What are the advantages and disadvantages of nickel plating? What are the advantages and disadvantages of gold plating? Why is gold plating better than nickel plating for soldering when pasting PCB boards? Nickel plating will have many false soldering, while gold plating will not.
Nickel plating: It is to increase the wear resistance of the spring or pin, and secondly to enhance the aesthetic appearance
The characteristics and applications of PCB copper coating and electroplated nickel layer are introduced separately in terms of copper coating and electroplated nickel layer.
1. Characteristics and main applications of copper coating:
copper coatingIt has a beautiful rose red color, soft characteristics, high plasticity, easy to polish, and excellent heat transfer and conductivity. But it is prone to air oxidation in the air, leading to rapid loss of luster, so it is not suitable as a surface layer for safety protection - decorative art coatings.
Copper coating is mainly used as the bottom layer during double-layer plating of steel parts, and is also commonly used as the bottom layer during electroplating, plating, and gold plating. Its function is to improve the adhesion between conventional metal materials and surface or (or middle) coatings, and it is also beneficial for the accumulation of surface coatings. When the copper coating has no holes, it can improve the corrosion resistance of the surface coating, such as in the selection of double-layer plating for safety protection decorative arts
Thick copper and thin nickelThe advantages of the plating processing technology depend on this and can save precious metal nickel.
2. Characteristics and main applications of nickel coating:
Metal nickel has strong passivation treatment ability and can quickly transform into a thin passivation treatment film on the surface of the product, which can resist the corrosion of air and some acids. Therefore, the reliability of nickel coating in air is very high. In the simple salt lithium battery electrolyte of nickel, a coating with extremely fine crystals can be obtained, which has high-quality polishing properties. The polished nickel coating has a mirror like glossiness and can maintain its glossiness in the air at all times. In addition, nickel coatings also have high strength and wear resistance. Based on the characteristics of nickel coatings, they are primarily used as the bottom layer, inner layer, and overall surface layer of safety protection decorative art coatings, such as nickel chromium coatings, nickel copper nickel chromium coatings, copper nickel chromium coatings, and copper nickel coatings.
Due to the high porosity of nickel coatings, they can only be considered non porous when the thickness of the coating is above 25 μ m, so nickel coatings are generally not required as protective coatings.
The total production of nickel coatings is quite large, and the amount of nickel consumed by electroplating nickel accounts for about 10% of the global nickel production value.
The above is the analysis of the characteristics of the two coatings on PCB.
When directly soldering gold-plated leads, the gold substance is a soluble metal in the alloy of liquid tin and lead, and dissolves quickly. When gold dissolves rapidly, a new gold tin alloy layer is formed, which contains gold components. When the gold content in the alloy layer is greater than 3%, it is evident that the mechanical strength of the solder joints is greatly reduced, the bonding performance becomes brittle, and the solder joint connection is unreliable. The solder joints have no luster or even virtual soldering, which is known as the phenomenon of gold brittleness. According to relevant experimental evidence, this diffusion process between metals can even occur in 0.08 seconds.
Several common situations that are prone to gold embrittlement
(1) Directly welding metal coatings, when enough gold is melted into tin and lead, once the gold content in the solder joint exceeds 3%, gold embrittlement occurs.
(2) When the tin pot is coated with tin, when the gold content melted in the solder reaches 3%, it can also cause gold brittleness.
(3) When impurity gold substances are mixed into the brazing material used for welding, gold embrittlement will occur once the gold content of the welding point reaches 3% during welding.
(4) When re soldering gold-plated components during maintenance, it is easy for them to diffuse into the solder and cause gold embrittlement, making welding repairs difficult.
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