A power module is fabricated, employing a clad metal that is formed by pressure-laminating aluminum and copper, in such a manner that the aluminum layer of the clad metal is bonded such as by ultrasonic bonding to the surface electrode of the power semiconductor chip and a wire is bonded to the copper layer thereof to establish electrical circuit. The clad metal is thermally treated in advance at a temperature higher than the operating temperature of the power semiconductor chip to sufficiently form intermetallic compounds at the interface between the aluminum layer and the copper layer for the intermetallic compounds so as not to grow in thickness after the bonding processes.

A bonding wire for a semiconductor device including a coating layer having Pd as a main component on the surface of a Cu alloy core material and a skin alloy layer containing Au and Pd on the surface of the coating layer has a Cu concentration of 1 to 10 at % at an outermost surface thereof and has the core material containing a metallic element of Group 10 of the Periodic Table of Elements in a total amount of 0.1 to 3.0% by mass, thereby achieving improvement in 2nd bondability and excellent ball bondability in a high-humidity heating condition. Furthermore, a maximum concentration of Au in the skin alloy layer is preferably 15 at % to 75 at %.

A bonding wire for a semiconductor device including a coating layer having Pd as a main component on the surface of a Cu alloy core material and a skin alloy layer containing Au and Pd on the surface of the coating layer has a Cu concentration of 1 to 10 at % at an outermost surface thereof and has the core material containing a metallic element of Group 10 of the Periodic Table of Elements in a total amount of 0.1 to 3.0% by mass, thereby achieving improvement in 2nd bondability and excellent ball bondability in a high-humidity heating condition. Furthermore, a maximum concentration of Au in the skin alloy layer is preferably 15 at % to 75 at %.

A bonding wire for a semiconductor device includes a Cu alloy core material and a Pd coating layer formed on a surface thereof. Containing an element that provides bonding reliability in a high-temperature environment improves the bonding reliability of the ball bonded part in high temperature. Furthermore, making an orientation proportion of a crystal orientation <100> angled at 15 degrees or less to a wire longitudinal direction among crystal orientations in the wire longitudinal direction 30% or more when measuring crystal orientations on a cross-section of the core material in a direction perpendicular to a wire axis of the bonding wire, and making an average crystal grain size in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire 0.9 to 1.5 m provides a strength ratio of 1.6 or less.

A bonding wire for a semiconductor device includes a Cu alloy core material and a Pd coating layer formed on a surface thereof. Containing an element that provides bonding reliability in a high-temperature environment improves the bonding reliability of the ball bonded part in high temperature. Furthermore, making an orientation proportion of a crystal orientation <100> angled at 15 degrees or less to a wire longitudinal direction among crystal orientations in the wire longitudinal direction 30% or more when measuring crystal orientations on a cross-section of the core material in a direction perpendicular to a wire axis of the bonding wire, and making an average crystal grain size in the cross-section of the core material in the direction perpendicular to the wire axis of the bonding wire 0.9 to 1.5 m provides a strength ratio of 1.6 or less.

A process for manufacturing a bonding wire containing a core having a surface. The core contains 98.0% copper and has a cross sectional area of 75,00 to 600,000 m.sup.2 and an elastic limit RP0.2 (yield strength) of 40 to 95 N/mm.sup.2. The process involves (a) providing a copper core precursor; (b) drawing the precursor until a final diameter of the wire core is reached; and (c) annealing the drawn wire at a minimum annealing temperature of 650 to 1000 C. through its entire cross section for a minimum annealing time of 4 seconds to 2 hours.

A process for manufacturing a bonding wire containing a core having a surface. The core contains 98.0% copper and has a cross sectional area of 75,00 to 600,000 m.sup.2 and an elastic limit RP0.2 (yield strength) of 40 to 95 N/mm.sup.2. The process involves (a) providing a copper core precursor; (b) drawing the precursor until a final diameter of the wire core is reached; and (c) annealing the drawn wire at a minimum annealing temperature of 650 to 1000 C. through its entire cross section for a minimum annealing time of 4 seconds to 2 hours.

A power module is fabricated, employing a clad metal that is formed by pressure-laminating aluminum and copper, in such a manner that the aluminum layer of the clad metal is bonded such as by ultrasonic bonding to the surface electrode of the power semiconductor chip and a wire is bonded to the copper layer thereof to establish electrical circuit. The clad metal is thermally treated in advance at a temperature higher than the operating temperature of the power semiconductor chip to sufficiently form intermetallic compounds at the interface between the aluminum layer and the copper layer for the intermetallic compounds so as not to grow in thickness after the bonding processes.

There is provided a bonding wire for a semiconductor device including a coating layer having Pd as a main component on a surface of a Cu alloy core material and a skin alloy layer containing Au and Pd on a surface of the coating layer, the bonding wire further improving 2nd bondability on a Pd-plated lead frame and achieving excellent ball bondability even in a high-humidity heating condition. The bonding wire for a semiconductor device including the coating layer having Pd as a main component on the surface of the Cu alloy core material and the skin alloy layer containing Au and Pd on the surface of the coating layer has a Cu concentration of 1 to 10 at % at an outermost surface thereof and has the core material containing either or both of Pd and Pt in a total amount of 0.1 to 3.0% by mass, thereby achieving improvement in the 2nd bondability and excellent ball bondability in the high-humidity heating condition. Furthermore, a maximum concentration of Au in the skin alloy layer is preferably 15 at % to 75 at %.

There is provided a bonding wire for a semiconductor device including a coating layer having Pd as a main component on a surface of a Cu alloy core material and a skin alloy layer containing Au and Pd on a surface of the coating layer, the bonding wire further improving 2nd bondability on a Pd-plated lead frame and achieving excellent ball bondability even in a high-humidity heating condition. The bonding wire for a semiconductor device including the coating layer having Pd as a main component on the surface of the Cu alloy core material and the skin alloy layer containing Au and Pd on the surface of the coating layer has a Cu concentration of 1 to 10 at % at an outermost surface thereof and has the core material containing either or both of Pd and Pt in a total amount of 0.1 to 3.0% by mass, thereby achieving improvement in the 2nd bondability and excellent ball bondability in the high-humidity heating condition. Furthermore, a maximum concentration of Au in the skin alloy layer is preferably 15 at % to 75 at %.