A preparation method of 9-micron electrolytic copper foil applied to HDI

Abstract

The application relates to a 9-micron electrolytic copper foil preparation method applied to HDI, and polydithiopropanesulfonic acid sodium, hydroxyethyl cellulose and N-dimethylthioformamide propane acid sodium are used as composite additives to be added into an electrolyte to prepare the 9-micron electrolytic copper foil. The core breakthrough of the 9-micron electrolytic copper foil preparation method is that the 9-micron electrolytic copper foil still has excellent mechanical properties while being extremely thinned. The higher tensile strength and elongation rate of the 9-micron electrolytic copper foil can effectively resist interlayer shear force generated by thermal stress and resin flow in a multi-layer pressing process, so that the risk of pressing wrinkles and tearing is significantly reduced. The 9-micron electrolytic copper foil lays a flat and solid foundation for subsequent fine line manufacturing, and is a physical prerequisite for improving the yield and reliability of high-end HDI boards.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic copper foil technology, and specifically relates to a method for preparing 9μm electrolytic copper foil for HDI. Background Technology

[0002] With the rapid development of technology, electronic products are constantly demanding higher processing capabilities. As the core carrier of electronic systems, printed circuit boards (PCBs) are experiencing rapid growth in market demand for high-end PCB products—especially high-multilayer boards and HDI (high-density interconnect) boards—driven by multiple trends such as the popularization of electric vehicles, 5G millimeter-wave communication, and the explosive growth of AI computing power. This is further driving the entire industry chain to demand higher standards for product performance and stability.

[0003] HDI boards, employing precision manufacturing processes such as laser drilling and multilayer lamination, have complex processing procedures and high technical barriers, giving them irreplaceable technological advantages over traditional PCBs. However, the electrolytic copper foil used in HDI is typically 12μm (1 / 3OZ). When the thickness is less than 12μm, the defect rate of wrinkles during PCB lamination increases significantly, severely impacting production quality and efficiency. Before laser drilling with 12μm thickness, a copper reduction process is required. In the micro-etching (or browning) stage before pattern transfer, the amount of copper removed needs to be precisely controlled (usually only 1-2μm). For 12μm copper foil, any slight over-etching can lead to insufficient copper thickness or complete penetration in certain areas, resulting in open circuits and a very narrow process window. Simultaneously, during electroplating to fill vias (especially stacked blind vias), current distribution is prone to unevenness. Using ultra-thin copper foil as the cathode makes it even more difficult to control the current density on its surface, potentially leading to insufficient copper filling within the vias or uneven copper thickness on the surface, creating reliability risks. Summary of the Invention

[0004] This invention provides a method for preparing 9μm electrolytic copper foil for HDI, which solves the production process of electrolytic copper foil for HDI, especially ensuring that the mechanical properties of the copper foil at high temperatures meet the requirements of downstream HDI manufacturing processes.

[0005] This invention provides a method for preparing 9μm electrolytic copper foil for HDI, which uses sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose and sodium N-dimethylthiocarbamate as composite additives added to the electrolyte to prepare 9μm electrolytic copper foil.

[0006] Preferably, the amount of sodium polydisulfide dipropane sulfonate added is 1-10 ppm, the amount of hydroxyethyl cellulose added is 1-10 ppm, and the amount of N-dimethylthiocarbamate sodium propane added is 1-5 ppm.

[0007] Preferably, the parameters of the electrolyte are: Cu 2+: 90-96g / L, H2SO4: 120-130g / L, temperature: 53-57℃.

[0008] Preferably, the preparation parameters are: current density of 5000-6000 A / m 2 The electrolyte flow rate is 40-50m³ / h. 3 / h.

[0009] Beneficial effects (1) Excellent physical properties lay the foundation for the process: The core breakthrough of this invention in preparing 9μm electrolytic copper foil lies in its ability to maintain excellent mechanical properties while achieving extreme thinness. Its high tensile strength and elongation effectively resist interlayer shear forces generated by thermal stress and resin flow during multilayer lamination, thereby fundamentally and significantly reducing the risk of lamination wrinkles and tears. This lays a flat and robust foundation for subsequent fine circuit fabrication, a physical prerequisite for improving the yield and reliability of high-end HDI boards.

[0010] (2) Revolutionary simplified process, directly addressing industry pain points: Even more noteworthy is the innovation this material brings to the manufacturing process. It enables "direct laser drilling after browning treatment," eliminating the need for the "copper reduction" (or "copper thinning") pretreatment step required for traditional ultra-thin copper foil.

[0011] Traditional copper reduction processes use chemical etching to uniformly thin the copper layer to the ideal thickness for laser drilling. However, this process is highly susceptible to uneven copper thickness due to minute fluctuations in the chemical concentration, temperature, or transmission speed. This unevenness directly affects the absorption and dissipation of subsequent laser energy, resulting in irregular hole shapes (such as flared holes or spiked holes), increased hole wall roughness, and even defects such as residual adhesive or insufficient copper penetration at the bottom of blind holes. These defects severely restrict the interconnect reliability of high-end HDI systems.

[0012] By eliminating the copper reduction step, laser energy is applied directly to the surface of a copper foil of uniform thickness, resulting in more precise and stable energy control. This ensures the production of micro-blind vias with more consistent hole shapes and smoother, cleaner hole walls, significantly improving the electrical performance and long-term reliability of the interconnect structure. This is crucial for high-speed 5G, AI computing, and high-speed automotive electronic devices.

[0013] (3) Achieve comprehensive efficiency improvement: a. Shortened production cycle: Reducing a key process step speeds up the overall process.

[0014] b. Reduced production costs: Saves on chemical consumption, equipment maintenance and energy costs in the copper reduction process, and reduces the scrap of boards due to defects in this process.

[0015] c. Enhanced environmental protection and traceability: Reducing chemical treatment steps lowers the burden of wastewater treatment, while the simplified process makes production process control and quality traceability clearer and more reliable. Detailed Implementation

[0016] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0017] Example 1 A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose, and sodium N-dimethylthioformamide propaneate as composite additives to the electrolyte. The electrolyte parameters Cu... 2+ 95 g / L, H2SO4: 125 g / L, temperature: 55℃, current density: 5500 A / m 2 Electrolyte flow rate: 45m³ 3 / h; the molecular weight of sodium didisulfide dipropane sulfonate is 1500-2500 Daltons, the concentration of sodium didisulfide dipropane sulfonate in the electrolyte is 10 ppm, hydroxyethyl cellulose is 5 ppm, and N-dimethylthioformamide propane acid sodium salt is 1 ppm. The parameters of the obtained copper foil are shown in Table 1.

[0018] Example 2 A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose, and sodium N-dimethylthioformamide propaneate as composite additives to the electrolyte. The electrolyte parameters Cu... 2+ 95 g / L, H2SO4: 125 g / L, temperature: 55℃, current density: 5500 A / m 2 Electrolyte flow rate: 45m³ 3 / h; the molecular weight of sodium didisulfide dipropane sulfonate is 1500-2500 Daltons, the concentration of sodium didisulfide dipropane sulfonate in the electrolyte is 10 ppm, hydroxyethyl cellulose is 5 ppm, and N-dimethylthioformamide propane acid sodium salt is 5 ppm. The parameters of the obtained copper foil are shown in Table 1.

[0019] Example 3 A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose, and sodium N-dimethylthioformamide propaneate as composite additives to the electrolyte. The electrolyte parameters Cu... 2+ 95 g / L, H2SO4: 125 g / L, temperature: 55℃, current density: 5500 A / m 2 Electrolyte flow rate: 45m³3 / h; the molecular weight of sodium didisulfide dipropane sulfonate is 1500-2500 Daltons, the concentration of sodium didisulfide dipropane sulfonate in the electrolyte is 10 ppm, hydroxyethyl cellulose is 10 ppm, and N-dimethylthioformamide propane acid sodium salt is 1 ppm. The parameters of the obtained copper foil are shown in Table 1.

[0020] Example 4 A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose, and sodium N-dimethylthioformamide propaneate as composite additives to the electrolyte. The electrolyte parameters Cu... 2+ 95 g / L, H2SO4: 125 g / L, temperature: 55℃, current density: 5500 A / m 2 Electrolyte flow rate: 45m³ 3 / h; the molecular weight of sodium didisulfide dipropane sulfonate is 1500-2500 Daltons, the concentration of sodium didisulfide dipropane sulfonate in the electrolyte is 10 ppm, hydroxyethyl cellulose is 1 ppm, and N-dimethylthioformamide propane acid sodium salt is 1 ppm. The parameters of the obtained copper foil are shown in Table 1.

[0021] Example 5 A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose, and sodium N-dimethylthioformamide propaneate as composite additives to the electrolyte. The electrolyte parameters Cu... 2+ 95 g / L, H2SO4: 125 g / L, temperature: 55℃, current density: 5500 A / m 2 Electrolyte flow rate: 45m³ 3 / h; the molecular weight of sodium didisulfide dipropane sulfonate is 1500-2500 Daltons, the concentration of sodium didisulfide dipropane sulfonate in the electrolyte is 5 ppm, hydroxyethyl cellulose is 1 ppm, and N-dimethylthioformamide propane acid sodium salt is 1 ppm. The parameters of the obtained copper foil are shown in Table 1.

[0022] Example 6 A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose, and sodium N-dimethylthioformamide propaneate as composite additives to the electrolyte. The electrolyte parameters Cu... 2+ 95 g / L, H2SO4: 125 g / L, temperature: 55℃, current density: 5500 A / m 2 Electrolyte flow rate: 45m³ 3 / h; the molecular weight of sodium didisulfide dipropane sulfonate is 1500-2500 Daltons, and the concentration of sodium didisulfide dipropane sulfonate in the electrolyte is 1 ppm, hydroxyethyl cellulose is 1 ppm, and N-dimethylthioformamide propane acid sodium salt is 1 ppm. The parameters of the obtained copper foil are shown in Table 1.

[0023] Table 1 Examples 1, 2, 3, and 4 show that, under the same concentration of sodium polydithiopropane sulfonate, the crystal size does not change significantly with the addition of hydroxyethyl cellulose and sodium N-dimethylthioformamide propaneate, and the high-temperature elongation decreases significantly, which is not conducive to the preparation of 9μm electrolytic copper foil for HDI. Examples 4, 5, and 6 show that, under the same and lower concentrations of hydroxyethyl cellulose and sodium N-dimethylthioformamide propaneate, the crystal size tends to increase with the decrease of sodium polydithiopropane sulfonate concentration, but stops increasing after reaching a certain level, and the high-temperature elongation shows a trend of first increasing and then decreasing. The experimental conditions of Example 5 are preferred.

Claims

1. A method for preparing 9μm electrolytic copper foil for HDI, characterized in that, A 9μm electrolytic copper foil was prepared by adding sodium polydisulfide dipropane sulfonate, hydroxyethyl cellulose and sodium N-dimethylthiocarbamate as composite additives to the electrolyte.

2. The method for preparing 9μm electrolytic copper foil for HDI according to claim 1, characterized in that, The amount of sodium polydisulfide dipropane sulfonate added is 1-10 ppm, the amount of hydroxyethyl cellulose added is 1-10 ppm, and the amount of N-dimethylthiocarbamate sodium propane added is 1-5 ppm.

3. The method for preparing 9μm electrolytic copper foil for HDI according to claim 1, characterized in that, The parameters of the electrolyte are: Cu 2+ : 90-96 g / L, H2SO4: 120-130 g / L, temperature: 53-57 °C.

4. The method for preparing 9μm electrolytic copper foil for HDI according to claim 1, characterized in that, The parameters for preparation are: current density of 5000-6000 A / m. 2 The electrolyte flow rate is 40-50m³ / h. 3 / h.

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