FJY Brush Plating

Conductive properties of aluminum and the role of aluminum-based busbars

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Aluminum is a commonly used metal material which is light in weight (specific gravity: 2.7), soft in texture, good in plasticity, and strong in electrical conductivity (at a temperature of 20 ° C, the electrical conductivity of aluminum is 3.53×lO7Sm-1), and is inexpensive. The electrical conductivity of pure aluminum is not much different from that of pure copper (the conductivity of copper is 5.71×10 7 Sm-1 at 20 ° C) and in the atmosphere, aluminum has good chemical stability. Therefore, in the fields of electric power, electric appliances, and electronics, it is often used as an electrical connection material for wires, cables, bus bars, electrical connectors, and the like. In the field of civil electrical materials, aluminum-based copper can reduce the weight of conductors by two times and raw material costs by more than five times.

 

However, in the atmospheric environment, the surface of the aluminum material is liable to form an oxide film with poor conductivity, so that there is a high contact resistance between the overlapping portions of the aluminum-based electrical connectors (such as bus bars, joints). In the process of high-current power transmission, the resistance heat generated by the contact resistance will further aggravate the chemical oxidation of the surface of the aluminum material. In severe cases, the joint may collapse or the electric corrosion pit may occur, thereby reducing the reliability of power transmission. In order to reduce the contact resistance of the lap joint of the aluminum-based electrical connector, it is common to use a surface silver plating or tin plating to reduce the contact resistance of the aluminum surface.

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Cyanide-free silver plating and neutral tin plating technology on aluminum surface

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Traditional brush plating process and its problems

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At present, the general process of aluminum brush plating used at home and abroad is: electric net → water washing → corrosion (diluted hydrochloric acid) → water washing → light (concentrated nitric acid) → water washing → zinc immersion (strong alkaline) → water washing → re-lighting (concentrated nitric acid) → water washing → secondary zinc immersion (strong alkaline) → water washing → brushing copper (alkaline copper, or cyanide copper plating) → water washing → brush plating conductive layer (cyanide silver plating or acid tin plating) → plating treatment.

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The process has the following main problems:

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1. The corrosive and light-emitting steps use strong acidic substances. When light is emitted from nitric acid, harmful nitrogen oxide gases (commonly known as "yellow smoke") are also produced.

2. The zinc immersion liquid contains a strong alkaline substance. Strong alkali can severely corrode the non-plated parts of aluminum or threaded holes. Necessary shielding protection must be applied to the non-plated parts or threaded holes so as to perform brush plating. This significantly increases production costs and reduces production efficiency.

3. The brush copper plating solution will produce a displacement reaction with the aluminum matrix to produce a floating copper layer that contaminates the non-plated surface. In order to reduce or avoid the displacement reaction, a cyanide copper plating solution must be used. Hence, it brings highly toxic substances and pollutes the environment.

4. There are serious environmental pollution problems with cyanide silver plating or acid tin plating.

  5. The process steps are numerous and the production efficiency is low.

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FJY series aluminum brush plating process

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The FJY series non-polluting brush plating process has solved a series of problems in the current aluminum brush plating technology. The process flow is as follows:

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Aluminum activation I → water washing → aluminum activation II → water washing → aluminum activation III → brush plating conductivity layer (no cyanide silver plating, or neutral bright tin plating) → post-plating treatment.

The main features of the process include:

1. The process of corrosion, light extraction, zinc immersion, and copper plating is eliminated, and there is no environmental pollution problem.

2. No strong corrosive substances (strong acid or strong alkali) are used, and the non-plated surface is not shielded, resulting in low cost.

3. The plating solution is not corrosive to the aluminum substrate and is suitable for large-area brush plating.

4. The process is simple and the production efficiency is high.

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Applications

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• Cyanide-free silver plating

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• Neutral tin plating

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