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Surface treating

Features and applications

The products are required to have first-class electrical conductivity and good corrosion resistance. In order to satisfy these increasing demands of our customers for end products such as connectors, which are used in very complex electrical and electronic systems, our material is repeatedly surface treated. This gives it excellent resistance to oxidation and external influences and reduces the so-called insertion force.

Three main processes are used for surface treatment: hot-dip tinning, electrolytic tinning, electrolytic tinning with a subsequent reflow treatment. Aurubis operates two hot-dip tinning lines and two electrolytic tinning lines in Europe and the USA. Hot-dip tinning complies with standard EN 13148: 2001

Copper and copper alloys can be surface treated with several metals. However, pure tin is very important due to its economic efficiency.

The most widely used surface treating in Europe - Hot dip tinning

Copper offers excellent conductivity and is relatively resistant to corrosion. These facts together with its durability make it ideal for electrical applications. The problem occurs when copper is used in a humid environment or in a high humidity environment. Under these conditions, copper will corrode and weaken much faster. Is there a way to prevent this? Yes. Tinning of copper.

The thoroughly pre-treated strip is passed through a ladle containing molten tin with a temperature between 250 ° and 290 °, depending on tinning requirement. After leaving the tin bath, the molten tin coating is usually leveled to the desired thickness by means of air knives. In this way, it is possible to achieve a coating thickness in the range of 0.8 to 16 µm.

Hot-dip tinning

Thickness (mm) Width (mm) Inner ø (mm) Max. outer ø (mm) Layer thickness incl. tolerances
(standard tin plating Sn 99,9)
0.10 - 0.18 11 - 300 76 / 100 / 150 525 1 - 3 µm
3 - 6 µm
4 - 8 µm
8 - 12 µm
0.19 - 1.5 10 - 400 300 / 400 1,180

Electrolytic tinned strips

In contrast to Europe where hot dip tinning is most frequently practiced most of the strips coated with tin for the North American and Asian markets are produced electrochemically. Conventional electroplating is therefore used.

During electrolytic tinning, the base material is not exposed to extreme temperatures which can be an advantage for heat-sensitive materials that are inclined to become soft during hot dip tinning.

Layer Matte / bright / brushed Reflow
Nickel (Ni) 0.2 to 3 µm / Flash 0.2 to 2.5 µm / Flash
Copper (Cu) 1.0 to 3µm / Flash 1.0 to 2.5 µm / Flash
Tin (Sn) 0.5 to 10 µm 0.5 to 3 µm

The layer thicknesses mentioned in the table above are the minimum required values.

Dimensions in mm Coating Main properties

Thickness *
0.20 - 1.50

Width **
10 - 310

Tin matte / bright / brushed Good electrical contact, low insertion force and / or corrosion protection
Tin reflowed Mitigates whiskers
Nickel Special applications and diffusion barrier (underlayer)

* Thickness of 0.2 - 0.3 mm avaible depending on the hardness of the strip.
** Width of 10 - 180 mm, slit to width (bare edges) 180 - 310 mm: full width tinned.

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Our slitting centre KME Slovakia supplies copper and copper alloys mainly to customers in Central and Eastern Europe

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