Preparation method of ultra-thin electrolytic copper foil

Abstract

The invention discloses a preparation method of an ultra-thin electrolytic copper foil, and belongs to the field of electronic circuits and lithium ion battery copper foils. According to the method, a non-traditional conductive material is used as a carrier, and the ultra-thin electrolytic copper foil is prepared in a chemical plating mode and an electro-deposition mode in sequence. The non-traditional conductive material is one or more of glass, ceramic and plastic. According to the novel preparation process, materials with different surface roughness are adopted as carriers, introduction of a stripping layer in a traditional process can be abandoned, and a series of production problems caused by the stripping layer and the problems of impurity invasion, failure and the like caused by introduction of heterogeneous substances are avoided; and the surface performance of the ultra-thin copper foil can be further regulated and controlled by controlling the subsequent electro-deposition process so as to meet different application scenes (thickness, roughness, tensile property and the like), the microstructure morphology of the copper foil can be further regulated and controlled by adding an additive into the plating solution, and the method has high industrial application value.

Description

Technical Field

[0001] This invention belongs to the fields of electronic circuits and lithium-ion battery current collectors, and specifically relates to a method for preparing ultra-thin electrolytic copper foil. It successfully achieves the preparation of ultra-thin electrolytic copper foil with a thickness of 1.5 μm without the need for traditional stripping layer processes. Background Technology

[0002] With the widespread adoption of emerging technologies such as smartphones, IoT devices, self-driving cars, and wearable devices, the demand for higher-performance and thinner circuit boards is increasing. Electrolytic copper foil, as a key material for lithium batteries and circuit boards, has naturally attracted significant attention from researchers. Electrolytic copper foil is a thin copper film formed by electrolytically extracting copper from a copper salt solution and depositing it onto a substrate. In electronic devices, it serves as the conductive layer of the circuit board, playing a crucial role in signal transmission and power distribution. Electrolytic copper foil is primarily used in the production of traditional double-sided and multilayer printed circuit boards (PCBs). It is one of the three main raw materials for copper-clad laminates (CCLs) in PCBs, often referred to as the neural network for signal and power transmission and communication in electronic products. It significantly impacts the performance, manufacturing process, manufacturing cost, and lifespan of PCBs, while the quality of the electrolytic copper foil directly affects the manufacturing level of the fine lines on the PCB. From a product perspective, as the PCB industry as a whole develops towards higher density, higher frequency, and higher speed, PCBs require higher line fineness and better signal integrity. Conventional circuit fabrication technologies can no longer meet the 10 μm / 10 μm to 30 μm / 30 μm line width / spacing requirements of existing high-density interconnect (HDI) boards, integrated circuit (IC) substrates, and substrate-like boards. The new circuit fabrication technology currently being used, namely the modified semi-additive process (mSAP), aims primarily at achieving ultra-thin copper foil in the PCB conductive layer. How to prepare extremely thin electrolytic copper foil has always been a major concern for high-density fine circuit PCB manufacturers and copper foil suppliers.

[0003] Ultra-thin copper foil, also known as super-thin copper foil, is defined by the industry standard IPC-410C as copper foil with a thickness of less than 9 μm. With the rapid development of the technology and energy industries, electronic devices are becoming smaller and thinner, new energy power batteries are becoming lighter and more energy-efficient, and information data transmission is becoming faster and with greater throughput. These developments place higher demands on copper foil products, leading to a growing demand for ultra-thin copper foil. A thickness of only 9 μm is no longer sufficient to meet the needs of downstream industries, and copper foil with a thickness of 5 μm or even lower is gradually becoming the mainstay of these industries.

[0004] In traditional ultra-thin electrolytic copper foil manufacturing processes, a release layer process is often used. Release layers are mainly of the single release layer and composite release layer. The introduction of release layers often brings a series of problems. For example, the improvement effect of a single release layer on the peel strength is often limited, which can easily lead to poor continuity and low yield in actual production. While multi-layer metal composite release layers can provide excellent high-temperature heat resistance, they also have other risks: the diffusion behavior of dissimilar metals at high temperatures can easily contaminate the surface of the ultra-thin copper foil, impairing its downstream application performance. Furthermore, the introduction of dissimilar metals often alters the copper ion reaction process at the interface, bringing a series of problems to the subsequent production of ultra-thin copper foil. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of poor continuity and low yield in the traditional ultra-thin electrolytic copper foil release layer preparation process, and to provide an ultra-thin electrolytic copper foil preparation method. In this invention, the bonding force between the copper foil and the tempered glass is relatively poor, and the surface is smooth and flat, which can significantly reduce the surface roughness of the copper foil. This method can be used in PCB circuit boards and other fields to reduce signal transmission losses and increase circuit signal communication efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing ultrathin electrolytic copper foil, wherein the method comprises: using a non-traditional conductive material as a carrier, and sequentially preparing ultrathin electrolytic copper foil by chemical plating and electrodeposition.

[0008] Furthermore, the non-traditional conductive material is one or more of glass, ceramics, and plastics.

[0009] Furthermore, the method specifically includes:

[0010] Step 1: First, use a cleaning agent to remove oil stains from the surface of the carrier, and then ultrasonically clean it for 5 minutes in turn in anhydrous ethanol, deionized water, acetone and deionized water.

[0011] Step 2: Prepare the three solutions required for chemical plating:

[0012] Sensitizing solution: 20 g / L stannous chloride dihydrate, 40 mL / L 37% hydrochloric acid solution, stir thoroughly and seal with plastic wrap for later use;

[0013] Activation solution: 1 g / L palladium chloride solution;

[0014] Preparation of electroless plating solution: 10 g / L copper sulfate pentahydrate, 40 g / L potassium sodium tartrate, 8 g / L sodium hydroxide, 2 g / L anhydrous sodium carbonate, 1 g / L nickel chloride hexahydrate, 0.2~0.5 g / L electroless plating additive (bipyridine or sodium dodecylbenzene sulfonate), place in a constant temperature water bath at 40 ℃ and stir for 3 h;

[0015] Step 3: Place the parts to be plated in the sensitization solution for 2-5 minutes, the activation solution for 5-10 minutes, and the 10% formaldehyde solution for 30-60 seconds in sequence to complete the pretreatment process of the parts to be plated.

[0016] Step 4: Place the part to be plated in the chemical plating solution and add 20 g / L 37% formaldehyde solution to start the reaction for 5~20 minutes; in this step, 37% refers to the concentration of the formaldehyde solution itself, and 20 g / L means adding 20g of 37% formaldehyde solution to 1L of chemical plating solution.

[0017] Step 5: The electroless plated part is controlled by insulating tape to regulate the electrodeposition area. Then, the electroless plating layer is thickened to 5 μm by controlling the current density and time of the electrodeposition process, resulting in an ultra-thin electrolytic copper foil. The surface roughness and microstructure of the copper foil are controlled by adjusting the current density in the electrodeposition step; the specific current density range depends on the actual electrodeposition solution system used. The thickness of the ultra-thin electrolytic copper foil can be controlled by adjusting the electrodeposition time to meet the needs of different applications.

[0018] Furthermore, in step five, the plating solution used in the electrodeposition process consists of VMS (Virgin Make-up Solution): 200 g / L Cu2SO4·5H2O, 50 g / L H2SO4, 60 mg / L NaCl, and additives: PEG 100 mg / L, SPS 2 mg / L.

[0019] Furthermore, in step five, the current density is 2~8 A / dm³. 2 .

[0020] Furthermore, in step five, an additive is added to the electrodeposition plating bath. The additive is one or more of an accelerator (brightener), inhibitor, and leveling agent, with a current density of 2-30 A / dm². 2 .

[0021] Further, the accelerator is one or more of sodium thiopropane sulfonate (HP), sodium dimethylformamide sulfonate (TPS), and thiamethoxamyl dithiopropane sulfonate (SH110); the inhibitor is one or more of tetrahydrothiazolium thione (H1), polyethyleneimine alkyl compound (GISS), fatty amine ethoxysulfonate (AESS), sodium mercaptoimidazolium propane sulfonate (MESS), and azozazine dye (MDD); and the leveling agent is polyethylene glycol (PEG). The tensile properties of copper foil can be improved by controlling the application of additives and the magnitude of current density in the electrodeposition plating bath. Commonly, the addition of additives alters the electrochemical process of copper ions, thus affecting the copper ion deposition potential; therefore, the addition of additives requires experimental investigation of the variable of current density.

[0022] The advantages of this invention compared to existing technologies are as follows: This invention can select various surfaces with different roughnesses as ultra-thin copper foil carriers. A copper film with a nanometer-thickness is deposited on the carrier surface through chemical plating, making the carrier conductive. Subsequently, a copper foil is deposited on the conductive carrier surface through electrodeposition. Then, according to production and application needs, the obtained ultra-thin copper foil is hot-pressed onto a PCB resin substrate. This technical solution completely eliminates the traditional release layer, avoids the introduction of dissimilar metals or other impurities, and ensures the continuity and reproducibility of the process. Attached Figure Description

[0023] Figure 1 Images of electrolytic copper foils prepared on different substrates; (a) conductive glass; (b) polytetrafluoroethylene sheet; (c) zirconia ceramic; (d) tempered glass;

[0024] Figure 2 Schematic diagram of surface roughness of electrolytic copper foil prepared under different current densities; (a) 5 A / dm 2 (b) 10A / dm 2 (c)15 A / dm 2 (d)20 A / dm 2 (e)25 A / dm 2 (f)30 A / dm 2 Four regions were selected for testing for each current density.

[0025] Figure 3 Scanning electron microscope (SEM) images of the surface of electrolytic copper foil prepared at different current densities; (a) 5 A / dm 2 (b) 10A / dm 2 (c) 15A / dm 2 (d)20 A / dm 2 (e)25 A / dm 2 (f)30 A / dm2 ;

[0026] Figure 4 A comparison of tensile strength and elongation of electrolytic copper foils prepared under different current densities;

[0027] Figure 5 Comparison of surface roughness of electrolytic copper foil at different thicknesses: (a) 1.5 μm (b) 3 μm (c) 6 μm (d) 9 μm;

[0028] Figure 6 Scanning electron microscope (SEM) images of the surface of electrolytic copper foil at different thicknesses. (a) 1.5 μm; (b) 3 μm; (c) 6 μm; (d) 9 μm. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0030] Example 1

[0031] (1) Clean the zirconia corundum ceramic sheet. First, use a cleaning agent to remove the surface oil, and then ultrasonically clean it for 5 minutes in anhydrous ethanol, deionized water, acetone and deionized water in sequence.

[0032] (2) Prepare the solutions required for chemical plating: Sensitizing solution: 20 g / L stannous chloride dihydrate, 40 mL / L 37% hydrochloric acid solution, stir thoroughly and seal with plastic wrap for later use; Activating solution: 1 g / L palladium chloride solution; Chemical plating solution preparation: 10 g / L copper sulfate pentahydrate, 40 g / L potassium sodium tartrate, 8 g / L sodium hydroxide, 2 g / L anhydrous sodium carbonate, 1 g / L nickel chloride hexahydrate, 0.2~0.5 g / L chemical plating additive (bipyridine or sodium dodecylbenzenesulfonate), place in a constant temperature water bath at 40 ℃ and stir for 3 h.

[0033] (3) Place the parts to be plated in the sensitizing solution for 2-5 min, in the activating solution for 5-10 min, and in the 10% formaldehyde solution for 30-60 s in sequence to complete the pretreatment process of the parts to be plated.

[0034] (4) Place the part to be plated in the chemical plating solution, add 20 g / L 37% formaldehyde solution and start the reaction for 10 min to obtain a zirconia corundum ceramic sheet after chemical plating. The coating thickness is 200 nm.

[0035] (5) The electroless plated parts are subjected to pretreatment before electroplating, and the electrodeposition area is controlled by insulating tape. Then, the electrodeposition process is performed at 10 A / dm². 2 The chemical plating layer was thickened to 5 μm, resulting in an extremely thin electrolytic copper foil, as shown in the image. Figure 1 As shown. The copper plating system used for electrochemical deposition in this step is an acidic copper plating system. The specific composition of the plating solution is: VMS: 200 g / L Cu2SO4·5H2O, 50 g / L H2SO4, 60 mg / L NaCl, additives: PEG 100 mg / L, SPS 2 mg / L.

[0036] Example 2:

[0037] The difference between this embodiment and Embodiment 1 is that a different carrier is used; in this embodiment, the carrier is a polytetrafluoroethylene sheet.

[0038] Example 3:

[0039] The difference between this embodiment and Embodiment 1 is that a different carrier is used; in this embodiment, the carrier is a tempered glass sheet.

[0040] Comparative Example 1:

[0041] The difference between this comparative example and Example 1 is that conductive glass was selected as the substrate material, and the pre-chemical plating step was omitted, with direct one-step electrodeposition. It was found that omitting the chemical plating step resulted in poor adhesion and failure to form a complete coating. The actual product image is shown below. Figure 1 As shown.

[0042] Example 4:

[0043] The difference between this embodiment and Embodiment 3 is that five sets of parallel experiments were set up, with current densities of 5 A / dm² for each electrodeposition step. 2 15 A / dm 2 20 A / dm 2 25 A / dm 2 30 A / dm 2 Roughness and electron microscopy scanning image testing, such as Figure 2 , Figure 3 As shown. The tensile property test results are as follows. Figure 4 As shown. Through the investigation of the surface roughness of copper foil under different current densities, it was found that when the current density is 25 A / dm... 2 Its copper foil has the lowest surface roughness and a smoother surface.

[0044] Example 5:

[0045] The difference between this embodiment and Embodiment 3 is that the current density in the electrodeposition step is 25 A / dm. 2Five parallel experiments were also conducted to control the electrodeposition time and prepare ultrathin copper foils of 1.5 μm, 3.0 μm, 6 μm, and 9 μm thicknesses. The surface roughness of the copper foils was tested to verify the application of this process in producing ultrathin copper foils of different thicknesses. Roughness test results and electron microscopy images are shown below. Figure 5 , Figure 6 As shown, the deposition time has a relatively low impact on the surface roughness of the copper foil. Therefore, this process can control the thickness of the copper foil by controlling the electrodeposition time, thus covering a wide range of industrial applications.

Claims

1. A method for preparing ultrathin electrolytic copper foil, characterized in that: The method is as follows: using a non-traditional conductive material as a carrier, ultra-thin electrolytic copper foil is prepared by sequentially employing chemical plating and electrodeposition.

2. The method for preparing an ultra-thin electrolytic copper foil according to claim 1, characterized in that: The non-traditional conductive material is one or more of glass, ceramics, and plastics.

3. The method for preparing an ultra-thin electrolytic copper foil according to claim 1, characterized in that: The method is specifically as follows: Step 1: First, use a cleaning agent to remove oil stains from the carrier surface, then ultrasonically clean it in anhydrous ethanol, deionized water, acetone, and deionized water for 5 minutes in sequence. Step 2: Prepare the three solutions required for chemical plating: Sensitization solution: 20 g / L stannous chloride dihydrate, 40 mL / L 37% hydrochloric acid solution, stir thoroughly and seal with plastic wrap for later use; Activation solution: 1 g / L palladium chloride solution; Preparation of electroless plating solution: 10 g / L copper sulfate pentahydrate, 40 g / L potassium sodium tartrate, 8 g / L sodium hydroxide, 2 g / L anhydrous sodium carbonate, 1 g / L nickel chloride hexahydrate, 0.2~0.5 g / L electroless plating additive (bipyridine or sodium dodecylbenzene sulfonate), place in a constant temperature water bath at 40 ℃ and stir for 3 h; Step 3: Place the parts to be plated in the sensitization solution for 2-5 minutes, in the activation solution for 5-10 minutes, and in the 10% formaldehyde solution for 30-60 seconds in sequence to complete the pretreatment process of the parts to be plated. Step 4: Place the part to be plated in the chemical plating solution, add 20 g / L 37% formaldehyde solution and start the reaction for 5~20 minutes; Step 5: Control the electrodeposition area of ​​the electroless plated part by using insulating tape, and then thicken the electroless plating layer to 5 μm by adjusting the current density and time of the electrodeposition process to obtain an extremely thin electrolytic copper foil.

4. The method for preparing an ultra-thin electrolytic copper foil according to claim 3, characterized in that: In step five, the plating solution used in the electrodeposition process consists of VMS (Virgin Make-up Solution): 200 g / L Cu2SO4·5H2O, 50 g / L H2SO4, 60 mg / L NaCl, and additives: PEG 100 mg / L, SPS 2 mg / L.

5. The method for preparing an ultra-thin electrolytic copper foil according to claim 3, characterized in that: In step five, the current density is 2~8 A / dm. 2 .

6. The method for preparing an ultrathin electrolytic copper foil according to claim 3, characterized in that: In step five, an additive is added to the electrodeposition plating bath. The additive is one or more of an accelerator (brightener), inhibitor, and leveling agent, and the current density is 2~30 A / dm. 2 .

7. The method for preparing an ultrathin electrolytic copper foil according to claim 6, characterized in that: The accelerator is one or more of sodium thiopropane sulfonate (HP), sodium dimethylformamide sulfonate (TPS), and thiamethoxamyl dithiopropane sulfonate (SH110); the inhibitor is one or more of tetrahydrothiazothione (H1), polyethyleneimine alkyl compound (GISS), fatty amine ethoxysulfonate (AESS), sodium mercaptoimidazolium propane sulfonate (MESS), and azozazine dye (MDD); and the leveling agent is polyethylene glycol (PEG).

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