Auxiliary cathode design for preparing uniform nickel-phosphorus alloy resistive film through electroplating

Abstract

The invention relates to an auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistive film by electroplating, which aims at the edge polarization effect generated by electroplating the nickel-phosphorus alloy resistive film, changes the distribution of electric field lines by adding an auxiliary cathode, and improves the uniformity of a plating layer by adjusting the width of a copper sheet, the front-back distance and the like. And the edge polarization effect caused by electroplating can be effectively solved. 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 in particular to an auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating, which is used for the nickel-phosphorus alloy resistance film. Background Art

[0002] In today's era of rapid advancements in electronic technology, market demand for multifunctional electronic devices continues to rise. These devices not only strive for smaller and lighter designs but also must ensure high power output and a high degree of integration. This trend presents unprecedented challenges for printed circuit board (PCB) design, requiring increasingly sophisticated and compact circuitry to free up more mounting space for chips and other electronic components. Embedded resistor technology utilizes resistor integration technology to embed resistors directly into the PCB substrate, effectively conserving surface space and increasing the density of electronic packaging.

[0003] Nickel-phosphorus alloy resistor films have been widely researched and adopted in the electronics industry due to their excellent corrosion resistance, high-temperature oxidation resistance, high resistivity, and excellent performance in harsh operating environments. However, current technologies used to produce nickel-phosphorus alloy resistor films, such as magnetron sputtering and evaporation, require sophisticated equipment and strict environmental control, which to some extent limits their large-scale application in the PCB manufacturing industry, especially in industries with low profit margins. Furthermore, the resistance value error of nickel-phosphorus alloy resistor films produced by sputtering often exceeds 15% after the etching process, which is far from meeting the production requirements of high-precision resistors. Therefore, existing nickel-phosphorus alloy resistor film technologies have many shortcomings in terms of manufacturing cost, equipment complexity, and resistance uniformity of the resistor material. Compared with magnetron sputtering, electroplating reduces production costs and improves production efficiency while maintaining the performance of the resistor film. It also ensures the accuracy and uniformity of the resistance value to meet the growing demand of the electronic device market. However, due to the application of external current during the electroplating process, the distribution of electric field lines is uneven, resulting in uneven thickness of the resulting coating, with thinner edges and thicker center. This in turn affects the resistance uniformity of the entire resistor film. Summary of the Invention

[0004] In view of the above uneven coating situation, in order to improve the uniformity of the nickel-phosphorus alloy resistance film through the process, the present invention provides an auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating.

[0005] An auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating includes the following steps:

[0006] Step 1. Use a glass substrate that is larger than the copper foil, and place a hollow rectangular copper sheet on the outer circle of the copper foil. The width of the copper sheet is 1-10mm, and use 4 plastic screws to fix the copper sheet and the glass substrate. The distance between the copper sheet and the copper foil can be changed by changing the length of the screws. The distance between the copper foil and the copper sheet is generally 0-5mm.

[0007] Step 2: Clean the required copper sheet and glass substrate.

[0008] Step 3: Fix the clean copper sheet vertically on the glass substrate with plastic screws and place it on the outside of the copper foil to form an auxiliary cathode.

[0009] Step 4: Place the copper foil plate with the auxiliary cathode obtained in step 3 in the electroplating solution, use a nickel plate of the same size as the copper foil as the anode, apply constant current direct current for electroplating, and obtain a copper foil with a nickel-phosphorus alloy coating.

[0010] Step 5: Clean and dry the coating obtained in step 4.

[0011] Step 6: Remove the coating on the auxiliary cathode copper sheet in step 4 and clean it to obtain a clean auxiliary cathode copper sheet.

[0012] Step 7: The plated layer obtained in step 5 is laminated together with the FR4 and the copper foil having the plated layer by lamination technology to achieve the effect of sealing the nickel-phosphorus alloy layer.

[0013] Step 8: Etch the laminated coating obtained in step 7 with an alkaline etching solution to obtain a laminate containing only the nickel-phosphorus alloy resistor film. After drying, perform a square resistance test (using an RTS-8 four-probe tester) to test the square resistance values at different positions to determine the coating uniformity of the entire nickel-phosphorus alloy resistor film.

[0014] Step 9: According to the uniformity of the nickel-phosphorus alloy resistor film obtained in step 8, the width of the copper sheet is appropriately adjusted and the position of the copper sheet is moved forward and backward, and then steps 4-8 are repeated until a nickel-phosphorus alloy resistor film with good uniformity is obtained.

[0015] Furthermore, in the above step 8, the process technology is in vacuum conditions, and the FR4 is placed on the side with the nickel-phosphorus alloy coating and hot-pressed at high temperature so that it is solidified onto the coating, thereby achieving a sealing effect.

[0016] Furthermore, the fixing screws are made of plastic.

[0017] Furthermore, the copper sheet and the glass substrate are fixed by nuts, and the width of the nuts between the copper sheet and the glass substrate is less than 2 mm.

[0018] Furthermore, the distance between the copper sheet and the copper foil is at most 4 mm.

[0019] In summary, the present invention addresses the edge polarization effect caused by electroplating nickel-phosphorus alloy resistor thin films by adding an auxiliary cathode to modify the distribution of electric field lines and improving the uniformity of the coating by adjusting the width of the copper sheet and the distance between the front and back. This effectively addresses the edge polarization effect caused by electroplating and is suitable for industries such as aerospace and electronic circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 3D schematic diagram of the auxiliary cathode structure in Example 1;

[0021] Figure 2 The three-view diagram of the auxiliary cathode structure in Example 1;

[0022] Figure 3 This is a flow chart of Example 1. DETAILED DESCRIPTION

[0023] The following examples and accompanying drawings will allow those skilled in the art to easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention may also be implemented or applied through different specific embodiments, and the details in this specification may be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] Example 1

[0025] Step 1: prepare a nickel-phosphorus alloy electroplating solution, including the following concentrations of each component: 360 g / L nickel sulfamate, 120 g / L phosphorous acid, 60 g / L sodium dihydrogen phosphate, and adjust the pH to 1.4 using aqueous ammonia.

[0026] Step 2: According to Figure 1 、 2 As shown, the plated component measures 200 mm x 170 mm. Therefore, a 5 mm wide copper sheet, 10 mm from the component, and 2 mm thick was used. Four 5 mm long plastic screws attached the copper sheet to the glass substrate, with a distance of 1 mm between the sheet and the copper foil. The copper sheet remained parallel to the copper foil, but not in the same plane.

[0027] Step 3: Preparation of nickel-phosphorus alloy resistor film

[0028] The glass substrate with copper foil was cleaned, alkaline degreased, pickled, and washed with water as the cathode. After washing, it was immediately placed in the plating tank. A nickel plate of the same size was used as the anode and the test was ready to begin. The test conditions were a plating bath temperature of 55°C and a current density of 2A / dm 2 , DC power supply was used for electroplating, and the electroplating time was controlled at 210s.

[0029] The copper foil containing the nickel-phosphorus alloy coating was cleaned and dried, and then placed in a constant temperature vacuum drying oven at 50° C. for 8 hours.

[0030] The dried alloy plating layer is laminated, and the epoxy resin is melted and cured on the nickel-phosphorus alloy layer using high temperature and high pressure.

[0031] The plated layer after lamination is etched, and the copper foil on the plated layer is etched away by an alkaline etching solution to obtain an FR4 board containing only the plated layer, which is then dried.

[0032] The alloy plated board is tested for square resistance using an RTS-8 four-probe tester. By testing the square resistance at different locations and performing mathematical statistics, the uniformity of the coating is determined.

[0033] The RTS-8 four-probe tester tested the nickel-phosphorus alloy resistor film to a square resistance of 53.1Ω / sq and a non-uniformity of 14% through the design of the auxiliary cathode.

[0034] Example 2

[0035] Step 1: prepare a nickel-phosphorus alloy electroplating solution, including the following concentrations of each component: 360 g / L nickel sulfamate, 120 g / L phosphorous acid, 60 g / L sodium dihydrogen phosphate, and adjust the pH to 1.4 using aqueous ammonia.

[0036] Step 2: According to Figure 1 、 2 As shown, the plated component measures 200 mm x 170 mm. Therefore, a 3 mm wide copper sheet, 7 mm from the plated component, and 2 mm thick was used. Four 5 mm long plastic screws attached the copper sheet to the glass substrate, with a distance of 3 mm between the sheet and the copper foil. The copper sheet remained parallel to the copper foil, but not in the same plane.

[0037] Step 3: Preparation of nickel-phosphorus alloy resistor film

[0038] The glass substrate with copper foil was cleaned, alkaline degreased, pickled, and washed with water as the cathode. After washing, it was immediately placed in the plating tank. A nickel plate of the same size was used as the anode and the test was ready to begin. The test conditions were a plating bath temperature of 55°C and a current density of 2A / dm 2 , DC power supply was used for electroplating, and the electroplating time was controlled at 210s.

[0039] The copper foil containing the nickel-phosphorus alloy coating was cleaned and dried, and then placed in a constant temperature vacuum drying oven at 50° C. for 8 hours.

[0040] The dried alloy plating layer is laminated, and the epoxy resin is melted and cured on the nickel-phosphorus alloy layer using high temperature and high pressure.

[0041] The plated layer after lamination is etched, and the copper foil on the plated layer is etched away by an alkaline etching solution to obtain an FR4 board containing only the plated layer, which is then dried.

[0042] The alloy plated board is tested for square resistance using an RTS-8 four-probe tester. By testing the square resistance at different locations and performing mathematical statistics, the uniformity of the coating is determined.

[0043] The RTS-8 four-probe tester tested the nickel-phosphorus alloy resistor film to a square resistance of 52.4Ω / sq and a non-uniformity of 9% through the design of the auxiliary cathode.

[0044] Example 3

[0045] Step 1: prepare a nickel-phosphorus alloy electroplating solution, including the following concentrations of each component: 360 g / L nickel sulfamate, 120 g / L phosphorous acid, 60 g / L sodium dihydrogen phosphate, and adjust the pH to 1.4 using aqueous ammonia.

[0046] Step 2: According to Figure 1 、 2 As shown, the plated component measures 200 mm x 170 mm. Therefore, a 7 mm wide copper sheet, 3 mm from the plated component, and 2 mm thick was used. Four 5 mm long plastic screws attached the copper sheet to the glass substrate, with a distance of 6 mm between the sheet and the copper foil. The copper sheet remained parallel to the copper foil, but not in the same plane.

[0047] Step 3: Preparation of nickel-phosphorus alloy resistor film

[0048] The glass substrate with copper foil was cleaned, alkaline degreased, pickled, and washed with water as the cathode. After washing, it was immediately placed in the plating tank. A nickel plate of the same size was used as the anode and the test was ready to begin. The test conditions were a plating bath temperature of 55°C and a current density of 2A / dm 2 , DC power supply was used for electroplating, and the electroplating time was controlled at 210s.

[0049] The copper foil containing the nickel-phosphorus alloy coating was cleaned and dried, and then placed in a constant temperature vacuum drying oven at 50° C. for 8 hours.

[0050] The dried alloy plating layer is laminated, and the epoxy resin is melted and cured on the nickel-phosphorus alloy layer using high temperature and high pressure.

[0051] The plated layer after lamination is etched, and the copper foil on the plated layer is etched away by an alkaline etching solution to obtain an FR4 board containing only the plated layer, which is then dried.

[0052] The alloy plated board is tested for square resistance using an RTS-8 four-probe tester. By testing the square resistance at different locations and performing mathematical statistics, the uniformity of the coating is determined.

[0053] The RTS-8 four-probe tester tested the nickel-phosphorus alloy resistor film to a square resistance of 49.7Ω / sq and a non-uniformity of 10% through the design of the auxiliary cathode.

Claims

1. An auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating, comprising the following steps: Step 1: Use a glass substrate that is larger than the copper foil, and place a hollow rectangular copper sheet on the outer circle of the copper foil. The width of the copper sheet is 1-10mm, and use 4 plastic screws to fix the copper sheet and the glass substrate. The distance between the copper sheet and the copper foil can be changed by changing the length of the screws. The distance between the copper foil and the copper sheet is generally 0-5mm. Step 2: Clean the required copper sheet and glass substrate. Step 3: Fix the clean copper sheet vertically on the glass substrate with plastic screws and place it on the outside of the copper foil to form an auxiliary cathode. Step 4: Place the copper foil plate with the auxiliary cathode obtained in step 3 in the electroplating solution, use a nickel plate of the same size as the copper foil as the anode, apply constant current direct current for electroplating, and obtain a copper foil with a nickel-phosphorus alloy coating. Step 5: Clean and dry the coating obtained in step 4. Step 6: Remove the coating on the auxiliary cathode copper sheet in step 4 and clean it to obtain a clean auxiliary cathode copper sheet. Step 7: The plated layer obtained in step 5 is laminated together with the FR4 and the copper foil having the plated layer by lamination technology to achieve the effect of sealing the nickel-phosphorus alloy layer. Step 8: Etch the laminated coating obtained in step 7 with an alkaline etching solution to obtain a laminate containing only the nickel-phosphorus alloy resistor film. After drying, perform a square resistance test (using an RTS-8 four-probe tester) to test the square resistance values at different positions to determine the coating uniformity of the entire nickel-phosphorus alloy resistor film. Step 9: According to the uniformity of the nickel-phosphorus alloy resistor film obtained in step 8, the width of the copper sheet is appropriately adjusted and the position of the copper sheet is moved forward and backward, and then steps 4-8 are repeated until a nickel-phosphorus alloy resistor film with good uniformity is obtained.

2. The auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating according to claim 1, characterized in that: The process technology in the above step 8 is in vacuum conditions, and the FR4 is placed on the side with the nickel-phosphorus alloy coating and hot-pressed at high temperature so that it solidifies onto the coating, thereby achieving a sealing effect.

3. The auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating as claimed in claim 1, characterized in that: The fixing screws are made of plastic.

4. The auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating as claimed in claim 1, characterized in that: The copper sheet and the glass substrate are fixed by nuts, and the width of the nuts between the copper sheet and the glass substrate is less than 2 mm.

5. The auxiliary cathode design for preparing a uniform nickel-phosphorus alloy resistance film by electroplating as claimed in claim 1, characterized in that: The distance between the copper sheet and the copper foil is at least 4mm.

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