Abstract: To provide a power-module substrate and a manufacturing method thereof in which small voids are reduced at a bonded part and separation can be prevented. Bonding a metal plate of aluminum or aluminum alloy to at least one surface of a ceramic substrate by brazing, when a cross section of the metal plate is observed by a scanning electron microscope in a field of 3000 magnifications in a depth extent of 5 ?m from a bonded interface between the metal plate and the ceramic substrate in a width area of 200 ?m from a side edge of the metal plate, residual-continuous oxide existing continuously by 2 ?m or more along the bonded interface has total length of 70% or less with respect to a length of the field.

Abstract: To provide a power-module substrate and a manufacturing method thereof in which small voids are reduced at a bonded part and separation can be prevented. Bonding a metal plate of aluminum or aluminum alloy to at least one surface of a ceramic substrate by brazing, when a cross section of the metal plate is observed by a scanning electron microscope in a field of 3000 magnifications in a depth extent of 5 ?m from a bonded interface between the metal plate and the ceramic substrate in a width area of 200 ?m from a side edge of the metal plate, residual-continuous oxide existing continuously by 2 ?m or more along the bonded interface has total length of 70% or less with respect to a length of the field.