Led PCB Board Design, Production and Assembly
What is the difference between common tin and lead-free tin in PCBA processing?
Appearance: the surface of common solder tin for circuit board appears to be bright white, while lead-free solder tin appears to be pale yellow (as LF solder tin contains copper).
Touch: Touch the solder with the hand, lead-free tin will leave the light yellow traces on the hand, while common tin will leave black traces.
Composition: there are two main factors of lead solder: tin and lead, while the content of lead for lead-free solder tin is less than 500PPM, and lead-free soldering tin generally contains tin, silver or copper elements.
Usage: common tin is used for the soldering of lead products. The tools and components used for production are with lead. LF solder tin is used for lead-free products exported to Europe, America and other countries. The tools and components used must be lead-free.
Why is PCBA cleaned
In the process of PCBA production, need to use solder paste(SMT) and welding flux(THROUGHHOLE) for soldering, the solder paste contain flux, too, flux can produce residues, residues contain organic acid and decomposable ions residue, including organic acid may cause corrosion to PCBA. In the process of electrification, the residues of ions will cause the movement of electrons due to the potential difference between the two pads, which may lead to short circuit and result in product failure. At present, the gap between the welding pads of electronic products is getting smaller and smaller, so the existence of residues increases short circuit possibility, so cleaning becomes very important in the production process.
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