It is desirable that a material used for metal powder 16 has such properties as a melting point higher than that of the solder used for bumps 7, that it does not produce oxide films on the surfaces of metal powder 16 in the air ambient, and has good wettability to the solder composing bumps 7 so as to allow the melted bumps 7 in a fluid state of the solder to flow and spread easily over the surfac