Method for preparing a self-supporting lightweight material, use

Abstract

The application belongs to the technical field of light materials, and particularly relates to a method for preparing a self-supporting light material and application. The steps are as follows: mixing and stirring heat-conducting core-shell particles, a prepolymer and a compatibilizer; adding a curing agent and an accelerator, and vacuum defoaming; loading the defoamed mixture into an injection cylinder; injection molding, demolding, and obtaining the self-supporting light material, wherein the heat-conducting core-shell particles comprise TiN@AlN particles in which TiN is coated with AlN, and the prepolymer comprises a prepolymer mixed with benzoxazole and epoxy resin. The self-supporting light material is applied to a chip structure. The material prepared by the application can simultaneously meet the comprehensive requirements of high heat conduction, low expansion and high mechanical performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lightweight materials, and particularly relates to a method for preparing a self-supporting lightweight material and application thereof. BACKGROUND

[0002] With the rapid development of electronic devices, aerospace and new energy fields, higher requirements are put forward for the performance of materials: on the one hand, the miniaturization and integration trend of electronic devices leads to an increasing demand for heat dissipation, and traditional polymer-based composite materials are prone to thermal failure due to insufficient thermal conductivity; on the other hand, extreme environments pose severe challenges to the mechanical strength and thermal stability of materials.

[0003] In the prior art, metal-based thermal conductive materials have excellent thermal conductivity, but have large density and poor corrosion resistance; ceramic-based materials have high temperature resistance and low expansion, but have large brittleness and are difficult to process; polymer-based composite materials are lightweight, but have insufficient thermal conductivity and weak interface bonding with inorganic fillers, and it is difficult to simultaneously meet the comprehensive requirements of high thermal conductivity, low expansion and high mechanical performance. SUMMARY

[0004] A first object of the present application is to provide a method for preparing a self-supporting lightweight material. A second object of the present application is to provide application of the method for preparing a self-supporting lightweight material.

[0005] To achieve the above objects and other related objects, the present application provides the following technical solutions:

[0006] The method for preparing a self-supporting lightweight material comprises the following steps:

[0007] The thermal conductive core-shell particles, the prepolymer and the compatibilizer are mixed and stirred; the curing agent and the accelerator are added and vacuum degassed; the degassed mixture is loaded into an injection cylinder; injection molding is performed, and the self-supporting lightweight material is obtained after demolding,

[0008] The thermal conductive core-shell particles comprise TiN@AlN particles in which TiN is coated with AlN, and the prepolymer comprises a prepolymer mixed with benzoxazole and epoxy resin.

[0009] Further, the method for preparing TiN@AlN particles comprises the following steps:

[0010] The TiO2 hollow spheres are immersed in a glucose aqueous solution, stirred, centrifuged, and dried to obtain pretreated TiO2 hollow spheres;

[0011] The pretreated TiO2 hollow spheres are heated to 800-1200℃ in an ammonia atmosphere, and kept at the temperature to obtain TiN hollow spheres; after cooling, the residues are removed, washed and dried for use;

[0012] Ultrasonic dispersion of TiN hollow spheres in anhydrous ethanol; add triethoxyaluminum; adjust the pH to 4-5; stir, centrifuge after reaction; vacuum drying of the precipitate; drying, calcination, cooling, to obtain TiN@AlN particles.

[0013] Further, the particle size of the TiO2 hollow sphere is 0.8-1.5 μm; calcination is: after drying, calcine under nitrogen protection at 400-600℃ for 1-2 hours, heat to 800-1200℃, and keep for 2-4 hours.

[0014] It should be noted that the above technical solutions are used to prepare TiN spheres with a hollow structure by using TiO2 hollow spheres as a precursor, carbon thermal reduction and calcination treatment in an ammonia atmosphere, to form a core with excellent thermal conductivity; through hydrolysis and condensation reaction of triethoxyaluminum on the surface of TiN, a uniform coating layer is formed, which is converted into a dense AlN shell layer after calcination, thereby constructing TiN@AlN core-shell structure particles. The AlN shell layer has the characteristics of high thermal conductivity, moderate surface energy, and strong stability, which not only maintains the overall thermal conductivity of the particles, but also enhances the physical and chemical bonding ability between the resin matrix and the particles in the later stage.

[0015] Further, the preparation method of the prepolymer mixed by benzoxazole and epoxy resin includes the following steps:

[0016] DAB and BTDA are dissolved in NMP, heated to 160-200℃, and kept for reaction; after reaction, a catalyst is added, heated to 200-240℃; keep for 1-3 hours, then cool down to obtain a benzoxazole prepolymer solution; add epoxy resin after cooling, stir and disperse; heat to 80-120℃, stir for 2-6 hours, cool down after reaction to obtain the prepolymer.

[0017] Further, the mass ratio of the benzoxazole prepolymer solution to the epoxy resin is 1:1-3; the catalyst includes sodium benzenesulfonate.

[0018] It should be noted that the above technical solutions are used to prepare TiN spheres with a hollow structure by using TiO2 hollow spheres as a precursor, carbon thermal reduction and calcination treatment in an ammonia atmosphere, to form a core with excellent thermal conductivity; through hydrolysis and condensation reaction of triethoxyaluminum on the surface of TiN, a uniform coating layer is formed, which is converted into a dense AlN shell layer after calcination, thereby constructing TiN@AlN core-shell structure particles. The AlN shell layer has the characteristics of high thermal conductivity, moderate surface energy, and strong stability, which not only maintains the overall thermal conductivity of the particles, but also enhances the physical and chemical bonding ability between the resin matrix and the particles in the later stage.

[0019] Further, the curing agent includes a phenolic curing agent, the compatibilizer includes styrene maleic anhydride, and the accelerator includes an epoxy accelerator.

[0020] It should be noted that the above technical solutions are used to prepare TiN spheres with a hollow structure by using TiO2 hollow spheres as a precursor, carbon thermal reduction and calcination treatment in an ammonia atmosphere, to form a core with excellent thermal conductivity; through hydrolysis and condensation reaction of triethoxyaluminum on the surface of TiN, a uniform coating layer is formed, which is converted into a dense AlN shell layer after calcination, thereby constructing TiN@AlN core-shell structure particles. The AlN shell layer has the characteristics of high thermal conductivity, moderate surface energy, and strong stability, which not only maintains the overall thermal conductivity of the particles, but also enhances the physical and chemical bonding ability between the resin matrix and the particles in the later stage.

[0021] Further, the injection molding parameters include: using an injection molding device, the mold temperature is set to 150-190 DEG C, the injection pressure is 40-60 MPa, the injection time is 10-50 s; after the mold in pressure holding, 160-200 DEG C is solidified for 1-3 hours.

[0022] It should be noted that, by using the above technical scheme, in the injection molding process, the heat-conducting core-shell particles are uniformly distributed in the prepolymer matrix to form a continuous heat conduction network; the synergistic effect of the curing agent and the accelerator enables the system to be rapidly cured to build a dense three-dimensional structure; after molding, the composite material has high thermal conductivity, mechanical properties of self-supporting structure and thermal stability, and is suitable for application scenarios with high requirements for heat conduction and mechanical properties.

[0023] It should be further noted that the injection molding used by the present application successfully solves the difficulties, 1) insufficient compatibility: TiN@AlN core-shell particles are inorganic ceramic phase (high hardness, strong surface inertness), and the prepolymer mixed with benzoxazole and epoxy resin is organic polymer phase (low polarity, flexible chain segment), the difference in surface energy is large, and "agglomeration-dispersion" imbalance is easy to occur. If the surface modification of the compatibilizer to the ceramic particles is not sufficient (such as the maleic anhydride group is not completely anchored to the hydroxyl group on the surface of the ceramic), or the dispersion process (such as insufficient ultrasonic dispersion time) does not eliminate the van der Waals force between the particles, the ceramic particles are easy to agglomerate during injection, resulting in local filler concentration being too high, forming stress concentration points after curing, and reducing the material structure density and mechanical properties (such as compressive strength). 2) Weak interfacial bonding: the surface energy of the ceramic particles is much lower than that of the polymer matrix, if the interface does not form effective chemical bonds (such as Ti-O-C or Al-O-C covalent bonds) or physical anchoring (such as hydrogen bonds), the high shear force during injection will cause the interface between the particles and the polymer to peel off, forming "voids" or "weak interface layers", and finally microcracks appear in the material, reducing the thermal conductivity (TiN / AlN thermal conduction network is broken) and mechanical strength. 3) Although the BOZ-EP prepolymer has a certain fluidity at a certain temperature, the viscosity of the material will increase significantly after mixing with TiN@AlN particles. During injection, high pressure is needed to push the high-viscosity material to quickly fill the mold cavity, if the pressure is insufficient or the injection speed is too slow, it is easy to cause "short shot" (the cavity is not filled); if the pressure is too high or the speed is too fast, the ceramic particles may be broken due to shear, which will damage the integrity of the core-shell structure and reduce the thermal conductivity. For example: after the AlN coating layer is broken, TiN comes into contact with air, the interfacial thermal resistance increases. 4) The setting of the mold temperature needs to meet the following conditions: the prepolymer is in a viscous flow state, which is convenient for injection filling; avoid BOZ from closing loop too early, and partial side reactions occur, such as incomplete dehydration and cyclization of polyamide acid, or premature curing of epoxy resin, which will cause the viscosity of the material to increase sharply during injection, and the material cannot flow. 5) Pressure setting: the solidification rate needs to be controlled during the mold in pressure holding stage to avoid local overheating due to the steep exothermic peak of the prepolymer, which will cause AlN to decompose and reduce the thermal stability of the material.

[0024] A second object, the present application provides the self-supporting lightweight material as a sacrificial layer of a chip structure, the self-supporting lightweight material is prepared according to the method for preparing the self-supporting lightweight material.

[0025] It should be noted that the present application does not use metal substrate in the raw material, and the prepared self-supporting lightweight material has insulation, which can be better applied in the chip structure.

[0026] Further, the sacrificial layer includes a temporary substrate.

[0027] Further, the preparation method of the chip structure comprises the following steps: using a chip mounter to paste the chip on the self-supporting lightweight material through an adhesive, and sequentially forming a three-layer structure of the chip, the adhesive and the self-supporting lightweight material.

[0028] The self-supporting lightweight material prepared by the synergistic effect of the core-shell structure design, the polymer matrix optimization and the composite forming process realizes the significant improvement of the comprehensive performance, and the specific beneficial effects are as follows:

[0029] 1. High thermal conductivity: TiN and AlN in the core-shell structure are both high thermal conductivity materials, and the two form a continuous interface through hydrolysis and condensation, effectively reducing the interface thermal resistance, and cooperating with the blending modification of benzoxazole prepolymer and epoxy resin, the rigid benzoxazole ring of benzoxazole prepolymer can improve the movement ability of polymer chain segment, and finally the thermal conductivity of the composite material is better than that of traditional polymer matrix material.

[0030] 2. Low thermal expansion coefficient: TiN and AlN are both materials with low thermal expansion coefficient, and the synergistic effect of the rigid benzoxazole ring and the epoxy resin makes the overall thermal expansion coefficient of the material as low as 12ppm / ℃, which is highly matched with the thermal expansion coefficient of electronic components (such as silicon chips), and can effectively avoid the interface failure caused by thermal stress.

[0031] 3. Excellent mechanical properties: TiN and AlN are both high modulus materials, and the TiN@AlN core-shell particles prepared therefrom have high modulus, which synergistically act with the rigid benzoxazole prepolymer, and cooperate with the reinforcement of the filler-polymer interface by the compatibilizer, so as to reduce the interface defects, and make the compressive strength of the material as high as 160MPa, which is much higher than the ordinary polymer-based composite material with a compressive strength of less than 50MPa.

[0032] 4. Dense structure: TiN and AlN are both low-density materials, and cooperating with the injection molding process, the material is densified, and finally the material realizes lightweight while maintaining high strength, which is suitable for weight-sensitive fields such as aerospace or electronics.

[0033] 5、Application range is wide: traditional high thermal conductive material (such as metal-based material) often cannot be directly used in the scene needing insulation due to strong conductivity. The self-supporting lightweight material prepared by the application not only has the characteristics of high thermal conductivity, low expansion and high strength, but also has excellent insulation performance. The prepolymer is blended from benzoxazole and epoxy resin, both of which are insulating materials. Although TiN itself has a certain conductivity, the TiN core is completely covered by the AlN shell, forming a core-shell structure of "conductive core-insulating shell". Even if the TiN core is partially exposed (such as interface defects), the AlN shell can still hinder the migration of charge carriers between the filler and the matrix through the "steric hindrance" effect, avoiding the formation of a continuous conductive path. The polar groups (such as ether bonds, hydroxyl groups) of the prepolymer and the hydroxyl groups on the surface of TiN@AlN form a dipole layer at the interface, generating interfacial polarization charges (bound charges), further hindering the migration of free carriers. Although the compatibilizer enhances the interfacial bonding between the filler and the matrix, the covalent bond formed between its anhydride group and the ester bond of the polymer is a "weak bond", and electrons need to cross this bond to migrate, further increasing the interfacial resistance. Therefore, the insulating property of the material makes it have better application value in the field of electronic packaging and power electronic devices. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0035] The equipment and materials used in the embodiments can be easily obtained from commercial companies if not specifically stated.

[0036] Embodiment 1

[0037] The thermal conductive core-shell particles were prepared by the following specific steps:

[0038] The TiO2 hollow spheres were immersed in a 20wt% glucose aqueous solution, stirred for 2 hours, centrifuged and dried at 80℃ to obtain pretreated TiO2 hollow spheres.

[0039] The pretreated TiO2 hollow spheres were heated to 1000℃ at 5℃ / min in an ammonia atmosphere, and kept for 4 hours to obtain TiN hollow spheres. After cooling, the residues were removed by soaking in dilute nitric acid, washed with deionized water and dried for use.

[0040] 1.0g of TiN hollow spheres were ultrasonically dispersed in 30mL of anhydrous ethanol; 1mmol of triethoxyaluminum was added; ice acetic acid was added dropwise to adjust the pH to 4-5; and stirring was carried out at room temperature for 8 hours to promote the hydrolysis and condensation of triethoxyaluminum on the surface of TiN.

[0041] The reaction solution was centrifuged and the supernatant was discarded; the precipitate was transferred to a vacuum drying oven, dried at 60°C and -0.08 MPa for 12 hours; after drying, the sample was calcined at 500°C for 1 hour, then the temperature was increased to 1000°C and the sample was kept at this temperature for 2 hours to complete the conversion reaction of aluminum triethoxide to AlN; after cooling, the heat-conducting core-shell particles were obtained, which were TiN@AlN particles with a core-shell structure, and TiN was coated with AlN.

[0042] The raw material information is as follows: TiO2hollow sphere: particle size 1.5 μm, available from Xi'an Qiyue Biology.

[0043] Example 2

[0044] The pre-polymer was synthesized according to the following steps:

[0045] A three-necked flask was charged with 212 g of DAB and 266 g of BTDA, which were dissolved in 100 mL of NMP, and the temperature was increased to 180°C and kept for 6 hours to form an intermediate polyamide acid; then 0.5 g of sodium benzenesulfonate was added as a catalyst, and the temperature was slowly increased to 220°C to form a benzoxazole structure; after keeping the temperature for 2 hours, the benzoxazole pre-polymer solution was obtained after cooling.

[0046] The benzoxazole pre-polymer solution was cooled to 80°C; epoxy resin E51 was added, and the mass ratio of the benzoxazole pre-polymer solution to the epoxy resin E51 was 1:1.5, and the mixture was fully stirred and dispersed; the temperature was increased to 100°C, and the mixture was stirred for 4 hours to form a stable blended state; after cooling to 60°C, the BOZ-EP pre-polymer was obtained.

[0047] The raw material information is as follows:

[0048] DAB: 3,3'-diaminobenzidine, BR grade. BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride. NMP: solvent, N-methyl pyrrolidone.

[0049] Example 3

[0050] The materials prepared in Examples 1 and 2 were used as raw materials to further prepare a self-supporting lightweight material according to the following steps:

[0051] According to weight parts, 150 parts of the heat-conducting core-shell particles, 100 parts of the pre-polymer, and 10 parts of the compatibilizer were mixed and uniformly stirred at 100°C; 15 parts of the curing agent and 1.5 parts of the accelerator were added, and the mixture was vacuum degassed; the degassed mixture was loaded into an injection cylinder; an injection molding device was used, the mold temperature was set to 170°C, the injection pressure was 50 MPa, and the injection time was 30 s; after pressure holding in the mold, the sample was cured at 180°C for 2 hours; after demolding, the self-supporting lightweight material with a dense structure was obtained.

[0052] The raw material information is as follows: the curing agent is a phenolic curing agent; the compatibilizer is styrene maleic anhydride, which can be selected as SMA1000; and the accelerator is DMP-30 (2,4,6-tris(dimethylaminomethyl) phenol).

[0053] The self-supporting lightweight material can be used in chip manufacturing. For example, the self-supporting lightweight material is used as a sacrificial layer of a chip structure. It is known that the sacrificial layer is a special material layer used in micro-nano manufacturing processes, which mainly provides necessary structural support or serves as a temporary substrate at a certain stage of device manufacturing, and then is intentionally removed in subsequent steps to release or form the required structure.

[0054] The main functions are: 1) structural support: in the process of manufacturing a multilayer structure, the sacrificial layer can serve as a temporary support structure to help form the upper structure; and 2) space maintenance: when forming a cavity or channel, the sacrificial layer can maintain the required space to ensure the integrity of the structure.

[0055] The coefficient of thermal expansion (CTE) of the self-supporting lightweight material of Example 3 is tested according to the ASTM E831 thermomechanical analyzer (TMA) method at 25-200℃.

[0056] The compressive strength of the self-supporting lightweight material of Example 3 is tested according to GB / T 1041-2008 with a universal material testing machine, and the sample size is 10mmx10mmx10mm.

[0057] Result: The compressive strength of the self-supporting lightweight material of Example 3 is 160MPa, and the coefficient of thermal expansion is 12ppm / ℃.

[0058] The coefficient of thermal expansion of the self-supporting lightweight material prepared by the present application is close to that of the BT substrate in the prior art, and is significantly lower than that of the CTE substrate.

[0059] Example 4

[0060] The sacrificial layer includes a temporary substrate, and the specific application method is as follows:

[0061] The self-supporting lightweight material is used as a temporary substrate, and a chip is adhered to the self-supporting lightweight material by a patch machine through an adhesive, that is, a three-layer structure of a chip, an adhesive, and a self-supporting lightweight material is formed in sequence. Subsequently, the adhesive is dissolved, and the chip and the self-supporting lightweight material are separated, and the adhesive is a conventional chip adhesive.

[0062] The above merely describes the preferred embodiments of the present application and is not used to limit the present application, and although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some technical features thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Process for the preparation of a self-supporting lightweight material, characterized in that, The method comprises the following steps: The heat-conducting core-shell particles, the prepolymer and the compatibilizer are mixed and stirred, the curing agent and the accelerator are added, and vacuum defoaming is performed; the defoamed mixture is loaded into an injection cylinder; injection molding is performed, and demolding is performed to obtain the self-supporting lightweight material, The heat-conducting core-shell particles comprise TiN@AlN particles in which TiN is coated with AlN, and the prepolymer comprises a prepolymer in which benzoxazole is mixed with epoxy resin. The preparation method of the TiN@AlN particles comprises the following steps: The TiO2 hollow spheres are immersed in a glucose aqueous solution, stirred, centrifuged, and dried to obtain pretreated TiO2 hollow spheres; The pretreated TiO2 hollow spheres are heated to 800-1200℃ in an ammonia atmosphere, and heat preservation is performed to obtain TiN hollow spheres; after cooling, residues are removed, washed, and dried for standby use; The TiN hollow spheres are ultrasonically dispersed in anhydrous ethanol; triethoxyaluminum is added; the pH is adjusted to 4-5; after stirring and reaction, centrifugation is performed; the precipitate is vacuum dried; drying and calcination are performed, and cooling is performed to obtain the TiN@AlN particles; The preparation method of the prepolymer in which benzoxazole is mixed with epoxy resin comprises the following steps: DAB and BTDA are dissolved in NMP, heated to 160-200℃, and heat preservation is performed; after reaction, a catalyst is added, and heating to 200-240℃ is performed; after heat preservation for 1-3 hours, cooling is performed to obtain a benzoxazole prepolymer solution; after cooling, epoxy resin is added, and stirring and dispersion are performed; heating to 80-120℃ is performed, and stirring and reaction are performed for 2-6 hours; after reaction, cooling is performed to obtain the prepolymer.

2. The method of making a self-supporting lightweight material according to claim 1, wherein, The particle size of the TiO2 hollow spheres is 0.8-1.5μm; the calcination is as follows: after drying, the TiO2 hollow spheres are calcined at 400-600℃ under nitrogen protection for 1-2 hours, heated to 800-1200℃, and heat preservation is performed for 2-4 hours.

3. The method of making a self-supporting lightweight material of claim 1, wherein, The mass ratio of the benzoxazole prepolymer solution to the epoxy resin is 1:1-3; the catalyst comprises sodium benzenesulfonate.

4. The method of making a self-supporting lightweight material of claim 1, wherein, The curing agent comprises a phenolic curing agent, the compatibilizer comprises styrene maleic anhydride, and the accelerator comprises an epoxy accelerator.

5. The method of making a self-supporting lightweight material of claim 1, wherein, The injection molding parameters comprise the following: an injection molding device is used, the mold temperature is set to 150-190℃, the injection pressure is 40-60MPa, and the injection time is 10-50s; after in-mold pressure retention, curing is performed at 160-200℃ for 1-3 hours.

6. Self-supporting lightweight material applied to chip structures, characterized by, The self-supporting lightweight material is prepared according to the method for preparing a self-supporting lightweight material according to any one of claims 1-5.

7. The self-supporting lightweight material for chip structure according to claim 6, wherein The sacrificial layer comprises a temporary substrate.

8. The self-supporting lightweight material for chip structure according to claim 6, wherein The method for preparing a chip structure comprises the following steps: a chip is adhered to the self-supporting lightweight material by using a chip mounter, and a chip, an adhesive, and the self-supporting lightweight material are sequentially formed into a three-layer structure.