The advantages of tin plating include good corrosion resistance, ductility, and solderability. Because of its low transfer resistance it is also commonly used in electric and electronic industry. Under the tin coating a mid-layer of copper or nickel (3-6µm) is used to prevent the mixing of base material and coating.
Pinnoitus Helin Oy’s tin plating
- Bath type: acid, bright
- Maximum dimensions of the object: 2700x900x250
- Barrel and rack
- Pretreatments: copper, aluminum, steel, and their alloys
Standard:
- Electroplated coatings of tin — Specification and test methods (ISO 2093:1986)
The use of tin is limited in some applications by the phenomenon ofwhisker growth, where thin tin crystals are growing from the coating. These whiskers can be up to 10 mm long and 2-3µm thick. Because tin crystals can easily conduct electricity, they increase the risk of shorting in electronic components. In pure tin surfaces this problem is always possible. However, this can be mitigated by controlling the thickness of the mid-layer. It is also possible to fuse the tin after coating. Some bath types presumably have the ability to mitigate the whiskers phenomenon.
Tin is normally easy to solder, but if problems appear in the solderability, it’s a good idea first to check the adhesion of the base material, mid-layer, and tin. If the adhesion between different layers is not strong, the solderability can be impossible because the tin will run away. Naturally a long storing period or bad climate conditions will complicate soft soldering. For this reason the tin coating can also be passivated.