Abstract: The armature of an engine starter direct current (d.c.) motor comprises a rotary shaft, an aluminum armature coil. The commutator a commutator disposed on the rotary shaft and has a plurality of copper commutator segments each including a main body portion having a sliding contact surface and a connecting portion having an aluminum connecting surface. The aluminum armature coil is electrically and mechanically connected to each of the aluminum connecting surfaces of the commutator segments to form an electrical and mechanical connection therebetween. The electrical and mechanical connection between the aluminum connecting surface and the armature coil is coated with an electrically insulating resin.

Abstract: A device for cooling semiconductor elements is constituted by a plate for cooling semiconductor elements, the plate being made of aluminum or an aluminum alloy, and a semiconductor element-mounting sheet which is made of aluminum or an aluminum alloy, the sheet having on one surface thereof a metal layer to which solder can be applied as desired, and the other surface of the sheet being secured by ultrasonic welding to the plate in a recessed portion formed in the cooling plate by ultrasonic welding.