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Matt tinning

Technical possibilities at Metoba

Metoba offers the following techniques for processing Matt tinning :

Reel-to-reel-finishingBulk-finishingVibrobot refinement

1. Characteristics and properties

The properties of matt tin coatings are the bright, low-reflection, coarse crystalline surface with a carbon content of 0.005-0.05%, a high ductility, low residual stresses and a purity content of 99.99%. The matt tin layers deposited with Metoba are whisker-free (Class I). Class I whisker-free coatings are accepted by the leading manufacturers of electronic contacts, as the whisker length does not exceed 50µm and therefore poses no risk to electronic circuits. Furthermore, matt tin layers are fully compatible with lead-free solders and the current lead-containing standard solders at a melting temperature of 231.8°C and have solderability according to DIN IEC 68II20 (155°C; 16h).

2. Benefits and areas of application

Matt tin is used, among other things, in all electronic areas where Class I whisker freedom is desirable and necessary. Galvanically deposited matt tin effectively counteracts whisker formation by excluding known influencing variables that lead to whisker formation. Known influencing variables for whisker formation include internal compressive stresses, formation of alloying elements, co-deposition of carbon, type of crystallization, grain size and the deposition of hydrogen.

3. Basic material

After a material-specific and application-specific pretreatment, all stainless steels, non-ferrous metals and their alloys as well as aluminium and zinc die-cast can be coated with matt tin without any problems. For CuZn materials it is absolutely necessary to apply a diffusion barrier of usually 1-3µm nickel in order to maintain solderability. This prevents diffusion of the zinc from the base material into the tin layer. With other base materials, a diffusion barrier should also be deposited.

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.

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