There are two common processes for printed circuit boards: tin spraying and tin sinking, both of which are surface treatment methods to meet the requirements of lead-free soldering. But in the circuit board process, tin sinking is not known to most people. The following editor will talk about the difference between tin spraying and tin sinking in detail.
The difference between spray tin and sink tin
1. Process flow
Tin spray: pre-treatment-spray tin-test-molding-appearance inspection.
Immersion Tin: Test-Chemical Treatment-Immersion Tin-Molding-Visual Inspection.
2. Process principle
Tin spraying: Mainly invading the PCB board directly into the molten tin paste. After being leveled by hot air, a dense tin layer will be formed on the copper surface of the PCB.
Tin sinking: It mainly uses displacement reaction to form a very thin tin layer on the PCB surface.
3. Physical properties
Tin spraying: The thickness of the tin layer is between 1um-40um, the surface structure is relatively dense, the hardness is large, and it is not easy to scratch; the spraying tin only has pure tin in the production process, so the surface is easy to clean, and it can be stored at normal temperature. Years, and the problem of surface discoloration is unlikely to occur during the welding process.
Immersion tin: The thickness of tin is about 0.8um-1.2um, the surface structure is loose, the hardness is small, and it is easy to cause surface scratches; Immersion tin undergoes a complex chemical reaction with more chemicals, so it is not easy to clean and the surface is easy Residual syrup will cause discoloration during welding. The storage time is short. It can be stored for three months at normal temperature. If it takes a long time, it will change color.
4. Appearance characteristics
Spray tin: The surface is brighter and beautiful.
Shen Tin: The surface is light white, dull, and easy to change color.