A liquid crystal polymer copper clad plate and a method for manufacturing the same

Abstract

This invention discloses a liquid crystal polymer copper-clad laminate and its preparation method, relating to the field of liquid crystal polymer technology. The invention involves melt-blending and granulating a liquid crystal polymer, modified polyetheretherketone (PEEK), nanofillers, and a lubricant via twin-screw extrusion, followed by single-screw extrusion casting or blown film production to obtain a thin film, which is then hot-pressed with copper foil to produce the copper-clad laminate. This invention uses fluorinated benzylamine-modified PEEK, utilizing the π-π stacking and van der Waals forces between the fluorinated benzene rings and the liquid crystal polymer to enhance interfacial compatibility, improve melt strength and processing stability, and significantly enhance peel strength. Simultaneously, boron nitride hollow microspheres and diamond powder, after acid treatment, synergistically construct a thermally conductive pathway. The hollow microspheres introduce a trace amount of air to reduce dielectric loss, resulting in a copper-clad laminate that combines high peel strength, excellent thermal conductivity, and low dielectric properties.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal polymer technology, specifically to a liquid crystal polymer copper-clad laminate and its preparation method. Background Technology

[0002] Liquid crystal polymers (LCPs) are a class of high-performance thermoplastic engineering plastics that exhibit an ordered liquid crystal state in the molten state. Liquid crystal polymer flexible copper clad laminates (LCP-FCCLs) combine the excellent properties of LCPs with the circuit functionality of copper clad laminates, offering outstanding advantages such as excellent broadband high-frequency performance, low moisture absorption, low dielectric loss, good chemical stability, and high dimensional stability. They meet the manufacturing requirements of high-speed digital and high-frequency circuits and are widely used in mobile internet devices, automotive radar, and interconnect systems. With the increasing demands for high-frequency signal transmission from next-generation information technologies such as 5G communication and millimeter-wave radar, LCP copper clad laminates, due to their stable and low-loss dielectric properties at high frequencies, have become an important material choice for high-frequency flexible circuit substrates.

[0003] However, LCP copper-clad laminates still face several technical bottlenecks in actual production and application. Firstly, the weak adhesion between LCP and copper foil is a common problem in the industry. Due to LCP's low surface energy and strong chemical inertness, the interfacial bonding is insufficient when directly hot-pressed with copper foil, resulting in insufficient peel strength and affecting the uniformity of lamination quality and the long-term reliability of the product. To solve this problem, existing technologies mainly use plasma treatment to modify the LCP film surface, introducing polar functional groups or increasing surface roughness to improve the adhesion between the copper foil and the LCP substrate. Another approach is to improve interfacial bonding by coating a thin LCP layer onto the copper foil surface before hot-pressing. However, plasma surface treatment requires sophisticated equipment, struggles to ensure uniformity, and its effectiveness diminishes significantly over time. While solution coating can improve adhesion, the process is lengthy, and solvent residue may affect dielectric properties. Furthermore, the LCP film itself has high rigidity and relatively low melt strength, making it prone to uneven film thickness and surface defects during extrusion casting and blown film processing, hindering the improvement of product yield.

[0004] Secondly, with the continuous increase in the integration and power density of electronic devices, thermal management issues are becoming increasingly prominent. Printed circuit boards (PCBs), as the carriers and interconnectors of power devices, directly affect the thermal conductivity of their substrate, impacting chip node temperatures and system reliability. In existing technologies, filling the polymer matrix with high thermal conductivity inorganic fillers such as aluminum nitride, boron nitride, and diamond is the main approach to improving the thermal conductivity of the insulation layer in copper-clad laminates. For example, boron nitride has high thermal conductivity and good electrical insulation, but when distributed in a lamellar pattern in the polymer matrix, it is difficult to form a continuous and complete thermal conductivity path in the vertical direction of the board thickness, thus hindering the full realization of its high thermal conductivity potential. Diamond has the ability to significantly improve the thermal conductivity of polymers, but in existing technologies, diamond particles are easily unevenly dispersed in polymer resins, resulting in precipitation or agglomeration, thereby deteriorating thermal conductivity and insulation performance. Simultaneously, large amounts of filler often accompany the side effects of deteriorated dielectric properties and decreased mechanical strength of the matrix. Achieving a balance between thermal conductivity, dielectric properties, and mechanical properties is currently a hot research topic and a challenge.

[0005] Furthermore, the blending modification technology of LCP with engineering plastics has a certain research foundation. Polyetheretherketone (PEEK) is a special engineering plastic with excellent heat resistance, low dielectric loss, and good mechanical properties. Existing research focuses on the compatibility, crystallization behavior, and mechanical properties of PEEK blends with thermotropic liquid crystal polymers (TLCPs). However, the compatibility between the two in the molten state is limited, and the blends are prone to significant phase separation and weak interfacial interactions, which limits the further improvement of the composite material's performance. How to improve the interfacial compatibility between PEEK and LCP through molecular design to achieve synergistic reinforcement is an important research direction in the development of high-performance LCP composite materials. Summary of the Invention

[0006] The purpose of this invention is to provide a liquid crystal polymer copper-clad laminate and its preparation method, so as to solve the problems existing in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a liquid crystal polymer copper-clad laminate, comprising the following steps: (1) Dissolve 2.0-3.0 parts of chloromethylated polyether ether ketone in 10.0-15.0 parts of organic solvent by mass, add 0.1-0.4 parts of modifier, react at room temperature for 4-8 hours; remove solvent by rotary distillation, wash with ethanol 3-5 times, and then vacuum dry to obtain modified polyether ether ketone. (2) Thoroughly mix boron nitride hollow microspheres with diamond powder, disperse them in nitric acid for pretreatment, then centrifuge and wash with water until neutral, and dry at 40-80℃ for 5-8 hours; (3) By mass, 90-100 parts of liquid crystal polymer, 1-10 parts of modified polyether ether ketone, 1-10 parts of nanofiller treated in step (3) and 0.1-1 parts of lubricant are mixed, melt-blended and granulated by a twin-screw extruder, and then the resulting modified liquid crystal polymer composition is extruded and cast or blown by a single screw to obtain a 50μm thick film; the film is drawn to a pressure roller and laminated with a 15μm copper foil at a pressure of 1.0MPa to obtain a copper-clad laminate.

[0008] Furthermore, the modifier in step (1) is one of p-fluorobenzylamine, 3-fluorobenzylamine, or 3,4-difluorobenzylamine.

[0009] Furthermore, the organic solvent in step (1) is N-methylpyrrolidone.

[0010] Furthermore, in step (2), the mass ratio of boron nitride hollow microspheres to diamond powder is 3-5:1-4.

[0011] Furthermore, the diamond powder in step (2) has a particle size of 100-500 nm.

[0012] Furthermore, the nitric acid concentration in step (2) is 10-30 wt%.

[0013] Furthermore, in step (2), the pretreatment temperature is 80-90℃ and the pretreatment time is 1-2h.

[0014] Furthermore, in step (3), the twin-screw extruder operates at a speed of 500 rpm / min and a temperature of 350-390℃.

[0015] Furthermore, in step (3), the blown film temperature is 340-400℃, the blow-up ratio is 6:4, and the stretching ratio is 3:1.

[0016] Furthermore, in step (3), the lubricant is a high-temperature lubricant, which is a granular or powdered GENIOPLAST Pellet S lubricant produced by Wacker GmbH in Germany.

[0017] Furthermore, in step (3), the liquid crystal polymer is a polyaryletherketone liquid crystal polymer, and the specific preparation method is referred to CN1141330C.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) In this invention, modified polyether ether ketone (PEEK) is used as one of the modifiers for liquid crystal polymers. PEEK has excellent heat resistance and low dielectric loss properties. Therefore, the addition of PEEK will not affect the properties of LCP itself, but will effectively toughen and strengthen LCP. PEEK is modified by introducing fluorinated benzene rings into the molecular side chain. These fluorinated benzene rings enhance the interfacial interaction between PEEK and LCP through van der Waals forces and π-π stacking, thereby enhancing the compatibility between PEEK and LCP, improving melt strength and processing performance, making subsequent extrusion film formation and hot pressing lamination processes more stable and efficient. Furthermore, adjusting the amount of PEEK can adjust the peel strength to the required strength. Too little PEEK will not significantly improve the peel strength, while too much PEEK will significantly reduce the peel strength.

[0019] (2) In this invention, hollow boron nitride microspheres and diamond powder are added to form nanofillers, which are then subjected to acid treatment. The acid treatment roughens the surface of the nanofillers, which is beneficial for forming more interfaces with the resin matrix and enhancing the interfacial interaction. In addition, the hollow structure and surface roughening of the boron nitride microspheres can introduce an appropriate amount of air into the resin matrix to reduce the dielectric properties. The inherent thermal conductivity of the hollow boron nitride microspheres, together with the diamond powder, optimizes the heat conduction path, which can efficiently conduct heat away from the copper foil conductive layer, significantly reducing the device operating temperature and improving the long-term thermal stability and service life of the system. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 (1) Add 12.0 parts of concentrated sulfuric acid to the reactor, slowly add 10.0 parts of polyether ether ketone powder (purchased from Jida Special Plastics Engineering Research Co., Ltd., melt index 10 g / 10 min) and 2.0 parts of condensing agent aluminum chloride at 0℃, stir the solution until clear, quickly add 5.0 parts of chloromethyl methyl ether, continue to react at 0℃ for 2 h and then stop stirring, pour the reactants into ice water to obtain a white flocculent product, filter, wash with distilled water until neutral, wash with ethanol 3 times and dry to obtain chloromethylated polyether ether ketone; (2) Dissolve 2.0 parts of chloromethylated polyether ether ketone in 10.0 parts of N-methylpyrrolidone, stir until dissolved, add 0.1 parts of p-fluorobenzylamine, react at room temperature for 4 hours, remove the solvent by rotary distillation, wash with ethanol 3 times and dry under vacuum to obtain modified polyether ether ketone. (3) Boron nitride hollow microspheres (prepared according to CN119039672A) are mixed with diamond powder with a particle size of 100 nm at a mass ratio of 3:1, dispersed in 10% nitric acid, pretreated at 80℃ for 1 h, centrifuged, rinsed with deionized water until neutral, and dried at 50℃ for 5 h. (4) Mix 90 parts of liquid crystal polymer, 1 part of modified polyether ether ketone, 1 part of nanofiller and 0.1 parts of lubricant for 5 min, put them into a twin-screw extruder, speed 500 rpm / min, temperature 350-390℃, melt blend and granulate; extrude the modified liquid crystal polymer composition into a blown film through a single-screw extruder at a temperature of 340-400℃, blow ratio 6:4, stretch ratio 3:1 to obtain a 50μm film; stretch the film and composite it with a 15μm copper foil on a pressure roller at a pressure of 1.0MPa to obtain a copper-clad laminate.

[0022] Example 2 (1) Add 15.0 parts of concentrated sulfuric acid to the reactor, slowly add 12.5 parts of polyether ether ketone powder (purchased from Jida Special Plastics Engineering Research Co., Ltd., melt index 10 g / 10 min) and 3.5 parts of condensing agent phosphoric acid at 0℃, stir the solution until clear, quickly add 7.0 parts of 1-chloro-4-(chloromethoxy)butane, continue to react at 0℃ for 3 h and then stop stirring, pour the reactants into ice water to obtain a white flocculent product, filter, wash with distilled water until neutral, wash with ethanol 4 times and dry to obtain chloromethylated polyether ether ketone; (2) Dissolve 2.5 parts of chloromethylated polyether ether ketone in 12.5 parts of N-methylpyrrolidone, stir until dissolved, add 0.2 parts of 3-fluorobenzylamine, react at room temperature for 6 hours, remove the solvent by rotary distillation, wash with ethanol 4 times and dry under vacuum to obtain modified polyether ether ketone. (3) Boron nitride hollow microspheres (prepared according to CN119039672A) were mixed with diamond powder with a particle size of 100 nm at a mass ratio of 4:2, dispersed in 20% nitric acid, pretreated at 85℃ for 1.5 h, centrifuged, rinsed with deionized water until neutral, and dried at 60℃ for 6 h. (4) Mix 95 parts of liquid crystal polymer, 5 parts of modified polyether ether ketone, 5 parts of nanofiller and 0.5 parts of lubricant for 5 min, put them into a twin-screw extruder, speed 500 rpm / min, temperature 350-390℃, melt blend and granulate; extrude the modified liquid crystal polymer composition into a blown film through a single-screw extruder at a temperature of 340-400℃, blow ratio 6:4, stretch ratio 3:1 to obtain a 50μm film; stretch the film and composite it with a 15μm copper foil on a pressure roller at a pressure of 1.0MPa to obtain a copper-clad laminate.

[0023] Example 3 (1) Add 18.0 parts of concentrated sulfuric acid to the reactor, slowly add 15.0 parts of polyether ether ketone powder (purchased from Jida Special Plastics Engineering Research Co., Ltd., melt index 10 g / 10 min) and 5.0 parts of condensing agent zinc chloride at 0℃, stir the solution until clear, quickly add 10.0 parts of chloromethyl methyl ether, continue to react at 0℃ for 4 h and then stop stirring, pour the reactants into ice water to obtain a white flocculent product, filter, wash with distilled water until neutral, wash with ethanol 5 times and dry to obtain chloromethylated polyether ether ketone; (2) Dissolve 3.0 parts of chloromethylated polyether ether ketone in 15.0 parts of N-methylpyrrolidone, stir until dissolved, add 0.4 parts of 3,4-difluorobenzylamine, react at room temperature for 8 hours, remove the solvent by rotary distillation, wash with ethanol 5 times and dry under vacuum to obtain modified polyether ether ketone. (3) Boron nitride hollow microspheres (prepared according to CN119039672A) were mixed with diamond powder with a particle size of 300 nm at a mass ratio of 5:3, dispersed in 30% nitric acid, pretreated at 90℃ for 2 h, centrifuged, rinsed with deionized water until neutral, and dried at 80℃ for 8 h. (4) Mix 100 parts of liquid crystal polymer, 10 parts of modified polyether ether ketone, 10 parts of nanofiller and 1.0 part of lubricant for 5 min, put them into a twin-screw extruder, speed 500 rpm / min, temperature 350-390℃, melt blend and granulate; extrude the modified liquid crystal polymer composition into a blown film through a single-screw extruder at a temperature of 340-400℃, blow ratio 6:4, stretch ratio 3:1 to obtain a 50μm film; stretch the film and composite it with a 15μm copper foil on a pressure roller at a pressure of 1.0MPa to obtain a copper-clad laminate.

[0024] Example 4 (1) Add 10.0 parts of concentrated sulfuric acid to the reactor, and slowly add 10.0 parts of polyether ether ketone powder (purchased from Jida Special Plastics Engineering Research Co., Ltd., melt index 10 g / 10 min) and 2.0 parts of condensing agent aluminum chloride at 0°C. Stir the solution until clear, and quickly add 5.0 parts of 1-chloro-4-(chloromethoxy)butane. Continue to react at 0°C for 2 hours and then stop stirring. Pour the reactants into ice water to obtain a white flocculent product. Filter, wash with distilled water until neutral, wash with ethanol 3 times and dry to obtain chloromethylated polyether ether ketone. (2) Dissolve 2.0 parts of chloromethylated polyether ether ketone in 10.0 parts of N-methylpyrrolidone, stir until dissolved, add 0.1 parts of 3-fluorobenzylamine, react at room temperature for 4 hours, remove the solvent by rotary distillation, wash with ethanol 3 times and dry under vacuum to obtain modified polyether ether ketone. (3) Boron nitride hollow microspheres (prepared according to CN119039672A) and diamond powder with a particle size of 500nm (mixed at a mass ratio of 5:4, dispersed in 10% nitric acid, pretreated at 80℃ for 1h, centrifuged, rinsed with deionized water until neutral, and dried at 40℃ for 5h). (4) Mix 90 parts of liquid crystal polymer, 10 parts of modified polyether ether ketone, 1 part of nanofiller and 0.1 parts of lubricant for 5 min, put them into a twin-screw extruder, speed 500 rpm / min, temperature 350-390℃, melt blend and granulate; extrude the modified liquid crystal polymer composition into a blown film through a single-screw extruder at a temperature of 340-400℃, blow ratio 6:4, stretch ratio 3:1 to obtain a 50μm film; stretch the film and composite it with a 15μm copper foil on a pressure roller at a pressure of 1.0MPa to obtain a copper-clad laminate.

[0025] Example 5 (1) Add 20.0 parts of concentrated sulfuric acid to the reactor, slowly add 15.0 parts of polyether ether ketone powder (purchased from Jida Special Plastics Engineering Research Co., Ltd., melt index 10 g / 10 min) and 5.0 parts of condensing agent phosphoric acid at 0℃, stir the solution until clear, quickly add 10.0 parts of chloromethyl methyl ether, continue to react at 0℃ for 4 h and then stop stirring, pour the reactants into ice water to obtain a white flocculent product, filter, wash with distilled water until neutral, wash with ethanol 5 times and dry to obtain chloromethylated polyether ether ketone; (2) Dissolve 3.0 parts of chloromethylated polyether ether ketone in 15.0 parts of N-methylpyrrolidone, stir until dissolved, add 0.4 parts of p-fluorobenzylamine, react at room temperature for 8 hours, remove the solvent by rotary distillation, wash with ethanol 5 times and dry under vacuum to obtain modified polyether ether ketone. (3) Boron nitride hollow microspheres (prepared according to CN119039672A) were mixed with diamond powder with a particle size of 500 nm at a mass ratio of 3:4, dispersed in 30% nitric acid, pretreated at 90℃ for 2 h, centrifuged, rinsed with deionized water until neutral, and dried at 70℃ for 7 h. (4) Mix 100 parts of liquid crystal polymer, 1 part of modified polyether ether ketone, 10 parts of nanofiller and 1.0 part of lubricant for 5 min, put them into a twin-screw extruder, speed 500 rpm / min, temperature 350-390℃, melt blend and granulate; extrude the modified liquid crystal polymer composition into a blown film through a single-screw extruder at a temperature of 340-400℃, blow ratio 6:4, stretch ratio 3:1 to obtain a 50μm film; stretch the film and composite it with a 15μm copper foil on a pressure roller at a pressure of 1.0MPa to obtain a copper-clad laminate.

[0026] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that unmodified polyether ether ketone is used instead of modified polyether ether ketone, while the other preparation steps are the same as in Example 2.

[0027] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that chloromethylated polyether ether ketone is used instead of modified polyether ether ketone, while the rest of the preparation steps are the same as in Example 2.

[0028] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that no modified polyether ether ketone is added; the other preparation steps are the same as in Example 2.

[0029] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that ordinary boron nitride is used instead of boron nitride hollow microspheres, while the rest of the preparation steps are the same as in Example 2.

[0030] Comparative Example 5 The difference between Comparative Example 5 and Example 2 is that the boron nitride hollow microspheres and diamond powder are not acid-treated, while the other preparation steps are the same as in Example 2.

[0031] Comparative Example 6 The difference between Comparative Example 6 and Example 2 is that boron nitride hollow microspheres are not added; the rest of the preparation steps are the same as in Example 2.

[0032] Comparative Example 7 The difference between Comparative Example 7 and Example 2 is that diamond powder is not added, while the rest of the preparation steps are the same as in Example 2.

[0033] Comparative Example 8 The difference between Comparative Example 8 and Example 2 is that no nanofiller is added; the rest of the preparation steps are the same as in Example 2.

[0034] Performance testing (1) Peel strength test: The test was conducted according to the test method of IPC-TM-6502.4.8. Peel test samples with a width of 1 mm were made using the flexible copper-clad laminates prepared in Examples 1 to 5 and Comparative Example 1. Under room temperature conditions, the bonding surface between the liquid crystal polymer film layer and the copper foil layer was peeled off from the edge. The copper foil layer was fixed on the flat plate with double-sided tape. The liquid crystal polymer film layer was peeled off in the 180° direction at a speed of 50 mm / min. The peel load was recorded using a tensile testing machine. Samples with a peel length greater than 100 mm were considered valid. The peel strength was calculated based on the average load during the peeling process. (2) Mechanical property testing: According to ASTM D882, the testing instrument was an INSTRON 5965 electronic universal tensile testing machine. The size of the cut strip was 100mm × 10mm, the clamp spacing was 50mm, the tensile rate was 25mm / min, and the tensile strength and elongation at break were tested and recorded; (3) Abrasion resistance test: A square block with a bottom surface of 10mm×15mm covered with fabric was placed on the surface of the liquid crystal polymer film. A 500g weight was loaded on the block. The block was then moved back and forth on the LCP film surface for 30mm. After 1 hour of continuous movement, the changes on the LCP film surface were observed. The presence of a large number of fibrils was evaluated as poor abrasion resistance, the absence of fibrils was evaluated as excellent abrasion resistance, and the intermediate condition was evaluated as moderate abrasion resistance.

[0035] Table 1 It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a liquid crystal polymer copper-clad laminate, characterized in that, Includes the following steps: (1) Dissolve 2.0-3.0 parts of chloromethylated polyether ether ketone in 10.0-15.0 parts of organic solvent by mass, add 0.1-0.4 parts of modifier, react at room temperature for 4-8 hours; remove solvent by rotary distillation, wash with ethanol 3-5 times, and then vacuum dry to obtain modified polyether ether ketone. (2) Thoroughly mix boron nitride hollow microspheres with diamond powder, disperse them in nitric acid for pretreatment, then centrifuge and wash with water until neutral, and dry at 40-80℃ for 5-8 hours; (3) By mass, 90-100 parts of liquid crystal polymer, 1-10 parts of modified polyether ether ketone, 1-10 parts of nanofiller treated in step (3) and 0.1-1 parts of lubricant are mixed, melt-blended and granulated by a twin-screw extruder, and then the resulting modified liquid crystal polymer composition is extruded and cast or blown by a single screw to obtain a 50μm thick film; the film is drawn to a pressure roller and laminated with a 15μm copper foil at a pressure of 1.0MPa to obtain a copper-clad laminate.

2. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, The modifier mentioned in step (1) is one of p-fluorobenzylamine, 3-fluorobenzylamine, or 3,4-difluorobenzylamine.

3. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, The organic solvent in step (1) is N-methylpyrrolidone.

4. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, The mass ratio of boron nitride hollow microspheres to diamond powder in step (2) is 3-5:1-4.

5. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, The diamond powder in step (2) has a particle size of 100-500 nm.

6. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, The nitric acid concentration in step (2) is 10-30 wt%.

7. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, In step (2), the pretreatment temperature is 80-90℃ and the pretreatment time is 1-2h.

8. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, In step (3), the twin-screw extruder operates at a speed of 500 rpm / min and a temperature of 350-390℃.

9. The method for preparing a liquid crystal polymer copper-clad laminate according to claim 1, characterized in that, In step (3), the blown film temperature is 340-400℃, the blow-up ratio is 6:4, and the stretching ratio is 3:1.

Images