Process for electroless nickel-gold plating of capacitive touch screen functional sheet

Abstract

The application discloses a process method for electroless nickel-gold plating of a capacitive touch screen functional sheet, which comprises the following steps: carrying out immersion treatment on a double-sided ITO substrate in a standard alkaline 1 mol / L alkaline solution; immersing the double-sided ITO glass after degreasing treatment in a 5 mol / L acidic etchant HCl solution for immersion treatment; immersing the double-sided ITO glass after micro-etching treatment in a 200 mg / L palladium activator solution for immersion treatment; immersing the double-sided ITO glass after activation treatment in a 30 g / L NaH2PO2 H2O solution of a reducing agent for immersion treatment; immersing the double-sided ITO glass after the post-immersion treatment in a plating solution formula for electroless nickel plating; and baking the double-sided ITO glass after the electroless nickel plating in an oven.

Description

Technical Field

[0001] This invention belongs to the field of touch screen manufacturing technology, specifically relating to a process for electroless nickel-gold plating of functional sheets in a capacitive touch screen. Background Technology

[0002] Touch panel technology originated in the 1970s, initially used in the US military. Subsequently, this technology gradually transitioned to civilian applications. With the development of electronic and network technologies and the widespread adoption of the internet, a new generation of multi-touch capacitive touchscreens (industry terminology: capacitive touchscreens) emerged, gaining widespread acceptance for their durability, fast response speed, space-saving design, and ease of use. Although capacitive touchscreen technology has only been used in my country for a little over a decade, it has already become the most widely accepted human-computer interaction input method after keyboards, mice, handwriting tablets, and voice input. Using this technology, users can operate the device simply by lightly touching icons or text on the display screen, making human-computer interaction more direct. Capacitive touchscreens are widely used in smart consumer electronics, industrial control and medical equipment, smart homes, office equipment, and automotive electronics.

[0003] Traditional manufacturing methods for surface metal layers of functional chips include three types: screen printing silver paste, laser silver paste, and molybdenum-aluminum plating. These products have drawbacks such as high line resistance, poor weather resistance, easy oxidation, unstable quality, high cost, and low cost-effectiveness. They are mainly used in consumer electronics devices and cannot meet the requirements of high reliability, high touch accuracy, and long service life in human-computer interaction applications such as military, industrial control, medical, aerospace, and automotive. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a process for electroless nickel-gold plating of functional chips in a capacitive touchscreen.

[0005] To achieve the above objectives, the present invention provides the following solution: (1) Defatting Double-sided ITO substrates were immersed in a standard alkaline solution of 1 mol / L. (2) Micro-etching The degreased double-sided ITO glass was immersed in a 5 mol / L acidic etchant HCl solution for immersion treatment. (3) Activation The double-sided ITO glass, after micro-etching, was immersed in a palladium activator solution with a concentration of 200 mg / L. (4) Post-immersion The activated double-sided ITO glass was immersed in a NaH2PO2·H2O solution with a reducing agent concentration of 30 g / L. (5) Electroless nickel plating The double-sided ITO glass, after post-immersion treatment, is placed in a plating solution formulation for chemical nickel plating; wherein the plating solution formulation includes: Main salt: NiSO4·6H2O 23g / L Reducing agent: NaH2PO2·H2O 18g / L Complexing agent: Sodium glycolate 20 g / L Buffer: Succinic acid 12g / L Stabilizer: Thiourea 0.5 mg / L Brightener: Sodium dodecyl sulfate 0.1 g / L; (6) Baking to remove hydrogen The double-sided ITO glass, after being electroless nickel-plated, is placed in an oven for baking.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention is based on the excellent properties of electroless nickel-gold plating, which reduces the resistance of the metal layer from... Reduce to This invention improves the adhesion of the metal layer in the lead area, enhances the reliability of signal transmission in high-temperature and high-humidity environments, and improves product performance. Compared with traditional screen-printed silver paste, laser silver paste, and molybdenum-aluminum-molybdenum technologies, the functional chips manufactured using the new chemical nickel-gold plating technology have significant advantages such as high performance, high reliability, high cost-effectiveness (50%-65% of the price of molybdenum-aluminum-molybdenum), low line resistance, and strong line adhesion. It effectively solves the problems of poor reliability of silver paste functional chips in high-temperature and high-humidity environments and insufficient adhesion of molybdenum-aluminum-molybdenum functional chips, effectively reduces signal attenuation, and ensures that the product can be used in harsh environments. Attached Figure Description

[0007] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a flowchart of the process for electroless nickel-gold plating of the capacitive touchscreen functional sheet according to an embodiment of the present invention; Figure 2 The process involves 71 steps for molybdenum-aluminum plating. Figure 3 It consists of 49 steps in the electroless nickel-gold plating process. Detailed Implementation

[0009] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0011] Example 1 like Figure 1 As shown, the present invention provides a process for electroless nickel-gold plating of a capacitive touchscreen functional chip, comprising: 1. Degreasing treatment Target material: Double-sided ITO substrate; Treatment solution: 1 mol / L alkaline solution (preferably sodium hydroxide solution, purity ≥ 99.5%). Process parameters: temperature 50±2℃, impregnation time 3±1 minutes; Post-processing: First wash with hot water at 60±5℃ for 2 minutes, then wash with cold water at 25±5℃ for 2 minutes to ensure that there is no oil residue on the substrate surface and that the water film is continuous and unbroken; Key improvements: Clearly define the specific type and purity of the alkaline solution, precisely control the temperature fluctuation range, and improve the consistency of degreasing.

[0012] 2. Micro-etching treatment Object to be processed: Degreased double-sided ITO glass; Treatment solution: 5 mol / L HCl solution (hydrochloric acid concentration 37%, industrial grade, superior quality); Process parameters: ambient temperature (20-25℃), immersion time 4±1 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time; Quality standard: The ITO surface has a uniform and fine roughness (Ra=0.1-0.3μm) and no excessive etching marks; Key improvements: By limiting the purity of hydrochloric acid and the quality of deionized water, and by clearly defining the roughness control range, the adhesion of the coating is guaranteed.

[0013] 3. Activation treatment Object of treatment: Double-sided ITO glass after micro-etching; Treatment solution: 200 mg / L palladium activator solution (palladium content ≥ 99.9%, dispersant addition 0.5 g / L); Process parameters: ambient temperature (20-25℃), immersion time 3±1 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time, to avoid residual activation solution; Optimization highlights: The purity requirements of the added activator and the ratio of the dispersant are met to reduce palladium particle agglomeration and improve activation uniformity.

[0014] 4. Post-immersion treatment Target material: Activated double-sided ITO glass; Treatment solution: 30 g / L NaH2PO2·H2O reducing agent solution (purity ≥98%, pH 4-5); Process parameters: temperature 50±2℃, impregnation time 3±1 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time; Key improvements: Clearly define the purity and pH range of the reducing agent to enhance the reduction effect and prepare the substrate for nickel plating.

[0015] 5. Electroless nickel plating Object to be processed: Double-sided ITO glass after post-immersion; Plating solution formulation (optimized): Main salt: NiSO4·6H2O 23g / L (purity ≥99.5%). Reducing agent: NaH2PO2·H2O 18g / L (purity ≥98%) Complexing agent: Sodium glycolate 20g / L (purity ≥99%) Buffer: Succinic acid 12g / L (purity ≥99%) Stabilizer: Thiourea 0.5 mg / L (purity ≥ 98%) Brightener: Sodium dodecyl sulfate 0.1 g / L (purity ≥ 98%); Process parameters: pH=4±0.5, temperature 80±2℃, plating bath stirring speed 30-50r / min, plating time 15-20 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time; Quality standards: Coating thickness 0.5-1.0μm, adhesion ≥5N / cm (cross-cut test), line resistance ≤0.5Ω / mm 2 ; Key improvements include the addition of stabilizers and brighteners, optimized stirring parameters and plating time, enhanced coating uniformity and gloss, and clear specifications for thickness and adhesion.

[0016] 6. Baking to remove hydrogen Object to be processed: Double-sided ITO glass after electroless nickel plating; Process parameters: temperature 150±5℃, holding time 30±5 minutes, heating rate 5℃ / min; Cooling method: Cool to room temperature in the furnace (to avoid cracking of the coating due to sudden cooling); Key improvements: By clearly defining the heating rate and cooling method, the internal stress of the coating is reduced, further enhancing adhesion.

[0017] 7. Chemical gold plating (supplementary process) Target of processing: Functional wafers after baking and hydrogen removal; Plating solution formula: Potassium gold cyanide 2g / L, potassium citrate 50g / L, pH=5.5-6.5; Process parameters: Temperature 60±5℃, plating time 3-5 minutes; Post-treatment: Rinse with deionized water 3 times, 1 minute each time, and dry with hot air (60℃, 5 minutes). Functions and effects: Improves the corrosion resistance and conductivity of the metal layer, and extends the product's service life; Optimization highlights: Added gold plating process to adapt to scenarios with higher weather resistance requirements.

[0018] Chemical plating is a novel metal surface treatment and modification technology that can deposit one or more coating layers on the surface of solid materials, thereby endowing the surface of parts with functional properties such as wear resistance, corrosion resistance, high-temperature oxidation resistance, electrical conductivity, magnetic permeability, and reflective heat absorption. It has advantages such as high efficiency, high quality, energy saving, material saving, and environmental protection. This invention, through research on nickel plating solution formulation, incorporation of metal ions to change the crystal lattice, and optimization of process flow, applies the chemical nickel-gold plating process to the manufacture of surface metal layers of functional chips, achieving a design with high reliability, narrow bezel, and high drive path count.

[0019] This invention simplifies the original molybdenum-aluminum plating process for the lead area of ​​capacitive touchscreens from 71 steps to 49 steps for nickel-gold plating. This not only significantly improves work efficiency but also achieves a product yield of over 90%. A comparison of the molybdenum-aluminum plating process and the electroless nickel-gold plating process is as follows: Figure 2 , 3 As shown.

[0020] Traditional electrode lead processing involves plating a full-surface layer of molybdenum-aluminum-molybdenum (MoA) metal onto the product, followed by coating with photosensitive emulsion, exposure, development, and etching to obtain the desired MoA / Mo leads. This invention innovatively achieves metallization of ultrafine electrode lead surfaces by studying the interaction mechanism between the electroless nickel plating layer and the substrate. Because the nickel plating solution only undergoes a reduction reaction on the ITO surface, a strong bond is formed even on nanoscale ITO surfaces. Using this ITO ultrafine electrode lead surface nickel plating process, lead widths and spacings are reduced to less than [a certain value]. This process is simple to operate, saves resources, and achieves green production.

[0021] The present invention has the following technical effects: 1. Performance Improvement: The metal layer line resistance has been reduced from 1.5Ω / mm in traditional processes. 2 Reduced to 0.5Ω / mm 2 The following results demonstrate a 30% improvement in signal transmission reliability under high temperature and high humidity (85℃ / 85%RH, 1000 hours) conditions, with coating adhesion ≥5N / cm and significantly superior corrosion resistance compared to screen printing silver paste and molybdenum plating processes. 2. Cost Optimization: The process cost is only 50%-65% of that of molybdenum-aluminum plating, the number of processes is simplified from 71 to 49, production efficiency is increased by more than 45%, and the product yield is consistently above 90%. 3. Structural Innovation: Achieves lead wire width and spacing ≤20μm, supports narrow bezel and high drive channel design, and adapts to the needs of high-end equipment. 4. Environmental advantages: Reduces the use of harmful chemicals such as photosensitive adhesives and etching solutions, and reduces wastewater discharge by 20%, meeting green production standards. 5. Scope of application: It can meet the high reliability requirements of various scenarios such as military, industrial control, medical, aerospace, and automotive, thus broadening the application fields of capacitive touch screens.

[0022] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A process for electroless nickel-gold plating of functional sheets in a capacitive touchscreen, characterized in that, include: (1) Defatting Double-sided ITO substrates were immersed in a standard alkaline solution of 1 mol / L. (2) Micro-etching The degreased double-sided ITO glass was immersed in a 5 mol / L acidic etchant HCl solution for immersion treatment. (3) Activation The double-sided ITO glass, after micro-etching, was immersed in a palladium activator solution with a concentration of 200 mg / L. (4) Post-immersion The activated double-sided ITO glass was immersed in a NaH2PO2·H2O solution with a reducing agent concentration of 30 g / L. (5) Electroless nickel plating After post-immersion treatment, double-sided ITO glass is placed in a plating solution for chemical nickel plating. (6) Baking to remove hydrogen The double-sided ITO glass, after being electroless nickel-plated, is placed in an oven for baking.

2. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, The plating solution formulation includes: Main salt: NiSO4·6H2O 23g / L Reducing agent: NaH2PO2·H2O 18g / L Complexing agent: Sodium glycolate 20 g / L Buffer: Succinic acid 12g / L Stabilizer: Thiourea 0.5 mg / L Brightener: Sodium dodecyl sulfate 0.1 g / L.

3. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, In the degreasing process Process parameters: temperature 50±2℃, immersion time 3±1 minutes; Post-processing: First wash with hot water at 60±5℃ for 2 minutes, then wash with cold water at 25±5℃ for 2 minutes to ensure that there is no oil residue on the substrate surface and that the water film is continuous and unbroken.

4. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, In the micro-etching process Process parameters: ambient temperature (20-25℃), immersion time 4±1 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time.

5. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, In the activation process Process parameters: ambient temperature (20-25℃), immersion time 3±1 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time.

6. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, In the post-immersion treatment Process parameters: temperature 50±2℃, immersion time 3±1 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time.

7. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, In the electroless nickel plating, Process parameters: pH=4±0.5, temperature 80±2℃, plating bath stirring speed 30-50r / min, plating time 15-20 minutes; Post-treatment: Rinse twice with deionized water (conductivity ≤10μS / cm), 2 minutes each time.

8. The process for electroless nickel-gold plating of the functional sheet of a capacitive touchscreen as described in claim 1, characterized in that, In the baking process to remove hydrogen Process parameters: temperature 150±5℃, holding time 30±5 minutes, heating rate 5℃ / min; Cooling method: Cool to room temperature along with the furnace.

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