We investigated whether high–quality fine copper wire could be manufactured at a low cost by combining three–roll rolling and die wire drawing. The roundness, surface quality, mechanical properties, and processing cost of fine wires finished from a copper wire rod by three–roll rolling and to the conventional die drawing method were compared. It is more difficult to obtain an exceptionally high quality of fine wires in terms of roundness value and surface quality by only three–roll rolling. However, the rolled wire is self–annealed by processing heat, so there is no need for the intermediate annealing work that is normally performed in the subsequent process on the troublesome task of threading wire to the die, so workability and productivity are improved while manufacturing cost is reduced. These are advantageous points. It was clarified that extremely high–quality copper fine wire can be manufactured at a low cost by first reducing the diameter of the rolled copper wire to 1.8 mm by the three–roll rolling method and then drawing the wire using the die.

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With the recent advances in the semiconductor industry, the demand for gold, copper and aluminum bonding wires has been increasing. Wire diameter has been decreasing due to the market demand for small and highly functional products. Also, a high degree of wire straightness is required to prevent short-circuit defects caused by contact between looped wires. Although methods of improving the straightness of superfine wires by tensile straightening have been examined, the number of such studies is limited and the mechanism of improving the straightness of wires has not yet been clarified. In this study, tensile straightening was carried out for superfine gold wires to examine the change in wire straightness under various conditions. We proposed a residual stress measurement method that allows us to quantitatively measure the residual stress in a wire specimen, which obtained by removing a part of the wire using a focused ion beam (FIB). We also demonstrated the relationship between straightness and residual stress. Furthermore, the effect of tensile strain on the crystalline structure was examined to clarify the effect of the tensile strain on the straightness of the wire and the crystal orientation rate.

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For obtaining a tube of high uniformity in wall thickness, the drawing should be done keeping the tube and die axes as well as the drawing direction strictly aligned, as has been mentioned in a previous report. In the present report the phenomena of changes in concentricity occurring when the tubes were deliberately drawn out of alignment have been studied. The following are results obtained.
(1) Even a small angle of inclination between the die axis and the drawing direction on the exit side of a die leads to continuous bending of the tube onto the exit die corner, and the wall thickness increases more at the side where it is bent.
(2) The misalignment between the die bore and the tube axis on the entry side of a die makes the wall thickness increase more at the side with least contact with the die face.
(3) By positive application of (1) and (2), placing the thinner side of a tube, for instance, on the side of greater wall thickening in a die bore, improves the concentricity in small numbers of drawing passes.
(4) Proper combination of small inclination angle with misalignment in sinking seems to improve the wall-thickness uniformity of the tube.

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Finite-element method (FEM) analysis of the straightening of drawn wires using rollers is carried out to discuss the optimum straightening conditions and the conditions of each part of the leveler used for straightening. Roller distribution of straightening conditions use slant distribution, it set up easily roller distribution and straighten easily. The conditions during straightening using roller leveller have been determined on the basis of the experience of on-site operators, and the number of related research reports is limited. In this study, roller position, roller diameter and change in roller pitch are examined by FEM analysis to clarify the optimum straightening conditions of wires using rollers.

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To improve motor performance, motor magnet copper wires are changing from conventional round copper wires to flat (rectangular) copper wires. The market strict demands on the dimensional accuracy, surface properties, and surface defects of flat drawn copper wires, but there is almost no research on drawing to derive the optimum processing conditions for manufacturing flat wires. In this paper, we have focused on typical flat magnet wire manufacturing processes by multiple times shaped drawing from a round wire, to obtain high–quality flat magnet copper wire. Optimal processing conditions (mother wire diameter, cross–sectional reduction) and derivation of the optimal drawing die shape (angle) were studied. By Finite Element Analysis, we have investigated the possibility of shaped drawing, the lack of thickness, and the dimensional accuracy of the drawn shaped wire, and clarified the optimum processing conditions. In addition, the drawing experiments were carried out to confirm the reliability of the FEM analysis results. Based on these results, we clarified the optimum mother wire diameter, the optimum drawing conditions (die angle and reduction per pass) in the production of flat magnet copper wires.

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