Modified PTFE-based copper-clad plate and preparation method thereof

Abstract

The invention discloses a modified PTFE-based copper-clad plate and a preparation method thereof, and belongs to the technical field of copper-clad plates. The modified PTFE-based copper-clad plate comprises a first copper layer, a first silver layer, a first insulating film, a second insulating film, a second silver layer and a second copper layer, each of the first insulating film and the second insulating film contains polytetrafluoroethylene, boron nitride and ceramic powder; the ceramic powder comprises MgO and TiO2. Wherein boron nitride can improve the heat conductivity coefficient of the copper-clad plate, MgO and TiO2 can cooperate to improve the thermal expansion coefficient of an insulating film, and the proportion of boron nitride in the insulating film is reduced; the arrangement of the silver layer can improve the peel strength of the copper-clad plate. The modified PTFE-based copper-clad plate provided by the invention has relatively good heat conduction, peel strength and thermal expansion coefficient at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper-clad plates, in particular to a modified PTFE-based copper-clad plate and a preparation method thereof. BACKGROUND

[0002] As a core material in the high-frequency electronic field, polytetrafluoroethylene (PTFE)-based copper-clad plates have become a key basic material for high-end technologies such as 5G communication, satellite radar, and automotive electronics, due to their unique performance advantages and extensive application requirements. As a high-performance fluoroplastic, PTFE has extremely low dielectric constant (D k about 2.1) and loss factor (D f about 0.0002), which can significantly reduce energy loss in high-frequency signal transmission, while also having excellent high-temperature resistance (continuous working temperature up to 260°C) and chemical stability, which can meet the stringent requirements of high-frequency high-speed scenarios for material stability. However, PTFE has low surface energy, which leads to difficulties in bonding with copper foil, complex high-temperature processing, and high costs. Moreover, the thermal expansion coefficient of PTFE (>100 ppm / K) is much larger than that of copper foil, resulting in insufficient heat resistance.

[0003] Currently, the conventional solution is to modify PTFE using fillers, but this often negatively affects dielectric properties and thermal conductivity, and excessive filler ratios can cause agglomeration and defects, while insufficient ratios cannot significantly improve the thermal expansion coefficient of the insulating substrate.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a modified PTFE-based copper-clad plate and a preparation method thereof to solve or improve the above technical problems.

[0006] The present application can be achieved as follows: In a first aspect, the present application provides a modified PTFE-based copper-clad plate, which includes a first copper layer, a first silver layer, a first insulating film, a second insulating film, a second silver layer, and a second copper layer. The first and second insulating films both contain polytetrafluoroethylene, boron nitride, and ceramic powder; the ceramic powder includes MgO and TiO2.

[0007] In optional embodiments, the modified PTFE-based copper-clad plate includes at least one of the following features: Feature 1: the D 50 of boron nitride is 5-30 μm; Feature 2: the boron nitride is hexagonal boron nitride powder; Feature 3: the weight ratio of MgO and TiO2 is 2:3 to 1:1; Feature 4: the particle size of TiO2 is 0.5 μm to 10 μm; Feature 5: the particle size of MgO is 1 μm to 20 μm; Feature 6: the thickness of the first copper layer is 10 μm to 40 μm; Feature 7: the thickness of the first silver layer is 2 nm to 50 nm; Feature 8: the thickness of the second copper layer is 10 μm to 40 μm; Feature 9: the thickness of the second silver layer is 2 nm to 50 nm.

[0008] In an optional embodiment, the modified PTFE-based copper-clad plate further contains inorganic fillers, coupling agents and thickening agents.

[0009] In an optional embodiment, the inorganic fillers include at least one of graphene, graphene oxide, diamond powder, silicon dioxide, silicon nitride, silicon carbide, aluminum oxide and aluminum nitride.

[0010] In an optional embodiment, the coupling agents include at least one of silane coupling agents and phthalate coupling agents.

[0011] In an optional embodiment, the thickening agents include at least one of hydroxyethyl cellulose, polyvinylpyrrolidone and fumed silica.

[0012] In an optional embodiment, the modified PTFE-based copper-clad plate further includes at least one of the following features: Feature 10: the thermal conductivity of the modified PTFE-based copper-clad plate is not less than 1.40 W / (m·K); Feature 11: the thermal expansion coefficient of the modified PTFE-based copper-clad plate is 17.3 ppm / K to 19 ppm / K; Feature 12: the peel strength of the modified PTFE-based copper-clad plate is not less than 1.7 N / mm; Feature 13: the dielectric loss of the modified PTFE-based copper-clad plate under the condition of 10 GHz is not more than 0.0017.

[0013] In a second aspect, the present application provides a preparation method of the modified PTFE-based copper-clad plate according to any one of the preceding embodiments, including the following steps: preparing a first silver layer and a first copper layer on one side surface of a first insulating base film in sequence to obtain a first insulating film; preparing a second silver layer and a second copper layer on one side surface of a second insulating base film in sequence to obtain a second insulating film; and pressing and forming the first insulating film and the second insulating film to obtain the modified PTFE-based copper-clad plate.

[0014] In an optional embodiment, the pressing and forming is performed by vacuum hot pressing.

[0015] In an optional embodiment, the first copper layer and the second copper layer are both prepared by electroplating.

[0016] In an optional embodiment, the electroplating conditions include an electroplating voltage of 2V-24V and a working time of 10min-120min.

[0017] In an optional embodiment, the first silver layer and the second silver layer are both prepared by magnetron sputtering.

[0018] In an optional embodiment, the magnetron sputtering conditions include a sputtering pressure of 0.1Pa-5Pa and a sputtering voltage of 100V-800V.

[0019] In an optional embodiment, the preparation of the first insulating base film and the second insulating base film independently includes: coating a glue solution on the surface of a substrate, drying to form a coating layer on the surface of the substrate; and separating the coating layer to obtain the insulating base film.

[0020] In an optional embodiment, the substrate includes at least one of a polyimide film, a polyethylene terephthalate film, a copper foil and an aluminum foil.

[0021] In an optional embodiment, the glue solution includes a glue solution body and a thickening agent; the glue solution body includes, in terms of weight percentage, 30%-50% of a polytetrafluoroethylene emulsion, 5%-10% of boron nitride, 5%-20% of ceramic powder, 15%-30% of inorganic filler, 0.5%-3% of a coupling agent and 15%-30% of water. The amount of the thickening agent is 0.5wt%-2wt% of the glue solution body.

[0022] In an optional embodiment, the preparation of the glue solution includes: mixing the polytetrafluoroethylene emulsion, the boron nitride, the ceramic powder, the inorganic filler, the coupling agent and the water to obtain the glue solution body; adding the thickening agent to the glue solution body to adjust the viscosity, and then vacuum defoaming.

[0023] In an optional embodiment, the viscosity of the glue solution is 90mPa·s-500mPa·s.

[0024] The beneficial effects of the present application include: The present application simultaneously modifies PTFE by using boron nitride and ceramic powder (MgO, TiO2), so as to adjust the thermal conductivity, the thermal expansion coefficient and the dielectric loss of the insulating film. Among them, boron nitride has a very high thermal conductivity and a relatively low dielectric loss relative to PTFE; the thermal expansion coefficient of the ceramic powder is relatively low, and by compounding MgO and TiO2, the thermal expansion coefficient of the copper-clad plate can be well controlled to be close to that of copper, and the cost of MgO and TiO2 is relatively low, which is suitable for mass production.

[0025] The application particularly adopts a magnetron sputtering method to prepare a silver layer on the surface of an insulating base film, and since silver has no magnetism, the silver will not affect the dielectric loss of the insulating base film. Then, a copper layer is electroplated on the surface of the silver layer, so that the copper layer and the silver layer have a large bonding force, and the thermal expansion coefficients of silver and copper are close, and the similar thermal expansion coefficients make them have strong stability at high temperature. Finally, the first insulating film and the second insulating film are pressed and formed into a shape by using a vacuum hot pressing method, so as to further improve the bonding strength between the coating layer and the substrate.

[0026] The modified PTFE-based copper-clad plate provided by the application can simultaneously have better thermal conductivity, peeling strength and thermal expansion coefficient. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be clearly and completely described below. If specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by manufacturers are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0028] The modified PTFE-based copper-clad plate and the preparation method thereof provided by the application will be specifically described below.

[0029] The application provides a modified PTFE-based copper-clad plate, which comprises a first copper layer, a first silver layer, a first insulating film, a second insulating film, a second silver layer and a second copper layer.

[0030] The first insulating film and the second insulating film both contain polytetrafluoroethylene, boron nitride and ceramic powder; the ceramic powder comprises MgO and TiO2.

[0031] In the modified PTFE-based copper-clad plate, the boron nitride can improve the thermal conductivity of the copper-clad plate, the MgO and TiO2 can cooperate to improve the thermal expansion coefficient of the insulating film, and the proportion of the boron nitride in the insulating film is reduced. The silver layer can improve the peeling strength of the copper-clad plate without affecting the dielectric loss of the copper-clad plate.

[0032] It should be noted that in the present application, boron nitride and ceramic powder (MgO, TiO2) are used to modify PTFE, which can adjust the thermal conductivity, thermal expansion coefficient and dielectric loss of the insulating film. Among them, boron nitride has a very high thermal conductivity (up to 200 W / m·K) and a lower dielectric loss (<0.001) relative to PTFE; the thermal expansion coefficient of ceramic powder is relatively low, such as the thermal expansion coefficient of MgO is about 18.7 ppm / K, and the thermal expansion coefficient of TiO2 is about 8.6 ppm / K, while the thermal expansion coefficients of other commonly used ceramics are relatively small, such as SiO2 (about 5 ppm / K), AlN (about 5.3 ppm / K), SiC (about 4.4 ppm / K), and the present application can better control the thermal expansion coefficient of the copper-clad plate to be close to copper (about 16.5 ppm / K) by compounding MgO and TiO2, and the cost of MgO and TiO2 is relatively low, which is suitable for mass production.

[0033] In some optional embodiments, the D 50 may be 5-30 μm, such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm, etc., or other values within the range of 5-30 μm. Illustratively, the boron nitride can be hexagonal boron nitride powder.

[0034] If the D 50 of the boron nitride is less than 5 μm, the viscosity of the glue solution is relatively high, which is not conducive to the control of the coating process; if the D 50 of the boron nitride is greater than 30 μm, it is difficult to disperse uniformly, which may cause stress concentration.

[0035] In some optional embodiments, the weight ratio of MgO and TiO2 can be 2:3 to 1:1, such as 2:3, 1:1.2 or 1:1, etc., or other values within the range of 2:3 to 1:1. In some more typical embodiments, the weight ratio of MgO and TiO2 is 2:3, and MgO and TiO2 are compounded in the above weight ratio, which is conducive to making the overall thermal expansion coefficient closer to the ideal value.

[0036] In some optional embodiments, the particle size of TiO2 can be 0.5-10 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., or other values within the range of 0.5-10 μm.

[0037] If the particle size of TiO2 is less than 0.5 μm, the viscosity of the glue solution is relatively high, which is not conducive to the control of the coating process; if the particle size of TiO2 is greater than 10 μm, it is difficult to disperse uniformly, which may cause stress concentration.

[0038] In some alternative embodiments, the particle size of MgO can be 1-20 μm, such as 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm, or other values within the range of 1-20 μm.

[0039] If the particle size of MgO is less than 1 μm, the viscosity of the glue solution is relatively high, which is not conducive to the control of the coating process; if the particle size of MgO is greater than 20 μm, it is difficult to disperse uniformly, which may cause stress concentration.

[0040] In some alternative embodiments, the thickness of the first copper layer can be 10-40 μm, such as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or 40 μm, or other values within the range of 10-40 μm. Similarly, the thickness of the second copper layer can also be 10-40 μm.

[0041] In some alternative embodiments, the thickness of the first silver layer can be 2-50 nm, such as 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm, or other values within the range of 2-50 nm. Similarly, the thickness of the second silver layer can also be 2-50 nm.

[0042] If the thickness of the first silver layer or the second silver layer is less than 2 nm, it is not conducive to improving or increasing the peel strength of the copper-clad plate; if the thickness of the first silver layer or the second silver layer is greater than 50 nm, it will greatly increase the cost.

[0043] In addition, in the present application, if the silver layer is replaced by other metal layers, such as a nickel layer, although it can improve the peel strength of the copper-clad plate to a certain extent, it will also affect the dielectric loss of the copper-clad plate, resulting in a high dielectric loss of the copper-clad plate.

[0044] In some alternative embodiments, the modified PTFE-based copper-clad plate further contains inorganic fillers, coupling agents, and thickening agents.

[0045] The inorganic fillers exemplarily but non-limitingly include at least one of graphene, graphene oxide, diamond powder, silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, and aluminum nitride.

[0046] The use of the above inorganic fillers can assist in improving the performance of the copper-clad plate, and when the types of inorganic fillers are 2 or more, it can prevent the phenomenon of agglomeration and cracking caused by a single filler with a high proportion. In addition, the use of the above fillers can make it easier to form a PTFE film than without fillers, which can improve the effect of subsequent sputtering and pressing processes.

[0047] The coupling agent may exemplarily but not limitatively include at least one of a silane coupling agent and a phthalate coupling agent. When boron nitride and ceramic powder are mixed with PTFE, agglomeration, defects, etc. may occur, thereby causing the performance such as peel strength to be reduced. By using the coupling agent, it is favorable to mix the above components with PTFE uniformly and sufficiently dispersed, preventing defects and voids from being generated.

[0048] The thickening agent may exemplarily but not limitatively include at least one of hydroxyethyl cellulose, polyvinylpyrrolidone and fumed silica.

[0049] In some optional embodiments, the thermal conductivity of the modified PTFE-based copper-clad plate is not less than 1.40 W / (m·K), such as 1.40 W / (m·K), 1.46 W / (m·K) or 1.55 W / (m·K), etc.

[0050] In some optional embodiments, the thermal expansion coefficient of the modified PTFE-based copper-clad plate is 17.3 ppm / K~19 ppm / K, such as 17.34 ppm / K, 18.65 ppm / K or 18.94 ppm / K, etc.

[0051] In some optional embodiments, the peel strength of the modified PTFE-based copper-clad plate is not less than 1.7 N / mm, such as 1.7 N / mm~1.8 N / mm.

[0052] In some optional embodiments, the dielectric loss of the modified PTFE-based copper-clad plate under the condition of 10 GHz is not more than 0.0017, such as 0.0014~0.0017.

[0053] As mentioned above, the modified PTFE-based copper-clad plate provided by the present application can simultaneously have better thermal conductivity, peel strength and thermal expansion coefficient.

[0054] Correspondingly, the present application also provides a preparation method of the above modified PTFE-based copper-clad plate, which may include the following steps: preparing a first silver layer and a first copper layer on one side surface of a first insulating base film in sequence to obtain a first insulating film; preparing a second silver layer and a second copper layer on one side surface of a second insulating base film in sequence to obtain a second insulating film; and pressing and forming the first insulating film and the second insulating film to obtain the modified PTFE-based copper-clad plate.

[0055] In some optional embodiments, the preparation of the first insulating base film and the second insulating base film independently includes: coating a glue solution on the surface of a substrate, drying to form a coating layer on the surface of the substrate; and separating the coating layer to obtain the insulating base film.

[0056] The base material can exemplarily but not limitatively include at least one of a polyimide film, a polyethylene terephthalate film, a copper foil, and an aluminum foil.

[0057] In some optional embodiments, the glue solution includes a glue solution body and a thickening agent; the glue solution body includes, in percentage by weight, 30-50% polytetrafluoroethylene emulsion, 5-10% boron nitride, 5-20% ceramic powder, 15-30% inorganic filler, 0.5-3% coupling agent, and 15-30% water. The amount of the thickening agent is 0.5-2 wt% of the glue solution body.

[0058] The amount of the polytetrafluoroethylene emulsion contained in the glue solution body can be 30%, 35%, 40%, 45%, or 50%, or other values within the range of 30-50%. The polytetrafluoroethylene emulsion is obtained by mixing polytetrafluoroethylene with pure water, and the concentration of the polytetrafluoroethylene emulsion can be 55%.

[0059] The amount of the boron nitride contained in the glue solution body can be 5%, 6%, 7%, 8%, 9%, or 10%, or other values within the range of 5-10%.

[0060] The amount of the ceramic powder contained in the glue solution body can be 5%, 8%, 10%, 12%, 15%, 18%, or 20%, or other values within the range of 5-20%.

[0061] By controlling the amounts of the boron nitride and the ceramic powder within the above ranges, the copper-clad plate is adjusted to have good electrical and thermal properties. If the amount of the boron nitride is less than 5%, it is not conducive to improving the thermal conductivity; if the amount of the boron nitride is greater than 10%, it is not conducive to improving the peel strength; if the amount of the ceramic powder is less than 5%, it is not conducive to reducing the thermal expansion coefficient; and if the amount of the ceramic powder is greater than 20%, it is not conducive to reducing the dielectric property.

[0062] The amount of the inorganic filler contained in the glue solution body can be 15%, 18%, 20%, 22%, 25%, 28%, or 30%, or other values within the range of 15-30%. In some preferable embodiments, the amount of the inorganic filler is 15-22%.

[0063] The amount of the coupling agent contained in the glue solution body can be 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%, or other values within the range of 0.5-3%.

[0064] The amount of the thickening agent added can be 0.5 wt%, 1 wt%, 1.5 wt%, or 2 wt% of the glue solution body, or other values within the range of 0.5-2 wt%.

[0065] In some optional embodiments, the preparation of the glue solution can include: mixing the polytetrafluoroethylene emulsion, boron nitride, ceramic powder, inorganic filler, coupling agent and water to obtain a glue solution body; adding a thickening agent to the glue solution body to adjust the viscosity, and then vacuum defoaming.

[0066] Exemplarily, the viscosity of the glue solution can be 90 mPa·s~500 mPa·s, such as 90 mPa·s, 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s, 350 mPa·s, 400 mPa·s, 450 mPa·s or 500 mPa·s, etc., and can also be other values in the range of 90 mPa·s~500 mPa·s.

[0067] In some optional embodiments, the first copper layer and the second copper layer can be prepared by electroplating.

[0068] The electroplating conditions can include: an electroplating voltage of 2 V~24 V (such as 2 V, 5 V, 10 V, 15 V, 20 V or 24 V, etc.), and a working time of 10 min~120 min (such as 10 min, 20 min, 40 min, 60 min, 80 min, 100 min or 120 min, etc.).

[0069] In some optional embodiments, the first silver layer and the second silver layer can be prepared by magnetron sputtering.

[0070] The magnetron sputtering conditions include: a sputtering gas pressure of 0.1 Pa~5 Pa (such as 0.1 Pa, 0.5 Pa, 1 Pa, 2 Pa, 3 Pa, 4 Pa or 5 Pa, etc.), and a sputtering voltage of 100 V~800 V (such as 100 V, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V or 800 V, etc.).

[0071] In some optional embodiments, the compression molding can be performed by vacuum hot pressing.

[0072] It should be noted that the total amount of boron nitride and ceramic powder in the present application is increased compared with conventional technology, which will lead to the adhesion between the coating layer and the substrate to be reduced to a certain extent. In order to ensure that the peeling strength of the copper-clad plate will not be reduced with the improvement of other performances, the present application specifically adopts a magnetron sputtering method to prepare a nanoscale silver layer on the surface of the insulating base film. Since silver does not have magnetism, silver will not affect the dielectric loss of the insulating base film, and the nanoscale silver layer will not bring a huge increase in cost. After that, a copper layer is electroplated on the surface of the silver layer, which can make the copper layer and the silver layer have greater bonding force, and the thermal expansion coefficients of silver and copper are close (about 19.5 ppm / K and 16.5 ppm / K respectively), and the similar thermal expansion coefficients make them have strong stability at high temperature. Finally, the first insulating film and the second insulating film are pressed and formed by using a vacuum hot pressing method, which can further improve the bonding strength between the coating layer and the substrate.

[0073] The features and performances of the present application are further described in detail in the following combined with embodiments.

[0074] Embodiment 1 The present embodiment provides a modified PTFE-based copper-clad plate, and a preparation method thereof comprises the following steps: S1: preparing a glue solution.

[0075] S1-1: 40% of PTFE emulsion, 8% of BN, 12% of ceramic powder (consisting of MgO and TiO2 with a mass ratio of 2:3), 18% of silicon dioxide, 2% of silane coupling agent and 20% of deionized water are mixed to obtain a glue solution main body.

[0076] The PTFE emulsion is obtained by mixing PTFE and pure water with a mass concentration of 55%. The boron nitride is D 50 The particle size of the TiO2 is 5 μm, and the particle size of the MgO is 10 μm.

[0077] S1-2: After the glue solution main body is stirred uniformly, hydroxyethyl cellulose is added to adjust the viscosity of the glue solution to 200 mPa·s (the addition amount of hydroxyethyl cellulose is 1 wt% of the glue solution main body), and then the glue solution is dispersed by continuous stirring, and then vacuum degassing is performed until no visible bubbles are present in the glue solution to obtain the glue solution.

[0078] S2: preparing an insulating base film.

[0079] The obtained glue solution is coated on a polyimide film using a coating machine, and the polyimide film coated with the glue solution is sent into an oven for drying (the temperature is 370℃, and the time is 20 min) to obtain a coating layer. After cooling, the coating layer as the insulating base film is torn off from the polyimide film.

[0080] S3: preparing a silver layer.

[0081] A silver layer was prepared on one side surface of an insulating base film in a magnetron sputtering device, and the thickness of the silver layer was 30 nm. The magnetron sputtering conditions were as follows: the sputtering pressure was 0.15 Pa, and the sputtering voltage was 400 V.

[0082] S4: A copper layer was prepared.

[0083] A copper layer was electroplated on the surface of the silver layer by using an electroplating method, and the thickness of the copper layer was 20 μm, thereby obtaining an insulating film. The electroplating conditions were as follows: the electroplating voltage was 12 V, and the working time was 60 min.

[0084] S5: A modified PTFE-based copper-clad plate was formed.

[0085] Two insulating films prepared in S4 were stacked, and specifically, the side surfaces of the two insulating films, on which no silver layer and no copper layer were arranged, were attached to each other, and then the two insulating films were pressed and formed in a vacuum press (the pressure was 400 psi, the temperature was 380°C, and the time was 60 min), thereby obtaining a modified PTFE-based copper-clad plate with the layers arranged in the order of a first copper layer-a first silver layer-a first insulating film-a second insulating film-a second silver layer-a second copper layer.

[0086] Example 2 The present embodiment provides a modified PTFE-based copper-clad plate, and a preparation method thereof includes the following steps. S1: A glue solution was prepared.

[0087] S1-1: 30% of PTFE emulsion, 10% of BN, 20% of ceramic powder (consisting of MgO and TiO2 at a mass ratio of 2:3), 22% of silicon carbide, 3% of silane coupling agent, and 15% of deionized water were mixed to obtain a glue solution main body.

[0088] The PTFE emulsion was the same as that in Example 1. The boron nitride was D 50 The particle size of the hexagonal boron nitride powder was 5 μm, the particle size of the TiO2 was 0.5 μm, and the particle size of the MgO was 1 μm.

[0089] S1-2: After the glue solution main body was stirred uniformly, polyvinylpyrrolidone was added to adjust the viscosity of the glue solution to 90 mPa·s (the amount of the polyvinylpyrrolidone added was 0.5 wt% of the glue solution main body), and then the glue solution was continuously stirred and dispersed, and then vacuum degassing was performed until no visible bubbles were present in the glue solution, thereby obtaining a glue solution.

[0090] S2: An insulating base film was prepared.

[0091] The obtained glue solution was coated on the polyimide film using a coater, and the polyimide film coated with the glue solution was sent into an oven for drying (temperature: 370°C, time: 20 min) to obtain a coating layer. After cooling, the coating layer as an insulating base film was torn off from the polyimide film.

[0092] S3: Preparation of a silver layer.

[0093] A silver layer with a thickness of 2 nm was prepared on one side surface of the insulating base film in a magnetron sputtering device. The magnetron sputtering conditions were as follows: sputtering pressure: 0.1 Pa, sputtering voltage: 100 V.

[0094] S4: Preparation of a copper layer.

[0095] A copper layer with a thickness of 10 μm was electroplated on the surface of the silver layer to obtain an insulating film. The electroplating conditions were as follows: electroplating voltage: 2 V, working time: 10 min.

[0096] S5: Forming of a modified PTFE-based copper-clad plate.

[0097] Two insulating films prepared in S4 were stacked, specifically, the side surfaces of the two insulating films not provided with the silver layer and the copper layer were attached to each other, and then were pressed and formed in a vacuum press (pressure: 400 psi, temperature: 380°C, time: 60 min) to obtain a modified PTFE-based copper-clad plate with the layers arranged as follows: first copper layer-first silver layer-first insulating film-second insulating film-second silver layer-second copper layer.

[0098] Example 3 The present example provides a modified PTFE-based copper-clad plate, and a preparation method thereof. S1: Preparation of a glue solution.

[0099] S1-1: 50% of PTFE emulsion, 5% of BN, 5% of ceramic powder (consisting of MgO and TiO2 with a mass ratio of 2:3), 15% of graphene, 0.5% of phthalate coupling agent, and 24.5% of deionized water were mixed to obtain a glue solution main body.

[0100] The PTFE emulsion was the same as that in Example 1. The boron nitride was D 50 The hexagonal boron nitride powder had a particle size of 30 μm; the particle size of TiO2 was 10 μm, and the particle size of MgO was 20 μm.

[0101] S1-2: After the glue solution main body was stirred uniformly, fumed silica was added to adjust the viscosity of the glue solution to 500 mPa·s (the addition amount of the fumed silica was 2 wt% of the glue solution main body), and the glue solution was continuously stirred and dispersed, and then was vacuum degassed until no visible bubbles were present in the glue solution to obtain the glue solution.

[0102] S2: Preparation of an insulating base film.

[0103] The obtained glue solution was coated on the polyimide film using a coater, and the polyimide film coated with the glue solution was sent into an oven for drying (temperature: 150°C, time: 60 min) to obtain a coating layer. After cooling, the coating layer as the insulating base film was torn off from the polyimide film.

[0104] S3: Preparation of a silver layer.

[0105] A silver layer was prepared on one side surface of the insulating base film in a magnetron sputtering device, and the thickness of the silver layer was 50 nm. The magnetron sputtering conditions were as follows: sputtering pressure: 5 Pa, sputtering voltage: 800 V.

[0106] S4: Preparation of a copper layer.

[0107] A copper layer was electroplated on the surface of the silver layer by electroplating, and the thickness of the copper layer was 40 μm to obtain an insulating film. The electroplating conditions were as follows: electroplating voltage: 24 V, working time: 240 min.

[0108] S5: Forming of a modified PTFE-based copper-clad plate.

[0109] Two insulating films prepared in S4 were stacked, specifically, the side surfaces of the two insulating films not provided with the silver layer and the copper layer were attached to each other, and then were pressed and formed in a vacuum press (pressure: 400 psi, temperature: 380°C, time: 60 min) to obtain a modified PTFE-based copper-clad plate with the layers arranged as first copper layer-first silver layer-first insulating film-second insulating film-second silver layer-second copper layer.

[0110] Comparative Example 1 The difference between this comparative example and Example 1 is that the amount of boron nitride in the glue solution main body is reduced to 0 wt%, and the amount of deionized water is increased to 28 wt%.

[0111] Comparative Example 2 The difference between this comparative example and Example 1 is that the amount of ceramic powder in the glue solution main body is reduced to 0 wt%, and the amount of deionized water is increased to 32 wt%.

[0112] Comparative Example 3 The difference between this comparative example and Example 1 is that no silver layer and copper layer are provided on the surface of the insulating base film, but the insulating base film is directly stacked with two copper foils and then pressed and formed to obtain a copper-clad plate with the structure of first copper foil-insulating base film-second copper foil.

[0113] Comparative Example 4 The difference between this comparative example and Example 1 is that the ceramic powder contained in the glue solution main body is composed of SiO2, SiC and AlN in a mass ratio of 3:3:2.

[0114] Comparative Example 5 The difference between this comparative example and Example 1 is that the total amount of the ceramic powder is unchanged, but only MgO is used.

[0115] Comparative Example 6 The difference between this comparative example and Example 1 is that the total amount of the ceramic powder is unchanged, but only TiO2 is used.

[0116] Comparative Example 7 The difference between this comparative example and Example 1 is that the D50 of the boron nitride is 2 μm. 50

[0117] Comparative Example 8 The difference between this comparative example and Example 1 is that the particle size of MgO is 0.5 μm.

[0118] Comparative Example 9 The difference between this comparative example and Example 1 is that the particle size of TiO2 is 15 μm.

[0119] Comparative Example 10 The difference between this comparative example and Example 1 is that the thickness of the silver layer is 1 nm.

[0120] Comparative Example 11 The difference between this comparative example and Example 1 is that the amount of boron nitride in the glue solution body is increased to 15%, and the water content is correspondingly reduced.

[0121] Comparative Example 12 The difference between this comparative example and Example 1 is that the amount of ceramic powder in the glue solution body is increased to 25%, and the water content is correspondingly reduced.

[0122] Comparative Example 13 The difference between this comparative example and Example 1 is that the glue solution body does not contain inorganic fillers, and the water content is correspondingly increased.

[0123] Comparative Example 14 The difference between this comparative example and Example 1 is that the silver layer is prepared by electroplating, and the electroplating conditions include: current density is 0.3 A / dm2, silver ion concentration is 2.0 g / L, and deposition time is 150 s.

[0124] Comparative Example 15 The difference between this comparative example and Example 1 is that the copper layer is prepared by electroless plating, and the electroless plating conditions include: copper ion concentration is 12 g / L, temperature is 55°C, and deposition rate is 5 μm / h.

[0125] Test Example The copper-clad plates prepared in Examples 1-3 and Comparative Examples 1-15 are subjected to performance tests, and the results are shown in Table 1. ​

[0126] wherein the thermal conductivity is tested according to ASTM D5470, the thermal expansion coefficient is tested according to IPC-TM-650 2.4.24.5, the peel strength is tested according to IPC-TM-650 2.4.9, and the dielectric loss is tested according to IEC61189-2-721:2015.

[0127] Table 1 Test results

[0128] As can be seen from Example 1 (the amount of boron nitride is 8%), Comparative Example 1 (the amount of boron nitride is 0%) and Comparative Example 11 (the amount of boron nitride is 15%), the addition of boron nitride can significantly improve the thermal conductivity of the copper-clad plate, and can improve the thermal expansion coefficient of the copper-clad plate and reduce the dielectric loss. However, too much boron nitride (such as Comparative Example 11) will also cause a significant decrease in the peel strength, because boron nitride has poor compatibility with PTFE, and high filling will easily form voids, thereby reducing the peel strength.

[0129] As can be seen from Example 1 (the amount of ceramic powder is 12%), Comparative Example 2 (the amount of ceramic powder is 0%) and Comparative Example 12 (the amount of ceramic powder is 25%), the addition of ceramic powder can significantly improve the thermal expansion coefficient of the copper-clad plate and reduce the dielectric loss of the copper-clad plate. However, the ceramic powder in a high filling amount is prone to agglomeration, and the ceramic filler has poor compatibility with PTFE, which is easy to form voids and reduce the peel strength.

[0130] As can be seen from Example 1 and Comparative Example 3, using a magnetron sputtering method to coat a layer of silver on the insulating substrate and then electroplating a copper layer will not significantly affect the dielectric loss, and can significantly improve the peel strength of the copper-clad plate.

[0131] As can be seen from Example 1 and Comparative Example 4, after replacing the components of the ceramic powder with SiO2, SiC and AlN, the thermal expansion coefficient of the copper-clad plate will decrease significantly, which will cause the deformation amount of the insulating substrate and the copper foil to be different during the heating process of the copper-clad plate, and thus cause delamination failure and other phenomena. The present application uses MgO and TiO2 as the ceramic powder, which can significantly improve the thermal expansion coefficient of the copper-clad plate without affecting other properties.

[0132] As can be seen from Example 1, Comparative Example 5 and Comparative Example 6, when only MgO is used as the ceramic powder, the thermal conductivity coefficient slightly increases, but the thermal expansion coefficient and the dielectric loss are both poor. When only TiO2 is used as the ceramic powder, the dielectric loss slightly decreases, but the thermal conductivity coefficient greatly decreases, and the thermal expansion coefficient also significantly deteriorates. The reason is that the thermal conductivity coefficient of MgO (36 W / mK) is higher than that of TiO2 (<10 W / mK), but the thermal expansion coefficient of MgO is relatively higher, and the dielectric performance is relatively poor. When only MgO is used as the ceramic powder for filling, it is difficult to balance the various performances of the copper-clad plate.

[0133] As can be seen from Example 1, Comparative Example 7 and Comparative Example 8, when the particle size of the used material is reduced, the viscosity of the glue solution suddenly increases, and even agglomeration occurs, resulting in that the insulation substrate cannot be coated. The reason is that the surface energy of the low particle size material is high, and the van der Waals force is strong, which easily increases the viscosity and then causes agglomeration.

[0134] As can be seen from Example 1 and Comparative Example 9, when a material with a larger particle size is used, the various performances are all poor, especially the dielectric loss. The reason is that the larger particle size reduces the uniformity inside the insulation substrate, causing the dielectric performance to fluctuate, and also reduces the flatness of the surface of the insulation substrate, reducing the bonding strength with the metal.

[0135] As can be seen from Example 1 and Comparative Example 10, when the thickness of the silver layer obtained by vacuum sputtering is reduced to 1 nm, the peel strength performance is greatly reduced. The reason is that the extremely thin silver layer cannot completely cover the texture on the surface of the insulation substrate, so that part of the copper foil is plated on the silver, and part of the copper foil is plated on the surface of the insulation substrate, making the overall peel strength uneven. In addition, it is difficult to obtain a 1 nm silver layer by sputtering, and a silver layer with uneven thickness may be obtained, thereby reducing the peel strength.

[0136] As can be seen from Comparative Example 1 and Comparative Example 13, when only boron nitride and ceramic powder (MgO and TiO2) are used to fill PTFE, the various performances are all decreased. The reason is that the other inorganic fillers used are also commonly used PTFE filling materials, which can improve the performance of the copper-clad plate. Adding more types of inorganic fillers is to prevent the phenomenon of agglomeration and cracks caused by too high proportion of a single filler. At the same time, increasing the overall proportion of the fillers in the glue solution also helps PTFE to be more easily formed into a film, so that the next process of sputtering, pressing and the like can be carried out.

[0137] As can be seen from Example 1 and Comparative Example 14, using electroplating method to obtain a silver layer on the surface of the insulation substrate does not bring too much performance change, only the peel strength has a small decrease. However, it is difficult to obtain a nanoscale silver layer by electroplating method, and a thicker silver layer will greatly increase the cost.

[0138] As can be seen from Example 1 and Comparative Example 15, obtaining a copper layer on the surface of a silver layer by chemical plating will result in a significant reduction in peel strength. This is because the silver layer may be corroded during the chemical plating process, thereby reducing the uniformity of the surface metal layer and thus negatively affecting the peel strength.

[0139] In summary, this invention utilizes both boron nitride and ceramic powders (MgO, TiO2) to modify PTFE, thereby adjusting the thermal conductivity, coefficient of thermal expansion, and dielectric loss of the insulating film. Boron nitride exhibits significantly higher thermal conductivity (up to 200 W / m·K) and lower dielectric loss (<0.001) compared to PTFE. The ceramic powders have lower coefficients of thermal expansion; for example, MgO has a coefficient of thermal expansion of approximately 13.8 ppm / K, and TiO2 has a coefficient of thermal expansion of approximately 8.6 ppm / K. Other commonly used ceramics also have relatively low coefficients of thermal expansion, such as SiO2 (approximately 5 ppm / K), AlN (approximately 5.3 ppm / K), and SiC (approximately 4.4 ppm / K). This invention, by combining MgO and TiO2, can effectively control the coefficient of thermal expansion of the copper-clad laminate to be close to that of copper (approximately 16.5 ppm / K). Furthermore, the relatively low cost of MgO and TiO2 makes it suitable for mass production.

[0140] In this invention, the total amount of boron nitride and ceramic powder is increased compared to conventional techniques, which to some extent leads to a decrease in the adhesion between the coating layer and the substrate. To ensure that the peel strength of the copper-clad laminate does not decrease with the improvement of other properties, this invention specifically employs magnetron sputtering to prepare a nanoscale silver layer on the surface of the insulating base film. Since silver is non-magnetic, it does not affect the dielectric loss of the insulating base film, and the nanoscale silver layer does not result in a significant increase in cost. Subsequently, a copper layer is electroplated onto the silver layer surface, which enables a strong bond between the copper and silver layers. Furthermore, the coefficients of thermal expansion of silver and copper are similar (approximately 19.5 ppm / K and 16.5 ppm / K, respectively), resulting in strong stability at high temperatures. Finally, a vacuum hot-pressing method is used to press the first and second insulating films together, further enhancing the adhesion strength between the coating layer and the substrate.

[0141] The modified PTFE-based copper clad laminate provided by this invention can simultaneously possess excellent thermal conductivity, peel strength, and coefficient of thermal expansion.

[0142] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified PTFE-based copper-clad laminate, characterized in that, The modified PTFE-based copper clad laminate includes a first copper layer, a first silver layer, a first insulating film, a second insulating film, a second silver layer, and a second copper layer; Both the first insulating film and the second insulating film contain polytetrafluoroethylene, boron nitride, and ceramic powder; the ceramic powder includes MgO and TiO2.

2. The modified PTFE-based copper-clad laminate according to claim 1, characterized in that, The modified PTFE-based copper-clad laminate includes at least one of the following characteristics: Feature 1: The D of the boron nitride 50 The thickness ranges from 5μm to 30μm. Feature 2: The boron nitride is hexagonal boron nitride powder; Feature 3: The weight ratio of MgO to TiO2 is 2:3 to 1:1; Feature 4: The particle size of the TiO2 is 0.5 μm to 10 μm; Feature 5: The particle size of the MgO is 1μm~20μm; Feature 6: The thickness of the first copper layer is 10μm~40μm; Feature 7: The thickness of the first silver layer is 2nm~50nm; Feature 8: The thickness of the second copper layer is 10μm~40μm; Feature 9: The thickness of the second silver layer is 2nm~50nm.

3. The modified PTFE-based copper-clad laminate according to claim 1 or 2, characterized in that, The modified PTFE-based copper clad laminate also contains inorganic fillers, coupling agents, and thickeners; Preferably, the inorganic filler includes at least one of graphene, graphene oxide, diamond powder, silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, and aluminum nitride. Preferably, the coupling agent includes at least one of silane coupling agents and phthalate coupling agents; Preferably, the thickener includes at least one of hydroxyethyl cellulose, polyvinylpyrrolidone, and fumed silica.

4. The modified PTFE-based copper-clad laminate according to claim 1, characterized in that, The modified PTFE-based copper clad laminate also includes at least one of the following features: Feature 10: The thermal conductivity of the modified PTFE-based copper clad laminate is not less than 1.40 W / (m·K); Feature 11: The coefficient of thermal expansion of the modified PTFE-based copper clad laminate is 17.3ppm / K~19ppm / K; Feature 12: The peel strength of the modified PTFE-based copper clad laminate is not less than 1.7 N / mm; Feature 13: The dielectric loss of the modified PTFE-based copper clad laminate under 10GHz conditions does not exceed 0.0017.

5. A method for preparing a modified PTFE-based copper-clad laminate as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The first silver layer and the first copper layer are sequentially prepared on one side surface of the first insulating base film to obtain the first insulating film; the second silver layer and the second copper layer are sequentially prepared on one side surface of the second insulating base film to obtain the second insulating film; the first insulating film and the second insulating film are pressed together to obtain the modified PTFE-based copper clad laminate. Preferably, the compression molding is carried out by vacuum hot pressing.

6. The preparation method according to claim 5, characterized in that, Both the first copper layer and the second copper layer are prepared by electroplating. Preferably, the electroplating conditions include: an electroplating voltage of 2V~24V and a working time of 10min~120min.

7. The preparation method according to claim 5, characterized in that, Both the first silver layer and the second silver layer were prepared by magnetron sputtering. Preferably, the magnetron sputtering conditions include: a sputtering gas pressure of 0.1 Pa to 5 Pa and a sputtering voltage of 100 V to 800 V.

8. The preparation method according to claim 5, characterized in that, The preparation of the first insulating base film and the second insulating base film independently includes: coating an adhesive solution onto the surface of a substrate, drying it to form a coating layer on the surface of the substrate; and separating the coating layer to obtain the insulating base film. Preferably, the substrate includes at least one of polyimide film, polyethylene terephthalate film, copper foil, and aluminum foil.

9. The preparation method according to claim 8, characterized in that, The adhesive comprises a main body and a thickener; by weight percentage, the main body comprises 30% to 50% polytetrafluoroethylene emulsion, 5% to 10% boron nitride, 5% to 20% ceramic powder, 15% to 30% inorganic filler, 0.5% to 3% coupling agent and 15% to 30% water. The amount of the thickener is 0.5wt% to 2wt% of the bulk adhesive.

10. The preparation method according to claim 9, characterized in that, The preparation of the adhesive includes: first mixing the polytetrafluoroethylene emulsion, the boron nitride, the ceramic powder, the inorganic filler, the coupling agent, and water to obtain the adhesive body; then adding the thickener to the adhesive body to adjust the viscosity, followed by vacuum degassing; Preferably, the viscosity of the adhesive solution is 90 mPa·s to 500 mPa·s.

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