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Surface Treatment of PCB Circuits Board

At present, there are several common PCB circuit board surface treatment methods in PCB manufacturing factory:

1. Chemical immersion silver PCB circuit board

Between OSP and electroless nickel/immersion gold, the process is simple and fast. Exposure to heat, humidity and pollution can still provide good electrical properties and maintain good solderability, but it will lose its luster. Because there is no nickel under the silver layer, the sinking silver does not have all the good physical strength of electroless nickel/immersion gold;

2, electroplated nickel gold PCB circuit board

The surface conductor of the PCB is first plated with a layer of nickel and then plated with a layer of gold. The nickel plating is mainly to prevent the diffusion between gold and copper. There are two types of electroplated nickel gold: soft gold (pure gold, gold indicates no light) and hard gold (the surface is smooth and hard, wear-resistant, contains other elements such as cobalt, and the surface looks brighter). Soft gold is mainly used for gold wire when the chip is packaged; hard gold is mainly used for electrical interconnections (such as gold fingers) that are not soldered.

3, PCB mixed surface treatment technology

Two or more surface treatment methods are selected for surface treatment. Common forms are: nickel-plated gold + anti-oxidation, electroplated nickel gold + nickel-plated gold, electroplated nickel gold + hot air leveling, nickel-plated gold + hot air leveling .

Hot air leveling (lead-free/lead-lead) is the most common and cheapest treatment for all surface treatments, but please note the EU RoHS regulations.

4, hot air leveling PCB circuit board

The surface of the PCB is coated with molten tin-lead solder and flattened (flattened) with heated compressed air to form a coating that is both resistant to copper oxidation and provides good solderability. When the hot air is leveled, the solder and the copper form a copper tin metal compound at the junction, and the thickness thereof is about 1 to 2 mils;

5, organic antioxidant (OSP) PCB circuit board

On the PCB circuit board clean bare copper surface, a layer of organic film is chemically grown. This film has anti-oxidation, thermal shock resistance and moisture resistance. It is used to protect the copper surface from rust (oxidation or vulcanization) in the normal environment. At the same time, it must be easily assisted in the subsequent high temperature of welding. The flux is quickly removed for soldering;

6. Chemical nickel-plated gold (ENIG) PCB circuit board

Wrap a thick layer of nickel-gold alloy with good electrical properties on the copper surface and protect the PCB for a long time. Unlike OSP, which acts only as a rust barrier, it can be useful and achieve good electrical performance during long-term use of the PCB. In addition, it also has environmental tolerance not available in other surface treatment processes.

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