Hot-dip tin-plated copper strip capable of reducing surface friction coefficient of copper strip and manufacturing method of hot-dip tin-plated copper strip

Abstract

The invention discloses a hot-dip tinning copper plate strip capable of reducing the surface friction coefficient of a copper strip and a manufacturing method of the hot-dip tinning copper plate strip, relates to the field of hot-dip tinning of copper plate strips, and aims to solve the problem that a product cannot have high hardness and good weldability and corrosion resistance at the same time in the prior art. The method comprises the following steps: plating a pure tin layer on the surface of a copper plate strip in a hot dipping manner, cooling to room temperature, annealing, and preserving heat, so that a Cu6Sn5 layer grows between the copper plate strip and the pure tin layer until the Cu6Sn5 layer grows to occupy more than half of the overall thickness of the plating layer, thereby improving the hardness of the tin plating layer of the copper plate strip. Therefore, the hot-dip tin-plated copper plate strip has high hardness and good weldability and corrosion resistance, and the pure tin layer on the outermost layer can enable the copper plate strip to have low friction coefficient and low insertion and extraction rate and can be used for multi-piece insertion.

Description

Technical Field

[0001] The invention relates to the technical field of hot-dip tinning of copper strips, and in particular to a hot-dip tinning copper strip with a reduced surface friction coefficient and a manufacturing method thereof. Background Art

[0002] The existing processing technology of tin-plated copper strip is to directly immerse pure tin on the copper strip or make a Cu3Sn layer directly attached to a Cu substrate and grow 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 tinning of copper and copper alloy strips". The product has the characteristics of good solderability and corrosion resistance, but poor hardness.

[0004] The process of making the Cu3Sn layer directly attached to the Cu substrate and growing the Cu6Sn5 layer on the Cu3Sn layer is described in Chinese patent CN110592515B, a hot-dip tinned copper material and its manufacturing method. The product features high hardness, but poor weldability and corrosion resistance. The alloy phase scanning electron microscope image is as follows Figure 1 shown.

[0005] From the above product characteristics, it can be seen that the existing processing technology cannot make the product have both high hardness and good weldability and corrosion resistance. 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 tinned copper strip with reduced surface friction coefficient and a manufacturing method thereof, which can effectively solve the problems in the background technology.

[0007] In order to achieve the above-mentioned object, the present invention discloses a hot-dip tinned copper strip for reducing the friction coefficient of the copper strip surface, and the technical scheme adopted is that the hot-dip tinned copper strip comprises a substrate and a coating, the coating is attached to the substrate, the substrate is a copper or copper alloy strip, the coating comprises 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, 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 occupies 50% or more of the thickness of the entire coating, and the thickness of the Sn layer occupies less than 50% of the thickness of the entire coating. The thick Cu6Sn5 layer (alloy phase layer) can improve the hardness of the copper strip, and the pure tin coating can improve the solderability and corrosion resistance of the copper strip.

[0008] As a preferred technical solution of the present invention, the overall thickness of the coating is 1-2 microns.

[0009] The present invention also discloses a method for preparing the hot-dip tinned copper strip, and the technical scheme adopted is comprising the following steps: Step 1, degreasing, removing impurities, cleaning, and pickling the substrate to improve the cleanliness of the substrate surface; Step 2, using a plating agent to assist plating on the substrate, and drying to obtain a pretreated substrate; Step 3, immersing the pretreated substrate obtained in step 2 into a pure tin metal liquid for hot dip plating. After the hot dip plating is completed, taking out the substrate after the hot dip plating, cooling it to room temperature, and obtaining a hot dip tinned copper strip. This step can attach a pure tin plating layer to the surface of the copper strip. Step 4, annealing and heat preservation of the hot-dip tinned copper strip; nitrogen, hydrogen or nitrogen-hydrogen mixed gas is used as a protective gas during annealing to prevent adhesion and oxidation of the tin layer. During the annealing and heat preservation process, the copper element in the substrate will diffuse into the tin layer, so that the Cu6Sn5 layer grows rapidly. As the thickness of the Cu6Sn5 layer increases, the hardness of the copper strip can be increased.

[0010] As a preferred technical solution of the present invention, in step 3, air cooling is used to cool the substrate after immersion plating to room temperature. Air cooling can control the cooling temperature and speed while avoiding the introduction of pollutants.

[0011] As a preferred technical solution of the present invention, in step 4, the annealing temperature is 90-150°C and the holding time is 5-15 hours. This temperature can help the Cu6Sn5 layer to grow rapidly.

[0012] As a preferred technical solution of the present invention, in the step 1, the substrate is degreased using an alkaline degreasing solution with a concentration of 0.3-2% and a temperature of 30-90°C; after the degreasing treatment, the surface of the substrate is scrubbed to remove impurities, and rinsed with clean water to remove impurities generated by scrubbing; the substrate is pickled using H2SO4 with a concentration of 10-20%, a temperature of 15-50°C, and a copper ion concentration of less than 40 g / l.

[0013] As a preferred technical solution of the present invention, in step 2, the substrate is activated by using ammonium bromide and hydrogen bromide and then dried.

[0014] As a preferred technical solution of the present invention, in step 3, the tinning temperature of hot-dip plating is 230-290°C.

[0015] Compared with the prior art, the invention has the following beneficial effects: the invention firstly hot-dip-plates a pure tin coating on the copper strip to improve the solderability and corrosion resistance of the copper strip, and then anneals and insulates the hot-dip tinned copper strip to grow an alloy phase layer, and the alloy phase layer grows to more than half of the coating thickness to improve the hardness of the tin coating of the copper strip. Thus, the hot-dip tinned copper strip can have both high hardness and good solderability and corrosion resistance, and the outermost pure tin layer can make the copper strip have a lower friction coefficient and a low plug-in / pull-out rate, and can be used for multiple single-to-single plug-in. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a scanning electron microscope image of the alloy phase of the hot-dip tin-plated material in the prior art; Figure 2 This is a scanning electron microscope image of the alloy phase of the hot-dip tin-plated material of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0018] This embodiment discloses the first implementation mode of the present invention, which first discloses a hot-dip tinned copper strip for reducing the surface friction coefficient of the copper strip. The technical solution adopted is that it includes a copper strip, on which is attached a Cu3Sn layer that is almost invisible under a 1000x scanning electron microscope. In this embodiment, the Cu3Sn layer is 2nm thick, and there is a Cu6Sn5 layer on the Cu3Sn layer, and there is a pure Sn layer on the Cu6Sn5 layer. The Cu3Sn layer, the Cu6Sn5 layer and the pure Sn layer together constitute a coating, and the overall thickness of the coating is 1 micron. In order to obtain greater strength, the thickness of the Cu6Sn5 layer is 0.75 micron, and the rest of the coating is a pure Sn layer.

[0019] This embodiment also discloses a method for preparing the hot-dip tinned copper strip, the technical solution adopted is, comprising the following steps: Step 1, degreasing the copper strip with alkaline degreasing solution, the concentration of which is 2% and the temperature is 30°C; after degreasing, brushing and removing impurities from the surface of the copper strip, and rinsing with clean water to remove impurities generated by brushing; pickling the copper strip with 10% H2SO4 solution at 50°C, and the copper ion concentration is less than 40 g / l; Step 2, using ammonium bromide and hydrogen bromide to assist plating on the copper strip, and drying to obtain a pretreated copper strip; Step 3, immersing the pretreated copper strip obtained in step 2 into a pure tin metal liquid at a temperature of 290° C. for hot-dip plating. After the plating is completed, taking out the plated copper strip and air-cooling it to room temperature to obtain a hot-dip tinned copper strip; Step 4, annealing the hot-dip tinned copper strip at 150°C and keeping it warm for 5 hours; nitrogen is used as a protective gas during annealing to prevent the tin layer from sticking and oxidizing. Example 2

[0020] This embodiment discloses a second implementation of the present invention, which first discloses a hot-dip tinned copper strip for reducing the surface friction coefficient of the copper strip. The technical solution adopted is that it includes a copper strip, on which is attached a Cu3Sn layer that is almost invisible under a 1000x scanning electron microscope. In this embodiment, the Cu3Sn layer is 5nm thick, and there is a Cu6Sn5 layer on the Cu3Sn layer. The Cu6Sn5 layer is a pure Sn layer. The Cu3Sn layer, the Cu6Sn5 layer and the pure Sn layer together constitute a coating, and the overall thickness of the coating is 2 microns. In order to obtain greater strength, the thickness of the Cu6Sn5 layer is 1.25 microns, and the rest of the coating is a pure Sn layer.

[0021] This embodiment also discloses a method for preparing the hot-dip tinned copper strip, the technical solution adopted is, comprising the following steps: Step 1, degreasing the copper strip with alkaline degreasing solution, the concentration of which is 0.3% and the temperature is 90°C; after degreasing, brushing and removing impurities from the surface of the copper strip, and rinsing with clean water to remove impurities generated by brushing; pickling the copper strip with 20% H2SO4 solution at 15°C, and the copper ion concentration is less than 40 g / l; Step 2, using ammonium bromide and hydrogen bromide to assist plating on the copper strip, and drying to obtain a pretreated copper strip; Step 3, immersing the pretreated copper strip obtained in step 2 into a pure tin metal liquid at a temperature of 230° C. for hot-dip plating. After the plating is completed, taking out the plated copper strip and air-cooling it to room temperature to obtain a hot-dip tinned copper strip; Step 4, annealing the hot-dip tinned copper strip at 90°C and keeping it warm for 15 hours; hydrogen is used as a protective gas during annealing to prevent the tin layer from sticking and oxidizing. Example 3

[0022] This embodiment discloses a third implementation of the present invention, which first discloses a hot-dip tinned copper strip for reducing the surface friction coefficient of the copper strip. The technical solution adopted is that it includes a copper strip, on which is attached a Cu3Sn layer that is almost invisible under a 1000x scanning electron microscope. In this embodiment, the Cu3Sn layer is 7nm thick, and there is a Cu6Sn5 layer on the Cu3Sn layer. The Cu6Sn5 layer is a pure Sn layer. The Cu3Sn layer, the Cu6Sn5 layer and the pure Sn layer together constitute a coating, and the overall thickness of the coating is 1.5 microns. In order to obtain greater strength, the thickness of the Cu6Sn5 layer is 1 micron, and the rest of the coating is a pure Sn layer.

[0023] This embodiment also discloses a method for preparing the hot-dip tinned copper strip, the technical solution adopted is, comprising the following steps: Step 1, degreasing the copper strip with alkaline degreasing solution, the concentration of which is 1% and the temperature is 60°C; after degreasing, brushing the surface of the copper strip to remove impurities, and rinsing with clean water to remove impurities generated by brushing; pickling the copper strip with 15% H2SO4 solution at 30°C, and the copper ion concentration is less than 40 g / l; Step 2, using ammonium bromide and hydrogen bromide to assist plating on the copper strip, and drying to obtain a pretreated copper strip; Step 3, immersing the pretreated copper strip obtained in step 2 into a pure tin metal liquid at a temperature of 260° C. for hot-dip plating. After the plating is completed, taking out the plated copper strip and air-cooling it to room temperature to obtain a hot-dip tinned copper strip; Step 4, annealing the hot-dip tinned copper strip at 120°C and keeping it warm for 10 hours; nitrogen-hydrogen mixed gas is used as a protective gas during annealing to prevent the tin layer from sticking and oxidizing.

[0024] Comparative Example 1: A tinned copper plate prepared by the hot-dip plating method described in Chinese Patent CN107587095B.

[0025] Comparative Example 2: A tinned copper plate prepared by the hot-dip plating method described in Chinese Patent CN110592515B.

[0026] Comparative Example 3: Electroplated tinned copper plate.

[0027] The friction coefficient, hardness, weldability and corrosion resistance of Examples 1-3 and Comparative Examples 1-3 were compared, and the comparison results are as follows:

[0028] Through the above comparison, it can be seen that the friction coefficients of Examples 1 and 3 are significantly lower than those of Comparative Examples 1 and 3, and the friction coefficient of Example 2 is significantly lower than that of Comparative Example 3, and is equivalent to that of Comparative Example 1; the hardness of Examples 1-3 is significantly higher than that of Comparative Example 1 and Comparative Example 3. Although its friction coefficient is higher than that of Example 2, and its hardness is lower than that of Comparative Example 2, its weldability and corrosion resistance have obvious advantages over Comparative Example 2. It can be seen that Examples 1-3 can have the characteristics of high hardness, good weldability and good corrosion resistance while having a lower friction coefficient.

[0029] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hot-dip tinned copper strip for reducing the surface friction coefficient of the copper strip, comprising a substrate and a coating, wherein the coating is attached to the substrate, and the substrate is a copper or copper alloy strip, characterized in that: The coating 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, 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 entire coating thickness, and the thickness of the Sn layer accounts for less than 50% of the entire coating thickness.

2. The hot-dip tinned copper strip for reducing the surface friction coefficient of the copper strip according to claim 1, characterized in that: The overall thickness of the coating is 1-2 microns.

3. A method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip as claimed in claim 1, characterized in that: The following steps are involved: Step 1, degreasing, removing impurities, cleaning and pickling the substrate; Step 2, using a plating agent to assist plating on the substrate, and drying to obtain a pretreated substrate; Step 3, immersing the pretreated substrate obtained in step 2 into a pure tin metal liquid for hot dip plating. After the plating is completed, taking out the substrate after the plating, cooling it to room temperature, and obtaining a hot dip tinned copper strip; Step 4, annealing and heat-insulating the hot-dip tinned copper strip; protective gas needs to be introduced during annealing to prevent the tin layer from sticking and oxidizing.

4. The method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip according to claim 3, characterized in that: In the step 3, air cooling is used to cool the substrate after immersion plating to room temperature.

5. The method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip according to claim 3, characterized in that: In step 4, the annealing temperature is 90-150° C., and the holding time is 5-15 h.

6. The method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip according to claim 3, characterized in that: In the step 1, the substrate is degreased using an alkaline degreasing solution with a concentration of 0.3-2% and a temperature of 30-90°C; after the degreasing treatment, the surface of the substrate is scrubbed to remove impurities, and rinsed with clean water to remove impurities generated by scrubbing; the substrate is pickled using H2SO4 with a concentration of 10-20%, a temperature of 15-50°C, and a copper ion concentration of less than 40 g / l.

7. The method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip according to claim 3, characterized in that: In the step 2, the substrate is activated by using ammonium bromide and hydrogen bromide, and then dried.

8. The method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip according to claim 3, characterized in that: In step 3, the tinning temperature of hot-dip plating is 230-290°C.

9. The method for preparing a hot-dip tinned copper strip with reduced surface friction coefficient of the copper strip according to claim 3, characterized in that: In step 4, the protective gas is nitrogen, hydrogen or a nitrogen-hydrogen mixture.

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