| 摘要 |
PROBLEM TO BE SOLVED: To uniformly distribute shearing stresses between a ceramic multilayered wiring board and a printed wiring board and electronic parts throughout electrodes by making low-temperature solder to exist to a line connecting the edges of the openings of recessed sections which are formed on the surface of the multilayer wiring board as the contacts of high-temperature solder balls. SOLUTION: Low-temperature solder is arranged in such a way that, when a tangential line 56 is drawn to a hightemperature solder ball 54 from the edge 60 of the opening of a recessed section, the low-temperature solder always exists on the outside of the line 56, namely, at least on the line 56. A solder electrode 55 is formed by putting the high-temperature solder ball 54 on printed low-temperature solder paste 52 and only melting the low-temperature solder by heat-treating the low-temperature solder 52 at a temperature between the melting points of the low- and high-temperature solder 52 and 54. When the heat treatment is performed, the solder ball 54 sinks by pushing away the molten low-temperature solder 52. To make the pushed-away of the molten low-temperature solder the maximum, inequalities B-√(B<2> -X<2> )>2t and B<=1.2X (where B, X and t respectively represent the diameter of the solder ball 54, diameter of the opening of the recessed section, and depth of the recessed section) may be met. |
