As FPC supplier knows that, the material used in SMT assembly includes solder paste, adhesive, flux, cleaning agent, heat transfer medium etc.

Solder paste

Solder paste in SMT assembly procedure plays a role of both solder material and adhesive to fix SMCs/SMDs onto PCB surface. The leading element of solder paste, Sn63/Pb37 and Sn62/Pb36/Ag2 features a comprehensive performance while Sn43/Pb43/Bi14 performs well in solder paste with low melting temperature. Sn-Pb IMC performs well in strength and wettability so it is regarded as the most suitable solder.

Flux

Flux in SMT assembly procedure plays a role in assisting soldering in being smoothly carried out. Flux is classified into acid flux and resin flux, playing a role in eliminating oxide and dirt from metal surface and getting metal surface wet.

Adhesive

Adhesive plays a role in fixing SMDs in SMT assembly to stop SMDs from being displaced and falling off.

Cleaning Agent

Cleaning agent is used to clean off the residues on board left by solder paste etc. Cleaning agent should chemically perform well and feature thermal stability. In addition, it should not be decomposed during storage and application, failing to have chemical reaction with other chemical substances. Plus, it shouldn’t corrode contact material with noninflammability and low toxicity. Cleaning should be implemented with safety and low loss during the procedure and it should be effectively done within set time and temperature.