PTFE low-thermal expansion coefficient copper clad plate and preparation method thereof

Abstract

The application belongs to the technical field of electronic circuits, and discloses a PTFE low-thermal-expansion-coefficient copper-clad plate and a preparation method thereof.The PTFE low-thermal-expansion-coefficient copper-clad plate comprises a fiber base cloth, the upper surface or / and the lower surface of the fiber base cloth is provided with a metal material layer, the metal material layer is connected with the fiber base cloth through an adhesive layer, and the fiber base cloth is woven by polytetrafluoroethylene fibers or woven by polytetrafluoroethylene fibers and mixed fibers.The copper-clad plate prepared by the application is prepared by hot pressing the fiber base cloth woven by the PTFE fibers with low dielectric constant after thermal stretching and the metal material after coating the adhesive, and has excellent electrical performance, low thermal expansion coefficient, and mature technology, so that the large-scale production of the copper-clad plate is relatively easy to realize.

Description

Technical Field

[0001] This invention belongs to the field of electronic circuits, specifically relating to a PTFE copper-clad laminate with a low coefficient of thermal expansion and its preparation method. Background Technology

[0002] In the high-frequency substrate industry, the dielectric properties, water absorption rate, and mechanical properties of copper-clad laminates (CCLs), as the substrate for printed circuit boards (PCBs), often play a decisive role in the overall performance of PCBs. Therefore, the development of novel CCLs has always been a focus of research. Especially when the product's operating frequency exceeds 10 GHz, only fluorinated resin CCLs are suitable. Thus, CCLs made from PTFE material, which has the lowest dielectric constant and dielectric loss, exhibit exceptionally good dielectric constant, dielectric loss, water absorption rate, and frequency characteristics, making them the inevitable choice for CCLs used in high-frequency, high-environment environments.

[0003] However, due to PTFE's poor flowability, the product has a large coefficient of thermal expansion, especially in the Z-axis direction, and requires stringent processing conditions, including high temperature and high pressure, resulting in high production costs. Currently, most copper-clad laminates are prepared using filler-reinforced PTFE emulsion casting. For example, most existing PTFE copper-clad laminates use glass fiber cloth impregnated with polytetrafluoroethylene resin as the substrate, with copper foil placed on both sides of the substrate to form the glass fiber coated cloth. The glass fiber cloth serves as a rigid support source, allowing for control of the coefficient of thermal expansion; simultaneously, the dielectric constant of glass fiber is higher than that of PTFE, and it occupies a high volume content in the composite material, thus being a major factor determining the dielectric properties of the composite material, allowing for adjustment of the dielectric constant range within a certain range. However, the glass fiber coated cloth preparation method still has some unresolved problems, such as the significant difference between the coefficient of thermal expansion in the Z-axis and in the X and Y-axis planes, and the limited adjustable range of the dielectric constant due to the commonly used E-glass fiber's dielectric constant of 7.2. Therefore, maintaining the excellent electrical properties of PTFE-based copper clad laminates (low dielectric constant, low dielectric loss factor, and very stable performance over a high temperature and frequency range), reducing the coefficient of thermal expansion, and improving processing performance are the key research areas for PTFE-based copper clad laminates. Summary of the Invention

[0004] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a PTFE copper clad laminate with a low coefficient of thermal expansion and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a PTFE low thermal expansion coefficient copper clad laminate, the copper clad laminate comprising a fiber base fabric, wherein a metal material layer is provided on the upper surface and / or the lower surface of the fiber base fabric, and the metal material layer is connected to the fiber base fabric by an adhesive layer;

[0007] The fiber base fabric is woven from polytetrafluoroethylene (PTFE) fibers or from PTFE fibers and blended fibers.

[0008] Preferably, the polytetrafluoroethylene (PTFE) fiber is formed by hot stretching and then cooling and shaping PTFE virgin fibers. Since the PTFE fibers remain within the tensile stress range after hot stretching and shaping, when heated again after being made into a copper-clad laminate, the PTFE fibers will naturally shrink due to the material memory effect, resulting in a negative coefficient of thermal expansion. Simultaneously, because the metal material in the copper-clad laminate is connected to the fiber base fabric (containing hot-stretched PTFE fibers) via adhesive, and the coefficients of thermal expansion of both the metal material and the adhesive remain, it is possible, under the combined influence of these factors, for the coefficient of thermal expansion of the copper-clad laminate dielectric layer (the adhesive-impregnated fiber base fabric) to decrease to a level comparable to that of the copper foil itself.

[0009] More preferably, a thermal stretching machine can be used to perform thermal stretching treatment on the polytetrafluoroethylene (PTFE) fibers. Furthermore, by setting a certain speed difference between adjacent heating rollers of the thermal stretching machine, the thermal stretching treatment of the fibers can be completed.

[0010] Preferably, the stretching ratio of the hot stretching treatment is 0-2 times.

[0011] Preferably, the hot stretching treatment temperature is 160-300℃. More preferably, the hot stretching treatment temperature is 160-250℃.

[0012] Preferably, the polytetrafluoroethylene (PTFE) fiber is a PTFE filament or / and a PTFE twisted filament. The PTFE twisted filament is prepared by twisting and sintering short PTFE fibers.

[0013] Furthermore, the polytetrafluoroethylene (PTFE) filaments or staple fibers can be commercially available finished products, or prepared by methods such as paste extrusion, carrier spinning, film splitting, or air jetting. Specifically, carrier spinning involves spinning PTFE with a carrier to obtain PTFE filaments; film splitting involves processing a PTFE preform into a film and then subjecting it to film splitting to obtain PTFE staple fibers.

[0014] More preferably, polytetrafluoroethylene (PTFE) filaments are prepared using a carrier spinning method, which is a simple process and produces fibers with relatively uniform linear density. Furthermore, depending on the carrier, spinning can be categorized into dry spinning and wet spinning.

[0015] As an alternative, when the spinning process is a wet spinning process, polyvinyl alcohol (PVA) is used as a carrier to spin PTFE emulsion through emulsion spinning. After fiber formation, PVA is removed by sintering, causing PTFE molecules to adhere and form PTFE filaments.

[0016] Preferably, the blended fiber is one or more of polyimide fiber, liquid crystal polymer fiber, and glass fiber.

[0017] More preferably, the blended fiber is a fiber filament.

[0018] Improved functional filaments or functional fiber base fabrics prepared by adding or impregnating functional materials to any raw filament material or fiber base fabric woven from raw filaments, based on the aforementioned basic materials, also fall within the scope of raw filaments or fiber base fabrics and are protected within the scope of this patent. For example, impregnating the fiber base fabric with a dispersion containing any material such as ceramics, boron nitride, or silicon dioxide.

[0019] More preferably, the glass fiber can be E-glass, alkali-free, medium-alkali, or high-alkali.

[0020] Preferably, when the fiber base fabric is woven from polytetrafluoroethylene fibers and blended fibers, the weaving method is alternating weaving; the warp and weft threads in the fiber base fabric both include polytetrafluoroethylene fibers and blended fibers, wherein the polytetrafluoroethylene fibers and blended fibers are arranged alternately in a ratio of (1-10) bundles: (1-10) bundles.

[0021] More preferably, during weaving, the mixing ratio of PTFE fibers and blended fibers can be arbitrarily changed. For example, it can be arranged in a 1:1 ratio initially, and then in a 1:n ratio. The weaving method is not limited. However, in the application field of copper clad laminates, considering the isotropic principle of copper clad laminates, this invention can fix the mixing ratio and weaving method as needed to adjust the PTFE fiber content, thereby adjusting the coefficient of thermal expansion and electrical properties of the copper clad laminate.

[0022] Preferably, the fiber base fabric has a mesh count of 50-600 mesh. This is because the fiber base fabric provides a large number of gaps between the PTFE fibers. By curing with vacuum hot-press adhesive, a certain proportion of air can be sealed in the gaps and the cavities formed by the cured adhesive, thereby reducing the dielectric constant and dielectric loss of the copper clad laminate. Therefore, a fiber base fabric with a certain mesh count is more conducive to reducing the dielectric constant and dielectric loss of the copper clad laminate.

[0023] More preferably, the fiber base fabric has a mesh count of 200.

[0024] More preferably, the fiber base fabric can be a single layer or two or more layers stacked together, without limitation. The fiber base fabric can also be made into fiber base fabrics of different thicknesses depending on the weaving method, without limitation.

[0025] Preferably, the adhesive is a thermoplastic adhesive or a thermosetting adhesive. More preferably, the adhesive is at least one selected from epoxy resin, phenolic resin, PPO resin, and polyacrylate.

[0026] More preferably, the metal material includes a metal film or a metal sheet, and the shape and size of the metal material are not limited, and can be selected according to the actual application needs. More preferably, the metal material is a copper foil with a thickness of 18 μm.

[0027] More preferably, the metal material can be disposed on one surface of the fiber base fabric or on two opposite surfaces of the fiber base fabric, without limitation.

[0028] The second aspect of the present invention provides a method for preparing the copper-clad laminate described in the first aspect above. The method comprises: coating an adhesive on the upper surface and / or lower surface of a fiber base fabric, bonding the adhesive-coated side of the fiber base fabric to a metal material, and then performing vacuum hot pressing to obtain the copper-clad laminate.

[0029] Preferably, the hot pressing temperature is 140-200℃, the pressure is 1-30MPa, and the time is 30min-180min. More preferably, the hot pressing pressure is 5-20MPa, and the time is 30min-120min.

[0030] The third aspect of the present invention provides the application of the copper-clad laminate described in the first aspect in electronic products.

[0031] A fourth aspect of the present invention provides an electronic component comprising a copper-clad laminate as described in the first aspect above.

[0032] In this invention, the electronic components include resistors, capacitors, connectors, electroacoustic devices, electronic display devices, optoelectronic devices, sensors, printed circuit boards, circuit boards, circuits, piezoelectric devices, etc. Specifically, the electronic components may be, but are not limited to, printed circuit boards, circuit boards, sensors, electronic circuits, etc. Specifically, the copper-clad laminate may be, but is not limited to, used in printed circuit boards. Each layer of the copper-clad laminate has low conductivity and low loss rate, which can improve the water and oxygen isolation performance of the electronic components; or when the material of the mixed fibers in the copper-clad laminate includes conductive fillers, the conductivity of the electronic components is improved; or when the material of the mixed fibers in the copper-clad laminate includes thermally conductive fillers, the thermal conductivity of the electronic components is improved.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) This invention first provides a PTFE hot-stretched fiber, which is woven into a fiber base fabric, impregnated with adhesive, and then hot-pressed with copper foil to prepare a PTFE low thermal expansion coefficient copper-clad laminate. The PTFE fiber after hot stretching is still within the tensile stress range. When the copper-clad laminate is made from it and then heated again, the PTFE fiber shrinks due to the memory effect, resulting in a negative thermal expansion coefficient. Simultaneously, because the metal material in the copper-clad laminate is connected to the fiber base fabric (containing PTFE fiber) through adhesive, and the thermal expansion coefficients of the metal material and adhesive remain, it is possible, under the combined effect of multiple factors, for the thermal expansion coefficient of the dielectric layer of the copper-clad laminate to decrease to a level comparable to that of the copper foil itself. In one embodiment, the PTFE low thermal expansion coefficient copper-clad laminate prepared by this invention has a thermal expansion coefficient of 18 / 18 / 131 along the X / Y / Z axes, a dielectric constant of 1.9, and a dielectric loss tangent of 0.0009, exhibiting both excellent electrical properties and a low thermal expansion coefficient.

[0035] (2) This invention also provides a copper-clad laminate prepared using a fiber base fabric made of PTFE fibers and functional blended fibers as the insulating base film. Specifically, PTFE thermally stretched fibers are blended with functional fibers such as polyimide fibers, liquid crystal polymer fibers, and glass fibers to obtain a fiber base fabric with multiple composite properties. At the same time, various product requirements can be met by slightly adjusting the weaving method, blending ratio, and fiber base fabric thickness. Moreover, the thermal stretching and weaving technologies are relatively mature and easy to achieve large-scale production of copper-clad laminates. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0038] It should be noted that the present invention measures the linear thermal expansion coefficients of the copper-clad laminate along the X, Y, and Z axes within the range of -55 to 288°C.

[0039] It should be noted that the PTFE filaments used in the embodiments of the present invention were prepared by the inventors through emulsion spinning of PTFE emulsion containing PVA, followed by sintering to remove PVA after fiber formation.

[0040] Example 1: Discussion on the tensile temperature in the preparation method of PTFE low thermal expansion coefficient copper clad laminate

[0041] To investigate the effect of stretching temperature on the coefficient of thermal expansion, dielectric constant, and dielectric loss of the prepared PTFE low thermal expansion coefficient copper clad laminate, the inventors conducted the following experiments, namely Examples 1-1 to 1-4, with corresponding stretching temperatures of 160℃, 200℃, 250℃, and 300℃, respectively. The measurement results are shown in Table 1.

[0042] Example 1-1

[0043] This embodiment provides a PTFE copper-clad laminate with a low coefficient of thermal expansion, comprising the following steps:

[0044] (1) The PTFE filament is heated and cooled after being heated by a hot traction machine to obtain PTFE hot-stretched fiber; wherein, the temperature of the heating roller of the hot traction machine is set to 160℃, and the speed difference between two adjacent heating rollers is set to stretch the fiber to 1 times its original length.

[0045] (2) PTFE thermally stretched fibers of the same thickness are woven into warp and weft threads to obtain PTFE fiber base fabric with 200 mesh.

[0046] (3) Coat the upper and lower surfaces of the PTFE fiber base fabric with epoxy resin adhesive, and then cover them with 18μm copper foil and vacuum press them together to obtain the PTFE low thermal expansion coefficient copper clad laminate. The pressing conditions are 140℃, 5MPa hot pressing treatment for 30min.

[0047] Examples 1-2

[0048] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 1-1, except that the temperature of the heating roller of the thermal traction machine is set to 200°C in step (1).

[0049] Examples 1-3

[0050] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 1-1, except that the temperature of the heating roller of the thermal traction machine is set to 250°C in step (1).

[0051] Examples 1-4

[0052] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 1-1, except that the temperature of the heating roller of the thermal traction machine is set to 300°C in step (1).

[0053] Table 1 Performance parameters of the copper-clad laminate samples prepared in Example 1

[0054]

[0055] As shown in Table 1, with increasing hot stretching temperature, the dielectric constant and dielectric loss tangent of the prepared copper-clad laminate remain relatively stable, but the coefficients of thermal expansion along the X / Y / Z axes show a trend of increasing in the Z direction and decreasing in the X / Y direction. This is because at higher stretching temperatures, PTFE fibers exhibit less deformation recovery, meaning greater deformation. During heating, this deformation needs to be compensated for before expansion, thus reducing the coefficients of thermal expansion in the X / Y directions. Furthermore, higher temperatures make the fibers easier to stretch, but since PTFE's melting point is around 320℃, its mechanical properties suddenly disappear at this temperature. Moreover, when the temperature rises to around 300℃, PTFE fibers become difficult to stretch into filaments and break easily. Additionally, fiber strength decreases at 250℃, making them prone to breakage. Therefore, a hot stretching temperature of 200℃ is preferred.

[0056] Example 2: Discussion on the stretching ratio in the preparation method of PTFE low thermal expansion coefficient copper clad laminate

[0057] To investigate the effect of stretching ratio on the coefficient of thermal expansion, dielectric constant, and dielectric loss of the prepared PTFE low thermal expansion coefficient copper clad laminate, the inventors conducted the following experiments, namely Examples 1-2, Examples 2-1 to 2-3, and Comparative Example 2-1, with corresponding stretching ratios of 1, 0.5, 1.5, 2, and 0, respectively. The measurement results are shown in Table 2.

[0058] Example 2-1

[0059] This embodiment provides a PTFE copper-clad laminate with a low coefficient of thermal expansion, comprising the following steps:

[0060] (1) The PTFE filament is heated and cooled after being heated by a hot traction machine to obtain PTFE hot-stretched fiber; wherein, the temperature of the heating roller of the hot traction machine is set to 200℃, and the speed difference between two adjacent heating rollers is set so that the PTFE filament is stretched to 0.5 times its original length.

[0061] (2) PTFE thermally stretched fibers of the same thickness are woven into warp and weft threads to obtain PTFE fiber base fabric with 200 mesh.

[0062] (3) Coat the upper and lower surfaces of the PTFE fiber base fabric with epoxy resin adhesive, and then cover them with copper foil and vacuum press them together to obtain a PTFE copper-clad laminate with a low coefficient of thermal expansion. The pressing conditions are 140℃ and 5MPa hot pressing for 30 minutes.

[0063] Example 2-2

[0064] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 2-1, except that in step (1), the original PTFE filament is stretched to 1.5 times its original length.

[0065] Example 2-3

[0066] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 2-1, except that in step (1), the original PTFE filament is stretched to twice its original length.

[0067] Comparative Example 2-1

[0068] The content of a PTFE copper clad laminate is basically the same as that of Example 2-1, except that: in step (1), there is no speed difference between the two adjacent heating rollers, and the original PTFE filament remains the original length.

[0069] Table 2 Performance parameters of copper-clad laminate samples prepared in Example 2 and Comparative Example 2

[0070] serial number Stretch ratio Coefficient of thermal expansion X / Y / Z axes (ppm / ℃) Dielectric constant Dielectric loss tangent Example 2-1 0.5 times 20 / 20 / 125 1.9 0.0009 Examples 1-2 1x 18 / 18 / 131 1.9 0.0009 Example 2-2 1.5 times 17 / 17 / 136 1.9 0.0009 Example 2-3 2 times 15 / 15 / 148 1.9 0.0009 Comparative Example 2-1 0 times 20 / 21 / 120 1.9 0.0009

[0071] Table 2 shows that the copper-clad laminates prepared from PTFE fibers exhibit varying degrees of shrinkage in both the X and Y directions after hot stretching. Furthermore, as the fiber stretching ratio increases, the fiber length is stretched further, resulting in more stable dielectric constants and dielectric loss tangents in the prepared copper-clad laminates. However, the coefficients of thermal expansion along the X / Y / Z axes show a decreasing trend in the X and Y directions and an increasing trend in the Z direction. This is because increasing the stretching ratio increases fiber deformation, and the expansion occurs after heating to compensate for this deformation. In addition, when the stretching ratio is greater than 2, the fibers are prone to breakage. Therefore, considering the degree of fiber stretching and subsequent hybridization discussions, a fiber stretching ratio of 2 is preferred.

[0072] Example 3: Discussion on the Mesh Count of Fiber Base Fabric in the Preparation Method of PTFE Low Thermal Expansion Copper Clad Laminates

[0073] To investigate the effect of fiber base fabric mesh size on the coefficient of thermal expansion, dielectric constant, and dielectric loss of the prepared PTFE low thermal expansion coefficient copper clad laminate, the inventors conducted the following experiments, namely Examples 3-1 to 3-5, with corresponding fiber base fabric mesh sizes of 50 mesh, 100 mesh, 200 mesh, 400 mesh, and 600 mesh, respectively. The measurement results are shown in Table 3.

[0074] Example 3-1

[0075] This embodiment provides a PTFE copper-clad laminate with a low coefficient of thermal expansion, comprising the following steps:

[0076] (1) The PTFE filament is heated and cooled after being heated by a hot traction machine to obtain PTFE hot-stretched fiber; wherein, the temperature of the heating roller of the hot traction machine is set to 200℃, and the speed difference between two adjacent heating rollers is set so that the PTFE filament is stretched to twice its original length.

[0077] (2) PTFE thermally stretched fibers of the same thickness are woven into warp and weft threads to obtain 50-mesh PTFE fiber base fabric.

[0078] (3) Coat the upper and lower surfaces of the PTFE fiber base fabric with epoxy resin adhesive, and then cover them with copper foil and vacuum press them together to obtain a PTFE copper-clad laminate with a low coefficient of thermal expansion. The pressing conditions are 140℃ and 5MPa hot pressing for 30 minutes.

[0079] Example 3-2

[0080] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 3-1, except that: in step (2), a 100-mesh PTFE fiber base fabric is obtained.

[0081] Example 3-3

[0082] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 3-1, except that: in step (2), a 200-mesh PTFE fiber base fabric is obtained.

[0083] Examples 3-4

[0084] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 3-1, except that: in step (2), a 400-mesh PTFE fiber base fabric is obtained.

[0085] Examples 3-5

[0086] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 3-1, except that: in step (2), a 600-mesh PTFE fiber base fabric is obtained.

[0087] Table 3 Performance parameters of the copper-clad laminate samples prepared in Example 3

[0088]

[0089] As shown in Table 3, with the increase of the fiber base fabric mesh count, the fiber base fabric mesh becomes finer, and the thermal expansion coefficients of the prepared copper clad laminate along the X / Y / Z axes are relatively stable. This is because the fibers used in the base fabrics with different mesh counts are the same, so the thermal dimensional stability tends to be the same. Meanwhile, the dielectric constant and dielectric loss tangent of the copper clad laminate show a trend of first decreasing and then increasing. This is because although decreasing the mesh count increases the number of holes, thus reducing the dielectric constant and loss, excessively large holes allow adhesive to enter the holes, leading to an increase in dielectric constant and dielectric loss. Therefore, considering overall performance, a fiber base fabric mesh count of 200 mesh is preferred.

[0090] Example 4: Discussion on the types and proportions of blended fibers in the preparation method of PTFE low thermal expansion coefficient copper clad laminate

[0091] To investigate the effects of the type and ratio of blended fibers on the coefficient of thermal expansion, dielectric constant, and dielectric loss of the prepared PTFE low thermal expansion coefficient copper clad laminate, the inventors conducted the following experiments, namely Examples 4-1 to 4-9. The corresponding types and ratios of blended fibers are shown in Table 4, and the measurement results are shown in Table 4.

[0092] Example 4-1

[0093] This embodiment provides a PTFE copper-clad laminate with a low coefficient of thermal expansion, comprising the following steps:

[0094] (1) The PTFE filament is heated and cooled after being heated by a hot traction machine to obtain PTFE hot-stretched fiber; wherein, the temperature of the heating roller of the hot traction machine is set to 200℃, and the speed difference between two adjacent heating rollers is set so that the PTFE filament is stretched to twice its original length.

[0095] (2) PTFE thermally stretched fibers and PI fiber filaments (blended fibers) are interwoven in warp and weft to obtain a 200-mesh PTFE fiber base fabric. Both the warp and weft threads of the resulting fiber base fabric contain PTFE thermally stretched fibers and PI fiber filaments, with the PTFE fibers and PI fiber filaments arranged alternately in a 1:1 ratio. The PI fiber filaments are not thermally stretched and have the same thickness as the PTFE thermally stretched fibers.

[0096] (3) Coat the upper and lower surfaces of the PTFE fiber base fabric with epoxy resin adhesive, and then cover them with copper foil and vacuum press them together to obtain a PTFE copper-clad laminate with a low coefficient of thermal expansion. The pressing conditions are 140℃ and 5MPa hot pressing for 30 minutes.

[0097] Example 4-2

[0098] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that the mixing ratio of PTFE thermally stretched fiber and PI fiber filament in step (2) is 1:2.

[0099] Example 4-3

[0100] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that the mixing ratio of PTFE thermally stretched fiber and PI fiber filament in step (2) is 1:5.

[0101] Example 4-4

[0102] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that: in step (2), PTFE hot-stretched fibers and LCP fiber filaments are interwoven with warp and weft threads; the mixing ratio of PTFE hot-stretched fibers and LCP fiber filaments is 1:1. Among them, the LCP fiber filaments are not hot-stretched and have the same thickness as PTFE hot-stretched fibers.

[0103] Examples 4-5

[0104] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that: in step (2), PTFE hot-stretched fibers and LCP fiber filaments are interwoven with warp and weft threads; the mixing ratio of PTFE hot-stretched fibers and LCP fiber filaments is 1:2. Among them, the LCP fiber filaments are not hot-stretched and have the same thickness as PTFE hot-stretched fibers.

[0105] Examples 4-6

[0106] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that: in step (2), PTFE hot-stretched fibers and LCP fiber filaments are interwoven with warp and weft threads; the mixing ratio of PTFE hot-stretched fibers and LCP fiber filaments is 1:5. Among them, the LCP fiber filaments are not hot-stretched and have the same thickness as PTFE hot-stretched fibers.

[0107] Examples 4-7

[0108] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that: in step (2), PTFE hot-stretched fibers and glass fiber filaments are interwoven with warp and weft threads; the mixing ratio of PTFE hot-stretched fibers and glass fiber filaments is 1:1. Among them, the glass fiber filaments are not hot-stretched and have the same thickness as PTFE hot-stretched fibers.

[0109] Examples 4-8

[0110] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that in step (2), PTFE hot-stretched fibers and glass fiber filaments are interwoven with warp and weft threads; the mixing ratio of PTFE hot-stretched fibers and glass fiber filaments is 1:2. Among them, the glass fiber filaments are not hot-stretched and have the same thickness as PTFE hot-stretched fibers.

[0111] Examples 4-9

[0112] The content of the PTFE low thermal expansion coefficient copper clad laminate is basically the same as that of Example 4-1, except that in step (2), PTFE hot-stretched fibers and glass fiber filaments are interwoven with warp and weft threads; the mixing ratio of PTFE hot-stretched fibers and glass fiber filaments is 1:5. Among them, the glass fiber filaments are not hot-stretched and have the same thickness as PTFE hot-stretched fibers.

[0113] Table 4 Performance parameters of the copper-clad laminate samples prepared in Example 4

[0114]

[0115] Table 4 shows that, for the same type of blended fiber, comparing Examples 4-1 to 4-3, Examples 4-4 to 4-6, and Examples 4-7 to 4-9, it can be seen that as the proportion of blended fibers increases, the coefficients of thermal expansion along the X / Y / Z axes of the copper-clad laminate gradually decrease, while the dielectric constant and dielectric loss tangent both increase. This is because PI, LCP, and glass fiber have worse dielectric properties than PTFE, but better thermal dimensional stability than PTFE after heat stretching treatment. Therefore, the ratio of PTFE fiber to blended fiber can be adjusted according to the required coefficient of thermal expansion.

[0116] For different blended fibers with the same blending ratio, such as in comparative examples 4-2, 4-5, and 4-8, it can be seen that the coefficient of thermal expansion along the X / Y / Z axes of the copper-clad laminate prepared with PI fiber blending is 18 / 18 / 112, the dielectric constant is 2.3, and the dielectric loss tangent is 0.002; the coefficient of thermal expansion along the X / Y / Z axes of the copper-clad laminate prepared with LCP fiber blending is 16 / 16 / 104, the dielectric constant is 2.2, and the dielectric loss tangent is 0.0018; and the coefficient of thermal expansion along the X / Y / Z axes of the copper-clad laminate prepared with glass fiber blending is 13 / 13 / 94, the dielectric constant is 2.7, and the dielectric loss tangent is 0.008. This is because the dielectric properties and thermal dimensional stability of the added materials are different. Therefore, from the perspective of reducing the coefficient of thermal expansion of copper clad laminates along the X / Y / Z axes, glass fiber is preferred as a blended fiber; from the perspective of reducing the dielectric constant and dielectric loss tangent of copper clad laminates, LCP fiber is preferred as a blended fiber.

[0117] Performance testing:

[0118] The PTFE low thermal expansion coefficient copper clad laminates prepared in Examples 1-2 of this invention were compared with two commercially available PTFE copper clad laminates whose main components are glass fiber and PTFE, and one glass fiber copper clad laminate whose main component does not contain PTFE, in terms of thermal expansion coefficient, dielectric constant, and dielectric loss. The results are shown in Table 5. Among them, Comparative Example 1 is the copper clad laminate of Rogers Corporation with part number RO5880; Comparative Example 2 is the copper clad laminate of Taconly Corporation with part number TYL-5; and Comparative Example 3 is the copper clad laminate of Shengyi Technology Corporation with part number S1141.

[0119] Table 5 Performance parameters of copper-clad laminate samples prepared in the examples and commercially available PTFE copper-clad laminates.

[0120] serial number Coefficient of thermal expansion X / Y / Z axes (ppm / ℃) Dielectric constant Dielectric loss tangent Examples 1-2 18 / 18 / 131 1.9 0.0009 Comparative Example 1 31 / 48 / 237 2.2 0.0009 Comparative Example 2 20 / 20 / 280 2.2 0.02 Comparative Example 3 45 / 42 / 350 4.6 0.015

[0121] As shown in Table 5, comparing Examples 1-2 with Comparative Example 1, it can be seen that, under the premise of the same dielectric loss, the dielectric constant and thermal expansion coefficients in the X / Y / Z directions of the PTFE low-expansion copper-clad laminate prepared by the present invention are both lower than those of Comparative Example 1, with the decrease in the thermal expansion coefficients in the X / Y / Z directions being particularly significant. Comparing Examples 1-2 with Comparative Example 2, it can be seen that, while the thermal expansion coefficient in the X / Y directions of the PTFE low-expansion copper-clad laminate prepared by the present invention is slightly lower than that of Comparative Example 2, the thermal expansion coefficient in the Z direction of the PTFE low-expansion copper-clad laminate prepared by the present invention is significantly lower than that of Comparative Example 2, and both the dielectric constant and dielectric loss are significantly reduced. Comparing Examples 1-2 with Comparative Example 3, it can be seen that the thermal expansion coefficients in the X / Y / Z directions and the dielectric properties of the PTFE low-expansion copper-clad laminate prepared by the present invention are superior to those of the copper-clad laminate in Comparative Example 3, which does not contain PTFE. Therefore, the copper-clad laminate samples prepared in Examples 1-2 of this application not only have low coefficients of thermal expansion in the X / Y / Z directions, superior low dielectric constant and dielectric loss tangent, but also have thermal expansion coefficients in the X / Y directions reduced to a level comparable to the thermal expansion coefficient of the copper foil itself, which can effectively improve the peel resistance of the copper foil and is more suitable for industrial applications, especially in the field of 5G high-frequency communication.

[0122] In summary, this invention effectively overcomes the shortcomings of the prior art and has high industrial applicability. The above embodiments are intended to illustrate the substantive content of this invention, but are not intended to limit the scope of protection of this invention. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this invention without departing from the essence and scope of protection of this invention.

Claims

1. A PTFE copper-clad laminate with a low coefficient of thermal expansion, characterized in that, The copper-clad laminate includes a fiber base fabric, and a metal material layer is provided on the upper surface and / or lower surface of the fiber base fabric. The metal material layer is connected to the fiber base fabric through an adhesive layer. The fiber base fabric is woven from polytetrafluoroethylene fibers or woven from polytetrafluoroethylene fibers and mixed fibers in an alternating ratio of (1-10) bundles: (1-10) bundles; The polytetrafluoroethylene fiber is formed by hot stretching polytetrafluoroethylene raw fiber at 160-300℃ and then shaping it; the stretching ratio of the hot stretching treatment is 0.5-2 times, and the stretching ratio is the ratio of the length increase after stretching to the original length before stretching.

2. The copper-clad laminate according to claim 1, characterized in that, The blended fiber is one or more of polyimide fiber, liquid crystal polymer fiber, and glass fiber.

3. The copper-clad laminate according to claim 2, characterized in that, When the fiber base fabric is woven from polytetrafluoroethylene fibers and blended fibers, both the warp and weft threads in the fiber base fabric include polytetrafluoroethylene fibers and blended fibers.

4. The copper-clad laminate according to claim 1, characterized in that, The fiber base fabric has a mesh size of 50-600.

5. The copper-clad laminate according to claim 1, characterized in that, The polytetrafluoroethylene (PTFE) filament is a PTFE filament or / and a PTFE twisted filament; the PTFE twisted filament is prepared by twisting and sintering PTFE short fibers.

6. The method for preparing the copper-clad laminate according to any one of claims 1 to 5, characterized in that, The preparation method is as follows: an adhesive is coated on the upper surface and / or lower surface of the fiber base fabric, and the side of the fiber base fabric coated with adhesive is bonded to a metal material, and then hot pressing is performed to obtain the copper-clad laminate.

7. The preparation method according to claim 6, characterized in that, The adhesive is a thermoplastic adhesive or a thermosetting adhesive; the hot pressing temperature is 140-200℃, the hot pressing pressure is 1-30MPa, and the hot pressing time is 30-180min.

8. The application of the copper-clad laminate according to any one of claims 1 to 5 in electronic products.

9. An electronic component, characterized in that, Including the copper-clad laminate as described in any one of claims 1 to 5.

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