external heater 40 fig1 may heat the semiconductor package 10 insert 16 substrate member 18 or a socket into which the substrate member fits by radiation or heated air 42 the solder bumps balls 12 may be of any diameter 32 including those of a fine ball grid array fbga where the balls have a pitch of less than one 1 mm the solder bumps balls 12 may be formed of various solder compositions including tin lead solders having a lead content of about 30 to 98 percent solder compositions having the higher lead concentrations often have a higher melting point a softening temperature t s of about 130 to about 180 degrees c has been found useful for reducing the compression force 38 to a relatively low value and simultaneously ensuring electrical contact of all solder bumps balls 12 as shown in drawing fig3 resistive heating elements 44 may be applied to the top surface 48 of the substrate member 18 preferably under the insert 16 and substantially beneath the semiconductor package 10 the heating elements 44 are shown as having power leads 54 56 for providing sufficient power to quickly heat the insert 16 including the electrical contact sites 20 not shown and the solder bumps balls 12 not shown which are in engagement with the contact sites 20 all.