Immersion tin

For nowadays all the solder material is tin-based, the tin layer can be matched with any type of solder, In this point, immersion tin process is very promising. However years ago, Aluminum pcb will exits tin whiskers after immersion tin process and tin migration and tin whiskers shall bring reliability problems in the welding which limited the use of immersion tin process. Later we found the solution that adding tin organic additives to the immersion tin liquid which makes tin layer to become granular structure, well solved the problems, and also make better thermal stability and weldability.
Immersion tin process can form the flat copper-tin intermetallic compounds, this feature makes the immersion tin has the same good weldability as hot air leveling but without the headaches flatness problem; Also do not have proliferation issues between gold metal compared to Electroless Nickel / Immersion;
But the immersion tin plate can not be stored for a long time.