Tinning

Tin is a collective term for various methods of surface finishing. By tinning a tin coating is produced on most metal objects. Although tin has a relatively good corrosion resistance, corrosion protection is not the main reason to choose this metal as a coating material - the most important properties of tin coatings consist in food safety and solderability.

Objects, which are plated, usually consist of steel, copper or copper alloys. Rare die-cast zinc, other metals or alloys and plastic are tinned.

Hot-dip tinning

In which method the objects to be tinned ( hot dipping ) are immersed for a suitable pre-treatment in a molten bath of tin. When lifting the objects from the tin bath, the tin adheres to the surface and upon cooling, a solid tin coating forms. This method was already known in ancient times and many hobbyists know today tinning a copper wire with soldering iron and solder. In modern times, the tin-coating on a large scale for the production of tinplate ( tinned sheet steel ) was used. With the advent of electroplating the hot-dipped tinplate fell sharply in favor of the galvanic tinplate.

In the tinning of copper strips and contacts the tin-coating was compared to the electroplating defend its position in some areas. An important advantage of Feuerverzinnens of copper in the formation of alloy layers at the boundary of the base metal and coating - this alloy layers result in an extremely good adhesive strength of the coating.

Tin plating

In the tin plating to be tinned articles are immersed for a suitable pre-treatment in a tin electrolyte. By applying an electrical voltage, a tin coating is deposited on the surface of the articles. This procedure can also be very thin layers of a few microns realize, whereby the material consumption is correspondingly low. Thus, this method has economic advantages over the hot-dip tinning. Great importance is the tin plating for the food industry (tinplate ) and for the electrical and electronics industry gained ( contacts, copper, copper strips, electronic components ).

Tin coatings can produce an equally dreaded as exotic appearance: Out of the tin coating grow under certain conditions fibers. Current up to 100 microns long whiskers pose a serious risk for highly miniaturized electronic components and circuits, and have already led to dysfunction in satellites, missiles and nuclear power plants.

It used to be commonly used tin -lead alloys because of the lower Whiskerneigung. Since the RoHS is the challenge to make without lead whisker- tin coatings ( by suitable additives and process parameters).

Reflow process

This method is a combination of the tin plating and a subsequent heat treatment above the melting point of the tin. One tries to combine the advantages of galvanic and hot-dip tinning: thin layers and formation of alloy layers.

Chemical tinning

By immersion of copper boards in a solution of a tin salt such as Tin sulfate, sulfuric acid and thiourea, and gloss and wetting agents, chemical ( electroless ) tinning of copper surfaces is possible. Due to the simplicity of the process this is interesting, among other things for the home for tinning of boards. The thus coated tin layer is very smooth and has a thickness in the micrometer range .. The low thickness, the tin alloy converts but after long storage by the diffusion of copper into a copper-tin phase or copper - tin.

Applications

In the packaging industry (tinplate ), electrical engineering, electronics, and in the Dachklempnerei and in the body, even in the Homogenverbleiung in chemical apparatus and cable technology.