Hot-dip tinned copper strip with reduced surface friction coefficient and manufacturing method thereof

Abstract

This invention discloses a hot-dip tin-plated copper strip with a reduced surface friction coefficient and its manufacturing method. It relates to the field of hot-dip tin plating of copper strips and aims to solve the problem that existing technologies cannot simultaneously achieve high hardness, good solderability, and corrosion resistance. The technical solution involves first hot-dip plating a pure tin layer onto the surface of the copper strip. After cooling to room temperature, annealing and heat preservation are performed to allow a Cu6Sn5 layer to grow between the copper strip and the pure tin layer. This process continues until the Cu6Sn5 layer occupies more than half of the overall plating thickness, thereby increasing the hardness of the tin plating on the copper strip. This achieves a hot-dip tin-plated copper strip that combines high hardness with good solderability and corrosion resistance. Furthermore, the outermost pure tin layer gives the copper strip a low coefficient of friction and a low insertion / extraction rate, making it suitable for multi-unit mating applications.

Description

Technical Field

[0001] This invention relates to the field of hot-dip tin plating technology for copper strips, specifically to a hot-dip tin-plated copper strip with reduced surface friction coefficient and its manufacturing method. Background Technology

[0002] The existing processing technology for tin-plated copper strips involves directly immersing pure tin onto the copper strip or directly attaching the Cu3Sn layer to the Cu substrate, and then growing a Cu6Sn5 layer on the Cu3Sn layer.

[0003] The process of direct immersion plating of pure tin is described in Chinese patent CN107587095B, ​​"An Environmentally Friendly Method for Hot-Dip Tin Plating of Copper and Copper Alloy Plates and Strips." The product is characterized by good solderability and corrosion resistance, but poor hardness.

[0004] The process of directly attaching a Cu3Sn layer to a Cu substrate and growing a Cu6Sn5 layer on top of the Cu3Sn layer is described in Chinese Patent CN110592515B, "A Hot-Dip Tin-Plated Copper Material and Its Manufacturing Method." The product is characterized by high hardness but poor solderability and corrosion resistance. Its alloy phase scanning electron microscope image is shown below. Figure 1 As shown.

[0005] As can be seen from the above product characteristics, existing processing technology cannot make the product have both high hardness and good weldability and corrosion resistance at the same time. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the existing defects and provide a hot-dip tin-plated copper strip with a reduced surface friction coefficient and a method for manufacturing the same, which can effectively solve the problems in the background art.

[0007] To achieve the above objectives, this invention discloses a hot-dip tin-plated copper strip for reducing the surface friction coefficient of copper strips. The technical solution includes a substrate and a plating layer. The plating layer is attached to the substrate, which is a copper or copper alloy strip. The plating layer includes a Cu3Sn layer, a Cu6Sn5 layer, and a Sn layer. The Cu3Sn layer is attached to the substrate, the Cu6Sn5 layer is attached to the Cu3Sn layer, and the Sn layer is attached to the Cu6Sn5 layer. The thickness of the Cu3Sn layer does not exceed 10 nm, the thickness of the Cu6Sn5 layer accounts for 50% or more of the total plating layer thickness, and the thickness of the Sn layer accounts for less than 50% of the total plating layer thickness. The thick Cu6Sn5 layer (alloy phase layer) can improve the hardness of the copper strip, while the pure tin plating layer can improve the solderability and corrosion resistance of the copper strip.

[0008] As a preferred embodiment of the present invention, the overall thickness of the coating is 1-2 micrometers.

[0009] This invention also discloses a method for preparing the above-mentioned hot-dip tin-plated copper strip, the technical solution of which includes the following steps:

[0010] Step 1 involves degreasing, removing impurities, cleaning, and pickling the substrate, thereby improving the cleanliness of the substrate surface.

[0011] Step 2: Apply a flux to the substrate and dry it to obtain a pretreated substrate;

[0012] Step 3: Immerse the pretreated substrate obtained in Step 2 into pure tin molten metal for hot-dip plating. After plating is completed, remove the plating substrate and cool it to room temperature to obtain hot-dip tin-plated copper strip. This step allows a pure tin plating layer to be attached to the surface of the copper strip.

[0013] Step 4: Anneal and heat-hold the hot-dip tin-plated copper strip. During annealing, nitrogen, hydrogen, or a nitrogen-hydrogen mixture is required as a protective gas to prevent the tin layer from sticking and oxidizing. During annealing and heat-holding, copper elements in the substrate diffuse into the tin layer, causing the Cu6Sn5 layer to grow rapidly. As the thickness of the Cu6Sn5 layer increases, the hardness of the copper strip increases.

[0014] In a preferred embodiment of the present invention, in step 3, air cooling is used to cool the substrate after immersion coating to room temperature. Air cooling can control the cooling temperature and rate while avoiding the introduction of contaminating components.

[0015] In a preferred embodiment of the present invention, in step 4, the annealing temperature is 90~150 ℃, and the holding time is 5~15 h. This temperature can help the Cu6Sn5 layer grow rapidly.

[0016] In a preferred embodiment of the present invention, in step 1, an alkaline degreasing solution is used to degrease the substrate at a concentration of 0.3-2% and a temperature of 30-90°C. After degreasing, the surface of the substrate is brushed to remove impurities and rinsed with clean water to remove impurities generated during brushing. The substrate is then pickled using H2SO4 at a concentration of 10-20%, a temperature of 15-50°C, and a copper ion concentration of less than 40 g / L.

[0017] In a preferred embodiment of the present invention, in step 2, the substrate is activated using ammonium bromide and hydrogen bromide, and then dried.

[0018] As a preferred embodiment of the present invention, in step 3, the tin plating temperature of hot-dip plating is 230-290℃.

[0019] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention improves the solderability and corrosion resistance of copper strips by first hot-dip tin plating, and then annealing and heat-holding the hot-dip tin-plated copper strip to allow the growth of an alloy phase layer, which grows to more than half the thickness of the plating layer, thereby increasing the hardness of the tin plating layer on the copper strip. This achieves a hot-dip tin-plated copper strip that combines high hardness with good solderability and corrosion resistance, and the outermost pure tin layer gives the copper strip a low coefficient of friction and a low insertion / extraction rate, making it suitable for multi-unit mating applications. Attached Figure Description

[0020] Figure 1 Scanning electron microscope (SEM) image of the alloy phase of hot-dip tin-plated materials in existing technology;

[0021] Figure 2 This is a scanning electron microscope (SEM) image of the alloy phase of the hot-dip tin-plated material of this invention. Detailed Implementation

[0022] 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. Example 1

[0023] This embodiment discloses the first implementation of the present invention, which first discloses a hot-dip tin-plated copper strip for reducing the surface friction coefficient of copper strip. The technical solution adopted includes a copper strip, on which a Cu3Sn layer that is almost invisible under a 1000x scanning electron microscope is attached. In this embodiment, the thickness of the Cu3Sn layer is 2nm, there is a Cu6Sn5 layer on the Cu3Sn layer, and a pure Sn layer on the Cu6Sn5 layer. The Cu3Sn layer, Cu6Sn5 layer and pure Sn layer together constitute the plating layer. The overall thickness of the plating layer is 1 micrometer. In order to obtain greater strength, the thickness of the Cu6Sn5 layer is 0.75 micrometers, and the remaining part of the plating layer is pure Sn layer.

[0024] This embodiment also discloses a method for preparing the above-mentioned hot-dip tin-plated copper strip, the technical solution of which includes the following steps:

[0025] Step 1: Degrease the copper strip using an alkaline degreasing solution at a concentration of 2% and a temperature of 30°C. After degreasing, brush the surface of the copper strip to remove impurities and rinse it with clean water to remove the impurities generated during brushing. Then, pickle the copper strip using a 10% H2SO4 solution at a temperature of 50°C, with a copper ion concentration of less than 40 g / L.

[0026] Step 2: Use ammonium bromide and hydrogen bromide to perform flux plating on the copper strip, then dry it to obtain a pretreated copper strip;

[0027] Step 3: Immerse the pretreated copper strip obtained in Step 2 into pure molten tin at a temperature of 290 °C for hot-dip tin plating. After the plating is completed, remove the plated copper strip and air-cool it to room temperature to obtain hot-dip tin-plated copper strip.

[0028] Step 4: Anneal the hot-dip tin-plated copper strip at 150 ℃ and hold for 5 h; nitrogen gas is required as a protective gas during annealing to prevent the tin layer from sticking and oxidizing. Example 2

[0029] This embodiment discloses a second implementation of the present invention, which first discloses a hot-dip tin-plated copper strip for reducing the surface friction coefficient of copper strip. The technical solution adopted includes a copper strip, on which a Cu3Sn layer that is almost invisible under a 1000x scanning electron microscope is attached. In this embodiment, the thickness of the Cu3Sn layer is 5nm, there is a Cu6Sn5 layer on the Cu3Sn layer, and a pure Sn layer on the Cu6Sn5 layer. The Cu3Sn layer, Cu6Sn5 layer and pure Sn layer together constitute the plating layer, and the overall thickness of the plating layer is 2 micrometers. In order to obtain greater strength, the thickness of the Cu6Sn5 layer is 1.25 micrometers, and the remaining part of the plating layer is pure Sn layer.

[0030] This embodiment also discloses a method for preparing the above-mentioned hot-dip tin-plated copper strip, the technical solution of which includes the following steps:

[0031] Step 1: Degrease the copper strip using an alkaline degreasing solution with a concentration of 0.3% at a temperature of 90℃. After degreasing, brush the surface of the copper strip to remove impurities and rinse it with clean water to remove the impurities generated during brushing. Then, pickle the copper strip using a 20% H2SO4 solution at a temperature of 15℃, with a copper ion concentration of less than 40 g / l.

[0032] Step 2: Use ammonium bromide and hydrogen bromide to perform flux plating on the copper strip, then dry it to obtain a pretreated copper strip;

[0033] Step 3: Immerse the pretreated copper strip obtained in Step 2 into pure tin liquid at a temperature of 230 °C for hot-dip tin plating. After the plating is completed, take out the plated copper strip and air-cool it to room temperature to obtain hot-dip tin-plated copper strip.

[0034] Step 4: Anneal the hot-dip tin-plated copper strip at 90 ℃ and hold for 15 h; hydrogen is required as a protective gas during annealing to prevent the tin layer from sticking and oxidizing. Example 3

[0035] This embodiment discloses a third implementation of the present invention, which first discloses a hot-dip tin-plated copper strip for reducing the surface friction coefficient of copper strip. The technical solution adopted includes a copper strip, on which a Cu3Sn layer that is almost invisible under a 1000x scanning electron microscope is attached. In this embodiment, the thickness of the Cu3Sn layer is 7nm, there is a Cu6Sn5 layer on the Cu3Sn layer, and a pure Sn layer on the Cu6Sn5 layer. The Cu3Sn layer, Cu6Sn5 layer and pure Sn layer together constitute the plating layer, and the overall thickness of the plating layer is 1.5 micrometers. In order to obtain greater strength, the thickness of the Cu6Sn5 layer is 1 micrometer, and the remaining part of the plating layer is pure Sn layer.

[0036] This embodiment also discloses a method for preparing the above-mentioned hot-dip tin-plated copper strip, the technical solution of which includes the following steps:

[0037] Step 1: Degrease the copper strip using an alkaline degreasing solution with a concentration of 1% at a temperature of 60°C. After degreasing, brush the surface of the copper strip to remove impurities and rinse it with clean water to remove the impurities generated during brushing. Then, pickle the copper strip using a 15% H2SO4 solution at a temperature of 30°C, with a copper ion concentration of less than 40 g / L.

[0038] Step 2: Use ammonium bromide and hydrogen bromide to perform flux plating on the copper strip, then dry it to obtain a pretreated copper strip;

[0039] Step 3: Immerse the pretreated copper strip obtained in Step 2 into pure tin liquid at a temperature of 260 °C for hot-dip tin plating. After the plating is completed, take out the plated copper strip and air-cool it to room temperature to obtain hot-dip tin-plated copper strip.

[0040] Step 4: Anneal the hot-dip tin-plated copper strip at 120 ℃ and hold for 10 h; nitrogen-hydrogen mixture is required as a protective gas during annealing to prevent tin layer adhesion and oxidation.

[0041] Comparative Example 1: Tin-plated copper plate prepared according to the hot-dip plating method described in Chinese Patent CN107587095B.

[0042] Comparative Example 2: Tin-plated copper plate prepared according to the hot-dip plating method described in Chinese Patent CN110592515B.

[0043] Comparative Example 3: Electroplated tin copper plate.

[0044] The friction coefficient, hardness, weldability, and corrosion resistance of Examples 1-3 and Comparative Examples 1-3 were compared, and the results are as follows:

[0045]

[0046] The above comparison shows that the coefficients of friction of Examples 1 and 3 are significantly lower than those of Comparative Examples 1 and 3, while the coefficient of friction of Example 2 is significantly lower than that of Comparative Example 3 and comparable to that of Comparative Example 1. The hardness of Examples 1-3 is significantly higher than that of Comparative Examples 1 and 3. Although their coefficients of friction are higher than those of Example 2 and their hardness is lower than that of Comparative Example 2, their weldability and corrosion resistance are significantly superior to those of Comparative Example 2. Therefore, Examples 1-3 can achieve a low coefficient of friction while possessing high hardness, good weldability, and good corrosion resistance.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing hot-dip tin-plated copper strip with reduced surface friction coefficient, characterized in that, Includes the following steps: Step 1: Degrease, remove impurities, clean, and pickle the substrate; the substrate is a copper or copper alloy plate or strip. Step 2: Apply a flux to the substrate and dry it to obtain a pretreated substrate; Step 3: Immerse the pretreated substrate obtained in Step 2 into pure molten tin for hot-dip plating. After the plating is completed, remove the plating substrate and cool it to room temperature to obtain hot-dip tin-plated copper strip. Step 4: Anneal and heat-hold the hot-dip tin-plated copper strip; a protective gas needs to be introduced during annealing to prevent the tin layer from sticking and oxidizing. In step 3, the tin plating temperature for hot-dip tin plating is 230-290 ℃; In step 4, the annealing temperature is 90~150 ℃, and the holding time is 5~15 h; thereby attaching a coating on the substrate, the coating including a Cu3Sn layer, a Cu6Sn5 layer, and a Sn layer, the Cu3Sn layer being attached to the substrate, the Cu6Sn5 layer being attached to the Cu3Sn layer, the Sn layer being attached to the Cu6Sn5 layer, the thickness of the Cu3Sn layer not exceeding 10 nm, the thickness of the Cu6Sn5 layer accounting for more than 50% of the total thickness of the coating, and the thickness of the Sn layer accounting for less than 50% of the total thickness of the coating.

2. The method for preparing hot-dip tin-plated copper strip with reduced surface friction coefficient according to claim 1, characterized in that: In step 3, air cooling is used to cool the dip-coated substrate to room temperature.

3. The method for preparing hot-dip tin-plated copper strip with reduced surface friction coefficient according to claim 1, characterized in that: In step 1, the substrate is degreased using an alkaline degreasing solution at a concentration of 0.3-2% and a temperature of 30-90℃. After degreasing, the substrate surface is brushed to remove impurities and rinsed with clean water to remove the impurities generated during brushing. The substrate is then pickled using H2SO4 at a concentration of 10-20%, a temperature of 15-50℃, and a copper ion concentration of less than 40 g / L.

4. The method for preparing hot-dip tin-plated copper strip with reduced surface friction coefficient according to claim 1, characterized in that: In step 2, the substrate is activated using ammonium bromide and hydrogen bromide, and then dried.

5. The method for preparing hot-dip tin-plated copper strip with reduced surface friction coefficient according to claim 1, characterized in that: In step 4, the protective gas is nitrogen, hydrogen, or a nitrogen-hydrogen mixture.

6. The method for preparing hot-dip tin-plated copper strip with reduced surface friction coefficient according to claim 1, characterized in that: The overall thickness of the coating is 1-2 micrometers.

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