Surface coating "made by Wieland" – a success
Hot-dip tinned strips set sales records
Wieland supplies large quantities of hot-dip tinned strips, whose coating is subject to the highest demands in many respects, to manufacturers of connectors. The strips are the result of intensive material science research and continuous further development.
Many metals are subject to corrosion over time – a chemical transformation that changes their original appearance and properties. These processes are undesirable for the function of the component – they can deteriorate the contacting or destroy the part completely. For the ever increasing demand for electromechanical components and plug contacts made of copper alloys, Wieland therefore developed and produced strips with a coating of pure tin or tin-lead mixtures as early as the 1960s. As tin is soft and has a low melting point of 232°C, it can be applied as a thin coating and its oxide layer protects the copper material.
In 1967, the craft workshops Ulm (HWA) developed a groundbreaking innovation for easier application of a tin coating: hot-dip tinning, in which the strip is immersed in a liquid tin bath. Initially, the tin was still brought to the desired thickness by mechanical stripping, usually using felt clamps. From 1970 onwards, the process was again improved significantly: the liquid tin that was not required would now be blown off by compressed air.
The then new technology was the basis of a success story for Wieland which is unparalleled. Hot-dip tinning of strips with blow-off technology provides properties which are required in many different ways in many industries. For example, manufacturers of connectors benefit from corrosion protection in the case of very thin tinning, from low insertion and withdrawal forces in the case of thin to medium layer thickness and from the excellent solderability of the components in the case of thicker tinning. These are used in the automotive industry and in many electrical engineering areas, among others.
No wonder that the quantity of hot-dip tinned strips produced has developed in leaps and bounds in recent decades. While 2,500 tonnes left the Vöhringen plant in 1983, this figure rose to 11,100 tonnes in 1999. Today, the global Wieland Group produces hot-dip tinned strips worldwide in tonnages well into the 5-digit range. This product’s unparalleled success is also founded on the fact that customers can rely on the physical and aesthetic quality as well as on advice and service and on the delivery of the strips in absolute conformity with the specifications.
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Three plants for the hot-dip tinning of strips are in operation at in Vöhringen, further plants are located at the Wieland sites in Villingen and Langenberg.
The microscope shows that there are two intermetallic phases between the copper strip and the tin layer. They make the coating harder, ensure excellent adhesion of the layer and thus prevent premature wear.
Schematic representation of a hot-dip tinning plant. The continuous measurement of the layer thickness with X-rays is immediately incorporated into the blow-off process via a control unit.
High demands are placed on modern plug contacts such as USB-C plugs – including uniform tin plating thicknesses and constant contact forces.
