LCP high frequency substrate with high Dk and low Df characteristics and preparation method

Abstract

The invention discloses an LCP high-frequency substrate with high Dk and low Df characteristics, comprising at least one copper foil layer, at least one high-dielectric LCP core layer and at least one high-dielectric adhesive layer, wherein the high-dielectric LCP core layer is located between the copper foil layer and the high-dielectric adhesive layer, the high-dielectric LCP core layer refers to a core layer with a Dk value of 6-100 and a Df value of 0.002-0.010, and the high-dielectric adhesive layer refers to an adhesive layer with a Dk value of 6-100 and a Df value of 0.002-0.010; the thickness of the copper foil layer is 1-35 μm; the thickness of the high-dielectric LCP core layer is 12-100 μm, and the thickness of the high-dielectric adhesive layer is 12-100 μm. In the present invention, since both the high-dielectric LCP core layer and the high-dielectric adhesive layer have the characteristics of high Dk and low Df, the prepared LCP high-frequency substrate has excellent high-speed transmission, low loss, high Dk and low Df performance, low roughness, ultra-low water absorption, low rebound force suitable for high-density assembly, good UV laser drilling ability and excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of FPC (flexible circuit board) and its preparation technology, and in particular to a high-frequency and high-transmission substrate and a preparation method thereof, which are mainly used in the field of high-frequency and high-speed transmission FPC, such as automotive radar, global positioning satellite antenna, cellular telecommunication system, wireless communication antenna, data link cable system, direct broadcast satellite, power backplane, etc. Background Art

[0002] With the rapid development of information technology, wireless communication has become a necessity in life. Wireless communication systems are composed of transmitters, receivers and antennas. The antenna is responsible for the conversion of electromagnetic energy values ​​between the circuit and the air, and is an indispensable basic equipment for communication systems. In the design of antenna-related circuits, passive components such as capacitors or inductors are sometimes relied on to match the antenna. As electronic products develop towards thinness, flexibility and high frequency and high speed of signal transmission, the active and passive components of related designs must be increased, and the density of circuits and components is bound to increase, resulting in electromagnetic interference, increased noise and reduced reliability. To solve this problem, it is necessary to improve passive components, such as the integration of capacitors. Embedded capacitors can reduce the area of ​​​​the circuit board, increase the density of component use and improve the reliability of the product. Therefore, the development of substrate materials with high dielectric constants and low dielectric losses is an important issue in this field.

[0003] At present, the market is dominated by high-frequency boards for PCBs, and their implementation methods and disadvantages are:

[0004] 1. Adding metal powder to the bonding layer can obtain a high Dk value of more than 45, but at the same time Df also increases, which cannot really meet the needs of high frequency and high speed. In addition, such materials are prone to high leakage current in practical applications, which greatly reduces their applicability.

[0005] 2. Only adding high-content high-dielectric ceramic powder to epoxy resin, but the ceramic powder dispersed in epoxy resin has irregular dipole arrangement, so the effect of electric dipole polarization will be offset, so the effect of improving the dielectric constant value is quite limited. And due to the excessive powder content, the mechanical strength of the substrate is reduced, and the adhesion between copper foils is greatly reduced.

[0006] In the field of high-frequency and high-speed materials used in the FPC process, the main high-frequency boards used in the industry are LCP (liquid crystal polymer) boards and PTFE (polytetrafluoroethylene) substrates. PTFE substrates are currently used as hard boards, which are not soft enough. In terms of electrical properties, the Dk value is 8.0 at a thickness of 6 mils and 10 at a thickness of 20 mils. The PTFE substrate is limited by the low Dk value of the impregnated glass fiber cloth in the stacking structure, so it is difficult to achieve a Dk value of more than 10, and it is even more difficult to produce a high Dk substrate with a thickness of 2-6 mils. LCP maintains an almost constant dielectric constant in the entire RF range up to 110 GHz, and the Df is only 0.002. The thermal expansion coefficient is small, and high-frequency and high-speed soft boards can be realized under the premise of high reliability. However, the Dk value of LCP is generally 2.9-3.3, which is not high enough to meet the requirements of high Dk.

[0007] For example, Chinese Patent No. 201590948U, Taiwan Patent No. M377823, Japanese Patent No. 2010-7418A and U.S. Patent No. 2011 / 0114371 all propose composite substrates with excellent workability, low cost and low energy consumption. Chinese Patent No. 202276545 U, Chinese Patent No. 103096612 B, Taiwan Patent No. M422159 and Taiwan Patent No. M531056 use fluorine-based materials to make high-frequency substrates. The Chinese patent CN 205105448U proposes a composite laminated high-frequency low-dielectric film, the Chinese patent CN 205255668U proposes a low-dielectric performance film, the Chinese patent CN 105295753B proposes a high-frequency adhesive glue layer structure and its preparation method, and the Chinese patent CN 206490891 U proposes a low-dielectric loss FRCC substrate with a composite laminated structure. The Chinese Taiwan patent No. TW098124978 capacitor substrate structure; the Chinese patent CN 206490897 U proposes a FRCC substrate with high heat dissipation efficiency. The Chinese patent CN206932462 U proposes a composite LCP high-frequency and high-speed FRCC substrate. The previous patents are still only high-frequency substrate materials with a Dk between 2.0-3.5, which cannot meet the needs of high Dk (Dk>8.0). Summary of the invention

[0008] In order to meet the market demand for high-frequency, high-speed flexible panels, the LCP high-frequency substrate provided by the present invention has the characteristics of high Dk and low Df in both the high-dielectric LCP core layer and the high-dielectric adhesive layer. The prepared LCP high-frequency substrate has excellent high-speed transmission, low loss, high Dk and low Df performance, low roughness, ultra-low water absorption, low rebound force suitable for high-density assembly, good UV laser drilling ability and excellent mechanical properties. It is superior to general LCP films and PI (polyimide) type adhesive sheets, and is suitable for wearable devices such as 5G smart phones and Apple watches.

[0009] In order to solve the above technical problems, a technical solution adopted by the present invention is: the present invention provides an LCP high-frequency substrate with high Dk and low Df characteristics, comprising at least one copper foil layer, at least one high-dielectric LCP core layer and at least one high-dielectric adhesive layer, wherein the high-dielectric LCP core layer is located between the copper foil layer and the high-dielectric adhesive layer, the high-dielectric LCP core layer refers to a core layer with a Dk value of 6-100 and a Df value of 0.002-0.010, and the high-dielectric adhesive layer refers to an adhesive layer with a Dk value of 6-100 and a Df value of 0.002-0.010;

[0010] The thickness of the copper foil layer is 1-35 μm; the thickness of the high dielectric LCP core layer is 12-100 μm, and the thickness of the high dielectric adhesive layer is 12-100 μm.

[0011] One implementation of the present invention is: the LCP high-frequency substrate is a single-sided copper-clad substrate, the single-sided copper-clad substrate includes a copper foil layer, a high-dielectric LCP core layer and a high-dielectric adhesive layer, the high-dielectric LCP core layer is located between the copper foil layer and the high-dielectric adhesive layer, and the thickness of the single-sided copper-clad substrate is 25-235μm.

[0012] Another implementation of the present invention is: the LCP high-frequency substrate is a double-sided copper-clad substrate, and the double-sided copper-clad substrate is one of the following two structures:

[0013] The first structure, the double-sided copper clad substrate comprises two copper foil layers, two high dielectric LCP core layers and a high dielectric adhesive layer, and the double-sided copper clad substrate is copper foil layer, high dielectric LCP core layer, high dielectric adhesive layer, high dielectric LCP core layer and copper foil layer from top to bottom, and the thickness of the double-sided copper clad substrate is 38-370 μm;

[0014] The second structure, the LCP high-frequency substrate is a double-sided copper-clad substrate, the double-sided copper-clad substrate includes two copper foil layers, a high dielectric LCP core layer and a high dielectric adhesive layer, and the double-sided copper-clad substrate is copper foil layer, high dielectric LCP core layer, high dielectric adhesive layer and copper foil layer from top to bottom, and the thickness of the double-sided copper-clad substrate is 26-270μm.

[0015] Furthermore, the high dielectric LCP core layer includes LCP and at least one of strong dielectric ceramic powder, conductive powder, sintered silica, Teflon, fluorine resin and flame retardant; the LCP is 5-98% (weight percentage) of the total solid content of the high dielectric LCP core layer, and the sum of the strong dielectric ceramic powder, conductive powder, fluorine resin, sintered silica, Teflon and flame retardant is 2-90% (weight percentage) of the total solid content of the high dielectric LCP core layer.

[0016] Further, the ferroelectric ceramic powder is at least one of BaTiO3, SrTiO3, Ba(Sr)TiO3, PbTiO3, CaTiO3 and Mg2TiO4; wherein the sum of the proportions of the ferroelectric ceramic powder is 0-90% (by weight) of the total solid content of the high dielectric LCP core layer;

[0017] The conductive powder is at least one of transition metal powder, transition metal alloy powder, carbon black, carbon fiber, carbon nanotubes and metal oxides, wherein the sum of the proportions of the conductive powder is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer.

[0018] Further, the proportion of the fluorine-based resin is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer, the proportion of the sintered silica is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer, the proportion of Teflon is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer, and the proportion of the flame retardant is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer.

[0019] Furthermore, the high dielectric adhesive layer includes at least one of component A and component B; the sum of the proportions of component A is 5-98% (weight percentage) of the total solid content of the high dielectric adhesive layer, and the component B is 5-80% (weight percentage) of the total solid content of the high dielectric adhesive layer;

[0020] The component A comprises at least one of sintered silica, strong dielectric ceramic powder, conductive powder, Teflon, fluorine resin and flame retardant;

[0021] The component B includes at least one of a high molecular polymer resin and a high molecular resin.

[0022] Furthermore, the ferroelectric ceramic powder is at least one of BaTiO3, SrTiO3, Ba(Sr)TiO3, PbTiO3, CaTiO3 and Mg2TiO4; wherein the sum of the proportions of the ferroelectric ceramic powder is 0-90% (by weight) of the total solid content of the high dielectric adhesive layer;

[0023] The conductive powder is at least one of transition metal powder, transition metal alloy powder, carbon black, carbon fiber, carbon nanotubes and metal oxides, wherein the sum of the proportions of the conductive powder is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer;

[0024] The proportion of the fluorine-based resin is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer, the proportion of the sintered silica is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer, the proportion of Teflon is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer, and the proportion of the flame retardant is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer.

[0025] The present invention also provides a method for preparing the LCP high-frequency substrate with high Dk and low Df characteristics, comprising the following steps: the single-sided copper-clad substrate further comprises a release layer, and the release layer is located on the surface of the high-dielectric adhesive layer;

[0026] Step 1: Coat the precursor of the high dielectric LCP core layer on one side of the copper foil layer, remove the solvent at 60-180°C, and then anneal it at 250°C for 10 hours;

[0027] Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer, and drying and pressing;

[0028] Step 3: Press the release layer on the surface of the high dielectric adhesive layer to obtain a finished single-sided copper-clad substrate.

[0029] The present invention further provides a method for preparing the LCP high-frequency substrate with high Dk and low Df characteristics. When the double-sided copper-clad substrate is of the first structure, the preparation method comprises the following steps:

[0030] Step 1: Coat the precursor of the high dielectric LCP core layer on one side of the copper foil layer, remove the solvent at 60-180° C., and then anneal it at 250° C. for 10 hours to obtain two semi-finished products A;

[0031] Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer of the semi-finished product A, drying and pressing the semi-finished product B;

[0032] Step 3: Lay and press the high dielectric LCP core layer of the other semi-finished product A and the high dielectric adhesive layer of the semi-finished product B, and cure them at 180° C. for more than 5 hours to obtain a finished double-sided copper clad substrate;

[0033] When the double-sided copper-clad substrate is of the second structure, the preparation method comprises the following steps:

[0034] Step 1: Coat the precursor of the high dielectric LCP core layer on one side of the copper foil layer, remove the solvent at 60-180°C, and then anneal it at 250°C for 10 hours;

[0035] Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer, drying and pressing the layer to obtain a single-sided copper-clad substrate;

[0036] Step 3: Laminating the copper foil layer with the high dielectric adhesive layer of the single-sided copper-clad substrate prepared in step 2, and curing at 180° C. for more than 5 hours to obtain a finished double-sided copper-clad substrate.

[0037] The beneficial effects of the present invention are:

[0038] 1. The LCP high-frequency substrate of the present invention has the characteristics of high Dk and low Df because both the high-dielectric LCP core layer and the high-dielectric adhesive layer have the characteristics of high Dk and low Df. Therefore, the prepared LCP high-frequency substrate has excellent high-speed transmission, low loss, high Dk and low Df performance, low roughness, ultra-low water absorption, low rebound force suitable for high-density assembly, and excellent mechanical properties. It is superior to general LCP films and PI-type adhesive sheets and is suitable for wearable devices such as 5G smart phones and Apple watches.

[0039] Furthermore, the laser drilling process of LCP high-frequency substrate is better, and the small aperture is suitable for small aperture processing less than 50 microns, and it is not easy to shrink. The film thickness is uniform during lamination, and the impedance control is good, which is suitable for high-frequency and high-speed transmission FPC.

[0040] Furthermore, the current coating method can only coat a film with a thickness of about 2 mil at most. At present, it is difficult to produce a film thicker than 38 μm, and the efficiency is low. The LCP high-frequency substrate prepared by the preparation method of the present invention has an appropriate thickness and good controllability. It has thick film preparation technology and can easily obtain a 100-micron substrate. In addition, in the case of a thick film, the present invention still has the characteristics of high Dk and low Df.

[0041] Furthermore, it can be seen from the test data that the LCP high-frequency substrate of the present invention has a low water absorption rate, which is as low as 0.04-0.06%;

[0042] Furthermore, the test data shows that the bonding strength of the high dielectric layer of the present invention is greater than 0.7 kgf / cm 2 ;

[0043] 2. The LCP high-frequency substrate with high Dk and low Df characteristics of the present invention has a simple structure and can save downstream processing steps.

[0044] The above description of the present invention is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of embodiment 1 of the present invention (single-sided copper-clad substrate, including release layer);

[0046] Figure 2 1 is a schematic structural diagram of embodiment 2 of the present invention (a structure of a double-sided copper-clad substrate);

[0047] Figure 3 It is a structural schematic diagram of embodiment 3 of the present invention (another structure of a double-sided copper-clad substrate);

[0048] The parts in the accompanying drawings are marked as follows:

[0049] Copper foil layer 10 , high dielectric LCP core layer 20 , high dielectric adhesive layer 30 and release layer 40 . DETAILED DESCRIPTION

[0050] The following is a specific embodiment of the present invention, and those skilled in the art can easily understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented in other different ways, that is, different modifications and changes can be made without departing from the scope disclosed by the present invention.

[0051] Implementation method: An LCP high frequency substrate with high Dk and low Df characteristics, such as Figures 1 to 3 As shown, it includes at least one copper foil layer, at least one high dielectric LCP (liquid crystal polymer) core layer and at least one high dielectric adhesive layer, the high dielectric LCP core layer is located between the copper foil layer and the high dielectric adhesive layer, the high dielectric LCP core layer refers to a core layer with a Dk (dielectric constant) value of 6-100 (10GHz) and a Df (dielectric loss factor) value of 0.002-0.010 (10GHz), and the high dielectric adhesive layer refers to a glue layer with a Dk value of 6-100 (10GHz) and a Df value of 0.002-0.010 (10GHz);

[0052] The thickness of the copper foil layer is 1-35 μm; the thickness of the high dielectric LCP core layer is 12-100 μm, and the thickness of the high dielectric adhesive layer is 12-100 μm.

[0053] The high dielectric adhesive layer has a bonding strength of >0.7kg / cm 2 The glue layer.

[0054] The high dielectric LCP core layer includes LCP and at least one of strong dielectric ceramic powder, conductive powder, sintered silica, Teflon, fluorine resin and flame retardant; the LCP is 5-98% (weight percentage) of the total solid content of the high dielectric LCP core layer, and the sum of the strong dielectric ceramic powder, conductive powder, fluorine resin, sintered silica, Teflon and flame retardant is 2-90% (weight percentage) of the total solid content of the high dielectric LCP core layer.

[0055] In the high dielectric LCP core layer, the strong dielectric ceramic powder is at least one of BaTiO3, SrTiO3, Ba(Sr)TiO3, PbTiO3, CaTiO3 and Mg2TiO4; wherein the sum of the proportions of the strong dielectric ceramic powder is 0-90% (weight percentage) of the total solid content of the high dielectric LCP core layer;

[0056] The conductive powder is at least one of transition metal powder, transition metal alloy powder, carbon black, carbon fiber, carbon nanotubes and metal oxides, wherein the sum of the proportions of the conductive powder is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer.

[0057] In the high dielectric LCP core layer, the proportion of the fluorine-based resin is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer, the proportion of the sintered silica is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer, the proportion of Teflon is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer, and the proportion of the flame retardant is 0-45% (weight percentage) of the total solid content of the high dielectric LCP core layer.

[0058] The high dielectric adhesive layer comprises at least one of component A and component B; the sum of the proportions of component A is 5-98% (weight percentage) of the total solid content of the high dielectric adhesive layer, and the proportion of component B is 5-80% (weight percentage) of the total solid content of the high dielectric adhesive layer;

[0059] The component A comprises at least one of sintered silica, strong dielectric ceramic powder, conductive powder, Teflon, fluorine resin and flame retardant;

[0060] The component B includes at least one of a high molecular polymer resin and a high molecular resin.

[0061] In the high dielectric adhesive layer, the strong dielectric ceramic powder is at least one of BaTiO3, SrTiO3, Ba(Sr)TiO3, PbTiO3, CaTiO3 and Mg2TiO4; wherein the sum of the proportions of the strong dielectric ceramic powder is 0-90% (weight percentage) of the total solid content of the high dielectric adhesive layer;

[0062] The conductive powder is at least one of transition metal powder, transition metal alloy powder, carbon black, carbon fiber, carbon nanotubes and metal oxides, wherein the sum of the proportions of the conductive powder is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer.

[0063] The strong dielectric ceramic powder in the high dielectric LCP core layer and the high dielectric adhesive layer may be doped with one or more metal ions, or may be undoped.

[0064] In the high dielectric adhesive layer, the proportion of the fluorine-based resin is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer, the proportion of the sintered silica is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer, the proportion of Teflon is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer, and the proportion of the flame retardant is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer.

[0065] The high molecular polymer resin is at least one of fluorine resin, epoxy resin, acrylic resin, urethane resin, silicone rubber resin, polyparacycloxylene resin, bismaleimide resin and polyimide resin;

[0066] The polymer resin is also at least one of fluorine resin, epoxy resin, acrylic resin, urethane resin, silicone rubber resin, polyparacycloxylene resin, bismaleimide resin and polyimide resin.

[0067] The fluorine-based resins in the high dielectric LCP core layer and the high dielectric adhesive layer are selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, vinyl fluoride and vinyl ether copolymers, tetrafluoroethylene and ethylene copolymers, polytrifluorochloroethylene and ethylene copolymers, tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, polytrifluorochloroethylene, polyvinyl chloride, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-vinyl fluoride copolymers and tetrafluoroethylene-hexafluoropropylene-trifluoroethylene copolymers.

[0068] The copper foil layer is a low-profile copper foil layer with an Rz (surface roughness) value of 0.1-2.0 μm, and the Rz value of the inner surface of the copper foil layer adhering to the high dielectric LCP core layer or high dielectric adhesive layer is 0.1-2.0 μm, and the Rz value of the outer surface of the copper foil layer is 0.1-0.7 μm.

[0069] The copper foil layer is a rolled copper foil layer or an electrolytic copper foil layer.

[0070] Embodiment 1: An LCP high frequency substrate with high Dk and low Df characteristics, such as Figure 1As shown, the LCP high-frequency substrate is a single-sided copper-clad substrate, which includes a copper foil layer, a high dielectric LCP core layer and a high dielectric adhesive layer. The high dielectric LCP core layer is located between the copper foil layer and the high dielectric adhesive layer. The thickness of the single-sided copper-clad substrate is 25-235 μm.

[0071] In this embodiment, the single-sided copper-clad substrate further includes a release layer, and the release layer is located on the surface of the high-dielectric adhesive layer.

[0072] The release layer may be a release film, the material of which is at least one of polypropylene, biaxially oriented polypropylene and polyethylene terephthalate, and may be a release film with double-sided release capability, or may be a release paper.

[0073] The preparation method of embodiment 1 comprises the following steps:

[0074] Step 1: Coat the precursor of the high dielectric LCP core layer on one side of the copper foil layer, remove the solvent at 60-180° C., and then anneal it at 250° C. for 10 hours;

[0075] Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer, and drying and pressing;

[0076] Step 3: Press the release layer on the surface of the high dielectric adhesive layer to obtain a finished single-sided copper-clad substrate.

[0077] Embodiment 2: An LCP high frequency substrate with high Dk and low Df characteristics, such as Figure 2 As shown, the LCP high-frequency substrate is a double-sided copper-clad substrate, which includes two copper foil layers, two high-dielectric LCP core layers and a high-dielectric adhesive layer, and the double-sided copper-clad substrate is composed of a copper foil layer, a high-dielectric LCP core layer, a high-dielectric adhesive layer, a high-dielectric LCP core layer and a copper foil layer from top to bottom, and the thickness of the double-sided copper-clad substrate is 38-370 μm.

[0078] The preparation method of embodiment 2 comprises the following steps:

[0079] Step 1: Coat the precursor of the high dielectric LCP core layer on one side of the copper foil layer, remove the solvent at 60-180° C., and then anneal it at 250° C. for 10 hours to obtain two semi-finished products A;

[0080] Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer of the semi-finished product A, drying and pressing the semi-finished product B;

[0081] Step 3: Lay and press the high dielectric LCP core layer of the other semi-finished product A and the high dielectric adhesive layer of the semi-finished product B, and cure them at 180° C. for more than 5 hours to obtain a finished double-sided copper clad substrate.

[0082] Embodiment 3: An LCP high frequency substrate with high Dk and low Df characteristics, such as Figure 3 As shown, the LCP high-frequency substrate is a double-sided copper-clad substrate, which includes two copper foil layers, a high dielectric LCP core layer and a high dielectric adhesive layer, and the double-sided copper-clad substrate is composed of a copper foil layer, a high dielectric LCP core layer, a high dielectric adhesive layer and a copper foil layer from top to bottom, and the thickness of the double-sided copper-clad substrate is 26-270 μm.

[0083] The preparation method of embodiment 3 comprises the following steps:

[0084] Step 1: Coat the precursor of the high dielectric LCP core layer on one side of the copper foil layer, remove the solvent at 60-180° C., and then anneal it at 250° C. for 10 hours;

[0085] Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer, drying and pressing the layer to obtain a single-sided copper-clad substrate;

[0086] Step 3: Laminating the copper foil layer with the high dielectric adhesive layer of the single-sided copper-clad substrate prepared in step 2, and curing at 180° C. for more than 5 hours to obtain a finished double-sided copper-clad substrate.

[0087] The following are the formulas of the high dielectric LCP core layer (see Table 1) and the formula of the high dielectric adhesive layer (see Table 2) of specific examples of embodiments 1-3 of the present invention, wherein Examples 1 to 7 are examples of embodiment 1, Examples 8 to 10 are examples of embodiment 3, Examples 11 to 14 are examples of embodiment 2, Table 3 is the physical property indicators of the single-sided copper-clad substrate of embodiment 1 and the comparative example; Table 4 is the physical property indicators of the double-sided copper-clad substrate of embodiments 2 and 3 and the comparative example.

[0088] Table 1: Formulation of high dielectric LCP core layer

[0089]

[0090] Table 2: Formula of high dielectric adhesive layer

[0091]

[0092]

[0093] Table 3: Physical properties of single-sided copper-clad substrate and comparative examples

[0094]

[0095] Table 4: Physical properties of double-sided copper-clad substrate and comparative examples

[0096]

[0097]

[0098] Note: The test methods for the physical properties of Table 3 and Table 4 are in accordance with the "Test Guidelines for Soft Board Assembly" (TPCA-F-002)

[0099] It can be seen from Tables 3 and 4 that the LCP high-frequency substrate of the present invention has excellent high-speed transmission, low loss, high Dk and low Df performance, low roughness, ultra-low water absorption, good UV laser drilling ability, low rebound force suitable for high-density assembly and excellent mechanical properties. It is superior to general LCP films and PI-type adhesive sheets and is suitable for wearable devices such as 5G smartphones and Apple watches.

[0100] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An LCP high frequency substrate with high Dk and low Df characteristics, characterized in that: It comprises at least one copper foil layer, at least one high dielectric LCP core layer and at least one high dielectric adhesive layer, wherein the high dielectric LCP core layer is located between the copper foil layer and the high dielectric adhesive layer, the high dielectric LCP core layer refers to a core layer with a Dk value of 6-100 and a Df value of 0.002-0.010, and the high dielectric adhesive layer refers to an adhesive layer with a Dk value of 6-100 and a Df value of 0.002-0.010; The thickness of the copper foil layer is 1-35 μm; the thickness of the high dielectric LCP core layer is 12-100 μm, and the thickness of the high dielectric adhesive layer is 12-100 μm; The high dielectric LCP core layer includes LCP, and also includes at least one of strong dielectric ceramic powder, conductive powder, sintered silica, fluorine resin and flame retardant; the LCP is 5-98% of the total solid content of the high dielectric LCP core layer, and the sum of the strong dielectric ceramic powder, conductive powder, fluorine resin, sintered silica and flame retardant is 2-90% of the total solid content of the high dielectric LCP core layer; The high dielectric adhesive layer includes at least one of component A and component B; the sum of the proportions of component A is 5-98% of the total solid content of the high dielectric adhesive layer, and the proportion of component B is 5-80% of the total solid content of the high dielectric adhesive layer; The component A comprises at least one of sintered silica, strong dielectric ceramic powder, conductive powder and flame retardant; The component B includes a high molecular polymer resin.

2. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, characterized in that: The LCP high-frequency substrate is a single-sided copper-clad substrate, which includes a copper foil layer, a high-dielectric LCP core layer and a high-dielectric adhesive layer. The high-dielectric LCP core layer is located between the copper foil layer and the high-dielectric adhesive layer. The thickness of the single-sided copper-clad substrate is 25-235 μm.

3. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, characterized in that: The LCP high-frequency substrate is a double-sided copper-clad substrate, and the double-sided copper-clad substrate is one of the following two structures: The first structure, the double-sided copper clad substrate comprises two copper foil layers, two high dielectric LCP core layers and a high dielectric adhesive layer, and the double-sided copper clad substrate is copper foil layer, high dielectric LCP core layer, high dielectric adhesive layer, high dielectric LCP core layer and copper foil layer from top to bottom, and the thickness of the double-sided copper clad substrate is 38-370 μm; The second structure, the LCP high-frequency substrate is a double-sided copper-clad substrate, the double-sided copper-clad substrate includes two copper foil layers, a high dielectric LCP core layer and a high dielectric adhesive layer, and the double-sided copper-clad substrate is copper foil layer, high dielectric LCP core layer, high dielectric adhesive layer and copper foil layer from top to bottom, and the thickness of the double-sided copper-clad substrate is 26-270μm.

4. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, characterized in that: The ferroelectric ceramic powder is at least one of BaTiO3, SrTiO3, Ba(Sr)TiO3, PbTiO3, CaTiO3 and Mg2TiO4; wherein the sum of the proportions of the ferroelectric ceramic powder is 0-90% of the total solid content of the high dielectric LCP core layer; The conductive powder is at least one of transition metal powder, transition metal alloy powder, carbon black, carbon fiber, carbon nanotubes and metal oxides, wherein the sum of the proportions of the conductive powder is 0-45% of the total solid content of the high dielectric LCP core layer.

5. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, characterized in that: The proportion of the fluorine-based resin is 0-45% of the total solid content of the high dielectric LCP core layer, the proportion of the sintered silica is 0-45% of the total solid content of the high dielectric LCP core layer, and the proportion of the flame retardant is 0-45% of the total solid content of the high dielectric LCP core layer.

6. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, characterized in that: The ferroelectric ceramic powder is at least one of BaTiO3, SrTiO3, Ba(Sr)TiO3, PbTiO3, CaTiO3 and Mg2TiO4; wherein the sum of the proportions of the ferroelectric ceramic powder is 0-90% of the total solid content of the high dielectric adhesive layer; The conductive powder is at least one of a transition metal powder, a transition metal alloy powder, carbon black, carbon fiber, carbon nanotubes and a metal oxide, wherein the proportion of the conductive powder and the total solid content of the high dielectric layer 0-45%; The proportion of the fluorine resin is 0-45% of the total solid content of the high dielectric adhesive layer, the proportion of the sintered silica is 0-45% of the total solid content of the high dielectric adhesive layer, and the proportion of the flame retardant is 0-45% of the total solid content of the high dielectric adhesive layer.

7. A method for preparing an LCP high-frequency substrate with high Dk and low Df characteristics according to claim 2, characterized in that: The method comprises the following steps: the single-sided copper-clad substrate further comprises a release layer, and the release layer is located on the surface of the high dielectric adhesive layer; Step 1: coating a high dielectric LCP core layer precursor on one side of a copper foil layer, removing the solvent at 60-180° C., and then annealing it at 250° C. for 10 hours; Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer, and drying and pressing; Step 3: Press the release layer on the surface of the high dielectric adhesive layer to obtain a finished single-sided copper-clad substrate.

8. A method for preparing an LCP high-frequency substrate with high Dk and low Df characteristics according to claim 3, characterized in that: When the double-sided copper-clad substrate is of the first structure, the preparation method comprises the following steps: Step 1: coating a high dielectric LCP core layer precursor on one side of the copper foil layer, removing the solvent at 60-180° C., and then annealing it at 250° C. for 10 hours to obtain two semi-finished products A; Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer of the semi-finished product A, drying and pressing the semi-finished product B; Step 3: Lay and press the high dielectric LCP core layer of the other semi-finished product A and the high dielectric adhesive layer of the semi-finished product B, and cure them at 180° C. for more than 5 hours to obtain a finished double-sided copper clad substrate; When the double-sided copper-clad substrate is of the second structure, the preparation method comprises the following steps: Step 1: coating a high dielectric LCP core layer precursor on one side of a copper foil layer, removing the solvent at 60-180° C., and then annealing it at 250° C. for 10 hours; Step 2: coating the precursor of the high dielectric adhesive layer on the surface of the high dielectric LCP core layer, drying and pressing the layer to obtain a single-sided copper-clad substrate; Step 3: Laminating the copper foil layer with the high dielectric adhesive layer of the single-sided copper-clad substrate prepared in step 2, and curing at 180° C. for more than 5 hours to obtain a finished double-sided copper-clad substrate.

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