木村 真晃

It is essential to measure the residual stress of resin material to evaluate the reliability of a resin packaged electron device. The leaky surface skimming compressional wave (LSSCW) velocity is determined by the V(z) curve obtained by the acoustic microscope. The LSSCW velocity depends on the stress, therefore, it is possible to evaluate the localized residual stress using the LSSCW velocity. The purpose of this study is to establish a stress measurement method of the resin material of the electron device with an acoustic microscope for basic research. The effect of surface roughness on the LSSCW velocity is investigated using acrylic resin as the resin material. In addition, the relationship between stress and the LSSCW velocity of the resin material is examined. On the basis of these results, a stress evaluation method of resin material using the acoustic microscope is proposed.

Corrosion current distributions of the friction welding joints between commercially pure titanium (Ti) and type 5083 aluminum alloy (A 5083) were measured in a 3.5% NaCl solution by using the scanning vibrating electrode technique. A 200nm-thick intermetallic compound layer was formed at the welded interface at the friction time of 3.0 s. This intermetallic compound layer reduces the tensile strength of the friction welding joint. It is suggested that the intermetallic compound layer were comprised of tau-Al (Ti₂Mg₃Al₁₈), Mg₂Al₃, and Al₃Ti phases. The friction welding joint with the intermetallic compound layer at the welded interface was less susceptible to galvanic corrosion, whereas pitting corrosion occurred in the friction welding joint having only the Mg concentrated area at the welded interface. Therefore, it is considered that the intermetallic compound layer can suppress the galvanic corrosion.