CN117183347B - Liquid crystal polymer film, manufacturing method thereof and flexible circuit board - Google Patents
Liquid crystal polymer film, manufacturing method thereof and flexible circuit board Download PDFInfo
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- CN117183347B CN117183347B CN202311461533.5A CN202311461533A CN117183347B CN 117183347 B CN117183347 B CN 117183347B CN 202311461533 A CN202311461533 A CN 202311461533A CN 117183347 B CN117183347 B CN 117183347B
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- 229920000106 Liquid crystal polymer Polymers 0.000 title claims abstract description 130
- 239000004977 Liquid-crystal polymers (LCPs) Substances 0.000 title claims abstract description 123
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 15
- 238000010438 heat treatment Methods 0.000 claims abstract description 50
- 239000002131 composite material Substances 0.000 claims abstract description 42
- 238000007731 hot pressing Methods 0.000 claims abstract description 14
- 239000011261 inert gas Substances 0.000 claims abstract description 11
- 238000010030 laminating Methods 0.000 claims abstract description 9
- 239000004974 Thermotropic liquid crystal Substances 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 28
- 239000011889 copper foil Substances 0.000 claims description 22
- 239000010410 layer Substances 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 17
- 238000002844 melting Methods 0.000 claims description 12
- 230000008018 melting Effects 0.000 claims description 12
- 238000003851 corona treatment Methods 0.000 claims description 7
- 239000012790 adhesive layer Substances 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 239000011888 foil Substances 0.000 claims description 6
- 229920001721 polyimide Polymers 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 abstract description 6
- 238000003825 pressing Methods 0.000 description 18
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 15
- 238000009998 heat setting Methods 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 13
- 239000000463 material Substances 0.000 description 13
- 239000004973 liquid crystal related substance Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 238000004891 communication Methods 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 6
- 239000010949 copper Substances 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 description 5
- 239000012459 cleaning agent Substances 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 description 4
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- 239000003599 detergent Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010096 film blowing Methods 0.000 description 2
- 238000003475 lamination Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000000930 thermomechanical effect Effects 0.000 description 2
- OCKGFTQIICXDQW-ZEQRLZLVSA-N 5-[(1r)-1-hydroxy-2-[4-[(2r)-2-hydroxy-2-(4-methyl-1-oxo-3h-2-benzofuran-5-yl)ethyl]piperazin-1-yl]ethyl]-4-methyl-3h-2-benzofuran-1-one Chemical compound C1=C2C(=O)OCC2=C(C)C([C@@H](O)CN2CCN(CC2)C[C@H](O)C2=CC=C3C(=O)OCC3=C2C)=C1 OCKGFTQIICXDQW-ZEQRLZLVSA-N 0.000 description 1
- 241001646851 Coleus Species 0.000 description 1
- 235000021508 Coleus Nutrition 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 206010061592 cardiac fibrillation Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 230000002600 fibrillogenic effect Effects 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012858 packaging process Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 235000019832 sodium triphosphate Nutrition 0.000 description 1
- 230000007847 structural defect Effects 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention relates to the technical field of liquid crystal polymers, and provides a liquid crystal polymer film, a manufacturing method thereof and a flexible circuit board, wherein the manufacturing method comprises the following steps: (1) Bonding a thermotropic liquid crystal polymer film as a primary film to a bonding layer at a first temperature T 1 Performing hot pressing to obtain an LCP composite film; (2) Heating the LCP composite film to a second temperature T 2 At the second temperature T 2 Heat treatment is carried out for 60-150 min, and then cooling is carried out to room temperature; (3) Heating the LCP composite film obtained in the step (2) to a third temperature T 3 In an atmosphere of inert gas at the third temperature T 3 Heat treatment is carried out for 40-70 min; (4) And (3) peeling the laminating layer in the LCP composite film obtained in the step (3) to obtain the treated liquid crystal polymer film. The manufacturing method of the invention improves the thermal expansion coefficient and the tensile strength of the original film.
Description
Technical Field
The invention relates to the technical field of liquid crystal polymers, in particular to a liquid crystal polymer film, a manufacturing method thereof and a flexible circuit board.
Background
With the continuous development of the 5G communication industry, the electronic communication frequency band gradually changes from centimeter to millimeter wave, and meanwhile, the demands of people for communication equipment are also continuously developing to miniaturization, thinness and high performance, which puts higher demands on substrate materials and packaging processes in electronic devices. At present, the most common substrate material in the market is mainly Polyimide (PI) film, but because the high hygroscopicity and the high dielectric constant and dielectric loss in the millimeter wave frequency band are difficult to meet the requirement of the transmission quality of 5G communication model, the development of the substrate material suitable for 5G/6G high frequency communication is very challenging.
Liquid Crystal Polymer (LCP) films are excellent circuit substrate materials for high frequency communications due to their good dielectric properties, excellent mechanical properties, low hygroscopicity and coefficient of thermal expansion. The LCP film raw material resin has extremely high technical barriers for film preparation due to the problems of extremely large difference of longitudinal and transverse orientation, difficult control of processing technology, easy fibrillation and the like, and the LCP film prepared by the traditional film blowing method/biaxial stretching method has the problems of large difference of thermal expansion coefficient and copper foil and generally low tensile strength.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent.
A first aspect of the present invention provides a method for producing a liquid crystal polymer film, comprising the steps of:
(1) Bonding a thermotropic liquid crystal polymer film as a primary film to a bonding layer at a first temperature T 1 Performing hot pressing to obtain an LCP composite film;
wherein, (T) m -30℃)≤T 1 ≤(T m -10℃)，T m Melting point of the primary film in degrees centigrade;
(2) Heating the LCP composite film to a second temperature T 2 At the second temperature T 2 Heat treatment is carried out for 60-150 min, and then cooling is carried out to room temperature;
wherein, (T) 0 -15℃)≤T 2 ≤T s ，T 0 Is the heat distortion temperature of the primary film, the unit is DEG C, T s The softening point temperature of the primary film is given in degrees celsius;
(3) Heating the LCP composite film obtained in the step (2) to a third temperature T 3 In an atmosphere of inert gas at the third temperature T 3 Heat treatment is carried out for 40-70 min;
wherein, (T) s +10℃)≤T 3 ≤T m ；
(4) And (3) peeling the laminating layer in the LCP composite film obtained in the step (3) to obtain the treated liquid crystal polymer film.
The invention relates to a method for manufacturing a liquid crystal polymer film, wherein the original film adopts a thermotropic liquid crystal polymer film, and the original film is at a first temperature T 1 After hot pressing, an LCP composite film is obtained, which is adhered with the adhesive layer, and then at a second temperature T 2 A lower heat setting treatment, during which the tension between the adhesive layer and the LCP film pre-adjusts the orientation of the liquid crystal unit, at a subsequent third temperature T 3 In the heat treatment again, the tension is continuously applied to the surface of the film at a third temperature T 3 In the heat treatment process, the LCP film is gradually changed from a solid state to a molten state, and the problem of large longitudinal and transverse orientation difference in the liquid crystal polymer film is solved under the synergistic effect of two factors, so that the thermal expansion coefficient and the tensile strength are improved.
According to an embodiment of the present invention, in step (1), the bonding layer is a copper foil, an aluminum foil or a polyimide film. Thereby providing support for the native film.
Optionally, the thickness of the attaching layer is 20-50 μm.
According to an embodiment of the present invention, in the step (1), the thickness of the native film is 25 to 100 μm.
According to the embodiment of the invention, in the step (2), the heating rate is 5-10 ℃/min, and the cooling rate is 5-12 ℃/min. Thereby, the thermal expansion coefficient and the tensile strength of the liquid crystal polymer film are improved.
According to the embodiment of the invention, in the step (3), the heating rate is 2-5 ℃/min. Thereby, the thermal expansion coefficient and the tensile strength of the liquid crystal polymer film are improved.
According to an embodiment of the present invention, further comprising step (5): and carrying out corona treatment on the treated liquid crystal polymer film under inert gas. Thereby, the binding force between the liquid crystal polymer film and the metal is improved.
Optionally, the corona treatment voltage is 8000-10000V, and the pulse frequency is 25-30 kHz.
In a second aspect, the present invention provides a liquid crystal polymer film obtainable by the manufacturing method according to the first aspect of the present invention. The liquid crystal polymer film has a thermal expansion coefficient close to that of the copper foil and has higher tensile strength.
According to the embodiment of the invention, the thermal expansion coefficient MD of the liquid crystal polymer film is 18-19 ppm/DEG C, and TD is 19-23 ppm/DEG C.
According to the embodiment of the invention, the tensile strength of the liquid crystal polymer film is 300-312 MPa.
A third aspect of the invention provides a flexible circuit board comprising a liquid crystal polymer film according to the second aspect of the invention.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is XRD of the native film employed in example 1;
FIG. 2 is XRD of the liquid crystal polymer film finally obtained in example 1.
Detailed Description
Embodiments of the present invention are described in detail below. The embodiments described below are exemplary only for explaining the present invention and are not to be construed as limiting the present invention.
At present, the LCP film prepared by the traditional film blowing method/biaxial stretching method has the problems of large difference between the thermal expansion coefficient of the LCP film and the copper foil and generally low tensile strength.
A first aspect of the present invention provides a method for producing a liquid crystal polymer film, comprising the steps of:
(1) Bonding a thermotropic liquid crystal polymer film as a primary film to a bonding layer at a first temperature T 1 Performing hot pressing to obtain an LCP composite film;
wherein, (T) m -30℃)≤T 1 ≤(T m -10℃)，T m Melting point of the primary film in degrees centigrade;
(2) The saidHeating the LCP composite film to a second temperature T 2 At the second temperature T 2 Heat treatment is carried out for 60-150 min, and then cooling is carried out to room temperature;
wherein, (T) 0 -15℃)≤T 2 ≤T s ，T 0 Is the heat distortion temperature of the primary film, the unit is DEG C, T s The softening point temperature of the primary film is given in degrees celsius;
(3) Heating the LCP composite film obtained in the step (2) to a third temperature T 3 In an atmosphere of inert gas at the third temperature T 3 Heat treatment is carried out for 40-70 min;
wherein, (T) s +10℃)≤T 3 ≤T m ；
(4) And (3) peeling the laminating layer in the LCP composite film obtained in the step (3) to obtain the treated liquid crystal polymer film.
The liquid crystal polymer film is prepared through adopting thermotropic liquid crystal polymer film as primary film at the first temperature T 1 After hot pressing, an LCP composite film is obtained, which is adhered with the adhesive layer, and then at a second temperature T 2 A lower heat setting treatment, during which the tension between the adhesive layer and the LCP film pre-adjusts the orientation of the liquid crystal unit, at a subsequent third temperature T 3 In the heat treatment again, the tension is continuously applied to the surface of the film at a third temperature T 3 In the heat treatment process, the LCP film is gradually changed from a solid state to a molten state, and the problem of extremely large longitudinal and transverse orientation difference in the liquid crystal polymer film is solved under the synergistic effect of two factors, so that the thermal expansion coefficient and the tensile strength are effectively improved, and the thermal expansion coefficient difference of the treated liquid crystal polymer film in the longitudinal and transverse directions is reduced and is close to that of copper.
In the step (1), the first temperature T adopted for hot pressing 1 For example T m -30℃、T m -24℃、T m -19℃、T m -14℃、T m -10℃。
In the step (1), the linear speed of the film pressing roller may be 1 to 1.3 m/min, for example, 1 m/min, and the pressure of the hot pressing may be 12 to 20 kN, for example, 15 kN.
Optionally, the primary membrane is cleaned by a cleaning agent to remove various inorganic matters, organic matters, dust, grease and other pollutants on the surface of the primary membrane. As one example, the cleaning agent includes one or more of citric acid, disodium edetate, sodium tripolyphosphate, deionized water, ethanol, and methylene chloride.
In general, one side of the primary film may be bonded with a bonding layer, and when rolling is performed using a hard film pressing roller (e.g., a cemented carbide roller), one bonding layer may be bonded to each of both sides of the primary film to protect the primary film.
In some embodiments, the bonding layer is a copper foil, aluminum foil, or polyimide film. Thus, it is more advantageous to provide support for the virgin film, maintaining its appearance.
Optionally, the thickness of the bonding layer is 20-50 μm, for example, 20 μm, 30 μm, 45 μm, 50 μm, etc.
Alternatively, the thickness of the native film is 25 to 100 μm, for example, 25 μm, 50 μm, 75 μm, 90 μm, etc.
In step (2), the LCP composite film is heated to a second temperature T 2 Heat treatment, (T) 0 -15℃)≤T 2 ≤T s . Second temperature T 2 For example T 0 -15℃、T 0 -9℃、T 0 -3℃、T s -13℃、T s -6℃、T s Etc. At the second temperature T 2 The heat treatment time is 60-150 min, such as heat treatment for 60min, 80min, 100min, 130min, 150min, etc.
In general, for LCP virgin films, heat distortion temperature T 0 Are all below the softening temperature T s The difference between the two is generally above 10 ℃, and the melting point T m Are all higher than softening temperature T s The difference between the two is generally above 15 ℃. As an example, the melting point T of the primary film m Can be 290-370 ℃ (such as 294 ℃), and the thermal deformation temperature T 0 Can be 250-265 ℃ (such as 259 ℃), and softening temperature T s Can be 270-280 ℃ (such as 276 ℃).
In the step (2), the device used for heating can be one or more of a vacuum oven and a hot air oven.
In step (2), in some embodiments, the heating rate is 5-10 ℃/min, e.g., 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, etc.; the cooling rate is 5-12 ℃/min, for example, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, etc.
In step (3), the LCP composite film obtained in step (2) is heated to a third temperature T 3 ，(T s +10℃)≤T 3 ≤T m . Third temperature T 3 For example T s +11℃、T s +12℃、T m -1℃、T m -4 ℃ and the like. Said at the third temperature T in an atmosphere of inert gas 3 And heat treatment is performed for 40-70 min, for example, 40 min, 50min, 60min, 70 min and the like.
The heat treatment in the step (3) can be performed in a hot air oven with the length of 40-50 m.
In step (3), in some embodiments, the heating rate is 2-5 ℃/min, e.g., 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, etc.
In some embodiments, the method further comprises step (5): and carrying out corona treatment on the treated liquid crystal polymer film under the protection of inert gas. Therefore, polarization occurs on the surface of the liquid crystal polymer film after corona treatment, a fine roughening effect can be generated on the liquid crystal polymer film, and the binding force between the film and metal can be remarkably improved.
Optionally, the corona treatment voltage is 8000-10000V, such as 8000V, 9000V, 10000V, etc., and the pulse frequency is 25-30 kHz, such as 25 kHz, 26 kHz, 28 kHz, 30 kHz, etc.
The inert gas is not particularly limited as long as it does not react with the LCP composite film, and generally includes at least one of nitrogen and argon.
In a second aspect, the present invention provides a liquid crystal polymer film obtained by the manufacturing method of the present invention. The liquid crystal polymer film has a thermal expansion coefficient close to that of the copper foil and has higher tensile strength.
In some embodiments, the liquid crystal polymer film has a coefficient of thermal expansion (MD) of 18 to 19 ppm/DEG C, e.g., 18 ppm/DEG C, 19 ppm/DEG C, etc. in the machine direction; the transverse thermal expansion coefficient (TD) is 19-23 ppm/DEG C, for example, TD is 19 ppm/DEG C, 21 ppm/DEG C, 23 ppm/DEG C, etc., and is close to 17.7 ppm/DEG C of the thermal expansion coefficient of the copper foil.
The thermal expansion coefficient was measured by heating the liquid crystal polymer film sample from room temperature to 200℃at a heating rate of 5℃per minute in an air atmosphere and applying a tensile force of 0.2. 0.2N, and measuring the thermal expansion coefficients in the longitudinal and transverse directions of the liquid crystal polymer film sample using a thermo-mechanical analyzer.
In some embodiments, the liquid crystal polymer film has a tensile strength of 300 to 312 MPa, e.g., 300 MPa, 304 MPa, 311 MPa, 312 MPa, etc. Tensile strength was determined according to GB/T1040.31-2006, at a tensile rate of 100 mm/min and 5 samples per group averaged.
A third aspect of the invention provides a flexible circuit board comprising the liquid crystal polymer film of the second aspect of the invention.
In some embodiments, the flexible circuit board further comprises a flexible copper clad laminate. In particular, the liquid crystal polymer film and the copper plate have close thermal expansion coefficients, and in the process of preparing the circuit board, the deformation degrees of the liquid crystal polymer film and the copper plate are consistent when the liquid crystal polymer film and the copper plate are subjected to hot pressing, so that the bonding degree is good, and the circuit board has excellent dimensional stability and processing formability. Thus, the flexible circuit board can be applied to 5G base station antennas and power amplifiers, 5G mobile phones, automatic driving vehicle-mounted millimeter wave radars and large-scale phased antenna arrays.
The following detailed description of embodiments of the invention is exemplary and intended to be illustrative of the invention and not to be construed as limiting the invention.
In the following examples and comparative examples, the virgin film was obtained from the company Coleus, japan, vecstar ™ series LCP film with the brand name SOK01, thickness 50 μm, T m At 294℃and heat distortion temperature T 0 Is at 259 ℃ and softTemperature T of melting s Is 276 ℃.
Example 1
S0, pretreatment of a base material: wiping the virgin film with a cleaning agent; the detergent comprises, by volume, 1% citric acid, 9% disodium ethylenediamine tetraacetate, 35% ethanol, 55% deionized water;
s1, laminating: and (3) bonding one side of the liquid crystal polymer film obtained in the previous step with copper foil, and hot-pressing the obtained composite film through three groups of film pressing rollers to obtain the multi-layer LCP composite film, wherein the temperature of the film pressing rollers is 270 ℃, the pressure of the film pressing rollers is 15 kN, the linear speed of the film pressing rollers is 1 m/min, and the thickness of the copper foil is 30 mu m.
S2, heat setting treatment: the LCP composite film obtained was heated to 250℃at a heating rate of 10℃per minute, incubated for 60 minutes, and then cooled to room temperature at a rate of 5℃per minute.
S3, heat treatment is carried out again: the multilayer LCP composite film after the previous heat treatment was passed through a hot air oven at 287℃and nitrogen protection at a constant speed of 2 m/min for a treatment time of 40 min.
S4, stripping: and stripping the copper foil in the composite film to obtain the liquid crystal polymer film.
Example 2
S0, pretreatment of a base material: the raw film is wiped with a cleaner. The detergent comprises, by volume, 1% citric acid, 9% disodium ethylenediamine tetraacetate, 35% ethanol, and 55% deionized water.
S1, laminating: and (3) bonding one side of the liquid crystal polymer film obtained in the previous step with copper foil, and hot-pressing the obtained composite film through three groups of film pressing rollers to obtain the multi-layer LCP composite film, wherein the temperature of the film pressing rollers is 275 ℃, the pressure of the film pressing rollers is 15 kN, the linear speed of the film pressing rollers is 1 m/min, and the thickness of the copper foil is 30 mu m.
S2, heat setting treatment: the resulting LCP composite film was heated to 256℃at a heating rate of 10℃per minute, incubated for 100 minutes, and then cooled to room temperature at a rate of 5℃per minute.
S3, heat treatment is carried out again: the multilayer LCP composite film after the previous heat treatment is passed through a hot air oven with the temperature of 290 ℃ and nitrogen protection at a constant speed of 2 m/min for 40 min.
S4, stripping: and stripping the copper foil in the composite film to obtain the liquid crystal polymer film.
Example 3
S0, pretreatment of a base material: the raw film is wiped with a cleaner. The detergent comprises 2% of citric acid, 15% of disodium ethylenediamine tetraacetate and 83% of deionized water by volume percent;
s1, laminating: and (3) bonding one side of the liquid crystal polymer film obtained in the previous step with copper foil, and hot-pressing the obtained composite film at a certain temperature through two groups of film pressing rollers to obtain a multi-layer LCP composite film, wherein the temperature of the film pressing rollers is 275 ℃, the pressure of the film pressing rollers is 15 kN, the linear speed of the film pressing rollers is 1 m/min, and the thickness of the copper foil is 50 mu m.
S2, heat setting treatment: the LCP composite film is heated to 263 ℃ at a heating rate of 10 ℃/min, kept for 120 min, and then cooled to room temperature at a rate of 10 ℃/min.
S3, heat treatment is carried out again: the multi-layer LCP composite film after the previous heat treatment is passed through a hot air oven with the temperature of 290 ℃ and inert gas protection at a constant speed of 3 m/min for 40 min.
S4, stripping: and stripping the copper foil in the composite film to obtain the liquid crystal polymer film.
Example 4
S0, pretreatment of a base material: the liquid crystal polymer film was used as a primary film, and the surface of the primary film was rubbed once with a cleaning agent. The cleaning agent comprises, by volume, 2% of citric acid, 15% of disodium ethylenediamine tetraacetate and 83% of deionized water;
s1, laminating: and (3) attaching the liquid crystal polymer film obtained in the previous step to an aluminum foil, and hot-pressing the obtained composite film at a certain temperature through two groups of film pressing rollers to obtain the multi-layer LCP composite film, wherein the temperature of the film pressing rollers is 280 ℃, the pressure of the film pressing rollers is 15 kN, the linear speed of the film pressing rollers is 1 m/min, and the thickness of the aluminum foil is 50 mu m.
S2, heat setting treatment: the LCP composite film obtained was heated to a temperature range of 270℃at a heating rate of 10℃per minute, incubated for 150 minutes, and then cooled to room temperature at a rate of 12℃per minute.
S3, heat treatment is carried out again: the multi-layer LCP composite film after the previous heat treatment is passed through a hot air oven with the temperature of 293 ℃ and the protection of inert gas at a constant speed of 5 m/min for 40 min.
S4, stripping: and stripping the aluminum foil in the composite film to obtain the liquid crystal polymer film.
Comparative example 1
A liquid crystal polymer film was produced in the same manner as in example 1 except that S2 to S3, that is, the lamination treatment by S1 was not performed, and then the peeling of the copper foil was performed, to obtain a liquid crystal polymer film.
Comparative example 2
A liquid crystal polymer film was produced in the same manner as in example 1 except that S3 was not conducted, and the heat-setting treatment time in S2 was 100 minutes, and the other conditions were the same as in example 1, to obtain a liquid crystal polymer film.
Comparative example 3
A liquid crystal polymer film was produced in the same manner as in example 1 except that the heat-setting treatment of S2 was not performed, and the time for the heat-again treatment of S3 was 100 minutes, under the same conditions as in example 1, to obtain a liquid crystal polymer film.
The tests of the examples and comparative examples are characterized as follows:
performance test:
1. XRD testing
The liquid crystal polymer films before and after the treatment were tested using an X-ray diffractometer. Test conditions: cu target, continuous scanning mode, scanning speed of 6 deg/min and scanning range of 2-70 deg.
2. Tensile Strength
According to GB/T1040.31-2006, a tensile tester is adopted for measurement, the tensile rate is 100 mm/min, and a tensile stress-strain curve is obtained, so that the tensile strength is obtained. The average value of 5 samples from each group was taken.
3. Coefficient of thermal expansion test
The thermal expansion coefficient of the liquid crystal polymer film sample in the process was measured by using a thermo-mechanical analyzer in an air atmosphere at a temperature rising rate of 5 ℃/min from room temperature to 200 ℃ with a tensile force of 0.2N. The average value of 5 samples from each group was taken.
4. Melting Point test
Testing was performed according to GB/T28724-2012. The average value of 5 samples from each group was taken.
5. Heat distortion temperature
The test was performed according to GB/T1634. The average value of 5 samples from each group was taken.
The test results are shown in Table 1.
TABLE 1
As can be seen from the data in Table 1, the heat stability of the LCP films of examples 1-4 after heat treatment is improved, the melting point is increased, the thermal expansion coefficient is effectively adjusted, the film is closer to the copper foil (17.7 ppm/. Degree.C.), and the tensile strength is effectively improved.
Comparative example 1 shows that the effect of protecting the LCP raw film and maintaining the appearance thereof can be achieved only by lamination hot press treatment, but the melting point, thermal expansion coefficient and mechanical properties are not optimized to some extent.
Comparative example 2A comparison with example 1 shows that the conditions of comparative example 2 are after hot pressing at a second temperature T 2 The heat setting is carried out for a long time (100 min), the melting point of the obtained LCP film material is obviously improved, but the thermal expansion coefficient is only slightly adjusted, the MD is 16 ppm/DEG C, the TD is 80 ppm/DEG C, and the difference exists between the thermal expansion coefficients of the LCP film and the laminating layer, and the heat setting is carried out at the second temperature T 2 During heat setting, the LCP film is subjected to a tensile force due to the difference in thermal expansion coefficients, acting like a "stretch" to pre-orient the liquid crystal cellThe effect of the adjustment, at the same time, of prolonging the second temperature T 2 The thermal expansion coefficient cannot be adjusted to be close to that of the copper foil.
Comparative example 3 compared to example 1, comparative example 3 was not subjected to the second temperature T 2 Is directly subjected to a third temperature T 3 The melting point is effectively improved, but the adjustment of the thermal expansion coefficient is limited, the MD is-20 ppm/DEG C, the TD is 87 ppm/DEG C, and the difference of the thermal expansion coefficient with the copper foil is larger; the reason for the adjustment of the thermal expansion coefficient is that during the heat treatment, the LCP is converted from a solid state to a molten state, during which the ordered arrangement of the liquid crystal is gradually converted to a liquid state disorder in the original solid state, resulting in a decrease in the crystallinity of the LCP film and a decrease in the anisotropy, thereby adjusting the thermal expansion coefficient of the film. However, since comparative example 3 does not pass through the second temperature T 2 The heat setting treatment does not undergo the process of pre-adjustment of the orientation of the liquid crystal unit, and although the thermal expansion coefficient is adjusted to a certain extent, the improvement of the thermal expansion coefficient is very limited, and the requirements of the heat setting treatment, which are close to those of copper foil, can not be met far.
The main reason why the melting points of comparative example 2 and comparative example 3 were effectively raised is that at the second temperature T 2 Heat setting or third temperature T 3 In the heat treatment process of (2), the internal part of the LCP film material is activated, and internal stress and local structural defects are eliminated, so that the heat stability of the LCP film material is improved to different degrees.
Referring to fig. 1 and 2, fig. 1 is an XRD of the as-grown film provided in example 1 of the present invention, and fig. 2 is an XRD of the liquid crystal polymer film finally obtained in example 1 of the present invention. As shown in fig. 1 and fig. 2, the peak position of the film is not significantly changed compared with the original film after the treatment of example 1, but the crystallinity is reduced to a certain extent, which indicates that the ordered arrangement of the liquid crystal unit is gradually changed to be disordered in liquid state when the liquid crystal unit is originally in solid state, the anisotropism is weakened, and the thermal expansion coefficients in the horizontal and longitudinal directions are effectively adjusted.
In summary, the manufacturing method of the invention adopts the thermotropic liquid crystal polymer film as the primary film, and after hot pressingTo obtain a laminated LCP composite film of a primary film and a laminated layer, and then at a second temperature T 2 A lower heat setting treatment, during which the tension between the adhesive layer and the LCP film pre-adjusts the orientation of the liquid crystal unit, at a subsequent third temperature T 3 In the heat treatment again, the tension is continuously applied to the surface of the film at a third temperature T 3 In the heat treatment process, the LCP film is gradually changed from a solid state to a molten state, and the problem of extremely large longitudinal and transverse orientation difference in the liquid crystal polymer film is solved under the synergistic effect of two factors, so that the thermal expansion coefficient and the tensile strength are effectively improved, and particularly, the thermal expansion coefficient difference of the liquid crystal polymer film after treatment in the longitudinal and transverse directions is reduced and is close to that of copper.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (10)
1. A method for manufacturing a liquid crystal polymer film, comprising the steps of:
(1) The thermotropic liquid crystal polymer film is used as a primary film to be adhered with the adhesive layer,at a first temperature T 1 Performing hot pressing to obtain an LCP composite film;
wherein, (T) m -30℃)≤T 1 ≤(T m -10℃)，T m Melting point of the primary film in degrees centigrade;
(2) Heating the LCP composite film to a second temperature T 2 At the second temperature T 2 Heat treatment is carried out for 60-150 min, and then cooling is carried out to room temperature;
wherein, (T) 0 -15℃)≤T 2 ≤T s ，T 0 Is the heat distortion temperature of the primary film, the unit is DEG C, T s The softening point temperature of the primary film is given in degrees celsius;
(3) Heating the LCP composite film obtained in the step (2) to a third temperature T under the protection of inert gas 3 At the third temperature T 3 Heat treatment is carried out for 40-70 min;
wherein, (T) s +10℃)≤T 3 ≤T m ；
(4) And (3) peeling the laminating layer in the LCP composite film obtained in the step (3) to obtain the treated liquid crystal polymer film.
2. The method according to claim 1, wherein in the step (1), the bonding layer is a copper foil, an aluminum foil, or a polyimide film; and/or
The thickness of the bonding layer is 20-50 mu m.
3. The method according to claim 1, wherein in the step (1), the thickness of the raw film is 25 to 100. Mu.m.
4. The method according to claim 1, wherein in the step (2), the heating rate is 5 to 10 ℃/min and the cooling rate is 5 to 12 ℃/min.
5. The method according to claim 1, wherein in the step (3), the heating rate is 2 to 5 ℃/min.
6. The method of manufacturing according to claim 1, further comprising the step (5) of: and carrying out corona treatment on the treated liquid crystal polymer film under the protection of inert gas.
7. The method according to claim 6, wherein the corona treatment is performed at a voltage of 8000 to 10000V and a pulse frequency of 25 to 30 kHz.
8. A liquid crystal polymer film obtained by the production method according to any one of claims 1 to 7.
9. The liquid crystal polymer film of claim 8, wherein the liquid crystal polymer film meets at least one of the following conditions:
the longitudinal thermal expansion coefficient MD is 18-19 ppm/DEG C, and the transverse thermal expansion coefficient TD is 19-23 ppm/DEG C;
the tensile strength is 300-312 MPa.
10. A flexible circuit board comprising the liquid crystal polymer film of claim 8 or 9.
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