(1) According to environmental protection requirements, it is divided into lead solder paste and lead-free solder paste (environmentally friendly solder paste):
Environmentally friendly solder paste contains only a small amount of lead. Lead is a substance harmful to humans. In electronic products exported to Europe and the United States, the content of lead is strictly required. Therefore, lead-free processes are used in SMT chip processing. In the national control of environmental protection, SMT chip processing industry in the next few years, SMT chip processing using lead-free process is a trend.
In the lead-free SMT chip processing technology, it is more difficult to tin than the lead-based technology. Especially when encountering BGA \ QPN, etc., a high-silver paste will be used. The common three-point silver and 0.3 points of silver. Among the solder pastes, silver-containing solder pastes are currently more expensive.
(2) According to the melting point, it can be divided into high temperature, medium temperature and low temperature:
Commonly used high temperature is tin silver copper 305,0307. There are tin, bismuth and silver in the middle temperature, and tin and bismuth are commonly used in the low temperature. It is selected according to the characteristics of the product in the SMT chip processing.
(3) According to the fineness of tin powder, it is divided into No. 3 powder, No. 4 powder, No. 5 powder solder paste