Method for controlling uniformity of tin coating of hot-dip tin-plated copper strip

Abstract

The invention discloses a method for controlling the uniformity of a tin coating of a hot-dip tin-plated copper strip, which comprises the following steps of: carrying out electrolytic cleaning and hydrogen deoxygenation treatment on the surface of the copper strip, and preheating; the copper strip is obliquely immersed in tin liquor in the running direction, the temperature of the tin liquor in the tin plating process is kept at 240-290 DEG C, the apparent viscosity of the tin liquor is 10-60 cp, and the tin plating speed is 0.3-1.5 m / min; after tin plating is finished, air cooling is conducted to the room temperature, and the stripping force of a tin plating layer of the copper strip obtained through the method ranges from 1 N / cm < 2 > to 8 N / cm < 2 >; the tin coating on the surface of the copper strip is uniform in thickness, and the thickness deviation is within + / -5%; the surface of the copper strip is flat and smooth, defects such as unevenness, blistering and air holes are avoided, and the service life and the application value of the hot-dip tin-plated copper strip are remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the field of copper strip surface treatment, and in particular to a method for controlling the uniformity of a tinning layer of a hot-dip tinned copper strip. Background Art

[0002] Tin is a white metal with metallic luster. It is resistant to discoloration, soft, non-toxic and ductile. Tin plating has excellent corrosion resistance, solderability and decorative properties, and is widely used in electronic components, sliding parts, connectors and decorative parts. The hot-dip plating process is a metallurgical alloy coating formed between the metal substrate and the plating metal through interpenetration, chemical reaction, diffusion and other methods.

[0003] Hot-dip tinned copper strip is an important material widely used in the fields of electronics, electrical engineering, communications, etc. The uniformity of the tinned layer on its surface has an important influence on the performance and service life of the material. However, there are some defects in the uniformity control of the tinned layer on the surface of ordinary hot-dip tinned copper strips on the market, such as uneven thickness of the tinned layer, looseness on the surface, pores and other defects, which shorten the service life of the material and reduce its application value.

[0004] At present, the method for controlling the uniformity of the tinning layer on the surface of hot-dip tinned copper strip is mainly achieved by controlling the temperature of the tinning solution, the immersion time, the stirring speed and other parameters. However, these methods have many defects, such as the inability to accurately control the thickness and uniformity of the tinning layer, and the inability to avoid defects such as looseness and pores on the surface. Summary of the invention

[0005] The object of the present invention is to provide a method for controlling the uniformity of the tinned layer of a hot-dip tinned copper strip, wherein the peeling force of the tinned layer of the copper strip obtained by the method is 1 to 8 N / cm 2 The tin plating thickness on the copper strip surface is uniform, and the thickness deviation at each location is within ±5%; the surface of the copper strip is flat and smooth, without defects such as unevenness, bubbles, and pores.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for controlling uniformity of a tinned layer of a hot-dip tinned copper strip, the method comprising the following steps:

[0008] (1) The copper strip surface is electrolytically cleaned and hydrogen deoxidized, and preheated to improve the adhesion, permeability and uniformity of the plating solution;

[0009] (2) Immerse the copper strip obliquely in the tin solution along the running direction, maintain the temperature of the tin solution at 240-290°C, the apparent viscosity of the tin solution at 10-60cp, and the tinning speed at 0.3-1.5m / min during the tinning process;

[0010] (3) After tinning, use normal temperature water mist to cool down to room temperature. This ensures that the cooling rate of the tinned layer on the surface of the copper strip is the same to achieve good cooling uniformity and avoid obvious dents or damage to the tin layer on the surface of the copper strip.

[0011] In step (1), the preheating temperature is 120-230° C., and the time is 5-25 min. After preheating by the large-area induction heating module, the temperature difference between the copper strip and the tin liquid when the copper strip is immersed in the tin liquid will be as small as possible, which can avoid the copper strip surface being unstable due to rapid heating, resulting in tinning (i.e., poor adhesion of the tin liquid).

[0012] The weight ratio of tin powder, acid solution and surfactant in the tin liquid is 90-98:2.8-3.5:2-2.5. This combination of raw materials can ensure that the tin liquid has suitable acidity, viscosity and tin ion concentration. Under the condition of a tin plating speed of 0.3-1.5m / min, the use of the tin liquid can form a tin plating layer of uniform thickness. In the tin liquid formula provided by the present invention, the weight proportion of tin powder in the entire formula ensures the stability of the chemical composition of the tin liquid; the acid liquid promotes the electrochemical reaction of tin by providing a suitable acidic environment, and ensures that the tin plating layer has the required quality and corrosion resistance; the surfactant can adjust the viscosity of the tin liquid and improve its fluidity, thereby making the tin plating process smoother.

[0013] When using this tin liquid for tin plating, the tin plating speed is set in the range of 0.3 to 1.5 m / min. This speed range can ensure that a uniform tin plating layer is formed within a certain period of time to meet application requirements. In addition, since the composition of the tin liquid is strictly controlled and the tin ion concentration is appropriate, the quality and performance of the tin plating layer are further ensured.

[0014] The preparation method of the tin liquid is as follows: mixing the raw materials in the formula amount and heating them to 240° C. to 250° C. to melt them.

[0015] The acid solution is hydrochloric acid or sulfuric acid.

[0016] The surfactant is any one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and dodecylphenol polyoxyethylene ether.

[0017] In step (2), when the copper strip is immersed in the tin liquid, the copper strip and the surface of the tin liquid form an angle of 10° to 40°. Such an angle of entry can increase the contact area between the copper strip and the tin liquid, thereby improving wettability. Improving wettability helps the copper strip to better interact and combine with the tin liquid, making the reaction between the copper strip and the tin liquid more complete and accelerating the reaction rate; and such an angle of entry can reduce the possibility of air being trapped under the coating, thereby reducing the formation of bubbles and defects, making the coating more evenly plated on the surface of the copper strip, improving the quality of the coating, and increasing the service life of the copper strip. An angle that is too large or too small will result in uneven coating, while an angle of 10° to 40° can provide a better balance, making the coating more evenly distributed.

[0018] In step (2), the temperature variation range of the tin liquid during the tin plating process does not exceed ±15°C, so as to prevent the tin liquid temperature at various locations from fluctuating greatly on the same copper plate substrate, resulting in uneven adhesion of the tin plating layer on the copper plate substrate due to excessive temperature differences, and ultimately resulting in uneven thickness of the tin plating layer on the surface or obvious tinning.

[0019] In step (2), the tinning time is 5 to 30 seconds.

[0020] The thickness of the coating is 0.1-2.5 μm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention pre-treats the copper strip and comprehensively controls the composition of the plating solution, the temperature of the plating solution, the viscosity and the tinning speed during the hot-dip tinning process to accurately control the thickness and uniformity of the tinning layer, thereby avoiding defects such as looseness and pores on the surface. The peeling force of the tinning layer of the copper strip obtained by the method is 1 to 8 N / cm 2 The thickness of the tinned layer on the surface of the copper strip is uniform, and the thickness deviation at each location is within ±5%; the surface of the copper strip is flat and smooth. This method can significantly improve the service life and application value of the hot-dip tinned copper strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of copper strip immersed in tin liquid. DETAILED DESCRIPTION

[0024] The present invention provides a method for controlling uniformity of a tinning layer of a hot-dip tinned copper strip, comprising the following steps:

[0025] (1) The surface of the copper strip is electrolytically cleaned and deoxidized with hydrogen, and preheated at 120 to 230° C. for 5 to 25 minutes;

[0026] (2) The copper strip is immersed in the tin liquid obliquely along the running direction, and the copper strip and the surface of the tin liquid are at an angle of 10° to 40° when the copper strip is immersed in the tin liquid. The temperature of the tin liquid is maintained at 240 to 290°C during the tinning process, and the temperature variation range does not exceed ±20°C. The apparent viscosity of the tin liquid is 10 to 60 cp, and the tinning speed is 0.3 to 1.5 m / min;

[0027] (3) After tin plating, spray with normal temperature water mist and cool to room temperature to obtain a coating with a thickness of 0.1 to 2.5 μm.

[0028] The tin liquid is composed of tin powder, acid solution and surfactant in a weight ratio of 90-98:2.8-3.5:2-2.5.

[0029] The acid solution is hydrochloric acid or sulfuric acid.

[0030] The surfactant is any one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and dodecylphenol polyoxyethylene ether.

[0031] The present invention is described in detail below with reference to the embodiments.

[0032] The copper strips in the various embodiments have a width of 650 mm and a thickness of 1.5 mm.

[0033] Example 1

[0034] A method for controlling uniformity of a tinned layer of a hot-dip tinned copper strip comprises the following steps:

[0035] (1) The copper strip surface is electrolytically cleaned and deoxidized with hydrogen, and preheated at 200°C for 10 minutes;

[0036] (2) tin powder, sulfuric acid, and sodium dodecylbenzene sulfonate are mixed in a weight ratio of 90:2.8:2.0 and melted at 240°C to obtain a tin liquid with an apparent viscosity of 32cp; the copper strip is immersed in the tin liquid obliquely along the running direction, and the copper strip and the surface of the tin liquid form an angle of 30° when the copper strip is immersed in the tin liquid. During the tin plating process, the temperature of the tin liquid is maintained at 265°C and the temperature variation range does not exceed ±2°C, the tin plating speed is 0.5m / min, and the tin plating time is 10s;

[0037] (3) After tin plating, the surface is cooled to room temperature by spraying with water mist at room temperature to obtain a coating with a thickness of 2.3 μm. The coating thickness deviation at each location is within ±5%.

[0038] Example 2

[0039] A method for controlling uniformity of a tinned layer of a hot-dip tinned copper strip comprises the following steps:

[0040] (1) The copper strip surface is electrolytically cleaned and deoxidized with hydrogen, and preheated at 160°C for 15 minutes;

[0041] (2) tin powder, sulfuric acid, and sodium dodecylbenzene sulfonate are mixed in a weight ratio of 98:3.5:2.3 and melted at 245°C to obtain a tin solution with an apparent viscosity of 37 cp; the copper strip is immersed in the tin solution obliquely along the running direction, and the copper strip and the surface of the tin solution form an angle of 15° when the copper strip is immersed in the tin solution. During the tin plating process, the temperature of the tin solution is maintained at 265°C and the temperature variation range does not exceed ±1°C, the tin plating speed is 0.8 m / min, and the tin plating time is 15 s;

[0042] (3) After tin plating, use normal temperature water mist spray to cool to room temperature to form a uniform coating, and the coating thickness deviation at each location is within ±5%.

[0043] Example 3

[0044] A method for controlling uniformity of a tinned layer of a hot-dip tinned copper strip comprises the following steps:

[0045] (1) The copper strip surface is electrolytically cleaned and deoxidized with hydrogen, and preheated at 220°C for 8 minutes;

[0046] (2) tin powder, sulfuric acid, and sodium dodecylbenzene sulfonate are mixed in a weight ratio of 97:3.5:2.5 and melted at 250°C to obtain a tin liquid with an apparent viscosity of 30 cp; the copper strip is immersed in the tin liquid obliquely along the running direction, and the copper strip and the surface of the tin liquid form an angle of 20° when the copper strip is immersed in the tin liquid. During the tin plating process, the temperature of the tin liquid is maintained at 265°C and the temperature variation range does not exceed ±5°C, the tin plating speed is 1.0 m / min, and the tin plating time is 20 s;

[0047] (3) After tin plating, use normal temperature water mist to cool to room temperature to obtain a uniform coating, and the coating thickness deviation at each location is within ±5%.

[0048] Comparative Example 1

[0049] The other steps are the same as those in Example 1, except that the copper strip is vertically inserted into the tin liquid when immersed in the tin liquid.

[0050] Comparative Example 2

[0051] The other steps are the same as those in Example 1, except that when the copper strip is immersed in the tin solution, the copper strip and the surface of the tin solution form an angle of 45°.

[0052] Comparative Example 3

[0053] The rest is the same as in Example 1, except that the temperature of the tin solution during the tin plating process is 295°C.

[0054] Comparative Example 4

[0055] The rest is the same as in Example 1, except that the tin liquid is composed of tin powder, sulfuric acid, and sodium dodecylbenzene sulfonate in a ratio of 90:10:0.5, and its apparent viscosity is 9 cp.

[0056] Comparative Example 5

[0057] The rest is the same as in Example 1, except that in step (1), the copper strip is not preheated.

[0058] The above embodiments can obtain a peeling force of 1 to 8 N / cm. 2 The thickness of the tinned layer is uniform, and the thickness deviation of each part is within ±5% of the tinned layer of the copper strip, and the surface of the copper strip is flat and smooth, without defects such as unevenness, bubbles, and pores.

[0059] In comparative example 1, the peeling force is unstable due to the poor control of the angle of the copper strip when it is immersed in the tin liquid, and it cannot meet the requirements of 1-8 N / cm 2 between the requirements.

[0060] In Comparative Example 2, the tin plating layer thickness is uneven due to poor control of the angle of the copper strip when immersed in the tin solution, and the thickness deviation limit within ±5% at each location cannot be met, resulting in the tin plating layer in some areas being too thick or too thin.

[0061] In Comparative Example 3, since the temperature of the tin solution is too high during the tin plating process, the viscosity of the tin solution is reduced to 8cp, resulting in insufficient cooling shrinkage of the coating, which affects the quality and thickness uniformity of the tin plating layer.

[0062] In Comparative Example 4, due to the low apparent viscosity of the tin solution, the surface of the copper strip is unevenly coated, resulting in defects such as unevenness or blistering.

[0063] In Comparative Example 5, the copper strip was not preheated before hot-dip tinning, resulting in weak adhesion between the coating and the substrate, resulting in peeling.

[0064] The above-mentioned detailed description of a method for controlling the uniformity of the tinning layer of a hot-dip tinned copper strip with reference to the embodiment is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for controlling uniformity of tinning layer of hot-dip tinned copper strip, characterized in that: The method comprises the following steps: (1) electrolytically cleaning and hydrogen deoxidizing the surface of the copper strip, and preheating; (2) Immerse the copper strip obliquely in the tin solution along the running direction, maintain the temperature of the tin solution at 240-290°C, the apparent viscosity of the tin solution at 10-60cp, and the tinning speed at 0.3-1.5m / min during the tinning process; (3) After tinning, cool to room temperature by spraying with normal temperature water mist.

2. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: In step (1), the preheating temperature is 120 to 230° C. and the preheating time is 5 to 25 minutes.

3. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: The tin liquid is composed of tin powder, acid solution and surfactant in a weight ratio of 90-98:2.8-3.5:2-2.

5.

4. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 3, characterized in that: The acid solution is hydrochloric acid or sulfuric acid.

5. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 3, characterized in that: The surfactant is any one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and dodecylphenol polyoxyethylene ether.

6. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: In step (2), when the copper strip is immersed in the tin liquid, the copper strip and the surface of the tin liquid form an angle of 10° to 40°.

7. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: In step (2), the temperature variation range of the tin solution during the tin plating process does not exceed ±20°C.

8. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: In step (2), the tinning time is 5 to 30 seconds.

9. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: The thickness of the coating is 0.8-2.5 μm.

10. The method for controlling uniformity of tinning layer of hot-dip tinned copper strip according to claim 1, characterized in that: The stripping force of the tinned layer of the copper strip obtained by the method is 1 to 8 N / cm 2 The tin plating thickness on the copper strip surface is uniform, and the thickness deviation at each location is within ±5%; the surface of the copper strip is flat and smooth.

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