High-frequency high-speed flexible copper-clad plate and preparation method and application thereof

Abstract

The application provides a high-frequency high-speed flexible copper-clad plate and a preparation method and application thereof. The high-frequency high-speed flexible copper-clad plate comprises a first copper foil layer, a first polyimide film layer, a first PFA film layer, a PTFE paint cloth layer, a second PFA film layer, a second polyimide film layer and a second copper foil layer arranged in sequence. The dielectric constant of the first polyimide film layer and the second polyimide film layer is independently 2.1-2.4, and the dielectric loss tangent is independently 0.0015-0.0025. The thickness of the first polyimide film layer and the second polyimide film layer accounts for 13-35% of the total thickness of the insulating layer. The copper-clad plate has excellent dimensional stability, better dielectric properties, better bending resistance and a lower thermal expansion coefficient.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of laminated boards, and relates to a high-frequency high-speed flexible copper-clad plate and a preparation method and application thereof. BACKGROUND

[0002] The fifth generation communication technology is a new generation of broadband mobile communication technology with the characteristics of high speed, low delay and large connection, which enables the network infrastructure of man-machine and interconnection to be widely applied, and its distinctive features also put forward further requirements on the performance of materials, which requires lower signal loss on the basis of existing materials. The traditional PI material can form a high-frequency material with certain properties after modification, which can cope with signal transmission below Sub-6G frequency, but it is a bit difficult at higher frequencies. LCP material is a new high-frequency material, which has been favored by major manufacturers due to its stable dielectric properties, but the high price caused by the problems of high processing difficulty and low material qualification rate. Although the fluorine material has obvious advantages in dielectric properties, its unstable expansion and contraction is also a obvious shortcoming, so the composite material can complement each other.

[0003] CN112549689A discloses a high-frequency flexible copper-clad plate, which comprises a first copper foil layer, a first polyimide film layer, a first PFA film layer, a PTFE paint cloth layer, a second PFA film layer, a second polyimide film layer and a second copper foil layer arranged in sequence, but the performance of the polyimide film layer is not outstanding, and some properties of MPI are exemplarily shown, including but not limited to low dielectric polyimide with dielectric constant Dk of 3.1-3.4 and dielectric loss tangent Df of 0.0038-0.0060, such as modified polyimide in “SL glue-free single-sided board” produced by Guangdong Shengyi Technology Co., Ltd. and / or Zhong Yuan Chemical MPI composite film SR-282#SW, etc. These reasons result in that the total thickness of the first polyimide film layer and the second polyimide film layer in the insulating layer is less than 25%, so that the high-frequency flexible copper-clad plate balances between bending resistance and dielectric properties. If the polyimide layer is too thick, the dielectric properties of the plate will be reduced, which cannot meet the high-frequency requirements; if the polyimide layer is too thin, the bending resistance of the plate will be reduced.

[0004] Therefore, in the art, it is desirable to develop a flexible copper-clad plate which can meet the high-frequency requirements and has better bending resistance without being too limited to set the polyimide layer to a relatively thin thickness. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a high-frequency high-speed flexible copper-clad plate and a preparation method and application thereof.The high-frequency high-speed flexible copper-clad plate of the present application has excellent dimensional stability, bending resistance and dielectric properties, and has high interlayer adhesion, low raw material cost, and can be pressed at a lower temperature and pressure, significantly reducing the process difficulty of the preparation of the high-frequency flexible copper-clad plate.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] In one aspect, the present application provides a high-frequency high-speed flexible copper-clad plate, which comprises a first copper foil layer, a first polyimide film layer, a first PFA film layer, a PTFE paint cloth layer, a second PFA film layer, a second polyimide film layer and a second copper foil layer arranged in sequence, the dielectric constant of the first polyimide film layer and the second polyimide film layer at 10GHz is independently 2.1-2.4, the dielectric loss tangent is independently 0.0015-0.0025, and the thickness ratio of the first polyimide film layer and the second polyimide film layer to the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE paint cloth layer, the second PFA film layer and the second polyimide film layer is 13-35%.

[0008] In the present application, the first polyimide film layer and the second polyimide film layer have lower dielectric constant and dielectric loss tangent values, and the thickness ratio of each layer is 13-35%, which makes the electrical properties of the three different insulating layers of MPI, PFA and paint cloth in the structure reach the same level, and the components with poor dielectric properties do not need to be designed to be thinner in design thickness, and the thickness of each layer of insulating layer can be randomly matched under the premise of ensuring functionality, and such structure design can ensure that the copper-clad plate has better bending resistance and lower thermal expansion coefficient.

[0009] In the present application, the copper foil can provide signal transmission function, the MPI film (polyimide film) can provide excellent dielectric properties and folding resistance, the PFA film can provide excellent dielectric properties and relatively low temperature adhesion for the whole plate, and the plate can be pressed under the condition of 310° / 15kgf; the PTFE paint cloth can provide excellent dielectric properties and good anti-swelling function, and is cheap and easy to obtain. The structure of the present application combines the functions of the materials, which can be organically combined and cooperated to produce good comprehensive effect, so that the copper-clad plate has excellent dimensional stability, better dielectric properties, better bending resistance and lower thermal expansion coefficient.

[0010] In the present application, PFA means polytetrafluoroethylene perfluoroalkyl vinyl ether, and the same description is referred to below, which all have the same meaning.

[0011] In the present application, the PTFE means polytetrafluoroethylene, the same description is referred to below, and all have the same meaning.

[0012] In the present application, the dielectric constant of the first polyimide film layer (MPI) and the second polyimide film layer (MPI) at 10 GHz is independently 2.1-2.4, for example, can be 2.1, 2.2, 2.25, 2.3, 2.35 or 2.4, etc.; the dielectric loss tangent is independently 0.0015-0.0025, for example, can be 0.0015, 0.0016, 0.0017, 0.0018, 0.0019, 0.0020, 0.0022, 0.0023, 0.0024, 0.0025, and specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range including the specific point values.

[0013] In the present application, the dielectric constant Dk and the dielectric loss tangent Df are tested according to the method in the standard IEC61189-1-721-2015, and the test frequency is 10 GHz.

[0014] In the present application, the thickness ratio of the first polyimide film layer and the second polyimide film layer is 13-35%, for example, 13%, 15%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32% or 35%, and specific point values between the above point values, limited to the length and for the sake of simplicity, the present application will not be listed in the range including the specific point values. In the present application, if the ratio is less than 13%, a relatively thin plate is prepared, for example, the insulation thickness (the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE paint layer, the second PFA film layer and the second polyimide film layer) is 50 μm, the thickness of the PI film is only 6.5 μm, the ability of the too thin PI film to support the copper foil is insufficient, resulting in reduced folding resistance of the plate; if the ratio is greater than 35%, the thickness ratio of the PTFE paint in the entire plate will be further reduced, and when the PTFE paint is thinned to a certain extent, its preparation difficulty will be relatively increased.

[0015] Preferably, the thickness of the first and second copper foil layers is independently 6-70 μm; for example, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 52 μm, 55 μm, 58 μm, 60 μm, 62 μm, 65 μm, or 68 μm, and specific point values between the above-mentioned point values. In view of the length of the specification and for the sake of simplicity, the present application does not exhaustively list the specific point values included in the range, and the thickness of the first and second copper foil layers is preferably 12-35 μm.

[0016] Preferably, the first and second copper foil layers are low-roughness copper foils having an Rz of ≤1.5 μm, for example, 1.5 μm, 1.3 μm, 1.0 μm, 0.8 μm, 0.5 μm, 0.3 μm, 0.2 μm, etc. In the present application, the roughness Rz of the copper foil layer is measured by a contact probe method.

[0017] In the present application, the PFA mainly functions to bond the MPI and the glass-fiber PTFE paint cloth, and the thickness of the first and second PFA film layers is independently preferably 5-20 μm. In view of the lower cost, the thinner the PFA, the better, and the thickness of the first and second PFA film layers is further preferably independently 5-10 μm.

[0018] In the present application, the thickness of each insulating layer (MPI, PFA, and glass-fiber PTFE paint cloth) can be arbitrarily selected as long as the functionality of each layer is ensured. In the present application, the first polyimide film layer, the first PFA film layer, the PTFE paint cloth layer, the second PFA film layer, and the second polyimide film layer can be collectively referred to as "insulating layers".

[0019] Preferably, the thickness of the first and second PFA film layers is uniform.

[0020] Preferably, the thickness of the first and second polyimide film layers is independently 5-35 μm; for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, 32 μm, or 35 μm, and specific point values between the above-mentioned point values. In view of the length of the specification and for the sake of simplicity, the present application does not exhaustively list the specific point values included in the range.

[0021] Preferably, the thickness of the first and second polyimide film layers is uniform.

[0022] Preferably, the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is less than or equal to 125 μm; for example, 125 μm, 120 μm, 115 μm, 110 μm, 105 μm, 100 μm, 95 μm, 90 μm, 85 μm, 80 μm, 75 μm, 70 μm, 65 μm, 60 μm, 55 μm or 50 μm, etc., preferably 50-100 μm.

[0023] In the present application, in order to make the copper-clad plate have better folding resistance, the tensile modulus of the first polyimide film layer and the second polyimide film layer is independently 6 GPa or more, for example, 6 Gpa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, etc. In the present application, the tensile modulus test method is IPC-TM-650 2.4.18.3.

[0024] Preferably, the thickness of the PTFE cloth layer is 20-80 μm; preferably 25-55 μm, for example, 22 μm, 24 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 52 μm or 55 μm, and specific point values between the above point values. Due to the consideration of brevity and simplicity, the present application does not list the specific point values included in the range.

[0025] In the present application, under the premise of ensuring the functionality of each layer of material, in order to make the copper-clad plate have better performance, the thickness and performance of the material can be optimized. For example, under the premise of obtaining excellent dimensional stability, the thickness ratio of the glass fiber PTFE cloth can be correspondingly increased; under the premise of obtaining excellent folding resistance, the thickness ratio of MPI can be correspondingly increased or the tensile modulus of MPI is increased. In order to obtain a low-cost copper-clad plate product, the thickness of the PFA layer can be reduced.

[0026] Preferably, the PTFE cloth layer comprises a glass fiber cloth and PTFE resin attached to the glass fiber cloth by impregnation.

[0027] Illustratively, the preparation method of the PTFE cloth is as follows: after the glass fiber cloth is impregnated with PTFE emulsion, drying and sintering are performed to obtain the PTFE cloth. The PTFE emulsion suitable for the present application is not particularly limited, and illustratively includes but is not limited to, for example, JF-4DCD, JF-4DC-A of Zhejiang Juhua Co., Ltd. or DISP30 of DuPont, etc.

[0028] On the other hand, the present application provides a preparation method of the high-frequency high-speed flexible copper-clad plate as described above, which comprises the following steps:

[0029] (1) coating PFA emulsion on the surface of polyimide film layer of the single-sided dry film, and after drying and sintering, a single-sided dry film containing PFA is obtained, the single-sided dry film containing PFA comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0030] (2) placing a PTFE cloth layer between two single-sided dry films containing PFA obtained in step (1), and pressing and curing to obtain the high-frequency high-speed flexible copper-clad plate.

[0031] Preferably, the temperature of drying in step (1) is 80-180℃, for example 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃ or 175℃, and specific point values between the above point values, the present application will not be exhaustively listed specific point values included in the range, limited to the length and for the sake of simplicity.

[0032] Preferably, the time of drying in step (1) is 5-10min, for example 5.5min, 6min, 6.5min, 7min, 7.5min, 8min, 8.5min, 9min or 9.5min, and specific point values between the above point values, the present application will not be exhaustively listed specific point values included in the range, limited to the length and for the sake of simplicity.

[0033] Preferably, the temperature of sintering in step (1) is 350-380℃, for example 353℃, 355℃, 358℃, 360℃, 363℃, 365℃, 368℃, 370℃, 372℃, 375℃ or 378℃, and specific point values between the above point values, the present application will not be exhaustively listed specific point values included in the range, limited to the length and for the sake of simplicity.

[0034] Preferably, the time of sintering in step (1) is 5-10min, for example 5.5min, 6min, 6.5min, 7min, 7.5min, 8min, 8.5min, 9min or 9.5min, and specific point values between the above point values, the present application will not be exhaustively listed specific point values included in the range, limited to the length and for the sake of simplicity.

[0035] Preferably, the temperature of pressing in step (2) is 300-330℃, for example 302℃, 305℃, 308℃, 310℃, 312℃, 315℃, 318℃, 320℃, 325℃ or 325℃, and specific point values between the above point values, the present application will not be exhaustively listed specific point values included in the range, limited to the length and for the sake of simplicity.

[0036] Preferably, the pressure of the pressing in step (2) is 10-30 kg / cm 2 , for example 11 kg / cm 2 , 13 kg / cm 2 , 15 kg / cm 2 , 17 kg / cm 2 , 19 kg / cm 2 , 20 kg / cm 2 , 21 kg / cm 2 , 23 kg / cm 2 , 25 kg / cm 2 , 27 kg / cm 2 or 29 kg / cm 2 , and specific point values between the above point values, the present application will not be listed again for the sake of brevity and conciseness of the range including specific point values.

[0037] Preferably, the time of the pressing in step (2) is 5-10 min, for example 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min or 9.5 min, and specific point values between the above point values, the present application will not be listed again for the sake of brevity and conciseness of the range including specific point values.

[0038] In the present application, as a preferred technical solution, the preparation method specifically comprises the following steps:

[0039] (1) coating PFA emulsion on the surface of the polyimide film layer of the glueless single-sided panel, drying at 80-180°C for 5-10 min, sintering at 350-380°C for 5-10 min, to obtain a PFA-containing glueless single-sided panel, the glueless single-sided panel comprising a copper foil layer and a polyimide film layer arranged on the surface thereof;

[0040] (2) placing a PTFE cloth layer between two PFA-containing glueless single-sided panels obtained in step (1), and pressing at a temperature of 300-330°C and a pressure of 10-30 kg / cm 2 for 5-10 min, to obtain the high-frequency high-speed flexible copper-clad plate.

[0041] On the other hand, the present application provides a printed circuit board, which comprises the high-frequency high-speed flexible copper-clad plate as described above.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] The high-frequency high-speed flexible copper-clad plate of the present application has excellent size stability, bending resistance and dielectric properties, high interlayer bonding force, low raw material cost, and can be pressed at low temperature and pressure, thus significantly reducing the difficulty of the preparation process of the high-frequency flexible copper-clad plate. DETAILED DESCRIPTION

[0044] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0045] The raw materials are as follows:

[0046] Copper foil: reverse copper foil produced by Japan Fukuda Metal Corporation, characteristic value CF-T49A-DS-HD2, thickness from 12 to 70 μm, roughness Rz = 1.1 ~ 1.5, different thickness, Rz value slightly different.

[0047] Glue-free single-sided board: composed of copper foil and polyimide film layer, which is a self-made product of Guangdong Shengyi Technology Co., Ltd., formed by coating polyimide precursor polyamide acid on the rough surface of copper foil and then heat imidizing.

[0048] PFA emulsion: AGC Corporation EA2000 emulsion JBA-001

[0049] PTFE paint cloth: glass fiber cloth impregnated with PTFE glue sheet produced by Jiangsu Shengyi Special Material Co., Ltd. Different thickness specifications of glass cloth (such as different models of Honghe Electronic Material Technology Co., Ltd. 101, 1067, 1080, etc.) are impregnated into PTFE emulsion (such as JF-4DCD, JF-4DC-A of Zhejiang Juhua Co., Ltd. or DISP30 of DuPont), and then dried and sintered to obtain PTFE paint cloth of different thickness.

[0050] Example 1

[0051] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (18 microns in thickness), a first polyimide film layer (7.5 microns in thickness), a first PFA film layer (5 microns in thickness), a PTFE cloth layer (25 microns in thickness), a second PFA film layer (5 microns in thickness), a second polyimide film layer (7.5 microns in thickness) and a second copper foil layer (18 microns in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer have a dielectric constant of 2.2 and a dielectric loss tangent of 0.002 at 10 GHz, and the thickness ratio of the first polyimide film layer and the second polyimide film layer to the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is 15%, and the PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth, and the tensile modulus of the first polyimide film layer and the second polyimide film layer is independently 8 GPa.

[0052] The preparation method comprises the following steps:

[0053] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 150 DEG C for 10 min, sintering at 380 DEG C for 5 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0054] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing and curing for 10 min under the conditions of a temperature of 320 DEG C and a pressure of 15 kg / cm 2 to obtain the high-frequency high-speed flexible copper-clad plate.

[0055] Embodiment 2

[0056] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (12 microns in thickness), a first polyimide film layer (12.5 microns in thickness), a first PFA film layer (5 microns in thickness), a PTFE cloth layer (40 microns in thickness), a second PFA film layer (5 microns in thickness), a second polyimide film layer (12.5 microns in thickness) and a second copper foil layer (12 microns in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer independently have a dielectric constant of 2.3 and a dielectric loss tangent of 0.0023 at 10 GHz. The first polyimide film layer and the second polyimide film layer account for 17% of the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer, and the PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth. The first polyimide film layer and the second polyimide film layer independently have a tensile modulus of 9 GPa.

[0057] The preparation method comprises the following steps:

[0058] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 80 DEG C for 10 min, sintering at 380 DEG C for 5 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0059] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing for 10 min under the condition that the temperature is 310 DEG C and the pressure is 15 kg / cm 2 to obtain the high-frequency high-speed flexible copper-clad plate.

[0060] Embodiment 3

[0061] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (18 microns in thickness), a first polyimide film layer (17.5 microns in thickness), a first PFA film layer (7.5 microns in thickness), a PTFE cloth layer (50 microns in thickness), a second PFA film layer (7.5 microns in thickness), a second polyimide film layer (17.5 microns in thickness) and a second copper foil layer (18 microns in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer independently have a dielectric constant of 2.4 and a dielectric loss tangent of 0.0018 at 10 GHz, and the thickness ratio of the first polyimide film layer and the second polyimide film layer to the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is 17.5%, and the PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth. The first polyimide film layer and the second polyimide film layer independently have a tensile modulus of 7 GPa.

[0062] The preparation method comprises the following steps:

[0063] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 180 DEG C for 8 min, sintering at 380 DEG C for 5 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0064] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing and curing for 5 min under the conditions of a temperature of 330 DEG C and a pressure of 30 kg / cm 2 to obtain the high-frequency high-speed flexible copper-clad plate.

[0065] Embodiment 4

[0066] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (35 mu m in thickness), a first polyimide film layer (25 mu m in thickness), a first PFA film layer (10 mu m in thickness), a PTFE cloth layer (55 mu m in thickness), a second PFA film layer (10 mu m in thickness), a second polyimide film layer (25 mu m in thickness) and a second copper foil layer (35 mu m in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer independently have a dielectric constant of 2.1 and a dielectric loss tangent of 0.0015 at 10 GHz. The total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is 100%, and the thickness of the first polyimide film layer and the second polyimide film layer accounts for 20%. The PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth. The first polyimide film layer and the second polyimide film layer independently have a tensile modulus of 6 GPa.

[0067] The preparation method comprises the following steps:

[0068] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 160 DEG C for 8 min, sintering at 360 DEG C for 8 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0069] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing and curing for 10 min under the conditions of a temperature of 300 DEG C and a pressure of 10 kg / cm 2 to obtain the high-frequency high-speed flexible copper-clad plate.

[0070] Embodiment 5

[0071] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (18 microns in thickness), a first polyimide film layer (12.5 microns in thickness), a first PFA film layer (5 microns in thickness), a PTFE cloth layer (65 microns in thickness), a second PFA film layer (5 microns in thickness), a second polyimide film layer (12.5 microns in thickness) and a second copper foil layer (18 microns in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer independently have a dielectric constant of 2.3 and a dielectric loss tangent of 0.002 at 10 GHz, and the thickness ratio of the first polyimide film layer and the second polyimide film layer to the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is 12.5%, and the PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth. The first polyimide film layer and the second polyimide film layer independently have a tensile modulus of 8 GPa.

[0072] The preparation method comprises the following steps:

[0073] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 100 DEG C for 5 min, sintering at 360 DEG C for 5 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0074] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing and curing for 5 min under the conditions of a temperature of 330 DEG C and a pressure of 10 kg / cm 2 to obtain the high-frequency high-speed flexible copper-clad plate.

[0075] Embodiment 6

[0076] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (18 microns in thickness), a first polyimide film layer (35 microns in thickness), a first PFA film layer (5 microns in thickness), a PTFE cloth layer (20 microns in thickness), a second PFA film layer (5 microns in thickness), a second polyimide film layer (35 microns in thickness) and a second copper foil layer (18 microns in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer independently have a dielectric constant of 2.2 and a dielectric loss tangent of 0.0018 at 10 GHz. The total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is 100%, and the thickness ratio of the first polyimide film layer and the second polyimide film layer is 35%. The PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth. The first polyimide film layer and the second polyimide film layer independently have a tensile modulus of 10 GPa.

[0077] The preparation method comprises the following steps:

[0078] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 150 DEG C for 5 min, sintering at 350 DEG C for 8 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0079] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing and curing at a temperature of 320 DEG C and a pressure of 25 kg / cm 2 for 8 min to obtain the high-frequency high-speed flexible copper-clad plate.

[0080] Embodiment 7

[0081] The embodiment provides a high-frequency flexible copper-clad plate, which comprises a first copper foil layer (70 microns in thickness), a first polyimide film layer (20 microns in thickness), a first PFA film layer (20 microns in thickness), a PTFE cloth layer (20 microns in thickness), a second PFA film layer (20 microns in thickness), a second polyimide film layer (20 microns in thickness) and a second copper foil layer (70 microns in thickness) arranged in sequence. The first polyimide film layer and the second polyimide film layer independently have a dielectric constant of 2.2 and a dielectric loss tangent of 0.002 at 10 GHz. The total thickness of the first polyimide film layer, the first PFA film layer, the PTFE cloth layer, the second PFA film layer and the second polyimide film layer is 100%, and the thickness of the first polyimide film layer and the second polyimide film layer accounts for 20%. The PTFE cloth layer is a PTFE cloth comprising a glass fiber cloth. The first polyimide film layer and the second polyimide film layer independently have a tensile modulus of 8 GPa.

[0082] The preparation method comprises the following steps:

[0083] (1) coating PFA emulsion on the surface of the polyimide film layer of the glue-free single-sided plate, drying at 180 DEG C for 10 min, sintering at 380 DEG C for 8 min, to obtain a glue-free single-sided plate containing PFA, wherein the glue-free single-sided plate comprises a copper foil layer and a polyimide film layer arranged on the surface of the copper foil layer;

[0084] (2) placing a PTFE cloth layer between two glue-free single-sided plates containing PFA obtained in step (1), and pressing and curing for 8 min under the conditions of a temperature of 320 DEG C and a pressure of 25 kg / cm 2 to obtain the high-frequency high-speed flexible copper-clad plate.

[0085] Embodiment 8

[0086] The embodiment is different from embodiment 1 only in that the first polyimide film layer and the second polyimide film layer have a tensile modulus of 4 GPa.

[0087] Embodiment 9

[0088] The embodiment is different from embodiment 1 only in that the high-frequency flexible copper-clad plate comprises a first copper foil layer (18 microns in thickness), a first polyimide film layer (7.5 microns in thickness), a first PFA film layer (10 microns in thickness), a PTFE cloth layer (15 microns in thickness), a second PFA film layer (10 microns in thickness), a second polyimide film layer (7.5 microns in thickness) and a second copper foil layer (18 microns in thickness) arranged in sequence.

[0089] Embodiment 10

[0090] The only difference between this example and Example 1 is that the thickness of the first PFA film layer and the second PFA film layer is each 4 μm, and the thickness of the PTFE cloth layer is 27 μm.

[0091] Example 11

[0092] The only difference between this example and Example 1 is that the high-frequency flexible copper-clad plate comprises, in order, a first copper foil layer (thickness 18 μm), a first polyimide film layer (thickness 25 μm), a first PFA film layer (thickness 20 μm), a PTFE cloth layer (thickness 80 μm), a second PFA film layer (thickness 20 μm), a second polyimide film layer (thickness 25 μm), and a second copper foil layer (thickness 12 μm).

[0093] Comparative Example 1

[0094] The only difference between this comparative example and Example 1 is that the dielectric constant at 10 GHz of the first polyimide film layer and the second polyimide film layer is independently 3.0, and the dielectric loss tangent is independently 0.0055.

[0095] Comparative Example 2

[0096] The only difference between this comparative example and Example 1 is that the high-frequency flexible copper-clad plate comprises, in order, a first copper foil layer (thickness 18 μm), a first polyimide film layer (thickness 5 μm), a first PFA film layer (thickness 5 μm), a PTFE cloth layer (thickness 30 μm), a second PFA film layer (thickness 5 μm), a second polyimide film layer (thickness 5 μm), and a second copper foil layer (thickness 18 μm).

[0097] Comparative Example 3

[0098] The only difference between this comparative example and Example 1 is that the high-frequency flexible copper-clad plate comprises, in order, a first copper foil layer (thickness 18 μm), a first polyimide film layer (thickness 36 μm), a first PFA film layer (thickness 5 μm), a PTFE cloth layer (thickness 18 μm), a second PFA film layer (thickness 5 μm), a second polyimide film layer (thickness 36 μm), and a second copper foil layer (thickness 18 μm).

[0099] The copper-clad plates of the examples and comparative examples were subjected to performance tests, and the test method was as follows:

[0100] (1) Dielectric constant (Dk) and dielectric loss tangent (Df): tested in accordance with IEC 61189-1-721-2015, test frequency 10 GHz;

[0101] (2) Interlayer adhesion strength: after burning about 20 mm between the single-sided board and the PTFE paint cloth layer at one end of the copper-clad plate sample (width 5 mm, length 150 mm) with a flame, continue to manually tear open the single-sided boards on both sides of the sample for at least 40 mm, fix the two sides of the sample strip torn open to the inner side of the material testing machine, set the initial clamp distance to 30±0.5 mm, and peel off at least 50 mm at a stretching rate of 50 mm / min in a 180-degree stretching mode, record the minimum peeling force, and divide the minimum peeling force by the sample width as the interlayer adhesion strength of the sample;

[0102] (3) Bending resistance: tested according to the test method specified in standard JIS C6471-1995, R=0.38 mm, G=4.9 N;

[0103] (4) Dimensional stability: test the dimensional change rate of double-sided copper-clad plate according to the method of standard IPC-TM-650 2.2.4, where "+" means expansion, "-" means shrinkage, and the finished product is divided into MD (Y axis) / TD (X axis) directions according to the direction of PI film;

[0104] (5) Coefficient of thermal expansion (CTE): tested by thermal mechanical analyzer TMA, the heating rate is 5 ℃ / min, tested according to the method in standard IPC-TM-650 2.4.24, and the finished product is divided into MD / TD directions according to the direction of PI film;

[0105] (6) Tensile modulus: tested according to standard IPC-TM-650 2.4.18.3.

[0106] The test results are shown in Table 1.

[0107] Table 1 Test performance data table of all examples and comparative examples

[0108]

[0109]

[0110] Since the present application uses three different raw materials with similar dielectric properties to form the flexible copper-clad plate, according to the performance test data in Table 1, under the premise of meeting the functionality, without deliberately designing the thickness ratio of each layer, we get the performance balanced finished plate material of examples 1-5. The dielectric performance is excellent, Dk is between 2.18-2.29 at 10 GHz, Df is between 0.0013-0.0019, the coefficient of thermal expansion (CTE) is between 15-17.5 ppm / K, the dimensional stability is good, and the interlayer adhesion strength is higher, above 0.9 N / mm.

[0111] Comparative folding resistance requires the selection of the same insulation thickness of the plate material, the same characteristic value and thickness of the copper foil of the plate material. For plate materials of different insulation thickness or plate materials with different copper foil thickness, the folding resistance of the plate material has a great difference, and cannot be compared in parallel. Relatively speaking, the thinner the insulation thickness of the plate material, the better the folding resistance; the thinner the copper foil, the better the folding resistance of the plate material. For example, example 7 and example 3 have the same insulation layer thickness, example 7 uses 70 μm thick copper foil, compared with example 3 using 18 μm, the folding resistance is greatly reduced, and because 20 microns thick PFA layer and 20 microns thick PTFE paint cloth layer are used, the cost of the plate material will be directly increased. Therefore, the thickness of the copper foil is preferably 12-35 μm, and the thickness of the PFA layer is preferably 5-10 μm.

[0112] Example 3 and example 5 have the same insulation layer thickness and copper foil thickness for comparison, the PTFE paint cloth 65 microns of example 5 is thicker, which leads to better dimensional stability, but the folding resistance is slightly worse; example 11 uses PTFE paint cloth 80 microns thicker and the overall insulation layer thickness is thicker, which also leads to good dimensional stability, but the folding resistance is worse; and example 3 and example 6 have the same insulation layer thickness and copper foil thickness for comparison, because the modulus of the PI film on the side close to the copper foil of example 6 is large, the folding resistance of the plate material is better, but the PTFE paint cloth selected by example 6 is 20 microns, which is very thin, causing certain difficulties in production yield, and the dimensional stability is poor; example 1 and example 9 have the same insulation layer thickness and copper foil thickness for comparison, the PTFE paint cloth of example 9 is relatively thin, which makes it difficult to prepare, and too thin PTFE paint cloth will cause poor dimensional stability and CTE of the plate material. Therefore, the thickness of the PTFE paint cloth layer is preferably 25-55 μm.

[0113] Example 1 and example 8 are compared, under the condition that all structures are consistent, the modulus of the PI film of example 8 is 4 Gpa, the tensile modulus of the plate material is reduced, and the folding resistance is only 54% of example 1. Therefore, in order to make the copper-clad plate have better folding resistance and tensile modulus, the tensile modulus of the first polyimide film layer and the second polyimide film layer is preferably more than 6 GPa.

[0114] Example 1 and example 10 have the same insulation layer thickness and copper foil thickness for comparison, example 10 uses a 4-micron-thick PFA layer, the interlayer adhesion strength is 0.5 N / mm, which meets the national standard requirements, but the performance of bonding PI film and PTFE paint cloth is poor, therefore the thickness of the PFA film layer is preferably 5-20 μm.

[0115] Example 1 and comparative example 1 have the same insulation layer thickness and copper foil thickness for comparison, it is found that comparative example 1 uses a PI film with slightly poor dielectric performance, which causes the dielectric performance, folding resistance and CTE of the plate material to be poor.

[0116] The same thickness of the insulating layer and the copper foil thickness of Example 1 and Comparative Example 2 are compared, and it is found that the single layer PI accounts for 10% of the total insulating thickness in Comparative Example 2, and the PI film accounts for too low a proportion, which will cause the folding resistance of the plate to decrease substantially, and the dimensional stability and CTE to become poor.

[0117] The same thickness of the insulating layer and the copper foil thickness of Example 3 and Comparative Example 3 are compared, and it is found that the single layer PI accounts for 36% of the total insulating thickness in Comparative Example 3, and the PI film accounts for too high a proportion, which will compress the proportion of the PTFE paint cloth, and will cause the difficulty of preparing the PTFE paint cloth to increase, thereby reducing the yield of the plate, and the dimensional stability and CTE also become poor.

[0118] The applicant declares that the high-frequency high-speed flexible copper-clad plate and the preparation method and application thereof of the present application are illustrated by the above examples, but the present application is not limited to the above examples, that is, it does not mean that the present application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A high-frequency, high-speed flexible copper-clad laminate, characterized in that, The high-frequency, high-speed flexible copper-clad laminate comprises a first copper foil layer, a first polyimide film layer, a first PFA film layer, a PTFE varnish layer, a second PFA film layer, a second polyimide film layer, and a second copper foil layer, arranged sequentially. The dielectric constant of the first polyimide film layer and the second polyimide film layer at 10 GHz is independently 2.1-2.4, and the dielectric loss tangent is independently 0.0015-0.0025. Furthermore, with the total thickness of the first polyimide film layer, the first PFA film layer, the PTFE varnish layer, the second PFA film layer, and the second polyimide film layer being 100%, the thickness percentage of the first polyimide film layer and the second polyimide film layer is 13-35%. The tensile modulus of the first polyimide film layer and the second polyimide film layer are independently greater than 6 GPa.

2. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The thickness of the first copper foil layer and the second copper foil layer are each independently 6 to 70 μm.

3. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The first and second copper foil layers are low-roughness copper foils with Rz≤1.5μm.

4. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The thickness of the first PFA thin film layer and the second PFA thin film layer are each independently 5-20 μm.

5. The high-frequency, high-speed flexible copper-clad laminate according to claim 4, characterized in that, The thickness of the first PFA thin film layer and the second PFA thin film layer are each 5-10 μm independently.

6. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The thicknesses of the first PFA film layer and the second PFA film layer are consistent.

7. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The thicknesses of the first polyimide film layer and the second polyimide film layer are independently 7.5–35 μm.

8. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The thicknesses of the first polyimide film layer and the second polyimide film layer are consistent.

9. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The total thickness of the first polyimide film layer, the first PFA film layer, the PTFE coated cloth layer, the second PFA film layer, and the second polyimide film layer is less than or equal to 125 μm.

10. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The total thickness of the first polyimide film layer, the first PFA film layer, the PTFE coated cloth layer, the second PFA film layer, and the second polyimide film layer is 50-100 μm.

11. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The thickness of the PTFE coated cloth layer is 20–80 μm.

12. The high-frequency, high-speed flexible copper-clad laminate according to claim 11, characterized in that, The thickness of the PTFE coated fabric layer is 25–55 μm.

13. The high-frequency, high-speed flexible copper-clad laminate according to claim 1, characterized in that, The PTFE coated fabric layer comprises glass fiber cloth and PTFE resin attached to the glass fiber cloth by impregnation.

14. The method for preparing a high-frequency, high-speed flexible copper-clad laminate according to any one of claims 1-13, characterized in that, The preparation method includes the following steps: (1) A PFA emulsion is coated on the surface of the polyimide film layer of the adhesive-free single panel, and after drying and sintering, an adhesive-free single panel containing PFA is obtained. The adhesive-free single panel includes a copper foil layer and a polyimide film layer disposed on its surface. (2) Place a PTFE lacquer cloth layer between two glue-free single-sided boards containing PFA obtained in step (1), press and cure them to obtain the high-frequency high-speed flexible copper-clad board.

15. The preparation method according to claim 14, characterized in that, The drying temperature in step (1) is 80–180°C.

16. The preparation method according to claim 14, characterized in that, The drying time in step (1) is 5 to 10 minutes.

17. The preparation method according to claim 14, characterized in that, The sintering temperature in step (1) is 350–380 °C.

18. The preparation method according to claim 14, characterized in that, The sintering time in step (1) is 5 to 10 minutes.

19. The preparation method according to claim 14, characterized in that, The pressing temperature in step (2) is 300-330℃.

20. The preparation method according to claim 14, characterized in that, The pressing pressure in step (2) is 10-30 kg / cm². 2 .

21. The preparation method according to claim 14, characterized in that, The pressing time in step (2) is 5 to 10 minutes.

22. A printed circuit board, characterized in that, The printed circuit board includes a high-frequency, high-speed flexible copper-clad laminate as described in any one of claims 1-13.

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