Preparation method of high-frequency and high-speed liquid crystal polyarylate fiber copper-clad plate

Abstract

The invention relates to a preparation method of a high-frequency and high-speed liquid crystal polyarylester fiber copper-clad plate, which is characterized by comprising the following steps of: providing liquid crystal polyarylester fiber cloth; forming a temporary enhancement layer of a thermal activation type polar small molecule auxiliary agent on at least one surface of the liquid crystal polyarylester fiber cloth; the temporary reinforcing layer is coated with an adhesive layer; laying a copper foil on the outer side of the adhesive layer; and pressing the laminated body at the temperature of 260 to 300 DEG C. The thermal activation type polar small molecule auxiliary temporary layer is constructed on the surface of the liquid crystal polyarylester fiber cloth, so that the wettability of an adhesive and liquid crystal polyarylester fibers is improved, the adhesive is promoted to fully permeate into fiber micropores to form mechanical anchoring, and finally the peel strength of the copper-clad plate is improved; and meanwhile, polar groups are prevented from being introduced into the liquid crystal polyarylate fibers, so that the copper-clad plate can keep relatively low dielectric constant and dielectric loss, and double requirements of 5G high-frequency communication on reliability and signal transmission efficiency are met.

Description

Technical Field

[0001] The present invention relates to the field of flexible circuit boards, and in particular to a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad board. Background Art

[0002] The rapid development of high-tech fields such as 5G communications, the Internet of Things, and aerospace is placing higher demands on the performance of high-frequency, high-speed electronic circuit boards. Liquid crystal polymers (LCP) and their fiber materials are becoming the mainstream substrates for high-frequency, high-speed circuit boards due to their low dielectric constant, low dielectric loss, low thermal expansion coefficient, and excellent mechanical properties. Liquid crystal polyarylate fibers, with their excellent dielectric and physical properties, can meet the signal integrity, reliability, and spatial adaptability requirements of high-end electronic products.

[0003] Although existing high-frequency LCP flexible copper clad laminates perform excellently in terms of dielectric properties and moisture absorption rate, due to the large anisotropy of the LCP film, there are differences in its mechanical properties, interface bonding strength (such as peel strength) and dimensional stability, making subsequent processing difficult, and it is difficult to further improve product yield and reliability.

[0004] Improving the peel strength of copper-clad laminates is of great significance. High peel strength can significantly improve the interface stability and reliability of flexible copper-clad laminates, reduce subsequent processing losses, and increase yields, meeting the higher requirements of high-end communication equipment for bending resistance, high temperature resistance, and high-frequency signal integrity.

[0005] However, existing technologies that directly increase the polarity or functional group content of LCP or its fibers can enhance interfacial bonding with adhesives, but this often leads to side effects such as increased dielectric loss and water absorption, which can affect performance in high-frequency applications. Therefore, improving the peel strength of liquid crystal polyarylate fiber copper-clad laminates while maintaining dielectric properties and low hygroscopicity has become a pressing technical challenge. Summary of the Invention

[0006] The present application provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0007] In a first aspect, the present application provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate, which is characterized in that it includes the following steps: providing a liquid crystal polyarylate fiber cloth; forming a temporary reinforcement layer of a heat-activated polar small molecule additive on at least one side of the liquid crystal polyarylate fiber cloth; coating an adhesive layer on the temporary reinforcement layer; laying copper foil on the outside of the adhesive layer; and pressing the laminate at 260-300°C.

[0008] The application improves the wettability of the adhesive and the liquid crystal polyarylate fiber by constructing a temporary layer of a heat-activated polar small molecule additive on the surface of the liquid crystal polyarylate fiber cloth, promotes the full penetration of the adhesive into the fiber micropores to form mechanical anchoring, and finally improves the peel strength of the copper-clad plate; during the pressing process at 260-300°C, the additive strengthens the interfacial bonding by thermal migration and synergistic effect with the adhesive, and at the same time, the additive or its decomposition products react with the adhesive, which does not cause the hydrophilicity of the liquid crystal polyarylate fiber to rise, thus avoiding the introduction of polar groups into the liquid crystal polyarylate fiber to cause the moisture absorption of the fiber to increase, so that the copper-clad plate can maintain a low dielectric constant and dielectric loss, meeting the dual demands of reliability and signal transmission efficiency of 5G high-frequency communication.

[0009] Further, the thickness of the liquid crystal polyarylate fiber cloth is 15-25 μm. This thickness range ensures the mechanical strength and dimensional stability of the substrate while meeting the demand for thinness of high-frequency circuits. Excessive thickness will increase signal transmission delay, and excessive thinness will easily lead to processing deformation.

[0010] Further, the heat-activated polar small molecule additive is selected from at least one of lactam, nylon monomer and low molecular weight hydroxy acid. The selected additive contains high-polarity groups such as amide groups, carboxyl groups or hydroxyl groups. During pressing, it chemically reacts with the adhesive or forms strong hydrogen bonds through thermal migration, directly enhancing the interfacial bonding force.

[0011] Further, the heat-activated polar small molecule additive is a solution, and the mass fraction of the additive in the solution is 1-3 wt%. Using a solution of this concentration can ensure that the temporary layer uniformly covers the fiber surface and the thickness is controllable.

[0012] Further, the thickness of the temporary reinforcing layer is 0.1-0.5 μm. This thickness is sufficient to improve the interfacial wettability and reactivity, but is insufficient to form continuous moisture absorption channels, maintaining low dielectric loss and low water absorption.

[0013] Further, the adhesive used in the adhesive layer is an epoxy adhesive, an acrylate adhesive or a polyester adhesive. The three types of adhesives contain active groups such as epoxy groups, carboxyl groups or double bonds, which can undergo ring-opening addition, condensation or polymerization reactions with the polar groups of the additive to form covalent bonds to strengthen the bonding.

[0014] Further, the thickness of the copper foil is 12-15 μm, and the surface roughness is 0.6-1.5 μm. A thickness of 12-15 μm balances flexibility and electrical conductivity, and the roughness does not excessively increase the skin effect, maintaining the integrity of high-frequency signals.

[0015] Further, after forming the temporary reinforcing layer, an oven drying step is further included, the oven drying temperature is 80-120°C, and the oven drying time is 2-5 minutes. Low-temperature rapid drying only removes the solvent, avoiding premature reaction of the additive or pre-curing of the adhesive.

[0016] Furthermore, the lamination pressure is 2-8 MPa and the lamination time is 4-7 minutes. The pressure drives the adhesive to fully penetrate the fiber micropores and the rough surface of the copper foil, forming a mechanical anchor. The time ensures that the adhesive is fully cured and the additive migration and reaction are completed.

[0017] Furthermore, the lamination line speed is 0.8 to 2.5 m / min. If the speed is too fast, the reaction time is insufficient and the peel strength decreases; if it is too slow, the production efficiency is reduced and the substrate may be damaged by overheating. DETAILED DESCRIPTION

[0018] For ease of understanding of the present application, the present application will be described more fully below. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0019] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of this application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0022] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0023] Unless otherwise specified, the percentage contents mentioned in this application refer to mass percentage for solid-liquid mixture and solid-solid mixture, and refer to volume percentage for liquid-liquid mixture.

[0024] The percentage concentrations mentioned in this application, unless otherwise specified, refer to the final concentration, which refers to the percentage of the added component in the system after the addition of the component.

[0025] The temperature parameters in this application, unless otherwise specified, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows for temperature fluctuations within the precision range of instrument control.

[0026] The "particles" mentioned in this application, or materials with a defined particle size distribution, are not necessarily spherical in shape but may be irregular, primary or secondary. The particle size of irregular particles is the average of their maximum and minimum diameters.

[0027] Example 1: This example provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0028] Polar additive solution formula (mass percentage): caprolactam 1%, deionized water 99%.

[0029] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0030] Preparation process: In a cleanroom, a 1wt% caprolactam solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / side. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 25μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (280°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0031] Example 2: This example provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0032] Polar additive solution formula (mass percentage): 2% glycolic acid, 98% deionized water.

[0033] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0034] Preparation Process: In a cleanroom, a polar additive solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / surface. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 25μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (280°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0035] Example 3: This example provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0036] Polar additive solution formula (mass percentage): caprolactam 1%, deionized water 99%.

[0037] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 25μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0038] Preparation process: In a cleanroom, a 1wt% caprolactam solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / surface. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 35μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (280°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0039] Example 4: This example provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0040] Polar additive solution formula (mass percentage): caprolactam 1%, deionized water 99%.

[0041] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); rolled copper foil (thickness 15μm, Ra=1.2μm)

[0042] Preparation process: In a cleanroom, a 1wt% caprolactam solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / side. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 25μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (280°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0043] Example 5: This example provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0044] Polar additive solution formula (mass percentage): caprolactam 1%, deionized water 99%.

[0045] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0046] Preparation process: In a cleanroom, a 1wt% caprolactam solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / surface. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 50μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (280°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0047] Example 6: This example provides a method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate.

[0048] Polar additive solution formula (mass percentage): caprolactam 1%, deionized water 99%.

[0049] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0050] Preparation process: In a cleanroom, a 1wt% caprolactam solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 20g / m² / side. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 25μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the upper and lower adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (300°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0051] Comparative Example 1: This comparative example provides a method for preparing a liquid crystal polyarylate fiber copper clad laminate.

[0052] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0053] Preparation Process: In a cleanroom, deionized water was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / surface. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. Degassing epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 25μm. The adhesive was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (280°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0054] Comparative Example 1: This embodiment provides a method for preparing a liquid crystal polyarylate fiber copper clad laminate.

[0055] Polar additive solution formula (mass percentage): caprolactam 1%, deionized water 99%.

[0056] Copper clad laminate laminate structure: liquid crystal polyarylate fiber cloth (Kuraray, thickness 15μm, pore size 0.8μm); epoxy adhesive (EXLUB, 0802); electrolytic copper foil (thickness 12μm, Ra=1.2μm)

[0057] Preparation process: In a cleanroom, a 1wt% caprolactam solution was evenly sprayed onto both sides of a liquid crystal polyarylate fiber cloth using a sprayer at a rate of 8g / m² / surface. The cloth was allowed to stand for 2 minutes. The coated cloth was placed in a forced air oven (100°C, 3 minutes) and allowed to cool to room temperature. A degassed epoxy adhesive was evenly applied to both sides of the cloth using a 300mm scraper to a wet film thickness of 25μm. The cloth was allowed to stand for 1 minute. Copper foil was placed on the top and bottom adhesive surfaces and gently pre-pressed with a dust-free roller (0.2MPa, 30 seconds, room temperature). The laminate was then fed into a steel belt press (200°C, 3MPa, 5 minutes, line speed 1.6m / min, tension 30N), pressed, and then cooled and reeled.

[0058] Performance tests were performed on the samples of the embodiments and comparative examples.

[0059] Peel strength test: Sample: Cut three 100 mm x 10 mm copper-clad laminate specimens. Test instrument: Instron 3345 electronic universal testing machine. According to IPC-TM-650 standard, peel at a 90° angle and a peel speed of 50 mm / min. Record the peel force and take the average of three measurements in N / cm.

[0060] The dielectric constant (Dk) and dielectric loss (Df) were tested using a Keysight E5071C vector network analyzer at 10 GHz and 110 GHz, according to the JIS C6471 standard. Each sample was tested three times, and the average value was taken.

[0061] Water absorption test: Cut the sample into 20mm×20mm, weigh it (m0), soak it in 23℃ pure water for 24 hours, wipe off the surface moisture and weigh it (m1). Water absorption = (m1-m0) / m0×100%. Each group has 3 pieces and the average value is taken.

[0062] Sample number Peel strength (N / cm) Dielectric constant Dk (10GHz) Dielectric loss Df(10GHz) Water absorption rate (%) Example 1 2.6 2.32 0.0012 0.12 Example 2 2.8 2.33 0.0013 0.13 Example 3 2.6 2.35 0.0014 0.14 Example 4 2.5 2.32 0.0012 0.12 Example 5 2.9 2.33 0.0013 0.15 Example 6 3.0 2.34 0.0014 0.16 Comparative Example 1 1.9 2.31 0.0012 0.12 Comparative Example 2 2.2 2.30 0.0011 0.35

[0063] As can be seen from the data in Table 1, the data in the embodiment is better than that in the comparative example. This is because the present application improves the wettability of the adhesive and the liquid crystal polyarylate fiber by constructing a temporary layer of heat-activated polar small molecule additives on the surface of the liquid crystal polyarylate fiber cloth, promotes the adhesive to fully penetrate into the fiber micropores to form a mechanical anchor, and ultimately improves the peel strength of the copper clad laminate; during the 260-300°C pressing process, the additive produces a synergistic effect with the adhesive through thermal migration to strengthen the interface bonding, while itself or the decomposition product reacts with the adhesive, which does not cause the hydrophilicity of the liquid crystal polyarylate fiber to increase, thus avoiding the introduction of polar groups in the liquid crystal polyarylate fiber. The copper clad laminate can maintain a low dielectric constant and dielectric loss, meeting the dual requirements of 5G high-frequency communication for reliability and signal transmission efficiency. Comparative Example 1 does not use polar small molecule additives and cannot play the above role; the pressure and temperature of Comparative Example 2 are too low, and the additive cannot effectively migrate or decompose during pressing, which will lead to an increase in water absorption.

[0064] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a high-frequency and high-speed liquid crystal polyarylate fiber copper-clad laminate, characterized in that: The method comprises the following steps: providing liquid crystal polyarylate fiber cloth; forming a temporary reinforcement layer of a heat-activated polar small molecule additive on at least one side of the liquid crystal polyarylate fiber cloth; coating an adhesive layer on the temporary reinforcement layer; laying copper foil on the outer side of the adhesive layer; and pressing the laminate at 260-300°C.

2. The preparation method according to claim 1, characterized in that The thickness of the liquid crystal polyarylate fiber cloth is 15 to 25 μm.

3. The preparation method according to claim 1, characterized in that The heat-activated polar small molecule auxiliary agent is at least one selected from caprolactam, nylon monomer, and low-molecular hydroxy acid.

4. The preparation method according to claim 1, characterized in that The heat-activated polar small molecule additive is a solution, and the mass fraction of the additive in the solution is 1 to 3 wt%.

5. The preparation method according to claim 1, characterized in that The thickness of the temporary reinforcement layer is 0.1-0.5 μm.

6. The preparation method according to claim 1, characterized in that The adhesive used in the adhesive layer is epoxy adhesive, acrylate adhesive or polyester adhesive.

7. The preparation method according to claim 1, characterized in that The copper foil has a thickness of 12 to 15 μm and a surface roughness of 0.6 to 1.5 μm.

8. The preparation method according to claim 1, characterized in that After the temporary reinforcement layer is formed, a drying step is further included, with a drying temperature of 80 to 120° C. and a drying time of 2 to 5 minutes.

9. The preparation method according to claim 1, characterized in that The pressing pressure is 2-8 MPa, and the pressing time is 4-7 minutes.

10. The preparation method according to claim 1, characterized in that The linear speed of the pressing is 0.8-2.5 m / min.