Tensile Straightening of Superfine Wire and Residual Stress Measurement Using Focused Ion Beam

The general method of reducing curving or bending for midsize wires or sheets is straightening using rollers and / or levelers. For superfine wires, similarly, high straightness is needed. However, it is very di ffi cult to deal with superfine wires due to their fineness and low tensile strength. In our study, warm tensile straightening processes for superfine gold wire, which is widely used as bonding material between leads and IC chips in semiconductors, were examined. Furthermore, finite element analyses of drawing and tensile straightening of superfine wires were carried out. The correlation between straightness and axial residual stress, which was calculated using the curve width when half of the wire was removed by sputtering with a focused ion beam (FIB), was studied. As a result of our studies, the improvement of straightness by tensile straightening of superfine gold wire was demonstrated, and the relationship between axial residual stress and straightness of wires was clarified.