Patent ID: 7193319

Claim:
A semiconductor device comprising: a silicon chip having a rectifying function; an upper, conductive buffer layer having a low coefficient of linear expansion and joined to an upper side of the silicon chip through a Pb-free solder containing no Pb; a lower, conductive buffer layer having a low coefficient of linear expansion and joined to a lower side of the silicon chip through a Pb-free solder containing no Pb; a conductive lead joined to an upper side of the upper buffer layer through a Pb-free solder containing no Pb; and a conductive base joined to a lower side of the lower buffer layer through a Pb-free solder containing no Pb, wherein the solder on the upper and lower sides of the silicon chip has a thickness of not more than 0.05 mm, wherein the solder on the upper side of the upper buffer layer has a thickness of not less than 0.15 mm, and the solder on the lower side of the lower buffer layer has a thickness of not less than 0.15 mm, and wherein the Pb-free solder containing no Pb has a melting point of not less than 250° C.