn on the high-shear disperser with a linear velocity ≥20 m / s and assist with ultrasonic treatment at 40 kHz and 300 W, disperse at a vacuum degree of -0.098 MPa for 105 min, and then further roll and disperse through a three-roll mill with the roll spacing being 50 μm → 20 μm → 10 μm in sequence to ensure that the filler particle size D90 ≤ 15 μm, forming a delicate and uniform rubber compound-filler composite system;

[0078] S4: Mix dicyandiamide and 2-ethyl-4-methylimidazole and then add 5% epoxy resin as the coating material, make microcapsules by high-speed dispersion, process them with a jet mill to an average particle size of 12.5 μm, and then slowly add the microcapsules to the rubber compound-filler mixture in the blender, add a hindered amine light stabilizer and nano cerium sesquioxide in sequence, stir at 900 rpm under a vacuum condition of -0.098 MPa for 50 min, and then carry out online homogenization through a static mixer;

[0079] S5: Use a twin-screw degassing machine to conduct final degassing on the composite rubber compound. Under a vacuum degree of -0.099 MPa and a temperature ≤50 °C, achieve efficient degassing through a screw structure with a length-diameter ratio ≥40:1, and then filter out impurity particles through 10-μm and 5-μm filters in sequence. The rubber compound is filled into a container under nitrogen protection. The curing stage adopts a stepwise temperature-rising process: first cure at 80 °C for 2.5 h for preliminary forming, then raise the temperature to 110 °C (apply a pressure of 0.5 MPa) and cure for 3.5 h, then post-cure at 145 °C (maintain a pressure of 0.5 MPa) for 4.5 h, and then control the cooling rate ≤5 °C / min to finally obtain a chip encapsulation adhesive with stable performance.

[0080] Comparative Example 1: This Comparative Example 1 is basically the same as Example 3, except that the epoxy resin is not modified.

[0081] Comparative Example 2: This Comparative Example 2 is basically the same as Example 3, except that step (2) is not included in the preparation process of the organosilicon-modified epoxy resin.

[0082] Comparative Example 2: This Comparative Example 2 is basically the same as Example 3, except that step (5) is not included in the preparation process of the organosilicon-modified epoxy resin.

[0083] Testing experiment:

[0084] Take the 6 chip encapsulation adhesives of Examples 1 - 3 and Comparative Examples 1 - 3 as test samples for testing, and the test results are shown in Table 1 below.

[0085] 1. Detection of basic physical and chemical properties of force

[0086] Viscosity and Rheological Properties: The initial viscosity (at 25°C), thixotropy index, and shear thinning characteristics are tested using a rotational rheometer (ASTM D4287) to evaluate the processing performance of the rubber compound (such as dispensing and filling ability) and ensure good fluidity and adaptability during the encapsulation process.

[0087] 2. Mechanical and Thermal Property Testing

[0088] Mechanical Properties: The tensile strength (MPa), elongation at break (%), and flexural strength (MPa) are tested using a universal material testing machine (ASTM D638, D790).

[0089] Thermal Properties: The thermal conductivity (W / m·K) is determined by the laser flash method (ASTM E1461), and the coefficient of thermal expansion (CTE, ppm / °C) is tested using a thermomechanical analyzer (TMA, ISO 11359).

[0090] 3. Electrical and Weather Resistance Property Testing

[0091] Electrical Insulation Property: The volume resistivity (Ω·cm) is tested using a high resistance meter (ASTM D257), and the dielectric strength (kV / mm) and dielectric constant (at 1 MHz) are determined using a withstand voltage tester (IEC 60243) to ensure that the encapsulation adhesive can maintain excellent electrical insulation properties under extreme environments such as high voltage and high humidity, and avoid the risks of leakage or breakdown.

[0092] Environmental Aging Resistance Property: Through high and low temperature cycling tests ( 1000 times, IPC-TM-650 2.6.8), damp heat aging tests (85°C / 85%RH, 1000 h, IPC-TM-650 2.6.11), and γ-ray irradiation tests (total dose 100 krad, MIL-STD-883), the effects of aerospace extreme environments on materials are simulated to evaluate their long-term weather resistance, radiation resistance, and corrosion resistance, and ensure the long-term reliability of the encapsulation adhesive under complex working conditions.

[0093] Table 1 Performance Test Results

[0094]

[0095] The test results show that the chip encapsulation adhesive for aerospace extreme environments provided by the present invention is significantly superior to traditional epoxy resin-based materials in terms of mechanical properties, thermal stability, and weather resistance through processes such as silicone modification, epoxy resin pre-activation, and supercritical treatment.

[0096] In terms of mechanical properties, the tensile strength of the examples reaches 35 - 38 MPa, the elongation at break is 12% - 13%, and the impact strength is 16 - 19 kJ / m 2, it is significantly improved compared with the unmodified Comparative Example 1 (tensile strength of 22 MPa, elongation at break of 4%, and impact strength of 5 kJ / m 2 ), indicating that the flexible Si-O-Si chain segments introduced by silicone effectively improve the brittleness of epoxy resin; the interfacial shear strength is 26-28 MPa, which is greater than that of Comparative Example 2 (18 MPa) without pre-activation, verifying that the pre-activation step enhances the chemical bonding between the resin and silicone by introducing carboxyl groups.

[0097] In terms of thermal properties, the glass transition temperature (Tg) of the examples is 165-172 °C, which is much higher than that of Comparative Example 1 (110 °C), and the coefficient of thermal expansion (CTE) is as low as 10-12 ppm / °C, only 1 / 3-1 / 2 of that of Comparative Example 1 (28 ppm / °C). Combining with the thermal conductivity of 3.2-4.8 W / m·K (2.1 W / m·K for Comparative Example 1), it shows that the multi-particle size filler grading and silicone modification synergistically achieve the balance of wide temperature range stability and efficient heat dissipation.

[0098] In the weather resistance test, the performance retention rate of the examples reaches 95%-96% after 1000 temperature shocks from -65 to 150 °C, the radiation resistance (100 krad) retention rate is 88%-90%, and the hygrothermal aging strength retention rate is 93%-94%, all of which are significantly better than those of the unmodified or un-pre-activated comparative examples (such as the temperature shock retention rate of Comparative Example 1 is only 65% and the radiation resistance retention rate is 55%), reflecting the free radical capture ability of the silicone chain segments and the anti-aging effect of the nano additives.

[0099] In Comparative Example 1 without silicone modification, due to the lack of flexible chain segments and radiation-resistant groups, the mechanical and weather resistance properties are comprehensively deteriorated; in Comparative Example 2 without pre-activation, due to weak interfacial bonding, the interfacial shear strength and aging resistance performance are significantly decreased; in Comparative Example 3 without supercritical CO2 treatment, due to insufficient cross-linking network uniformity, the temperature shock retention rate is slightly lower than that of the examples.

[0100] In summary, through molecular structure design and process optimization, the present invention successfully solves the problems of brittleness, thermal mismatch and aging of traditional encapsulation adhesives in extreme environments. Its comprehensive performance meets the requirements of aerospace electronic equipment for high-reliability encapsulation materials, and has significant technological innovation and engineering application value.

[0101] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A high-stability weather-resistant chip encapsulant for use in extreme aerospace environments, characterized in that: The invention comprises the following components in the following weight percentage ranges: 25% to 35% of bisphenol A epoxy resin, 10% to 15% of alicyclic epoxy resin, 8% to 12% of organosilicon modified epoxy resin, 15% to 25% of terminal hydroxyl polyether polyol, 5% to 8% of core-shell rubber, 15% to 20% of micron boron nitride, 25% to 30% of aluminum oxide, 5% to 8% of nano silicon carbide, 0.5% to 1% of graphene, 4% to 6% of dicyandiamide, 3% to 5% of 2-ethyl-4-methylimidazole, 0.5% to 1% of hindered amine light stabilizer, 2% to 3% of nano cerium oxide, and 5% to 8% of benzyl glycidyl ether.

2. The high-stability weather-resistant chip encapsulant for extreme aerospace environments according to claim 1, characterized in that: The bisphenol A type epoxy resin is bisphenol A diglycidyl ether, and the alicyclic epoxy resin is 3,4-epoxycyclohexyl methyl epoxy resin.

3. A highly stable and weather-resistant chip encapsulation adhesive for aerospace extreme environments according to claim 1, characterized in that, The aluminum oxide is composed of three particle size grades of 20 μm: 10 μm: 5 μm = 5:3:

2.

4. A high-stability weather-resistant chip encapsulation adhesive for aerospace extreme environments according to claim 1, characterized in that, The particle size of the nano silicon carbide is 50 to 100 nm, and the particle size of the micron boron nitride is spherical and is 10 to 20 μm.

5. A highly stable and weather-resistant chip encapsulation adhesive for aerospace extreme environments according to claim 1, characterized in that, The preparation method of the organosilicon-modified epoxy resin comprises the following specific steps: (1) Synthesis of organosilicon oligomers: 50% to 60% of dimethyldiethoxysilane, 25% to 35% of diphenyldiethoxysilane, 3% to 5% of 5 wt% hydrochloric acid, and 5% to 10% of xylene were added to a three-necked flask by mass percentage, and mechanically stirred at a speed of 100 to 200 rpm under a nitrogen atmosphere. After the raw materials were fully mixed, the temperature was raised to 80 to 90° C. and the reaction was maintained at this temperature for 4 to 6 hours to promote the hydrolysis and polycondensation reaction of the raw materials, thereby forming polysiloxane oligomers. After the reaction was completed, the polysiloxane oligomers were further purified by vacuum distillation at -0.095 MPa and 80° C. to remove the by-product ethanol. (2) Epoxy resin preactivation: 1% to 3% by weight of maleic anhydride and 0.1% to 0.3% by weight of triethylamine are added to bisphenol A epoxy resin, and the mixture is stirred at 80 to 100° C. for 1 to 2 hours to perform carboxylation preactivation on the bisphenol A epoxy resin; (3) Epoxy resin grafting modification reaction: 10% to 15% of the organosilicon oligomer prepared in step (1) is mixed with 40% to 50% of the bisphenol A epoxy resin pre-activated in step (2) by mass percentage, and then 0.5% to 1% of butyl titanate and 40% to 45% of xylene are added. Under nitrogen protection, the mixture is dispersed at a high speed of 400 to 500 rpm for 10 to 15 minutes, and then the temperature is raised in stages for reaction. The temperature is first raised to 80 to 85°C for 1 to 1.5 hours for pre-reaction, and then raised to 120 to 125°C for reaction for 3 to 5 hours. 30 minutes before the end of the reaction, 3% to 5% of nano-silicon dioxide by mass of the bisphenol A epoxy resin is added. Ultrasonic treatment is carried out at 40kHz and 300W for 20 to 30 minutes, and the system is cooled to 60°C for standby use. (4) Post-treatment: Transfer the reaction solution from step (3) to a rotary evaporator, and carry out vacuum desolvation at -0.098 MPa and 80 - 90 °C to remove the xylene solvent until the volatile content is less than 0.5%. After desolvation, pre-treat the product by hot pressing and forming at 120 °C for 2 - 4 h, then filter it through a 0.2-μm filter to remove unreacted gel particles and impurities, and finally obtain the modified epoxy resin intermediate; (5) Performance enhancement treatment: Place the filtered modified epoxy resin intermediate and 0.3% - 0.5% polyetheramine in a high-pressure reactor, introduce carbon dioxide gas until the pressure reaches 5 - 8 MPa, maintain at 3 MPa for 1 h first, then gradually increase the pressure to 5 - 8 MPa and maintain for 1 - 2 h. After treatment, introduce oxygen at 0.1 MPa and react at 60 °C for 2 h, then release the pressure and cool down to finally obtain a transparent and homogeneous modified epoxy resin.

6. The high-stability weather-resistant chip encapsulation adhesive for use in extreme aerospace environments according to claim 5, characterized in that: In step (2), the bisphenol A-type epoxy resin is bisphenol A diglycidyl ether, and in step (3), the nano-silica is surface-treated with the silane coupling agent KH-560.

7. The preparation method of a highly stable weather-resistant chip encapsulation adhesive for aerospace extreme environments according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: S1: Heat-treat micron boron nitride in a nitrogen atmosphere at 200 - 300 °C to remove surface hydroxyl groups, calcine aluminum oxide at 400 - 500 °C for 30 min, and ultrasonically disperse and modify nano-silicon carbide with the KH-560 silane coupling agent; S2: Weigh the raw materials according to the formula. Add bisphenol A-type epoxy resin, alicyclic epoxy resin, organosilicon-modified epoxy resin, hydroxyl-terminated polyether polyol, core-shell rubber, and benzyl glycidyl ether to the mixing container in sequence, stir at a speed of 400 - 500 rpm in a high-speed disperser for 30 - 40 min to fully blend the resin system. Then transfer the mixture to a vacuum degassing device and treat it under a vacuum of -0.095 MPa for 30 min to remove the air bubbles introduced during stirring and avoid the formation of pore defects after curing, obtaining a uniform and stable base rubber compound; S3: Put the base rubber compound into a mixer, add micron boron nitride and aluminum oxide in batches. First, stir at a low speed for 15 - 20 min and then increase the speed to 800 - 1000 rpm and stir for 50 - 70 min. Then add nano-silicon carbide and graphene, turn on the high-shear disperser with a linear velocity ≥20 m / s and assist with ultrasonic treatment at 40 kHz and 300 W, disperse under a vacuum of -0.098 MPa for 90 - 120 min, and then further roll and disperse through a three-roll mill to ensure that the filler particle size D90 ≤ 15 μm, forming a delicate and uniform rubber compound-filler composite system; S4: Mix dicyandiamide and 2-ethyl-4-methylimidazole, add 5% epoxy resin as the coating material, make microcapsules by high-speed dispersion, process them with a jet mill to an average particle size of 10 - 15 μm, then slowly add the microcapsules to the rubber compound-filler mixture in the mixer, add hindered amine light stabilizer and nano-cerium oxide in sequence, stir at 800 - 1000 rpm under a vacuum of -0.098 MPa for 40 - 60 min, and then carry out on-line homogenization through a static mixer; S5: Use a twin-screw degassing machine to perform final degassing on the composite rubber material. Under a vacuum degree of -0.099 MPa and a temperature of ≤50°C, achieve efficient degassing through a screw structure with a length-diameter ratio of ≥40:

1. Then, filter out impurity particles through 10-μm and 5-μm filter elements in sequence. The rubber material is filled into a container under nitrogen protection. During the curing stage, adopt a stepwise temperature-rising process to finally obtain a chip encapsulation adhesive with stable performance.

8. The preparation method of a highly stable weather-resistant chip encapsulation adhesive for aerospace extreme environments according to claim 7, characterized in that In step S3, the roller spacings of the three-roll grinder are 50 μm → 20 μm → 10 μm in sequence.

9. The preparation method of a highly stable weather-resistant chip encapsulation adhesive for aerospace extreme environments according to claim 7, characterized in that, In step S5, the stepwise temperature-rising process is adopted during the curing stage: first cure at 80°C for 2 - 3 h for preliminary forming, then raise the temperature to 100 - 120°C, apply a pressure of 0.5 MPa, and cure for 3 - 4 h. Then, at 140 - 150°C, maintain a pressure of 0.5 MPa and post-cure for 4 - 5 h. Subsequently, control the cooling rate ≤5°C / min.

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