Recently, because the micro-machine is noticed and electronic equipments are made much lighter and smaller, the demand for micro materials is increasing. However the mechanical properties data of the micro materials obviously run short and the evaluation method of micro materials is different according to the researcher. Therefore, the establishment of the test method for the micro materials is very necessary. In this study, the tensile strength tests were carried out using the bonding wires of Cu as the material. Its diameters were 20μm and 50μm. The gauge lengths of the specimens were three kinds of 20mm, 60mm, and 100mm. As the results, in the case of all materials, Young's moduli were almost equal regardless of the gauge lengths. Therefore, it was found that Young's modulus could be measured with high accuracy. But, Young's modulus for Cu wire of 20μm is greatly different from that of 50μm. It is considered that the orientation is a cause. The tensile strengths also were almost equal regardless of the gage length. The elastic limit and proof stress for gauge length of 20mm were the largest regardless of the materials.
