Study On The Property Of Single Crystal Copper For The Bonding Wire

In recent years, a lot of studies have shown that copper wires are the best materials to replace gold in some high-end, ball and wedge bonding applications. Copper wire has cost-effective , high thermal conductivity, low electrical resistance, and high pull strength allowing for a reduced wire diameter, which leads to reduced pad size and pad pitch. This contributes to higher packing density of IC chips.This thesis is investigated the single crystal copper properties for bonding wire . This research began with analysis of the fracture of traditional continuously cast copper wires and imposed vacuum system on the traditional continuous unidirectional solidification equipment to purify metals . In order to research the effects of plastic deformation of the single crystal copper , which are drawn out from having different plastic deformation of single crystal copper wire (08 mm) ,the microstructure , the texture, the properties of deformed and intermediate annealing operations of the single crystal copper are measured precisely. The results show:1. The wiredrawing properties of copper wire were worsen during wire drawing have been found to correlate with the amount of oxygen, sulfur, hydrogen etc.For the more ,the drawing force and the surface of rod during drawing, lubrication are result in wire breakage.2. By appropriate process parameters, the single crystal copper were made good surface , microstructure , mechnical and electric properties. On the same vacuum conditions, the amount of H,O,S are in same lowly,in spite of differet purity materials.3. Under the different plastic deformation value, Work-hardening velocity of the copper wire increase rapidly and go into the II stage of linear work-hardening directly. Work-hardening velocity became slowly while the plastic deformation value reaches 90%.The plastic deformation beginning with cracking of crystal grain and partial slipping first, then being twinning deformation and then occurring new slipping; cracking, breaking and thinning of crystal grain, and non-homogeneous deformation in radial and axial directions through the whole process of plastic deformation, forming fibrous structure in the end.The resistivity of single crystal copper wire increase with the the drawing stress , and then decrease with the critical compress stress, the cut-off points isψ=58.5% ; in the end the resistivity enhance slowly. The curve of resistivity p vs. plastic deformation can be expressed as Fit Lorentzian. From the study, it is found that the break load and electrical resistivity became low and elongation became large when the temperature and times increased. For 0.25mm single crystal copper wire, the break load and elongation were excellent at intermediate annealing operations in 430℃and 2s.The property and the reliability on single crystal copper boding wire were investigated.