What are the causes of false welding and cold welding？FPC supplier believe that here the reasons:
1. Reasons for falsewelding
The base metal surface loses solderability.
The black disk phenomenon occurred in the electroless nickel plating /immersion gold process.
The solderability protective coating does not match the flux.
The flux activity is too strong.
The solderability protective layer is too thin.
2. Causes of cold welding
The main reason for cold welding is that the heat supply is insufficient duringwelding, the welding temperature does not reach the wetting temperature of thesolder, so no IMC or IMC is formed on the bonding interface.