Complete summary of PCB surface treatment process

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The most basic purpose of PCB surface treatment is to ensure good solderability or electrical properties. Since natural copper tends to exist in the form of oxides in the air, it is unlikely to remain as original copper for a long time, so other treatments are needed for copper.

1. Hot air leveling (spray tin)
Hot air leveling is also known as hot air solder leveling (commonly known as tin spraying). It is a process of coating molten tin (lead) solder on the surface of the PCB and flattening (blowing) it with heated compressed air to form a layer that is resistant to copper oxidation. It can also provide a coating layer with good solderability.
2. Organic Solderability Preservative (OSP)
OSP is to chemically grow a layer of organic film on the clean bare copper surface. This layer of film has anti-oxidation, thermal shock resistance, and moisture resistance to protect the copper surface from rusting in a normal environment (oxidation or vulcanization, etc.)
3. The whole plate is nickel-plated gold
The nickel-gold plating of the board is to plate a layer of nickel and then a layer of gold on the surface of the PCB. The nickel plating is mainly to prevent the diffusion between gold and copper.
4. Immersion gold
Immersion gold is a thick layer of nickel-gold alloy with good electrical properties on the copper surface, which can protect the PCB for a long time; in addition, it also has environmental tolerance that other surface treatment processes do not have. In addition, immersion gold can also prevent the dissolution of copper, which will benefit lead-free assembly.
5. Shen Xi
The tin-immersion process can form a flat copper-tin intermetallic compound. This feature makes tin-immersion have the same good solderability as hot-air leveling without the headache flatness problem of hot-air leveling; tin-immersion boards cannot be stored for too long , The assembly must be carried out according to the order of sinking tin.
6. Immersion Silver
Immersion silver process is between organic coating and electroless nickel/immersion gold. The process is relatively simple and fast; even if exposed to heat, humidity and Flexible PCB pollution, silver can still maintain good solderability, but will lose its luster .
7. Chemical nickel palladium gold
Compared with immersion gold, chemical nickel-palladium-gold has an extra layer of palladium between nickel and gold. Palladium can prevent corrosion caused by substitution reaction and make full preparations for immersion gold. gold
8. Plating hard gold
In order to improve the wear resistance of the product, increase the number of insertion and removal and electroplating of hard gold.

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