Semiconductor device having lead free solders between semiconductor chip and frame and fabrication method thereof

1. A semiconductor device, comprising:

a semiconductor chip including a current path between a first principal surface and a second principal surface opposite from the first principal surface, the semiconductor chip having a rectangular shape defined by a longer side and a shorter side in plan view;

a first conductive frame electrically connected via a plurality of column-shaped lead-free solders to the first principal surface, each of the plurality of column-shaped lead-free solders being arranged in a gap between the first principal surface and the first conductive frame and within a circle drawn around a center of the semiconductor chip and having diameter corresponding to a length of the shorter side;

a second conductive frame electrically connected via an electrical connection member to a pad formed on the second principal surface; and

a filler which is filled in a remaining gap between the first conductive frame, the first principal surface of the semiconductor chip and the plurality of column-shaped lead-free solders.

2. The semiconductor device according to claim 1 , wherein the semiconductor chip constitutes at least one of a transistor and a diode.

3. The semiconductor device according to claim 1 , wherein a position of arranging the column-shaped lead-free solders is adjusted so that the pad formed on the second principal surface overlaps the column-shaped lead-free solders in a plan view, and

wherein, when a length in a narrow side direction of the pad is W 1 , a minimum length in a direction parallel to W 1 of a lead-free solder arranged in a position in which the lead-free solder overlaps the pad connected to the current path in a plan view is W 2 , a minimum space distance between adjoining lead-free solders is W 3 , and a height of the lead-free solder is H, the following <formula 1> and <formula 2> are satisfied;

W2≧W1  <Formula 1<

W3≦H.  <Formula 2>

4. The semiconductor device according to claim 1 , wherein the electrical connection member comprises a wire.

5. The semiconductor device according to claim 1 , wherein the electrical connection member comprises a clip and another plurality of column-shaped lead-free solders,

wherein the clip is electrically connected between the second conductive frame and the another plurality of column-shaped lead-free solders, and the another plurality of column-shaped lead-free solders are further electrically connected to the second principal surface.

6. The semiconductor device according to claim 4 , further comprising a third conductive frame electrically connected via another wire to the second principal surface.

7. The semiconductor device, according to claim 5 , further comprising a third conductive frame electrically connected via a wire to the second principal surface.

8. The semiconductor device according to claim 5 , wherein the another plurality of column-shaped lead-free solders electrically connected to the second principal surface are arranged within a circle drawn around the center of the semiconductor chip and having a diameter corresponding to the length of the shorter side, and a gap between the clip, the second principal surface of the semiconductor chip and the another plurality of the column-shaped lead-free solders is filled with another filler.

9. A semiconductor device, comprising:

a semiconductor chip having rectangular shape defined by a longer side and a shorter side in a plan view and comprising a vertical MOSFET, a drain electrode of the vertical MOSFET being formed on a first principal surface of the semiconductor chip, and a source and a gate electrode of the vertical MOSFET being formed on a second principal surface of the semiconductor chip opposite to the first principal surface;

a die pad with a drain lead made of a first conductive frame, the drain electrode is electrically connected via a plurality of column-shaped lead-free solders to the die pad, each of the plurality of column-shaped lead-fee solders being arranged in a gap between the first principal surface and the first conductive frame and within a circle drawn around a center of the semiconductor chip and having a diameter corresponding to a length of the shorter side;

a source lead made of a second conductive frame and electrically connected via a first electrical connection member to the source electrode;

a gate lead made of a third conductive frame and electrically connected via a second electrical connection member to the gate electrode; and

a filler which is filled in a remaining gap between the first conductive frame, the first principal surface of the semiconductor chip and the plurality of column-shaped lead-free solders.

10. The semiconductor device according to claim 9 , wherein each of the first and second electrical connection members is formed with a conductive wire.

11. The semiconductor device according to claim 9 , wherein the first electrical connection member comprises a clip and another plurality of column-shaped lead-free solders,

the clip is electrically connected between the source lead and the another plurality of column-shaped lead-free solders,

the another plurality of column-shaped lead-fee solders are further electrically connected to the source electrode, and

the second electrical connection member is formed with a conductive wire.