Low dielectric gel and preparation method thereof

Abstract

The present invention discloses a preparation method and application of a low-dielectric organic / inorganic aerogel composite material formed by impregnating a low-dielectric aerogel into a polymer solution. The proposed preparation method is completed through the following steps: (1) mixing, (2) hydrolysis, (3) condensation, (4) aging, (5) drying, (6) impregnating with a polymer solution, (7) curing and phase separation, and (8) drying and crosslinking. The present invention prepares a high-strength low-dielectric organic / inorganic aerogel composite material. This low-dielectric aerogel has a porous structure with a porosity above 70%, a density of about 0.12 to 0.42 g / cm<supgt;3< / supgt>, and its dielectric properties decrease with the increase of the pore rate. The dielectric constant is 1.28 to 1.93 and the dielectric loss is 0.0026 to 0.014. It can be applied to dielectric layers in high-frequency circuits, insulating layers in semiconductor devices, or microwave circuits in communication integrated circuits and other materials.

Description

Technical Field

[0001] The invention relates to a preparation technology of a low dielectric organic / inorganic aerogel composite material formed by directly preparing an inorganic aerogel and impregnating the inorganic aerogel with a polymer dilute solution. The low dielectric organic / inorganic aerogel composite material is a porous structure. Background Art

[0002] It is known that the dielectric properties of materials gradually decrease with the increase of internal porosity of the materials. Therefore, aerogel materials and related composite materials will become low-dielectric related products required by the future 5G industry. As we all know, aerogel is a porous material with a three-dimensional network structure. The porosity is higher than 80% (even higher than 95%), making aerogel material with low density (about 0.005 to 0.2g / cm 3 ), high specific surface area (500 to 2000m 2 / g), low thermal conductivity (k = 15 to 40mW / mk) and low dielectric properties (Dk = 0.1 to 2.5), low dielectric loss (Df <0.001 or less) of technological products. Since aerogel is a material with a large amount of porosity and extremely low density, it can be used in applications such as high thermal insulation, cold insulation, sound insulation or low dielectric properties. In the future 5G high-frequency transmission applications, dielectric materials with low dielectric constants (Dk <2.5) and low signal loss (Df <0.005) are urgently needed. Since porosity causes lower electron-hole transport properties, the higher the porosity in the structure of inorganic or organic materials, the lower the dielectric properties. Therefore, in the future 5G high-frequency applications, porous materials will need to be the main substrate. Japanese Patent Publication No. 8-228105 discloses a method for manufacturing a semiconductor device. In this method, a wet glue film is formed on a substrate, and the solvent containing the wet glue film is evaporated by supercritical and subcritical drying procedures to form an aerogel film. The prepared dry aerogel film still maintains the mesh structure of the wet glue film, and is a porous material with high porosity and low dielectric constant. Based on this, aerogel can be used as a new material for dielectric layers and insulating inner layers. However, the use of supercritical or subcritical drying procedures in the transistor structure process will lead to disadvantages such as complicated procedures and expensive equipment investment. "Supercritical drying" means that water and organic solvents are in a supercritical state under high temperature and high pressure, so that the organic solvent and water have gas-liquid mixing properties at the same time, and the solvent is directly vaporized and dried under the supercritical state. Therefore, the remaining solvent in the mesh structure is removed under supercritical conditions without causing the wet glue to shrink. However, in the preparation of transistor structures, the time from solution preparation to coating of low dielectric films varies. In addition, during the condensation process of aerogel solution, silica gel molecules will immediately aggregate and condense, so the viscosity of the aerogel solution will increase with time. When spin coating is performed at a fixed rate, the film thickness on the substrate also increases. Similarly, the thickness of the transistor thin film structure coating will vary as the process time increases, so it is impossible to prepare a high-quality transistor thin film structure.

[0003] The traditional method for preparing aerogels is the sol-gel synthesis method, which mainly involves mixing precursors such as alkoxysilane, methyl orthosilicate or water glass with organic solvents, and then adding an acid catalyst to perform a hydrolysis reaction. After the hydrolysis reaction has been in progress for a certain period of time, an alkali catalyst is added to perform a condensation reaction. During the condensation reaction, a sol is gradually formed, and the molecules in the sol continue to react and bond, gradually forming a semi-solid polymer gel. After a period of aging, the gel forms a three-dimensional network structure with a stable structure. Finally, solvent replacement is performed using solvents such as n-butanol, n-hexanol, n-hexane or cyclohexane, and then the solvent of the aerogel system is extracted and dried using supercritical drying technology.

[0004] The preparation method of hydrophobic aerogel is a sol-gel synthesis method, which mainly involves mixing methyl alkoxide silicon precursors such as methyltrimethoxysilane (MTMS) or methyltriethoxysilane (MTES) with an organic solvent, and then adding an alkaline catalyst to perform a hydrolysis reaction. After a certain period of hydrolysis reaction, a condensation reaction is performed, and a sol is gradually formed during the condensation reaction. The molecules in the sol continue to react and bond, gradually forming a semi-solid polymer gel. After a period of aging, solvent replacement is performed for two to three days using solvents such as isopropanol, acetone, n-hexane or cyclohexane, so that the hydrophobic gel forms a stable three-dimensional network structure. Finally, the solvent of the aerogel system is dried using atmospheric pressure drying technology to obtain a porous dry aerogel block.

[0005] Since the drying technology used in the above-mentioned aerogel preparation method is supercritical drying technology or multiple solvent replacements for two to three days, the aerogel can be prevented from being broken by the surface tension of water during the normal pressure drying process. However, since supercritical drying technology must be carried out under high pressure, it is only suitable for a very small amount of aerogel; using multiple solvent replacements is also quite time-consuming, which is not conducive to mass production and reducing the production cost of aerogel.

[0006] The U.S. invention patent publication number US8,945,677B2, "Manufacturing electronic devices using low-K dielectric materials", mainly uses low dielectric materials (including polyimide aerogels) to manufacture materials and methods for electronic devices and semiconductor components. This patent case also provides a method for manipulating the properties of dielectric materials and affecting the overall dielectric properties of the system. Specifically, a polyurethane presol, a catalyst and a polar solvent are mixed into a sol mixture layer, and then the sol components are cross-linked to form a wet gel material, and the solvent is removed using a supercritical fluid to form a polyimide aerogel film. This technology is used to combine it with a polyimide aerogel film on the surface of a non-porous, low-k template substrate. This previous case uses low-K dielectric materials to manufacture electronic devices and uses supercritical fluid technology to remove solvents in multiple stages by pressure cycling. The overall technology is time-consuming and costly, and the process takes too long, which is not cost-effective.

[0007] The Chinese invention patent publication number CN102044525A, "Low-K dielectric layer structure, semiconductor device structure and formation method thereof", mainly uses silica aerogel to form a low-K dielectric layer structure. This patent predecessor also provides a semiconductor device structure and a formation method thereof, wherein the formation method includes: providing a substrate, a first dielectric layer and an etching barrier layer are formed on the substrate, the first dielectric layer and the etching barrier layer are both formed with openings, and the openings are filled with metal as plugs; forming a sacrificial oxide layer on the etching barrier layer and the plug; forming an opening in the sacrificial oxide layer, and filling the opening with metal to form an interconnection structure, wherein such an interconnection structure is electrically connected to the plug; selectively removing the sacrificial oxide layer to form a gap between the interconnection structures; forming silica aerogel as a low-K dielectric layer in the gap between the interconnection structures. This patent predecessor uses a low-K dielectric layer structure and utilizes tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) as a material structure. In addition, the drying process utilizes room temperature or supercritical fluid technology to prepare low dielectric thin films in multiple stages. The overall technology is time-consuming and costly, and the process takes too long, which is not cost-effective.

[0008] The Chinese invention patent publication number CN105189104A, "Aerogel insulation panel and its preparation method", mainly uses polyimide aerogel to prepare an insulation panel, which can be used in aerospace application laminate panels. This panel includes a polyimide aerogel surface layer and a reflective protective layer on the surface layer. The process of polyimide aerogel in this patent case includes: (a) a mixture of dianhydride and diamine monomers is polymerized in a bipolar alkaline solvent (DMAc or NMP) to form a polyamic acid solution; (b) the polyamic acid solution is cast into fiber flocs; (c) acetic anhydride and pyridine are used to gel the polyamic acid solution by chemical imidization reaction; (d) supercritical or sub-supercritical CO is used to form a polyamide acid solution. 2 The drying technique removes the solvent from the gel to form a fiber / polyimide aerogel composite.

[0009] The "aerogel / polymer composite material" of US invention patent publication number US9,777,126B2 includes aerogel and thermoplastic polymer materials, and the weight ratio of aerogel to thermoplastic polymer is less than 20: 100. This composite material has excellent insulation properties and has better softness and lower brittleness in low temperature environments.

[0010] The Chinese invention patent publication number CN108203516A, "Method for preparing cross-linked polyimide aerogel", mainly adopts the sol-gel method, which includes: (a) polymerizing a mixture of dianhydride and diamine monomers in a bipolar alkaline solvent (DMAc or NMP) to form a polyamic acid solution; (b) casting the polyamic acid solution into fiber flocs; (c) using acetic anhydride and pyridine to gel the polyamic acid solution by chemical imidization reaction; (d) using supercritical or sub-supercritical CO 2 The drying technique removes the solvent from the gel to form a fiber / polyimide aerogel composite.

[0011] When making nanoporous dielectrics, it is preferred to subject the wet gel film to a conventional aging process. At the gel point, the hydrolysis and condensation reactions have not stopped, but continue to change the gel structure (or age) until the reaction is deliberately terminated. During aging, portions of the solid structure are preferentially dissolved and redeposited, which can produce beneficial results, such as higher strength, better pore uniformity, and better resistance to micropore shrinkage during drying. Summary of the invention

[0012] According to the applicant's previous block aerogel production technology, the linear shrinkage of block aerogel preparation is reduced to less than 7% by using rapid condensation technology, and there is no need to immerse the wet aerogel in a solvent for solvent replacement, so the crystal structure can be prepared quickly. This previous technology uses rapid gelation technology to quickly form a gel structure, and rinses it in deionized water to remove ions in the structure to reduce ion accumulation in subsequent applications. In addition, the overall process eliminates the steps of immersing the wet gel film in liquid and removing the solvent using supercritical fluid technology, and surprisingly, a porous low-dielectric film can be aged in about a few minutes.

[0013] Therefore, in order to improve the shortcomings of the past low-dielectric gel manufacturing and low-dielectric polymer aerogel manufacturing in the application of optoelectronic or electronic components, such as: the uneven structure of the low-dielectric gel, the insignificant reduction in the dielectric properties or dielectric loss of the aerogel, and the difficulty in applying the supercritical drying technology to the preparation of integrated circuit structures, the present invention proposes a method for preparing a low-dielectric inorganic aerogel or a low-dielectric organic / inorganic aerogel composite plate or a low-dielectric inorganic aerogel film with a thickness ranging from tens of millimeters to hundreds of millimeters by combining sol-gel synthesis technology, which comprises the following steps: (1) mixing a siloxane compound or a hydrophobic modified siloxane compound with an organic mixed solvent to form mixed solution; (2) a hydrolysis step: adding an acid catalyst to the mixed solution to carry out a hydrolysis reaction; (3) a condensation step: adding an alkali catalyst to the hydrolyzed mixed solution to carry out a condensation reaction, and adding a trace amount of a surfactant during the condensation reaction to reduce the aerogel interfacial tension and avoid the aerogel structure from breaking; (4) an aging step: aging the formed aerogel sheet at a specific temperature to promote further condensation of the aerogel structure and structural stability; and (5) a drying step: after the aerogel sheet structure is gelled and stabilized, high-temperature drying is carried out under normal pressure and high temperature environment to obtain a low-dielectric inorganic aerogel sheet with uniform structure, high porosity and high specific surface area, especially a silicon-based aerogel sheet. In addition, the method for preparing a low dielectric organic / inorganic aerogel composite sheet further comprises the following steps: (6) a polymer solution impregnation step: impregnating the prepared low dielectric silicon-based aerogel sheet with a polymer dilute solution, so that the polymer chains are uniformly infiltrated into the silicon-based aerogel sheet to form a wet polymer / silicon-based composite material; (7) a phase separation and drying step: subjecting the wet polymer / silicon-based composite material to a specific temperature to vaporize the solvent in the polymer dilute solution. At this stage, the polymer inside the wet polymer / silicon-based composite material will undergo phase separation and drying. - Solid phase separation to coat the polymer chains on the low dielectric silicon-based aerogel mesh skeleton structure and gradually dry; and (8) cross-linking and curing steps: the dried polymer / silicon-based composite material is placed in a specific high temperature environment to cause the polymer chains coated on the low dielectric silicon-based aerogel mesh skeleton structure to undergo a cross-linking reaction. In the cross-linking reaction, the polymer chains react with each other and with the silicon-based aerogel molecules to form a chemical reaction, thereby obtaining a porous, lightweight and low dielectric organic / inorganic aerogel composite sheet after high temperature cross-linking. This method can quickly produce low dielectric inorganic aerogels or organic / inorganic aerogel composite sheets. The overall preparation is simple and can prepare thin films of tens to hundreds of millimeters or aerogel sheets of several millimeters to centimeters in size. The overall preparation speed can be quickly shortened to 12 to 36 hours, thereby improving the production efficiency of preparing low dielectric inorganic aerogels or organic / inorganic aerogel composite sheets.

[0014] Furthermore, the alkoxysilane compound is one or more substances selected from the group consisting of tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), and the hydrophobic modified siloxane compound is one or more substances selected from the group consisting of methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES). The hydrophobic modified siloxane is added here mainly to reduce the cracking phenomenon of the aerogel system during the drying process; and the addition of the siloxane is mainly to provide regulation of the internal microstructure of the aerogel system and increase the pore content in the structure.

[0015] Furthermore, the organic mixed solvent is one or more substances selected from the group consisting of: water, pure water, deionized water, alcohols, acids, ketones, alkanes, and aromatics.

[0016] Furthermore, in the hydrolysis step, when the content ratio of the acid catalyst in the mixed solution is higher, the hydrolysis rate is faster. However, relatively speaking, the higher the content ratio of the acid catalyst, the greater the ion content in the overall aerogel structure, and the higher the dielectric loss of the aerogel. Therefore, deionized water can be used to prepare the aerogel during the preparation process to reduce the dielectric properties in the aerogel structure.

[0017] Furthermore, the purpose of adding a small amount of surfactant during the condensation reaction is to reduce the interfacial tension of the aerogel structure after condensation and to reduce cracking of the aerogel caused by the interfacial tension during the drying process.

[0018] Furthermore, the drying step allows the aged and stabilized inorganic aerogel to evaporate the aqueous solvent in the system under normal pressure and high temperature. In addition, due to the addition of a trace amount of surfactant in the present invention, the cracking behavior of the inorganic aerogel can be significantly inhibited during the drying process, and a low-density and high-porosity low-dielectric inorganic aerogel sheet can be prepared, especially a low-dielectric silicon-based aerogel sheet.

[0019] Furthermore, in the present invention, a low dielectric organic / inorganic aerogel composite plate can be further prepared, especially by using the step of impregnating the prepared low dielectric silicon-based aerogel plate with a polymer solution, so that the polymer chain is uniformly infiltrated into the internal pores of the silicon-based aerogel plate with the solvent to form a wet polymer-impregnated silicon-based aerogel composite material. In addition, the lower the polymer concentration, the better the efficiency of the polymer infiltrating the internal pores of the silicon-based aerogel. Conversely, the higher the polymer concentration, the higher the content of the polymer coated inside the silicon-based aerogel, and the better the strength of the prepared low dielectric organic / silicon-based aerogel composite plate.

[0020] Furthermore, in the phase separation and drying steps, the polymer dilute solution inside the wet polymer impregnated silicon-based aerogel composite material will first undergo phase separation, causing the polymer molecular chains to coat the aerogel skeleton structure inside the high-porosity silicon-based aerogel. At the same time, the organic solvent inside the high-porosity silicon-based aerogel is also vaporized, causing the wet polymer impregnated silicon-based aerogel composite material to gradually dry.

[0021] Furthermore, in this process, a low dielectric gel structure is first prepared, and then the prepared low dielectric gel is further used to contact with a polymer dilute solution by impregnation, spraying, pouring or soaking, so that the polymer chain is uniformly infiltrated into the internal pores of the low dielectric gel sheet with the solvent, and mixed with the inorganic aerogel structure to form a wet polymer impregnated silicon-based aerogel composite. Then, an organic / inorganic aerogel composite material with high strength, high porosity and low dielectric can be obtained by normal pressure high temperature drying and high temperature crosslinking, especially a low dielectric polymer / silicon-based aerogel composite material. Overall, the process is simple, the manufacturing cost is low, the process speed is fast, and there is no need to use complex preparation methods such as supercritical drying. The batch process speed of the organic / inorganic aerogel composite sheet can be quickly reduced to within 24 to 36 hours, or the organic / inorganic aerogel film can be prepared in a continuous production manner to improve production efficiency.

[0022] The present invention has the following effects:

[0023] 1. The preparation method of the present invention utilizes the traditional sol-gel reaction process to simply prepare an inorganic aerogel material with high porosity and low dielectric. In addition, during the preparation, the porosity, pore size and compactness of the aerogel structure can be easily regulated by using different ratios of siloxane compounds or hydrophobically modified siloxane compounds, the content of water-containing organic solvents, the content and ratio of acid catalysts and alkali catalysts, and other factors, and further the dielectric properties of the prepared aerogel can be regulated to improve the practical properties of the aerogel.

[0024] 2. The preparation method of the present invention can be used to prepare pure inorganic aerogel materials, and can also be further used to prepare high-strength, high-porosity, low-dielectric organic / inorganic aerogel composite materials by impregnation with various polymer dilute solutions, especially low-dielectric polymer / silicon-based aerogel composite materials.

[0025] 3. The step of impregnating the silicon-based aerogel plate with a polymer solution in the preparation method of the present invention is to immerse the silicon-based aerogel plate in a dilute polymer solution, so that the relevant polymer chains are uniformly infiltrated into the internal pores of the silicon-based aerogel plate along with the solvent to form a wet polymer-impregnated silicon-based aerogel composite. Among them, the lower the polymer concentration, the better the efficiency of the polymer infiltrating the internal pores of the silicon-based aerogel; conversely, the higher the polymer concentration, the higher the content of the polymer coating inside the silicon-based aerogel, and the better the strength of the prepared low-dielectric organic / silicon-based aerogel composite plate. Therefore, the dielectric constant and strength of the prepared low-dielectric organic / silicon-based aerogel composite plate can be regulated by the concentration of the dilute polymer solution.

[0026] 4. The polymer dilute solution described in the preparation method of the present invention can be composed of one of the following polymers or a mixture thereof: thermoset polymer, liquid crystal polymer, and general thermoplastic polymer. Specifically, for example: epoxy resin, polyimide resin, phenolic resin, melamine resin, polyetherketone liquid crystal polymer (PEK), polyetheretherketone liquid crystal polymer (PEEK), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyamide (PA), polyamide ester (PEA), polyester (PET), or polytetrafluoroethylene (PTFE). The method can prepare low dielectric polymer / silicon-based aerogel composite materials with various properties by mixing various polymer solutions, so as to adjust the strength, durability temperature, bonding with other materials, and the dielectric constant (approximately 1.23 to 1.89) and dielectric loss (0.0052 to 0.023) of the low dielectric polymer / silicon-based aerogel composite materials.

[0027] 5. The acid catalyst and the base catalyst added in the preparation method of the present invention can accelerate the hydrolysis and condensation reaction of siloxane and hydrophobically modified siloxane. The molar ratio of the total content of the mixture of siloxane and hydrophobically modified siloxane to the content of the acid catalyst in the reaction system is 1:0.05 to 1:0.00001; and the molar ratio of the acid catalyst to the base catalyst in the condensation reaction is 1:0.8 to 1:1.05. The higher the content of the acid catalyst and the base catalyst in the mixed solution, the faster the reaction rate; correspondingly, the higher the content of the acid catalyst and the base catalyst, the higher the ion content in the overall aerogel structure, and the greater the dielectric loss of the aerogel. In this way, the process rate and product properties can be adjusted.

[0028] 6. The overall process of the low dielectric polymer / silicon-based aerogel composite material of the present invention is simple, low in manufacturing cost, fast in process speed, and does not require the use of complex preparation methods such as supercritical drying. The batch process speed of this organic / inorganic aerogel composite sheet can be quickly reduced to 24 to 36 hours, or prepared in a continuous production manner, thereby improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the process steps of low-dielectric gelling according to an embodiment of the present invention.

[0030] Figure 2 This is a photo of the appearance of the low-dielectric silicon-based aerogel sheet prepared by the present invention.

[0031] Figure 3 This is a scanning electron microscope photograph of the cross section of the low-dielectric silicon-based aerogel sheet prepared by the present invention.

[0032] Figure 4 The figure is a schematic diagram of the process steps for manufacturing a low dielectric organic / silicon-based aerogel composite board according to an embodiment of the present invention.

[0033] Figure 5 This is a photo of the appearance of the low dielectric polyimide / silicon-based aerogel composite plate prepared by the present invention.

[0034] Figure 6 This is a scanning electron microscope photograph of the low dielectric polyimide / silicon-based aerogel composite plate prepared by the present invention.

[0035] Figure 7 This is a photo of the appearance of the low dielectric epoxy plastic / silicon-based aerogel composite board prepared by the present invention.

[0036] Figure 8 This is a scanning electron microscope photograph of the low dielectric epoxy plastic / silicon-based aerogel composite board prepared by the present invention. DETAILED DESCRIPTION

[0037] See also Figure 1, discloses a method for preparing a low dielectric silica-based aerogel sheet according to a first embodiment of the present invention, comprising the following steps: a mixing step (S1), a hydrolysis step (S2), a condensation step (S3), an aging step (S4) and a drying step (S5), wherein:

[0038] The mixing step (S1) is to mix a siloxane compound or a hydrophobic modified siloxane compound with an organic solvent to form a mixed solution. The siloxane compound (alkoxysilane) is one or more substances selected from the group consisting of tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), and the hydrophobic modified siloxane compound is one or more substances selected from the group consisting of hydrophobic methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES). The purpose of adding the hydrophobic modified siloxane is to reduce the cracking phenomenon of the aerogel system during the drying process; and the purpose of adding the siloxane is to regulate the internal microstructure of the aerogel system and increase the pore content in the structure. In the overall mixed solution, the total molar percentage of siloxane and hydrophobic modified siloxane is between 3.0 mol% and 60 mol%, and the molar ratio of the organic solvent is between 97 mol% and 40 mol%. The molar ratio of the siloxane compound to the hydrophobic modified siloxane compound is from 0:100 to 35:65, and the preferred ratio is 22:78.

[0039] The organic mixed solvent in the mixing step (S1) can be water, treated water, deionized water, C1-C16 alcohols, C3-C16 ketones, C3-C16 alkanes, or C3-C16 aromatics, etc. Specifically, for example, water, treated water, deionized water, ethanol, acetone, cyclohexane, toluene, etc., or a mixture of different compositions.

[0040] The hydrolysis step (S2): adding an acid catalyst to the mixed solution to perform a hydrolysis reaction. The molar ratio of the total content of the mixture of siloxane and hydrophobically modified siloxane to the content of the acid catalyst is 1:0.05 to 1:0.00001. The higher the content ratio of the acid catalyst in the mixed solution of siloxane and hydrophobically modified siloxane, the faster the hydrolysis rate; that is, the higher the content ratio of the acid catalyst, the greater the ion content in the overall aerogel structure, and the greater the dielectric loss of the aerogel. In this embodiment, the preferred condition is that the molar ratio of the total content of the mixture of siloxane and hydrophobically modified siloxane to the content of the acid catalyst is 1:0.0075.

[0041] The condensation step (S3): adding an alkaline catalyst to the mixed solution to carry out a condensation reaction at a specific temperature. In addition, a trace amount of surfactant is added during the condensation reaction. The weight ratio of the added trace amount of surfactant and the total content of the mixture of siloxane and hydrophobically modified siloxane is 1:100 to 1:3000; in this embodiment, the preferred condition is a weight ratio of 1:1000. The purpose of adding a trace amount of surfactant is to reduce the interfacial tension of the aerogel structure after condensation and to reduce the cracking of the aerogel during the drying process. The alkaline catalyst is mixed with a mixed solution of water and ethanol and then added to carry out a condensation reaction. The molar ratio of water to ethanol is, for example, 100:0.1 to 4:1. In this embodiment, the preferred condition is, for example, 50:1.

[0042] The increase in temperature in the condensation step helps to significantly shorten the condensation reaction time (i.e., the gelation time of the aerogel), wherein when the weight ratio of the alkali catalyst to the acid catalyst is 1.0:1.0, the gelation time at a condensation reaction temperature of room temperature 25°C is about 220 minutes, and the gelation time at a condensation reaction temperature of 70°C is about 10 minutes. In addition, in a mixed solution of alkali catalyst, water and ethanol, an increase in the alkali catalyst content will also significantly shorten the condensation reaction time. When the volume ratio of 1M alkali catalyst to 1M acid catalyst is 0.8:1.0, the gelation time is about 360 minutes; when the content ratio of 1M alkali catalyst to 1M acid catalyst is 1.2:1.0, the gelation time drops to about 15 minutes.

[0043] The aging step (S4) is to age the formed low dielectric silicon-based aerogel sheet at a specific temperature to stabilize the aerogel wet glue structure. In this embodiment, the preferred aging temperature is 70°C.

[0044] The drying step (S5): After the low dielectric silicon-based aerogel sheet structure is aged and stabilized, the aqueous solvent in the aerogel system is evaporated under normal pressure and high temperature. Since the material contains a surfactant, the bonding force of the surfactant is used to quickly reduce the cracking behavior of the gel during drying, thereby preparing a low-density and high-porosity low dielectric silicon-based aerogel sheet. Please refer to Figure 2 and 3 The appearance and internal microstructure of the low dielectric silicon-based aerogel sheet prepared by the present invention are Figure 3 It shows that the prepared low-dielectric silicon-based aerogel sheet utilizes aerogel particles with uniform appearance structure to combine with each other into a three-dimensional network structure, and the size of the aerogel particles ranges from several microns to sub-micron, and the particle size can be controlled by the ratio of acid catalyst to alkaline catalyst.

[0045] See also Figure 4, discloses a method for preparing a low dielectric organic / silicon-based aerogel composite plate according to a second embodiment of the present invention, comprising the following steps: a mixing step (S1), a hydrolysis step (S2), a condensation step (S3), an aging step (S4), a drying step (S5), an impregnation step with a polymer solution (S6), a phase separation and drying step (S7), and a cross-linking and curing step (S8), wherein:

[0046] The mixing step (S1) is to mix a siloxane compound or a hydrophobically modified siloxane compound into an organic solvent to form a mixed solution, wherein (alkoxysilane) is one or more substances selected from the group consisting of tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), and the hydrophobically modified siloxane compound is one or more substances selected from the group consisting of hydrophobic methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES). Adding the hydrophobically modified siloxane here can mainly reduce the cracking phenomenon of the aerogel system during the drying process; however, adding the siloxane can mainly regulate the internal microstructure of the aerogel system and increase the pore content in the structure. In the overall mixed solution, the total molar ratio of the siloxane and hydrophobic modified siloxane mixture is between 3.0 mol% and 60 mol%, and the molar ratio of the organic solvent is between 97 mol% and 40 mol%. The molar ratio of the siloxane compound to the hydrophobic modified siloxane compound is from 0:100 to 35:65, preferably 5:95.

[0047] The organic mixed solvent used in the mixing step (S1) can be water, treated water, deionized water, C1-C16 alcohols, C3-C16 ketones, C3-C16 alkanes, or C3-C16 aromatics, etc. Specifically, for example, water, treated water, deionized water, ethanol, acetone, cyclohexane, toluene, etc., or a mixture of different compositions.

[0048] The hydrolysis step (S2): adding an acid catalyst to the mixed solution to perform a hydrolysis reaction. The molar ratio of the total content of the mixture of siloxane and hydrophobically modified siloxane to the content of the acid catalyst is 1:0.05 to 1:0.00001. The higher the content ratio of the acid catalyst in the mixed solution of siloxane and hydrophobically modified siloxane, the faster the hydrolysis rate. In other words, the higher the content ratio of the acid catalyst, the greater the ion content in the overall aerogel structure, and the greater the dielectric loss of the aerogel. In this embodiment, the preferred condition is that the molar ratio of the total content of the mixture of siloxane and hydrophobically modified siloxane to the content of the acid catalyst is 1:0.0075.

[0049] The condensation step (S3): adding an alkali catalyst to the mixed solution to carry out a condensation reaction at a specific temperature. During the condensation reaction, a trace amount of surfactant is added to reduce the interfacial tension of the aerogel structure after condensation and to avoid cracking during drying. In the mixed solution containing the acid catalyst, the alkali catalyst, and the surfactant, the content of the surfactant is 0.01 mol% to 0.5 mol%, preferably 0.2 mol%. In addition, the weight ratio of the added trace amount of surfactant and the total content of the mixture of siloxane and hydrophobic modified siloxane is 1:100 to 1:3000; in this embodiment, the preferred condition is a weight ratio of 1:1000. Furthermore, the alkali catalyst is mixed with a mixed solution of water and ethanol and then added to carry out a condensation reaction, and the molar ratio of water to ethanol is, for example, 100:0.1 to 4:1, and in this embodiment, the preferred condition is, for example, 50:1.

[0050] The increase in temperature in the condensation step helps to significantly shorten the condensation reaction time (i.e., the gelation time of the aerogel), wherein the weight ratio of the alkali catalyst to the acid catalyst is 1.0:1.0, the gelation time at room temperature (25°C) is about 220 minutes, and the gelation time at 70°C is about 10 minutes. In addition, in the mixed solution of alkali catalyst, water and ethanol, the increase in the alkali catalyst content will also significantly shorten the condensation reaction time. When the volume ratio of the 1M alkali catalyst to the 1M acid catalyst is 0.8:1.0, the gelation time is about 360 minutes; when the content ratio of the 1M alkali catalyst to the 1M acid catalyst is 1.2:1.0, the gelation time is reduced to about 15 minutes, wherein the preferred content ratio of the 1M alkali catalyst to the 1M acid catalyst is 1.05:1.0.

[0051] The aging step (S4) is to age the formed silicon-based aerogel sheet at a specific temperature to stabilize the aerogel wet glue structure. In this embodiment, the preferred temperature is 70°C.

[0052] The drying step (S5): After the silicon-based aerogel sheet structure is aged and stabilized, the water-containing solvent in the aerogel system is evaporated under normal pressure and high temperature. Since the material contains a surfactant, the bonding force of the surfactant causes the cracking behavior of the gel to decrease rapidly during drying, thereby preparing a low-density and high-porosity low-dielectric silicon-based aerogel sheet.

[0053] The step of impregnating the polymer solution (S6): when the silicon-based aerogel sheet structure forms a silicon-based aerogel sheet with a complete structure and appropriate strength after drying, the silicon-based aerogel sheet is then impregnated with a polymer dilute solution, so that the polymer chain is uniformly infiltrated into the internal pores of the silicon-based aerogel sheet along with the solvent to form a wet polymer impregnated silicon-based aerogel composite. Here, the concentration of the polymer dilute solution can be 0.01wt% to 60wt%, preferably 0.05wt% to 60wt%, wherein the lower the polymer concentration, the better the efficiency of the polymer infiltrating the pores inside the silicon-based aerogel; conversely, the higher the polymer concentration, the higher the content of the polymer coated inside the silicon-based aerogel, and the better the strength of the prepared low-dielectric organic / silicon-based aerogel composite board. That is, the dielectric constant and strength of the prepared low-dielectric organic / silicon-based aerogel composite board can be regulated by the concentration of the polymer dilute solution. Among them, the more preferred concentration of the polymer dilute solution is 3.0wt% to 8.5wt%.

[0054] The phase separation and drying step (S7): After the wet polymer impregnated silicon-based aerogel composite is impregnated, the solvent in the wet polymer impregnated silicon-based aerogel composite is evaporated under normal pressure and high temperature. During the drying process, the polymer thin solution inside the wet polymer impregnated silicon-based aerogel composite will first undergo liquid-solid phase separation, resulting in the polymer molecular chain being coated on the aerogel skeleton structure inside the high-porosity silicon-based aerogel. At the same time, the organic solvent inside the high-porosity silicon-based aerogel is also vaporized, so that the wet polymer impregnated silicon-based aerogel composite is gradually dried. The drying temperature used here depends on the boiling point of the organic solvent. If the solvent is ethanol, the drying temperature is 60 to 65°C; if the solvent is butanone, the drying temperature is 80 to 85°C, so that a dry polymer impregnated silicon-based aerogel composite can be prepared.

[0055] The cross-linking and curing step (S8) is to place the dried polymer impregnated silicon-based aerogel composite material in a specific high temperature environment to cause the polymer chains coated on the silicon-based aerogel network skeleton to undergo a cross-linking reaction. In this cross-linking reaction, the polymer chains coated on the silicon-based aerogel network skeleton undergo a cross-linking reaction with each other and between the polymer chains and the silicon-based aerogel molecules to bond with each other. Therefore, in this high temperature environment, after the polymer is cross-linked, a porous, lightweight and low-dielectric polymer / silicon-based aerogel composite material is obtained. Please refer to Figure 5 and 6The general appearance and cross-sectional microstructure of the prepared low dielectric polyimide / silicon-based aerogel composite board show that the prepared low dielectric polyimide / silicon-based aerogel composite board has a porous aerogel structure with uniform appearance structure formed by the polymer coating the mesh structure of the aerogel particles. In general, the structural uniformity, shrinkage rate and strength of the polymer / silicon-based aerogel composite material can be regulated by the following factors: the content of the siloxane compound or the hydrophobically modified siloxane compound, the total solvent content, the hydrolysis conditions, the condensation rate, the surfactant content, the aging rate, the drying rate, the concentration of the polymer dilute solution, the uniformity of the polymer chain penetration, and the degree of polymer chain crosslinking.

[0056] See also Figure 7 and 8 , which is the general appearance and cross-sectional microstructure of the low dielectric epoxy resin / silicon-based aerogel composite board prepared by the present invention, showing that the low dielectric epoxy resin / silicon-based aerogel composite board has a porous aerogel structure with a uniform appearance structure formed by the macromolecules coating the mesh structure of the aerogel particles.

[0057] Please refer to Table 1, which is a basic physical property table of the low dielectric silicon-based aerogel board, low dielectric polyimide / silicon-based aerogel composite board, and low dielectric epoxy resin / silicon-based aerogel composite board prepared by the present invention, wherein a water-soluble natural adhesive is added in the condensation process of this embodiment. It can be seen from the table that the density of the dielectric silicon-based aerogel board prepared by the present invention increases from about 0.178 g / cm to about 0.178 g / cm as the content of the hydrophobically modified siloxane compound in the mixture of the siloxane compound and the hydrophobically modified siloxane compound increases. 3 Down to 0.123g / cm 3 . In addition, the dielectric constant and dielectric loss were determined by using an SPDR dielectric resonator to measure the dielectric constant of the Agilent substrate at a frequency of 10 GHz (test standard: IPC TM6502.5.5.13). The dielectric constant gradually decreases from 1.526 to 1.276 as the content of the hydrophobic modified siloxane compound in the mixture of the siloxane compound and the hydrophobic modified siloxane compound increases. On the other hand, it can be seen from the table that the density of the prepared low dielectric polyimide / silicon-based aerogel composite board increases from about 0.178 g / cm 3 Increased to 0.456 g / cm 3 In addition, the dielectric constant of the prepared low dielectric epoxy resin / silicon-based aerogel composite board gradually increased from 0.178 g / cm to 1.987 as the content of polyimide increased when tested at a frequency of 10 GHz. 3 Increased to 0.461g / cm 3In addition, the dielectric constant of the substrate tested at a frequency of 10 GHz gradually increased from 1.526 to 1.821 as the epoxy resin content increased. The above shows that the low dielectric silicon-based aerogel plate and the low dielectric polymer silicon-based aerogel composite plate prepared by the present invention both have extremely excellent dielectric properties.

[0058] Table 1

[0059]

[0060]

[0061] Please refer to Table 2, which is a table of basic physical properties of the low dielectric silicon-based aerogel board, low dielectric polyimide / silicon-based aerogel composite board, and low dielectric epoxy resin / silicon-based aerogel composite board prepared by the present invention, wherein no water-soluble natural adhesive is added in the condensation process of this embodiment. It can be seen from the table that the density of the dielectric silicon-based aerogel board prepared by the present invention increases from about 0.178 g / cm to about 0.178 g / cm as the content of the hydrophobically modified siloxane compound in the mixture of the siloxane compound and the hydrophobically modified siloxane compound increases. 3 Down to 0.123g / cm 3 . In addition, the dielectric constant and dielectric loss were determined by using an SPDR dielectric resonator to measure the dielectric constant of the Agilent substrate at a frequency of 10 GHz (test standard: IPC TM6502.5.5.13). The dielectric constant gradually decreases from 1.526 to 1.276 as the content of the hydrophobic modified siloxane compound in the mixture of the siloxane compound and the hydrophobic modified siloxane compound increases. On the other hand, it can be seen from the table that the density of the prepared low dielectric polyimide / silicon-based aerogel composite board increases from about 0.178 g / cm 3 Increased to 0.652g / cm 3 In addition, its dielectric constant gradually increases from about 1.350 to 1.821 as the polyimide content increases. Finally, it can be seen from the table that the density of the prepared low dielectric epoxy resin / silicon-based aerogel composite board increases from about 0.178 g / cm 3 Increased to 0.421g / cm 3 In addition, the dielectric constant thereof gradually increases from about 1.526 to 1.933 with the increase of epoxy resin content. The above shows that the low dielectric silicon-based aerogel plate and the low dielectric polymer silicon-based aerogel composite plate prepared by the present invention both have extremely excellent dielectric properties.

[0062] Table 2

[0063]

[0064]

[0065] The present invention first mixes siloxane compounds, and then uses a sol-gel preparation method to prepare an inorganic aerogel material under normal pressure, wherein the silicon-based aerogel is the main component, and the porosity is higher than 70%, and the density is about 0.12g / cm 3 Up to 0.18g / cm 3 . Moreover, the dielectric properties of this product decrease with the increase of porosity, with the dielectric constant being 1.28 to 1.53 and the dielectric loss being 0.0026 to 0.0087, so it has low dielectric constant and low dielectric loss properties. Related products can be used as dielectric layers in future 5G high-frequency circuits or insulating layers in high-frequency devices. Subsequently, the inorganic aerogel material is directly impregnated with thermosetting polymers such as polyimide or epoxy resin or other liquid crystal polymer solutions (polysemi-aromatic liquid crystal polymers and poly-fully aromatic liquid crystal polymers), and then dried and cross-linked or cured in a high temperature environment to form an organic / inorganic aerogel composite material with a porosity of more than 60% and a density of approximately 0.12g / cm 3 Up to 0.42g / cm 3 (Preferably 0.2 g / cm 3 Up to 0.32g / cm 3 ), its dielectric constant is about 1.35 to 1.93 and its dielectric loss is 0.0033 to 0.0144, so it has low dielectric constant and low dielectric loss properties. The present invention can first quickly prepare an inorganic aerogel with high porosity and low dielectric under normal pressure, and then produce an organic / inorganic composite aerogel. The present invention does not require lengthy solvent replacement and does not require the use of supercritical drying equipment. The overall process is simple, fast and low-cost. After coating with polymers such as polyimide, the strength can be significantly improved. In addition, this low-dielectric product can be used in dielectric layers in high-frequency circuits or insulating layers in semiconductor devices; furthermore, it can also be used in microwave circuits and related low-dielectric materials in 5G communication circuits.

[0066] Based on the description of the above embodiments, one can fully understand the manufacture, application and effects of the present invention. However, the above embodiments are only preferred embodiments of the present invention and cannot be used to limit the patent protection scope of the present invention. That is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the invention description all fall within the patent protection scope of the present invention.

Claims

1. A method for preparing a low dielectric organic / inorganic aerogel composite material, comprising the following steps: Mixing step: mixing one or all of the siloxane compound and the hydrophobically modified siloxane compound with an organic mixed solvent to form a mixed solution; Hydrolysis step: adding an acid catalyst to the mixed solution to perform a hydrolysis reaction; Condensation step: adding an alkali catalyst to the hydrolyzed mixed solution to carry out a condensation reaction, and adding a surfactant during the condensation reaction, wherein the weight ratio of the surfactant content to the total content of the siloxane compound and the hydrophobically modified siloxane compound is 1:100 to 1:3000; Aging step: aging the aerogel sheet formed in the condensation step at a specific temperature to promote further condensation of the aerogel structure and stabilize the structure; Drying step: After the aerogel sheet structure is gelled and stabilized, high-temperature drying is performed under normal pressure and high temperature environment to obtain a low-dielectric silicon-based aerogel sheet with uniform structure, high porosity and high specific surface area; The step of impregnating the low dielectric silicon-based aerogel sheet is to impregnate the prepared low dielectric silicon-based aerogel sheet into a dilute polymer solution, so that the polymer chains are uniformly infiltrated into the silicon-based aerogel sheet to form a wet polymer / silicon-based composite material; Phase separation and drying step: vaporizing the solvent in the polymer dilute solution of the wet polymer / silicon-based composite material at a specific temperature, thereby performing liquid-solid phase separation of the polymer inside the wet polymer / silicon-based composite material, and making the polymer chains coated on the low dielectric silicon-based aerogel network skeleton structure and gradually drying; as well as Cross-linking and curing steps: The dried polymer / silicon-based composite material is placed in a specific high temperature environment to cause the polymer chains coated on the low dielectric silicon-based aerogel network skeleton structure to undergo a cross-linking reaction. In the cross-linking reaction, the polymer chains are chemically reacted with each other and with the silicon-based aerogel molecules to form a porous, lightweight and low dielectric polymer / silicon-based aerogel composite material.

2. The preparation method according to claim 1, Features: The siloxane compound is tetramethoxysilane or tetraethoxysilane, the hydrophobic modified siloxane compound is methyltrimethoxysilane or methyltriethoxysilane, and the molar ratio between the siloxane compound and the hydrophobic modified siloxane compound is from 0:100 to 35:

65.

3. The preparation method according to claim 1, Features: The polymer concentration of the polymer dilute solution used in the polymer solution impregnation step ranges from 0.01wt% to 60wt%. The lower the polymer concentration, the faster and more uniform the polymer penetrates into the aerogel, so that the polymer chain evenly penetrates into the silicon-based aerogel sheet to form the wet polymer / silicon-based composite material.

4. The preparation method according to any one of claims 1 to 3, Features: The polymer in the polymer dilute solution includes thermosetting polymer, thermoplastic polymer and liquid crystal polymer.

5. The preparation method according to claim 4, Features: The thermosetting polymer is selected from one of the following or a mixture thereof: epoxy resin, polyimide resin, phenolic resin, and polymelamine-formaldehyde resin.

6. The preparation method according to claim 4, Features: The thermoplastic polymer is selected from the following one or a mixture thereof: polyethylene, polypropylene, polytetrafluoroethylene, polycarbonate, polyamide, polyesteramide, and polyester.

7. The preparation method according to claim 4, Features: The liquid crystal polymer is selected from the following one or a mixture thereof: polysemi-aromatic liquid crystal polymer and polyfully aromatic liquid crystal polymer.

8. The preparation method according to claim 1, Features: The structural uniformity, shrinkage rate and strength of the polymer / silicon-based aerogel composite material can be regulated by the following preparation factors: the content of the siloxane compound or the hydrophobically modified siloxane compound, the total solvent content, the hydrolysis conditions, the condensation rate, the surfactant content, the aging rate, the drying rate, the concentration of the polymer dilute solution, the polymer chain penetration uniformity, and the polymer chain cross-linking degree.

9. The preparation method according to claim 1, Features: in, The low dielectric polymer / silicon-based aerogel composite material has a porosity of more than 60% and a density of 0.12 to 0.42 g / cm 3 , and its dielectric properties decrease with increasing porosity, where its dielectric constant is 1.28 to 1.93 and its dielectric loss is 0.0026 to 0.014, and it is used as a dielectric layer in high-frequency circuits, an insulating layer in semiconductor devices, or a microwave circuit in communication integrated circuits.

Images