A copper foil for PTFE ultra-high frequency copper-clad laminate and preparation method thereof

Abstract

The present invention belongs to the technical field of copper clad laminate materials, and specifically relates to a copper foil for PTFE ultra-high frequency copper clad laminate and a preparation method thereof. The preparation method is: subjecting the copper foil to a nodularization treatment, a heat-resistant treatment, an anti-oxidation treatment and an organic transition layer treatment in sequence to obtain the copper foil for PTFE ultra-high frequency copper clad laminate; the organic transition layer treatment refers to a fluorocarbon-based silicone oil solution containing a coupling group prepared by a specific method, followed by a drying and curing treatment after coating. The present invention uses a fluorocarbon-based silicone oil containing a coupling group to perform an organic transition layer treatment on the copper foil, improves the binding force with the copper foil by introducing a coupling group, improves the binding force with the PTFE varnish cloth and improves the dielectric properties by introducing a fluorocarbon group, and improves the toughness and compatibility by introducing a long-chain polysiloxane. The application of the obtained copper foil in the PTFE ultra-high frequency copper clad laminate has a higher binding force and a lower high-frequency signal transmission loss.

Description

Technical Field

[0001] The invention belongs to the technical field of copper-clad laminate materials, and particularly relates to a copper foil for a PTFE ultra-high frequency copper-clad laminate and a preparation method thereof. Background Art

[0002] With the development of the Internet of Things, Internet of Vehicles, cloud computing / servers and smart phones, human life has entered an era of "speedy communications". High-frequency copper clad laminates are one of the core raw materials for the construction of TD-LTE, FDD-LTE base stations, NB-IoT (Internet of Everything) networks and 5G base stations in the current mobile communications field. They are important emerging materials required for the upgrading of technologies such as unmanned millimeter-wave radar and high-precision satellite navigation. They are also key basic materials urgently needed by industries such as communication equipment, aerospace and military. High-frequency copper clad laminates are the research focus of the "high-speed era". Copper foil, resin and glass fiber cloth are the three major raw materials of copper clad laminates, and their quality directly affects PCB signal transmission.

[0003] There are many resin materials suitable for the production of high-frequency copper clad laminates, such as polytetrafluoroethylene (PTFE), polyphenylene ether (PPO / PPE), cyanate ester (CE), polyimide (PI), liquid crystal polymer (LCP), etc. The corresponding dielectric properties are as follows: the dielectric constant Dk of polytetrafluoroethylene (PTFE) is 2.1, and the dielectric loss Df is 0.0005; the dielectric constant Dk of polyphenylene ether (PPO / PPE) is 2.5, and the dielectric loss Df is 0.0007; the dielectric constant Dk of cyanate ester (CE) is 2.9, and the dielectric loss Df is 0.0030; the dielectric constant Dk of polyimide (PI) is 3.1, and the dielectric loss Df is 0.0028; the dielectric constant Dk of liquid crystal polymer (LCP) is 3.3, and the dielectric loss Df is 0.0020. According to the dielectric properties of each material, it can be seen that PTFE resin has excellent dielectric properties and is most suitable for ultra-high frequency copper clad laminates.

[0004] However, due to the characteristics of PTFE resin, such as insolubility, self-lubricity, and non-stickiness, the bonding strength between it and copper foil after high-temperature lamination is low, affecting the stability of its application. The current common treatment method is to improve the bonding strength between copper foil and PTFE varnished cloth by spraying silane coupling agent, but the surface tension difference between the organic polysiloxane layer generated by surface treatment with a simple silane coupling agent and the PTFE resin is still large, and the highly cross-linked silicone resin generated by the self-condensation reaction of the silane coupling agent is relatively brittle and has poor compatibility with the PTFE resin, resulting in less than ideal improvement effect.

[0005] Patents CN 102490413 A and CN 205167727 U both disclose that a fluororesin film such as PFA, PTFE, or FEP is provided between the PTFE varnished cloth and the copper foil to improve the bonding strength with the PTFE varnished cloth. However, the bonding strength between the fluororesin film and the copper foil is also poor, resulting in limited improvement effect. Summary of the invention

[0006] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a method for preparing copper foil for PTFE ultra-high frequency copper-clad laminate.

[0007] Another object of the present invention is to provide a PTFE copper foil for ultra-high frequency copper-clad laminate prepared by the above method.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing copper foil for PTFE ultra-high frequency copper-clad laminate comprises the following preparation steps:

[0010] The copper foil is sequentially subjected to anode treatment, heat resistance treatment, anti-oxidation treatment and organic transition layer treatment to obtain the copper foil for PTFE ultra-high frequency copper clad laminate;

[0011] The method for treating the organic transition layer is as follows:

[0012] (1) subjecting hydroxyl hydrogen-containing silicone oil and fluorosilane coupling agent to dealcoholization condensation reaction under heating and water catalyst conditions to obtain fluorocarbon hydrogen-containing silicone oil;

[0013] (2) adding the fluorocarbon-based hydrogenated silicone oil obtained in step (1), a vinyl silane coupling agent and a chloroplatinic acid catalyst into an organic solvent, removing water with nitrogen, and then heating to carry out a hydrosilylation reaction to obtain a fluorocarbon-based silicone oil solution containing a coupling group;

[0014] (3) applying the fluorocarbon-based silicone oil solution containing coupling groups obtained in step (2) to the surface of the copper foil after anti-oxidation treatment, drying and curing, and obtaining an organic transition layer.

[0015] Preferably, the structural formula of the hydroxyl hydrogen-containing silicone oil is as follows:

[0016] In the formula, m is an integer of 2 to 50, and n is an integer of 0 to 50.

[0017] The above-mentioned hydroxyl hydrogen silicone oil is a conventional raw material in the art, which can be obtained by ring-opening polymerization of a hydrogen-containing ring body (D4H) without adding a capping agent or with a small amount of water as a capping agent, or by ring-opening copolymerization of a hydrogen-containing ring body (D4H) and methylcyclosiloxane (D4).

[0018] Preferably, the fluorosilane coupling agent is one or more of tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane and heptadecafluorodecyltriethoxysilane.

[0019] Preferably, the molar ratio of the hydroxyl hydrogen silicone oil to the fluorosilane coupling agent is 1 to 1.5: 1. Under the above molar ratio conditions, the copper foil treated with the organic transition layer has better bonding strength with the PTFE varnished cloth.

[0020] Preferably, the dealcoholization condensation reaction is carried out at a temperature of 60 to 100° C. and for a time of 1 to 5 hours.

[0021] Preferably, the amount of the vinyl silane coupling agent added is 0.4 to 1.2 times the molar amount of silicon and hydrogen in the fluorocarbon-based hydrogen-containing silicone oil.

[0022] Preferably, the organic solvent is at least one of isopropanol, n-hexane and ethyl acetate; more preferably, it is a mixed solvent of isopropanol and n-hexane or ethyl acetate in a volume ratio of 1:1.5 to 3.

[0023] Preferably, the temperature of the hydrosilylation reaction is 60-100° C. and the time is 2-10 hours.

[0024] Preferably, the drying and curing refers to first vacuum drying at 80-100° C. to remove the solvent, and then heating to 120-140° C. to cure in air for 5-30 minutes.

[0025] Preferably, the anode treatment refers to electroplating anode treatment using an electrolyte containing copper sulfate, sulfuric acid, sodium molybdate and glucose, and the current density of the anode treatment is 10 to 40A / dm 2 The anode treatment time is 1 to 10 seconds; the heat-resistant treatment refers to the electroplating coating heat-resistant layer treatment using an electrolyte containing zinc sulfate, indium sulfate and potassium sodium tartrate, and the current density of the heat-resistant treatment is 0.1 to 1A / dm 2 The anti-oxidation treatment refers to electroplating with a chromium plating solution, the pH of the anti-oxidation treatment is 2 to 6, and the current density is 1 to 5A / dm 2 .

[0026] A copper foil for PTFE ultra-high frequency copper-clad laminate is prepared by the method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention uses a fluorocarbon silicone oil solution containing a coupling group prepared by a specific method to treat the surface of the copper foil, improves the binding force with the copper foil by introducing a coupling group, improves the binding force with the PTFE varnished cloth and improves the dielectric properties by introducing a fluorocarbon group, and improves the toughness and compatibility by introducing a long-chain polysiloxane. The resulting copper foil has a higher binding force and a lower high-frequency signal transmission loss when used in a PTFE ultra-high frequency copper clad laminate.

[0029] (2) The cured organic transition layer of the present invention has good toughness and bonding strength, and can resist the surface deformation and increased roughness of the copper foil caused by stress. The introduction of fluorocarbon groups is beneficial to improving the dielectric properties, thereby reducing the signal transmission loss under high-frequency conditions and improving the performance stability of the copper clad laminate. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0031] Example 1

[0032] A method for preparing copper foil for PTFE ultra-high frequency copper-clad laminate comprises the following preparation steps:

[0033] (1) A 18 μm thick raw copper foil was placed in an electrolyte containing 60 g / L copper sulfate, 125 g / L sulfuric acid, 0.4 g / L sodium molybdate, and 6 g / L glucose at 25 A / dm 2 The anode treatment was carried out with a current density of , and the anode treatment time was 4s.

[0034] (2) The copper foil obtained in step (1) was electroplated at 1.2 A / dm using an electroplating solution containing 50 g / L zinc sulfate, 0.5 g / L indium sulfate, and 80 g / L potassium sodium tartrate. 2 The electroplating treatment is carried out at a current density of to obtain a copper foil coated with a heat-resistant layer.

[0035] (3) The copper foil obtained in step (2) was plated with a chromium plating solution having a chromium ion concentration of 5 g / L at a temperature of 1.5 A / dm 2 The electroplating treatment was carried out at a current density of , and the pH of the electroplating treatment was 4.5 to obtain a copper foil coated with an anti-oxidation layer.

[0036] (4) The copper foil obtained in step (3) is surface-coated with a fluorocarbon-based silicone oil solution containing a coupling group, firstly vacuum-dried at 90° C. to recover the solvent, then heated to 130° C. and cured in air for 15 min to obtain a PTFE ultra-high frequency copper-clad laminate copper foil.

[0037] The preparation method of the fluorocarbon silicone oil solution containing a coupling group is as follows:

[0038] 1) Hydroxy hydrogenated silicone oil (hydroxyl value of 1 wt%, hydrogen content of 0.90 wt%, average molecular weight of 3500) and tridecafluorooctyl triethoxysilane in molar ratios of 0.8, 1.0, 1.2, 1.5, 1.8, respectively, were subjected to dealcoholization condensation reaction at 80°C and 0.5 wt% water catalyst for 3 h to obtain fluorocarbon hydrogenated silicone oil.

[0039] 2) The fluorocarbon-based hydrogenated silicone oil obtained in step (1) is added to a mixed solvent of isopropanol:ethyl acetate in a volume ratio of 1:2, with the amount of vinyltriethoxysilane added being 0.6 times the molar amount of silicon and hydrogen in the fluorocarbon-based hydrogenated silicone oil. After deoxygenation and dehydration with nitrogen, the mixture is heated to 90° C. for a silylation reaction for 4 hours to obtain a fluorocarbon-based silicone oil solution containing a coupling group.

[0040] The molecular weight (GPC determination) of the fluorocarbon-based hydrogenated silicone oil obtained in this embodiment under different molar ratios of hydroxyl hydrogenated silicone oil to fluorosilane coupling agent and the application performance of the obtained copper foil in PTFE ultra-high frequency copper-clad laminate were tested (the obtained copper foil and PTFE varnished cloth were hot-pressed under a protective atmosphere and then the bonding strength and signal transmission loss at high frequency (16 GHz) were tested). The results are shown in Table 1 below.

[0041] Table 1

[0042] Molar Ratio Molecular weight Binding force (kgf / cm) Signal transmission loss (dB / in) 0.8 56240 1.35 0.82 1.0 39500 1.47 0.79 1.2 32450 1.54 0.76 1.5 24680 1.50 0.81 1.8 15270 1.41 0.85

[0043] It can be seen from the results in Table 1 that with the decrease in the proportion of fluorosilane coupling agent, the molecular weight of the obtained fluorocarbon-based hydrogenated silicone oil shows a decreasing trend. The reason is that the fluorosilane coupling agent plays a role in chain extension and cross-linking, and the reduction in its addition ratio leads to a decrease in the degree of polymerization of the condensation reaction. When the proportion of fluorosilane coupling agent is too high, its self-condensation reaction tendency increases and the degree of cross-linking of the copolymerization condensation product is too large, and the subsequent coupling modification effect deteriorates, resulting in poor bonding effect and toughness of the organic transition layer, and to a certain extent, an increase in the signal transmission loss of the obtained copper clad laminate. When the proportion of fluorosilane coupling agent is too low, the molecular weight of the fluorocarbon-based hydrogenated silicone oil is low, and the modification ratio of the fluorocarbon group is reduced, resulting in poor bonding effect with PTFE varnish cloth and a decrease in the dielectric properties of the organic transition layer, and ultimately leading to a significant increase in the signal transmission loss of the obtained copper clad laminate.

[0044] Example 2

[0045] A method for preparing copper foil for PTFE ultra-high frequency copper-clad laminate. Compared with Example 1, the method for preparing the fluorocarbon-based silicone oil solution containing a coupling group is as follows:

[0046] 1) Hydroxyl hydrogen silicone oil (hydroxyl value of 3.2wt%, hydrogen content of 1.5wt%, average molecular weight of 1000) and heptadecafluorodecyl triethoxysilane in a molar ratio of 1.2 were subjected to dealcoholization condensation reaction for 5h under heating to 60°C and 0.5wt% water catalyst to obtain fluorocarbon hydrogen silicone oil.

[0047] 2) The fluorocarbon-based hydrogenated silicone oil obtained in step (1) is added to a mixed solvent of isopropanol:n-hexane in a volume ratio of 1:3 with a vinyl triethoxysilane coupling agent and a chloroplatinic acid catalyst, wherein the amount of vinyl triethoxysilane added is 0.4 times the molar amount of silicon and hydrogen in the fluorocarbon-based hydrogenated silicone oil. After deoxygenation and dehydration with nitrogen, the mixture is heated to 90° C. for a silylation reaction for 4 hours to obtain a fluorocarbon-based silicone oil solution containing a coupling group.

[0048] The molecular weight of the fluorocarbon-based hydrogen-containing silicone oil obtained in this example was determined by GPC to be 33620. The application performance test results of the obtained copper foil in PTFE ultra-high frequency copper-clad laminate showed that the bonding force was 1.52 kgf / cm and the signal transmission loss at high frequency (16 GHz) was 0.78.

[0049] Example 3

[0050] A method for preparing copper foil for PTFE ultra-high frequency copper-clad laminate. Compared with Example 1, the method for preparing the fluorocarbon-based silicone oil solution containing a coupling group is as follows:

[0051] 1) Hydroxyl hydrogen silicone oil (hydroxyl value of 0.64wt%, hydrogen content of 0.8wt%, average molecular weight of 5000) and tridecafluorooctyltrimethoxysilane in a molar ratio of 1.2 were heated to 100°C and 0.5wt% water catalyst for dealcoholization condensation reaction for 1h to obtain fluorocarbon hydrogen silicone oil.

[0052] 2) The fluorocarbon-based hydrogenated silicone oil obtained in step (1) is added to a mixed solvent of isopropanol:ethyl acetate in a volume ratio of 1:1.5, wherein the amount of vinyltriethoxysilane added is 0.8 times the molar amount of silicon and hydrogen in the fluorocarbon-based hydrogenated silicone oil. After deoxygenation and dehydration with nitrogen, the mixture is heated to 90° C. for a silylation reaction for 4 hours to obtain a fluorocarbon-based silicone oil solution containing a coupling group.

[0053] The molecular weight of the fluorocarbon-based hydrogen-containing silicone oil obtained in this example was determined by GPC to be 46800. The application performance test results of the obtained copper foil in PTFE ultra-high frequency copper-clad laminate showed that the bonding force was 1.55 kgf / cm and the signal transmission loss at high frequency (16 GHz) was 0.79.

[0054] Comparative Example 1

[0055] Compared with Example 1, this comparative example uses an equal amount of tridecafluorooctyl triethoxysilane coupling agent solution to replace the fluorocarbon silicone oil solution containing coupling groups to perform surface coating treatment on the copper foil, and the rest is the same.

[0056] The application performance test results of the copper foil obtained in this comparative example in the PTFE ultra-high frequency copper clad laminate show that the bonding force is 1.02 kgf / cm and the signal transmission loss at high frequency (16 GHz) is 0.86 dB / in.

[0057] From the above results, it can be seen that the bonding force between the copper foil and the PTFE varnished cloth obtained by directly using the fluorosilane coupling agent for treatment is significantly reduced, and the signal transmission loss at high frequency is higher than that of the present invention. The reason is that the organic transition layer formed by directly using the fluorosilane coupling agent has too high a degree of crosslinking, poor toughness and compatibility, resulting in a significant deterioration in the bonding effect with the copper foil and the PTFE varnished cloth, and at the same time, the signal transmission loss of the obtained copper clad laminate at high frequency is also increased to a certain extent.

[0058] Comparative Example 2

[0059] Compared with Example 1, this comparative example directly uses a physical mixed solution of fluorocarbon-based hydrogenated silicone oil and vinyl triethoxysilane coupling agent to replace the fluorocarbon-based silicone oil solution containing coupling groups to carry out surface coating treatment on the copper foil, and the rest is the same.

[0060] The preparation method of the physical mixed solution of the fluorocarbon-based hydrogenated silicone oil and the vinyl triethoxysilane coupling agent is as follows:

[0061] The same amount of fluorocarbon-based hydrogenated silicone oil and vinyl triethoxysilane coupling agent as in Example 1 was added to a mixed solvent of isopropanol:ethyl acetate in a volume ratio of 1:2, and after deoxygenation and dehydration with nitrogen, the mixture was stirred and mixed evenly to obtain a physical mixed solution of fluorocarbon-based hydrogenated silicone oil and vinyl triethoxysilane coupling agent.

[0062] The application performance test results of the copper foil obtained in this comparative example in the PTFE ultra-high frequency copper clad laminate show that the bonding force is 1.20 kgf / cm and the signal transmission loss at high frequency (16 GHz) is 0.85 dB / in.

[0063] It can be seen from the above results that the organic transition layer formed by the simple physical mixing of fluorocarbon-based silicone oil and silane coupling agent still has poor bonding effect with copper foil and PTFE varnished cloth, resulting in reduced bonding strength and increased signal transmission loss.

[0064] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing copper foil for PTFE ultra-high frequency copper-clad laminate, characterized in that: The method comprises the following preparation steps: The copper foil is sequentially subjected to anode treatment, heat resistance treatment, anti-oxidation treatment and organic transition layer treatment to obtain the copper foil for PTFE ultra-high frequency copper clad laminate; The method for treating the organic transition layer is as follows: (1) subjecting hydroxyl hydrogen-containing silicone oil and fluorosilane coupling agent to dealcoholization condensation reaction under heating and water catalyst conditions to obtain fluorocarbon hydrogen-containing silicone oil; (2) adding the fluorocarbon-based hydrogenated silicone oil obtained in step (1), a vinyl silane coupling agent and a chloroplatinic acid catalyst into an organic solvent, removing water with nitrogen, and then heating to carry out a hydrosilylation reaction to obtain a fluorocarbon-based silicone oil solution containing a coupling group; (3) The fluorocarbon-based silicone oil solution containing coupling groups obtained in step (2) is applied to the surface of the copper foil after anti-oxidation treatment, and dried and solidified to obtain an organic transition layer.

2. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, wherein: The structural formula of the hydroxyl hydrogen-containing silicone oil is as follows: , where m is an integer from 2 to 50, and n is an integer from 0 to 50.

3. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The fluorosilane coupling agent is one or more of tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane and heptadecafluorodecyltriethoxysilane.

4. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The molar ratio of the reaction of the hydroxyl hydrogen-containing silicone oil and the fluorosilane coupling agent is 1-1.5:

1.

5. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The dealcoholization condensation reaction is carried out at a temperature of 60-100° C. and for a time of 1-5 hours.

6. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The amount of the vinyl silane coupling agent added is 0.4 to 1.2 times the molar amount of silicon and hydrogen in the fluorocarbon-based hydrogen-containing silicone oil.

7. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The organic solvent is at least one of isopropanol, n-hexane and ethyl acetate; the temperature of the hydrosilylation reaction is 60-100° C. and the time is 2-10 hours.

8. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 7, characterized in that: The organic solvent is a mixed solvent of isopropanol and n-hexane or ethyl acetate in a volume ratio of 1:1.5-3.

9. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The drying and curing refers to first vacuum drying at 80-100° C. to remove the solvent, and then heating to 120-140° C. to cure in air for 5-30 minutes.

10. The method for preparing a PTFE ultra-high frequency copper-clad laminate copper foil according to claim 1, characterized in that: The anode treatment refers to electroplating anode treatment using an electrolyte containing copper sulfate, sulfuric acid, sodium molybdate and glucose, and the current density of the anode treatment is 10~40A / dm 2 The anode treatment time is 1~10s; the heat-resistant treatment refers to the electroplating coating heat-resistant layer treatment using an electrolyte containing zinc sulfate, indium sulfate and potassium sodium tartrate, and the current density of the heat-resistant treatment is 0.1~1A / dm 2 The anti-oxidation treatment refers to electroplating with a chromium plating solution, the pH of the anti-oxidation treatment is 2 to 6, and the current density is 1 to 5A / dm 2 .

11. A copper foil for PTFE ultra-high frequency copper-clad laminate, characterized in that: It is prepared by the method according to any one of claims 1 to 10.

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