​Pcb factory: what are the main components of lead-free solder paste?

Pcb factory: what are the main components of lead-free solder paste?

The lead-free solder paste does not absolutely prohibit the existence of lead in the solder paste, but requires that the lead content must be reduced to less than 1000ppm (<0.1%), which means that the electronic manufacturing must meet the lead-free assembly process requirements. "Electronic lead-free" is also commonly used to generally mean that the content of six toxic and harmful materials, including lead, must be controlled within 1000 ppm. The lead-free solder paste is mainly composed of tin, silver and copper, with silver and copper replacing the original lead. In the composition of alloy composition, alloy Sn95.4Ag3.1Cu1.5 is considered to be the best

Lead free solder paste is widely used in SMT processing, and with the popularization of RoHS standard, it has become the mainstream instead of lead solder paste. However, lead-free solder paste does not represent 0% lead. Solder paste is a kind of alloy composition paste, and the appropriate composition formula has decisive significance for the welding quality of the entire circuit board.

The lead-free solder paste does not absolutely prohibit the existence of lead in the solder paste, but requires that the lead content must be reduced to less than 1000ppm (<0.1%), which means that the electronic manufacturing must meet the lead-free assembly process requirements. "Electronic lead-free" is also commonly used to generally mean that the content of six toxic and harmful materials, including lead, must be controlled within 1000 ppm.

The lead-free solder paste is mainly composed of tin, silver and copper, with silver and copper replacing the original lead.

In the composition of alloy composition, alloy Sn95.4Ag3.1Cu1.5 is considered to be the best. Its good performance is the result of the formation of fine microstructure, which gives high fatigue life and plasticity. For 0.5~0.7% copper solder alloy, any silver content higher than about 3% will increase the volume fraction of Ag3Sn particles, thus obtaining higher strength.

Different solder paste manufacturers have different lead-free solder paste formulations and production technologies, so in actual measurement, the proportion of lead-free solder paste components is slightly different. In addition, the composition of solder paste will also be adjusted according to the feedback of the actual PCBA processing process to make it more consistent with specific welding requirements. However, the proportion of lead-free solder paste components is small, and its quality is still directly related to the production process of solder paste.

PCB manufacturers and PCB designers will explain the main components of lead-free solder paste.