Wire drawing of ultra-fine copper wires

Wire drawing is a forming process widely used in the manufacture of metal wires, and has already been discussed in this treatise [4][5][6] . The aim of this article is to present the techniques used to draw ultra-fine wires made of copper and copper alloys, with or without a metallic coating, and with a diameter of the order of a hundredth of a millimetre.

Wire can generally be classified into four categories according to diameter (see table 1 ). Drawing techniques (machines, tools, drawing conditions, etc.) differ to a greater or lesser extent from one category to another. Table 2 lists, by no means exhaustively, the families of ultra-fine wires we know how to manufacture today, along with their applications. This article is limited to presenting the current state of the art in the drawing of ultra-fine wires in copper and copper alloys, whether coated or not, mainly for electrical applications.

As part of the miniaturization and lightening of electronic components, which have a considerable economic and technological impact on the performance of electronic equipment, the development of miniature electrical cables has been one of the main trends in the technological evolution of electrical connections in recent years. The metal wires making up the conductive core and secondary shielding layer of these cables are made of copper or copper alloys with diameters ranging from 15 to 50 µm (finer than a human hair: on average 70 µm). This has led to the development of drawing techniques specific to this type of extremely fine wire.