Exchanging Principal
·It is mainly used in Immersion Tin surface treatment of PCB. In Sn trough, Thiourea is the deoxidizer to bring reacted potential between Sn and Cu for their exchange. It makes tin deposit on the copper of PCB for steady and the best solderability.
·Formula:
2Cu → 2Cu+ + 2e-
2Cu+ + 8CS(NH2)2 → 2Cu[NH2]2]4+

Flow Chart：