阅读说明：本技术 具高Dk和低Df特性的LCP高频基板及制备方法 (LCP high-frequency substrate with high Dk and low Df characteristics and preparation method thereof ) 是由 李建辉 林志铭 何家华 于 2018-07-25 设计创作，主要内容包括：本发明公开了一种具高Dk和低Df特性的LCP高频基板,包括至少一铜箔层、至少一高介电LCP芯层和至少一高介电胶层,高介电LCP芯层位于铜箔层和高介电胶层之间,高介电LCP芯层是指Dk值为6-100,且Df值为0.002-0.010的芯层,高介电胶层是指Dk值为6-100,且Df值为0.002-0.010的胶层；铜箔层的厚度为1-35μm；高介电LCP芯层的厚度为12-100μm,高介电胶层的厚度为12-100μm。本发明中由于高介电LCP芯层和高介电胶层皆具有高Dk和低Df的特性,使制得的LCP高频基板具有极佳的高速传输性、低损耗性、高Dk和低Df性能、低粗糙度、超低吸水率、适合高密度组装的低反弹力、良好的UV激光钻孔能力以及极佳的机械性能。(The invention discloses an LCP high-frequency substrate with high Dk and low Df characteristics, which 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 positioned between the copper foil layer and the high-dielectric adhesive layer, the high-dielectric LCP core layer is 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 is 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 invention, because the high-dielectric LCP core layer and the high-dielectric glue layer both have the characteristics of high Dk and low Df, the prepared LCP high-frequency substrate has excellent high-speed transmission, low loss factor, high Dk and low Df performances, low roughness, ultralow water absorption, low rebound force suitable for high-density assembly, good UV laser drilling capability and excellent mechanical performance.)

1. An LCP high-frequency substrate with high Dk and low Df characteristics, comprising: the LCP core layer is positioned between the copper foil layer and the high-dielectric adhesive layer, the high-dielectric LCP core layer is 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 is 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 mu m, and the thickness of the high-dielectric adhesive layer is 12-100 mu m.

2. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, wherein: the LCP high-frequency substrate is a single-sided copper-clad substrate, the single-sided copper-clad substrate comprises 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 25-235 microns.

3. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, wherein: 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 double-sided copper-clad substrate comprises two copper foil layers, two high-dielectric LCP (liquid Crystal Polymer) core layers and a high-dielectric glue layer, wherein the copper foil layers, the high-dielectric LCP core layers, the high-dielectric glue layer, the high-dielectric LCP core layers and the copper foil layers are sequentially arranged from top to bottom, and the thickness of the double-sided copper-clad substrate is 38-370 mu m;

the LCP high-frequency substrate is a double-sided copper-clad substrate, the double-sided copper-clad substrate comprises two copper foil layers, a high-dielectric LCP core layer and a high-dielectric glue layer, the double-sided copper-clad substrate sequentially comprises the copper foil layers, the high-dielectric LCP core layer, the high-dielectric glue layer and the copper foil layers from top to bottom, and the thickness of the double-sided copper-clad substrate is 26-270 mu m.

4. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, wherein: the high-dielectric LCP core layer comprises LCP and at least one of ferroelectric ceramic powder, conductive powder, sintered silicon dioxide, teflon, fluorine resin and a 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 ferroelectric ceramic powder, the conductive powder, the fluorine resin, the sintered silicon dioxide, the teflon and the flame retardant is 2-90% (weight percentage) 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 4, wherein: the ferroelectric ceramic powder is BaTiO₃、SrTiO₃、Ba(Sr)TiO₃、PbTiO₃、CaTiO₃And Mg₂TiO₄At leastOne kind of the material is selected; wherein the sum of the ferroelectric ceramic powder proportion is 0-90% (weight percentage) 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 nanotube and metal oxide, wherein the sum of the proportion of the conductive powder is 0-45% (weight percentage) 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 4, wherein: the proportion of the fluorine-based resin is 0-45% (weight percent) of the total solid content of the high-dielectric LCP core layer, the proportion of the sintered silica is 0-45% (weight percent) of the total solid content of the high-dielectric LCP core layer, the proportion of the Teflon is 0-45% (weight percent) of the total solid content of the high-dielectric LCP core layer, and the proportion of the flame retardant is 0-45% (weight percent) of the total solid content of the high-dielectric LCP core layer.

7. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 1, wherein: the high-dielectric glue layer comprises at least one of a component A and a component B; the sum of the proportions of the components 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;

the component A comprises at least one of sintered silicon dioxide, ferroelectric ceramic powder, conductive powder, teflon, fluorine resin and a flame retardant;

the component B comprises at least one of high molecular polymer resin and high molecular resin.

8. The LCP high frequency substrate with high Dk and low Df characteristics according to claim 7, wherein: the ferroelectric ceramic powder is BaTiO₃、SrTiO₃、Ba(Sr)TiO₃、PbTiO₃、CaTiO₃And Mg₂TiO₄At least one of; wherein the ratio of the ferroelectric ceramic powderThe sum of the weight percentages of the high-dielectric glue layer and the high-dielectric glue layer is 0-90 percent of the total solid content;

the conductive powder is at least one of transition metal powder, alloy powder of transition metal, carbon black, carbon fiber, carbon nanotube and metal oxide, wherein the sum of the proportion of the conductive powder is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer;

the proportion of the fluorine-series resin is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer, the proportion of the sintered silicon dioxide is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer, the proportion of the teflon is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer, and the proportion of the flame retardant is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer.

9. A method for preparing LCP high frequency substrate with high Dk and low Df characteristics according to claim 2, wherein: the method comprises the following steps: the single-sided copper-clad substrate further comprises a release layer, and the release layer is positioned on the surface of the high-dielectric adhesive layer;

step one, coating the precursor of the high-dielectric LCP core layer on one surface of a copper foil layer, removing a solvent at 60-180 ℃, and then annealing at 250 ℃ for 10 hours;

coating the precursor of the high-dielectric glue layer on the surface of the high-dielectric LCP core layer, and drying and pressing;

and step three, laminating a release layer on the surface of the high-dielectric adhesive layer to obtain the finished product of the single-sided copper-clad substrate.

10. A method for preparing LCP high frequency substrate with high Dk and low Df characteristics according to claim 3, wherein: when the double-sided copper-clad substrate is in a first structure, the preparation method comprises the following steps:

step one, coating the precursor of the high-dielectric LCP core layer on one surface of a copper foil layer, removing a solvent at 60-180 ℃, and then performing annealing at 250 ℃ for 10 hours to obtain two semi-finished products A;

coating the precursor of the high-dielectric glue layer on the surface of the high-dielectric LCP core layer of the semi-finished product A, drying and pressing to obtain a semi-finished product B;

thirdly, the other half of the high-dielectric LCP core layer of the finished product A is bonded and pressed with the surface of the high-dielectric glue layer of the semi-finished product B, and the high-dielectric LCP core layer and the high-dielectric glue layer are cured at 180 ℃ for more than 5 hours to obtain a finished product of the double-sided copper-clad substrate;

when the double-sided copper-clad substrate is in a second structure, the preparation method comprises the following steps:

step one, coating the precursor of the high-dielectric LCP core layer on one surface of a copper foil layer, removing a solvent at 60-180 ℃, and then annealing at 250 ℃ for 10 hours;

coating the precursor of the high-dielectric glue layer on the surface of the high-dielectric LCP core layer, drying and pressing to obtain a single-sided copper-clad substrate;

and step three, laminating the copper foil layer on the high dielectric adhesive layer surface of the single-sided copper-clad substrate prepared in the step two, and curing at 180 ℃ for more than 5 hours to obtain a finished product of the double-sided copper-clad substrate.

Technical Field

The invention relates to the technical field of FPC (flexible printed circuit) and preparation thereof, in particular to a high-frequency high-transmission substrate and a preparation method thereof, which are mainly used in the field of high-frequency high-speed transmission FPC, such as automobile radars, global positioning satellite antennas, cellular telecommunication systems, wireless communication antennas, data link cable systems, direct broadcasting satellites, power supply back plates and the like.

Background

With the rapid development of information technology, wireless communication has become a necessity of life. The wireless communication system consists of a transmitting antenna, a receiving antenna and an antenna, wherein the antenna is responsible for the conversion of the electromagnetic energy value in the air and is an indispensable basic equipment for the communication system. In circuit design related to an antenna, passive components such as a capacitor and an inductor may be used to match the antenna. As electronic products are developed to be light, thin, flexible and high-frequency and high-speed signal transmission, active devices and passive devices of related designs must be increased, and the density of circuits and devices must be increased, resulting in increased electromagnetic interference, noise and reliability. To solve this problem, there is a need for improved integration of passive components, such as capacitors. The embedded capacitor can reduce the area of the circuit board, increase the density of the components and improve the reliability of the product, so the development of substrate materials with high dielectric constant and low dielectric loss is an important issue in this field.

At present, most of the high-frequency plates for the PCB are on the market, and the realization approaches and the defects thereof are as follows:

1. the addition of metal powder to the subsequent layer can obtain a high Dk value of 45 or more, but Df is increased, so that the requirement of high frequency and high speed cannot be really met, and the material is easy to have high leakage current in practical application, so that the applicability of the material is greatly reduced.

2. Only the pure high-content high-dielectric ceramic powder is added into the epoxy resin, but the ceramic powder in the dispersed epoxy resin can counteract the electric dipole polarization effect due to the irregular dipole arrangement, so that the effect of improving the dielectric constant value is quite limited. And the mechanical strength of the substrate is reduced and the bonding force between the copper foils is greatly reduced due to the excessively high powder content.

In the field of using high-frequency high-speed materials in the FPC process, the high-frequency plates mainly used in the industry currently are LCP (liquid crystal polymer) plates and PTFE (polytetrafluoroethylene) substrates. The PTFE substrate is not flexible enough when using hard plates at present, and in the aspect of electrical property, the Dk value is 8.0 when the thickness is 6mil, the Dk value is 10 when the thickness is 20mil, and the PTFE substrate is limited by that the Dk value of the impregnated glass fiber cloth in the stack is not high, so that the Dk value is difficult to be more than 10, and the high Dk substrate with the thickness of 2-6mil is difficult to be manufactured. LCP keeps constant dielectric constant in the whole radio frequency range up to 110GHz, Df is only 0.002, the thermal expansion coefficient is small, and the high-frequency high-speed soft board can be realized on the premise of higher reliability. However, the Dk value of LCP is not high enough between 2.9-3.3, which does not meet the requirement of high Dk.

For example, in china patent No. 201590948U, taiwan patent No. M377823, japanese patent No. 2010-7418A and us patent No. 2011/0114371, composite substrates having excellent workability, low cost and low energy consumption are proposed, and in china patent No. 202276545U, chinese patent No. 103096612B, taiwan patent No. M422159 and taiwan patent No. M531056, high frequency substrates are made of fluorine-based materials. CN 205105448U, CN 205255668U, CN 105295753B, and CN 206490891U, both of which propose composite laminated high frequency low dielectric constant adhesive film, high frequency adhesive glue layer structure and preparation method thereof, and composite laminated low dielectric loss FRCC substrate. The capacitance substrate structure of the patent No. TW098124978 Taiwan; CN 206490897U chinese patent proposes an FRCC substrate with high heat dissipation efficiency. CN 206932462U proposes a composite LCP high-frequency high-speed FRCC substrate. The prior patents are still only high frequency substrate materials with Dk between 2.0-3.5, and cannot meet the requirement of high Dk (Dk > 8.0).

Disclosure of Invention

In order to meet the market demand for high-frequency high-speed flexible plates, the LCP high-frequency substrate provided by the invention has the characteristics of high Dk and low Df of the high-dielectric LCP core layer and the high-dielectric adhesive layer, so that the prepared LCP high-frequency substrate has excellent high-speed transmission, low loss factor, high Dk and low Df performance, low roughness, ultralow water absorption, low rebound force suitable for high-density assembly, good UV laser drilling capability and excellent mechanical performance, is superior to a common LCP film and a PI (polyimide) type bonding sheet, and is suitable for wearable equipment such as 5G smart phones, Apple watch and the like.

In order to solve the technical problems, the invention adopts a technical scheme that: the invention provides an LCP high-frequency substrate with high Dk and low Df characteristics, which 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 positioned between the copper foil layer and the high-dielectric adhesive layer, the high-dielectric LCP core layer is 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 is 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 mu m, and the thickness of the high-dielectric adhesive layer is 12-100 mu m.

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 comprises 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 25-235 microns.

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:

the double-sided copper-clad substrate comprises two copper foil layers, two high-dielectric LCP (liquid Crystal Polymer) core layers and a high-dielectric glue layer, wherein the copper foil layers, the high-dielectric LCP core layers, the high-dielectric glue layer, the high-dielectric LCP core layers and the copper foil layers are sequentially arranged from top to bottom, and the thickness of the double-sided copper-clad substrate is 38-370 mu m;

the LCP high-frequency substrate is a double-sided copper-clad substrate, the double-sided copper-clad substrate comprises two copper foil layers, a high-dielectric LCP core layer and a high-dielectric glue layer, the double-sided copper-clad substrate sequentially comprises the copper foil layers, the high-dielectric LCP core layer, the high-dielectric glue layer and the copper foil layers from top to bottom, and the thickness of the double-sided copper-clad substrate is 26-270 mu m.

Further, the high-dielectric LCP core layer comprises LCP and at least one of ferroelectric ceramic powder, conductive powder, sintered silicon dioxide, teflon, fluorine resin and a 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 ferroelectric ceramic powder, the conductive powder, the fluorine resin, the sintered silicon dioxide, the teflon and the flame retardant is 2-90% (weight percentage) of the total solid content of the high-dielectric LCP core layer.

Further, the ferroelectric ceramic powder is BaTiO₃、SrTiO₃、Ba(Sr)TiO₃、PbTiO₃、CaTiO₃And Mg₂TiO₄At least one of; wherein the sum of the ferroelectric ceramic powder proportion is 0-90% (weight percentage) 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 nanotube and metal oxide, wherein the sum of the proportion of the conductive powder is 0-45% (weight percentage) of the total solid content of the high-dielectric LCP core layer.

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

Further, the high dielectric glue layer comprises at least one of a component A and a component B; the sum of the proportions of the components 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;

the component A comprises at least one of sintered silicon dioxide, ferroelectric ceramic powder, conductive powder, teflon, fluorine resin and a flame retardant;

the component B comprises at least one of high molecular polymer resin and high molecular resin.

Further, the ferroelectric ceramic powder is BaTiO₃、SrTiO₃、Ba(Sr)TiO₃、PbTiO₃、CaTiO₃And Mg₂TiO₄At least one of; wherein the ferroelectric ceramic powderThe sum of the proportions is 0 to 90 percent (weight percentage) of the total solid content of the high dielectric glue layer;

the conductive powder is at least one of transition metal powder, alloy powder of transition metal, carbon black, carbon fiber, carbon nanotube and metal oxide, wherein the sum of the proportion of the conductive powder is 0-45% (weight percentage) of the total solid content of the high dielectric adhesive layer;

the proportion of the fluorine-series resin is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer, the proportion of the sintered silicon dioxide is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer, the proportion of the teflon is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer, and the proportion of the flame retardant is 0-45% (weight percentage) of the total solid content of the high-dielectric glue layer.

The invention also provides a preparation method of the LCP high-frequency substrate with high Dk and low Df characteristics, which comprises the following steps: the single-sided copper-clad substrate further comprises a release layer, and the release layer is positioned on the surface of the high-dielectric adhesive layer;

step one, coating the precursor of the high-dielectric LCP core layer on one surface of a copper foil layer, removing a solvent at 60-180 ℃, and then annealing at 250 ℃ for 10 hours;

coating the precursor of the high-dielectric glue layer on the surface of the high-dielectric LCP core layer, and drying and pressing;

and step three, laminating a release layer on the surface of the high-dielectric adhesive layer to obtain the finished product of the single-sided copper-clad substrate.

The invention also provides a preparation method of the LCP high-frequency substrate with high Dk and low Df characteristics, when the double-sided copper-clad substrate is of a first structure, the preparation method comprises the following steps:

step one, coating the precursor of the high-dielectric LCP core layer on one surface of a copper foil layer, removing a solvent at 60-180 ℃, and then performing annealing at 250 ℃ for 10 hours to obtain two semi-finished products A;

coating the precursor of the high-dielectric glue layer on the surface of the high-dielectric LCP core layer of the semi-finished product A, drying and pressing to obtain a semi-finished product B;

thirdly, the other half of the high-dielectric LCP core layer of the finished product A is bonded and pressed with the surface of the high-dielectric glue layer of the semi-finished product B, and the high-dielectric LCP core layer and the high-dielectric glue layer are cured at 180 ℃ for more than 5 hours to obtain a finished product of the double-sided copper-clad substrate;

when the double-sided copper-clad substrate is in a second structure, the preparation method comprises the following steps:

step one, coating the precursor of the high-dielectric LCP core layer on one surface of a copper foil layer, removing a solvent at 60-180 ℃, and then annealing at 250 ℃ for 10 hours;

coating the precursor of the high-dielectric glue layer on the surface of the high-dielectric LCP core layer, drying and pressing to obtain a single-sided copper-clad substrate;

and step three, laminating the copper foil layer on the high dielectric adhesive layer surface of the single-sided copper-clad substrate prepared in the step two, and curing at 180 ℃ for more than 5 hours to obtain a finished product of the double-sided copper-clad substrate.

The invention has the beneficial effects that:

according to the LCP high-frequency substrate, the high-dielectric LCP core layer and the high-dielectric glue layer have the characteristics of high Dk and low Df, so that the prepared LCP high-frequency substrate has excellent high-speed transmission, low loss factor, high Dk and low Df performance, low roughness, ultralow water absorption, low rebound force suitable for high-density assembly and excellent mechanical performance, is superior to a common LCP film and a PI type bonding sheet, and is suitable for wearable equipment such as a 5G smart phone, an Apple watch and the like;

moreover, the LCP high-frequency substrate has better laser drilling process, the small aperture is suitable for small aperture processing smaller than 50 microns, and the inner shrinkage condition is not easy to occur; the film thickness is uniform during pressing, the impedance control is good, and the device is suitable for high-frequency high-speed transmission FPC;

moreover, the current technology of the coating method can only coat a film with the thickness of about 2mil at most, the thick film with the thickness of more than 38 micrometers is not easy to produce and the efficiency is low, but the LCP high-frequency substrate prepared by the preparation method has proper thickness and good controllability, has the thick film preparation technology, can obtain a base material with the thickness of 100 micrometers more easily, and still has the characteristics of high Dk and low Df under the condition of the thick film;

moreover, test data show that the LCP high-frequency substrate has low water absorption rate which is as low as 0.04-0.06%;

furthermore, it can be seen from the test data that the adhesive strength of the high dielectric adhesive layer of the present invention is > 0.7kgf/cm²；

Secondly, the LCP high-frequency substrate with high Dk and low Df characteristics has simple matching structure and composition, and can save downstream processing procedures.

The foregoing description of the present invention is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clear and clear, and to implement the technical solutions according to the content of the description, the following detailed description of the preferred embodiments of the present invention is provided with the accompanying drawings.

Drawings

Fig. 1 is a schematic structural view of embodiment 1 of the present invention (single-sided copper-clad substrate, including a release layer);

fig. 2 is a schematic structural view of embodiment 2 of the present invention (one structure of a double-sided copper-clad substrate);

fig. 3 is a schematic structural view of embodiment 3 of the present invention (another structure of a double-sided copper-clad substrate);

the parts in the drawings are marked as follows:

a copper foil layer 10, a high dielectric LCP core layer 20, a high dielectric adhesive layer 30, and a release layer 40.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and the present invention will be described in detail with reference to the accompanying drawings. The invention may be embodied in other different forms, i.e. it is capable of various modifications and changes without departing from the scope of the invention as disclosed.