Semiconductor device with wire including a surface metal layer covering a core metal

1 . A semiconductor device comprising:

a first circuit including a first semiconductor element;

a second circuit including a third semiconductor element;

a second semiconductor element that is electrically connected to each of the first semiconductor element and the third semiconductor element, the second semiconductor element relaying a mutual signal between the first circuit and the second circuit and insulating the first circuit and the second circuit from each other;

a first terminal lead electrically connected to the first semiconductor element and included in the first circuit;

a second terminal lead electrically connected to the third semiconductor element and included in the second circuit;

a first wire connected to the first semiconductor element and the second semiconductor element and included in the first circuit;

a second wire connected to the first semiconductor element and the first terminal lead and included in the first circuit;

a third wire connected to the second semiconductor element and the third semiconductor element and included in the second circuit;

a fourth wire connected to the third semiconductor element and the second terminal lead and included in the second circuit; and

a sealing resin covering the first semiconductor element, the second semiconductor element, the third semiconductor element, the first wire, the second wire, the third wire and the fourth wire,

wherein an electric potential of the second circuit is higher than an electric potential of the first circuit,

each of the first wire and the third wire contains a first metal,

the second wire includes a first core containing a second metal, and a first surface layer containing a third metal and covering the first core,

the fourth wire includes a second core containing the second metal, and a second surface layer containing the third metal and covering the second core,

an atomic number of the second metal is smaller than an atomic number of the first metal, and

the third metal has a greater bonding strength with respect to each of the first terminal lead and the second terminal lead than the second metal.

2 . The semiconductor device according to claim 1 , further comprising a first island lead,

wherein

the first island lead is included in the first circuit, and

the first semiconductor element is mounted on the first island lead.

3 . The semiconductor device according to claim 2 , further comprising a second island lead located away from the first island lead and included in the second circuit,

wherein the third semiconductor element is mounted on the second island lead.

4 . The semiconductor device according to claim 3 , wherein the second semiconductor element is mounted on the first island lead.

5 . The semiconductor device according to claim 3 , wherein the second semiconductor element is mounted on the second island lead.

6 . The semiconductor device according to claim 2 , wherein in a first direction, the third semiconductor element is located opposite from the first semiconductor element with respect to the second semiconductor element.

7 . The semiconductor device according to claim 2 , further comprising a fifth wire and a metal block,

wherein the first island lead has a first island portion on which the first semiconductor element is mounted, and a first terminal portion extending from the first island portion,

the fifth wire is connected to the first semiconductor element and the first terminal portion, and

the metal block is bonded to a connecting portion of the fifth wire that is connected to the first terminal portion.

8 . The semiconductor device according to claim 1 , wherein the first metal is gold.

9 . The semiconductor device according to claim 1 , wherein the second metal is copper.

10 . The semiconductor device according to claim 1 , wherein the third metal is palladium.

11 . The semiconductor device according to claim 1 ,

wherein the second wire has a first main portion, and a first end portion positioned between the first main portion and the first terminal lead,

the first end portion includes a first tapered portion adjacent to the first main portion, and a dimension of the first tapered portion in a thickness direction of the first terminal lead decreases with distance from the first main portion, and

a bonding interface between the first terminal lead and the second wire extends over the first main portion and the first end portion as viewed in the thickness direction of the first terminal lead.

12 . The semiconductor device according to claim 1 ,

wherein the fourth wire has a second main portion, and a second end portion positioned between the second main portion and the second terminal lead,

the second end portion includes a second tapered portion adjacent to the second main portion, and a dimension of the second tapered portion in a thickness direction of the second terminal lead decreases with distance from the second main portion, and

a bonding interface between the second terminal lead and the fourth wire extends over the second main portion and the second end portion as viewed in the thickness direction of the second terminal lead.

13 . The semiconductor device according to claim 1 ,

wherein the first semiconductor element has a first metal layer connected to the second wire, and a second metal layer overlapping with the first metal layer as viewed in a thickness direction of the first semiconductor element and positioned inward in the thickness direction of the first semiconductor element, and

the first metal layer has higher flexural rigidity than the second metal layer.

14 . The semiconductor device according to claim 1 ,

wherein a sulfur content of the sealing resin per unit mass is no greater than 300 μg/g.

15 . The semiconductor device according to claim 1 , wherein the second semiconductor element is of an inductive type.