Method for preparing oversized nickel-phosphorus alloy resistive film by chemical plating method

Abstract

The invention provides a method for preparing an oversized nickel-phosphorus alloy resistive film by a chemical plating method, which comprises a chemical plating solution formula and process parameters (pH, temperature and time), and aims to improve the conductivity of a plating solution and find proper process parameters so as to improve the performance of a plating layer and improve the resistance uniformity of the nickel-phosphorus alloy resistive film. The method is suitable for aerospace, electronic circuit and other industries.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit boards, and more particularly, to a method for preparing an extra-large-sized nickel-phosphorus alloy resistive film by electroless plating, which is applicable to the printed circuit board electronic circuit industry. Background Art

[0002] In the context of the rapid development of current electronic technologies, the market's pursuit of multifunctional electronic devices remains unabated. While these devices pursue a thin and light design, they also need to ensure high power output and high integration. This trend poses unprecedented challenges to the design of printed circuit boards (PCBs), requiring more refined and dense circuit designs to leave more space for chips and other electronic components. The embedded resistor technology effectively saves surface space and improves the density of electronic packaging by directly integrating resistors into the PCB substrate.

[0003] Nickel-phosphorus (Ni-P) alloy resistive films have been widely studied and applied in the electronics industry due to their excellent corrosion resistance, high-temperature oxidation resistance, and relatively high resistivity, enabling them to maintain excellent performance in harsh environments. However, current technologies for preparing Ni-P alloy resistive films, such as magnetron sputtering and evaporation plating, require expensive precision equipment and strict environmental control, which to some extent limits their large-scale application in the PCB manufacturing industry, especially in cost-sensitive industries. More critically, the resistance value error of Ni-P alloy resistive films prepared by sputtering often exceeds 15% after etching, failing to meet the production standards of high-precision resistors. Therefore, existing Ni-P alloy resistive film technologies have many problems in terms of manufacturing cost, equipment complexity, and resistance value uniformity. Compared with magnetron sputtering, electroless plating is simple to operate, can carry out autocatalytic reactions without a power supply, reduces production costs, improves production efficiency, and ensures the accuracy and uniformity of resistance values while maintaining the performance of the resistive film, meeting the requirements of the electronic device market. However, uneven local concentration of the plating solution and improper setting of process parameters during electroless plating may lead to poor uniformity of the nickel-phosphorus alloy resistive film coating. Summary of the Invention

[0004] The present invention provides a method for preparing an extra-large-sized nickel-phosphorus alloy resistive film by electroless plating, including an electroless plating solution formulation and process parameters (pH, temperature, time), aiming to improve the conductivity of the plating solution, find suitable process parameters to improve the coating performance and enhance the resistance value uniformity of the nickel-phosphorus alloy resistive film.

[0005] A method for preparing an extra-large-sized nickel-phosphorus alloy resistive film by electroless plating includes the following steps:

[0006] Step 1: Prepare an electroless plating solution using nickel sulfate as the nickel source and sodium hypophosphite as the phosphorus source, and add a complexing agent and a stabilizer.

[0007] Furthermore, the concentration of nickel sulfate is 40 g / L and the concentration of sodium hypophosphite is 20 g / L.

[0008] Furthermore, use succinic acid as the complexing agent and thiourea as the stabilizer.

[0009] Step 2: Clean the copper foil and glass substrate by alkali washing, acid washing, and water washing.

[0010] Furthermore, use 8% dilute sulfuric acid for acid washing.

[0011] Step 3: Place the workpiece in the plating bath for electroless plating to obtain a copper foil with a nickel-phosphorus alloy coating.

[0012] Furthermore, use a metal wire to induce electroless plating.

[0013] Furthermore, the electroless plating temperature is 80 °C and the pH is 3.4.

[0014] Step 4: Clean and dry the coating obtained in Step 3.

[0015] Step 5: Use the high-temperature vacuum hot pressing technology of a laminator to melt and solidify FR4 onto the nickel-phosphorus alloy coating obtained in Step 4 to seal the nickel-phosphorus alloy layer.

[0016] Step 6: Etch the laminated coating obtained in Step 5 with an alkaline etching solution to obtain a laminate containing only the nickel-phosphorus alloy resistance thin film, dry it, and then perform a sheet resistance test (using an RTS-8 four-probe tester) to measure the sheet resistance values at different positions to judge the coating uniformity of the entire nickel-phosphorus alloy resistance thin film.

[0017] Furthermore, the etching temperature is 60 °C and the time is 3 min.

[0018] Furthermore, after etching, place the workpiece in a vacuum oven for 24 h.

[0019] In summary, the present invention aims at the problem of coating resistance uniformity of electroless nickel-phosphorus alloy resistance thin films, and improves the coating uniformity by changing the plating solution formula and optimizing process parameters, which can effectively solve the problem of coating thickness uniformity of electroless nickel-phosphorus alloy resistance thin films. It is applicable to industries such as aerospace and electronic circuits. Description of the Drawings

[0020] Figure 1 SEM images of the nickel-phosphorus alloy resistance film before and after etching (Figure a is before etching and Figure b is after etching);

[0021] Figure 2It is a flow chart for preparing an extra-large-sized nickel-phosphorus alloy resistance film by electroless plating method. Detailed implementation mode

[0022] In combination with the following examples and drawings, the present invention can also be implemented or applied through a variety of different technical solutions. Without departing from the technical concept of the present invention, the technical details described in this technical specification can be subjected to corresponding technical modifications or technical adaptation changes according to different technical perspectives and application requirements.

[0023] Example 1

[0024] Step 1: Configure the electroless plating of nickel-phosphorus alloy, including the concentrations of each component as follows: nickel sulfate 40 g / L, sodium hypophosphite 20 g / L, succinic acid 10 g / L, thiourea 0.5 g / L. Use ammonia water to adjust the pH to 3.4.

[0025] Step 2: Immerse the glass substrate containing copper foil in the alkaline solution for 10 minutes for degreasing and defatting. After cleaning it with deionized water, then immerse it in the acidic solution for 10 minutes and clean it with deionized water.

[0026] Step 3: Start the electroless plating of nickel-phosphorus alloy resistance film. The test conditions are that the temperature of the plating solution is 80 °C, the pH is 3.4, and a metal iron wire is used for the induction reaction.

[0027] Step 4: After obtaining the coating, wash it with water, pickle it with acid, wash it with water again, and then put it into a constant temperature vacuum drying oven for 24 hours. The oven temperature is maintained at 50 °C.

[0028] Step 5: Place the coating plate in a laminator for lamination. Place FR4 on the nickel-phosphorus alloy layer and kraft paper under the copper foil. Melt and solidify FR4 onto the nickel-phosphorus alloy coating through the high-temperature vacuum hot pressing technology of the laminator.

[0029] Step 6: Etch the base copper foil of the nickel-phosphorus alloy resistance film solidified on FR4. Etch off the copper foil on the coating through the alkaline etching solution to obtain the nickel-phosphorus alloy coating, and put it into the oven for drying at a temperature of 50 °C.

[0030] The square resistance of the coating plate is measured by an RTS-8 four-probe tester. The uniformity of the square resistance value is judged by measuring the square resistance at different places of the plated parts. The square resistance of the nickel-phosphorus alloy resistance film is 53.1 Ω / sq, and the non-uniformity is 30%.

[0031] Example 2

[0032] Step 1: Configure the electroless plating of nickel-phosphorus alloy, including the concentrations of each component as follows: nickel sulfate 35 g / L, sodium hypophosphite 25 g / L, succinic acid 12 g / L, thiourea 0.3 g / L.

[0033] Step 2: Immerse the glass substrate with copper foil in an alkaline solution for 10 minutes for degreasing, clean it with deionized water, then immerse it in an acidic solution for 10 minutes, and clean it with deionized water again.

[0034] Step 3: Start electroless plating the nickel - phosphorus alloy resistance film. The test conditions are that the plating solution temperature is 84 °C, the pH is 3.6, and a metal iron wire is used to induce the reaction.

[0035] Step 4: After obtaining the coated layer, wash it with water, pickle it with acid, wash it with water again, and then put it into a constant - temperature vacuum drying oven for 24 hours. The oven temperature is maintained at 50 °C.

[0036] Step 5: Place the coated layer in a laminator for lamination. Place FR4 on the nickel - phosphorus alloy layer and kraft paper under the copper foil. Melt and cure FR4 onto the nickel - phosphorus alloy coating through the high - temperature vacuum hot - pressing technology of the laminator.

[0037] Step 6: Etch the base copper foil of the nickel - phosphorus alloy resistance film cured on FR4. Etch away the copper foil on the coating with an alkaline etching solution to obtain a nickel - phosphorus alloy coating, and put it into an oven for drying at a temperature of 50 °C.

[0038] Measure the sheet resistance of the coated plate using an RTS - 8 four - probe tester. Judge the uniformity of the sheet resistance value by measuring the sheet resistance at different places of the plated part. The sheet resistance of the nickel - phosphorus alloy resistance film is 48.7 Ω / sq, and the non - uniformity is 21.4%.

[0039] Example 3

[0040] Step 1: Prepare the electroless plating of nickel - phosphorus alloy, including the following concentrations of each component: nickel sulfate 45 g / L, sodium hypophosphite 30 g / L, succinic acid 14 g / L, thiourea 0.6 g / L.

[0041] Step 2: Immerse the glass substrate with copper foil in an alkaline solution for 10 minutes for degreasing, clean it with deionized water, then immerse it in an acidic solution for 10 minutes, and clean it with deionized water again.

[0042] Step 3: Start electroless plating the nickel - phosphorus alloy resistance film. The test conditions are that the plating solution temperature is 88 °C, the pH is 3.8, and a metal iron wire is used to induce the reaction.

[0043] Step 4: After obtaining the coated layer, wash it with water, pickle it with acid, wash it with water again, and then put it into a constant - temperature vacuum drying oven for 24 hours. The oven temperature is maintained at 50 °C.

[0044] Step 5: Place the coating into a laminator for lamination. Place FR4 on the nickel-phosphorus alloy layer and kraft paper under the copper foil. Melt and cure the FR4 onto the nickel-phosphorus alloy coating through the high-temperature vacuum hot pressing technology of the laminator.

[0045] Step 6: Etch the base copper foil of the nickel-phosphorus alloy resistance thin film cured on the FR4. Etch away the copper foil on the coating with an alkaline etching solution to obtain a nickel-phosphorus alloy coating, and place it in an oven for drying at a temperature of 50°C.

[0046] Use an RTS-8 four-probe tester to measure the sheet resistance of the coated plate. Judge the uniformity of the sheet resistance value by measuring the sheet resistance at different places on the coated part. The sheet resistance of the nickel-phosphorus alloy resistance thin film is 52.5 Ω / sq, and the non-uniformity is 12.4%.

Claims

1. A method for preparing an extra-large-sized nickel-phosphorus alloy resistive thin film by electroless plating, comprising the following steps: Step 1: Prepare an electroless plating solution using nickel sulfate as the nickel source and sodium hypophosphite as the phosphorus source, and add a complexing agent and a stabilizer. Step 2: Alkaline wash, acid wash, and water wash the copper foil and the glass substrate for cleaning. Step 3: Place the workpiece to be plated in a plating bath for electroless plating to obtain a copper foil with a nickel-phosphorus alloy coating. Step 4: Wash and dry the coating obtained in Step 3. Step 5: Use the high-temperature vacuum hot pressing technology of a laminator to melt and solidify FR4 onto the nickel-phosphorus alloy coating obtained in Step 4 to achieve the effect of sealing the nickel-phosphorus alloy layer. Step 6: Etch the laminated coating obtained in Step 5 with an alkaline etching solution to obtain a laminate containing only the nickel-phosphorus alloy resistive thin film, dry it, and then perform sheet resistance testing (using an RTS-8 four-probe tester) to judge the coating uniformity of the entire nickel-phosphorus alloy resistive thin film by testing the sheet resistance values at different positions.

2. The method for preparing an extra-large-sized nickel-phosphorus alloy resistive film by electroless plating according to claim 1, wherein: In the above Step 1, the concentration of nickel sulfate is 40 g / L, the concentration of sodium hypophosphite is 20 g / L, succinic acid is the complexing agent, and thiourea is the stabilizer.

3. The method for preparing an extra-large-sized nickel-phosphorus alloy resistance thin film by electroless plating according to claim 1, wherein: In the above Step 2, 8% dilute sulfuric acid is used for acid washing.

4. The method for preparing an extra-large-sized nickel-phosphorus alloy resistive film by electroless plating according to claim 1, wherein: In the above Step 3, metal iron wire is used to induce electroless plating, the electroless plating temperature is 80 °C, and the pH is 3.

4.

5. A method for preparing an extra-large-sized nickel-phosphorus alloy resistance thin film by electroless plating according to claim 1, characterized in that: In the above Step 6, the etching temperature is 60 °C and the time is 3 min. After etching, place the workpiece in a vacuum oven for 24 h.

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