Acid sulfate electrocoppering solution

Abstract

The invention discloses an acidic sulfate copper electroplating solution, which comprises the following components: 100 to 300 g / L of copper sulfate pentahydrate, 50 to 300 g / L of sulfuric acid, 50 to 500 mg / L of polyethylene glycol, 0.1 to 5 mg / L of Jannao green, 0.1 to 1 mg / L of sodium phenyl dithiopropanesulfonate, 0.2 to 5 mg / L of sodium isothiourea propanesulfonate and trace chloride ions. The plating solution is used for electroplating of display panel glass or a PI substrate, and Rad can be realized; the thickness is 12 nm, the mount density is 0 / 100 [mu] m, no streak stripe exists, and the photoetching precision requirement of a superfine metal grid smaller than or equal to 2 [mu] m is met; the coating elongation reaches 24%, the resistance is smaller than or equal to 90 m omega / sq, bubbling and cracking are avoided after 280 DEG C reflow soldering, and the electric strength reliability and the mechanical strength reliability are both considered. The method disclosed by the invention is not limited to a low-current interval, and the Ralt can be obtained in a wide process window applied with the current density of 0.1-4 ASD and the temperature of 18-40 DEG C; the mirror surface copper layer with the thickness of 12 nm and without protrusions and flow lines is directly compatible with an existing PCB acid copper production line, and can be used for manufacturing OLED / Mini-LED driving back plates, electromagnetic shielding grids and heat dissipation metal layers without additional equipment transformation.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology, specifically relating to an acidic sulfate copper plating solution suitable for novel display panel glass / PI substrates and its application. Background Technology

[0002] As new display panels such as OLED and Mini-LED evolve towards higher resolutions (4K, 8K) and refresh rates (120Hz and above), their driving backplanes need to form ultra-fine metal meshes (linewidth / spacing ≤ 2 μm, thickness 3–8 μm) on glass or PI substrates. Unlike printed circuit boards (PCBs), panel-level copper plating generally employs a low current density, long-time process of 0.1–2 ASD to control the total thickness deviation (TTV) within ±0.5 μm. However, within this low current range, existing acidic sulfate ternary systems (containing copper salts, sulfuric acid, trace amounts of chloride ions, and conventional additives) still exhibit the following two types of appearance defects:

[0003] 1) Protrusions: Submicron to nanometer-scale mound protrusions formed by localized over-deposition can easily cause tip discharge or poor coverage in subsequent processes;

[0004] 2) Flow marks: Periodic streak patterns along the fluid direction, which cause rainbow-like patterns after optical coating, affecting the optical appearance and the uniformity of subsequent coatings.

[0005] The aforementioned defects lead to problems such as protrusions, flow marks, and rough crystals in the copper plating of the display panel. Figure 1 As shown, the aforementioned defects largely stem from the insufficient micro-area electrochemical coupling strength caused by the dynamic mismatch of adsorption-desorption on the cathode surface in the low-current region of conventional plating solutions. Therefore, it is urgent to develop a novel plating solution system to expand the existing process window while eliminating surface roughness problems caused by protrusions and flow marks, thereby better meeting the photolithographic precision requirements of new high-resolution panels. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a plating solution system suitable for panel-level low-current acidic sulfate copper plating, which can effectively suppress micro-bumps and flow lines, achieving mirror-like copper deposition with Ra<15 nm and zero defects.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An acidic sulfate copper plating solution, characterized by comprising the following components in the following proportions:

[0009] Copper sulfate pentahydrate 100–300 g / L

[0010] Sulfuric acid 50–300 g / L

[0011] Chloride ions 30-80 ppm

[0012] Polyethylene glycol (PEG) 50–500 mg / L

[0013] JGB (Jenner Green) 0.1–5 mg / L

[0014] Sodium phenyl dithiopropane sulfonate 0.1–1 mg / L

[0015] Sodium isothiourea propanesulfonate 0.2–5 mg / L;

[0016] The mass ratio of sodium phenyl dithiopropane sulfonate to sodium isothiourea propane sulfonate is 1:2 to 1:5.

[0017] Furthermore, the present invention provides a method for electroplating copper on display panel glass or PI substrate using the above-mentioned acidic sulfate copper plating solution, characterized in that: the acidic sulfate copper plating solution is used to electroplat the substrate under the conditions of applying current density of 0.1 to 4 ASD and temperature of 18 to 40°C until a copper layer with a thickness of 2 to 50 μm, surface roughness Ra ≤ 12 nm, and no mound protrusions or strand flow lines is formed.

[0018] Furthermore, in the above-mentioned method of electroplating copper, the electroplating time on the substrate is 10 to 60 minutes, and the resulting copper layer has a bright mirror finish and an elongation of ≥20%.

[0019] Furthermore, the copper layer obtained by the above-mentioned electroplating method is applied in the preparation of ultra-fine metal meshes with line width and line spacing ≥ 2 μm.

[0020] Furthermore, the above-mentioned acidic sulfate copper plating solution is used in the manufacture of OLED, Mini-LED, or Micro-LED display panels.

[0021] Furthermore, the application of the aforementioned acidic sulfate electroplating copper plating solution in the manufacture of OLED, Mini-LED, or Micro-LED display panels specifically includes: forming copper electrodes, electromagnetic shielding grids, or heat dissipation metal layers for driving backplates.

[0022] The beneficial effects of this invention are as follows:

[0023] 1) Electroplating for display panel glass or PI substrate can achieve Ra<12 nm, mound density of 0 / 100μm², no streak visible to the naked eye or optical microscope, and meet the photolithography precision requirements of ≤2 μm ultra-fine metal mesh;

[0024] 2) The coating elongation reaches 24%, the resistance is ≤90 mΩ / sq, and there is no blistering or cracking after reflow soldering at 280℃, which takes into account both electrical and mechanical strength and reliability;

[0025] 3) This invention is not limited to the low current range. It can obtain a mirror copper layer with Ra<12 nm and no mound protrusions or streak patterns within a wide process window of application current density 0.1 to 4 ASD and temperature 18 to 40℃. It is directly compatible with existing PCB acid copper production lines and can be used for the manufacture of OLED / Mini-LED driver backplanes, electromagnetic shielding grids and heat dissipation metal layers without additional equipment modification. Attached Figure Description

[0026] Figure 1 The copper plating on the panel shows bumps, flow marks, and rough crystals; where a is a bump (enlarged view), b is a flow mark, and c is rough crystals.

[0027] Figure 2 The appearance of the coating obtained in Example 1; where a is an optical photograph and b is a SEM scan image.

[0028] Figure 3 The appearance of the coating obtained in Example 2; where a is an optical photograph and b is a scanning electron microscope (SEM) image.

[0029] Figure 4 The appearance of the coating obtained in Example 3; where a is an optical photograph and b is a SEM scan image.

[0030] Figure 5 The appearance of the coating obtained in Example 4; where a is an optical photograph and b is a SEM scan image. Detailed Implementation Plan

[0031] The invention's technical solution will be further explained below with reference to specific embodiments.

[0032] Example 1

[0033] After cleaning and pre-treatment with seed layer sputtering on the glass substrate, electroplating is performed using the acidic sulfate copper plating solution of this invention. The composition of the plating solution is as follows:

[0034] Copper sulfate pentahydrate 200 g / L

[0035] Sulfuric acid 100 g / L

[0036] Chloride ions 50ppm

[0037] PEG6000 200 mg / L

[0038] JGB 1.0 mg / L

[0039] Sodium phenyl dithiopropane sulfonate 0.2 mg / L

[0040] Sodium isothiourea propanesulfonate 0.5 mg / L;

[0041] The glass substrate was immersed in the plating solution and electroplated at a current density of 2 ASD (DC, 0.77 A) and a temperature of 25°C for 20 minutes. After removal from the plating bath, the substrate was sequentially sprayed with deionized water, dried by blowing, and then cooled to room temperature. The resulting substrate coating was bright and smooth. Optical photography revealed a mirror-like finish on the copper layer, clearly reflecting the image. Figure 2 As shown in a), further SEM scanning results showed that the coating surface had fine crystals and a dense arrangement (as shown in a). Figure 2 (as shown in b).

[0042] After the cross-sectional sample of the substrate coating was cut by ion beam, the average thickness of 5 points was measured by FE-SEM and found to be 5.8 ± 0.1 μm.

[0043] AFM (tapping mode, 10×10μm², 512×512 pixels) surface roughness test results are: Ra=4.5nm, Rq=5.6nm, indicating that the surface has low undulations and no sharp peaks or deep valleys, consistent with the glossy appearance of a specular surface. Optical microscopy (100×, field of view 150 × 150μm², 10 random fields of view) mound count results are: 0 mounds / 100 μm²; no streak was observed with the naked eye or under OM.

[0044] The micro-stretched sample (dog-bone shaped, gauge length 10 mm, width 2 mm, thickness 5.8 μm) tested on a universal testing machine (1 mm / min) showed an elongation of 24 ± 2% and a tensile strength of 215 MPa. This indicates strong adhesion between the coating and the seed layer / glass, with no risk of coating peeling or cracking. The plating solution of this invention can also be used on flexible PI substrates or bendable OLED surfaces to form a heat-dissipating metal layer or electromagnetic shielding mesh with high elongation.

[0045] Example 2

[0046] The acidic sulfate copper plating solution of this invention was used to electroplate a pretreated glass substrate. The composition of the plating solution is as follows:

[0047] Copper sulfate pentahydrate 100 g / L

[0048] 200 g / L sulfuric acid

[0049] Chloride ions 50ppm

[0050] PEG6000 300 mg / L

[0051] JGB 2.0 mg / L

[0052] Sodium phenyl dithiopropane sulfonate 0.5 mg / L

[0053] Sodium isothiourea propanesulfonate 2.0 mg / L.

[0054] The glass substrate was immersed in the plating solution and electroplated at a current density of 4 ASD (DC, 1.54 A) and a temperature of 30°C for 20 minutes. After removal from the plating bath, the substrate was sequentially sprayed with deionized water, dried by blowing, and then cooled to room temperature. The resulting substrate coating was bright and smooth, and optical imaging showed that the copper layer had a mirror-like shine, clearly reflecting the image. Figure 3 As shown in a), the SEM scanning results are similar to those in Example 1, with fine crystallization on the coating surface. Figure 3 (as shown in b).

[0055] The coating thickness, surface roughness, and mechanical strength were tested using the same method as in Example 1. The results are as follows:

[0056] The average thickness of the substrate coating cross-section sample measured at 5 points using FE-SEM was 7.7 ± 0.1 μm.

[0057] The surface roughness test results were: Ra=6.4nm, Rq=8.2nm, indicating no undulations and no sharp peaks or deep valleys; the mound count results under optical microscopy were: 0 mounds / 100 μm²; no streak was observed by the naked eye or under OM.

[0058] Micro-tensile testing results showed that the sample elongation was 22±2% and the tensile strength was 206MPa. This indicates strong adhesion between the coating and the seed layer / glass, with no risk of coating peeling or cracking.

[0059] Electroplating experiments on glass substrates were conducted using different conventional acidic sulfate copper plating solutions (containing different brighteners) in Examples 3 and 4.

[0060] Example 3

[0061] Electroplating was performed on the glass substrate according to the electroplating method of Example 2. After electroplating, the substrate was sprayed with deionized water, dried by blowing, and then cooled to room temperature. The resulting coating had uneven color and some areas were charred. Figure 4 a) SEM scanning results show that the coating has rough crystal structure and poor surface smoothness. Figure 4 b). AFM test results show that the surface roughness Ra=144nm and Rq=181nm, indicating that the coating surface has significant undulations.

[0062] Example 4

[0063] Electroplating was performed on the glass substrate according to the electroplating method of Example 2. After electroplating, the substrate was sprayed with deionized water, dried by blowing, and then cooled to room temperature. The resulting coating was matte throughout the entire board, without any mirror-like gloss. Figure 5 a) SEM scanning results show that the coating has rough crystal structure and poor surface smoothness. Figure 5 b). AFM test results show that the surface roughness Ra=127.6nm and Rq=156.8nm, indicating that the coating surface has obvious undulations and a large number of micro defects.

Claims

1. An acidic sulfate copper plating solution, characterized in that... It contains the following components in the following proportions: Copper sulfate pentahydrate 100–300 g / L Sulfuric acid 50–300 g / L Chloride ions 30-80 ppm polyethylene glycol 50–500 mg / L Gentamicin Green 0.1–5 mg / L Sodium phenyl dithiopropane sulfonate 0.1–1 mg / L Sodium isothiourea propanesulfonate 0.2–5 mg / L; The mass ratio of sodium phenyl dithiopropane sulfonate to sodium isothiourea propane sulfonate is 1:2 to 1:

5.

2. A method for electroplating copper on display panel glass or PI substrate using the acidic sulfate copper plating solution according to claim 1, characterized in that: The acidic sulfate copper plating solution is used to electroplate the substrate under the conditions of current density of 0.1 to 4 ASD and temperature of 18 to 40°C until a copper layer with a thickness of 2 to 50 μm, surface roughness Ra ≤ 12 nm, and no mound protrusions or strand flow lines is formed.

3. The copper electroplating method according to claim 2, wherein the electroplating time on the substrate is 10 to 60 minutes, and the resulting copper layer has a bright mirror finish and an elongation of ≥20%.

4. The application of the copper layer obtained by the electroplating copper method according to claim 2 or 3 in the preparation of ultra-fine metal meshes with line width and line spacing ≥ 2 μm.

5. The application of the acidic sulfate copper plating solution according to claim 1 in the manufacture of OLED, Mini-LED or Micro-LED display panels.

6. The application of the acidic sulfate copper plating solution according to claim 5 in the manufacture of OLED, Mini-LED, or Micro-LED display panels, characterized in that... include: Copper electrodes, electromagnetic shielding grids, or heat dissipation metal layers are formed on the drive backplate.

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