Power semiconductor device

1. A power semiconductor device comprising a switching power semiconductor element, and a free wheeling diode in anti-parallel connection to the switching power semiconductor element, characterized in that:

a reverse electrode of the switching power semiconductor element and a reverse electrode of the free wheeling diode are bonded and mounted on a circuit pattern formed on a main surface of the first substrate;

a circuit pattern, which is so formed on a main surface of the second substrate as to oppose a surface electrode of the switching power semiconductor element and a surface electrode of the free wheeling diode, is connected to the surface electrodes of the switching power semiconductor element and the free wheeling diode through connective conductors to be soldered, respectively, at least the contacting surfaces of the connective conductors each having a curved surface which directly contacts the circuit pattern or the surface electrode;

a first string-like partitioning material is a U-shaped partitioning material laid in the vicinity of and alongside the outer peripheral edges of the first substrate and the second substrate, and is bonded to the first substrate and the second substrate;

a gel-like insulation and heat resistant filler is inserted from an opening of said U-shaped partitioning material or is inserted using a syringe from the bases of the three sides of said U-shaped partitioning material; and

a second partitioning material is disposed on said opening and is bonded to the first substrate and the second substrate to thereby seal and confine the insulation and heat resistant filler.

2. A power semiconductor device according to claim 1 , wherein an IC for controlling the driving of the switching power semiconductor element is mounted on the reverse of the second substrate, the surface of which is opposed to the first substrate.

3. A power semiconductor device according to claims 1 , wherein at least the first substrate is a ceramic insulating substrate, and a heat sink divided into a plurality of portions is bonded to the reverse of the ceramic substrate.

4. A power semiconductor device according to claims 1 , wherein at least the first substrate is a ceramic insulating substrate, and a portion so shaped as to function as a heat sink is formed on the reverse of the ceramic substrate.

5. A power semiconductor device according to claims 1 , wherein, when one end of an external lead is soldered to the substrate, all of such soldering is made on the circuit pattern formed on the main surface of the first substrate.

6. A power semiconductor device according to claim 1 , wherein the connective conductors are flexible enough to absorb stress.

7. A power semiconductor device according to claims 1 , wherein at least three substrates are comprised.