Question: What is the difference between pure tin, bright tin, and matte tin?
Pure tin has long been used in food packaging applications and as a cosmetic overlay. Recently, pure tin has been introduced as a non-toxic replacement for lead-containing solders. The maximum service temperature of pure tin solders is higher because of the higher melting temperature of tin (450°F / 232°C).
- Soft, ductile, silvery-white metal
- Not easily oxidized in air
- Has good conductivity and corrosion resistance while enhancing the solderability of substrates
- Non-toxic and non-carcinogenic
There are two types of electroplated pure tin:
- Bright tin is coated in electroplating solutions containing brighteners, which are organic additives causing the formation of fine Grain structure deposits. Bright tin coatings have excellent cosmetic appearance; however, they are characterized by high internal stresses and contain a higher amount of organics.
- Mirror-like reflectivity
- average grain size below one micron
- high degree of luster and is generally preferred for electrical contact applications, such as bus bars, terminals and switching components that are not soldered
- If bright tin plating is soldered, the co-deposited organics in the deposit can burn, resulting in a de-wetting of the solder and a visible charring of the solder joint.
- Matte tin coatings are made in electrolytes without the addition of brighteners. Matte tin has a dull appearance, but the level of internal stresses in matte tin depositions is much loiwer than it is in bright tin depositions. Matte tin (in contrast to bright tin) is characterized by low whiskers growing. Therefore, it is used in electronics.
- a dull, semi-bright or satin-bright appearance
- disperse reflectivity
- existence of grains with an average size in the range of a few microns
- the deposit is free of the co-deposited brighteners found in bright tin plating