Patent ID: 7690551

Claim:
A method of manufacturing a semiconductor device, comprising: providing a semiconductor wafer; providing a temperature gradient lead free soft solder metal film having a film alloy composition, a higher melting temperature near a middle portion of the solder metal film, and a lower melting temperature near first and second surfaces of the solder metal film; forming a heat vaporizable polymer adhesive layer over the solder metal film; mounting the semiconductor wafer to the polymer adhesive layer over the solder metal film; dicing the semiconductor wafer and solder metal film to form a solder metal film laminated semiconductor die; providing a leadframe having a die paddle; pre-heating the leadframe to a reflow temperature above the melting temperature of the middle portion of the solder metal film prior to mounting the solder metal film laminated semiconductor die to the die paddle of the leadframe; and mounting the solder metal film laminated semiconductor die to the die paddle of the pre-heated leadframe in less than 50 milliseconds to avoid melting of the polymer adhesive layer before making contact between the solder metal film laminated semiconductor die and the die paddle of the pre-heated leadframe, wherein the reflow temperature of the leadframe raises the middle portion and first and second surfaces of the solder metal film above the respective melting temperatures and the polymer adhesive layer is completely vaporized at the reflow temperature after mounting the solder metal film laminated semiconductor die to the die paddle of the leadframe.