4, 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 is tightly covered on palladium, providing a good contact surface.

　　 5. Immersion gold

　　Immersion gold is a thick, good electrical nickel-gold alloy 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.

　　 6, Shen Xi

　　 Since all current solders are tin-based, the tin layer can match any type of solder. The tin sinking process can form a flat copper-tin intermetallic compound. This feature makes the tin sinking have the same good solderability as the hot air leveling without the headache flatness problem of the hot air leveling; the tin plate can not be stored for too long , When assembling, *** is carried out according to the order of Shen Xi.

　　7, 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 pollution, silver can still maintain good solderability, but will lose its luster . Immersion silver does not have the good physical strength of electroless nickel/immersion gold because there is no nickel under the silver layer.

　　 8. Plating hard gold

　　In order to improve the wear resistance of the product and increase the number of insertion and removal, hard gold is electroplated.

　　As user requirements are getting higher and higher, environmental requirements are becoming stricter and more and more surface treatment processes are increasing. Where the PCB surface treatment process will go in the future, it is impossible to predict accurately now. In any case, meet user requirements and protect the environment*** do it first!