Being the LSI package where it possesses the two-layer structure of the LSI package

摘要

PROBLEM TO BE SOLVED: To form a good solder-connected part, even if an LSI package is warped due to heat when the LSI package having a solder bump, such as CSP, BGA, etc. is mounted to a printed circuit board.;SOLUTION: The solder bump with core 3, formed of a core 31 and a coater 32, is arranged to a pad 4 of the LSI package 1. The core 31 and the coater 32 are constituted with solder alloys having different compositions, and a melting point of the coater 32 is lower than that of the core. Thus, when the heat treatment is started, the coater 32 melts first in the stage where the warpage of the LSI package 1 is a little, getting the wet condition for the core 31 and solder paste 7. Even when temperature rises and warpage becomes large thereafter, the core 31 and solder paste 7 are maintained in the state connected with the melted coater 32. Accordingly, when the temperature reaches the melting temperature of the core 31 and solder paste 7, these are condensed to form proper solder-connected parts.;COPYRIGHT: (C)2007,JPO&INPIT