There are many surface treatment processes for PCB circuit boards, including hot air leveling, organic coating (OSP), chemical nickel plating/immersion gold, silver deposition, tin deposition, etc.

1. Hot air leveling

Hot air leveling, also known as tin spraying, is a commonly used treatment process for PCB boards in the early stages. It involves coating the PCB with molten tin lead solder and leveling it with heated compressed air to form a coating layer that is both resistant to copper oxidation and provides excellent solderability. During hot air conditioning, solder and copper form a copper tin metal compound at the junction, with a thickness of approximately 1-2 mil.

2. OSP organic coating

OSP process is different from other surface treatment processes, as it acts as a barrier layer between copper and air; Simply put, OSP is the chemical process of growing an organic film on a clean bare copper surface. This layer of film has oxidation resistance, heat shock resistance, and moisture resistance, mainly used to protect the copper surface from continuous rusting in normal environments; It is also necessary to be easily and quickly removed by the soldering flux during the subsequent high temperature welding, in order to facilitate the welding process. OSP technology is simple, cost-effective, and widely used in circuit board manufacturing.

3. Chemical nickel plating/immersion gold

Chemical nickel plating/immersion gold is not as simple as OSP process, which requires a thick layer of coating on the copper surface. Unlike OSP, which only serves as a rust proof barrier layer, nickel gold alloy with excellent electrical function can protect PCB for a long time and achieve outstanding electrical function. It also has a tolerance for the environment that other surface treatment processes do not possess, effectively preventing damage to the PCB board.

4. Sinking Silver

The silver deposition process is relatively simple and fast, and is between OSP and electroless nickel plating/immersion gold. Silver deposition does not require a thick layer of armor to be applied to the PCB board, and can provide excellent electrical functionality and maintain outstanding solderability in hot, humid, and polluted environments. The defect is that it will lose its luster. Other types of sunk silver also have outstanding storage properties, and usually can be assembled after several years without major problems.

5. Sinking tin

Due to the fact that all solder materials nowadays are based on tin, the tin layer can match any type of solder, which also makes the tin deposition process have great development prospects. When the tin deposition process was not perfect in the past, tin whiskers briefly appeared on PCB boards after tin deposition. During the soldering process, tin whiskers and tin relocation would cause reliability issues. Organic additives have now been added to the tin deposition solution to give the tin layer a granular structure, overcoming the problem of tin whiskers, and also possessing good thermal stability and weldability, enhancing its applicability.

That's all for today's introduction about the common surface processes of PCB circuit boards. There are other types of surface processes for PCB circuit boards, such as nickel gold plating, nickel palladium plating, etc., which are more difficult and costly to manufacture than the aforementioned processes, and therefore have not been widely used.

Article source: Jiangmen PCB Customizationhttp://www.yonghongpcb.com/