JP2958380B

PURPOSE:To cool a semiconductor device of several tens watt class while proving high speed signal propagating characteristic by covering a part between a semiconductor chip and a heat radiator and the entire chip surface with a soft material having specific elastic modulus. CONSTITUTION:Parts among a semiconductor chip 1, a heat diffusing plate 2 to be connected with the chip 2 and a heat radiator formed of a heat sink 9, etc., and the entire chip surface are covered with a soft material 8 having 0.001-100kg/mm of elastic modulus. Accordingly, a misalignment generated due to a difference of expansion coefficients of materials for forming a package can be prevented, heat generated from the chip 1 is rapidly transferred to the sink 9 through the plate 2, while capacity between wirings, inductance of wirings and resistance are minimized in a circuit board 4 containing wiring layers to prevent deterioration of signal propagating characteristic. Thus, sufficient heat radiation can be performed without loss of the signal propagating characteristic.