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Bright tin coatings

Technical possibilities at Metoba

Metoba offers the following techniques for processing Bright tin coatings :

Reel-to-reel-finishingRack-finishingBulk-finishingVibrobot refinement

1. Characteristics and properties

Tin is a silver-white, shiny metal with a low hardness and a low melting point (232°C). The corrosion resistance of electrolytically produced tin layers is good against atmospheric air, humidity, aqueous solutions, mineral acids and oxidizing acids. In aqueous solutions, organic acids, including those of food, tin coatings provide cathodic corrosion protection to underlying steel.

Tin-coated workpieces are food-safe and have excellent solderability when properly pre-treated. The tin layers deposited with Metoba are fine crystalline, very ductile, easily remeltable and highly specular. Bright tin layers tend to form whiskers, which can cause short circuits in electronic components. The risk of whisker formation can be significantly reduced by a diffusion barrier layer of usually 1-3µm nickel.

2. Benefits and areas of application

Bright tin is ideally suited for all types of electrical components where good solderability is required, as well as all current-carrying components and workpieces that come into direct contact with foodstuffs. The coating offers a technical surface with a decorative, glossy finish that also has a lubricating property that is particularly suitable for all plug contacts. Galvanic bright tin is used in the automotive industry, the household appliance industry, the food industry and many current-carrying systems and circuits.

3. Basic material

After a material- and application-specific pretreatment, all stainless steels, steels, non-ferrous metals and their alloys as well as aluminium and zinc die-cast can be coated with bright tin without any problems.

In order to guarantee a long solderability of the tinned workpieces, it is absolutely necessary to deposit a diffusion barrier layer of copper or nickel under the tin layer of brass materials in order to avoid diffusion of the zinc into the tin layer. The solderability is standardised according to DIN IEC 60068-2-20.

4. Required delivery condition

The goods provided must be largely metallically bright. Residual oils or residual impurities must be removable with conventional aqueous alkaline degreasers. Oils containing silicone, alkali/alkaline earth and high-pressure additives must be avoided at all costs.