| 摘要 |
PURPOSE:To shorten working time with lowering of the working temp. and easiness of the work and to prevent the occurrence of defect in the joined surface by reducing tin content and increasing lead content as leaving far from the joined surface in the distance and making the equal composition between a thin film layer and high temp. solder in the joined surface. CONSTITUTION:Both metals 1, 2 are joined by soldering with the tin-lead eutectic type solder. The composition of the solder is the high temp. solder having <=30wt.% tin content and in the soldered surfaces between the main high temp. soldered layer 3 and both metals 1, 2, the thin film layer 4 having fine thickness as diffusion layers formed by mutually diffusing the high temp. solder and a middle and low temp. solder having m.p. lower than the high temp. solder by tens of deg.C are interposed. As the middle and low temp. solder having tin- riched composition is formed on the soldered surfaces 5 of the metals 1, 2 to be soldered, the solder having such comparatively low m.p. has extremely good soldering workability, and the good thin film without any defect is easily formed and the reliability of the joining can drastically be improved. |
