| 摘要 |
PURPOSE: To make it possible to maintain an allowable interval between a substrate and a chip package under ordinary reflow condition, by using a plurality of solder balls inferior in temperature resistance in addition to a plurality of solder balls which withstand elevated temperature. CONSTITUTION: A main BGA package 23 is mounted on a substrate 27. The substrate 27 contains at least two substrate layers 27a, 27b, and conductive signal wires placed between them provide communication connection in conjunction with a plurality of wire leads 24a-24n when the substrate 27 is joined with connecting section. This joint is obtained by a combination of a plurality of eutectic solder balls 28a-28n of a low melting point and high-temperature solder balls 29a-29n of a high melting point. The solder balls 29a-29n of high temperature resistance are so designed as to withstand reflow temperature, and placed at at least the corners of the main BGA package 23 in order to prevent the BGA package 23 from being crashed. |
