A liquid crystal polymer powder, a liquid crystal polymer emulsion, an LCP copper clad plate and a preparation method and application thereof

Abstract

The application provides a liquid crystal polymer powder, a liquid crystal polymer emulsion, an LCP copper-clad plate and a preparation method and application thereof, and focuses on developing a liquid crystal polymer powder for type I and type II thermotropic liquid crystal polymers, wherein the aspect ratio is less than 3.1, and the particle size D90 is less than or equal to 10 microns, and then a liquid crystal polymer emulsion with a solid content of 15-50 wt% can be prepared, the application fundamentally solves the problem of small LCP melt processing window by using LCP ultrafine powder + normal-temperature coating technology, and simultaneously solves the technical problem of significant in-plane anisotropy of LCP film in the prior art, the application provides an isotropic coating film with an in-plane CTE anisotropy index of less than 0.15, and provides a high-performance-price-ratio domestic substitute product for 5G / 6G mobile phone antennas, new energy automobile power modules or low-orbit satellite chips.

Description

Technical Field

[0001] This invention relates to the field of flexible copper clad laminate technology, and in particular to a liquid crystal polymer powder, a liquid crystal polymer emulsion, an LCP copper clad laminate, and their preparation methods and applications. Background Technology

[0002] Flexible copper clad laminate (FCCL) is the core substrate of flexible printed circuit boards (FPC) and is hailed as the "industrial grain" of the electronics industry. With the rapid development of 5G / 6G, AI servers, new energy vehicles, and low-orbit satellite industries, the demand for FCCL has exploded. High-end ultra-thin films (<0.03mm) represent a technological high ground, and over 80% of the high-end market has long been monopolized by international industry giants.

[0003] Currently, the most commonly used flexible copper-clad laminates on the market primarily use PI (polyimide) film as the dielectric material. While these products offer advantages such as low cost, good heat resistance, high flexibility, high physical strength, and low dielectric constant (Dk) / dielectric loss (Df), PI film also has significant disadvantages: firstly, its high water absorption can easily lead to drastic changes in its dielectric properties, making it unsuitable for millimeter-wave transmission; secondly, signal transmission is unstable at high frequencies, with a sharp increase in loss, failing to meet the high-frequency, high-speed signal transmission requirements of emerging industries such as 5G / 6G communications, autonomous driving, and industrial internet, etc. Specific manifestations include: (1) 5G / 6G mobile phone antenna manufacturers: PI film FCCL has high high-frequency loss and unstable signal transmission, requiring ultra-thin FCCL of <0.03mm to achieve multi-layer stacking; (2) New energy vehicle power modules: SiC modules, BMS, domain controllers, etc., all require high heat-resistant FCCL. Due to the high price, long import delivery time and technical barriers, the development of related industries is seriously restricted; (3) Low-orbit satellite manufacturers: Low-orbit satellites have higher requirements for chip lightweighting and high reliability. At present, there is a lack of qualified suppliers that can completely replace imports, and they rely 100% on imports.

[0004] Liquid crystal polymer (LCP) flexible copper clad laminates (LCP-FCCL) based on liquid crystal polymer (LCP) exhibit superior performance for high-frequency device packaging, thus showing substitutability for PI (polyimide) flexible copper clad laminates and attracting widespread market attention. However, the LCP-FCCL market has three fatal flaws: (1) Market monopoly: There are few institutions and companies engaged in research on liquid crystal polymer flexible copper clad laminate (LCP-FCCL) technology, which widens the technological gap; (2) Technological barriers: As the core raw material for ultra-thin liquid crystal polymer flexible copper clad laminates, liquid crystal polymer (LCP) has excellent performance, but it also has disadvantages such as difficulty in controlling the molding process, anisotropic physical properties of the products, poor mechanical properties in the direction of shear flow at right angle during molding, and easy susceptibility to fibrils, which makes its processing and molding process complex and extremely difficult, and the synthesis of liquid crystal polymer flexible copper clad laminate (LCP-FCCL) is even more difficult. (3) High cost: Due to the high price of imported liquid crystal polymers, the price of liquid crystal polymer flexible copper clad laminate (LCP-FCCL) remains high, which is 3-5 times that of PI-FCCL. The downstream cost pressure is huge, which greatly hinders its use and promotion.

[0005] Liquid crystal polymers (LCPs) are mainly classified into Type I, Type II and Type III based on their heat resistance, molecular structure and processing performance. Type I liquid crystal polymers are classified as high heat-resistant, with a heat distortion temperature typically ranging from 250 to 355°C. Their main monomer components include p-hydroxybenzoic acid (HBA), biphenyl (BP) / hydroquinone (HQ), and terephthalic acid (TA) / isophthalic acid (IA). Typical applications include high-heat-resistant electronic connectors and SMT components. Type II liquid crystal polymers are classified as medium heat-resistant, with a heat distortion temperature typically ranging from 180 to 250°C. Their main monomer components include p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA). Typical applications include antenna materials and high-frequency communications. Type III liquid crystal polymers are classified as general heat-resistant, with a heat distortion temperature typically ranging from 100 to 200°C. Their main monomer components include p-hydroxybenzoic acid (HBA) and polyethylene terephthalate (PET). Typical applications include low-cost applications such as cooling fans and connecting pipes.

[0006] Commercially available LCP copper-clad laminates produced by coating methods generally use type III LCP solutions. However, their toughness and electrical properties are inferior to those of films obtained through type I and type II LCP processes. Therefore, some companies add PI to increase the toughness of the film, but this leads to even worse electrical properties. Due to the extremely high rigidity and linearity of the molecular chains of type I and type II liquid crystal polymers, as well as their strong heat resistance, the processing temperature is high, making molding more difficult. Currently, there is a need to develop a new LCP molding process, especially an LCP ultrathin film molding process. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a liquid crystal polymer powder, a liquid crystal polymer emulsion, an LCP copper clad laminate, and their preparation methods and applications. The present invention focuses on developing a liquid crystal polymer powder for type I and type II thermotropic liquid crystal polymers, with an aspect ratio <3.1 and a particle size D90 ≤10μm. Specifically, it is prepared by sequential coarse grinding, pre-embrittlement, cryogenic gas milling, air classification, collection, and post-treatment. A liquid crystal polymer emulsion with a solid content of 15-50wt% can then be prepared, which is coated onto copper foil at room temperature. After drying, a uniformly distributed and tightly stacked LCP powder layer is obtained. After heat treatment under an inert atmosphere, the LCP powder layer is completely melted, and the molecular chain is restructured... The new LCP film is bonded and cured to form a uniform LCP film, thus preparing an LCP copper-clad laminate. This invention fundamentally solves the problem of the small melting processing window of LCP by using LCP ultrafine powder + room temperature coating technology, and also solves the technical problem of significant in-plane anisotropy of LCP film in the prior art. This invention provides an isotropic coating film with an in-plane CTE anisotropy index of <0.15, which can not only achieve precise control of LCP film thickness (±2μm), but also achieve an ultra-smooth surface of LCP film with Ra<10nm. It can fill the mass production gap of ultra-thin LCP-FCCL <0.03mm, and provide a cost-effective domestic alternative for 5G / 6G mobile phone antennas, new energy vehicle power modules or low-orbit satellite chips.

[0008] To achieve this objective, the present invention adopts the following technical solution: One of the objectives of this invention is to provide a liquid crystal polymer powder, wherein the liquid crystal polymer powder is made of a thermotropic liquid crystal polymer with a melting point >280°C, the aspect ratio of the liquid crystal polymer powder is <3.1, and the particle size D90 of the liquid crystal polymer powder is ≤10μm.

[0009] As a preferred embodiment of the present invention, the liquid crystal polymer powder satisfies at least one of the following (a) to (d): (a) The liquid crystal polymer powder is made of type I thermotropic liquid crystal polymer with a particle size D90 of 3~5μm.

[0010] (b) The liquid crystal polymer powder is made of type II thermotropic liquid crystal polymer with a particle size D90 of 5~10μm.

[0011] (c) The Span value of the liquid crystal polymer powder is <1.5.

[0012] (d) The specific surface area of ​​the liquid crystal polymer powder is 0.95 ± 0.15 m². 2 / g.

[0013] A second objective of this invention is to provide a method for preparing the liquid crystal polymer powder described in the first objective, the method comprising the following steps: Prepare liquid crystal polymer raw materials, and sequentially perform coarse crushing, pre-embrittlement, cryogenic gas milling, air classification, collection and post-processing to obtain the liquid crystal polymer powder; The coarse crushing is carried out by shear crushing; the pre-embrittlement is carried out at -60~-120℃; the cryogenic gas milling includes: using liquid nitrogen vapor gas at ≤-80℃ as carrier gas, spraying the pre-embrittled particles onto a ceramic target or performing impact crushing.

[0014] As a preferred embodiment of the present invention, the method for preparing the liquid crystal polymer powder satisfies at least one of the following (e) to (i): (e) The target particle size of the coarse crushing is 3~5 mm.

[0015] (f) The cryogenic gas mill uses a nozzle to spray onto the ceramic target or to perform counter-pulverization, and the spray pressure of the nozzle is 8~14 bar.

[0016] (g) The feed rate of the cryogenic flow mill is 0.05~0.5 kg / h.

[0017] (h) The speed of the classifier wheel in the airflow classification is 6000~9000 rpm.

[0018] (i) The collection and post-processing includes cyclone separation, bag filter dust collection, and sintered metal filter dust collection performed in sequence.

[0019] A third objective of this invention is to provide a liquid crystal polymer emulsion comprising a dispersion medium and liquid crystal polymer powder; wherein the liquid crystal polymer powder is the liquid crystal polymer powder described in the first objective, or the liquid crystal polymer powder is prepared by the preparation method described in the second objective.

[0020] As a preferred embodiment of the present invention, the liquid crystal polymer emulsion satisfies at least one of the following (j) to (m): (j) The solid content of the liquid crystal polymer emulsion is 15~50wt%.

[0021] (k) The dispersion medium comprises any one or a combination of at least two of N-methylpyrrolidone, N,N-dimethylformamide or haloalkanes.

[0022] (l) The pressure difference increment of the liquid crystal polymer emulsion through the 20μm filter element is less than 5%.

[0023] (m) The viscosity of the liquid crystal polymer emulsion is 2000~30000cps, and the viscosity change does not exceed ±10% after being stored in a sealed container at room temperature for 30 days.

[0024] The fourth objective of this invention is to provide a method for preparing an LCP copper-clad laminate, the method comprising the following steps: The liquid crystal polymer emulsion described in Objective 3 is coated onto copper foil and dried. The resulting laminate is then heat-treated under an inert atmosphere to obtain an LCP copper-clad laminate.

[0025] As a preferred embodiment of the present invention, the method for preparing the LCP copper-clad laminate satisfies at least one of the following (n) to (s): (n) During the coating process, the copper foil tension is 0.5~5kg.

[0026] (o) During the coating process, the dry film thickness of the coating film is <30μm, preferably 15~25μm.

[0027] (p) The coating temperature is 20~80℃.

[0028] (q) The drying is carried out in an oven with a copper foil linear velocity of 1.5~15m / min, an oven length of >20m, and a target drying temperature of 60~180℃.

[0029] (r) During the heat treatment process, the target temperature is 300~350℃, the duration is 3~10h, and the tension is <1kg.

[0030] (s) The oxygen content of the inert atmosphere is <100ppm.

[0031] The fifth objective of this invention is to provide an LCP copper-clad laminate, wherein the LCP copper-clad laminate is prepared by the preparation method described in the fourth objective, and the dielectric constant Dk is 3.0~3.2 and the dielectric loss Df is 0.003~0.004.

[0032] The sixth objective of this invention is to provide an application of LCP copper-clad laminate, that is, applying the LCP copper-clad laminate described in objective five to any one of the manufacturing processes of 5G / 6G mobile phone antennas, new energy vehicle power modules or low-orbit satellite chips.

[0033] Compared with existing technical solutions, the present invention has at least the following beneficial effects: (1) The present invention focuses on developing a liquid crystal polymer powder for type I and type II thermotropic liquid crystal polymers, with an aspect ratio of <3.1 and a particle size D90≤10μm. Specifically, it is prepared by sequential coarse crushing, pre-embrittlement, cryogenic gas milling, gas classification, collection and post-treatment, and then a liquid crystal polymer emulsion with a solid content of 15~50wt% can be prepared.

[0034] (2) The present invention uses a liquid crystal polymer emulsion with a solid content of 15~50wt% to coat onto copper foil. After drying, a uniformly distributed and tightly stacked LCP powder layer can be obtained. After heat treatment under an inert atmosphere, the LCP powder layer is completely melted and solidified by molecular chain recombination to form a uniform LCP film. The preparation method of LCP copper clad laminate described in the present invention only requires room temperature coating, drying and oxygen-free heat treatment, without hot pressing, to prepare LCP copper clad laminate with excellent performance. It is not only simple to operate and low in cost, but also has a pilot line yield of ≥90%.

[0035] (3) The LCP copper-clad laminate prepared by the present invention can not only achieve precise control of LCP film thickness (±2μm), but also achieve an ultra-smooth surface of LCP film with Ra<10nm. It can fill the mass production gap of ultra-thin LCP-FCCL <0.03mm and provide a high-performance domestic alternative for 5G / 6G mobile phone antennas, new energy vehicle power modules or low-orbit satellite chips.

[0036] (4) The LCP copper-clad laminate described in this invention not only possesses excellent mechanical properties (tensile strength ≥ 100 MPa, elongation at break 15~25%, flexural modulus 3.0~3.5 GPa), but also excellent thermal properties (heat distortion temperature ≥ 280℃, coefficient of thermal expansion ≤ 40 ppm / K), and excellent electrical properties (volume resistivity ≥ 1.0 × 10⁻⁶). 15 Ω‧cm, dielectric constant Dk (10GHz) ≤3.5, dielectric loss Df (10GHz) is 0.003~0.004. Attached Figure Description

[0037] Figure 1 This is a schematic flowchart of a method for preparing LCP copper-clad laminate in another specific embodiment of the present invention.

[0038] Figure 2 This is a length-to-diameter ratio distribution diagram of the liquid crystal polymer powder in Example 1 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0040] One specific embodiment of the present invention provides a liquid crystal polymer powder, wherein the liquid crystal polymer powder is made of a thermotropic liquid crystal polymer with a melting point >280°C, the aspect ratio of the liquid crystal polymer powder is <3.1, and the particle size D90 of the liquid crystal polymer powder is ≤10μm.

[0041] Liquid crystal polymers (LCPs) are high-performance specialty engineering plastics with a highly oriented, rigid molecular chain structure. They exhibit high toughness, high modulus, and self-reinforcing effects at room temperature, making them difficult to break down to submicron / micron scale using conventional mechanical crushing. Therefore, by utilizing the brittle transition property of LCPs below their glass transition temperature (Tg), and by reducing fracture toughness (KIC) through thermodynamic state alteration, efficient ultrafine processing can be achieved.

[0042] Preferably, the liquid crystal polymer powder satisfies at least one of the following (a) to (d): (a) The liquid crystal polymer powder is made of type I thermotropic liquid crystal polymer with a particle size D90 of 3~5μm, such as 3μm, 3.5μm, 4μm, 4.5μm or 5μm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] It should be noted that because type I thermotropic liquid crystal polymers have good brittle fracture characteristics and a lower particle size limit, they are easier to obtain at the submicron level, such as poly(p-hydroxybenzoate) (PHB) homopolymers, which have highly linear rigid chains.

[0044] (b) The liquid crystal polymer powder is made of type II thermotropic liquid crystal polymer with a particle size D90 of 5~10μm, such as 5μm, 6μm, 7μm, 8μm, 9μm or 10μm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] It should be noted that because type II thermotropic liquid crystal polymers are prone to plastic deformation particles, excessively fine particles can lead to a decrease in grading efficiency. Examples include copolyesters containing naphthalene ring / biphenyl structures and flexible spacers.

[0046] (c) The Span value of the liquid crystal polymer powder is <1.5.

[0047] It should be noted that the Span value = (D90-D10) / D50. The smaller the Span value, the more uniform the particle size distribution of the liquid crystal polymer powder described in this invention, and the more irregular the particle shape, rather than the fibrous shape.

[0048] (d) The specific surface area of ​​the liquid crystal polymer powder is 0.95 ± 0.15 m². 2 / g.

[0049] Another specific embodiment of the present invention provides a method for preparing liquid crystal polymer powder, the method comprising the following steps: Prepare liquid crystal polymer raw materials, and sequentially perform coarse crushing, pre-embrittlement, cryogenic gas milling, air classification, collection and post-processing to obtain the liquid crystal polymer powder; The coarse crushing is carried out by shear crushing; the pre-embrittlement is carried out at -60~-120℃; the cryogenic gas milling includes: using liquid nitrogen vapor gas at ≤-80℃ as carrier gas, spraying the pre-embrittled particles onto a ceramic target or performing impact crushing.

[0050] Liquid crystal polymers (LCPs) are high-performance specialty engineering plastics with a highly oriented, rigid molecular chain structure. They exhibit high toughness, high modulus, and self-reinforcing effects at room temperature, making them difficult to break down to submicron / micron scale using conventional mechanical crushing. Therefore, by utilizing the brittle transition property of LCPs below their glass transition temperature (Tg), and by reducing fracture toughness (KIC) through thermodynamic state alteration, efficient ultrafine processing can be achieved.

[0051] In the preparation method of liquid crystal polymer powder described in this invention, each step plays a crucial role. Specifically, coarse grinding is used to obtain liquid crystal polymer particles with smaller particle sizes, avoiding the phenomenon of the particle surface becoming too cold while the core remains unembrittled during the subsequent pre-embrittlement process, thereby preventing a decrease in the efficiency of the subsequent cryogenic gas milling. The pre-embrittlement temperature is controlled at -60 to -120°C because the secondary transition temperature (β-transition) of thermotropic liquid crystal polymers (mainly type I and type II LCPs) with melting points >280°C is usually in the range of -60°C to -100°C. Pre-embrittlement at 120℃ ensures that the material fully enters the glassy brittle region. During the cryogenic gas milling process, liquid nitrogen vapor at ≤-80℃ is used as the carrier gas, which has the dual functions of deep cryogenic maintenance and carrier gas delivery. After cryogenic gas milling, the pre-embrittled particles can be further broken into irregular particles with a length-to-diameter ratio of <3.1. The cryogenic gas milling process selects whether to spray onto the ceramic target or to perform impact crushing based on the hardness of LCP. Airflow classification is based on the principle of centrifugal field and Stokes resistance balance to achieve cutting, which helps to obtain liquid crystal polymer powder with the target particle size (particle size D90≤10μm).

[0052] It should be noted that the pre-embrittlement described in this invention is carried out at -60 to -120°C, such as -60°C, -70°C, -80°C, -90°C, -100°C, -110°C, or -120°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0053] Preferably, the method for preparing the liquid crystal polymer powder satisfies at least one of the following (e) to (i): (e) The target particle size of the coarse crushing is 3 to 5 mm, such as 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0054] It should be noted that the coarse crushing described in this invention is carried out by a shear-type coarse crusher, which can avoid the problem of LCP melting and sticking to the wall caused by local overheating due to impact crushing; the resulting smaller-sized liquid crystal polymer particles can avoid the problem of the particle surface being too cold while the core is not embrittled during the subsequent pre-embrittlement process, thereby avoiding the decrease in efficiency of the subsequent cryogenic gas flow mill.

[0055] (f) The cryogenic gas mill uses a nozzle to spray onto the ceramic target or to perform impact crushing. The spray pressure of the nozzle is 8 to 14 bar, such as 8 bar, 9 bar, 10 bar, 11 bar, 12 bar, 13 bar or 14 bar, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0056] It should be noted that when the nozzle injection pressure is below 8 bar, the nozzle Mach number is insufficient, the particle collision kinetic energy is too low, and the crushing efficiency drops sharply; when the nozzle injection pressure is above 14 bar, the gas-solid two-phase flow density increases, the interference between particles intensifies, which leads to increased energy consumption and a wider particle size distribution.

[0057] (g) The feed rate of the cryogenic flow mill is 0.05~0.5 kg / h, such as 0.05 kg / h, 0.1 kg / h, 0.15 kg / h, 0.2 kg / h, 0.25 kg / h, 0.3 kg / h, 0.35 kg / h, 0.4 kg / h, 0.45 kg / h or 0.5 kg / h, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0058] It should be noted that the feed rate of the cryogenic gas mill is 0.05~0.5 kg / h, which is matched with the grinding chamber volume and airflow field, and belongs to the low-load, high-energy-density operation mode. If the feed rate is too high, on the one hand, it will cause the particle concentration in the classification zone to be overloaded, resulting in a "back-mixing" phenomenon; on the other hand, the heat absorbed by liquid nitrogen vaporization is insufficient to offset the heat of grinding, and the temperature rise may cause LCP to spring back to a tough state.

[0059] (h) The speed of the classifier wheel in the airflow classification is 6000~9000 rpm, such as 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm, 8000 rpm, 8500 rpm or 9000 rpm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0060] It should be noted that setting the speed of the classifier wheel in the airflow classification to 6000~9000 rpm can control the cutting particle size D90 to 5~10μm, which meets the requirement of <10μm.

[0061] (i) The collection and post-processing includes cyclone separation, bag filter dust collection, and sintered metal filter dust collection in sequence, which can avoid the loss of ultrafine powder (<5μm) through the layer.

[0062] Another specific embodiment of the present invention provides a liquid crystal polymer emulsion, the liquid crystal polymer emulsion comprising a dispersion medium and liquid crystal polymer powder.

[0063] Preferably, the liquid crystal polymer emulsion satisfies at least one of the following (j) to (m): (j) The solid content of the liquid crystal polymer emulsion is 15 to 50 wt%, such as 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt% or 50 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0064] (k) The dispersion medium comprises any one or a combination of at least two of N-methylpyrrolidone, N,N-dimethylformamide or haloalkanes.

[0065] (l) The pressure difference increment of the liquid crystal polymer emulsion through the 20μm filter element is less than 5%.

[0066] (m) The viscosity of the liquid crystal polymer emulsion is 2000~30000cps, and the viscosity change does not exceed ±10% after being stored in a sealed container at room temperature for 30 days.

[0067] This invention uses liquid crystal polymer powder in a specific state to formulate a liquid crystal polymer emulsion with a uniform distribution and a solid content as high as 15-50 wt%. The amount of solvent used is reduced, which can shorten the drying time, significantly increase the coating line speed at room temperature, reduce solvent evaporation, and reduce the solvent recovery and treatment load. Moreover, the wet film formed after coating with the high solid content liquid crystal polymer emulsion is thinner, the shrinkage rate after drying is reduced, and the thickness uniformity of the LCP ultrathin film is easier to control.

[0068] Another specific embodiment of the present invention provides a method for preparing an LCP copper-clad laminate, the method comprising the following steps: applying the above-mentioned liquid crystal polymer emulsion onto a copper foil and drying it, and then heat-treating the resulting laminate under an inert atmosphere to obtain an LCP copper-clad laminate.

[0069] like Figure 1 As shown, in another specific embodiment of the present invention, the preparation method of LCP copper-clad laminate includes three main stages: first, liquid crystal polymer powder for type I and type II thermotropic liquid crystal polymers is prepared, with an aspect ratio <3.1, a particle size D90≤10μm, and irregular granular shape; then, liquid crystal polymer emulsion with a solid content of 15~50wt% is prepared; and finally, LCP copper-clad laminate is prepared by room temperature coating + oxygen-free heat treatment.

[0070] The method for preparing LCP copper-clad laminates described in this invention only requires room temperature coating, drying, and oxygen-free heat treatment, without the need for hot pressing, to obtain high-performance LCP copper-clad laminates. It is not only simple to operate and low in cost, but also has a pilot line yield of ≥90%.

[0071] Preferably, the method for preparing the LCP copper-clad laminate satisfies at least one of the following (n) to (s): (n) During the coating process, the copper foil tension is 0.5~5kg, such as 0.5kg, 1kg, 1.5kg, 2kg, 2.5kg, 3kg, 3.5kg, 4kg, 4.5kg or 5kg, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0072] (o) During the coating process, the dry film thickness of the coated film is <30μm, preferably 15~25μm, such as 15μm, 17μm, 18μm, 20μm, 21μm, 23μm or 25μm, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0073] (p) The coating temperature is 20~80°C, such as 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0074] (q) The drying is carried out in an oven with a copper foil linear speed of 1.5~15m / min, such as 1.5m / min, 3m / min, 5m / min, 6m / min, 8m / min, 10m / min, 13m / min or 15m / min, etc. The length of the oven is >20m, and the target drying temperature is 60~180℃, such as 60℃, 80℃, 100℃, 120℃, 140℃, 160℃ or 180℃, etc., but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0075] (r) During the heat treatment process, the target temperature is 300~350℃, such as 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, etc., and the duration is 3~10h, such as 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc., and the tension is <1kg.

[0076] (s) The oxygen content of the inert atmosphere is <100ppm.

[0077] Another specific embodiment of the present invention provides an LCP copper-clad laminate, which is prepared by the above-described preparation method, and has a dielectric constant Dk of 3.0~3.2 and a dielectric loss Df of 0.003~0.004.

[0078] The LCP copper-clad laminate described in this invention not only possesses excellent mechanical properties (tensile strength ≥100MPa, elongation at break 15~25%, flexural modulus 3.0~3.5GPa), but also excellent thermal properties (heat distortion temperature ≥280℃, coefficient of thermal expansion ≤40ppm / K), and excellent electrical properties (volume resistivity ≥1.0×10⁻⁶). 15 Ω‧cm, dielectric constant Dk (10GHz) ≤3.5, dielectric loss Df (10GHz) is 0.003~0.004.

[0079] The LCP film thickness of the LCP copper-clad laminate described in this invention can be precisely controlled (±2μm), and the LCP film has an ultra-smooth surface with Ra<10nm. It can fill the mass production gap of ultra-thin LCP-FCCL (<0.03mm), providing a cost-effective domestic alternative for 5G / 6G mobile phone antennas, new energy vehicle power modules, or low-orbit satellite chips. Another specific embodiment of the present invention provides an application of LCP copper clad laminate, which is applied to any one of the manufacturing processes of 5G / 6G mobile phone antennas, new energy vehicle power modules or low-orbit satellite chips.

[0080] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows: Example 1 <Preparation of Liquid Crystal Polymer Powder> Vectra® A950 liquid crystal polymer manufactured by Celanese Corporation was prepared and coarsely crushed using a shear crusher to avoid local overheating caused by impact crushing, which could lead to LCP melting and adhesion to the walls. The rotor linear speed was controlled to <15m / s to prevent frictional heat generation, resulting in a material with an average particle size of 4.0mm. The coarsely crushed material was then directly immersed in liquid nitrogen at -90℃ for pre-embrittlement. Using liquid nitrogen vapor at ≤-80℃ as the carrier gas, the pre-embrittled particles were sprayed onto a ceramic target through a nozzle and subjected to cryogenic gas milling. The nozzle spray pressure was 15bar, and the feed rate of the cryogenic gas mill was 0.5kg / h. The material obtained from the cryogenic gas milling was then subjected to air classification, with the classifier wheel speed controlled at 8000rpm, followed by cyclone separation, bag filtration dust collection, and sintered metal filter dust collection to obtain liquid crystal polymer powder.

[0081] For the aforementioned liquid crystal polymer powder, random samples were taken for particle image analysis. The test revealed 293 particles in the sample with an average aspect ratio of 2.09, satisfying the requirement of aspect ratio < 3.1. The aspect ratio distribution of this sample is shown in the figure below. Figure 2 As shown, the red dashed line indicates that the sample has an average aspect ratio of 2.09, which is close to the aspect ratio of 1 (perfect sphere) indicated by the green dashed line, and much lower than the aspect ratio of 5 (the aspect ratio threshold for typical fibers) indicated by the purple dashed line.

[0082] Further testing revealed that the liquid crystal polymer powder obtained in this embodiment had the following properties: D10 = 2.1 μm, D50 = 5.4 μm, and D90 = 8.9 μm, satisfying D90 < 10 μm; a Span value of 1.27, satisfying Span < 1.5; and a specific surface area of ​​0.92 m². 2 / g, satisfying 0.95±0.15m 2 / g; the fracture surface of the liquid crystal polymer powder is clear, without melting or stringing; the ΔHf of the raw material is 30 J / g, and the ΔHf of the prepared liquid crystal polymer powder is 28.5 J / g, a decrease of 5%, which meets the requirement of ΔHf reduction rate ≤15%; the Hausner ratio is 1.18, which meets the requirement of Hausner ratio <1.25, indicating that the prepared liquid crystal polymer powder has good flowability; the moisture content of the prepared liquid crystal polymer powder is 180 ppm, which meets the requirement of moisture content <300 ppm.

[0083] The liquid crystal polymer powder preparation method provided in this embodiment has advantages such as energy input-embrittlement gain balance, non-destructive material thermal history, and excellent powder engineering performance.

[0084] <Preparation of Liquid Crystal Polymer Emulsions> Mix the above-mentioned liquid crystal polymer powder with N-methylpyrrolidone uniformly, stir uniformly at 500 rpm at 100°C, and conduct vacuum degassing to obtain a liquid crystal polymer emulsion with a solid content of 20 wt%.

[0085] After testing, the original raw materials cannot be made into an emulsion. The viscosity of the liquid crystal polymer emulsion obtained in this example is 20000 cps, which meets the coatable viscosity range of 2000-30000 cps; after the liquid crystal polymer emulsion obtained in this example is stored in a sealed condition at room temperature for 30 days, the viscosity is still 19000 cps, and the viscosity change does not exceed ±10%; after FTIR ester carbonyl detection, the liquid crystal polymer emulsion obtained in this example is at 1720 cm -1 there is a characteristic peak, the half-peak width is normal, and the drift is ≤2 cm -1 .

[0086] <Preparation Method of LCP Copper Clad Laminate> Using the liquid crystal polymer emulsion prepared above, coat it onto a copper foil, the coating temperature is 30°C, the unwinding tension of the copper foil is 2 kg, the dry film thickness of the coating film is 20 μm, and drying is carried out in an oven, the linear speed of the copper foil is 5 m / min, the length of the oven is 24 m, which includes 6 temperature sections each with a length of 4 m, and the set temperatures of each temperature section are 60°C, 100°C, 150°C, 150°C in sequence; the obtained laminate is subjected to heat treatment in an inert atmosphere (nitrogen with an oxygen content <100 ppm), the target temperature is 320°C, the duration is 5 h, and the tension is <1 kg, so as to obtain the LCP copper clad laminate.

[0087] The test results of the LCP copper clad laminate obtained in this example are summarized in Table 1.

[0088] Table 1 Example 2 <Preparation of Liquid Crystal Polymer Powder> Liquid crystal polymer (LCP) produced by Polyplastics (Japan) under the trade name LAPEROS® B230 was prepared. Coarse crushing was performed using a shear crusher to avoid localized overheating caused by impact crushing, which could lead to LCP melting and adhesion to the walls. The rotor linear speed was controlled to <15m / s to prevent frictional heat generation, resulting in a material with an average particle size of 4.0mm. The coarsely crushed material was then directly immersed in liquid nitrogen at -90℃ for pre-embrittlement. Using liquid nitrogen vapor at ≤-80℃ as the carrier gas, the pre-embrittled particles were sprayed onto a ceramic target through a nozzle and subjected to cryogenic gas milling. The nozzle spray pressure was 15bar, and the feed rate of the cryogenic gas mill was 0.5kg / h. The material obtained from the cryogenic gas milling was then subjected to air classification, with the classifier wheel speed controlled at 8000rpm. The mixture underwent cyclone separation, bag filtration dust collection, and sintered metal filter dust collection sequentially to obtain liquid crystal polymer powder.

[0089] After testing, the liquid crystal polymer powder obtained in this embodiment has the following properties: D10=3.6μm, D50=12.3μm, and D90=24.6μm, which does not meet the requirement of D90<10μm; Span value=1.71, which does not meet the requirement of Span value<1.5; Aspect ratio of 4.8, which does not meet the requirement of aspect ratio<3.1; The liquid crystal polymer powder exhibits a large number of filamentous particles and tough tear lines, that is, it exhibits a typical hydrogen bond undissociated morphology; The Hausner ratio is 1.35, which does not meet the requirement of Hausner ratio<1.25, indicating that the prepared liquid crystal polymer powder has serious soft agglomeration.

[0090] This embodiment demonstrates that pre-embrittlement was performed at -90℃. Insufficient pre-embrittlement temperature resulted in the material being in a "semi-tough, semi-brittle" state. In the Jet Mill, particles absorbed kinetic energy and underwent plastic deformation rather than brittle fracture, leading to fiber drawing, excessive aspect ratio, and graded failure. A D90 as high as 24.6μm indicates that coarse powder directly penetrated the layers. Experiments showed that the liquid crystal polymer powder obtained in this embodiment could not be used to formulate a uniformly dispersed liquid crystal polymer emulsion.

[0091] Example 3 <Preparation of Liquid Crystal Polymer Powder> Liquid crystal polymer (LCP) produced by Polyplastics (Japan) under the trade name LAPEROS® B230 was prepared. Coarse crushing was performed using a shear crusher to avoid localized overheating caused by impact crushing, which could lead to LCP melting and adhesion to the walls. The rotor linear speed was controlled to <15m / s to prevent frictional heat generation, resulting in a material with an average particle size of 4.0mm. The coarsely crushed material was then directly immersed in liquid nitrogen at -120℃ for pre-embrittlement. Using liquid nitrogen vapor at ≤-80℃ as the carrier gas, the pre-embrittled particles were sprayed onto a ceramic target through a nozzle and subjected to cryogenic gas milling. The nozzle spray pressure was 20 bar, and the feed rate of the cryogenic gas mill was 0.15kg / h. The material obtained from the cryogenic gas milling was then subjected to air classification, with the classifier wheel speed controlled at 8000rpm. The mixture underwent cyclone separation, bag filtration dust collection, and sintered metal filter dust collection sequentially to obtain liquid crystal polymer powder.

[0092] After testing, the liquid crystal polymer powder obtained in this embodiment has the following properties: D10 = 1.8 μm, D50 = 4.9 μm, and D90 = 7.8 μm, satisfying D90 < 10 μm; Span value = 1.22, satisfying Span value < 1.5; Aspect ratio = 2.0, satisfying aspect ratio < 3.1; The fracture surface of the liquid crystal polymer powder is clear, without melting or stringing; The ΔHf of the raw material is 31.5 J / g, and the ΔHf of the prepared liquid crystal polymer powder is 27.5 J / g, a decrease of 12.7%, satisfying the ΔHf reduction rate ≤ 15%; The Hausner ratio is 1.15, satisfying Hausner ratio < 1.25, indicating that the prepared liquid crystal polymer powder has good flowability.

[0093] Compared to Example 2, this example focuses on optimizing the pre-embrittlement operation. Deep cryogenic treatment at -120°C increases Φ(T) to 4.0, equivalent to Series A. The feed rate is reduced to 0.15 kg / h to compensate for the higher specific energy consumption of Series B, resulting in a final D50 of 4.9 μm, even better than the Series A benchmark. This demonstrates that Series B is not incapable of ultrafine powdering, but rather extremely sensitive to temperature windows.

[0094] <Preparation of Liquid Crystal Polymer Emulsions> The above liquid crystal polymer powder was mixed evenly with N-methylpyrrolidone and stirred evenly at 500 rpm at 100°C. After vacuum degassing, a liquid crystal polymer emulsion with a solid content of 20 wt% was obtained.

[0095] Tests show that the raw materials cannot be used to prepare an emulsion; the viscosity of the liquid crystal polymer emulsion obtained in this example is 18000 cps, which falls within the applicable coating viscosity range of 2000-30000 cps. After the liquid crystal polymer emulsion obtained in this example is sealed and stored at room temperature for 30 days, its viscosity is still 18500 cps, and the viscosity change does not exceed ±10%. Through FTIR ester carbonyl detection, the liquid crystal polymer emulsion obtained in this example has an absorption at 1530 cm -1 characteristic peak exists, and the intensity is consistent with that of the raw material.

[0096] <Preparation method of LCP copper clad laminate> The liquid crystal polymer emulsion prepared as above is coated on a copper foil, wherein the coating temperature is 30°C, the unwinding tension of the copper foil is 2 kg, and the dry film thickness of the coating film is 20 μm. The coated product is dried in an oven, the linear speed of the copper foil is 5 m / min, and the length of the oven is 24 m, which comprises 6 temperature sections each with a length of 4 m, and the set temperatures of the temperature sections are 60°C, 100°C, 150°C, and 150°C in sequence. The obtained laminate is subjected to heat treatment in an inert atmosphere (nitrogen with an oxygen content < 100 ppm) at a target temperature of 320°C for 5 hours with a tension < 1 kg, so as to obtain the LCP copper clad laminate.

[0097] The test results of the LCP copper clad laminate obtained in this example are summarized in Table 2.

[0098] Table 2 In summary, this invention provides a liquid crystal polymer powder, a liquid crystal polymer emulsion, an LCP copper-clad laminate, and their preparation methods and applications. The invention focuses on developing a liquid crystal polymer powder for type I and type II thermotropic liquid crystal polymers, with an aspect ratio <3.1 and a particle size D90 ≤10μm. Specifically, it is prepared by sequentially performing coarse grinding, pre-embrittlement, cryogenic gas milling, air classification, collection, and post-treatment. This allows for the formulation of a liquid crystal polymer emulsion with a solid content of 15-50wt%, which is then coated onto copper foil at room temperature. After drying, a uniformly distributed and tightly stacked LCP powder layer is obtained. Following heat treatment under an inert atmosphere, the LCP powder layer completely melts, and the molecular chains recombine and... A uniform LCP film is formed by curing, thus preparing an LCP copper-clad laminate. This invention fundamentally solves the problem of excessively small LCP melting processing window by using LCP ultrafine powder + room temperature coating technology, and also solves the technical problem of significant in-plane anisotropy of LCP film in the prior art. This invention provides an isotropic coating film with an in-plane CTE anisotropy index of <0.15, which can not only achieve precise control of LCP film thickness (±2μm), but also achieve an ultra-smooth surface of LCP film with Ra<10nm. It can fill the mass production gap of ultra-thin LCP-FCCL <0.03mm, and provide a cost-effective domestic alternative for 5G / 6G mobile phone antennas, new energy vehicle power modules or low-orbit satellite chips.

[0099] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0100] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0101] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0102] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A liquid crystal polymer powder, characterized in that, The liquid crystal polymer powder is made of a thermotropic liquid crystal polymer with a melting point >280℃, the aspect ratio of the liquid crystal polymer powder is <3.1, and the particle size D90 of the liquid crystal polymer powder is ≤10μm.

2. The liquid crystal polymer powder according to claim 1, characterized in that, Satisfy at least one of the following (a) to (d): (a) The liquid crystal polymer powder is made of type I thermotropic liquid crystal polymer with a particle size D90 of 3~5μm; (b) The liquid crystal polymer powder is made of type II thermotropic liquid crystal polymer with a particle size D90 of 5~10μm; (c) The Span value of the liquid crystal polymer powder is <1.5; (d) The specific surface area of ​​the liquid crystal polymer powder is 0.95 ± 0.15 m². 2 / g.

3. A method for preparing the liquid crystal polymer powder according to claim 1 or 2, characterized in that, The preparation method includes the following steps: Prepare liquid crystal polymer raw materials, and sequentially perform coarse crushing, pre-embrittlement, cryogenic gas milling, air classification, collection and post-processing to obtain the liquid crystal polymer powder; The coarse crushing is carried out by shear crushing; the pre-embrittlement is carried out at -60~-120℃; the cryogenic gas milling includes: using liquid nitrogen vapor gas at ≤-80℃ as carrier gas, spraying the pre-embrittled particles onto a ceramic target or performing impact crushing.

4. The method for preparing liquid crystal polymer powder according to claim 3, characterized in that, Satisfy at least one of the following (e) to (i): (e) The target particle size of the coarse crushing is 3~5 mm; (f) The cryogenic gas mill uses a nozzle to spray the material onto the ceramic target or to perform counter-impact crushing, and the spray pressure of the nozzle is 8~14 bar; (g) The feed rate of the cryogenic gas mill is 0.05~0.5 kg / h; (h) The speed of the stager wheel in the airflow stage is 6000~9000 rpm; (i) The collection and post-processing includes cyclone separation, bag filter dust collection, and sintered metal filter dust collection performed in sequence.

5. A liquid crystal polymer emulsion, characterized in that, The liquid crystal polymer emulsion comprises a dispersion medium and a liquid crystal polymer powder; wherein the liquid crystal polymer powder is the liquid crystal polymer powder according to claim 1 or 2, or the liquid crystal polymer powder is prepared by the preparation method according to claim 3 or 4.

6. The liquid crystal polymer emulsion according to claim 5, characterized in that, Satisfy at least one of the following (j)~(m): (j) The solid content of the liquid crystal polymer emulsion is 15~50wt%; (k) The dispersion medium comprises any one or a combination of at least two of N-methylpyrrolidone, N,N-dimethylformamide or haloalkanes; (l) The pressure difference increment of the liquid crystal polymer emulsion passing through the 20μm filter element is less than 5%; (m) The viscosity of the liquid crystal polymer emulsion is 2000~30000cps, and the viscosity change does not exceed ±10% after being stored in a sealed container at room temperature for 30 days.

7. A method for preparing an LCP copper-clad laminate, characterized in that, The preparation method includes the following steps: The liquid crystal polymer emulsion described in claim 5 or 6 is coated onto a copper foil and dried. The resulting laminate is then heat-treated under an inert atmosphere to obtain an LCP copper-clad laminate.

8. The method for preparing LCP copper-clad laminate according to claim 7, characterized in that, Satisfy at least one of the following (n)~(s): (n) During the coating process, the copper foil tension is 0.5~5kg; (o) During the coating process, the dry film thickness of the coated film is <30μm, preferably 15~25μm; (p) The coating temperature is 20~80℃; (q) The drying is carried out in an oven with a copper foil linear velocity of 1.5~15m / min, an oven length of >20m, and a target drying temperature of 60~180℃; (r) During the heat treatment process, the target temperature is 300~350℃, the duration is 3~10h, and the tension is <1kg; (s) The oxygen content of the inert atmosphere is <100ppm.

9. An LCP copper-clad laminate, characterized in that, The LCP copper-clad laminate is prepared by the preparation method described in claim 7 or 8, and has a dielectric constant Dk of 3.0 to 3.2 and a dielectric loss Df of 0.003 to 0.

004.

10. An application of an LCP copper-clad laminate, characterized in that, The LCP copper-clad laminate described in claim 9 can be applied to any one of the fabrication processes of 5G / 6G mobile phone antennas, new energy vehicle power modules, or low-orbit satellite chips.

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